Study of the Wellbore Instability Mechanism of Shale in the Jidong Oilfield under the Action of Fluid

Wellbore instability is the primary technical problem that restricts low-cost drilling of long-interval horizontal wells in shale formation Jidong Oilfield. Based on evaluation mineral composition, structure and physicochemical properties shale, this paper investigates mechanical behavior characteristics under fluid action by combining theoretical analysis, experimental numerical simulation. Due to existence bedding microcracks, strength deteriorates after soaking fluid. The conductivity weak surface much higher than rock matrix. penetration into along directly reduces structural which prone wellbore collapse. collapse pressure Nanpu block oilfield was calculated. well inclination angle, azimuth angle time were substituted deterioration model mechanics parameters, safe density target layer given. This work has important guiding significance for realizing stability hard brittle