鱼台凹陷边部玄武岩覆盖区地热勘探方法及应用效果

研究区位于鱼台凹陷边部，上覆较厚的沉积地层，为地热形成提供了良好的盖层，热储层为奥陶纪马家沟群，其顶板埋深均超1000m，最大埋深可达3000m。理论上在该地区开展地震勘探寻找目标体是一种效果较佳的物探方法，但地表下约300~600m隐伏新生代玄武岩，其对地震波具有强屏蔽作用,造成玄武岩下伏地层的地震反射信息很弱，甚至无地震反射信息，严重影响玄武岩下伏地层的成像效果；CSAMT法在该低阻沉积地层覆盖区电磁信号同样存在低阻屏蔽，衰减很快，近场效应明显，勘探深度不超过1000m。本文以区域重力场对嘉祥断裂初步推断为基础，大地电磁测深（MT）为主，常规电测深为佐证的物探手段，能够较好地降低玄武岩及低阻屏蔽的影响，提高深部勘探能力，划分地热盖层与热储层的分界线，圈定导热导水构造，最终获得鲁西南地区温度最高的灰岩热储地热井。

Geothermal Exploration Method and Application Effect in Basalt Covered Area at the Edge of Yutai Depression

the working area is located at the edge of Yutai depression, which is covered with thick sedimentary strata. It provides a good cover for geothermal formation. The thermal reservoir is Ordovician Majiagou group. The buried depth of its roof exceeds 1000m, and the maximum buried depth can reach 3000m. Theoretically, it is a better geophysical method to carry out seismic exploration to find the target in this area, but the buried Cenozoic basalt about 300m to 600m below the surface has a strong shielding effect on seismic waves, resulting in weak seismic reflection information or even no seismic reflection information of the underlying strata of basalt, which seriously affects the imaging effect of the underlying strata of basalt; CSAMT method also has low resistance shielding in the coverage area of low resistance sedimentary strata, with rapid attenuation, obvious nearfield effect, and the exploration depth is no more than 1000m. Based on the preliminary inference of regional gravity field on the Jiaxiang fault, geophysical exploration method mainly based on magnetotelluric sounding (MT) and supported by conventional electrical sounding can better reduce the influence of basalt and low resistance shielding, improve the deep exploration ability, divide the boundary between geothermal caprock and thermal reservoir, delineate the heat conduction and water diversion structure, and finally drill the geothermal well of limestone thermal reservoir with the highest temperature in southwestern Shandong province.