Well Yitan-1: A drilling technology practice of a risk exploration well

Well Yitan-1 is placed in the western margin thrust belt of the Ordos Basin. Due to the high dip angle of strata, well-developed fractures of the Liujiagou and Shiqianfeng Formations and complex geologic structure, the well inclination prevention, leakoff prevention and plugging, and wellbore instability are the main technical challenges of the well construction operation. Given the excessive dogleg severity of the upper strata, fault-related in-situ stress anomaly, inferior wellbore stability, and low pressure-bearing capacity of strata in Well Yitan-1, the BHA optimization was performed, and the casing anti-abrasion technology, high-performance drilling fluid, and flexible cement borehole wall protection were applied. These implemented measures solved the technical difficulties during drilling, such as bit sticking, frequent tool breaking, and wellbore instability and ensured the safety and operation smoothness of drilling. The drilling practice and obtained understanding effectively promote the advancement of safe high-efficiency drilling of risk exploration wells in complex geological structures.