Coal bed gas mining method for promoting microbial gasification synergy under electric-magnetic double-field action

Abstract

The invention discloses a coal bed gas exploitation method for promoting microbial gasification synergy under the action of electric-magnetic double fields, and belongs to the technical field of coal bed gas exploitation. The method comprises the following steps: fracturing a coal reservoir through an injection well to form a fracture network; injecting an electrolyte solution and a microbial solution into the fracture network, wherein the microbial solution contains flora induction particles; applying an electric field to the coal reservoir, and controlling the flora of the microbial solution and flora-induced particles to migrate in the fracture network; then applying a low voltage field to promote further communication of branch fractures in the fracture network, and inducing migration again; applying a magnetic field to the coal reservoir; microorganism proliferation and uniform distribution are promoted, organic matter decomposition and methane release in the coal seam are accelerated, and the coal seam gas yield is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of coalbed methane exploitation, and relates to a coalbed methane exploitation method for promoting microbial gasification efficiency under the action of an electric-magnetic double field. Background Art

[0002] The efficient extraction of coalbed methane (CBM) is of great significance to energy utilization. Traditional CBM extraction methods have the problems of low gasification efficiency and low methane conversion efficiency. In recent years, microbial gasification technology has been studied in CBM extraction, and microorganisms convert coal into methane gas through metabolic processes. However, the existing microbial gasification technology has bottlenecks such as limited microbial diffusion and gasification rate. If in the underground in-situ state, the microbial flora is unevenly dispersed, which greatly reduces the efficiency of CBM extraction.

[0003] Patent CN107387044A discloses a method for increasing the production of biogas by utilizing native fungi in coal seams. This method collects data from the target coal seam gas field, analyzes the in-situ fungal community structure of the coal seam, and further cultivates efficient bacterial communities, ultimately achieving in-situ biological methane conversion of the coal seam to increase the production of coal seam gas. On this basis, patent CN110259423A discloses a method for increasing the production of coal seam gas by combining an external direct current electric field with microbial degradation. Based on the exploration of relevant data such as coal reservoir geology and enrichment of microbial communities, efficient bacterial communities are enriched, and culture fluid is injected through the well network for fracturing, and a direct current electric field network is established. After that, efficient bacterial communities are injected to activate the electric field network, thereby achieving the combined increase in the production of coal seam gas by combining an external electric field with microbial degradation.

[0004] Patent CN104031905A discloses a method for enhancing the activity of anaerobic ammonium oxidizing bacteria by electric field, wherein the activity of anaerobic ammonium oxidizing bacteria is enhanced by applying an electric field strength of 1~4V / cm, and the electric field acts intermittently, wherein the intermittent action time of the electric field is 3h, 6h or 12h, and the electric field action time is 12h / 24h.

[0005] In addition, patent CN215756658U demonstrates the application of electric field and magnetic field enhancement technology in anaerobic sludge bed reactors, which improves the treatment efficiency of microorganisms through the synergistic effect of the dual fields, indicating the potential of electromagnetic fields in microbial efficiency enhancement. However, this type of technology is mainly applicable to fixed reaction environments and does not solve the cost and efficiency issues in large-scale, open geological applications.

[0006] In practical applications, injecting microorganisms into underground coal reservoirs to increase coalbed methane production still faces many challenges. Complex geological conditions make it difficult for the bacterial community to achieve uniform diffusion, resulting in low gasification efficiency. Although the introduction of electric and magnetic fields can improve the efficiency of microbial gasification to a certain extent, it also exposes some obvious shortcomings. On the one hand, it is difficult to accurately control the movement of microorganisms by relying solely on electric or magnetic fields. At the same time, if the fracture channel is not supported in time, the fracture shrinks, which easily leads to the formation of blind holes in the pores and poor distribution uniformity. In this case, only some areas with dense colonies can form local gasification efficiency enhancement zones, and the overall gasification area is limited, which in turn affects the improvement of gasification efficiency. On the other hand, even if the gasification effect can be enhanced by applying electric and magnetic fields at the same time, this method greatly increases the cost. In addition, the long-term use of electric fields may also cause excessive consumption of electrolytes. When the electrolyte cannot effectively fill the reservoir pores and fractures, it is difficult for microorganisms to diffuse through the solution to the entire reservoir and adsorb smoothly on the coal seam surface, which leads to a significant decrease in methane conversion efficiency. Therefore, the existing technology still has difficult-to-overcome bottlenecks in improving the overall gasification efficiency, and further innovation and optimization are needed. Summary of the invention

[0007] The present invention overcomes the shortcomings of the prior art and proposes a coalbed methane extraction method that promotes microbial gasification efficiency under the action of an electric-magnetic dual field, further improving the methane conversion efficiency and coalbed methane recovery efficiency while reducing energy consumption.

[0008] In order to achieve the above object, the present invention is achieved through the following technical solutions: A coalbed methane extraction method for promoting microbial gasification efficiency under the action of an electric-magnetic dual field comprises the following steps: S1. Fracturing the coal reservoir to form a fracture network through an injection well; injecting an electrolyte solution and a microbial solution into the fracture network, wherein the microbial solution contains bacterial flora inducing particles; S2. Apply an electric field to the coal reservoir, the intensity of which is 0.1-1 V / cm, to control the migration of the bacterial colonies and bacterial colony-induced particles in the microbial solution in the fracture network, and monitor the migration conditions to distribute the bacterial colonies and bacterial colony-induced particles in the fracture network; S3, adjusting the voltage of the electric field in the coal reservoir to 1.5~5V and the current to 10~50mA, so as to promote the electrolysis of the electrolyte solution in the coal reservoir and promote the further connection of the branch fractures in the fracture network; then adjusting the intensity of the electric field to 0.1~1V / cm again, so that the bacterial colony-induced particles can migrate again, and the migration time is 0.5~2h; S4, applying a magnetic field to the coal reservoir, the magnetic field operating frequency range is 1Hz~100kHz, the magnetic field intensity is 5~50mT; the time is 1.5~2.5h; S5. Cycle steps S3 and S4. During this process, the pressure of the extraction well is monitored synchronously. When the pressure in the extraction well increases to a predetermined value, the extraction well is opened to extract the coalbed methane.

[0009] Furthermore, the electrolyte is dissolved in the fracturing fluid to form an electrolyte solution, which is injected into the fracture network together with the fracturing fluid. The concentration of the electrolyte in the fracturing fluid is 0.1~5mol / L.

[0010] Furthermore, at least two rows of boreholes are arranged on the ground as injection wells, and extraction wells are arranged between two adjacent rows of injection wells; the extraction wells enter the coal reservoir in a single horizontal comb-like well arrangement; an electro-magnetic field generator is provided at the bottom of the injection well; and electric and magnetic fields are applied to the coal reservoir through the electro-magnetic field generator.

[0011] Furthermore, the electro-magnetic field generator includes a particle migration control device, an auxiliary electrolysis reaction device, an electrochemical sensor and a magnetic field generating device; the particle migration control device controls the migration of the bacterial colony and the bacterial colony induced particles by applying an electric field; the auxiliary electrolysis reaction device promotes the electrolysis of the electrolyte and forms pores in the coal reservoir by applying a low voltage field; and the magnetic field generating device provides a magnetic field.

[0012] Furthermore, the particle migration control device, the auxiliary electrolytic reaction device, the electrochemical sensor and the magnetic field generating device are electrically connected to the ground control center respectively.

[0013] Furthermore, in step S2, the migration of the bacterial colony and the bacterial colony-inducing particles is monitored by an electrochemical sensor until the bacterial colony density is uniform and the intersection area of ​​the bacterial colony around two adjacent injection wells gradually replaces the blank area without bacterial colony until the blank area disappears completely.

[0014] Furthermore, an injection well valve and an injection pump are connected to the top of the injection well; the injection pump is connected to a fracturing fluid storage tank; the fracturing pipeline valve set at the outlet end of the fracturing fluid storage tank is opened; the fracturing fluid in the fracturing fluid storage tank enters the coal reservoir through the injection well to perform fracturing until a fracture network appears in the coal reservoir, and the fracturing pipeline valve is closed.

[0015] Furthermore, the microbial solution is methanogens, and the bacterial colony-inducing particles are graphene oxide.

[0016] Further, in step S5, the extraction well valve on the extraction well is opened to extract the coalbed methane, and the extraction well is connected to an extraction pump and a pressure and gas component monitoring meter; 2 When the gas concentration rises to 20% and the methane concentration drops to 30%, the extraction is stopped; the extraction well is shut down and then reopened until the coalbed methane production drops by 60%, ending the coalbed methane extraction work.

[0017] The beneficial effects of the present invention compared with the prior art are as follows: 1. The present invention achieves uniform distribution of microbial flora by coordinating the distribution of flora inducing particles with an electro-magnetic field. The metabolic activity of the flora is monitored by changes in electrical signals, so as to flexibly regulate the diffusion range of the flora and further achieve visual regulation of its diffusion process. It is difficult to accurately control the flow of the colony with existing magnetic-electric fields, and the pores and fissures will shrink under the action of ground stress. The present invention uses inductive particles to induce the colony, which also acts as a proppant, and is visually and effectively moved under the control of the electro-magnetic field, ultimately controlling the uniform dispersion of the colony in the fissure network.

[0018] 2. “Multi-well-multi-electrode” auxiliary electrolysis realizes large-area auxiliary electrolysis of coal and electrolyte mixed medium. The CO generated by auxiliary electrolysis 2 and H 2 It reacts with organic carbon on the pore surface to form methanogens, promoting the development of pore structure and expanding the distribution area of ​​bacterial colonies, thereby improving gasification efficiency. 2 and H 2 Provide additional metabolic substrates for microorganisms to support their growth in coal seams.

[0019] 3. Under the mutual promotion of magnetic field and electric field, the transmission of nutrients in the cracks is improved, the proliferation of microorganisms is promoted, the excessive consumption of electrolyte is avoided, and additional metabolic substrates are provided for microorganisms, which accelerates the decomposition of organic matter and methane release in coal seams, and increases the coalbed methane yield and methane concentration.

[0020] 4. Adopt intermittent electric field application mode with alternating electric and magnetic fields and alternating positive and negative polarity cycles to avoid long-term inhibition of microorganisms by strong electric fields and improve their metabolic efficiency. Applying electric fields during the intermittent period further promotes efficient metabolism of the bacterial community during the recovery period and prevents electrode corrosion or excessive consumption of electrolyte. Polarity reversal technology improves the multi-directional migration of charged particles, optimizes particle distribution, eliminates gasification blind spots, improves methane conversion efficiency, and realizes green and efficient extraction of coalbed methane.

[0021] In the prior art, the long-term electric field causes the electrolyte to be consumed, so that the electrolyte in the pore structure cannot fill the pore space, resulting in the inability of the migration particles to migrate effectively, and then causing the colonies to be unable to diffuse quickly through the solution-adsorbed on the surface of the coal seam; the control method of the present invention is divided into two stages, the electric field and the magnetic field are intermittently alternating to ensure the effective migration and diffusion of the induced particles and the colonies, and the electric-magnetic field has a driving effect on the induced particles. In the electric field action stage, a certain amount of H is generated due to the electrolysis of water and organic matter in the coal. 2 With CO 2 As a supplementary source of bacterial colony reactants, it can reduce the injection of ground hydrogen while promoting methanogenesis reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the ground well pattern arrangement in Example 1; Figure 2 It is a schematic diagram of the ground well pattern arrangement in Example 2; Figure 3 It is a schematic diagram of the coalbed methane extraction device for promoting microbial gasification efficiency under the action of electric-magnetic dual field in Examples 1 and 2; Figure 4 Schematic diagram of horizontal slices of uniform diffusion of microorganisms injected in Examples 1 and 2; Figure 5 Schematic diagram of injecting microbial solution into the fracture network in Examples 1 and 2; Figure 6 Schematic diagram of the stage of further migration of particles induced by the auxiliary bacteria under the action of the electric field in Examples 1 and 2; Figure 7 Schematic diagram of the accelerated growth stage of microbial flora under the action of the electric-magnetic dual field in Examples 1 and 2; Figure 8 Schematic diagram of the efficient gasification stage of microbial flora under the action of magnetic field in Examples 1 and 2.

[0023] Numbers in the figure: 1-injection well; 2-extraction well; 3-injection well valve; 4-injection pump; 5-fracturing fluid storage tank; 6-fracturing pipeline valve; 7-microorganism storage tank; 8-microorganism pipeline valve; 9-extraction well valve; 10-pressure and gas composition monitoring table; 11-extraction pump; 12-ground control center; 13-electro-magnetic field generator; 1301-particle migration control device; 1302-auxiliary electrolysis reaction device; 1303-electrochemical sensor; 1304-electric current; 1305-magnetic field generating device; 1306-electromagnetic wave; 14-crack network; 15-bottom plate; 16-bacterial community inducing particles; 17-top plate; 18-bacterial community; 19-intersecting area; 20-blank area; 21-coal reservoir; 22-fracturing fluid. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0025] Example 1 See also Figure 1 , Figures 3 to 8This embodiment proposes a coalbed methane extraction method for promoting microbial gasification efficiency under the action of an electric-magnetic dual field, and extracts coalbed methane from a coal reservoir 21 with a depth of 200m and a thickness of 15m. The specific implementation steps are as follows: S1. Arrange two rows of boreholes on the ground as injection wells 1, with a spacing of 50m between the two rows of injection wells 1; an electric-magnetic field generator 13 is provided at the bottom of the injection well 1; the spacing between the bottom of the injection well 1 and the bottom plate 15 is 1m. The extraction well 2 is arranged between the two rows of injection wells 1, and enters the coal reservoir 21 in a single horizontal comb well arrangement, and the horizontal comb well is 7m away from the top plate 17; The electro-magnetic field generator 13 includes a particle migration control device 1301, an auxiliary electrolysis reaction device 1302, an electrochemical sensor 1303 and a magnetic field generating device 1305; the particle migration control device 1301, the auxiliary electrolysis reaction device 1302, the electrochemical sensor 1303 and the magnetic field generating device 1305 are all existing devices, wherein the relevant product names and models are respectively particle flow control system-Fritsch Analysette 22, electrolysis reactor-Waldmann Electrolysis Cells, electrochemical sensor-Metrohm 6.0555.000, and magnetic field generating device-Bruker Superconducting Magnet.

[0026] S2, connect the fracturing fluid storage tank 5 to the injection well valve 3 and injection pump 4 connected to the top of the injection well 1, and open the fracturing pipeline valve 6 set at the outlet end of the fracturing fluid storage tank 5; the fracturing fluid 22 in the fracturing fluid storage tank 5 enters the coal reservoir 21 through the injection well 1 to perform fracturing until a fracture network 14 appears in the coal reservoir 21, and close the fracturing pipeline valve 6. In this embodiment, the fracturing fluid 22 in the fracturing fluid storage tank 5 contains an electrolyte with a concentration of 3.5 mol / L, and the electrolyte is NaCl. While the electrolyte maintains the electric field environment in the coal reservoir 21, it positively promotes the electrolysis reaction and the methanation reaction, and further promotes the connectivity of the pore structure.

[0027] S3, connect the microbial storage tank 7 to the injection well valve 3 and injection pump 4 connected to the top of the injection well 1, and open the microbial pipeline valve 8 at the outlet of the microbial storage tank 7. The concentration of the bacterial colony 18 in the microbial solution in the microbial storage tank 7 is 1×10 6CFU / mL. The microbial solution is mixed with bacterial colony-inducing particles 16; the microbial solution enters the fracture network 14 through the injection well 1; at the same time, the particle migration control device 1301 in the electric-magnetic field generator 13 is turned on to control the bacterial colony-inducing particles 16 in the fracture network 14, so that the bacterial colony-inducing particles 16 are evenly distributed in the fracture network 14; the particle migration control device 1301 controls the migration of bacterial colonies 18 and bacterial colony-inducing particles 16 in the coal seam fractures by applying an electric field, and the electric field strength is set to 0.5V / cm. The particle migration control device 1301 is connected to the ground control center 12. The migration of bacterial colonies 18 is monitored synchronously through the electrochemical sensor 1303 until the density points of the bacterial colonies 18 are relatively uniform, and the intersection area 19 of the bacterial colonies 18 around the two adjacent injection wells 1 in the horizontal slice image gradually replaces the blank area 20 without bacterial colonies 18 until the blank area 20 completely disappears (see Figure 4 ).

[0028] The electrochemical sensor 1303 is also connected to the ground control center 12 . The metabolic activity of the bacterial community 18 in the crack will change the local conductivity. The electrochemical sensor 1303 records the changes in electrical signals to monitor the metabolic activity and distribution of the bacterial community 18 , and then transmits the data to the ground control center 12 .

[0029] It should be noted that the microbial solution is mainly composed of anaerobic fermentation bacteria. In this embodiment, a combination of multiple methanogenic bacteria such as Methanogens and Methanomonas is used, which are purchased existing bacteria. The bacterial colony inducing particles 16 are graphene oxide. Under the action of the electric field, the bacterial colony inducing particles 16 can guide the uniform distribution and diffusion of the bacterial colony 18.

[0030] S4, turn on the auxiliary electrolysis reaction device 1302 in the electric-magnetic field generator 13, set the electric field voltage to 2V, and the current 1304 to a low voltage field of 20mA to promote the electrolysis of the electrolyte. During the electrolyte electrolysis process, the coal reservoir 21 will be prompted to generate pores and fissures, thereby promoting further connectivity of the pores and fissures; the initial electrolysis is carried out for 5 hours. After that, turn on the particle migration control device 1301 in the electric-magnetic field generator 13 again to induce the bacterial colony-induced particles 16 and bacterial colony 18 to further migrate. The time for inducing migration in this step is 1.5 hours; after the migration of the bacterial colony-induced particles 16 is basically stable, the auxiliary electrolysis stage is completed.

[0031] The auxiliary electrolysis reaction device 1302 includes multiple sets of positive and negative electrodes, which assist the electrolyte in the low-voltage electrolysis reaction in the electrolyte-rich coal reservoir 21. Under the electric field condition, the electrolyte, water and coal are electrolyzed to promote H 2 , CO 2The generation of methanogenic reaction gas is induced, which further increases the local fracture pore structure. The related reactions that may occur in the electrolyte-rich coal reservoir 21 are: ; .

[0032] S5. Turn on the magnetic field generating device 1305 in the electro-magnetic field generator 13 to radiate electromagnetic waves 1306. The working frequency is set to 75 Hz, the magnetic field strength is set to 50 mT, and the magnetic field acts for 2 hours to further increase the activity of the bacterial colony 18. The ground control center 12 connects the electrochemical sensor 1303 to monitor the density changes of the microbial bacterial colony 18 until the density of the bacterial colony 18 shows a significant increase.

[0033] The electromagnetic waves 1306 generated by the magnetic field generating device 1305 can make up for the disadvantages of the current-dependent medium (electrolyte-rich solution environment), thereby constructing a large-area regional magnetic field, significantly improving the metabolic activity of microorganisms, and enhancing the electron transfer ability of cells.

[0034] S6. Repeat steps S4 and S5. Intermittent application of the electric field can prevent the bacterial colony 18 from being suppressed by the strong electric field for a long time. Applying the magnetic field during the intermittent period can further promote more efficient metabolism of the bacterial colony 18 during the recovery period, while preventing the electrode from being corroded or the electrolyte solution from being over-consumed.

[0035] During this process, the pressure of extraction well 2 is monitored synchronously. When the pressure in extraction well 2 shows an obvious increasing trend, the extraction well valve 9 on extraction well 2 is opened to extract the coalbed methane mainly composed of methane. The extraction well 2 is connected to an extraction pump 11 and a pressure and gas component monitoring meter 10. When the CO in the coalbed methane increases significantly, the extraction well valve 9 on the extraction well 2 is opened to extract the coalbed methane mainly composed of methane. 2 When the gas concentration increases to 20% and the methane concentration decreases to 30%, the extraction is stopped. The well is shut down and the extraction well 2 is opened again after a period of time until the coalbed methane production decreases by 60%, and the coalbed methane extraction work is ended.

[0036] It should be noted that: under the alternating action of low-voltage electric field and magnetic field, the nutrient transmission efficiency in the cracks can be improved, the proliferation of microorganisms can be accelerated, and the distribution density of bacterial colonies 18 can be increased. By enhancing electron transfer and promoting energy metabolism, the gasification process of microorganisms in coalbed methane is accelerated, and the hydrogen (H 2 ) and carbon dioxide (CO 2 ) can provide additional metabolic substrates for microorganisms, further promoting their decomposition of organic matter in the coal reservoir 21 and release of methane gas. The relevant reaction relationship is as follows: ; .

[0037] Example 2 See also Figures 2 to 8 This embodiment proposes a coalbed methane extraction method for promoting microbial gasification efficiency under the action of an electric-magnetic dual field, and extracts coalbed methane from a large-area coal reservoir 21 with a depth of 300m, a thickness of 8m, and a working face length of 180m. The specific implementation steps are as follows: S1. Arrange three rows of boreholes on the ground as injection wells 1, and the distance between two adjacent rows of injection wells 1 is 60m; an electro-magnetic field generator 13 is provided at the bottom of the injection well 1; the electro-magnetic field generator 13 includes a particle migration control device 1301, an auxiliary electrolysis reaction device 1302, an electrochemical sensor 1303 and a magnetic field generating device 1305; the electro-magnetic field generator 13 is the same as that in Example 1; The bottom of the injection well 1 is 0.5 m away from the bottom plate 15. An extraction well 2 is provided between two adjacent rows of injection wells 1. The extraction well 2 enters the coal reservoir 21 in a single horizontal comb well arrangement. The horizontal comb well is 4 m away from the top plate 17.

[0038] S2, connect the fracturing fluid storage tank 5 to the injection well valve 3 and injection pump 4 connected to the top of the injection well 1, and open the fracturing pipeline valve 6 set at the outlet end of the fracturing fluid storage tank 5; the concentration of the electrolyte in the fracturing fluid 22 in the fracturing fluid storage tank 5 is 5 mol / L, and the fracturing fluid 22 enters the coal reservoir 21 through the injection well 1 to perform fracturing until a fracture network 14 appears in the coal reservoir 21, and then close the fracturing pipeline valve 6; in this embodiment, the electrolyte is NaHCO 3 .

[0039] S3, connect the microbial storage tank 7 to the injection well valve 3 and injection pump 4 connected to the top of the injection well 1, and open the microbial pipeline valve 8 at the outlet of the microbial storage tank 7. The concentration of the bacterial colony 18 in the microbial solution in the microbial storage tank 7 is 1×10 8 CFU / mL. At the same time, the particle migration control device 1301 in the electro-magnetic field generator 13 is turned on to control the bacterial colony-inducing particles 16 in the fracturing fluid 22, so that the bacterial colony-inducing particles 16 are evenly distributed in the fracture network 14; the electric field strength is set to 1.5V / cm, and the migration of the bacterial colony 18 is monitored synchronously through the electrochemical sensor 1303 until the density points of the bacterial colony 18 are relatively uniform, and the intersection area 19 of the bacterial colony 18 around the two adjacent injection wells 1 is gradually replaced by the blank area 20 without the bacterial colony 18 in the horizontal slice image, until the blank area 20 completely disappears.

[0040] S4, the auxiliary electrolysis reaction device 1302 in the electric-magnetic field generator 13 is turned on, the electric field voltage is set to 2V, the current 1304 is set to a low voltage field of 50mA, and the initial electrolysis is performed for 3 hours. The particle migration control device 1301 in the electric-magnetic field generator 13 is turned on again, and the further migration of the bacterial colony 18 is induced, and the process continues for 1 hour.

[0041] S5. Turn on the magnetic field generating device 1305 in the electro-magnetic field generator 13 to radiate electromagnetic waves 1306. The operating frequency is set to 60 Hz, the magnetic field strength is set to 40 mT, and the magnetic field acts for 2 hours to further increase the activity of the bacterial colony 18. The ground control center 12 connects the electrochemical sensor 1303 to monitor the density changes of the microbial bacterial colony 18.

[0042] S6, cycle the operations of S4 and S5, monitor the pressure of extraction well 2 simultaneously, and when the pressure in extraction well 2 shows an obvious increasing trend, open extraction well 2 to extract the coalbed methane mainly composed of methane. 2 When the gas concentration rises to 30% and the methane concentration drops to 30%, the extraction is stopped. The well is shut down and the extraction well 2 is opened again after a period of time until the coalbed methane production decreases by 60%, and the coalbed methane extraction work is ended.

[0043] The working principle of Example 2 is the same as that of Example 1.

[0044] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A coalbed methane extraction method for promoting microbial gasification efficiency under the action of electric-magnetic dual fields, characterized in that: The following steps are involved: S1, fracturing a coal reservoir (21) through an injection well (1) to form a fracture network (14); injecting an electrolyte solution and a microbial solution into the fracture network (14), wherein the microbial solution contains bacterial colony-inducing particles (16); S2, applying an electric field to the coal reservoir (21), wherein the intensity of the electric field is 0.1-1 V / cm, controlling the migration of the bacterial colony (18) and the bacterial colony-inducing particles (16) in the microbial solution in the fracture network (14), and monitoring the migration status, so that the bacterial colony (18) and the bacterial colony-inducing particles (16) are distributed in the fracture network (14); S3, adjusting the voltage of the electric field in the coal reservoir (21) to 1.5-5V and the current to 10-50mA, so as to promote electrolysis of the electrolyte solution in the coal reservoir (21) and promote further connectivity of the branch fractures in the fracture network (14); then adjusting the intensity of the electric field to 0.1-1V / cm again, so as to allow the bacterial colony-induced particles (16) to migrate again, and the migration time is 0.5-2h; S4, applying a magnetic field to the coal reservoir (21), wherein the magnetic field operating frequency range is 1 Hz to 100 kHz, the magnetic field intensity is 5 to 50 mT, and the time is 1.5 to 2.5 hours; S5, looping steps S3 and S4, during which the pressure of the extraction well (2) is synchronously monitored, and when the pressure in the extraction well (2) increases to a predetermined value, the extraction well (2) is opened to extract the coalbed methane.

2. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 1 is characterized in that: The electrolyte is dissolved in the fracturing fluid (22) to form an electrolyte solution, which is injected into the fracture network (14) together with the fracturing fluid. The concentration of the electrolyte in the fracturing fluid is 0.1-5 mol / L.

3. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 1 is characterized in that: At least two rows of boreholes are arranged on the ground as injection wells (1), and extraction wells (2) are arranged between two adjacent rows of injection wells (1); the extraction wells (2) enter the coal reservoir (21) in a single horizontal comb-shaped well arrangement; an electric-magnetic field generator (13) is provided at the bottom of the injection well (1); and an electric field and a magnetic field are applied to the coal reservoir (21) through the electric-magnetic field generator (13).

4. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 3 is characterized in that: The electric-magnetic field generator (13) comprises a particle migration control device (1301), an auxiliary electrolysis reaction device (1302), an electrochemical sensor (1303) and a magnetic field generating device (1305); the particle migration control device (1301) controls the migration of the bacterial colony (18) and the bacterial colony-induced particles (16) by applying an electric field; the auxiliary electrolysis reaction device (1302) promotes the electrolysis of the electrolyte and forms pores in the coal reservoir (21) by applying a low voltage field; and the magnetic field generating device (1305) provides a magnetic field.

5. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 4 is characterized in that: The particle migration control device (1301), the auxiliary electrolytic reaction device (1302), the electrochemical sensor (1303) and the magnetic field generating device (1305) are electrically connected to the ground control center (12) respectively.

6. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 4 is characterized in that: In step S2, the migration of the bacterial colony (18) and the bacterial colony-inducing particles (16) is monitored by an electrochemical sensor (1303) until the density of the bacterial colony (18) is uniform and the intersection area (19) of the bacterial colony (18) around two adjacent injection wells (1) gradually replaces the blank area (20) without the bacterial colony (18) until the blank area (20) completely disappears.

7. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 2, characterized in that: The top of the injection well (1) is connected to an injection well valve (3) and an injection pump (4); the injection pump (4) is connected to a fracturing fluid storage tank (5); a fracturing pipeline valve (6) provided at the outlet end of the fracturing fluid storage tank (5) is opened; the fracturing fluid (22) in the fracturing fluid storage tank (5) enters the coal reservoir (21) through the injection well (1) to perform fracturing until a fracture network (14) appears in the coal reservoir (21), and the fracturing pipeline valve (6) is closed.

8. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 1 is characterized in that: The microbial solution is methanogens, and the bacterial colony-inducing particles (16) are graphene oxide.

9. The method for coalbed methane extraction by promoting microbial gasification efficiency under the action of electric-magnetic dual fields according to claim 1, characterized in that: In step S5, the extraction well valve (9) on the extraction well (2) is opened to extract the coalbed methane, and the extraction well (2) is connected to an extraction pump (11) and a pressure and gas composition monitoring meter (10); when the CO2 gas concentration in the coalbed methane increases to 20% and the methane concentration decreases to 30%, the extraction is stopped; the extraction well (2) is shut down, and then the extraction well (2) is opened again until the coalbed methane production decreases by 60%, thereby terminating the coalbed methane extraction work.

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