Abstract

The Pikes Peak heavy oil field is situated 40 km east of Lloydminster and is presently the site of a steam stimulation pilot project, producing from sands that are part of a major channel system within the Waseca Formation (Lower Cretaceous Mannville Group). Viscous oil (15,000 mpa.s at 21°C) is trapped in sand bodies up to 35 m thick within this north-south oriented channel system at a depth of approximately 500 m. The pilot project is located on a structural high axis created by solution of Devonian salt and much of the site contains no bottom water.

The stratigraphy and sedimentology of the Waseca Formation in the Pikes Peak field are reviewed with the aid of geophysical well logs and 24 cores. The channel facies of the formation are informally subdivided into three successive units: (A) the Homogeneous Sand Unit, the main reservoir sand, at the base; (B) the Interbedded Sand and Shale Unit, which flanks and overlies the main reservoir sand; and (C) the Sideritic Shale Unit capping the Interbedded and Homogeneous Units.

The quartzose, medium to fine grained reservoir sands are well sorted, laminated and planar cross bedded. The dominant clay is authigenic kaolinite. The sands are generally unconsolidated, but are occasionally cemented by calcite and siderite. Reservoir quality decreases upward.

The degree of bioturbation, type of microfauna and stratigraphic relationships suggest that the Waseca reservoir sand is tidal/estuarine in origin.