Hydrogen peroxide fracturing anti-reflection method for coal mine gas control

Abstract

The invention relates to a hydrogen peroxide fracturing anti-reflection method for coal mine gas control, which comprises the following steps of: injecting a hydrogen peroxide solution with a specific concentration into a high-pressure-resistant sealed drill hole, releasing a powdery catalyst after a capsule is dissolved in hydrogen peroxide, and under the clamping of the catalyst, enabling the hydrogen peroxide to be easily subjected to decomposition reaction, generating a large amount of oxygen and releasing a large amount of heat, water in the solution is heated into water vapor; under the combined action of oxygen and water vapor, the pressure of gas in the drill hole is sharply increased, the coal body is fractured, the pressure of the gas in the fractured drill hole is sharply reduced, gas-liquid balance is damaged, then liquid in the drill hole is promoted to be exploded and boiled, cracks are promoted to be further expanded, a crack network is finally formed, and regional anti-reflection pressure relief is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of gas pressure relief and permeability enhancement in the process of coal mining, and particularly relates to a hydrogen peroxide cracking and permeability enhancement method for coal mine gas control. Background Art

[0002] Gas refers to the general term for various gases that emerge from coal and rock during coal mining, mainly methane, and is one of the main natural factors that seriously threaten coal mine safety production. Gas explosions and coal and gas outbursts have caused a large number of casualties and economic losses. At the same time, gas is also an excellent clean energy, and it is necessary to mine it as a resource.

[0003] Gas extraction, as the most core technical measure for coal mine gas control, has been fully promoted in various high-gas mining areas across the country. The fundamental factor restricting the effect of gas extraction is the poor permeability of the coal body, which leads to low extraction concentration and rapid attenuation.

[0004] There are various gas control technologies, and technologies such as protective layer mining and ground drilling extraction have relatively high requirements for on-site conditions. For underground gas extraction technology, the most commonly used measures include directional blasting, hydraulic fracturing, hydraulic punching, etc., especially in recent years, gas control measures have become more and more stringent. In many provinces, coal seam gas extraction is gradually decreasing, and bottom extraction and cross-layer gas control measures are replacing them. The cost of gas control is high and the efficiency is low, which seriously restricts the high-yield and efficient mining of coal mines. Therefore, how to achieve low-cost and efficient mining of coal seam gas has always been a problem that plagues mine production. Summary of the invention

[0005] The purpose of the present invention is to provide a coal mine gas control hydrogen peroxide fracturing and permeability enhancement method, which solves the problems of high cost, low efficiency and poor effect of underground gas extraction technology in the prior art.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problem is to provide a hydrogen peroxide cracking and permeability enhancement method for coal mine gas control, comprising the following steps:

[0007] Step 1: Select the construction site for fracturing and permeability enhancement;

[0008] Step 2: Determine the drilling construction plan, specifically the drilling parameters, including the number of holes, length, diameter, inclination and azimuth;

[0009] Step 3: Determine the hydrogen peroxide fracturing scheme, specifically the spacing between fracturing boreholes, hydrogen peroxide concentration, catalyst and its injection method;

[0010] Step 4: On-site drilling construction, which includes drilling on-site according to the designed drilling parameters, including the construction of permeability enhancement drilling and fracturing drilling;

[0011] Step 5: Drilling and high pressure resistance sealing, specifically sealing the permeability enhancement drilling and fracture-inducing drilling according to the set sealing parameters and requirements;

[0012] Step 6: Conduct on-site hydrogen peroxide fracturing, specifically conducting hydrogen peroxide fracturing according to the set parameters, including the formulation of emergency plans and safety measures;

[0013] Step 7: Collect and count hydrogen peroxide cracking gas parameters to test the hydrogen peroxide cracking effect.

[0014] In the first step, the fracturing and permeability enhancement construction site is selected in a bottom extraction tunnel where the coal has a self-ignition tendency that is not easy to self-ignite, and through-layer drilling fracturing is adopted or, under the premise of ensuring safety, along-layer drilling fracturing is adopted.

[0015] The number of holes drilled in the second step should be designed according to the impact radius, and regional pressure relief should be achieved without leaving any blank zones. The drilling length parameter requirements are that if it is a through-layer drilling, the length of the rock hole section should not be less than 8m, and it should pass through the coal seam by 0.5m. If it is a layer-parallel drilling, the drilling length can be greater than 20m. The total length of the drilling hole needs to be determined based on the actual on-site conditions of the fracturing and permeability enhancement construction site.

[0016] The second step of fracturing borehole spacing requires that the influence range of the single holes overlap in the direction of the borehole connection line, eliminate the pressure relief blank zone, and achieve regional pressure relief. The borehole spacing 2r can be determined by the following formula:

[0017] P max =Ae -4r

[0018] Among them, P max is the peak value of gas pressure. The pressure of the gas produced by a given content of hydrogen peroxide can be calculated according to the ideal gas state equation. A is the supercritical pressure of oxygen, which changes with temperature. r is the maximum distance of crack expansion.

[0019] The temperature of the fluid produced by hydrogen peroxide in the third step is determined by the following formula:

[0020] PV=nRT

[0021] The gas pressure generated by hydrogen peroxide in the third step is determined by the following formula:

[0022]

[0023] The calculated results were obtained and verified by the following hydrogen peroxide decomposition reaction formula:

[0024] 2H2O2=2H2O+O2+54.25kJ / mol, ΔrH°=-195.9kJ·mol -1If all water is converted into water vapor during the reaction, the pressure generated by the water vapor is also calculated according to the above formula, and the total pressure is the sum of the water vapor pressure and the oxygen pressure;

[0025] Where P is the gas pressure inside the borehole, V is the sum of the pore volumes of the borehole and the surrounding areas, n is the amount of gas, R is the molar gas constant, and T is the temperature. m is the maximum temperature, is the hydrogen peroxide concentration, T a is the adiabatic temperature rise, T0 is the temperature of hydrogen peroxide solution, E a is the activation energy.

[0026] In the sixth step, a catalyst for increasing the reaction rate of hydrogen peroxide needs to be added during the hydrogen peroxide cracking process. The catalyst can be titanium dioxide or other metals. The catalyst is required to be in powder form to increase the contact area with the liquid and improve the reaction efficiency. The catalyst is loaded into a capsule shell, which can be dissolved under the oxidation conditions of hydrogen peroxide to release the catalyst. The dissolution rate is adjusted by setting the thickness of the capsule shell.

[0027] In the fifth step, a galvanized pipe or a seamless steel pipe is selected as a fracturing pipe, a capsule shell containing a catalyst is first placed inside the top of the fracturing pipe, the fracturing pipe is sent into the borehole, cement mortar is injected to seal the borehole, and a high-pressure ball valve, a one-way valve and a pipe support fixture are respectively installed from the inside to the outside of the part of the fracturing pipe exposed from the borehole, and the pipe support fixture fixes the fracturing pipe on the tunnel wall of the bottom extraction tunnel.

[0028] The sealed boreholes are sealed by grouting in a "two-blocking and one-injection" manner, wherein the sealing length is required to be no less than 8m when sealing through-layer boreholes, and the sealing section length is required to be no less than 15m when sealing along-layer boreholes. The water-cement ratio of cement mortar is not greater than 0.5, and the sealing is allowed to stand for 48 hours after completion to ensure the sealing effect of the cement mortar.

[0029] After the hydrogen peroxide fracturing in the seventh step is completed, the pressure holding time shall not exceed 30 minutes. Then, the one-way valve shall be removed, and the sealing ball valve shall be slowly opened to release the fluid in the hole. Then, the extraction system shall be connected to carry out extraction to minimize the impact of oxygen on the coal body. During the extraction process, the CO concentration in the hole shall be detected in real time. If the CO concentration exceeds the standard, the drilling extraction valve shall be closed and the borehole shall be filled with clean water to prevent further expansion of spontaneous combustion of the coal body.

[0030] Inside the sealed borehole, by adding a catalyst, the decomposition reaction of hydrogen peroxide is promoted, which is an exothermic reaction. The catalyst promotes the decomposition of hydrogen peroxide to produce a large amount of gas and heat, which causes the pressure inside the borehole to increase, and then causes the coal body to rupture. After the rupture, the gas pressure in the borehole drops sharply, causing the gas-liquid balance to be destroyed, which in turn causes the liquid in the borehole to boil, causing the cracks to further expand, and finally forming a fracture network, achieving regional permeability increase and pressure relief.

[0031] By adopting the above technical solution, compared with the prior art, the present invention can achieve the following beneficial effects:

[0032] 1. The main substances used in the present invention, hydrogen peroxide and catalyst, are conventional chemical substances with stable output, low price, detailed transportation and storage specifications, and strong operability.

[0033] 2. In the present invention, the hydrogen peroxide product is mainly oxygen, which is a non-harmful gas and will not increase the potential safety hazard of the mine. Under the action of high temperature and high pressure, oxygen and water vapor enter the micropores of the coal body. Even if an oxidation reaction occurs and a small amount of carbon monoxide is produced, it can be controlled by real-time monitoring, extraction and water injection.

[0034] 3. The concentration of hydrogen peroxide in the present invention is controllable and adjustable. During the decomposition reaction, the liquid generates gas, the volume expands, the pressure increases quickly, and the impact is strong, so it is easy to form a crack network in the coal body. After the coal body breaks, it can also promote the further expansion of the cracks in the state of explosive boiling, increase the impact range, and achieve regional pressure relief. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a construction schematic diagram of the present invention;

[0036] Figure 2 A schematic plan view of the design of the fracture-inducing drilling hole and the anti-permeability drilling hole of the present invention;

[0037] Figure 3 It is a schematic diagram of the high pressure sealing of the present invention.

[0038] Figure numerals: 1. Bottom pumping tunnel; 2. Injection pump; 3. Pipeline support fixture; 4. Control valve; 5. Check valve; 6. Fracturing pipe; 7. Coal seam; 8. Flower hole; 9. Towel; 10. Polyurethane; 11. Grouting pipe; 12. Return grouting pipe. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and beneficial effects of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0040] like Figure 1 As shown, the present invention provides a hydrogen peroxide cracking and permeability enhancement method for coal mine gas control, comprising the following steps:

[0041] Step 1: Select the construction site for fracturing and permeability enhancement;

[0042] The fracturing and permeability enhancement construction site of this embodiment is the bottom extraction tunnel below the 11037 coal mining face and the 11039 coal mining face of a coal mine as the experimental site, wherein the coal seams of the 11037 coal mining face and the 11039 coal mining face are non-combustible coal seams, and through-layer drilling is used to cause fracturing.

[0043] Step 2: Determine the drilling construction plan;

[0044] like Figure 2 As shown in the figure, the plane distance between the fracturing borehole and other developed tunnels should be greater than 50m; the distance between the fracturing borehole and the structural fracture zone should be greater than 100m; the straight-line distance between the fracturing borehole opening point and the coal point should be no less than 50m; the normal distance between the fracturing borehole opening point and the coal seam should be greater than 30m; the length of the rock hole section of the fracturing borehole is not less than 8m and it passes through the coal seam by 0.5m; the number of fracturing boreholes is set at 4, at 136m, 222m, 267m and 317m of the bottom extraction lane, and permeability enhancement boreholes are constructed on both sides of the fracturing boreholes that meet the conditions, and the spacing between the permeability enhancement borehole and the fracturing borehole is 20m respectively; the specific parameters of the fracturing borehole and the permeability enhancement borehole are shown in Table 1:

[0045] Table 1 Design parameters of fracture-inducing drilling and permeability-enhancing drilling

[0046]

[0047]

[0048] Step 3: Determine the hydrogen peroxide fracturing scheme, set the hole spacing between fracturing holes to 40m, set the hydrogen peroxide fracturing fluid concentration to 25% mol / L, and use titanium dioxide as a catalyst. Titanium dioxide is in powder form to increase the contact area with the hydrogen peroxide fracturing fluid and improve the reaction efficiency. The titanium dioxide powder is loaded into a capsule shell, which can be dissolved under the oxidation conditions of hydrogen peroxide to release the titanium dioxide powder. The dissolution rate is adjusted by setting the thickness of the capsule shell.

[0049] Step 4: On-site construction of permeability enhancement drilling and fracturing drilling. According to the parameters set in Table 1, the gas extraction drilling rig ZDY1250 is used. During the drilling construction, attention should be paid to the situation of drill clamping and drill sticking.

[0050] In order to prevent the borehole from collapsing and clogging during fracturing, a borehole protection pipe must be installed throughout the process. The fracturing pipe designed this time also serves as a borehole protection pipe. The fracturing pipe adopts a seamless steel pipe with an outer diameter of 73mm and a wall thickness of 8mm. The fracturing pipe is a solid pipe section throughout the rock section and a flower hole section throughout the coal seam. The end of the fracturing pipe is sealed, and the diameter of the flower hole is 10mm, and the holes are evenly arranged around the pipe wall.

[0051] Step 5: High-pressure sealing of permeability-enhancing drilling holes and fracture-causing drilling holes, such as Figure 3 As shown in the figure, after the construction of the permeability enhancement drilling hole and the fracturing drilling hole is completed, the fracturing pipe, the grouting pipe and the return grouting pipe are respectively inserted into the holes, and the two adjacent fracturing pipes and the grouting pipes are connected by threads, and the method of two plugging and one injection and secondary grouting is adopted. The sealing material is the high-strength cement mortar of No. 425, wherein the inner sealing section of the permeability enhancement drilling hole and the fracturing drilling hole is sealed by wrapping the fracturing pipe with a towel, and the end of the grouting pipe is located outside the inner sealing section of the permeability enhancement drilling hole and the fracturing drilling hole, and the outer sealing section of the permeability enhancement drilling hole and the fracturing drilling hole is sealed by using a polyurethane foaming agent, and the inner sealing section of the permeability enhancement drilling hole and the fracturing drilling hole is sealed. After the sealing of the closed section and the outer closed section is completed, a grouting pump is used to perform the first grouting of the permeability enhancement borehole and the fracturing borehole. The depth of the first grouting is 8m. After the cement mortar solidifies and can withstand pressure, a second grouting is performed on the permeability enhancement borehole and the fracturing borehole. After the grouting pipe is slurried, the grouting pipe valve is closed and pressurized grouting is performed. The grouting pressure is not less than 1.5MPa. After the grouting pressure is reached, the grouting is stopped and the pressure is maintained for 5 minutes. The exposed drilling part of the fracturing pipe is respectively equipped with a high-pressure ball valve, a one-way valve and a pipe support fixture from the inside to the outside. The pipe support fixture fixes the fracturing pipe on the tunnel wall of the bottom extraction tunnel.

[0052] Step 6: Conduct on-site hydrogen peroxide fracturing, where the pressure pump uses BYW65 / 400 model produced by Xi'an Research Institute Co., Ltd. of China Coal Technology and Engineering Group. The pressure of the pressure pump is set between 15-20MPa, and the fracturing time is set to 3-5 hours.

[0053] Step 7: Collect and count hydrogen peroxide cracking gas parameters to test the hydrogen peroxide cracking effect.

[0054] In order to test the fracturing effect of hydrogen peroxide, it is necessary to monitor the fracturing data. The data monitoring system consists of a mine-use flameproof and intrinsically safe soft starter QJR-400 / 1140 (660) Z, a mine-use flameproof and intrinsically safe fracturing pump group control box KXJ-1140 (660), a mine-use communication cable, a mine-use flameproof and intrinsically safe computer and an electric regulating valve. Signal detection and control are controlled by a remote mine-use flameproof and intrinsically safe computer. The data monitoring system also displays 8 parameters: main pump discharge pressure, main pump discharge instantaneous flow and cumulative flow, hydraulic transmission oil temperature, oil pressure, gear position, main pump current and other working status monitoring, which can flexibly and conveniently display pressure, flow curves, and data. The maximum range of pressure monitoring is 65MPa; the flow monitoring range is 2~70.0m 3 / min, accuracy 0.5 level; temperature monitoring range 0 ~ 150 ℃; sampling time minimum 1 time / s, can be flexibly set.

[0055] The explosion-proof video monitoring system mainly consists of two fiber optic cameras KBA166, one display control box KXJ127, and one control keyboard FHJ18, which can display the fracturing pump group and fracturing drilling site in real time.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the invention claimed for protection.

Claims

1. A method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement, characterized in that: The following steps are involved: Step 1: Select the construction site for fracturing and permeability enhancement; Step 2: Determine the drilling construction plan, specifically the drilling parameters, including the number of holes, length, diameter, inclination and azimuth; Step 3: Determine the hydrogen peroxide fracturing scheme, specifically the spacing between fracturing boreholes, hydrogen peroxide concentration, catalyst and its injection method; Step 4: On-site drilling construction, which includes drilling on-site according to the designed drilling parameters, including the construction of permeability enhancement drilling and fracturing drilling; Step 5: Drilling and high pressure resistance sealing, specifically sealing the permeability enhancement drilling and fracture-inducing drilling according to the set sealing parameters and requirements; Step 6: Conduct on-site hydrogen peroxide fracturing, specifically conducting hydrogen peroxide fracturing according to the set parameters, including the formulation of emergency plans and safety measures; Step 7: Collect and count hydrogen peroxide cracking gas parameters to test the hydrogen peroxide cracking effect.

2. A coal mine gas control hydrogen peroxide cracking and permeability enhancement method according to claim 1, characterized in that: In the first step, the fracturing and permeability enhancement construction site is selected in a bottom extraction tunnel where the coal has a self-ignition tendency that is not easy to self-ignite, and through-layer drilling fracturing is adopted or, under the premise of ensuring safety, along-layer drilling fracturing is adopted.

3. A coal mine gas control hydrogen peroxide cracking and permeability enhancement method according to claim 1, characterized in that: The number of holes drilled in the second step should be designed according to the impact radius, and regional pressure relief should be achieved without leaving any blank zones. The drilling length parameter requirements are that if it is a through-layer drilling, the length of the rock hole section should not be less than 8m, and it should pass through the coal seam by 0.5m. If it is a layer-parallel drilling, the drilling length can be greater than 20m. The total length of the drilling hole needs to be determined based on the actual on-site conditions of the fracturing and permeability enhancement construction site.

4. A coal mine gas control hydrogen peroxide cracking and permeability enhancement method according to claim 1, characterized in that: The second step of fracturing borehole spacing requires that the influence range of the single holes overlap in the direction of the borehole connection line, eliminate the pressure relief blank zone, and achieve regional pressure relief. The borehole spacing 2r can be determined by the following formula: P max =Ae -4r Among them, P max is the peak value of gas pressure. The pressure of the gas produced by a given content of hydrogen peroxide can be calculated according to the ideal gas state equation. A is the supercritical pressure of oxygen, which changes with temperature. r is the maximum distance of crack expansion.

5. The method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement according to claim 1, characterized in that: The temperature of the fluid produced by hydrogen peroxide in the third step is determined by the following formula: PV=nRT The gas pressure generated by hydrogen peroxide in the third step is determined by the following formula: The calculated results were obtained and verified by the following hydrogen peroxide decomposition reaction formula: 2H2O2=2H2O+O2+54.25kJ / mol,ΔrH°=-195.9kJ·mol -1 If all water is converted into water vapor during the reaction, the pressure generated by the water vapor is also calculated according to the above formula, and the total pressure is the sum of the water vapor pressure and the oxygen pressure; Where P is the gas pressure inside the borehole, V is the sum of the pore volumes of the borehole and the surrounding areas, n is the amount of gas, R is the molar gas constant, and T is the temperature. m is the maximum temperature, is the hydrogen peroxide concentration, T a is the adiabatic temperature rise, T0 is the temperature of hydrogen peroxide solution, E a is the activation energy.

6. The method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement according to claim 1, characterized in that: In the sixth step, a catalyst for increasing the reaction rate of hydrogen peroxide needs to be added during the hydrogen peroxide cracking process. The catalyst can be titanium dioxide or other metals. The catalyst is required to be in powder form to increase the contact area with the liquid and improve the reaction efficiency. The catalyst is loaded into a capsule shell, which can be dissolved under the oxidation conditions of hydrogen peroxide to release the catalyst. The dissolution rate is adjusted by setting the thickness of the capsule shell.

7. The method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement according to claim 1, characterized in that: In the fifth step, a galvanized pipe or a seamless steel pipe is selected as the fracturing pipe, and the top of the fracturing pipe is a closed structure. The capsule shell containing the catalyst is first placed inside the top of the fracturing pipe, and the fracturing pipe is sent into the borehole. The borehole is sealed with cement mortar, and a high-pressure ball valve, a one-way valve and a pipe support fixture are installed from the inside to the outside of the exposed borehole portion of the fracturing pipe. The pipe support fixture fixes the fracturing pipe on the tunnel wall of the bottom extraction tunnel.

8. The method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement according to claim 7, characterized in that: The sealed boreholes are sealed by grouting in a "two-blocking and one-injection" manner, wherein the sealing length is required to be no less than 8m when sealing through-layer boreholes, and the sealing section length is required to be no less than 15m when sealing along-layer boreholes. The water-cement ratio of cement mortar is not greater than 0.5, and the sealing is allowed to stand for 48 hours after completion to ensure the sealing effect of the cement mortar.

9. The method for coal mine gas control by hydrogen peroxide cracking and permeability enhancement according to claim 1, characterized in that: After the hydrogen peroxide fracturing in the seventh step is completed, the pressure holding time shall not exceed 30 minutes. Then, the one-way valve shall be removed, and the sealing ball valve shall be slowly opened to release the fluid in the hole. Then, the extraction system shall be connected to carry out extraction to minimize the impact of oxygen on the coal body. During the extraction process, the CO concentration in the hole shall be detected in real time. If the CO concentration exceeds the standard, the drilling extraction valve shall be closed and the borehole shall be filled with clean water to prevent further expansion of spontaneous combustion of the coal body.

10. The method for coal mine gas control by hydrogen peroxide fracturing and permeability enhancement according to claim 1, characterized in that: Inside the sealed borehole, by adding a catalyst, the decomposition reaction of hydrogen peroxide is promoted, which is an exothermic reaction. The catalyst promotes the decomposition of hydrogen peroxide to produce a large amount of gas and heat, which causes the pressure inside the borehole to increase, and then causes the coal body to rupture. After the rupture, the gas pressure in the borehole drops sharply, causing the gas-liquid balance to be destroyed, which in turn causes the liquid in the borehole to boil, causing the cracks to further expand, and finally forming a fracture network, achieving regional permeability increase and pressure relief.

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