Coal mine underground multi-hole synchronous quantitative fracturing device and control method thereof

Abstract

The invention relates to a coal mine underground porous synchronous quantitative fracturing device and a control method thereof, and belongs to the technical field of coal mine gas extraction. The quantitative fracturing device is connected through a high-pressure pipeline in a union mode to form a structure with a main pipeline and three branch pipelines. A digital display type pressure sensor, an electric control plug valve, a high-pressure one-way valve, an electric needle-shaped throttle valve, a digital display type pressure sensor and an electric control plug valve are sequentially installed on each branch pipeline from the front end to the rear end, and the working conditions of injection pressure, valve opening and closing degree and the like of each branch drill hole can be measured in real time under the condition that a high-pressure pump is started. And according to the measured data, the injection flow parameters of all the branch pipelines are measured in real time through a preset model, and all the branch pipelines are adjusted in real time according to the working state of all the branch drill holes. The invention further provides a control method of the multi-hole synchronous quantitative fracturing device, and by optimizing the control logic of the electric control valve set, it is guaranteed that high-pressure pipeline adjustment is conducted safely and smoothly under the high-pressure large-displacement injection condition.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine gas extraction, and relates to a multi-hole synchronous quantitative fracturing device in an underground coal mine and a control method thereof. Background Art

[0002] In 2024, my country's total annual energy consumption will be approximately 5.96 billion tons of standard coal, of which coal consumption will account for 53.2%, making coal a key primary energy source in my country. With the continued development of the national economy, my country's mines are deepening at a rate of 10 to 30 meters per year. Under deep mining conditions, coal-rock gas dynamics are becoming increasingly complex, with ambiguous characteristics and common hazard characteristics. Conventional coal seam gas extraction measures alone cannot fully meet the needs of efficient and safe production in underground mines.

[0003] Hydraulic fracturing technology creates a network of artificial fractures by injecting high-pressure fluid into coal seams, breaking down the coal's original dense structure and expanding gas flow channels. Furthermore, the injection of high-pressure fluid reduces the coal seam's gas adsorption capacity and accelerates its desorption process. This effect can increase coal seam permeability by several to dozens of times, significantly shortening gas pre-extraction time and ensuring safe coal mining operations.

[0004] However, under the conditions of high-intensity mining of thick coal seams in the central and western mining areas of my country, the cracks generated by hydraulic fracturing in a single borehole are difficult to cover the entire thickness of the coal seam. The problem of uneven permeability is prone to occur inside the coal seam, forming a blank zone for coal seam gas control, which poses a hidden danger to safe production. To address the above problems, hydraulic fracturing is carried out simultaneously in multiple boreholes. By injecting high-pressure fluids at different positions at the same time, a superimposed stress field is formed, artificially changing the stress distribution state in the coal seam. By adjusting the injection fluid pressure and flow rate of each borehole, the cracks are guided to extend in the preset direction, the crack extension range is expanded, and the connectivity of the crack network is enhanced. The cracks in each borehole intersect during the expansion process to form a three-dimensional network. The fracturing cracks fully cover the entire thickness of the coal seam, improving the permeability of the coal seam as a whole, thereby eliminating the blank zone for gas disaster control.

[0005] The key to the above technology lies in the precise measurement of the high-pressure fluid injection parameters of each single borehole during the multi-hole synchronous fracturing process, so as to achieve real-time control of the multi-hole high-pressure fracturing state, among which the injection volume of the single-hole fracturing fluid is particularly important. At present, there is a pressure upper limit for the flow monitoring of high-pressure pipelines in underground coal mines, which cannot fully meet the pressure and flow requirements of multi-hole hydraulic fracturing. The technical transformation of existing non-coal mine safety standard products is also limited by the power wall under the intrinsic safety requirements of mining products. Therefore, there is an urgent need for a multi-hole synchronous quantitative fracturing device and its control method for underground coal mines to provide safety guarantees for the high-intensity mining of thick coal seams in the central and western mining areas of my country. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a multi-porous synchronous quantitative fracturing device and a control method for an underground coal mine, which can measure the injection pressure, flow rate and other working parameters of each branch borehole in real time when the high-pressure pump is turned on, and adjust the working status of each branch borehole in real time to ensure that the high-pressure pipeline adjustment is safe and smooth under the conditions of high-pressure and large-displacement injection.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A multi-hole synchronous quantitative fracturing device for underground coal mines, comprising a main pipeline and a branch pipeline, wherein one end of the branch pipeline is a water inlet and the other end is a water outlet, and the water inlet is connected to the main pipeline;

[0009] The main pipeline is connected in sequence with a short joint, a high-pressure tee, a male-female adapter 1, a high-pressure tee, a male-female adapter 1, a high-pressure tee, and a male-female adapter 2. The end of the short joint away from the high-pressure tee is connected to the water supply pipeline through a high-pressure pump, and the end of the male-female adapter 2 away from the high-pressure tee is provided with a plug for sealing.

[0010] The branch pipeline is connected in sequence from the water inlet to the water outlet with a three-way joint, three male-female adapters, an electric-controlled plug valve, a high-pressure one-way valve, a double-female short joint, an electric needle throttle valve, a right-angle adapter, a three-way joint, and an electric-controlled plug valve. The end of the electric-controlled plug valve away from the three-way joint is connected to the drilled high-pressure pipeline; a digital pressure sensor is provided on the three-way joint.

[0011] Optionally, at least three branch pipelines are provided; adjacent branch pipelines are parallel to each other and are vertically connected to the main pipeline respectively.

[0012] Optionally, it also includes an integrated control console electrically connected to the digital pressure sensor, the electric stopcock, the electric needle throttle valve and the integrated control console, which is used to control the opening and closing control of the electric stopcock, the opening adjustment of the electric needle throttle valve, and the data processing of the digital pressure sensor.

[0013] Optionally, the digital pressure sensor, the electric plug valve, the electric needle throttle valve and the integrated control console are all connected by wire via a quick-plug method.

[0014] Optionally, it also includes a support frame and a base, and several support frames are arranged in sequence along the base to form a supporting structure. The male-female adapter, double female short connector, three-way connector, and electric-controlled plug valve are respectively connected to the support frame by bolts and steel belts.

[0015] Optionally, the base includes a longitudinal beam arranged along the branch pipeline, and a cross beam arranged at both ends of the longitudinal beam, and the cross beam and the longitudinal beam are cross-welded.

[0016] Optionally, the short joint, high-pressure tee, male-female adapter 1, and male-female adapter 2 are connected through a union joint; the tee joint, male-female adapter 3, electric-controlled plug valve, high-pressure one-way valve, double female short joint, electric needle throttle valve, right-angle adapter, tee joint, electric-controlled plug valve, and drilled high-pressure pipeline are connected through a union joint.

[0017] Optionally, the inner diameter of the main pipeline and the branch pipeline is 48mm to 52mm.

[0018] A control method for a multi-hole synchronous quantitative fracturing device in an underground coal mine according to any of the above-mentioned methods, wherein, along the direction from the water inlet to the water outlet, the two electric needle throttle valves on the same branch pipeline are respectively a front electric needle throttle valve and a rear electric needle throttle valve, and the two electric-controlled plug valves on the same branch pipeline are respectively a front electric-controlled plug valve and a rear electric-controlled plug valve;

[0019] Before the high-pressure pump is turned on, the electric needle throttle valve is in a fully open state, and the electric-controlled plug valves are all in a fully open state;

[0020] After the high-pressure pump is turned on, when the unused branch pipeline is closed, the control logic of the electric control valve group is: first close the front electric control plug valve, then close the rear electric control plug valve, and finally close the electric needle throttle valve;

[0021] After the high-pressure pump is turned on, when the closed branch pipeline is reopened, the control logic of the electronically controlled valve group is: first open the front-end electronically controlled plug valve, then fully open the electric needle throttle valve, and finally open the rear-end electronically controlled plug valve;

[0022] After turning on the high-pressure pump, when adjusting the flow of the branch pipeline, the control logic of the electronically controlled valve group is: first close the front-end electronically controlled plug valve, then close the rear-end electronically controlled plug valve, then adjust the opening of the electric needle throttle valve, and finally open the front-end electronically controlled plug valve and the rear-end electronically controlled plug valve in turn.

[0023] Optionally, the two digital pressure sensors at the front and rear ends of the electric needle throttle valve on each branch pipeline constitute a set of measurement units, and the real-time flow calculation model of each branch pipeline is:

[0024]

[0025] Where: q i A is the real-time flow rate of the i-th branch pipeline at the moment of measurement; ij is the flow area when the electric needle throttle valve of the i-th branch line is in the j-gear position; u i is the real-time flow velocity of the i-th branch pipeline at the time of measurement; g is the acceleration of gravity; a ijP is the ratio of the flow cross-sectional area of the electric needle valve to the flow cross-sectional area of the three-way joint when the electric needle throttle valve of the i-th branch pipeline is in the j-gear position; i1 The real-time pressure of the fluid is measured by the digital pressure sensor installed at the front end of the electric needle throttle valve on the i-th branch pipeline; P i2 The real-time pressure of the fluid is measured by the digital pressure sensor provided at the rear end of the electric needle throttle valve on the i-th branch pipeline; ξ ij is the local resistance coefficient of the electric needle throttle valve of the i-th branch pipeline when it is in gear j; wherein along the direction from the water inlet to the water outlet, the two electric needle throttle valves on the same branch pipeline are the front electric needle throttle valve and the rear electric needle throttle valve, and the two electric-controlled plug valves on the same branch pipeline are the front electric-controlled plug valve and the rear electric-controlled plug valve;

[0026] The calculation model of the cumulative flow in each branch pipeline at time t is:

[0027]

[0028] Where: t is the injection time; Q i The cumulative injection flow of the i-th branch pipeline up to time t.

[0029] The beneficial effects of the present invention are:

[0030] The present invention sets a straight section composed of a tee joint and a male-female adapter at the front end of the electric needle throttle valve, and sets a digital pressure sensor in a hole on the front tee joint housing; sets a straight section composed of a right-angle adapter, a tee joint, and a male-female adapter at the rear end of the electric needle throttle valve, and sets a digital pressure sensor in a hole on the rear tee joint housing. The pressure values measured by the digital pressure sensors at the front and rear ends are combined with the flow cross-sectional area A of the electric needle valve at different calibrated gears measured in advance. ij , local resistance coefficient ξ ij And the ratio of the flow cross-sectional area of the electric needle valve to the flow cross-sectional area of the three-way joint a ij The real-time flow of the branch pipeline is calculated by the preset model to solve the problem that there is no corresponding equipment with mining product safety mark certificate for real-time flow monitoring of high-pressure pipelines with fluid pressure higher than 50MPa in underground coal mines.

[0031] The branch pipeline valve group system designed in the present invention is composed of a plug valve, a one-way valve, a needle valve, and a plug valve in sequence. The valve group system can adjust the valve opening degree of each branch pipeline in real time when the high-pressure pump is turned on; the pipeline system is composed of a short circuit and a union, and the electric needle throttle valve, electric plug valve, digital pressure sensor and integrated control console are connected by a wired quick-connect connection, which is convenient for rapid disassembly under confined space working conditions in coal mines.

[0032] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0034] Figure 1 It is a plan view of the multi-hole synchronous quantitative fracturing device for underground coal mines of the present invention;

[0035] Figure 2 It is a cross-sectional view of the multi-hole synchronous quantitative fracturing device for underground coal mines of the present invention.

[0036] Reference numerals:

[0037] 1 base, 2 support frame, 3 short connector, 4 high-pressure tee, 5 male-female adapter 1, 6 male-female adapter 2, 7 tee connector, 8 digital pressure sensor, 9 male-female adapter 3, 10 electric control plug valve, 11 high-pressure check valve, 12 double female short connector, 13 electric needle throttle valve, 14 right-angle adapter, 15 integrated control console. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0040] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] Example 1

[0042] See also Figures 1 and 2 This is a multi-hole synchronous quantitative fracturing device for underground coal mines. It includes a main pipeline and branch pipelines. The branch pipelines have a water inlet at one end and a water outlet at the other end, and the water inlet is connected to the main pipeline. There are at least three branch pipelines, and adjacent branch pipelines are parallel to each other and connected vertically to the main pipeline. The inner diameter of the main pipeline and branch pipelines ranges from 48mm to 52mm. In some embodiments of the present invention, the inner diameter is preferably 50mm.

[0043] The main pipeline is provided with a short joint 3, a high-pressure tee 4, a male-female adapter 1 5, a high-pressure tee 4, a male-female adapter 1 5, a high-pressure tee 4, and a male-female adapter 2 6, which are connected in sequence through a union joint. The end of the short joint 3 away from the high-pressure tee 4 is connected to the water supply pipeline through a high-pressure pump, and the end of the male-female adapter 2 6 away from the high-pressure tee 4 is provided with a plug for sealing.

[0044] On the branch pipeline, from the water inlet to the water outlet, the three-way joint 7, the male-female adapter 9, the electric-controlled plug valve 10, the high-pressure one-way valve 11, the double-female short joint 12, the electric needle throttle valve 13, the right-angle adapter 14, the three-way joint 7, and the electric-controlled plug valve 10 are connected in sequence through the union joint. The end of the electric-controlled plug valve 10 away from the three-way joint 7 is connected to the drilled high-pressure pipeline; the three-way joint 7 is provided with a digital pressure sensor 8.

[0045] The electric needle throttle valve 13 on each branch pipeline is calibrated with 5 gears, corresponding to fully closed, 25% open, 50% open, 75% open, and fully open. The flow cross-sectional area of the three-way connector 7 and the flow cross-sectional area A of the electric needle throttle valve 13 at the fully closed gear, 25% open, 50% open, 75% open, and fully open gear are measured in advance. ij and the local drag coefficient ξ ij .

[0046] Along the direction from the water inlet to the water outlet, the two connectors, sensors, and valves on the same branch pipeline are the front end connector, sensor, and valve and the rear end connector, sensor, and valve respectively.

[0047] The front end electric control plug valve 10 and the rear end electric control plug valve 10 of the same branch pipeline electric needle throttle valve 13 are calibrated to two control positions of fully open and fully closed, and at the same time, the front end electric control plug valve 10 and the rear end electric control plug valve 10 execute the same control logic.

[0048] The pressure measuring port of the digital pressure sensor 8 is placed on the housing of the tee connector 7. The cross-sectional profile and inner diameter of the tee connector 7, on which the front-end digital pressure sensor 8 is installed, are consistent with those of the male and female adapter 3 9. The length of the internal union thread at the corresponding position is consistent with the sum of the lengths of the two adjacent sections of external threads. The total length of the corresponding pipeline section is 30 times the inner diameter of the pipeline. The cross-sectional profile and inner diameter of the tee connector 7, on which the rear-end digital pressure sensor 8 is installed, are consistent with those of the right-angle adapter 14 and the male and female adapter 3 9. The length of the internal union thread at the corresponding position is consistent with the sum of the lengths of the two adjacent sections of external threads. The total length of the corresponding pipeline section is 30 times the inner diameter.

[0049] The multi-hole synchronous quantitative fracturing device for underground coal mines also includes an integrated control console electrically connected to the digital pressure sensor 8, the electrically controlled plug valve 10, the electric needle throttle valve 13, and an integrated control console 15. This console is used to control the opening and closing of the electrically controlled plug valve 10, adjust the opening of the electric needle throttle valve 13, and process data from the digital pressure sensor 8. The integrated control console 15 is enclosed in a housing with coal safety and explosion-proof properties. In some embodiments of the present invention, the digital pressure sensor 8, the electrically controlled plug valve 10, the electric needle throttle valve 13, and the integrated control console 15 are all connected via quick-plug wires. The integrated control console 15 is PLC-controlled and has 15 built-in plug points and 3 spare points.

[0050] The multi-hole synchronous quantitative fracturing device for underground coal mines also includes a support frame 2 and a base 1. Several support frames 2 are arranged in sequence along the base 1 to form a supporting structure. A male-female adapter 9, a double female short connector 12, a tee connector 7, and an electrically controlled plug valve 10 are connected to the support frame 2 via bolts and steel straps. The base 1 includes longitudinal beams arranged along the branch pipelines and cross beams at both ends of the longitudinal beams. The cross beams are cross-welded to the longitudinal beams.

[0051] Assembly process of multi-hole synchronous quantitative fracturing device in underground coal mines:

[0052] All parts are disassembled and transported to the coal mine and reassembled at the work site. The three-way connector 7 and the digital pressure sensor 8 are assembled and debugged on the ground, and the two parts are lowered into the mine as a whole. The mechanical actuator part and the electric actuator part of the electric control plug valve 10 and the electric needle throttle valve 13 are assembled and debugged on the ground, and the two parts are lowered into the mine as a whole.

[0053] Check the integrity of the top plate at the installation site and whether the floor is flat, and ensure that the supporting structure composed of the base 1 and the support frame 2 is placed on a concrete platform with an inclination of no more than 5°.

[0054] Use unions to sequentially connect short connector 3, high-pressure tee 4, male-female adapter 1 5, high-pressure tee 4, male-female adapter 1 5, high-pressure tee 4, and male-female adapter 2 6. Install the plug on the airside of male-female adapter 2 6. Secure the two male-female adapters 1 5 to support frame 2 with bolts and steel straps to complete the main pipeline assembly.

[0055] Use unions to sequentially connect the tee 7, male-female adapter 3 9, electric-controlled plug valve 10, high-pressure check valve 11, and double-female short connector 12. Use bolts and steel bands to secure the male-female adapter 3 9 and double-female short connector 12 to the support frame 2. Use unions to sequentially connect the electric needle throttle valve 13, right-angle adapter 14, tee 7, and electric-controlled plug valve 10. Connect the electric needle throttle valve 13 to the double-female short connector 12. Finally, secure the tee 7 to the support frame 2 with bolts and steel bands to complete the branch pipeline assembly.

[0056] The electric needle throttle valve 13, the electric control plug valve 10 and the digital pressure sensor 8 of each branch pipeline are connected to the integrated control console 15 using quick connectors to complete the assembly of the three-hole synchronous quantitative fracturing device in the coal mine.

[0057] A high-pressure pipe is led out from the high-pressure pump and connected to the short joint 3 of the three-hole synchronous quantitative fracturing device in the coal mine. The high-pressure pipe is used to connect the drill hole orifice valve group to the air side of the electric-controlled plug valve 10, so as to integrate the fracturing device into the multi-porous injection system. The flow direction of the high-pressure fluid in the multi-porous injection system is high-pressure pump → three-hole synchronous quantitative fracturing device in the coal mine → orifice valve group.

[0058] After the fracturing device is connected to the porous injection system, a pressure test is first carried out before formal use. The pressure in the pipeline is gradually increased from 0 to the rated working pressure of 50MPa according to the pressure gradient of 5MPa and the pressure is maintained for 15 minutes. After checking for leakage and looseness, it can be used normally.

[0059] A control method of the above-mentioned multi-hole synchronous quantitative fracturing device in underground coal mines is as follows:

[0060] Before starting the high-pressure pump, all electric needle throttle valves 13 are in a fully open state, and all electric-controlled plug valves 10 are in a fully open state;

[0061] After turning on the high-pressure pump, first close the branch pipeline that is not in use temporarily. The operation sequence is: first close the front-end electric control plug valve 10, then close the rear-end electric control plug valve 10, and finally close the electric needle throttle valve 13;

[0062] Secondly, adjust the branch pipeline to the appropriate opening. The operation sequence is: first close the front-end electric-controlled plug valve 10, then close the rear-end electric-controlled plug valve 10, then adjust the opening of the electric needle throttle valve 13, and finally open the front-end electric-controlled plug valve 10 and the rear-end electric-controlled plug valve 10 in sequence;

[0063] When the injection of one or two branch pipelines is completed and another branch pipeline needs to be opened, the operation sequence is: first open the front-end electric control plug valve 10, then fully open the electric needle throttle valve 13, and finally open the rear-end electric control plug valve 10;

[0064] After the operation of the newly opened branch pipeline is completely completed, close the previously used branch pipeline.

[0065] The two digital pressure sensors 8 at the front and rear ends of the electric needle throttle valve 13 on each branch pipeline form a set of measurement units. The real-time flow calculation model of each branch pipeline is:

[0066]

[0067] Where: q i A is the real-time flow rate of the i-th branch pipeline at the moment of measurement; ij u is the flow area when the electric needle throttle valve 13 of the i-th branch line is in the j-gear position; i is the real-time flow velocity of the i-th branch pipeline at the time of measurement; g is the acceleration of gravity; a ij P is the ratio of the flow cross-sectional area of the electric needle valve 13 to the flow cross-sectional area of the three-way joint 7 when the electric needle throttle valve 13 of the i-th branch pipeline is in the j-gear position; i1 The real-time pressure of the fluid is measured by the digital pressure sensor 8 provided at the front end of the electric needle throttle valve 13 on the i-th branch pipeline; i2 The digital pressure sensor 8 provided at the rear end of the electric needle throttle valve 13 on the i-th branch pipeline measures the real-time pressure of the fluid; ξ ij is the local resistance coefficient of the electric needle throttle valve 13 of the i-th branch pipeline when it is in the j-gear position; wherein, along the direction from the water inlet to the water outlet, the two electric needle throttle valves 13 on the same branch pipeline are the front electric needle throttle valve 13 and the rear electric needle throttle valve 13, respectively; and the two electric-controlled plug valves 10 on the same branch pipeline are the front electric-controlled plug valve 10 and the rear electric-controlled plug valve 10, respectively;

[0068] The calculation model of the cumulative flow in each branch pipeline at time t is:

[0069]

[0070] Where: t is the injection time; Q iThe cumulative injection flow of the i-th branch pipeline up to time t.

[0071] Example 2

[0072] On the basis of the above embodiment 1, the number of branch pipeline groups in this embodiment is preferably three, and they are arranged side by side. The digital pressure sensor 8 at the front end of the first group of branch pipelines measures the fluid pressure value P 11 , the rear end digital pressure sensor 8 measures the fluid pressure value P 12 The digital pressure sensor 8 at the front end of the second branch pipeline measures the fluid pressure value P 21 , the rear end digital pressure sensor 8 measures the fluid pressure value P 22 The digital pressure sensor 8 at the front end of the third branch pipeline measures the fluid pressure value P 31 , the rear end digital pressure sensor 8 measures the fluid pressure value P 32 , bring the above measured fluid pressure values into the real-time flow calculation model of each branch pipeline:

[0073]

[0074] The real-time flow rate q of each branch pipeline at the time of measurement can be obtained i .

[0075] Then, the cumulative flow rate calculation model of each branch pipeline up to time t is as follows:

[0076]

[0077] Substitute the above calculated real-time flow rate q of each branch pipeline at the time of measurement into i , calculate the cumulative injection flow Q of each branch pipeline to time t i .

[0078] Example 3

[0079] Building on the previous second embodiment, this embodiment features three longitudinal beams arranged side by side along the branch pipelines on the base 1. Support frames are fixed to the longitudinal beams perpendicularly, forming a single-layer sled-like structure with the support frames 2. The two transverse beams are each constructed from two thick-walled steel pipes. The device's support structure, formed by the longitudinal beams, transverse beams, and support frames 2, supports the main and branch pipelines and ensures a secure connection between them.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-hole synchronous quantitative fracturing device for underground coal mines, characterized by: It includes a main pipeline and a branch pipeline, one end of the branch pipeline is a water inlet, and the other end is a water outlet, and the water inlet is connected to the main pipeline; The main pipeline is connected in sequence with a short joint (3), a high-pressure tee (4), a male-female adapter (5), a high-pressure tee (4), a male-female adapter (5), a high-pressure tee (4), and a male-female adapter (6). The end of the short joint (3) away from the high-pressure tee (4) is connected to the water supply pipeline through a high-pressure pump, and the end of the male-female adapter (6) away from the high-pressure tee (4) is provided with a plug for sealing. The branch pipeline is connected in sequence from the water inlet to the water outlet with a three-way joint (7), a male-female adapter (9), an electric-controlled plug valve (10), a high-pressure one-way valve (11), a double-female short joint (12), an electric needle throttle valve (13), a right-angle adapter (14), a three-way joint (7), and an electric-controlled plug valve (10); one end of the electric-controlled plug valve (10) away from the three-way joint (7) is connected to the drilled high-pressure pipeline; and a digital pressure sensor (8) is provided on the three-way joint (7).

2. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 1, characterized in that: At least three branch pipelines are provided; adjacent branch pipelines are parallel to each other and are respectively connected to the main pipeline vertically.

3. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 1, characterized in that: The invention also includes an integrated control console electrically connected to the digital pressure sensor (8), the electric-controlled plug valve (10), the electric needle throttle valve (13) and the integrated control console (15), and is used to control the opening and closing of the electric-controlled plug valve (10), the opening adjustment of the electric needle throttle valve (13), and the data processing of the digital pressure sensor (8).

4. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 3, characterized in that: The digital pressure sensor (8), the electric cock valve (10), the electric needle throttle valve (13) and the integrated control console (15) are all connected by wire in a quick-plug manner.

5. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 1, characterized in that: It also includes a support frame (2) and a base (1), wherein a plurality of support frames (2) are sequentially arranged along the base (1) to form a supporting structure, and the male-female adapter (9), the double female short connector (12), the three-way connector (7), and the electric control plug valve (10) are respectively connected to the support frame (2) by bolts and steel belts.

6. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 5, characterized in that: The base (1) comprises a longitudinal beam arranged along the branch pipeline, and a transverse beam arranged at both ends of the longitudinal beam, wherein the transverse beam and the longitudinal beam are cross-welded and connected.

7. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 1, characterized in that: The short connector (3), the high-pressure tee (4), the first male-female adapter (5), and the second male-female adapter (6) are connected via a union; the tee (7), the third male-female adapter (9), the electric-controlled plug valve (10), the high-pressure one-way valve (11), the double-female short connector (12), the electric needle throttle valve (13), the right-angle adapter (14), the tee (7), the electric-controlled plug valve (10), and the drilled high-pressure pipeline are connected via a union.

8. The multi-hole synchronous quantitative fracturing device for underground coal mines according to claim 1, characterized in that: The inner diameters of the main pipeline and the branch pipeline are 48 mm to 52 mm.

9. A method for controlling a multi-hole synchronous quantitative fracturing device in an underground coal mine according to any one of claims 1 to 8, characterized in that: Along the direction from the water inlet to the water outlet, the two electric needle throttle valves (13) on the same branch pipeline are respectively a front-end electric needle throttle valve (13) and a rear-end electric needle throttle valve (13), and the two electric-controlled plug valves (10) on the same branch pipeline are respectively a front-end electric-controlled plug valve (10) and a rear-end electric-controlled plug valve (10); Before the high-pressure pump is turned on, the electric needle throttle valve (13) is in a fully open state, and the electric-controlled plug valve (10) is in a fully open state; After the high-pressure pump is turned on, when the unused branch pipeline is closed, the control logic of the electric control valve group is: first close the front electric control plug valve (10), then close the rear electric control plug valve (10), and finally close the electric needle throttle valve (13); After the high-pressure pump is turned on, when the closed branch pipeline is reopened, the control logic of the electric control valve group is: first open the front electric control plug valve (10), then fully open the electric needle throttle valve (13), and finally open the rear electric control plug valve (10); After the high-pressure pump is turned on, when adjusting the flow rate of the branch pipeline, the control logic of the electric control valve group is: first close the front electric control plug valve (10), then close the rear electric control plug valve (10), then adjust the opening of the electric needle throttle valve (13), and finally open the front electric control plug valve (10) and the rear electric control plug valve (10) in sequence.

10. The control method of the multi-hole synchronous quantitative fracturing device in underground coal mines according to claim 9, characterized in that: The two digital pressure sensors (8) at the front and rear ends of the electric needle throttle valve (13) on each branch pipeline form a set of measurement units. The real-time flow calculation model of each branch pipeline is: Where: q i A is the real-time flow rate of the i-th branch pipeline at the moment of measurement; ij u is the flow area when the electric needle throttle valve (13) of the i-th branch line is in the j-gear position; i is the real-time flow velocity of the i-th branch pipeline at the time of measurement; g is the acceleration of gravity; a ij P is the ratio of the flow cross-sectional area of the electric needle valve (13) to the flow cross-sectional area of the three-way joint (7) when the electric needle throttle valve (13) of the i-th branch pipeline is in the j-gear position; i1 The digital pressure sensor (8) provided at the front end of the electric needle throttle valve (13) on the i-th branch pipeline measures the real-time pressure of the fluid; P i2 The digital pressure sensor (8) provided at the rear end of the electric needle throttle valve (13) on the i-th branch pipeline measures the real-time pressure of the fluid; ξ ij is the local resistance coefficient when the electric needle throttle valve (13) of the i-th branch pipeline is in the j-gear position; wherein, along the direction from the water inlet to the water outlet, the two electric needle throttle valves (13) on the same branch pipeline are respectively the front electric needle throttle valve (13) and the rear electric needle throttle valve (13); and the two electric control plug valves (10) on the same branch pipeline are respectively the front electric control plug valve (10) and the rear electric control plug valve (10); The calculation model of the cumulative flow in each branch pipeline at time t is: Where: t is the injection time; Q i The cumulative injection flow of the i-th branch pipeline up to time t.

Images