Study On Generating Mechanism And Evaluation Of Low-medium Temperature Geothermal System In Tangshi County Of Zixing City

Hunan province is located in the intersection of Yangtze and Cathaysia Block,with its unique geographical location,complex structure,frequent magmatic activities,creating good conditions for the formation of geothermal,hot groundwater occurs mainly in the limestone area of karst aquifer and granite structure broken zone.The province is rich in geothermal resources,divided with the more obvious,in low temperature water and geothermal system of convective type majority,has good prospects in development.In this paper,the geothermal field in Zixing city of Hunan Province Tangshi geological conditions of low temperature convection type geothermal system in the case study,the occurrence regularity of geothermal resources,distribution characteristics and formation mechanism,reasonable reservoir resources evaluation,the development and utilization of geothermal resources in Hunan province has very important significance,at the same time enrich Hunan the formation of scientific system of geothermal technology and method of mechanism theory and assessment of geothermal resources.The main research contents are as follows:?1?This paper analyzes the geological conditions of geothermal field Tangshi,the hot water causes were judged,and the establishment of conceptual model of thermal cycling.The geothermal field covered only by a thin layer of Quaternary alluvium,the horizontal heat preservation conditions are poor,surface water and shallow groundwater by high lying areas along the fracture and fracture of granite broken down to recharge ground water in deep rock after heating along the fault F1 fault and F fault at the junction with aggregation rise broken,discharge surface formation of Tangshi hot spring.?2?In the research area of underground water cation is mainly Na+,Ca2+,anion is dominated by HCO₃-,the three line diagram of underground water chemical Piper determine the water chemistry type is HCO₃-Na type.The basic research area in geothermal water and groundwater chemical characteristics mainly from shallow to deep aluminosilicate,runoff and rock the interaction of carbonate,sulfate and other mineral components.This paper uses PHREEQC hydrogeochemical simulation software,the component distribution model and mass balance model based on the water rock interaction processes were simulated earth chemical reaction,to lay the foundation for research on the formation mechanism of the geothermal system.?3?Calculation of geothermal heat storage resources,using the volume method,according to the reservoir volume and temperature field characteristics of the geothermal field is divided into 3 temperature zones,respectively,calculated 500 m,1000m depth of thermal resources;and by using the Q-S curve extrapolation method to calculate recoverable resources,the geothermal field Tangshi at all levels can be the exploitation of geothermal water resources.The geothermal resources in the process of evaluation,accurate calculation of heat storage temperature is extremely important,and the water-Method of chemical balance based on the scale of rock is most commonly used,this paper calculates the geothermal fieldbasedheat reservoir temperature average value of 82.90 degrees by using potassium magnesium geothermometer.No steam loss SiO₂ geothermometer is calculated by the method of ground hot water when the average temperature is 122.5 ?;and the use of PHREEQC to calculate the balance of underground water in the mineral part at 70-120 ? saturated,can be regarded as a heat reservoir formation temperature at 70¹20 ?,two geothermal Is the calculated heat reservoir temperature values are within this range.