A novel approach for using silica nanoparticles in a proppant pack to fixate coal fines

Abstract

Hydraulic fracturing operations in coal seam gas reservoirs are highly prone to release coal fines. Coal fines inevitably cause mechanical pump failure and permeability damage as a result of their hydrophobicity, aggregation in the system and pore-throat blockage. One approach to affix these coal fines at their source, and to retard generation, is to introduce a nanoparticle-treated proppant pack. Thus, this research explores coal fines retention (known as adsorption) in a proppant pack using nanoparticles. In the study, the electrolytic environment, pH, flow rate, temperature and pressure were kept constant, while the variables were concentration of silica nanoparticles (0–0.1 wt%) and coal fines concentration (0.1–1 wt%). The objective was to identify silica nano-formulations that effectively fixate coal fine dispersions. Subsequently, the coal suspensions flowed through a glass-bead proppant pack treated with and without nanoparticles, and were then analysed via a particle counter. The quantitative results from particle counter analysis showed that the proppant pack with nanoparticle treatment strongly affected the fixation ability of coal fines. The proppant pack without nanoparticle treatment showed up to 30% adsorption and flowed through the proppant untreated, while proppant pack treated with nanoparticles showed up to 74% adsorption; hence, more exceptional affixation ability to the coal fines. Further, the results indicated that the zeta-potential of silica nanoparticles at higher salinity became unstable, i.e. approximately –20 mV; this low value helped the proppant pack treated with nanoparticles to attach coal fines to it. The ability of nanoparticles to adsorb coal fines is due to their highly active surface, and high specific surface area.