A study of the formation mechanism and resource development prospect of the high-temperature geothermal system in the Yanggao-Tianzhen area

Under the background of “dual carbon”, Shanxi Province continues to promote the development of clean energy. In March 2020, high-temperature and high-pressure geothermal fluid was discovered near the Shuitongsi Village in Tianzhen County in Datong. In order to explore the high temperature geothermal system and its genetic mechanism in the Yanggao-Tianzhen area in Datong, an area of 20km² in the Gushan Village-Pingshan Village of Yanggao County is selected as the key research area. Geological survey, geophysics, drilling, logging and other methods are used to find out the occurrence conditions and rules of geothermal energy in the study area. The results show that (1) the geothermal resources in the Yanggao-Tianzhen area are mainly hosted in the Archean metamorphic rocks and water-bearing formations in fault zones. The direct heat source may be from the uncooled magma chamber in the middle and upper crust, and the caproks are the Quaternary accumulation, Neogene and Paleogene gravel layer. (2) The high-temperature geothermal system in this area is the convection and conduction geothermal system. On the one hand, atmospheric precipitation and surface water may infiltrate into the geothermal reservoir through pores and fault-fissure channels to form hot water. Then, it ascends to the shallow surface by convection along the fault-channels and forms a hot spring. On the other hand, the continuous extensional environment since the Cenozoic has led to the upwelling of the asthenosphere. The basaltic magma formed by partial melting of the upper mantle rises to the middle and upper crust through deep fault channels to form multiple magma pockets. Heat is transferred to the shallow surface through faults or Archean metamorphic rocks with high thermal conductivity to form geothermal anomalies. (3) The pumping test results of the YG-1 well show that, hydrothermal geothermal resources in this area are mainly static reserves, and non-interference heat exchange technology should be considered for the development and utilization.Through a comprehensive analysis of regional geological conditions, combined with geophysical prospecting and drilling results, it is believed that there may be dry-hot rock geothermal resources in the deep part of the region, which needs further investigation.