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ABSTRACT: Old fault controlled structures, reservoir development and the petroleum systems of eastern Irian Jaya and western PNG

McConachie, Dr Bruce Alan1, Elio Lanzilli1, R. Dan Kendrick1, Dr James Iliffe2 , (1) Santos Asia Pacific Pty Ltd, Brisbane, Australia (2) Conoco Inc, Aberdeen, United Kingdom

Foldbelts characteristically reactivate pre-existing structures during foreland cannibalisation. Because of this situation, earlier growth faults controlling reservoir thickness can form major thrust fronts with deep detachments. This evolution creates reservoir involved hanging wall anticline traps that focus primary and secondary petroleum migration.

A unique situation occurs in western PNG and eastern Irian Jaya. The Komewu, Kiunga, Kariem, Baliem trend ("3KB trend") is a fault system that forms the underlying structural control to the western margin of the Digul Arch and has been reactivated to constitute the frontal thrust in central Warim. The system crosscuts the foldbelt through the Baliem Valley and eventually continues to the northwest through Wamena. Although similar trends can be recognised at locations such as Kutubu, the 3KB trend provides a unique window by virtue of its geographic continuity from the foreland where high quality regional seismic analysis is available through to the fold/thrust belt.

A series of excellent quality wave dominated ramp margin reservoirs are developed in the Papuan Akimeugah Basin. These reservoirs consist of reworked, well sorted shoreface sandstone deposits with high levels of lateral continuity deposited during times of relative sea level lows and subsequent increasing accommodation.

The first oil flow in the eastern Akimeugah Basin occurred in 1998 at Kau 2 on the Digul Arch. The oil flowed from the LJ5 sandstone equivalent Iagifu Sandstone of PNG. Prior to the Kau 2 drillhole, good oil shows were observed in several wells in the area. At least one active petroleum system based on widespread black Kimmeridgian source rock shales (D. swanense) currently operates in the area (Noordwest 1, Cross Catalina 1, Digul 1 and Kariem 1). The character, timing and reactivation history of the 3KB trend provides a special opportunity to further evaluate the demonstrated petroleum systems of the New Guinea Fold Belt within the Warim area.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia