Session 3: Drilling and Completions - 2H Offshore...Vetco HD H4 wellhead connector (4000 kip-ft @...

Session 3: Drilling and Completions

SPE Workshop

20th October 2011

Shreenaath Natarajan

Drilling Riser Design Challenges and Improving Integrity

Learn more at www.2hoffshore.com


Should we be concerned?



Objectives

• Loading

• Design Issues and Field Problems

• Strength and Fatigue Assessment

• Past Failures

• Integrity Monitoring and Effective Operations Management



Design Challenges

• Uncertainty in soils and currents

• Limited or no data for new regions

• Uncertainty in rig selection

• Want to assess fitness-for-purpose before selection

• Data may not be available

• Lack of guidance on wellhead selection

• Why choose one over another

• Variability in casing programme

• No two programmes are the same

• Variability in soil properties

• Even when data is defined we have to work between bounds



Loading

• Well Construction Loads (Exploration and Development)

• Weight of casing

• Pressure from mud, cement and formation fluids

• Temperature

• Drilling Mode (Exploration and Development)

• Weight of BOP and LMRP

• Loads due to vessel offset

• Wave action and first order vessel motions

• VIV response of riser (currents)



Loading

• Intervention/Workover Mode (Development)

• Loading from drilling riser with horizontal tree in place

• Loading from WO/completion riser (like drilling riser) – applicable on the wellhead and conductor system

• Production Mode (Development)

• Snag loading from fishing gear

• Thermal and pressure loading from well fluids

• Seismic (Development)

BOP

LMRP

Flex-joint

Riser

36” x 1.5” seam welded conductor pipe

36” x 1” seam welded conductor pipe

3.5m 1.5m

6.2m

13m

19m

-10.5m Weld-on connector

Housing extension weld

Tree

HP and LP housing

Riser tension Cyclic loading



Unknowns

• How many slick/buoyant joints to use?

• Optimum top tension to pull?

• Limiting seastate/current loading for drilling operations

• Limiting seastate/current for staying connected to the wellhead with the BOP

• Response time to disconnect riser during mooring line/DP failure

• Strength and fatigue capacity



Operating Envelope

• Minimise rig down time with prior knowledge of field specific operating limits

Shell - Drilling Riser and Conductor AnalysisOPERATING ENVELOPE WITH CURRENT ONLY

300kips Base Tension - 350m WD - 13.6ppg Mud Weight - Operating Pressure

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

-20 -15 -10 -5 0 5 10 15 20

Vessel Offset (% of Water Depth)

Surf

ace

Cu

rren

t V

eloc

ity

(m/s

)

SurvivalFJ Rotation < 90% maxVM / Yield Stress < 1.0Connector Bending MomentLimit < 1.0

Connected (Not Drilling)FJ Rotation < 90% maxVM / Yield Stress < 0.8Connector Bending MomentLimit < 0.8

DrillingFJ Rotation < 2deg (mean)FJ Rotation < 4deg (max)VM / Yield Stress < 0.67

Motion Upstream Motion Downstream

1 Year Current0.1% Ex. CurrentStroke Limit



Operating Envelope

• Minimise rig down time with prior knowledge of field specific operating limits

DYNAMIC DRILLING ENVELOPE 181 Te Base Tension - Mud Filled 1.35SG - Soft Soil Profile

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-8 -6 -4 -2 0 2 4 6 8

Vessel Offset (% of water depth)

Surf

ace

Cu

rren

t V

eloc

ity

(m/s

)

Hs < 3m

Hs < 4m

Hs < 5m

Hs < 6m



Wellhead and Conductor System

• Wellhead and conductor components are integral part of the whole system

• Know the component limits and maximise rig operabilityWhat-Breaks-First Analysis For 350m Water Depth

30in Conductor, Moderate Loading, 300kips Base Tension, 13.6ppg Mud

1.43.3

10.213.9

18.016.6

22.5

9.910.7

5.88.2

8.99.39.3

10.414.0

19.3

9.912.6

20.421.9

18.7

>26.0

>26.0

>26.0

>26.0>26.0>26.0

>26.0

>26.0>26.0>26.0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

upper flex-joint (mean 2deg)lower flex-joint (mean 2deg)

18 3/4" API 10M BOP flange, 5000psi shut-in (bolt makeup=50% σy, 1920 kip-ft)18 3/4" API 10M BOP flange, 3000psi shut-in (bolt makeup=50% σy, 2470 kip-ft)

18 3/4" API 10M BOP flange, mud head (bolt makeup=50% σy, 3063 kip-ft)18 3/4" API 10M BOP flange, 5000psi shut-in (bolt makeup=75% σy, 2870 kip-ft)18 3/4" API 10M BOP flange, 3000psi shut-in (bolt makeup=75% σy, 3700 kip-ft)

18 3/4" API 10M BOP flange, mud head (bolt makeup=75% σy, 4595 kip-ft)

18 3/4" API 5M LMRP flange (1632 kip-ft)

conductor pipe (52ksi)conductor pipe (56ksi)

DrilQuip D60 conductor connector (2440 kip-ft)XLC-S conductor connector (3369 kip-ft)

DrilQuip D90 conductor connector (3660 kip-ft)Vetco RL-4 conductor connector (3800 kip-ft)

Vetco RL-4RB conductor connector (3800 kip-ft)Vetco ALT-2HT conductor connector (4200 kip-ft)

DrilQuip HC-100 conductor connector (5560 kip-ft)Viper conductor connector (7456 kip-ft)

Vetco H4 E wellhead connector (2050 kip-ft @ 5000psi)Vetco ExF H4 wellhead connector (2500 kip-ft @ 5000psi)Cameron HC wellhead connector (3770 kip-ft @ 5000psi)Vetco HD H4 wellhead connector (4000 kip-ft @ 5000psi)DrilQuip DX wellhead connector (6450 kip-ft @ 5000psi)

slip joint/tensioner stroke out (19ft)

lower flex-joint max. rating, upper bound soil (9deg)lower flex-joint max. rating, lower bound soil (9deg)

upper flex-joint max. rating (13.5deg)

LMRP max. release angle, 300kips at LFJ base (10°)

moonpool clearance fore-aft (20.3ft)moonpool clearance port-stdboard (beam in - 12.5ft)

moonpool clearance port-stdboard (beam away - 30ft)

Vessel Offset (% Water Depth)



Fatigue Capacity

• How long can I stay connected to the wellhead

• Do I expect to re-enter the well for intervention/workover?

• Is it possible to extend the drilling duration due to side-tracking of the well?

Shell - Drilling Riser and Conductor Analysis

CONDUCTOR VIV FATIGUE LIFE (UNFACTORED)Fatigue Life At Connector and Welded Connection - 1370m WD

1E-02

1E-01

1E+00

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+08

1E+09

-20 -15 -10 -5 0 5

Elevation above Mudline (m)

Fati

gue

Life

(Y

ears

)

LB Soil

Conductor Coupling Weld

DnV E/SCF=1.3

30" Wellhead

18 3/4" WellheadConductor Pipe

DnV B/SCF=1.0

Conductor Coupling

DnV B/SCF=5.0

Wellhead Housing Weld

DnV E/SCF=1.3

Seabed

30" Conductor LPH HPH BOP

Shell - Drilling Riser and Conductor AnalysisRISER VIV FATIGUE LIFE (UNFACTORED)DnV E Class (SCF 1.3) - 150kips Base Tension

1E+00

1E+02

1E+04

1E+06

1E+08

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

Elevation above Mudline (m)

Fati

gue

Life

(Y

ears

)

LB Soil UB Soil

Seabed

UFJLFJ



Can Failure Happen?

• High pressure housing to surface casing weld fatigue failure

• Facts

• West of Shetland Region

• 440m water depth

• Run from a drill ship

• Fatigue life – 29 days?Censored intentionally



Can Failure Happen?

• Soft soil coupled with large motions

Censored intentionally



Field Problems

• Design Issues

• Inadequate fatigue life, usually VIV driven

• Changes in vessel and riser arrangement

• Field Problems

• External cement shortfall

• Conductor-casing cement shortfall

• Wellhead stick-up

• LP to HP housing lock malfunction

• Extended drilling /workover operations



Conductor and Casing Installation Issues

• Elevation Tolerance

• +2m not uncommon (drilling or jetting)

• Adds to lever arm of loading on wellhead

• Can make VIV response severe

• Inclination Tolerance

• Typical target +/- 1.5degrees

• Expectation less than 0.5degrees due to weight of conductor

• Quality dependent on care during initial penetration

• Vessel position

• Current conditions

• Soil uniformity



Improving System Integrity

• BP Schiehallion – severe currents and high VIV in 350-500m West of Shetland

• BP GoM – severe currents

• BP West Nile Delta VIV (4 well campaign)

• Statoil – old wells, new vessels with big BOP’s and large motions observed

• Total – severe currents and high VIV in 350-500m West of Shetland

• Woodside, Petronas, Repsol, and many others ..

1 LOGGER ON STACK BELOW LOWER FLEX JOINT

5LOGGERS SPACED APPROX .1 EVERY 2 JOINTS

1 LOGGER ON VESSEL

5 LOGGERS SPACED APPROX. 1 EVERY 2 JOINTS



Improving System Integrity

• Norwegian North Sea

• Motions and Fatigue

• West Nile Delta

• Fatigue

• 3 Axis Accelerometer

• Dual axis angular rate

• Loggers located on

• BOP

• Wellhead

• Conductor

• Template

• Magnetic Holders

• ROV Installed



Conclusions

• Design issues due to complex response and lack of prior field specific data can be overcome by the following:

• Develop operating envelopes and incorporate in to a manual

• Observe requirements of the manuals

• Record operating conditions and confirm limits are not exceeded

• Record times on well

• Monitoring riser/wellhead to confirm acceptable fatigue response

• Calibrate analysis software

• Verify design data – soils, currents etc


Session 3: Drilling and Completions - 2H Offshore...Vetco HD H4 wellhead connector (4000 kip-ft @...

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