Abstract

New Guinea hosts diverse petroleum systems ranging from the giant Tangguh/Bintuni Basin gasfields and Salawati Basin oilfields in the Bird's Head area, through the Hides gasfield and Kutubu oilfields in the Papuan Fold Belt to the large Pandora gasfield in the Gulf of Papua. In between lies the sparsely explored Irian Jaya Fold Belt (IJFB) with common oil shows and two non-commercial oil discoveries. Three new play concepts are proposed.

1) Along the front of IJFB, thick Late Miocene-Recent molasse buries potential Mesozoic source rocks to >5km, currently in the oil window and charging foothills and southern IJFB structures, and perhaps stratigraphic traps in the foreland. Structural traps formed in the Pliocene-Recent, pre-dating or synchronous with expulsion. A favorable petroleum system in the southern IJFB depends on porosity preservation within the Cretaceous Ekmai and Woniwogi Formations.

2) Middle-Late Miocene marls deposited in a restricted foreland basin provide a potential new play opportunity, as in the northern Lengguru Fold Belt. In the foothills of the IJFB, these rocks are interpreted to be in the oil window at maximum temperatures and in thrust contact with thick Ekmai Formation sandstones. Involvement of the Ekmai Formation as the primary reservoir minimizes the main risk of deep burial and resulting poor reservoir quality.

3) A basement high separating the western IJFB from the Waghete area is flanked by a series of long-lived marginal graben. These provide important depocenters for Mesozoic source rocks, potentially including turbiditic facies of the Tipuma Formation redbeds. Plio-Pleistocene inversion of these graben forward of the main uplift in the IJFB resulted in relatively simple structures. Reservoir quality is maintained near the basement high due to the relative decrease in burial compared to adjacent areas.