A microbial oil recovery method using green plants as raw materials

Abstract

The application discloses a kind of microbial oil extraction methods using green plants as raw material, comprising the following steps: (1) target reservoir screening;(2) target reservoir endogenous microbial community structure analysis;(3) target reservoir methanogen analysis;(4) green plant injection preparation;(5) green plant injection on-site injection, the application is applicable to the field of microbial oil extraction technology, for the reservoir that complete flora exists in endogenous microorganism, on the one hand, carbon fixation is used to green plants, and the emission of carbon dioxide is reduced;On the other hand, endogenous microorganism in reservoir uses green plant injection as nutrition, and acid and gas are produced after degradation, reduce the cost of microbial oil extraction technology, greatly improve the effect of microbial oil extraction;For the reservoir without complete flora, by supplementing functional bacteria, various complex organic matter can be hydrolyzed into relatively simple organic matter, and anaerobic fermentation is carried out to produce gas, effectively improve the recovery efficiency of crude oil, improve the development effect of middle and late reservoir.

Description

Technical Field

[0001] This invention belongs to the field of microbial enhanced oil recovery technology, specifically a method for microbial enhanced oil recovery using green plants as raw materials. Background Technology

[0002] Microbial enhanced oil recovery (MEOR) technology typically utilizes the growth and metabolism of microorganisms in oil reservoirs to produce a large number of metabolites, such as biopolysaccharides, biosurfactants, small-molecule organic matter, and biogas. These metabolites act on residual oil, improving its fluidity and altering the wettability of the reservoir's porous media, thus facilitating crude oil flow. Biogas, mainly composed of methane and carbon dioxide, increases reservoir pressure and dissolves in crude oil, reducing its viscosity and thereby increasing production and recovery rate. MEOR requires the injection of substantial nutrients, including carbon and nitrogen sources, to support microbial growth and metabolism; this constitutes a major cost component. Currently, commonly used activators include glucose, sucrose, peptone, and yeast extract, which are expensive, leading to high activator costs. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microbial oil recovery method using green plants as raw materials.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for microbial enhanced oil recovery using green plants as raw materials includes the following steps:

[0006] (1) Target reservoir screening;

[0007] (2) Analysis of the endogenous microbial community structure of the target reservoir;

[0008] (3) Analysis of methanogenic bacteria in the target reservoir;

[0009] (4) Preparation of green plant injection solution;

[0010] (5) On-site injection of green plant injection.

[0011] Preferably, in step (1), the target reservoir screening conditions include: permeability greater than 0.8 Darcy, sandstone reservoir, burial depth 800-1200m, reservoir temperature less than or equal to 65℃, and salinity less than or equal to 150000mg / L.

[0012] Preferably, in step (2), the method used for analyzing the endogenous microbial community structure of the target reservoir is high-throughput sequencing.

[0013] Preferably, in step (2), the analysis of the endogenous microbial community structure of the target reservoir includes:

[0014] The study aimed to analyze whether the reservoir's endogenous microbial community included microorganisms with important metabolic functions, such as anaerobic fermenting bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria.

[0015] Preferably, in step (3), the analysis of whether the reservoir endogenous microbial community includes methanogens is performed using the real-time quantitative PCR method.

[0016] Preferably, the methanogens include Methanobacterium bristlenoides, Methanocytozoa, Methanobacterium thermophilum, and Methanobacterium tumefaciens.

[0017] Preferably, in step (4), the preparation of the green plant injection includes:

[0018] For algae and green plants, an automated scraping film technology is used for harvesting, and the harvested algae are injected into the formation along with the injected water.

[0019] Preferably, in step (4), the preparation of the green plant injection further includes:

[0020] Other plants larger than algae are crushed to form a paste-like injection that is easy to inject.

[0021] Preferably, during the preparation of the injection, inorganic salts need to be formulated according to the ionic composition of the injection water.

[0022] Preferably, the injection preparation process includes:

[0023] First, determine whether the injected water contains potassium, sodium, magnesium, and calcium ions. If any of these ions are lacking or the concentration is too low, add inorganic salts to supplement the concentration of each ion to 0.6–1.5 g / L.

[0024] Preferably, the added inorganic salts include one or more of the following: calcium chloride, potassium chloride, sodium nitrate, magnesium sulfate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

[0025] Preferably, the added inorganic salt is calcium chloride.

[0026] Preferably, in step (4), the green plants include algae, ferns, and mosses.

[0027] Preferably, in step (4), the green plant is an algae.

[0028] Preferably, the algae include *Microchlorophyll*, *Tabernaecia*, *Chlorella*, *Dunaliella*, and *Chlamydomonas*.

[0029] Preferably, the algae is *Microchlorophyllariae*.

[0030] Preferably, in step (5), the on-site injection of the green plant injection agent is carried out by fracturing injection method.

[0031] Preferably, in step (5), the on-site injection of the green plant injection includes the following steps:

[0032] Using fracturing equipment, green plant preparations are injected underground under high pressure, with each well receiving 600-1000 cubic meters of plant preparation per day. 3 The injection time is 8-12 hours per day, then the injection is stopped to allow the underground pressure to be released before starting the next cycle of injection. The injection is carried out continuously for 1-2 months, then the well is shut off to enter the biogas production stage. The wellhead pressure is monitored to predict the underground biogas production.

[0033] Preferably, the cycle is 1-2 days and the well shut-in time is 14-30 days.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] In this invention, for reservoirs with complete microbial communities in their endogenous microorganisms, on the one hand, carbon fixation by green plants is utilized to reduce carbon dioxide emissions; on the other hand, the endogenous microorganisms in the reservoir use green plant injections as nutrients, and after degradation, produce acid and gas, reducing the cost of microbial enhanced oil recovery technology and significantly improving the effect of microbial enhanced oil recovery. For reservoirs without complete microbial communities, one or more of anaerobic fermentation bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria are compounded in the green injections, which can also achieve the hydrolysis of various complex organic matter into simpler organic matter and carry out anaerobic fermentation to produce gas, effectively improving the crude oil recovery rate and improving the reservoir development effect in the middle and late stages.

[0036] This invention can effectively improve crude oil recovery rate to over 15%; it also has the advantages of simple process, economic and environmental protection, and high input-output ratio, with an input-output ratio greater than 1:20. Attached Figure Description

[0037] Figure 1 This is a flowchart of a microbial oil recovery method using green plants as raw materials according to the present invention;

[0038] Figure 2 This is a daily circulating injection pressure curve of a microbial oil recovery method using green plants as raw materials according to the present invention;

[0039] Figure 3 This is a flowchart of the preparation of green plant injection agent in a microbial oil recovery method using green plants as raw materials according to the present invention;

[0040] Figure 4 This is a flowchart of the injection process of plant-based oil recovery in a microbial oil recovery method using green plants as raw materials according to the present invention. Detailed Implementation

[0041] The following is in conjunction with the appendix Figure 1-4 This invention further illustrates specific embodiments of a microbial enhanced oil recovery (EOR) method utilizing green plants as raw materials. The EOR method of this invention is not limited to the descriptions in the following embodiments.

[0042] Example 1:

[0043] This embodiment provides a specific implementation method for a microbial enhanced oil recovery (EOR) method using green plants as raw materials, such as... Figure 1 As shown, it includes the following steps:

[0044] (1) Target reservoir screening;

[0045] (2) Analysis of the endogenous microbial community structure of the target reservoir;

[0046] (3) Analysis of methanogenic bacteria in the target reservoir;

[0047] (4) Preparation of green plant injection solution;

[0048] (5) On-site injection of green plant injection.

[0049] Furthermore, in step (1), the target reservoir is screened, and the screening conditions include: permeability greater than 0.8 Darcy, sandstone reservoir, burial depth of 800m, reservoir temperature less than or equal to 65℃, and mineralization less than or equal to 150000mg / L.

[0050] Furthermore, in step (2), the analysis of the endogenous microbial community structure of the target reservoir was performed using high-throughput sequencing.

[0051] Furthermore, in step (2), the analysis of the endogenous microbial community structure of the target reservoir includes:

[0052] The study aimed to analyze whether the reservoir's endogenous microbial community included microorganisms with important metabolic functions, such as anaerobic fermenting bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria.

[0053] Furthermore, in step (3), the presence of methanogenic bacteria in the reservoir's endogenous microbial community is analyzed using quantitative real-time PCR.

[0054] Furthermore, methanogens include Methanobacterium bristlenoides, Methanocytozoa, Methanobacterium thermophilum, and Methanobacterium tumefaciens.

[0055] Furthermore, in step (4), the preparation of the green plant injection includes:

[0056] For algae and green plants, an automated scraping film technology is used for harvesting, and the harvested algae are injected into the formation along with the injected water.

[0057] Furthermore, in step (4), the preparation of the green plant injection also includes:

[0058] Other plants larger than algae are crushed to form a paste-like injection that is easy to inject.

[0059] Furthermore, during the preparation of the injection, it is necessary to formulate inorganic salts according to the ionic composition of the injection water.

[0060] Furthermore, the preparation process of the injection includes:

[0061] First, determine whether the injected water contains potassium, sodium, magnesium, and calcium ions. If any of these ions are lacking or the concentration is too low, add inorganic salts to supplement the concentration of each ion to 0.6 g / L.

[0062] Furthermore, the types of inorganic salts added include one or more of the following: calcium chloride, potassium chloride, sodium nitrate, magnesium sulfate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

[0063] Furthermore, the inorganic salt added is calcium chloride.

[0064] Furthermore, in step (4), green plants include algae, ferns, and mosses.

[0065] Furthermore, in step (4), the green plants are algae.

[0066] Furthermore, algae include Microchlorophyll, Microcystis, Chlorella, Dunaliella, and Chlamydomonas.

[0067] Furthermore, the algae are *Microchlorophyllaria*.

[0068] Furthermore, in step (5), the on-site injection of the green plant injection agent is carried out using the fracturing injection method.

[0069] Furthermore, in step (5), the on-site injection of the green plant injection includes the following steps:

[0070] Using fracturing equipment, green plant preparations are injected underground under high pressure, with each well receiving 600m³ of plant preparation per day. 3 The injection time is 8 hours per day, then the injection is stopped to allow the underground pressure to be released before starting the next cycle of injection. The injection is continued for 1 month, then the well is shut off to enter the biogas production stage. The wellhead pressure is monitored to predict the underground biogas production.

[0071] Furthermore, the cycle is 1 day, and the well shut-in time is 14 days.

[0072] Example 2:

[0073] This embodiment provides a specific implementation method for a microbial enhanced oil recovery (EOR) method using green plants as raw materials, such as... Figure 1 As shown, the other steps are largely the same as in Example 1. In step (5), the on-site injection of the green plant injection includes the following steps:

[0074] Using fracturing equipment, green plant preparations are injected underground under high pressure, with each well receiving 1000m³ of plant preparation per day. 3 The injection time is 12 hours per day, then the injection is stopped to allow the underground pressure to be released before starting the next cycle of injection. After two months of continuous injection, the well is shut off and enters the biogas production stage. The underground biogas production can be predicted by monitoring the wellhead pressure.

[0075] Furthermore, the cycle is 2 days, and the well shut-in time is 30 days.

[0076] Example 3:

[0077] This embodiment provides a specific implementation method for a microbial enhanced oil recovery (EOR) method using green plants as raw materials, such as... Figure 1 As shown, the other steps are largely the same as in Example 1. In step (5), the on-site injection of the green plant injection includes the following steps:

[0078] Using fracturing equipment, green plant preparations are injected underground under high pressure, with each well receiving 800m³ of plant preparation per day. 3 The injection time is 10 hours per day, then the injection is stopped to allow the underground pressure to be released before starting the next cycle of injection. The injection is continued for 1.5 months, then the well is shut off and enters the biogas production stage. The underground biogas production can be predicted by monitoring the wellhead pressure.

[0079] Furthermore, the cycle is 1.5 days, and the well shut-in time is 22 days.

[0080] Example 4:

[0081] Overview of the test reservoir: The reservoir in Block C of Shengli Oilfield has a thickness of 4.5 m, a reservoir temperature of 55℃, a reservoir pressure of 12 MPa, a salinity of 23566 mg / L, and a permeability of 850 × 10⁻⁶ m. -3 μm 2 The reservoir has a porosity of 20.5%, is a sandstone reservoir, and has a crude oil viscosity of 1155 mPa·s and a water cut of 98.2%. Analysis of samples from block C revealed the presence of *Thermoplasticum* and *Pseudomonas*.

[0082] The method of the present invention is used to implement the present invention in this oil well, such as... Figure 1-4 As shown, the specific steps are as follows:

[0083] (1) Target reservoir screening

[0084] The Shengli Oilfield C block in the test area has a reservoir temperature of 55℃, a permeability of 850×10⁻³ μm², a crude oil viscosity of 1155 mPa·s, and a water cut of 98.2%. Thermoplastic bacteria and Pseudomonas bacteria were present in Block C. This meets the screening criteria of this invention.

[0085] (2) Analysis of the endogenous microbial community structure of the target reservoir

[0086] The endogenous microbial community structure was analyzed using high-throughput sequencing. The universal primers 341F (5'-CCTAYGGGRBGCASCAG-3') and 806R (5'-GGACTACHVGGGTWTCAAT-3') were used for community structure analysis. The PCR reaction conditions were: 95℃ for 3 min; 98℃ for 15 s, 51℃ for 15 s, 72℃ for 20 s, for 25 cycles; 72℃ for 1 min. PCR reaction system (20 μL): 4 μL 5×FastPfu buffer, 2 μL dNTPs (2.5 mmol / L), 0.8 μL each of forward and reverse primers (5 μmol / L), 0.4 μL TransStart FastPfu DNA polymerase, 10 ng DNA template, and ultrapure water to a final volume of 20 μL. After sequencing, corresponding bioinformatics analysis was performed. First, sequence quality was screened to remove low-quality sequences. The remaining high-quality sequences were spliced ​​using FLASH (Fast length adjustment of short reads, V1.2.11) based on their overlap relationship. Then, the spliced ​​sequences were clustered into operational taxonomic units (OTUs) using USEARCH (V7.0.1090) software. The OTU representative sequences were compared with the database using RDP classifier (V2.2) software for species annotation. It was found that Thermophyton floccosum and Pseudomonas aeruginosa were present in the endogenous microorganisms in experimental block C.

[0087] (3) Analysis of methanogenic bacteria in the target reservoir

[0088] Methanogen analysis was performed using quantitative real-time PCR (qPCR) with the methyl-CoM reductase gene (mcrA) as the marker gene. The SYBR Green Supermix kit was used as the reaction reagent. The PCR reaction mixture consisted of 1 pmol / L upstream and downstream primers, 10 μL of Supermix, and 1 μL of the sample or standard plasmid. The volume was adjusted to 20 μL with sterile deionized water. PCR conditions were: 95℃ for 2 min; 95℃ for 15 s, 60℃ for 30 s, for 30 cycles, during which fluorescence signals were collected. The standard plasmid and the sample reacted simultaneously. qPCR and data analysis were performed on an iQ5 qPCR instrument. The results showed the presence of *Methanogen filamentosa* in the reservoir.

[0089] (4) Preparation of green plant injection

[0090] During the preparation of the injection agent, the ionic composition of the water in the block was first analyzed, and the test results are shown in Table 1 below.

[0091] Table 1 Analysis of Ionic Composition of Water Quality in Block C

[0092]

[0093] Ion composition analysis revealed that the injected water contained potassium, sodium, magnesium, and calcium ions, with a low magnesium concentration. Magnesium sulfate (0.4 g / L) was added to the injected water. Automated film scraping technology was used to harvest Chlorella, which was then pulverized into a paste and injected into the formation along with the prepared inorganic salt-containing injection water.

[0094] (5) On-site injection of green plant injection.

[0095] The plant-based fracturing injection method is employed, with the following specific steps: A plant-based injection agent is injected into the ground under high pressure using fracturing equipment, with 600m³ of the agent injected into each well per day. 3 The injection time is 8 hours per day, then the injection is stopped to allow the underground pressure to be released before the next cycle of injection begins. The injection is carried out continuously for 1 month, after which the well needs to be shut in to enter the biogas production stage. The underground biogas production can be predicted by monitoring the wellhead pressure. The cycle is 2 days, and the well shut-in time is 14 days.

[0096] Field test results: 3.5 × 10⁻⁶ methane gas produced. 6 m 3 The water content decreased from 98.2% to 93.5%, resulting in a cumulative increase of 985 tons of oil production. The field test results were good.

[0097] Example 5:

[0098] Overview of the test reservoir: The reservoir in Block F of Shengli Oilfield has a thickness of 6.5 m, a reservoir temperature of 60℃, a reservoir pressure of 10.5 MPa, a salinity of 6770 mg / L, and a permeability of 900 × 10⁻⁶. -3 μm 2 Porosity 15.8%, sandstone reservoir, crude oil viscosity 1354 mPa·s, water cut 97.8%.

[0099] The method of the present invention is used to implement the present invention in this oil well, such as... Figure 1-4 As shown, the specific steps are as follows:

[0100] (1) Target reservoir screening

[0101] The reservoir temperature in Block F of the Shengli Oilfield, a test block, is 60℃, and the permeability is 900×10⁻⁶. -3 μm 2 The crude oil viscosity is 1354 mPa·s, and the water content is 97.8%.

[0102] (2) Analysis of the endogenous microbial community structure of the target reservoir

[0103] The endogenous microbial community structure was analyzed using high-throughput sequencing. The universal primers 341F (5'-CCTAYGGGRBGCASCAG-3') and 806R (5'-GGACTACHVGGGTWTCAAT-3') were used for community structure analysis. The PCR reaction conditions were: 95℃ for 3 min; 98℃ for 15 s, 51℃ for 15 s, 72℃ for 20 s, for 25 cycles; 72℃ for 1 min. PCR reaction system (20 μL): 5×FastPfu buffer 4 μL, dNTPs (2.5 mmol / L) 2 μL, forward and reverse primers (5 μmol / L) 0.8 μL each, TransStart FastPfu DNA polymerase 0.4 μL, DNA template 10 ng, and ultrapure water to bring the volume to 20 μL. After sequencing, corresponding bioinformatics analysis was performed. First, sequence quality screening was performed to remove low-quality sequences. The remaining high-quality sequences were spliced ​​using FLASH (Fast length adjustment of short reads, V1.2.11) based on their overlap relationship. Then, the spliced ​​sequences were clustered into operational taxonomic units (OTUs) using USEARCH (V7.0.1090) software. The OTU representative sequences were compared with the database using RDP classifier (V2.2) software for species annotation. It was found that the endogenous microbial species in experimental block C were incomplete, lacking anaerobic fermentation bacteria and hydrogen-producing and acid-producing bacteria.

[0104] (3) Analysis of methanogenic bacteria in the target reservoir

[0105] Methanogen analysis was performed using quantitative real-time PCR (qPCR) with the methyl-CoA reductase gene (mcrA) as the marker. The SYBR Green Supermix kit was used as the reaction reagent. The PCR reaction mixture consisted of 1 pmol / L upstream and downstream primers, 10 μL of Supermix, and 1 μL of the test sample or standard plasmid. The volume was adjusted to 20 μL with sterile deionized water. PCR conditions were: 95℃ for 2 min; 95℃ for 15 s, 60℃ for 30 s, for 30 cycles, during which fluorescence signals were collected. The standard plasmid and test sample reacted simultaneously. The qPCR reaction and data analysis were performed on an iQ5 qPCR instrument. The results showed the presence of thermophilic methanogens in the reservoir.

[0106] (4) Preparation of green plant injection

[0107] During the preparation of the injection agent, the ion composition of the water in the block was first analyzed, and the test results are shown in Table 2 below.

[0108] Table 2 Analysis of Ionic Composition of Water Quality in Block C

[0109]

[0110] Ion composition analysis revealed that the injected water contained potassium, sodium, magnesium, and calcium ions, with low concentrations of calcium and magnesium ions. Therefore, calcium chloride (0.6 g / L) and magnesium sulfate (0.8 g / L) were added to the injected water. Chlamydomonas was harvested using automated scraping technology, pulverized into a paste, and injected into the formation along with the prepared injection water containing inorganic salts, Pseudomonas aeruginosa, Acinetobacter, and Bacillus thermophilus.

[0111] (5) On-site injection of green plant injection.

[0112] The plant-based fracturing injection method was employed, with the following specific steps: A plant-based injection agent was injected into the ground under high pressure using fracturing equipment, with each well receiving 800m³ of the agent per day. 3 The injection time is 10 hours per day, then the injection is stopped to allow the underground pressure to be released before the next cycle of injection begins. The injection is carried out continuously for 1 month, after which the well needs to be shut in to enter the biogas production stage. The underground biogas production can be predicted by monitoring the wellhead pressure. The cycle is 2 days, and the well shut-in time is 20 days.

[0113] Field test results: 4.0 × 10⁻⁶ methane gas produced. 6 m 3 The water content decreased from 97.8% to 91.6%, resulting in a cumulative increase of 1,254 tons of oil production. The field test results were good.

[0114] principle:

[0115] This invention utilizes green plants, including algae, ferns, and bryophytes, to first convert carbon dioxide and water in the air into sugars. These sugars can serve as nutrient activators for endogenous microorganisms in microbial oil recovery. Under anaerobic conditions in the oil reservoir, organic matter ferments to produce biogas. This process is similar to biogas fermentation, where organic matter, including plant matter and straw, undergoes microbial fermentation under anaerobic conditions to produce a mixed gas. In a closed biogas digester, under anaerobic (oxygen-free) conditions, the organic matter is decomposed and transformed by a wide variety of biogas-fermenting microorganisms, thus producing biogas. The main component of biogas is methane, consisting of 50%-80% methane (CH4), 20%-40% carbon dioxide (CO2), and small amounts of N2 and H2.

[0116] Experiments show that one ton of organic matter can produce 25 tons of biogas, and these gases generated in oil reservoirs can all enhance oil recovery. Furthermore, many biogas reservoirs in my country are also examples of early biomass deposition underground, where natural gas was produced by microorganisms under anaerobic conditions. Carbon isotope dating has confirmed that the abundant natural gas is of biogenic origin. This is the basic principle upon which this invention is based. However, this invention artificially injects organic matter (mainly plant matter) into the underground environment and provides suitable conditions for microbial growth and metabolism, accelerating the rate of microbial hydrolysis, degradation, and gas production. The large amount of gas produced in the reservoir increases reservoir pressure, providing energy for reservoir development. On the other hand, a large amount of methane gas can permeate into the upper part of the reservoir and dissolve in the residual oil, reducing its viscosity and increasing its fluidity, especially in medium-rhythmic oil layers. Simultaneously, the hydrolysis and degradation of plant matter also produces a large amount of organic acids and alcohols. These substances, to a certain extent, reduce the oil-water interfacial tension and change the wettability of the reservoir rocks, which is beneficial to the flow of crude oil. The combined effects of these factors can significantly improve the development effect and recovery rate of the oil reservoir.

[0117] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for microbial enhanced oil recovery using green plants as raw materials, characterized in that, Includes the following steps: (1) Screening of target reservoirs. Screening conditions include: permeability greater than 0.8 Darcy, sandstone reservoir, burial depth 800-1200m, reservoir temperature less than or equal to 65℃, and salinity less than or equal to 150000mg / L. (2) Analysis of the structure of the endogenous microbial community in the target reservoir. The method used was high-throughput sequencing, including: analyzing whether the endogenous microbial community in the reservoir includes anaerobic fermentation bacteria, hydrogen-producing and acetic acid-producing bacteria, and methanogenic bacteria. (3) Analysis of methanogens in the target reservoir: whether methanogens are included in the endogenous microbial community of the reservoir was analyzed by quantitative real-time PCR. (4) Preparation of green plant injection agent, including: for algae green plants, use automated scraping film technology for harvesting and inject them into the formation along with the injection water; other plants that are larger than algae green plants are crushed to form a paste-like injection agent for easy injection. During the preparation of the injection, it is necessary to formulate inorganic salts according to the ionic composition of the injected water, including: First, determine whether the injected water contains potassium, sodium, magnesium, and calcium ions. If any of these ions are lacking or the concentration is too low, add inorganic salts to supplement the concentration of each ion to 0.6–1.5 g / L. In step (4), green plants include algae, ferns, and bryophytes; (5) On-site injection of green plant growth regulators, including the following steps: Using fracturing equipment, green plant preparations are injected underground, with each well receiving 600-1000 cubic meters of plant preparation per day. 3 The injection time is 8-12 hours per day, then the injection is stopped to allow the underground pressure to be released before starting the next cycle of injection. The injection is carried out continuously for 1-2 months, then the well is shut off to enter the biogas production stage. The wellhead pressure is monitored to predict the underground biogas production. In step (5), the on-site injection of green plant injection agent is carried out using the fracturing injection method; The cycle is 1-2 days, and the well shut-in time is 14-30 days.

2. The method for microbial enhanced oil recovery using green plants as raw materials as described in claim 1, characterized in that: The methanogens include Methanobacterium bristlenoides, Methanocytozoa, Methanobacterium thermophilum, and Methanobacterium tumefaciens.

3. The method for microbial enhanced oil recovery using green plants as raw materials as described in claim 1, characterized in that, The types of inorganic salts added include one or more of the following: calcium chloride, potassium chloride, sodium nitrate, magnesium sulfate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.

4. The method for microbial enhanced oil recovery using green plants as raw materials as described in claim 1, characterized in that, The inorganic salt added is calcium chloride.

5. The method for microbial enhanced oil recovery using green plants as raw materials as described in claim 1, characterized in that: The algae include Microchlorophyll, Cotyledon, Chlorella, Dunaliella, and Chlamydomonas.

6. The method for microbial enhanced oil recovery using green plants as raw materials as described in claim 5, characterized in that: The algae mentioned are *Microchlorophyll*.

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