Optimization design of the geothermal wellbore structure in karst reservoir

Abstract:

The main geothermal reservoir is of a thermal karst type in the Niutuo geothermal field in Xiongan New District. In the past， the development was concentrated mainly at the depth less than 1800m， where the length of karst reservoir is 300 to 500m with short open hole section， hence simple drilling. In order to strengthen the exploration of deep geothermal resources and satisfy the needs of the planning and construction of Xiongan New District， investigation of deep geothermal resources was carried out with Wumishan Formation and Gaoyuzhuang Formation as the main targets. The main difficulties included the long open-hole section in the Karst Reservoir， broken formation， circulation loss over long well sections， poor stability of the upper strata. With analysis of drilling problems and difficulties encountered in drilling of the deep thermal exploration wells， the optimization suggestions are put forward for design of the well structure， and the key techniques for drilling in the karst thermal reservoir are summarized so as to effectively improve the safety and stability.