Drilling fluid waste treatment using polysaccharide-grafted copolymers

Abstract

A large amount of drilling fluid waste is produced as effluents during exploration and production of oil and gas. Such effluents need to be treated before their final disposal. Efficient coagulation/flocculation can reduce the total amount of disposed effluent, and both coagulation by inorganic salts and flocculation by synthetic flocculants are found to be very effective. The graft-copolymers-based flocculants were prepared using a potassium persulfate initiator solution made by grafting copolymerisation of polyacrylamide onto polysaccharide backbones (starch, guar gum and amylose) in our laboratory. The synthesised graft copolymers have been characterised using various instrumental methods of analysis. The effects of various synthetic flocculants and their concentrations have been studied in combination with the coagulants on coagulation/flocculation of bentonite-based drilling fluid waste have been studied. The effects of coagulant/flocculant dosage, electrolyte concentration and pH on the degree of flocculation of bentonite-based drilling fluid waste was investigated. It was observed that the increase in coagulant/flocculant dosage reduces the residual turbidity and improves the settling rate of the drilling fluid waste. At higher pH conditions, drilling fluid waste dispersions are highly flocculated and have high settling rates and low supernatant turbidity. The combined effect of salt concentration and coagulant/flocculant dosage improves the overall flocculation efficiency of the system.