Production and application of schizophyllan in microbial enhanced heavy oil recovery

Generally partially hydrolyzed polyacrylamides (HPAM) are used worldwide for polymer-based oil recovery processes. However there aree some problems associated with HPAM applications such as, treatment of produced water, oil-water separation and toxicity issues associated with degradation products of HPAM. Schizophyllan biopolymer is biodegradable and environmental friendly alternative to chemical polymers used for EOR applications. In present work we studied the schizophyllan production by fungi Schizophyllum commune ATCC38548, its structural characterization and potential applications in Microbial Enhanced Heavy Oil Recovery (MEOR). Different minimal production media containing carbohydrate based carbon sources were screened for better biopolymer production. During the course of experiments we studied microbial growth profile, biopolymer production, and rheological properties of biopolymer, chemical characterization and application of biopolymer in enhancing heavy oil recovery using Berea sandstone cores. The biopolymer was produced in significant quantities and increased the viscosity of the production medium after 9 days of incubation. Viscosities were measured using rheometer at different shear rates (0.1-100 s^-1) and temperatures, where it was found to be isothermal over a wide range of temperature with strong shear thinning behavior. After 14 days of incubation, the viscosity was 21535-43 cP at shear rate from 0.1-100 s^-1, respectively. Thermogravimetric analysis (TGA) analysis showed that the moisture content in purified biopolymer was 6.3%; it was quite stable till 100-200 °C and melted at temperatures higher than 250 °C. It was characterized as schizophyllan by MALDI-TOF-MS and NMR (¹H and proton decoupled ¹³C NMR) analysis. The repeating tetrasaccharide unit of schizophyllan structure comprised of homoglucan with β-1, 3-linked backbone and single β-1, 6-linked laterally glucose side chains at every third residue. The biopolymer was used for MEOR experiments at 45 °C, using Berea sandstone core plugs. The biopolymer injection resulted in 28% additional heavy oil recovery over residual oil saturation (Sor).