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Polymers for enhanced oil recovery (EOR) purposes are required to have long term mechanical, thermal, chemical, and biological stability across a wide variety of conditions throughout field deployment. In this work we expand upon initial studies of scleroglucan biopolymer stability and demonstrate that scleroglucan solutions retain a significant proportion of their initial viscosity over a large range of stresses. Thermal stability of the biopolymer, scleroglucan, was tested at temperatures of up to 115°C, wherein the samples retained >95 % of the original viscosity over several months, and at 105 °C sclergolucan maintained >95 % viscosity over the course of 720 days. Scleroglucan was found to be chemically compatible with formaldehyde, glutaraldehyde, tetrakis(hydroxymethyl)-phosphonium sulfate (THPS), and 1,3,4,6-tetrakis(hydroxymethyl)tetrahydroimidazo-[4,5-d]imidazole-2,5(1H,3H)-dione (TMAD) for six months at 37 °C, 85 °C, and 95 °C, indicating these biocides have the potential for use in microbial control during scleroglucan implementation under various conditions. Rheological studies indicate the viscosifying power of scleroglucan is largely unimpacted by common reservoir salts (including divalents and trivalents) even through 20 % (wt/wt) salt addition. Microbial risks to polymer stability were also investigated. The susceptibility of scleroglucan to microbial degradation was assessed under reservoir relevant conditions using a bottle test system in which the polymer was incubated with active microbial cultures under various conditions that simulate reservoirs spanning 3.5 % to 17 % salinity and 30 °C to 90 °C. Our tests of microbial degradation found that anaerobic samples incubated with active microbial consortia under lower salinities and temperature lost viscosity with concomitant microbial growth indicating the presence of scleroglucan degrading organisms in the inoculum. However, anaerobic samples at temperatures above 60 °C and salinities greater than 7 % retained viscosity during the experiment illustrating polymer stability under conditions similar to those of harsh reservoirs. This study further refines the window of operation where scleroglucan maintains functional viscosity and may be employed for EOR use.

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Abstract:In recent years combined chemical-biological wastewater treatment processes have received increasing interest. In the present study wastewater from soil remediation processes were treated by means of 1-step processes like Fenton, aerobic degradation and 2-steps combined method. The effluents resulting from soil remediation processes consist of high surfactant concentration solutions, mobilized oils and oil-in-water (o/w) emulsions. The effectiveness of wastewater treatment was evaluated by COD reduction and surfactant removal. The application of Fenton process alone showed around 80% of COD and surfactant removal, and in case of aerobic process only 60% of COD and 50% of surfactant removal was accomplished. However, the maximum COD reduction and surfactant removal from wastewater samples, above 90%, was obtained in aerobic degradation with Fenton process as pretreatment. Thus, the Fenton process could be effectively applied as a pretreatment step to improve the reduction of both COD and surfactant from wastewater resulting from soil remediation.