Foam fracturing and fire blast synergistic advanced presplitting roof caving method for coal mine

Abstract

The invention discloses a coal mine foam fracturing and fire blast synergistic advanced presplitting roof caving method. The method comprises the following steps that S1, drilling is constructed; constructing a drill hole in a proper position of the top rock stratum of the coal seam; s2, preparing a foam fracturing fluid; the preparation and foaming of the foam fracturing fluid are realized through the foam preparation device, and combustible gas is injected during foaming; s3, fracturing is carried out; a fracturing system is arranged at the drill hole, foamed foam fracturing fluid is injected into the drill hole through the fracturing system, and a crack is formed; s4, blasting and caving; and when the hole fracture of the roof rock stratum meets the fire blast requirement, injection of the foam fracturing fluid is stopped, and then ignition and detonation are conducted. Foam fracturing is combined with burning and explosion, the foam fracturing enables a roof rock stratum to generate a large number of hole cracks, the strength of the roof rock stratum is weakened, a burning and explosion space is provided for the burning and explosion technology, the safety of caving of a mining working face is guaranteed, advanced caving can be achieved, and the safety problem caused by the fact that a hard roof is difficult to fall in a goaf is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of foam fracturing and explosion, and in particular relates to a coal mine foam fracturing and explosion coordinated advance pre-cracking and roof caving method. Background Art

[0002] Coal has long been a dominant force in my country's energy consumption structure. Under the complex and ever-changing situation of the international energy market, as one of my country's basic energy sources, its stable supply is of great strategic significance for ensuring national energy security. Ensuring the safe production of coal resources is the premise and guarantee for promoting the sustainable development of the industry. In the mining face, the stability of the roof directly affects the continuity of mining work. The problem of the hard roof being difficult to drop has become a major safety hazard in the mining face operation. This will not only affect the continuous advancement of the mining work on the face, but also affect a series of subsequent production links such as transportation and ventilation.

[0003] In order to improve the stability of the roof, blasting technology is widely used at home and abroad to promote roof collapse, that is, the shock wave and stress wave generated by the explosion of explosives act on the roof rock, destroying the integrity of the rock, causing the roof to collapse under the dual action of its own gravity and blasting force. The main purpose of doing this is to prevent a large area of ​​the roof from being suspended in the air and avoid sudden collapses that cause safety accidents. It is also beneficial to the treatment of goafs and subsequent mining work. Since blasting has a strong shock wave, it has a better effect in breaking the rock structure. On the other hand, traditional blasting has poor controllability of the blasting range. When a local area of ​​the roof collapses or deforms greatly due to blasting, the adjacent roof rock blocks may collapse in a chain reaction due to the loss of the original support. It is difficult to control the blasting range, affecting the safety of underground workers and equipment operation. Summary of the invention

[0004] The present invention proposes a method for pre-cracking and roof caving in a coal mine by coordinating foam fracturing with blasting. The foam fracturing technology is combined with the blasting technology. Foam fracturing causes a large number of pores and cracks to form in the roof rock strata, which not only weakens the strength of the roof rock strata, but also provides blasting space for the blasting technology, thereby ensuring the safety of roof caving in the mining working face, achieving advanced roof caving, and avoiding safety problems caused by the difficulty in caving the hard roof in the goaf.

[0005] To this end, the technical solution adopted by the present invention is: a coal mine foam fracturing and explosion coordinated advance pre-cracking and top caving method, comprising the following steps:

[0006] S1: Construction drilling: According to the characteristics of the roof rock layer and the requirements of the coal mining process, a drilling hole is constructed at a suitable position of the top rock layer of the coal seam to facilitate the transportation and pressure increase of the foam fracturing fluid;

[0007] S2: preparing foam fracturing fluid; preparing and foaming the foam fracturing fluid through a foam preparation device, and injecting combustible gas during the foaming of the foam fracturing fluid;

[0008] S3: Fracturing: a fracturing system is arranged at the borehole, and the foamed fracturing fluid is injected into the borehole through the fracturing system to destroy the inside of the roof rock layer to form cracks of a certain size, and at the same time, the foamed fracturing fluid is allowed to enter the cracks under the action of the fracturing system;

[0009] S4: Explosion and roof release; when the pores and cracks in the roof rock strata meet the explosion requirements, stop injecting the foam fracturing fluid and then ignite and detonate.

[0010] As a preferred embodiment of the above scheme, the foam fracturing fluid comprises the following components in parts by weight: 5-6 parts of diesel, 0.5-1 parts of guar gum, 1-2 parts of ammonium nitrate and 1-2 parts of rock cuttings.

[0011] Further preferably, the rock cuttings are obtained by crushing broken rock blocks during drilling, and the particle size of the rock cuttings is 40-80 mesh.

[0012] Further preferably, the foam preparation device includes a preparation container for achieving component mixing and a foaming container for achieving foaming of the foam fracturing fluid, the foaming container can be in a sealed state, an electric stirring device is arranged in the foaming container, a vacuum hole for achieving a vacuum state of the foaming container and an air inlet hole for achieving the intake of combustible gas are arranged in the foaming container, the air inlet hole is arranged at the bottom of the foaming container, and a feeding port is also arranged in the foaming container, the vacuum hole is connected to a vacuum pump through a vacuum pipeline, the air inlet hole is connected to a combustible gas injection system through an air inlet pipeline, both the vacuum tube and the air inlet pipeline are provided with a one-way valve, and the combustible gas injection system includes a storage bottle containing combustible gas, a pressure-stabilizing bottle and a pressure gauge arranged on the air inlet pipeline.

[0013] Further preferably, the preparation step in S2 includes: putting diesel into a preparation container, then adding guar gum and stirring until it is completely dissolved, then adding ammonium nitrate and stirring until it is evenly dissolved, then sealing the foaming container, and then extracting the air in the foaming container by a vacuum pump, and then transferring the dissolved solution to the foaming container, and then stirring it by an electric stirring device, while injecting combustible gas through the air inlet and adding rock cuttings through the feeding port, and adding the rock cuttings in multiple times until the foaming is completed.

[0014] More preferably, the combustible gas is acetylene.

[0015] Further preferably, the fracturing system includes a fracturing operation control system, a high-pressure pump, a fracturing pipeline, an electric sparking device and a storage container. The storage container can be in a sealed state and is used to store the foamed foam fracturing fluid. One end of the fracturing pipeline is connected to the storage container, and the other end can extend into the borehole. The high-pressure pump is arranged on the fracturing pipeline, and the electric sparking connecting line of the electric sparking device is laid in the borehole together with the high-pressure pipeline. The fracturing operation control system is electrically connected to the high-pressure pump and the electric sparking device, and is used to control whether the high-pressure pump is working and the working pressure, and to control the operation of the electric sparking device.

[0016] Beneficial effects of the present invention:

[0017] 1) Foam fracturing creates a large number of pores and cracks inside the rock formation, which not only destroys the integrity of the rock formation and reduces its strength, but also increases the distribution range of the foam liquid in the cracks, making the explosion source mainly composed of combustible gas widely distributed. Since foam fracturing can control the range and pore size of the fracturing pores and cracks through conditions such as drilling depth and fracturing pressure, foam fracturing is controllable, thereby ensuring the accuracy of the explosion and caving process.

[0018] 2) After fracturing, the foam fracturing fluid is ignited and detonated. Since it is filled with combustible gas, an explosion can occur, which allows the boreholes and cracks to further expand and improve the connectivity of the cracks under the combined effects of mechanical, thermochemical and vibration pulses. The shock waves generated by the explosion can vibrate the roof rock formation, thereby achieving the purpose of advanced roof collapse and ensuring the safe operation of the coal mining face.

[0019] 3) The present invention gives full play to the controllability of the fracturing range of foam fracturing and the high efficiency of high-energy explosion, greatly improves the controllability of the explosion range and blasting effect, effectively controls the stability of the roof rock layer, reduces the occurrence of accidents such as roof collapse and pressure, and provides a safer environment for coal mining operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the coordinated operation of foam fracturing and explosion in the present invention.

[0021] Figure 2 It is a schematic diagram of the foam fracturing crack and explosion structure principle in the present invention.

[0022] Figure 3 It is a schematic diagram of the configuration, foaming and injection of the foam fracturing fluid in the present invention.

[0023] Figure numerals: 1-high-pressure pump, 2-foaming container (storage container), 3-cuttings adding device, 4-storage bottle, 5-preparation container, 6-coal seam, 7-borehole, 8-fracturing pipeline, 9-fracturing and explosion weakening area, 10-stratum, 11-roof rock stratum, 12-collapsed roof, 13-mining working face. DETAILED DESCRIPTION

[0024] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0025] like Figure 1-3 As shown, a method for pre-cracking and caving in a coal mine in cooperation with foam fracturing and blasting comprises the following steps:

[0026] Step 1: Drilling: According to the characteristics of the top rock layer and the requirements of the coal mining process, a drill hole 7 is constructed at a suitable position of the top rock layer of the coal seam to facilitate the delivery and pressure increase of the foam fracturing fluid.

[0027] Specifically, the fracturing radius is designed in combination with the mechanical properties of the coal seam roof, and then according to the construction plan, the stress concentration position of the roof rock layer 11 is selected, and drilling is carried out at a high position in the underground tunnel construction. When the hole depth reaches the fracturing requirement, the drilling is ended and the drilling withdrawal process is carried out, that is, the drill bit and drill rod are lifted and removed in turn until the drilling is completed, and the drill hole is cleaned after the drilling is completed.

[0028] Step 2: Prepare the foam fracturing fluid. The foam fracturing fluid is prepared and foamed by the foam preparation device, and the combustible gas is injected during the foaming of the foam fracturing fluid. The second step can also be carried out after the first step.

[0029] According to the characteristics of coal mines, acetylene is used as combustible gas. The foam fracturing fluid includes the following components by weight: 5-6 parts of diesel, 0.5-1 parts of guar gum, 1-2 parts of ammonium nitrate and 1-2 parts of rock chips. Among them, diesel as a foam base liquid has an ignition effect. Guar gum plays a thickening role. After addition, it increases the viscosity of the stock solution, thereby increasing the foaming rate and foaming amount. Preferably, hydroxypropyl guar gum is used. Ammonium nitrate reacts at high temperatures to release a large amount of oxygen, allowing it to be used as a flame retardant. Rock chips are used to improve the stability and strength of the foam during foaming. Preferably, the rock chips are obtained by crushing the broken rocks during drilling, and the particle size of the rock chips is 40-80 mesh. Other rock chips that do not meet the particle size requirements are disposed of as waste and backfilled in the goaf.

[0030] Among them, the foam preparation device includes a preparation container 5 for achieving component mixing and a foaming container 2 for achieving foaming of foam fracturing fluid, and the foaming container can be in a sealed state. An electric stirring device is arranged in the foaming container to facilitate stirring and foaming. A feeding port is also arranged in the foaming container to facilitate the addition of foam stabilizer cuttings during the foaming process. A vacuum hole for achieving a vacuum state of the foaming container and an air inlet hole for achieving the intake of combustible gas are arranged in the foaming container. The air inlet hole is arranged at the bottom of the foaming container. The vacuum hole is connected to a vacuum pump through a vacuum pipeline. The air inlet hole is connected to a combustible gas injection system through an air inlet pipeline, and a one-way valve is arranged on both the vacuum tube and the air inlet pipeline. Specifically, the combustible gas injection system includes a storage bottle 4 containing combustible gas, a pressure-stabilizing bottle and a pressure gauge arranged on the air inlet pipeline. The electric stirring device is a prior art.

[0031] The specific production process is as follows: first put the diesel into the preparation container, then add guar gum and stir until it is completely dissolved, then add ammonium nitrate and stir until it is evenly dissolved, then seal the foaming container, and then use a vacuum pump to extract the air in the foaming container, then transfer the dissolved solution to the foaming container, and then stir it with an electric stirring device, while injecting combustible gas through the air inlet and the combustible gas injection system, and adding rock chips through the feeding port, and the rock chips are added in multiple times until the foaming is completed.

[0032] The rock cuttings are produced by conveying the rock cuttings generated during drilling directly to a crusher for crushing, placing the crushed rock cuttings into a screen, and screening out rock cuttings with a particle size of 40-80 mesh for storage. To facilitate the addition of rock cuttings, a rock cuttings adding device is provided above the feeding port, and the rock cuttings adding device can add small amounts of rock cuttings to the foaming container multiple times as needed. Preferably, a conveying pipeline is provided between the preparation container and the foaming container.

[0033] Step 3: Fracturing. A fracturing system is arranged at the borehole, and the foamed fracturing fluid is injected into the borehole through the fracturing system to destroy the inside of the roof rock layer, forming cracks of a certain size, and at the same time, the foamed fracturing fluid is allowed to enter the cracks under the action of the fracturing system.

[0034] The fracturing system includes a fracturing operation control system, a high-pressure pump 1, a fracturing pipeline 8, an electric ignition device and a storage container 2, and the storage container can be in a sealed state and is used to store the foamed fracturing fluid. Preferably, the storage container is a foaming container. One end of the fracturing pipeline is connected to the storage container, and the other end can be extended into the borehole. The high-pressure pump is arranged on the fracturing pipeline, and the electric ignition connection line of the electric sparking device is laid in the borehole together with the high-pressure pipeline. The fracturing operation control system is electrically connected to the high-pressure pump and the electric ignition device, and is used to control whether the high-pressure pump is working and the working pressure, and control the operation of the electric sparking device.

[0035] To facilitate overall operation control, the fracturing operation system is also electrically connected to the stirring device, combustible gas injection system, vacuum pump, etc., so that it can realize the operation control of the entire device. The fracturing operation system adopts the structure with information sending, receiving, processing and other functions in the prior art, and the fracturing operation system also includes an operation panel with information interaction and information input functions.

[0036] The storage container and the foaming container are integrated, and the cuttings adding device is arranged at the feed port, so that the entire fracturing device is an integrated device, which not only simplifies the structure and reduces costs, but also greatly improves the fracturing efficiency of foam fracturing. The cuttings are crushed and screened and then added to the foam to improve the foam stability, which facilitates the improvement of the foam utilization rate, thereby achieving economical and efficient fracturing.

[0037] Step 4: Explosion and blasting. When the pores and cracks in the roof rock strata meet the explosion requirements, stop injecting the foam fracturing fluid and then ignite and detonate.

[0038] The specific operation is to stop the high-pressure pump, remove the high-pressure hose, and then start the electric ignition device to ignite and detonate when the pores and cracks in the roof rock strata meet the requirements for combustion and explosion. Since most foams will release a large amount of acetylene gas when they burst, the acetylene concentration in the pores will increase rapidly and reach the explosion concentration range. At the same time, the foam-based liquid diesel can play an ignition role. The gas in the pores will explode immediately when it encounters a fire source. The high temperature causes the ammonium nitrate in the foam liquid to react and release a large amount of oxygen, further enhancing the combustion and explosion effect. Under the combined effects of mechanical, thermochemical and vibration pulses, the explosion process can further expand the cracks and improve the connectivity of the cracks; at the same time, the shock wave generated by the combustion and explosion can cause the roof rock strata to vibrate, promoting the rupture and collapse of the rock strata.

[0039] like Figure 1 As shown, it is a schematic diagram of the coordinated operation of fracturing and explosion in coal seams when a foam fracturing fluid configuration, foaming and pressing device is used.

Claims

1. A method for pre-cracking and caving in a coal mine by combining foam fracturing and blasting, characterized in that: The following steps are involved: S1: Construction drilling: According to the characteristics of the roof rock layer and the requirements of the coal mining process, a drilling hole is constructed at a suitable position of the top rock layer of the coal seam to facilitate the transportation and pressure increase of the foam fracturing fluid; S2: preparing foam fracturing fluid; preparing and foaming the foam fracturing fluid through a foam preparation device, and injecting combustible gas during the foaming of the foam fracturing fluid; S3: Fracturing: a fracturing system is arranged at the borehole, and the foamed fracturing fluid is injected into the borehole through the fracturing system to destroy the inside of the roof rock layer to form cracks of a certain size, and at the same time, the foamed fracturing fluid is allowed to enter the cracks under the action of the fracturing system; S4: Explosion and roof release; when the pores and cracks in the roof rock strata meet the explosion requirements, stop injecting the foam fracturing fluid and then ignite and detonate.

2. The method for pre-cracking and caving in a coal mine by combining foam fracturing and blasting according to claim 1, characterized in that: The foam fracturing fluid comprises the following components in parts by weight: 5-6 parts of diesel, 0.5-1 parts of guar gum, 1-2 parts of ammonium nitrate and 1-2 parts of rock cuttings.

3. The method for pre-cracking and caving by combining foam fracturing and blasting in coal mines according to claim 2 is characterized in that: The rock chips are obtained by crushing broken rock blocks during drilling, and the particle size of the rock chips is 40-80 meshes.

4. The method for pre-cracking and caving in a coal mine in cooperation with foam fracturing and blasting according to claim 1 or 2, characterized in that: The foam preparation device includes a preparation container for mixing components and a foaming container for foaming foam fracturing fluid. The foaming container can be in a sealed state. An electric stirring device is arranged in the foaming container. A vacuum hole for putting the foaming container in a vacuum state and an air inlet hole for intake of combustible gas are arranged in the foaming container. The air inlet hole is arranged at the bottom of the foaming container. A feeding port is also arranged in the foaming container. The vacuum hole is connected to a vacuum pump through a vacuum pipeline. The air inlet hole is connected to a combustible gas injection system through an air inlet pipeline. Both the vacuum tube and the air inlet pipeline are provided with a one-way valve. The combustible gas injection system includes a storage bottle containing combustible gas, a pressure-stabilizing bottle and a pressure gauge arranged on the air inlet pipeline.

5. The method for pre-cracking and caving by combining foam fracturing and blasting in coal mines according to claim 3 is characterized in that: The preparation steps in S2 include: putting diesel into a preparation container, then adding guar gum and stirring until it is completely dissolved, then adding ammonium nitrate and stirring until it is evenly dissolved, then sealing the foaming container, and then extracting the air in the foaming container by a vacuum pump, and then transferring the dissolved solution to the foaming container, and then stirring it by an electric stirring device, while injecting combustible gas through the air inlet and adding cuttings through the feeding port, and adding the cuttings in multiple times until the foaming is completed.

6. The method for pre-cracking and caving in a coal mine by combining foam fracturing and blasting as described in claim 1 is characterized by: The combustible gas is acetylene.

7. The method for pre-cracking and caving in a coal mine by combining foam fracturing and blasting as described in claim 1 is characterized by: The fracturing system includes a fracturing operation control system, a high-pressure pump, a fracturing pipeline, an electric sparking device and a storage container. The storage container can be in a sealed state and is used to store foamed fracturing fluid. One end of the fracturing pipeline is connected to the storage container, and the other end can extend into the borehole. The high-pressure pump is arranged on the fracturing pipeline, and the electric sparking connection line of the electric sparking device is laid in the borehole together with the high-pressure pipeline. The fracturing operation control system is electrically connected to the high-pressure pump and the electric sparking device, and is used to control whether the high-pressure pump is working and the working pressure, and to control the operation of the electric sparking device.

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