Evaluation of sulfonated acrylamide-based tetrapolymer as a rheology modifier in water-based drilling fluid
College of Petroleum Engineering, Yangtze University, Wuhan, China; College of Geophysics and Oil Resources, Yangtze University, Wuhan, China; Faculty of Engineering, Kumasi Polytechnic, Kumasi, Ghana
The need for improved water-based drilling fluid systems for application in unfavourable wellbore con-ditions is a persistent challenge to oilwell drilling operation. This study evaluates the appropriateness of a synthetic tetrapolymer as a rheology modifier in water-based drilling fluid for application at elevated temperatures. The tetrapolymer, comprising acrylamide, sodium 2-acrylamido-2-methylpropanesulfonate, N-vinyl pyrrolidone and N-butyl propenoate (TPM4) was synthesized in aqueous medium by free-radi-cal polymerization and characterized by Fourier transform infra-red (FTIR) spectroscopy. Experimental design using six factors involving monomer molar ratios, total monomer concentration, initiator dosage, reaction temperature, pH and reaction time, was used to establish the optimum conditions of synthesis of the tetrapolymer. Rheological and fluid loss properties of the tetrapolymer were assessed in water-based drilling fluids. The tetrapolymer effected about four-fold filtration loss control in 4% KCl bentonite-based mud compared to the blank at 140°C. It also exhibited good viscosification of the mud and favourably retained mud viscosity up to 150°C.