Analysis of Wellbore Stability considering the Interaction between Fluid and Shale

Reservoir shale has the characteristics of bedding planes, strong anisotropy, and imbibition ability under ultralow water saturation, which an important impact on wellbore stability horizontal wells. Therefore, physical chemical properties reservoir were analyzed, a mechanics model was established considering elasticity strength anisotropy. The analyzed anisotropy parameters formation conditions. results show that condition are for evaluating borehole. Considering interaction between fluid shale, weakening structure is reason instability shale. Bedding planes microfractures provide rapid channel, volume increases, further causes fracture expansion weakening, then leads to instability. Multistage effective plugging bedding, microcracks macroholes during drilling key maintain wellbore.