Exploring the Jurassic of the Bomberai Peninsula, West Papua

Woodroof, Peter B.
Genting Oil & Gas, Kuala Lumpur, Malaysia.

A new phase of petroleum exploration has begun in West Papua. Leading this revitalized exploration is Genting Oil Kasuri Pte Ltd ("GOKPL"). GOKPL is actively exploring the onshore Kasuri Block located on the Bomberai Peninsula south of both the giant Vorwata Gasfield and other Tangguh Project gasfields.

The Kasuri Block was awarded to GOKPL in May 2008 under a Production Sharing Contract with BPMIGAS. Since 2008 GOKPL has acquired extensive 2D seismic covering most of the block, started drilling, made a significant Jurassic gas discovery and begun a 3D seismic survey.

Thick Jurassic strata occur everywhere in the subsurface of the Bomberai Peninsula, frequently at depths of more than 3,000m, and beneath thick often cavernous New Guinea Limestone. As a result, Jurassic strata are hard to clearly image on seismic data. To the north the Jurassic is thin or absent and no Jurassic rocks relevant to the subsurface stratigraphy of the Bomberai Peninsula are exposed in outcrop. Determining the Jurassic stratigraphy, structure and petroleum potential of Bomberai requires good seismic and deep well data.

Marine and fluvial Jurassic strata unconformably onlap both Triassic and Permian rocks in Bomberai such that much of the Lower Jurassic is absent through non-deposition. However, thick Middle and Upper Jurassic sections were deposited everywhere, with the Middle Jurassic containing a major wave-dominated sand-prone delta and the Upper Jurassic containing thick claystones that provide excellent seals.

Important in understanding the petroleum potential of Bomberai is that no tectonism affected Jurassic strata until the late Oligocene, by which time the underlying source rocks were expelling hydrocarbons. This not only protected the Jurassic strata from erosion, but also helped preserve reservoir quality, especially as gas was readily available to fill traps.

The Oligocene stress regime created E-W sinistral strike-slip faults and NW-SE anticlines forming petroleum traps. In transpressional areas the Jurassic strata are highly folded and faulted and seismic imaging poor. However, in less faulted areas good quality imaging of the Jurassic can be achieved using appropriate acquisition and processing parameters. New insights into the Jurassic of Bomberai and its petroleum potential will be presented.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012