Jiang Yang is a Professor at Xi'an Petroleum University, China. Previously, he has worked in Baker Hughes and PetroChina for over 10 years. His research interests include oilfield chemicals such as corrosion inhibitors, fracturing fluid, surfactant, foam, emulsion, etc. He holds a PhD degree in Chemistry from the University of Missouri-Rolla. He has authored and/or coauthored more than 80 technical papers and holds 40 patents.

The viscoelastic surfactant (VES) fluids have been used in stimulation for many years. VES fluids have low formation damage as it is originated from entanglement of wormlike micelle from selfassociation of small surfactant molecule. In comparison, the metallic cross-linked guar fracturing fluids have residues which cause formation damage. However, VES fluids are used at much higher concentration than that of crosslinked guar fluids. The application of VES fluid is also limited below 130°C. This paper studies a new fracturing fluid based on mixture of cellulose nanofiber and VES with reduced VES concentration and higher temperature limit. The cellulose nanofiber with 4-10  in diameter is an environmental-friendly and biodegradable material, which is the unit in plant cell wall. The VES is an ultralong-chain betaine surfactant. Cellulose nanofibers with hydroxyl group, carboxylate and quaternary derivatives were studied. It was found that the cellulose nanofibers with carboxylate derivatives give better enhancement in viscosity of VES fluid. The more carboxylate group in the cellulose nanofibers is, the higher viscosity in the mixture will be. Addition of 0.2% cellulose nanofibers to 1.4% VES fluid increases the upper temperature limit from 130 to 150°C. In comparison, there is no enhanced  and upper temperature limit with conventional cellulose. The increased viscosity and higher temperature limit for the mixed fluid of cellulose nanofiber and VES is due to their cooperative force among hydrogen bonding and electrostatic interaction with nanoscale fiber. The mixed fluid is more shear thinning than cellulose and has high viscosity at low shear rates and low viscosity at high shear rates. This rheological property gives good proppant suspension at flow rate in the fracture and low friction during high shear pumping in the wellbore. The gel can be completely broken by breaker as VES itself. Hence, fluid with cellulose nanofibers and viscoelastic surfactant could be an effective fracturing fluid for fracturing operation.