Renewable assessment for geothermal resources in the karst area of Chongqing City

The geothermal resources of the main city of Chongqing karst area are mainly located in the layered heat storage structure of five anticlines. The geothermal fields are mainly in the limbs and south or north plunging ends of the anticlines. The Triassic Jialingjiang limestone is a heat reservoir, with overlying Xujiahe Formation and Jurassic strata, and with the marl of the Triassic Feixianguan Formation serving as the lower heat insulation layer. With increasing geothermal economic development and engineering construction, Chongqing City geothermal water resources renewability has been affected. In this paper, based on years of geothermal resource exploration and monitoring in Chongqing City, the five anticline reservoir structures in the karst area were divided into spring outcrops and deeply buried anticline, zones and the renewability of the geothermal resources was evaluated using the comprehensive index method. The results show that, the geothermal resources in the karst area can be classified as: 5 strong renewable, 10 moderately-strong, 8 moderate and 7 weak, comprising 12.95 %, 32.2 %, 32.15 % and 22.7 % by area, respectively, and shows a moderately-strong to moderate renewability overall. Moderately-strong and moderate renewable spring-type geothermal resources account for 33.6 % and 33.95 %, respectively, by area. Strong and moderately-strong renewable deeply buried resources account for 25.9 % and 30.8 % by area. Strong to moderately-strong renewable geothermal resources are mainly located in the northern anticline, moderate to weak renewable geothermal resources are found in the middle and southern anticlines. In general, deeply buried geothermal resources are more strongly renewable than spring-type resources. Therefore, this article suggests strengthening the exploration and development of geothermal water resources in the deeply buried area of the northern anticline limbs. At the same time, in order to ensure the sustainable utilization of geothermal resources, the scale of mining should be controlled in the moderate to weak renewable geothermal resources areas, the deeply buried anticline limbs areas in the south and the part - Hot Springs outcrop areas.