Geothermal reservoir boundary delineation using 3D magnetotelluric inversion. case study: The "delta" geothermal field of Indonesia

The "DELTA" geothermal field is a brown geothermal field in Indonesia. The field has been produced for many years. Most of productions wells are in the center of the reservoir, need to have step-out wells to reduce the well intervention risk. The first step-out well was drilled near reservoir boundary of conceptual model which is refer to "old" 3D Magnetotelluric (MT) inversion. The step-out well failed to produce steam and well data indicated outside the reservoir. After careful analysis, it found that the 3D MT model does not match with the well data. On this study, the author conducts 3D MT inversion re-modeling to re-delineate the reservoir boundary. To have comprehensive interpretation, the result of new 3D model which generate independently then compared with available data sets such as MEQ, gravity, geology map, geochemistry data and well data. The new 3D MT model shows better match to well data, re-delineate the reservoir boundary and give recommendation for well targeting areas.