Publications

Three different organic facies for source rocks are recognized in the NW Java Basin based on biomarker composition of oils. The largest group of oils, derived from a deltaic source rock, typically has a high concentration of oleanane, C27/C29 sterane > 1, hopanehterane > 4, and a predominance of medium weight n-alkanes. A second group of oils, probably of lacustrine origin, has an abundance of botryococcane, hopanehterane > 8, an unusual sterane distribution (C28 > C29 > C27), and a slight odd-carbon n-alkane predominance in the C21 - C33 range. A third type, represented by two oils,. is characterized by a predominance of low molecular weight n-alkanes (n-C11 to n-C17), low diasteranehterane, hopanehterane > 2, C23 tricyclic terpane higher than C24 tetracyclic terpane, C29/C30 hopane > 1, a high homohopane index, C35/C34 homohopane > 1, and an intermediate to high sulfur content. These features suggest a marine carbonate depositional setting for the source rock, although high pristane/phytane (4 to 5 ) and high concentrations of C19 and C20 tricyclic terpanes conflict with this interpretation. Accordingly, these two oils may have been mixed with oil from a noncarbonate source rock. This is the first indication that a carbonate source rock, probably the Baturaja Formation, is present in the NW Java Basin.