Effects of silica nanoparticles on the performance of water-based drilling fluids

Abstract

In this research, two groups of experiments were conducted to investigate the effects of silica (SiO2) nanoparticles on the filtration and rheological properties of water-based drilling fluids. In the first group, bentonite, chrome-free lignosulfonate (CFL) and carboxymethyl cellulose (CMC) were used in different concentrations to obtain base fluids. Nanofluids were prepared by adding 0.5 g of four different silica nanoparticles into these drilling fluids. Comparison of rheological properties, fluid loss amounts and mud cake thicknesses were performed at two different temperatures (25 °C and 49 °C). It was concluded that all of the nanoparticles reduced the filtration efficiency of bentonite muds. On the contrary, a reduction in fluid loss was observed for some lignosulfonate muds containing nanoparticle. However, no significant change in mud cake thickness and rheological properties was seen for both drilling fluids.Since no positive effect was observed in the first part, further investigation was done with higher bentonite and nanoparticle concentrations than previous experiments. Moreover, only bentonite was used as additive to eliminate other parameters and to see more clearly the effect of nanoparticles in bentonite mud. Samples were formulated with 7% by weight of bentonite and 0.5% and 1.5% by weight of nanoparticles. It was seen that the amount of fluid loss is directly proportional to the nanoparticle concentration. Therefore, Darcy's Law was used to compare the permeability of mud cakes and it was confirmed that nanofluids form permeable mud cakes compared to base fluid.