Abstract

3D data visualisation and structural modelling were used to investigate the Gunung Salak geothermal field and surrounding area. The objectives of this investigation were to improve the understanding of the structural geology, especially the structural controls on reservoir permeability.

The Gunung Salak geothermal field is located in a Late Quaternary volcanic massif framed by the volcanic build-ups of Gunung Salak, Gagak, Perbakti and Endut. Gunung Salak, in the northern part of the massif and the highest volcano, straddles the main topographic divide in West Java, separating drainages flowing north into the Java Sea and south into the Indian Ocean. The volcanics are underlain by Early Oligocene to Late Miocene siliciclastics and limestone.

3D models were created using Geosec2D™, 3DMove™ and Geosec3D™, combining diverse geological information including data from over 90 wells and side-tracks, surface data, remote sensing imagery and a high-resolution, digital terrain model (DTM). Linking structures at surface with those indicated in the subsurface by well or micro-earthquake data was a key issue in creating the structural models. Field mapping identified key structural features that could be tied to the subsurface model. Relative timing of structural domains was established by a comprehensive lineament, fault and fracture-scale analysis. These data enabled the creation of detailed structural models.