ABSTRACT: Search for Oil in Papua New Guinea: Evolution of Structural Interpretations in a Difficult Physical Environment

Richard H. Matzke

Chevron Nuigini Ply Ltd. and its partners are exploring for oil in the foreland folded belt of Papua New Guinea's Southern Highlands province, one of the remaining frontier areas of the world that offers the potential for the discovery of giant oil fields. The search has been focused on the Lower Cretaceous Toro sandstone, an excellent reservoir rock unit about 100 m thick. It is overlain by up to 1200 m of Upper Cretaceous marine shales, siltstones, and fine sandstones (Ieru formation) and, finally, at the surface by the thick (1000 m) Miocene Darai limestone. The entire stratigraphic sequence was folded during the Pliocene-Pleistocene into a broad belt of thrusted anticlines that have good surface expression throughout the highland valleys and ridges. The thick carapace of folded limestone is heavily karsted and extremely rugged, circumstances that have prohibited effective seismic surveying of the region. Prospecting for oil has consequently relied almost entirely on structural interpretation of surface geologic data, including images from satellites and airborne radar, and, most particularly, on the results of wildcat drilling. Fortunately, early drilling was rewarded with encouraging quantities of gas, gas condensate, and oil. Structural models and concepts are continuing to evolve as the results of successive wells become available, thus providing the critical insight into the habitat of hydrocarbons in this complex environment.

AAPG Search and Discovery Article #91000©1990 AAPG Conference-Giant Oil and Gas Fields of the Decade 1978-1988 Conference, Stavanger, Norway, September 9-12, 1990