Proceedings The 5th Indonesia International Geothermal Convention & Exhibition (IIGCE) 2017 2 - 4 August 2017, Cendrawasih Hall - Jakarta Convention Center, Indonesia

Indonesia is considered to have the largest geothermal potential in the world, estimated at 29,000 MW and distributed from high, medium and low enthalpy geothermal systems. To date, only less than 5% have been utilized, but many other geothermal concessions are being developed and offered for further exploration and development. The Sorik Marapi geothermal field has been recently drilled with results indicating the existence of a high temperature-neutral resource. Maximum temperature measured so far has been recorded as 290°C, with three wells currently tested and producing an average of 11.5 MW.

Initial modeling works in the field has been completed and discussed in FEDCO (2017) NORC report paving the way forward for a strategy that prioritizes the development of the Sibanggor area. This paper deals with the 3D modeling studies conducted in the geothermal field, based on available data from surface exploration (3G-geological, geochemical and geophysical) surveys, and shallow and deep drilling in the 4 identified prospect areas. The 3D modeling utilizes Petrel® software from Schlumberger which allows interfacing of limited and non-standard data formats for easy and fast processing. The 3D model is structured to integrate the structural model, lithology and alteration zone, the 3D MT resistivity model and the temperature distribution collected from the 6 wells in the area.

The workflow in the models starts with data loading and quality control, creation of structural framework for fault modeling and generating 3D grid for reservoir property modeling to capture the lithology, resistivity and temperature distribution. Special workaround algorithms are required to ensure correct data loading. The final result of this study is the 3D subsurface static model defining the vertical and lateral resource boundaries as well as the prime resource areas which would be the basis of designing future well targets to achieve the targeted 240 MW installed capacity in the field. The same model would then be expanded in constructing the numerical model to match the natural state condition of the resource, and subsequently for making forecasts on the future reservoir behavior at different operating conditions.