Microbial Enhanced Oil Recovery In The Low Permeability Oil Reservoir Of Yan9

Currently, knowledge of ecological structures and functions of the microbes related to the mechanism of the microbial enhanced oil recovery (MEOR) in low permeability reservoirs is limited, which results in the slow development of MEOR. Therefore, it is theoretically and practically significant to know the diversities and the activities of the microbes in this type of oil reservoir. In this study,16S rDNA gene clone library technique was used to analyze the bacterial communities in the water samples collected from the low permeability reservoir of Yan9in ChangQing oil-filed. Nutrients that can stimulate the microorganisms for MEOR were obtained. In addition, two strains of microorganisms for MEOR were isolated, moreover, study of oil biodegradation by the two strains were carried out.Obtained results in the study are as follows:(1) Results of the16S rDNA clone library showed that a total of21,20and20operational taxanomic units (OTUs) were detected in the Liu28-46, Liu28-47and Liu27-45clone libraries, respectively, which indicated that the bacterial diversities in Yan9low permeability reservoir are rich. Sequential analysis of a representative clone of each OTU showed that the predominant sequences in the three clone libraries were Pseudomonas aeruginos occupied a percentage of32.8%,32%and42.9%, respectively. Pseudomonas aeruginos is one of the most popular microorganisms for MEOR. In addition, sulfide-reducing bacteria (SRB) were also dominant in the three clone libraries.(2) The optimal medium for MEOR contained JHAR (0.1%),NaN03(0.2%), solid molasses (0.25%), JHM2(0.12%). Stimulated microbes by the medium could degrade crude oil effectively. The emulsification level of crude oil, after degradation, was the fifth grade. The degraded oil could disperse in water, suspend on the inner wall of the flask, and gather on the top of the water after keeping static. Pseudomonas aeruginos and Bacillus subtilis, two potential strains of bacteria for MEOR, were separated from the enrichment cultures of stimulated medium. The analysisof the gas chromatopraphy mass spectrometric (GC-MS) and fourier transform ion cyclotron resonance mass spectrometer (FI-ICRMS) showed that crude oil was subjected to degradation by the two isolated strains. (3) After injection of the nutrients, the diversity of the microorganisms became less; However, Pseudomonas aeruginos appeared to be predominant in all clone libraries with increase as2-3times as before; and the SRB disappeared gradually, which proved that the nutrients were potential for MEOR in Yan9low permeability reservoir.(4) The diversity of archaea in Yan9was less than that of bacteria. Methanosaeta sp., before and after injection of the nutrients, existed in water samples, which indicated that Methanosaeta sp. was uncated on changes of environments.The bacterial diversity in the low permeability reservoir of Yan9was rich. Application of MEOR in the oil reservoir was feasible and could break through the difficulty of exploitation and the low oil recovery in this kind of oil reservoir. Obtained results could be a valuable reference for MEOR in low permeability reservoirs.