Impact of Intra-Reservoir Faults on Fluid Connectivity and Recoverable Volumes in Reservoir Blocks That Have Shown Over Production – A Case Study of a Niger Delta Field

Abstract

The impact of intra-reservoir faults on fluid connectivity and recoverable volumes in any reservoir depends principally on structural uncertainties (fault extent, fault throws, fault zone, fault heave, fault sealing capacities etc.) associated with the reservoir. This paper focuses on the integrated approaches used to determine block by block fluid connectivity, re-assignment of estimated hydrocarbon initially in-place volume and its associated recoverable volumes in different reservoir blocks in view of production performance and complex fault architecture in the field. In this study, we have explored the feasibility of determining fluid connectivity across reservoir blocks and their associated recoverable volumes by integrating reservoir performance (post-production data) with the reservoir structural uncertainties. Over 50 wells have been drilled in the field and their penetrations spread across the reservoirs. Pressure data were acquired across most of the blocks in the reservoir. The reservoir is sub-divided into separate blocks and it has over 25 years of production with evidence of over-production (Np > Ultimate Recoveries) experienced in some of these blocks. This over-production triggered the need to integrate available data (Performance, Pressure data, Fluid Contacts, structural morphology etc.) to re-evaluate the impact of the intra reservoir faults on the estimation of the hydrocarbon in-place volume and recovery in the field. The integrated approach has aided the re-estimation and re-assignment of the associated volumes on a block by block basis thereby promoting the opportunity for a robust infill well planning and further development of the field.