Static Adsorption and Retention of Viscoelastic Surfactant in Porous Media: EOR Implication

The mass loss of surfactant during flowing through porous media is one of the major concerns to surfactant-based Enhanced Oil Recovery (EOR) techniques and also a critical issue for viscoelastic surfactant (VES), which is a novel and promising flooding agent compared against the traditional displacing chemicals. This paper comprehensively investigated the interactions between a VES and several minerals. The static adsorption tests of VES on quartz, montmorillonite and kaolinite were first carried out at 65 °C. Empirical models were established to describe the VES adsorptive isothermal beahviors on the mineral surfaces. The data indicated that the VES showed L, S and LS adsorption isotherm patterns on quartz, montmorillonite, and kaolinite, respectively. The adsorption of VES was notably influenced by temperature, pH value, salinity and Ca2+. As a result of adsorption on clay surfaces, the viscosity and surface activity of the VES solution were significantly decreased. Moreover, the large hydrodynamic size of VES aggregates caused an inaccessible pore volume (IPV) during flowing through porous media. The magnitude of VES retention was considerably impacted by permeability (pore radius), VES concentration, displacing velocity and salinity under reservoir conditions. This work provided some new insights into oil recovery mechanisms of viscoelastic surfactant flooding.