Publications

The Pinang Dome, located in Kalimantan Timur, is superficially an anticlinal structural feature. The core of the dome is composed of Pamaluan Formation sediments (predominantly marls and claystones) and covers an area of over 50 km2, these sediments are overlain on the flanks first by Pulaubalang, and then by Balikpapan Formations (both are mostly sandstones, siltstones and coal). A Bouguer gravity anomaly survey indicates a coincidence of higher gravity values with the western and southern parts of the Pinang Dome, this suggests the presence of dense rock material closer to the surface, as compared to the surrounding area. Vitrinite reflectance (Vr) studies show an increase in rank from 0.34% (to the south the Pinang Dome) to 0.71% (west and adjacent to the Pinang Dome) over a lateral distance of ~15 km. In the six wells examined in this study, Vr increases at different rates down hole depending on geographic position. Although the data density is not ideal, the rates seem to increase in a south-east to north-west direction, but not necessarily in direct relation to proximity with the Pinang Dome. These data seem to indicate that the relationship between coal rank and the Pinang Dome is more complex than originally thought. The geothermal gradient through the coal measures within the general area of the Pinang Dome appears to be high (~50ºC/km) compared to most other areas in the Kutai Basin (27º to 39º C/km). On balance, these data do support an igneous diapir as the origin of the Pinang Dome. Regardless of root cause, the increased coal rank has resulted in a premium quality export product of significant economic value. Similarly, reservoir properties related to the generation of thermogenic gas within the higher rank coal seams in this area will add significant value to any exploited coalbed methane plays.