Experimental evaluation of surfactant-stabilized microemulsions for application in reservoir conformance improvement technology

Abstract

The field of microemulsion-assisted conformance improvement technology (ME-CIT) requires workflow planning in order to effectively decrease the water-to-oil ratio during production operations. This article deals with the implementation of a suitable ME-CIT route via experimental validation. The ternary diagram identified the different Winsor regions to classify phase behavior. The aggregation behavior of micellar structures in ME phase was studied via dynamic light scattering tests. Relative phase behavior experiments depicted the presence of Winsor I phase at low salinity upto 20,000 ppm total dissolved salts (TDS) content. At nearly 25,000ppm, this altered into a Winsor III system. This phase behavior further changed into a Winsor Type III phase at 50,000 ppm. The surfactant-based microemulsion exhibited favorable time-dependent flow attributes, as evident from the observation that the steady-state viscosity did not alter markedly with elapse of time. The pseudoplastic rheology of microemulsion has been explained on a macroscopic level and micelle morphology on a microscopic scale with two phenomena: electro-shielding and micelle deformation. With increasing salinity, the viscosity versus salt concentration plots revealed a unique ‘M’ shape at 7.34 s−1. This describes an initial increase, then a decreasing trend, followed by a increase and eventually a near-constant viscosity as salt content increases further. Porous media flow experiments were conducted for optimized microemulsion slug using a sandstone core model. A favorable pressure drop and reduction in water-cut percentages were recorded during microemulsion flooding stage in the laboratory. In summary, the proposed methodology contributes toward developing potential surfactant-based microemulsions systems for application in conformance improvement technology.