Toward an Alternative Bio-Based SP Flooding Technology: II. Biopolymer Screening and Evaluation

Abstract

Abstract Surfactant-polymer (SP) flooding is one of the most promising methods in enhanced oil recovery, especially where an existing waterflooding infrastructure is in place. Surfactants lower the interfacial tension between the injection brine and crude oil, which improves microscopic displacement efficiency by mobilizing trapped oil. In contrast, polymers increase the viscosity of injected water, which improves macroscopic sweep efficiency by stabilizing the displacing front and counteracting heterogeneity effects. This work is part of a broader research theme in which our group is evaluating the potential of biochemicals for chemical enhanced oil recovery (CEOR). Previously, the potential of a non-ionic alkyl polglycoside biosurfactant was demonstrated for a CEOR application in a carbonate reservoir characterized by high temperature and high salinity. In this work, we evaluate the potential of several biopolymers obtained from various manufacturers. We evaluate biopolymer compatibility, viscosibility, stability, injectivity, and adsorption. We benchmark its performance against a synthetic polymer that had previously proven potent. Compatibility with the field brines (injected and connate) were investigated by observation of solution appearances. Viscosibility was investigated by measuring viscosity of solutions at various concentrations, temperatures, and shear rates. Viscosities after prolonged heating were used to investigate the stability of the biopolymers. Injectivity was studied by measuring filtration ratios. Finally, static adsorption tests using crushed core plugs were conducted, and changes in surfactant concentration, i.e., adsorption, was inferred using a total organic content analyzer. Among the tested biopolymers, one biopolymer showed potential in terms of compatibility, stability, viscosibility, injectivity, and adsorption. Compared to the synthetic polymer, the biopolymer exhibited superb viscosibility. Concentrations around 750 ppm were sufficient to achieve the targeted viscosity at reservoir conditions. This translates to lower chemical usage and possibly improved economics. A coreflood, where the biopolymer was injected in a tertiary mode, demonstrated an additional production of around 5.2% original oil in the core (OOIC). A subsequent biopolymer/biosurfactant flood achieved an ultimate additional production of 15.5% OOIC. This performance is comparable but slightly lower (2.5% OOIC lower) than recoveries obtained with the benchmark polymer when applied as part of an SP slug. The results discussed in this paper constitute a major advancement toward developing an alternative bio-based SP flooding technology.