| Abstract |
The heat transfer and accumulation mechanisms of geothermal anomalies in sedimentary basins remain under explored. Using 2D finite element numerical simulation technology, this study investigates the relationship between geothermal anomaly size and factors, such as basement uplift morphology, basement thermal conductivity, and cap layer thickness, based on the diverse geothermal geological model of the Bohai Bay Basin. A geological profile in the middle of the Bohai Bay Basin is used to explore the formation mechanisms, controlling factors, and geothermal prospecting of geothermal anomaly belts. The formation of geothermal anomalies in sedimentary basins is driven by the rapid transmission of uniform deep heat flow in high thermal conductivity uplifts of the basement that accumulate in low thermal conductivity cap layers at shallow depths, leading to a thermal flow deficit in the deep basement and a thermal flow enriching in the shallow cap layers. Basement uplift amplitude and thermal conductivity are the main factors influencing geothermal anomaly size, and sufficient cap layer thickness guarantees the formation of these anomalies. The theoretical models predict temperature increases of up to 31.3℃ and positive anomaly amplitudes of up to 41.8% in the top layer of the basement geothermal reservoir (2 km depth). Based on differences in their geothermal anomalies caused by varying uplift amplitudes of the bedrocks, According to the difference of the bedrock bulge amplitude and its resulting geothermal anomalies, the Bohai Bay Basin is divided into seven types of geothermal fields, namely, high convex type, convex type, low convex type, concave type, gentle slope type, basin edge faulting-uplift type and shallow buried type, decreasing in turn the geothermal gradient of their cap rocks from > 5.0℃/l00m to < 2.0℃/l00m. Among them, the high-convex and the convex types are favorable targets for exploring shallow basement geothermal-reserves, and the low-convex and the concave types are the main targets for exploring deep high-temperature geothermal reserves of bed rocks (>150℃). |