摘要：
Aiming at the pollution and damage of the fracturing fluid on the reservoir in low-permeability or tight reservoir, the mechanism of using microbial method to remediate the formation damage caused by guar gum fracturing fluid was studied. Guar gum degrading strains were isolated and screened by dilution-plate method using guar gum as sole carbon source.Then the bacterial strain was identified through the colony morphology, physiological-biochemical tests and 16S rDNA sequence a-nalysis.And the effect of bacterial degradation on the guar gum fracturing fluid was investigated by the apparent viscosity, av-erage molecular weight change, as well as the degradation of fracturing fluid residueand particle size..In addition, the effec-tiveness of microbial remediation was researched through the artificial sand pack.It is found that 7 bacterial strains are isola-ted and one strain of them is screened for the follow-up tests, which is identified as Bacillus paralicheniformis (CGS).After using this bacterial strain to degrade the guar-based fracturing fluid, the apparent viscosity decreases from 117 mPa· s to 3.3 mPa· s with the degradation rate of 97.00%and the average molecular weight reduces from 119062 to 28089.CO2and N2O are produced in the biodegradation and the active substrate can be synthesized by CGS to degrade the guar gum.And the in-soluble residue of guar gum changes from 81.67 mg to 51.67 mg with the reduction rate of 36.73%.The particle size of the insoluble residue decreases from 78.598 μm to 59.905 μm with the reduction rate of 23.78%.The original permeability of sand packs are 108.70×10-3and 16.90×10-3μm2, respectively, and the permeability decreases to 5.18×10-3and 7.93× 10-3μm2due to the fracturing fluid damage.However, the permeability can be recovered to 92.58×10-3and 16.32×10-3 μm2with recovery rates of 85.17%and 96.57%after the microbial remediation.%针对低渗致密砂岩油藏压裂中压裂液对油层的污染和伤害,研究采用微生物方法修复胍胶压裂液地层伤害的机制.从油藏产出水中,以胍胶为唯一碳源采用稀释平板法分离筛选出胍胶降解菌;通过菌落和细胞形态、生理生化特征以及16S rDNA序列分析对菌株进行鉴定;通过测定菌株降解胍胶中表观黏度、平均相对分子质量变化以及对压裂液残渣和粒径的分析,评价菌株对胍胶压裂液的降解效果;并通过岩心流动模拟实验,研究压裂液对岩心的伤害及微生物修复效果.结果表明:从地层产出水中分离的7株细菌中,1株细菌可高效降解胍胶,经鉴定为Bacillus paralicheniformis(CGS).该菌降解胍胶压裂液后,表观黏度从117 mPa· s 降低到3.3 mPa· s,降黏率达到97.0%;平均相对分子质量从119 062降低到28 089;降解过程中有CO2、N2O气体的产生并代谢产生了可使胍胶降解的活性物质;压裂液残渣从81.67 mg变为51.67 mg,降低了36.73%,残渣粒径从78.598 μm 变为59.905 μm,降低了23.78%.原始渗透率为108.70×10-3和16.90×10-3μm2的岩心在压裂液污染后渗透率分别为5.18×10-3和7.93× 10-3μm2,经微生物修复后,渗透率恢复为92.58×10-3和16.32×10-3μm2,恢复率分别为85.17%和96.57%.
