Method for synchronously draining and exhausting water in anticline room-pillar type re-mining area

Abstract

The invention provides a synchronous drainage and air exhaust method for an anticline room-pillar type re-mining area, and belongs to the technical field of coal mining. The problems that the water and gas accumulation condition of the anticline room-column type re-mining area is complex, the discharging process is difficult to effectively monitor, and the discharging effect is difficult to evaluate are solved. Comprising the following steps: collecting geological data of an anticline room-pillar type re-mining area, estimating the total amount of accumulated water and accumulated gas in the re-mining area, and preliminarily estimating the drainage and exhaust period according to the drainage and exhaust capacity; according to the water accumulation and gas accumulation distribution characteristics of the re-mining area, exhaust drill holes, drainage drill holes and monitoring drill holes are constructed in the anticline room-pillar type re-mining area by utilizing an existing roadway; the accumulated water and the accumulated gas in the re-mining area are synchronously discharged, the accumulated water and accumulated gas conditions in the re-mining area are monitored in real time through the monitoring drill holes, and the real-time discharging effect of the accumulated water and the accumulated gas in the re-mining area is judged by comparing the real-time accumulated gas concentration decreasing rate and the accumulated water level decreasing rate with the estimated theoretical result; the device is applied to drainage and air exhaust of the re-mining area.

Description

Technical Field

[0001] The present application relates to the technical field of coal mining, and in particular to a method for synchronous drainage and gas extraction in anticline room-and-pillar complex mining areas. Background Art

[0002] Coal is my country's basic energy and important industrial raw material, and it occupies a dominant position in my country's energy system. At present, my country's energy demand is still on the rise. Although the proportion of coal in total energy consumption continues to decline, considering that renewable energy is difficult to replace traditional fossil energy on a large scale in the short term, coal will still be the "ballast stone" and "stabilizer" of my country's energy supply.

[0003] At present, my country's coal mining technology is constantly improving, and efforts are being made to increase scientific and technological innovation, promote the application of advanced equipment such as comprehensive mechanization, automation, and intelligence; strengthen resource integration and optimal allocation, close and withdraw backward small coal mines, and improve indicators such as raw coal washing rate. The coal recovery rate and efficient utilization rate are constantly improving.

[0004] However, although my country's coal mining technology and recovery rate have reached a relatively high level, before the 1990s, my country mostly adopted coal mining techniques and methods such as tunnel pillar and tunnel caving, and the development level of coal industry equipment and technology at that time was relatively backward, resulting in a low coal recovery rate, which caused a great waste of coal resources and formed a large amount of legacy coal resources, and a large part of which was special and scarce coal, which is an important industrial raw material. Therefore, realizing the recovery of the legacy coal pillar is an important direction to ensure my country's energy supply and sustainable development.

[0005] The re-mining of coal pillars left behind by the anticline room-pillar mining method is an important part of the efficient recovery of the coal pillars left behind. The efficient recovery and re-mining of coal pillars left behind in the anticline room-pillar mining area is of great significance to improving the recovery rate of coal resources. However, water and gas accumulation often exist simultaneously in the anticline room-pillar mining area. In addition, due to the complex distribution of tunnels in the anticline room-pillar mining area, it is required to be put into production as soon as possible. As a result, the discharge of water and gas in the anticline room-pillar mining area faces the problems of unknown underground tunnel conditions, long production cycle, and inability to monitor and evaluate the discharge effect of water and gas in the mining area in real time. Summary of the invention

[0006] In order to solve the problems of complex water and gas accumulation in anticline room-pillar mining areas, difficulty in effectively monitoring the discharge process, and difficulty in evaluating the discharge effect, this application proposes a method for synchronous drainage and gas extraction in anticline room-pillar mining areas.

[0007] The technical solution adopted in this application is: a method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas, comprising the following steps:

[0008] S1: Collect geological data of the anticline room-pillar mining area;

[0009] S2: Estimate the total amount of accumulated water and gas in the re-mining area based on the geological data collected in step S1, and preliminarily estimate the drainage and exhaust period based on the drainage and exhaust capacity;

[0010] S3: Based on the distribution characteristics of water and gas accumulation in the re-mining area, a number of exhaust boreholes are constructed on the coal seam roof at the highest level of the coal seam dip in the anticline room-pillar re-mining area using the existing tunnels, and a number of drainage boreholes are constructed on the coal seam floor at the lowest level of the coal seam dip in the anticline room-pillar re-mining area. Monitoring boreholes are evenly constructed in the existing tunnels in the dip direction of the anticline room-pillar re-mining area; the dip level of the coal seam refers to the height of a certain point along the dip direction of the coal seam relative to the reference plane with the deepest burial depth of the coal seam as the reference plane;

[0011] S4: The accumulated water and gas in the re-mining area are discharged synchronously, and the accumulated water and gas in the re-mining area are monitored in real time by monitoring the boreholes. The real-time gas concentration decrease rate and the water level decrease rate are compared with the theoretical results estimated in step S2 to determine the real-time discharge effect of the accumulated water and gas in the re-mining area, and the exhaust and drainage strategy is dynamically adjusted according to the discharge effect.

[0012] Furthermore, in step S1, geological data of the anticline room-pillar mining area are obtained based on the coalfield mining history and geological data of nearby mines. For the anticline room-pillar mining area with no geological data or incomplete geological data, drilling projects or detection methods are needed to supplement the geological data of the anticline room-pillar mining area.

[0013] Furthermore, only gas and air are considered in the estimation of gas accumulation in the re-mining area, and the ideal gas state equation and the multi-component partial pressure law are used to calculate the molar concentration of gas in the re-mining area, thereby estimating the gas volume in the re-mining area.

[0014] Furthermore, the estimation of water accumulation in the re-mining area is obtained by using the historical recovery rate, historical mined coal seam thickness and historical mined coal seam area.

[0015] Furthermore, the monitoring boreholes in step S3 include water accumulation monitoring boreholes and gas accumulation monitoring boreholes. A water level sensor is fixed in the water accumulation monitoring borehole, and a gas concentration detection sensor is fixed in the gas accumulation monitoring borehole.

[0016] The arrangement of the exhaust boreholes and the drainage boreholes in step S3 is determined by using an optimization model, wherein the expression of the optimization model is as follows:

[0017]

[0018] Where: Z is the total layout cost; c i is the construction cost of the ith borehole; di is the distance weight of the ith borehole; N is the total number of boreholes.

[0019] Furthermore, after the exhaust and drainage are finally completed, the drainage and exhaust in the entire re-mining area are checked by the emission efficiency to determine whether it has met the requirements for re-mining work. The expression of emission efficiency is:

[0020]

[0021] Where: E gas is the gas emission efficiency; V removed is the volume of gas discharged, V total is the total amount of gas in the re-mining area; E water is the water discharge efficiency; W removed is the volume of accumulated water discharged; W total It is the total amount of accumulated water in the re-mining area.

[0022] Furthermore, for the complex mining area with complicated water and gas accumulation, the drainage and exhaust efficiency will change dynamically over time, which can be described by the following formula:

[0023]

[0024] Where: η(t) gas is the cumulative gas emission efficiency; η(t) water is the cumulative discharge efficiency of accumulated water; Q(t') gas is the instantaneous gas emission flow rate; Q(t') water is the instantaneous discharge flow of accumulated water; t' is the integral time variable.

[0025] Furthermore, the gas concentration drop rate in the re-mining area is monitored in real time through the detection borehole. If the difference between the monitoring result and the theoretical calculation result is within the set range, it means that the gas emission effect in the re-mining area is good; if the difference between the monitoring result and the theoretical calculation result exceeds the set range, it means that the gas emission in the re-mining area has a regional poor effect, and further regional targeted gas extraction methods need to be adopted;

[0026] The water level drop rate in the re-mining area is monitored in real time by detecting the drilling holes. If the difference between the monitoring result and the theoretical calculation result is within the set range, it means that the drainage effect of accumulated water in the re-mining area is good; if the difference between the monitoring result and the theoretical calculation result exceeds the set range, it means that the drainage of accumulated water in the re-mining area has poor regional effect, and further regional targeted drainage methods are needed.

[0027] Furthermore, the exhaust and drainage strategy is dynamically adjusted according to the emission effect as follows:

[0028] If the exhaust efficiency is basically consistent with the theoretical calculation, but the drainage effect does not meet expectations, the drainage effect can be enhanced by adjusting the exhaust extraction intensity, adding auxiliary drainage measures, rearranging the drilling holes and / or combining gas-water separation technology;

[0029] If the drainage efficiency is basically consistent with the theoretical calculation, but the exhaust effect does not meet expectations, the exhaust effect can be enhanced by optimizing the drilling position, increasing horizontal directional drilling, increasing the negative pressure of the exhaust system and / or checking the sealing of the pipeline system.

[0030] The beneficial effects of the present application compared to the prior art are as follows: the method provided by the present application utilizes the existing available tunnels underground for drilling construction, thereby reducing the workload of tunnel construction and the length of drilling holes; utilizes the remaining tunnels in the room-and-pillar type re-mining area to connect the accumulated water and gas in the re-mining area, simplifies the drainage and exhaust system, and realizes the efficient discharge of accumulated water and gas in the re-mining area; real-time monitoring of the drainage and exhaust conditions in the re-mining area can dynamically evaluate the discharge effect of accumulated water and gas in the re-mining area; utilizes existing tunnels to discharge accumulated water and gas in the room-and-pillar type re-mining area, thereby reducing the workload of tunnel excavation and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present application is further described below with reference to the accompanying drawings:

[0032] Figure 1 A schematic diagram of drilling construction in a drilling field provided in an embodiment of the present application;

[0033] Figure 2 A cross-sectional view of the exhaust drilling arrangement provided in an embodiment of the present application;

[0034] Figure 3 A cross-sectional view of the arrangement of drainage drilling holes provided in an embodiment of the present application;

[0035] Figure 4 A cross-sectional view of the drilling distribution provided in the embodiment of the present application;

[0036] In the figure: 1 is the exhaust drilling construction drilling site, 2 is the existing tunnel, 3 is the gas accumulation monitoring borehole, 4 is the drainage drilling construction drilling site, 5 is the coal seam bottom plate, 6 is the drainage borehole, 7 is the exhaust borehole, 8 is the coal seam roof, 9 is the water accumulation monitoring borehole, and 10 is the coal pillar. DETAILED DESCRIPTION

[0037] like Figures 1 to 4 As shown, the present application provides a method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas, which utilizes existing tunnels to implement synchronous drainage and gas extraction in anticline room-pillar re-mining areas, and prepares for coal pillar re-mining in the re-mining areas. The main implementation steps are as follows:

[0038] S1: Collect existing geological data and make a preliminary evaluation of the water and gas accumulation in the coal seams in the re-mining area based on the coalfield mining history and the geological data of nearby mines. For re-mining areas with no geological data or incomplete geological data, drilling projects or other detection methods such as geophysical exploration are needed to supplement the geological data of the re-mining area.

[0039] S2: Estimate the total amount of accumulated water and gas in the re-mining area, and preliminarily estimate the mine drainage and exhaust period based on the drainage and exhaust capacity;

[0040] The principle of estimating the total amount of accumulated gas is as follows:

[0041] For an ideal multi-component gas, take a point P (x, y, z) with a micro-volume ΔV, which contains a mass Δm. Then the total mass density ρ at the particle point P is:

[0042]

[0043] If there are N components in the gas, each of which is represented by i, then the mass density ρ of the i-th component at point P is i for:

[0044]

[0045] Where: Δm i is the mass of the i-th gas component in the micro-volume ΔV;

[0046] At the same time, the relationship between the overall mass density at point P and the mass density of each component is:

[0047]

[0048] Therefore, the relative mass concentration of the i-th component, or the mass percentage concentration, is defined as Y i for:

[0049]

[0050] Due to the relationship between density and the amount of substance, then:

[0051] ρ = CM(5);

[0052] ρ i =C i M i (6);

[0053] Where: C, C i are the total amount of substance (molar concentration) and the amount of substance (molar concentration) of component i per unit volume, M and M respectively. iare the average relative molecular mass of the mixed gas and the relative molecular mass of the i-th component respectively. In addition, in the mixed gas, the total amount of substance is equal to the sum of the amounts of each component, that is:

[0054]

[0055] Therefore, the relative concentration of the i-th component, or the percentage concentration of the substance, is i Then:

[0056]

[0057] Then Y i and χ i The relationship between them is:

[0058]

[0059] It is generally believed that multi-component gases obey the perfect gas law, which can be obtained from the state equation:

[0060]

[0061] From this we can get:

[0062]

[0063] According to the law of partial pressure of multiple components, the total pressure p of the gas is equal to the partial pressure p of each component gas. i sum:

[0064]

[0065] Therefore, the mixed gas density ρ in the re-mining area is:

[0066]

[0067] Then we have:

[0068]

[0069] Where: χ is the molar concentration of gas in the re-mining area, in mol / L; ρ is the density of the mixed gas, in kg / m 3 ; p is the total pressure of the re-mining area, in Pa; R is the universal gas constant, which is 8.31 J / (mol·K); T is the temperature in Kelvin; M 1 is the molar mass of air, in kg / mol; M 2 is the molar mass of the gas, in kg / mol.

[0070] The volume of gas accumulation space in the re-mining area is:

[0071]

[0072] Where: V total is the gas accumulation space capacity in the re-mining area, in m 3 ; S is the area of ​​the re-mining area, in m 2 ; h is the historical mining height of the coal seam in the re-mining area, in meters; is the gas accumulation space ratio coefficient in the re-mining area, which is obtained through preliminary detection. It is the ratio of the space volume occupied by gas in the re-mining area to the total space volume that can store water and gas in the re-mining area. The total storage space in the re-mining area × is the gas volume in the initial state; η is the recovery rate of the re-mining area; P 2 Mine drainage capacity, in m 3 / h; t is the drainage time of the re-mining area, unit is h.

[0073] The gas volume in the re-mining area is:

[0074]

[0075] Where: V 1 is the gas volume in the re-mining area, in m 3 ρ 1 is the gas density, in kg / m 3 .

[0076] The formula for estimating the amount of water accumulation is as follows:

[0077]

[0078] Where: W total is the total water volume in the re-mining area, in m 3 ; η is the historical recovery rate; h is the historical coal seam thickness, unit is m; S is the historical coal seam area, unit is m 2 ;

[0079] The total time of gas emission in the re-mining area is estimated as:

[0080]

[0081] Where: T 1 is the total gas extraction time in the re-mining area, in h; P 1 is the mine gas drainage capacity, in m 3 / h.

[0082] The total time for draining water from the re-mining area is estimated to be:

[0083]

[0084] Where: T 2is the total drainage time of the re-mining area, in h; P 2 Mine drainage capacity, in m 3 / h.

[0085] S3: construct a drilling site in the existing tunnel for drilling construction;

[0086] According to the distribution characteristics of water and gas accumulation in the re-mining area, a number of exhaust drill holes are constructed towards the coal seam roof at the highest dip level of the anticline room-pillar re-mining area using the existing tunnels, and a number of drainage drill holes are constructed towards the coal seam floor at the lowest dip level of the anticline room-pillar re-mining area. Monitoring drill holes are evenly constructed in the existing tunnels in the dip direction of the anticline room-pillar re-mining area. The dip level of the coal seam refers to the height of a point along the dip direction of the coal seam relative to the reference plane with the deepest burial depth of the coal seam as the reference plane.

[0087] The optimization model is used to determine the arrangement of exhaust and drainage boreholes, where the expression of the optimization model is as follows:

[0088]

[0089] Where: Z is the total layout cost; c i is the construction cost of the ith borehole; d i is the distance weight of the ith borehole; N is the total number of boreholes;

[0090] S4: The accumulated water and gas in the re-mining area are discharged simultaneously, and the accumulated water and gas in the re-mining area are monitored in real time to determine the discharge effect of the accumulated water and gas in the re-mining area.

[0091] The final drainage and exhaust effects are verified using the emission efficiency to determine whether they meet the requirements for re-mining.

[0092] The emission efficiency is defined in the embodiment of the present application as:

[0093]

[0094] Where: E gas is the gas emission efficiency; V removed is the volume of gas discharged, in m 3 , V total is the total amount of gas in the re-mining area, in m 3 ; E water is the water discharge efficiency; W removed is the volume of accumulated water discharged, in m 3 ; W total is the total amount of water in the re-mining area, in m 3 .

[0095] For the complex mining area with complicated underground water and gas accumulation, the drainage and exhaust efficiency will also change dynamically over time, which can be described by the following formula:

[0096]

[0097] Where: η(t) gas is the cumulative gas emission efficiency; η(t) water is the cumulative discharge efficiency of accumulated water; Q(t') gas is the instantaneous gas emission flow rate, in m 3 ; Q(t') water is the instantaneous discharge flow of accumulated water, in m 3 ; t' is the integral time variable, which is used to describe the change of the emission process over time.

[0098] According to the calculation results of the formula, the emission strategy is dynamically adjusted to maximize emission efficiency.

[0099] The technical solution of the present application is further described below based on specific embodiments.

[0100] 1. Collect geological data

[0101] A preliminary evaluation of the coal seams in the re-mining area is carried out based on the mining history of the coalfield and the geological data of nearby mines. For re-mining areas with no geological data or incomplete geological data, it is necessary to carry out drilling projects on the ground or in existing tunnels underground, or adopt other detection methods such as geophysical exploration to supplement the geological data of the re-mining area.

[0102] First, it is necessary to clarify the basic situation of the re-mining coal seam, including the coal seam floor contour, coal seam thickness, coal seam water accumulation in the re-mining area, gas accumulation and other data. And based on the detection results, it is judged whether the re-mining area is suitable for this method. This method can be used for anticline room-pillar re-mining areas, and other drainage and exhaust methods need to be selected for other types of coal seams or non-room-pillar re-mining areas for initial mining.

[0103] For example, the No. 15 coal seam in a certain experimental mine has been mined in a room-type manner. The single-side coal seam inclination angle is 8°~12°, which is an anticline coal seam. The average thickness of the coal seam is 6.5m, the historical mining height is 2.5m~3m, the historical recovery rate is 17%, the coal seam is buried 80~200m, and the length and width of the remaining coal pillars are both about 20m. It is now found that the water accumulation height in the re-mining area reaches 1 / 2 of the coal seam dip height, and there is gas accumulation in the remaining re-mining area. The historical mining area of ​​the No. 15 coal seam is 2 million m 2 The single-side strike length is 2000m and the dip length is 500m.

[0104] According to the above geological data, the room-pillar mining area of ​​anticline No. 15 in this mine can use the method of discharging accumulated water and gas in this application.

[0105] 2. Estimate the total amount of water and gas accumulation in the re-mining area, as well as the drainage and exhaust construction period

[0106] Estimation of gas accumulation in re-mining area

[0107] In this estimation, it is assumed that all tunnels in the re-mining area are connected and evenly distributed; the main component of gas accumulation in the re-mining area is gas, so only air and gas are considered in the estimation of gas accumulation in the re-mining area; the total amount of gas accumulated in the re-mining area is much larger than the subsequent gas seepage, and the amount of water accumulated in the re-mining area is much larger than the subsequent water inflow, so the dynamic gas changes and water changes caused by subsequent gas seepage and water inflow are not considered; the total gas volume is used to estimate the total gas volume, assuming that the gas composition of the re-mining area is only gas and air, and the gas is evenly distributed, and the space of the re-mining area is completely closed before the re-mining preparation work begins, then the gas volume can be calculated according to formulas (1)-(17).

[0108] Estimation of total water accumulation in No. 15 coal mining area:

[0109] The total amount of water accumulation in the re-mining area is estimated based on the historical mining conditions of the coal seam. According to the existing data, the historical recovery rate of the No. 15 coal seam is 17%, so the volume of water accumulation in the re-mining area accounts for 17% of the total volume of the coal seam. Therefore, the total amount of water accumulation in the re-mining area of ​​the No. 15 coal seam can be calculated according to formula (18).

[0110] Based on the calculated gas volume and total water accumulation, the total gas discharge time and total water discharge time are estimated using formulas (19) and (20), respectively.

[0111] 3. Carry out drilling and drilling construction

[0112] In such Figure 1 The positions shown are respectively used for the construction of the drainage drilling site 4 and the exhaust drilling site 1, to provide a working space for the subsequent construction of the exhaust drilling 7 and the drainage drilling 6. The constructed drilling site needs to meet the requirements of the working space required by the equipment for the subsequent drilling construction;

[0113] The distance between the drainage drilling site 4 and the exhaust drilling site 1 needs to meet the requirement of maintaining the stability of the coal seam where the existing tunnel 2 where the drilling site is located is located;

[0114] At the exhaust drilling site 1, if Figure 2 A number of exhaust boreholes 7 are constructed toward the coal seam roof 8 at the highest dip level of the anticline room-pillar re-mining area. It should be noted that the diameter, number and position of the boreholes shown in the figure are only for indicating the uniform distribution of the boreholes;

[0115] like Figure 3As shown, at the drainage drilling site 4 under construction, a group of drainage boreholes 6 are constructed toward the coal seam floor 5 at the lowest dip level of the anticline room-pillar re-mining area. It should be noted that the diameter, number and position of the boreholes shown in the figure are only for indicating the uniform distribution of the boreholes;

[0116] The exhaust boreholes 7 constructed are evenly distributed along the roof of the coal seam with a high inclination level in the re-mining area. It is particularly important to note that the upper corner of the re-mining area is a location with a higher risk of gas accumulation, so the exhaust boreholes 7 need to be constructed in the upper corner to prevent gas accumulation at the upper corner to cause poor exhaust effect. Similarly, the drainage boreholes 6 are also evenly distributed at the bottom of the coal seam with a low inclination level in the re-mining area to improve the drainage effect of the re-mining area.

[0117] 4. Calculation of drainage and exhaust effects

[0118] like Figure 4 In the existing tunnel 2, monitoring holes are constructed every 100m on one side of the re-mining area to monitor the drainage and exhaust conditions of the re-mining area in real time and evaluate the drainage and exhaust effects of the re-mining area;

[0119] The monitoring boreholes constructed include gas accumulation monitoring borehole 3 and water accumulation monitoring borehole 9. The gas accumulation monitoring borehole 3 is constructed from the existing tunnel 2 to the upper coal seam roof 8 of the re-mining area, and the water accumulation monitoring borehole 9 is constructed from the existing tunnel 2 to the coal seam bottom 5 of the re-mining area.

[0120] The theoretical calculation of real-time gas situation in the re-mining area is:

[0121]

[0122] Where: v c It is the real-time gas concentration decrease rate in the re-mining area, in % / h.

[0123] The gas concentration decrease rate in the re-mining area is monitored in real time through detection drilling. If the monitoring result is basically equal to the theoretical calculation result, it means that the gas emission effect in the re-mining area is good; if the monitoring result is much greater than the theoretical calculation result, it means that the gas emission in the re-mining area has poor regional effect, and further regional targeted gas extraction methods are needed.

[0124] The theoretical calculation of real-time water accumulation in the re-mining area is:

[0125]

[0126] Where: v h is the rate of decline of water level in the re-mining area, in m / h; l is the strike length of the coal seam in the re-mining area.

[0127] The water level drop rate in the re-mining area is monitored in real time through detection drilling. If the monitoring result is basically equal to the theoretical calculation result, it means that the drainage effect of accumulated water in the re-mining area is good; if the monitoring result is much greater than the theoretical calculation result, it means that the drainage of accumulated water in the re-mining area has poor regional effect, and further regional targeted drainage methods are needed.

[0128] Specifically, the following adjustment strategies are provided in the embodiments of the present application.

[0129] If the exhaust efficiency is basically consistent with the theoretical calculation, but the drainage effect does not meet expectations, it can be judged from the following aspects:

[0130] 1. Monitor water level changes in drainage boreholes

[0131] The water accumulation situation of the coal seam floor 5 is monitored in real time through the water accumulation monitoring borehole 9 .

[0132] If the water level drop rate is significantly lower than the theoretical calculated value, it means that water discharge is obstructed.

[0133] 2. Observe the changes in mine pressure

[0134] If the mine pressure measured near the exhaust borehole 7 continues to drop but the water level does not drop significantly, it may be due to the negative pressure causing the water flow direction to change or the water blocking the exhaust channel.

[0135] 3. Borehole gas-water mixing

[0136] If a large amount of gas is found to escape from the drainage borehole 6, it indicates that there may be a water-gas mixed flow phenomenon, and the drilling arrangement needs to be optimized.

[0137] If the flow rate of the drainage borehole 6 is abnormally low, it may indicate that the drainage path is blocked by coal dust, sediment or coal lumps.

[0138] The following adjustment strategies can be adopted:

[0139] 1) Adjust the exhaust extraction intensity

[0140] Reduce the exhaust gas extraction rate: appropriately reduce the exhaust gas extraction negative pressure of the exhaust borehole 7, reduce the shrinkage of coal seam fissures, and restore water permeability.

[0141] Increase the density of local drainage boreholes: Add additional drainage boreholes 6 near the exhaust boreholes 7 to avoid excessive gas extraction affecting the drainage process.

[0142] 2) Add auxiliary drainage measures

[0143] Use pulse drainage: restore the water flow channel of the coal seam through intermittent drainage (i.e. periodically suspend pumping to allow water to seep naturally).

[0144] Conduct hydraulic fracturing: Conduct small-scale hydraulic fracturing in water-blocked areas to increase the permeability of coal seams.

[0145] 3) Rearrange drilling

[0146] Adjust the depth and arrangement of the drainage boreholes: It may be necessary to arrange the drainage boreholes 6 more densely on the coal seam floor 5, or change the drilling angle to make the drainage path smoother.

[0147] Optimize the location of monitoring boreholes: Add additional water accumulation monitoring boreholes 9 in local areas to accurately understand the distribution of water accumulation.

[0148] 4) Combined with gas-water separation technology

[0149] Use water-gas separation device in drilling: Use water-gas separation device to ensure that water and gas can be discharged separately to prevent the gas extraction process from affecting water penetration.

[0150] If the drainage efficiency is basically consistent with the theoretical calculation, but the exhaust effect does not meet expectations, it can be judged from the following aspects:

[0151] 1. The exhaust drilling arrangement is unreasonable, which may be due to the following reasons:

[0152] The location of the exhaust drilling hole 7 does not completely cover the gas-rich area, resulting in the inability to effectively discharge gas in local areas.

[0153] The depth or angle of some holes is not appropriate, which prevents gas from flowing smoothly to the exhaust system.

[0154] Judgment method:

[0155] Compare the layout of the exhaust drilling holes 7 with the gas-rich areas to check whether there are areas with high gas concentration that are not effectively covered.

[0156] By monitoring the boreholes, we can observe the local gas concentration distribution. If we find that the concentration in some areas is high, it may be that the borehole layout is insufficient.

[0157] Adjustment strategy:

[0158] 1) Optimize drilling position:

[0159] Additional exhaust boreholes 7 are added in the upper corners and high gas-rich areas of the coal seam roof 8.

[0160] If the drilling depth is insufficient, re-drill and increase the drilling depth to the high gas concentration layer.

[0161] 2) Increase horizontal directional drilling:

[0162] Directional drilling is used instead of traditional vertical drilling to increase the exhaust coverage and improve the extraction efficiency.

[0163] 2. Insufficient exhaust negative pressure: There may be several reasons:

[0164] The negative pressure of the exhaust system is set too low to effectively extract the gas.

[0165] The mine's extraction and drainage pipelines are aging or leaking, resulting in the inability to effectively transmit negative pressure.

[0166] Judgment method:

[0167] Use an air pressure monitor to measure the negative pressure value at the exhaust borehole 7. If it is much lower than the design value, it means that there may be leakage in the exhaust system or insufficient negative pressure.

[0168] Observe whether there is air leakage in the exhaust duct, especially whether there is abnormal airflow at the joints and valves.

[0169] Adjustment strategy:

[0170] 1) Increase the negative pressure of the exhaust system:

[0171] Adjust the extraction pressure setting of the mine vacuum pump to increase the negative pressure to improve the extraction efficiency.

[0172] 2) Check the piping system:

[0173] Repair aging exhaust pipes and conduct regular sealing tests to prevent gas leakage.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with 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 embodiments of the present application.

Claims

1. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas, characterized by: The following steps are involved: S1: Collect geological data of the anticline room-pillar mining area; S2: Estimate the total amount of accumulated water and gas in the re-mining area based on the geological data collected in step S1, and preliminarily estimate the drainage and exhaust period based on the drainage and exhaust capacity; S3: Based on the distribution characteristics of water and gas accumulation in the re-mining area, a number of exhaust boreholes are constructed on the coal seam roof at the highest level of the coal seam dip in the anticline room-pillar re-mining area using the existing tunnels, and a number of drainage boreholes are constructed on the coal seam floor at the lowest level of the coal seam dip in the anticline room-pillar re-mining area. Monitoring boreholes are evenly constructed in the existing tunnels in the dip direction of the anticline room-pillar re-mining area; the dip level of the coal seam refers to the height of a certain point along the dip direction of the coal seam relative to the reference plane with the deepest burial depth of the coal seam as the reference plane; S4: The accumulated water and gas in the re-mining area are discharged synchronously, and the accumulated water and gas in the re-mining area are monitored in real time by monitoring the boreholes. The real-time gas concentration decrease rate and the water level decrease rate are compared with the theoretical results estimated in step S2 to determine the real-time discharge effect of the accumulated water and gas in the re-mining area, and the exhaust and drainage strategy is dynamically adjusted according to the discharge effect.

2. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 1, characterized in that: In step S1, geological data of the anticline room-pillar mining area are obtained based on the coalfield mining history and geological data of nearby mines. For anticline room-pillar mining areas with no geological data or incomplete geological data, drilling projects or detection methods are needed to supplement the geological data of the anticline room-pillar mining area.

3. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 1, characterized in that: Only gas and air are considered in the estimation of gas accumulation in the re-mining area, and the ideal gas state equation and the multi-component partial pressure law are used to calculate the molar concentration of gas in the re-mining area, thereby estimating the gas volume in the re-mining area.

4. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 1, characterized in that: The estimation of water accumulation in the re-mining area is obtained by the historical recovery rate, historical mined coal seam thickness and historical mined coal seam area.

5. The method for synchronous drainage and gas extraction in anticline room-pillar re-mining area according to claim 1, characterized in that: The monitoring boreholes in step S3 include water accumulation monitoring boreholes and gas accumulation monitoring boreholes. A water level sensor is fixed in the water accumulation monitoring borehole, and a gas concentration detection sensor is fixed in the gas accumulation monitoring borehole.

6. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 5, characterized in that: The arrangement of the exhaust boreholes and the drainage boreholes in step S3 is determined by using an optimization model, wherein the expression of the optimization model is as follows: Where: Z is the total layout cost; c i is the construction cost of the ith borehole; d i is the distance weight of the ith borehole; N is the total number of boreholes.

7. The method for synchronous drainage and gas extraction in anticline room-pillar re-mining area according to claim 1, characterized in that: After the exhaust and drainage are finally completed, the drainage and exhaust in the entire re-mining area are checked by the emission efficiency to determine whether it has met the requirements for re-mining. The expression of emission efficiency is: Where: E gas is the gas emission efficiency; V removed is the volume of gas discharged, V total is the total amount of gas in the re-mining area; E water is the water discharge efficiency; W removed is the volume of accumulated water discharged; W total It is the total amount of accumulated water in the re-mining area.

8. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 7, characterized in that: For complex mining areas with complex water and gas accumulation, the drainage and exhaust efficiency will change dynamically over time, which can be described by the following formula: Where: η(t) gas is the cumulative gas emission efficiency; η(t) water is the cumulative discharge efficiency of accumulated water; Q(t') gas is the instantaneous gas emission flow rate; Q(t') water is the instantaneous discharge flow of accumulated water; t' is the integral time variable.

9. The method for synchronous drainage and gas extraction in anticline room-pillar re-mining area according to claim 1, characterized in that: The gas concentration drop rate in the re-mining area is monitored in real time through detection boreholes. If the difference between the monitoring result and the theoretical calculation result is within the set range, it means that the gas emission effect in the re-mining area is good; if the difference between the monitoring result and the theoretical calculation result exceeds the set range, it means that the gas emission in the re-mining area has a regional poor effect, and further regional targeted gas extraction methods need to be adopted; The water level drop rate in the re-mining area is monitored in real time by detecting the drilling holes. If the difference between the monitoring result and the theoretical calculation result is within the set range, it means that the drainage effect of accumulated water in the re-mining area is good; if the difference between the monitoring result and the theoretical calculation result exceeds the set range, it means that the drainage of accumulated water in the re-mining area has poor regional effect, and further regional targeted drainage methods are needed.

10. A method for synchronous drainage and gas extraction in anticline room-pillar re-mining areas according to claim 9, characterized in that: Dynamically adjust the exhaust and drainage strategy according to the emission effect as follows: If the exhaust efficiency is basically consistent with the theoretical calculation, but the drainage effect does not meet expectations, the drainage effect can be enhanced by adjusting the exhaust extraction intensity, adding auxiliary drainage measures, rearranging the drilling holes and / or combining gas-water separation technology; If the drainage efficiency is basically consistent with the theoretical calculation, but the exhaust effect does not meet expectations, the exhaust effect can be enhanced by optimizing the drilling position, increasing horizontal directional drilling, increasing the negative pressure of the exhaust system and / or checking the sealing of the pipeline system.

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