英山地热田区深大断裂的控水控热作用及地热系统成因研究

The impacts of deep faults on fluid migration,heat accumulation with implication to genesis of Yingshan geothermal system

目前对英山地区深部地温场的分布情况以及构造控热模式尚无系统研究,不利于地热资源科学的开发利用。基于野外裂隙测量、浅层连续测温、钻孔压水试验等成果,建立了英山裂隙岩体地下水渗流-传热三维模型,对深部储层在不同构造组合模式下的压力场、温度场和达西流速场进行分析。研究结果表明:研究区深部温度场和压力场受断裂系统影响较大,在致密基岩及隔水断层处,流体运动微弱,热量运移以热传导为主,导水断层处以热对流为主;在深部导水断层区域温度和水压偏低,与导水断层处相比,隔水断层处水压偏高;在2 000 m深度以深,高温区和水力交换强烈区与导水断层带处完全对应,表明断层是储层中最主要的流体和热量运移通道;区内断层组合模式为复合模式,北东向断层为英山地区主要导水导热构造,热水在沿北东向断层向上运移的过程中,受南北向断层的阻隔,最终在两组断层的交叉复合位置处形成温泉。该研究可为研究区内的地热资源科学勘查和合理开发利用提供参考。

The distribution of the deep geothermal field and the tectonic thermal control mode in the Yingshan area were not understood systematically,which would bring in constraints to the sustainable exploration of local geothermal resources.Based on the field survey on continuous temperature,fracture measurements in the outcrops of granite rock,slug-test,and pumping test in the boreholes,a three-dimensional model coupling fluid flow and heat transfer process in fractured rock reservoir was established.Then the distribution of fluid pressure temperature and the Darcy velocity in the whole geothermal reservoir were calculated considering different treatment combinations of main faults.The results show that the deep temperature field and fluid pressure distribution are greatly affected by the faults system.At the location of bedrock and impermeable fault,the fluid movement is very weak,and the heat transfer is mainly controlled by heat conduction,while in the high permeable fault,it is mainly controlled by heat convection.Low temperature and fluid pressure occurred in the deep,high-permeable fault zone whereas high fluid pressure occurred in the impermeable fault zone.At a depth larger than 2000 m,the zones with high temperatures and intense hydraulic exchange coincide with the conductive fault zones,which indicates that the high-permeable faults are the most important channel for seepage and heat transfer in the reservoir.Therefore,the northeast faults are the dominant channel for fluid migration and heat conduction in the Yinshan area.Hot water migrates upward along the northeast faults and is blocked by the north-south fault.The hot spring is formed at the intersecting position of two groups of faults.This study is helpful for scientific,sustainable exploration of geothermal resources in the Yingshan area.