TAF PUBLISHING

The objective of this study is to predict the location of the geothermal reservoir through interpretation of Magnetotelluric depth-resistivity maps, with reference to Lili-Sepporaki geothermal area. Lili-Sepporaki is a non- magmatic prospect located in Polewali Mandar, Western Sulawesi-Indonesia. The study area is dominated by andesitic to trachytic to trachytic tertiary volcanic products. The only thermal manifestations in the area are the hot springs and rock alterations. Previous geochemical studies found out the hot spring water has temperature of 98^oC and the reservoir temperature of 190^oC. A big portion of the surface rocks are weathered and hydrothermally altered owing to findings from magnetic and Bouguer gravity surveys. This research utilized two-dimensional magnetotellurics data to locate resistivity anomalies in the subsurface. MT data was processed using SSMT2000 and MTEditor software programs while WinGLink software was used in the interpretation of the data. Four resistivity maps were obtained, each corresponding to one of the depths: 500 m; 1000 m; 1500 m; and 2000 m. There is a general sharp reduction in resistivity as opposed to the conventional resistivity of fresh igneous rocks. Analysis shows that the reservoir appears between depths of 1000 m and 2000 in different parts of the survey area, with prospect boundaries located in the South, South West and South East. A three-dimensional MT data analysis and exploration drilling are recommendable in order to get a detailed geothermal model.