This paper is the result of geothermal survey engineering.

Objective Building genetic model of the geothermal system plays an important guiding role in the evaluation of the geothermal resources of the geothermal field and the later selection of favorable zones. Daming Sag is a secondary structural unit at the southern of Guantao Uplift in Linqing Sag, Bohai Bay Basin. The sandstone thermal reservoir of Guantao Formation can form a complete geothermal system.

Methods Combining previous research results and regional geothermal drilling data, through analysis and research on the main geological factors of the "source, reservoir, migration, and cover", the conceptual model of the geothermal system was established in Daming Sag, Linqing Depression. On this basis, a evaluation of geothermal resources was carried out.

Results The thermal reservoirs of the Guantao Formation are uniformly distributed in the area, the floor depth is between 1550-2000 m, the thickness of the reservoir is between 268-324m, the porosity is between 14%-32%, and the reservoir-thickness ratio can reach up to 70%. The geothermal wells drilled into the Guantao Formation in the area, its water temperature is about 54-60℃, and the water chemistry type is mainly Cl×SO₄-Na. The upper Quaternary and Minghuazhen Formation strata have a geothermal gradient between 22-60℃/km, forming a good cap layer. The heat source comes from the high geothermal value background of the Cenozoic rift basin, about 52-57 mW/m². The Linzhang-Daming fault in the south and the Guanxian fault in the east are favorable channels for the upward transportation of deep heat. The geothermal system receives the atmospheric precipitation replenishment from the Taihang Mountains in the west and the southwestern Luxinan uplift in the east. After being warmed by deep heat conduction and local heat convection, it is enriched in the reservoir.

Conclusions The evaluation results of the geothermal resources in the Damingci Depression show that the sandstone geothermal system resources of the Guantao Formation are more than 127.42×10⁸ GJ, the annual geothermal resources that can be exploited are 31.86×10⁶ GJ equivalent to 1.09×10⁶ t of standard coal. The annual exploitation of geothermal resources can meet the heating area over 3.14×10⁷ m², and the development potential is great.