An Experimental Investigation into the Potential of a Green Alkali-Surfactant-Polymer Formulation for Enhanced Oil Recovery in Sandstone Reservoir

Despite the promising nature of alkali-surfactant-polymer (ASP) flooding, its application is limited by various technical issues and environmental concerns. The goal of mitigating the impact of these limitations has led to research into the oil recovery potential of alternative chemical agents. This study, therefore, focuses on investigating the potential of a "green" ASP formulation composed of monoethanolamine (ETA), sodium cocoyl alaninate (SCA) and Schizophyllan (SPG) for its enhanced oil recovery application. A conventional ASP formulation comprising sodium carbonate (Na2CO3), Sodium Dodecyl Sulfate (SDS) and partially hydrolyzed polyacrylamide (HPAM)was deployed for comparative purposes. The hardness tolerance of the green ASP shows that surfactant precipitation and scale formation could be mitigated. Lower surfactant concentration required to achieve low IFT and contact angle upon addition of alkali shows synergism in interfacial properties and wettability alteration. The ETA–SCA system yielded a better synergy in IFT reduction (minimum IFT of 4.73 × 10-2 mN/m) and wettability alteration (contact angle of 3° in 600 seconds) than the Na2CO3–SDS system (minimum IFT of 0.22 mN/m and contact angle of 5° in 600 seconds). Nevertheless, the conventional AS formulation exhibited better synergism with brine yielding minimum IFT of 1.52 × 10-2 mN/m. The ETA–SCA system also exhibited the ability to emulsify crude oil and form stable emulsions, a desirable property in chemical EOR processes. ETA had an insignificant impact on SPG's rheology, and the viscosity increased when SCA was added. The ETA–SCA–SPG solution showed shear thinning behavior at low shear rates. The oscillatory studies showed that both SPG and HPAM possess viscoelastic properties, with the green ASP retaining the viscoelasticity of SPG while HPAM loses its viscoelasticity in the presence of Na2CO3. SCA adsorption onto the sand surface was made unfavourable at a threshold of 0.3 wt% ETA. The green ASP formulation achieved an additional recovery of ~22%, while the conventional ASP formulation achieved ~19% additional recovery. Therefore, the green ASP formulation proves to have excellent oil recovery potential compounded by its environmentally benign nature.