The Improvement And Application Of Microbial-flooding Technology Of High Water Cut Stage In Low Permeability Oilfield

With the constant breakthroughs in oil exploration and development of theory and technology, oil exploration and development level has been rising. More and more of the low permeability oilfield came into the people’s vision, and gradually grow into the main force to increase the oil production. Because of its own characteristics of low permeability, the recovery rate of the oil field is low, which has been the bottleneck of the development of low permeability oil field.Microbial enhanced oil recovery technology as a low permeability oilfield water flooding development in the late stage enhanced oil recovery technology are important means, because of its low price, simple process, strong adaptability, safety and environmental protection, no damage to the production layer, etc. has been widely attented and applied. However, the development and application of microbial oil recovery technology is far from reaching people’s expectation. Microbial production technology is not stable, which is the main reason for having not been popularized in large area. The previous studies mainly focus on screening of the functional strains for microbial enhanced oil recover, microbial flooding mechanism and underground flora structure, but the studies for principles of the well and layer selection, screening of high efficient oil displacement functional bacteria, construction of high activity oil displacement strains, microbial flooding process optimization are less and incomplete.This paper takes the field tests of microbial oil displacement at the 9 reservoir of Jurassic Yan’an formation at Jianshan oil field in Ordos Basin as the background. Through the analysis of geological data, dynamic data of oil and water wells, test data, monitoring data on microbial quantity and metabolic level, studied on microbial flooding in low permeability oil field, selecting well and layer selection conditions, the structure of the original flora in oil reservoir, screening of high efficiency oil displacement functional bacteria, construction of engineering bacteria and its application in the field. The main results are as follows:1. Law of microbial oil displacement is characterized by injection pressure rising, water absorption profile improvement. The number of beneficial bacteria increases in the near well zone of the injection well, bacterial flora structure was steady. According to the effect type, the oil increasing effect is one-way, two-way and multi direction effect. In the case of connectivity similarity, the later the injected bacteria is detected, the longer the bacteria multiplication time is, the better the increasing oil effect is. Improve the physical property of crude oil and increase the fluidity of the crude oil.2. The geological influence factors of microbial enhanced oil is remaining oil saturation, physical property, waterline advancing speed, watery, heterogeneity, pressure rise space and other parameters.3. The conditions for the selection of the selected wells of the 9 reservoirs in the Jurassic Yanan formation in the Jianshan oil field are as follows:Remaining oil saturation^40%; Water-front advance velocity lm/d-5m/d; Pressure rise space≥3MPa; Pressure stabilization time≥150d; Plane heterogeneous coefficients<8.4; The water content of well group is between 80%-98%; Porosity ≥11%; Permeability≤20 ×10-3μm2; Porosity and permeability ratio> 0.5.4. Comparison of sequencing results of 11 reservoir microbial samples show that, the microbial content in oil reservoir samples is extremely rich. Detected a total of 11100 different microorganism belonging to the genus (i.e. the number of OTUs total 11100), belonging to 34 phylum,82 classes,122 orders,191 families,292 genera. The most abundant microorganisms in the reservoir samples is Proteobacteria bacteria, The second is Firmicutes, Actinobacteria,. Bacteroidetes, Euryarchaeota, Synergistetes, Thermotogae, Fusobacteria, Tenericutes, Cyanobacteria, Chloroflexi, Spirochaetes, etc. The mainly bacteria genera of reservoir sample were Arcobacter genera and Pseudomonas, Halomonas, Marine bacterium, Marinobacter genera and Sulphurmonas, etc.5. From the produced water of 3 research block oil well,2 strains of high efficiency oil displacement functional bacteria were isolated and screened, named HJS-1 and HJS-2. HJS-1 was identified as Bacillus subtilis and HJS-2 was Pseudomonas aeruginosa, by means of reservoir adaptability test, biochemical test and rDNA 16S sequencing.6. The analysis of the main metabolites of 2 strains of high efficiency oil displacement function bacteria shows that:Bacillus subtilis HJS-1 metabolize to produce lipopeptide biosurfactants, the metabolic level 2.146g/L. Pseudomonas aeruginosa HJS-2 metabolize to produce Rhamnolipid biosurfactant, metabolic level 32.72g/L. The viscosity reduction rate of crude oil is more than 50%, the degradation rate is more than 20%, oil displacement efficiency is higher than that of water flooding by 10%. In a word, the system has high activity of oil displacement.7. By construction of microbial joint transfer system for oil production, DNA recombinant plasmid which containing rhamnolipid transferase and alkane degrading enzyme was injected into functional bacterium receptor of indigenous microorganism for oil recovery, and the verification is carried out. The content of metabolism of rhamnolipid was 67.23g/L,105.48% higher than the wild strain. The degradation rate of alkane degrading bacteria was 20.55% higher than that of the wild strain.8. Comprehensive analysis of the 7 blocks in Hu Jianshan oilfield was made by applying the optimization principles of well and layer selection. Determined the yuan 72 block as the test area. On this basis, optimization selected the yuan 73-11 well group, and designed of the process scheme, in June 29,2015 started the implementation of the scene. By the end of February 24,2016, well group increasing oil 916.64t, achieved good oil increasing effect.