Effect of Silica Nanoparticles on the Rheological Properties and Filtration Performance of Surfactant-Based and Polymeric Fracturing Fluids and Their Blends
Authors: Fakoya M. F. , Shah S. N. 
Published: May 2018

Summary
The investigation of nanotechnology applications in the oil and gas industry is increasing gradually; therefore, this technology needs more exploration to unveil promising applications. In this study, an experimental investigation of nanotechnology on the apparent viscosity, viscoelastic properties, and filtration performance of surfactant-based fluids (SBFs) or viscoelastic surfactants (VESs), polymeric fluids, and SBF/polymeric-fluid blends is presented. The concentration of SBF is 5 vol%, whereas that of polymeric fluids is 33 lbm/1,000 gal guar. Besides, both fluids contained 4 wt% potassium chloride (KCl). In addition, Blend-A and Blend-B were prepared by mixing SBF and polymeric fluids in the ratio of 75/25 and 25/75 vol%, respectively. Nanofluids were prepared by adding 20-nm silica nanoparticles, at concentrations of 0.058, 0.24, and 0.4 wt%, to the clean fluids. Apparent viscosity and viscoelastic data were gathered with a rheometer within a temperature range of 75 to 175°F, whereas filtration tests were conducted with a wall-mount filter press at ambient temperature and 100-psi differential pressure.
The results indicate an enhancement in the apparent viscosity and viscoelastic properties of surfactant-based and polymeric nanofluids up to a nanoparticle concentration of 0.24 and 0.4 wt%, respectively. Blend-A nanofluids show improvement in apparent viscosity and viscoelastic properties at a nanoparticle concentration of 0.058%. Similarly, Blend-B displayed favorable results up to a nanoparticle concentration of 0.24 wt% at temperatures of 125 to 175°F. Promising filtration results were displayed with surfactant-based nanofluids and Blend-A nanofluids at all nanoparticle concentrations, but the performance at 0.24 and 0.4 wt%, respectively, is slightly better. Polymeric nanofluids and Blend-B nanofluids revealed very good filtration results at all nanoparticle concentrations, but the performance at 0.24 and 0.058 wt%, respectively, is slightly better with a percentage reduction in API filtrate volume of 70.2 and 69.8%, respectively. A trial run was made with a commercially available fluid-loss additive [polyanionic cellulose (PAC)] in polymeric fluids at the same nanoparticle concentrations; the result confirmed that nanosilica facilitates the achievement of a superior filtration property. Comparison of apparent viscosity, viscoelastic properties, filtration performance, and economic analysis revealed Blend-A nanofluid as the preferred choice.
Further, Blend-A nanofluid (at 0.058 wt%) is selected as the best on the basis of filtration performance. The selected fluid was optimized at lower nanoparticle concentrations (0.02, 0.01, and 0.002 wt%). Interestingly, using Blend-A nanofluid at 0.002 wt%, compared with the initial recommendation of 0.058 wt%, which costs USD 171.7/bbl, reduces the cost of nanoparticles required for preparing 1 bbl of this fluid to USD 5.8. Therefore, from a filtration-performance standpoint, Blend-A nanofluid is recommended for use at a nanoparticle concentration of 0.002 wt%.
The application of nanotechnology on the apparent viscosity, viscoelastic behavior, and filtration properties of SBF, polymeric fluids, and SBF/polymeric-fluid blends can deliver some benefits, if nanoparticle concentrations are selected carefully. These nanofluids will be applicable for oilfield operations such as hydraulic fracturing.