Exploration and study on carbonate thermal reservoirs in fault basins: A case from Yutai Sag

Abstract

Yutai Sag is a Mesozoic synsedimentary fault basin. It is characterized by much fault intersection and massive Ordovician carbonate rock in the deep, which indicates a good prospect of geothermal development. To study the characteristics of carbonate thermal reservoirs in this fault basin and evaluate its geothermal resource potential, a hole with a depth of 2 309.31 m was drilled in Yutai Sag. Through comprehensive logging, productivity testing, hydrochemical analysis, gas composition analysis, and geothermal water 14C age determination, the sources and supply of thermal fluid, heat source storage, and ion migration in the interior of the basin are analyzed.The result shows that the temperature anomaly presented in the geothermal well temperature curve and the fault position characterized by many fractures are consistent, indicating the source direction of geothermal water.The geothermal water with high content of Cl- and Na- is related to halite dissolution. The apparent age of geothermal water is 43.5 ka BP near the confluence of faults in the southeastern Yutai Sag, and the corrected age is 10.752 ka BP which is from the late Quaternary Pleistocene to the early Holocene.The study shows that there are relatively active or young geological structures in Yutai Sag, which are one of the thermal sources of thermal reservoirs. The recoverable geothermal resources of the Ordovician thermal reservoir in the area are approximately 2.12×109 GJ, equivalent to 7.27×107 t of standard coal, implying great resource potential and good prospects for development and utilization.

Keywords

• geothermal
• fault basin
• carbonate rock
• hydrochemistry
• gas composition
• yutai sag