Located in Partition Neutral Zone over Kuwait and Saud Arabia border, Wafra Ratawi is a carbonate reservoir having formation dip ranging from 0.5 to 3.5 degrees at edge of the field. Waterflood is to be implemented by new injectors or converting producers to water injectors. Reservoir studies were undertaken to determine whether inject down-dip or in a central location. While the down-dip injector has gravity advantage in displacement process, the central injector may support other four producers no more than two rows away. A reservoir simulation model suggested converting the central producer over the immediate down-dip well at a reservoir edge of 0.9° dip. Reasons to draw this conclusion is not clear due to a complicated reservoir structure in this area. A five-well simulation sector model was therefore taken to investigate this issue.

This study derived a correlation of recovery as a function of dip angle, relative permeability, edge aquifer strength, and injection to production ratio. The model results showed that the central injector performs better than the down-dip injector in a five-well line drive pattern when Ratawi formation dip was less than 2.6 degrees. The central well in the five-well line drive was then converted to an injector in the Ratawi reservoir. The other four producers responded to injection with prompt increase in production and pressure, demonstrating a successful water injector conversion.

This study explained the impacts of formation dip and injector location on wterflood recovery. The derived correlation helped the reservoir management team optimize recovery by selecting the injector location as a function of the reservoir dip.

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