Stratigraphy and Depositional Systems of the Frontier Formation and Their Controls on Reservoir Development, Moxa Arch, Southwest Wyoming. Topical Report, April 1989-March 1991

摘要

By controlling sandstone continuity and detrital clay content, depositional systems influence reservoir development in low-permeability gas-bearing sandstones of the Upper Cretaceous Frontier Formation along the Moxa Arch in the Green River Basin, southwest Wyoming. Original depositional porosity and permeability are highest in clean Frontier sandstones, which even after diagenetic modification comprise the most prolific reservoirs. The Frontier was deposited in a fluvial-deltaic system, in which most reservoirs lie in fluvial channel-fill and marine shoreface sandstone facies. The fluvial channel-fill sandstones form southeast-trending belts, which are a few miles wide, several tens of feet thick, and separated by interchannel shale and sandy shale. Within the channel belts, clean sandstone occurs as discontinuous lenses up to 20 feet thick that are interlayered and laterally gradational with mud-clast-rich shaly sandstone. The marine shoreface facies forms a continuous northeast-thinning sheet of sandstone, 40 to 120 feet thick. Clean sandstone is best developed near the top of the shoreface facies in northeast-thinning trends 5 to 40 feet thick.