Geothermal Field Distribution Characteristics and Controlling Factors in the Moliqing Fault Depression, Yitong Basin
Abstract
The Moliqing Fault Depression, located in the southwestern part of the Yitong Basin, is a Cenozoic strike–slip pull-apart basin controlled by the northern segment of the Tan-Lu Fault Zone. Based on measured formation temperature data from 41 wells and rock thermophysical property data from 41 wells in the study area, terrestrial heat flow values were calculated using a one-dimensional steady-state heat conduction model. On this basis, temperature distribution maps at different depths, a terrestrial heat flow contour map, a formation temperature distribution map of the Shuangyang Formation, and well-to-well geothermal profiles were systematically constructed. The principal factors controlling the geothermal field were further investigated in terms of basement relief, basement lithology, and the spatial distribution of volcanic vents. The results indicate that the geothermal field in the study area exhibits pronounced lateral heterogeneity. Subsurface temperatures range from 39 to 66 °C at a depth of 1000 m, from 65 to 133 °C at 2000 m, and from 91 to 182 °C at 3000 m. The geothermal gradient ranges from 3.0 to 4.9 °C/100 m, with an average of approximately 3.6 °C/100 m. Terrestrial heat flow values range from 58 to 122 mW/m2, averaging approximately 84 mW/m2. Measurements of rock thermophysical properties show that thermal conductivity ranges from 1.9 to 2.7 W/(m·K), with an average of 2.3 W/(m·K). Radiogenic heat production ranges from 0.985 to 1.3 μW/m3, averaging 1.1 μW/m3. Well-to-well geothermal profiles indicate that basement relief exerts a strong control on the distribution of isotherms. The relatively high radiogenic heat production of the basement granites provides an important internal heat source for the geothermal field. Geothermal gradients increase markedly near volcanic vents, reflecting the perturbing effects of deep-seated thermal activity. These findings provide a scientific basis for hydrocarbon exploration and geothermal resource assessment in the Moliqing Fault Depression.