Commercial application of enhanced oil recovery (EOR) technology requires reservoir specific engineering to achieve optimum economy of operations, production and ultimate recovery. Appropriate engineering strategies must be founded in detailed geological models tailored to individual reservoirs. Recent research on heavy oil pools in the Lower Cretaceous Mannville Group indicates some generalisations which contribute to the basic geological framework for characterisation of specific reservoirs in the Lloydminster area. The bulk of established oil in place in the Lloydminster area is contained in tabular, wave-generated sand bodies less than 7m thick. The apparent upper limit on reservoir thickness is interpreted to represent some paleohydraulic control on sand deposition, such as water depth. Thin sands are characterised by high porosity and permeability, with significant anisotropies due to internal sedimentary structures, intercalations of shale, and cemented zones. Common lateral and vertical transitions to shalier strata create complex reservoir geometries. Anomalously thick sands contain subsidiary quantities of oil in place. They predominantly comprise deposits of channel systems characterised by rapid vertical degradation. Such reservoirs are generally composed of slightly coarser sand than thin reservoirs, with very high porosity and permeability. Physical properties of channel sands are more isotropic than those of thin sands, due to less common internal lamination and shale intercalations. EOR development of thick reservoirs is more attractive, insofar as capital and operating costs and potential heat loss to non-reservoir strata (especially in processes involving steam injection) are considerably lower than in typical thin reservoirs. Moreover, the relative homogeneity of channel reservoirs is expected to result in superior sweep efficiency and ultimate recovery. The isotropic character of channel reservoirs facilitates effective geological and engineering modelling, whereas the inhomogeneities more typical of thinner reservoirs present a greater challenge. The technical difficulties associated with EOR applications in thin sands are compounded by the economic detractions of most such projects at present. However, the largest volume of Saskatchewan heavy oil reserves occurs in lithologically complex, thin reservoirs. Efficient commercial exploitation of the resource is dependent upon vigorous, timely development of geological and engineering models for such reservoirs.
Commercial application of enhanced oil recovery (EOR) technology requires reservoir specific engineering in order to achieve optimum economy of operations and to maximise ultimate recovery of original nil in place. Extensive experience gained from experimental projects has increased confidence in the essential commercial viability of EOR. Operating procedures have improved substantially, with increased potential for greater ultimate recovery. Nonetheless, profitable application of EOR technology in most Saskatchewan heavy oil reservoirs depends upon further sophistication of engineering techniques. Appropriate engineering strategies must be founded in comprehensive, detailed geological models tailored to each reservoir. A thorough understanding of reservoir geology is required for technical and economic assessment of EOR applications and for choice of a specific process to be implemented in a particular reservoir. Moreover, adequate geological models are essential to effective management of such problems as poor injectivity, low sweep efficiency (e.g., "chanelling"), fracturing and excessive heat loss to non-reservoir strata.
