Compound performance of XJ-21 strain in guar gum fracturing fluid system
During the process of reservoir fracturing modification,guanidine gum fracturing fluid is difficult to break gel at low temperature and has poor reservoir reconstruction effect,which needs to be solved urgently in reservoir development of Xinjiang Oilfield.Herein,microbial enhanced oil recovery technique was applied in guar gum fracturing fluid trying to solve these problems.The oil sludge was collected from the Shaofanggou group in Ji 7 block of Xinjiang Oilfield,and a strain named XJ-21,which was capable of producing high-yield surfactant,was obtained after enrichment culture,isolation and screening.This strain was identified as Bacillus subtilis based on its morphology,Gram Staining and 16S rRNA sequence analysis.Moreover,FTIR analysis revealed that the biosurfactant in XJ-21 metabolites had the same structure as cyclic lipopeptides.When XJ-21 strain was combined with an exogenous strain ZW-027,the formed compound system exhibited wide adaptability to reservoir environment,could produce biological enzymes to break guanidine gel in the temperature ranging 35~55℃,also could reduce the crude oil viscosity in the sample block at 50℃with the viscosity reduction rate reaching 95.45%.The oil displacement efficiency could be improved by 10.14%by flooding with the combination system compared with water flooding only.