| Title | Permeability Control of Tompaso Geothermal Field and Its Relationship to Regional Tectonic Setting |
|---|---|
| Authors | SARDIYANTO, SaptoTrianggo NURSETO, Imam Muhammad PRASETYO, Mochamad Husni THAMRIN, Muhammad Yustin KAMAH |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | structure, permeability, Tompaso |
| Abstract | Tompaso geothermal field is located in the northern arm of Sulawesi Island, Indonesia. This field can be separated as a different geothermal system from Lahendong field that successfully developed by Pertamina. The hot fluid upflow at Tompaso postulate to be located in Riendengan – Sempu volcanic complex and it is moving to NE controlled by ENE-WSW trending fault indicated by manifestation appearances lineament. Comprehensive structural geology analysis was conducted using satellite images, digital terrain model (DTM), and supported by two borehole fracture imaging log. Fault at the surface generally identified have trending NE-SW Tompaso Fault. The major fault identified ENE-WSW sinistral strike-slip Soputan Fault which control manifestation distribution in Riendengan – Sempu and Tempang - Toraget. The other fault have trending NW-SE Sonder Fault. The open fractures from borehole imaging log trending dominant NE-SW, and sealed or close fractures mainly trending NW-SE. The local maximum horizontal stress (Shmax) trending NE-SW identified from drilling induced tensile fractures and borehole breakouts orientation. It is agree with the trend of open fracture patterns. There is a contradictive stress orientation between Shmax (NE-SW) and the direction of regional stress derived from Molluca Sea collision zone that trends North West. Both those two stress vector are almost perpendicular. The stress resultant from north and south part of Minahasa due to their difference of plate movement vectors suspected as the primary cause of the local stress regime. It is also resulting a parallel couple strike slip fault in North and South of Minahasa (Manado-Kema Fault and Amurang-Malompar Fault) that have opposite slip movement. This local stress regime controls the Soputan Fault that provides the permeability for geothermal fluids in the Tompaso geothermal system. |