Geological assessment of heavy-oil reservoirs in the Lloydminster area, using a computerized data base

Heavy-oil reservoirs of the Lower Cretaceous Mannville Group in the Lloydminster area (Western Canada) occur in a sequence of complexly arranged sandstones, siltstones, shales, and coals. Trapping mechanisms vary, and the precise geological controls governing hydrocarbon accumulations are not well understood. For a nine township area surrounding Aberfeldy field, Saskatchewan, geological data pertaining to some 2000 wells have been systematically collected and organized into a computer data base. Such depth-dependent properties as stratigraphic markers, character of markers, and lithologic types, are recorded for each well. In addition, a file containing digitized well-log traces has been integrated with the geological data. Within this area there is a need to portray geologic relationships on a regional scale, at the scale of producing fields and at the scale of enhanced oil recovery pilot sites. Using a variety of retrieval, analytical, and display programs, the effectiveness of the data base approach will be demonstrated for each level of application. Computer-generated structure maps, cross sections, three-dimensional perspectives, isopach, and lithology maps are used to illustrate the spatial and temporal variation in structure and rock body geometry. A similar approach is used to portray fluid distribution. Reconstruction of paleotopography and the use of a variety of cross-plots is seen to provide considerable insight on regional and local controls on hydrocarbon distribution.