Coaxial sleeve gas-heat co-extraction method

Abstract

The invention discloses a gas-heat co-extraction method for a coaxial sleeve. The gas-heat co-extraction method comprises the following steps that S1, a plurality of extraction holes are drilled; s2, a coaxial sleeve extraction heat exchanger is installed in the extraction hole; s3, an extraction pipeline, an electric submersible pump, a gas-liquid separation device, a heat pump unit and a water injection pipeline are arranged on the ground; and S4, water is injected into the coaxial sleeve extraction heat exchanger for heat exchange, gas and hot water are extracted at the same time through an electric submersible pump and then separated through a cyclone type gas-liquid separator, and finally heat in water is extracted through a heat pump unit, so that gas and heat co-extraction is achieved. The method is scientific in principle, gas in the coal seam can be extracted while geothermal resources are exploited, and gas-heat co-mining of the deep coal seam is achieved; the coal bed gas and the geothermal resources belong to the clean energy category, the deep coal bed gas and the geothermal resources are exploited together, the resource comprehensive utilization efficiency and the resource comprehensive development benefit can be improved, and great significance is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of deep coalbed methane and geothermal coordinated exploitation, and specifically relates to a coaxial casing gas-heat co-exploitation method. Background Art

[0002] Coal resources are non-renewable one-time energy sources. With the high-intensity mining of coal resources in China, shallow coal resources are gradually decreasing, and mine mining in my country is gradually shifting to deep areas. However, with the increase in the depth of mine mining, the number of high-geothermal mines is gradually increasing, and the impact of high-temperature heat damage is relatively large, which seriously restricts the safe and efficient mining of deep coal resources. Therefore, the geothermal problem of deep mines has been mainly aimed at heat damage control for many years. Against this background, the idea of ​​deep coalbed methane and thermal co-mining came into being. On the one hand, the high temperature environment of the mine can be alleviated by mining geothermal resources during coal mining; on the other hand, geothermal energy, as a clean energy, can achieve efficient utilization of resources and reduce carbon emissions through coordinated mining with coal, which meets the requirements of sustainable development. Therefore, it is urgent to develop a gas-heat co-mining method that can extract gas while mining geothermal resources to improve economic benefits. Summary of the invention

[0003] In order to solve the above technical problems existing in the prior art, the present invention provides a coaxial casing gas-heat co-extraction method which is applicable to heat-storage rock formations with heat but no water and can perform gas extraction while exploiting geothermal resources.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a coaxial casing gas-heat co-production method, comprising the following steps: S1. Drilling a number of extraction holes vertically downward on the ground, the extraction holes passing through the pre-mined coal seam and entering the rock layer below to a certain depth; S2. A coaxial casing extraction heat exchanger is installed in each extraction hole, the upper end of the coaxial casing extraction heat exchanger extends out of the ground, and the lower end of the coaxial casing extraction heat exchanger extends into the rock formation; S3. Arrange the extraction pipeline, electric submersible pump, gas-liquid separation device, heat pump unit and water injection pipeline on the ground, connect the inlet of the electric submersible pump to the outlet of the coaxial casing extraction heat exchanger through the extraction pipeline, connect the outlet of the electric submersible pump to the inlet of the gas-liquid separation device, connect the water outlet of the gas-liquid separation device to the hot water inlet of the heat pump unit, connect the gas outlet of the gas-liquid separation device to the exhaust pipe, and connect the cold water outlet of the heat pump unit to the inlet of the coaxial casing extraction heat exchanger through the water injection pipeline; S4. Start the electric submersible pump, gas-liquid separation device and heat pump unit, and inject low-temperature water into the coaxial casing extraction heat exchanger through the water injection pipeline. The water flows down along the outer channel of the coaxial casing extraction heat exchanger to fully absorb the heat in the coal seam and the rock formation. The electric submersible pump draws the hot water after the heat exchange between the gas in the coal seam and the rock formation upward from the central channel of the coaxial casing extraction heat exchanger. The gas-liquid separation device separates the gas and water. The separated high-temperature water extracts heat through the heat pump unit and is re-injected into the coaxial casing extraction heat exchanger through the water injection pipeline for heat exchange, thereby realizing gas and heat co-production.

[0005] The coaxial sleeve extraction heat exchanger in step S2 includes an outer tube arranged vertically and an inner tube arranged coaxially inside the outer tube. The inner wall of the outer tube and the outer wall of the inner tube are connected by a plurality of radially arranged cross bars. A plurality of connecting pipes are arranged between the outer tube and the inner tube in a section of the pre-mined coal seam. The two ends of the connecting pipes are respectively connected to the pre-mined coal seam and the inside of the inner tube. A one-way valve adjacent to the inner tube is arranged on the connecting pipe. A plugging plate is provided at the lower end of the outer tube. The edge of the lower end of the inner tube is higher than the upper surface of the plugging plate. The annular channel between the outer tube and the inner tube forms a baffled water passage with the inner cavity of the inner tube. The upper end of the inner tube is the outlet of the coaxial sleeve extraction heat exchanger and is connected to the lower end of the extraction pipeline. The upper end of the outer tube is provided with an annular cover plate which is sleeved on the outside of the inner tube. A water inlet hole is opened on the upper side of the outer tube. The water inlet hole is the inlet of the coaxial sleeve extraction heat exchanger and is connected to the outlet of the water injection pipeline.

[0006] The diameter of the extraction hole in the pre-mined coal seam section is larger than the outer diameter of the outer pipe, and an annular extraction cavity is formed between the extraction hole in the pre-mined coal seam section and the outer pipe. The diameter of the extraction hole in the rock formation section is equal to the outer diameter of the outer pipe. The outer pipe is made of a material with good thermal conductivity and corrosion resistance, and the inner pipe is made of a material with good thermal insulation.

[0007] A bracket is provided at the lower end of the inner tube, a rotating shaft is rotatably provided between the bracket and the center of the blocking plate, and a spiral blade located inside the inner tube above the bracket and an anti-sedimentation scraper located inside the outer tube below the bracket are provided on the rotating shaft.

[0008] The specific process of step S4 is: start the electric submersible pump, the gas-liquid separation device and the heat pump unit, inject low-temperature water into the outer pipe through the water injection pipeline, and the low-temperature water flows down along the outer pipe. During the downward flow, the low-temperature water fully absorbs the heat in the coal seam and the rock formation with the pre-mined coal seam and the rock formation, and the hot water after absorbing heat enters the inner pipe upward from the plugging plate at the bottom of the outer pipe. At the same time, the gas in the pre-mined coal seam is subjected to the upward suction negative pressure of the hot water in the inner cavity of the inner pipe in the annular extraction chamber, and the gas enters the inner pipe through the connecting pipe and the one-way valve to mix with the hot water. The one-way valve prevents The hot water in the inner tube enters the annular extraction chamber along the connecting pipe, and the electric submersible pump extracts the gas in the inner tube and the hot water after heat exchange upward, and the electric submersible pump sends the hot water to the gas-liquid separation device, which separates the gas and water. The separated gas is collected through the exhaust pipe, and the separated high-temperature water enters the heat pump unit again. The heat pump unit extracts the heat from the hot water and stores it or uses it directly. The heat pump unit then re-injects the low-temperature water into the coaxial sleeve extraction heat exchanger through the water injection pipeline for heat exchange, thereby realizing gas and heat co-extraction and hot water circulation.

[0009] After the water in the outer tube flows downward through the deflected water channel and enters the inner cavity of the inner tube, the upward power of the water flow drives the spiral blades to rotate, and the active rotating blades drive the lower anti-sedimentation scraper to rotate through the rotating shaft, thereby avoiding the accumulation of sediment or scaling on the blocking plate.

[0010] By adopting the above technical solution, compared with the prior art, the innovation of the present invention is mainly reflected in the following aspects: (1) Structure of coaxial casing heat exchanger The coaxial casing extraction heat exchanger mainly includes an outer tube and an inner tube. The inner and outer casings are fixed by cross-shaped flat cross bars to ensure that the inner tube and the outer tube are connected as a whole, and the structure is more stable. The inner tube and the outer tube are connected through a connecting pipe inside the pre-mined coal seam, and a one-way valve is installed on each connecting pipe near the inner tube. The one-way valve only allows gas to pass from the outside to the inside in the connecting pipe to prevent water inside the inner tube from flowing into the connecting pipe and affecting the gas extraction effect. The outer tube is made of materials with good thermal conductivity so that the heat can be fully transferred to the low-temperature water, and the inner tube is made of materials with good thermal insulation to prevent heat loss.

[0011] A spiral blade is arranged inside the lower port of the inner tube. When hot water flows upward from the lower port of the inner tube, the spiral blade is driven to rotate, and the anti-sedimentation scraper above the blocking plate is driven to rotate through the rotating shaft, so that the water in the dead corner at the lower end of the outer tube is always kept in a stirring state, and the sedimentation and scaling here will not be deposited again, thereby avoiding the accumulation of sedimentation and scaling here and blocking the deflected water channel.

[0012] (2) Adoptionability evaluation To achieve the goal of coordinated exploitation of gas and thermal resources, it is necessary to consider the overall situation from the exploration stage, from the initial exploration of favorable blocks (including regional geological surveys, geophysical exploration, gas and thermal resource potential evaluation, etc.) to the drilling of early exploration parameter wells, the comprehensive exploration and development of gas and thermal resources need to be considered comprehensively. The specific exploration work can be determined according to the relevant specifications for coal-measure gas and geothermal resource exploration, and the comprehensive resource exploration work plan can be determined.

[0013] The present invention is applicable to blocks with good potential for gas and heat resources. The preliminary exploration parameter wells need to comprehensively consider the parameter test work of gas and heat reservoirs. For coal-bearing gas reservoirs, the reservoir pressure, porosity, permeability, gas content and other parameters are mainly evaluated, and fracturing well tests are carried out for favorable layers. For heat reservoirs, well temperature measurement, heat reservoir coring and thermal physical parameter testing are required.

[0014] (3) Technical process of gas and heat co-production Before implementing gas-heat co-extraction, it is necessary to first drill several extraction holes vertically downward into the pre-extracted coal seam on the ground. The extraction holes pass through the pre-extracted coal seam and enter the rock layer to a certain depth, and then arrange the coaxial casing extraction heat exchanger in the hole; inject low-temperature water into the outer pipe through the water injection pipeline, and the water flows down along the outer pipe to fully absorb the heat in the coal seam and the rock layer; when the extraction starts, the gas is allowed to enter the inner pipe along the connecting pipe through the one-way valve, and the electric submersible pump extracts the gas and water together along the extraction pipeline to the ground; the other end of the electric submersible pump is connected to the gas-liquid separation device to separate the gas and water to realize gas-heat co-extraction.

[0015] The gas-liquid separation device adopts a cyclone gas-liquid separator. The mixture of gas and water rotates at high speed in the device. Due to the relatively large density of water, it will be thrown to the inner wall of the cyclone gas-liquid separator and flow out from the drain below. The separated gas moves upward along the central axis and is discharged from the exhaust port; the drain port is connected to the heat pump unit, and the separated hot water enters the heat pump for heat exchange, and finally is re-injected into the outer pipe of the coaxial casing extraction heat exchanger along the water injection pipeline, realizing the circulation of the entire gas-heat co-extraction system.

[0016] To sum up, the principle of the present invention is scientific, and it can extract coalbed gas while exploiting geothermal resources, thereby realizing the co-exploitation of gas and heat in deep coal seams; coalbed methane and geothermal resources belong to the category of clean energy. The co-exploitation of deep coalbed methane and geothermal resources can improve the comprehensive utilization efficiency of resources and the comprehensive development benefits of resources, which is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a connection diagram of various equipment in the process flow of the gas-heat co-production method in the present invention.

[0018] Figure 2 yes Figure 1 Schematic diagram of the overall structure of the coaxial casing heat exchanger; Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure between the outer tube and the inner tube; DETAILED DESCRIPTION

[0019] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0020] like Figure 1-Figure 3 As shown, a coaxial casing gas-heat co-production method of the present invention comprises the following steps: S1, drilling a plurality of extraction holes 2 vertically downward on the ground 1, the extraction holes 2 passing through the pre-mined coal seam 3 and entering the rock layer 4 below to a certain depth; S2. A coaxial casing extraction heat exchanger 5 is installed in each extraction hole 2, the upper end of the coaxial casing extraction heat exchanger 5 extends out of the ground 1, and the lower end of the coaxial casing extraction heat exchanger 5 extends into the rock layer 4; S3, arranging the extraction pipeline 6, the electric submersible pump 7, the gas-liquid separation device 8, the heat pump unit 9 and the water injection pipeline 10 on the ground 1, connecting the inlet of the electric submersible pump 7 to the outlet of the coaxial casing extraction heat exchanger 5 through the extraction pipeline 6, connecting the outlet of the electric submersible pump 7 to the inlet of the gas-liquid separation device 8, connecting the water outlet of the gas-liquid separation device 8 to the hot water inlet of the heat pump unit 9, connecting the gas outlet of the gas-liquid separation device 8 to the exhaust pipe, and connecting the cold water outlet of the heat pump unit 9 to the inlet of the coaxial casing extraction heat exchanger 5 through the water injection pipeline 10; S4, start the electric submersible pump 7, the gas-liquid separation device 8 and the heat pump unit 9, and inject low-temperature water into the coaxial casing extraction heat exchanger 5 through the water injection pipeline 10. The water flows down along the outer channel of the coaxial casing extraction heat exchanger 5, fully absorbing the heat in the coal seam and the rock layer 4. The electric submersible pump 7 draws the hot water after the heat exchange between the gas in the coal seam and the rock layer 4 upward from the central channel of the coaxial casing extraction heat exchanger 5. The gas-liquid separation device 8 separates the gas and water. The separated high-temperature water extracts heat through the heat pump unit 9 and is re-injected into the coaxial casing extraction heat exchanger 5 through the water injection pipeline 10 for heat exchange, thereby realizing gas and heat co-production.

[0021] The coaxial casing extraction heat exchanger 5 in step S2 comprises an outer tube 11 arranged vertically and an inner tube 12 arranged coaxially inside the outer tube 11. The inner wall of the outer tube 11 and the outer wall of the inner tube 12 are connected by a plurality of radially arranged cross bars 13. A plurality of connecting pipes 14 are arranged between the outer tube 11 and the inner tube 12 at a section of the pre-mined coal seam 3. The two ends of the connecting pipe 14 are respectively connected to the pre-mined coal seam 3 and the inside of the inner tube 12. A one-way valve 15 adjacent to the inner tube 12 is arranged on the connecting pipe 14. The lower end of the outer tube 11 is connected to the inner tube 12. A plugging plate 16 is provided at the mouth, and the lower edge of the inner tube 12 is higher than the upper surface of the plugging plate 16. The annular channel between the outer tube 11 and the inner tube 12 and the inner cavity of the inner tube 12 form a baffle water passage 17. The upper port of the inner tube 12 is the outlet of the coaxial sleeve extraction heat exchanger 5 and is connected to the lower port of the extraction pipeline 6. The upper port of the outer tube 11 is provided with an annular cover plate 18 which is sleeved on the outside of the inner tube 12. A water inlet hole is opened on the upper side of the outer tube 11, which is the inlet of the coaxial sleeve extraction heat exchanger 5 and is connected to the outlet of the water injection pipeline 10.

[0022] The diameter of the extraction hole 2 in a section of the pre-mined coal seam 3 is larger than the outer diameter of the outer tube 11, and an annular extraction chamber 19 is formed between the extraction hole 2 in a section of the pre-mined coal seam 3 and the outer tube 11. The diameter of the extraction hole 2 in a section of the rock layer 4 is equal to the outer diameter of the outer tube 11; the outer tube 11 is made of a material with good thermal conductivity and corrosion resistance, and the inner tube 12 is made of a material with good heat preservation.

[0023] A bracket 20 is provided at the lower end of the inner tube 12, and a rotating shaft 21 is rotatably provided between the bracket 20 and the center of the blocking plate 16. The rotating shaft 21 is provided with a spiral blade 22 located inside the inner tube 12 above the bracket 20 and an anti-sedimentation scraper 23 located inside the outer tube 11 below the bracket 20.

[0024] The specific process of step S4 is as follows: start the electric submersible pump 7, the gas-liquid separation device 8 and the heat pump unit 9, inject low-temperature water into the outer tube 11 through the water injection pipeline 10, and the low-temperature water flows down along the outer tube 11. During the downward flow, the low-temperature water fully absorbs the heat in the coal seam and the rock layer 4 with the pre-mined coal seam 3 and the rock layer 4, and the hot water after absorbing heat enters the inner tube 12 upward from the plugging plate 16 at the bottom of the outer tube 11. At the same time, the gas in the pre-mined coal seam 3 is subjected to the upward suction negative pressure of the hot water in the inner cavity of the inner tube 12 in the annular extraction chamber 19, and the gas enters the inner tube 12 through the connecting pipe 14 and the one-way valve 15 to mix with the hot water. The valve 15 prevents the hot water in the inner tube 12 from entering the annular extraction chamber 19 along the connecting pipe 14. The electric submersible pump 7 extracts the gas in the inner tube 12 and the hot water after heat exchange upward, and the electric submersible pump 7 sends the hot water to the gas-liquid separation device 8. The gas-liquid separation device 8 separates the gas and water. The separated gas is collected through the exhaust pipe, and the separated high-temperature water enters the heat pump unit 9. The heat pump unit 9 extracts the heat from the hot water and stores it or uses it directly. The heat pump unit 9 then injects the low-temperature water into the coaxial sleeve extraction heat exchanger 5 through the water injection pipeline 10 for heat exchange, thereby realizing gas and heat co-extraction and hot water circulation.

[0025] After the water in the outer tube 11 flows downward through the deflected water channel 17 and enters the inner cavity of the inner tube 12, the upward power of the water flow drives the spiral blade 22 to rotate, and the active rotating blade drives the lower anti-sedimentation scraper 23 to rotate through the rotating shaft 21, thereby preventing sediment or scaling from accumulating on the blocking plate 16.

[0026] The extraction pipeline 6 and the water injection pipeline 10 in the present invention are also provided with conventional components such as a solenoid valve, a temperature gauge, and a pressure gauge, which are not shown in the figure.

[0027] The above embodiments illustrate the basic principles and features of the present invention, but the above only illustrates the preferred embodiments of the present invention and is not limited to the embodiments. Under the inspiration of this patent, a person skilled in the art can make many forms of deformation and improvement without departing from the scope of protection of the present invention and the claims, which are all within the protection scope of the present invention. Therefore, the patent and protection scope of the present invention shall be subject to the attached claims.

Claims

1. A coaxial casing gas-heat co-production method, characterized in that: The following steps are involved: S1. Drilling a number of extraction holes vertically downward on the ground, the extraction holes passing through the pre-mined coal seam and entering the rock layer below to a certain depth; S2. A coaxial casing extraction heat exchanger is installed in each extraction hole, the upper end of the coaxial casing extraction heat exchanger extends out of the ground, and the lower end of the coaxial casing extraction heat exchanger extends into the rock formation; S3. Arrange the extraction pipeline, electric submersible pump, gas-liquid separation device, heat pump unit and water injection pipeline on the ground, connect the inlet of the electric submersible pump to the outlet of the coaxial casing extraction heat exchanger through the extraction pipeline, connect the outlet of the electric submersible pump to the inlet of the gas-liquid separation device, connect the water outlet of the gas-liquid separation device to the hot water inlet of the heat pump unit, connect the gas outlet of the gas-liquid separation device to the exhaust pipe, and connect the cold water outlet of the heat pump unit to the inlet of the coaxial casing extraction heat exchanger through the water injection pipeline; S4. Start the electric submersible pump, gas-liquid separation device and heat pump unit, and inject low-temperature water into the coaxial casing extraction heat exchanger through the water injection pipeline. The water flows down along the outer channel of the coaxial casing extraction heat exchanger to fully absorb the heat in the coal seam and the rock formation. The electric submersible pump draws the hot water after the heat exchange between the gas in the coal seam and the rock formation upward from the central channel of the coaxial casing extraction heat exchanger. The gas-liquid separation device separates the gas and water. The separated high-temperature water extracts heat through the heat pump unit and is re-injected into the coaxial casing extraction heat exchanger through the water injection pipeline for heat exchange, thereby realizing gas and heat co-production.

2. A coaxial casing gas-heat co-mining method according to claim 1, characterized in that: The coaxial sleeve extraction heat exchanger in step S2 includes an outer tube arranged vertically and an inner tube arranged coaxially inside the outer tube. The inner wall of the outer tube and the outer wall of the inner tube are connected by a plurality of radially arranged cross bars. A plurality of connecting pipes are arranged between the outer tube and the inner tube in a section of the pre-mined coal seam. The two ends of the connecting pipes are respectively connected to the pre-mined coal seam and the inside of the inner tube. A one-way valve adjacent to the inner tube is arranged on the connecting pipe. A plugging plate is provided at the lower end of the outer tube. The edge of the lower end of the inner tube is higher than the upper surface of the plugging plate. The annular channel between the outer tube and the inner tube forms a baffled water passage with the inner cavity of the inner tube. The upper end of the inner tube is the outlet of the coaxial sleeve extraction heat exchanger and is connected to the lower end of the extraction pipeline. The upper end of the outer tube is provided with an annular cover plate which is sleeved on the outside of the inner tube. A water inlet hole is opened on the upper side of the outer tube. The water inlet hole is the inlet of the coaxial sleeve extraction heat exchanger and is connected to the outlet of the water injection pipeline.

3. A coaxial casing gas-heat co-mining method according to claim 2, characterized in that: The diameter of the extraction hole in the pre-mined coal seam section is larger than the outer diameter of the outer pipe, and an annular extraction cavity is formed between the extraction hole in the pre-mined coal seam section and the outer pipe. The diameter of the extraction hole in the rock formation section is equal to the outer diameter of the outer pipe. The outer pipe is made of a material with good thermal conductivity and corrosion resistance, and the inner pipe is made of a material with good thermal insulation.

4. A coaxial casing gas-heat co-mining method according to claim 3, characterized in that: A bracket is provided at the lower end of the inner tube, a rotating shaft is rotatably provided between the bracket and the center of the blocking plate, and a spiral blade located inside the inner tube above the bracket and an anti-sedimentation scraper located inside the outer tube below the bracket are provided on the rotating shaft.

5. A coaxial casing gas-heat co-mining method according to claim 4, characterized in that: The specific process of step S4 is: start the electric submersible pump, the gas-liquid separation device and the heat pump unit, inject low-temperature water into the outer pipe through the water injection pipeline, and the low-temperature water flows down along the outer pipe. During the downward flow, the low-temperature water fully absorbs the heat in the coal seam and the rock formation with the pre-mined coal seam and the rock formation, and the hot water after absorbing heat enters the inner pipe upward from the plugging plate at the bottom of the outer pipe. At the same time, the gas in the pre-mined coal seam is subjected to the upward suction negative pressure of the hot water in the inner cavity of the inner pipe in the annular extraction chamber, and the gas enters the inner pipe through the connecting pipe and the one-way valve to mix with the hot water. The one-way valve prevents The hot water in the inner tube enters the annular extraction chamber along the connecting pipe, and the electric submersible pump extracts the gas in the inner tube and the hot water after heat exchange upward, and the electric submersible pump sends the hot water to the gas-liquid separation device, which separates the gas and water. The separated gas is collected through the exhaust pipe, and the separated high-temperature water enters the heat pump unit again. The heat pump unit extracts the heat from the hot water and stores it or uses it directly. The heat pump unit then re-injects the low-temperature water into the coaxial sleeve extraction heat exchanger through the water injection pipeline for heat exchange, thereby realizing gas and heat co-extraction and hot water circulation.

6. A coaxial casing gas-heat co-mining method according to claim 5, characterized in that: After the water in the outer tube flows downward through the deflected water channel and enters the inner cavity of the inner tube, the upward power of the water flow drives the spiral blades to rotate, and the active rotating blades drive the lower anti-sedimentation scraper to rotate through the rotating shaft, thereby avoiding the accumulation of sediment or scaling on the blocking plate.

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