Abstract

Rocks of various lithology constitute the (economic) basement of the Northwest Java oilbasin.

Data obtained from recently carried out geophysical surveys i.e. seismic, aeromagnetic and gravity, have furthermore increased the knowledge concerning the basement formation and have enabled the mapping of its configuration. Some deep drillings within the basin have been also very instrumental in its delineation.

The volcanic tuffs (pyroclastic and/or other extrusive rocks) of Eocene to Oligocene age which have a wide distribution within the basin and which in some areas are to be regarded as prospective reservoir rocks, seem also to influence geophysical interpretations.

Within the Northwest Java basin three sub-basins may be distinguished, namely the Jatibarang, the Ciputat and the Pasirputih sub-basin.

A better understanding of the basement configuration will lead into a more efficient approach in the search for hydrocarbons.