Three Dimensional Geological Model of Pohang EGS Pilot Site, Korea

Abstract

Geothermal investigations of Pohang site has been carried out for more than a decade, since Korea Institute of Geoscience and Mineral Resources (KIGAM) had launched a geothermal development project for a large scale space heating in 2003. Several surface geological and geophysical surveys, including seismic, gravity, magnetic and magneto-telluric (MT) have been conducted during that period. A total of five deep boreholes have been drilled so far, some of which were drilled for exploration purposes and the others for production of geothermal water. After the Korean EGS pilot project was launched in 2010, well PX-1 was drilled. It reached a depth of 4,127 m by October 2013. Well PX-1 is recorded as the deepest well ever drilled in Korea. The drilling results showed that the area has a flat-layered structure with some plutonic intrusions. Specifically, the Heunghae Basin, which is the main target for the geothermal exploration, is covered with Quaternary alluvium deposits underlain by thick Tertiary sediments which is quite uncommon in Korea. The basement rock of granite or granodiorite appears at a depth of around 2,200 m. According to the geophysical surveys carried out (gravity, magnetic and MT) it is expected the presence of lineaments and fractures mainly running NNE-SSW together with crossing conjugates fractures at the southern part of Heunghae Basin. In this study, we first collected and correlated all the data generated by these surveys with the drilling results, and then it was integrated as a common 3D geological model using commercial software GoCAD TM .