A novel nonionic surfactant for inhibiting shale hydration

Abstract The demand for cost effective and environmentally shale inhibitor is increasing in drilling industry. This paper reports for the first time the use of Zizyphus spina-christi extract (ZSCE), a newly developed nonionic surfactant, for inhibiting shale hydration. The adsorption behavior of ZSCE onto shale cuttings was determined through conductivity technique. Adsorption isotherm coincides with the characteristics of Freundlich isotherm. The inhibitive property of ZSCE was assessed through a number of inhibition evaluation methods. All experimental findings verify that ZSCE can act as a potential shale inhibitor; nevertheless, its inhibitive potential has no significant improvement at concentrations above the CMC. Moreover, ZSCE has a better performance compared to potassium chloride and polyamine. According to compatibility tests, the ZSCE is compatible with conventional water-based drilling fluids (WBDF) additives. Scanning electron microscopy (SEM) observations clearly indicate the stability of sodium bentonite particles in ZSCE aqueous solution. The hydrogen bonding between hydrophilic tail of ZSCE molecules and oxygen atoms available on silica surface of clay, which results in formation of hydrophobic shell on the clay surface, is believed to be the main inhibition mechanism for ZSCE. This research paves the way for selection and implementation of surfactants, especially plant-based, as shale inhibitors in WBDF.