Nitrogen injection displacement enhanced gas extraction system and method

Abstract

The application discloses a nitrogen injection displacement enhanced gas extraction system and method, and belongs to the technical field of gas extraction. The output end of a nitrogen generation mechanism of the system is in communication with one end of a nitrogen injection main pipe; the nitrogen injection branch pipes include a plurality of nitrogen injection branch pipes, and one end of each of the plurality of nitrogen injection branch pipes is in communication with the other end of the nitrogen injection main pipe; the other end of one nitrogen injection branch pipe extends into one gas injection borehole; one pressure sensor and one first electrically-operated branch valve are arranged on each nitrogen injection branch pipe; the extraction branch pipes include a plurality of extraction branch pipes, one end of one extraction branch pipe extends into one extraction borehole; one gas extraction sensor is arranged on each extraction branch pipe; the other end of each of the plurality of extraction branch pipes is in communication with one end of an extraction main pipe; the other end of the extraction main pipe is in communication with the input end of a gas extraction pump; the nitrogen generation mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump and the first electrically-operated branch valve are electrically connected with a control mechanism. The application can improve the gas extraction efficiency and realize intelligent and accurate monitoring and control.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas extraction, in particular to a nitrogen injection displacement enhanced gas extraction system and method. BACKGROUND

[0002] With the gradual increase in demand for coal, the current shallow coal resources are depleted, and coal development is moving to the deep, and the development of deep coal resources is becoming increasingly normalized. With the increase in mining depth, the ground stress is continuously increasing, the gas content and pressure continue to increase, the low permeability coal seam with high gas content increases, and the gas disaster prevention and control pressure is large, which has become an important factor restricting the safety of coal mining in China.

[0003] Traditional borehole pre-drainage technology is difficult to overcome the problem of low permeability of coal seam, and the pre-drainage time is long, the borehole gas flow decay rate is fast, and it cannot meet the mining replacement and safety production requirements. In order to solve the problem of low permeability of coal seam, the permeability and flow rate are increased by protective layer mining, hydraulic fracturing or slotting, loose blasting, large diameter drilling and dense drilling, etc. The gas extraction is strengthened in order to improve the permeability of coal seam and realize the safe mining of coal and gas.

[0004] Although the above-mentioned permeability and flow rate increasing technology improves the permeability of coal seam, the problem of decreased extraction efficiency due to the decrease in coal seam pressure in the later stage of mining cannot be fundamentally solved. In addition, the permeability and flow rate increasing technology of protective layer mining is difficult to achieve for single coal seam. The permeability and flow rate increasing technology of hydraulic fracturing or slotting has the problems of large water consumption and water locking effect. The permeability and flow rate increasing technology of loose blasting is easy to cause secondary damage. The permeability and flow rate increasing technology of large diameter drilling and dense drilling has high construction cost. Therefore, most of the permeability and flow rate increasing technologies are not widely applied due to complex process and poor extraction effect. Therefore, there is an urgent need for a new way to simply and effectively improve the permeability of coal seam and improve the gas extraction efficiency.

[0005] With the continuous progress of science and technology, gas injection displacement gas technology has made breakthrough progress. ECBM test proposes to apply gas injection to underground, uses gas injection displacement (waterless permeability improvement) to improve the gas extraction efficiency of coal seam, and has achieved great success. At present, the gas injection sources mainly include CO2, N2, air and other single or multi-component mixed gas. Due to the wide source of N2, mature nitrogen production process, low N2 injection hazard, no pollution of N2 outburst and other advantages, the application of underground N2 injection displacement coal seam gas is becoming more and more widely. Nitrogen injection displacement gas technology has good application prospect, not only increases the internal gas pressure of coal body and improves the mixed gas seepage speed, but also reduces the effective partial pressure of gas, promotes the desorption of adsorbed gas, makes up for the problem of coal seam pressure drop in the later stage of mining, provides sufficient power and reliable migration channel for coal seam flow field, and is an important means to improve the gas extraction efficiency.

[0006] The existing method of nitrogen injection displacement gas extraction will lead to the decrease of gas extraction concentration in the later stage of nitrogen injection, and it is difficult to improve the gas extraction efficiency. SUMMARY

[0007] The embodiment of the present application can solve the problem that the existing method of nitrogen injection displacement gas extraction leads to a decrease in gas extraction concentration in the late stage of nitrogen injection and makes it difficult to improve the gas extraction efficiency.

[0008] To achieve the above object, the technical scheme of the embodiment of the present application is as follows:

[0009] In a first aspect, the embodiment of the present application provides a nitrogen injection displacement enhanced gas extraction system, comprising a nitrogen generation mechanism, a nitrogen injection main pipe, a nitrogen injection branch pipe, a pressure sensor, a first electrically-operated valve, an extraction branch pipe, an extraction main pipe, a gas extraction sensor, a gas extraction pump and a control mechanism.

[0010] A gas injection borehole is constructed on the coal seam, and an extraction borehole is constructed within the nitrogen displacement radius of the gas injection borehole.

[0011] The output end of the nitrogen generation mechanism is in communication with one end of the nitrogen injection main pipe.

[0012] The nitrogen injection branch pipe comprises a plurality of pipes, and one end of each of the plurality of pipes is in communication with the other end of the nitrogen injection main pipe.

[0013] The other end of one of the nitrogen injection branch pipes extends into one of the gas injection boreholes.

[0014] One pressure sensor and one first electrically-operated valve are arranged on each of the nitrogen injection branch pipes.

[0015] The extraction branch pipe comprises a plurality of pipes, and one end of one of the extraction branch pipes extends into one of the extraction boreholes.

[0016] One gas extraction sensor is arranged on each of the extraction branch pipes.

[0017] The other end of each of the extraction branch pipes is in communication with one end of the extraction main pipe.

[0018] The other end of the extraction main pipe is in communication with the input end of the gas extraction pump.

[0019] The nitrogen generation mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump and the first electrically-operated valve are electrically connected to the control mechanism.

[0020] In combination with the first aspect, in a possible implementation manner, the nitrogen generation mechanism comprises a nitrogen generator and a pressure boosting structure.

[0021] The nitrogen generator is in communication with the pressure boosting structure.

[0022] An output end of the pressurizing structure is in communication with the nitrogen injection main pipe;

[0023] The nitrogen generator and the pressurizing structure are electrically connected with the control mechanism.

[0024] In combination with the first aspect, in a possible implementation manner, the nitrogen generator comprises an electric control structure, a low-purity nitrogen tank, a pressure swing adsorption tower, a high-purity nitrogen tank and an oxygen-rich exhaust pipeline;

[0025] An output end of the low-purity nitrogen tank is in communication with an input end of the pressure swing adsorption tower;

[0026] An output end of the pressure swing adsorption tower is in communication with an input end of the high-purity nitrogen tank;

[0027] An output end of the high-purity nitrogen tank is in communication with an input end of the pressurizing structure;

[0028] One end of the exhaust pipeline is in communication with the low-purity nitrogen tank and the pressure swing adsorption tower respectively, and the other end is exhausted;

[0029] The electric control structure is electrically connected with the control mechanism, the pressure swing adsorption tower, the high-purity nitrogen tank and the pressurizing structure.

[0030] In combination with the first aspect, in a possible implementation manner, the control mechanism comprises a monitoring substation, an editable logic controller, an underground ring network switch and a ground core switch;

[0031] The nitrogen generation mechanism, the pressure sensor, the gas drainage sensor, the gas drainage pump and the first electrically-operated valve are electrically connected with the monitoring substation;

[0032] The monitoring substation is electrically connected with the editable logic controller;

[0033] The editable logic controller is electrically connected with the underground ring network switch;

[0034] The underground ring network switch and the ground core switch are electrically connected.

[0035] In combination with the first aspect, in a possible implementation manner, the nitrogen injection displacement enhanced gas drainage system further comprises an explosion-proof power supply;

[0036] The explosion-proof power supply is electrically connected with the monitoring substation and the editable logic controller respectively.

[0037] In combination with the first aspect, in a possible implementation manner, the nitrogen injection displacement enhanced gas drainage system further comprises an automatic water drainer;

[0038] The other end of the drainage main pipe is in communication with an input end of the automatic water drainer;

[0039] The output end of the automatic water drainer is communicated with the input end of the gas drainage pump.

[0040] In combination with the first aspect, in a possible implementation manner, the gas injection borehole and the extraction borehole are arranged alternately.

[0041] In combination with the first aspect, in a possible implementation manner, the nitrogen injection displacement enhanced gas extraction system further comprises a CH4 concentration sensor and a CO concentration sensor.

[0042] Each of the extraction branch pipes is further provided with a CH4 concentration sensor and a CO concentration sensor.

[0043] The CH4 concentration sensor and the CO concentration sensor are electrically connected with the control mechanism.

[0044] In combination with the first aspect, in a possible implementation manner, the nitrogen injection displacement enhanced gas extraction system further comprises a first electrically-operated master valve.

[0045] The first electrically-operated master valve is arranged on the nitrogen injection main pipe.

[0046] The first electrically-operated master valve is electrically connected with the control mechanism.

[0047] The second aspect, the embodiment of the present application provides a kind of nitrogen injection displacement enhanced gas extraction method, it is characterized in that, based on the nitrogen injection displacement enhanced gas extraction system described above, comprising:

[0048] Gas injection borehole is constructed on coal seam, and extraction borehole is constructed in the nitrogen injection displacement radius range of the gas injection borehole;

[0049] The extraction step is executed multiple times.

[0050] The extraction step comprises:

[0051] The generated nitrogen is injected into the gas injection borehole through the nitrogen injection branch pipe, and the gas of the extraction borehole is extracted through the extraction branch pipe.

[0052] When the gas concentration of the extraction branch pipe reaches the maximum, the injection pressure of nitrogen is reduced to the stable gas concentration in the extraction branch pipe.

[0053] Nitrogen injection is suspended for 30min to 60min until the gas concentration rises.

[0054] The one or more technical solutions provided in the embodiment of the present application have at least the following technical effects or advantages:

[0055] The nitrogen injection displacement enhanced gas extraction system provided in this invention, during actual gas extraction, firstly, gas injection boreholes are constructed on the coal seam, and extraction boreholes are constructed within the nitrogen displacement radius of the gas injection boreholes. Since the output end of the nitrogen generating mechanism is connected to one end of the nitrogen injection main pipe, multiple nitrogen injection branch pipes are included, each with one end connected to the other end of the nitrogen injection main pipe. The other end of each nitrogen injection branch pipe extends into a gas injection borehole. Nitrogen generated by the nitrogen generating mechanism is injected into each gas injection borehole through the nitrogen injection main pipe and nitrogen injection branch pipes. During nitrogen injection, the nitrogen displaces the adsorbed gas in the porous structure of the coal body, enhancing gas extraction efficiency. One end of each extraction branch pipe extends into an extraction borehole, and the other ends of multiple extraction branch pipes are connected to one end of the extraction main pipe, the other end of which is connected to the input end of the gas extraction pump. When the gas extraction pump is turned on, the gas in the extraction borehole is extracted through the extraction branch pipes. Each nitrogen injection branch pipe is equipped with a pressure sensor and a first electrically operated valve, while each extraction branch pipe is equipped with a gas extraction sensor. The gas extraction sensor measures the gas concentration in the extraction branch pipe. When the gas concentration in the extraction branch pipe reaches its maximum, the nitrogen generation mechanism, pressure sensor, gas extraction sensor, and first electrically operated valve are all electrically connected to the control mechanism. The control mechanism controls the operating state of the nitrogen generation mechanism and the first electrically operated valve to reduce the nitrogen injection pressure until the gas concentration in the extraction branch pipe stabilizes. Afterward, the control mechanism pauses nitrogen injection for 30-60 minutes until the gas concentration rises. Repeating the above extraction steps achieves non-uniform pressure time-sharing nitrogen injection displacement enhanced gas extraction control and monitoring, improving gas extraction efficiency and utilizing nitrogen gas more effectively. The control mechanism enables intelligent and precise monitoring and control of the system. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a schematic diagram of the overall structure of the nitrogen injection displacement enhanced gas extraction system provided in the embodiments of this application;

[0058] Figure 2 A partial structural diagram of the nitrogen injection displacement enhanced gas extraction system provided in this application embodiment. Figure 1 ;

[0059] Figure 3 A partial structural diagram of the nitrogen injection displacement enhanced gas extraction system provided in this application embodiment. Figure 2 .

[0060] Icon: 1 - nitrogen generating mechanism; 11 - nitrogen generator; 111 - electric control structure; 112 - low-purity nitrogen tank; 113 - pressure swing adsorption tower; 114 - high-purity nitrogen tank; 115 - oxygen-rich exhaust pipeline; 12 - booster structure; 121 - front-end filter; 122 - booster; 2 - nitrogen injection main pipe; 3 - nitrogen injection branch pipe; 4 - pressure sensor; 5 - flow sensor; 6 - first electrically operated sub-valve; 7 - second electrically operated sub-valve; 8 - CH4 concentration sensor; 9 - CO concentration sensor; 10 - extraction branch pipe; 20 - extraction main pipe; 30 - gas extraction sensor; 40 - gas extraction pump; 50 - control mechanism; 501 - monitoring substation; 502 - editable logic controller; 503 - underground ring network switch; 504 - ground core switch; 60 - explosion-proof power supply; 70 - automatic water drain; 80 - first electrically operated main valve; 90 - second electrically operated main valve; A - coal seam; B - gas injection borehole; C - extraction borehole. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of, rather than all of, the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0062] In the description of the embodiments of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The terms "first", "second", "third" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance. In addition, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements inside. For those of ordinary skill in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0063] Please refer to Figures 1 to 3As shown, the embodiment of the present application provides a nitrogen injection displacement enhanced gas extraction system, which comprises a nitrogen generation mechanism 1, a nitrogen injection main pipe 2, nitrogen injection branch pipes 3, pressure sensors 4, first electrically-operated valve doors 6, extraction branch pipes 10, extraction main pipes 20, gas extraction sensors 30, gas extraction pumps 40, and a control mechanism 50.

[0064] A gas injection borehole B is constructed on the coal seam A, and an extraction borehole C is constructed within the nitrogen displacement radius of the gas injection borehole B. The integrity of the gas injection borehole B and the extraction borehole C is ensured, and the gas injection borehole B and the extraction borehole C are sealed by using a sealing device.

[0065] The displacement radius refers to the radius of the circumscribed circle of the diffusion range of the injected fluid (such as water, gas, or a chemical agent, and nitrogen is injected in the embodiment of the present application) in the coal seam when the injected fluid is used to displace gas or other fluids in the process of gas injection flow enhancement and extraction in the coal seam. The size of the displacement radius directly affects the extraction effect of the injected fluid on the gas and the amount of gas extraction.

[0066] As shown in Figure 1 , the output end of the nitrogen generation mechanism 1 is in communication with one end of the nitrogen injection main pipe 2. The nitrogen injection branch pipes 3 comprise a plurality of nitrogen injection branch pipes 3, and one end of each of the plurality of nitrogen injection branch pipes 3 is in communication with the other end of the nitrogen injection main pipe 2.

[0067] The other end of one of the nitrogen injection branch pipes 3 extends into one of the gas injection boreholes B. As shown in Figure 1 , the other end of the nitrogen injection branch pipe 3 extends into the bottom of the gas injection borehole B, so that the gas injection borehole B can be filled with nitrogen. One pressure sensor 4 and one first electrically-operated valve door 6 are arranged on each of the nitrogen injection branch pipes 3. The pressure sensor 4 can monitor the pressure on each of the nitrogen injection branch pipes 3. The first electrically-operated valve door 6 can control the amount of nitrogen injection of each of the nitrogen injection branch pipes 3.

[0068] By arranging one pressure sensor 4 and one first electrically-operated valve door 6 on each of the nitrogen injection branch pipes 3, the working conditions of each of the gas injection boreholes B can be finely monitored and controlled.

[0069] As shown in Figure 1 and Figure 2 , the nitrogen injection displacement enhanced gas extraction system provided by the embodiment of the present application further comprises a flow sensor 5 arranged on each of the nitrogen injection branch pipes 3. The flow sensor 5 is electrically connected to the control mechanism 50 (specifically, the flow sensor 5 is electrically connected to the monitoring substation 501), so as to accurately measure the gas flow input from the nitrogen injection branch pipe 3 and transmit the measurement data to the control mechanism 50.

[0070] The extraction branch pipes 10 comprise a plurality of extraction branch pipes 10, and one end of each of the extraction branch pipes 10 extends into one of the extraction boreholes C. As shown in Figure 1As shown, the other end of the extraction branch pipe 10 extends into the top of the gas injection borehole B, so that the gas in the extraction borehole C can be completely extracted. A gas extraction sensor 30 is arranged on each extraction branch pipe 10. The gas extraction sensor 30 can monitor the gas flow on each extraction branch pipe 10.

[0071] The other end of the plurality of extraction branch pipes 10 is communicated with one end of the extraction main pipe 20. The other end of the extraction main pipe 20 is communicated with the input end of the gas extraction pump 40. The output end of the gas extraction pump 40 is communicated with the mine gas extraction main pipe.

[0072] The nitrogen generating mechanism 1, the pressure sensor 4, the gas extraction sensor 30, the gas extraction pump 40, and the first electrically operated valve 6 are electrically connected with the control mechanism 50.

[0073] The nitrogen injection displacement enhanced gas extraction system provided by the embodiment of the present application, in the actual gas extraction, first constructs the gas injection borehole B on the coal seam A, and constructs the extraction borehole C within the nitrogen displacement radius of the gas injection borehole B. Since the output end of the nitrogen generating mechanism 1 is communicated with one end of the nitrogen injection main pipe 2, the nitrogen injection branch pipe 3 includes a plurality of, one end of the plurality of nitrogen injection branch pipes 3 is communicated with the other end of the nitrogen injection main pipe 2, the other end of one nitrogen injection branch pipe 3 extends into one gas injection borehole B, and the nitrogen generated by the nitrogen generating mechanism 1 is injected into each gas injection borehole B through the nitrogen injection main pipe 2 and the nitrogen injection branch pipe 3. When the nitrogen is injected, the nitrogen displaces the gas adsorbed in the porous structure of the coal body, and the gas extraction efficiency is enhanced. One end of one extraction branch pipe 10 extends into one extraction borehole C, and the other end of the plurality of extraction branch pipes 10 is communicated with one end of the extraction main pipe 20. The other end of the extraction main pipe 20 is communicated with the input end of the gas extraction pump 40. The gas extraction pump 40 is opened, and the gas in the extraction borehole C is extracted through the extraction branch pipe 10. Since one pressure sensor 4 and one first electrically operated valve 6 are arranged on each nitrogen injection branch pipe 3, and one gas extraction sensor 30 is arranged on each extraction branch pipe 10, the gas concentration of the extraction branch pipe 10 can be measured by the gas extraction sensor 30. When the gas concentration of the extraction branch pipe 10 reaches the maximum, since the nitrogen generating mechanism 1, the pressure sensor 4, the gas extraction sensor 30, and the first electrically operated valve 6 are electrically connected with the control mechanism 50. The control mechanism 50 controls the working state of the nitrogen generating mechanism 1 and the first electrically operated valve 6, so as to reduce the injection pressure of the nitrogen into the extraction branch pipe 10 to stabilize the gas concentration. Then the control mechanism 50 controls the nitrogen generating mechanism 1 and the first electrically operated valve 6 to suspend the nitrogen injection for 30min-60min until the gas concentration rises. The above extraction steps are repeated, the non-uniform pressure time-sharing nitrogen injection displacement enhanced gas extraction control and monitoring are realized, the gas extraction efficiency can be improved, and the nitrogen gas can be more effectively used. The control mechanism 50 is arranged, the intelligent and accurate monitoring and control of the system can be realized.

[0074] In practice, the gas extraction of high-gas low-permeability coal seam A is difficult, and the use of nitrogen displacement gas can improve the efficiency of gas extraction under the premise of ensuring underground safety. The non-uniform pressure time-sharing nitrogen injection displacement of the embodiment of the application can improve the efficiency of nitrogen injection displacement under the condition of full monitoring and control, real-time monitoring of extraction parameters, accurate control of nitrogen injection parameters, and improvement of gas extraction rate. Real-time monitoring and control of nitrogen injection mode, nitrogen injection pressure, gas concentration, negative pressure, nitrogen injection flow rate, etc. (can be monitored and adjusted), accurate observation of the nitrogen injection of a single gas injection borehole B and the gas extraction efficiency within the displacement radius.

[0075] In practice, if the gas injection borehole B is always uniformly pressurized and nitrogen is injected, when the gas concentration reaches the highest, the gas concentration will decay, and most of the nitrogen will be extracted from the extraction borehole C, and the extraction efficiency is difficult to improve. In order to improve the extraction efficiency, it is necessary to ensure that most of the extraction borehole C is gas. Non-uniform pressure is not uniform pressure injection of nitrogen, and time-sharing is not continuous injection of nitrogen, but time-sharing injection of nitrogen. Non-uniform pressure time-sharing nitrogen injection gradually increases the gas concentration by slowly reducing the nitrogen injection pressure, so that the gas continues to accumulate. Non-uniform pressure time-sharing nitrogen injection can improve the efficiency of gas extraction while reducing the amount of nitrogen injection and resource consumption through discontinuous and non-uniform pressure injection.

[0076] As shown in Figure 1 and Figure 2 , the nitrogen generating mechanism 1 includes a nitrogen making machine 11 and a pressurizing structure 12. The nitrogen making machine 11 communicates with the pressurizing structure 12. The output end of the pressurizing structure 12 communicates with the nitrogen injection main pipe 2. The nitrogen making machine 11 and the pressurizing structure 12 are both electrically connected with the control mechanism 50.

[0077] The nitrogen making machine 11 can produce high-purity nitrogen that meets the requirements, and the pressurizing structure 12 can pressurize the output nitrogen, so that the nitrogen can be better injected into the gas injection borehole B. The nitrogen making machine 11 and the pressurizing structure 12 are both electrically connected with the control mechanism 50, and the control mechanism 50 can accurately control the working state of the nitrogen making machine 11 and the pressurizing structure 12.

[0078] Further, the nitrogen making machine 11 includes an electric control structure 111, a low-purity nitrogen tank 112, a pressure swing adsorption tower 113, a high-purity nitrogen tank 114, and an oxygen-rich exhaust pipeline 115.

[0079] The output end of the low-purity nitrogen tank 112 communicates with the input end of the pressure swing adsorption tower 113.

[0080] The output end of the pressure swing adsorption tower 113 communicates with the input end of the high-purity nitrogen tank 114.

[0081] The output end of the high-purity nitrogen tank 114 is communicated with the input end of the pressurization structure 12. The low-purity nitrogen tank 112 is used to collect nitrogen in the air to obtain initial gas. Then the initial gas is input into the pressure swing adsorption tower 113. The pressure swing adsorption tower 113 adsorbs the nitrogen in the initial gas and filters the nitrogen to obtain high-purity nitrogen which is input into the high-purity nitrogen tank 114. The high-purity nitrogen tank 114 pressurizes the high-purity nitrogen and then outputs the high-purity nitrogen to the pressurization structure 12.

[0082] One end of the exhaust pipeline is communicated with the low-purity nitrogen tank 112 and the pressure swing adsorption tower 113 respectively, and the other end is exhausted.

[0083] The electric control structure 111 is electrically connected with the control mechanism 50, the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the pressurization structure 12 through optical fibers. The electric control structure 111 can monitor the pressure of the pressurization structure 12, the temperature, flow rate and purity of the pressure swing adsorption tower 113 and the high-purity nitrogen tank 114 on line by connecting sensors in the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the pressurization structure 12, and sensors in the pressurization structure 12, and then transmits the data to the control mechanism 50 (specifically, the monitoring substation 501 of the control mechanism 50). The control mechanism 50 controls the working state of the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the pressurization structure 12 to realize automatic operation of the system.

[0084] The pressurization structure 12 includes a front filter 121 and a pressurizer 122. The output end of the high-purity nitrogen tank 114 is communicated with the input end of the pressurization structure 12, and the output end of the front filter 121 is communicated with the input end of the pressurizer 122. The output end of the pressurizer 122 is communicated with one end of the nitrogen injection main pipe 2. The electric control structure 111 of the nitrogen making machine 11 is electrically connected with sensors in the pressurizer 122 to monitor the pressure and other data of the pressurizer 122 on line, and then transmits the data to the control mechanism 50 (specifically, the monitoring substation 501 of the control mechanism 50). The control mechanism 50 controls the working state of the pressurizer 122.

[0085] The front filter 121 filters the high-purity nitrogen again to further purify the nitrogen and improve the purity of the nitrogen input into the pressurizer 122. Then the pressurizer 122 pressurizes the nitrogen to meet the requirements of the nitrogen injection displacement enhanced gas recovery operation.

[0086] At present, most of the nitrogen input on site can only reach a low pressure of about 0.5MPA. The pressurization structure 12 provided in the embodiment can realize input of high-pressure nitrogen and fine regulation and control under high pressure.

[0087] Referring to Figure 1 The control mechanism 50 includes a monitoring substation 501, an editable logic controller 502, a downhole ring network switch 503 and a ground core switch 504.

[0088] The nitrogen generating mechanism 1, the pressure sensor 4, the gas drainage sensor 30, the gas drainage pump 40 and the first electrically operated valve 6 are electrically connected with the monitoring substation 501 through optical fibers. Specifically, the electric control structure 111 and the booster 122 of the nitrogen generating mechanism 1 are electrically connected with the monitoring substation 501.

[0089] The monitoring substation 501 is electrically connected with the editable logic controller 502 through optical fibers. The monitoring substation 501 plays a role of transmitting information and exchanging, that is, receiving information of each component and signals collected by sensors, and transmitting the information to the editable logic controller 502 after processing according to set parameters, and transmitting instruction information of the editable logic controller 502 to each component.

[0090] The editable logic controller 502 is electrically connected with the downhole ring network switch 503 through optical fibers. Through the editable logic controller 502, sensor data can be collected, and ground instructions can be transmitted to each component.

[0091] The downhole ring network switch 503 and the ground core switch 504 are electrically connected through optical fibers. The downhole ring network switch 503 is responsible for data transmission and instruction transmission between the ground and the downhole.

[0092] The nitrogen injection displacement enhanced gas drainage system of the embodiment of the application integrates the nitrogen generator 11, the booster structure 12, the gas drainage pump 40, the gas drainage sensor 30, the pressure sensor 4, the monitoring substation 501, the editable logic controller 502, the downhole ring network switch 503, the ground core switch 504, the nitrogen injection main pipe 2, the nitrogen injection branch pipe 3, the drainage main pipe 20 and the drainage branch pipe 10 into one, and realizes intelligent monitoring and control in the process of nitrogen injection displacement enhanced gas drainage.

[0093] The nitrogen generator 11, the booster structure 12, the gas drainage pump 40, the gas drainage sensor 30 and the pressure sensor 4 support the ModBus communication protocol, and through the communication protocol, the set of devices can be connected to an integrated control platform. Remote control of the nitrogen generator 11, the booster structure 12 and sensors is realized, remote control of the nitrogen generator 11 is realized, remote stop of the nitrogen generator 11 is realized, remote control of the booster structure 12 is realized, and remote stop of the booster structure 12 is realized. All the devices and sensors involved are equipped with a general protocol, and can be uniformly monitored and controlled.

[0094] The control platform includes a user management module, a system management module, a data monitoring module, a nitrogen injection parameter control module, a safety risk monitoring module and a report printing module. The control platform can realize real-time monitoring and control of the nitrogen injection and drainage effect of a single gas injection borehole B, and can provide optimization suggestions according to the evaluation of the nitrogen injection displacement effect.

[0095] Optionally, the nitrogen injection displacement enhanced gas extraction system further comprises an explosion-proof power supply 60. The explosion-proof power supply 60 is electrically connected with the monitoring substation 501 and the programmable logic controller 502 respectively, so as to supply power for the monitoring substation 501 and the programmable logic controller 502. In addition, the monitoring substation 501 is used in combination with the explosion-proof power supply 60, and can provide power for each component connected with the monitoring substation 501.

[0096] As shown in Figure 1 , the nitrogen injection displacement enhanced gas extraction system further comprises an automatic water drain 70. The other end of the extraction main pipe 20 is in communication with the input end of the automatic water drain 70. The output end of the automatic water drain 70 is in communication with the input end of the gas extraction pump 40. The automatic water drain 70 can drain the waste water in the gas extraction process in advance, so as to ensure the purity of the extracted gas.

[0097] As shown in Figure 1 , the gas injection borehole B and the extraction borehole C are arranged alternately, so that the drilling is not too close, and the extraction borehole C has high utilization efficiency. Of course, the extraction borehole C can also be arranged above and below the gas injection borehole B.

[0098] As shown in Figure 1 and Figure 3 , the nitrogen injection displacement enhanced gas extraction system provided by the embodiment of the application further comprises a CH4 concentration sensor 8 and a CO concentration sensor 9. One CH4 concentration sensor 8 and one CO concentration sensor 9 are arranged on each extraction branch pipe 10. The CH4 concentration sensor 8 and the CO concentration sensor 9 are electrically connected with the control mechanism 50 (specifically, the CH4 concentration sensor 8 and the CO concentration sensor 9 are electrically connected with the monitoring substation 501) by being arranged on the extraction branch pipe 10. The CH4 concentration sensor 8 and the CO concentration sensor 9 can accurately measure the CH4 and CO contents in the extracted gas from the extraction borehole C respectively, and transmit the measurement data to the control mechanism 50.

[0099] The nitrogen injection displacement enhanced gas extraction system of the embodiment of the application further comprises a first electrically operated main valve 80. The first electrically operated main valve 80 is arranged on the nitrogen injection main pipe 2. The first electrically operated main valve 80 is electrically connected with the control mechanism 50.

[0100] The first electrically operated main valve 80 can control the size of the nitrogen injection amount of the nitrogen injection main pipe 2. By being electrically connected with the control mechanism 50, the control mechanism 50 controls the first electrically operated main valve 80 and the first electrically operated branch valve 6 to jointly act, so as to well control the nitrogen injection amount into the gas injection borehole B.

[0101] Further, the nitrogen injection displacement enhanced gas extraction system of the embodiment of the present application further comprises a second electrically operated main valve 90 and a second electrically operated branch valve 7. The second electrically operated main valve 90 is arranged on the extraction main pipe 20. One second electrically operated branch valve 7 is arranged on each extraction branch pipe 10. The second electrically operated main valve 90 and the second electrically operated branch valve 7 are electrically connected with the control mechanism 50.

[0102] The second electrically operated main valve 90 can control the negative pressure and flow rate of the gas extraction of the extraction main pipe 20. The second electrically operated branch valve 7 can control the negative pressure and flow rate of the gas extraction of the extraction branch pipe 10. The control mechanism 50 controls the second electrically operated main valve 90 and the second electrically operated branch valve 7 to work together, so that the extraction amount of the extraction borehole C can be well controlled.

[0103] Another embodiment of the present application provides a nitrogen injection displacement enhanced gas extraction method based on the above-mentioned nitrogen injection displacement enhanced gas extraction system, which comprises the following steps:

[0104] Step 1: constructing the gas injection borehole B on the coal seam A and constructing the extraction borehole C within the nitrogen displacement radius of the gas injection borehole B.

[0105] Step 2: executing the extraction step for multiple times. Optionally, the execution times are 3-6 times.

[0106] The extraction step comprises the following steps:

[0107] Step 21: injecting the generated nitrogen into the gas injection borehole B through the nitrogen injection branch pipe 3 (the nitrogen enters the porous medium structure of the coal body to displace the gas) and extracting the gas of the extraction borehole C through the extraction branch pipe 10.

[0108] Specifically, the output end of the nitrogen generation mechanism 1 is communicated with one end of the nitrogen injection main pipe 2, the nitrogen injection branch pipe 3 comprises a plurality of nitrogen injection branch pipes, one end of each of the plurality of nitrogen injection branch pipes 3 is communicated with the other end of the nitrogen injection main pipe 2, the other end of one nitrogen injection branch pipe 3 extends into one gas injection borehole B, and the nitrogen generated by the nitrogen generation mechanism 1 is injected into each gas injection borehole B through the nitrogen injection main pipe 2 and the nitrogen injection branch pipe 3. When the nitrogen is injected, the nitrogen displaces the adsorbed gas in the porous structure of the coal body, thereby enhancing the gas extraction efficiency.

[0109] The injection pressure of the nitrogen is 0.1-1 MPa.

[0110] Step 22: when the gas concentration of the extraction branch pipe 10 reaches the maximum, the injection pressure of the nitrogen is reduced to the stable gas concentration in the extraction branch pipe 10.

[0111] Specifically, one end of one extraction branch pipe 10 extends into one extraction borehole C, the other end of the plurality of extraction branch pipes 10 is communicated with one end of an extraction main pipe 20, and the other end of the extraction main pipe 20 is communicated with an input end of a gas extraction pump 40. The gas in the extraction borehole C is extracted through the extraction branch pipe 10 by opening the gas extraction pump 40. Since one pressure sensor 4 and one first electrically-driven branch valve 6 are arranged on each nitrogen injection branch pipe 3, and one gas extraction sensor 30 is arranged on each extraction branch pipe 10, the gas extraction sensor 30 can measure the gas concentration of the extraction branch pipe 10, and when the gas concentration of the extraction branch pipe 10 reaches the highest, since the nitrogen generating mechanism 1, the pressure sensor 4, the gas extraction sensor 30 and the first electrically-driven branch valve 6 are all electrically connected with the control mechanism 50. The control mechanism 50 controls the working state of the nitrogen generating mechanism 1 and the first electrically-driven branch valve 6, so as to reduce the injection pressure of the nitrogen into the extraction branch pipe 10 to stabilize the gas concentration.

[0112] Step 23: pause the nitrogen injection for 30min-60min until the gas concentration rises. The nitrogen injection is paused because the nitrogen is extracted all the time. The nitrogen injection is paused so that some gas can be desorbed and extracted. Specifically, the control mechanism 50 controls the nitrogen generating mechanism 1 and the first electrically-driven branch valve 6 to pause the nitrogen injection for 30min-60min until the gas concentration rises.

[0113] The nitrogen injection displacement enhanced gas extraction method provided by the embodiments of the present application can realize non-uniform pressure time-sharing nitrogen injection displacement enhanced gas extraction control and monitoring, can improve the gas extraction efficiency, and can more effectively utilize the nitrogen gas. The control mechanism 50 is arranged, and the intelligent and accurate monitoring and control of the system can be realized.

[0114] The embodiments in the specification are described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

[0115] The above embodiments are only used to illustrate the technical solutions of the present application, and are not limited to the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A nitrogen injection displacement enhanced gas extraction system, characterized in that, It includes a nitrogen generation mechanism, a nitrogen injection main pipe, nitrogen injection branch pipes, a pressure sensor, a first electric branch valve, an extraction branch pipe, an extraction main pipe, a gas extraction sensor, a gas extraction pump, and a control mechanism. Gas injection boreholes are constructed on the coal seam, and extraction boreholes are constructed within the nitrogen displacement radius of the gas injection boreholes. The output end of the nitrogen generating mechanism is connected to one end of the nitrogen injection manifold; The nitrogen injection branch pipe includes multiple pipes, and one end of each of the multiple nitrogen injection branch pipes is connected to the other end of the nitrogen injection main pipe; The other end of one of the nitrogen injection branch pipes extends into one of the gas injection holes; Each of the nitrogen injection branch pipes is equipped with a pressure sensor and a first electric branch valve; The extraction branch pipe includes multiple pipes, and one end of each extraction branch pipe extends into one extraction borehole; One gas extraction sensor is installed on each of the extraction branch pipes; The other end of each of the multiple extraction branch pipes is connected to one end of the extraction main pipe; The other end of the extraction main pipe is connected to the input end of the gas drainage pump; The nitrogen generating mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump, and the first electric valve are all electrically connected to the control mechanism. The control mechanism includes a monitoring substation, a programmable logic controller, an underground ring network switch, and a surface core switch. The nitrogen generating mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump, and the first electric valve are all electrically connected to the monitoring substation. The monitoring substation is electrically connected to the programmable logic controller; The programmable logic controller is electrically connected to the downhole ring network switch; The downhole ring network switch and the surface core switch are electrically connected; It also includes CH4 concentration sensors and CO concentration sensors; Each of the extraction branch pipes is also equipped with a CH4 concentration sensor and a CO concentration sensor; Both the CH4 concentration sensor and the CO concentration sensor are electrically connected to the control mechanism. It also includes the first electric main valve; The first electric main valve is installed on the nitrogen injection main pipe; The first electric main valve is electrically connected to the control mechanism; When the gas concentration in the extraction branch pipe reaches its maximum, the control mechanism controls the working status of the nitrogen generation mechanism and the first electric branch valve to reduce the nitrogen injection pressure until the gas concentration in the extraction branch pipe stabilizes.

2. The nitrogen injection displacement enhanced gas extraction system according to claim 1, characterized in that, The nitrogen generating mechanism includes a nitrogen generator and a pressurization structure; The nitrogen generator is connected to the pressurization structure; The output end of the booster structure is connected to the nitrogen injection main pipe; Both the nitrogen generator and the pressurization structure are electrically connected to the control mechanism.

3. The nitrogen injection displacement enhanced gas extraction system according to claim 2, characterized in that, The nitrogen generator includes an electronic control structure, a low-purity nitrogen tank, a pressure swing adsorption tower, a high-purity nitrogen tank, and an oxygen-enriched venting pipeline. The output end of the low-purity nitrogen gas tank is connected to the input end of the pressure swing adsorption tower; The output end of the pressure swing adsorption tower is connected to the input end of the high-purity nitrogen tank; The output end of the high-purity nitrogen tank is connected to the input end of the pressurization structure; One end of the venting pipeline is connected to a low-purity nitrogen tank and a pressure swing adsorption tower, respectively, and the other end is used for venting. The electrical control structure is electrically connected to the control mechanism, the pressure swing adsorption tower, the high-purity nitrogen tank, and the pressurization structure.

4. The nitrogen injection displacement enhanced gas extraction system according to claim 1, characterized in that, It also includes explosion-proof power supplies; The explosion-proof power supply is electrically connected to the monitoring substation and the programmable logic controller, respectively.

5. The nitrogen injection displacement enhanced gas extraction system according to claim 1, characterized in that, It also includes automatic water dispensers; The other end of the extraction main pipe is connected to the input end of the automatic water discharge device; The output end of the automatic water drainer is connected to the input end of the gas drainage pump.

6. The nitrogen injection displacement enhanced gas extraction system according to claim 1, characterized in that, The gas injection boreholes and the extraction boreholes are set up alternately.

7. A nitrogen injection displacement enhanced gas extraction method, characterized in that, The nitrogen injection displacement enhanced gas extraction system according to any one of claims 1 to 6 includes: Gas injection boreholes are constructed on the coal seam, and extraction boreholes are constructed within the nitrogen displacement radius of the gas injection boreholes. The sampling process is performed multiple times; The extraction steps include: The generated nitrogen gas is injected into the gas injection borehole through the nitrogen injection branch pipe, and the gas in the extraction borehole is extracted through the extraction branch pipe. When the gas concentration in the extraction branch pipe reaches its maximum, reduce the nitrogen injection pressure until the gas concentration in the extraction branch pipe stabilizes. Suspend nitrogen injection for 30 to 60 minutes until the gas concentration rises.

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