Maximizing Production from Mature Asset Through Wells and Reservoir Reviews: Case Study of a Complex Reservoir

Abstract Mature assets particularly those with complex reservoirs, require thorough review and optimization to maximize production. This paper presents a case study of a complex reservoir in the Niger Delta, highlighting the importance of integrating wells and reservoir review to identify opportunities for production enhancement. The study demonstrates how a comprehensive approach, combining geological, petrophysical, and engineering data, can be used to optimize production from mature assets. The results show that the integrated review identified several opportunities for production enhancement, including infill drilling, workovers, and water shut-off, resulting in a significant increase in oil production. The case study is a producing conventional oil field onshore Niger Delta with ten hydrocarbon-bearing sands including the E1000X. The E1000X contains approximately 95% of the Stock tank oil initial in place (STOIIP) and 90% the gas initially in-place (GIIP) in the field. The E1000X is a complex, heavily faulted, and highly heterogeneous sandstone reservoir. Production from the E1000X started in 1973, peaked at 46.2Mbopd before rapidly declining to the current level of approximately 10Mbopd from 9 drainage points. The decline in production was due to high gas oil ratio (HGOR) and water ingress. An uneven reservoir sweep observed from the producing conduits necessitated the need for a deeper understanding of the performance, challenges, and uncertainties inherent in E1000X complex. This helped in defining opportunities in the reservoir to arrest the decline and bridge the gap in the Top Quartile (TQ)-Estimated Ultimate Recovery (EUR). This case study explores the process of optimizing production in a mature reservoir in the Niger Delta by conducting an in-depth wells and reservoir reviews as well as implementation of extensive data acquisition programs thus enabling reservoir pressure and time lapse saturation monitoring which fed into a structural model reassessment and re-calibration of dynamic models subsequently used to identify the oil generating opportunities. The findings from this provide valuable insights into best practices for managing complex reservoirs in the Niger Delta, underscoring the need for integrated reservoir management. The results showed a significant improvement in production rates, highlighting the importance of a well-planned and data-driven approach in managing mature asset