Toward an Alternative Bio-Based SP Flooding Technology: I. Biosurfactant Evaluation

Abstract

Abstract Surfactant-polymer (SP) flooding is one of the most promising methods in enhanced oil recovery (EOR), especially where an existing waterflooding infrastructure is in place. 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). Biosurfactants belong to a diverse group of surface-active chemicals generated by microbial fermentation. Recently, the use of biosurfactants in a CEOR formulation has gained greater attention due to their biodegradability, low toxicity, and effectiveness at high temperature and salinity. In this work, we evaluate the potential of a particular biosurfactant for CEOR application in a carbonate reservoir that is characterized by high temperature and high salinity. We evaluate the biosurfactant compatibility, interfacial tension (IFT) reduction, stability, and adsorption. We benchmark its performance against a synthetic surfactant that had previously proved potent. Compatibility with the field brines (injected and connate) is investigated by observation of solution appearances. IFT reduction is measured using a spinning drop tensiometer. IFT, after prolonged heating, was also measured to investigate the stability of the biosurfactant. Finally, static adsorption tests were conducted using crushed rock samples where changes in biosurfactant concentration, and adsorption, was inferred using a total organic content analyzer. The biosurfactant showed excellent compatibility with field brines at reservoir temperature. It exhibited low static adsorption of 0.65 mg/g. Most importantly, at a concentration of 2000 ppm, the biosurfactant resulted in a very low IFT in the order of 10−2 mN/m. The biosurfactant resulted in an IFT reduction that is comparable to that achieved with the benchmark surfactant. A coreflood, where the biosurfactant was injected in a tertiary mode, demonstrated an additional production of around 6.5% OOIC (original oil in the core). The expected performance of this biosurfactant was further compared to the benchmark surfactant using numerical simulation. Core-scale simulation results suggest the biosurfactant can yield incremental recoveries that are comparable to those obtained using the benchmark surfactant. At the core-scale, a tertiary SP flood, in which a biochemical surfactant is used, can yield an additional production of around 17% OOIC. The results discussed in this paper constitute the first step toward developing an alternative bio-based SP flooding technology for carbonate reservoirs with harsh conditions.