Direct Exploration of Geothermal Reservoir by Mise-a-la-masse Method

本文作者在日本首次将米氏法应用于地热调查。该方法是在导电体内部或附近用套管作为电流极，然后用类似于自然电位法的方法测量地面电位分布。针对地热资源与周围地层的高对比度，设计并改进了直接前景寻找类似地热储层的导电体的方法。本研究从实验室水槽模型实验开始，通过电子计算机数值模拟，达到地热区的实际现场应用。在数值计算中，采用有限差分法计算了不同模型上电流极线源不同位置下的地面响应，并利用HT-8井套管进行了现场测量 ...更多信息 在Hatchobaru著名的地热区，以描绘地热储层。由于地热流体、热液蚀变带和周围地层的折射率对比度高，测量产生了轮廓清晰的残余异常。从数据处理中得出的等值线图清楚地表明了几个有希望的低电阻率区，包括目前生产能力为55 MW的生产区，几乎所有的生产威尔斯都位于该生产区。该方法与斯伦贝谢电阻率反演分析得到的低阻层分布和在Hatchoburu地热区的相同区域进行了大地电磁（MT）勘测。特别是在八丈原地热田现今生产区的资料中，mise-a-la-dam方法的结果与地面地球物理方法的解释结果有着惊人的相似性，因此，mise-a-la-dam方法可以充分地应用于地热调查，而该方法已用于采矿业的找矿。少

The mise-a-la-masse method was firstly applied to the geothermal investigations by the present authors in Japan. The method using a casing pipe as a current electrode inside or nearby a conductive mass, then the established potential distribution of ground surface is measured similarly with the self potential method. This study has been designed and improved to prospect a conductive body like a geothermal reservoir directly by taking notice of the high contrast of resistivities between the geothermal resources and the surrounding formations. The present study stars from the tank model experiments in the laboratory, through numerical simulation by the electronic computer, and reach to the actual field application to the geothermal area. In the numerical calculation, the surface responses has been obtained by the finite difference method with different locations of a line source of current electrode over the various models.The field survey was carried out using a casing pipe of HT-8 well … More in the well known geothermal area in the Hatchobaru in order to delineate the geothermal reservoirs. The measurement produced the sharply contoured residual anomaliesdue to high contrast of resistivities among the geothermal fluid, hydrothermally altered zones and surrounding formations. The contour maps derived from the data processing clearly indicated several promissing low resistivity zones of interest, including the present production zone of 55 MW capacity where the almost all of productive wells located in.It was confirmed that the apparent resistivity contour map obtained by the mise-a-la-masse method showed a good correlation with the low resistivity layer distribution derived from the inversion analysis of the Schlumberger resistivity and the magneto-telluric (MT) surveys made in the same zones of Hatchoburu geothermal area. The similarities between the mise-a-la-masse result and the interpreted result from the surface geophysical methods are striking in particular of the data over the present production zone in the Hatchobaru geothermal field.It is concluded that the mise-a-la-masse method can be adequately applied to the geothermal investigations while the method has been used for the ore prospecting in the mining industry. Less