Sedimentology and petroleum reservoir characteristics of the Mississippian Pekisko Formation, northern Alberta, Canada

Abstract

The Lower Mississippian (Tournaisian) Pekisko Formation in the Hawk Hills area of northern Alberta consists of skeletal-peloidal limestones with local shaly beds, and hosts a large, medium to heavy-gravity oil resource. It has been divided into the lower carbonate, lower shaly, upper carbonate, and upper shaly units. Three lithofacies associations, consisting of the outer ramp to slope, outer ramp, and mid- to inner ramp, are interpreted to represent deposition on a low-energy, temperature-stratified, homoclinal to distally-steepened ramp along the northern flank of the Peace River Embayment. Depositional patterns were strongly controlled by reactivated basement faulting and differential subsidence. Diagenetic features are interpreted to be marine, early meteoric, burial, and late meteoric in origin. Late burial and meteoric dissolution, which produced the reservoir porosity, was texturally controlled and associated with the Pekisko subcrop edge. The best quality reservoir units occur in the mid- to inner ramp lithofacies association.