Method for producing methane from crude oil

Abstract

The invention relates to the technical field of further improvement of oil field recovery efficiency and CCUS in the later stage of CO2 oil displacement, and discloses a method for producing methane from crude oil, which comprises the step of degrading the crude oil in a crude oil produced liquid sample in the presence of a biological surface active substance to generate a first product containing methane. According to the invention, exogenous microorganisms are cooperated with indigenous microorganisms to form an oil extraction system for producing methane by using CO2 and crude oil, and biological factors are combined with non-biological factors to integrally improve the efficiency of converting CO2 into methane.

Description

Technical Field

[0001] The present invention relates to the field of further improving oilfield recovery in the later stage of CO2 flooding and CCUS technology, and in particular to a method for producing methane from crude oil. Background Art

[0002] According to the International Energy Agency (IEA), the world will still have 76 million tons of carbon dioxide in 2050. 8 tCarbon emissions need to be completely sealed by negative carbon technologies such as CO2 utilization and storage, of which China accounts for (5-15)×10 8 t. CCUS refers to an industrial process that achieves CO2 emission reduction while capturing and separating CO2 from industrial emission sources and utilizing it. CO2, as an excellent oil recovery medium, is a valuable resource for reservoir development and utilization. Combining CO2 oil recovery with CCUS can realize the resource utilization of CO2, which has a "win-win" characteristic of social and economic benefits. After CO2 oil recovery, there is still 30-40% of residual oil in underground reservoirs that is difficult to mobilize. In the reservoir environment, microorganisms such as native hydrocarbon degrading bacteria, acetic acid decomposing bacteria, hydrogen-producing bacteria, and methanogens are widely present. The burial of CO2 in underground reservoirs provides important conditions for reservoir microorganisms to play a biogeochemical role. Methanogens can use CO2 and crude oil to produce methane. Mayumi et al. reported (Nature Communication, 2013, DOI: 10.1038 / ncomms2998|www.nature.com / naturecommunications) that high concentrations of CO2 activated the acetic acid-methane production pathway, making the rate of methane production after adding CO2 nearly twice that of without CO2. Ma et al. (IBB, 2021, https: / / doi.org / 10.1016 / j.ibiod.2017.12.002) reported that adding 13 After CO2 injection, 46% of the methane comes from the injected gas and 54% from the degradation of residual oil through the action of reservoir microorganisms. Tyne et al. (Nature, 2021, http: / / doi.org / 10.1038 / s41586-O21-O4153-3) reported that for the Olla oil field in Louisiana, USA, which carried out CO2-EOR from 1983 to 1986, 29 years later, it was found that 13-19% of the CO2 injected into the reservoir was converted into methane by microorganisms. This shows that the use of CO2 stimulates the biogeochemical action of the reservoir to regenerate methane.

[0003] Anaerobic microorganisms convert CO2 into methane, usually using small molecules such as CO2, H2, formic acid, acetic acid, and methyl compounds as substrates. These small molecules come from the degradation of crude oil to form large molecular organic matter, which is then decomposed into small molecules. In a large number of indoor studies, fumaric acid was used as the main activator to increase the production of methane (Ji et al., AEM, 2019, https: / / doi.org / 10.1128 / AEM.00985-19). Fumaric acid promotes the opening of the carbon chain under the catalysis of fumaric acid, and finally regenerates fumaric acid through carbon skeleton reconstruction. In addition, inorganic salt culture medium, trace elements, vitamins (CN 109022495B, CN 114958643 A, CN114958696 A), zero-valent iron (CN 108424947 A), titanium dioxide (CN 107557395 B), etc. are added to the methanogenic culture medium to improve the efficiency of methanogenesis by supplementing the elements, coenzyme factors, and electron shuttles required for microbial growth and metabolism. Summary of the invention

[0004] The applicant of this application has found that the current technologies all use abiotic factors to promote the efficiency of methanogenesis, ignoring the problem of improving the yield through interactions between reservoir microorganisms. There is no report on the way microorganisms improve efficiency through interspecies interactions. In order to further approach the interaction of microorganisms in the reservoir environment to increase the yield of methane, it is necessary to study the formation of an oil recovery system that utilizes CO2 and crude oil to produce methane by combining the effects of exogenous microorganisms with native microorganisms, and the combination of biological factors and abiotic factors to improve the efficiency of CO2 conversion to methane.

[0005] It should be noted that the endogenous microorganisms in the present invention refer to the microorganisms sampled from the studied oil reservoir block (crude oil sampling block); exogenous microorganisms refer to microorganisms obtained from other oil fields other than the main studied oil reservoir block, or microorganisms from other environments (such as soil, hydrosphere, ocean, land, etc.). The seed liquid in the present invention refers to a spore suspension having the ability to produce surfactant (such as lipopeptides and glycolipids).

[0006] The present invention discloses a method for producing methane from crude oil, the method comprising:

[0007] S1. In the presence of a biosurfactant, the crude oil in the crude oil production fluid sample is degraded to generate a first product containing methane.

[0008] In order to enable the method of increasing methane production through biological factors to be implemented indoors and achieve the purpose of indoor simulation, in some embodiments of the present invention, in S1, the crude oil production fluid sample includes: a core after saturated formation water, saturated crude oil, and water drive; specifically, the biological surfactant strips the crude oil from the core pores and emulsifies it to expand the oil-water interface, which is beneficial for the microbial community to carry out biochemical metabolic processes near the oil-water interface to generate the first product.

[0009] In some embodiments of the present invention, in S1, the volume ratio of 0.1-1 g / L biosurfactant: crude oil produced liquid sample is 0.1-0.2 PV: 1 PV.

[0010] In some embodiments of the present invention, the biosurfactant of the present invention comprises one or more of rhamnolipid, lipopeptide, surfactin, bioemulsifier and trehalose lipid.

[0011] In some embodiments of the present invention, in S1, the biological surfactant comes from surfactant-producing microorganisms, and the surfactant-producing microorganisms include one or more strains of the genera Pseudomonas, Dietzia, Thauera, Acinetobacter, Gordonia, Rhodococcus and Geobacillus.

[0012] In some embodiments of the present invention, the preparation method of biological surfactants includes: culturing surfactant-producing microorganisms by conventional methods of the prior art, such as separating and purifying endogenous microorganisms from crude oil production fluid, screening strains with crude oil emulsification ability, and improving the ability of strains to produce biological surfactants by optimizing the components of single-bacteria culture medium; or purchasing strains with high production of biological surfactants from a strain collection center, such as the collection numbers CGMCC No. 24711, No. 16105, and No. 24606.

[0013] The present invention aerobically cultivates microorganisms capable of degrading crude oil, utilizes surfactants produced by the microorganisms, and injects them into a methanogenic system to promote the degradation of crude oil, thereby facilitating further degradation of crude oil by other reservoir microorganisms in the community system, forming a "chain reaction" and achieving improved methane metabolic efficiency.

[0014] In some embodiments of the present invention, when the methane generation in S1 is stable, S2 is performed;

[0015] S2. In the presence of biological surfactants and directed domesticated microorganisms, the first product is further degraded and converted into methane.

[0016] In some embodiments of the present invention, the inoculation amount of the directed domesticated microorganisms in the degradation system in S2 is OD600 Final concentration>0.2.

[0017] In some embodiments of the present invention, the directed domesticated microorganisms in S2 include at least one of degrading bacteria, acidophilic bacteria, fermentative bacteria, symbiotic bacteria or methanogens.

[0018] In some embodiments of the present invention, when the increase in methane generation is 0.01%, it is determined that the methane generation is stable.

[0019] In some embodiments of the present invention, the existing technology is used to prepare the directed domesticated microorganisms, for example, including: the culture medium is an oil-water mixture and N2 is injected, under anaerobic conditions, at the temperature and pressure conditions of the in-situ oil reservoir environment of the crude oil, fumaric acid and NaHCO3 aqueous solution are added, the microorganisms are domesticated and cultured to form a robust community that can adapt to the temperature and pressure of the reservoir, and the generation of hydrogenophilic methanogens is enhanced to form a robust community that can adapt to the temperature and pressure of the reservoir, and then injected into the core to interact with the native microorganisms in the crude oil to form a synergistic system, so as to achieve an improvement in the efficiency of CO2 and crude oil conversion to methane.

[0020] In some embodiments of the present invention, the crude oil comes from a reservoir after water flooding or CO2 flooding, preferably from a reservoir in the late stage of CO2 flooding in CCUS. This can solve the problem of the efficiency of converting CO2 and crude oil into methane through microorganisms after CO2 flooding in underground oil reservoirs. The present invention can utilize the species interaction of microorganisms to improve the utilization rate of residual oil and the metabolic yield of methane.

[0021] In some embodiments of the present invention, the method of the present invention is carried out in a simulated reservoir environment, and the simulated reservoir environment simulates the in-situ reservoir environment of crude oil; specifically, the simulation parameters of the simulated reservoir environment include: the temperature, pressure and porous medium environment of the in-situ reservoir of crude oil; more preferably, the temperature of the simulated reservoir environment is 20-70°C, the pressure is 5-50MPa, and the air permeability of the porous medium environment is greater than 50mD.

[0022] In some embodiments of the present invention, the step of constructing the reservoir environment includes:

[0023] A core is selected, saturated with water and placed in a core holder 1, saturated with crude oil under simulated reservoir pressure, and water-flooded at reservoir temperature, and then liquid-flooded for ≥7 days to form a crude oil production fluid sample having the aforementioned reservoir environment;

[0024] The liquid displacement agent is the bacterial solution or metabolites that produce the aforementioned biological surfactants (it can be understood that if it is a metabolite, a 0.2 μm filter membrane can be added at the injection port to filter the bacteria) and the culture solution after domesticating the directional microorganisms.

[0025] In some embodiments of the present invention, the core clamp includes a clamping section 11 and a fixing member 12 arranged at both ends of the clamping section 11, wherein the clamping section 11 includes an inner cylinder 111 and an outer cylinder 112 nested inside and outside, and the core is placed in the inner cylinder 111 to simulate the environment of the porous medium of the oil reservoir; the fixing member 12 is used to fix and make the inner cylinder 111 and the outer cylinder 112 spaced apart.

[0026] In some embodiments of the present invention, pistons 113 are installed at both ends of the core in the inner cylinder 111, and the pistons 113 can move along the length direction of the inner cylinder to achieve pressure control on the core.

[0027] In some embodiments of the present invention, the material of the fixing member 12 includes a titanium alloy that is resistant to high pressure (50 MPa) and CO2 corrosion; thus, unlike the traditional material of stainless steel, the present invention avoids the reaction of acids produced by microbial metabolism with iron-containing substances. The specific composition of the titanium alloy has no special requirements, as long as it can resist CO2 corrosion and avoid reaction with microbial bacterial liquid, such as the titanium alloy of Baoji Titanium Industry brand and material number TC4 (Ti-6Al-4V Grade 5), which will not be elaborated in the present invention.

[0028] In order to obtain information such as the occurrence state and oil saturation of oil, gas and water through a scanning imaging system, and to perform a visual analysis of the in-situ environmental simulation effect, in some embodiments of the present invention, the material of the clamping section 11 can be penetrated by X-rays, and the material of the outer cylinder 112 preferably includes polyetheretherketone (PEEK). It should be noted that the present invention has no special requirements for the material of the outer cylinder 112, as long as it can be penetrated by X-rays. For example, polyetheretherketone of Junhua Special Plastics brand and numbered PEEK5600CF30 (black) can be used in the present invention.

[0029] In some embodiments of the present invention, the inner cylinder is made of rubber material. The present invention has no special requirements on the material rubber of the inner cylinder. For example, the FFKM perfluoroether rubber material of the Xulong brand (high temperature resistant up to 320°C) can be used in the present invention to prevent CO2 from corroding the inner cylinder.

[0030] In some embodiments of the present invention, the core is selected from an artificial core or a natural core, preferably an American Berea core.

[0031] It should be noted that the current experimental research on methanogenesis by microorganisms in oil reservoirs is mainly conducted in a two-phase liquid system of oil and water, and the research on simulating environmental conditions of oil reservoirs is mainly to simulate the temperature and pressure of oil reservoirs. In fact, underground oil reservoirs are porous media environments with heterogeneous characteristics. The present invention further simulates the environment of porous media in oil reservoirs on the basis of simulating the in-situ temperature and pressure environment of oil reservoirs.

[0032] In some embodiments of the present invention, the fixing member is as followsFigure 6 As shown, Figure 6 The left side is a cross-sectional view of the top fixing member, and the right side is a cross-sectional view of the bottom fixing member. It should be noted that the fixing member includes a U-shaped cover body, the inner wall of the U-shaped cover body is connected to the outer wall of the outer cylinder body through the outer cylinder connecting block 115; the inner top wall of the U-shaped cover body is provided with a first positioning block 126 and a second positioning block 127 extending toward the clamping section, wherein the first positioning block 126 and the second positioning block 127 can be set in an annular shape and spaced apart, and the first positioning block 126 is clamped in the annular gap formed between the inner cylinder 111 and the outer cylinder 112. In order to achieve a better positioning effect, The longitudinal section of the first positioning block can be set to be a wedge-shaped shape that tapers from the top wall to the clamping section; the second positioning block 127 is located in the space defined by the first positioning block 126, and annular members 114 are provided at both ends of the core in the inner cylinder 111, and the annular member 114 surrounds and forms a piston cavity that cooperates with the piston. The second positioning block 127 is used to position the annular member 114 to prevent the annular member from moving axially along the clamping section, and the radial size of the second positioning block 127 in the clamping section is larger than the annular member 114, which can be used to limit the piston 113 to prevent the piston from overtravel; wherein, as Figure 4-Figure 5 As shown, the piston rod of the piston 113 extends outside the cover body and is set to be hollow, so that the piston rod can serve as the second material port 122 for feeding materials into the core or the fifth material port 125 for discharging materials from the inner cylinder, and N2 can be injected through the second material port 122 to form an anaerobic environment; the U-shaped cover body is also provided with a third material port 123 connected to the piston cavity (the third material port 123 in the top fixing part and the fourth material port 124 in the bottom fixing part), and the third material port 123 is used to pass distilled water into the piston cavity (area 1) on one side of the piston rod to promote the movement of the piston to achieve pressure control of area 1 on area 2. At the same time, after the reaction in the core clamp forms methane, the system pressure is increased, and a constant reservoir pressure can be maintained by adjusting area 1, and the fourth material port 124 is the same.

[0033] In some embodiments of the present invention, the annular member and the outer cylinder connecting block are each configured as a titanium ring, and the material of the titanium ring may be the aforementioned Baoji Titanium brand titanium alloy with a material number of TC4 (Ti-6Al-4V Grade 5).

[0034] In some embodiments of the present invention, the first positioning block of the top fixing member and / or the bottom fixing member is penetrated by a first material port 121 communicating with the annular gap between the inner cylinder and the outer cylinder. The first material port 121 can be connected to a confining pressure pump to control the confining pressure of the core clamp.

[0035] In some embodiments of the present invention, the fixing piece at one end of the core holder of the present invention is connected to the CT support connector to facilitate X-ray scanning. It should be noted that the present invention has no special requirements for the CT support connector, and can be used as follows: Figure 4 The supporting connector shown only needs to be able to ensure that the clamp remains stable during the movement and scanning of the stage.

[0036] The present invention also provides a simulation of methane production by microbial action on CO2 and crude oil, the system comprising: a core holder, an aerobic culture tank 31, and an anaerobic culture tank 21, wherein:

[0037] The active microorganisms can be cultured in the aerobic culture tank 31, in which a stirring device 32 is installed and a feed port 33 and a discharge port 34 are provided on the tank wall, and the discharge port 34 is connected to the second material port 122 of the core holder 1 through a pipeline. In some embodiments of the present invention, a bacterial cell filter 35 is preferably installed on the discharge port 34 to separate the bacterial cells and bacterial metabolites in the aerobic culture tank 31, such as Figure 1 As shown, the bacterial filter element can be a bacterial filter membrane installed on the discharge port 34, and a filtration pump, a bacterial metabolite container 36 and a booster pump are sequentially arranged along the material flow direction on the pipeline connecting the discharge port 34 and the core clamp 1.

[0038] Directed domesticated microorganisms are cultured in an anaerobic culture tank 21. Under anaerobic conditions, the directed domesticated microorganisms are prepared using existing technology to form a robust community that can adapt to the temperature and pressure of the oil reservoir and enhance the generation of hydrogenophilic methanogens. The anaerobic culture tank 21 is equipped with a pressure detection device and is connected to a gas pipeline 22, a culture liquid pipeline 23 and a directed domesticated microorganism discharge pipeline 24. The directed domesticated microorganism discharge pipeline 24 is connected to the second material port 122 of the core holder 1. Figure 1 As shown, in some embodiments of the present invention, the anaerobic culture tank is a high temperature and high pressure resistant culture tank, and a piston is provided in the tank. The piston divides the tank body of the anaerobic culture tank into an upper space and a lower space, wherein the upper space is used to cultivate directionally domesticated microorganisms, and a pressure gauge is installed in the upper space and a gas pipeline 22, a culture liquid pipeline 23 and a seed liquid discharge pipeline 24 are arranged; the lower space is connected to a pipeline equipped with an injection pump.

[0039] In some embodiments of the present invention, Figure 3 As shown, the first material inlet 121 of the core clamp 1 is connected to the confining pressure pump for adjusting the confining pressure in the core clamp, and the fifth material port 125 is connected to the gas collecting tank 13, and the outlet of the gas collecting tank 13 is connected to the sampling port of the gas chromatograph to collect the gas phase product in the core clamp 1, and the existing technology is used to analyze the content of methane, CO2, and H2 in the product. In addition, the core clamp is also provided with a liquid phase outlet for collecting bacteria-containing liquid. After the liquid collects the bacteria through the filter membrane, the existing technology is used to perform high-throughput sequencing of the metagenomics, 16S rRNA gene, etc., and the filtrate is subjected to organic acid analysis, ion concentration detection, etc., which will not be repeated in the present invention.

[0040] Through the above technical scheme, compared with the prior art, in the study of microorganisms converting CO2 and crude oil into methane, the present invention utilizes the characteristics of exogenous reservoir microbial metabolites and exogenous reservoir microbial functional characteristics to form an experimental system for promoting methanogenic metabolism under simulated reservoir in-situ environmental conditions. The present invention provides a device design for realizing the experimental system, using biological factors to promote chain reactions, forming an experimental device for promoting the conversion of native microorganisms CO2 and crude oil by exogenous microorganisms. The present invention has clear ideas, simple processes, strong pertinence and strong operability; at the same time, it has the advantages of cultivating, domesticating and regulating microbial communities under in-situ physical model cultivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of a simulation system for producing methane from crude oil according to an embodiment of the present invention;

[0042] Figure 2 It is the core vacuum flow chart;

[0043] Figure 3 It is the flow chart of the saturated oil physical model experimental device.

[0044] Figure 4 yes Figure 1 Schematic diagram of the structure of the core holder;

[0045] Figure 5 yes Figure 4 Structural schematic diagram of the middle clamping section;

[0046] Figure 6 yes Figure 4 Longitudinal section of the fixing.

[0047] Description of Reference Numerals

[0048] 4 pressure-resistant intermediate container; 5 six-way valve; 6 injection pump; 7 crude oil storage tank; 1 core clamp; 11 clamping section, 12 fixing piece; 13 gas collecting tank; 21 anaerobic culture tank; 22 gas pipeline; 23 culture liquid pipeline; 24 seed liquid discharge pipeline; 31 aerobic culture tank; 32 stirring device; 33 feed inlet; 34 discharge outlet; 35 bacterial filter; 36 bacterial metabolite container. DETAILED DESCRIPTION

[0049] The present invention is described in detail below by way of embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0050] In the following examples and comparative examples, the crude oil comes from the oil reservoir in Jiuxi Basin, China after water flooding, wherein the sample composition includes: 50% saturated hydrocarbons, 21% aromatic hydrocarbons, 23% colloids, and 6% asphaltenes.

[0051] Example 1

[0052] (1) Aerobic culture experiment of surface-active microorganisms. The aerobic culture tank 31 was placed in the first incubator, the temperature was set to 30°C, and the culture medium was n-hexadecane culture medium (g / L): NaCl 5, MgSO4 0.2, K2HPO4 1, (NH4)2SO4 1.0, n-hexadecane 0.3% (v:v), NH4H2PO4 1.0, KNO3 3.0, pH 6.8-7.2. The aerobic culture tank 31 was inoculated with surface-active microorganisms capable of emulsifying crude oil, and the inoculation amount OD 600 The final concentration is 0.02, Pseudomonas (selected strains are stored in CGMCC No. 24711), Dietzia (selected strains are stored in CGMCC No. 16105), Thauera (selected strains are stored in CGMCC No. 24606) (in a ratio of 1:1:1) can produce biological surface active substances such as glycolipids, lipopeptides and other substances. Under the condition of continuous air supplementation, the fermentation liquid is continuously multiplied by the action of a stirrer (stirring speed 110-180rpm) until OD 600 The final concentration is 1.5. Periodically (at intervals of 5-7 days), the surface-active substances are filtered out from the filter membrane using a suction pump and placed in the container 36 for bacterial metabolites.

[0053] (2) Anaerobic culture experiment for directional domestication of microorganisms and enrichment. First, add an oil-water mixture (the volume ratio of the oil-water mixture is 0.5-2%, and the oil comes from an oil field in the Jiuxi Basin) to the anaerobic culture tank 21, and then inject high-purity nitrogen N2 (concentration higher than 99.998%) from the gas pipeline 22 into the anaerobic culture tank 21. The anaerobic culture tank is placed in a second incubator, and the temperature of the second incubator is 30°C, the reservoir temperature. At the reservoir temperature, the pressure of the culture tank is pressurized to the reservoir pressure of 6MPa.

[0054] In this embodiment, the microorganisms for targeted domestication are from the in-situ microbial community of crude oil, and are not additionally inoculated. The natural community composition structure is retained during the initial culture, and the targeted domestication is only to add a targeted substrate / activator (the substrate / activator includes an oil-water mixture, NaHCO3 and fumaric acid, wherein the final concentration of the injected NaHCO3 is 10 g / L, and the final concentration of the fumaric acid is 10 mM). The resulting targeted domesticated microorganisms are injected into the core holder 1 to participate in the transmethanation reaction.

[0055] (3) Methane production culture experiment.

[0056] use Figure 4-Figure 6The core clamp shown in the figure includes a bottom fixing part, a core clamping section 11, and a top fixing part connected in sequence from bottom to top, wherein the core clamping section includes an inner cylinder 111 and an outer cylinder 112 nested inside and outside, and the core is placed in the inner cylinder 111. The outer cylinder is made of polyetheretherketone (PEEK) of Junhua Special Plastics brand and numbered PEEK5600CF30 (black), and the inner cylinder material is FFKM perfluoroether rubber material of Xulong brand (high temperature resistant up to 320°C).

[0057] The first positioning block 126 of the fixing member 12 at each end is connected to the outer cylinder through the annular outer cylinder connecting block 115, and the second connecting block 127 is connected to the inner cylinder through the annular member 114. The cavity surrounded by the annular member is a piston cavity, in which a piston is installed. The piston 113, the annular member 114 and the outer cylinder connecting block 115 are each made of a titanium alloy of Baoji Titanium Industry brand and material number TC4 (Ti-6Al-4V Grade 5).

[0058] The American Bailey core (hereinafter referred to as core) is used to simulate the porous medium of the reservoir. The core size D*L is 38mm*300mm. Figure 4 As shown, the core permeability is 250mD.

[0059] ①Core preparation

[0060] (a) Measure the core dimensions and calculate the core volume V. For a cylindrical core: Where: D-diameter, L-length.

[0061] (b) Dry in an oven at 110°C for 12 h to remove the moisture. After constant weight is achieved, use a balance to measure the dry mass m1.

[0062] (c) The core after drying and weighing is used Figure 2 The process shown is to evacuate for 4 hours (vacuum degree -100KPa), then saturate with water and weigh its wet mass m2.

[0063] (d) The mass of saturated water W is obtained by subtracting the dry mass of the core m1 from the wet mass of the core m2, from which the pore volume V of the core is calculated. P , calculate the porosity Where ρ is the density of water and the porosity is 18%.

[0064] ② Water permeability

[0065] Connect the pipelines between the anaerobic culture tank and the core holder. Place the core in the core holder 1 and increase the confining pressure to 2.5-3.0 MPa higher than the injection pressure. Inject the produced fluid at a pump speed of 0.30 mL / min until the pressure is balanced. Record the equilibrium pressure P0 and calculate the water permeability K of the core according to Darcy's law as 165 x 10 -3 μm 2 , Where: K- water permeability; P0- equilibrium pressure (pressure difference) when water passes through the core; μ- viscosity of water; L- length of the core; A- cross-sectional area of ​​the core; Q- flow rate through the core at P0.

[0066] ③Saturated oil

[0067] according to Figure 3 As shown, the crude oil storage tank 7 and the pressure-resistant intermediate container 4 are connected with pipelines. The core is placed in the core holder 1, and the confining pressure is increased to 2.5-3.0 MPa higher than the injection pressure; the oil sample is injected at the pump speed of 0.05 mL / min, 0.10 mL / min, and finally 0.80 mL / min, and the mass of the effluent is recorded and the oil saturation is calculated until the oil saturation reaches more than 70%.

[0068] ④ Water drive

[0069] The core in core holder 1 is kept at a constant temperature for 12 hours in a thermostat simulating the reservoir temperature. Turn on the back pressure pump and record the back pressure pump zero point; set the back pressure of the back pressure pump. Water drive (using the culture medium that has been domesticated for a long time in the anaerobic culture tank) at a pump speed of 0.05 mL / min, and the confining pressure should be adjusted at the same time, maintaining the confining pressure 2.5-3.0 MPa higher than the injection pressure, and gradually increase the pump speed to 0.30 mL / min until the water content reaches 98%. Record the oil and liquid output, and calculate the water drive recovery factor of 60%. Calculate the water volume V in the porous medium a It is 36.73mL.

[0070] ⑤ Methanogenic culture

[0071] The biosurfactant filtered from the aerobic culture tank is injected into the core holder regularly (at intervals of 5-7 days), wherein the volume ratio of biosurfactant (1g / L): crude oil production liquid sample is 0.2:1, and the crude oil in the pores is emulsified. The interface between the injection end and the production end of the core holder is then sealed for long-term culture, and gas is collected from the production end using an air bag for analysis at 0 days, 30 days, 60 days, 90 days, 120 days, 150 days, etc. (until the methane generation is stable).

[0072] After the methane production is stable (when the production does not increase for one month, the increase in the n+1 week is 0.01% of the nth week, which is considered as no increase in production), the directional domesticated microorganisms in the anaerobic culture tank can be injected again. Among them, metabolites (1g / L): directional microorganism seed solution (OD 600 =1): The volume ratio of the crude oil produced liquid sample is 0.2:0.8:1, so that the entire system continuously converts CO2 and residual oil into methane under the discontinuous activation of the "biological factor".

[0073] (4) After the experiment, the pore structure and oil and gas saturation of the core were obtained by CT imaging system or nuclear magnetic resonance scanning, revealing the distribution of oil, gas and water after the reservoir microorganisms used CO2 to produce methane. The results are shown in Table 1.

[0074] Example 2

[0075] Different from Example 1, after the methane generation amount stabilized, no biosurfactant and directional enrichment seed solution were injected. The results are shown in Table 1.

[0076] Comparative Example 1

[0077] Different from Example 1, only abiotic factors NaHCO3 (final concentration 10 g / L) and fumaric acid (final concentration 10 mM) were added to the core holder 1, and the biological surfactant and directed domesticated microorganisms of the present invention were not added. The results are shown in Table 1.

[0078] Table 1 The percentage concentration of methane in the gas products changes with time

[0079]

[0080]

[0081] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any appropriate manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention;

[0082] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0083] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to up, down, left, right as shown in the reference drawings; "inside and outside" refer to inside and outside relative to the outline of each component itself.

Claims

1. A method for producing methane from crude oil, characterized in that: The method includes: S1. In the presence of a biosurfactant, the crude oil in the crude oil production fluid sample is degraded to generate a first product containing methane.

2. The method according to claim 1, wherein: In S1, The crude oil produced fluid sample includes: cores after saturated formation water, saturated crude oil, and water flooding; and / or 0.1-1g / L of biosurfactant: the volume ratio of crude oil produced fluid sample is 0.1-0.2PV:1PV; and / or The biological surfactant includes one or more of rhamnolipid, lipopeptide, surfactin, biological emulsifier and trehalose lipid.

3. The method according to claim 1 or 2, wherein: In S1, the biological surfactant is derived from surfactant-producing microorganisms, and the surfactant-producing microorganisms include one or more strains of the genera Pseudomonas, Dietzia, Thauera, Acinetobacter, Gordonia, Rhodococcus and Geobacillus.

4. The method according to any one of claims 1 to 3, wherein: When the methane production in S1 is stable, proceed to S2; S2. In the presence of the biosurfactant and the directed domesticated microorganisms, the first product is further degraded and converted into methane.

5. The method according to claim 4, wherein: The inoculation amount of the directed domesticated microorganisms in the degradation system described in S2 is OD 600 Final concentration > 0.2; and / or The directed domesticated microorganisms described in S2 include at least one of degrading bacteria, acidophilic bacteria, fermentative bacteria, symbiotic bacteria or methanogens.

6. The method according to claim 4 or 5, wherein: When the increase in the amount of methane generated was 0.01%, it was determined that the amount of methane generated was stable.

7. The method according to any one of claims 1 to 6, wherein: The crude oil comes from a reservoir after water flooding or CO2 flooding, preferably from a reservoir in the late stage of CO2 flooding in CCUS; and / or The method is performed in a simulated reservoir environment, wherein the simulated reservoir environment simulates the in-situ reservoir environment of the crude oil; Preferably, the simulated reservoir environment simulation parameters include: the temperature, pressure and porous medium environment of the in-situ reservoir of crude oil; More preferably, the temperature of the simulated reservoir environment is 20-70° C., the pressure is 5-50 MPa, and the air permeability of the porous medium environment is greater than 50 mD.

8. The method according to claim 7, wherein: The steps to construct a reservoir environment include: A core is selected, saturated with water and placed in a core holder (1), saturated with crude oil under simulated reservoir pressure, and water-flooded at reservoir temperature, and then liquid-flooded for ≥7 days to form a crude oil production fluid sample having the reservoir environment; The displacement agent of the liquid flooding is a bacterial solution or metabolites that produce biological surfactants and a culture solution after taming directional microorganisms.

9. The method according to claim 8, wherein: The core holder (1) comprises: The clamping section (11) comprises an inner cylinder (111) and an outer cylinder (112) which are nested inside and outside, and the core is placed in the inner cylinder (111); The fixing members (12) are arranged at both ends of the clamping section (11) and are used for fixing and allowing the inner cylinder (111) and the outer cylinder (112) to be arranged at intervals.

10. The method according to claim 9, wherein: Pistons (113) are installed at both ends of the core in the inner cylinder (111), and the pistons (113) can move along the length direction of the inner cylinder to achieve pressure control on the core; and / or The material of the fixing member (12) includes titanium alloy; and / or The material of the clamping section (11) is capable of being penetrated by X-rays, and preferably the material of the outer cylinder (112) includes polyetheretherketone.

11. The method according to any one of claims 8 to 10, wherein: The core is selected from artificial core or natural core, preferably American Berea core.

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