The main reservoir objective in the western Papuan Basin is the Upper Jurassic-Lower Cretaceous Toro Sandstone with the Ieru Formation providing a thick regional shale seal. Deeper sandstones (Koi-Iange and Magobu) provide good secondary targets and facilitate migration. The Toro Sandstone is well developed across the Fly River Platform but does lap on to basement in the far west. Structures across the Papuan Basin foreland are subdued compared to those of the Highlands area. However, global analogues demonstrate the ability of subtle structures in a foreland setting to hold major reserves. The major structural play types in the Papuan Basin foreland region include gentle anticline structures, localised folds and flower structures, tilted fault blocks and drapes over basement highs. Stratigraphic pinch outs (eg. Lake Murray-1 and -2) also provide potential.
Early exploration efforts since the 1930's in the Papuan Basin foreland concentrated on the drilling of surface-mapped anticlines. These early foreland wells were sparsely located and in most cases not valid structural tests, with wells often located close to accessable rivers with little or no seismic control. Despite the lack of early success, these early wells have helped to provide stratigraphic control for later exploration campaigns which have increased in number and success since the late 1980's. Modern exploration efforts have been successful in terms of the number of discoveries (Stanley, Juha, Iagifu-Hedinia, Agogo, Elevala, Ketu, Ubuntu, Douglas and Puk-Puk), although individual volumes are not yet able to support further LNG developments. To put the foreland region into context, comparison with other oil and gas provinces around the world shows that much of the world's oil reserves occur in foreland areas adjacent to fold-thrust belts similar in settings to the onshore Papuan Basin. Analogous settings show initial exploration success concentrates on fold belt areas where there are large surface structures. The largest finds are usually made later as exploration moves into the more gentle structural platform areas. This is typically because the foreland areas have had access to mature source rocks for longer, thus the foreland area of the Papuan Basin remains an exciting place to continue exploring.