Weak Point Analysis
Development Driller 2 Drilling Riser on Horizon Lower Stack
4992 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
Report Limitations
The 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.
2
Purpose
Part 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.
3
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.
4
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
5
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
6
Riser Configuration (Weight Factors 1.02/0.96 Included)
# of Joints
Length
(ft)
Distance of Top of
Component
from Mudline (ft)
Outer
Diameter
(in)
Wall
Thickness
(in)
Bare Joint
(Steel)
Dry Weight
(lbf)
Low Pressure Housing
1
3.47
10.00
37.260
3.322
2570
High Pressure Housing
1
6.63
13.00
27.000
4.245
7881
Horizon BOP Connector
1
6.33
16.64
66.000
23.625
Horizon BOP
1
24.05
40.69
50.000
15.625
DD2 BOP Connector
1
5.73
43.73
66.000
23.625
DD2 BOP
1
30.70
74.44
50.000
DD2 LMRP
1
12.43
85.07
Lower Flex Joint
1
0.00
85.07
Riser Adaptor
1
10.18
Bare w/ 1 x 7500 Buoyancy Module
9
675.00
Bare w/ 1 x 5500 Buoyancy Module
2
7500 ft Buoyancy Joint
12
5500 ft Buoyancy Joint
Buoyancy
Module
Weight
(lbf)
Component/
Joint Dry
Weight (lbf)
Component/
Joint Wet Weight
(lbf)
Dry Weight
per unit length
(lb/ft)
Wet Weight
per unit length
(lb/ft)
2570
2233
741.5
644.4
7881
6849
1189.6
1033.7
28600
28600
24853
4518.2
3926.3
306715
306715
266535
12753.2
11082.6
28600
28600
24853
4990.5
4336.8
15.625
451400
451400
392267
14701.6
12775.7
50.000
15.625
298082
298082
259033
23982.4
20840.7
95.25
21.000
0.8750
1918
0.00
0.000
1918
1667
188.4
163.8
770.25
21.000
0.8750
31154
3640
3840
35417
23928
472.2
319.0
150.00
920.25
21.000
0.8130
30239
3479
3999
34323
22964
457.6
306.2
900.00
1820.25
21.000
0.8750
30459
21840
23040
52908
4880
705.4
65.1
26
1950.00
3770.25
21.000
0.8130
29544
20874
23994
51009
3153
680.1
42.0
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
5500 ft Buoyancy Joint
1
75.00
4895.25
21.000
0.8130
29544
20874
23994
51009
3153
680.1
42.0
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
Component Name
Inner Barrel Stroke =
32.20
Total available stroke =
60.00
7
25
Please Enlarge
Lift (lbf)
5079.58 ft
Drill Floor
5065.24 ft
Riser
Configuration
Schematic
(tensioner
suspension points)
5066.09 ft
(upper flex joint)
+/- 15-deg, 6500 ft-lbf/deg
TJ Inner Barrel
5025.15 ft
5018.69 ft
Tension Ring
Mean Water Line
4992.00 ft
Telescopic Jt (TJ) Outer Barrel
4955.25 ft
10 ft Pup Jt (1)
4945.25 ft
50 ft Pup Jt (1)
Development Driller 2 Riser
and Stack on Deepwater
Horizon BOP.
The riser configuration does
not include a subsea tree
4895.25 ft
75 ft 5500 ft Rated
Buoyancy Jt (1)
4820.25 ft
75 ft Bare Jt w /1 x 5500 ft
Buoyancy Module (2)
4670.25 ft
150 ft Stagg w /1 x 5500 ft
Buoyancy Module (6)
3770.25 ft
75 ft 5500 ft Rated
Buoyancy Jt (26)
1820.25 ft
75 ft 7500 ft Rated
Buoyancy Jt (12)
920.25 ft
75 ft Bare Jt w/ 1 x 5500
Buoyancy Module (2)
770.25 ft
75 ft Bare Jt w/ 1 x 7500
Buoyancy Module (9)
85.07 ft
DD2 LMRP + BOP
(lower flex joint)
+/- 10-deg, 68000 ft-lbf/deg
43.73 ft
Horizon BOP/Lower
Stack (NO LMRP)
Mudline (0.00 ft)
8
13.0 ft Wellhead
(HP Housing) Stickup
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
9
Reference : Email from Mark Heironimus, dated Tuesday May 11th 2010 (10:48 am)
Horizon Stack Used in the Analysis
10
Horizon Stack Used in the Analysis
11
Wellhead Details
12
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
Casing Information
Component Name
Location of
Location of
Length Top from
Material
Bottom from
(ft)
Mudline
Definition
Mudline (ft)
(ft)
Outer
Diameter
(in)
Inner
Diameter
(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
13
Soils


API RP2A P-Y curves are developed from the soil
shear strength, submerged unit weight and e50.
Soil data is assumed per:
From: Jeanjean, Philippe [mailto:Philippe.Jeanjean@bp.com]
Sent: Friday, February 27, 2009 2:48 PM
To: Scherschel, Craig; Todd Veselis
Cc: Karlsen, Geir G (Clover)
Subject: RE: Macundo Soil Data
Todd,
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 strength
Depth (ft) Su (psf)
0
30
10
50
100
700
Use a sensitivity of 2.0 to calculate the remolded shear strength.
Depth (ft) Submerged unit weight (pcf)
0
20
30
37
100
43
14
PART 1
Weak Point Analysis – Riser Connected
15
Case Matrix
Case 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 2
Intermediate vertical slip ring tension of 1425 kips
Corresponding Tensioner Setting: 1500 kips
Case 3
Maximum vertical slip ring tension of 2565 kips
Corresponding Tensioner Setting: 2700 kips (90% of DTL)
Tension calculations
were based on 4992 ft
water depth; plus, the
added height of the
Horizon BOP results in
a slightly different riser
configuration.
Tension setting
for Case 2 is
based on this
16
Therefore, the tensions
in the above table may
not match the values in
the report provided by
BP
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-toWellhead
Connector)
(106 ft-lbf)
3.30
@ 10% vessel
offset
6.37
@ 10% vessel
offset
CASE 1
1018
11
11
59.4
@ 11% vessel offset
CASE 2
1425
11
11
59.4
@ 11% vessel offset
2.94
@ 10% vessel
offset
5.83
@ 10% vessel
offset
11
59.9
@ 11% vessel offset
1.98
@ 10% vessel
offset
4.38
@ 10% vessel
offset
CASE 3
17
2565
11
Load Capacity Envelope: SS15 Wellhead System
18
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
19
HD-H4 Connector or SHD-H4 with adapter kit - Capacity
Based on Typical “H-4” Profile Connector at 2/3 Yield
 @ 15 ksi pressure, 1500 kips tension: 4.0 million ft-lbf
Based on Typical “H-4” Profile Connector at Yield
 @ 15 ksi pressure, 1500 kips tension: 6.0 million ft-lbf
20
Detailed Results – Case 1
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
1018
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
1003
295
-312
-350
-85
185
-7231
-4058
-1022
0.00
0.00
0.00
0.00
0.00
25.3
1005
296
-310
-348
-85
187
-7230
-4056
-1021
-0.35
0.37
0.59
0.30
0.15
26.1
1009
301
-306
-344
-84
191
-7225
-4051
-1019
-0.70
0.78
1.14
0.63
0.32
27.4
1017
309
-298
-336
-84
199
-7217
-4043
-1014
-1.05
1.24
1.62
1.02
0.54
29.1
1027
319
-287
-325
-83
210
-7207
-4033
-1008
-1.41
1.77
2.03
1.47
0.81
31.4
1040
332
-274
-312
-81
223
-7194
-4020
-1000
-1.77
2.37
2.34
1.99
1.16
34.1
1055
348
-258
-296
-80
239
-7178
-4004
-991
-2.13
3.06
2.55
2.60
1.60
37.2
1073
366
-240
-277
-78
257
-7159
-3985
-980
-2.51
3.83
2.65
3.30
2.13
40.9
1093
387
-218
-256
-76
278
-7137
-3964
-967
-2.89
4.68
2.65
4.06
2.76
45.0
1116
411
-193
-231
-74
301
-7113
-3939
-952
-3.27
5.58
2.57
4.89
3.47
49.35
1178
473
-130
-168
-67
364
-7050
-3876
-915
-3.58
6.55
2.19
5.79
4.32
49.43
2436
1743
1141
1104
55
1633
-5779
-2604
-168
-2.42
7.35
0.02
6.75
6.02
49.48
4171
3395
2794
2757
214
3286
-4126
-951
802
-2.22
7.84
-0.39
7.45
8.03
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.61
0.00
0.39
0.60
0.59
0.04
0.00
1.26
0.00
0.79
1.21
1.19
0.08
0.00
1.96
0.00
1.20
1.83
1.80
0.11
0.00
2.72
0.01
1.62
2.48
2.43
0.14
0.00
3.55
0.01
2.05
3.13
3.08
0.16
0.00
4.44
0.01
2.49
3.80
3.73
0.17
0.00
5.38
0.01
2.93
4.47
4.39
0.18
0.00
6.37
0.01
3.38
5.14
5.04
0.18
0.00
7.39
0.05
3.81
5.79
5.68
0.17
0.00
8.42
0.22
4.20
6.37
6.24
0.15
0.00
8.82
1.22
3.45
5.16
5.04
0.00
0.00
8.86
3.19
2.42
3.53
3.42
0.03
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
3.8
4.6
4.6
4.5
15.3
7.3
4.6
6.5
6.1
15.4
11.4
4.6
9.8
7.8
15.6
16.0
4.7
13.5
9.3
15.8
21.0
4.9
17.4
10.6
16.0
26.4
5.1
21.7
11.8
16.3
32.2
5.3
26.4
12.6
16.7
38.4
5.6
31.4
13.2
17.1
44.9
5.8
36.6
13.6
17.5
51.5
6.0
41.9
13.8
18.0
58.2
6.1
47.2
13.8
23.3
59.4
11.8
47.9
30.5
175.8
64.4
34.2
52.8
61.4
358.4
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
21
Detailed Results – Case 1
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1018-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
10
9
Wellhead Bending
Moment = 6.37
million ft-lb
Bending Moment, ft-Mlb
8
7
36" x 2" Casing (X-65)
6
Low Pressure Housing
5
4
3
High Pressure Housing
Just Below Connector
2
1
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
22
9
10
11
12
Detailed Results – Case 1
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1018-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
23
8
9
10
11
12
Detailed Results – Case 2
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
1425
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
1411
702
95
57
-46
592
-6824
-3650
-784
0.00
0.00
0.00
0.00
0.00
25.3
1413
704
97
59
-46
594
-6822
-3648
-782
-0.41
0.44
0.32
0.36
0.18
26.1
1419
710
103
65
-45
600
-6816
-3642
-779
-0.83
0.92
0.61
0.76
0.40
27.3
1429
720
114
76
-44
611
-6805
-3632
-773
-1.24
1.46
0.83
1.21
0.68
29.0
1442
734
128
90
-43
625
-6791
-3617
-764
-1.66
2.05
1.00
1.73
1.02
31.1
1460
752
146
108
-41
643
-6773
-3600
-754
-2.07
2.70
1.11
2.31
1.43
33.7
1480
773
167
129
-39
664
-6752
-3578
-741
-2.49
3.40
1.16
2.94
1.93
36.8
1505
798
193
155
-36
688
-6727
-3553
-726
-2.91
4.15
1.16
3.63
2.50
40.4
1532
826
222
184
-34
717
-6698
-3524
-709
-3.34
4.93
1.11
4.34
3.13
44.4
1564
858
254
216
-30
749
-6665
-3491
-690
-3.77
5.73
1.02
5.10
3.83
48.86
1599
894
291
253
-27
785
-6628
-3454
-668
-4.20
6.56
0.89
5.87
4.60
49.39
2867
2146
1544
1506
94
2036
-5376
-2202
68
-2.98
7.27
-0.12
6.73
6.24
49.44
4593
3797
3196
3158
253
3688
-3724
-550
1038
-2.62
7.77
-0.40
7.42
8.27
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.72
0.00
0.45
0.68
0.67
0.02
0.00
1.47
0.00
0.88
1.35
1.33
0.04
0.00
2.26
0.00
1.31
2.01
1.97
0.06
0.00
3.08
0.01
1.73
2.64
2.59
0.07
0.00
3.93
0.01
2.14
3.25
3.19
0.07
0.00
4.80
0.01
2.52
3.83
3.76
0.08
0.00
5.68
0.01
2.89
4.38
4.30
0.08
0.00
6.55
0.07
3.24
4.90
4.80
0.07
0.00
7.42
0.21
3.56
5.39
5.28
0.07
0.00
8.28
0.41
3.86
5.83
5.70
0.06
0.00
8.63
1.49
3.14
4.67
4.56
0.01
0.00
8.71
3.56
2.19
3.17
3.07
0.03
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
2.9
3.4
3.4
11.7
21.6
6.8
3.4
5.9
12.6
21.8
11.7
3.4
9.8
13.6
22.0
16.8
3.5
13.8
14.4
22.2
22.1
3.7
18.1
15.1
22.6
27.7
3.9
22.6
15.8
22.9
33.4
4.1
27.1
16.3
23.4
39.1
4.2
31.7
16.7
23.9
44.8
4.4
36.2
17.1
24.5
50.5
4.5
40.8
17.4
25.2
56.1
5.4
45.2
17.7
25.9
59.4
15.5
48.0
38.1
174.5
64.6
38.8
53.2
68.7
356.6
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
24
Detailed Results – Case 2
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1425-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
10
9
Bending Moment, ft-Mlb
36" x 2" Casing (X-65)
Wellhead Bending
Moment = 5.83
million ft-lb
8
7
6
Low Pressure Housing
5
4
3
High Pressure Housing
Just Below Connector
2
1
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
25
9
10
11
12
Detailed Results – Case 2
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1425-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
26
8
9
10
11
12
Detailed Results – Case 3
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
2565
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
2551
1840
1234
1196
64
1731
-5685
-2512
-115
0.00
0.00
0.00
0.00
0.00
25.3
2555
1844
1238
1200
64
1735
-5682
-2508
-113
-0.48
0.52
0.13
0.43
0.23
26.1
2566
1855
1249
1211
65
1746
-5670
-2497
-107
-0.96
1.07
0.23
0.91
0.52
27.2
2584
1874
1267
1229
67
1764
-5652
-2478
-96
-1.43
1.67
0.28
1.43
0.88
28.8
2608
1899
1293
1255
69
1789
-5626
-2453
-81
-1.91
2.30
0.31
2.00
1.32
30.9
2639
1931
1325
1287
73
1821
-5594
-2420
-62
-2.38
2.96
0.30
2.61
1.82
33.4
2677
1969
1363
1325
76
1859
-5556
-2382
-39
-2.85
3.64
0.26
3.25
2.40
36.4
2720
2012
1408
1370
81
1903
-5512
-2338
-13
-3.33
4.33
0.21
3.90
3.04
39.8
2769
2062
1458
1420
85
1953
-5461
-2287
17
-3.80
5.04
0.14
4.57
3.74
43.7
2825
2119
1515
1477
91
2009
-5405
-2230
50
-4.28
5.75
0.06
5.26
4.50
48.07
2887
2182
1579
1541
97
2072
-5341
-2167
88
-4.75
6.46
-0.04
5.95
5.33
49.33
3975
3269
2667
2629
202
3159
-4253
-1079
727
-3.98
7.10
-0.29
6.69
6.87
49.39
5657
4910
4308
4270
360
4800
-2612
562
1690
-3.44
7.61
-0.41
7.35
8.94
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.83
0.00
0.48
0.73
0.72
0.01
0.00
1.67
0.00
0.92
1.39
1.37
0.01
0.00
2.50
0.00
1.30
1.98
1.94
0.02
0.00
3.32
0.00
1.64
2.49
2.44
0.02
0.00
4.13
0.01
1.94
2.93
2.87
0.02
0.00
4.92
0.09
2.20
3.32
3.25
0.02
0.00
5.68
0.23
2.44
3.66
3.58
0.01
0.00
6.43
0.43
2.64
3.95
3.86
0.01
0.00
7.15
0.71
2.80
4.19
4.09
0.00
0.00
7.85
1.07
2.94
4.38
4.28
0.00
0.00
8.22
2.33
2.41
3.54
3.44
0.02
0.00
8.35
4.57
1.66
2.36
2.28
0.03
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
2.5
2.6
2.6
32.2
39.4
7.3
2.7
6.2
32.6
39.5
12.7
2.9
10.6
33.1
39.8
18.2
3.2
14.9
33.6
40.2
23.7
3.4
19.3
34.1
40.7
29.1
3.7
23.7
34.7
41.4
34.4
3.9
28.0
35.3
42.1
39.6
4.6
32.1
35.9
43.0
44.6
6.4
36.2
36.6
44.0
49.5
8.8
40.1
37.4
45.1
54.3
12.1
44.0
38.5
46.3
59.9
26.4
49.1
58.8
171.1
65.4
51.2
54.4
88.8
350.9
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
27
Detailed Results – Case 3
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 2565-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
9
Wellhead Bending
Moment = 4.38
million ft-lb
8
Bending Moment, ft-Mlb
7
36" x 2" Casing (X-65)
6
5
Low Pressure Housing
4
3
2
High Pressure Housing
Just Below Connector
1
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
28
9
10
11
12
Detailed Results – Case 3
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 2565-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
29
8
9
10
11
12
PART 2
Response After DD2 LMRP Disconnection
30
Cases Considered
 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
31
Results: No Initial Inclination
No Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios
0.3 knot Background Current
100
Stack
Angle
Relative to
Vertical =
0.03 deg
Stack
Angle
Relative to
Vertical =
0.01 deg
Distance from Mudline (ft)
50
Stack
Angle
Relative to
Vertical =
0.08 deg
Stack
Angle
Relative to
Vertical =
0.04 deg
Mudline
0
-0.025
0
0.025
0.05
0.075
0.1
0.125
0.15
0.175
0.2
0.225
-50
No Initial Inclination Lateral Displacement Profile
at 0 ft Vessel Offset - Riser Connected
After DD2 LMRP Disconnection - 0 ft Soil Removed
-100
After DD2 LMRP Disconnection - 44 ft Soil Removed
-150
After DD2 LMRP Disconnection - 54 ft Soil Removed
After DD2 LMRP Disconnection - 70 ft Soil Removed
-200
Lateral Displacement (ft)
32
0.25
Results: 1 deg Initial Inclination
1 deg Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios
0.3 knot Background Current; Initial Wellhead/Casing Inclination of 1 degree
Stack
Angle
Relative to
Vertical =
1.5 deg
120
Stack
Angle
Relative to
Vertical =
2.2 deg
70
Stack
Angle
Relative to
Vertical =
2.7 deg
Stack
Angle
Relative to
Vertical =
4.3 deg
20
Distance from Mudline (ft)
Mudline
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
-30
-80
-130
1 deg Initial Inclination Lateral Displacement Profile
at 0 ft Vessel Offset - Riser Connected
After DD2 LMRP Disconnection - 0 ft Soil Removed
-180
After DD2 LMRP Disconnection - 44 ft Soil Removed
After DD2 LMRP Disconnection - 54 ft Soil Removed
-230
After DD2 LMRP Disconnection - 70 ft Soil Removed
-280
Lateral Displacement (ft)
33
10
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.
34
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)
35
Soil Data
Lateral resistance-deflection relationship comparison
(shown for example at 10 ft penetration depth)
Undrained Shear Strength (psf)
0
500
1000
1500
2000
2500
3000
6
3500
4000
4500
0
5
Penetration Depth (ft)
50
New Soil Data
100
150
Lateral Resistance (psi)
Old Soil Data
4
3
2
200
Old Soil Data
1
New Soil Data
250
0
0
300
5
10
15
20
25
Displacement (inch)
36
OLD
NEW
Undrained
Undrained
Penetration
Shear Strength Shear Strength
Depth
(ft)
(psf)
(psf)
0
30
60
10
50
100
100
700
1400
280
2000
4000
(Note: values at 280 ft penetration
depth are linearly extrapolated from
values given at 10 ft and 100 ft)
30
35
40
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”
(X65) 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-toWellhead
Connector)
(106 ft-lbf)
3.60
@ 11% vessel
offset
7.02
@ 11% vessel
offset
CASE 1B
1018
11
11
62.9
@ 11% vessel offset
CASE 2B
1425
11
11
64.3
@ 11% vessel offset
3.39
@ 11% vessel
offset
6.73
@ 11% vessel
offset
11
67.4
@ 11% vessel offset
3.15
@ 10% vessel
offset
6.22
@ 10% vessel
offset
CASE 3B
2565
11
(Note: analysis assumes linear elastic material properties; stress values above yield are because of this assumption)
37
Bending Moment Distribution Near Mudline
100
DD2 LMRP-to-BOP Connector (0.5 million lbf-ft)
75
Distance from Mudline (ft)
DD2 BOP-to-Horizon BOP Connector
(3.6 million lbf-ft)
50
Horizon BOP-to-Wellhead Connector
(7.0 million lbf-ft)
25
0
-13
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
Bending Moment Distribution;
CASE 1B; 11% Vessel Offset
Bending Moment Distribution;
CASE 2B; 11% Vessel Offset
Bending Moment Distribution;
CASE 3B; 10% Vessel Offset
-1
0
-25
-50
-75
-100
Bending Moment (million lbf-ft)
Bending moment distribution near the mudline for Cases 1B, 2B, and 3B
38
(respective offsets corresponding to the maximum bending moment considered)
Detailed Results – Case 1B
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
1018
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
1003
295
-312
-350
-85
185
-7231
-4058
-1022
0.00
0.00
0.00
0.00
0.00
25.3
1005
296
-310
-348
-85
187
-7230
-4056
-1022
-0.35
0.33
0.62
0.25
0.11
26.1
1009
301
-306
-344
-84
191
-7225
-4051
-1019
-0.70
0.66
1.23
0.52
0.23
27.4
1017
309
-298
-336
-84
199
-7217
-4044
-1014
-1.05
1.03
1.79
0.81
0.36
29.1
1027
319
-288
-326
-83
210
-7207
-4033
-1008
-1.41
1.43
2.31
1.13
0.52
31.4
1040
332
-274
-312
-81
223
-7194
-4020
-1000
-1.78
1.86
2.76
1.49
0.71
34.1
1055
348
-259
-297
-80
239
-7178
-4004
-991
-2.15
2.33
3.15
1.88
0.92
37.3
1073
367
-240
-278
-78
257
-7160
-3986
-980
-2.53
2.82
3.49
2.29
1.15
41.0
1094
388
-219
-257
-76
278
-7139
-3965
-968
-2.91
3.35
3.76
2.74
1.41
45.1
1117
412
-195
-233
-74
302
-7115
-3941
-954
-3.31
3.90
3.97
3.21
1.70
49.36
1200
496
-111
-149
-66
386
-7030
-3856
-904
-3.57
4.61
3.74
3.83
2.10
49.43
2472
1780
1177
1139
58
1670
-5743
-2569
-148
-2.43
6.33
0.97
5.49
3.52
49.49
4217
3451
2849
2812
219
3342
-4070
-896
834
-2.25
7.25
0.20
6.53
4.85
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.59
0.00
0.38
0.59
0.58
0.04
0.00
1.19
0.00
0.77
1.19
1.17
0.08
0.00
1.83
0.00
1.17
1.79
1.76
0.12
0.00
2.50
0.00
1.57
2.41
2.37
0.15
0.00
3.20
0.01
1.98
3.04
2.99
0.18
0.00
3.93
0.01
2.41
3.69
3.63
0.21
0.00
4.68
0.01
2.83
4.35
4.27
0.23
0.00
5.46
0.01
3.27
5.01
4.92
0.25
0.00
6.26
0.01
3.71
5.68
5.58
0.27
0.00
7.26
0.01
4.22
6.45
6.34
0.25
0.00
9.32
0.01
4.64
7.02
6.88
0.06
0.00
10.16
0.01
4.09
6.13
5.99
0.01
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
3.8
4.6
4.6
4.5
15.3
7.1
4.6
6.3
6.2
15.4
10.9
4.6
9.4
8.0
15.6
15.1
4.6
12.7
9.8
15.8
19.5
4.7
16.2
11.4
16.0
24.1
4.9
19.9
13.0
16.3
28.8
5.1
23.7
14.4
16.7
33.8
5.2
27.6
15.7
17.1
38.8
5.4
31.7
16.8
17.6
44.1
5.6
35.9
17.9
18.1
50.4
5.7
40.9
18.7
26.1
62.9
4.5
50.7
33.8
180.0
73.3
9.7
60.0
61.9
364.3
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
39
Detailed Results – Case 1B
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1018-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
12
Bending Moment, ft-Mlb
10
36" x 2" Casing (X-65)
Wellhead Bending
Moment = 7.02
million ft-lb
8
Low Pressure Housing
6
4
High Pressure Housing
Just Below Connector
2
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
40
9
10
11
12
Detailed Results – Case 1B
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1018-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
41
8
9
10
11
12
Detailed Results – Case 2B
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
1425
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
1411
702
95
57
-46
592
-6824
-3650
-784
0.00
0.00
0.00
0.00
0.00
25.3
1413
704
97
59
-46
594
-6822
-3648
-782
-0.41
0.40
0.36
0.31
0.14
26.1
1419
710
103
65
-45
600
-6816
-3642
-779
-0.83
0.81
0.70
0.64
0.29
27.3
1429
720
114
76
-44
611
-6805
-3632
-773
-1.24
1.26
1.01
1.01
0.47
29.0
1443
735
128
90
-43
625
-6791
-3618
-764
-1.66
1.74
1.28
1.41
0.68
31.1
1460
752
146
108
-41
643
-6774
-3600
-754
-2.08
2.25
1.51
1.83
0.92
33.8
1481
773
167
129
-39
664
-6752
-3579
-741
-2.51
2.78
1.71
2.28
1.18
36.9
1505
798
192
154
-37
689
-6727
-3554
-727
-2.93
3.33
1.88
2.76
1.46
40.4
1533
827
221
183
-34
717
-6699
-3525
-710
-3.36
3.90
2.02
3.25
1.78
44.5
1564
859
253
215
-31
749
-6666
-3492
-691
-3.80
4.50
2.11
3.78
2.12
48.96
1600
895
290
252
-27
785
-6630
-3456
-669
-4.24
5.13
2.17
4.33
2.49
49.39
2902
2184
1581
1543
97
2074
-5339
-2165
89
-2.99
6.42
0.68
5.62
3.72
49.45
4642
3855
3253
3215
258
3745
-3667
-492
1071
-2.64
7.25
0.12
6.57
5.02
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.71
0.00
0.45
0.70
0.68
0.02
0.00
1.45
0.00
0.91
1.39
1.37
0.05
0.00
2.21
0.00
1.36
2.08
2.04
0.07
0.00
2.99
0.01
1.80
2.76
2.71
0.09
0.00
3.77
0.01
2.24
3.43
3.37
0.10
0.00
4.58
0.01
2.68
4.10
4.03
0.11
0.00
5.39
0.01
3.12
4.77
4.68
0.13
0.00
6.21
0.01
3.55
5.42
5.32
0.13
0.00
7.05
0.01
3.98
6.06
5.95
0.14
0.00
7.91
0.01
4.39
6.69
6.57
0.14
0.00
9.36
0.01
4.46
6.73
6.59
0.04
0.00
10.11
0.03
3.88
5.79
5.66
0.01
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
2.9
3.4
3.4
11.7
21.6
6.7
3.4
5.8
12.7
21.8
11.5
3.4
9.6
13.8
22.0
16.4
3.4
13.6
14.9
22.2
21.5
3.6
17.6
15.9
22.6
26.7
3.8
21.7
16.9
23.0
31.9
4.0
25.9
17.9
23.4
37.2
4.1
30.1
18.8
23.9
42.6
4.3
34.4
19.7
24.5
48.0
4.4
38.8
20.5
25.2
53.6
4.5
43.2
21.4
25.9
64.3
5.7
52.1
40.3
178.9
74.1
11.0
60.8
68.9
362.8
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
42
Detailed Results – Case 2B
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1425-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
12
Bending Moment, ft-Mlb
10
36" x 2" Casing (X-65)
Wellhead Bending
Moment = 6.73
million ft-lb
8
Low Pressure Housing
6
4
High Pressure Housing
Just Below Connector
2
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
43
9
10
11
12
Detailed Results – Case 2B
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 1425-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
44
8
9
10
11
12
Detailed Results – Case 3B
RISER CONFIGURATION:
Mud Weight, ppg
Vertical Tension at Top of Ring (at zero offset), kips
4992-ft Water Depth; Development Driller 2, GOM
Top of High Pressure Housing 13-feet Above Mudline; Top of Low Pressure Housing 10-feet Above Mudline
Elevation from
Mudline (ft)
8.56
2565
Maximum Tensioner stroke = 50-ft
Available Tensioner stroke =25-ft
Tensioner Strokeout = 25-ft
Pinned
Pinned
Nonlinear
Rigid
0.00
5018.68
Tensioner/Wire Rope Stroke, ft
Bottom Boundary Condition
Top Boundary Condition
Tensioner Stiffness, before stroke out
Tensioner Stiffness, After stroke out
Surface Current, kt
OUTPUT:
Vessel Offset, % water depth
-280.00
5066.09
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
5018.68
85.07
43.73
38.00
13.00
85.07
43.73
38.00
6.37
5066.09
85.07
85.07
0.00
0.00
25.0
2551
1840
1234
1196
64
1731
-5685
-2512
-115
0.00
0.00
0.00
0.00
0.00
25.3
2555
1844
1238
1200
64
1735
-5682
-2508
-113
-0.48
0.49
0.16
0.39
0.18
26.1
2566
1855
1249
1211
65
1746
-5670
-2497
-107
-0.96
1.00
0.30
0.81
0.39
27.2
2584
1874
1267
1229
67
1764
-5652
-2478
-96
-1.44
1.53
0.41
1.26
0.64
28.9
2608
1899
1293
1255
69
1790
-5626
-2453
-81
-1.91
2.09
0.50
1.74
0.92
30.9
2640
1931
1325
1287
73
1822
-5594
-2420
-62
-2.39
2.66
0.58
2.24
1.23
33.5
2677
1969
1363
1325
76
1860
-5556
-2382
-39
-2.87
3.25
0.63
2.75
1.56
36.4
2720
2013
1408
1370
81
1904
-5512
-2338
-13
-3.35
3.85
0.67
3.28
1.93
39.9
2770
2063
1458
1420
85
1954
-5461
-2287
17
-3.83
4.46
0.69
3.83
2.32
43.8
2826
2120
1515
1477
91
2010
-5404
-2230
50
-4.31
5.08
0.69
4.40
2.75
48.17
2889
2183
1579
1541
97
2074
-5340
-2166
88
-4.79
5.72
0.67
4.98
3.21
49.33
4017
3311
2709
2671
206
3202
-4211
-1037
751
-3.98
6.54
0.26
5.84
4.19
49.39
5716
4973
4371
4334
366
4864
-2549
626
1727
-3.46
7.24
-0.03
6.67
5.44
6.53 to -114
-114 to -280
6.53 to 10.00
6.37 to 13.00
11.59
85.07
5015.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.86
0.00
0.52
0.79
0.78
0.01
0.00
1.74
0.00
1.02
1.55
1.52
0.02
0.00
2.61
0.00
1.48
2.25
2.21
0.03
0.00
3.47
0.01
1.92
2.92
2.86
0.03
0.00
4.32
0.01
2.34
3.55
3.48
0.04
0.00
5.15
0.01
2.74
4.15
4.07
0.04
0.00
5.99
0.01
3.12
4.73
4.63
0.04
0.00
6.82
0.01
3.47
5.26
5.16
0.05
0.00
7.65
0.01
3.81
5.76
5.64
0.05
0.00
8.47
0.01
4.11
6.22
6.09
0.04
0.00
9.32
0.01
3.92
5.88
5.75
0.02
0.00
9.96
0.27
3.34
4.95
4.83
0.00
0.00
6.53 to -114
-114 to -280
9.37 to -314
85.07
5015.80
2.5
2.6
2.6
32.2
39.4
7.5
2.7
6.4
32.7
39.5
13.2
2.9
11.0
33.3
39.8
19.0
3.2
15.6
34.0
40.2
24.7
3.5
20.2
34.7
40.7
30.4
3.8
24.7
35.5
41.4
36.0
4.1
29.3
36.3
42.1
41.6
4.5
33.8
37.2
43.0
47.3
4.8
38.3
38.2
44.0
52.9
5.1
42.8
39.2
45.1
58.5
5.5
47.4
40.3
46.4
67.4
9.1
55.1
59.5
176.0
76.3
14.7
63.2
88.9
357.6
Tensions and Deflections
Maximum Tensioner Stroke, ft
Effective Tension at Top of Ring, kips
Effective Tension at Top of DD2 LMRP, kips
Effective Tension at Top of the Connector, kips
Effective Tension at Bottom of the Connector, kips
Effective Tension at Top of the HPHSG, kips
Actual Tension at Top of DD2 LMRP, kips
Actual Tension at Top of Connector, kips
Actual Tension at Bottom of Connector, kips
Actual Tension at Bottom of HPHSG, kips
Upper Flex Joint Angle, deg
LMRP Angle relative to vertical, deg
Lower Flex Joint Angle, deg
Angle of Riser at sea bed, deg
Displacement of Riser at sea bed, ft
Bending Moments (MM ft-lb)
36" x 2" Casing (X-65)
36" x 1.5" Casing (X-56)
Low Pressure Housing
High Pressure Housing Just Below Connector
Total Moment at HPHSG-Connector Interface
Top of BOP+LMRP
Outer Barrel at Bottom of Tension Ring
"WEAK" POINTS (Von-Mises combined stress, ksi)
36" x 2" Casing (65 ksi)
36" x 1.5" Casing (56 ksi)
28" x 0.75" Casing (52 ksi)
Bottom of the Riser Adapter
Outer Barrel at Bottom of Tension ring
45
Detailed Results – Case 3B
Wellhead Connector Bending Moment
Variation of Bending Moment
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 2565-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
12
Bending Moment, ft-Mlb
10
36" x 2" Casing (X-65)
Wellhead Bending
Moment = 6.22
million ft-lb
8
Low Pressure Housing
6
4
High Pressure Housing
Just Below Connector
2
0
0
1
2
3
4
5
6
7
8
Offset, % of Water Depth
46
9
10
11
12
Detailed Results – Case 3B
Casing Stresses
Variation of Maximum von-Mises Equivalent Stress in Casing
Development Driller 2; 4992-ft Water Depth; GOM
Initial Tension = 2565-kips (vertical slip ring tension) & Mud Weight =8.56-ppg
100
90
80
36" x 2" Casing
(65 ksi)
Stress, ksi
70
60
36" x 1.5"
Casing (56 ksi)
50
40
30
28" x 0.75"
Casing (52 ksi)
20
10
0
0
1
2
3
4
5
6
7
Offset, % of Water Depth
47
8
9
10
11
12
Soil Plasticity Concerns
Lateral
Displacement
for Max Vessel
Offset
 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.
Stack
 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).
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.
Check
Displacements
 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.
48
Results: 1 deg Initial Inclination with
Vertical – Updated Soil Data
1 deg Initial Inclination - Lateral Displacement Profiles for Various Disconnection Scenarios
0.3 knot Background Current; Initial Wellhead/Casing Inclination of 1 degree
120
Stack
Angle
Relative to
Vertical =
Stack
1.4 deg
Angle
Relative to
Vertical =
1.7 deg
Distance from Mudline (ft)
70
20
-5
-4
-3
-2
-1
0
-30
-80
-130
-180
Lateral Displacement (ft)
49
1
2
3
1 deg Initial Inclination Lateral
Displacement Profile
at 0 ft Vessel Offset
- Riser Connected
After DD2 LMRP Disconnection
- 0 ft Soil Removed
After DD2 LMRP Disconnection
- 28 ft Soil Removed
4
Contact Information
Atul Ganpatye, atul.ganpatye@stress.com
Kenneth Bhalla, kenneth.bhalla@stress.com
Stress Engineering Services
13800 Westfair East Drive
Houston, Texas 77041
Phone: (281) 955-2900
Fax: (281) 955-2638
www.stress.com
50