Study on Wellbore Stability of Shale Oil Drilling

Abstract With conventional oil and gas development entering the middle and late stage, unconventional oil and gas development is the focus of resource replacement and stable production. The South China Sea is rich in shale oil resources and has great development potential. However, the experience of shale oil exploitation in the South China Sea is not enough. The performance of oil shale rock in the target block is unclear, the anisotropy caused by bedding has great influence, the formation has abnormal high pressure, and various factors affect the wellbore stability. In the process of drilling, complex conditions occur frequently, which seriously limits the efficiency of exploration and development. Therefore, this paper studies the wellbore stability of shale oil drilling in the South China Sea, carries out rock mechanics experiments, analyzes the strength of oil shale rock, and studies the influence of oil-based drilling fluid and anisotropy caused by bedding on rock strength. Combined with logging data, the change law of formation caving pressure is analyzed and formation pressure is predicted. The research shows that the oil shale rock in this area has low strength, the core is hard and brittle, and the core is anisotropic under the influence of bedding. The strength weakening law of oil shale soaked in oil-based drilling fluid is studied, and the formation collapse pressure variation law is further obtained. The fracture pressure, caving pressure and pore pressure of the proposed drilling are predicted, which provides technical support for the safe and efficient drilling of shale oil drilling in the South China Sea.