The Niobrara formation in the Southern Powder river basin, Wyoming: An emerging giant continuous petroleum accumulation

摘要

The Niobrara Total Petroleum System (TPS) covers an extensive area across the Rocky Mountain Region, US. In the Powder River Basin (PRB), the petroleum system consists of source beds in the Upper Cretaceous Niobrara Formation as well as reservoirs in the Upper Cretaceous Frontier, Turner, Niobrara, Sussex, Shannon, Parkman, Teapot, and Teckla. The Niobrara is a deep-water hemipelagic carbonate mudrock and is Coniacian to early Campanian in age and approximately 150-650 ft thick. The formation, where productive, has low porosity (< 10%), low permeability (<0.01 md), and pore throat sizes less than 0.1 micron. The immature-mature present-day depth boundary is approximately 8000 ft. The formation is subdivided informally into three units in the PRB (A, B, and C). The units consist of cycles of marls and chalks.