Characteristics and development potential of geothermal resources in northern Cangxian uplift

This paper is the result of geothermal geological survey engineering.

Objective The characteristics and development potential of geothermal resources is an important basis for the development of regional geothermal resources.

Methods Combined the previous research results with the latest drilling data, the geothermal reservoir model is established based on the analysis of the main factors such as geothermal geological background, thermal reservoir distribution, geothermal field characteristics and hydrochemical resource types in the northern Cangxian uplift.

Results Under the background of high heat flow value in the extensional sedimentary basin of Bohai Bay, the atmospheric precipitation received by the bedrock in the exposed area of Yanshan Mountain in the north is used as the near source water supply. The cold water enters the bedrock, is heated by the deep heat source in the deep circulation process, and migrates and enriches along the fracture zone and unconformity surface, and forms the geothermal heat transfer mechanism dominated by conduction system.

Conclusions The geothermal resources in this area are characterized by many types thermal reservoirs, high geothermal gradient of caprock, rapid recharge rate and huge resources. It is mainly shown as follows: Three sets of main hot water reservoir, sandstone thermal reservoir of Guantao Formation, karst thermal reservoir of Ordovician and Jixian Wumishan Formation are distributed in the area; the distribution of geothermal field is mainly controlled by basement structure, and the average geothermal gradient in bedrock uplift area is 45 ℃/km; with the increase of groundwater depth, the groundwater type changes from HCO₃-Na, HCO₃·SO₄-Na to mature Cl-Na; the recoverable geothermal resources in this area is 1.67×10¹⁰ GJ, equivalent to 5.72×10⁸t of standard coal. The annual exploitable geothermal resources can meet the heating area of 2×10⁸ m², considering the balance of exploiting and irrigation, the annual exploitable resource of geothermal fluid in the northern part of Cangxian uplift is 7.06×10⁷ GJ, equivalent to 2.41×10⁶t of standard coal, which can meet the heating area of 8.5×10⁷ m², which has a good prospect of geothermal market development.