Sandstone injectivity and salt stability of cellulose nanocrystals (CNC) dispersions-Premises for use of CNC in enhanced oil recovery

Reservoir production is frequently supported by using flooding fluids, often seawater. The efficiency is affected by various factors, such as the wettability of the reservoir rock and the mobility ratio between reservoir oil and injected fluid phase. These factors again influence sweep efficiency, which is the fraction of the total reservoir oil volume in contact with injected fluid during oil recovery. Addition of nanopartides can affect the sweep efficiency on a macroscopic level by increasing the volume of petroleum in contact with the flooding fluid. Presented here are core-flooding studies performed using cellulose nanocrystals (CNC) of different concentrations in low-saline water. The studies were performed to investigate the injectivity of CNC into a high-permeable sandstone core, and to observe the effects addition of electrolytes had on the rheological properties of a low concentration dispersion of CNC. Zeta- potential and shear viscosity of dilute dispersions containing CNC was investigated under increasing electrolyte concentration. The flooding experiments show that the CNC has good injectivity in sandstone for all concentrations used, and the viscosity measurements performed on the effluent prove that the particles are able to travel through the core. Being sufficiently small for injection into sandstone and showing good colloidal stability at low salinities, CNC particles have the premises necessary to function properly as a flooding additive for enhanced oil recovery (EOR) in sandstone reservoirs. (C) 2016 Elsevier B.V. All rights reserved.