Biodegradation and toxicity of scleroglucan for enhanced oil recovery

Abstract

Polymer flooding consists of injecting polymer-augmented water into the reservoir to control the water-oil mobility ratio, resulting in an increase in the volumetric sweep efficiency compared to water flooding. Synthetic polymers (polyacrylamides) and biopolymers (scleroglucan, xanthan gum, schizophyllan) are the two families of polymers usually evaluated for enhanced oil recovery (EOR). Scleroglucan (SCG) is resistant to electrolytes, hydrolysis, pH (3-10) and temperature (30-100°C) and has remarkable rheological properties, but it is quite susceptible to microbiological degradation. The primary objective of this study was to evaluate the biodegradation of SCG in the injection and production processes and its aquatic toxicity. The anaerobic biodegradation of the SCG solutions was determined through the viscosity changes of the solutions, while the aerobic biodegradation was calculated with the changes in the SCG concentration. It was observed that the viscosity reduction of the SCG solution was 30% and the SCG concentration decreased from 100 ppm to 52 ppm because bacteria can metabolize the biopolymer. Daphnia Pulex, Scenedesmus Acutus and Oreochromis sp. were the organisms used in the ecotoxicological assays of the SCG solutions. The acute ecotoxicological bioassays showed that there was no evidence of acute deleterious effects of SCG on any of the three organisms. From the chronic ecotoxicological bioassays, it was concluded that there was no effect of SCG on the mortality of Daphnia Pulex, regardless of the tested SCG concentration.

Evaluation of the Thermal, Chemical, Mechanical, and Microbial Stability of New Nanohybrids Based on Carboxymethyl-Scleroglucan and Silica Nanoparticles for EOR Applications

“…In our previous work [ 24 ], the viscosity change as a function of time of the SG solutions in sterilized injection water (RSW/SG), synthetic brine (SB/SG), and injection water with biocide (RW/SG/B) and without biocide (RW/SG) was reported as shown in Figure 7 A. Likewise, Figure 7 B,C show the viscosity changes as a function of time for NH-A and NH-B nanohybrids.…”

“…This result was attributed to the absence of microorganisms (-abiotic systems- synthetic and sterile media) and SG’s non-ionic nature, making them salt-resistant [ 29 ]. In contrast, the viscosity reduction of SG solution in injection water without biocide (RW/SG) and with biocide (RW/SG/B) was 92% (from 49.5 to 3.9 cP) and 32% (from 49 to 33.3 cP), respectively, suggesting growth of endogenous bacteria and use of SG for their metabolism [ 24 ]. In contrast, the viscosity of the NH-A and NH-B in injection water without the biocide showed an increase in viscosity of 9%, changing from 69 to 75 cP for RW/NH-A and from 74.8 to 81.2 cP for RW/NH-B.…”

“…Rodriguez et al [ 24 ] reported the methodology used for the anaerobic biodegradation tests. All biopolymer solutions (sterile water, synthetic brine, injection water with and without biocide) and injection water were bubbled with sterile nitrogen to assimilate the anaerobic environment until the dissolved oxygen concentration was close to 0 mg/L.…”

“… Viscosity change as a function of time of ( A ) SG solutions in sterilized injection water (RSW/SG), synthetic brine (SB/SG), injection water with biocide (RW/SG/B) and without biocide (RW/SG) [ 24 ], ( B ) NH-A solutions in sterilized injection water (RSW/NH-A), synthetic brine (SB/NH-A), injection water with biocide (RW/NH-A /B) and without biocide (RW/NH-A), and ( C ) NH-B solutions in sterilized injection water (RSW/NH-B), synthetic brine (SB/NH-B), injection water with a biocide (RW/NH-B/B) and without biocide (RW/NH-B). All systems at TDS = 1311 ppm, 7.3 s −1 , and 30 °C.…”

Synthesis and Characterization of New Nanohybrids Based on Carboxymethyl Scleroglucan and Silica Nanoparticles

“…These polysaccharides are good candidates for EOR applications because they are environmentally friendly [ 7 ] and most of them are resistant to salinity, temperature, and shear [ 8 ]. However, their main disadvantage is their high susceptibility to biodegradation and oxidation [ 9 , 10 ].…”