5. CONCLUSION & RECOMMENDATIONS
5.2 Recommendations
In this study, the simulation model assumes isothermal condition, which is not realistic as compared to an actual wellbore with increasing temperature along the depth. Variation in temperature affects the rheology of the drilling mud, which will significantly affect the annular flow profile and frictional pressure loss. Therefore, in the future, a dynamic temperature model may be included into the simulation for more accurate results.
In addition, this study considers only the drilling fluid without the presence of drill cuttings. Drill cuttings will affect the wellbore fluid column density, which will affect the annular flow profile and frictional pressure loss.
Moreover, this study considers horizontal well, deviated well and vertical can be modelled to study the effects of well trajectory on annular flow profile and frictional pressure loss.
Last but not least, open hole has a higher roughness and a more irregular geometry than a cased hole. In this study, the latter is considered. In future, it is recommended to model open hole section to understand how the annular flow profile and frictional pressure loss are affected differently.
48
REFERENCES
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in SPETT 2012 Energy Conference and Exhibition, 2012.
[2] M. Enfis, A. Ramadan. and A. Saasen, “The Hydraulic Effect of Tool-joint on Annular Pressure Loss,” in SPE Production and Operations Symposium, 2011.
[3] A. P. Singh, and R. Samuel, “Effect of Eccentricity and Rotation on Annular Frictional Pressure Losses With Standoff Devices,” in SPE Annual Technical Conference and Exhibition, 2009.
[4] A. K. Vajargah, F. N. Fard, M. Parsi and B. B. Hoxha, “Investigating the Impact of the “Tool Joint Effect” on Equivalent Circulating Density in Deep-Water Wells,” in SPE Production and Operations Symposium, 2014.
[5] Y. T. Jeong and S. N. Shah, “Analysis of Tool Joint Effects for Accurate Friction Pressure Loss Calculations,” in IADC/SPE Drilling Conference, 2014.
[6] S. G. Bared, “Another Method Depicting the Effect of Rotation of Drillig Fluids in a Pipe on the Pressure Drop,” 1990.
[7] S. A. Hansen and N. Sterri, “Drill Pipe Rotation Effects on Frictional Pressure Losses in Slim Annuli,” in SPE Annual Technical Conference & Exhibition, 1995.
[8] R. C. McCann, M. S. Quigley, M. Zamora and K. S. Slater, “Effects of High-Speed Pipe Rotation on Pressures in Narrow Annuli,” SPE Drilling & Completion, 1995.
[9] C. D. Marken, X. J. He and A. Saasen, “The Influence of Drilling Conditions on Annular Pressure Losses,” in SPE Annual Technical Conference and Exhibition, 1992.
[10] D. J. Bode, R. B. Noffke and H. V. Nickens, “The Influence of Drilling Conditions on Annular Pressure Losses,” Journal of Petroleum Technology, 1991.
[11] R. A. Delwiche, M. W. D. Lejeune, P. F. B. N Mawet and Vighetto, “Slimhole Drilling Hydraulics,” in SPE Annual Technical Conference and Exhibition, 1992.
[12] R. E. Walker and A. Othmen, “Helical Flow of Bentonite Slurries,” in Fall Meeting of the Society of Petroleum Engineers of AIME, 1970.
[13] T. Hemphill, P. Bern, J. C. Rojas and K. Ravi, “Field Validation of Drillpipe Rotation Effects on Equivalent Circulating Density,” in SPE Annual Technical Conference and Exhibition, 2007.
49
[14] M. E. Ozbayoglu, A. Saasen, M. Sorgun and K. Svanes, “Effect of Pipe Rotation on Hole Cleaning for Water-Based Drilling Fluids in Horizontal and Deviated Wells,”
in IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, 2008.
[15] A. O. Omosebi and K. A. A. Adenuga, “Pressure Drop versus Flow Rate Profiles for Power-Law and Herschel-Bulkley Fluids,” in Nigeria Annual International Conference and Exhibition, 2012.
[16] Y. J. Luo and J. M. Peden, “Reduction of Annular Friction Pressure Drop Caused By Drillpipe Rotation,” Texas: Society of Petroleum Engineers, 1990.
[17] T. N. Ofei, S. Irawan and W. Pao, “CFD Method for Predicting Annular Pressure Losses and Cuttings Concentration in eccentric Horizontal Wells,” in Journal of Petroleum Engineering, 2014.
[18] V. Dokhani, M. P. Shahri, M. Karimi and S. Salehi, “Laminar Non-Newtonian Flow in an Eccentric Annulus, a Numerical Solution,” in SPE Annual Technical Conference and Exhibition, 2013.
[19] S. Simoes, M. Yu, S. Miska and N. E. Takach, “The Effect of Tool Joints on ECD While Drilling,” in SPE Production and Operations Symposium, 2007.
[20] T. J. Lockett, S. M. Richardson and W. J. Worraker, “The Importance of Rotation Effects for Efficient Cuttings Removal During Drilling,” in SPE/IADC Drilling Conference, 1993.
[21] S. Chandrasekhar, “Hydrodynamic and Hydromagnetic Stability,” Oxford, 1961.
[22] ANSYS, Inc., “ANSYS CFX-Solver Theory Guide,” Canonsburg, 2011.
[23] T. N. Ofei, S. Irawan, W. Pao and R. E. Osgouei, “Modified Yield Power-Law Fluid In Narrow Annuli with Inner Rotating Pipe,” in The Canadian Journal Of Chemical Engineering, 2015.
[24] M. S. Enfis, The Effects of Tool-Joint on Annular Pressure Loss, Oklahoma:
University of Oklahoma, 2011.
[25] AMERICAN SOCIETY FOR QUALITY, 'What Is Design of Experiments (DOE)?', 2015. [Online]. Available: http://asq.org/learn-about-quality/data-
collection-analysis-tools/overview/design-of-experiments.html. [Accessed: 10- Jan- 2015].
ii
APPENDICES
Appendix 1: ANSYS-CFX Simulation Result Formats
Figure A-1.1: Graph of pressure versus the entire annulus length
Figure A-1.2: Velocity streamline
i
ii Figure A-1.3: Dynamic viscosity contour
Figure A-1.4: Volume rendering of pressure distribution in CFD-Post
iii
Appendix 2: Benchmarking - CFD Model Adjustments To Improve Benchmarking Table A-2.1: Adjustments made on CFD model to improve Benchmarking
Adjustments Effect(s) on CFD
simulation result (pressure loss readings)
Improvement on CFD model benchmarking?
Geometry Add 3 ft of casing and drill-string after outlet.
No effect. X
Increase the total length from 12.167 ft to 20 ft by adding the extra length in front of the inlet.
Lower than the experimental data.
X
Decrease the total length from 12.167 ft to 8.167 ft by cutting the extra length at the inlet.
Lower than the experimental data.
X
Setup:
inlet >
boundary details >
turbulence >
option
Use “intensity and auto compute length” option and input different values.
No effect (despite different input values) and does not improve the result to be closer to the experimental data.
X
Use “high” intensity. Higher than the experimental data.
X Use “zero gradient”
intensity.
Lower than the experimental data.
X Setup:
fluid flow rate
Suspected that the thesis may be using UK GPM, upon verification, is US GPM.
- √
Compare results when CFD simulation is carried out using flow rate (US GPM) or velocity (ft/s), to ensure Equation 1 is correct.
No effect, use either parameters will yield similar result.
√
Setup:
fluid > fluid models >
turbulence >
k-epsilon >
advanced
Increase Ce1 from 1.44 (default) to 2 and 20; Ce2 from 1.92 (default) to 3 &
30.
Lower than the experimental data.
X
Decrease Ce1 to 0.1 and 0.0001; Ce2 to 0.2 and 0.0001
Lower than the experimental data.
X
iv turbulence
control
Change “curvature
correction” from 1 (default) to 30.
No convergence X
Change “epsilon flux closure” from 1.3 (default) to 1000
No convergence X
Setup:
fluid > fluid models >
Turbulence
K-epsilon Pressure loss value
is more similar to experimental data for higher flow rates.
√
Laminar Pressure loss value
is more similar to experimental value for lower flow rates.
√
Shear stress transport / SSG / BSL.
Pressure loss is either too high or too low as compared to experimental data.
X
Setup:
outlet >
boundary details >
mass and momentum
Change pressure profile blend from 0.05 (default) to 0 and 0.5.
Pressure loss is lower than the experimental data.
Different blend values have no effect on result.
X
Change outlet relative pressure from 0 to 1 psi
No effect. X
Solution:
“Reynolds number out of range”
warning
During each simulation, if this warning appears, “k-epsilon turbulence model”
is used.
- √
v Appendix 3: Benchmarking – Tabulated Results
Table A-3.1: P1: 36” tool joint section pressure loss values at various flow rates for fluid E at 0 RPM (CFD simulation and experimental results)
Operating parameters
Drill pipe rotation (RPM) 0
Fluid (refer to Table 4) E
P1 (36" tool joint section, 9.167ft – 12.167 ft)
Flow rate (USGPM) 3.60 6.22 10.75 18.58 26.75
P1 (CFD) (psi) 0.700 0.980 1.430 2.135 2.785
P1 (Experiment) (psi) 0.700 0.990 1.440 2.140 2.770
Percentage Error (%) 0.1 1.0 0.7 0.2 0.5
Mean Percentage Error (%) 0.5
Table A-3.2: P2: 12” section without tool joint pressure loss values at various flow rates for fluid E at 0 RPM (CFD simulation and experimental results)
P2 (12" section without tool joint, 8 ft – 9 ft)
Flow rate (USGPM) 3.60 6.22 10.75 18.58 26.75
P1 (CFD) (psi) 0.18 0.26 0.38 0.3 0.412
P1 (Experiment) (psi) 0.16 0.22 0.32 0.46 0.62
Percentage Error (%) 14.0 18.2 18.8 34.8 33.5
Mean Percentage Error (%) 23.9
Table A-3.3: P3: 12” tool joint section pressure loss values at various flow rates for fluid E at 0 RPM (CFD simulation and experimental results)
P3 (12" tool joint section, 10.167 ft – 11.167 ft)
Flow rate (USGPM) 3.60 6.22 10.75 18.58 26.75
P1 (CFD) (psi) 0.32 0.45 0.67 1.463 1.912
P1 (Experiment) (psi) 0.35 0.5 0.75 1.21 1.69
Percentage Error (%) 7.5 10.0 10.7 20.9 13.1
Mean Percentage Error (%) 12.4
Table A-3.4: P2: 12” section without tool joint pressure loss values at various flow rates for fluid G 60 RPM and 180 RPM (CFD simulation and experimental results)
P2 (12" section without tool joint, 8 ft – 9 ft)
Flow rate (USGPM) 3.55 6.19 10.67 18.52 26.79
Rotation (RPM) 60
P2 (CFD) (psi) 0.28 0.34 0.48 0.65 0.82
P2 (Experiment) (psi) 0.24 0.29 0.38 0.53 0.69
Percentage Error (%) 2.1 3.4 0 7.5 7.2
vi
Mean Percentage Error (%) 4.1
Rotation (RPM) 180
P2 (CFD) (psi) 0.27 0.35 0.49 0.68 0.84
P2 (Experiment) (psi) 0.22 0.29 0.39 0.56 0.75
Percentage Error (%) 0 3.4 2.6 8.9 8.0
Mean Percentage Error (%) 4.6
Table A-3.5: P3: 12” tool joint section pressure loss values at various flow rates for fluid G for 60 RPM and 180 RPM (CFD simulation and experimental results)
P3 (12" tool joint section, 10.167 ft – 11.167 ft)
Flow rate (USGPM) 3.55 6.19 10.67 18.52 26.79
Rotation (RPM) 60
P3 (CFD) (psi) 0.45 0.532 0.752 1.049 1.388
P3 (Experiment) (psi) 0.431095 0.579505 0.848057 1.30742 1.84452
Percentage Error (%) 0 1.7 9.4 7.6 8.2
Mean Percentage Error (%) 5.4
Rotation (RPM) 180
P3 (CFD) (psi) 0.43 0.559 0.773 1.102 1.433
P3 (Experiment) (psi) 0.4311 0.5795 0.8481 1.3145 1.7739
Percentage Error (%) 0 3.4 16.5 10.7 14.7
Mean Percentage Error (%) 9.1
vii
Appendix 4: Design of Experiment – Tabulated Results
Table A-4.1: Frictional pressure loss due to tool joint(s) at 0 RPM drill-string rotation speed
Factor Response
Remark Number of tool joint Frictional pressure loss
(8.667 – 11.667 ft) (psi)
0 1.953
Drill-string rotation speed is 0 RPM.
1 3.044
2 3.976
Table A-4.2: Frictional pressure loss due to drill-string rotation without tool joint
Factor Response
Remark Drill-string rotation speed
(RPM)
Pressure loss (8.667 – 11.667 ft) (psi)
0 1.953
Drill-string has no tool joint.
60 1.950
120 1.941
180 1.930
240 1.917
300 1.903
420 1.878
540 1.857
600 1.842