The Geological Challenge Challenge for Development of Heavy Crude and Oil Sands of Western Canada

摘要

Many years of drilling has delineated the Heavy Crude and Oil Sands Deposits of Western Canada. Although the vast areal extent of these deposits is relatively well-known, an understanding of their depositional history is less clear. For the geologist, the challenge is not the discovery of new reserves, but rather the search for suitable recovery targets within the complex stratigraphy of the deposits. There are four major deposits: Athabasca, Peace River, Cold Lake and Lloydminster, which are defined by their stratigraphic position within the Lower Cretaceous Mannville Group of Alberta and Saskatchewan. Overall, the Mannville Group consists of a "background" stratigraphy of stacked highstand deposits made up of prograding deltaic to marine shoreface environments. These units are generally widespread sheet sands that are easy to correlate. However, the complexity is introduced with lowstand/transgressive deposits consisting of channels and valleys that have been incised into this "background" stratigraphy. The channels are of various dimensions and generations, and are filled with complex fluvial and estuarine sediments, which generally can be correlated and differentiated only with great difficulty. There are major economic reserves in both the highstand and the lowstand deposits, but sand-filled channels are the typically the most attractive reservoirs. The complex channel environments dominate the Lower Mannville (Athabasca, Peace River), whereas the shoreface/deltaic environments dominate the Upper Mannville (Cold Lake, Lloydminster). The major challenge in the exploitation of Western Canada's heavy oils and bitumen in the 21~(st) Century will no doubt be the development of a suite of effective recovery techniques. But these techniques will require integration with suitable reservoir configurations, which can best be delineated by detailed geological analysis framed within a regional basin perspective.