A study on wellbore stability in fractured rock masses with impact of mud infiltration

Stability Analysis in Determining Safety Drilling Fluid Pressure Windows in Ice Drilling Boreholes

“…Maintaining the stability of a borehole is one of the most important tasks in oil and gas exploration [1]. When drilling into the earth's crust, using certain drilling fluids in the borehole wall is the most common way to balance the formation pressure [2].…”

A wellbore stability analysis model with chemical-mechanical coupling for shale gas reservoirs

“…Some researchers have addressed this issue; however, most of them have only focused on hydromechanical coupling or thermo-hydro-mechanical coupling (Cui et al, 1997;Abousleiman and Cui, 1998;Ekbote, 2002;Yuan et al, 2013Yuan et al, , 2014. And while a large number of researchers have studied the influence of mechanical and chemical coupling on wellbore stability related to hydration and interactions with drilling mud (Chen et al, 2003a;Cheng et al, 2006;Lu et al, 2012Lu et al, , 2013Li et al, 2012a;Yan et al, 2013;Ma and Chen, 2014a), these researchers have still failed to consider the influence of comprehensive factors such as wellbore inclination, anisotropic in situ stress, anisotropic rock strength, mechanical and chemical coupling, downhole pressure (or EMW), the changes in the shale strength, etc., on the unstable zone around the borehole or the critical collapse pressure. Therefore, the main objective of this research is to propose a semi-analytical model and method of wellbore stability analysis for shale gas formations, in which the rock material is assumed to be poroelastic, have anisotropic strength behaviors and have variable strength, while the multifield coupling is assumed to be both mechanical and chemical; in addition, the anisotropic elasticity behavior and dynamic conditions of wellbore pressure are ignored.…”

Factors influencing wellbore stability during underbalanced drilling of horizontal wells – When fluid seepage is considered

“…For overbalanced drilling, types of formation rocks and drilling fluid have certain impact on wellbore stability. Chen et al (2003) presented coupled numerical analyses to investigate the influence of fractures in the rock and Zhang et al (2003) used dual-porosity poroelastic theory to solve the problem of horizontal well stability. Zeynali (2012) summed up types of wellbore instability from the mechanical and physico-chemical aspect during overbalanced drilling operations; and he concluded that properties of drilling mud and its interaction with the formation would affect the mechanical properties of the formation rocks and the stresses around the wellbore, especially for shale (van Oort, 2003).…”