Publications

Sea-floor sediments collected during an extensive geophysical and coring project in several deepwater basins of Indonesia have been analyzed in detail using a range of geochemical techniques. The results show clear evidence of oil and thermogenic gas seepage, including basins or sub-basins that are largely unexplored. Biogenic gas was also commonly detected, although its presence was readily distinguished from thermogenic gas components. In many cases, oil was found in sufficient quantity to yield a full suite of biological markers. The biomarkers in turn were used to derive information about the parent source rock and to correlate the seep with known subsurface accumulations of oil. The ten areas of Indonesia examined in this study are: SW Sunda, North Makassar, Bone Bay, Banggai Sula, Gorontalo, Cendrawasih, Misool, Seram, Kumawa-Keras and Jamdena (Figure 1). The probable types of source rock for oil seeps in these areas have been determined using biomarker and isotopic compositions. Characteristics for both Mesozoic and Tertiary source rocks, including carbonate and clastic lithofacies, were observed. In some instances, the seeps tied directly to crude oils that are being produced in the basin. In other cases, the seeps showed sufficient difference to known subsurface accumulations to indicate a source rock of a different type or age was active. The sea-floor seeps have provided an extraordinary opportunity to gain insights into areas of active hydrocarbon migration in undrilled or under-explored basins. In some areas, this represents the first evidence for the existence of an underlying petroleum system, which in the future, may provide targets for wildcat exploration drilling.