Surfactant synergy on rheological properties, injectivity, and enhanced oil recovery of viscoelastic polymers.

This article investigates the rheological behavior, injectivity, and enhanced oil recovery (EOR) performance of a surfactant-synergized viscoelastic polymer composite system based on modified carboxymethyl cellulose (mCMC). It systematically examines how polymer concentration, surfactant type (notably zwitterionic surfactants), preparation methods, and salt concentration affect the shear rheology and injectivity of mCMC solutions, revealing that viscoelasticity induces extensional viscosity that influences injection performance and optimal injection velocity. Comparative oil displacement experiments with mCMC and partially hydrolyzed polyacrylamide (HPAM) of similar shear rheology demonstrate that mCMC's viscoelasticity contributes significantly to improved oil recovery, with its EOR contribution increasing at higher injection velocities. The study highlights the balance between thickening properties and injectivity as critical for optimizing polymer flooding in enhanced oil recovery applications.