Application of Viscoelastic Surfactants as Mobility-Control Agents in Low-Tension Surfactant Floods

Abstract

Abstract Since the recent trend of oil price opened new vistas in IOR/EOR scenario, the laboratory study looked at different new type of super (S) and viscoelastic (Sv) surfactants that provide both IFT lowering and mobility control. The paper is basically focusing on evaluation of viscoelastic surfactants as mobility controlling agents used as pre-flush, co-surfactant and post-buffer media. The experimental work is extended to their effects on bulk phase and interfacial rheological properties, surface and interfacial tension, phase behavior, wettability, flow properties in porous media and displacement efficiency using various injection protocol. Beside determination of mobility, mobility ratio, normal and differential displacement curves, the solution structure was analyzed by transmission and backscattering photon correlation spectroscopy. Measurements and core studies confirmed that the viscoelastic surfactants might be used to replace traditional mobility controlling agents (polymers) over a wide temperature and pressure range. Their sensitivity to shear rate and other degrading effects is much less than found for high molecular weight synthetic and biopolymers. Thus, the viscoelastic surfactants may offer an excellent opportunity for mobility control in various enhanced oil recovery techniques independent of injection protocol. Their positive influence on recovery efficiently can be explained by mobility control, front stabilization (buffering) and profile correction. The viscoelastic surfactants may also improve the "microscopic displacement efficiency", which is not widely recognized as a significant part of the displacement mechanism, and hence the recovery efficiency. General conclusion of the laboratory studies is that viscoelastic surfactants may open new vistas in chemical flooding.