| Title | Geophysics Field Camp (GFC): A Student Project Aimed to Investigate the Low to Moderate Temperature Geothermal System in Mt. Pancar Area, Bogor (Indonesia) |
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| Authors | Yunus DAUD, M. Syamsu ROSID, Supriyanto SUPARNO, Dzil Mulki HEDITAMA, Wambra Aswo NUQRAMADHA, Fikri FAHMI, Surya Aji PRATAMA, Agus SULISTYO |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | : geophysics field camp, low to moderate, temperature, geothermal system, Mt Pancar, Indonesia |
| Abstract | Geophysics Field Camp (GFC) is a curriculum related project conducted by undergraduate students of the Department of Physics (Geothermal Laboratory), the University of Indonesia. The project is designed to educate the students in understanding geophysical project from survey design, data acquisition, data processing, through modeling and interpretation. In addition, geological mapping and geochemical survey are also added for supporting the geophysical data. Mt Pancar geothermal prospect is located in the Bogor district, West Java Province, Indonesia. The geological condition of the area consists of Tertiary volcanic formation of the Mt. Pancar and Quaternary volcanic formation of Mt. Panisan covering Tertiary sedimentary formation. The surface manifestations found in this geothermal area are hot springs, warm grounds and altered rocks. The hot springs are found in Kawah Merah (T = 70oC) and Kawah Putih (T = 51oC) with neutral pH and minor silica sinter. No indication of thermal activity on the summit of Mt Pancar. The subsurface temperature as indicated by Na/K geothermometry is in the range of 180-190 oC. Based on the preliminary information it can be concluded that the Mt Pancar geothermal area can be classified as a low to moderate geothermal resource. To develop initial conceptual model of the geothermal system, geophysical investigations including Audio-frequency Magnetotelluric (AMT) and gravity surveys were then carried out. Ten soundings of AMT data were accomplished along two profiles both crossing Mt Pancar summit and the other ends crossing Kawah Merah (Line A) and Kawah Putih (Line B) hot springs area, respectively. Whereas gravity survey was conducted on 155 stations in a grid survey design. Three-dimensional inversion of AMT data was then carried out along the profile lines using MT3DInv-X software. The results show a conductive layer (less than 15 ohm-m) from near surface down to about 2000 meter depth. The conductive layer is interpreted as the clay cap of geothermal system distributed between Mt. Pancar dan Kawah Merah (Line AB) dan Mt. Pancar dan Kawah Putih (Line CD). The slightly resistive layer (20 – 100 ohm-m) was also found underlying the clay cap which is interpreted as reservoir zone. A more resistive basement (more than 100 ohm-m) was encountered forming structure-like graben. The graben structure possibly controls the hydrothermal system in Mt Pancar area. In addition, 2-dimensional gravity modeling using Grav2D-X software supports the resistivity inversion results. Integrated interpretation was then accomplished by incorporating AMT and gravity data supported by geological and geochemical data. Based on this study, a conceptual model of the Mt Pancar Geothermal Area was developed to explain the geothermal occurrence in this area. |