Study on structural controlled geothermal reservoirs across the Boye Area, central North China Craton

The geological structure of a region critically influences the occurrence and distribution of geothermal resources. This study elucidates the structural controls on geothermal reservoirs in the Boye area of the Jizhong Depression, central North China Craton, using gas geochemistry, controlled-source electromagnetics, geophysical well logging, and structural analysis. The primary faults in Boye are NE-SW trending normal faults formed in an extensional regime, with NW and SE dips, steeper near the surface, and gentler at depth. Fault orientations vary locally due to deep structural influences. Angular unconformities are identified between the Wumishan Formation (Jixian System) and Kongdian Formation (Paleogene), and between the Dongying Formation (Paleogene) and Guantao Formation (Neogene). Local parallel unconformities exist between the Kongdian and Shahejie Formations (Paleogene), and between the Shahejie and Dongying Formations. Structural attributes and fault properties significantly control geothermal resource enrichment. The deep carbonate geothermal reservoirs in Boye primarily comprise Jixian System Wumishan dolomite, including chert-banded, muddy sandy fine-grained, and stromatolitic dolomite, characterized by abundant fractures and cavities. Geothermal resources are governed by an integrated system of source, migration, reservoir, and cap structures. Source structures control crust-mantle heat flow. Migration structures, including faults and unconformities, act as conduits for water and heat transfer. Reservoir structures encompass fractures and cavities, providing storage space. Cap structures facilitate atmospheric precipitation infiltration, though local faults can partially compromise insulation. This comprehensive structural analysis establishes a mechanism linking geological structures to geothermal resource development in Boye.