Toward Successful Petroleum Production from Unconventional and Conventional Reservoirs in the Central Alaska North Slope

The Alaska North Slope is a world-class petroleum province, with ~40 years of production from conventional hydrocarbon accumulations. Declining volumes in the Trans Alaska Pipeline demand a new look at the presence and effectiveness of unconventional accumulations. The Great Bear Petroleum technical team is evaluating the petroleum producibility of ~600,000 acres (2,500 km 2 ) located on the central North Slope between the National Petroleum Reserve, Alaska (NPRA) and the Arctic National Wildlife Refuge (ANWR) just south of Prudhoe Bay. Strategically located close to existing infrastructure, this area includes the region’s most important source rocks: Hue Shale, pebble shale unit (Kalubik Formation), Kingak Shale, and Shublik Formation. The key to understanding unconventional oil and gas lies in the integration of geologic, geochemical, and geophysical data. Our team will accomplish this using a 3-D petroleum system model within an area of interest that spans 145° to 153° W longitude and 69° to 71° N latitude. The geologic model will be visualized as a series of stacked risk elements within traditional play fairways at the scale of a regional development plan (1 km). To accomplish this, we combine legacy geochemical analyses with ~2,400 new analyses to map source rock properties across the leasehold. Further, we apply rigorous data standards to the interpretation of organic geochemical data; this approach includes tuning vitrinite reflectance measurements to Rock-Eval pyrolysis Tmax measurements in the area of interest. Preliminary results indicate that for all source rock units, the Great Bear Petroleum leasehold lies within the liquid or liquid-plus-gas fairway; this fairway is defined by the 0.6 %Ro contour in the north (up-dip direction) and by the 2 %Ro contour to the south (down-dip direction). In the southern half of the acreage position, the oldest source rocks are in the late-oil zone, which is a favorable state of thermal maturity in that it provides gas to drive oil out of tight mudstone reservoirs. Tectonic uplift of hydrocarbon-saturated hydrocarbon source rocks provides additional drive in that gas exsolves from the liquid below the critical point.