Preliminary geothermal gradient and heat flow compilation from Western Java, Indonesia

Compilation of geothermal gradient and heat flow data from petroleum and geothermal wells of western Java, Indonesia is conducted in order to provide basic data for geosciences study and for exploration of mineral, hydrocarbon and geothermal resources. The geothermal gradient is calculated from 45 oil and gas and 3 geothermal wells. The data include bottom hole temperatures (BHT) and drill stem test results (DST). Heat flow data are compiled from 67 oil and gas and 3 geothermal exploration wells. The petroleum well data consists of results from 33 new heat flow surveys (this study) with 13 recalculated data and 21 adopted as is from a previous study. Result show that heat flow in Northwest Java tertiary sedimentary basin is slightly higher than normal terrestrial heat flow. The heat flow varies from 60.8 mW m^-2 to 135.2 mW m ^-2 and the temperature gradients range from 3.70°C/100 m to 6.6°C/100m. The very high heat flows are found in the southern part of this basin. Heat flow of a dome unit in the Bogor-Cimandiri zone from one geothermal well is about 188.41 mW m^-2. In the volcanic area, which is mainly in the central part of study area, the heat flow is about 186.5 mW m^-2, but low heat flow values may also occur depending on local geological conditions. Comparison of the heat flow map and gravity data shows that high heat flow outside the volcanic area is located at the border of gravity highs and gravity lows which are interpreted as faults. However further study is needed in interpreting this phenomenon.