Wellbore Stability in Shale Formation Using Analytical and Numerical Simulation


1 Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Iran Young Researchers Society

2 Department of Petroleum Engineering, Shahid Bahonar University of Kerman, Iran


Optimization of drilling fluid parameters such as mud weight, salt concentration, and temperature is essential to alleviate instability problems during drilling through shale sections. The selection of suitable mud parameters can benefit from analyses that consider significant instability processes involved in shale-drilling–fluid interactions. This paper describes the development of analytical and numerical method for describing shale deformation. Appropriate and optimum mud pressure in which the highest consistency happens is calculated with analytical and numerical methods. It was found that, the predicted mud pressures obtained from two methods are approximately equal. The stress condition is considered non-hydrostatic. From the analytical and extensive numerical simulation it was concluded that with applying any mud pressure the well shape changes from spherical to elliptical. As the selection of the optimum mud pressure is based on the less movement and maintaining the well shape constant.


[1] Ghassemi, A., Diek, A. andRoegiers, J.-C. (1998). "A solution for stress distribution around an inclined borehole in shale."Int. J. Rock Mech. Min. Sci. Vol. 35. pp. 4–7.
[2] Guizhong, C., Chenevert, M.E., Sharma, M.M. and Yu, M. (2001). "Poroelastic, chemical,and thermal effects on wellbore stability in shales."Proc. 38th U.S. Rock Mech. Symp.Balkema, The Netherlands, pp. 11–18.
[3] Aoki, T., Tan, C.P. and Bamford, W.E. (1993). "Effect of deformation and strength anisotropy on borehole failure in saturated shales. "Int. J. Rock Mech. Min. Sci. & Geomech. Abstr, Vol. 30, pp. 1031-1034.
[4] Cheep. Tan, Brian G. Richards, Sheikh S. Rahman, RivanoAndika. (1997). "Effects of swelling and hydrational stress in shales on wellbore stability." SPE 38057, Presented at the Asia Pacific Oil and Gas Conference and Exhibition held in Kuala Lumpur. 14 April 1997.
[5] Xiangjun Liu, PingyaLuo, Hong Liu, Dachun Liang and FaqianLuo. (2009). "Keeping Shale Formation Stability by Optimizing Drilling Fluids, in Yangta Oil Field." Western China. IPTC 13313, Presented at The International Petroleum Technology Conference held in Doha, Qatar, 7-9 December.
[6] John F. Jones and Robert D. Barree. (1996). "Mechanical Stability Analysis from Drilling Data Aloe."SPE36443 ,presented at the 71 st Annual Technical Conference and Exhibition held in Denver, Colorado , U.S.A , 6-9 October.
[7] Chen, X., Tan, C.P. and Detournay, C. (2002). "The impact of mud infiltration on wellbore stability in fractured rock masses."SPE/ISRM 78241 presented at the SPE/ISRM rock mechanics conference held in Irving, Texas, 20-23 , pp. 1-10.
[8] Ottesen, S. and Kwakwa, K.A. (1991). "A multidisciplinary approach to in-situ stress determination and its application to wellbore stability analysis." SPE21915., pp. 2-5.
[9] Awal, M.R., Khan, M.S., Mohiuddin, M.A., Abdulraheem, A. and Azeemuddin, M. (2001). A new approach to borehole trajectory optimization for increased hole stability. SPE 68092, pp. 1-10.
[10] Al-Ajmi, A.M., and Zimmerman, R. W. (2006). Stability analysis of vertical boreholes using the Mogi-Coulomb failure criterion. Int. J. Rock Mech. & Min. Sci. & Geomech. pp. 1-15, 10.1016.