Predicting Future Performance of a Field with Complex Reservoir Heterogeneities Undergoing Water Injection – a Case Study of a Niger Delta Field

Abstract

Structural heterogeneity is one of the critical factors that can strongly impact on the performance of a reservoir. A compartmentalized reservoir (A1) in a mature Niger-Delta field, having two blocks separated by a fault was shown from seismic mapping to be non-sealing. The initial pressure data obtained for both the East and West blocks through a Repeat Formation Test (RFT) were similar; suggesting that they were in hydraulic communication. After about 15 years of production from the West block, water injection was introduced, and this resulted in a successful pressure build-up and appreciable oil production in this block. RFT information, however, showed a larger pressure depletion than expected in the East block since there was no producing well in it. In this work, a highly costeffective integrated approach, involving an analytical tool known as the multi-tank material balance (MBAL) model was used to effectively characterize the complex heterogeneous reservoir and revise the field development plan. The result derived from this study suggests that the multi-tank material balance method sufficiently characterizes this complex reservoir applying a degree of transmissibility of about 30%. This is further shown in the result section, where values of production parameters such as the average oil production rate, average water production rate, water cut and reservoir pressure closely match the current performance of the field.