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Wellbore Stability In Water-Sensitive Shales, Qingfeng Tao

Theses and Dissertations

Wellbore instability is a widespread problem, especially when drilling in deep, low strength shale formations at high temperature and pressure. The instability can be caused by the high compressive effective stress or tensile stress due to the stress concentration and pore pressure increase while drilling. In addition to the in-situ stress and shale strength, shale instability is affected by drilling mud properties including mud weight, temperature and salinity. To assess wellbore stability in these situations, Diek and Ghassemi (2004) developed a non-linear coupled chemo-poro-thermoelasticity theory. The linearized version of the theory allows one to analytically investigate the coupled impacts of …