| Title | Structural Control of the Sorik Marapi Geothermal Field – Surface and Subsurface Evidences |
|---|---|
| Authors | Maria Jhonnie VILLAREAL, Armando LICUP, Xyza OMAC-CANARIAS, Zosimo SARMIENTO |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Sorik Marapi, Sumatran Fault Zone, Sumatra, structural geology, subsurface geology, drilling, well-fault intersection, well permeability, |
| Abstract | Geothermal sites in Sumatra are typically associated with the Sumatran Fault System (SFS) and young volcanic centers of Barisan Mountain range - the volcanic arc related to the Sunda trench. The SFS is a highly segmented, 1,900 km long, right lateral strike-slip fault which traverses the entire length of Sumatra. The Barisan Mountain is comprised of at least 35 volcanoes, one of which is the active strato-volcano – Sorik Marapi (2,145m). A complex fault system exists within the Sorik Marapi geothermal field. The main structural feature is the 35 km wide Panyabungan pull-apart basin which extends in the NNW–SSE direction along the prominent strikeline of the SFS. The fault trace of SFS in Sorik Marapi is delineated as a highly segmented fracture network with conjugate sets of strike-slip faults (synthetic and antithetic fault sets) which developed oblique to the main SFS. The fracture network is characterized by parallel right-stepping strike-slip faults, oblique normal faults, and anastomosing secondary faults. Prior to the aggressive drilling campaign in Sorik Marapi geothermal field between 2016 to 2018, structural mapping was undertaken in order to identify fault permeability targets. The use of Lidar images coupled with ground-truthing proved to be an indispensable method in identifying structural targets for the drilling campaign. To date, a total of eighteen (18) deep wells have been drilled in five (5) pads across the field which confirms the existence of a commercial, high-temperature resource. These wells have provided an important insight of the subsurface geology, hydrothermal alteration at depth, and permeability potential of the SFS in Sorik Marapi geothermal field. |