Water alternative gas (WAG) optimization for a heterogeneous Brazilian pre-salt carbonate reservoir

Journal Article · 28 July 2023 · Journal of Geophysics and Engineering

DOI: https://doi.org/10.1093/jge/gxad053 · OSTI ID:2424664

Ali Elbaloula, Husham A.  ^[1]; de Oliveira, Gonçalo Soares ^[2]; Schiozer, Denis J. ^[2]

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1. University of Campinas, Sao Paulo (Brazil); Alfa Star Global Oil Fields Services LLC, Dubai (United Arab Emirates)
2. University of Campinas, Sao Paulo (Brazil)

Water alternating gas (WAG) is a cyclical process that involves alternating water and gas injections with the primary goal to improve sweep efficiency by maintaining initial high pressure, slowing water and gas breakthrough, and lowering oil viscosity. The objective of this work is to apply and optimize a WAG strategy on a carbonate field with light oil, compare it to the initially planned water-flooding strategy, and investigate the capability of WAG to improve field production. In this research, a compositional reservoir simulator was used to model a WAG process by injecting produced gas into the reservoir, using the same well structure as an optimized water-flooding strategy. Subsequently, a WAG strategy was created, optimizing the number and locations of wells, to facilitate a comparative analysis of the two recovery methods. The WAG optimization involved a detailed assessment of variables such as bottom hole pressure (BHP), WAG cycle duration, maximum gas oil ratio (GOR), and well positioning, to achieve a high net present value (NPV). The study focuses on the application of WAG optimization modeling in unconventional reservoirs, specifically pre-salt carbonate reservoirs, and investigates its implications on production strategy and forecast, emphasizing its potential for maximizing NPV and oil recovery in a recently producing field. The results showed that WAG improved reservoir performance when compared to water injection and produced a greater amount of oil. This solution showed potential to be tested under uncertainties (reservoir heterogeneity, faults, fractures, karsts, vugs, etc.) as future steps.

• Research Organization: University Estadual Campinas, Sao Paulo (Brazil)
• Sponsoring Organization: USDOE
• OSTI ID: 2424664
• Journal Information: Journal of Geophysics and Engineering, Journal Name: Journal of Geophysics and Engineering Journal Issue: 5 Vol. 20; ISSN 1742-2132
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United States
• Language: English