Petroleum Geochemistry of oils and rocks in the Arctic National Wildlife Refuge, Alaska - Abstract

Abstract Thirteen oil seeps or oil-stained outcrops in or adjacent to the coastal plain of the Arctic National Wildlife Refuge (ANWR) in northeastern Alaska indicate that commercial quantities of hydrocarbons may be present in the subsurface. The area ia flanked by two important petroleum provinces, the Prudhoe Bay area on the west and the Mackenzie delta on the east. Organic carbon content, organic matter type and pyrolysis hydrocarbon yield show that all rock units, except the Hue Shale which contains type II organic matter, are predominantly type III organic matter. Pre-Cretaceous rocks that crop out in the Brooks Range could not be adequately evaluated because of the high thermal maturity of their organic matter. Thermal maturity threshold of oil, condensate, and gas from calculated vitrinite reflectance gradients in the Point Thomson area are 4,000, 7,300, and 9,330 m, respectively (12,000, 22,500, and 28,000 ft). TTI calculations for the Beli-1 and Point Thomson-1 wells indicate that maturity first occurred in the south and progressed north. The Hue shale matured in the Beli-1 well during the Eocene and in the Point Thomson-1 well in late Miocene to early Pliocene time. In the Point Thomson area, the condensate and gas recovered from the Thomson sandstone and basement complex is probably from the pebble shale unit, and the oil recovered from the Canning Formation probably came from the Hue Shale. The gas recovered from the three wells in the Kavik area is probably thermal gas from overmature source rocks in the immediate area. None of the oils in or adjacent to ANWR correlate with oils from the Prudhoe Bay area or farther west. However, the Jago oil type, which includes oil from Marsh Creek anticline, Jago River, and Angun Point, do correlate well with the Hue Shale.