Injection of alkaline (A), polymer (P), and surfactant (S) chemicals in enhanced oil recovery (cEOR) processes increases output by changing the properties of the injected fluid. In this work, micellar fluid interactions were studied via microemulsion rheological analysis. Crude oil and stimulated brine with ASP or SP was used for bottle testing. The results revealed that no microemulsion was produced when ASP (Alkaline, Surfactant, and Polymer) or SP (Surfactant and Polymer) was left out during the bottle testing phase. The addition of ASP and SP led to the formation of microemulsions—up to 29% for 50% water cut (WC) ASP, and 36% for 40% WC SP. This shows that the addition of ASP and SP can be applied to flooding applications. The results of the rheological analysis show that the microemulsions behaved as a shear-thinning micellar fluid by decreasing viscosity with increase in shear rate. As per the power-law equation, the ASP micellar fluid viscoelastic behavior shows better shear-thinning compared to SP, suggesting more efficiency in fluid mobility and sweep efficiency. Most of the microemulsions exhibited viscoelastic fluid behavior (G’ = G”) at angular frequency of 10 to 60 rad s⁻¹, and stable elastic fluid behavior (G’ > G’’) below 10 rad s⁻¹ angular frequency. The viscosity of microemulsion fluids decreases as temperature increases; this indicates that the crude oil (i.e., alkanes) was solubilized in core micelles, leading to radial growth in the cylindrical part of the wormlike micelles, and resulting in a drop in end-cap energy and micelle length. No significant difference was found in the analysis of viscoelasticity evaluation and viscosity analysis for both ASP and SP microemulsions. The microemulsion tendency test and rheology test show that the addition of ASP and SP in the oil-water interface yields excellent viscoelastic properties.

Preferential-weld-corrosion (PWC) remains a critical threat to the integrity of pipelines in the oil and gas industry, particularly in aggressive CO2-saturated flowline environments containing organic acids. This study introduces an integrated approach to mitigate PWC on A333 carbon steel by synthesizing and applying three novel quaternary ammonium Gemini surfactant inhibitors with varying spacer groups: 2B-Benzene, 2B-Ether, and 2B-Ketone. The chemical structures were confirmed via FTIR and NMR spectroscopy, while the performance of these inhibitors in mitigating uniform and localised corrosion was investigated using a combination of conventional electrochemical tests (LPR and ZRA) and advanced local electrochemical techniques including the Wire-Beam Electrode (WBE) method that provide spatially resolved insights into localized anodic and cathodic electrochemical activities across the weld metal (WM), heat-affected zone (HAZ), and parent metal (PM). Results show that at temperatures up to 50 °C, all synthesized inhibitors effectively reduced self-corrosion rates. However, at an elevated temperature of 70 °C, only 2B-Ether maintained superior inhibition efficiency (>90%), significantly reducing the WM corrosion rate from 3.45 mm/yr to 0.50 mm/yr. This work demonstrates that the rational molecular design of Gemini surfactants, coupled with localized electrochemical characterization, provides a robust framework for developing targeted corrosion mitigation strategies for heterogeneous welded structures.

Preferential weld corrosion (PWC) remains a critical threat to the integrity of pipelines in the oil and gas industry, particularly in aggressive CO2-saturated flowline environments containing organic acids. This study introduces an integrated approach to mitigate PWC on A333 carbon steel by synthesizing and applying three novel quaternary ammonium Gemini surfactant inhibitors with varying spacer groups: 2B-Benzene, 2B-Ether, and 2B-Ketone. The chemical structures were confirmed via FTIR and NMR spectroscopy, while the performance of these inhibitors in mitigating uniform and localised corrosion was investigated using a combination of conventional electrochemical tests (LPR and ZRA) and advanced local electrochemical techniques including the Wire-Beam Electrode (WBE) method that provide spatially resolved insights into localized anodic and cathodic electrochemical activities across the weld metal (WM), heat-affected zone (HAZ), and parent metal (PM). Results show that at temperatures up to 50 °C, all synthesized inhibitors effectively reduced self-corrosion rates. However, at an elevated temperature of 70 °C, only 2B-Ether maintained superior inhibition efficiency (>90%), significantly reducing the WM corrosion rate from 3.45 mm/yr to 0.50 mm/yr. This performance is attributed to the flexible ether spacer and stable Fe–O coordination, which facilitate strong surface anchoring even under thermal stress. Localized polarization analysis (LPA) using the WBE further elucidated the inhibition mechanisms at the most active micro regions. This work demonstrates that the rational molecular design of Gemini surfactants, coupled with localized electrochemical characterization, provides a robust framework for developing targeted corrosion mitigation strategies for heterogeneous welded structures.