The regional tectonic setting and Tertiary stratigraphy of west Indonesian basins suggest that they are similar in stratigraphic successions, sedimentation history, and structural development. Each basin underwent a megacycle of sedimentation, beginning with a transgression, followed immediately by bathyal conditions, and terminating with a regression at the end of basin evolution. There are, however, differences in the time sequence between basins.

In the basins, with one exception, oil is in the upper regressive facies. In south and central Sumatra and in southeast Borneo (Kalimantan), oil also is present in the lower transgressive facies. A study of reservoir rocks suggests that the oil is confined largely to coarse clastic beds of the transgressive and regressive facies.

Possibilities are excellent for petroleum discovery in the transgressive facies of all basins, and this sequence potentially has greater reserves than the regressive facies. A heavy paraffinic oil is to be expected in the transgressive strata in contrast to the light paraffinic or asphaltic oil in the regressive facies.