Present-day temperature-pressure field and its implications for the geothermal resources development in the Baxian area, Jizhong Depression of the Bohai Bay Basin

The Baxian area in the Jizhong Depression, west of the Bohai Bay Basin, is rich in geothermal resources, where Xiong County was built as the first smokeless city in China and the Xiong-county Model has become the geothermal resources demonstration model in China. In this study, the present-day geothermal gradient and the horizontal distribution characteristics of the temperature and pressure at different depths in the Baxian area were studied based on massive measured temperature and pressure data of the boreholes, and then the relationship was also discussed between the temperature-pressure field and the geothermal resources. The following findings were obtained. (1) The present-day geothermal gradient of the Baxian area is within the range of 21.8-73.5 °C/km, averaging 33.5 °C/km. (2) Its strata temperature increases as the depth increases. The horizontal variations of the geothermal gradient and strata temperature correspond to the basement relief very well. As the abnormally high temperature areas, the northern Niutuozhen Uplift, the Central Baxian Depression and the central East Langgu Depression possess huge geothermal resources and will be the most favorable exploration targets. (3) The formation pressure of the Baxian area is characterized by normal pressure and weak overpressure, and its horizontal distribution varies at different depths. The middle-strong overpressure generally developed at the depth of 4000 m in the southern Langgu Depression and southern Baxian Depression. This study is of important guiding significance for the exploration and development of geothermal resources in the Baxian area.