Other Applications of Optimized Casing Design
The next, six examples illustrate some of the many studies that ran be done using the casing program described. The discussions provided in the solutions should provide sufficient insight into the analysis of complex casing problems.
EXAMPLE 5-7: Well Trajectory Impact on Casing Cost
Rarely, if ever, will the planning of a directional well profile depend upon the cost of the casing string; however, casing cost is dependent upon the well’s trajectory. In this example, the costs of two different well trajectories with the same vertical and measured depths are compared. Figure 5.11 depicts the trajectories.
Other relevant data are:
Borehole friction factor: 0.4 True vertical depth:
— 8,998 ft for Well A
— 9,000 ft for Well В Type of casing: 9|-in. Production Mud density: 12 lb/gal
Smallest allowable casing section length: 1.000 ft Design factors:
— Burst: 1.000
— Collapse: 1.125
— Pipe body yield: 1.800
— Running loads: 1.800 Design method: minimum cost Number of sections: < 3
Solution:
The results are shown in Tables 5.13 and 5.14. For both wells, a minimum section length of 2,500 ft was chosen because it complies with the maximum number of sections allowed (three for this problem). The results show that the well profiles have a considerable effect on the final casing cost. The production casing costs $24,002 more for Well A than for Well B.
PRODUCTION CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
TRUE VERTICAL DEPTH AT CASING SEAT= 8998. FT DENSITY OF THE MUD THE CASING IS SET IN’ =12.0 PPG. MINIMUM CASING STRING LENGTH= 2500. FT. DESIGN FACTOR: BUR=1.000: COL=1.125: B. YIELD = 1.800 .DESIGN FACTOR FOR RUNNING LOADS= 1.800 KICK OFF POINT= 2000. FT
.MEASURED DEPTH AT END OF BUILD UP= 3240. FT. MEASURED DEPTH AT DROP OFF POINT= 5240. FT. MEASURED DEPTH AT END OF DROP OFF = 0480. FT. TOTAL MEASURED DEPTH= 10000. FT. BUILD UP RATE= 4.0 DEG/100FT. DROP OFF RATE= 4.0 DEG/100FT. PSEUDO FRICTION FACTOR= .400 DIMENSIONLESS. BUOYANCY CONSIDERED ON STATIC LOADS. DESIGN METHOD: MINIMUM COST
9 5/8" CASING PRICE LIST. FILE REF.:PRICE958.C’PR MAIN PROGRAM: CASING3D
TOTAL PRICE=330487. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=326851. LB PULLING OUT LOAD = 484859. LB
DI=10000- 7480 L= 2520 NN = 14 W=47.0 M = 2 MB=1.68 MC=1.26 MY=10.9 P=3240.61
DI= 7480- 4960 L= 2520 NN=13 W=43.5 M=2 MB=1.55 MC=1.36 MY= 5.4 P=3007.88
DI= 4960- 0 L= 4960 NN = 18 W=43.5 M=3 MB=1.79 MC=1.63 MY= 4.2 P=3488.41
Table 5.14: Well B: Production casing design for Example 5-7.
PRODUCTION CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
.TRUE VERTICAL DEPTH AT CASING SEAT= 9000. FT. DENSITY OF THE MUD THE CASING IS SET IN =12.0 PPG. MLNLMUM CASING STRING LENGTH= 2500. FT. DESIGN FACTOR: BUR=1.000: COL=1.125: B. YIELD = 1.800 .DESIGN FACTOR FOR RUNNING LOADS= 1.800 KICK OFF POINT= 4080. FT
.MEASURED DEPTH AT END OF BUILD UP = 10000. FT MEASURED DEPTH AT DROP OFF POINT=10000. FT. MEASURED DEPTH AT END OF DROP OFF =10000. FT TOTAL MEASURED DEPTH = 10000. FT. BUILD UP RATE= 1.0 DEG/100FT. DROP OFF RATE= 1.0 DEG/100FT PSEUDO FRICTION FACTOR= .400 DIMENSIONLESS. BUOYANCY CONSIDERED ON STATIC LOADS DESIGN METHOD: MINIMUM COST
9 5/8" CASING PRICE LIST. FILE REF.:PRICE958.CPR MAIN PROGRAM: CASING3D
TOTAL PRICE=295513. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=310515. LB PULLING OUT LOAD = 354489. LB
DI=10000- 7480 L= 2520 NN = 14 W=47.0 M = 2 MB=1.68 MC=1.26 MY=lfi.0 P=3240.61 DI= 7480- 4960 L= 2520 NN=13 W=43.5 M=2 MB = 1.55 MC= 1.22 MY= 6.5 P=3007.88
DI= 4960- 0 L= 4960 NN = 13 W=40.0 M=2 MB=1.41 MC=1.29MY= 2.8 P = 2783.29
THE MEANING OF SYMBOLS:
DI, DEPTH INTERVAL (FT)
.L. LENGTH (FT)
.NN, TYPE OF GRADE (SEE THE GRADE CODE BELOW)
.W, UNIT WEIGHT (LB/FT)
.M IS THE TYPE OF THREAD: 1…SHORT: 2…LONG: 3 . BUTTRESS
.MB. MG’, MY, MINIMUM SAFETY FACTORS FOR BURST. COLLAPSE. AND YIELD
.P, UNIT CASING PRICE S/100FT
GRADE CODE:
NN 1= …H40 NN 2= …J55 NN 3= …K55 NN 4= …C75 NN 5= …L80
NN 6= …N80 NN 7= …C95 NN 8= ..Р110 NN 9= ..V150 NN13= …S95
NN14= .CYS95 NN15= ..S105 NN1S= …S80 NN17= ..SS95 NN18= .LSI 10
NN19= .LS125
SURFACE CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
.EQUIVALENT FRACTURE GRADIENT AT CASING SEAT=15.0 PPG. TRUE VERTICAL DEPTH AT CASING SEAT=10000. FT. DENSITY OF THE MUD THE CASING IS SET IN = 12.0 PPG. MINIMUM CASING STRING LENGTH= 2500. FT. DESIGN FACTOR: BUR=1.000: COL=1.125: B. YIELD = 1.800 •TRUE VERTICAL DEPTH OF THE CASING SEAT = 10000. FT. DESIGN METHOD: MINIMUM COST
9 5/8" CASING PRICE LIST. FILE REF.:PRICE958.C’PR MAIN PROGRAM: CASING3D
TOTAL PRICE=295513. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=348270. LB
DI=10000- 7480 L= 2520 NN = 14 W=47.0 M=2 MB=2.02 MC = 1.14 MY=10.9 P = 3240.B1 DI= 7480- 4960 L= 2520 NN=13 W=43.5 M=2 MB = 1.53 MC=1.18 MY= 5.1 P = 3007.88
DI= 4960- 0 L= 4960 NN=13 W=40.0 M = 2 MB = 1.03 MC=1.27 MY= 2.5 P = 2783.29
THE MEANING OF SYMBOLS:
■ Dl. DEPTH INTERVAL (FT)
.L, LENGTH (FT)
NN, TYPE OF GRADE (SEE THE GRADE CODE BELOW)
,W. UNIT WEIGHT (LB/FT)
.M IS THE TYPE OF THREAD: 1…SHORT: 2…LONG: 3 . BUTTRESS
.MB, MC. MY, MINIMUM SAFETY FACTORS FOR BURST. COLLAPSE. AND YIELD
.P, UNIT CASING PRICE S/100FT
GRADE CODE:
NN 1= …H40 NN 2= …J55 NN 3= …K55 NN 4= …C75 NN 5= …L80
NN 6= …N80 NN 7= …C95 NN 8= ..P110 NN 9= ..V150 NN’13= …S95
NN14= .CYS95 NN15= ..S105 NN16= …S80 NN17= ..SS95 NN’18= LSI 10
NN19= .LSI 25
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Table 5.16: Impact of casing load type on cost (Example 5-8).
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EXAMPLE 5-8: Impact of Casing Load Type on Cost
Use data from Example 5-5 and change the load pattern of the casing assuming:
(i) surface casing loads.
(ii) production casing loads.
Also, use the minimum cost criteria for casing design.
Solution:
Using the data provided in Example 5-5 and the program С ASIXG3D, the original load file, CSGLOAD. DAT, must be altered to include the option of surface casing loads. The result of this run is the file DESIGN. OUT, as shown in Table 5.15.
Repeating the same procedure for production loads, the data file shown in Table 5.17 is obtained. Table 5.16 summarizes the results of the three runs.
An increase in cost (§11,525 or 4.19?) is observed when going from intermediate to production or surface casing loads. This is due to the scenarios used in the maximum load criteria assumptions that result in lower loads for the intermediate casing string design. In this particular example, the loads for production and surface casing resulted in the same cost. However, this is not always the case because the load patterns for surface and production casing are different.
Table 5.17: Impact of Production load on cost (Example 5-8).
PRODUCTION CASING DESIGN’
THE WELL DATA USED IN THIS PROGRAM WAS:
.TRUE VERTICAL DEPTH AT CASING SEAT=10000. FT. DENSITY OF THE MUD THE CASING IS SET IN =12.0 PPG. MINIMUM CASLNG STRING LENGTH= 2500. FT DESIGN FACTOR: BUR= 1.000: COL=1.125: B. YIELD = 1.800 .TRUE VERTICAL DEPTH OF THE CASING SEAT=10000. FT. DESIGN METHOD: MINIMUM COST
9 5/8" CASING PRICE LIST. FILE REF.:PRICE9SS. CPR MAIN PROGRAM: CASING3D
TOTAL PRICE=295S13. U. S.DOLLARS TOTAL STRUNG BUOYANT WEIGHT=348270. LB
DI=10000- 7480 L= 2520 NN=14 W=47.0 M = 2 1B = 1.53 MC’= 1.14 MY= 10.9 P = 3240.(>1 DI= 7480- 4960 L= 2520 NN = 13 W=43.5 M = 2 MB = 1.41 MC= 1.18 MY= 5.1 P = 3007.88
DI= 4960- 0 L= 4960 NN = 13 W = 40.0 M = 2 MB=1.28 MC=1.27 MY= 2.5 P=2783.2i>
THE MEANING OF SYMBOLS:
.Dl, DEPTH INTERVAL (FT)
,L, LENGTH (FT)
..N. N, TYPE OF GRADE (SEE THE GRADE CODE BELOW)
W. UNIT WEIGHT (LB/FT)
.M IS THE TYPE OF THREAD: 1…SHORT: 2…LONG: 3…BUTTRESS
MB. MC. MY, MINIMUM SAFETY FACTORS FOR BURST. COLLAPSE. AND YIELD
.P. UNIT CASING PRICE S/100FT
GRADE CODE:
NN 1= …H40 NN 2= …J55 NN 3= …K55 NN 4= …C75 NN 5= …L80
NN 6= …N80 NN 7= …C95 NN 8= ..P110 NN 9= ..V150 NN13= …S95
NN14= CYS95 NN15= ..S105 NN16= …S80 NN17= ..SS95 NN18= .LSI 10
NN19= .LS125
EXAMPLE 5-9: Optimized Design with Production Liner
Given the casing program in Fig. 5.12. determine the cost savings achieved with the production liner instead of the full production string. Consider the necessary changes of design of the 9|-in. intermediate string (Example 5-4) to provide for load pattern changes associated with the liner design option.
Solution:
To solve this problem, the 7-in. casing is designed from 15.000 ft to surface using the production load criteria. Then, the top 10.000 ft is discarded and the lower 5,000 ft constitutes the casing liner design. Since the 9|-in. casing string
30" CONDUCTOR CASING J 200 ft
20“ SURFACE CASING 2000 ft
t3S/g INTERMEDIATE CASING 6000 ft
9% INTERMEDIATE CASING 10000 ft
7" PRODUCTION LINER 15000 ft
Fig. 5.12: Casing program for Example 5-9.
in Example 5-4 was designed on the basis of the intermediate load rather than production load a redesign of this casing is necessary. The following data is used:
9|-in. production casing set at 10.000 ft Smallest casing section allowed: 1.000 ft Design factor for burst: 1.0 Design factor for collapse: 1.125 Design factor for pipe body yield: 1.8 Mud density while running casing: 12 lb/gal
7-in. production casing set at 15,000 ft Smallest casing section allowed: 1.000 ft Design factor for burst: 1.0 Design factor for collapse: 1.125
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LINER DESIGN |
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TOTAL COST: $ 436,542 U. S.DOLLARS |
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I) 9 5/S" CASING DOWN TO 10,000 FT: THE WELL DATA USED IN THIS PROGRAM WAS: .TRUE VERTICAL DEPTH AT CASING SEAT= 10000. FT. DENSITY OF THE MUD THE CASING IS SET IN =12.0 PPG .MINIMUM CASING STRING LENGTH= 2500. FT. DESIGN FACTOR: BUR= 1.000; COL=1.125: B. YIELD = 1.800 .TRUE VERTICAL DEPTH OF THE CASING SEAT = 10000. FT. DESIGN METHOD: MINIMUM COST |
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9 5/8" CASING PRICE LIST. FILE REF.:PRICE958.CPR MAIN PROGRAM: CASING3D |
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PARTIAL PRICE=295513. U. S.DOLLARS NOTE: THE GRADE CODE IS DIFFERENT FOR BOTH DESIGNS DI=10000- 7480 L= 2520 NN = 14 W=47.0 M=2 MB=1.53 MC=1.14 MY=10.9 DI= 7480- 4960 L= 2520 NN = 13 W=43.5 M = 2 MB=1.41 MC=1.18 1Y= 5.1 DI= 4960- 0 L= 4960 NN=13 VV=40.0 M = 2 MB=1.28 MC=1.27 MY= 2.5 |
P=3240.61 P=3007.88 P=2783.29 |
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GRADE CODE: NN13=…S95 NN14=..CYS95 |
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II) 7" CASING BETWEEN 9,800 and 15,000 FT |
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THE WELL DATA USED IN THIS PROGRAM WAS: .TRUE VERTICAL DEPTH AT CASING SEAT=15000. FT. DENSITY OF THE MUD THE CASING IS SET IN =15.0 PPG .MINIMUM CASING STRING LENGTH= 2600. FT. DESIGN FACTOR: BUR=1.000: COL=1.125: B. YIELD=1.800 .TRUE VERTICAL DEPTH OF THE CASING SEAT=15000. FT. DESIGN METHOD: MINIMUM COST |
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7” CASING PRICE LIST. FILE REF.: PRICE7.CPR MALN PROGRAM: CASING3D |
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PARTIAL PRICE= 141029 U. S.DOLLARS DI= 15000-12400 L= 2600 NN=12 W=.38.0 M=2 MB=1.17 MC’=1.20 MY = I2.7 DI= 12400- 9800 L= 2600 NN=12 W=32.0 M = 2 MB=1.14 MC=1.13 MY= 5.8 |
P = 2939.24 P = 2484.98 |
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GRADE CODE: NN12= ..S105 |
Design factor for pipe body yield: 1.8 Mud density while running casing: 15 lb/gal Casing overlap: 200 ft
Program CASING3D was run for the 9|-in. and 7-in. casing. Table 5.18 shows the output data in a slightly modified form to highlight the changes. The 9|-in. casing string was designed to withstand production loads.
EXAMPLE 5-10: Impact of Design Factor on Casing Cost
In this example, the effect of varying design factors on the final string design is considered. Using the input data for Example 5-5 . a minimum section length of
2,500 ft and the minimum cost design criteria, investigate the effect of changing the design factors for burst, collapse, yield and running loads.
|
Design Factor |
Step Size |
Design Factor Value |
Casing Cost USS |
|
Burst |
0.100 |
1.000 |
243.037 |
|
Burst |
0.100 |
1.100 |
254.442 |
|
Burst |
0.100 |
1.200 |
263.190 |
|
Burst |
0.100 |
1.300 |
274.620 |
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Collapse |
0.125 |
1.000 |
243,037 |
|
Collapse |
0.P25 |
1.125 |
257,813 |
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Collapse |
0.125 |
1.250 |
281.776 |
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Collapse |
0.125 |
1.375 |
284,607 |
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Pipe Body Yield |
0.250 |
1.000 |
243,037 |
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Pipe Body Yield |
0.250 |
1.250 |
243,037 |
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Pipe Body Yield |
0.250 |
1.500 |
243.037 |
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Pipe Body Yield |
0.250 |
1.750 |
243,037 |
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Pipe Body Yield |
0.250 |
2.000 |
243,037 |
|
Running Load |
0.250 |
1.000 |
243.037 |
|
Running Load |
0.250 |
1.250 |
243.037 |
|
Running Load |
0.250 |
1.500 |
243,037 |
|
Running Load |
0.250 |
1.750 |
243.037 |
|
Running Load |
0.250 |
2.000 |
248,811 |
Solution: This is a sensitivity analysis problem. One approach is to hold three of the four design factors constant at 1. while changing the fourth according to the range and step size shown in Table 5.19.
The cost results are shown in Table 5.19. The table indicates that the pipe body yield and running load design factor changes are not the dominant constraints in this design because, in general, they did not affect the final casing cost (except for running loads with a design factor of 2.0). Conversely, burst and collapse are the dominant factors in the design. The final choice of design factor values is quite subjective and, more often than not. is determined by company policy and not by individual design engineers.
EXAMPLE 5-11: Typical Deviated Well Profile
Using the computer program and the data in Table 4.5. rework the example problem on page 186 of Chapter 4 regarding a well with the same trajectory as shown in Fig. 4.1, for which the maximum surface pulling load was calculated using the analytical solution equations.
Solution:
PRODUCTION CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
.TRUE VERTICAL DEPTH AT CASING SEAT=15120. FT. DENSITY OF THE MUD THE CASING IS SET IN =16.8 PPG MINIMUM CASING STRING LENGTH= 2500. FT. DESIGN FACTOR: BUR=1.IOO: COL=1.125: B. YIELD = 1.800 .DESIGN FACTOR FOR RUNNING LOADS=1.000 .KICK OFF POINT= 5000. FT
.MEASURED DEPTH AT END OF BUILD UP= 7000. FT MEASURED DEPTH AT DROP OFF POINT=12480. FT .MEASURED DEPTH AT END OF DROP OFF =14480. FT. TOTAL MEASURED DEPTH= 16720. FT .BUILD UP RATE= 2.0 DEG/100FT. DROP OFF RATE= 2.0 DEG/100FT. PSEUDO FRICTION FACTOR= .350 DIMENSIONLESS. BUOYANCY CONSIDERED ON STATIC LOADS DESIGN METHOD: MLNIMUM COST
T CASING PRICE LIST. FILE REF.: PRICE7.CPR MAIN PROGRAM: CASING3D
TOTAL PRICE=433137. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=37602S. LB PULLING OUT LOAD = 484623. LB
DI= 16720-14200 L= 2520 NN= 8 W=38.0 M=2 MB=1.20 MC=1.15 MY = 15.3 P=2948.74
DI=14200-11520 L= 2680 NN= 8 W = 35.0 M= 2 MB=1.20 MC= 1.15 MY= 7.6 P = 2715.94
DI=11520- 0 L=11520 NN= 8 W=32.0 M=2 MB=1.18 MC=1.13 MY= 2.4 P=2483.00
THE MEANING OF SYMBOLS:
■ Dl, DEPTH INTERVAL (FT)
.L, LENGTH (FT)
.NN. TYPE OF GRADE (SEE THE GRADE CODE BELOW)
.W. UNIT WEIGHT (LB/FT)
.M IS THE TYPE OF THREAD: 1…SHORT: 2…LONG: 3…BUTTRESS • MB. MC, MY. MINIMUM SAFETY FACTORS FOR BURST. COLLAPSE. AND YIELD. P. UNIT CASING PRICE S/100FT
GRADE CODE: NN 1= …H40 NN 6= …N80 NN11= .CYS95 NN16= .LS125
NN 2= ….155 NN 7= …C95 NN12= ..S105 NN17= .LS140
NN 3= …K55 NN 8= ..P110 NN13= …S80 NN18=
NN 4= …C75 NN 9= ..VI50 NN14= . .SS95 NN19=
NN 5= …L80 NN10= …S95 NN15= .LS110 NN20=
Solution:
The input and output data of the casing design is shown again in Table 5.20
The hand calculation (using the analytical solution equations) and the computer — calculated pulling-out. load agree within -1.2%.
EXAMPLE 5-12: Two Horizontal Well Profiles: Single — and DoubleBuild Types.
Again, using the computer program and the data in Table 4.5 on page 208, rework the example problem on page 196 of Chapter 4 regarding a well with the same trajectory as shown in Fig. 4.15, for which the maximum surface pulling load was calculated using the analytical solution equations.
Solution:
The input and output data of the casing design is shown again in Tables 5.21 and
PRODUCTION CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
.TRUE VERTICAL DEPTH AT CASING SEAT= 5865. FT. DENSITY OF THE MUD THE CASING IS SET IN =10.0 PPG. MINIMUM CASING STRING LENGTH= 2000. FT. DESIGN FACTOR: BUR=1.100: COL=1.125: B. Y1ELD = 1.800 .DESIGN FACTOR FOR RUNNING LOADS=1.400 .KICK OFF POINT= 3000. FT
MEASURED DEPTH AT END OF BUILD UP= 7500. FT. MEASURED DEPTH AT DROP OFF POINT = 12500. FT. MEASURED DEPTH AT END OF DROP OFF =12500. FT. TOTAL MEASURED DEPTH=12S00. FT. BUILD UP RATE= 2.0 DEG/100FT. DROP OFF RATE= 2.0 DEG/100FT. PSEUDO FRICTION FACTOR= .350 DIMENSIONLESS. BUOYANCY CONSIDERED ON STATIC LOADS. DESIGN METHOD: MINIMUM COST
7" CASING PRICE LIST. FILE REF.: PRICE7.CPR MAIN PROGRAM: CASING3D
TOTAL PRICE=125820. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=114281. LB PULLING OUT LOAD = 169839. LB
DI=12500- 0 L=12500 NN = 10 W=23.0 M=3 MB=2.73 MC = 1.85 MY= 5.5 P=1006.56
THE MEANING OF SYMBOLS:
.DI, DEPTH INTERVAL (FT)
.L, LENGTH (FT)
.NN, TYPE OF GRADE (SEE THE GRADE CODE BELOW)
.W. UNIT WEIGHT (LB/FT)
.M IS THE TYPE OF THREAD: 1…SHORT: 2…LONG; 3…BUTTRESS
.MB. MC, MY, MINIMUM SAFETY FACTORS FOR BURST, COLLAPSE, AND YIELD
.P, UNIT CASING PRICE S/100FT
GRADE CODE: NN 1= …H40 NN 6= …N80 NN11= CYS95 NN16= .LS125
NN 2= …155 NN 7= …C95 NN12= ..S105 NN17= .LS140
NN 3= …K55 NN 8= ..PI 10 NN13= …S80 NN18=
NN 4= …C75 NN 9= ..VI50 NN14= . .SS95 NN19=
NN 5= …L80 NN10= …S95 NN15= LS110 NN20=
5.22.
For the single-build horizontal well, the hand calculations (using the analytical solution equations) agree within 10% compared to the computer-calculated pulling out load. Use a pipe length of 50 ft instead of 40 ft.
For the double-build horizontal well, the hand calculations (using the analytical solution equations) agree within -6.2% compared to the computer calculated pulling out load. Enter -5 for the 5° build in the second section.
(1) Repeat Example 5-1 for an 8,000-ft deep well.
(2) What happens in Example 5-1 if the design factor for pipe body yield is 1.6 ?
(3) What happens in Example 5-1 if the mud weight, while running casing, is 14
PRODUCTION CASING DESIGN THE WELL DATA USED IN THIS PROGRAM WAS:
.TRUE VERTICAL DEPTH AT CASING SEAT=11449. FT. DENSITY OF THE MUD THE CASING IS SET IN =16.8 PPG. MINIMUM CASING STRING LENGTH= 2500. FT • DESIGN FACTOR: BUR=1.000; COL=1.125; B. YIELD=1.800 .DESIGN FACTOR FOR RUNNING LOADS=1.000 .KICK OFF POINT= 5000. FT
.MEASURED DEPTH AT END OF BUILD UP= 7000. FT. MEASURED DEPTH AT START OF SECOND BUILD=12480. FT. MEASURED DEPTH AT END OF SECOND BUILD=13480. FT. TOTAL MEASURED DEPTH=16720. FT. FIRST BUILD UP RATE= 2.0 DEG/100FT. SECOND BUILD UP RATE= 5.0 DEG/100FT. PSEUDO FRICTION FACTOR= .350 DIMENSIONLESS. BUOYANCY CONSIDERED ON STATIC LOADS. DESIGN METHOD: MINIMUM COST
7" CASING PRICE LIST. FILE REF.: PRICE7.CPR MAIN PROGRAM: CASING3D
TOTAL PRICE=366835. U. S.DOLLARS TOTAL STRING BUOYANT WEIGHT=236684. LB PULLING OUT LOAD = 336018. LB
DI= 16720-12280 L= 4440 NN=12 W=32.0 M=2 MB=1.29 MC=1.13 MY=60.7 P=2484.98
DI= 12280- 9760 L= 2520 NN= 8 W=32.0 M=2 MB=1.49 MC=1.13 MY=15.1 P=2483.00
DI= 9760- 7240 L= 2520 NN=10 W=29.0 M=2 MB=1.16 MC=1.14 MY= 6.9 P=2130.43
DI= 7240- 0 L= 7240 NN=10 W=26.0 M=2 MB=1.03 MC=1.20 MY= 2.5 P=1937.07
THE MEANING OF SYMBOLS:
.DI, DEPTH INTERVAL (FT)
.L, LENGTH (FT)
.NN, TYPE OF GRADE (SEE THE GRADE CODE BELOW)
,W, UNIT WEIGHT (LB/FT)
• M IS THE TYPE OF THREAD: 1…SHORT; 2…LONG; 3…BUTTRESS ■ MB, MC, MY, MINIMUM SAFETY FACTORS FOR BURST. COLLAPSE, AND YIELD, P, UNIT CASING PRICE S/100FT
GRADE CODE:
NN 1= …H40 NN 2= …J55 NN 3= …K55 NN 4= …C75 NN 5= …L80
NN 6= …N80 NN 7= …C95 NN 8= ..PUO NN 9= ..V150 NN10= …S95
NN11= .CYS95 NN12= ..S105 NN13= …S80 NN14= ..SS95 NN15= .LS110
NN16= .LS125 NN17= .LS140 NN18=……………………………………………………………………………. NN19= NN20=
lb/gal?
(4) Alter the program CSG3DAPI such that the largest number of casing sections is an entry to the problem. Hint: introduce a DO LOOP and alter the length of the smallest casing section allowed.
(5) Using the data from Example 5-1 in addition to the minimum weight design method and a maximum of two sections in the combination casing string run the program developed in Exercise 4.
(6) Repeat Example 5-2 using loads with values of 5,500 psi for burst, 6,500 psi for collapse and 950,000 lbf for tension.
(7) Using the Quick Design Chart of Fig. 5.2 and the data in Table 5.23, design a combination casing string.
(8) Referring to the previous exercise, what would be the casing design if only
Table 5.23: Data on an intermediate casing string to be designed.
9|-in. intermediate casing set at 6.700 ft.
Smallest casing section allowed: engineers’ decision.
Design factor for burst: 1.1.
Design factor for collapse: 1.1 о Design factor for pipe body yield: 1.5 Production casing depth (next casing): 11.700 ft Mud density while running casing: 11 lb/gal
Equivalent circulating density to fracture tlie casing shoe: 13.о lb/gal Heaviest mud to drill to target depth: 12.7 lb/gal Blowout preventer working pressure: 5.000 psi
(9) Using data from Table 5.23. design a combination casing string that has no more than four sections. Use the minimum weight method. Compare the results with Exercise 7. In addition, design a single-section string from surface to bottom, and compare the results with those found in Exercise 8.
(10) Repeat exercise 8 using the minimum cost design method. Discuss the difference between the two designs.
(11) Using the data from Table 5.2.3. plot the casing loads for collapse and burst. On the plot, include the properties of the combination casing strings designed in Exercises 8. 9. and 10. Compare the results and the costs. Check for tension. (Hint: Use Figs. 5.5 and 5.6 as a reference.)
(12) In Table 5.18. why is the minimum length of 2.520 ft not adequate for the 7in. casing? (Hint: Run the program using this length as the minimum allowable casing section length.)
(13) A vertical well drilled to 7.500 ft is planned. The pore pressure and fracture gradient predictions obtained from an offset well drilled nearby are shown in fig. 5.13; the price of the casing is shown in Tables B. l. B.2 and B.3 (in Appendix B). The BOP working pressure on the rig is 5.000 psi. and the trip margin is 0.1 ppg. Disregard gas kick and find the casing setting depths for: (i) the 7-in. production casing; (ii) the 9|-in. intermediate casing: and (iii) the 13|-in. surface casing. Design each casing string assuming design factors for burst, collapse and yield of 1.1. 1.125. and 1.5. respectively. Make reasonable assumptions for any missing data needed for the design.
(14) Repeat all casing depths and designs for Exercise 13 considering: (i) zero volume kick of 0.5 ppg equivalent shut-in drillpipe pressure (SIDPP) while drilling at the production casing depth with a specific mud weight of 0.1 ppg over the formation pressure equivalent density: and (ii) zero volume kick of 0.5 ppg SIDPP over a specific mud weight of 0.4 ppg over the formation pressure equivalent
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Equivalent Mud Weight fopqt 8 9 10 11 12 13 14 15 16 |
Fig. 5.13: Pore pressures and fracture gradient predictions for Exercise 13.
(15) Repeat all casing depths and designs for Exercise 14 considering: (i) kick of ’20-bbl equivalent shut-in drillpipe pressure (SIDPP) while drilling at the production casing depth with a specific mud weight of 0.4 ppg over the formation pressure equivalent specific weight (assume that methane gas is entering the mud column as a single bubble); and (ii) kick of 20-bbl SIDPP over a specifc mud weight of 0.4 ppg over the formation pressure equivalent specific weight just before setting the intermediate casing string.
(16) Using an intermediate casing instead of a liner reconsider the solution for the case of a 20-bbl kick at the production casing depth (Exercise 15).
(17) Reconsidering the case of a 20-bbl gas kick at the production casing depth (Exercise 15) design the intermediate and production casings for a ‘’build and hold” directional well profile that kicks off at the surface casing setting depth and has a buildup rate of 3°/100 ft up to a maximum inclination of 40°. The true vertical depth is maintained at 7.500 ft. A 0.3 borehole friction factor is estimated.