Crude Oil And Asphalt Degradation By Oil Displacement Microorganisms And Their Effects On Simulated Displacement

Microbial Enhanced Oil Recovery?MEOR?is a technology to increase oil recovery rate by using microbial activities in oil reservoirs and their metabolites?including polymers,surfactants,gases,organic acids and organic solvents?to increase oil production.Enzyme Enhanced Oil Recovery?EEOR?is a new way and method of oil recovery by using enzyme to degradate the heavy fractions into little fractions.In this paper,4 oil-displacement bacteria and 4 oil-displacement fungi were isolated from 6 groups of oil wells and oil-contaminated soil at the well head of Yanchang Oilfield in Shaanxi Province,China,and their species were identified.The physical and chemical properties of crude oil and pure asphalt were studied by using oil-displacement bacteria?fermentation broth and bacterial enzyme compounds?and oil-displacement fungi?crude enzyme solution?.The oil displacement effect and mechanism of bacteria fermentation broth?MEOR?,fungal enzyme solution?EEOR?,MEOR+EEOR,MEOR-EEOR and indigenous bacterial were studied systematically.The main research results are as follows:1.Two Pseudomonas aeruginosa strains can extremely degradate asphalt and had effect on physicochemical properties of crude oilTwo Pseudomonas aeruginosa strains,designated Gx and Fx,were identified by morphological observation and 16S rDNA sequence analysis.The potential of Gx and Fx for oil displacement was assessed by the group composition analysis of pure asphalt and crude oil,and gas chromatography analysis of the vaporizable fraction?230°C?of crude oil after treatment with bacterial fermentation broth.Gx and Fx were able to degrade 10.07%?P<0.05?and 9.77%?P<0.05?of pure asphalt,respectively,while their degradation efficiencies were much higher?58.6%and 72.4%,respectively?for asphaltenes in crude oil.The thin,uniform micromorphology of pure asphalt adhered to glass slide changed to a raised,aggregated appearance.Gx and Fx increased light fractions?alkanes and aromatics,maximum11.2%?and decreased heavy fractions?resins and unknown,maximum 74.7%?in the degraded crude oil samples compared with the control.The total quantity of vaporizable components?230°C?in crude oil was increased by 9.52%and 19.25%,with seven and eight new components being found after treatment with Gx and Fx,respectively.There were removed the majority?90.5%and 88.3%,respectively?of crude oil adsorbed on filter paper and reduced oil viscosity?35°C?by 56.9%?P<0.05?and 37.2%?P<0.05?,respectively,and the adhesion of crude oil to the bottle wall was markedly decreased after treatment.Both Gx and Fx produced surfactants when growing in broth medium with crude oil as the sole carbon source,and the diameter of oil spreading ranged from 17.2 to 17.3 cm.After culture,the pH of the fermentation solution decreased by 0.6¹.0 units.2.New found oil-displacement strain-Pseudomonas taiwanensis,has effect on crude oil and asphalt degradation and oil displacementOne strain of bacteria,numbered for C-2,that had good emulsifying activity and oil discharge activity and potential oil displacement,identified as Pseudomonas taiwanensis?P.taiwanensis?by using 16s rDNA sequence analysis.The desorption rate of crude oil adsorbed by filter paper was 90.1%after treatment by C-2 fermentation broth.the crude oil viscosity significantly lower than control?P<0.05?,reduce 34.6%?35??;The diameter of oil-spreading is 36.6 times of that of the control group.After culture,the pH of the fermentation liquor decreased by 2.4 units,which was significantly different from the control?P<0.05?.The degradation rate of asphalt in crude oil is 41.1%?P<0.05?,and the degradation rate of pure asphalt is 8.8%.The proportion of 230°C vaporizable fractions in crude oil content was increased by 15.2%than control.In the process of bacterial C-2 fermentation,the microbial biomass of the fermentation solution reached the highest value at 72h of culture,the pH first decreased and then increased,the diameter of oil-spreading and the concentration of surfactant increased with the increase of culture time,and the culture of 60h-96h was significantly higher than 0h-48h?P<0.05?.The surfactant was identified as 4-methyl-phenol.The total oil displacement rate of C-2 fermentation broth was significantly higher than that of control water flooding?P<0.05?.In the two times of displacement,the oil displacement rate and oil displacement amount treated by the fermentation broth were all higher than that of the control water flooding,and the difference in the second time reached a significant level?P<0.05?.3.Dietzia cercidiphylli has strong ability to degradate asphalt and crude oil,and coule increase oil recoveryA bacteria strain,isolated from the crude oil that in the Yanchang Oilfield,numbered for X9,had the potential to the displacement the crude oil,was identified as Dietzia cercidiphylli.After its fermented broth treatment,the degradation rate of asphaltene in crude oil was 70.5%?P<0.05?,the pure asphalt degradation rate was 9.9%?P<0.05?,in the pure asphalt saturated hydrocarbon content,aromatics,resins,and the unknown component content decreased,the liquidity of pure asphalt increased.The proportion of 230°C vaporizable fractions in crude oil was increased by 8.5%than control.The desorption rate of adsorbed crude oil on filter paper was 84.7%,2.9 times of the control?P<0.05?.The crude oil viscosity?35??significantly lower than control?P<0.05?,reduce the rate of 42.5%.In the process of X9 fermentation broth displacing crude oil,the total oil displacement rate was significantly higher than that of the control water flooding?P<0.05?.In the displacement process of the second time,the oil displacement rate and oil displacement amount of fermentation broth were higher than that of the control water flooding and reached a significant level?P<0.05?,and were significantly lower than that of the first displacement?P<0.05?.4.Bacterial enzyme compounds can change the physicochemical properties of crude oilFour oil-adding bacteria were used to prepare the bacterial enzyme compounds by liquid culture and soild-state fermentation.During 15h water extraction of the solid bacteria,the number of bacteria increased slowly,and there was no obvious rule in the oil-spreading.pH value decreased with the increase of extraction time.The number of bacteria and pH were significantly?P<0.05?or extremely significantly?P<0.01?negatively correlated.The desorption rate of crude oil filter paper was up to 88.97%after the action of the microbial extract?P<0.05?.The viscosity of crude oil at 35?are reduced,decreased to 5.45%to36.82%?P<0.05?.The content of light fractions?saturated hydrocarbon and aromatic hydrocarbon?increased and the content of heavy fractions?gel and asphalt,etc.?decreased.The proportion of 230°C vaporizable fractions was increased up to 65.82%.5.The addition of available nutrients markedly improve the efficiency of oil displacementThe displacement efficiency of indigenous bacterial flooding was determined using salt solution?controls?supplemented with exogenous NH₄NO₃?N?,glucose?G?,or both?N+G?.The number of indigenous bacteria and the composition of dominant bacterial species in displaced fluid were determined along with the physicochemical properties of displaced oil,residual oil,and the displacing fluid.The results showed that NH₄NO₃-containing treatments?N and N+G?promoted indigenous bacterial growth in oil sand tubes by up to 704-fold compared with controls,whereas the G treatment inhibited growth by 71.7-91.1%.Both nutrient type and displacement time affected the composition of dominant bacteria.Cumulative displacement efficiencies for N,G,and N+G treatments were 102.9%?P<0.05?,22.1%,and 64.6%?P<0.05?higher than controls,respectively.The proportion of 230°C vaporizable fractions in residual oil was 0.6-35.8%higher,4.2-64.2%lower,and3.6-141.1%higher for the three treatments compared with controls.After displacement,levels of saturates,asphaltenes,and other materials in residual oil from the upper portion of oil sand tubes were respectively 5.3-13.4%?P<0.05?,7.2-22.3%?P<0.05?,and 16.6-31.9%?P<0.05?lower for the NH₄NO₃-containing treatments compared with controls.The pH and surface tension of displaced fluid were respectively 2.5-36.8%and 1.0-23.7%lower than the injected fluid.Surface-active substances and dehydrogenase activity were lost during displacement.6.Enzymatic transformation of fungal crude enzyme preparation can significantly increase the content of gasified oil in crude oilThis study studied four fungi that can degrade crude oil,identified the Z03 as Aspergillus oryzae,the Z05 as Aspergillus spelunceus,the Z06 as Aphanocladium aranearum,and the Z10 as Aspergillus sydowii by 16S ITS analyze.The effects of enzymatic transformation of four fungal crude enzyme preparations on crude oil group composition and vaporizable components?230°C?were studied.The enzymatic hydrolysis of asphalt by fungal enzymes was verified by pure asphalt.The results show that enzymatic transformation can degrade the high molecular components of crude oil,including asphalt,into small molecule gasification components.The gasification oil?total content of saturated hydrocarbon and aromatic hydrocarbon?in crude oil component increased by 30.3%to 44.4%compared with the control.Increase the output of gasified oil components such as gasoline,kerosene and diesel oil during the subsequent processing of crude oil;Can greatly improve crude oil?the total oil?,as well as a floating state oil vaporizable components?230°C?content,improve gasified oil content;The degradation rate of pure asphalt by fungal enzymes was up to 14.2%,which was 61.6 times as high as the control?P<0.05?,and the content of gasified oil in pure asphalt could increase by17.5%.7.Low cell density fermentation broth and alternating microbial and enzymolysis enhanced oil recovery can improve oil displacement efficiencyA simulated oil displacement test was conducted to determine the displacement efficiency of bacterial?Pseudomonas aeruginosa?fermentation broth with different cell densities?high,HCF;low,LCF?,crude fungal?Aspergillus oryzae?enzyme solution?CES?,and MEOR alternating EEOR?HCF–CES and LCF–CES?.The displacement efficiency of LCF was 1.7-fold that of HCF,and the displacement efficiency of CES was 4.6–6.0-fold that of water?control?.The total displacement efficiencies of LCF–CES and HCF–CES for five displacements were 9.4-and 6.2-fold of water,respectively.The relative quantity of vaporizable fractions in the displaced oil decreased after MEOR and increased after EEOR.The residual oil in the upper portion of the displacement tube contained decreased saturates?nearly half or higher?and increased resins?nearly 2-fold or higher?for LCF–CES and HCF–CES compared with water flooding.Compared with the injected fluid,the displaced fluid showed decreased pH,oil-spreading diameter,and surface tension,with substantial gas production and no dehydrogenase activity.The displaced fluid contained numerous culturable bacteria mainly dominated by injected?P.aeruginosa?and indigenous species?Bacillus atrophaeus,and B.cereus?.8.The oil displacement rate of MEOR is higher than that of EEORThe oil displacement effect of MEOR and EEOR combined with fungal crude enzyme preparation was compared.The results show that the oil displacement rate of MEOR is higher than that of EEOR.The amount of culturable bacteria in the oil sands determines the oil displacement rate.In 9 displacement times,from 6^th,the number of dominant bacteria and the total number of culturable bacteria were significantly correlated with the oil displacement rate?P<0.01?or?P<0.05?.A large number of bacteria were found in oil sands,the number of bacteria and the dominant bacteria in MEOR and EEOR was different.A large number of H2and CO2 gases were generated in MEOR processes involving exogenous bacteria Gx,while acid was produced to reduce the pH of the displacing fluid.No gas was generated in all EEOR treatments and CK control.Bacterial and fungal enzyme in the training process of oil displacement can degrade the heavy components to small molecular components,increased vaporizable components?230°C?in crude oil.The gasoline and part of the low boiling point kerosene and diesel oil content was augmented,the quality of the crude oil was improved.During the displacement process,the pH value of the displacement fluid and the diameter of the oil-spreading all decreased,the surface tension increased,and dehydrogenase activity disappeared in EEOR treatment.These changes were significantly correlated with the number of bacteria in the displacement fluid?P<0.05?or extremely significant?P<0.01?.9.Mechanisms of MEOR,EEOR and indigenous bacterial flooding are differentThough the simlute displacement,we found the mechanisms of MEOR,EEOR and indigenous bacterial flooding were different.In MEOR,oil displacement was achieved through multiple mechanisms,including surfactants,bacterial degradation of crude oil,and production of acids and gases.In EEOR,crude fungal enzymes showed a strong ability to degrade high-molecular-weight fractions of crude oil.In indigenous bacterial flooding,the addition of available nutrients markedly improved the efficiency of oil displacement via the plugging effect of indigenous bacterial growth,bacterial degradation of crude oil,and surface and interface effects of indigenous bacteria.