In-House Synthesized Amphoteric Amphiphiles for Shale Swelling Inhibition and Wellbore Integrity Enhancement in Oil and Gas Reservoirs

Abstract Shale swelling, triggered by the interaction between shale formations and water-based mud (WBM), presents significant challenges during hydrocarbon drilling, including formation damage, wellbore instability, and the potential for well blowouts. In this invention, we introduced two novel in-house synthesized amphoteric amphiphiles, Lauryl polyoxyethylene amidopropyl hydroxy sulfobetaine (S1) and lauryl polyoxyethylene amidopropyl carboxybetaine sulfonate (S2), as environmentally friendly and efficient additives for inhibiting shale swelling and enhancing wellbore integrity. The inhibition of shale swelling was thoroughly assessed using linear shale swelling and capillary suction timer tests. The impact of amphiphiles on the electrokinetic properties, particle dispersion, and aggregation in water-based mud (WBM) was systematically evaluated using zeta potential and particle size measurements. Additionally, rheological assessments were conducted to determine their influence on drilling fluid performance. Their performance was compared with the commonly used commercial additive, choline chloride (CC). Experimental findings revealed that incorporating amphiphiles S1 and S2 effectively reduced shale swelling by 16% and 21%, respectively, compared to the water-based control. CC mixed solution resulted in the lowest swelling compared to all the tested fluids. The addition of amphiphiles reduced the negative zeta potential of clay particles, with a more pronounced effect observed in the presence of S2. Furthermore, particle size analysis indicated an increase in clay aggregation, while rheological tests demonstrated that WBM formulations containing amphiphiles exhibited lower shear stress, contributing to enhanced wellbore stability. The reduction in viscosity of clay-mixed mud further reinforced the role of amphiphiles in mitigating clay swelling. Overall, this study underscores the potential of in-house synthesized amphoteric amphiphiles as effective additives for improving WBM performance. Their ability to minimize shale swelling and enhance wellbore integrity positions them as promising candidates for optimizing drilling fluid formulations in oil and gas operations.