Abstract

The stratigraphic and areal distribution of oil and gas source rocks in Eastern Indonesia has been determined by extensive analyses of well sections and field samples from the area. Source rocks ranging in age from Pliocene to Cambrian have been identified, primarily in basins with Australian crustal affinity.

Continued refinement of the stratigraphy has enabled a better understanding of controls on source rock development during particular time periods and has allowed intra-basin comparison of source rock units. Geochemical analyses of selected tested oils and oil seeps have also allowed correlation of these oils and the identified source rocks.

Pre-Tertiary source rocks are widespread in Eastern Indonesia but source rock accumulation has been mainly restricted to three time periods; Late Permian, Late Triassic, Early-Middle Jurassic. Source rocks range from fluvio-lacustrine shales and coals to marine carbonates and shales, which have been correlated with oils from the area. Regional paleogeographic reconstructions, based on biostratigraphic results from both field samples and numerous well sections combined with documented structural information, have provided insight into the possible areal extent of these source rocks.

Tertiary source rocks have accumulated in several basins during the Middle-Upper Miocene and Pliocene and show many similarities to fluvio-delatic coals in Western Indonesia. In the Salawati and Tomori Basins, however, source rocks comprise interbedded coals, calcareous shales and argillaceous limestones containing a mixture of marine-derived and terrestrial organic matter. These source rocks have been correlated with tested oils from the basins.

The development of pre-Tertiary and Tertiary source rock depositional models for Eastern Indonesia will assist assessment of, and exploration in, presently undrilled frontier areas.