Investigation of cellulose nanofiber enhanced viscoelastic fracturing fluid system: Increasing viscoelasticity and reducing filtration

Abstract

Viscoelastic fracturing fluid (VFF) is considered to have great potential as fracturing agent with no residues and low damage to formation. However, traditional VFF composed of surfactant and salt is difficult to form filter cake due to its low molecular weight components, resulting in high filtration during fracturing operation. In order to solve this problem, cellulose nanofiber (CNF) enhanced viscoelastic fracturing fluid (CNEVFF) formed by sodium oleate (NaOA)/potassium chloride (KCl) and CNF was proposed and studied. The rheological properties of CNEVFF were investigated by rheometer. With the addition of CNF, the zero-shear viscosity of CNEVFF is higher than that of VFF. Moreover, the microstructures of core surface filtrated by different systems were detected by scanning electron microscopy (SEM) measurement, proving the formation of filter cake. The dynamic filtration damage (DFD) measurement was employed to investigate the damage effect of different fracturing fluids on the cores with different permeabilities. In addition, more details of different flooding stages during DFD experiment were measured by nuclear magnetic resonance (NMR) technology, exhibiting the damaging process of CNEVFF to the core dynamically. The removal of filter cake and an appropriate mechanism describing the formation and destruction of novel network formed by VFF and CNF was discussed.