Evaluation of methyl ester sulphonate spacer fluid additive for efficient wellbore clean-up

Abstract

Oil-based drilling fluid (OBDF) is used to drill through high permeable pay zone to prevent possible damage to the formation. However, the oil based drilling fluid leaves behind filter cake residue and oil-wet surfaces which hinder cement bonding. Spacer fluid is usually introduced to clean up the wellbore prior to cementing job. This work presents a spacer fluid designed with environment-friendly anionic methyl ester sulphonate (MES) surfactant and evaluated through a series of experimental tests to ascertain its effectiveness to clean wellbore. Addition of methyl ester sulphonate to confected water-based drilling fluid at high amount (0.15 g and 0.20 g) showed good rheological properties, compatibility with OBDF and cement and low contact angle on steel and sandstone in the range of 21.9o-34.7°. Furthermore, results show that it requires less amount of MES spacer fluid to revert oil-wet OBDF aqueous phase to water external continuous phase, validating the low contact angle measurements. Cleaning efficiencies for two best performing MES spacer fluids achieved 83.27% and 94.3% respectively. Shear bond strength were measured to be 1.3 MPa and 1.05 MPa for steel and sandstone respectively, above the minimum allowable shear bond strength for oil well cementing. Hence, MES spacer fluid can be used to clean up wellbores in high permeable formations and in well completion, where strong cement bonding is required.