Screening For Paraffin Removal Prevention Bacterium And Its Performance Research

The paraffin deposits on the walls of crude pipelines severely impacts crude oil production.Microbial treatment method of paraffin deposition has unique properties that conventional treatment methods do not have,such as environmental friendliness,biodegradation,simple construction,low operating costs and not affecting the oil quality.Two microorganisms used in this study were screened from oil production wells in Daqing Oilfield of China,which can make use of paraffin as the only carbon sources.Two paraffin-degradation strain were named W1 and W2,respectively.Through experiments of physiologieal-bioehemical charaeteristies and 16S rDNA sequences were identified that W1 was affiliated to Bacillus subtilis KC492497,W2 was affiliated to Bacillus cereus KC679984.The result's of laboratory performance evaluation showed that:using a gravimetric method to analyze the microbial degradation rate of the paraffin,after 21 days,the degradation rate of the dispersing paraffin of strains W1,W2 and the mixed bacteria was 36%,31%,and 42%,respectively;the degradation rate of the paraffin block was 21%,15%,and 24%,respectively;in the content of crude oil,the reduction rate of Asphaltene was 16%,13%,and 27%,respectively;the reduction rate of Wax was 17%,15%,and 26%,respectively;the reduction rate of Colloid was 16%,13%,and 26%,respectively;the maximum reduction rate of crude oil viscosity was 38%,37%,and 43%,all of oil freezing point reduced by 3?;the reduction rate of Pr/Ph was 28%,8%,and 6%,the reduction rate of C28+C29/C21+C22 was 40%,72%,and 72%,respectively.The influencing factors including nitrogen sources,phosphorus source,pH value,time,temperature,salinity,inoculation amount,activation number were analyzed,respectively.The results showed that the carbon sources was crude oil,nitrogen source was NaNO3,phosphorus sources was K2HPO4-KH2PO4,initial pH value was 6.5-7.5,the degradation time was 21 days,incubation temperature was 40?-45?,the mineralization content was 4000-5000mg·L-1,the inoculation amount was 4%,the activation time was 4,the mixed bacteria had a higher paraffin degradation rate.The conditions of mixed bacteria degrading paraffin was investigated by orthogonal experiment and additional experiment.The optimum process conditions were as follows:nitrogen source was NaNO3,phosphorus sources was K2HPO4,initial pH value was 7,the degradation time was 21 days,incubation temperature was 45?,the mineralization content was 5000mg·L-1,the inoculation amount was 4%,the activation time was 5.Analysis of variance showed that the main factors affecting degradation rate were nitrogen source,degradation time.Based on the best degradation conditions,Paraffin degradation rate reached 53.6%.