A device and method for improving oil and gas recovery rate in oil-rich coal seams

Abstract

The present invention discloses a device and method for improving the oil and gas recovery rate of an oil-rich coal seam, wherein the device comprises a plurality of pairs of injection wells and extraction wells, a high-voltage power-frequency power-on system and a water vapor injection system, each injection well and each extraction well extends into the oil-rich coal seam, each pair of injection wells and extraction wells is respectively composed of an anode well and a cathode well, forming a pair of electrode wells; the high-voltage power-frequency power-on system comprises a plurality of metal electrode cylinders and a plurality of graphite particle layers, a metal electrode cylinder is arranged in each electrode well, a plurality of filter holes are arranged on the cylinder wall of the filter cylinder part of the metal electrode cylinder, and a circle of graphite particle layers is arranged between the filter cylinder part of the metal electrode cylinder and the oil-rich coal seam; the water vapor injection system comprises a water vapor heating system and a plurality of air compressors, the inlet of each air compressor is connected to the outlet of the water vapor heating system through a pipeline, and the outlet of each air compressor is connected to the cylinder mouth of the metal electrode cylinder of one of the electrode wells through a pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of in-situ mining of oil-rich coal, and in particular to a device and method suitable for improving the oil and gas recovery rate of an oil-rich coal seam. Background Art

[0002] my country's energy structure presents the resource endowment characteristics of "lack of oil, little gas, and relatively rich in coal". In the short term, coal will still be the main energy source in my country. Oil-rich coal is a coal-based oil and gas resource, rich in hydrogen-rich structures that can generate oil and gas products. It is difficult to mine, and the main development direction is in-situ heating technology. Chinese patent documents CN201310078978.5 and CN202110779067.X propose an underground in-situ heating method, which can penetrate the underground rock mass through high voltage electricity. The resistance of the rock and soil layer after the breakdown is reduced, and it can be heated by industrial frequency electricity. Through this high-voltage industrial frequency in-situ heating technology, the oil-rich coal seam can be penetrated along the formation direction, and the formation can be heated by the resistance heat of the breakdown channel. The heating of this technology is concentrated on the breakdown of the rock formation, with fast heat transfer and high energy utilization, which has good application prospects for the exploitation of unconventional oil and gas resources in my country. However, patent document CN201310078978.5 mentions that the rock mass still has a linear resistance of 10-100Ω / cm after breakdown, and the heating efficiency is still low at an engineering scale of tens of meters between wells. In addition, the oil and gas produced by pyrolysis of oil-rich coal is prone to blockage and deposition when it migrates to the low-temperature zone, and the components with higher viscosity are easily enriched in the coal seam, resulting in a low oil and gas recovery rate. The steam injection in-situ heating technology proposed in the Chinese patent document CN201610326217.0 heats and pyrolyzes the rock mass by injecting high-temperature water vapor into the underground rock formation. This method has high heat transfer efficiency, and an emulsion will be generated in the area below 90°C to reduce viscosity. However, when the temperature is higher than 90°C, the cracking oil will be separated from the water. In the case of two-phase separation, the relative permeability of the cracking oil in the cracks is greatly reduced, and the viscosity of the cracking oil is still large when it is lower than 200°C. Therefore, the in-situ mining of oil-rich coal by steam injection technology will still face the problem of poor fluidity of cracking oil and gas blocking pores. It can be seen that the existing in-situ heating technology for oil-rich coal still faces the problem of low heating efficiency and low oil and gas recovery rate in actual engineering scale application. It is extremely important to improve the existing technology and increase the heating efficiency and oil and gas recovery rate of the in-situ heating process.

[0003] In summary, the existing technology for in-situ mining of oil-rich coal has the problem of low oil and gas recovery rate. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a device and method suitable for improving the oil and gas recovery rate of oil-rich coal seams, which is used to solve the problem of low oil and gas recovery rate in the existing technology of in-situ mining of oil-rich coal.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention discloses a device for improving oil and gas recovery rate in an oil-rich coal seam, comprising:

[0007] A plurality of pairs of injection wells and extraction wells, each of which extends into the oil-rich coal seam, and each pair of injection wells and extraction wells is respectively composed of an anode well and a cathode well, forming a pair of electrode wells;

[0008] A high-voltage power-frequency power supply system includes a plurality of metal electrode cylinders and a plurality of graphite particle layers. A metal electrode cylinder is arranged in each electrode well. The metal electrode cylinder corresponding to the oil-rich coal seam is a filter cylinder part. A plurality of filter holes are arranged on the cylinder wall of the filter cylinder part. A circle of graphite particle layers is arranged between the filter cylinder part of the metal electrode cylinder and the oil-rich coal seam.

[0009] The water vapor injection system includes a water vapor heating system and several air compressors. The inlet of each air compressor is connected to the outlet of the water vapor heating system through a pipeline, and the outlet of each air compressor is connected to the tube mouth of the metal electrode tube of one of the electrode wells through a pipeline.

[0010] Preferably, when high voltage electricity is transmitted to the graphite particle layer through the metal electrode cylinder, the graphite particle layer transmits the high voltage electricity of the metal electrode cylinder to the oil-rich coal seam, and the high voltage electricity is discharged into the oil-rich coal seam, forming a breakdown channel in the oil-rich coal seam;

[0011] The water vapor heating system is used to generate high-temperature water vapor, and the air compressor, the metal electrode cylinder of the electrode well, a plurality of filter holes, a circle of graphite particle layers and the breakdown channel together constitute a water vapor flow path.

[0012] Preferably, the metal electrode cylinder comprises a solid cylinder portion and a filter cylinder portion, wherein the metal electrode cylinder corresponding to the overlying rock stratum of the oil-rich coal seam is the solid cylinder portion, and the metal electrode cylinder corresponding to the oil-rich coal seam is the filter cylinder portion.

[0013] Preferably, the solid cylinder portion of the metal electrode cylinder and the overlying rock formation of the oil-rich coal seam are sealed by a cement sealing layer.

[0014] Preferably, the high-voltage power-frequency power supply system further comprises a high-voltage power-frequency power supply, and a plurality of metal electrode cylinders are connected to the high-voltage power-frequency power supply via wires.

[0015] Preferably, it also includes a water vapor circulation system, which includes a plurality of pump bodies and a centrifugal separation and extraction system.

[0016] The inlet of each pump body is connected to the oil-rich coal seam through the water vapor flow path of one of the electrode wells, the outlet of each pump body is connected to the inlet of the centrifugal separation and extraction system through a pipeline, and the outlet of the centrifugal separation and extraction system is connected to the air inlet of the water vapor heating system.

[0017] Preferably, the centrifugal separation and extraction system is a centrifugal extractor.

[0018] Preferably, the anode of the electrode well arranged in the injection well constitutes an anode well, the cathode of the electrode well arranged in the extraction well constitutes a cathode well, and an anode well and a cathode well together constitute a pair of electrode wells.

[0019] In a second aspect, the present invention further discloses a method for improving the oil and gas recovery rate of an oil-rich coal seam, using the above-mentioned device for improving the oil and gas recovery rate of an oil-rich coal seam, comprising:

[0020] Step A: high voltage electricity is supplied to the metal electrode cylinder through a high voltage power frequency power supply, and the high voltage electricity is transmitted to the graphite particle layer through the metal electrode cylinder. The graphite particle layer transmits the high voltage electricity of the metal electrode cylinder to the oil-rich coal seam, and discharges into the oil-rich coal seam, thereby forming a breakdown channel in the oil-rich coal seam;

[0021] Step B: starting the steam heating system, the steam heating system generates high-temperature steam; the high-temperature steam is compressed by the air compressor to form high-pressure high-temperature steam; the high-pressure high-temperature steam passes through the metal electrode cylinder to reach the filter cylinder part of the metal electrode cylinder, and flows out from the filter hole of the metal electrode cylinder, then passes through the graphite particle layer, and finally flows into the oil-rich coal seam along the breakdown channel;

[0022] Step C: Repeat steps A to B until the breakdown channels between the filter cartridge parts of the metal electrode cartridges of the electrode wells on the same pair of injection wells and extraction wells are connected.

[0023] In step C, during the process of continuously injecting high-pressure and high-temperature water vapor into the oil-rich coal seam, the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam and enhances the conductivity of the oil-rich coal seam, and at the same time, the water vapor mixes with the oil to form an oil-water mixture, and convective heat transfer is formed between the oil-water mixture and the oil-rich coal seam, thereby improving the heating efficiency of the oil-rich coal seam and accelerating the decomposition of the oil-rich coal seam; on the other hand, the water vapor is continuously sheared and mixed with the oil during its migration in the oil-rich coal seam, forming an emulsion mixed with oil and / or water in the low temperature zone;

[0024] At the same time, high voltage electricity passes through the metal electrode tube and the graphite particle layer directly to the oil-rich coal seam, and generates a horizontal electric field in the oil-rich coal seam. The horizontal electric field prompts the formation of horizontal water chains in the emulsion, and the water chains in turn promote the expansion of the temperature range for the formation of the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction and enhancing the oil and gas recovery rate of the oil-rich coal seam.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (I) The present invention discloses a device suitable for improving the oil and gas recovery rate of an oil-rich coal seam, comprising a plurality of pairs of injection wells and extraction wells, a high-voltage power-frequency power supply system and a water vapor injection system, each injection well and each extraction well extends into the oil-rich coal seam, each pair of injection wells and extraction wells is respectively composed of an anode well and a cathode well, forming a pair of electrode wells; the high-voltage power-frequency power supply system comprises a plurality of metal electrode cylinders and a plurality of graphite particle layers, a metal electrode cylinder is arranged in each electrode well, the metal electrode cylinder corresponding to the oil-rich coal seam is a filter cylinder part, a plurality of filter holes are arranged on the cylinder wall of the filter cylinder part, and a circle of graphite particle layers is arranged between the filter cylinder part of the metal electrode cylinder and the oil-rich coal seam; the water vapor injection system comprises a water vapor heating system and a plurality of air compressors, the inlet of each air compressor is connected to the outlet of the water vapor heating system through a pipeline, and the outlet of each air compressor is connected to the cylinder mouth of the metal electrode cylinder of one of the electrode wells through a pipeline. In the process of continuously injecting high-temperature water vapor into the oil-rich coal seam, the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam and enhances the conductivity of the oil-rich coal seam. At the same time, the water vapor mixes with the oil to form a mixture of oil and water, and forms convection heat transfer with the oil-rich coal seam, thereby improving the heating efficiency of the oil-rich coal seam and accelerating the decomposition of the oil-rich coal seam. On the other hand, the water vapor is continuously sheared and mixed with the oil during its migration in the oil-rich coal seam, forming an emulsion of oil and / or water in the low temperature zone. At the same time, the high voltage of the high-voltage power supply directly reaches the oil-rich coal seam through the metal electrode tube and the graphite particle layer, generating a horizontal electric field in the oil-rich coal seam. The horizontal electric field promotes the formation of a horizontal water chain in the emulsion, which in turn promotes the expansion of the temperature range of the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction and enhancing the oil and gas recovery rate of the oil-rich coal seam.

[0027] (ii) The present invention discloses a method for improving the oil and gas recovery rate of an oil-rich coal seam, comprising: step A: supplying high voltage electricity to a metal electrode tube through a high voltage industrial frequency power supply, the high voltage electricity is transmitted to a graphite particle layer through the metal electrode tube, the graphite particle layer transmits the high voltage electricity of the metal electrode tube to the oil-rich coal seam, and discharges into the oil-rich coal seam to form a breakdown channel in the oil-rich coal seam; step B: starting a water vapor heating system, the water vapor heating system generates high-temperature water vapor; the high-temperature water vapor is compressed by an air compressor to form high-pressure high-temperature water vapor; the high-pressure high-temperature water vapor passes through the metal electrode tube to reach the filter tube portion of the metal electrode tube, flows out from the filter holes of the metal electrode tube, passes through the graphite particle layer, and finally flows into the oil-rich coal seam along the breakdown channel; step C: repeating steps A to B until the breakdown channels between the filter tube portions of the metal electrode tubes of the electrode wells on the same pair of injection wells and extraction wells are connected. Among them, in the process of continuously injecting high-pressure and high-temperature water vapor into the oil-rich coal seam, the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam and enhances the conductivity of the oil-rich coal seam. At the same time, the water vapor mixes with the oil to form an oil-water mixture. The oil-water mixture forms convective heat transfer with the oil-rich coal seam, thereby improving the heating efficiency of the oil-rich coal seam and accelerating the decomposition of the oil-rich coal seam. On the other hand, due to continuous shear mixing with the oil during its migration in the oil-rich coal seam, an emulsion of oil and / or water is formed in the low temperature zone. At the same time, high voltage electricity directly reaches the oil-rich coal seam through the metal electrode tube and the graphite particle layer, and generates a horizontal electric field in the oil-rich coal seam. The horizontal electric field prompts the formation of horizontal water chains (water films) in the emulsion. The water chains in turn promote the expansion of the temperature range for forming the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction and enhancing the oil and gas recovery rate of the oil-rich coal seam.

[0028] In addition, the present invention also has the following advantages:

[0029] 1. After high voltage electricity treatment of oil-rich coal seams, the resistivity of the coal seams is effectively reduced;

[0030] 2. After water vapor is injected into the oil-rich coal seam under power frequency electricity, the electrical conductivity increases, the heating efficiency increases, and the coal seam generates convective heat transfer after water vapor is injected, and the heat transfer efficiency increases;

[0031] 3. Water and the oil and gas produced by pyrolysis will generate an emulsion below 90°C under shear flow conditions, effectively enhancing the fluidity of oil and gas products as they migrate to the low-temperature zone of the coal seam;

[0032] 4. The unpenetrated part of the coal seam is affected by the potential difference between the metal electrode tubes and is in a horizontal electric field. The water molecules in the emulsion are rearranged in the same direction under the influence of the electric field. Under the action of hydrogen bonds, the water molecules in the same direction are more likely to connect end to end and attract each other, forming a horizontal "water film" in the emulsion. The flow of the emulsion in the oil-rich coal seam can provide part of the energy for the "water film" to balance its gravity, so as to keep the water film suspended and maintain the emulsified state;

[0033] 5. The formation of "water film" greatly reduces the horizontal viscosity of the emulsion, and at the same time makes it difficult for water molecules to precipitate and demulsify in the environment of surrounding oil and gas molecules, so that the emulsion can exist at a higher temperature, effectively increasing the temperature range for forming oil-water emulsions, avoiding the problem of reduced relative permeability of cracked oil caused by oil-water two-phase flow at lower temperatures, and improving the fluidity of oil and gas products in the area below 200°C in the coal seam, effectively improving the oil and gas recovery rate of in-situ heating technology of oil-rich coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the overall structure of a device for improving oil and gas recovery efficiency in an oil-rich coal seam provided in Example 1 of the present invention;

[0035] Figure 2 for Figure 1 A schematic diagram of the structure of a device for improving the oil and gas recovery rate of an oil-rich coal seam after omitting a water vapor heating system, a centrifugal separation and extraction system and its connecting lines;

[0036] Figure 3 for Figure 2 A cross-sectional view taken longitudinally through one of the metal electrode cylinders.

[0037] Description of reference numerals:

[0038] 100-oil-rich coal seam, 101-overburden of the oil-rich coal seam, 102-cement sealing layer, 103-breakdown channel;

[0039] 1-Electrode well;

[0040] 21-high voltage power frequency power supply, 22-metal electrode cylinder, 220-filter hole, 221-solid cylinder part, 222-filter cylinder part 222, 23-graphite particle layer;

[0041] 31-steam heating system, 32-air compressor;

[0042] 40- pump body, 41- centrifugal separation and extraction system.

[0043] Among them, “-” means “for”. DETAILED DESCRIPTION

[0044] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0045] In order to solve the problem of low oil and gas recovery rate in the existing technology of in-situ mining of oil-rich coal, the present invention discharges electricity into the oil-rich coal seam 100 and forms a breakdown channel 103 in the oil-rich coal seam 100, thereby forming an emulsion mixed with oil and / or water in the low temperature zone; at the same time, high-temperature water vapor is injected into the oil-rich coal seam 100 and flows along the breakdown channel 103, thereby reducing the shear viscosity of the emulsion in the horizontal direction, and finally enhancing the oil and gas recovery rate of the oil-rich coal seam 100.

[0046] Example 1: A device for improving oil and gas recovery from oil-rich coal seams

[0047] Embodiment 1 of the present invention provides a device suitable for improving the oil and gas recovery rate of oil-rich coal seams, which acts on several pairs of injection wells and extraction wells. The structure thereof is described in detail below in conjunction with the accompanying drawings.

[0048] refer to Figures 1 to 3 The device for improving the oil and gas recovery rate of oil-rich coal seams includes a plurality of injection wells and extraction wells, a set of high-voltage power supply system, a set of water vapor injection system and a set of water vapor circulation system.

[0049] Each injection well and each extraction well passes through the overlying rock stratum 101 of the oil-rich coal seam and extends into the oil-rich coal seam 100; each pair of injection wells and extraction wells is composed of an anode well and a cathode well, respectively, forming a pair of electrode wells 1.

[0050] Specifically, the anode of the electrode well 1 arranged in the injection well constitutes an anode well, and the cathode of the electrode well 1 arranged in the extraction well constitutes a cathode well. An anode well and a cathode well together constitute a pair of electrode wells 1.

[0051] The high-voltage power-frequency power supply system includes a high-voltage power-frequency power supply 21 , a plurality of metal electrode cylinders 22 and a plurality of graphite particle layers 23 .

[0052] A metal electrode cylinder 22 is arranged in each electrode well 1, and the metal electrode cylinder 22 includes a solid cylinder portion 221 and a filter cylinder portion 222, wherein the metal electrode cylinder 22 corresponding to the overlying rock stratum 101 of the oil-rich coal seam is the solid cylinder portion 221, and the metal electrode cylinder 22 corresponding to the oil-rich coal seam 100 is the filter cylinder portion 222, and a plurality of filter holes 220 are arranged on the cylinder wall of the filter cylinder portion 222;

[0053] The solid cylinder portion 221 of the metal electrode cylinder 22 is sealed with the overlying rock stratum 101 of the oil-rich coal seam by a cement sealing layer 102 ; a circle of graphite particle layer 23 is provided between the filter cylinder portion 222 of the metal electrode cylinder 22 and the oil-rich coal seam 100 .

[0054] The cement sealing layer 102 insulates the metal electrode tube 22 from other rock formations to prevent the injected water vapor and the oil and gas produced by cracking from leaking in the gap between the metal electrode tube 22 and the wall of the electrode well 1 .

[0055] A circle of graphite particle layer 23 is formed between the filter cylinder portion 222 of the metal electrode cylinder 22 and the oil-rich coal seam 100 by filling graphite particles.

[0056] The physical properties of graphite particles are that they are not only porous but also conductive. Therefore, the graphite particle layer 23 can electrically connect the metal electrode cylinder 22 to the oil-rich coal seam 100 , and water vapor can enter the oil-rich coal seam 100 through the graphite particle layer 23 .

[0057] Specifically, a plurality of metal electrode cylinders 22 are connected to a high voltage power frequency power supply 21 through wires, such as Figure 1 shown.

[0058] The high-voltage power frequency power supply 21 is used to provide 50HZ power frequency power and 10KV / m high voltage power;

[0059] The graphite particle layer 23 is composed of graphite particles and can transmit the high voltage electricity of the metal electrode cylinder 22 to the oil-rich coal seam 100 .

[0060] When high voltage electricity is transmitted to the graphite particle layer 23 through the metal electrode tube 22 , the graphite particle layer 23 transmits the high voltage electricity of the metal electrode tube 22 to the oil-rich coal seam 100 , and the high voltage electricity is discharged into the oil-rich coal seam 100 , forming a breakdown channel 103 in the oil-rich coal seam 100 .

[0061] The water vapor injection system includes a water vapor heating system 31 and several air compressors 32.

[0062] The inlet of each air compressor 32 is connected to the outlet of the water vapor heating system 31 through a pipeline, and the outlet of each air compressor 32 is connected to the tube mouth of the metal electrode tube 22 of one of the electrode wells 1 through a pipeline;

[0063] Wherein, the water vapor heating system 31 is used to generate high-temperature water vapor;

[0064] The air compressor 32 , the metal electrode cylinder 22 of the electrode well 1 , a plurality of filter holes 220 , a circle of graphite particle layer 23 and the breakdown channel 103 together constitute a water vapor flow path.

[0065] Specifically, high-temperature water vapor passes through the metal electrode cylinder 22 of the electrode well 1 to reach the filter cylinder portion 222 of the metal electrode cylinder 22 , flows out from the filter hole 220 , passes through the graphite particle layer 23 , and flows into the oil-rich coal seam 100 along the breakdown channel 103 .

[0066] Among them, in the process of continuously injecting high-temperature water vapor into the oil-rich coal seam 100, the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam 100 and enhances the conductivity of the oil-rich coal seam 100. At the same time, the water vapor mixes with the oil to form a mixture of oil and water, and forms convection heat transfer with the oil-rich coal seam 100, thereby improving the heating efficiency of the oil-rich coal seam 100 and accelerating the decomposition of the oil-rich coal seam 100. On the other hand, due to continuous shear mixing with the oil during its migration in the oil-rich coal seam 100, an emulsion mixed with oil and / or water is formed in the low temperature zone.

[0067] The high voltage electricity of the high-voltage industrial frequency power supply 21 directly reaches the oil-rich coal seam 100 through the metal electrode tube 22 and the graphite particle layer 23, generating a horizontal electric field in the oil-rich coal seam 100. The horizontal electric field prompts the formation of horizontal water chains in the emulsion, and the water chains in turn promote the expansion of the temperature range for forming the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction and enhancing the oil and gas recovery rate of the oil-rich coal seam 100.

[0068] As a specific implementation, the water vapor circulation system includes a plurality of pump bodies 40 and a centrifugal separation and extraction system 41 .

[0069] The inlet of each pump body 40 is connected to the oil-rich coal seam 100 through the water vapor flow path of one of the electrode wells 1, and the outlet of each pump body 40 is connected to the inlet of the centrifugal separation and extraction system 41 through a pipeline, and the outlet of the centrifugal separation and extraction system 41 is connected to the air inlet of the water vapor heating system 31;

[0070] Among them, the centrifugal separation and extraction system 41 can generate and separate water vapor with residual heat;

[0071] The separated steam with residual heat is introduced into the steam heating system 31 again.

[0072] The water vapor heating system 31 is used for secondary utilization of the energy of the separated water vapor with waste heat.

[0073] Specifically, the centrifugal separation and extraction system 41 is a centrifugal extractor.

[0074] The assembly method of the device for improving the oil and gas recovery rate of the oil-rich coal seam comprises the following steps:

[0075] An even number of electrode wells 1 are drilled in the coal seam of the selected target mining area, a metal electrode cylinder 22 is placed in each of the electrode wells 1, and a high-voltage power frequency power supply 21 is connected to the metal electrode cylinder 22 through a wire;

[0076] After the metal electrode cylinder 22 is arranged, graphite particles are poured into the gap between the metal electrode cylinder 22 and the electrode well 1, so that a graphite particle layer 23 is formed between the metal electrode cylinder 22 and the oil-rich coal seam 100;

[0077] Pour cement slurry into the gap between the metal electrode cylinder 22 and the electrode well 1 to form a cement sealing layer 102 between the solid cylinder portion 221 of the metal electrode cylinder 22 and the overlying rock stratum 101 of the oil-rich coal seam, wherein the cement sealing layer 102 forms a seal between the metal electrode cylinder 22 and the electrode well 1;

[0078] An air compressor 32 and a pump body 40 are respectively arranged at the wellheads of the injection well and the extraction well. The inlet of the air compressor 32 is connected to the outlet of the water vapor heating system 31 through a pipeline, and the outlet of the air compressor 32 is connected to the oil-rich coal seam 100 through the water vapor flow path of the electrode well 1.

[0079] The inlet of each pump body 40 is connected to the oil-rich coal seam 100 through the water vapor flow path of one of the electrode wells 1, and the outlet of each pump body 40 is connected to the inlet of the centrifugal separation and extraction system 41 through a pipeline, and the outlet of the centrifugal separation and extraction system 41 is connected to the air inlet of the water vapor heating system 31.

[0080] Example 2: A method for improving oil and gas recovery from oil-rich coal beds

[0081] Embodiment 2 of the present invention provides a method for improving the oil and gas recovery rate of an oil-rich coal seam, using the device for improving the oil and gas recovery rate of an oil-rich coal seam provided in Embodiment 1, and the method comprises the following steps:

[0082] Step A: high voltage electricity is supplied to the metal electrode cylinder 22 through the high voltage power frequency power supply 21, and the high voltage electricity is transmitted to the graphite particle layer 23 through the metal electrode cylinder 22. The graphite particle layer 23 transmits the high voltage electricity of the metal electrode cylinder 22 to the oil-rich coal seam 100, and discharges into the oil-rich coal seam 100, forming a breakdown channel 103 in the oil-rich coal seam 100;

[0083] Step B: Start the steam heating system 31, the steam heating system 31 generates high-temperature steam; the high-temperature steam is compressed by the air compressor 32 to form high-pressure high-temperature steam; the high-pressure high-temperature steam passes through the metal electrode cylinder 22 to reach the filter cylinder portion 222 of the metal electrode cylinder 22, and flows out from the filter hole 220 of the metal electrode cylinder 22, then passes through the graphite particle layer 23, and finally flows into the oil-rich coal seam 100 along the breakdown channel 103;

[0084] Step C: Repeat steps A to B until the breakdown channels 103 between the filter cartridge parts 222 of the metal electrode cartridges 22 of the electrode wells 1 on the same pair of injection wells and extraction wells are connected.

[0085] In the process of continuously injecting high-pressure and high-temperature water vapor into the oil-rich coal seam 100, the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam 100 and enhances the conductivity of the oil-rich coal seam 100, and at the same time, the water vapor mixes with the oil to form an oil-water mixture, and convective heat transfer is formed between the oil-water mixture and the oil-rich coal seam 100, thereby improving the heating efficiency of the oil-rich coal seam 100 and accelerating the decomposition of the oil-rich coal seam 100; on the other hand, the water vapor is continuously sheared and mixed with the oil during its migration in the oil-rich coal seam 100, and an emulsion of oil and / or water is formed in the low temperature zone;

[0086] At the same time, high voltage electricity directly reaches the oil-rich coal seam 100 through the metal electrode tube 22 and the graphite particle layer 23, and generates a horizontal electric field in the oil-rich coal seam 100. The horizontal electric field prompts the formation of horizontal water chains (i.e., water films) in the emulsion. The water chains in turn promote the expansion of the temperature range for forming the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction and enhancing the oil and gas recovery rate of the oil-rich coal seam 100.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for improving oil and gas recovery rate in oil-rich coal seams, characterized in that: include A plurality of pairs of injection wells and extraction wells, each of which extends into the oil-rich coal seam (100), and each pair of injection wells and extraction wells is respectively composed of an anode well and a cathode well, forming a pair of electrode wells (1); A high-voltage power-frequency power supply system, comprising a plurality of metal electrode cylinders (22) and a plurality of graphite particle layers (23), wherein a metal electrode cylinder (22) is arranged in each electrode well (1), the metal electrode cylinder (22) corresponding to the oil-rich coal seam (100) is a filter cylinder portion (222), a plurality of filter holes (220) are arranged on the cylinder wall of the filter cylinder portion (222), and a circle of graphite particle layers (23) is arranged between the filter cylinder portion (222) of the metal electrode cylinder (22) and the oil-rich coal seam (100); The water vapor injection system comprises a water vapor heating system (31) and a plurality of air compressors (32), wherein the inlet of each air compressor (32) is connected to the outlet of the water vapor heating system (31) via a pipeline, and the outlet of each air compressor (32) is connected to the tube mouth of a metal electrode tube (22) of one of the electrode wells (1) via a pipeline.

2. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 1, characterized in that: When high voltage electricity is transmitted to the graphite particle layer (23) through the metal electrode cylinder (22), the graphite particle layer (23) transmits the high voltage electricity of the metal electrode cylinder (22) to the oil-rich coal seam (100), and the high voltage electricity is discharged into the oil-rich coal seam (100), forming a breakdown channel (103) in the oil-rich coal seam (100); The water vapor heating system (31) is used to generate high-temperature water vapor, and the air compressor (32), the metal electrode cylinder (22) of the electrode well (1), a plurality of filter holes (220), a circle of graphite particle layers (23) and the breakdown channel (103) together constitute a water vapor flow path.

3. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 1, characterized in that: The metal electrode cylinder (22) comprises a solid cylinder portion (221) and a filter cylinder portion (222), wherein the metal electrode cylinder (22) corresponding to the overlying rock layer (101) of the oil-rich coal seam is the solid cylinder portion (221), and the metal electrode cylinder (22) corresponding to the oil-rich coal seam (100) is the filter cylinder portion (222).

4. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 3, characterized in that: The solid cylinder portion (221) of the metal electrode cylinder (22) and the overlying rock layer (101) of the oil-rich coal seam are sealed via a cement sealing layer (102).

5. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 1, characterized in that: The high-voltage power-frequency power supply system also includes a high-voltage power-frequency power supply (21), and a plurality of metal electrode cylinders (22) are connected to the high-voltage power-frequency power supply (21) via wires.

6. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 1, characterized in that: It also includes a water vapor circulation system, wherein the water vapor circulation system includes a plurality of pump bodies (40) and a centrifugal separation and extraction system (41). The inlet of each pump body (40) is connected to the oil-rich coal seam (100) through a water vapor flow path of one of the electrode wells (1), the outlet of each pump body (40) is connected to the inlet of the centrifugal separation and extraction system (41) through a pipeline, and the outlet of the centrifugal separation and extraction system (41) is connected to the air inlet of the water vapor heating system (31).

7. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 6, characterized in that: The centrifugal separation and extraction system (41) is a centrifugal extractor.

8. The device for improving oil and gas recovery rate in oil-rich coal seams according to claim 1, characterized in that: The anode of the electrode well (1) arranged in the injection well constitutes an anode well, and the cathode of the electrode well (1) arranged in the extraction well constitutes a cathode well. An anode well and a cathode well together constitute a pair of electrode wells (1).

9. A method for improving oil and gas recovery from oil-rich coal seams, using the device for improving oil and gas recovery from oil-rich coal seams as claimed in any one of claims 1 to 8, comprising: Step A: high voltage electricity is supplied to the metal electrode cylinder (22) through a high voltage power frequency power supply (21), the high voltage electricity is transmitted to the graphite particle layer (23) through the metal electrode cylinder (22), the graphite particle layer (23) transmits the high voltage electricity of the metal electrode cylinder (22) to the oil-rich coal seam (100), and discharges into the oil-rich coal seam (100), thereby forming a breakdown channel (103) in the oil-rich coal seam (100); Step B: starting the steam heating system (31), the steam heating system (31) generates high-temperature steam; the high-temperature steam is compressed by the air compressor (32) to form high-pressure high-temperature steam; the high-pressure high-temperature steam passes through the metal electrode cylinder (22) to reach the filter cylinder portion (222) of the metal electrode cylinder (22), and flows out from the filter hole (220) of the metal electrode cylinder (22), then passes through the graphite particle layer (23), and finally flows into the oil-rich coal seam (100) along the breakdown channel (103); Step C: Repeat steps A to B until the breakdown channels (103) between the filter cartridge parts (222) of the metal electrode cartridges (22) of the electrode wells (1) on the same pair of injection wells and extraction wells are connected.

10. The method for improving oil and gas recovery rate in oil-rich coal seams according to claim 9, In step C, during the process of continuously injecting high-pressure and high-temperature water vapor into the oil-rich coal seam (100), the water vapor, on the one hand, dissolves the minerals of the oil-rich coal seam (100), thereby enhancing the conductivity of the oil-rich coal seam (100), and at the same time, the water vapor mixes with the oil to form an oil-water mixture, and convective heat transfer is formed between the oil-water mixture and the oil-rich coal seam (100), thereby improving the heating efficiency of the oil-rich coal seam (100) and accelerating the decomposition of the oil-rich coal seam (100); on the other hand, the water vapor is continuously sheared and mixed with the oil during migration in the oil-rich coal seam (100), thereby forming an emulsion of oil and / or water in the low-temperature zone; At the same time, high voltage electricity directly reaches the oil-rich coal seam (100) through the metal electrode tube (22) and the graphite particle layer (23), and generates a horizontal electric field in the oil-rich coal seam (100). The horizontal electric field promotes the formation of horizontal water chains in the emulsion, and the water chains in turn promote the expansion of the temperature range for forming the emulsion, thereby reducing the shear viscosity of the emulsion in the horizontal direction, thereby enhancing the oil and gas recovery rate of the oil-rich coal seam (100).

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