Insights from the 3D Modeling of a Densely Faulted, Stacked Reservoir System

Abstract

The field presented in this paper is a structurally complex onshore oil field in the Niger Delta, with a densely faulted succession of stacked reservoirs. From previous field studies, three of the reservoir units have been interpreted as a single stacked reservoir complex beneath a top seal, and the vertical and lateral communication between these units is largely controlled by the inter-reservoir shales and intense fault configuration.Integrated 3D reservoir modeling has been used to investigate the production performance from this stacked reservoir complex, with a view to identifying the features that contribute to the observed communication across the reservoirs, quantifying the contribution of each reservoir unit to each well's production, estimating the ultimate recovery for the complex and evaluating the current redevelopment plan for the reservoir complex to identify opportunities for further oil development.The results from the study indicate that oil recovery is majorly influenced by communication across faults. A tracer model was used to demonstrate that some wells produce from adjacent blocks on the same reservoir unit as well as the other reservoir units across the fault, giving an indication of the presence of non-sealing faults across juxtaposed oil-bearing sands. Also the application of the 3D model in evaluating the current redevelopment plan for the reservoir complex resulted in the identification of 5 new opportunities in existing wells, to increase the ultimate recovery of the reservoir complex by 7.8MMstb. More so, there exists an opportunity to recover 7.5MMstb from a by-passed section of the complex with a new vertical well.