Shoreline, Deltaic and Fluvial Reservoirs
Published:January 01, 1988
Gulf Canada Resources has carried out extensive evaluation studies in the Athabasca oil sands deposit in northern Alberta. The Sandalta project near Fort McMurray was aimed at developing an open-pit mining operation to recover oil from the oil-saturated sands in the McMurray Formation.
The McMurray Formation is the result of a gradual Lower Cretaceous marine transgression into a well defined basin. A sequence of fluvial sands followed by estuarine sediments and subsequent marginal marine sediments is widespread. Four main depositional environments have been recognized for the McMurray Formation in the area. Within the Sandalta project itself, two of these depositional environments account for the bulk of the sediments present and virtually all of the oil-bearing sands. Three-dimensional sedimentological studies have shown that, of the 22 facies identified in these two environments, only three of the sand facies (tidal channel, distributary channel and fluvial-estuarine sand) have any appreciable lateral extent and consistency in oil saturation. These three sands are therefore (he prime targets for exploration and development in the study area, whether through surface mining or in situ recovery techniques. This model can be used for most of the Athabasca deposit with modifications for local conditions. Conventional techniques of outlining areas for development based on economic surface mineability factors or isopach maps will be misleading if the variability of the pay zones themselves is not accounted for by studying the depositional environments. A three-dimensional computer block model can be used to store the facies data from numerous core holes. This computer data base then becomes a valuable tool for mapping the lateral variations in the subsurface geology, prospect evaluation for development potential, and conceptual mine planning.
Figures & Tables
This volume is a collection of papers which focus on the sedimentology of siliciclastic sandstone and carbonate reservoirs. The papers were selected to show how detailed sedimentologic descriptions, when combined with engineering or other subsurface geologic techniques, yield reservoir models which may be used for reservoir management during field development and during secondary or tertiary enhanced oil recovery. In all the papers the framework for the field descriptions relies heavily of full-diameter cores. In addition to conventional 4-inch-diameter cores, frozen and rubber-sleeve cores were utilized in one or more of the studies. In addition to cores, at least one other geologic or engineering technique is integrated into each study. This integration of sedimentologic descriptions with other techniques gives rise to synergism.