A New Approach to the Fracture Detection in Geothermal Resource Development with DAS-VSP

Abstract

　This technical paper was contributed to the 75th Anniversary Symposium of the Geophysical Exploration Society of Japan and presents the latest in geophysical exploration in the resources session (oil, natural gas, metals, geothermal). JOGMEC has developed the DAS-VSP technology as part of its geothermal power generation technology research and development project. As a technique for exploring fracture systems in an area of about 500 m around a well, we have developed a new exploration method using diffraction imaging, which utilizes the phenomenon in which the opening part becomes a prominent secondary source when seismic waves pass through the fracture and have achieved field implementation. In addition, DAS-VSP can be applied not only in the active type using artificial seismic sources, but also in the passive type using AE in the area as the seismic source, and the applicability of each method may differ depending on the field, so we have classified them according to the surface conditions of geothermal areas, microseismic activity, and the number of wells that can be used for observation, and have proposed a survey method suitable for each type.