SUBSURFACE ENVIRONMENTAL FACIES AND RESERVOIR RELATIONSHIPS OF THE McMURRAY OIL SANDS, NORTHEASTERN ALBERTA.

Analyses of cores and wireline logs from 28 wells within an eight-township area demonstrate that the Lower Cretaceous McMurray Formation consists of three fundamental progradational depositional units bounded by time-stratigraphic markers. The reservoir quality and continuity of the oil-bearing sands are intimately related to the environmental facies. Statistical analyses show the distributary-type sands are coarser-grained, thicker-bedded, and have a lower percentage of muddy matrix and higher oil saturations than any of the other identified facies types. Petrographic and X-ray analyses reveal that the McMurray oil sands in the Athabasca area have a grain-and-matrix composition that is significantly different from those in the Cretaceous sands of the Cold Lake and Peace River heavy-oil areas.