REINSON, GERALD E.
Sproule Associates Limited, Calgary, Alberta, Canada

Abstract: Depositional Systems Control of Reservoir Distribution, Geometry and Heterogeneity, Albian Viking Formation, Alberta Basin

Regional stratigraphic correlations combined with facies and sequence stratigraphic analyses indicate that the Albian Viking Formation and coeval Bow Island Formation (Muddy Sandstone equivalent) in central and southern Alberta, respectively, comprise a regressive-transgressive couplet containing a basin-wide sequence boundary that extends southward into Montana and Wyoming. This sequence boundary bears directly on the distribution, external geometry, internal heterogeneity and reservoir quality of hydrocarbon-bearing sand bodies throughout the basin. Highly prospective reservoir trends occur associated with this major bounding surface and, to a lesser extent, with parasequence boundaries within both the transgressive and regressive (highstand) systems tracts.

Viking/Bow Island reservoirs can be divided, on the basis of whether they are related to the regressive or transgressive systems tract, into three depositional types: progradational shoreface bars, transgressive bars and sheets, and estuary/tidal channel deposits. Shoreface bars, which consist of fine- to medium-grained sandstones, are tens of kilometres long, kilometres wide, and three to eight metres thick. Coarse-grained to conglomeratic transgressive bar and sheet sandstones are up to tens of kilometres long, can be relatively narrow, or several kilometres wide, and range in thickness from less than one up to four metres. Estuary and tidal-channel sandstones vary from fine-grained to conglomeratic and occur in isolated channel-like deposits often greater than ten metres thick. Internal heterogeneity and reservoir quality vary substantially between reservoir depositional types; transgressive bar and sheet sandstones exhibit the most favourable characteristics with respect to these two important reservoir parameters.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas