Application of Guar Gum Degrading Bacteria in Microbial Remediation of Guar-Based Fracturing Fluid Damage

Microbial remediation of fracturing fluid damage is for the first time to be presented in this paper. One guar gum degrading bacterial strain, Bacillus sonorensis, numbered by XSJ, was isolated from oilfield produced water and identified through 16S rDNA. The characterizations show that strain XSJ is mesophilic, alkalophilic, facultative, and halophilic, which is suitable for the reservoir environment. In addition, the guar gum degrading performance of this strain was investigated through apparent viscosity of the guar gum solution, the average molecular weight of guar gum, and gas chromatography. Besides, the degrading performance of insoluble residue of guar gum was analyzed through the measurement of particle size distribution using a laser particle size analyzer and total weight of insoluble residue using a weighing method. Finally, a kind of sand-pack column was designed to determine the recovery of permeability. The results indicate the following: (1) Bacillus sonorensis can efficiently degrade guar-based fracturing fluids to less than 5.0 mPa·s of apparent viscosity and 50 000 average molecular weight. (2) The bacterial strain can decrease the average particle size of insoluble residue from 105.56 to 72.40 μm and total weight of insoluble residue with the microbial degradation rate of 25.30%. (3) This strain can improve effectively the permeability of sand-pack column (max 90.32%) in laboratory simulation experiments. In conclusion, it is believed that the microbial remediation seems to be a new approach for remediation of guar-based fracturing fluid damage and has great potential in oilfield application.