The Lower Liaohe Depression is rich in geothermal resources, though current development focuses primarily on sandstone reservoirs, which face challenges such as low thermal temperatures, reinjection difficulties and poor economic returns. As a secondary thermal resource beneath the sandstone reservoirs, bedrock reservoirs have been less studied, and their thermal state and heat convergence mechanisms remain unclear. Based on regional geothermal-geological conditions and statistical analysis of borehole temperature data, the spatial characteristics of geothermal gradients in the bedrock thermal reservoir caprock were revealed. These characteristics include the geothermal gradient of the bedrock caprock is higher in Paleogene strata than in Neogene-Quaternary strata vertically, higher in the western depression than in the eastern depression horizontally, and higher in the southern part than in the northern part of the depression spatially. A 2D geological profile model was constructed with COMSOL Multiphysics to simulate heat transfer at depths of up to 12 km. Results show a wavy temperature field that corresponds to bedrock relief, with opposite distribution patterns above and below the depth of 3 200 m. The results demonstrate that regional terrestrial heat flow is mainly conductive, with local high-temperature anomalies formed by convective heat accumulation in karst reservoirs and fault zones. For the first time, heat flow values are quantitatively determined as 40~70 mW/m² in the western depression, 52~65 mW/m² in the central uplift, and 36~60 mW/m² in the eastern depression. An innovative “four-element heat control” model was proposed, including deep heat conduction, structural diversion and accumulation of heat in uplifts and depressions, convective heat control by fault zones, as well as convective heat control by karst systems. Low-uplift areas in the western depression’s slope zone are identified as high-efficiency drilling targets for obtaining higher bottom-hole temperatures. In addition, strong convective circulation in carbonate formations in this area is inferred to significantly enhance reinjection efficiency. These results offer theoretical and technical support for the exploration and development of bedrock geothermal reservoirs.