Genesis Mechanism of Deep Carbonate Reservoir in Jizhong Depression

Abstract

Abstract The occurrence condition of geothermal resources in Jizhong depression is good for development, but the thermal genetic mechanism of thermal reservoir has been lack of systematic and theoretical research, which leads to large number of failure cases in the process of geothermal well location. In this paper, the thermal genetic mechanism of thermal reservoir in Jizhong depression is explored in the aspects of heat source, heat source channel, and thermophysical structure by means of core thermophysical property test, magnetotelluric sounding, and natural seismic P wave velocity imaging. According to the study, the heat of deep carbonate reservoir in Jizhong depression mainly comes from the deep mantle. Heat from the mantle enters deep thermal reservoir in the form of thermal conduction and thermal convection which flows through deep faults such as Niudong-Hexiwu fault. Cenozoic sandstone and mudstone caprock whose thermal conductivities are low is more than 1000 meters, which is favorable for heat storage. In comparison, the thermal conductivity of deep carbonate thermal reservoir is much higher than that of sandstone and mudstone. Therefore, differences in thermal conductivity and thermal convection from deep faults are the reasons why the heat reservoir temperature in the uplift area is higher than that in the subdepression area at the same depth.