Methane in-situ burning explosion fracturing auxiliary system based on thermoelectric effect

Abstract

The utility model discloses a methane in-situ burning explosion fracturing auxiliary system based on a thermoelectric effect, and belongs to the field of ultralow-permeability unconventional gas reservoir fracturing extraction. Comprising a U-shaped thermoelectric well and an L-shaped burning and explosion well which are arranged in a stratum, and an electrochemical energy storage station and a burning and explosion work station which are arranged on the ground; a composite assembly is arranged in the U-shaped thermoelectric well, and a P-type semiconductor cable and an N-type semiconductor cable are arranged on the two vertical well sections; the horizontal well section of the L-shaped blasting well is internally provided with a blasting pipe, and the electrochemical energy storage station transmits power to the U-shaped thermoelectric well so as to cool the unconventional gas reservoir to achieve reservoir preliminary fracturing and promote methane desorption; and gas extraction is performed after the blasting operation is completed, and heat energy is collected along with the electrochemical energy storage station through thermoelectric power generation. According to the method, the pyroelectric effect is utilized to strengthen the burning and explosion fracturing operation effect, the burning and explosion heat energy of the reservoir is collected, the gas extraction effect and extraction efficiency are remarkably improved, and the method is suitable for fracturing transformation of unconventional gas reservoirs such as shale gas reservoirs, coal bed gas reservoirs and tight sandstone gas reservoirs.

Description

Technical Field

[0001] The utility model relates to a methane in-situ explosion fracturing auxiliary system based on thermoelectric effect, belonging to the field of gas extraction from unconventional gas reservoirs. Background Art

[0002] Unconventional gas reservoirs mostly exhibit low permeability, with fractures typically at the micro-nanoscale. This results in low methane desorption and slow migration, significantly hindering the efficient development and utilization of the gas. Currently, mainstream natural gas reservoir reconstruction methods include hydraulic fracturing, perforation, and pulse explosion. These methods typically utilize high pressure or impact to promote fracture development and derive complex secondary fracture structures, thereby increasing network conductivity and boosting gas well production. As an emerging water-free fracturing technology, in-situ methane explosion fracturing is gaining widespread attention from industry practitioners and relevant experts and scholars due to its advantages of low pollution, high practicality, and excellent fracturing effects. The difficulty of in-situ methane explosion underground lies in guiding the development and extension of fractures. Specifically, pre-fractures are constructed around the wellbore. The explosive gas then fractures and destroys the rock mass along these pre-fractures or toward the weak planes within them, thereby constructing a larger fracture network. In the past, the method of constructing pre-fractures was to use perforation with high-pressure water or explosives. However, with the increase in mining scale and civilian demand, the problem of operational residues contaminating gas reservoir formations and interfering with gas flow has become increasingly prominent. Utility Model Content

[0003] The purpose of the utility model is to provide a methane in-situ explosion fracturing auxiliary system based on the thermoelectric effect to solve the problems existing in the above-mentioned prior art. The operation process is simple, the methane explosion fracturing effect is enhanced, and the heat energy released by the explosion is recovered and can be recycled.

[0004] To achieve the above-mentioned purpose, the utility model discloses a methane in-situ explosion fracturing auxiliary system based on thermoelectric effect, which includes a thermoelectric system and an explosion system arranged in an unconventional gas reservoir.

[0005] The thermoelectric system includes a ceramic column 8 for exchanging heat horizontally arranged on the surface of an unconventional gas reservoir, a composite component 3 arranged in an implementation stratum, and an electrochemical energy storage station 10. The ceramic column 8 is arranged by a bracket 9, and an electrode ball 7 is provided at both ends of the ceramic column 8. A U-shaped thermoelectric well 1 is provided in the implementation stratum below the ceramic column 8, wherein a composite component 3 for releasing cold and heat is provided in the lowest horizontal section of the U-shaped thermoelectric well 1, and the head and tail ends of the composite component 3 are respectively connected to the two ends of the ceramic column 8 through a P-type semiconductor cable 5 and an N-type semiconductor cable 6 passing through the U-shaped thermoelectric well 1, and an insulating protective sleeve 4 is provided on the outside of the P-type semiconductor cable 5 and the N-type semiconductor cable 6, wherein the electrode balls 7 at both ends of the ceramic column 8 are respectively connected to the electrochemical energy storage station 10 for storage and discharge through wires, and the electrochemical energy storage station 10 is connected to the power grid 11;

[0006] The blasting system includes a blasting pipe 13 and a blasting workstation 14 horizontally arranged in the implementation formation. The blasting pipe 13 is located directly below the composite assembly 3. The blasting pipe 13 and the composite assembly 3 are located in two different horizontal planes above and below and do not contact each other. The blasting pipe 13 and the two groups of composite assemblies 3 are in a cross-shaped state when viewed from a top-down angle. The blasting pipe 13 is connected to the blasting workstation 14 through a flexible pipe 12, wherein a downhole safety valve 15 is provided at the connecting end of the flexible pipe 12 and the blasting pipe 13, and a ground safety valve 16 is provided at the connecting end of the flexible pipe 12 and the blasting workstation 14.

[0007] Furthermore, the bracket 9 is a trapezoidal high-temperature resistant alloy bracket 9.

[0008] Furthermore, the composite component 3 includes an electrode core 303 , a foam metal shell 301 is provided on the outside of the electrode core 303 , a ceramic interlayer 302 is provided between the foam metal shell 301 and the electrode core 303 , wherein the electrode core 303 is a spherical structure located at both ends of the composite component 3 .

[0009] Furthermore, the electrode ball 7 and the electrode core 303 are both made of graphene material.

[0010] Furthermore, the ceramic column 8 and the ceramic interlayer 302 are both zirconium diboride ceramics.

[0011] Furthermore, the foam metal layer is foam nickel alloy.

[0012] Furthermore, the ceramic columns 8 and composite components 3 of the thermoelectric system each include two groups arranged in parallel. Two groups of U-shaped thermoelectric wells 1 are arranged in parallel in the implementation formation. The bottom end of each group of U-shaped thermoelectric wells 1 is provided with a horizontal well section for accommodating the composite component 3. Multiple composite components 3 are arranged as needed and connected end to end to cover the entire horizontal well section. Vertical well sections for accommodating P-type semiconductor cables 5 and N-type semiconductor cables 6 are arranged in parallel on both sides of the horizontal well section. The length of the horizontal well section of the U-shaped thermoelectric well 1 should be greater than the ceramic column 8, and ensure that the ceramic column 8 is between the wellheads of the U-shaped thermoelectric well 1 on the bottom surface.

[0013] Furthermore, the blasting pipe 13 is set in the implementation formation through the L-shaped blasting well 2. The L-shaped blasting well 2 includes a horizontal well section for setting the blasting pipe 13 and a horizontal well section for setting the flexible pipe 12. The L-shaped blasting well 2 includes two groups arranged in parallel. Each group of L-shaped blasting wells 2 includes a blasting pipe 13 and a flexible pipe 12. The distance between the two groups of L-shaped blasting wells 2 is 20 to 30 meters. At the same time, at least two U-shaped thermoelectric wells 1 are continuously arranged in parallel in the forward direction of the horizontal well section of the L-shaped blasting well 2, and ensure that the horizontal well section of the U-shaped thermoelectric well 1 is perpendicular to the horizontal well section cross-section of the L-shaped blasting well 2.

[0014] Beneficial Effects: This method utilizes the thermoelectric effect to enhance explosive fracturing operations and capture reservoir thermal energy, significantly improving gas extraction effectiveness and efficiency. It is suitable for fracturing of unconventional gas reservoirs, such as shale gas, coalbed methane, and tight sandstone gas reservoirs. This method produces large volumes, leaves minimal residual pollution, and does not interfere with gas flow. Furthermore, it can directly generate electricity, converting poorly burned gas directly into grid-connected power for easy transport. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of a U-shaped thermoelectric well in the methane in-situ explosion fracturing auxiliary system based on the thermoelectric effect of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of an L-shaped explosion well in the methane in-situ explosion fracturing auxiliary system based on the thermoelectric effect of the present invention;

[0017] Figure 3 This is a schematic diagram of the structure of the composite components in the methane in-situ explosion fracturing auxiliary system based on the thermoelectric effect of the present invention;

[0018] Figure 4 This is a schematic diagram of the drilling distribution of U-shaped thermoelectric wells and L-shaped explosion wells in the methane in-situ explosion fracturing auxiliary system based on the thermoelectric effect of the present invention.

[0019] In the figure: 1-U-type thermoelectric well; 2-L-type explosion well; 3-composite component; 4-insulating protective cover; 5-P-type semiconductor cable; 6-N-type semiconductor cable; 7-electrode ball; 8-ceramic column; 9-bracket; 10-electrochemical energy storage station; 11-power grid; 12-flexible pipe; 13-explosion pipe; 14-explosion workstation; 15-downhole safety valve; 16-ground safety valve; 301-foam metal shell; 302-ceramic interlayer; 303-electrode core. DETAILED DESCRIPTION

[0020] The following is a further description of the embodiments of the present invention with reference to the accompanying drawings:

[0021] like Figure 1 and Figure 2As shown, the utility model discloses a methane in-situ explosion fracturing auxiliary system based on thermoelectric effect, comprising a U-shaped thermoelectric well 1 and an L-shaped explosion well 2 set in the formation, and an electrochemical energy storage station 10 and an explosion workstation 14 assigned to the ground; composite components 3 are continuously installed in the horizontal well section of the U-shaped thermoelectric well 1 to cover the entire horizontal well section, and P-type semiconductor cables 5 and N-type semiconductor cables 6 are respectively arranged in the two vertical well sections; electrode balls 7 are embedded at both ends of the ceramic column 8; the P-type semiconductor cable 5 and the N-type semiconductor cable 6 are respectively in contact with the electrode balls 7 at both ends of the ceramic column 8 on the ground; the L-shaped explosion well 1 is provided with a plurality of holes, each containing a plurality of holes, and a plurality of holes. A blasting pipe 13 is installed in the horizontal section of well 2, and is connected to a flexible pipe 12 arranged in the vertical section via a downhole safety valve 15; a ground safety valve 16 is provided between the blasting workstation 14 and the flexible pipe 12; the electrochemical energy storage station 10 transmits electricity to the U-shaped thermoelectric well 1 to cool the unconventional gas reservoir to achieve initial fracturing of the reservoir and promote methane desorption; when the temperature in the blasting well drops below -160°C, power supply is stopped, and methane in-situ blasting fracturing operations are carried out to transform the unconventional gas reservoir; after the blasting operation is completed, gas extraction is carried out, accompanied by the electrochemical energy storage station 10 collecting heat energy through temperature difference power generation.

[0022] like Figure 3 As shown, the composite component 3 comprises three layers from the inside to the outside, including a foam metal shell 301, a ceramic interlayer 302 and an electrode core 303. The electrode core 303 extends to both ends of the composite component 3 to form a spherical shape; the electrode ball 7 is half-embedded in both ends of the ceramic column 8; the electrode ball 7 and the electrode core 303 are both preferably graphene materials; the bracket 9 is a preferably trapezoidal high-temperature resistant alloy bracket 9; the ceramic column 8 and the ceramic interlayer 302 are both preferably zirconium diboride ceramics; the foam metal layer of the composite component 3 is a preferably foam nickel alloy.

[0023] like Figure 4 As shown, the horizontal sections of the L-type combustion and explosion well 2 and the U-type thermoelectric well 1 are perpendicular to each other in the reservoir space, and the horizontal section of the L-type combustion and explosion well 2 is higher than the horizontal section of the U-type thermoelectric well 1; the vertical section of the U-type thermoelectric well 1 and the vertical section of the L-type combustion and explosion well 2 are parallel to each other in the reservoir space, and the wellheads are arranged in a finished product shape on the surface; the L-type combustion and explosion well 2 adopts a double-well parallel arrangement with a spacing of 20 to 30 meters between the two wells, and at the same time, at least two U-type thermoelectric wells 1 are continuously arranged in parallel in the forward direction of the horizontal section of the L-type combustion and explosion well 2.

[0024] like Figure 1 、 Figure 2 and Figure 4 As shown in FIG9 , a working method of a methane in-situ explosion fracturing auxiliary system based on thermoelectric effect, the steps are as follows:

[0025] S1 determines the formation and distance between the U-shaped thermal power well 1 and the L-shaped explosion well 2 based on the geological background of the reservoir area, and directionally drills from the ground into the reservoir area and uses dry airflow for cleaning;

[0026] S2 continuously installs composite assemblies 3 in the horizontal section of the U-shaped thermoelectric well 1 to cover the entire horizontal section. P-type semiconductor cables 5 and N-type semiconductor cables 6 are respectively arranged in the two vertical sections of the U-shaped thermoelectric well 1. Brackets 9 are set up on the ground to fix ceramic columns 8. The P-type semiconductor cables 5 and N-type semiconductor cables 6 contact electrode balls 7 at both ends of the ceramic columns 8 on the ground. The P / N-type semiconductor cables 6 are covered with an insulating protective sleeve 4.

[0027] S3 installs a blasting pipe 13 in the horizontal section of the L-shaped blasting well 2, which is connected to the flexible pipe 12 arranged in the vertical section via a downhole safety valve 15. A ground safety valve 16 is installed between the blasting workstation 14 and the flexible pipe 12. The blasting pipe 13 has a built-in igniter, a temperature and pressure sensor, and a methane concentration detector.

[0028] S4 transmits electricity to the composite assembly 3 in the U-shaped thermoelectric well 1 through the power grid 11 connected to the electrochemical energy storage station 10. The potential difference drives the migration of electrons. Downhole, the electrons move from the P-type semiconductor cable 5 to the N-type semiconductor cable 6 through the electrode core 303 of the composite assembly 3. The electrons absorb heat and transition to a high-energy state. The electrode core 303 exchanges heat with the ceramic interlayer 302, and the ceramic interlayer 302 absorbs heat from the reservoir. On the ground, when the electrons flow from the N-type semiconductor cable 6 to the P-type semiconductor cable 5 through the electrode ball 7, the electrons release heat and transition to a low-energy state. The electrode ball 7 exchanges heat with the ceramic column 8, and the ceramic column 8 releases heat to the atmosphere. The temperature of the reservoir area is reduced, forming extensive pre-cracks in the reservoir and promoting methane desorption.

[0029] S5 When the temperature detected by the temperature sensor installed in the horizontal well section of the L-shaped explosion well 2 is lower than -160°C, the electrochemical energy storage station 10 stops transmitting power, and then the explosion workstation 14 controls the explosion pipe 13 in the L-shaped explosion well 2 to perform methane in-situ explosion fracturing operation. The high-temperature and high-pressure gas generated by the explosion operation is guided through the sieve holes of the explosion pipe 13 to form directional cracks, which extend, expand, and connect to the pre-cracks to form a crack network;

[0030] After the S6 blasting operation, heat diffuses and the temperature of the reservoir area rises. A temperature difference occurs between the ground end and the downhole end of the P-type semiconductor cable 5 and the N-type semiconductor cable 6. The temperature of the downhole end of the P-type semiconductor cable 5 and the N-type semiconductor cable 6 is generally higher than that of the ground end. The direction of the thermoelectric potential of the P-type semiconductor cable 5 is from the ground end to the downhole end, and the direction of the thermoelectric potential of the N-type semiconductor cable 6 is from the downhole end to the ground end. The electrochemical energy storage station 10 is responsible for energy storage, thereby forming a complete circuit. Electrons move under the thermoelectric potential to generate current. The electrochemical energy storage station 10 stores electricity or transmits electricity to the power grid 11. At the same time, the blasting workstation 14 extracts gas.

[0031] S7 When the gas content in the L-type explosion well 2 decreases or the gas production is insufficient, the extraction requirements can be met by circulating steps S4 to S6.

[0032] Here's how it works:

[0033] The electrochemical energy storage station 10 transmits electricity to the composite component 3 in the U-shaped thermoelectric well 1, and uses the ceramic column 8 to exchange heat and release cold in the unconventional gas reservoir, thereby initially fracturing the unconventional gas reservoir and promoting methane desorption through low temperature; when the temperature near the explosion tube 13 drops below -160°C, the power supply is stopped, and the explosion tube 13 is used to perform in-situ methane explosion fracturing operations to transform the unconventional gas reservoir; after the explosion is completed, gas extraction is carried out, and at the same time, the electrochemical energy storage station 10 collects heat energy through temperature difference power generation.

[0034] Power is transmitted to the U-shaped thermoelectric well 1 to cool the gas reservoir through the Peltier effect, creating pre-cracks distributed around the horizontal well section of the L-shaped explosion well 2; the thermoelectric cooling reservoir promotes methane desorption in the reservoir, providing more sufficient in-situ methane; ultra-low temperature reduces the strength of the reservoir rock mass and enhances the explosion fracturing effect; temperature difference power generation is used to store electrical energy and collect heat dissipated by the explosion; ultra-low temperature and ultra-high temperature cycle to fracture the reservoir and improve the reservoir seepage capacity.

Claims

1. A methane in-situ explosion fracturing auxiliary system based on thermoelectric effect, characterized by: Including thermal power systems and explosion systems installed in unconventional gas reservoirs, The thermoelectric system comprises a ceramic column (8) for exchanging heat and arranged horizontally on the surface of an unconventional gas reservoir, a composite component (3) arranged in an implementation stratum, and an electrochemical energy storage station (10), wherein the ceramic column (8) is arranged by a bracket (9), and electrode balls (7) are respectively arranged at both ends of the ceramic column (8), and a U-shaped thermoelectric well (1) is arranged in the implementation stratum below the ceramic column (8), wherein a composite component (3) for releasing cold and heat is arranged in the horizontal section at the bottom of the U-shaped thermoelectric well (1), and the head and tail ends of the composite component (3) are respectively connected to the two ends of the ceramic column (8) through a P-type semiconductor cable (5) and an N-type semiconductor cable (6) passing through the U-shaped thermoelectric well (1), and the outer sides of the P-type semiconductor cable (5) and the N-type semiconductor cable (6) are both provided with an insulating protective sleeve (4), wherein the electrode balls (7) at both ends of the ceramic column (8) are respectively connected to the electrochemical energy storage station (10) for storing and discharging through wires, and the electrochemical energy storage station (10) is connected to the power grid (11); The blasting system comprises a blasting pipe (13) and a blasting workstation (14) horizontally arranged in the implementation stratum, wherein the blasting pipe (13) is located directly below the composite assembly (3), the blasting pipe (13) and the composite assembly (3) are located at two different horizontal planes and do not contact each other, and the blasting pipe (13) and the two groups of composite assemblies (3) are in a cross-shaped state when viewed from above, and the blasting pipe (13) is connected to the blasting workstation (14) through a flexible pipe (12), wherein a downhole safety valve (15) is provided at the connection end between the flexible pipe (12) and the blasting pipe (13), and a ground safety valve (16) is provided at the connection end between the flexible pipe (12) and the blasting workstation (14).

2. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 1 is characterized in that: The bracket (9) is a trapezoidal high-temperature resistant alloy bracket (9).

3. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 1 is characterized in that: The composite component (3) comprises an electrode core (303), a foam metal shell (301) is provided on the outside of the electrode core (303), a ceramic interlayer (302) is provided between the foam metal shell (301) and the electrode core (303), wherein the electrode core (303) is located at both ends of the composite component (3) and has a spherical structure.

4. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 3 is characterized by: The electrode ball (7) and the electrode core (303) are both made of graphene material.

5. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 3 is characterized by: The ceramic column (8) and the ceramic interlayer (302) are both zirconium diboride ceramics.

6. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 3 is characterized by: The foam metal shell (301) is a foam nickel alloy.

7. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 1 is characterized by: The ceramic columns (8) and composite components (3) of the thermoelectric system are both arranged in parallel. Two groups of U-shaped thermoelectric wells (1) are arranged in parallel in the implementation stratum. The bottom end of each group of U-shaped thermoelectric wells (1) is provided with a horizontal well section for accommodating the composite component (3). Multiple composite components (3) are arranged as needed and connected end to end to cover the entire horizontal well section. Vertical well sections for accommodating P-type semiconductor cables (5) and N-type semiconductor cables (6) are arranged in parallel on both sides of the horizontal well section. The horizontal well section length of the U-shaped thermoelectric well (1) should be greater than the ceramic column (8), and ensure that the ceramic column (8) is between the wellheads of the U-shaped thermoelectric well (1) on the bottom surface.

8. The methane in-situ explosion fracturing auxiliary system based on thermoelectric effect according to claim 7 is characterized in that: The blasting pipe (13) is set in the implementation formation through the L-shaped blasting well (2). The L-shaped blasting well (2) includes a horizontal well section for setting the blasting pipe (13) and a horizontal well section for setting the flexible pipe (12). The L-shaped blasting well (2) includes two groups of parallel sets, and each group of L-shaped blasting wells (2) includes a blasting pipe (13) and a flexible pipe (12). The two groups of L-shaped blasting wells (2) are spaced 20 to 30 meters apart. At the same time, at least two U-shaped thermoelectric wells (1) are continuously arranged in parallel in the forward direction of the horizontal well section of the L-shaped blasting well (2), and it is ensured that the horizontal well section of the U-shaped thermoelectric well (1) and the horizontal well section of the L-shaped blasting well (2) are perpendicular to each other.

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