This study presents an assessment of heterogeneity on vertical and areal scales and discusses the development of methodology for a proposed waterflood scheme in a heavy oil field in Northern Kuwait. The field produces average 15° API crude of 50-100 cp at 100° F. The field has a complex geologic and stratigraphic architecture, and the associated reservoirs are highly heterogeneous in nature. Both numerical simulation and analytical models were used to assess the performance of the proposed waterflood.
Vertical and areal heterogeneity of the oil bearing formation were evaluated using Dykstra-Parsons coefficient, Lorenz coefficient and coefficient of variance methodologies. Both numerical simulation and analytical models were deployed to evaluate the waterflood performance under 5-spot and inverted 9-spot patterns for 20 and 10 acre spacing. An analytical excercise was carried out as a pre-check for the expected waterflood recovery factors.
Results from all three methods of heterogeneity assessment indicated the existence of a highly heterogeneous reservoir with average Dykstra-Parsons coefficients being greater than 0.8. A heterogeneity distribution map shows strong presence of areal heterogeneity. Ratio of the injectors to producers, pressure depletion schedule and associated recovery factors for planned pattern configurations were assessed from numerical simulation. Pattern by pattern heterogeneity indices were estimated and attempted to correlate to predicted flood performances.
This work highlights the impact of heterogeneity on the waterflood performance for a heavy oil reservoir to assess a more realistic production target, with integrated results from analytical and numerical methodologies.