Amphoteric surfactant-based inhibitors for controlling clay swelling in water-based drilling fluids

Shale swelling remains a substantial concern during oil and gas drilling due to the interaction of shale formations with water-based mud (WBM). In the current work, we introduced shale swelling inhibition using in-house prepared amphoteric amphiphiles: Lauryl polyoxyethylene amidopropyl hydroxy sulfobetaine (ZS1) and Lauryl polyoxyethylene amidopropyl carboxybetaine sulfonate (ZS2). These zwitterionic surfactants demonstrate environmentally friendly behavior, dual electrostatic interaction, and increased surface adsorption, which prominently improved the swelling inhibition capability with a low environmental footprint. The developed WBMs show adaptability towards changing conditions, which proves them to be an alternative to traditional shale inhibitors. The effectiveness of the synthesized amphiphiles was carefully estimated through linear swelling and capillary suction timer (CST) tests. The effect of the surfactants on the particle distribution and electrokinetic behavior was assessed using particle size measurements and zeta potential. Furthermore, the influence of the surfactants on the rheology of the WBM was analyzed. Experimental results indicate that ZS1 and ZS2 diminished shale swelling by 16% and 21%, as compared to deionized water. The zeta potential of the clay particles decreased with the addition of surfactants, with a greater decrease observed in the presence of ZS2. The particle size of the clay particles increased with the addition of surfactants. Moreover, rheology analysis showed that surfactants with WBM demonstrated decreased shear stress compared to conventional WBM. The drop in viscosity of WBM indicated the inhibition of clay occurs in the presence of the surfactant-based shale inhibitors. Overall, this invention demonstrates that in-house synthesized zwitterionic surfactants are suitable additives for shale swelling inhibition in WBM.