1
Response Analysis of the
Deepwater Steel Lazy-Wave Riser for the
Turret Moored Floating Production Storage Off-loading System
By
Shangzhan Li
Bachelor of Engineering
College of Shipbuilding Engineering
Harbin Engineering University
Harbin, China
2011
A thesis submitted to Florida Institute of Technology
In partial fulfillment of the requirements
For the degree of
Master of Science
In
Ocean Engineering
Melbourne, Florida
December, 2014
We the undersigned committee hereby recommend that the attached document be
accepted as fulfilling in part of the requirements of the degree of
Master of Ocean Engineering.
“Response Analysis of the Deepwater Steel Lazy-Wave Riser for the Turret Moored
Floating Production Storage Off-Loading System,”
a thesis by Shangzhan Li
________________________________________
Dr. Stephen Wood
Professor and Ocean Engineering Program Chair, Marine and Environmental Systems
_________________________________________
Dr. Ronnal Reichard
Professor, Marine Environmental Systems
_______________________________________
Dr. Shengyuan Yang
Assistant Professor, Mechanical Aerospace Eng.
iii
Abstract
Response Analysis of the
Deepwater Steel Lazy-Wave Riser for the
Turret Moored Floating Production Storage Off-loading System
By
Shangzhan Li
Major Advisor: Stephen Wood, Ph.D., P.E.
With the continuous increase of exploration and development in deepwater (over 2,000
feet) and ultra-deepwater (over 5,000 feet) fields, technical challenges have arisen.
The environmental conditions in the Gulf of Mexico (GoM) make the development of
a traditional operation unit of a Floating Production Storage Off-loading (FPSO)
system with a simple Steel Catenary Riser (SCR) challenging. For example, the
pipeline would buckle at the touchdown zone due to the vessel motion caused by the
waves and the current. In recent years, the Steel Lazy-Wave Riser (SLWR) has been a
popular solution for deepwater operations, as it can improve the riser system’s fatigue
and strength response performance. In this paper, the feasibility, of developing a turret
moored FPSO-SLWR operation unit in the GoM, is investigated. The production risers
in the lazy-wave configuration are designed and analyzed in contrast with the simple
SCR design. Both designs are based on the same criteria and the same environmental
conditions. Using the Finite Element Analysis (FEA) software, Orcaflex, strength
iv
analysis, including static and dynamic analysis, for both in-place condition and
disconnection condition, is performed to simulate the response of the riser system to
different load cases. The robustness of the riser system is also demonstrated through
the sensitivity study. In addition, buoyancy module properties, which affect the global
performance of the riser system, are discussed and compared. The partial optimization
of the buoyancy module arrangement is also accomplished. The results of this study
indicate developing an FPSO-SLWR operation unit as feasible.
v
Table of Contents
Abstract ........................................................................................................................ iii
Table of Contents ...........................................................................................................v
List of Figures ............................................................................................................. vii
List of Tables .............................................................................................................. viii
Chapter 1 ........................................................................................................................1
INTRODUCTION .........................................................................................................1
1.1 Literature Review ......................................................................................................... 2
1.1.1 Riser ..................................................................................................................... 2
1.1.2 FPSO – Floating Production Storage Offloading ................................................. 2
1.1.3 SCR and Lazy-Wave SCR ................................................................................... 3
1.2 Statement of Problem ................................................................................................... 6
Chapter 2 ........................................................................................................................8
DESIGN BASIS AND ANALYSIS THEORY ..............................................................8
2.1 Design Basis ................................................................................................................. 8
2.1.1 General ................................................................................................................. 8
2.1.2 Riser System ........................................................................................................ 9
2.1.3 FPSO Vessel Data ..............................................................................................14
2.1.4 Internal Fluid Data, Design Pressure, and Temperature .....................................22
2.1.5 Environmental Data ...........................................................................................23
2.1.6 Hydrodynamic Coefficients ...............................................................................26
2.2 Analysis Software....................................................................................................... 28
2.3 Analysis Theory ......................................................................................................... 29
2.3.1 General ...............................................................................................................29
2.3.2 Load Case Matrix ...............................................................................................30
2.3.3 Analysis Methodology .......................................................................................33
2.3.4 Design Requirement and Acceptance Criteria ...................................................44
Chapter 3 ......................................................................................................................46
RISER DESIGN AND ANALYSIS .............................................................................46
3.1 Steel Catenary Riser Approach ................................................................................... 46
3.2 Lazy-Wave Steel Catenary Riser Approach ............................................................... 49
3.3 BM Analysis and Optimization .................................................................................. 52
3.4 SLWR Sensitivity Analysis ........................................................................................ 54
3.5 SLWR Disconnection Analysis .................................................................................. 55
vi
Chapter 4 ......................................................................................................................56
RESULTS AND DISCUSSIONS ................................................................................56
4.1 SCR Approach ............................................................................................................ 56
4.1.1 SCR configuration .............................................................................................56
4.1.2 SCR Strength Analysis .......................................................................................57
4.2 Lazy-Wave SCR Approach ......................................................................................... 62
4.2.1 SLWR Configuration .........................................................................................62
4.2.2 SLWR Strength Analysis....................................................................................63
4.2.3 SLWR Regular Wave Directional Analysis ........................................................70
4.3 Comparison of Two Design Approaches: SCR vs. SLWR ......................................... 79
4.4 BM Optimization ........................................................................................................ 81
4.5 Sensitivity Analysis .................................................................................................... 84
4.6 Disconnection Strength Analysis ................................................................................ 87
Chapter 5 ......................................................................................................................90
CONCLUSIONS AND RECONMMENDATIONS ....................................................90
5.1 Conclusions ................................................................................................................ 90
5.2 Recommendations ...................................................................................................... 93
REFERENCES ............................................................................................................94
APPENDIX A ..............................................................................................................96
vii
List of Figures
Figure 1.1.1 Free Hanging SCRs with and without intermediate buoys ....................... 4
Figure 1.1.2 Example configuration of Lazy-Wave Catenary Riser .............................. 6
Figure 2.1.1 Mooring System Layout .......................................................................... 15
Figure 2.1.2 Mooring System Configuration ............................................................... 16
Figure 2.1.3 STP Turret Buoy Geometry ..................................................................... 17
Figure 2.1.4 FPSO Coordinate System ........................................................................ 18
Figure 2.1.5 Wave Heading Convention ...................................................................... 19
Figure 2.3.1 FPSO Offset consideration ...................................................................... 31
Figure 2.3.2 Finite Element Model of a Line in Orcaflex ........................................... 35
Figure 2.3.3 Detailed Structure Model of Line in Orcaflex ......................................... 37
Figure 2.3.4 Frame of Reference for Stress Calculation in Orcaflex........................... 42
Figure 3.2.1 Snapshot of SLWR Orcaflex Model ........................................................ 51
Figure 3.5.1 Snapshot of SLWR Orcaflex Model in Disconnection Condition ........... 55
viii
List of Tables
Table 2.1.1 Thermal Performance Requirement ............................................................ 9
Table 2.1.2 Elevation of Riser Hang-off Location at FPSO .......................................... 9
Table 2.1.3 Riser Hang-off Arrangement ..................................................................... 10
Table 2.1.4 Flex Joint Rotational Stiffness .................................................................. 11
Table 2.1.5 Riser Line Pipe Material Properties .......................................................... 12
Table 2.1.6 Thermal Insulation Coating Properties ..................................................... 12
Table 2.1.7 VIV Strake Properties ............................................................................... 13
Table 2.1.8 Standard Rigid Joints Tolerances .............................................................. 14
Table 2.1.9 Main Particulars of the FPSO ................................................................... 14
Table 2.1.10 Segments Properties of Mooring System ................................................ 16
Table 2.1.11 FPSO Extreme Offset Data ..................................................................... 21
Table 2.1.12 Internal Fluid Properties and Design Pressures ...................................... 22
Table 2.1.13 Vertical Profile of Sea Water Temperature .............................................. 23
Table 2.1.14 Extreme Wave Data - Hurricane ............................................................. 24
Table 2.1.15 Extreme Wave Data - Winter Storm ........................................................ 24
Table 2.1.16 Extreme Loop Current Profiles ............................................................... 25
Table 2.1.17 Soil Friction Coefficients ........................................................................ 25
Table 2.1.18 Hydrodynamic Coefficients of Riser Pipe .............................................. 26
Table 2.1.19 Normal Drag Coefficients of Flexible Pipe ............................................ 27
Table 2.3.1 Load Case Matrix for the Production SLWR ............................................ 32
Table 2.3.2 Design Codes for Wall Thickness Sizing .................................................. 44
Table 2.3.3 Allowable Riser Stress Level .................................................................... 45
Table 2.3.4 Design Case Factor ................................................................................... 45
Table 3.3.1 Load Case Matrix for BM Arrangement Analysis .................................... 53
Table 4.1.1 Global Configuration for SCR .................................................................. 56
Table 4.1.2 Production SCR Nominal Static Analysis Results .................................... 58
ix
Table 4.1.3 Load Case Matrix for SCR Configuration Approach ................................ 58
Table 4.1.4 Riser Top Angular Response for simple SCR ........................................... 59
Table 4.1.5 Production SCR Combined Stress Results ................................................ 59
Table 4.1.6 Production SCR Stress Utilization Factors ............................................... 60
Table 4.1.7 Production SCR Effective Tensions and Bending Moments .................... 61
Table 4.2.1 Global Configuration of the designed SLWR ........................................... 62
Table 4.2.2 FPSO Vessel Offset for Different Load Case in Analysis ......................... 64
Table 4.2.3 Summary Results of Production Lazy-Wave SCR Nominal Static Analysis
...................................................................................................................................... 64
Table 4.2.4 Summary of SLWR Top Angular Response Results ................................. 65
Table 4.2.5 Summary of SLWR Stress Results – Riser Top ........................................ 66
Table 4.2.6 Summary of SLWR Stress Results – Arch Bend ...................................... 67
Table 4.2.7 Summary of SLWR Stress Results – TDP Area ........................................ 67
Table 4.2.8 Summary of Maximum SLWR Stress Utilization Factors ........................ 68
Table 4.2.9 Summary of SLWR Maximum Tension Results ....................................... 69
Table 4.2.10 Summary of SLWR Minimum Tension Results ...................................... 69
Table 4.2.11 Summary of SLWR Maximum Bending Moment Results ...................... 70
Table 4.2.12 Directional Riser Top Angular Response for Production SLWR ............ 71
Table 4.2.13 Directional Combined Stress Results of the SLWR– Riser Top ............. 72
Table 4.2.14 Directional Combined Stress Results of the SLWR– Arch Bend ........... 73
Table 4.2.15 Directional Combined Stress Results of the SLWR – TDP Area ............ 74
Table 4.2.16 Directional Stress Utilization Factors of the SLWR ............................... 75
Table 4.2.17 Directional Results of the SLWR – Maximum Tension .......................... 76
Table 4.2.18 Directional Results of the SLWR – Minimum Tension .......................... 77
Table 4.2.19 Directional Results of the SLWR – Maximum Bending Moment .......... 78
Table 4.3.1 Comparison Results of Riser Top Angular Responses .............................. 79
Table 4.3.2 Comparison Results of Von Mises Stress .................................................. 79
Table 4.3.3 Comparison Results of API Stress Utilization Factors ............................. 80
x
Table 4.3.4 Comparison Results of Effective Tensions ............................................... 80
Table 4.3.5 Comparison Results of Bending Moments ............................................... 80
Table 4.4.1 BM Optimization Analysis Results – Effective Tension ........................... 81
Table 4.4.2 BM Optimization Analysis Results - Bending Moment ........................... 82
Table 4.4.3 BM Optimization Analysis Results - Von Mises Stress ............................ 82
Table 4.4.4 BM Optimization Analysis Results - Stress Utilization Factors ............... 83
Table 4.5.1 Sensitivity Analysis Results – Von Mises Stress ....................................... 84
Table 4.5.2 Sensitivity Analysis Results - API Stress Utilization Factors ................... 85
Table 4.5.3 Sensitivity Analysis Results - Effective Tensions ..................................... 86
Table 4.5.4 Contrast Results for Sensitivity Analysis .................................................. 86
Table 4.6.1 Disconnection Analysis Results of the SLWR - Stresses and Stress
Utilization Factors ........................................................................................................ 88
Table 4.6.2 Disconnection Analysis Results of the SLWR – Effective Tensions ........ 89
1
Chapter 1
Introduction
The environmental conditions in the Gulf of Mexico (GoM), such as seasonal
hurricanes and strong loop currents, make it very challenging to develop an operation
unit consisting of a Floating Production Storage Off-loading (FPSO) system with
simple Steel Catenary Risers (SCR). The weather-induced vessel motions can easily
cause the riser pipe to buckle at the touchdown area. In recent years, Steel Lazy-Wave
Risers (SLWR) have been considered as a popular solution to de-couple the vessel
motions with the riser responses at the touchdown area. However, it is not a
traditional option for offshore production facilities to develop turret moored FPSO
with SLWR in the GoM. An investigation is required to determine the feasibility of
developing an FPSO with SLWRs.
In this paper, the feasibility of developing an FPSO-SLWR in the GoM is investigated
and established. In order to obtain the riser response results, the static and dynamic
analysis is conducted for the specific design conditions, based on a water depth of
7000 ft. These results draw the basis for the riser performance analysis. The Buoyancy
Modules (BM) are attached onto a section of the riser pipe to provide lifting force for
the SLWR. The global performance of the SLWR is improved by optimizing the BM’s
arrangement. The riser responses, based on different BM material properties, total
attaching lengths, and buoyancy force ratios, are obtained and analyzed to achieve the
2
SLWR global configuration optimization. Additionally, the alternative SCR
configuration option is discussed as a comparison case. The SLWR responses, when
disconnected from the FPSO, are also investigated. Lastly, a sensitivity analysis is
conducted to check the robustness of the system.
1.1 Literature Review
1.1.1 Riser
A riser is a unique common element to many floating offshore structures. Risers
connect the floating drilling/production facility with subsea wells and are critical to
safe field operations. They are used to contain fluids for well control (drilling risers)
and to convey hydrocarbons from the seabed to the platform (production risers). Riser
systems are a key component for offshore drilling and floating production operations.
However, for deepwater operation facility development, riser design is one of the
biggest challenges [1].
1.1.2 FPSO – Floating Production Storage Offloading
Generally, the FPSOs are ship-shaped floaters with provisions for storing and
offloading oil simultaneously. Nowadays, FPSOs are the most prolific floating
production platforms, especially for fields in harsh environments and far away from
existing pipeline infrastructures [2]. The early FPSOs with the spread mooring
systems were developed in the 1970s to support the production in the smaller, remote
fields, where fixed structures would not be economical. They were restricted to mild
3
environments until the turret mooring system was introduced. This made it possible
for the FPSOs to operate in more severe environmental conditions [1].
One of the most important factors governing riser design is the vessel motion,
especially the heave motion, at the riser hang-off location. The vessel motion is a
combination resulting from environmental conditions and vessel responses to the
weather [3]. FPSO, a type of vessel with more dynamic motions, is typically used in
relatively less severe environmental conditions, such as in West Africa [3]. For this
study, the limited weather-vanning capacity of the vessel, provided by the turret
mooring system, makes it possible to adopt the FPSO in the GoM [1]. In addition, the
turret mooring system could allow the vessel to become disconnected from the SLWR;
thus, the FPSO does not have to be designed to accommodate the most critical
wave/current motions associated with hurricane and typhoon conditions [2].
The trend of using FPSOs for exploration and production in deepwater fields brought
to light the requirement for studying this type of offshore system [4], especially for
the fields in the GoM.
1.1.3 SCR and Lazy-Wave SCR
A simple steel catenary riser (SCR) is considered a cord of uniform density and
cross-section area hanging on two ends under gravity and buoyancy force in water
[10]. A typical SCR is characterized by downward wet weight along its length.
4
SCR has a free-hanging configuration with no intermediate BMs or floating devices,
as shown in Figure 1.1.1. It is now one of the most cost-effective alternatives for oil
and gas production and export in deepwater fields, where the large diameter, flexible
risers present technical and economic limitations [1]. SCRs are designed by referring
to the analytical results in accordance with the American Petroleum Institute (API)
codes, which includes API RP 1111 (2009) [5] and API RP 2RD (2006) [6], or the
DNV codes (DNV-OS-F101 [7] and DNV-OS-F201 [8]). In recent years, SCR has
been the preferred riser solution for deepwater floating production facilities in the
GoM [2].
Figure 1.1.1 Free Hanging SCRs with and without intermediate buoys [1]
However, there are some very critical design issues with the simple SCR application
5
in deepwater fields: the compression of the riser at the touchdown area; and, over
payload at the vessel’s riser hang-off location. SCR is very sensitive to vessel heave
motion, which may lead to the infeasibility of its application with FPSO in severe
environmental conditions [2]. One of the options to mitigate the compression at the
SCR touchdown area is to adopt a lazy-wave configuration of the riser by attaching a
set of buoyancy modules on a section of the riser pipe. SLWR has been considered to
mitigate the compression at the riser touchdown area due to the flexibility of
lazy-wave configuration [2]. So far, no such type of offshore production facility has
been developed in the GoM.
As shown in Figure 1.1.2, SLWR is similar to the traditional SCR with simple
catenary configuration, but with a section of riser pipe suspended. The suspended riser
section is attached with a set of BMs that can provide a certain amount of lifting force.
This provides a compliant arch bend at a specific water depth above the seabed [1].
A typical SLWR consists of three sections, which include hang-off catenary, the
buoyancy catenary, and the touchdown catenary [13], as illustrated in Figure 1.1.2.
The buoyancy catenary lies between the hang-off catenary and the touchdown
catenary. The buoyancy force provided by the BMs is around twice the submerged
weight of the flooded steel pipe with BMs attached [13].
6
Figure 1.1.2 Example configuration of Lazy-Wave Catenary Riser [4]
1.2 Statement of Problem
Based on the functional requirements of the riser, the design criteria and the design
data (including the data of the riser system, the environmental conditions, and the
FPSO vessel), the proposed study scope includes:
1. Riser Concept Selection
2. Riser Configuration Design
3. Strength Analysis:
i. Static Analysis
ii. Dynamic Analysis
7
4. API RP 2RD [6] code check
5. BM Optimization Analysis
6. Sensitivity Study
7. Disconnection Analysis
The optimization for the BMs is conducted according to the results of the above
analysis. It takes several variables into account:
1. Material properties of the buoyancy modules
2. Buoyancy force ratio vs. submerged weight of the riser pipe with buoyancy
modules attached
3. Total length of the riser pipe with BMs attached
4. Position along the riser pipe where the BMs are attached
In order to obtain the global response of the SLWR, the equivalent continuous model
of the riser pipe section with BMs attached is developed for analysis, which is more
conservative than the discontinuous model with single BMs attached in designated
positions on the riser pipe. However, for a detailed future design, the discontinuous
model is more suitable, because the local performance (such as the stress
concentration of the riser pipe with BMs attached) needs to be analyzed thoroughly
not only conservatively.
8
Chapter 2
Design Basis and Analysis Theory
2.1 Design Basis
In this section, the assumed environmental information and the FPSO data are
presented in detail. In addition, the design criteria and functional requirements, as
specified in API RP 2RD [6] are specified as well.
2.1.1 General
The assumed general design data for the production riser, including the water depth,
the riser design life, and the thermal performance requirements, are defined in the
following section.
Water Depth
In this study, the selected water depth is 7,000 ft.
Design Life
The design life for the production riser system is 25 years.
Thermal Performance Requirement
The production riser requires thermal insulation with the following assumed
requirements:
9
Table 2.1.1 Thermal Performance Requirement [11]
2.1.2 Riser System
This section presents a set of consistent data for developing the FPSO-SLWR system
used in this study, including riser pipe properties, FPSO and environmental data.
Riser Hang-Off System Data
The flexible jumpers are attached to the submerged turret located within the FPSO.
The elevation of the hang-off location is given in Table 2.1.2 for both the normal
operating and disconnection conditions.
Table 2.1.2 Elevation of Riser Hang-off Location at FPSO [11]
The assumed hang-off angles and azimuth angles of all export and production risers
are detailed in Table 2.1.3.
U-value (Inner Diameter based) 0.9 BTU/ft2/hr/°F
Cool down time 12 hrs from 100°F to 63°F
Buoy Condition Depth from MWL (ft)
Operating 69.3
Disconnected 232.9
10
Table 2.1.3 Riser Hang-off Arrangement [11]
Riser Description Exit Angle (deg) Azimuth Angle (deg)
1 Export 1 8 81.5
2 Production Riser 1 8 177.5
3 Production Riser 2 8 197.5
4 Production Riser 3 8 304.5
5 Production Riser 4 8 324.5
11
SCR Flex Joint Data
For this concept design, it is assumed that the flex joint will be used to terminate the
production SLWR at the top. The Table 2.1.4 presents the assumed rotational stiffness
of the flex joint.
Table 2.1.4 Flex Joint Rotational Stiffness [11]
Alternating Angle
degree
Max Design Rotational
Stiffness
ft-kips/deg
Max Design Rotational
Moment
ft-kips
0 0 0
0.01 93.33 0.93
0.02 76.28 1.70
0.03 67.79 2.37
0.04 62.35 3.00
0.05 58.43 3.58
0.06 55.41 4.14
0.07 52.98 4.67
0.08 50.96 5.18
0.09 49.24 5.67
0.1 47.76 6.15
0.2 39.03 10.05
0.3 34.69 13.52
0.4 31.90 16.71
0.5 29.90 19.70
0.6 28.35 22.53
0.7 27.11 25.24
0.8 26.08 27.85
0.9 25.20 30.37
1 24.44 32.82
1.5 21.72 43.67
2 19.97 53.66
3 17.75 71.41
4 16.33 87.74
6 14.51 116.75
8 13.34 143.44
10 12.50 168.45
12 11.86 192.16
14 11.34 214.84
17 10.72 246.98
20 10.22 277.64
12
Rigid Riser Line Pipe Data
The API 5L X-70 [12] steel grade has been selected for the production Lazy-Wave
SCR. The properties of the standard rigid riser line pipe material are detailed in Table
2.1.5.
Table 2.1.5 Riser Line Pipe Material Properties [12]
Parameter Unit Production
Material Grade API 5L X-70
Material Yield Stress ksi 70
Ultimate Tensile Strength ksi 82
Young Modulus ksi 3.0E+04
Poisson Ratio -- 0.3
Steel Density lb/ft3 490
SCR Pipe Coating Data
1. Thermal Insulation Coating
The production riser insulation coating properties are assumed to be 5-layer PP. The
properties are listed in Table 2.1.6 below. The total thickness of the insulation coating
is 0.024 ft.
Table 2.1.6 Thermal Insulation Coating Properties [11]
Layer No. Parameter Density (pcf)
1 FBE 85.5
2 PP adhesive 55.6
3 PP solid 55.6
4 PP syntactic 40.0
5 PP solid 55.6
48.0Average Total
13
2. Corrosion Coating
The riser is protected by a cathode protection system in combination with a Fusion
Bonded Epoxy (FBE) coating system. For the SLWR in this study, it is assumed the
FBE is included in the insulation.
VIV Strake Data
Anti-VIV strakes are mounted on the rigid riser section. The assumed strakes
properties used in the analysis are shown below.
Table 2.1.7 VIV Strake Properties [11]
Description Unit Production Riser
Strake ID inch 11.54
Strake OD inch 12.54
Fin Height - 0.15D
Fin Period - 15D
Strake Part length inch 65.35
Weight in Air per part lbs 28
Weight in Seawater per part lbs -2.36
SCR Pipe Tolerance
The maximum and minimum weight tolerances for standard rigid riser joints [11] are
provided as in Table 2.1.8:
14
Table 2.1.8 Standard Rigid Joints Tolerances
Corrosion Allowance
The corrosion allowance of 3.0 mm is used for the riser pipe design.
2.1.3 FPSO Vessel Data
The FPSO data used in this riser study is based on assumptions of a typical FPSO in
the GoM.
FPSO Main Particulars
Main particulars of the FPSO are given in Table 2.1.9. Three vessel load conditions
are considered, i.e., ballast, intermediate, and fully loaded condition.
Table 2.1.9 Main Particulars of the FPSO
Wall Thickness Tolerance -8% / +12.5%
Weight Tolerance -5% / +6.5%
Description Unit Ballast Interm. Full
Overall Length ft
Length between Perpendiculars ft
Breadth Moulded ft
Depth ft
Draught, AP ft 22 36 46
Draught at Midship ft 19 32 45
Draught, FP ft 16 28 44
Vertical COG above baseline (free
surface included)ft 44 39 43
795
760
140
67
15
Submerged Turret Production System
As assumed, the turret location fore of midship is 295.3 ft. The cylindrical turret
extended below the vessel baseline has a height of 32.8 ft. and 44.3 ft. in diameter.
Mooring System
The mooring system is a 4+4+3 leg system comprised of chain segments, polyester
segments, wire rope segments, and a mooring line buoyancy element. Mooring line
directions are shown in Figure 2.1.1. The mooring line configuration is shown in
Figure 2.1.2. The properties of the individual segments of the mooring system are
provided in Table 2.1.10.
Figure 2.1.1 Mooring System Layout [11]
16
Figure 2.1.2 Mooring System Configuration [11]
Table 2.1.10 Segments Properties of Mooring System [11]
1 Studless Chain (R3S) 820 3.5 160963 0.9
2 Link 3 - - 7.5
3 Polyester Rope 8038 6.5 Nonlinear 0
4 Link 3 - - 7.5
5 Spiral Strand Wire Rope 1476 3.1 137133 0.2
6 Mooring Line Buoyancy Element 16 - - -60.5
7 Spiral Strand Wire Rope 262 3.1 137133 0.2
8 Link 3 - - 9.6
9 Studless Chain (R3S) 82 3.5 160963 0.9
10 Link 3 - - 9.6
11 Polyester Rope 33 6.5 Nonlinear 0
12 Link 3 - - 9.6
13 Studless Chain (R3S) 82 3.5 160963 0.9
14 Link 3 - - 9.6
15 Spiral Strand Wire Rope 394 3.1 137133 0.2
16 Link 3 - - 11.6
Segment
NumberSegment Type
Size
Diameter
[inch]
Axial
Stiffness
[kips]
Building
Length
[ft]
Equivalent
Submerged
Weight
(kips/ft)
17
STP Turret Buoy System
The geometry of the STP buoyancy, the jumper guide tubes, the umbilical guides, and
buoyancy element characteristics are shown in Figure 2.1.3.
Figure 2.1.3 STP Turret Buoy Geometry [11]
First Order Motion Transfer Function
1. Coordinate System
The coordinate system has the origin placed in the waterline level at midship. For
the right–handed system, the x–axis points forward towards the bow, the y–axis points
towards portside and the z–axis points upwards. Vessel axes relative to the global axis
are defined in Figure 2.1.4 [11].
18
Figure 2.1.4 FPSO Coordinate System [11]
2. Wave Directions
The heading convention is as follows, as shown in Figure 2.1.5:
Following Sea: 0° direction of the waves is defined as waves propagating along the
positive x–axis
Beam Sea: 90° direction of the waves is defined as waves propagating along the
positive y–axis
19
Head Sea: 180° direction of the waves is defined as waves propagating along the
negative x–axis
Figure 2.1.5 Wave Heading Convention [11]
3. RAO Definition
The RAOs refer to the origin of the coordinate system.
The wave is defined as
𝜁 = 𝐴 cos[𝜔𝑡 − 𝑘𝑥 cos(𝛽) − 𝑘𝑦 sin(𝛽)]
Where
A = wave amplitude
ω= wave frequency (rad/s)
20
t = time (s)
k = wave number
β= wave direction
x = position in x–direction
y = position in y–direction
The response X is defined as
𝑋 = 𝐴 × 𝑅𝐴𝑂 × cos(𝜔𝑡 + 𝜑)
Where
X = response
RAO = response amplitude operator
𝜑 = phase angle of response
Units are ft./ft. and rad./ft. for translational and rotational RAOs, respectively.
FPSO Vessel Offset
The maximum vessel offsets analysis for collinear wind and current loading are given
in Table 2.1.11.
21
Table 2.1.11 FPSO Extreme Offset Data [11]
The FPSO mooring system is required to be designed such that the turret offset shall
not exceed 6% of water depth for the intact mooring case and 8% of water depth for
the one-broken-mooring-line case. These requirements apply to both the 100-year
winter storm and the 1000-year loop current conditions. The actual offsets may be less.
However, this is depending on the mooring system design, asymmetry of the mooring
system, and the directionality of the environment.
1. Assuming a minimum offset of 1.5% of water depth and a maximum offset of 6%
of water depth for the intact mooring case for the 100-year winter storm and
1000-year loop current conditions, independent of the environment direction (i.e.,
assume that the FPSO offset magnitude is omni-directional).
2. Assuming a minimum offset of 2.0% of water depth and a maximum offset of 8%
of water depth for the one-broken-mooring-line case for the 100-year winter storm
and 1000-year loop current conditions, independent of the environment direction.
3. For less severe environmental conditions, deriving the minimum and maximum
offsets by linear interpolation.
Mooring Condition Percentage of Water Depth (%)
Intact 1.5 ~ 6
One Line Broken 2 ~ 8
22
Where the primary surface environment is wind driven, linear interpolation of FPSO
offset should be based on wind speed. Where the primary surface environment is
loop current, linear interpolation should be based on surface current speed. See the
examples below. Since the offsets are at this time assumed to be omnidirectional,
the interpolation should be calculated using the omnidirectional wind speed (or
current speed, as applicable). Analysis should be performed for both the minimum and
maximum FPSO offsets, if it is not clear which extreme will govern the design.
2.1.4 Internal Fluid Data, Design Pressure, and Temperature
As assumed, internal fluid density, pressure and temperature data for the SLWR are
presented in Table 2.1.12.
Table 2.1.12 Internal Fluid Properties and Design Pressures [11]
Component Unit Production
Max. Allowable Operating Pressure psi 10,000
Hydro-Test Pressure psi 20,000
Shut-In / Design Pressure psi 16,000
Location of pressure definition ft below MWL surface
Design Temperature, Maximum °F 230
Design Temperature, Minimum °F 35
Fluid density (lb/ft3, kg/m
3) pcf 55
23
2.1.5 Environmental Data
Seawater Data
1. Seawater Temperature
The seawater temperature profiles for the SLWR design are assumed as shown in the
following table. The extreme low temperature, annual average temperature, and
extreme high temperature are detailed.
Table 2.1.13 Vertical Profile of Sea Water Temperature [11]
2. Seawater Density
Seawater density is taken as 64 𝑙𝑏 𝑓𝑡3⁄ .
Seawater Kinematic Viscosity
The value of the kinematic viscosity is used to determine the value of the Reynolds
number and the corresponding hydrodynamic drag coefficients.
: 1.4 × 10−5 𝑓𝑡2 𝑠⁄
Marine Growth
Marine growth of 1.5 inches from the mean sea level to 150 ft water depth is
Extreme Low Annual Average Extreme High
Surface, 3 below MSL 48 76 88
-656 45 63 74
-1640 41 48 55
-3281 39 41 43
-7200 = seabed 37 40 41
Depth (ft)Temperature (°F)
24
considered. The densities of marine growth in air and in water are assumed to be
95.76 𝑙𝑏 𝑓𝑡3⁄ and 74.91 𝑙𝑏 𝑓𝑡3⁄ , respectively.
Wave Data
1. Extreme Wave Data
The assumed extreme wave data is given in Table 2.1.14 and Table 2.1.15.
Table 2.1.14 Extreme Wave Data - Hurricane [11]
Table 2.1.15 Extreme Wave Data - Winter Storm [11]
1 Year 10 Year 100 Year 1000 Year
m/s 10.4 20.2 31.2 46.4
Hs m 2.9 7 11.2 17.5
Tp s 9 11.9 13.7 15.8
Hmax m 5.5 11.3 21.3 33.3
Tmax s 8.3 10.9 12.6 14.5
Surface m/s 0.42 1.28 0.63 2.14
30m depth m/s 0.28 0.99 2.14 1.59
40m depth m/s 0.05 0.05 1.7 0.05
bottom m/s 0.05 0.05 0.05 0.05
Current Profile Should be Taken as Linear between Depths
Associated Wave
Conditions
Associated Current
Speed
Associated Wind Speed
1 Year 5 Year 10 Year 100 Year
m/s 17.3 22.2 23.7 28.3
Hs m 3.8 5.9 6.6 8.7
Tp s 9 10.4 10.8 11.9
Hmax m 7.2 11.2 12.5 16.5
Tmax s 8.3 9.6 9.9 10.9
Surface m/s 0.52 0.67 0.71 0.85
75m depth m/s 0.05 0.05 0.05 0.05
bottom m/s 0.05 0.05 0.05 0.05
Associated Current
Speed
Current Profile Should be Taken as Linear between Depths
Associated Wave
Conditions
Associated Wind Speed
25
Current Data
Extreme Currents:
Extreme current data is given in Table 2.1.16. Current profiles associated with 1-year,
10-year, and 100-year return periods are considered.
Table 2.1.16 Extreme Loop Current Profiles [11]
Soil Data
The friction coefficients, shown in Table 2.1.17, are used for the riser design and
analysis in this study.
Table 2.1.17 Soil Friction Coefficients [11]
Detailed analysis on soil stiffness is not planned for this study. Instead, a simplified
equation is used to estimate the soil stiffness K.
1 Year 10 Year 100 Year
m/s m/s m/s
Surface 1.1 1.7 2.1
50m depth 1.1 1.7 2.1
150m depth 0.7 1.1 1.4
300m depth 0.4 0.6 0.7
600m depth 0.2 0.3 0.4
800m depth 0.1 0.1 0.1
Bottom 0.1 0.1 0.1
Current Profile Should be Taken as Linear between Depths
Friction Coefficient Value
Longitudinal 0.3
Transverse 0.5
26
𝐾 = 40𝑁𝑐𝑆𝑢 (1)
In the equation (1) Su is the undrained shear strength of the soil and Nc is the
non-dimensional shape and depth factor. Since Nc is less than 7.5,
𝐾 ≤ 300𝑆𝑢 (2)
Using the undisturbed, undrained shear strengths at 0.25D below the mud line, the
vertical soil stiffness for the production riser is 10500 lb/ft/ft.
2.1.6 Hydrodynamic Coefficients
The riser system drag coefficients values selected, depend upon the Reynolds number
and the presence of vortex induced vibrations (VIV). Where unsuppressed VIV is
predicted to occur, the drag coefficients are modified accordingly.
For a stationary smooth circular cylinder, the drag coefficient is selected depending
upon the mean Reynolds number (Re) as defined in API RP 2RD [6], and shown in
Table 2.1.18.
Table 2.1.18 Hydrodynamic Coefficients of Riser Pipe [11]
Drag Coefficient Added Mass Coefficient
API RP 2RD
(Appendix C)1
1.4 1
Bare pipe
(depending on roughness)
Bare pipe
(VIV is anticipated)
27
The drag and added mass coefficients of the riser pipe are presented in the Table
2.1.19 [11]. Axial drag coefficient is set to zero.
Table 2.1.19 Normal Drag Coefficients of Flexible Pipe [11]
Reynolds Drag Coefficient
1000 1
10,000 1.2
200,000 1.2
300,000 0.6
1,000,000 0.6
4,000,000 0.8
100,000,000 0.8
Added mass coefficient Ca = 1, Where Cm = Ca + 1
28
2.2 Analysis Software
Orcaflex is utilized to accomplish all the configuration design, strength analysis,
sensitivity analysis, and buoyancy module optimization analysis of the SCR and
Lazy-Wave SCR.
Orcaflex is a marine dynamic program developed by Orcina for static and dynamic
analysis on a wide range of offshore systems, including all types of marine risers
(rigid and flexible), global analysis, moorings, installation and towed systems [9].
For this thesis research, fast and accurate analysis, of BMs attached catenary system
under wave and current loads and externally imposed motion, is provided by Orcaflex.
The program is operated in both single mode and batch mode, as needed, for routine
analysis work using Orcaflex; as well the special facilities for post-processing the
results.
Orcaflex is a fully 3D non-linear, time-domain, finite-element-based program, capable
of dealing with arbitrarily large deflections of the flexible structure from the initial
configuration [9].
29
2.3 Analysis Theory
2.3.1 General
Strength analysis, of the SCR and SLWR for the riser design, buoyancy module
optimization, and system robustness check, in both operation and disconnection
conditions, is conducted in accordance with the prescriptions specified in API RP
2RD [6]. In addition, the riser system design and the analysis conducted include:
Riser global configuration
Material selection and wall thickness sizing
Riser flex joint interface engineering
Design riser flex joint nipple extension dimension
Riser coating design
Riser VIV suppression device selection
This section outlines the analysis requirements for the production SLWR.
30
2.3.2 Load Case Matrix
To perform dynamic analysis, the load case matrix is set up first per the API RP 2RD
[6] definition, taking into consideration the different load conditions, to include:
1. Temporary condition
2. Operating condition
3. Extreme condition
4. Survival condition
For each load condition, several independent load cases are defined taking into
consideration environmental conditions, pressure, FPSO offset, mooring line
conditions (intact or broken) and FPSO turret buoy conditions (connected vs.
disconnected).
In addition, five directions of FPSO positions, including near, far, trans+, trans- and
270 degree, are considered in the analysis. Figure 2.3.1 below defines the NEAR,
FAR, TRANS directions with respect to the FPSO offset direction. NEAR is defined
as the FPSO offset in the riser plane and makes it slack. While the FPSO offset in the
riser plane and makes it taut, it is defined as FAR. TRANS is defined when the FPSO
offset in the plane 45 degree to the riser plane (+ taut; - slack).
It should be mentioned that the wave and current are conservatively assumed as
31
co-linear and applied in the same plane as FPSO offset direction. Wave, propagating
in direction of 270 degree, is identified associated the worst response of the FPSO.
Figure 2.3.1 FPSO Offset consideration [11]
The Production SLWR is analyzed according to the load case matrix defined in
Table 2.3.1.
32
1 HY01N N
2 HY01F F
3 HY02N N
4 HY02F F
5 OP01N N
6 OP01T T
7 OP01F F
8 OP02N N
9 OP02T T
10 OP02F F
11 EX01N N
12 EX01T T
13 EX01F F
14 EX02N N
15 EX02T T
16 EX02F F
17 EX03NN NN
18 EX03FF FF
19 EX04N N
20 EX04T T
21 EX04F F
22 EX05N N
23 EX05T T
24 EX05F F
25 EX06N N
26 EX06T T
27 EX06F F
28 EX07N N
29 EX07T T
30 EX07F F
31 SU01N N
32 SU01T T
33 SU01F F
34 SU02N N
35 SU02T T
36 SU02F F
37 SU03N N
38 SU03T T
39 SU03F F
40 SU04N N
41 SU04T T
42 SU04F F
43 SU05N N
44 SU05T T
45 SU05F F
Note: 1) Shut dow n pressure is 400 psig for production;
2) The reference elevation of internal pressure is MSL;
3) FPSO position relative to the riser should be interpreted as the turret buoy, and corresponding turret buoy motion at
particular w ater depth shall be used.
GoM FPSO Riser Strength Analysis Load Case Matrix
Wave
1 yr WS*
10 yr WS*
1 yr WS
Associated
10 yr WS*
100 yr H*
Load
Case
No.
NameAPI 2RD Load
Category
Mooring
Line
Condition
FPSO
Position
Pressure
(psig)
Temperature
(oF)
Density
(pcf)
FPSO -
Turret
Buoy
100 yr WS
10 yr WS*
Extreme
Yes
API 2RD
Allow able
Unity SUF
Associated
Associated
10 yr LC*
1 yr LC
100 yr LC*
Associated
Associated
100 yr H*
100 yr WS
Associated
Associated
10 yr WS*
Design Design Design Intact
Associated 10 yr LC*
Yes
Yes
0.67
Intact No
Design Damaged Yes
0.80
10 yr LC*
Shut Dow n 40 Dissel
Associated
Yes 1.0
Associated 100 yr LC*
Yes 1.0Damaged
Associated
Design
100 yr WS
Design Intact
Design Intact
Associated
Associated
Design Design
100 yr LC*
Design Design
1.0NoDamaged
Operating
Design Design
Design Design
Environmental Condition
Design Design Design Intact
Survival
Associated Dissel40.0Shut Dow n
Current
Hydrotest1.25 x
Design40 64 Intact Yes 0.90
Table 2.3.1 Load Case Matrix for the Production SLWR [11]
33
2.3.3 Analysis Methodology
1. Strength Analysis
For in-place condition, which means the FPSO turret buoy is connected with the
vessel and ready for operation, strength analysis is performed using Orcaflex to
establish the global configuration of riser in both SCR and SLWR approaches by
conducting static analysis. And in order to obtain dynamic results of hang-off
declinations, effective tensions at top connection, Von Mises stress, API RP 2RD [6]
stress utilization, bending moment, the riser system is analyzed dynamically for
different load cases and FPSO vessel offsets in different directions.
For static analysis, Orcaflex is used to perform the calculation, and determine the
nominal position and equilibrium of each line in two steps, of which the first step is
applying the Catenary Method [9] and the second step is applying the Full Static
Method [9].
Catenary Method
In Orcaflex, the equilibrium position of the line is calculated applying catenary
method, with including all effects, weight, buoyancy, axial elasticity, current drag and
seabed touchdown and friction, but ignoring the effects of bending and torsional
34
stiffness of the line or its end terminations, and the possible contact forces between
the line and any solid shapes in the model [9].
At this point, in the condition of no compression in the line, the robustness and
efficiency of the catenary algorithm is satisfying, while it cannot handle cases where
the line is in compression [9].
The Catenary algorithm calculate and determine the static position of the line based
on the iterative catenary calculation process, which is controlled by a number of
convergence parameters including Max Iterations, Tolerance, Min Damping and Mag.
of Std. Error, Mag. of Std. Change. These parameters are normally left default and can
be modified when the calculation fail to obtain converge [9].
Full Static Method
The Full Static Method is a line statics calculation process that includes all forces
modeled in Orcaflex, comparing to ignoring bending and torsional stiffness in The
Catenary Method. In particular, the effects of bending stiffness and interaction with
shapes are included in the calculation process, which will avoid the occurrence of
shock loads at the start of the simulation. Such shock loads are more likely to occur
when the bending stiffness is not included in the calculation [9].
Thus, the accurate equilibrium position of each line can be obtained in the second step
of static analysis applying the Full Static Method, which is based on the configuration
35
obtained in the first step as starting shape for the line [9].
Line Theory
A finite element model for a line is used in Orcaflex, as shown in the figure below.
Figure 2.3.2 Finite Element Model of a Line in Orcaflex [9]
The line is divided into a series of line segments which are then modeled by straight
massless model segments with a node at each end. The model segments only model
the axial and torsional properties of the line. The other properties (mass, weight,
36
buoyancy, etc.) are all lumped to the nodes, as indicated by the arrows in the figure
above. Nodes and segments are numbered 1, 2, 3 … sequentially from the top end of
the line to the other. So segment n joins nodes n and (n+1) [9].
Each node is effectively a short straight rod that represents the two half-segments
either side of the node. The exception to this is end nodes, which have only one
half-segment next to them, and so represent just one half-segment [9].
Each line segment is divided into two halves and the properties (mass, weight,
buoyancy, drag etc.) of each half-segment are lumped and assigned to the node at that
end of the segment [9].
Forces and moments are applied at the nodes – with the exception that weight can be
applied at an offset. Where a segment pierces the sea surface, all the fluid related
forces (e.g., buoyancy, added mass, drag) are calculated allowing for the varying
wetted length up to the instantaneous water surface level [9].
Each model segment is a straight massless element that models just the axial and
torsional properties of the line. A segment can be thought of as being made up of two
co-axial telescoping rods that are connected by axial and torsional spring+dampers
[9].
The bending properties of the line are represented by rotational spring+dampers at
each end of the segment, between the segment and the node. The line does not have to
37
have axial symmetry, since different bend stiffness values can be specified for two
orthogonal planes of bending [9]
38
Structure Model
In the calculation and analysis conducted by Orcaflex, the detailed structure model of
line, as shown in the figure below, includes various spring + dampers that model the
structural properties of the line, as well the coordinates frame of reference and the
angles that are used in the calculation theory [9].
Figure 2.3.3 Detailed Structure Model of Line in Orcaflex [9]
39
There are 3 types of spring + dampers in the model: axial spring + damper, bending
spring + damper and torsion spring + damper.
The axial stiffness and damping of the line are modelled by the axial spring + damper at
the center of each segment, which applies an equal and opposite effective tension force
to the nodes at each end of the segment [9].
The bending properties are represented by rotational spring + dampers either side of the
node, spanning between the node's axial direction Nz and the segment's axial direction
Sz [9].
Tension Force
The tensions in the segments are calculated at first. Distance between the nodes at the
ends at the end of the segment, and the segment axial direction Sz are calculated by
Orcaflex to obtain the tension results [9].
Linear Axial Stiffness:
In the case of linear axial stiffness the tension in the axial spring+damper at the center
of each segment is calculated as follows. It is the vector in direction Sz whose
magnitude is given by:
𝑇𝑒 = 𝑇𝑤 + (𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) [9]
40
Where,
𝑇𝑒 = effective tension
𝑇𝑤 = wall tension = 𝐸𝐴𝜀 − 2𝛾(𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) + 𝐸𝐴𝑒 (𝑑𝐿 𝑑𝑡⁄ ) 𝐿0⁄
In this equation of Tw, the first term is the contribution from axial stiffness, the
second term is the contribution from external and internal pressure (via the Poisson
ratio effect) and the third term is the axial damping contribution. And the variables are
given by [9]:
EA = axial stiffness of line, as specified on the line types form (= effective
Young's modulus x cross-section area)
ε = total mean axial strain = (𝐿 − 𝜆𝐿0) 𝜆𝐿0⁄
𝐿 = instantaneous length of segment
λ = expansion factor of segment
𝐿0 = unstretched length of segment
ν = Poisson ratio
𝑃𝑖, 𝑃0 = internal pressure and external pressure, respectively
𝐴𝑖, 𝐴0 = internal and external cross sectional stress areas, respectively
41
e = damping coefficient of the line, in seconds
𝑑𝐿 𝑑𝑡⁄ = rate of increase of length.
This effective tension force vector is then applied (with opposite signs) to the nodes at
each end of the segment. Each mid-node therefore receives two tension forces, one
each from the segments on each side of it.
Non-linear Axial Stiffness:
When the axial stiffness is non-linear then the tension calculation is as follows. It is
the vector in direction Sz whose magnitude is given by:
𝑇𝑒 = 𝑉𝑎𝑟𝑇𝑤(𝜀) + (1 − 2𝜈)(𝑃0𝐴0 − 𝑃𝑖𝐴𝑖) + 𝐸𝐴𝑛𝑜𝑚.𝑒 (𝑑𝐿 𝑑𝑡⁄ ) 𝐿0⁄ [9]
Where
𝑉𝑎𝑟𝑇𝑤 is the function relating strain to wall tension, as specified by the
variable data source defining axial stiffness.
𝐸𝐴𝑛𝑜𝑚. is the nominal axial stiffness which is defined to be the axial
stiffness at zero strain.
As in the linear case the effective tension force vector is then applied (with opposite
signs) to the nodes at each end of the segment. Each mid-node therefore receives two
effective tension forces, one each from the segments on each side of it [9].
42
Damping Coefficient e:
The damping coefficient e represents the numerical damping in the line. It is
calculated automatically based on the Axial Target Damping value specified for the
study:
𝑒 = 𝑒(𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙) ∙ (𝑇𝑎𝑟𝑔𝑒𝑡 𝐴𝑥𝑖𝑎𝑙 𝐷𝑎𝑚𝑝𝑖𝑛𝑔)/100 [9]
Where
𝑒(𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙) = (2 × 𝑆𝑒𝑔𝑚𝑒𝑛𝑡 𝑀𝑎𝑠𝑠 × 𝐿0 𝐸𝐴⁄ )1
2 [9]
is the critical damping value for a segment and Segment Mass includes the mass of
any contents but not the mass of any attachments [9].
Pipe Stress Calculation
The stress calculation in Orcaflex based on the assumption that the loads on the line
are taken by a simple cylinder, made of uniform material, whose inside and outside
diameters are given by the stress diameters specified before calculation [9].
As shown in the following figure, a cross-section through a mid-segment point in the
frame of reference is being considered. The origin O of the frame of reference is at the
pipe centerline, Oz along the pipe axis (positive towards End B) and Ox and Oy
normal to the pipe axis (and so in the plane of the cross-section) [9].
43
Figure 2.3.4 Frame of Reference for Stress Calculation in Orcaflex [9]
At this cross-section, Orcaflex calculates the following values [9]:
i. Internal and external pressures, Pi and Po respectively.
ii. Effective tension and resulting wall tension. These are both vectors in the
z-direction, with magnitudes Te and Tw respectively.
iii. Curvature, which is a vector in the xy-plane, with components Cx and Cy in the
Ox and Oy directions, respectively.
iv. Bend Moment, which is a vector in the xy-plane, with magnitude M and
components Mx and My in the Ox and Oy directions, respectively.
v. Shear force, which is also a vector in the xy-plane, with magnitude S and
components Sx and Sy in the Ox and Oy directions, respectively.
vi. Torque, which is a vector in the z-direction with magnitude τ.
44
2. BM Arrangement Analysis and Optimization
Generally, SLWR has been proven that it could improve the fatigue and strength
performance of traditional SCR at touchdown area by decoupling the vessel motion
with riser. In addition, the payload on support vessel can be adjustable by utilizing the
lazy-wave configuration on steel catenary riser.
Besides, the current trial and error or iterative procedures to determine a lazy-wave
configuration of riser has been widely adopted in industry, even it’s not the most cost
effective approach. For this thesis research, this approach is also adopted for the BM
arrangement optimization analysis.
A variety of input parameters, which include equivalent pipe outer diameter of riser
pipe section with BM attached, total mass per unit length of the riser pipe with BM
attached, total length of riser pipe section with BM attached and the position along the
riser where BM attached, corresponding to the arrangement, position and material
properties of buoyancy modules, are investigated in the analysis to accomplish the
optimization of BM arrangement. Driving factors that make a major influence on the
vessel payload, Von Mises stress, declination angle and bending moment of the riser
pipe are analyzed and summarized.
45
2.3.4 Design Requirement and Acceptance Criteria
The riser is designed in order to satisfy all the design criteria listed in Table 2.3.2. For
Von Mises Stress check, the stress is calculated in accordance with the requirements
in API RP 2RD [6].
1. Wall Thickness Criteria
Wall thickness design of the risers shall be in accordance with the following codes, as
shown in Table 2.3.2 below:
Table 2.3.2 Design Codes for Wall Thickness Sizing
Criteria Design Code
Burst API RP 1111[5]
Collapse due to external pressure API RP 2RD [6]
Please note that pipe is not sized to withstand buckle propagation. The Pipe is needed
to be replaced if a buckle is observed.
2. Strength Criteria
Strength performance of the SLWR shall comply with API RP 2RD [6]. The allowable
stress levels and the design case factor Cf are given in Table 2.3.3 and Table 2.3.4.
46
Table 2.3.3 Allowable Riser Stress Level
Note: y = SMYS, a = basic allowable stress =2/3 y
Table 2.3.4 Design Case Factor
Load Category Design Case Factor, Cf Allowable Stress (% yield)
Operating 1 67
Extreme 1.2 80
Temporary 1.35 90
Survival 1.5 100
Installation 1.2 80
Stress Category Allowable Stress Reference
Primary membrane (Von Mises) Cf a API RP 2RD
Primary membrane plus bending 1.5 Cf a API RP 2RD
Primary membrane plus bending plus secondary 2 y 1 API RP 2RD
47
Chapter 3
Riser Design and Analysis
3.1 Steel Catenary Riser Approach
As a contrast approach, the simple SCR design approach for the same design
requirements and environmental conditions is performed and analyzed.
For the simple SCR configuration approach, the FPSO turret is in the in-place
condition, which means the turret is connected with the FPSO vessel during the whole
simulation period.
Dynamic strength analysis is performed for only 270 degree vessel position for each
load case, in time domain. For analysis simplification, only the 3 most critical extreme
load cases are selected and applied for the simulation.
First, the static analysis is performed to determine the global configuration of the SCR
system. This is done, in order to check the geometrical suitability of the riser system
before conducting the dynamic analysis. Next, the static analysis and the dynamic
strength analysis are conducted for the 3 most critical load cases, as stated above, with
corresponding regular wave loads, FPSO vessel offsets, current loads are applied to
each load condition. No directional cases with different vessel positions, hang-off
locations and departure angles are analyzed in the SCR approach. Only the most
critical load cases and the worst vessel positions are applied.
48
This is the same approach taken with the lazy-wave configuration, the static analysis
with and without mean FPSO offset and current loading has first been performed to
determine nominal tension at hang-off connection point, MBR and TDP location. A
detailed description includes:
1. Bending radius of curvature along the riser (touchdown area)
2. Declination angle at the top end of the riser
3. Maximum top tension
4. Touchdown Point (TDP) location (Arc length from top of riser)
For the dynamic analysis, the behavior of the riser configuration in the extreme
conditions is studied using the regular wave loads applied. Detailed results determined
and to be supplied include:
1. Maximum riser top tension at FPSO connection
2. Minimum bending radius and maximum bending moment along the riser
3. Maximum and minimum tension at TDP area
4. Maximum API RP 2RD [6] stress utilization factor along the riser
5. Minimum Effective Tension along the riser (likelihood of compression)
49
Orcaflex Model
The hang-off location in the model is taken as being the same with the STP turret,
which is located 295.3 ft. forward of midship, 32.8 ft. above the keel. The total length
of the modeled production SLWR is 12,790 ft.
The azimuth angle of riser is 304.5 degree in the computer model from the FPSO
north clockwise.
The mesh length varies from 0.5 ft. to 50 ft. Finer meshes are applied to the vicinity of
hang-off point and TDP area.
In the Orcaflex model, the top termination of the production SLWR is taken as
connected to the FPSO via a flexible joint. An articulation element is used to model
the flex joint with given bending stiffness. The SLWR extremity on seabed is fixed in
all translational direction with sufficient length on the seabed. This will eliminate the
boundary condition effect on critical riser response in the TDP area.
Flat seabed is selected at water depth of 7000 ft.
50
3.2 Lazy-Wave Steel Catenary Riser Approach
For in-place condition, which means the FPSO turret buoy is connected to the vessel,
strength analysis is performed for near, far, cross and 270 degree FPSO positions,
vessel offsets for each loading condition, in time domain.
The static analysis is performed in order to check the geometrical suitability of the
riser system before conducting the dynamic analysis. Considering the number of load
cases and computational efforts, the regular-wave-based dynamic analysis is
conducted first to identify the governing load cases for each load category. Then, the
directional analysis is performed, with 22.5 degree increments of FPSO position,
ranging from 0 to 360 degree. This is done to determine the worst result in
evaluating the riser response based on the vessel’s position. Thus, the governing load
cases with FPSO position corresponding with the worst riser motion response are
selected based on stress utilization, likelihood of compression, etc. As the regular
wave analysis is always more conservative compared to irregular wave analysis, the
irregular wave approach is not necessary to conduct if no compression occurs during
the regular wave analysis.
Static analysis taking into consideration mean FPSO offset and current loading has
first been performed to determine nominal tension at hang-off, MBR and TDP
location. Detailed description shall include:
1. Bending radius of curvature along the riser (Arch bend, and TDP)
51
2. Maximum top tension
3. TDP location (Arc length from riser top)
For the dynamic analysis, the behavior of the riser configuration in the extreme
conditions is studied using both the regular wave and irregular wave approach.
Detailed results determined and to be supplied include:
1. Maximum riser top tension at FPSO connection
2. Maximum and minimum tension at TDP
3. Maximum API RP 2RD [6] utilization factor along the riser
4. Minimum Effective Tension along the riser (likelihood of compression)
Orcaflex Model
The hang-off location in the model is taken being same with the STP turret, which is
located 295.3 ft. forward of midship, 32.8 ft. above the keel. The total length of the
modeled production SLWR is 12710 ft.
The azimuth angle of riser is 304.5 degree in the computer model from the FPSO
north clockwise.
The mesh length varies from 0.5 ft. to 50 ft. Finer meshes are applied to the vicinity of
hang-off point, suspended BMs attached riser pipe section and TDP area.
52
In the Orcaflex model, the top termination of the production SLWR is taken as
connected to the FPSO via a flexible joint. An articulation element is used to model
the flex joint with given bending stiffness. The SLWR extremity on seabed is fixed in
all translational direction with sufficient length on the seabed. This could eliminate
the boundary condition effect on critical riser response in the TDP area.
Flat seabed is selected at water depth of 7000 ft.
Figure 3.2.1 Snapshot of SLWR Orcaflex Model
53
3.3 BM Analysis and Optimization
SLWR has been considered as a popular solution in the deep and ultra-deepwater
operation due to the improvement performance of this type of riser in response to
vessel motions, especially the heave motion (motion in vertical direction), or saying,
to the harsh environmental condition. The improvement is achieved by suspending
part of the steel riser pipe in the seawater, by attaching a set of BMs on a section of
riser pipe, instead of adopting the simple catenary configuration. The material
property, arrangement and position along the riser where the BMs are attached, are the
major factors that influence the global response of the SLWR. Thus, the modification
range and values of input parameters for the BM optimization analysis are established
according to the input parameters matrix shown in the table below. The original load
case selected for the BM arrangement analysis is the most critical extreme case with
the worst load direction in 270 degree FPSO position, which can be referred in Table
3.3.1.
As shown in the load matrix table, for the first six cases, positions along the riser
where BMs are attached remain the same as in the original case. Among the other
three parameters, one is fixed, while the other two parameters increase or reduce by 5%
and 10%. For the last five cases, the first three parameters, equivalent outer diameter,
mass per unit length and the total length of the BM attached steel line pipe, are all
fixed, while the position of the BM attached on the steel pipe line varies -500 ft. to
54
+1000 ft. compared to the original case. Negative means that the starting point of the
BM attached zone further from the riser top than the original case, and vice versa.
Table 3.3.1 Load Case Matrix for BM Arrangement Analysis
In addition, all parameters vary to provide the same total buoyancy force as the
original case. With the equivalent outer diameter of the BMs attached pipe line being
fixed, and both total length and mass per unit length being variable, there are two
driving factors to consider: material property and stress concentration. With the mass
per unit length being fixed, and the other two parameters being variable, the driving
factors investigated are buoyancy force ratio and stress concentration. For the case No.
5 and No. 6, the total length of the BM attached pipe is fixed, thus the only factor
being investigated is the density of the BM material.
OD Mass per Unit Length BM Total Length Total Buoyancy Force Position
ft kpf/ft3 kp/ft kpf ft
0 2.8 0.198 1200 224.08 Original
1 2.8 0.22 1360 224.04 Original
2 2.8 0.2079 1267 224.05 Original
3 3.08 0.198 831 223.95 Original
4 2.52 0.198 2004 224.16 Original
5 3.08 0.2805 1200 224.39 Original
6 2.94 0.2385 1200 223.95 Original
7 2.8 0.198 1200 224.08 -200
8 2.8 0.198 1200 224.08 -500
9 2.8 0.198 1200 224.08 200
10 2.8 0.198 1200 224.08 500
11 2.8 0.198 1200 224.08 1000
Load Case: 5 Extreme 100Y Winter Storm 10Y Loop Current 270 degree
55
3.4 SLWR Sensitivity Analysis
A sensitivity study was conducted for the designed SLWR to prove the robustness of
the system to adverse uncertainties in the analysis data and tolerances in
manufacturing and installation. The following parameters are studied for sensitivity:
1. Hang-off angle increased by one degree.
2. Hang-off angle reduced by one degree.
3. FPSO offset increased by 10 percent.
4. Soil vertical stiffness increased by 10 percent.
Four load cases are considered in total, including: hydrotest, operation, extreme, and
survival load conditions. All four load cases, are analyzed and studied in the
sensitivity analysis.
56
3.5 SLWR Disconnection Analysis
For disconnection strength analysis, the STP and the mooring system are also
included in the Orcaflex model. A schematic of the computer model is shown in
Figure 3.5.1.
The disconnection strength analysis is performed for near, far, and transverse loading
conditions. For survival conditions, any one of the mooring lines is assumed to be
disabled for each load case.
Figure 3.5.1 Snapshot of SLWR Orcaflex Model in Disconnection Condition
Regular-wave-based strength analysis is conducted in time domain using Orcaflex.
The simulation duration is specified as 400 sec, and the motion responses of the last
100 sec are extracted and analyzed.
57
Chapter 4
Result and Discussion
4.1 SCR Approach
In this section, all analysis results from the SCR approach are detailed, including riser
configuration, static analysis results and dynamic results.
4.1.1 SCR configuration
Global configuration for the FPSO production SCR at in-place condition is obtained
and shown in Table 4.1.1.
Table 4.1.1 Global Configuration for SCR
Parameter Unit SCR
OD inch 8.625
Nominal Wall Thickness inch 1.725
Nominal Operating Top Tension kips 640
Top Hang Off Angle degree 8
Riser Heading Angle from FPSO North degree 304.5
Water Depth at Touchdown ft 7,000
Seabed Slope degree 0
Strake Length ft 4,570
Suspended Length from Hang Off to Nominal TDP ft 7,995
Horizontal Projection from Hang Off to Nominal TDP ft 2,883
Grounded Pipe Length from Nominal TDP to Transition Point ft 4,795
Total Riser Length from Analysis ft 12,790
58
4.1.2 SCR Strength Analysis
1. Static Analysis
Before performing global dynamic analysis, static analyses have been first conducted
in order to determine the global nominal configuration of the SCR and have better
understanding of the dynamic riser response to the main parameters of vessel and
weather below:
Offset directions
Current velocity
Load cases associated with all loading conditions in Table 2.3.1.
The vessel offset in 270 degree for different load conditions are derived according to
the method defined in section 2.1.3, as shown in Table 2.1.11. For different wave and
current load applied, vessel offsets varies and for conservatively considering, the
larger offset of both offsets corresponding to winter storm and loop current has been
taken to be used in the analysis.
The static analysis results for the SCR configuration approach with FPSO vessel in
the nominal position are presented in Table 4.1.2.
59
Table 4.1.2 Production SCR Nominal Static Analysis Results
Export Riser Units Values
Top Tension kpf 786.0
Hang-off Angle degree 7.95
TDP Location (Arc length from Riser Top) ft 7,995
TDP Area bend radius ft 1,151
TDP Tension kpf 108.26
Max Tension along line kpf 786.0
2. Regular Wave Analysis
The load cases studied for SCR configuration approach are listed in Table 4.1.3.
Table 4.1.3 Load Case Matrix for SCR Configuration Approach
Riser Top Motion
Riser top declination for various load cases are shown in Table 4.1.4. Maximum flex
joint rotation angles are highlighted.
X Y
1 100Y WS Associated 420 0 -420
2 10Y WS 100Y LC 351.73 0 -351.73
3 10Y WS Associated 468.98 0 -468.98
4 Associated 10Y LC 342.33 0 -342.33
Load Category: Extreme
Environmental Condition
Pressure
Design
Case
Factor
Mooring Total
Offset
Offset
Wave Current270
Design 1.2 Intact
Design 1.2 Damaged
60
Table 4.1.4 Riser Top Angular Response for simple SCR
Regular Wave Stress Results
Combined stress results of the analysis for the simple SCR are shown in Table 4.1.5.
Maximum stress of 128.2 ksi is observed at riser touchdown area in Extreme-A load
condition with 270 degree FPSO position. Several worst results are highlighted.
Table 4.1.5 Production SCR Combined Stress Results (ksi)
The API RP 2RD [6] utilization factor is the normalized factor of stress result vs.
stress limits according to API RP 2RD [6]. Stress utilization factor greater than 1
means the steel pipe structure would fail.
The API RP 2RD [6] utilization factor results at the SCR top and the touchdown area
are shown in Table 4.1.6. Maximum stress utilization of 2.31 is observed at the
Angular Deflection
Min Max Mean degree
1 Extreme A 270 156.02 176.54 168.37 15.98
2 Extreme B 270 149.56 171.80 161.21 22.44
3 Extreme C 270 161.29 176.62 170.50 10.71
4 Extreme D 270 166.27 172.23 169.61 5.73
Load CaseFPSO
Position
Top Angle (degree)
FPSO Direction TDP
degree Hoop Axial Bend VMS ft Hoop Axial Bend V M
1 EX A 270 34.0 40.3 43.1 46.3 7920 30.0 13.8 152.3 128.2
3 EX C 270 34.0 40.7 37.2 46.4 7612 30.0 11.4 150.6 123.5
4 EX D 270 33.9 37.5 26.0 39.4 7674 30.0 10.8 72.0 66.5
Load
Case
TOP Stress TDA Stress
61
touchdown area in Extreme-A load condition with 270 degree FPSO position, as
highlighted in red in the table below. All utilization factors greater than 1 are
highlighted in the Table as well.
Table 4.1.6 Production SCR Stress Utilization Factors
Effective Tensions and Bending Moments
The maximum and minimum effective tensions and bending moments for various
load cases are shown in Table 4.1.7. Maximum effective tension at riser top is 1194.9
kips in Extreme-C load condition with 270 degree FPSO position. Maximum bending
moment (BM) observed at the riser top is 414.7 kips-ft. for the Extreme-C load
condition with 270 degree FPSO position. Minimum effective tension observed at
touchdown area is -169.3 kips in Extreme-C load condition with 270 degree FPSO
position. Significant compression force is observed at riser touchdown area, which
means the riser pipe failed under such conditions.
FPSO Direction TDP
degree Top Ext TDP Max Top Ext TDP Max
1 EX A 270 45.2 46.3 128.2 128.2 7920 0.81 0.83 2.31 2.31
2 EX C 270 44.8 46.4 123.5 123.5 7612 0.80 0.83 2.30 2.30
3 EX D 270 33.0 39.4 66.5 66.5 7674 0.59 0.70 1.19 1.19
Utilization FactorLoad
Case
Max Von Mises Stress
(API Code/ksi)
62
Table 4.1.7 Production SCR Effective Tensions and Bending Moments
Min Ten Max Ten BM Min Ten Max Ten BM
kips kips kips-ft kips kips kips-ft
1 EX A 270 131.4 1179.1 414.7 -165.6 305.3 696
2 EX C 270 155.7 1194.9 358.2 -169.3 215.7 687.9
3 EX D 270 265.8 1073.9 249.6 -54.8 191.2 329.1
Load
Case
FPSO
Position
TOP TDP
63
4.2 Lazy-Wave SCR Approach
In this section, all analysis results according to SLWR approach are detailed,
including the riser configuration, static analysis results, and dynamic results.
4.2.1 SLWR Configuration
Global configuration of the designed SLWR for in-place condition is given in Table
4.2.1.
Table 4.2.1 Global Configuration of the designed SLWR
Parameter SLWR
OD inch 8.625
Nominal Wall Thickness inch 1.725
Nominal Operating Top Tension kips 640
Top Hang Off Angle degree 8
Riser Heading Angle from FPSO North degree 304.5
Water Depth at Touchdown ft 7000
Seabed Slope degree 0
Strake Length ft 4,570
Buoyancy Module Length ft 1,200
Starting Buoyancy Module Clearance with Seabed ft 1,486
End Buoyancy Module Clearance With Seabed ft 1,057
Suspended Length from Hang Off to Nominal TDP ft 10,060
Horizontal Projection from Hang Off to Nominal TDP ft 5,155
Grounded Pipe Length from Nominal TDP to Transition Point ft 2,650
Total Riser Length from Analysis ft 12,710
Final Riser Length Recommended ft 13,500
64
4.2.2 SLWR Strength Analysis
1. Static Analysis
Before performing global dynamic analysis, static analyses have been conducted in
order to determine the global nominal configuration of the designed SLWR and have
better understanding of the dynamic riser response to the main parameters of vessel
and weather below:
Vessel Position
Current velocity
Load cases associated with all loading conditions in Table 2.3.1.
The 5-direction vessel offset data for different load conditions are derived according
to the method defined in section 2.1.3, as shown in Table 2.1.11. For different wave
and current load applied, vessel offsets varies and for conservatively considering, the
larger offset of both offsets corresponding to winter storm and loop current has been
taken to be used in the analysis.
Table 4.2.2 presents the calculated FPSO vessel offsets applied in the analysis. The
static analysis results with the designed SLWR configuration and nominal FPSO
vessel position are presented in Table 4.2.3.
65
Table 4.2.2 FPSO Vessel Offset for Different Load Case in Analysis
Table 4.2.3 Summary Results of Production Lazy-Wave SCR Nominal Static Analysis
Wave Current ft
1 1Y WS Associated 257
2 Associated 1Y LC 257
3 10Y WS Associated 352
4 1Y WS 10Y LC 257
5 100Y WS Associated 420
6 10Y WS 100Y LC 352
7 10Y WS Associated 469
8 Associated 10Y LC 342
9 100Y WS Associated 560
10 Associated 100Y LC 469
Offset
Intact
Extreme design 1.2 Damaged
Survival design 1.5 Damaged
Hydrotest 1.25*design 1.35 Intact
Operation
design 1 Intact
design 1.2
Load
Category
Environmental ConditionPressure
Design
Case
Factor
Mooring
SLWR Units Values
Top tension kN 805
Riser Top Declination deg. 11.87
TDP Location (Arc length from Hang-off) ft 9866
TDP bend radius ft 3380
TDP Tension kN 165
Max Tension along line kN 805
66
2. Regular Wave Analysis
Riser Top Motion
Maximum riser top declination results for each load condition are shown in Table
4.2.4. And riser top declination results of all load cases are detailed in Appendix A.
Maximum flex joint rotation angles are observed in Extreme-B load case with 270
degree FPSO position, as highlighted in the table below.
Table 4.2.4 Summary of SLWR Top Angular Response Results
Min Max Mean
1 Hydro test A 270 169.71 174.59 172.37 2.59
6 Hydro test B 270 166.64 172.24 169.74 5.36
11 Operation A 270 159.13 176.13 169.16 12.87
16 Operation B 270 164.72 171.22 168.4 7.28
21 Extreme A 270 154.12 176.19 167.45 17.88
26 Extreme B 270 149.66 171.84 161.29 22.34
31 Extreme C 270 159.36 176.23 169.34 12.64
36 Extreme D 270 164.89 171.46 168.61 7.11
41 Survival A 270 154.31 176.2 167.35 17.69
46 Survival B 270 149.7 172.1 161.4 22.30
Load CaseFPSO
Position
Top Angle (degree) Angular
DeflectionNo.
67
Regular Wave Stress Results
Maximum stress results for each load condition in 3 catenary sections (riser top, arch
bend and touchdown area) are shown in the tables below. The stress results, of the
regular wave analysis with the SLWR approach, are detailed in Appendix A.
Maximum Von Mises Stress of 45.9ksi is observed at riser top for Extreme-A load
condition with 270 degree FPSO position. This most critical case occurs at the 1st
welding point under the flex joint taper tip. Bending stress governs the maximum
stress. The maximum results are highlighted in the tables as well.
Table 4.2.5 Summary of SLWR Stress Results – Riser Top (ksi)
Hoop Axial Bend V M
1 Hydrotest A 270 42.5 33.9 21.4 42.5
7 Hydrotest B Far 42.5 35.4 12.4 42.5
11 Operation A 270 34.0 35.6 39.5 43.7
17 Operation B Far 33.9 33.1 13.9 37.2
21 Extreme A 270 34.0 36.5 45.1 45.9
26 Extreme B 270 34.0 38.7 50.5 42.3
31 Extreme C 270 34.0 35.6 39.1 43.7
37 Extreme D Far 33.9 33.1 13.5 37.3
41 Survival A 270 34.0 36.5 44.8 45.9
46 Survival B 270 34.0 38.6 50.3 43.0
Load Case FPSO Position Riser Top (ksi)
68
Table 4.2.6 Summary of SLWR Stress Results – Arch Bend
Table 4.2.7 Summary of SLWR Stress Results – TDP Area
The maximum API RP 2RD Utilization Factors at the SLWR top and touchdown area
for each load condition are shown in Table 4.2.8. Maximum stress utilization of 0.936
Hoop Axial Bend V M
1 Hydrotest A 270 40.1 13.4 29.1 42.7
6 Hydrotest B 270 40.1 13.4 28.6 42.6
11 Operation A 270 30.9 10.9 32.9 38.7
16 Operation B 270 30.9 10.9 30.3 37.4
21 Extreme A 270 30.9 10.9 34.8 39.8
26 Extreme B 270 30.9 10.9 16.8 39.9
31 Extreme C 270 30.9 10.8 33.9 39.2
38 Extreme D Near 30.9 10.8 31.5 37.9
41 Survival A 270 30.9 10.8 36.2 40.6
46 Survival B 270 30.9 10.8 36.1 40.4
Load Case FPSO Position Arch Bend (ksi)
Hoop Axial Bend V M
1 Hydrotest A 270 39.4 10.2 14.4 37.5
6 Hydrotest B 270 39.4 10.2 14.1 37.4
11 Operation A 270 30.0 7.6 16.2 30.8
18 Operation B Near 30.0 7.5 14.9 30.3
21 Extreme A 270 30.0 7.5 16.9 31.0
26 Extreme B 270 30.0 7.5 17.1 31.1
31 Extreme C 270 30.0 7.5 16.7 30.9
38 Extreme D Near 30.0 7.5 15.6 30.5
41 Survival A 270 30.0 7.4 17.7 31.2
46 Survival B 270 30.0 7.4 17.7 31.3
TDP Area (ksi)Load Case FPSO Position
69
is observed at the flex joint extension in the Operation-A load case with 270 degree
FPSO position. The maximum stress and stress utilization factor results are
highlighted in the table.
Table 4.2.8 Summary of Maximum SLWR Stress Utilization Factors
Effective Tensions and Bending Moments
The maximum effective tension, minimum effective tensions and maximum bending
moment at 3 sections (riser top, arch bend and touchdown area) of SLWR for each
load condition are shown in the following tables. The complete summary of effective
tensions and bending moments results with SLWR approach are detailed in Appendix
A. All the most critical results are highlighted in the tables. The maximum effective
tension at riser top is 1118.9 kips in the Extreme-B load condition with 270 degree
FPSO position. The maximum bending moment at riser top is 486.0 kips-ft in the
3 Hydro test A Near 29.9 41.9 42.7 37.5 48% 67% 68% 60%
6 Hydro test B 270 33.7 42.0 42.6 37.4 54% 67% 68% 59%
11 Operation A 270 39.4 43.7 38.7 30.8 84% 94% 83% 66%
16 Operation B 270 30.1 35.9 37.4 30.3 65% 77% 80% 65%
21 Extreme A 270 40.8 45.9 39.8 31.0 73% 82% 71% 55%
26 Extreme B 270 43.0 42.3 39.9 31.1 77% 76% 71% 51%
31 Extreme C 270 39.5 43.7 39.2 30.9 71% 78% 70% 55%
36 Extreme D 270 30.1 35.8 37.9 30.5 54% 64% 68% 54%
41 Survival A 270 41.0 45.9 40.6 31.2 59% 66% 58% 45%
46 Survival B 270 43.0 42.5 40.4 31.3 62% 61% 58% 45%
TDP
Max. Von Mises Stress
(API, ksi)Load Case
FPSO
PositionTop Ext Arch
Utilization Factor (%)
Top Ext Arch TDP
70
Extreme-B load condition with 270 degree FPSO position. Minimum effective tension
at riser touchdown area is 4.2 kips in Survival B load condition with 270 degree FPSO
position, which indicates no compression observed at the touchdown area at all.
Hence, the irregular wave analysis is not necessary to be conducted, as the regular
wave analysis has over predicted the compression at the touchdown area.
Table 4.2.9 Summary of SLWR Maximum Tension Results
Table 4.2.10 Summary of SLWR Minimum Tension Results
Riser Top Arch Bend TDP Area
2 Hydro test A Far 914.9 111.2 105.5
7 Hydro test B Far 914.2 122.7 101.3
11 Operation A 270 1005.8 109.9 71.6
17 Operation B Far 909.4 114.4 108.4
21 Extreme A 270 1040.2 113.8 70.8
26 Extreme B 270 1118.9 119.9 69.4
31 Extreme C 270 1004.3 104.3 67.9
37 Extreme D Far 912.7 137.3 115.1
41 Survival A 270 1038.8 107.8 66.1
46 Survival B 270 1116.3 117.2 65.9
Max Tension (kips)No. Load Case
FPSO
Position
Riser Top Arch Bend TDP Area
1 Hydro test A 270 310.7 47.1 69.1
6 Hydro test B 270 294.2 46.7 70.6
11 Operation A 270 183.7 20.1 61.3
16 Operation B 270 278.4 42.7 66.6
21 Extreme A 270 169.8 7.7 58.4
26 Extreme B 270 134 4.5 57.2
31 Extreme C 270 185 19 58.7
36 Extreme D 270 278.4 41.1 64.3
41 Survival A 270 170.8 7.1 55.8
46 Survival B 270 135 4.2 55.1
Min Tension (kips)No. Load Case
FPSO
Position
71
Table 4.2.11 Summary of SLWR Maximum Bending Moment Results
4.2.3 SLWR Regular Wave Directional Analysis
In addition, the directional dynamic analysis considering different directions of vessel
positions (22.5 degree increment, range from 0 to 360 degree and all of near, far,
trans+ and trans- directions) is performed. The results are analyzed and compared to
identify the vessel position corresponding to the worst riser response (270 degree).
The load condition which is applied in the directional analysis is the Extreme-B
condition.
Riser Top Arch Bend TDP Area
1 Hydro test A 270 205.7 132.9 65.7
6 Hydro test B 270 243.6 130.7 64.3
11 Operation A 270 380.2 150.2 73.9
16 Operation B 270 265.0 138.4 67.6
21 Extreme A 270 433.8 159.1 77.2
26 Extreme B 270 486.0 160.0 78.3
31 Extreme C 270 376.1 155.0 76.4
36 Extreme D 270 263.5 142.9 70.0
41 Survival A 270 431.3 165.6 80.8
46 Survival B 270 484.1 164.8 80.9
No. Load CaseFPSO
Position
Max Bending Moment (kips-ft)
72
Riser Top Motion
The riser top declinations results in the Extreme-B condition with all considered
FPSO position directions are shown in Table 4.2.12. Maximum flex joint rotation
angles are highlighted.
Table 4.2.12 Directional Riser Top Angular Response for Production SLWR
Regular Wave Stress Results
The directional combined stress results at 3 sections (riser top, arch bend and
touchdown area) of SLWR are presented in the following tables. The overall
Angular Deflection
Min Max degree
1 Extreme B 0 168.75 171.08 3.25
2 Extreme B 22.5 168.51 172.18 3.49
3 Extreme B 45 165.95 173.75 6.05
4 Extreme B 67.5 157.8 174.73 14.2
5 Extreme B 90 159.96 175.27 12.04
6 Extreme B 112.5 169.61 178.39 6.39
7 Extreme B 135 173.99 179.59 7.59
8 Extreme B 157.5 173.67 176.06 4.06
9 Extreme B 180 172.99 173.61 1.61
10 Extreme B 202.5 170.96 172.48 1.04
11 Extreme B 225 166.97 171.51 5.03
12 Extreme B 247.5 159.81 170.73 12.19
13 Extreme B 270 149.66 171.84 24.42
14 Extreme B 292.5 147.58 172.34 22.34
15 Extreme B 315 158.74 171.59 13.26
16 Extreme B 337.5 166.79 171.08 5.21
17 Extreme B Near 152.39 171.95 19.61
18 Extreme B Far 174.03 179.04 7.04
19 Extreme B Trans+ 167.89 173.01 4.11
20 Extreme B Trans- 169.33 171.96 2.67
Load CaseFPSO
Position
Declination (degree)
73
maximum stress of 46.12 ksi is observed at the riser top (1st weld under flex joint
taper tip) in 270 degree FPSO position. The maximum results of each riser are
highlighted in the tables.
Table 4.2.13 Directional Combined Stress Results of the SLWR– Riser Top
Hoop Axial Bend V M
1 Extreme B 0 33.94 29.3 14.54 35.38
2 Extreme B 22.5 33.95 30.77 17.51 36.18
3 Extreme B 45 33.95 34.02 29.41 37.92
4 Extreme B 67.5 33.95 39.81 48.66 44.67
5 Extreme B 90 33.95 39.73 52.61 45.49
6 Extreme B 112.5 33.95 34.74 41.53 41.59
7 Extreme B 135 33.95 34.73 26.95 39.09
8 Extreme B 157.5 33.95 32.79 16.41 37.29
9 Extreme B 180 33.95 31.93 13.97 24.6
10 Extreme B 202.5 33.95 32.83 16.37 25.26
11 Extreme B 225 33.95 35.2 25.4 28.92
12 Extreme B 247.5 33.96 35.07 38.5 35.13
13 Extreme B 270 33.95 38.66 50.54 46.12
14 Extreme B 292.5 33.95 38.91 48.25 43.51
15 Extreme B 315 33.95 33.17 29 35.58
16 Extreme B 337.5 33.95 30.5 16.65 29.4
17 Extreme B Near 33.95 35.99 39.17 39.58
18 Extreme B Far 33.95 34.85 33.86 40.29
19 Extreme B Trans+ 33.95 32.31 22.41 36.98
20 Extreme B Trans- 33.95 34.07 20.21 26.44
Load CaseFPSO
Direction
Riser Top (ksi)
74
Table 4.2.14 Directional Combined Stress Results of the SLWR– Arch Bend (ksi)
Hoop Axial Bend V M
1 Extreme B 0 30.9 10.92 28.16 36.27
2 Extreme B 22.5 30.89 11.11 26.71 35.69
3 Extreme B 45 30.87 11.46 25.43 35.29
4 Extreme B 67.5 30.86 11.94 26.35 36.01
5 Extreme B 90 30.86 11.95 28.38 36.86
6 Extreme B 112.5 30.86 12.1 27.85 36.4
7 Extreme B 135 30.85 12.17 25.06 35.17
8 Extreme B 157.5 30.86 11.85 22.78 34.21
9 Extreme B 180 30.86 11.58 23.3 34.36
10 Extreme B 202.5 30.88 11.42 25.62 35.36
11 Extreme B 225 30.89 11.33 29.42 37.23
12 Extreme B 247.5 30.91 11.12 32.71 38.86
13 Extreme B 270 30.93 10.9 35.03 39.87
14 Extreme B 292.5 30.92 9.36 33.86 39.17
15 Extreme B 315 30.92 10.84 31.95 38.1
16 Extreme B 337.5 30.91 10.84 30.31 37.27
17 Extreme B Near 30.92 10.87 32.86 38.58
18 Extreme B Far 30.86 12.21 26.72 35.84
19 Extreme B Trans+ 30.88 11.27 26.03 35.49
20 Extreme B Trans- 30.88 11.36 27.46 36.25
Load CaseFPSO
Direction
Arch Bend
75
Table 4.2.15 Directional Combined Stress Results of the SLWR – TDP Area (ksi)
The directional results of API RP 2RD Utilization Factors [6] at SLWR top and
touchdown area are shown in the two tables below. The maximum stress utilization of
0.822 is observed at the flex joint extension with 270 degree FPSO position direction.
TDP
ft Hoop Axial Bend V M
1 Extreme B 0 10010 29.96 7.64 14.19 30.18
2 Extreme B 22.5 10050 29.96 7.8 13.4 29.99
3 Extreme B 45 10070 29.96 8.24 12.54 29.8
4 Extreme B 67.5 10140 29.96 8.66 12.05 29.73
5 Extreme B 90 10160 29.96 8.69 12.33 29.82
6 Extreme B 112.5 10150 29.96 8.93 11.89 29.72
7 Extreme B 135 10140 29.96 8.99 11.31 29.54
8 Extreme B 157.5 10120 29.96 8.69 11.05 29.5
9 Extreme B 180 10100 29.96 8.4 11.46 29.56
10 Extreme B 202.5 10060 29.96 8.2 12.63 29.81
11 Extreme B 225 10020 29.96 8.02 14.3 30.23
12 Extreme B 247.5 10000 29.96 7.78 15.95 30.7
13 Extreme B 270 10000 29.96 7.5 17.14 31.08
14 Extreme B 292.5 9990 29.96 7.47 16.82 30.99
15 Extreme B 315 9990 29.96 7.47 15.88 30.65
16 Extreme B 337.5 9990 29.96 7.51 15.22 30.45
17 Extreme B Near 10000 29.96 7.47 16.3 30.8
18 Extreme B Far 10150 29.96 9.02 11.43 29.61
19 Extreme B Trans+ 10050 29.96 8.04 12.89 29.87
20 Extreme B Trans- 10050 29.96 8.11 13.46 30
TDP AreaLoad Case
FPSO
Direction
76
Table 4.2.16 Directional Stress Utilization Factors of the SLWR
Effective Tensions and Bending Moments
The directional results of the maximum effective tensions, minimum effective
tensions and max bending moments at 3 sections (riser top, arch bend and TDP area)
of SLWR are presented in the following tables. The maximum effective tension is
1 Extreme B 0 50.1% 63.2% 64.8% 53.9%
2 Extreme B 22.5 53.8% 64.6% 63.7% 53.6%
3 Extreme B 45 65.7% 67.7% 63.0% 53.2%
4 Extreme B 67.5 79.8% 80.1% 64.4% 53.1%
5 Extreme B 90 81.2% 80.3% 66.0% 53.2%
6 Extreme B 112.5 67.4% 74.3% 65.0% 53.1%
7 Extreme B 135 53.0% 69.8% 62.8% 52.8%
8 Extreme B 157.5 45.3% 66.6% 61.1% 52.6%
9 Extreme B 180 43.9% 65.3% 61.4% 52.8%
10 Extreme B 202.5 45.1% 66.5% 63.1% 53.2%
11 Extreme B 225 51.6% 69.5% 66.5% 54.0%
12 Extreme B 247.5 62.7% 72.0% 69.4% 54.8%
13 Extreme B 270 76.8% 82.2% 71.2% 55.5%
14 Extreme B 292.5 77.7% 79.4% 70.0% 55.4%
15 Extreme B 315 63.5% 66.7% 68.0% 54.7%
16 Extreme B 337.5 52.5% 64.1% 66.7% 54.4%
17 Extreme B Near 70.7% 72.9% 68.9% 55.0%
18 Extreme B Far 59.4% 72.0% 64.0% 52.9%
19 Extreme B Trans+ 58.7% 66.0% 63.3% 53.3%
20 Extreme B Trans- 47.2% 67.8% 64.7% 53.6%
Arch TDP
FPSO
Direction
degree
Load Case
Utilization Factor
Top Ext
77
1118.9 kips with 270 degree FPSO position direction. The maximum bending moment
at riser top is 486.0 kips-ft. with 270 degree FPSO position. The minimum effective
tension at touchdown area is 4.2 kips with 270 degree FPSO position. No
compression is observed at the riser touchdown area at all.
Table 4.2.17 Directional Results of the SLWR – Maximum Tension
Riser Top Arch Bend TDP Area
degree kips kips kips
1 Extreme B 0 768.1 83.5 72.5
2 Extreme B 22.5 823.2 96.0 82.9
3 Extreme B 45 945.2 123.7 97.0
4 Extreme B 67.5 1107.2 156.2 112.6
5 Extreme B 90 1101.1 165.4 114.0
6 Extreme B 112.5 972.3 171.5 122.9
7 Extreme B 135 972.4 165.3 125.2
8 Extreme B 157.5 899.3 135.5 113.9
9 Extreme B 180 867.0 119.5 103.2
10 Extreme B 202.5 901.1 117.4 95.6
11 Extreme B 225 990.2 131.3 88.9
12 Extreme B 247.5 985.2 131.5 79.7
13 Extreme B 270 1119.0 119.9 69.4
14 Extreme B 292.5 1113.5 107.2 68.8
15 Extreme B 315 913.4 88.9 68.3
16 Extreme B 337.5 813.0 82.6 70.0
17 Extreme B Near 1019.3 95.5 68.7
18 Extreme B Far 976.9 174.5 126.3
19 Extreme B Trans+ 881.0 108.2 89.6
20 Extreme B Trans- 947.7 122.2 92.0
Load Case
Max. Effective TensionFPSO
Position
78
Table 4.2.18 Directional Results of the SLWR – Minimum Tension
Riser Top Arch Bend TDP Area
degree kips kips kips
1 Extreme B 0 488.2 63.0 69.9
2 Extreme B 22.5 439.4 64.9 76.4
3 Extreme B 45 358.2 64.2 81.8
4 Extreme B 67.5 368.0 46.5 86.2
5 Extreme B 90 199.8 23.4 84.7
6 Extreme B 112.5 169.3 28.0 86.6
7 Extreme B 135 256.0 50.6 91.4
8 Extreme B 157.5 378.0 72.8 93.9
9 Extreme B 180 418.9 74.3 89.8
10 Extreme B 202.5 362.1 61.3 81.2
11 Extreme B 225 219.8 33.0 69.6
12 Extreme B 247.5 118.4 9.9 61.3
13 Extreme B 270 134.0 4.5 57.1
14 Extreme B 292.5 300.0 25.9 58.8
15 Extreme B 315 388.2 51.0 62.7
16 Extreme B 337.5 442.4 55.7 65.8
17 Extreme B Near 403.5 42.8 61.0
18 Extreme B Far 201.3 38.0 88.9
19 Extreme B Trans+ 396.4 64.2 79.0
20 Extreme B Trans- 298.1 48.7 75.3
Load Case
FPSO
Position
Min. Effective Tension
79
Table 4.2.19 Directional Results of the SLWR – Maximum Bending Moment
Riser Top Arch Bend TDP Area
degree kips-ft kips-ft kips-ft
1 Extreme B 0 139.8 128.7 64.9
2 Extreme B 22.5 168.4 122.0 61.2
3 Extreme B 45 282.9 116.2 57.3
4 Extreme B 67.5 468.0 120.4 55.0
5 Extreme B 90 472.0 129.7 56.3
6 Extreme B 112.5 399.4 127.2 54.3
7 Extreme B 135 259.2 114.5 51.7
8 Extreme B 157.5 157.8 104.1 50.5
9 Extreme B 180 867.0 106.4 52.4
10 Extreme B 202.5 157.4 117.1 57.7
11 Extreme B 225 244.3 134.4 65.3
12 Extreme B 247.5 370.3 149.5 72.9
13 Extreme B 270 486.0 160.0 78.3
14 Extreme B 292.5 464.1 154.7 76.8
15 Extreme B 315 278.9 146.0 72.5
16 Extreme B 337.5 160.1 138.5 69.5
17 Extreme B Near 376.8 150.1 74.5
18 Extreme B Far 325.6 122.1 52.2
19 Extreme B Trans+ 215.5 118.9 58.9
20 Extreme B Trans- 194.3 125.5 61.5
Max Bending Moment
Load Case
FPSO
Position
80
4.3 Comparison of Two Design Approaches: SCR vs. SLWR
The comparison results, including the maximum and minimum effective tensions,
maximum bending moments, Von Mises stresses and API stress utilization factors [6]
according to both SCR and SLWR configuration approaches are presented in the
tables below. It can be established that the results obtained from analysis based on the
SCR approach indicates that the simple SCR configuration cannot satisfy the stress,
tension and bending moment requirements specified.
This is expected, since the environmental condition in the GoM is too harsh for the
simple steel catenary configuration riser with a turret moored FPSO facility.
Significant compressions are observed at touchdown area in all load conditions, which
leads to the explosively increase of the bending moment, Von Mises stress and stress
utilization factor. Thus, the pipe is very likely to clash or buckle locally.
Table 4.3.1 Comparison Results of Riser Top Angular Responses
Table 4.3.2 Comparison Results of Von Mises Stress
SCR SLWR
1 Extreme A 270 15.98 17.88
2 Extreme C 270 10.71 12.64
3 Extreme D 270 5.73 7.11
Load Case FPSO PositionAngular Deflection (degree)
Top Ext TDP Top Ext Hog TDA
1 Extreme A 270 81% 83% 231% 73% 82% 71% 55%
2 Extreme C 270 80% 83% 230% 71% 78% 70% 55%
3 Extreme D 270 59% 70% 119% 54% 64% 68% 54%
Load CaseFPSO
Position
API Stress Utilization Factor
SCR SLWR
81
Table 4.3.3 Comparison Results of API Stress Utilization Factors
Table 4.3.4 Comparison Results of Effective Tensions
Table 4.3.5 Comparison Results of Bending Moments
Top Ext TDP Top Ext Hog TDA
1 Extreme A 270 80.6% 82.8% 230.7% 72.9% 81.9% 71.1% 55.3%
2 Extreme C 270 80.0% 82.9% 229.6% 70.6% 78.0% 70.1% 55.2%
3 Extreme D 270 59.0% 70.4% 118.7% 53.8% 64.0% 67.6% 54.4%
Load CaseFPSO
Position
API Stress Utilization Factor
SCR SLWR
Top Max TDP Min Top Max Sag Min TDA Min
1 Extreme A 270 1179.1 -165.6 1040.2 7.7 58.4
2 Extreme C 270 1194.9 -169.3 1004.3 19 58.7
3 Extreme D 270 1073.9 -54.8 855.1 41.1 64.3
Load CaseFPSO
Position
Effective Tension (kips)
SCR SLWR
Top Max TDP Max Top Max Sag Max TDA Max
1 Extreme A 270 414.7 696.0 433.8 159.1 77.2
2 Extreme C 270 358.2 687.9 376.1 155.0 76.4
3 Extreme D 270 249.6 329.1 263.5 142.9 70.0
Load CaseFPSO
Position
Bending Moment (kips-ft)
SCR SLWR
82
4.4 BM Optimization
The angle deflections at riser top, clearances between the top of BMs attached riser
pipe and the seabed, maximum top effective tensions, maximum bending moment,
maximum Von Mises Stress and the API code utilization factors at three riser sections
(riser top, arch bend, TDP area) are considered and investigated for the BM
arrangement optimization. The load cases are selected based on the load matrix shown
in Table 3.3.1, Section 2.3.4. The results of analysis are presented in the following
tables.
Table 4.4.1 BM Optimization Analysis Results – Effective Tension
Angle Deflection TDP Seabed Clearance
degree ft ft TOP Sag TDP
0 5.878 10000 1097 1040.2 7.7 58.4
1 5.683 10130 1247 1036.0 4.6 55.3
2 5.795 10057 1160 1038.2 6.4 57.3
3 6.487 9731 779 1052.0 13.9 66.6
4 5.057 10704 1823 1025.2 -0.3 44.7
5 5.907 10000 1103 1039.5 4.2 58.3
6 5.892 10020 1100 1039.8 6.0 58.7
7 5.756 10390 946 1093.2 8.0 65.8
8 5.828 10180 1038 1061.8 7.9 61.7
9 5.951 9860 1162 1017.3 7.6 56.0
10 6.078 9630 1256 983.0 7.2 52.1
11 6.345 9215 1414 922.2 6.3 45.7
Effective Tension (kips)
83
Table 4.4.2 BM Optimization Analysis Results - Bending Moment
Table 4.4.3 BM Optimization Analysis Results - Von Mises Stress
Angle Deflection TDP Seabed Clearance
degree ft ft TOP Hog TDP
0 5.878 10000 1097 433.8 159.1 77.2
1 5.683 10130 1247 432.1 147.5 81.3
2 5.795 10057 1160 433.1 154.0 80.4
3 6.487 9731 779 439.2 199.1 67.1
4 5.057 10704 1823 426.3 120.8 98.6
5 5.907 10000 1103 434.1 161.8 79.4
6 5.892 10020 1100 434.0 160.5 78.9
7 5.756 10390 946 432.2 141.0 70.2
8 5.828 10180 1038 433.2 152.1 73.7
9 5.951 9860 1162 434.7 167.0 81.0
10 6.078 9630 1256 436.2 180.8 87.6
11 6.345 9215 1414 439.3 208.7 95.4
Bending Moment(kips-ft)
Seabed Clearance
ft Top Hog TDA
0 5.878 10000 1097 45.9 39.8 31.0
1 5.683 10130 1247 45.7 38.3 31.3
2 5.795 10057 1160 45.8 39.2 31.2
3 6.487 9731 779 46.1 45.4 30.4
4 5.057 10704 1823 45.6 35.3 32.8
5 5.907 10000 1103 45.9 40.2 31.2
6 5.892 10020 1100 45.9 40.0 31.1
7 5.756 10390 946 46.7 37.8 30.5
8 5.828 10180 1038 46.2 39.0 30.8
9 5.951 9860 1162 45.5 40.7 31.2
10 6.078 9630 1256 45.0 42.5 31.7
11 6.345 9215 1414 44.1 46.1 32.4
Angle Deflection TDPAPI RP 2RD Stress
84
Table 4.4.4 BM Optimization Analysis Results - Stress Utilization Factors
Seabed Clearance
ft Top Hog TDA
0 5.878 10000 1097 81.9% 71.1% 55.3%
1 5.683 10130 1247 81.7% 68.4% 55.8%
2 5.795 10057 1160 81.9% 69.9% 55.7%
3 6.487 9731 779 82.3% 81.0% 54.2%
4 5.057 10704 1823 81.4% 63.1% 58.5%
5 5.907 10000 1103 81.9% 71.7% 55.6%
6 5.892 10020 1100 81.9% 71.5% 55.5%
7 5.756 10390 946 83.4% 67.5% 54.5%
8 5.828 10180 1038 82.5% 69.7% 54.9%
9 5.951 9860 1162 81.2% 72.8% 55.7%
10 6.078 9630 1256 80.3% 75.8% 56.7%
11 6.345 9215 1414 78.7% 82.2% 57.9%
Stress UtilizationAngle Deflection TDP
85
4.5 Sensitivity Analysis
The sensitivity analysis results of the Von Mises stresses, stress utilization factors and
effective tensions are summarized and presented in the following tables. The
robustness of the designed system is established from the analysis results. In addition,
it is indicated based on the results that the Von Mises stress is the most sensitive to
Hang-off angle increase. The maximum change of 5.92% in Von Mises results is
caused by 1 degree increase of hang-off angle, as highlighted in Table 4.5.1. For this
same scenario, the maximum change in stress utilization factor results is observed as
well. Besides, Small changes (about 10%) in soil vertical stiffness and vessel offsets
influence the riser response results insignificantly.
Table 4.5.1 Sensitivity Analysis Results – Von Mises Stress
Top Arch TDP Top Hog TDP
Hydrotest A 42.5 44.9 38.7 0.1% 5.0% 3.2%
Operation B 36.1 39.6 30.9 0.6% 5.9% 2.0%
Extreme A 46.0 41.9 31.6 0.2% 5.1% 1.9%
Survival A 46.0 43.0 32.0 0.2% 5.9% 2.3%
Hydrotest A 42.7 43.6 37.8 0.6% 2.0% 0.8%
Operation B 35.9 38.8 30.8 0.2% 3.7% 1.5%
Extreme A 46.0 41.2 31.4 0.2% 3.4% 1.6%
Survival A 45.9 42.0 31.8 0.1% 3.6% 1.8%
FPSO Offset +10% Hydrotest A 42.7 42.9 38.2 0.4% 0.5% 1.9%
FPSO Offset +10% Operation B 35.9 37.5 30.4 0.1% 0.4% 0.1%
FPSO Offset +6% Extreme A 45.9 39.9 31.0 0.1% 0.1% 0.0%
FPSO Offset +10% Survival A 45.9 40.9 31.3 0.0% 0.7% 0.4%
Hydrotest A 42.7 43.1 38.2 0.4% 0.8% 2.0%
Operation B 35.9 37.4 30.3 0.0% 0.0% 0.0%
Extreme A 45.9 39.8 31.0 0.0% 0.0% 0.0%
Survival A 45.9 40.6 31.2 0.0% 0.0% 0.0%
Sensitivity Case Load CaseVon Mises Stress (ksi) Difference (%)
Soil Vertical Stiffness
+10%
Hang-off Angle
+1 degree
Hang-off Angle
-1 degree
86
Table 4.5.2 Sensitivity Analysis Results - API Stress Utilization Factors
Top Hog TDP Top Hog TDP
Hydrotest A 67% 64% 58% 0% 5% 3%
Operation B 77% 75% 64% 1% 6% 2%
Extreme A 82% 68% 54% 0% 5% 2%
Survival A 66% 55% 44% 0% 6% 2%
Hydrotest A 67% 68% 59% 1% 0% 1%
Operation B 77% 83% 66% 0% 4% 1%
Extreme A 82% 74% 56% 0% 4% 2%
Survival A 65% 60% 45% 0% 3% 2%
FPSO Offset +10% Hydrotest A 67% 68% 58% 0% 0% 2%
FPSO Offset +10% Operation B 77% 80% 65% 0% 0% 0%
FPSO Offset +6% Extreme A 82% 71% 55% 0% 0% 0%
FPSO Offset +10% Survival A 66% 58% 45% 0% 1% 0%
Hydrotest A 67% 67% 58% 0% 1% 2%
Operation B 77% 80% 65% 0% 0% 0%
Extreme A 82% 71% 55% 0% 0% 0%
Survival A 66% 58% 45% 0% 0% 0%
Soil Vertical Stiffness
+10%
Sensitivity Case Load CaseUtilization Fator % Change
Hang-off Angle
+1 degree
Hang-off Angle
-1 degree
87
Table 4.5.3 Sensitivity Analysis Results - Effective Tensions
Table 4.5.4 Contrast Results for Sensitivity Analysis
Top (kips) Difference (%)
Hydrotest A 859.9 0.4%
Operation B 873 1.8%
Extreme A 1047.2 0.7%
Survival A 1044.8 0.6%
Hydrotest A 838.7 2.1%
Operation B 851.5 0.7%
Extreme A 1037.4 0.3%
Survival A 1036.4 0.2%
FPSO Offset +10% Hydrotest A 844 1.4%
FPSO Offset +10% Operation B 856.7 0.1%
FPSO Offset +6% Extreme A 1040 0.0%
FPSO Offset +10% Survival A 1038.2 0.1%
Hydrotest A 844.7 1.4%
Operation B 857.3 0.0%
Extreme A 1040.2 0.0%
Survival A 1038.8 0.0%
Sensitivity Case Load CaseEffective Tension
Hang-off +1 deg
Hang-off -1 deg
Soil Vertical Stiffness +10%
Top Arch TDP Top Arch TDP Top ft
Hydrotest A 42.5 42.7 37.5 67.5% 67.8% 59.5% 856.4 9980
Operation B 35.9 37.4 30.3 76.8% 80.1% 65.0% 857.3 10000
Extreme A 45.9 39.8 31.0 81.9% 71.1% 55.3% 1040.2 10000
Survival A 45.9 40.6 31.2 65.5% 58.0% 44.6% 1038.8 9990
Tension
(kips)TDP
Load CaseVon Mises Stress (ksi) Utilization Fator
88
4.6 Disconnection Strength Analysis
Stress results of the disconnection analysis for the production SLWR are shown in
Table 4.6.1 and Table 4.6.2. Maximum stress of 42.247 ksi is observed at the riser
arch bend in survival near condition with mooring line 7 damaged.
The API RP 2RD Utilization Factors [6] at the riser top, arch bend and touchdown
area are presented in Table 4.6.1. The maximum stress utilization of 0.725 is observed
at the riser arch bend in the extreme near condition. At riser top, the maximum stress
utilization of 0.725 is observed at the stress joint extension in extreme far condition.
The maximum and minimum effective tensions results of the designed disconnected
SLWR for various load cases are shown in Table 4.6.2. Maximum effective tension of
788.3 kips is observed at riser top in the survival far condition with the mooring line
11 damaged, as highlighted in Table 4.6.2. The minimum effective tension of 76.1
kips is observed at the riser touchdown area in survival near case with the mooring
line six damaged. The overall minimum effective tension of 63.4 kips is observed at
the riser sag bend before arch section, which means no compression is not present at
the touchdown area in disconnection analysis.
89
Table 4.6.1 Disconnection Analysis Results of the SLWR - Stresses and Stress Utilization Factors
Top Arch TDP Top Arch TDA
1 EX03 Near 39.3 40.6 36.4 70.2% 72.5% 65.0%
2 EX03 Far 39.5 40.3 36.3 70.6% 72.0% 64.8%
3 SU05N#1 Near 40.7 40.9 36.4 58.1% 58.4% 51.9%
4 SU05T#1 Trans 40.7 40.1 36.2 58.2% 57.3% 51.7%
5 SU05F#1 Far 41.0 39.8 36.1 58.6% 56.8% 51.5%
6 SU05N#2 Near 40.6 41.0 36.4 58.0% 58.5% 52.0%
7 SU05T#2 Trans 40.7 40.2 36.2 58.1% 57.5% 51.7%
8 SU05F#2 Far 41.0 39.9 36.1 58.6% 56.9% 51.6%
9 SU05N#3 Near 40.6 41.0 36.4 58.0% 58.6% 52.0%
10 SU05T#3 Trans 40.7 40.3 36.2 58.1% 57.6% 51.7%
11 SU05F#3 Far 40.9 39.9 36.1 58.5% 57.1% 51.6%
12 SU05N#4 Near 40.5 41.1 36.4 57.9% 58.7% 52.0%
13 SU05T#4 Trans 40.6 40.4 36.2 58.0% 57.8% 51.8%
14 SU05F#4 Far 40.9 40.0 36.1 58.4% 57.2% 51.6%
15 SU05N#5 Near 40.2 42.2 36.8 57.4% 60.3% 52.5%
16 SU05T#5 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%
17 SU05F#5 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%
18 SU05N#6 Near 40.2 42.2 36.8 57.4% 60.3% 52.5%
19 SU05T#6 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%
20 SU05F#6 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%
21 SU05N#7 Near 40.2 42.2 36.8 57.4% 60.4% 52.5%
22 SU05T#7 Trans 40.4 41.4 36.5 57.8% 59.2% 52.1%
23 SU05F#7 Far 40.6 40.9 36.4 58.0% 58.4% 51.9%
24 SU05N#8 Near 40.6 41.0 36.4 58.0% 58.6% 52.0%
25 SU05T#8 Trans 40.7 40.3 36.2 58.1% 57.5% 51.7%
26 SU05F#8 Far 41.0 39.9 36.1 58.6% 57.0% 51.6%
27 SU05N#9 Near 40.6 40.9 36.4 58.0% 58.5% 52.0%
28 SU05T#9 Trans 40.7 40.2 36.2 58.1% 57.4% 51.7%
29 SU05F#9 Far 41.1 39.8 36.1 58.7% 56.9% 51.6%
30 SU05N#10 Near 40.7 40.8 36.4 58.1% 58.3% 51.9%
31 SU05T#10 Trans 40.7 40.1 36.2 58.2% 57.3% 51.7%
32 SU05F#10 Far 41.1 39.7 36.1 58.7% 56.8% 51.5%
33 SU05N#11 Near 40.7 40.8 36.3 58.2% 58.2% 51.9%
34 SU05T#11 Trans 40.8 40.0 36.1 58.2% 57.1% 51.6%
35 SU05F#11 Far 41.2 39.6 36.1 58.8% 56.6% 51.5%
Load CaseFPSO
Position
API RP 2RD Stress (ksi) API RP 2RD Utilization
90
Table 4.6.2 Disconnection Analysis Results of the SLWR – Effective Tensions
Riser Top - Max TDP Area - Min
kips kips
1 EX03NN Near 695.1 77.3
2 EX03FF Far 705.2 79.9
3 SU05N#1 Near 758.5 73.7
4 SU05T#1 Trans 770.2 80.8
5 SU05F#1 Far 784.4 85.1
6 SU05N#2 Near 757 73.1
7 SU05T#2 Trans 769.5 79.7
8 SU05F#2 Far 780.9 84
9 SU05N#3 Near 755.9 72.5
10 SU05T#3 Trans 768.5 78.7
11 SU05F#3 Far 778 82.9
12 SU05N#4 Near 755.2 72
13 SU05T#4 Trans 767.7 77.8
14 SU05F#4 Far 775.3 81.9
15 SU05N#5 Near 744.3 63.6
16 SU05T#5 Trans 748.1 69.4
17 SU05F#5 Far 758.2 73.2
18 SU05N#6 Near 744.1 63.4
19 SU05T#6 Trans 746.5 69.4
20 SU05F#6 Far 758.9 73.1
21 SU05N#7 Near 743.9 63.4
22 SU05T#7 Trans 745.3 69.5
23 SU05F#7 Far 759.8 73
24 SU05N#8 Near 756.1 73.4
25 SU05T#8 Trans 769.9 80.5
26 SU05F#8 Far 780.3 83.4
27 SU05N#9 Near 757.1 74
28 SU05T#9 Trans 772.9 81.3
29 SU05F#9 Far 782.7 84.5
30 SU05N#10 Near 758.3 74.6
31 SU05T#10 Trans 776 82.2
32 SU05F#10 Far 785.5 85.6
33 SU05N#11 Near 759.6 75.2
34 SU05T#11 Trans 779.7 83.2
35 SU05F#11 Far 788.3 86.8
FPSO
Position
Effective Tension
Load Case
91
Chapter 5
Conclusions and Recommendations
5.1 Conclusions
According to the calculation and analysis results obtained in this study, the following
conclusions can be drawn:
1. The simple SCR demonstrated it is not feasible for the FPSO to be developed
in the GoM. Based on the results obtained from the strength analysis,
including the static and regular-wave-based dynamic analysis, significant
compression forces are observed at the riser touchdown area and the combined
stresses are over the limiting design criteria.
2. The nominal global configuration of the SLWR is established by conducting
the static and the regular-wave-based dynamic analysis using Orcaflex. The
total length of the SLWR is 12,710 ft. and the suspended length of the SLWR
is 10,060 ft. All functional requirements and strength criteria specified in API
RP 2RD [6] are satisfied with the designed SLWR.
3. The strength responses of the in-place designed SLWR, to different
environmental factors and vessel motions in all load conditions, are
investigated by analyzing the designed FPSO-SLWR system dynamically with
the regular-wave-based method using Orcaflex. The maximum angular
92
deflection of the flex joint at the riser top is 22.34 degree. The maximum stress
and the maximum stress utilization factor along the riser are both observed at
the flex joint tip and with 270 degree of FPSO position. The maximum stress
is 45.7 ksi for extreme-A load condition, while the maximum stress utilization
is 93.6% for operation-A load condition. The maximum top tension is 1118.9
ksi for extreme-B load condition with 270 degree of FPSO position. The
minimum tension of 4.2 kips is observed at the riser section with BMs
attached and no compression force of the SLWR is observed at all. The
maximum bending moment of 486 kips-ft. is observed at top end of the
SLWR.
4. The extreme-B load condition is selected for SLWR directional analysis. 22.5
degree increment, ranging from 0 to 337.5 degree of the FPSO position, is
applied. The maximum results of the top angular deflection, stress, stress
utilization factor, top tension and bending moment of the SLWR are all
observed at the load case with 270 degree FPSO position. Thus, the FPSO
position of 270 degree is considered as associated with the most severe SLWR
responses.
5. The robustness of the FPSO-SLWR system is demonstrated by the sensitivity
analysis performed for SLWR. Four sensitivity factors are considered: riser
hang-off angle increased and decreased by 1 degree; FPSO offset increased by
93
10%; soil vertical stiffness increased by 10%. According to the analysis results,
the most sensitive factor for the riser response is the increased riser hang-off
angle.
6. In case the SLWR becomes disconnected from the FPSO, the dynamic
responses of the SLWR is investigated and analyzed using Orcaflex. The
integrity of the SLWR, during the disconnection period, is demonstrated. The
maximum stress observed along the SLWR is 42.2 ksi at the riser section
attached with the BMs. The maximum stress utilization factor observed along
the SLWR is 72.5% in extreme load condition, and the maximum top tension
is 788 kips, which is observed at the riser top in survival load condition.
7. The BM arrangement is partially optimized, by analyzing and comparing
the global performances of the SLWRs attached with the BMs in different
material properties, arrangements or attaching positions along the riser. All
arrangement factors vary correspondingly to achieve a constant total buoyancy
force.
In summary, the development, of the FPSO with SLWR in the GoM, is feasible as
indicated from the riser response results obtained in this study.
94
5.2 Recommendations
1. As one of the major conclusions of this study, the feasibility of developing
a FPSO-SLWR operation unit in the GoM is demonstrated according to the
analysis results obtained in the research. However, the feasibility is not
demonstrated conditionally. The fatigue analysis and the
Vortex-Induced-Vibration (VIV) analysis of the designed SLWR are not
conducted in this study. Additional research may be required to indicate
the feasibility of the development more comprehensively.
2. Besides considering the design and the long-term performance of the
SLWR, the uncertainties can also be significantly increased when
considering the risk caused by the SLWR installation in the GoM. For
example, when the entire riser section, with BMs attached, is deployed just
below the water surface, the bending moment and bending strain could
have very critical due to the current-induced force applied on the
large-diameter BMs. The limiting sea states for the SLWR installation in
the GoM could be too low (Hs lower than 1m) to be accepted. Future
corresponding investigations are required to establish the feasibility of
developing FPSO-SLWR in the GoM.
95
References
[1] Subrata K. Chakrabarti, “Drilling and Production Risers” HANDBOOK OF
OFFSHORE ENGINEERING, ISBN-10: 0-080044569-1, 2005, Volume 2, Chapter 9,
pp. 709-854.
[2] Jingyun Cheng, Peimin Cao, “Design of Steel Lazy Wave Riser for Disconnectable
FPSO,” Offshore Technology Conference (2013) 24166
[3] Bin Yue, David Walters, Weiwei Yu, Kamaldev Raghavan and Hugh Thompson,
“Lazy Wave SCR on Turret Moored FPSO,” ISOPE 2011
[4] Ana Lucia F. Lima Torres, Enrique Casaprima Gonzalez, Marcos Queija de
Siqueria, Claudio Marcio Silva Dantas, Marcio Martins Mourelle and Renato Marques
Correia DaSilva, “Lazy-Wave Steep Rigid Risers for Turret moored FPSO,”
Proceedings of OMAE’02-28124, 21st International Conference on Offshore
Mechanics and Artic Engineering pp. 1-2
[5] American Petroleum Institute, “Design, construction, operation and maintenance
of offshore hydrocarbon pipelines”, API RP 1111(3rd ed.), 2009, pp. 5-14
[6] American Petroleum Institute, “Recommended practice for design of risers for
floating production systems (FPSs) and Tension Leg Platforms (TLPs)”, API RP 2RD
(Second ed.), 2006, pp. 5-59
96
[7] Det Norske Veritas, “Submarine Pipeline System,s,” DNV-OS-F101, 2013
[8] Det Norske Veritas, “Dynamic Risers,” DNV-OS-F201, 2001
[9] Orcina Ltd, “OrcaFlex Manual, Version 9.6a,” 2013
[10] Hugh Howell, “Advances in Steel Catenary Riser Design: Advances in Steel
Catenary Riser Design”, DEEPTEC, 02/1995
[11] Ruxin Song, “Gulf of Mexico FPSO Riser System Design Basis Report,” 2013,
Unpublished document
[12] API, “Specifications for Pipe Line,” API 5L (43rd ed.), 2004
[13]Songcheng Li and Chau Nguyen, “Dynamic Response of Deepwater Lazy-Wave
Catenary Riser,” DEEP OFFSHORE TECHNOLOGY INTERNATIONAL, 12/2010
97
APPENDIX A
Results Summary of Regular Wave Analysis in SLWR Approach
1. Summary of SLWR Top Angular Response Results in All Load Cases
Table 1.1 SLWR Top Angular Response Results – Hydrotest A Load Condition
Table 1.2 SLWR Top Angular Response Results – Hydrotest B Load Condition
Table 1.3 SLWR Top Angular Response Results – Operation A Load Condition
Min Max Mean
1 Hydro test A 270 169.71 174.59 172.37 2.59
2 Hydro test A Far 171.24 172.4 171.81 0.76
3 Hydro test A Near 171.35 174.11 172.73 2.11
4 Hydro test A Trans- 171.99 172.78 172.41 0.78
5 Hydro test A Trans+ 172.23 172.69 172.47 0.69
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
6 Hydro test B 270 166.64 172.24 169.74 5.36
7 Hydro test B Far 173.13 174.37 173.71 2.37
8 Hydro test B Near 168.7 172.15 170.5 3.3
9 Hydro test B Trans- 171.69 172.64 172.21 0.64
10 Hydro test B Trans+ 172.24 172.55 172.42 0.55
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
11 Operation A 270 159.13 176.13 169.16 12.87
12 Operation A Far 167.34 178.11 172.8 6.11
13 Operation A Near 163.17 178.11 171.15 6.11
14 Operation A Trans- 171.57 172.94 172.21 0.94
15 Operation A Trans+ 171.17 174.58 172.64 2.58
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
98
Table 1.4 SLWR Top Angular Response Results – Operation B Load Condition
Table 1.5 SLWR Top Angular Response Results – Extreme A Load Condition
Table 1.6 SLWR Top Angular Response Results – Extreme B Load Condition
Min Max Mean
16 Operation B 270 164.72 171.22 168.4 7.28
17 Operation B Far 173.91 175.47 174.68 3.47
18 Operation B Near 167.11 171.39 169.37 0.61
19 Operation B Trans- 171.06 172.39 171.79 0.94
20 Operation B Trans+ 171.95 172.14 172.02 0.14
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
21 Extreme A 270 154.12 176.19 167.45 17.88
22 Extreme A Far 165.3 179.26 172.62 7.26
23 Extreme A Near 157.45 179.55 170.17 14.55
24 Extreme A Trans- 169.82 173.6 171.56 2.18
25 Extreme A Trans+ 170.23 175.82 172.38 3.82
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
26 Extreme B 270 149.66 171.84 161.29 22.34
27 Extreme B Far 174.03 179.04 176.11 7.04
28 Extreme B Near 152.39 171.95 163.35 19.61
29 Extreme B Trans- 169.33 171.96 170.68 2.67
30 Extreme B Trans+ 167.89 173.01 170.63 4.11
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
99
Table 1.7 SLWR Top Angular Response Results – Extreme C Load Condition
Table 1.8 SLWR Top Angular Response Results – Extreme D Load Condition
Table 1.9 SLWR Top Angular Response Results – Survival A Load Condition
Min Max Mean
31 Extreme C 270 159.36 176.23 169.34 12.64
32 Extreme C Far 166.68 177.69 172.28 5.69
33 Extreme C Near 163.47 178.41 171.3 8.53
34 Extreme C Trans- 171.56 172.94 172.22 0.94
35 Extreme C Trans+ 171.15 174.59 172.68 2.59
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
36 Extreme D 270 164.89 171.46 168.61 7.11
37 Extreme D Far 173.52 175.13 174.32 3.13
38 Extreme D Near 167.35 171.63 169.61 4.65
39 Extreme D Trans- 171.08 172.4 171.81 0.92
40 Extreme D Trans+ 171.97 172.16 172.04 0.16
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Min Max Mean
41 Survival A 270 154.31 176.2 167.35 17.69
42 Survival A Far 164.52 179.63 172.43 7.63
43 Survival A Near 157.85 179.83 170.13 7.83
44 Survival A Trans- 169.8 173.68 171.6 2.20
45 Survival A Trans+ 170.27 175.84 172.35 3.84
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
100
Table 1.10 SLWR Top Angular Response Results – Survival B Load Condition
2. Complete Summary of SLWR Stress Results of 3 Riser Sections in All Load
Cases
Table 1.11 SLWR Stress Results at Riser Top – Hydrotest A Load Condition
Table 1.12 SLWR Stress Results at Riser Top – Hydrotest B Load Condition
Min Max Mean
46 Survival B 270 149.7 172.1 161.4 22.30
47 Survival B Far 173.37 179.57 176.07 7.57
48 Survival B Near 152.77 172.26 163.49 19.23
49 Survival B Trans- 169.35 171.99 170.74 2.65
50 Survival B Trans+ 167.94 173.06 170.67 4.06
Load CaseFPSO
Position
Top Angle (degree) Angular
Deflection
Hoop Axial Bend V M
1 Hydro test A 270 42.5 33.9 21.4 42.5
2 Hydro test A Far 42.5 35.5 9.7 42.5
3 Hydro test A Near 42.5 34.5 10.9 41.9
4 Hydro test A Trans- 42.5 32.2 6.9 40.6
5 Hydro test A Trans+ 42.5 30.6 5.8 39.8
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
6 Hydro test B 270 42.5 34.2 25.3 42.0
7 Hydro test B Far 42.5 35.4 12.4 42.5
8 Hydro test B Near 42.5 34.5 12.8 41.9
9 Hydro test B Trans- 42.5 32.2 9.2 40.6
10 Hydro test B Trans+ 42.5 30.6 7.9 40.0
Load Case FPSO Position Riser Top
101
Table 1.13 SLWR Stress Results at Riser Top – Operation A Load Condition
Table 1.14 SLWR Stress Results at Riser Top – Operation B Load Condition
Table 1.15 SLWR Stress Results at Riser Top – Extreme A Load Condition
Hoop Axial Bend V M
11 Operation A 270 34.0 35.6 39.5 43.7
12 Operation A Far 34.0 33.9 25.5 38.9
13 Operation A Near 34.0 35.1 27.2 39.9
14 Operation A Trans- 34.0 33.7 13.1 37.3
15 Operation A Trans+ 33.9 32.5 13.4 36.4
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
16 Operation B 270 33.9 31.7 27.5 35.9
17 Operation B Far 33.9 33.1 13.9 37.2
18 Operation B Near 33.9 31.9 15.0 36.0
19 Operation B Trans- 33.9 29.7 11.8 34.7
20 Operation B Trans+ 33.9 28.0 10.3 34.1
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
21 Extreme A 270 34.0 36.5 45.1 45.9
22 Extreme A Far 34.0 35.7 31.3 42.0
23 Extreme A Near 34.0 36.1 34.6 41.6
24 Extreme A Trans- 34.0 35.3 18.5 38.5
25 Extreme A Trans+ 34.0 34.6 20.7 37.9
Load Case FPSO Position Riser Top
102
Table 1.16 SLWR Stress Results at Riser Top – Extreme B Load Condition
Table 1.17 SLWR Stress Results at Riser Top – Extreme C Load Condition
Table 1.18 SLWR Stress Results at Riser Top – Extreme D Load Condition
Hoop Axial Bend V M
26 Extreme B 270 34.0 38.7 50.5 42.3
27 Extreme B Far 34.0 34.9 33.9 40.3
28 Extreme B Near 34.0 36.0 39.2 40.8
29 Extreme B Trans- 34.0 34.1 20.2 38.0
30 Extreme B Trans+ 33.9 32.3 22.4 37.0
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
31 Extreme C 270 34.0 35.6 39.1 43.7
32 Extreme C Far 34.0 34.1 25.1 39.0
33 Extreme C Near 34.0 35.0 26.8 39.8
34 Extreme C Trans- 34.0 33.7 13.1 37.3
35 Extreme C Trans+ 33.9 32.5 13.3 36.4
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
36 Extreme D 270 33.9 31.6 27.4 35.8
37 Extreme D Far 33.9 33.1 13.5 37.3
38 Extreme D Near 33.9 31.9 14.7 35.9
39 Extreme D Trans- 33.9 29.7 11.7 34.7
40 Extreme D Trans+ 33.9 28.0 10.1 34.1
Load Case FPSO Position Riser Top
103
Table 1.19 SLWR Stress Results at Riser Top – Survival A Load Condition
Table 1.20 SLWR Stress Results at Riser Top – Survival B Load Condition
Table 1.21 SLWR Stress Results at Arch Bend – Hydrotest A Load Condition
Hoop Axial Bend V M
41 Survival A 270 34.0 36.5 44.8 45.9
42 Survival A Far 34.0 35.9 30.7 42.2
43 Survival A Near 34.0 36.1 34.1 41.5
44 Survival A Trans- 34.0 35.1 18.4 38.5
45 Survival A Trans+ 34.0 34.6 20.6 37.9
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
46 Survival B 270 34.0 38.6 50.3 43.0
47 Survival B Far 34.0 35.0 33.4 40.5
48 Survival B Near 34.0 35.9 38.9 40.7
49 Survival B Trans- 34.0 34.1 20.1 38.0
50 Survival B Trans+ 33.9 32.3 22.2 37.0
Load Case FPSO Position Riser Top
Hoop Axial Bend V M
1 Hydro test A 270 40.1 13.4 29.1 42.7
2 Hydro test A Far 40.1 14.1 22.6 40.5
3 Hydro test A Near 40.1 13.3 29.2 42.7
4 Hydro test A Trans- 40.1 13.6 24.8 41.1
5 Hydro test A Trans+ 40.1 13.5 24.4 40.9
Load Case FPSO Position Arch Bend
104
Table 1.22 SLWR Stress Results at Arch Bend – Hydrotest B Load Condition
Table 1.23 SLWR Stress Results at Arch Bend – Operation A Load Condition
Table 1.24 SLWR Stress Results at Arch Bend – Operation B Load Condition
Hoop Axial Bend V M
6 Hydro test B 270 40.1 13.4 28.6 42.6
7 Hydro test B Far 40.1 14.0 23.3 40.8
8 Hydro test B Near 40.1 13.4 28.2 42.4
9 Hydro test B Trans- 40.1 13.6 24.9 41.1
10 Hydro test B Trans+ 40.1 13.5 24.5 40.9
Load Case FPSO Position Arch Bend
Hoop Axial Bend V M
11 Operation A 270 30.9 10.9 32.9 38.7
12 Operation A Far 30.9 12.0 25.0 35.2
13 Operation A Near 30.9 10.9 31.6 38.1
14 Operation A Trans- 30.9 11.3 27.3 36.1
15 Operation A Trans+ 30.9 11.3 26.3 35.6
Load Case FPSO Position Arch Bend
Hoop Axial Bend V M
16 Operation B 270 30.9 10.9 30.3 37.4
17 Operation B Far 30.9 11.7 22.5 34.1
18 Operation B Near 30.9 10.9 30.2 37.3
19 Operation B Trans- 30.9 11.1 25.1 35.0
20 Operation B Trans+ 30.9 11.1 24.7 34.7
Load Case FPSO Position Arch Bend
105
Table 1.25 SLWR Stress Results at Arch Bend – Extreme A Load Condition
Table 1.26 SLWR Stress Results at Arch Bend – Extreme B Load Condition
Table 1.27 SLWR Stress Results at Arch Bend – Extreme C Load Condition
Hoop Axial Bend V M
21 Extreme A 270 30.9 10.9 34.8 39.8
22 Extreme A Far 30.9 12.2 30.1 37.3
23 Extreme A Near 30.9 10.9 16.3 39.3
24 Extreme A Trans- 30.9 11.4 29.4 37.1
25 Extreme A Trans+ 30.9 11.4 27.7 36.4
Arch Bend Load Case FPSO Position
Hoop Axial Bend V M
26 Extreme B 270 30.9 10.9 16.8 39.9
27 Extreme B Far 30.9 12.2 26.4 35.8
28 Extreme B Near 30.9 10.9 32.9 38.6
29 Extreme B Trans- 30.9 11.4 27.4 36.3
30 Extreme B Trans+ 30.9 11.3 26.0 35.5
Load Case FPSO Position Arch Bend
Hoop Axial Bend V M
31 Extreme C 270 30.9 10.8 33.9 39.2
32 Extreme C Far 30.9 12.2 24.7 35.0
33 Extreme C Near 30.9 10.8 33.4 38.9
34 Extreme C Trans- 30.9 11.3 27.2 36.1
35 Extreme C Trans+ 30.9 11.3 26.2 35.6
Arch Bend Load Case FPSO Position
106
Table 1.28 SLWR Stress Results at Arch Bend – Extreme D Load Condition
Table 1.29 SLWR Stress Results at Arch Bend – Survival A Load Condition
Table 1.30 SLWR Stress Results at Arch Bend – Survival B Load Condition
Hoop Axial Bend V M
36 Extreme D 270 30.9 10.9 31.3 37.9
37 Extreme D Far 30.9 10.0 21.7 33.8
38 Extreme D Near 30.9 10.8 31.5 37.9
39 Extreme D Trans- 30.9 11.1 25.1 34.9
40 Extreme D Trans+ 30.9 11.1 24.7 34.7
Load Case FPSO Position Arch Bend
Hoop Axial Bend V M
41 Survival A 270 30.9 10.8 36.2 40.6
42 Survival A Far 30.9 12.5 30.6 37.5
43 Survival A Near 30.9 10.8 35.9 40.3
44 Survival A Trans- 30.9 11.5 29.3 37.2
45 Survival A Trans+ 30.9 11.4 27.6 36.3
Arch Bend Load Case FPSO Position
Hoop Axial Bend V M
46 Survival B 270 30.9 10.8 36.1 40.4
47 Survival B Far 30.9 12.5 26.7 35.8
48 Survival B Near 30.9 10.8 34.6 39.4
49 Survival B Trans- 30.9 11.4 27.4 36.2
50 Survival B Trans+ 30.9 11.3 25.9 35.4
Arch Bend Load Case FPSO Position
107
Table 1.31 SLWR Stress Results at Touchdown Area – Hydrotest A Load Condition
Table 1.32 SLWR Stress Results at Touchdown Area – Hydrotest B Load Condition
Table 1.33 SLWR Stress Results at Touchdown Area – Operation A Load Condition
Table 1.34 SLWR Stress Results at Touchdown Area – Operation B Load Condition
TDP
Arc Length Hoop Axial Bend V M
1 Hydro test A 270 9980 39.4 10.2 14.4 37.5
2 Hydro test A Far 10060 39.4 11.0 11.1 36.9
3 Hydro test A Near 9970 39.4 10.1 14.6 37.5
4 Hydro test A Trans- 10020 39.4 10.4 12.2 37.1
5 Hydro test A Trans+ 10010 40.1 10.4 12.2 37.1
FPSO Position Touchdown Area
Load Case
TDP
Arc Length Hoop Axial Bend V M
6 Hydro test B 270 9990 39.4 10.2 14.1 37.4
7 Hydro test B Far 10050 40.1 10.8 11.4 37.0
8 Hydro test B Near 9980 39.4 10.2 14.0 35.9
9 Hydro test B Trans- 10010 39.4 10.4 12.3 37.1
10 Hydro test B Trans+ 10020 39.4 10.4 12.2 37.1
Load Case FPSO Position Touchdown Area
TDP
Arc Length Hoop Axial Bend V M
11 Operation A 270 10000 30.0 7.6 16.2 30.8
12 Operation A Far 10130 30.0 8.8 11.7 29.7
13 Operation A Near 10010 30.0 7.6 15.8 30.6
14 Operation A Trans- 10030 30.0 8.1 13.4 30.0
15 Operation A Trans+ 10060 30.0 8.0 13.0 29.9
Touchdown AreaLoad Case FPSO Position
TDP
Arc Length Hoop Axial Bend V M
16 Operation B 270 10000 30.0 7.6 14.8 30.3
17 Operation B Far 10100 30.0 8.5 10.7 29.4
18 Operation B Near 10010 30.0 7.5 14.9 30.3
19 Operation B Trans- 10060 30.0 7.9 12.2 29.7
20 Operation B Trans+ 10060 30.0 7.9 12.1 29.7
Touchdown AreaLoad Case FPSO Position
108
Table 1.35 SLWR Stress Results at Touchdown Area – Extreme A Load Condition
Table 1.36 SLWR Stress Results at Touchdown Area – Extreme B Load Condition
Table 1.37 SLWR Stress Results at Touchdown Area – Extreme C Load Condition
Table 1.38 SLWR Stress Results at Touchdown Area – Extreme D Load Condition
TDP
Arc Length Hoop Axial Bend V M
21 Extreme A 270 10000 30.0 7.5 16.9 31.0
22 Extreme A Far 10180 30.0 9.0 12.0 29.7
23 Extreme A Near 9980 30.0 7.5 16.5 30.8
24 Extreme A Trans- 10050 30.0 8.2 14.2 30.2
25 Extreme A Trans+ 10050 30.0 8.1 13.5 30.0
Touchdown AreaFPSO Position Load Case
TDP
Arc Length Hoop Axial Bend V M
26 Extreme B 270 9990 30.0 7.5 17.1 31.1
27 Extreme B Far 10150 30.0 9.0 11.4 29.6
28 Extreme B Near 9990 30.0 7.5 16.3 30.8
29 Extreme B Trans- 10040 30.0 8.1 13.5 30.0
30 Extreme B Trans+ 10060 30.0 8.0 12.9 29.9
Touchdown AreaLoad Case FPSO Position
TDP
Arc Length Hoop Axial Bend V M
31 Extreme C 270 9970 30.0 7.5 16.7 30.9
32 Extreme C Far 10140 30.0 9.0 11.1 29.5
33 Extreme C Near 9980 30.0 7.4 16.5 30.8
34 Extreme C Trans- 10030 30.0 8.1 13.3 30.0
35 Extreme C Trans+ 10070 30.0 8.0 13.0 29.9
Touchdown AreaFPSO Position Load Case
TDP
Arc Length Hoop Axial Bend V M
36 Extreme D 270 9990 30.0 7.5 15.3 30.5
37 Extreme D Far 10140 30.0 8.7 10.3 29.4
38 Extreme D Near 9990 30.0 7.5 15.6 30.5
39 Extreme D Trans- 10060 30.0 7.9 12.1 29.7
40 Extreme D Trans+ 10050 30.0 7.9 12.1 29.7
Touchdown AreaLoad Case FPSO Position
109
Table 1.39 SLWR Stress Results at Touchdown Area – Survival A Load Condition
Table 1.40 SLWR Stress Results at Touchdown Area – Survival B Load Condition
3. Complete Summary of Von Mises Stress and Stress Utilization Results along
Riser Catenary in All Load Cases
Table 1.41 SLWR Von Mises Stress Results – Hydrotest A Load Condition
TDP
Arc Length Hoop Axial Bend V M
41 Survival A 270 9990 30.0 7.4 17.7 31.2
42 Survival A Far 10190 30.0 9.3 11.5 29.6
43 Survival A Near 9980 30.0 7.4 17.6 31.2
44 Survival A Trans- 10040 30.0 8.2 14.1 30.2
45 Survival A Trans+ 10080 30.0 8.2 13.4 30.0
Touchdown AreaFPSO Position Load Case
TDP
Arc Length Hoop Axial Bend V M
46 Survival B 270 9970 30.0 7.4 17.7 31.3
47 Survival B Far 10170 30.0 9.3 10.8 29.5
48 Survival B Near 9970 30.0 7.4 17.2 31.1
49 Survival B Trans- 10040 30.0 8.1 13.4 30.0
50 Survival B Trans+ 10080 30.0 8.0 12.9 29.9
Touchdown AreaLoad Case FPSO Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
1 Hydro test A 270 35.5 42.5 42.7 37.5 42.7
2 Hydro test A Far 29.9 42.5 40.5 36.9 42.5
3 Hydro test A Near 29.9 41.9 42.7 37.5 42.7
4 Hydro test A Trans- 27.9 40.6 41.1 37.1 41.1
5 Hydro test A Trans+ 26.8 39.8 40.9 37.1 40.9
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
110
Table 1.42 SLWR Von Mises Stress Results – Hydrotest B Load Condition
Table 1.43 SLWR Von Mises Stress Results – Operation A Load Condition
Table 1.44 SLWR Von Mises Stress Results – Operation B Load Condition
Table 1.45 SLWR Von Mises Stress Results – Extreme A Load Condition
Riser Top TSJ Ext. Arch Bend TDP Area Max.
6 Hydro test B 270 33.7 42.0 42.6 37.4 42.6
7 Hydro test B Far 28.6 42.5 40.8 37.0 42.5
8 Hydro test B Near 29.3 41.9 42.4 35.9 42.4
9 Hydro test B Trans- 27.4 40.6 41.1 37.1 41.1
10 Hydro test B Trans+ 27.7 40.0 40.9 37.1 40.9
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
11 Operation A 270 39.4 43.7 38.7 30.8 43.7
12 Operation A Far 35.4 38.9 35.2 29.7 38.9
13 Operation A Near 32.9 39.9 38.1 30.6 39.9
14 Operation A Trans- 29.1 37.3 36.1 30.0 25.0
15 Operation A Trans+ 28.0 36.4 35.6 29.9 36.4
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
16 Operation B 270 30.1 35.9 37.4 30.3 37.4
17 Operation B Far 25.7 37.2 34.1 29.4 37.2
18 Operation B Near 26.7 36.0 37.3 30.3 37.3
19 Operation B Trans- 24.1 34.7 35.0 29.7 35.0
20 Operation B Trans+ 25.2 34.1 34.7 29.7 34.7
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
21 Extreme A 270 40.8 45.9 39.8 31.0 45.9
22 Extreme A Far 37.8 42.0 37.3 29.7 42.0
23 Extreme A Near 36.7 41.6 39.3 30.8 41.6
24 Extreme A Trans- 32.5 38.5 37.1 30.2 38.5
25 Extreme A Trans+ 32.2 37.9 36.4 30.0 37.9
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
111
Table 1.46 SLWR Von Mises Stress Results – Extreme B Load Condition
Table 1.47 SLWR Von Mises Stress Results – Extreme C Load Condition
Table 1.48 SLWR Von Mises Stress Results – Extreme D Load Condition
Table 1.49 SLWR Von Mises Stress Results – Survival A Load Condition
Riser Top TSJ Ext. Arch Bend TDP Area Max.
26 Extreme B 270 43.0 42.3 39.9 31.1 43.0
27 Extreme B Far 33.3 40.3 35.8 29.6 40.3
28 Extreme B Near 39.6 40.8 38.6 30.8 40.8
29 Extreme B Trans- 26.4 38.0 36.3 30.0 38.0
30 Extreme B Trans+ 32.9 37.0 35.5 29.9 37.0
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
31 Extreme C 270 39.5 43.7 39.2 30.9 43.7
32 Extreme C Far 35.9 39.0 35.0 29.5 39.0
33 Extreme C Near 33.0 39.8 38.9 30.8 39.8
34 Extreme C Trans- 29.1 37.3 36.1 30.0 37.3
35 Extreme C Trans+ 27.9 36.4 35.6 29.9 36.4
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
36 Extreme D 270 30.1 35.8 37.9 30.5 37.9
37 Extreme D Far 25.5 37.3 33.8 29.4 37.3
38 Extreme D Near 26.5 35.9 37.9 30.5 37.9
39 Extreme D Trans- 24.0 34.7 34.9 29.7 34.9
40 Extreme D Trans+ 25.1 34.1 34.7 29.7 34.7
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
41 Survival A 270 41.0 45.9 40.6 31.2 45.9
42 Survival A Far 38.4 42.2 37.5 29.6 42.2
43 Survival A Near 36.4 41.5 40.3 31.2 41.5
44 Survival A Trans- 32.6 38.5 37.2 30.2 38.5
45 Survival A Trans+ 32.2 37.9 36.3 30.0 41.5
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
112
Table 1.50 SLWR Von Mises Stress Results – Survival B Load Condition
Table 1.51 SLWR API Stress Utilization Factor Results – Hydrotest A Load Condition
Table 1.52 SLWR API Stress Utilization Factor Results – Hydrotest B Load Condition
Table 1.53 SLWR API Stress Utilization Factor Results – Operation A Load Condition
Riser Top TSJ Ext. Arch Bend TDP Area Max.
46 Survival B 270 43.0 42.5 40.4 31.3 43.0
47 Survival B Far 33.0 40.5 35.8 29.5 40.5
48 Survival B Near 39.3 40.7 39.4 31.1 40.7
49 Survival B Trans- 26.4 38.0 36.2 30.0 38.0
50 Survival B Trans+ 32.8 37.0 35.4 29.9 37.0
Max. Von Mises Stress(API, ksi)Load Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
1 Hydro test A 270 56.4% 67.5% 67.8% 59.5% 67.8%
2 Hydro test A Far 47.4% 67.5% 64.3% 58.6% 67.5%
3 Hydro test A Near 47.5% 66.5% 67.8% 59.6% 67.8%
4 Hydro test A Trans- 44.2% 64.4% 65.2% 58.9% 65.2%
5 Hydro test A Trans+ 42.6% 63.2% 64.9% 58.9% 64.9%
Utilization FactorFPSO
Position Load Case
Riser Top TSJ Ext. Arch Bend TDP Area Max.
6 Hydro test B 270 53.5% 66.6% 67.6% 59.4% 67.6%
7 Hydro test B Far 45.4% 67.5% 64.7% 58.7% 67.5%
8 Hydro test B Near 46.4% 66.5% 67.3% 59.4% 67.3%
9 Hydro test B Trans- 43.4% 64.4% 65.2% 58.9% 65.2%
10 Hydro test B Trans+ 44.0% 63.4% 64.9% 58.9% 64.9%
Utilization FactorLoad Case
FPSO
Position
113
Table 1.54 SLWR API Stress Utilization Factor Results – Operation B Load Condition
Table 1.55 SLWR API Stress Utilization Factor Results – Extreme A Load Condition
Table 1.56 SLWR API Stress Utilization Factor Results – Extreme B Load Condition
Table 1.57 SLWR API Stress Utilization Factor Results – Extreme C Load Condition
Riser Top TSJ Ext. Arch Bend TDP Area Max.
11 Operation A 270 84.3% 93.6% 83.0% 65.9% 93.6%
12 Operation A Far 75.9% 83.3% 75.4% 63.5% 83.3%
13 Operation A Near 70.6% 85.5% 81.5% 65.6% 85.5%
14 Operation A Trans- 62.3% 79.8% 77.3% 64.3% 79.8%
15 Operation A Trans+ 60.0% 78.0% 76.3% 64.1% 78.0%
Utilization FactorLoad Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
16 Operation B 270 64.5% 76.8% 80.1% 65.0% 80.1%
17 Operation B Far 55.0% 79.7% 73.1% 62.0% 79.7%
18 Operation B Near 57.3% 77.1% 79.9% 65.0% 79.9%
19 Operation B Trans- 51.6% 74.3% 74.9% 63.6% 74.9%
20 Operation B Trans+ 54.0% 73.1% 74.4% 63.6% 74.4%
Utilization FactorFPSO
Position Load Case
Riser Top TSJ Ext. Arch Bend TDP Area Max.
21 Extreme A 270 72.9% 81.9% 71.1% 55.3% 81.9%
22 Extreme A Far 67.6% 74.9% 66.6% 53.0% 74.9%
23 Extreme A Near 65.4% 74.3% 70.2% 55.0% 74.3%
24 Extreme A Trans- 58.1% 68.7% 66.4% 51.6% 68.7%
25 Extreme A Trans+ 57.6% 67.7% 64.9% 53.6% 67.7%
Utilization FactorLoad Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
26 Extreme B 270 76.8% 75.6% 71.2% 51.3% 76.8%
27 Extreme B Far 59.4% 72.0% 64.0% 52.9% 72.0%
28 Extreme B Near 70.7% 72.9% 68.9% 55.0% 72.9%
29 Extreme B Trans- 47.2% 67.8% 64.7% 53.6% 67.8%
30 Extreme B Trans+ 58.7% 66.0% 63.3% 53.3% 66.0%
Utilization FactorLoad Case
FPSO
Position
114
Table 1.58 SLWR API Stress Utilization Factor Results – Extreme D Load Condition
Table 1.59 SLWR API Stress Utilization Factor Results – Survival A Load Condition
Table 1.60 SLWR API Stress Utilization Factor Results – Survival B Load Condition
Riser Top TSJ Ext. Arch Bend TDP Area Max.
31 Extreme C 270 70.6% 78.0% 70.1% 55.2% 78.0%
32 Extreme C Far 64.1% 69.6% 62.3% 52.7% 69.6%
33 Extreme C Near 59.0% 71.1% 69.4% 55.1% 71.1%
34 Extreme C Trans- 51.9% 66.5% 64.3% 53.6% 66.5%
35 Extreme C Trans+ 49.8% 65.0% 63.6% 53.4% 65.0%
Utilization FactorFPSO
Position Load Case
Riser Top TSJ Ext. Arch Bend TDP Area Max.
36 Extreme D 270 53.8% 64.0% 67.6% 54.4% 67.6%
37 Extreme D Far 45.5% 66.5% 60.3% 52.4% 66.5%
38 Extreme D Near 47.4% 64.2% 67.7% 54.5% 67.7%
39 Extreme D Trans- 42.9% 61.9% 62.4% 53.0% 62.4%
40 Extreme D Trans+ 44.9% 60.9% 62.0% 53.0% 62.0%
Utilization FactorLoad Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
41 Survival A 270 58.6% 65.5% 58.0% 44.6% 65.5%
42 Survival A Far 54.9% 60.2% 53.6% 42.3% 60.2%
43 Survival A Near 52.0% 59.3% 57.6% 44.5% 59.3%
44 Survival A Trans- 46.6% 54.9% 53.1% 43.1% 54.9%
45 Survival A Trans+ 45.9% 54.2% 51.9% 42.8% 54.2%
Utilization FactorLoad Case
FPSO
Position
Riser Top TSJ Ext. Arch Bend TDP Area Max.
46 Survival B 270 61.5% 60.8% 57.8% 44.7% 61.5%
47 Survival B Far 47.1% 57.8% 51.1% 42.2% 57.8%
48 Survival B Near 56.2% 58.1% 56.4% 44.4% 58.1%
49 Survival B Trans- 37.7% 54.3% 51.7% 42.9% 54.3%
50 Survival B Trans+ 46.9% 52.8% 50.6% 42.7% 52.8%
Utilization FactorFPSO
Position Load Case
115
4. Complete Summary of Von Mises Stress and Stress Utilization Results along
Riser Catenary in All Load Cases
Table 1.61 SLWR Maximum Effective Tension Results – Hydrotest A Load Condition
Table 1.62 SLWR Maximum Effective Tension Results – Hydrotest B Load Condition
Table 1.63 SLWR Maximum Effective Tension Results – Operation A Load Condition
Riser Top Arch Bend TDP Area
1 Hydro test A 270 856.4 94.6 75.2
2 Hydro test A Far 914.9 111.2 105.5
3 Hydro test A Near 877.4 86.8 73.7
4 Hydro test A Trans- 790.3 95.6 84.9
5 Hydro test A Trans+ 731.2 86.5 84.3
Max Tension (kips)Load Case
FPSO
Position
Riser Top Arch Bend TDP Area
6 Hydro test B 270 866.5 100.1 77.8
7 Hydro test B Far 914.2 122.7 101.3
8 Hydro test B Near 879.9 94.5 76.3
9 Hydro test B Trans- 791.4 95.6 85.3
10 Hydro test B Trans+ 730.5 90.2 84.4
Load CaseFPSO
Position
Max Tension (kips)
116
Table 1.64 SLWR Maximum Effective Tension Results – Operation B Load Condition
Table 1.65 SLWR Maximum Effective Tension Results – Extreme A Load Condition
Table 1.66 SLWR Maximum Effective Tension Results – Extreme B Load Condition
Riser Top Arch Bend TDP Area
11 Operation A 270 1005.8 109.9 71.6
12 Operation A Far 942.3 153.9 117.2
13 Operation A Near 985.2 98.6 71.4
14 Operation A Trans- 934.8 119.3 91.2
15 Operation A Trans+ 888.1 109.3 89.5
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
16 Operation B 270 857.3 96 73.4
17 Operation B Far 909.4 114.4 108.4
18 Operation B Near 866.3 88.8 70.4
19 Operation B Trans- 782.1 87.9 84.8
20 Operation B Trans+ 718.8 89.6 83.9
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
21 Extreme A 270 1040.2 113.8 70.8
22 Extreme A Far 1007.2 174.2 123.7
23 Extreme A Near 1024.7 102.8 71
24 Extreme A Trans- 992.3 144.4 94.9
25 Extreme A Trans+ 966 130.2 93.7
Load CaseFPSO
Position
Max Tension (kips)
117
Table 1.67 SLWR Maximum Effective Tension Results – Extreme C Load Condition
Table 1.68 SLWR Maximum Effective Tension Results – Extreme D Load Condition
Table 1.69 SLWR Maximum Effective Tension Results – Survival A Load Condition
Table 1.70 SLWR Maximum Effective Tension Results – Survival B Load Condition
Riser Top Arch Bend TDP Area
26 Extreme B 270 1118.9 119.9 69.4
27 Extreme B Far 976.9 174.5 126.3
28 Extreme B Near 1019.4 95.5 68.2
29 Extreme B Trans- 947.8 122.2 92
30 Extreme B Trans+ 881 108.2 89.6
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
31 Extreme C 270 1004.3 104.3 67.9
32 Extreme C Far 946.3 165.5 127.1
33 Extreme C Near 983.1 92.9 66.7
34 Extreme C Trans- 934.7 119.3 91.6
35 Extreme C Trans+ 888.6 109.7 89.6
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
36 Extreme D 270 855.1 91.8 70.5
37 Extreme D Far 912.7 137.3 115.1
38 Extreme D Near 864.6 85 67.3
39 Extreme D Trans- 782.2 95.5 85
40 Extreme D Trans+ 718.7 89.7 84.2
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
41 Survival A 270 1038.8 107.8 66.1
42 Survival A Far 1013.9 191.6 137.1
43 Survival A Near 1022.3 95.8 64.3
44 Survival A Trans- 987.3 144.1 95.6
45 Survival A Trans+ 966.8 131 93.8
Load CaseFPSO
Position
Max Tension (kips)
118
Table 1.71 SLWR Minimum Effective Tension Results – Hydrotest A Load Condition
Table 1.72 SLWR Minimum Effective Tension Results – Hydrotest B Load Condition
Table 1.73 SLWR Minimum Effective Tension Results – Operation A Load Condition
Table 1.74 SLWR Minimum Effective Tension Results – Operation B Load Condition
Riser Top Arch Bend TDP Area
46 Survival B 270 1116.3 117.2 65.9
47 Survival B Far 981.2 187.8 137.5
48 Survival B Near 1017.2 90.2 63.6
49 Survival B Trans- 947.8 123.2 92.4
50 Survival B Trans+ 881.6 109.4 89.5
Load CaseFPSO
Position
Max Tension (kips)
Riser Top Arch Bend TDP Area
1 Hydro test A 270 310.7 47.1 69.1
2 Hydro test A Far 395.2 85.8 92.6
3 Hydro test A Near 412.0 57.9 68.9
4 Hydro test A Trans- 505.7 72.5 81.8
5 Hydro test A Trans+ 568.6 81.1 82.8
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
6 Hydro test B 270 294.2 46.7 70.6
7 Hydro test B Far 388.7 69.4 89.8
8 Hydro test B Near 414.4 57.1 71.2
9 Hydro test B Trans- 503.9 72.2 81.8
10 Hydro test B Trans+ 568.9 77.5 82.8
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
11 Operation A 270 183.7 20.1 61.3
12 Operation A Far 235.2 49.3 87.7
13 Operation A Near 378.2 45.8 63.5
14 Operation A Trans- 309.7 51.3 75.7
15 Operation A Trans+ 385.0 62.1 78.3
Load CaseFPSO
Position
Min Tension (kips)
119
Table 1.75 SLWR Minimum Effective Tension Results – Extreme A Load Condition
Table 1.76 SLWR Minimum Effective Tension Results – Extreme B Load Condition
Table 1.77 SLWR Minimum Effective Tension Results – Extreme C Load Condition
Table 1.78 SLWR Minimum Effective Tension Results – Extreme D Load Condition
Riser Top Arch Bend TDP Area
16 Operation B 270 278.4 42.7 66.6
17 Operation B Far 381.0 86.6 94.6
18 Operation B Near 406.1 53.1 66.2
19 Operation B Trans- 493.7 78.2 81.4
20 Operation B Trans+ 560.9 77.1 82.2
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
21 Extreme A 270 169.8 7.7 58.4
22 Extreme A Far 199.1 25.5 86
23 Extreme A Near 351.4 37.3 60.4
24 Extreme A Trans- 226.2 28.9 71.1
25 Extreme A Trans+ 307.5 49 75.2
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
26 Extreme B 270 134.0 4.5 57.2
27 Extreme B Far 201.3 38 89.2
28 Extreme B Near 403.4 42.8 61
29 Extreme B Trans- 298.1 48.7 75.3
30 Extreme B Trans+ 396.4 64.2 79
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
31 Extreme C 270 185.0 19 58.7
32 Extreme C Far 239.4 52.4 92.7
33 Extreme C Near 375.0 42.9 59.8
34 Extreme C Trans- 310.1 51.6 76
35 Extreme C Trans+ 384.8 62.2 78.7
Load CaseFPSO
Position
Min Tension (kips)
120
Table 1.79 SLWR Minimum Effective Tension Results – Survival A Load Condition
Table 1.80 SLWR Minimum Effective Tension Results – Survival B Load Condition
Table 1.81 SLWR Maximum Moment Results – Hydrotest A Load Condition
Table 1.82 SLWR Maximum Moment Results – Hydrotest B Load Condition
Riser Top Arch Bend TDP Area
36 Extreme D 270 278.4 41.1 64.3
37 Extreme D Far 383.9 77.4 99.1
38 Extreme D Near 404.6 50.6 63.4
39 Extreme D Trans- 493.7 71.7 81.6
40 Extreme D Trans+ 561.4 77.3 82.5
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
41 Survival A 270 170.8 7.1 55.8
42 Survival A Far 203.5 26.9 90.6
43 Survival A Near 346.9 34.6 56.4
44 Survival A Trans- 226.6 29.1 71.4
45 Survival A Trans+ 307.0 49.1 76
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
46 Survival B 270 135.0 4.2 55.1
47 Survival B Far 205.0 40.2 94
48 Survival B Near 399.3 40.2 57.7
49 Survival B Trans- 298.5 49 75.7
50 Survival B Trans+ 396.1 64.3 79.6
Load CaseFPSO
Position
Min Tension (kips)
Riser Top Arch Bend TDP Area
1 Hydro test A 270 205.7 132.9 65.7
2 Hydro test A Far 93.6 103.4 50.7
3 Hydro test A Near 104.8 133.4 66.5
4 Hydro test A Trans- 66.1 113.4 55.9
5 Hydro test A Trans+ 55.6 111.7 55.9
Load CaseFPSO
Position
Bending Moment (kips-ft)
121
Table 1.83 SLWR Maximum Moment Results – Operation A Load Condition
Table 1.84 SLWR Maximum Moment Results – Operation B Load Condition
Table 1.85 SLWR Maximum Moment Results – Extreme A Load Condition
Table 1.86 SLWR Maximum Moment Results – Extreme B Load Condition
Riser Top Arch Bend TDP Area
6 Hydro test B 270 243.6 130.7 64.3
7 Hydro test B Far 118.9 107 51.9
8 Hydro test B Near 123.5 129 64.1
9 Hydro test B Trans- 88.2 113.6 56
10 Hydro test B Trans+ 76.2 111.7 55.9
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
11 Operation A 270 380.2 150.2 73.9
12 Operation A Far 245.6 59.3 53.6
13 Operation A Near 261.4 144.6 72.1
14 Operation A Trans- 126.1 124.6 61.2
15 Operation A Trans+ 129.2 120.2 59.6
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
16 Operation B 270 265 138.4 67.6
17 Operation B Far 134.1 102.8 49
18 Operation B Near 144.6 138 68
19 Operation B Trans- 113.2 114.9 55.5
20 Operation B Trans+ 98.6 112.9 55.3
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
21 Extreme A 270 433.8 159.1 77.2
22 Extreme A Far 300.9 137.6 55.5
23 Extreme A Near 332.4 154.7 75.4
24 Extreme A Trans- 178.2 65.1 64.4
25 Extreme A Trans+ 199.1 126.5 61.7
Load CaseFPSO
Position
Bending Moment (kips-ft)
122
Table 1.87 SLWR Maximum Moment Results – Extreme C Load Condition
Table 1.88 SLWR Maximum Moment Results – Extreme D Load Condition
Table 1.89 SLWR Maximum Moment Results – Survival A Load Condition
Table 1.90 SLWR Maximum Moment Results – Survival B Load Condition
Riser Top Arch Bend TDP Area
26 Extreme B 270 486 160 78.3
27 Extreme B Far 325.6 65.3 52.2
28 Extreme B Near 376.7 150.1 74.5
29 Extreme B Trans- 194.3 125.5 61.5
30 Extreme B Trans+ 215.5 118.9 58.9
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
31 Extreme C 270 376.1 155 76.4
32 Extreme C Far 241 112.7 50.6
33 Extreme C Near 257.3 152.5 75.4
34 Extreme C Trans- 126.2 124.3 61
35 Extreme C Trans+ 128.1 119.9 59.3
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
36 Extreme D 270 263.5 142.9 70
37 Extreme D Far 129.4 99 47.1
38 Extreme D Near 141.6 143.8 71.2
39 Extreme D Trans- 112.2 114.6 55.4
40 Extreme D Trans+ 97.5 112.7 55.2
Load CaseFPSO
Position
Bending Moment (kips-ft)
Riser Top Arch Bend TDP Area
41 Survival A 270 431.3 165.6 80.8
42 Survival A Far 294.9 139.8 52.6
43 Survival A Near 327.9 164.1 80.2
44 Survival A Trans- 177.2 133.7 64.3
45 Survival A Trans+ 197.7 126.1 61.2
Load CaseFPSO
Position
Bending Moment (kips-ft)
123
Riser Top Arch Bend TDP Area
46 Survival B 270 484.1 164.8 80.9
47 Survival B Far 321 110.4 49.5
48 Survival B Near 374.5 158 78.6
49 Survival B Trans- 193.3 125 61.1
50 Survival B Trans+ 213.8 118.5 58.8
Load CaseFPSO
Position
Bending Moment (kips-ft)
Top Related