Abstract:

To explore the karstic reservoir distribution in the North China Platform, and enhance the geothermal energy utilization in the Xianxian high and Fucheng sag geothermal field, we analyzed the distribution of karst reservoir of Xianxian high and the Fucheng sag and the four major influencing factors (i.e.source, reservoir, migration channel, and cover) geothermal fields. Based on logging, seismic, and hydro-chemical data, a conceptual model for the geothermal field is established, and the geothermal resource evaluated. It is considered that the geothermal field is a conductive one, which was formed in a continental extension basin and controlled by deep faults. It formed a medium-low temperature conductive geothermal system, which is characterized by good caprock and geothermal gradient (3.63 to 5.31 ℃/100 m), whose recharged water source comes from atmospheric precipitation in the Taihangshan and Yanshan, and concentrated in karst heat reservoir of the Xianxian high and Fucheng sag. Specifically, the burial depth of the Jixian karst thermal reservoir is 1,400 to 1,500 m (effective thickness 336.1 m) in the Xianxian high geothermal field, whilst the Ordovician karstic reservoir is 2,000 to 2,500 m (effective thickness 55.3 m) in the Fucheng sag geothermal field. The total extractable geothermal resource of Jixian karstic reservoir in the Xianxian high geothermal field is 3.75×10⁹ GJ, (1.28×10⁸ t standard coal eqv.), and the annual geothermal resource can meet the indoor heating demand of 45.23 million. The total extractable geothermal resource of the Ordovician karstic reservoir in the Fucheng sag geothermal field is 0.80×10⁹ GJ, (0.27×10⁸ t standard coal eqv.), and the annual geothermal resource can meet the indoor heating demand of 9.54 million. The geothermal field development potential is likely immense.

Key words: geothermal, karst reservoir, geothermal field, Xianxian high, Fucheng sag, geothermal resources evaluation