Cracking and yield increasing device for coal bed gas ground well

Abstract

The utility model relates to the technical field of coal bed gas exploitation, and discloses a coal bed gas ground well fracturing and yield increasing device which comprises fracturing main body units, fracturing device connecting pieces, variable connecting pieces, a drainage pipe, a hole sealing device and a cable, the fracturing device connecting pieces are installed between the fracturing main body units, the variable connecting pieces are installed at the upper ends and the lower ends of the fracturing main body units, and the drainage pipe is installed between the fracturing main body units. The drainage pipe is installed on the surface of the variable connecting piece, the hole sealing device is installed on the surface of the drainage pipe, and the cable is electrically connected to the fracturing body unit. The coal bed gas ground well fracturing yield increasing device is convenient, stable, safe and efficient for the CO2 fracturing coal bed gas control technology, the direct acting radius of the CO2 fracturing technology is 1.5-5 m, the influence radius can reach 15 m, the gas extraction drilling work amount is reduced by 30%-60%, the duration time of high-concentration and large-flow gas extraction is long, the gas extraction lower limit is effectively reduced, and the gas extraction efficiency is improved. The method is suitable for coal seams with different firmness coefficients, and has a better application effect in coal seams with strong gas adsorbability.

Description

Technical Field

[0001] This utility model relates to the field of coalbed methane extraction technology, specifically to a fracturing and production enhancement device for coalbed methane surface wells. Background Technology

[0002] Mine gas not only poses a significant threat to coal production safety but also has a strong negative impact on the environment. The main component of methane is CH4, and existing data shows that CH4's ozone-depleting capacity is equivalent to 7 times that of CO2, and its greenhouse effect is equivalent to 21 times that of CO2. At the same time, CH4 is a clean, high-calorific-value energy source. High-flow-rate, high-concentration methane extraction can significantly improve the comprehensive utilization rate of methane. Methane extraction is the fundamental approach and the most important means of controlling mine gas.

[0003] Since most coal seams in my country's mines are low-permeability, both underground and surface well extraction methods suffer from long extraction cycles and rapid methane decay. Therefore, improving the efficiency of methane extraction from low-permeability coal seams has become a pressing issue, necessitating the development of new, more cost-effective, and efficient methane extraction technologies and processes to increase methane concentration and extraction volume. Utility Model Content

[0004] The purpose of this invention is to provide a fracturing and production enhancement device for coalbed methane surface wells to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a fracturing and production enhancement device for coalbed methane surface wells, comprising a fracturing main unit, fracturing device connectors, adapters, a drainage pipe, a sealing device, and a cable. The fracturing main unit consists of a main pressure boosting valve, a flow guide valve, etc. Each unit has an outer diameter of 50mm and a length of 2m, and is filled with 1.5kg of liquid carbon dioxide. A phase change is triggered by heating through a temperature control device. When the temperature is >31℃, the liquid carbon dioxide vaporizes and expands 600 times within 40ms, generating a pulse pressure of 50-150MPa. The flow guide valve guides the gas to be released in a directional manner, forming a complex fracture network at the nm-cm level, with a direct effect radius of 1.5-5m and an influence radius of up to 15m.

[0006] Preferably, the fracturing device connector is used to connect multiple fracturing main units in series to support fracturing of a single coal seam of full thickness, such as 2-8m coal seams or segmented fracturing of multiple coal seams.

[0007] Preferably, the adapter uses a 73mm to 50mm metal sealing joint to connect the cracking unit and the Φ73mm drain pipe to ensure sealing.

[0008] Preferably, the sealing device uses an expandable sealing material to seal within a 5m range above and below the cracking unit, with a length ≥2m, a reserved Φ8mm cable hole, a sealing pressure ≥10MPa, and can withstand 10³~10 4 MPa / s boost rate.

[0009] Preferably, the two-core cable is used for one-time cracking, while the four-core or higher cable supports multiple cracking operations, with independent control of cracking units at different layers.

[0010] Compared with the prior art, the beneficial effects of this utility model are:

[0011] 1. This coalbed methane surface well fracturing and production enhancement device is a convenient, stable, safe and efficient technology for CO2-induced fracturing coalbed methane control.

[0012] 2. The fracturing and production enhancement device for coalbed methane surface wells has a direct effect radius of 1.5 to 5 meters and an influence radius of up to 15 meters due to CO2 fracturing technology.

[0013] 3. This coalbed methane surface well fracturing and production enhancement device reduces the amount of gas drainage drilling work by 30% to 60%, and allows for long-term high-concentration, high-flow-rate gas drainage, effectively lowering the lower limit of gas drainage.

[0014] 4. This fracturing and production enhancement device for coalbed methane surface wells is suitable for coal seams with different strength coefficients, and its application effect is even better in coal seams with strong gas adsorption. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the installation of the equipment of this utility model;

[0016] Figure 2 This is a schematic diagram of the internal structure of the fracture-inducing main unit of this utility model.

[0017] In the diagram: 1. Main fracturing unit; 101. Main pipe; 102. Pressure boosting valve; 103. Flow guide valve; 104. Temperature control device; 105. Control system; 106. Liquid carbon dioxide; 2. Fracturing device connector; 3. Adapter; 4. Drain pipe; 5. Sealing device; 6. Cable. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] Please see Figure 1-2This utility model provides the following technical solution: a fracturing and production enhancement device for coalbed methane surface wells, comprising a fracturing main unit 1, a fracturing device connector 2, a transformer 3, a drainage pipe 4, a sealing device 5, and a cable 6. The fracturing device connector 2 is fixedly installed between the fracturing main units 1. The transformer 3 is fixedly installed at the upper and lower ends of the fracturing main unit 1. The drainage pipe 4 is fixedly installed on the surface of the transformer 3. The sealing device 5 is fixedly installed on the surface of the drainage pipe 4. The cable 6 is electrically connected to the fracturing main unit 1.

[0020] The fracturing main unit 1 comprises a main pipe 101, a booster valve 102, a flow guide valve 103, a temperature control device 104, a control system 105, and liquid carbon dioxide 106. The booster valve 102 is fixedly connected to the side of the main pipe 101, the flow guide valve 103 is fixedly connected to the other side of the main pipe 101, the temperature control device 104 is integrated inside the main pipe 101, the control system 105 is fixedly connected to the inside of the main pipe 101, and the inside of the main pipe 101 contains liquid carbon dioxide 106.

[0021] The above technical solution has the following two embodiments:

[0022] Example 1:

[0023] Single-coal-seam fracturing is suitable for single thick coal seams, such as low-permeability coal seams with a thickness of 6m and a firmness coefficient f=0.5. The goal is to rapidly increase the concentration and flow rate of gas extraction from a single coal seam.

[0024] Based on the coal seam thickness, three fracturing main units 1 were selected and connected in series via fracturing device connectors 2, with a total length of 6m, covering the entire coal seam (well depth 280-286m). The fracturing units were sealed to the Φ73mm drainage pipe 4 via a 73mm to 50mm adapter 3. The unit was lowered to the middle of the target coal seam (well depth 283m) using a drilling rig. Sealing devices 5 were installed 5m above and below the fracturing units (well depths 278m and 288m), using expandable rubber material for sealing, with a sealing length of 2m on each side. A Φ8mm cable hole was reserved at the upper end for inserting a double-core armored cable 6. The resistance of the circuit was tested on the ground and found to be 350Ω (<500Ω, meeting the start-up conditions), confirming that the sealing performance was good.

[0025] In summary, by triggering the temperature control device 104 through the ground control system, liquid carbon dioxide 106 is heated and vaporized (temperature > 31℃), generating a 100MPa pulse pressure within 40ms, which completes the fracturing of the coal seam in one go. After fracturing, radial main fractures and nm-cm scale network fractures are formed, with a direct effect radius of 4m and an influence radius of 12m. After holding the pressure for 1 hour, the borehole pressure drops from 9MPa to 0.7MPa. After the device is removed, it is connected to the extraction system, and the gas extraction concentration increases from 12% to 40%, and the flow rate increases from 0.8m³ / min to 2.5m³ / min.

[0026] Example 2:

[0027] Multi-coal-seam fracturing is suitable for complex geological conditions where three thin coal seams are stacked, such as well depths of 200m, 220m, and 240m, each with a thickness of 2m, an interlayer spacing of 20m, and significant differences in gas content (8m³ / t, 12m³ / t, and 6m³ / t, respectively).

[0028] For the three coal seams, three fracturing main units 1 are selected to correspond to each seam. They are connected in sections by four-core armored cables 6. Each seam is controlled independently, with a total length of 3×2m=6m. First, the first fracturing unit, corresponding to the 200m coal seam, is lowered to a depth of 199-201m and connected to the drainage pipe 4 through the adapter 3. Then, the second (219-221m) and third (239-241m) seams are lowered in sequence. Each unit is connected in series through the fracturing device connector 2. The upper and lower 5m ranges of each fracturing unit are sealed to ensure pressure isolation between the seams.

[0029] Adjust the fracturing parameters according to the gas content of each layer:

[0030] First layer (200m, 8m³ / t): Pressure 120MPa, reaction time 30ms;

[0031] Second layer (220m, 12m³ / t): Pressure 150MPa, reaction time 25ms;

[0032] Third layer (240m, 6m³ / t): pressure 90MPa, reaction time 40ms.

[0033] First fracturing: The first fracturing unit is activated, generating a pressure of 120 MPa, forming a fracture network centered on this layer, displacing adsorbed gas.

[0034] Two hours later: the second fracturing unit is activated, generating a pressure of 150 MPa. The CO2 density difference is used to drive the residual gas in the first layer upward, while forming denser cracks in the second layer.

[0035] Two hours later: the third fracturing unit is activated, generating a pressure of 90 MPa to form a cross-layer interconnected fracture network, expanding the overall impact range.

[0036] In summary, after the three-layer fracturing is completed, the pressure is maintained for 1 hour until the total borehole pressure drops to 0.6 MPa. The equipment is then removed and gas extraction is carried out uniformly. The total gas extraction volume is increased by 85% compared with the traditional process.

[0037] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A coal bed methane surface well fracturing stimulation device, comprising a fracturing main unit (1), a fracturing device connector (2), a variable connector (3), a drainage pipe (4), a hole sealing device (5) and a cable (6), characterized in that: The fracturing device connector (2) is fixedly installed between the fracturing main unit (1), the adapter (3) is fixedly installed at the upper and lower ends of the fracturing main unit (1), the drain pipe (4) is fixedly installed on the surface of the adapter (3), the sealing device (5) is fixedly installed on the surface of the drain pipe (4), and the cable (6) is electrically connected to the fracturing main unit (1). The fracturing main unit (1) comprises a main pipe (101), a booster valve (102), a flow guide valve (103), a temperature control device (104), a control system (105), and liquid carbon dioxide (106). The booster valve (102) is fixedly connected to the side of the main pipe (101), the flow guide valve (103) is fixedly connected to the other side of the main pipe (101), the temperature control device (104) is integrated inside the main pipe (101), the control system (105) is fixedly connected to the inside of the main pipe (101), and the inside of the main pipe (101) contains liquid carbon dioxide (106).

2. The coal bed methane surface well fracturing and stimulation device of claim 1, wherein: The sealing device (5) uses expandable sealing material, with a sealing length of not less than 2m, a cable perforation hole with a diameter of ≤8mm reserved at the upper end, a sealing pressure of ≥10MPa, and can withstand 10³~10 MPa when cracking occurs. 4 The boost rate is MPa / s.

3. The coal bed methane surface well fracturing and stimulation device of claim 1, wherein: The cable (6) is a two-core or four-core or more armored cable.

4. The coal bed methane surface well fracturing and stimulation device of claim 1, wherein: The adapter (3) is a 73mm to 50mm metal sealing joint, which is sealed to the cracking main unit (1) with an outer diameter of 50mm and the drain pipe (4) with an outer diameter of 73mm. The connection is filled with sealant to ensure that there is no leakage during the cracking process.

5. The coal bed methane surface well fracturing and stimulation device of claim 1, wherein: The main fracturing unit (1) is filled with 1.5 kg of liquid carbon dioxide (106) per unit. A single fracturing operation generates a pulse pressure of 50-150 MPa, a reaction time of 20-40 ms, a direct action radius of 1.5-5 m, and an influence radius of up to 15 m.

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