Zwitterionic Surfactant as Shale Swelling Inhibition Additive in Water-Based Drilling Mud

Abstract Shale swelling occasioned by the interactivity of clay minerals and water-based mud (WBM) remains a major source of concern during drilling for hydrocarbons. This is because the interaction has the tendency for causing formation damage, wellbore instability, and well blowout if not properly managed. Herein, novel synthesized carboxybetaine zwitterionic surfactant was investigated as a shale swelling inhibition additive in WBM. Firstly, the effect of the surfactant on the electro-kinetic and dispersion stability of the WBM was determined. Moreover, the surfactant effect on the rheological property of the WBM was measured. Subsequently, linear shale swelling test was conducted to evaluate the clay hydration inhibition potential of the surfactant using an OFITE dynamic linear tester. Experimental result depicts that the carboxybetaine zwitterionic surfactant reduced shale swelling by ≈ 42% compared to the conventional WBM. Moreover, rheological test indicates that the WBM containing surfactants exhibited lower shear stress compared conventional WBM. Finally, the surfactant-stabilized drilling mud displayed high colloidal and dispersion stability compared to conventional WBM. The mechanism of zwitterionic surfactants for clay hydration and shale swelling inhibition additive was perused. Overall, this study indicates that betaine-type zwitterionic surfactants are suitable as shale swelling inhibition additive in WBM.