Atul Ganpatye, Kenneth Bhalla May 17, 2009

Weak Point AnalysisDevelopment Driller 2 Drilling Riser on Horizon Lower Stack4992 ft Water Depth (Macondo Site)

Atul Ganpatye, Kenneth Bhalla May 17, 2009

Part 1: Weak Point Analysis – Riser Connected Part 2: Response After DD2 LMRP Disconnection

2

Report LimitationsThe scope of this report is limited to the matters expressly covered. This report is prepared for the sole benefit of BP.

In preparing this report, Stress Engineering Services, Inc. has relied on information provided by BP. Stress Engineering, Inc. has made no independent investigation as to the accuracy or completeness of such information and has assumed that such information was accurate and complete. Further, Stress Engineering Services, Inc. is not able to direct or control the operation or maintenance of the client’s equipment or processes.

All recommendations, findings, and conclusions stated in this report are based upon facts and circumstances as they existed at the time of this report and changes to these may adversely affect the recommendations, findings, and conclusions expressed in this report.

NO IMPLIED WARRANTY MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE SHALL APPLY. STRESS ENGINEERING SERVICES, INC. MAKES NO REPRESENTATION OR WARRANTY THAT THE IMPLEMENTATION OR THE USE OF RECOMMENDATIONS, FINDINGS, OR CONCLUSIONS OF THIS REPORT WILL RESULT IN COMPLIANCE WITH APPLICABLE LAW OR PERFECT RESULTS.

3

PurposePart 1: Weak Point Analysis – Riser Connected

Given that the DD2 riser and stack are installed on the Horizon BOP at Macondo, the aim of this work is to assess riser & well system component strength/integrity in the event of extreme vessel offsets with the riser still connected for the following event(s):

- Drive-Off or a Drift-Off Event- Failure of the Emergency Disconnect System

Determine potential weak-points and approximate critical vessel offsets Determine bending moments and loads on the wellhead and connector Determine the maximum casing stresses

Part 2: Response After DD2 LMRP Disconnection

This part of the analyses was conducted to estimate the response of the casing after the riser has been disconnected at the DD2 LMRP - in light of the fact that some of the soil may have plasticized and can no longer provide lateral support to the casing and the BOP system may be leaning at some angle.

4

Important Assumptions (Weakpoint analysis with riser connected)

It has been assumed that the soil properties are the same as those assumed for earlier project (PN 119681) at SES. This implicitly assumes that the Deepwater Horizon incident have NOT resulted in any localized changes in the soil properties in the vicinity of the well

The wellhead/stack assembly has been assumed to be vertical at the start of the analysis when the vessel is on the well location (zero vessel offset). This precludes the possibility of any plastic (permanent) deformation and subsequent inclination of the casing system following the Deepwater Horizon incident

Damage to the wellhead/wellhead connector has not been accounted for.

5

Additional Assumptions

Global ABAQUS model of: riser, tensioners, telescopic joint, flex joints, casing, wellhead, wellhead connector and soils

Tensioners are assumed to operate at mid-stroke at 0% offset It should be noted that if the tensioners have larger allowable stroke,

the wellhead bending moment and the casing stresses may increase over the mid-stroke case.

Planar offset Weakpoint analysis is quasi-static analysis rather than time

domain Lateral P-Y Soil Response No dynamic vessel motion or seastate is imposed Linear elastic material models utilized

6

General Information

Development Driller 2 drilling riser configuration in 4992-ft (GOM)

Casing program specified per BP Deepwater Horizon BOP Stack on Wellhead Development Driller 2 vessel, tensioners, drilling

riser, LMRP and BOP on top of Deepwater Horizon BOP Stack

8.56 ppg mud weight Tolerance factors of fwt =1.02 and fbt = 0.96

assumed 2 of 12 tensioners subject to failure

7

Riser Configuration (Weight Factors 1.02/0.96 Included)

Please Enlarge

Component Name # of JointsLength

(ft)

Distance of Top of Component

from Mudline (ft)

Outer Diameter

(in)

Wall Thickness

(in)

Bare Joint (Steel)

Dry Weight (lbf)

Buoyancy Module Weight

(lbf)

Lift (lbf)Component/

Joint Dry Weight (lbf)

Component/Joint Wet Weight

(lbf)

Dry Weight per unit length

(lb/ft)

Wet Weightper unit length

(lb/ft)

Low Pressure Housing 1 3.47 10.00 37.260 3.322 2570 2570 2233 741.5 644.4

High Pressure Housing 1 6.63 13.00 27.000 4.245 7881 7881 6849 1189.6 1033.7

Horizon BOP Connector 1 6.33 16.64 66.000 23.625 28600 28600 24853 4518.2 3926.3

Horizon BOP 1 24.05 40.69 50.000 15.625 306715 306715 266535 12753.2 11082.6

DD2 BOP Connector 1 5.73 43.73 66.000 23.625 28600 28600 24853 4990.5 4336.8

DD2 BOP 1 30.70 74.44 50.000 15.625 451400 451400 392267 14701.6 12775.7

DD2 LMRP 1 12.43 85.07 50.000 15.625 298082 298082 259033 23982.4 20840.7

Lower Flex Joint 1 0.00 85.07

Riser Adaptor 1 10.18 95.25 21.000 0.8750 1918 0.00 0.000 1918 1667 188.4 163.8

Bare w/ 1 x 7500 Buoyancy Module 9 675.00 770.25 21.000 0.8750 31154 3640 3840 35417 23928 472.2 319.0

Bare w/ 1 x 5500 Buoyancy Module 2 150.00 920.25 21.000 0.8130 30239 3479 3999 34323 22964 457.6 306.2

7500 ft Buoyancy Joint 12 900.00 1820.25 21.000 0.8750 30459 21840 23040 52908 4880 705.4 65.1


Stagg w/ 1 x 5500 ft Buoyancy Module 6 900.00 4670.25 21.000 0.8130 59783 24353 27993 85332 26117 568.9 174.1

Bare w/ 1 x 5500 ft Buoyancy Module 2 150.00 4820.25 21.000 0.8130 30239 3479 3999 34323 22964 457.6 306.2


50 ft Pup Joint 1 50.00 4945.25 21.000 0.8750 21101 0.00 0.00 21523 18704 430.5 374.1

10 ft Pup Joint 1 10.00 4955.25 21.000 0.8750 7656 0.00 0.00 7809 6786 780.9 678.6

TJ OB Below Water 1 36.76 4992.00 26.000 0.812 30581.84 0.00 0.00 31193 27107 848.7 737.5

TJ OB Above Water/Below Ring 1 24.60 5016.60 26.000 0.812 20469.71 20879 20879 848.7 848.7

Tensioner Ring 1 2.08 5018.685 81.000 27.500 19863.43 20261 20261 9725.1 9725.1

TJ OB Above Ring 1 6.46 5025.15 26.000 0.812 5375.02 5483 5483 848.7 848.7

TJ IB up to Upper Flex Joint 1 40.94 5066.09 21.000 0.625

Upper Flex Joint 1 3.05 5069.13 21.000 0.6250

Diverter & Drill Floor 1 10.45 5079.58 100.000 40.250

Inner Barrel Stroke = 32.20 25

Total available stroke = 60.00

8

Riser Configuration

Schematic

Horizon BOP/Lower Stack (NO LMRP)

Telescopic Jt (TJ) Outer Barrel

Mean Water Line

Tension Ring

TJ Inner Barrel

Drill Floor

Mudline (0.00 ft)

85.07 ft (lower flex joint) +/- 10-deg, 68000 ft-lbf/deg

4992.00 ft

5018.69 ft

5025.15 ft

5065.24 ft (tensioner suspension points)

5079.58 ft

5066.09 ft (upper flex joint) +/- 15-deg, 6500 ft-lbf/deg

75 ft Bare Jt w/ 1 x 7500 Buoyancy Module (9)

4945.25 ft

1820.25 ft

770.25 ft

3770.25 ft

50 ft Pup Jt (1)

75 ft 5500 ft Rated Buoyancy Jt (26)


10 ft Pup Jt (1)

4955.25 ft

DD2 LMRP + BOP

43.73 ft

13.0 ft Wellhead (HP Housing) Stickup


920.25 ft

150 ft Stagg w /1 x 5500 ft Buoyancy Module (6)

75 ft Bare Jt w /1 x 5500 ft Buoyancy Module (2)

4670.25 ft

4820.25 ft


4895.25 ft

Horizon BOP/Lower Stack (NO LMRP)

Telescopic Jt (TJ) Outer Barrel

Mean Water Line

Tension Ring

TJ Inner Barrel

Drill Floor

Mudline (0.00 ft)

85.07 ft (lower flex joint) +/- 10-deg, 68000 ft-lbf/deg

4992.00 ft

5018.69 ft

5025.15 ft

5065.24 ft (tensioner suspension points)

5079.58 ft

5066.09 ft (upper flex joint) +/- 15-deg, 6500 ft-lbf/deg


4945.25 ft

1820.25 ft

770.25 ft

3770.25 ft

50 ft Pup Jt (1)



10 ft Pup Jt (1)

4955.25 ft

DD2 LMRP + BOP

43.73 ft

13.0 ft Wellhead (HP Housing) Stickup


920.25 ft

150 ft Stagg w /1 x 5500 ft Buoyancy Module (6)

75 ft Bare Jt w /1 x 5500 ft Buoyancy Module (2)

4670.25 ft

4820.25 ft


4895.25 ftDevelopment Driller 2 Riser and Stack on Deepwater Horizon BOP.

The riser configuration does not include a subsea tree

9

DD2 Stack Used in the Analysis

Dry weights:

LMRP (including riser adapter): 257 kips

BOP (including connector): 480 kips

Total BOP + LMRP = 737 kips

Weight left on Horizon Lower BOP after DD2 LMRP disconnection = 480 kips

Reference : Email from Mark Heironimus, dated Tuesday May 11th 2010 (10:48 am)

10

Horizon Stack Used in the Analysis

11

Horizon Stack Used in the Analysis

12

Wellhead Details

SS-15

HP Housing

SS-15

LP Housing

18.75" HP 36.00" LP

OD (in) 27.00 36.00

ID (in) 18.51 33.00

Length (ft) 6.63 3.75

Weight (lbf/ft) 1189.6 553.2

13

Casing Information

Component NameLength

(ft)

Location of Top from Mudline

(ft)

Location of Bottom from Mudline (ft)

Material Definition

Outer Diameter

(in)

InnerDiameter

(in)

Wall Thickness

(in)

Dry Weight per unit length (lb/ft)

Wet Weight per unit length (lb/ft)

36" x 2" (X-65) 121 6.53 -114 X-65 36.00 32.00 2.000 726.93 631.99

36" x 1.5" (X-56) 166 -114 -280 X-56 36.00 33.00 1.500 553.22 480.97

28" x 0.75" (X-52) 280 0.00 -280 X-52 28.00 26.50 0.750 218.27 189.76

22" x 1.0" (X-80) 286 6.38 -280 X-80 22.00 20.00 1.000 224.28 194.99

14

Soils API RP2A P-Y curves are developed from the soil

shear strength, submerged unit weight and 50. Soil data is assumed per:

From: Jeanjean, Philippe [mailto:[email protected]] Sent: Friday, February 27, 2009 2:48 PMTo: Scherschel, Craig; Todd VeselisCc: Karlsen, Geir G (Clover)Subject: RE: Macundo Soil DataTodd,I have confirmed with Craig that the seismic section he sent is representative of ALL the anchor locations. Based on BP's database of soil borings in the area (Na Kika, Horn Mountain, Pompano), I would propose the following soil properties for your analysis: Undisturbed shear strengthDepth (ft) Su (psf) 0 3010 50100 700Use a sensitivity of 2.0 to calculate the remolded shear strength. Depth (ft) Submerged unit weight (pcf)0 2030 37 100 43

15

PART 1Weak Point Analysis – Riser Connected

16

Case MatrixCase No. Initial Vertical Slip Ring Tension at 0 ft Vessel Offset

Case 1

Minimum vertical slip ring tension for 8.56 ppg mud 1.02/0.96 factors

1018 kips for 50 kips minimum overpull on LMRP

Corresponding Tensioner Setting: 1071 kips

Case 2Intermediate vertical slip ring tension of 1425 kips

Corresponding Tensioner Setting: 1500 kips

Case 3Maximum vertical slip ring tension of 2565 kips

Corresponding Tensioner Setting: 2700 kips (90% of DTL)

Tension setting for Case 2 is based on this

Tension calculations were based on 4992 ft water depth; plus, the added height of the Horizon BOP results in a slightly different riser configuration.

Therefore, the tensions in the above table may not match the values in the report provided by BP

17

Results Summary

Case Number

Initial Slip Ring Tension at 0 ft Vessel Offset

(kips)

Vessel Offset at which the

Tensioners Bottom Out

(% of water depth)

Vessel Offset at which the von Mises Stress in the TJ Outer Barrel

Below the Tension Ring Exceeds Yield

(% of water depth)

von Mises Stress in the 36” x 2” (X-

65) Casing when the Stress in the TJ

Outer Barrel Exceeds Yield

(ksi)

Maximum Wellhead

Bending Moment

(DD2 BOP Connector)

(106 ft-lbf)

Maximum Wellhead Bending

Moment

(Horizon BOP-to-Wellhead

Connector)

(106 ft-lbf)

CASE 1 1018 11 1159.4

@ 11% vessel offset

3.30

@ 10% vessel offset

6.37

@ 10% vessel offset

CASE 2 1425 11 1159.4

@ 11% vessel offset

2.94

@ 10% vessel offset

5.83

@ 10% vessel offset

CASE 3 2565 11 1159.9

@ 11% vessel offset

1.98

@ 10% vessel offset

4.38

@ 10% vessel offset

18

Load Capacity Envelope: SS15 Wellhead System

19

Wellhead Capacity

High and Low Pressure Housing Wellhead is Dril-Quip SS-15 System SS-15 is rated for 4 million ft-lb (15-ksi pressure and

1500-kips tension) at 2/3 yield : Working Capacity SS-15 is rated for 6 million ft-lb (15-ksi pressure and

1500-kips tension) at yield : Survival Capacity

20

@ 15 ksi pressure, 1500 kips tension: 4.0 million ft-lbf

Based on Typical “H-4” Profile Connector at 2/3 Yield

HD-H4 Connector or SHD-H4 with adapter kit - Capacity

@ 15 ksi pressure, 1500 kips tension: 6.0 million ft-lbf

Based on Typical “H-4” Profile Connector at Yield

21

RISER CONFIGURATION:Elevation from

Mudline (ft)

Mud Weight, ppgVertical Tension at Top of Ring (at zero offset), kips 5018.68

Tensioner/Wire Rope Stroke, ft

Bottom Boundary Condition -280.00Top Boundary Condition 5066.09Tensioner Stiffness, before stroke outTensioner Stiffness, After stroke outSurface Current, ktOUTPUT:Vessel Offset, % water depth 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

Tensions and Deflections

Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.4 29.1 31.4 34.1 37.2 40.9 45.0 49.35 49.43 49.48Effective Tension at Top of Ring, kips 5018.68 1003 1005 1009 1017 1027 1040 1055 1073 1093 1116 1178 2436 4171Effective Tension at Top of DD2 LMRP, kips 85.07 295 296 301 309 319 332 348 366 387 411 473 1743 3395Effective Tension at Top of the Connector, kips 43.73 -312 -310 -306 -298 -287 -274 -258 -240 -218 -193 -130 1141 2794Effective Tension at Bottom of the Connector, kips 38.00 -350 -348 -344 -336 -325 -312 -296 -277 -256 -231 -168 1104 2757Effective Tension at Top of the HPHSG, kips 13.00 -85 -85 -84 -84 -83 -81 -80 -78 -76 -74 -67 55 214Actual Tension at Top of DD2 LMRP, kips 85.07 185 187 191 199 210 223 239 257 278 301 364 1633 3286Actual Tension at Top of Connector, kips 43.73 -7231 -7230 -7225 -7217 -7207 -7194 -7178 -7159 -7137 -7113 -7050 -5779 -4126Actual Tension at Bottom of Connector, kips 38.00 -4058 -4056 -4051 -4043 -4033 -4020 -4004 -3985 -3964 -3939 -3876 -2604 -951Actual Tension at Bottom of HPHSG, kips 6.37 -1022 -1021 -1019 -1014 -1008 -1000 -991 -980 -967 -952 -915 -168 802Upper Flex Joint Angle, deg 5066.09 0.00 -0.35 -0.70 -1.05 -1.41 -1.77 -2.13 -2.51 -2.89 -3.27 -3.58 -2.42 -2.22LMRP Angle relative to vertical, deg 85.07 0.00 0.37 0.78 1.24 1.77 2.37 3.06 3.83 4.68 5.58 6.55 7.35 7.84Lower Flex Joint Angle, deg 85.07 0.00 0.59 1.14 1.62 2.03 2.34 2.55 2.65 2.65 2.57 2.19 0.02 -0.39Angle of Riser at sea bed, deg 0.00 0.00 0.30 0.63 1.02 1.47 1.99 2.60 3.30 4.06 4.89 5.79 6.75 7.45Displacement of Riser at sea bed, ft 0.00 0.00 0.15 0.32 0.54 0.81 1.16 1.60 2.13 2.76 3.47 4.32 6.02 8.03

Bending Moments (MM ft-lb)

36" x 2" Casing (X-65) 6.53 to -114 0.00 0.61 1.26 1.96 2.72 3.55 4.44 5.38 6.37 7.39 8.42 8.82 8.8636" x 1.5" Casing (X-56) -114 to -280 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.05 0.22 1.22 3.19Low Pressure Housing 6.53 to 10.00 0.00 0.39 0.79 1.20 1.62 2.05 2.49 2.93 3.38 3.81 4.20 3.45 2.42High Pressure Housing Just Below Connector 6.37 to 13.00 0.00 0.60 1.21 1.83 2.48 3.13 3.80 4.47 5.14 5.79 6.37 5.16 3.53Total Moment at HPHSG-Connector Interface 11.59 0.00 0.59 1.19 1.80 2.43 3.08 3.73 4.39 5.04 5.68 6.24 5.04 3.42Top of BOP+LMRP 85.07 0.00 0.04 0.08 0.11 0.14 0.16 0.17 0.18 0.18 0.17 0.15 0.00 0.03Outer Barrel at Bottom of Tension Ring 5015.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

"WEAK" POINTS (Von-Mises combined stress, ksi)

36" x 2" Casing (65 ksi) 6.53 to -114 3.8 7.3 11.4 16.0 21.0 26.4 32.2 38.4 44.9 51.5 58.2 59.4 64.436" x 1.5" Casing (56 ksi) -114 to -280 4.6 4.6 4.6 4.7 4.9 5.1 5.3 5.6 5.8 6.0 6.1 11.8 34.228" x 0.75" Casing (52 ksi) 9.37 to -314 4.6 6.5 9.8 13.5 17.4 21.7 26.4 31.4 36.6 41.9 47.2 47.9 52.8Bottom of the Riser Adapter 85.07 4.5 6.1 7.8 9.3 10.6 11.8 12.6 13.2 13.6 13.8 13.8 30.5 61.4Outer Barrel at Bottom of Tension ring 5015.80 15.3 15.4 15.6 15.8 16.0 16.3 16.7 17.1 17.5 18.0 23.3 175.8 358.4

4992-ft Water Depth; Development Driller 2, GOMTop of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline

8.561018

Maximum Tensioner stroke = 50-ftAvailable Tensioner stroke =25-ft

Tensioner Strokeout = 25-ft

PinnedPinned

NonlinearRigid0.00

Detailed Results – Case 1

22

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10 11 12

Offset, % of Water Depth

Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)

Low Pressure Housing

High Pressure HousingJust Below Connector

Variation of Bending Moment

Development Driller 2; 4992-ft Water Depth; GOMInitial Tension = 1018-kips (vertical slip ring tension) & Mud Weight =8.56-ppg

Detailed Results – Case 1Wellhead Connector Bending Moment

Wellhead Bending Moment = 6.37 million ft-lb

23

Detailed Results – Case 1Casing Stresses

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si

36" x 2" Casing(65 ksi)

36" x 1.5"Casing (56 ksi)

28" x 0.75"Casing (52 ksi)

Variation of Maximum von-Mises Equivalent Stress in Casing


24

Detailed Results – Case 2RISER CONFIGURATION:

Elevation from Mudline (ft)





Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.3 29.0 31.1 33.7 36.8 40.4 44.4 48.86 49.39 49.44Effective Tension at Top of Ring, kips 5018.68 1411 1413 1419 1429 1442 1460 1480 1505 1532 1564 1599 2867 4593Effective Tension at Top of DD2 LMRP, kips 85.07 702 704 710 720 734 752 773 798 826 858 894 2146 3797Effective Tension at Top of the Connector, kips 43.73 95 97 103 114 128 146 167 193 222 254 291 1544 3196Effective Tension at Bottom of the Connector, kips 38.00 57 59 65 76 90 108 129 155 184 216 253 1506 3158Effective Tension at Top of the HPHSG, kips 13.00 -46 -46 -45 -44 -43 -41 -39 -36 -34 -30 -27 94 253Actual Tension at Top of DD2 LMRP, kips 85.07 592 594 600 611 625 643 664 688 717 749 785 2036 3688Actual Tension at Top of Connector, kips 43.73 -6824 -6822 -6816 -6805 -6791 -6773 -6752 -6727 -6698 -6665 -6628 -5376 -3724Actual Tension at Bottom of Connector, kips 38.00 -3650 -3648 -3642 -3632 -3617 -3600 -3578 -3553 -3524 -3491 -3454 -2202 -550Actual Tension at Bottom of HPHSG, kips 6.37 -784 -782 -779 -773 -764 -754 -741 -726 -709 -690 -668 68 1038Upper Flex Joint Angle, deg 5066.09 0.00 -0.41 -0.83 -1.24 -1.66 -2.07 -2.49 -2.91 -3.34 -3.77 -4.20 -2.98 -2.62LMRP Angle relative to vertical, deg 85.07 0.00 0.44 0.92 1.46 2.05 2.70 3.40 4.15 4.93 5.73 6.56 7.27 7.77Lower Flex Joint Angle, deg 85.07 0.00 0.32 0.61 0.83 1.00 1.11 1.16 1.16 1.11 1.02 0.89 -0.12 -0.40Angle of Riser at sea bed, deg 0.00 0.00 0.36 0.76 1.21 1.73 2.31 2.94 3.63 4.34 5.10 5.87 6.73 7.42Displacement of Riser at sea bed, ft 0.00 0.00 0.18 0.40 0.68 1.02 1.43 1.93 2.50 3.13 3.83 4.60 6.24 8.27





PinnedPinned

NonlinearRigid0.00


8.561425



25

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10 11 12


Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)







26


0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si



28" x 0.75"Casing (52 ksi)



27

Detailed Results – Case 3RISER CONFIGURATION:






Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.2 28.8 30.9 33.4 36.4 39.8 43.7 48.07 49.33 49.39Effective Tension at Top of Ring, kips 5018.68 2551 2555 2566 2584 2608 2639 2677 2720 2769 2825 2887 3975 5657Effective Tension at Top of DD2 LMRP, kips 85.07 1840 1844 1855 1874 1899 1931 1969 2012 2062 2119 2182 3269 4910Effective Tension at Top of the Connector, kips 43.73 1234 1238 1249 1267 1293 1325 1363 1408 1458 1515 1579 2667 4308Effective Tension at Bottom of the Connector, kips 38.00 1196 1200 1211 1229 1255 1287 1325 1370 1420 1477 1541 2629 4270Effective Tension at Top of the HPHSG, kips 13.00 64 64 65 67 69 73 76 81 85 91 97 202 360Actual Tension at Top of DD2 LMRP, kips 85.07 1731 1735 1746 1764 1789 1821 1859 1903 1953 2009 2072 3159 4800Actual Tension at Top of Connector, kips 43.73 -5685 -5682 -5670 -5652 -5626 -5594 -5556 -5512 -5461 -5405 -5341 -4253 -2612Actual Tension at Bottom of Connector, kips 38.00 -2512 -2508 -2497 -2478 -2453 -2420 -2382 -2338 -2287 -2230 -2167 -1079 562Actual Tension at Bottom of HPHSG, kips 6.37 -115 -113 -107 -96 -81 -62 -39 -13 17 50 88 727 1690Upper Flex Joint Angle, deg 5066.09 0.00 -0.48 -0.96 -1.43 -1.91 -2.38 -2.85 -3.33 -3.80 -4.28 -4.75 -3.98 -3.44LMRP Angle relative to vertical, deg 85.07 0.00 0.52 1.07 1.67 2.30 2.96 3.64 4.33 5.04 5.75 6.46 7.10 7.61Lower Flex Joint Angle, deg 85.07 0.00 0.13 0.23 0.28 0.31 0.30 0.26 0.21 0.14 0.06 -0.04 -0.29 -0.41Angle of Riser at sea bed, deg 0.00 0.00 0.43 0.91 1.43 2.00 2.61 3.25 3.90 4.57 5.26 5.95 6.69 7.35Displacement of Riser at sea bed, ft 0.00 0.00 0.23 0.52 0.88 1.32 1.82 2.40 3.04 3.74 4.50 5.33 6.87 8.94





PinnedPinned

NonlinearRigid0.00


8.562565



28

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9 10 11 12


Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)







29


0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si



28" x 0.75"Casing (52 ksi)



30

PART 2Response After DD2 LMRP Disconnection

31

Two scenarios were considered for this analysis: No initial wellhead/casing inclination 1 deg initial wellhead/casing inclination

For each scenario, four cases were considered: 0 ft of soil removed 44 ft of soil removed 54 ft of soil removed 70 ft of soil removed

A 0.3 knot background current was assumed for all cases

Cases Considered

32

Results: No Initial InclinationNo Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios

0.3 knot Background Current

-200

-150

-100

-50

0

50

100

-0.025 0 0.025 0.05 0.075 0.1 0.125 0.15 0.175 0.2 0.225 0.25

Lateral Displacement (ft)

Dis

tanc

e from

Mud

line

(ft)

No Initial Inclination Lateral Displacement Profile at 0 ft Vessel Offset - Riser Connected

After DD2 LMRP Disconnection - 0 ft Soil Removed




Stack Angle Relative to Vertical = 0.01 deg




Mudline

33

Results: 1 deg Initial Inclination1 deg Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios

0.3 knot Background Current; Initial Wellhead/Casing Inclination of 1 degree

-280

-230

-180

-130

-80

-30

20

70

120

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10


Dis

tanc

e from

Mud

line

(ft)

1 deg Initial Inclination Lateral Displacement Profile at 0 ft Vessel Offset - Riser Connected









Mudline

34

Conclusions For the GOM site (4992-ft), with the Development Driller 2 Drilling Riser and

Stack on top of Horizon BOP, the following can be concluded: PART 1 (Weakpoint Analysis – Riser Connected):

The working capacity of the SS15 wellhead system (4 million ft-lbf) is exceeded for all three cases analyzed. However, the survival capacity of the wellhead (6 million ft-lbf) is NOT exceeded for CASE 2 and CASE 3. The survival capacity is exceeded for CASE 1 (minimum tension for 8.56 ppg mud).

The conductor casing yields after the tensioners bottom out and after the riser potentially fails in the outer barrel below the tension ring. Thus, the integrity of the casing is NOT compromised.

PART 2 (After DD2 LMRP Disconnection): In the scenario where the wellhead/casing is initially assumed to be vertical, the

inclination of the BOP system (Horizon BOP + DD2 BOP) is not significant. In the case where the wellhead/casing is assumed to be inclined at an angle of 1-deg

initially, the angle of inclination of the BOP system after disconnection could be as high as 4.3 deg, based on an assumption of 70 ft of soil being plasticized.

All recommendations, findings, and conclusions stated in this report are based upon facts and circumstances as they existed at the time of this report and changes to these may adversely affect the recommendations, findings, and conclusions expressed in this report.

35

Results with Updated Soils Data(doubled soil undrained shear strength and used API 2A-WSD lateral

resistance-deflection relationship for short term static load case: per suggestion from Philippe Jeanjean)

36

Soil Data

(Note: values at 280 ft penetration depth are linearly extrapolated from values given at 10 ft and 100 ft)

Lateral resistance-deflection relationship comparison (shown for example at 10 ft penetration depth)

0

1

2

3

4

5

6

0 5 10 15 20 25 30 35 40

Displacement (inch)L

ate

ral

Re

sis

tan

ce

(p

si)

Old Soil Data

New Soil Data

0

50

100

150

200

250

300

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Undrained Shear Strength (psf)

Pen

etra

tio

n D

epth

(ft

)

Old Soil Data

New Soil Data

Penetration Depth

(ft)

OLDUndrained

Shear Strength (psf)

NEWUndrained

Shear Strength (psf)

0 30 6010 50 100100 700 1400280 2000 4000

37

Results Summary – Updated Soil Data

Case Number

Initial Slip Ring Tension at 0 ft Vessel Offset

(kips)

Vessel Offset at which the

Tensioners Bottom Out

(% of water depth)

Vessel Offset at which the von Mises Stress in the TJ Outer Barrel

Below the Tension Ring Exceeds Yield

(% of water depth)

von Mises Stress in the 36” x 2” (X-

65) Casing when the Stress in the TJ

Outer Barrel Exceeds Yield

(ksi)

Maximum Wellhead Bending Moment

(DD2 BOP Connector)

(106 ft-lbf)

Maximum Wellhead Bending

Moment

(Horizon BOP-to-Wellhead

Connector)

(106 ft-lbf)

CASE 1B 1018 11 1162.9

@ 11% vessel offset

3.60

@ 11% vessel offset

7.02

@ 11% vessel offset

CASE 2B 1425 11 1164.3

@ 11% vessel offset

3.39

@ 11% vessel offset

6.73

@ 11% vessel offset

CASE 3B 2565 11 1167.4

@ 11% vessel offset

3.15

@ 10% vessel offset

6.22

@ 10% vessel offset

(Note: analysis assumes linear elastic material properties; stress values above yield are because of this assumption)

38

Bending Moment Distribution Near Mudline

-100

-75

-50

-25

0

25

50

75

100

-13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

Bending Moment (million lbf-ft)

Dis

tanc

e fr

om M

udlin

e (f

t)

Bending Moment Distribution;CASE 1B; 11% Vessel Offset



DD2 LMRP-to-BOP Connector (0.5 million lbf-ft)

DD2 BOP-to-Horizon BOP Connector (3.6 million lbf-ft)

Horizon BOP-to-Wellhead Connector (7.0 million lbf-ft)

Bending moment distribution near the mudline for Cases 1B, 2B, and 3B

(respective offsets corresponding to the maximum bending moment considered)

39

RISER CONFIGURATION:Elevation from

Mudline (ft)





Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.4 29.1 31.4 34.1 37.3 41.0 45.1 49.36 49.43 49.49Effective Tension at Top of Ring, kips 5018.68 1003 1005 1009 1017 1027 1040 1055 1073 1094 1117 1200 2472 4217Effective Tension at Top of DD2 LMRP, kips 85.07 295 296 301 309 319 332 348 367 388 412 496 1780 3451Effective Tension at Top of the Connector, kips 43.73 -312 -310 -306 -298 -288 -274 -259 -240 -219 -195 -111 1177 2849Effective Tension at Bottom of the Connector, kips 38.00 -350 -348 -344 -336 -326 -312 -297 -278 -257 -233 -149 1139 2812Effective Tension at Top of the HPHSG, kips 13.00 -85 -85 -84 -84 -83 -81 -80 -78 -76 -74 -66 58 219Actual Tension at Top of DD2 LMRP, kips 85.07 185 187 191 199 210 223 239 257 278 302 386 1670 3342Actual Tension at Top of Connector, kips 43.73 -7231 -7230 -7225 -7217 -7207 -7194 -7178 -7160 -7139 -7115 -7030 -5743 -4070Actual Tension at Bottom of Connector, kips 38.00 -4058 -4056 -4051 -4044 -4033 -4020 -4004 -3986 -3965 -3941 -3856 -2569 -896Actual Tension at Bottom of HPHSG, kips 6.37 -1022 -1022 -1019 -1014 -1008 -1000 -991 -980 -968 -954 -904 -148 834Upper Flex Joint Angle, deg 5066.09 0.00 -0.35 -0.70 -1.05 -1.41 -1.78 -2.15 -2.53 -2.91 -3.31 -3.57 -2.43 -2.25LMRP Angle relative to vertical, deg 85.07 0.00 0.33 0.66 1.03 1.43 1.86 2.33 2.82 3.35 3.90 4.61 6.33 7.25Lower Flex Joint Angle, deg 85.07 0.00 0.62 1.23 1.79 2.31 2.76 3.15 3.49 3.76 3.97 3.74 0.97 0.20Angle of Riser at sea bed, deg 0.00 0.00 0.25 0.52 0.81 1.13 1.49 1.88 2.29 2.74 3.21 3.83 5.49 6.53Displacement of Riser at sea bed, ft 0.00 0.00 0.11 0.23 0.36 0.52 0.71 0.92 1.15 1.41 1.70 2.10 3.52 4.85





PinnedPinned

NonlinearRigid0.00


8.561018



Detailed Results – Case 1B

40

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10 11 12


Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)





Detailed Results – Case 1BWellhead Connector Bending Moment


41

Detailed Results – Case 1BCasing Stresses

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si



28" x 0.75"Casing (52 ksi)



42

Detailed Results – Case 2BRISER CONFIGURATION:






Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.3 29.0 31.1 33.8 36.9 40.4 44.5 48.96 49.39 49.45Effective Tension at Top of Ring, kips 5018.68 1411 1413 1419 1429 1443 1460 1481 1505 1533 1564 1600 2902 4642Effective Tension at Top of DD2 LMRP, kips 85.07 702 704 710 720 735 752 773 798 827 859 895 2184 3855Effective Tension at Top of the Connector, kips 43.73 95 97 103 114 128 146 167 192 221 253 290 1581 3253Effective Tension at Bottom of the Connector, kips 38.00 57 59 65 76 90 108 129 154 183 215 252 1543 3215Effective Tension at Top of the HPHSG, kips 13.00 -46 -46 -45 -44 -43 -41 -39 -37 -34 -31 -27 97 258Actual Tension at Top of DD2 LMRP, kips 85.07 592 594 600 611 625 643 664 689 717 749 785 2074 3745Actual Tension at Top of Connector, kips 43.73 -6824 -6822 -6816 -6805 -6791 -6774 -6752 -6727 -6699 -6666 -6630 -5339 -3667Actual Tension at Bottom of Connector, kips 38.00 -3650 -3648 -3642 -3632 -3618 -3600 -3579 -3554 -3525 -3492 -3456 -2165 -492Actual Tension at Bottom of HPHSG, kips 6.37 -784 -782 -779 -773 -764 -754 -741 -727 -710 -691 -669 89 1071Upper Flex Joint Angle, deg 5066.09 0.00 -0.41 -0.83 -1.24 -1.66 -2.08 -2.51 -2.93 -3.36 -3.80 -4.24 -2.99 -2.64LMRP Angle relative to vertical, deg 85.07 0.00 0.40 0.81 1.26 1.74 2.25 2.78 3.33 3.90 4.50 5.13 6.42 7.25Lower Flex Joint Angle, deg 85.07 0.00 0.36 0.70 1.01 1.28 1.51 1.71 1.88 2.02 2.11 2.17 0.68 0.12Angle of Riser at sea bed, deg 0.00 0.00 0.31 0.64 1.01 1.41 1.83 2.28 2.76 3.25 3.78 4.33 5.62 6.57Displacement of Riser at sea bed, ft 0.00 0.00 0.14 0.29 0.47 0.68 0.92 1.18 1.46 1.78 2.12 2.49 3.72 5.02





PinnedPinned

NonlinearRigid0.00


8.561425



43

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10 11 12


Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)







44


0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si



28" x 0.75"Casing (52 ksi)



45

Detailed Results – Case 3BRISER CONFIGURATION:






Maximum Tensioner Stroke, ft 25.0 25.3 26.1 27.2 28.9 30.9 33.5 36.4 39.9 43.8 48.17 49.33 49.39Effective Tension at Top of Ring, kips 5018.68 2551 2555 2566 2584 2608 2640 2677 2720 2770 2826 2889 4017 5716Effective Tension at Top of DD2 LMRP, kips 85.07 1840 1844 1855 1874 1899 1931 1969 2013 2063 2120 2183 3311 4973Effective Tension at Top of the Connector, kips 43.73 1234 1238 1249 1267 1293 1325 1363 1408 1458 1515 1579 2709 4371Effective Tension at Bottom of the Connector, kips 38.00 1196 1200 1211 1229 1255 1287 1325 1370 1420 1477 1541 2671 4334Effective Tension at Top of the HPHSG, kips 13.00 64 64 65 67 69 73 76 81 85 91 97 206 366Actual Tension at Top of DD2 LMRP, kips 85.07 1731 1735 1746 1764 1790 1822 1860 1904 1954 2010 2074 3202 4864Actual Tension at Top of Connector, kips 43.73 -5685 -5682 -5670 -5652 -5626 -5594 -5556 -5512 -5461 -5404 -5340 -4211 -2549Actual Tension at Bottom of Connector, kips 38.00 -2512 -2508 -2497 -2478 -2453 -2420 -2382 -2338 -2287 -2230 -2166 -1037 626Actual Tension at Bottom of HPHSG, kips 6.37 -115 -113 -107 -96 -81 -62 -39 -13 17 50 88 751 1727Upper Flex Joint Angle, deg 5066.09 0.00 -0.48 -0.96 -1.44 -1.91 -2.39 -2.87 -3.35 -3.83 -4.31 -4.79 -3.98 -3.46LMRP Angle relative to vertical, deg 85.07 0.00 0.49 1.00 1.53 2.09 2.66 3.25 3.85 4.46 5.08 5.72 6.54 7.24Lower Flex Joint Angle, deg 85.07 0.00 0.16 0.30 0.41 0.50 0.58 0.63 0.67 0.69 0.69 0.67 0.26 -0.03Angle of Riser at sea bed, deg 0.00 0.00 0.39 0.81 1.26 1.74 2.24 2.75 3.28 3.83 4.40 4.98 5.84 6.67Displacement of Riser at sea bed, ft 0.00 0.00 0.18 0.39 0.64 0.92 1.23 1.56 1.93 2.32 2.75 3.21 4.19 5.44






8.562565



PinnedPinned

NonlinearRigid0.00

46

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10 11 12


Ben

ding

Mom

ent, ft-

Mlb

36" x 2" Casing (X-65)







47


0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12


Stre

ss, k

si



28" x 0.75"Casing (52 ksi)



48

Soil Plasticity Concerns

Stack

Casing

Soil

Per API 2A WSD, soil will not be able to bear lateral loads that exceed the ultimate lateral bearing capacity of the soil (P > Pu) for the short-term static load case.

With guidance from the API document, the actual lateral deflection corresponding to this point of “failure” is assumed to be given by y = 8 yc = 8 (2.5) εc D; where εc is the strain corresponding to half the maximum stress on undrained compression test samples, and D is the casing diameter.

In our case, the value of εc is assumed to be 0.02 (soft clay); for a 36 inch casing this implies that the soil will not be able to bear lateral loads at all points where the lateral deflection is more than about 14.4 inch (1.2 ft).

To conservatively estimate the penetration depth up to which the soil has “failed”, 11% vessel offset was considered for the intermediate top tension case (CASE 2B) and the lateral deflection of soil is noted, with the riser still connected to the stack. If the deflection is more than 14.4 inch, the soil is considered as “failed”, and the corresponding soil springs, over the appropriate penetration depths, are then removed for the riser disconnected analysis. For CASE 2B at 11% vessel offset, the deflection is more than 14.4 inch over a penetration depth of 28 ft.

Now, the DD2 LMRP disconnected case is analyzed with 28 ft of soil removed to estimate the response of the wellhead/casing system after disconnection.

Check Displacements

Lateral Displacement for Max Vessel Offset

49

1 deg Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios0.3 knot Background Current; Initial Wellhead/Casing Inclination of 1 degree

-180

-130

-80

-30

20

70

120

-5 -4 -3 -2 -1 0 1 2 3 4


Dis

tanc

e fr

om M

udlin

e (f

t)

1 deg Initial Inclination LateralDisplacement Profile at 0 ft Vessel Offset - Riser Connected



Stack Angle Relative to Vertical = 1.4 deg Stack

Angle Relative to Vertical = 1.7 deg

Results: 1 deg Initial Inclination with Vertical – Updated Soil Data

50

Contact Information

Atul Ganpatye, [email protected]

Kenneth Bhalla, [email protected]

Stress Engineering Services13800 Westfair East Drive

Houston, Texas 77041

Phone: (281) 955-2900Fax: (281) 955-2638

www.stress.com

Documents

Atul Ganpatye, Kenneth Bhalla May 17, 2009