Inversion of the Temperature and Depth of Geothermal Reservoirs Using Controlled Source Audio Frequency Magnetotellurics and Hydrogeochemical Method

The detection of the depth and temperature of deep geothermal reservoirs suffers great uncertainty if it is completed using the simple combination of traditional geophysical and geochemical methods. Given this, this study investigated the combined utilization of multiple methods including the multi-information joint detection using the controlled source audio frequency magnetotellurics (CSAMT) method and geothermometers in the Qutan geothermal field. First, the reservoir temperature and the depth of geothermal water circulation in the geothermal field were estimated using the geochemical method. Afterward, the relationship between the CSAMT resistivity and temperature of strata was explored through borehole temperature measurement. Based on this, the depth and temperature of geothermal reservoirs in the geothermal field were estimated again. According to the comprehensive analysis and comparison of the thermal reservoir temperatures and depths obtained using the two methods, the shallow reservoirs in the Qutan geothermal field have a top burial depth of approximately 423 m, a thickness of about 300 m, a temperature of about 79°C, and a fluid circulation depth of about 1959 m.