Modelling Alkali Surfactant Polymer Chemical System for Sandstone Oil Reservoirs of Upper Assam Basin

Abstract Alkali-Surfactant-Polymer (ASP) flooding is a chemical-enhanced oil recovery (EOR) method that improves oil recovery from depleted oil fields. Modelling the Alkali-Surfactant-Polymer (ASP) chemical system involves synergistic chemical interaction and focuses on phase behavior and interfacial tension (IFT) reduction. The chemical models integrate fluid chemistry and predict optimal concentrations, compatibility, and performance under reservoir conditions. The combination of alkali and surfactant result in a significant reduction in IFT, which is more effective than using either component alone. This enhanced reduction leads to better mobilization of residual oil. Both alkali and surfactant contribute to altering the wettability of the reservoir rock to more water-wet conditions, facilitating better oil displacement. The addition of polymer increases the viscosity of the injected water, lowering the mobility ratio and stabilizing the displacement front, which enhances macroscopic sweep efficiency. Laboratory experiments are conducted to measure properties like IFT, emulsion stability, rheology and core flooding efficiency across a range of chemical concentrations. This experimental data is used to develop models to represent the actual reservoir. The optimization of SDS, NaOH and PAM concentrations in an ASP (Alkaline-Surfactant-Polymer) system was conducted for a sandstone reservoir core plug with 18% porosity from the Tipam Formation at a depth of 1600 meters. Laboratory experiments were combined with Response Surface Methodology (RSM) and reservoir modelling in TNAVIGATOR software. SDS was found to reduce the IFT effectively and the combination of SDS and NaOH improved wettability, altering the rock surface to a more water-wet state. PAM contributed to viscosity control, improving the mobility ratio and macroscopic sweep efficiency of the reservoir. RSM and contour plots demonstrated the synergistic effects of SDS, NaOH, and PAM, identifying optimal concentration ranges for the system. In sandstone reservoirs, the use of anionic surfactant Sodium Dodecyl Sulphate (SDS) with an alkali, Sodium Hydroxide (NaOH), and Polymer Polyacrylamide (PAM) for Enhanced Oil Recovery (EOR) has shown significant potential for improving oil displacement efficiency. The optimization of their concentration involves a series of laboratory experiments to assess their interactions with crude oil and the reservoir rock, particularly under the specific conditions of sandstone reservoirs. Optimization techniques, such as Design of Experiments (DOE) and Response Surface Methodology (RSM), are employed to determine the best combination of chemical concentration