Modeling reservoir heterogeneities

Studies from various sources indicate that most reservoirs are heterogeneous mixtures of rock type, porosity, permeability, and saturation. Successful enhanced recovery requires knowledge of these heterogeneities. Reservoir engineers and geologists are increasingly aware of the presence of reservoir variation and its potential effect, not only on enhanced recovery operations but on other reservoir projects such as volumetric calculations and infill drilling. Three-dimensional volume modeling allows proper spatial placement of varying critical reservoir parameters. Both vertical and lateral changes in reservoir character can now be properly modeled and the output used for editing, introducing new data, calculating volumes, mapping, and analyzing multiple interpretations. A three-dimensional, geocellular computer modeling program called the Stratamodel system is available. It credibly depicts the natural state of a reservoir by dividing the reservoir volume into cells. Each cell may have varying vertical dimensions, and cells are in layers placed within the model to approximately parallel the strata boundaries or depositional surfaces (time lines). Interval strings of data are introduced at wells from which various attributes can be allocated to individual cells along each cell layer. Complex stratigraphic, facies, and structural relationships can be modeled with a resulting realistic representation of reservoir heterogeneity. An increase of moremore » than 20% recovered hydrocarbons could be realized through the recognition and proper portrayal of reservoir heterogeneities. Three-dimensional geocellular volume modeling is one method of accomplishing this desirable goal.« less