Abstract

The original Mickelson Creek field, discovered in 1960, produces from discontinuous Mesaverde Formation fluvial sandstones draped over a structural closure. The field is in a small subsidiary thrust feature in front of the leading edge of the Prospect fault. Drilling in 1982 discovered a separate accumulation down-flank that is completely stratigraphic.

Fluvial reservoir sandstones of the Cretaceous Mesaverde Formation angularly subcrop beneath the predominantly non-reservoir Paleocene-age Fort Union Formation. Stratigraphic traps are formed in several different sandstone beds. The most areally extensive of these covers about 1800 acres with an average pay thickness of 15 ft. Deposition was in a floodplain environment, with channel sands grading laterally into overbank muds, crevasse-splay sands, and fresh-water marsh deposits. Porosity has been enhanced by dissolution of unstable framework grains (primarily feldspars) in proximity to the unconformity, but poor interconnection of pores and small average pore-throat size have resulted in relatively low permeabilities. The reservoirs respond well to large foam fracture stimulations, with recoverable reserves ranging from 1.5 to 4 bcf of gas per well.