Post on 05-Apr-2018
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 1/32
GoM Offshore StructuresDesign Criteria
SNAME Texas Section Meeting
Abdel Ghoneim and Craig Colby, DNV Houston
13 Dec 2005
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 2/32
Version Slide 213 December 2005
Agenda:
Fixed New/Existing Platform Criteria
Floating System Environmental Criteria
MODU Station Keeping Design Criteria
Mast / Derrick Foundation Criteria
Pipeline Design/Protection Criteria
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 3/32
Version Slide 313 December 2005
Hurricanes Andrew 1992 & Katrina 2005
© MMS Assessment Workshop 9/23&24/03
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 4/32
Version Slide 413 December 2005
Source: MMS
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 5/32
Version Slide 513 December 2005
Offshore GoM: Hurricane Aftermath
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 6/32
Version Slide 613 December 2005
Summary of Recent Hurricane Damage:
Ivan Katrina Rita
Platforms Destroyed 7 46 65
Platforms Severely Damaged 20 20 32
Rigs Destroyed (JU’s) 1 4 4
Rigs Severely Damaged 4 9 10
Rigs Adrift (Semi’s and JU’s) 5 6 13
Source: MMS
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 7/32
Version Slide 713 December 2005
BP Ivan Platform Damage
Ivan Wave Observations: Pompano:
Observed damage to cable trays at EL (+) 63 ft.
3rd order stream function , 55% of wave above MSL
Estimated wave height = 105 ft assuming 6ft tide & surge.
Ultimate strength analyses correlate to Pompano surviving event.
Ivan Track at Virgo:
Observed damage to cable trays at EL (+) 70 ft. 3rd order stream function , 55% of wave above MSL
Estimated wave height = 116 ft assuming 6ft tide & surge.
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 8/32
Version Slide 813 December 2005
API Offshore Structures Design Practice
API RP 2A 21st edition 2000. Fixed Jackets
- First created in 1969. Major Updates 9th Ed. 1978, 20th Ed. 1993
- Water depth limitation of critieria is 1000 ft linearly extrapolated from 400 ft.
- Specifies 100 year design criteria
API RP 2SK 2nd edition 1996 for Moored Station Keeping
- First edition in 1994
- Derived from
- API 2P in 1987 for mobile offshore units- API 2FP1 in 1993 for floating production systems
- Specifies 100 year design criteria for permanent systems
- Specifies 5 year or 10 year criteria for mobile systems
API RP 2T 2nd edition 1997
- First edition in 1987
- Specifies 100 year criteria
API RP 2FPS 1st Ed. 2001
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 9/32
Version Slide 913 December 2005
API RP-2A Vintage
‘64 ‘69 ‘84 ‘92
1950 1960 1970 1980 1990
‘78 ‘93 ‘97
HildaFailures
CamilleFailures
Juan
Failures
(manned)
AndrewFailures
H u r r i c a n e s
API RP 2A
20th Edition
API RP 2A
1st Edition
API RP 2A
9th Edition
API RP 2A
19th Edition
API RP 2A
Supplement 1
Section 17
I n d
u s t r y
S t a n
d a r d s
D e s i g n
P
r a c t i c e
25- year to 100 -year
Criteria ?
Quality
Joint
Equations
Modern
Design
Code
Reassessment
Activities
(AIM)
Updated
Wave Load
Recipe
Existing
Platform
Assessment
MMS
Inspection
Program
Begins
Pre -RP 2A Early -
RP 2AModern -RP 2A
‘91‘8‘82‘82‘72‘72‘48‘48
‘64 ‘69 ‘84
1950 1960 1970 1980 1990
‘78 ‘93
HildaFailures
CamilleFailures
Juan
Failures
(manned)
AndrewFailures
H u r r i c a n e s
API RP 2A
20th Edition
API RP 2A
1st Edition
API RP 2A
9th Edition
API RP 2A
19th Edition
API RP 2A
Supplement 1
Section 17
I n d
u s t r y
S t a n
d a r d s
D e s i g n
P
r a c t i c e
25- year to 100 -year
Criteria ?
Quality
Joint
Equations
Modern
Design
Code
Reassessment
Activities
(AIM)
Updated
Wave Load
Recipe
Existing
Platform
Assessment
MMS
Inspection
Program
Begins
Pre -RP 2A Early -
RP 2AModern -RP 2A
‘91‘89‘82‘82‘72‘72‘48‘48
MMS Workshop Sept. 23-24, 2003
Pat O’Connor’s Presentation
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 10/32
Version Slide 1013 December 2005
API 2A 100 yr Criteria
API 21st Ed. Fig. 2.3.4-3
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 11/32
Version Slide 1113 December 2005
API RP-2A 20th Edition
1 10 100 1 .103
1 .104
20
40
60
80
100
120
Return Period (Years)
M o s t P r o b a b l e M a x i m u m W a v e H e i g h t ( f t )
Hm
Tr Hm( )OTC-7484 Petrauskas, et. al., 1994
For
MLLW= 400 ft
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 12/32
Version Slide 1213 December 2005
ISO/FDIS 19901-1 Final Draft 9/28/05
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 13/32
Version Slide 1313 December 2005
ISO API Comparison
GoM Design Criteria (ISO Includes Ivan)
Wind (mph): 10 minute 1 Hour
ISO 103 94
API 2A 101 92
Wave: Hmax (ft) Period (s)
ISO 85 14.9 Tp
API 2A 70.5 13 Tm
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 14/32
Version Slide 1413 December 2005
Load Nonlinearity
Jacket Wave Loading
0
1000
2000
3000
4000
5000
6000
7000
40 50 60 70 80
Wave Height (ft)
L a t e r a l F o r c e ( K i p )
MMS Dissemination Meeting 11/15/05 Frank Puskar Presentation
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 15/32
Version Slide 1513 December 2005
ISO Wind Design
500 1000 1500 2000 2500 3000 350040
45
50
55
60
65
Duration (s)
S p
e e d ( m / s )
Uzt t( )
t
3s Gust Local
5s b < 50m
15s b >= 50m
20s + Wave Dyns.
1 min+Wave Mod. Dyns.
1 h Neg. Dyns.
Duration DesignCond.
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 16/32
Version Slide 1613 December 2005
Comparison of Wind Speeds in Lili
MMS Study 469 by RTCI, October 2002
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 17/32
Version Slide 1713 December 2005
API 2SK and API 2T
No design criteria values specified.
Operators case by case specification.
- Deepstar generic criteria
Significant wave heights derived from GUMSHOE and well calibrated.
- Site specific vs. regional criteria
- Sensitivity of site location to historical storm tracks
- Must properly account for pooling of sites due to limited historical base
Hmax, Airgap Specification
Wind models
- More diverse models used in industry.
- Floaters more sensitive to wind force than fixed platform
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 18/32
Version Slide 1813 December 2005
DeepStar Metocean Criteria
Deepstar DSVI CTR 6401-5, July 2004
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 19/32
Version Slide 1913 December 2005
MODU Station Keeping Criteria
Floating MODUs
- Operator Requirements
- API 2SK Recommended Practices- IMO MODU Code
- Classification Society Rules
Jackup MODUs- Operator Requirements
- Marine Warranty Company Requirements
- SNAME
- IMO MODU Code
- Classification Society Rules
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 20/32
Version Slide 2013 December 2005
Hurricane Katrina
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 21/32
Version Slide 2113 December 2005
API RP 2SK
Current criteria
- 100-yr event for permanent, manned, or with restrictions
- 10-yr event for MOU’s in vicinity of other structures
- 5-yr event, otherwise
Upgrade from API 2P in 1987 which specified 99.9% non-exceedance (3 months) to the 5 and 10 years.
Requires one line damage criterion and a transient analysis whenoperating in close proximity of other structures
Studies have been commissioned by MMS and Industry (MMS JIP)
to review the experience during recent hurricanes and proposemodifications to reduce mooring failures and reduce damage tosubsea pilpelins
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 22/32
Version Slide 2213 December 2005
API RP 2T and RP 2FPS
2T:
- 100-yr criterion br referencing RP 2A.
- “The Largest Responses of TLP’s are not necessarily produced by the
highest wave conditions”- Four frequency bands of environmental loads identified:
1. Steady forces: Wind, Current and Wave drift
2. Low Frequency: 1-3 minutes sway, yaw, and surge
3. Wave Frequency: 5-20 s Member and Mooring forces4. High Frequency: 1-5 s
2FPS:
- 100-yr Ref. 2A for Category 1 (>5 year Dev.),- Lower return period for Cat 2 ( 60days-2 years), and Cat. 3 (<= 120 days).
- References 2SK and RCS for Cat.3.
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 23/32
Version Slide 2313 December 2005
IMO MODU Code and RCS
IMO MODU Code- Does not address floating units to any
significance
Classification Society Rules- DNV
- POSMOOR optional class notation – 100 year criteria DNV-OS-E301October 2004
- Extensive update and calibration- New POSMOOR, Drill Rigs, and
NMD- Main class requirements for
inspection of chain / wire every 5
years
- ABS- Refers to Owner’s (API RP’s)- Main class requirements do not
require inspection of chain
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 24/32
Version Slide 2413 December 2005
GOM Regulatory Requirements
USCG
- Compliance with IMO MODU code
- Does not cover station keeping
MMS- Operators/MODUs require MMS permit for drilling operations
- MMS has traditionally focused on API compliance if any invovlement
- Has no jurisdiction on stacked rigs
Nov 17th meeting called by DoI:
- Risk analysis assumptions
- Special performance requirements in deepwater
- Inspection requirements/schedule of mooring systems
- Securing platform rigs
- All L-1?
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 25/32
Version Slide 2513 December 2005
Derrick / Mast Design Criteria
Before Katrina After Katrina
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 26/32
Version Slide 2613 December 2005
API 4F Criteria
First published as 4E in 1970 with 3rd Edition in 1988. 4F 1st Ed. In1985 and 2nd Ed. In 1995.
Derricks are getting larger and larger using dual designs and drilling in
deeper waters and deeper wells.
Wind Criteria:
- 123 mph wind for derricks >140’ in height (107 mph w/ setback)
Wind force calculation methods- Draft for updated wind loading was never adopted since it was proposed
around 2000/2001.
Dynamic derricks account for platform motions. No dynamic effectsrelated to the installation response
No guidelines regarding modeling assumptions especially w.r.t. derrickfootings.
H i IVAN MMS S di
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 27/32
Version Slide 2713 December 2005
Hurricane IVAN – MMS Studies
SCR
PLATFORM (shallow water fixed) (Energo)
CONVENTIONAL RISER
PLATFORM (deepwater
Floater (seafastening, mooring) (OTRC)MODU stationkeeping (ORTC))
Mudslide effects (Lettis & OTRC)
Pipelines (DNV)
Hurricane IVAN: Sept 5, 2004
IVAN GOM production shut-in:
80% - week of Sept 12, 2004
30% - mid October, 2005
10% - early Jan 2005
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 28/32
Version Slide 2813 December 2005
Pipeline Damage – 180 reports Ivan & Mudslides
Damage causedistribution
Submerged
Pipeline
Departing Riser
Receiving Riser
Both Risers
Tie-in
pull apart
riser bent
line dented
line kinked
Unknow
line pulled up
line rupture
twisted/bent
other
Damages
Distribution by
pipeline Type 72
49
43
79
64
24
4
40
7
25
9 5
24 of these
damage reports
noted mudslides
as cause.
I d t F db k
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 29/32
Version Slide 2913 December 2005
Industry Feedback
Include recent hurricanes in the metocean database and updatecriteria accordingly
Problem of MODU’s set adrift by hurricanes is to be addressed
Assess the risks associted with design optimization
Derrick and Mast Specification.
- Often done by drillers
- Only specifies 4F compliance in derrick design
- Engineers with dynamics and motion background often not invovled
Tie Down Study
- MMS Ivan white paper by OTRC focusing on tie downs as weak link.
- Need for more rigorous guidelines/specs.
API OS SC2 R
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 30/32
Version Slide 3013 December 2005
API OS SC2 Response
Re-evaluate Standards
- RP 2A – Fixed Structures
- RP 2T – Tension Leg Platforms- SPEC 4F – Drilling and Well Servicing Structures
- RP 2SK – Station Keeping
Metocean Criteria
- Calculate GoM criteria using various area averaging models
- Update API GoM metocean criteria to reflect latest storm data
- Update ISO Metocean Regional Annex to include Katrina and Rita- Produce background guidance document for design engineers
R d M
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 31/32
Version Slide 3113 December 2005
Road Map:
Understanding levels of safety in standards
Including all hurricane exposures
Reducing future damage Significant differences between hindcast results
High risk of MODU’s going adrift and high potential consequences
Realistic calculation methods
Instrumentation and inspection of critical areas
Verification and certification Experience feedback and follow-up system
Cost sharing and incentives system
7/31/2019 GoM Offshore Structures Design Criteria
http://slidepdf.com/reader/full/gom-offshore-structures-design-criteria 32/32
Version Slide 3213 December 2005