Evaluation Of Effect Of Drilling Fluids On Wellbore Stability

Year 2022, Volume 43, Issue 3, 279 - 286, 23.12.2022

Hasan KARAKUL

Abstract

Wellbore stability evaluation is one of the important applications of rock mechanics and should be regarded to prevent instabilities that may develop in the wells for various reasons (such as complex field conditions, interaction between rock and drilling fluid, directional drilling etc.). The saturation of rocks by drilling fluids causes significant changes on mechanical properties of rocks. However the level of these variations may be changed due to drilling fluid compositions. In this study, the effect of these variations on wellbore stability was examined for different well profiles. In order to assess the effect of saturation on stability of wellbores, three different drilling fluid compositions (bentonite, KCl and polymer based muds) were considered. The results of assessment suggested that the saturation by bentonite and KCl based drilling fluids create adverse effect on critical fracture and collapse pressures. However the pressure values determined as a result of saturation by polymer based drilling fluid are close to those obtained for dry condition. It should be also stated that the range of mud pressure ensuring the stability of wellbore is also significantly affected by variation of collapse and fracture pressures calculated under drilling fluid saturation.

Keywords

Rock mechanics, drilling fluid, wellbore stability, collapse pressure, fracture pressure

References

• Aadnoy, B., Cooper, I., Miska, S., Mitchell, R.F., Payne, M.L., 2009. Advanced Drilling and Well Technology. Society of Petroleum Engineers, USA.
• Aadnoy, B., Looyeh, R., 2011. Petroleum rock mechanics – Drilling operations and well design. Gulf Professional Publishing, Oxford.
• Aadnoy, B., Looyeh, R., 2019. Petroleum rock mechanics – Drilling operations and well design. Gulf Professional Publishing, United Kingdom.
• Azar, J.J., Samuel, G.R., 2007. Drilling engineering. PennWell Corporation, Tulsa, Oklahoma, USA.
• Ewy, R.T., Bovberg, C.A., Stankovich, R.J., 2008. Shale Triaxial strength alteration due to brine exposure. 42nd U.S. Rock Mechanics Symposium (USRMS), San Francisco, California, ARMA-08-304.
• Karakul, H., 2018. Effects of drilling fluids on the strength properties of clay-bearing rocks. Arabian Journal of Geosciences,11, 450.
• Karakul, H., 2021. Investigation of fracture properties of rocks under drilling fluid saturation. Environmental Earth Sciences,80, 496.
• Liu, C., Huang, Y., Stout, M.G., 1998. Enhanced mode-II fracture toughness of an epoxy resin due to shear banding. Acta Materialia, 46 (16), 5647-5661.
• Mkpoikana, R., Dosunmu, A., Eme, C., 2015. Prevention of shale instability by optimizing drilling fluid performance. SPE Nigeria Annual International Conference and Exhibition, Nigeria, SPE-178299-MS.
• Okoro, E.E., Alaba, A.O., Sanni, S.E., Ekeinde, E.B., Dosunmu, A., 2019. Development of an automated drilling fluid selection tool using integral geometric parameters for effective drilling operations. Heliyon, 5 (5), e01713.
• Yan, C., Deng, J., Yu, B., 2013. Wellbore stability in oil and gas drilling with chemical-mechanical coupling. The Scientific World Journal, Vol. 2013, Article ID 720271.
• Yu, B., Yan, C., Nie, Z., 2013. Chemical effect on wellbore instability of Nahr Umr shale. The Scientific World Journal, Vol.2013, Article ID 931034.
• Zhang, F, Liu, H.B., Cui, S., Meng, Y.F. and Wang, J.J., 2021. Influence of the Weakening Effect of Drilling Fluid on Wellbore Stability in Anisotropic Shale Formation. Frontiers in Physics, Vol. 9, 745075.
• Zosel, A., 1985. Adhesion and tack of polymers: influence of mechanical properties and surface tensions. Colloid and Polymer Science ,263, 541-553.