Swelling Mechanisms Assessment of Water-Based Drilling Mud by Polyvinyl Alcohol

Swelling control is an elaborated balancing of solid-liquid ratios in the mud, influencing crucial physiochemical features. Mechanical swelling control methods showing limitations drove recent researchers to consider chemical agents, including polyvinyl alcohol (PVOH). PVOH is known to have a swelling ability to improve mud rheology. The present study investigates the synergy of PVOH and Bentonite in an aqueous environment by analyzing the effluents samples. Three types of PVOH were selected: a standard PVOH and two modified PVOHs (a non-ionic group PVOH and a cationic group PVOH-3 attached to the carbon backbone. Except for the control sample (sample without polymer), PVOHs were added to different mud samples at ranging concentrations of 0.1 wt.% to 0.5 wt.%; each has a bulk volume of 400 ml. Each mud sample was filtrated at room temperature under an applied pressure of 1.28 MPa for 5 hours. The samples' effluents were then analyzed for polymer adsorption. Preliminary filtration tests revealed further effluent production reduction with increased PVOH concentration. Compared to the control sample, samples containing standards PVOH-1, Non-ionic PVOH-2, and Cationic PVOH-3, respectively, had their mud cake mass increase of 48%, 36%, and 38%, while respectively having filtrate recovery reduction of 21%, 19%, and 43%. Adsorption tests showed mud swelling owes primarily to hydrogen bonding which is counteracted by the presence of a charged group. Mud swelling is, therefore, dependent on the rate of hydrogen bounding in a system.