Poly (sodium p-styrene sulfonate) modified Fe3O4 nanoparticles as effective additives in water-based drilling fluids

In this work, a series of low solid phase, economic and excellent performance water-based drilling fluids (WBDFs) were obtained by introducing nanoparticles into conventional WBDFs. Fe3O4 nanoparticles which were surface modified by poly (sodium p-styrene sulfonate) (PSSS) through 3-(trimethoxysilyl) proryl methacrylate (TMSPMA) were adopted in low solid WBDFs containing 4 wt % bentonite (BT). The effect of temperature on rheological property and fluid filtration was investigated. When the concentration of Fe3O4/PSSS nanoparticles reached 0.1 wt %, shear thinning of WBDFs will be perfect at different temperatures. When the concentration of Fe3O4/PSSS nanoparticles reached 0.25 wt %, the WBDFs had superior rheological properties, as compared to other concentrations of the particles in salt environment. Rheological curves provide a closely fit for the Bingham model at low temperature, however, the curves fit Herschel-Bulkley model at higher temperature. Rheological tests indicated that higher concentration of Fe3O4/PSSS nanoparticles can effectively improve salt (KCl) tolerance. Under high temperature and high press (HTHP) filtration test, WBDFs with Fe3O4/PSSS nanoparticles exhibited minimum filtration loss volume with the concentration of Fe3O4/PSSS nanoparticles as low as 0.1 wt % at different temperatures. For salt tolerance test, the higher concentration of the Fe3O4/PSSS nanoparticles leads to the lower the amount of fluid loss at the same concentration of KCl. With the concentration of nanoparticles grows to 0.1 wt %, the amount of fluid loss volume was minimum, indicating that Fe3O4/PSSS nanoparticles in WBDFs improve the filtration. The WBDFs with performance improved by Fe3O4/PSSS nanoparticles can be used as effective drilling fluids even under high temperature and high salinity, demonstrating that the modified fluids are potential candidates for drilling in deep and salty formation.