AMT方法在地热勘探中的应用——以田湾河大热水地热勘探为例

Application of AMT Method in Geothermal Exploration:A Case Study of Dareshui Geothermal Exploration in Tianwan River

为探测石棉县田湾河流域的地热构造,查明该区域地热资源的赋存特征,基于野外地质调查,在田湾河流域大热水温泉区布置了4条AMT(音频大地电磁法)测线进行地热勘探。结果显示:研究区发育一条东-西走向的断裂(猫猫石-草科断裂),断裂形成宽度大约60 m的断裂破碎带,AMT电阻率在工作区断裂破碎带和热储层上均有异常反应,断裂破碎带与周围围岩范围内电阻率有较大差异且呈不连续变化(高-低-高),热储层表现为明显的低阻异常。钻探结果与AMT探测反演结果吻合。推测猫猫石-草科断裂是控制田湾河两岸一系列温泉、地热井和地热异常的主要控制性断裂,也是地下热水上涌的主要通道,同时说明AMT方法在山区地热探测中能有效识别热储层的分布情况。

In order to detect the geothermal structure of the Tianwan River Basin in Shimian County and identify the occurrence characteristics of geothermal resources in the area,based on the field geological surveys,four AMT(Audio magnetotelluric method)survey lines were arranged in the Dareshui hot spring area in the Tianwan River Basin for geothermal exploration.The results show that there is an east-west trending fault(Maomaoshi-Caoke fault)developing in the study area,and the fault forms a fault fracture zone with a width of about 60 m.The AMT resistivity is abnormal in the fault fracture zone and thermal reservoir in the work area.The resistivity between the fractured zone and the surrounding rock is quite different and shows a discontinuous change(high-low-high),and the thermal reservoir shows an obvious low-resistivity anomaly.The drilling results are consistent with the AMT detection inversion results.It is speculated that the Maomaoshi-Caoke fault is the main controlling fault that controls a series of hot springs,geothermal wells and geothermal anomalies on both sides of the Tianwan River,and is also the main channel for the upwelling of underground hot water.And it also indicates that the AMT method can effectively identify the distribution of thermal reservoirs in geothermal exploration in mountainous areas.