Abstract

The G. Patuha geothermal area is located in the western part of the Java Island, approximately 35 km southwest of Bandung. Volcanic activity in the area dates from Lower to Upper Pleistocene, and is associated with G. Kendang (NW of Patuha) and G. Patuha itself. Eruptions have been characterized by basaltic andesite lava breccias which covered mainly the middle part of the area.

A photogeological interpretation made in 1985 identified the presence of continuing strong hydrothermal activity near the top of G. Patuha and at Kw. Ciwidey.

Faulting is most prevalent in an arcuate swath south and west of G. Patuha and G. Kendang. The near radial pattern is thought to result from south to north compression brought about by movement of the Samudra Hindia plate.

A geochemical study of surface and ground waters from several discharge features in the Patuha area showed the waters to be of a neutral-bicarbonate chloride type. Geothermometry calculations indicate that underground reservoir temperatures may exceed 215°C. This is supported by the presence of a 14 sq. km. low resistivity (< 10 ohms) anomaly centered NE of G. Patuha. This data was derived using the Schlumberger technique for determining apparent resistivity and the results further confirmed by the drilling of seven shallow (100m - 230m) wells. The hottest of these (PT-1), near Kw. Putih, had a bottom hole temperature of 160°C. High temperatures coincide with the low resistivity anomaly and the PT-I hot spot may be located in the upflow zone of a geothermal reservoir.

By knowing the extent of the resistivity anomaly and the estimated underground temperature, the potential of the Patuha geothermal area can be inferred using a "stored heat calculation", the results of which are in the range 400 - 445 MW (e).

It is therefore apparent that the G. Patuha area has significant potential to meet the electric power demands of West Jawa and further exploration activity should be encouraged to confirm and develop this resource potential.