Establishing Pressure Profiles and Casing Program Optimization in the Southern Shunbei No. 5 Fault Zone

The southern part of the Shunbei No. 5 fault zone is affected by structural fault movement. Numerous drilling problems such as severe leakage and low drilling efficiency frequently occur. Based on adjacent well logging data and drilling data, a leakage pressure model was established, and a four-pressure profile (pore pressure, fracture pressure, collapse pressure and leakage pressure) of the southern formation in Shunbei No.5 fault zone was obtained. According to the pressure profile and drilling technical problems, casing program without invasive body was optimized from original five-section to four-section. As a result, the borehole size was reduced and the the drilling cycle was shortened. For areas with an invasive body, a unconventional four-section casing program with stronger formation pressure-bearing capacity and a conventional five-section sealing casing program with reduced borehole size was designed. The wellbore stability dramatically improved. The field test demonstrated that the prediction accuracy of leakage pressure is high. The average time for dealing with complex situation is shortened by 27.8 days and the average drilling period reduced by 14.6% after applying the five-section sealing casing program. The research showed that the optimized casing program in Shunbei No. 5 fault zone can solve the problems such as leakage and low drilling efficiency during drilling process, and provide technical guidance for complex ultra-deep formation casing program design.