Publications

The Ubadari field is located in the Berau PSC, about 50 km southwest of Tangguh LNG area in Bird’s Head region, West Papua, Indonesia. Ubadari-1 well was drilled in 1997, discovering gas in the Middle Jurassic “Roabiba” sandstone and in Paleocene sandstone reservoirs. The Roabiba sandstone was deposited in a fluvial to marginal marine environment. Following the discovery in 1998, Ubadari-2 was drilled to test a structure down dip of the Ubadari-1 well, but no hydrocarbon accumulation was encountered. Why was Ubadari-2 dry? That is a question that has been an issue for further exploration in the Western Berau region. In order to unravel this puzzle a paleoreconstruction study was undertaken to understand the structural evolution. The Bird’s Head region has experienced three main erosion events: Permo-Triassic erosion, Oligocene erosion, and Pliocene erosion. The Oligocene and Pliocene erosion events have had the greatest effect on the Ubadari structural development, both occurring post deposition of the reservoir. Therefore, understanding the amount of section removed by these two events is fundamental to understanding the results of Ubadari-1 vs. Ubadari-2. Results of the study suggest that Ubadari field was a low relief structure before Pliocene time while the structure at Ubadari-2 was down flank on the structure. Ubadari-2 was located on the flank of the structure between culmination to the north and a low to the south prior to Pliocene age and the present structural configuration was formed post hydrocarbon charge. Both structures continued to grow to produce the present day structural configuration. That is why at present day there are two separate structures.