The K.A. Clark volume: a collection of papers on the Athabasca Oil Sands presented to K.A. Clark on the 75th anniversary of his birthday

This paper has been taken from parts of a more comprehensive and detailed report published by the Alberta Oil and Gas Conservation Board that embodied a study involving the nonconfidential data associated with over 1200 oil-sands evaluation holes and 600 wells. The purpose of this paper is to identify the oil-sands deposits of the Province and to present the Conservation Board's estimate of the reserves that they contain.

The oil-sands deposits are classified into three main groups distinguished from each other by the stratigraphic unit and the area in which they occur. The Athabasca deposit occurs almost entirely within the Wabiskaw-McMurray unit and is located in the northeastern part of Alberta; the Bluesky-Gething deposits exist in the Bluesky-Gething Formations and are situated in the northwestern part of the Province; the Grand Rapids deposits occupy portions of the Grand Rapids Formation and are located in the central part of northern Alberta.

The evaluated portion of the Athabasca deposit occupies about five and one-half million acres and is buried by zero to 2000 feet of overburden. The evaluated portions of the other two groups of deposits together cover over two million acres in area and are buried by between 300 and 2600 feet of overburden.

Reserves have been estimated for those oil sands that, in the opinion of the Board, warrant an evaluation on the basis of the magnitude of the reserves and the adequacy of the data. The majority of the reserves in place were estimated by deriving oil-pay values by isopachs and measuring the reserve volume by means of a planimeter. Intervals having a weight saturation of less than two percent were excluded from the estimate.

Recovery factors were selected by the Board to convert reserves in place to recoverable reserves of raw oil-sand oil and recoverable reserves of upgraded synthetic crude oil.

The following estimates are listed in terms of reserves in place, recoverable reserves of raw oil-sand oil and recoverable reserves of upgraded synthetic crude oil, respectively, for the deposit or group deposits designated: Athabasca deposit: 626, 369 and 267 billion barrels; Bluesky-Gething deposits: 51, 28 and 21 billion barrels; Grand rapids deposits: 33, 18 and 13 billion barrels. The Athabasca reserves are further classified into overburden, oil-saturation and drilling-definition categories. The Bluesky-Gething and Grand Rapids reserves are classified into the drilling-definition categories only.

The Oil and Gas Conservation Board believes that its estimate of the grand total of oil-sands reserves is in reasonable agreement with the actual total reserves in existence within the area evaluated, but it believes that a considerable amount of additional evaluation drilling is needed to establish, with confidence, the magnitude of the reserves within certain widespread portions of these area. Furthermore, it expects that future evaluation drilling undertaken beyond the evaluated areas will warrant additions to its present reserve estimate.