| 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. Various surface geological and geophysical surveys including seismic, gravity, magnetic, magnetotelluric (MT) have been conducted during the period. A total of 5 deep boreholes have been drilled so far, some of which are for exploration and the others are for production of geothermal water. After the Korean EGS pilot project have launched in 2010, a well PX-1 for injection or production has reached down to 4,127 m in October 2013, which is recorded as the deepest well ever in Korea. All those drilling results showed that the area is generally flat layered structure and partly showing heterogeneity of plutonic intrusions. Heunghae basin, the main target of the geothermal exploration, is covered with Quaternary alluvium underlain by these thick Tertiary sediments, which is quite uncommon in Korea. The basement rock of granite or granodiorite appears at around 2,200 m depth. According to analyses of gravity/magnetic and MT data, there exist lineaments and possible fractures mainly running NNE-SSW and crossing conjugates at the southern part of Heunghae basin. In this study, we first collect and correlate all those survey and drilling results, and then will integrate as a common 3D geological model using commercial software GoCADTM. |