Genetic analysis and resource evaluation of Dazhuang geothermal reservoir in the Minle Basin

Abstract

To understand the characteristics of geothermal resources of the Dazhuang geothermal reservoir in the Minle Basin, regional geothermal geological data of the Minle Basin were collected. Combined with the Dazhuang geothermal reservoir survey, drilling and logging data, the main thermal control factors of Dazhuang geothermal reservoir “source-reservoir-pass-cover” are analysed, and a geothermal model of Dazhuang geothermal reservoir is established. The Dazhuang geothermal reservoir is based on the geothermal flow of the pull-apart basin formed on the basis of a right-handed strike-slip fault. It uses atmospheric precipitation as well as melted ice and snow in the southern Qilian Mountains as replenishment sources and flows into the thermal reservoir of the basin through the Neogene pore strata. The heat flow generated by the asthenosphere in the longitudinal direction of the Earth’s crust normally increases to form a medium–low-temperature conduction geothermal system. The Dazhuang geothermal reservoir has the characteristics of large caprock thickness, many thermal reservoir sections and rapid replenishment. The thermal reservoir caprock is mainly Quaternary and Neogene Pliocene, with a thickness of 1798 m. The thermal reservoir is composed of sandstone in the Quanzi member of the Baiyanghe Formation in the Miocene, and the cumulative thickness of the aquifer can reach 390m. The resource evaluation of the Dazhuang geothermal reservoir research area is performed using the heat storage method. The total geothermal resources in the study area are 2.08 × 108 GJ, equivalent to 612.1 × 104 t of standard coal, which has a significant development value.