| Title | A REVISED TECTONIC MODEL OF MINAHASA DISTRICT BASED ON LiDAR, IMAGE LOG AND FRACTURE STABILITY ANALYSIS IN TOMPASO |
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| Authors | M. Ikhwan, M.H. Thamrin & I.B. Raharjo |
| Year | 2021 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Tompaso, Sulawesi, Tondano, tectonic, permeability, geology, geothermal system, structure, geomechanics |
| Abstract | This paper investigates the tectonic setting of the Minahasa district by using the updated surface and subsurface data of the Tompaso geothermal field, North Sulawesi, Indonesia. The update includes a detailed analysis of the high-resolution surface topographic map, a borehole image structural interpretation, feedzone identification from the well-test, and stress analysis from the geomechanics study. These methods lead us to a new tectonic concept of the Minahasa district, which consistent with the geothermal conceptual model in the Tompaso area. In line with this, we also evolve the previous well-known literature of Minahasa district tectonic as we used more detailed surface and subsurface data. This paper assesses subsurface geology uncertainty in the Minahasa district, which is mainly hindered by surface interpretation. We argue the local ENE-striking fault existence that suggested by previous literature. We define the local Minahasa district on surface and subsurface, dominantly controlled by NE-striking fractures due to North Sulawesi subduction and East Sangihe subduction. The geomechanics study describes the regional and local stress direction to construct our tectonic concept and corroborates the local Tompaso area`s structural framework. This interpretation also supports the mechanism of Tondano Caldera forming explanation as a classic ellipsoidal natural collapse caldera that follows the maximum horizontal stress trend, rather than occurring as a result of the step-over mechanism. Our permeability investigation through detailed integrated analysis of the borehole image with the injection spinner data suggests the NE-trend fluid flow direction, either from reservoir scale or well scale without showing a robust existence of ENE-striking fractures. |