Nitrogen injection displacement enhanced gas extraction system and method

Abstract

The invention 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 communicated with one end of a nitrogen injection header pipe; one end of each nitrogen injection branch pipe is communicated with the other end of the nitrogen injection main pipe; the other end of one nitrogen injection branch pipe extends into one gas injection drill hole; a pressure sensor and a first electric branch valve are arranged on each nitrogen injection branch pipe; the multiple extraction branch pipes are arranged, and one end of one extraction branch pipe extends into one extraction drill hole. A gas drainage sensor is arranged on each extraction branch pipe; the other ends of the plurality of extraction branch pipes are communicated with one end of the extraction main pipe; the other end of the extraction header pipe is communicated with the input end of the gas drainage pump; the nitrogen generation mechanism, the pressure sensor, the gas drainage sensor, the gas drainage pump and the first electric branch valve are all electrically connected with the control mechanism. The gas extraction efficiency can be improved, and intelligent and accurate monitoring and control are achieved.

Description

Technical Field

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

[0002] As the demand for coal gradually increases, shallow coal resources are exhausted, coal development is shifting to deep areas, and deep coal resource development is becoming increasingly normalized. As mining depth increases, ground stress continues to increase, gas content and pressure continue to increase, and low-permeability coal seams with high gas content increase. The pressure of gas disaster prevention and control is high, which has become an important factor restricting my country's safe coal mining.

[0003] Traditional drilling pre-extraction technology is difficult to overcome the problem of low permeability of coal seams. Pre-extraction takes a long time, and the gas flow rate of the borehole decays quickly, which cannot meet the needs of mining and replacement and safe production. In order to solve the problem of low permeability of coal seams, gas extraction is strengthened through permeability and flow enhancement technologies such as protective layer mining, hydraulic fracturing or slitting, loosening blasting, large-diameter drilling and dense drilling, in order to improve the permeability of coal seams and achieve safe co-mining of coal and gas.

[0004] Although the above-mentioned permeability and flow-increasing technologies have improved the permeability of coal seams, the problem of decreased extraction efficiency due to decreased coal seam pressure in the later stage of mining cannot be fundamentally solved. In addition, the permeability and flow-increasing technologies for protective layer mining are difficult to implement for a single coal seam. Hydraulic fracturing or slit permeability and flow-increasing technologies have large water consumption and water lock effects. Loosening blasting permeability and flow-increasing technologies are prone to secondary hazards. The construction cost of large-diameter drilling and dense drilling permeability and flow-increasing technologies is relatively high. Therefore, most permeability and flow-increasing technologies are not widely used due to their complex processes and poor extraction effects. Therefore, there is an urgent need for a new way to simply and effectively improve the permeability of coal seams and improve gas extraction efficiency.

[0005] With the continuous progress of science and technology, breakthrough progress has been made in gas injection technology for gas displacement. The ECBM test proposed to apply gas injection underground, and adopted gas injection displacement (waterless permeability enhancement) to improve the efficiency of coal seam gas extraction, which has achieved great success. At present, the main sources of gas injection are single or multiple mixed gases such as CO2, N2, and air. Due to the advantages of wide sources of N2, mature nitrogen production technology, low risk of N2 injection, and pollution-free N2 outburst, the application of underground gas injection to displace coal seam gas through N2 is becoming more and more widespread. Nitrogen injection to displace gas technology has good application prospects. It not only increases the internal gas pressure of the coal body and increases the seepage velocity of mixed gas, but also reduces the effective partial pressure of gas, promotes the desorption of adsorbed gas, makes up for the pressure drop problem of coal seams in the later stage of mining, and provides sufficient power and reliable migration channels for the coal seam flow field. It is an important means to improve the efficiency of gas extraction.

[0006] The existing method of replacing gas extraction with nitrogen injection will cause the gas extraction concentration to decrease in the later stage of nitrogen injection through nitrogen injection throughout the process, and it is difficult to improve the gas extraction efficiency. Summary of the invention

[0007] The embodiments of the present application provide a nitrogen injection displacement enhanced gas extraction system and method, which can solve the problem that the existing nitrogen injection displacement gas extraction method will cause the gas extraction concentration to decrease in the later stage of nitrogen injection and it is difficult to improve the gas extraction efficiency through the whole process of nitrogen injection.

[0008] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0009] In a first aspect, an embodiment of the present invention provides a nitrogen injection displacement enhanced gas extraction system, comprising a nitrogen generating mechanism, a nitrogen injection main pipe, a nitrogen injection branch pipe, a pressure sensor, a first electric sub-valve, an extraction branch pipe, an extraction main pipe, a gas extraction sensor, a gas extraction pump, and a control mechanism;

[0010] Constructing a gas injection borehole on the coal seam, and constructing an extraction borehole within the nitrogen displacement radius of the gas injection borehole;

[0011] The output end of the nitrogen generating mechanism is connected to one end of the nitrogen injection main pipe;

[0012] The nitrogen injection branch pipes include a plurality of them, one end of each of the plurality of nitrogen injection branch pipes is connected to 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] Each of the nitrogen injection branch pipes is provided with a pressure sensor and a first electric valve;

[0015] The extraction branch pipes include a plurality of branch pipes, one end of each extraction branch pipe extends into one extraction borehole;

[0016] A gas extraction sensor is provided on each extraction branch pipe;

[0017] The other ends of the plurality of extraction branch pipes are all connected to one end of the extraction main pipe;

[0018] The other end of the extraction main pipe is connected to the input end of the gas extraction pump;

[0019] 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.

[0020] In combination with the first aspect, in a possible implementation, the nitrogen generation mechanism includes a nitrogen generator and a pressurizing structure;

[0021] The nitrogen generator is in communication with the pressurizing structure;

[0022] The output end of the boost structure is connected to the nitrogen injection main pipe;

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

[0024] In combination with the first aspect, in a possible implementation, 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 exhaust pipeline;

[0025] The output end of the low-purity nitrogen tank is connected to the input end of the pressure swing adsorption tower;

[0026] The output end of the pressure swing adsorption tower is connected to the input end of the high-purity nitrogen tank;

[0027] The output end of the high-purity nitrogen tank is connected to the input end of the boosting structure;

[0028] One end of the exhaust pipeline is connected to 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 to the control mechanism, the pressure swing adsorption tower, the high-purity nitrogen tank and the pressurization structure.

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

[0031] The nitrogen generating mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump, and the first electric sub-valve are all electrically connected to the monitoring substation;

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

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

[0034] The underground ring network switch is electrically connected to the ground core switch.

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

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

[0037] In combination with the first aspect, in a possible implementation, the nitrogen injection enhanced gas extraction system further includes an automatic water release device;

[0038] The other end of the main extraction pipe is connected to the input end of the automatic water discharger;

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

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

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

[0042] Each extraction branch pipe is also provided with a CH4 concentration sensor and a CO concentration sensor;

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

[0044] In combination with the first aspect, in a possible implementation, the nitrogen injection displacement enhanced gas extraction system further includes a first electric main valve;

[0045] The first electric main valve is arranged on the nitrogen injection main pipe;

[0046] The first electric main valve is electrically connected to the control mechanism.

[0047] In a second aspect, an embodiment of the present invention provides a method for enhancing gas extraction by nitrogen injection displacement, characterized in that the method is based on the above-mentioned nitrogen injection displacement enhanced gas extraction system, comprising:

[0048] Constructing a gas injection borehole on the coal seam, and constructing an extraction borehole within the nitrogen displacement radius of the gas injection borehole;

[0049] Perform the extraction step multiple times;

[0050] The extraction steps include:

[0051] Injecting the generated nitrogen into the gas injection borehole through the nitrogen injection branch pipe, and extracting the gas in the extraction borehole through the extraction branch pipe;

[0052] When the gas concentration in the extraction branch pipe reaches the highest, reducing the injection pressure of nitrogen until the gas concentration in the extraction branch pipe is stable;

[0053] Suspend nitrogen injection for 30 to 60 minutes until the gas concentration rises.

[0054] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0055] The nitrogen injection displacement enhanced gas extraction system provided by the embodiment of the present invention, when actually performing gas extraction, first constructs a gas injection borehole on the coal seam, and constructs an extraction borehole within the nitrogen displacement radius of the gas injection borehole. Since the output end of the nitrogen generating mechanism is connected to one end of the nitrogen injection main pipe, the nitrogen injection branch pipe includes multiple branches, one end of the multiple nitrogen injection branch pipes are connected to the other end of the nitrogen injection main pipe, and the other end of a nitrogen injection branch pipe extends into a gas injection borehole, and the nitrogen generated by the nitrogen generating mechanism is injected into each gas injection borehole through the nitrogen injection main pipe and the nitrogen injection branch pipe. When nitrogen is injected, nitrogen displaces the gas adsorbed in the porous structure of the coal body, thereby enhancing the gas extraction efficiency. One end of an extraction branch pipe extends into an extraction borehole, and the other ends of the multiple extraction branch pipes are connected to one end of the extraction main pipe, and the other end of the extraction main pipe is connected to the input end of the gas extraction pump. Turn on the gas extraction pump, and the gas in the extraction borehole is extracted through the extraction branch pipe. Since a pressure sensor and a first electric sub-valve are provided on each nitrogen injection branch pipe, and a gas extraction sensor is provided on each extraction branch pipe, the gas extraction sensor can measure the gas concentration of the extraction branch pipe. When the gas concentration of the extraction branch pipe reaches the highest, the nitrogen generation mechanism, the pressure sensor, the gas extraction sensor and the first electric sub-valve are all electrically connected to the control mechanism. The control mechanism controls the working state of the nitrogen generation mechanism and the first electric sub-valve to reduce the injection pressure of nitrogen until the gas concentration in the extraction branch pipe is stable. After that, the control mechanism controls the nitrogen generation mechanism and the first electric sub-valve to suspend nitrogen injection for 30 minutes to 60 minutes until the gas concentration rises. Repeating the above extraction steps to realize non-uniform pressure time-sharing nitrogen injection displacement to strengthen gas extraction control and monitoring can improve gas extraction efficiency and make more effective use of nitrogen gas. The setting of the control mechanism can realize intelligent and precise monitoring and control of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0057] Figure 1 A schematic diagram of the overall structure of a nitrogen injection enhanced gas extraction system provided in an embodiment of the present application;

[0058] Figure 2 A schematic diagram of a partial structure of a nitrogen injection enhanced gas extraction system provided in an embodiment of the present application Figure 1 ;

[0059] Figure 3 A schematic diagram of a partial structure of a nitrogen injection enhanced gas extraction system provided in an embodiment of the present application Figure 2 .

[0060] Icons: 1-nitrogen generation 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-enriched exhaust pipeline; 12-boosting structure; 121-front filter; 122-boosting machine; 2-nitrogen injection main pipe; 3-nitrogen injection branch pipe; 4-pressure sensor; 5-flow sensor; 6-first electric sub-valve; 7-second electric 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 release device; 80-first electric main valve; 90-second electric main valve; A-coal seam; B-gas injection borehole; C-extraction borehole. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] In the description of the embodiments of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present invention. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to the specific circumstances.

[0063] Please refer to Figures 1 to 3As shown, an embodiment of the present invention provides a nitrogen injection enhanced gas extraction system, including a nitrogen generating mechanism 1, a nitrogen injection main pipe 2, a nitrogen injection branch pipe 3, a pressure sensor 4, a first electric sub-valve 6, an extraction branch pipe 10, an extraction main pipe 20, a gas extraction sensor 30, a gas extraction pump 40, and a control mechanism 50.

[0064] Construct gas injection borehole B on coal seam A, and construct extraction borehole C within the nitrogen displacement radius of gas injection borehole B. Ensure the integrity of gas injection borehole B and extraction borehole C, avoid hole collapse and cross-hole, and use hole sealers to seal gas injection borehole B and extraction borehole C.

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

[0066] like Figure 1 As shown, the output end of the nitrogen generating mechanism 1 is connected to one end of the nitrogen injection main pipe 2. The nitrogen injection branch pipes 3 include multiple ones, and one end of the multiple nitrogen injection branch pipes 3 is connected to the other end of the nitrogen injection main pipe 2.

[0067] The other end of a nitrogen injection branch pipe 3 extends into a gas injection borehole B. Figure 1 As shown, 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. A pressure sensor 4 and a first electric valve 6 are arranged on each nitrogen injection branch pipe 3. The pressure sensor 4 can monitor the pressure on each nitrogen injection branch pipe 3. The first electric valve 6 can control the amount of nitrogen injection in each nitrogen injection branch pipe 3.

[0068] For each individual gas injection borehole B, a pressure sensor 4 and a first electric sub-valve 6 are arranged on the nitrogen injection branch pipe 3, so that the working condition of each gas injection borehole B can be finely monitored and controlled.

[0069] like Figure 1 and Figure 2 As shown, the nitrogen injection displacement enhanced gas extraction system provided in the embodiment of the present application further includes a flow sensor 5, and a flow sensor 5 is arranged on each nitrogen injection branch pipe 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 that the gas flow input from the nitrogen injection branch pipe 3 can be accurately measured, and the measurement data can be transmitted to the control mechanism 50.

[0070] The extraction branch pipes 10 include a plurality of branch pipes, and one end of each extraction branch pipe 10 extends into an extraction borehole C. 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 provided 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 ends of the plurality of extraction branch pipes 10 are all connected to one end of the extraction main pipe 20. The other end of the extraction main pipe 20 is connected to the input end of the gas extraction pump 40. The output end of the gas extraction pump 40 is connected to the gas extraction main pipe of the mining area.

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

[0073] The nitrogen injection displacement enhanced gas extraction system provided by the embodiment of the present invention, when actually performing gas extraction, first constructs a gas injection borehole B on the coal seam A, and constructs an 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 connected to one end of the nitrogen injection main pipe 2, the nitrogen injection branch pipe 3 includes multiple branches, one end of the multiple nitrogen injection branch pipes 3 is connected to the other end of the nitrogen injection main pipe 2, and the other end of a nitrogen injection branch pipe 3 extends into a 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 nitrogen is injected, the nitrogen displaces the gas adsorbed in the porous structure of the coal body, thereby enhancing the gas extraction efficiency. One end of an extraction branch pipe 10 extends into an extraction borehole C, and the other ends of the multiple extraction branch pipes 10 are connected to one end of the extraction main pipe 20, and the other end of the extraction main pipe 20 is connected to the input end of the gas extraction pump 40. The gas extraction pump 40 is turned on, and the gas in the extraction borehole C is extracted through the extraction branch pipe 10. Since a pressure sensor 4 and a first electric sub-valve 6 are provided on each nitrogen injection branch pipe 3, and a gas extraction sensor 30 is provided on each extraction branch pipe 10, the gas extraction sensor 30 can measure the gas concentration of the extraction branch pipe 10. When the gas concentration of the extraction branch pipe 10 reaches the highest, since the nitrogen generation mechanism 1, the pressure sensor 4, the gas extraction sensor 30 and the first electric sub-valve 6 are all electrically connected to the control mechanism 50. The control mechanism 50 controls the working state of the nitrogen generation mechanism 1 and the first electric sub-valve 6 to reduce the injection pressure of nitrogen until the gas concentration in the extraction branch pipe 10 is stable. After that, the control mechanism 50 controls the nitrogen generation mechanism 1 and the first electric sub-valve 6 to suspend nitrogen injection for 30min to 60min until the gas concentration rises. Repeating the above extraction steps to realize non-uniform pressure time-sharing nitrogen injection to enhance gas extraction control and monitoring can improve gas extraction efficiency and make more effective use of nitrogen gas. Setting the control mechanism 50 can realize intelligent and accurate monitoring and control of the system.

[0074] In practice, it is difficult to extract gas from high-gas, low-permeability coal seam A. Using nitrogen to displace gas can improve gas extraction efficiency while ensuring underground safety. The non-uniform pressure time-sharing nitrogen injection displacement in the embodiment of the present application can improve the efficiency of nitrogen injection to displace gas under full monitoring and control, monitor the extraction parameters in real time, accurately control the nitrogen injection parameters, and improve the gas extraction rate. The nitrogen injection method, nitrogen injection pressure, gas concentration, negative pressure, nitrogen injection flow rate, etc. can be monitored and controlled in real time (can be monitored and adjusted), and the nitrogen injection situation of a single gas injection borehole B and the gas extraction efficiency within the displacement radius can be accurately observed.

[0075] In practice, if the gas injection borehole B is always injecting nitrogen at uniform pressure, when the gas concentration reaches the highest, the gas concentration will decay, and most of the gas extracted from the extraction borehole C is nitrogen, and the extraction efficiency is difficult to improve. If the extraction efficiency is to be improved, it is necessary to ensure that most of the gas in the extraction borehole C is gas. Non-uniform pressure means that nitrogen is not injected at uniform pressure, and time-sharing means that nitrogen is not injected all the time, but in time periods. Non-uniform pressure time-sharing nitrogen injection slowly reduces the nitrogen injection pressure, gradually increases the gas concentration, and allows the gas to continue to accumulate. Non-uniform pressure time-sharing nitrogen injection can improve gas extraction efficiency while reducing the amount of nitrogen injection and resource consumption by discontinuous and non-uniform pressure nitrogen injection.

[0076] like Figure 1 and Figure 2 As shown, the nitrogen generating mechanism 1 includes a nitrogen generator 11 and a pressurizing structure 12. The nitrogen generator 11 is connected to the pressurizing structure 12. The output end of the pressurizing structure 12 is connected to the nitrogen injection main pipe 2. The nitrogen generator 11 and the pressurizing structure 12 are both electrically connected to the control mechanism 50.

[0077] The nitrogen generator 11 can produce high-purity nitrogen that meets the requirements, and the booster structure 12 can boost the output nitrogen so that the nitrogen can be better injected into the gas injection borehole B. The nitrogen generator 11 and the booster structure 12 are both electrically connected to the control mechanism 50, and the control mechanism 50 can accurately control the working states of the nitrogen generator 11 and the booster structure 12.

[0078] Furthermore, the nitrogen generator 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-enriched exhaust pipeline 115 .

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

[0080] The output end of the pressure swing adsorption tower 113 is connected to the input end of the high purity nitrogen tank 114 .

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

[0082] One end of the exhaust pipeline is connected to 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 to the control mechanism 50, the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the boosting structure 12 through optical fibers. The electric control structure 111 can monitor the pressure of the boosting structure 12, the temperature, flow rate, purity and other data of the pressure swing adsorption tower 113 and the high-purity nitrogen tank 114 online by connecting the sensors in the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the boosting structure 12, and the sensors in the boosting structure 12, and then transmit the data to the control mechanism 50 (specifically, the monitoring substation 501 of the control mechanism 50), and the control mechanism 50 controls the working state of the pressure swing adsorption tower 113, the high-purity nitrogen tank 114 and the boosting structure 12 to realize the automatic operation of the system.

[0084] The boost structure 12 includes a front filter 121 and a booster 122. The output end of the high-purity nitrogen tank 114 is connected to the input end of the boost structure 12, and the output end of the front filter 121 is connected to the input end of the booster 122. The output end of the booster 122 is connected to one end of the nitrogen injection main pipe 2. The electric control structure 111 of the nitrogen generator 11 is electrically connected to the sensor in the booster 122, and can monitor the pressure and other data of the booster 122 online, and then transmit the data to the control mechanism 50 (specifically, the monitoring substation 501 of the control mechanism 50), and the control mechanism 50 controls the working state of the booster 122.

[0085] The front filter 121 filters the high-purity nitrogen again and further purifies it to improve the purity of the nitrogen input to the booster 122. The booster 122 then pressurizes the nitrogen to meet the needs of nitrogen injection displacement and enhanced gas mining operations.

[0086] Currently, most nitrogen input on site can only achieve a low pressure of about 0.5 MPA. The boost structure 12 provided in the embodiment of the present application can realize the input of high-pressure nitrogen and can also achieve fine regulation under high pressure.

[0087] Reference Figure 1 As shown, the control mechanism 50 includes a monitoring substation 501, an editable logic controller 502, an underground ring network switch 503 and a ground core switch 504.

[0088] The nitrogen generating mechanism 1, the pressure sensor 4, the gas extraction sensor 30, the gas extraction pump 40, and the first electric valve 6 are all electrically connected to 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 to the monitoring substation 501.

[0089] The monitoring substation 501 is electrically connected to the editable logic controller 502 via an optical fiber. The monitoring substation 501 plays the role of transmitting information and exchanging information, that is, receiving information from various components and signals collected by sensors, and transmitting them to the editable logic controller 502 according to set parameters after processing, and transmitting the command information of the editable logic controller 502 to various components.

[0090] The editable logic controller 502 is electrically connected to the underground ring network switch 503 through an optical fiber. The editable logic controller 502 can realize the collection of sensor data and transmit ground instructions to various components.

[0091] The underground ring network switch 503 and the ground core switch 504 are electrically connected via optical fiber. The underground ring network switch 503 is responsible for data transmission and command transmission between the underground and the underground.

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

[0093] A series of equipment including nitrogen generator 11, booster structure 12, gas extraction pump 40, gas extraction sensor 30, and pressure sensor 4 support ModBus communication protocol, through which this set of equipment can be connected to an integrated control platform. Remote control of nitrogen generator 11, booster structure 12, sensors, etc. can be realized, nitrogen generator 11 nitrogen production pressure can be remotely controlled, nitrogen production can be remotely stopped, booster structure 12 gas transmission can be remotely controlled, and booster structure 12 can be remotely stopped. All equipment and sensors involved are equipped with universal protocols, which can be monitored and regulated in a unified manner.

[0094] The control platform includes: user management module, system management module, data monitoring module, nitrogen injection parameter control module, safety risk monitoring module and report printing module, etc. The control platform can realize real-time monitoring and control of the nitrogen injection and gas extraction effects of a single gas injection borehole B and gas extraction boreholes in the system, and can provide optimization suggestions based on the evaluation of nitrogen injection displacement effects.

[0095] Optionally, the nitrogen injection displacement enhanced gas extraction system further includes an explosion-proof power supply 60. The explosion-proof power supply 60 is electrically connected to the monitoring substation 501 and the editable logic controller 502 through cables, so as to supply power to the monitoring substation 501 and the editable logic controller 502. In addition, the monitoring substation 501 is used in conjunction with the explosion-proof power supply 60 to provide power to various components connected to the monitoring substation 501.

[0096] like Figure 1 As shown, the nitrogen injection enhanced gas extraction system also includes an automatic water discharger 70. The other end of the extraction main pipe 20 is connected to the input end of the automatic water discharger 70. The output end of the automatic water discharger 70 is connected to the input end of the gas extraction pump 40. The automatic water discharger 70 can discharge wastewater in the gas extraction process in advance to ensure the purity of the extracted gas.

[0097] like Figure 1 As shown, the gas injection boreholes B and the extraction boreholes C are arranged alternately, so that the holes are not drilled too closely, and the extraction boreholes C are used efficiently. Of course, the extraction boreholes C can also be arranged above and below the gas injection boreholes B.

[0098] like Figure 1 and Figure 3 As shown, the nitrogen injection displacement enhanced gas extraction system provided in the embodiment of the present application also includes a CH4 concentration sensor 8 and a CO concentration sensor 9. A CH4 concentration sensor 8 and a CO concentration sensor 9 are also provided on each extraction branch pipe 10. By providing the CH4 concentration sensor 8 and the CO concentration sensor 9 on the extraction branch pipe 10, the CH4 concentration sensor 8 and the CO concentration sensor 9 are both electrically connected to the control mechanism 50 (specifically, the CH4 concentration sensor 8 and the CO concentration sensor 9 are both electrically connected to the monitoring substation 501). It is possible to accurately measure the CH4 and CO contents in the gas extracted 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 present application further includes a first electric main valve 80. The first electric main valve 80 is disposed on the nitrogen injection main pipe 2. The first electric main valve 80 is electrically connected to the control mechanism 50.

[0100] The first electric main valve 80 can control the amount of nitrogen injected into the nitrogen injection main pipe 2. By being electrically connected to the control mechanism 50, the control mechanism 50 controls the first electric sub-valve 6 and works together with the first electric sub-valve 6 to control the amount of nitrogen injected into the gas injection borehole B well.

[0101] Furthermore, the nitrogen injection displacement enhanced gas extraction system of the embodiment of the present application further includes a second electric main valve 90 and a second electric sub-valve 7. The second electric main valve 90 is arranged on the extraction main pipe 20. A second electric sub-valve 7 is arranged on each extraction branch pipe 10. The second electric main valve 90 and the second electric sub-valve 7 are both electrically connected to the control mechanism 50.

[0102] The second electric main valve 90 can control the negative pressure and flow rate of the gas extracted by the extraction main pipe 20. The second electric sub-valve 7 can control the negative pressure and flow rate of the gas extracted by the extraction branch pipe 10. The control mechanism 50 controls the second electric main valve 90 and the second electric sub-valve 7 to work together, which can well control the extraction amount of the extraction borehole C.

[0103] Another embodiment of the present invention provides a method for enhancing gas extraction by nitrogen injection displacement, based on the above-mentioned nitrogen injection displacement enhanced gas extraction system, comprising:

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

[0105] Step 2: Execute the extraction step multiple times. Optionally, the number of executions is 3 to 6 times.

[0106] The extraction steps include:

[0107] Step 21: Inject 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 extract the gas from the extraction borehole C through the extraction branch pipe 10.

[0108] Specifically, the output end of the nitrogen generating mechanism 1 is connected to one end of the nitrogen injection main pipe 2, and the nitrogen injection branch pipes 3 include multiple ones, one end of each of the multiple nitrogen injection branch pipes 3 is connected to the other end of the nitrogen injection main pipe 2, and the other end of one nitrogen injection branch pipe 3 extends into a gas injection borehole B. 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 pipes 3. When the nitrogen is injected, the nitrogen displaces the gas adsorbed in the porous structure of the coal body, thereby enhancing the gas extraction efficiency.

[0109] The injection pressure of nitrogen is 0.1 MPA to 1 MPA.

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

[0111] Specifically, one end of an extraction branch pipe 10 extends into an extraction borehole C, and the other ends of the plurality of extraction branch pipes 10 are all connected to one end of the extraction main pipe 20, and the other end of the extraction main pipe 20 is connected to the input end of the gas extraction pump 40. The gas extraction pump 40 is turned on, and the gas in the extraction borehole C is extracted through the extraction branch pipe 10. Since a pressure sensor 4 and a first electric sub-valve 6 are provided on each nitrogen injection branch pipe 3, and a gas extraction sensor 30 is provided on each extraction branch pipe 10, the gas extraction sensor 30 can measure the gas concentration of the extraction branch pipe 10. When the gas concentration of the extraction branch pipe 10 reaches the highest, the nitrogen generation mechanism 1, the pressure sensor 4, the gas extraction sensor 30 and the first electric sub-valve 6 are all electrically connected to the control mechanism 50. The control mechanism 50 controls the working state of the nitrogen generation mechanism 1 and the first electric sub-valve 6 to reduce the injection pressure of nitrogen until the gas concentration in the extraction branch pipe 10 is stable.

[0112] Step 23: suspend nitrogen injection for 30 to 60 minutes until the gas concentration rises. The nitrogen injection is suspended because nitrogen is continuously injected and what is extracted is nitrogen. Suspending nitrogen injection allows some gas to be desorbed from the nitrogen before the gas can be extracted. Specifically, the control mechanism 50 controls the nitrogen generating mechanism 1 and the first electric valve 6 to suspend nitrogen injection for 30 to 60 minutes until the gas concentration rises.

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

[0114] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0115] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A nitrogen injection enhanced gas extraction system, characterized in that: It includes a nitrogen generating mechanism, a nitrogen injection main pipe, a nitrogen injection branch pipe, a pressure sensor, a first electric sub-valve, an extraction branch pipe, an extraction main pipe, a gas extraction sensor, a gas extraction pump, and a control mechanism; Constructing a gas injection borehole on the coal seam, and constructing an extraction borehole within the nitrogen displacement radius of the gas injection borehole; The output end of the nitrogen generating mechanism is connected to one end of the nitrogen injection main pipe; The nitrogen injection branch pipes include a plurality of them, one end of each of the plurality of 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 boreholes; Each of the nitrogen injection branch pipes is provided with a pressure sensor and a first electric valve; The extraction branch pipes include a plurality of branch pipes, one end of each extraction branch pipe extends into one extraction borehole; A gas extraction sensor is provided on each extraction branch pipe; The other ends of the plurality of extraction branch pipes are all 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 extraction 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.

2. The nitrogen injection enhanced gas extraction system according to claim 1, characterized in that: The nitrogen generation mechanism includes a nitrogen generator and a pressurizing structure; The nitrogen generator is in communication with the pressurizing structure; The output end of the boost structure is connected to the nitrogen injection main pipe; The nitrogen generator and the pressurizing structure are both electrically connected to the control mechanism.

3. The nitrogen injection enhanced gas extraction system according to claim 2, characterized in that: 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-enriched exhaust pipeline; The output end of the low-purity nitrogen 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 boosting structure; One end of the exhaust pipeline is connected to the low-purity nitrogen tank and the pressure swing adsorption tower respectively, and the other end is exhausted; The electric 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 enhanced gas extraction system according to claim 1, characterized in that: The control mechanism includes a monitoring substation, an editable logic controller, an underground ring network switch and a ground core switch; The nitrogen generating mechanism, the pressure sensor, the gas extraction sensor, the gas extraction pump, and the first electric sub-valve are all electrically connected to the monitoring substation; The monitoring substation is electrically connected to the editable logic controller; The editable logic controller is electrically connected to the underground ring network switch; The underground ring network switch is electrically connected to the ground core switch.

5. The nitrogen injection enhanced gas extraction system according to claim 4, characterized in that: Also includes an explosion-proof power supply; The explosion-proof power supply is electrically connected to the monitoring substation and the editable logic controller respectively.

6. The nitrogen injection enhanced gas extraction system according to claim 1, characterized in that: Also includes an automatic water release; The other end of the main extraction pipe is connected to the input end of the automatic water discharger; The output end of the automatic water drainer is communicated with the input end of the gas extraction pump.

7. The nitrogen injection enhanced gas extraction system according to claim 1, characterized in that: The gas injection boreholes and the extraction boreholes are arranged alternately.

8. The nitrogen injection enhanced gas extraction system according to claim 1, characterized in that: It also includes a CH4 concentration sensor and a CO concentration sensor; Each extraction branch pipe is also provided with a CH4 concentration sensor and a CO concentration sensor; The CH4 concentration sensor and the CO concentration sensor are both electrically connected to the control mechanism.

9. The nitrogen injection enhanced gas extraction system according to claim 1, characterized in that: Also included is a first electric master valve; The first electric main valve is arranged on the nitrogen injection main pipe; The first electric main valve is electrically connected to the control mechanism.

10. A method for enhancing gas extraction by nitrogen injection displacement, characterized in that: The nitrogen injection and displacement enhanced gas extraction system according to any one of claims 1 to 9 comprises: Constructing a gas injection borehole on the coal seam, and constructing an extraction borehole within the nitrogen displacement radius of the gas injection borehole; Perform the extraction step multiple times; The extraction steps include: Injecting the generated nitrogen into the gas injection borehole through the nitrogen injection branch pipe, and extracting the gas in the extraction borehole through the extraction branch pipe; When the gas concentration in the extraction branch pipe reaches the highest, reducing the injection pressure of nitrogen until the gas concentration in the extraction branch pipe is stable; Suspend nitrogen injection for 30 to 60 minutes until the gas concentration rises.

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