Terpolymer with rigid side chain as filtrate reducer for water-based drilling fluids

Synthetic copolymers as filtrate reducers for water-based drilling fluids (WBDFs) are difficult to meet the needs of drilling engineering only by changing the type and proportion of functional groups of copolymers, especially under ultra-high temperature and high salinity. In this study, an anionic terpolymer (named PSDI) with rigid side chain was synthesized using sodium p-styrenesulfonate, N, N-Dimethylacrylamide, and itaconic acid by free-radical copolymerization. The chemical structure of PSDI was characterized by Fourier transform infrared spectroscopy and H-1-NMR spectrum. The high-temperature/high-pressure filtration loss (FLHTHP) and the American Petroleum Institute filtration loss (FLAPI) of the WBDFs containing 1.5 wt/vol% PSDI were 35.0 and 17.0 ml after thermal rolling at 240 degrees C for 16 h, respectively. The FLHTHP and FLAPI of the WBDFs containing saturated NaCl were with control of 60.0 and 12.0 ml. The FLAPI of WBDFs containing 1.5 wt/vol% CaCl2 reduced to 6.0 ml. Results indicate that the addition of PSDI can improve the anti-high-temperature performance and resistance to salt and calcium contamination of WBDFs. Results of rheological tests through fitting four rheological models suggest that rheological parameters can be improved as a result of forming the spatial network structure between the PSDI and bentonite flakes.