Heat accumulation effect of groundwater convective activity in karst geothermal reservoir in Jizhong Depression,Bohai Bay Basin
Groundwater flow can be driven by both topographic fluctuation and buoyancy.In this process,heat is transferred rapidly by convection,and then the temperature distribution pattern is changed,resulting in obvious local thermal anomalies.It is of great significance for the heat accumulation of geothermal resources in karst reservoir.Karst geothermal reservoir was well developed in Jizhong Depression,in which karst fracture-cavity system provided good vertical and horizontal conditions for groundwater convection,and formed a unique convection-conduction geothermal system.Through numerical simulation of coupled temperature and hydrodynamic fields,this paper focuses on the model of combined forced convection and free convection,and its heat accumulation effect in Jizhong Depression.The results of 2D finite element numerical simulation show that the superimposed effect of topography-driven forced convection on the base of the free convection model increases the groundwater flow rate within the karst reservoir significantly.The topography-driven fluid can push free convection units to roll downslope,which reinforces the heat accumulation effect of groundwater convection.The significant thermal anomalies in Gaoyang Uplift and Xian County Uplift were mainly attributed to the geothermal transfer effect of free convection in the karst reservoir and the fault zones,which meant the heat refraction accumulation effect caused by basement fluctuation was secondary.In addition,driven by topography,the advance of free convection units to the downstream of the basin may be an important reason for the more significant thermal anomaly of Xian County Uplift than that of Gaoyang Uplift.
万方数据
维普
