Discussion on main occurrence characteristics of geothermal resources in Yutai sag of West Shandong

Abstract

Geothermal energy is a type of green energy and it has been highly valued in recent years. According to the division of geothermal fields in Shandong Province, this area is a Yutai geothermal prospective area. However, few researchers conducted in-depth research in this area. This study is based on the project “Investigation and Evaluation of Geothermal Resources in Yutai Sag, Shandong Province”. Through data collection, ground investigation, geothermal field measurement, geophysical exploration, geothermal well drilling, pumping test, water quality analysis, and other means, the occurrence conditions of geothermal resources, thermal reservoir characteristics, and geothermal fluid chemical characteristics in this area are analyzed and studied by using the relevant data of geothermal exploration wells. The depth of the constant temperature zone is 20 m, the temperature of the constant temperature layer is 16°C, the Cretaceous geothermal gradient is about 1.26 °C/100 m, the geothermal gradient is about 2.94 °C/100 m, and the Ordovician geothermal gradient is about 3.98 °C/100 m. The limestone roof depth of the geothermal well is 2,089 m, the well depth is 2,309 m, the bottom-hole geophysical temperature measurement is 74.5 °C, the wellhead temperature is 68.5 °C, the maximum water inflow is 552 m3/d, the radius of influence is 852 m, the water chemical type is Cl-Na type, and the salinity is 26454.54 mg/L. It is a hot water geothermal resource in low-temperature geothermal resources. Geothermal water contains fluorine, bromine, strontium, and iron concentrations that met the standards of named mineral water. The contents of lithium and boron can reach the mineral water concentration, with a high physiotherapy value. This study provides a geological basis for the exploration and utilization of geothermal resources in this area and related areas.