The Sunda basin is one of the Tertiary ideogeosynclines bordering the stable Sundaland. Twenty-one prospects have been drilled since offshore exploration started in late 1968 with oil and/or gas being discovered in 52% of these ventures.

A north-south horst and graben framework on a rugged Late Cretaceous surface governed erosion, deposition, and tectonic growth throughout the Tertiary in all but the northeastern extremities of the basin.

Volcanic and fluvial rocks constitute initial sedimentary deposits. Quantity of sediment influx was primarily responsible for differential sinking of graben blocks during early basin development and resulted in thick deltaic deposits during early Miocene. Downwarp of the backdeep continued with sea invasion through island passages in the geanticline on the south. High tectonic blocks prevented segments of the basin from being invaded during early basin development. With continued denudation and downwarp, Miocene transgression expanded over the Sunda basin. Local high areas persisted, but transgression continued dominant.

As basin segments filled, a nearby flat depositional surface developed. Slight lowering of sea level resulted in regional regression, followed by major transgression in post mid-Miocene time. Late in this second transgressive period, most disconnected ideogeosynclines became one regional geosyncline surrounding the Sundaland. Final regional regression occurred in late Miocene, culminating in complete emergence during Pleistocene. Worldwide melting of Pleistocene ice caused a resubmergence of the basin to present marine conditions.

Production has been established in principal intervals producing in Sumatra. Major new pays have been established in Oligocene volcanic tuffs and in Oligocene (?)-Miocene sandstones of the Talang Akar. Possible commercial shows have been found in Miocene Batu Radja transgressive limestone and in weathered basement rocks. Major oil production is indicated from Air Benakat sandstone bodies. Gas production has been established in the Parigi Limestone.

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