Development Implications Arising from the Reinterpretation of the Results of a 3D MT Inversion at Bedugul, Bali, Indonesia

Abstract

Exploration drilling in 1997-1998 of the Bedugul geothermal field in Bali discovered a deep, but hot, exploitable geothermal reservoir. However, the wells are poorly permeable. A 3D MT inversion has been reinterpreted in light of the results from the wells in order to further assess the field. The general resistivity pattern of geothermal fields in andesitic terranes is found. A near surface high resistivity layer overlies a shallow conductor that wraps around a moderately resistive core. A fainter repeat of this pattern towards the northeast above a gravity high along the trend of younger volcanism may represent an older, colder geothermal system in this direction. In the hot system to the southwest an elongate southeast trending higher resistivity zone in the conductor to the northwest may represent the recharge zone. Another southeast elongate zone further south may represent the outflow; given that the majority of the system’s surface thermal features lie in this direction. The two southeast trending zones are offset in a fashion suggestive of a pull-apart feature between them. If this is the case it could form a broad permeable zone in which the field could be developed.