Flocculation of submicron particles in water-based drilling fluids by CMC-g-DMDAAC

During the process of recirculating drilling fluids, the removal of useless solids, especially submicron particles, in drilling fluids is the most problematic issue in drilling operations. The cost and efficiency of currently used technologies are the two issues that have to be addressed urgently. In this study, the novel flocculant CMC-g-DMDAAC was synthesized by grafting diallyl dimethyl ammonium chloride (DMDAAC) onto carboxymethyl chitosan (CMC). The physicochemical structure of the CMC-g-DMDAAC product was characterized by Fourier-transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and determination of the ζ-potential. A kaolinite suspension, a bentonite suspension, and drilling fluids from an oilfield were selected to evaluate the flocculation performance of CMC-g-DMDAAC by testing the products' turbidities and particle size distributions. In comparison, the flocculation performances of chitosan, CMC, and commercial hydrolyzed polyacrylamide (HPAM) were also tested under the same conditions. The results showed that CMC-g-DMDAAC exhibited steady flocculation performances for all clay suspensions and drilling fluids at all pH ranges at low dosage. The scavenging capacity of submicron particles in drilling fluids was also excellent for the tested product.