Enhancing Oil Recovery through Coupled Low-Salinity Water and Alkaline-Polymer Flooding for Naturally Fractured Reservoirs: A Numerical Approach

Abstract

This research addresses the gradual decline in the world’s proven oil reserves due to increased production and the discovery of fewer new fields. As a result, enhancing oil recovery from existing fields has gained substantial attention. In particular, low salinity waterflooding, traditionally used in secondary recovery, is being explored for tertiary recovery phases. Additionally, chemical flooding has proven effective, especially as chemical costs have decreased relative to oil prices. This study investigates the application of these techniques using a robust mathematical multiphase fluid flow model in a three-dimensional space, developed with the finite element method in a poro-elastic framework. 3-D permeability tensors are calculated for subsurface fractures using the boundary element technique, which allowed to conduct a comprehensive evaluation of various flooding techniques. This study findings indicate that low salinity water flooding significantly aids in altering reservoir wettability from oil-wet to water-wet states. While the initial phases of low salinity flooding show positive effects, the overall recovery does not differ drastically when compared to traditional methods. However, combining low salinity with chemical solutions enhances oil recovery across all combinations, primarily by increasing the viscosity of polymer solutions and improving sweep efficiency. Moreover, the results underscore the importance of optimizing salinity conditions in alkaline solutions to minimize interfacial tension (IFT). The advantages of low salinity extend to tertiary water flooding, confirming its efficacy over high salinity alternatives.