Performance evaluation of different cationic surfactants as anti-swelling agents for shale formations

Abstract

In this study, three different novel cationic surfactants decyl-trimethyl-ammonium bromide (S1), Octyl-trimethyl-ammonium bromide (S2), hexyl-trimethyl-ammonium bromide (S3) were used to formulate water-based drilling formulations to comprehend the interactions between drilling fluids components and with wellbore formations. The modified drilling formulations were prepared by incorporating novel surfactants in the base mud along with other additives such as bentonite, PAL-C, xanthan gum, and barite. The effect of the surfactant's chemical structure was assessed by rheology and filtration experiments, and colloidal dispersion stability was determined by particle size distribution analysis and sedimentation tests. The shale swelling inhibition characteristics of surfactant-based formulations were accessed by hot rolling dispersion tests, linear swelling rates, and capillary suction time tests. The performance of surfactant-based formulations for shale swelling inhibition was compared with KCl-based and conventionally used base mud formulations. The surface wettability of shale in the presence of different formulations was assessed by a high-resolution optical tensiometer. Shale inhibition properties of surfactant-based formulations depict that shale dispersion recovery increased to 98% for BS1 formulation compared to all other used formulations. Linear swelling of shale pellet show that the swelling rate of BS1 formulation was only 13% compared to all other formulations. The contact angle experiments showed that the BS1 formulation increased the contact angle of a water droplet and reduced the wettability of drilling fluids. The experimental results showed that S1 surfactant has enhanced shale inhibition characteristics compared to other surfactants and conventionally used shale inhibitors.