Difficulty analysis and countermeasure discussion on drilling and completion of mid-deep geothermal well in Xiong’an New Area

The geological conditions of Xiong’an New Area are complex. In recent years, the drilling of exploration wells in the exploration blank area are complex and the accident rate is high, which has adverse effects on the large-scale development and utilization of geothermal resources in the new area. In order to reduce the risk of drilling in Xiong’an New Area, through the study of regional geological conditions and the analysis of regional geothermal well construction experience, it is considered that the main technical difficulties faced by the geothermal well construction in Xiong’an New Area are the serious leakage of weathering crust at the top of Jixian System, the high risk of continuous leakage drilling in carbonate well section, the strong deviation ability of regional strata, the excessive deviation of wells and the poor drillability of strata. In view of this series of problems, three kinds of well structure optimization design schemes are put forward, such as calculation of sealing point, expansion pipe sealing and adjustment to four section structure. And discusses the principle, application effect analysis and construction unfavorable factors of three kinds of underbalanced drilling processes, such as water-filled air positive circulation drilling process, air-lift reverse circulation drilling process and air-lift positive circulation drilling process. Based on the analytic hierarchy process, the evaluation and optimization model of the three processes is established, and the most suitable technology can be selected based on the project conditions. The proposed wellbore trajectory control scheme, coring drilling tool and bit optimization scheme solve the problems of excessive deviation, low coring recovery rate and short bit life of regional geothermal wells to a certain extent. The reliability of the technical countermeasures is proved by field application effect analysis.