Method for extracting pressure relief gas of protected layer through bedding drilling

Abstract

The invention discloses a method for extracting pressure relief gas of a protected layer through bedding drilling. The method specifically comprises the following steps that 1, a first protection layer working face of a protection layer coal seam is exploited; 2, a gas roadway is constructed in a protected layer coal seam protected by the first protection layer working face and serves as a gas control roadway for exploiting an adjacent second protection layer working face, and bedding drilling is constructed from the gas roadway; and 3, when the working face of the second protective layer is stoped, pressure relief gas of the coal seam of the protected layer is extracted through the gas roadway and the bedding drill hole. The method has the advantages that the gas roadway is constructed in the protected layer coal seam effectively protected by the adjacent protection layer, the gas roadway is a coal roadway, the construction is safe, reliable and high in efficiency, the gas roadway can also serve as a mining roadway, and preparation roadways for mine production are saved; the pressure relief gas of the protected layer is extracted from the bedding drilling in the gas roadway construction, the bedding drilling construction efficiency is high, the extraction effect is good, the pressure relief gas of the protected layer can be extracted timely and efficiently, and the drilling amount and the drilling cost are saved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mine gas control, and in particular to a method for extracting gas from a protected layer by drilling holes along the layer. Background Art

[0002] Coal and gas outbursts seriously threaten the safe production of coal mines. The pressure relief effect of mining the protective layer on the protected layer is very uniform, and it is the most reliable and effective measure to prevent outbursts; therefore, in the outburst danger zone with the conditions for mining the protective layer, the protective layer must be mined. When mining the protective layer, the gas of the protected layer must be extracted at the same time to improve the protection effect of the protected layer and prevent the gas of the protected layer from flowing into the working face of the protective layer and threatening production safety. Conventional measures for extracting and unloading gas from the protected layer include the tunnel method coal and gas co-mining mode, the pillarless coal and gas co-mining mode, and the ground drilling method coal and gas co-mining mode.

[0003] The tunnel method coal and gas co-mining mode requires the construction of a roof (bottom) lane as a special gas control lane, and the construction of a through-layer borehole from the gas control lane to the protected layer to extract the gas from the protected layer to relieve pressure. This method requires the construction of a roof (bottom) lane in the rock layer and the construction of through-layer boreholes, which is a large amount of work and a long preparation period, affecting the safety and efficiency of mine production. In addition, it is difficult to find a suitable rock layer for the construction of a roof (bottom) lane for the protective layer of a close-range coal seam group mining. Therefore, this aspect is restricted in the application of the protective layer working face of a close-range coal seam group mining. The non-coal pillar coal and gas co-mining mode constructs through-layer boreholes from the track or transportation of the lane left in the protective layer working face to the protected layer. It is suitable for the working face with a lane left. The borehole is easily damaged by the ground stress caused by mining, and the extraction effect is limited. It is not suitable for the working face without a lane left. The ground drilling method coal and gas co-mining mode is suitable for the mining of the lower protective layer, and is affected by the ground environment and the underground coal seam cover, and has certain limitations. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to effectively protect the construction of a gas tunnel in the protected layer and efficiently extract the gas from the protected layer by depressurizing it.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for extracting gas from a protected layer by drilling holes along the layer, specifically comprising the following steps:

[0007] Step 1: mining the first protective layer working face of the protective layer coal seam;

[0008] Step 2: construct a gas tunnel in the protected coal seam protected by the first protective layer working face as a gas control tunnel for mining the adjacent second protective layer working face, and construct a borehole along the layer from the gas tunnel;

[0009] Step 3: When mining the second protective layer working face, use gas tunnels and in-layer drilling holes to extract and release gas from the protected coal seam.

[0010] The method of the present invention constructs a gas tunnel in a protected coal seam which is effectively protected by an adjacent protective layer. The gas tunnel is a coal tunnel, and the construction is safe, reliable and efficient. It can also be used as a mining tunnel, saving mine production preparation tunnels. The gas tunnel is constructed by drilling holes along the layer to extract the pressure-relief gas from the protected layer. The drilling holes along the layer have high construction efficiency and good extraction effect, and the pressure-relief gas from the protected layer can be extracted in a timely and efficient manner, saving drilling volume and drilling costs.

[0011] Preferably, after the first protective layer working face is mined in step 1, a coal pillar segment of no more than 4 m is left until the mining of the protective layer coal seam is completed, and the first protective layer working face is arranged at the working face with the lowest elevation of the protective layer coal seam.

[0012] Preferably, in step 2, the gas tunnel is constructed in advance before the second protective layer working face is mined.

[0013] Preferably, in step 2, the gas tunnel is constructed along the roof of the protected coal seam, the horizontal projection of the gas tunnel is located within the protection range of the working surface of the first protective layer and is not less than 30m away from the protection range of the working surface of the second protective layer, and the tunnel cross-section of the gas tunnel is not less than 16㎡.

[0014] Preferably, in step 2, the in-layer drilling is carried out in advance before the second protective layer working face is mined.

[0015] Preferably, in step 2, the in-layer drilling holes are opened in the protective layer coal seam corresponding to the first protective layer working face and constructed perpendicularly to the gas tunnel into the protected layer coal seam corresponding to the second protective layer working face. The diameter of the in-layer drilling holes is not less than 94mm, and protective casing is installed throughout the in-layer drilling holes; the spacing of the in-layer drilling holes is 10-40m.

[0016] Preferably, in step 2, if the gas pressure of the protected layer exceeds 3 MPa or the length of the working face of the second protective layer is relatively large, short boreholes along the layer are constructed first to intercept and drain the gas from the coal seam of the protected layer and flow into the gas tunnel.

[0017] Preferably, in step 2, compressed air is used for deslagging during the in-layer drilling construction, and the air pressure is not less than 0.8 MPa; if rock is seen at the end of the in-layer drilling for more than 30m and coal is not seen as expected, additional in-layer drilling is constructed nearby.

[0018] Preferably, in step 3, during the mining process of the second protective layer working face, the protected coal seam is extracted to relieve pressure on the gas. If the in-layer drill holes for extracting the second protective layer working face designed in the gas tunnel are completed before the mining of the second protective layer working face, after taking measures to prevent flooding in the gas tunnel, the gas tunnel is closed before the mining of the second protective layer working face, and all the extraction drill holes are opened before closing. Extraction pipelines are buried in the closed wall of the gas tunnel, and the gas in the in-layer drill holes and the gas tunnel is extracted by the extraction pipelines pre-buried in the closed wall of the gas tunnel; if the gas tunnel is not closed during the mining of the second protective layer working face, an extraction pipeline is laid in the gas tunnel, and each in-layer drill hole is tightly connected to the extraction pipeline.

[0019] Preferably, the ventilation volume of the gas tunnel is not less than 1000m 3 / min.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method of the present invention constructs a gas tunnel in a protected coal seam which is effectively protected by an adjacent protective layer. The gas tunnel is a coal tunnel, and the construction is safe, reliable and efficient. It can also be used as a mining tunnel, saving mine production preparation tunnels. The gas tunnel is constructed by drilling holes along the layer to extract the pressure-relief gas from the protected layer. The drilling holes along the layer have high construction efficiency and good extraction effect, and the pressure-relief gas from the protected layer can be extracted in a timely and efficient manner, saving drilling volume and drilling costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0023] Figure 2 is a cross-sectional view of an embodiment of the present invention;

[0024] Figure 3 This is a diagram showing changes in gas mechanical parameters of the protected coal seam after the protective layer working face is mined in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0026] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] In this application, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically limited.

[0028] It should be noted that in the field of mining engineering, the protective coal seam refers to the coal seam or mineral layer that is mined first during the mining process to prevent gas outbursts. Its function is to release gas pressure and reduce the gas content of adjacent coal seams, thereby reducing the risk of gas outbursts. The protected coal seam is the coal seam that is protected by mining the protective coal seam.

[0029] See also Figure 1 to Figure 2 This embodiment discloses a method for extracting gas from a protected layer by drilling holes along the layer, which specifically includes the following steps:

[0030] Step 1: Mining the first protective layer working face 11 of the protective layer coal seam 1.

[0031] After the first protective layer working face 11 is mined, a section coal pillar 2 of no more than 4 m is left until the mining of the protective layer coal seam 1 is completed. The first protective layer working face 11 is arranged at the working face with the lowest elevation of the protective layer coal seam 1.

[0032] Step 2: construct a gas tunnel 4 in the protected coal seam 3 protected by the first protective layer working face 11 as a gas control tunnel for mining the adjacent second protective layer working face 12, and construct a layer-coordinated borehole 5 from the gas tunnel 4.

[0033] Specifically, the gas tunnel 4 and the in-layer drill hole 5 are both constructed in advance before the second protective layer working face 12 is mined, wherein the gas tunnel 4 is constructed along the roof of the protected coal seam 3, and the horizontal projection of the gas tunnel 4 is located within the protection range of the first protective layer working face 11 and is not less than 30m away from the protection range of the second protective layer working face 12, and the tunnel section of the gas tunnel 4 is not less than 16㎡.

[0034] The design position of the gas tunnel 4 is mainly determined by the impact of mining on the second protective layer working face 12, the gas mechanical properties of the protected coal seam 3, and whether the gas tunnel 4 has other functions. The gas tunnel 4 is generally located in the original stress area of ​​the second protective layer working face 12, such as Figure 3 As shown. In addition to constructing the borehole 5 along the layer to extract the decompressed gas from the protected coal seam 3, the gas lane 4 can also be used as the mining lane of the protected coal seam 3, the lane for investigating the original gas parameters of the protected coal seam 3 and the protective layer effect of the protected coal seam 3, and the gas lane for treating the working face of the protected coal seam 3 corresponding to the first protective layer working face 11, etc., to achieve "one lane for multiple uses".

[0035] The in-layer drill hole 5 is opened in the protective layer coal seam 1 corresponding to the first protective layer working face 11 and is constructed perpendicular to the gas lane 4 into the protected layer coal seam 3 corresponding to the second protective layer working face 12. The diameter of the in-layer drill hole 5 is not less than 94mm, and a protective casing is installed throughout the in-layer drill hole 5; the spacing of the in-layer drill holes 5 is 10-40m, which is determined according to the expected gas outburst volume, borehole diameter, etc.; the length of the in-layer drill hole 5 is determined according to the length of the second protective layer working face 12, and must cover the effective protection range of the second protective layer working face 12.

[0036] It should be noted here that the effective protection range refers to the area where the gas content and gas pressure of the protected layer can be reduced after the protective layer is mined, thereby eliminating the danger of outburst of the protected layer. This range is usually expressed as a pressure relief angle, including the pressure relief range along the strike and dip of the coal seam; the boundary of the effective protection range of the protected layer is determined by the boundary of the mined protective layer. The spacing between the protective layer and the protected layer, the mining thickness of the protective layer, the mining method, the inclination of the coal seam, the physical properties of the coal seam (such as porosity and permeability), etc. will all affect the pressure relief range. The effective protection range of the protected layer needs to take into account a variety of factors and be determined in combination with on-site measurements or numerical simulation results.

[0037] Specifically, the depth of the in-layer drilling hole 5 is determined according to factors such as the original gas pressure, gas content, and coal seam solidity coefficient of the protected coal seam 3. If the gas pressure of the protected coal seam 3 exceeds 3MPa or the length of the second protective layer working face 12 is relatively large, it is difficult to construct the in-layer drilling hole 5 in advance to cover the effective protection range of the second protective layer working face 12. It is necessary to construct a short in-layer drilling hole first to intercept and extract the gas from the protected coal seam 3 and flow into the gas lane. The opening parameters of the short drilling hole are consistent with those of the in-layer drilling hole, and the length is not less than 50m. The in-layer drilling hole 4 is constructed 15-40m after the mining position of the second protective layer working face 12 to cover the effective protection range of the second protective layer working face 12.

[0038] In view of the fact that the protected coal seam 3 is soft and has high gas pressure in its original state, a bed drill hole 5 is constructed from the gas lane 4. Pressurized air is used to remove slag during the construction of the bed drill hole 5, and the wind pressure is not less than 0.8MPa. If rock is seen at the end of the bed drill hole 5 for more than 30m and coal is not seen as expected, an additional bed drill hole 5 is constructed nearby.

[0039] Step 3: When mining the second protective layer working face 12, use the gas tunnel 4 and the in-layer boreholes 5 to extract the gas from the protected coal seam 3 to relieve pressure. During the mining process, if the in-layer boreholes 5 designed in the gas tunnel 4 for extracting the second protective layer working face 12 are completed before the second protective layer working face 12 is mined, and after taking measures to prevent flooding of the gas tunnel 4, the gas tunnel 4 is closed before the mining of the second protective layer working face 12. All the extraction boreholes are open before closing, and extraction pipelines are buried in the closed wall of the gas tunnel 4. The extraction pipelines pre-buried in the closed wall of the gas tunnel 4 are used to extract the gas from the in-layer boreholes 5 and the gas tunnel 4. If the gas tunnel 4 is not closed during the mining of the second protective layer working face 12, an extraction pipeline is laid in the gas tunnel 4, and each in-layer borehole 5 is tightly connected to the extraction pipeline, and the ventilation volume of the gas tunnel 4 is not less than 1000m 3 / min, and full negative pressure ventilation should be achieved if conditions permit. A gas sensor is installed in gas lane 4, and the gas is checked as required to ensure that the gas concentration in the gas lane meets the requirements.

[0040] Specific implementation example: The test site is to construct a gas tunnel in the coal seam adjacent to the protected layer. A 113mm diameter in-layer borehole is constructed every 20m in the gas tunnel, with a hole depth of 210m, and the borehole covers the effective protection range of the protective layer. Before the protective layer working face is mined, all the drilling holes are completed and the gas tunnel is closed. Before closing, all the extraction boreholes are open, and two 12-inch extraction pipelines are buried in the closed wall of the gas tunnel, which are connected to the permanent ground extraction system. All in-layer boreholes are elevation boreholes, but the lowest point of the gas tunnel is in the middle of the tunnel. Since the lower protective layer is mined, a through-layer borehole is constructed from the lower protective layer to the vicinity of the lowest point of the gas tunnel as a drainage hole for the gas tunnel. During the mining of the protective layer working face, the extraction pipeline pre-buried in the closed wall of the gas tunnel is used to extract gas from the in-layer boreholes and the gas tunnel. The gas extraction concentration is 26%-53%, the extraction mixture is 80-130m 3 / min, pure gas extraction volume 28-52m 3 / min, the average pure gas extraction volume is 41.8m 3 / min.

[0041] The method in this embodiment constructs a gas tunnel in the protected coal seam which is effectively protected by the adjacent protective layer. The gas tunnel is a coal tunnel, which is safe, reliable and efficient to construct. It can also be used as a mining tunnel, saving the mine production preparation tunnel. The gas tunnel is constructed by drilling holes in the layer to extract the pressure relief gas from the protected layer. The drilling holes in the layer are efficient and have good extraction effects. The pressure relief gas from the protected layer can be extracted in a timely and efficient manner, which saves drilling volume and drilling costs, and has significant safety and economic benefits.

[0042] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0043] The embodiments described above only represent implementation methods of the invention. The protection scope of the present invention is not limited to the embodiments described above. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for extracting gas from a protected layer by drilling holes along the layer, characterized in that: The specific steps include: Step 1: mining the first protective layer working face of the protective layer coal seam; Step 2: construct a gas tunnel in the protected coal seam protected by the first protective layer working face as a gas control tunnel for mining the adjacent second protective layer working face, and construct a borehole along the layer from the gas tunnel; Step 3: When mining the second protective layer working face, use gas tunnels and in-layer drilling holes to extract and release gas from the protected coal seam.

2. A method for extracting gas from a protected layer by drilling holes in the layer according to claim 1, characterized in that: After the first protective layer working face is mined in step 1, a section coal pillar of no more than 4m is left until the mining of the protective layer coal seam is completed, and the first protective layer working face is arranged at the working face with the lowest elevation of the protective layer coal seam.

3. A method for extracting gas from a protected layer by drilling holes in the layer according to claim 1, characterized in that: In the step 2, the gas tunnel is constructed in advance before the second protective layer working face is mined.

4. The method for extracting gas from a protected layer by drilling holes in the layer according to claim 1 is characterized in that: In step 2, the gas tunnel is constructed along the roof of the protected coal seam, the horizontal projection of the gas tunnel is located within the protection range of the first protective layer working surface and is not less than 30m away from the protection range of the second protective layer working surface, and the tunnel section of the gas tunnel is not less than 16㎡.

5. The method for extracting gas from a protected layer by drilling holes in the layer according to claim 1 is characterized in that: In the step 2, the in-layer drilling is carried out in advance before the second protective layer working face is mined.

6. The method for extracting gas from a protected layer by drilling holes in the layer according to claim 1, characterized in that: In step 2, the in-layer drilling holes are opened from the protective layer coal seam corresponding to the first protective layer working face and constructed perpendicularly to the gas tunnel into the protected layer coal seam corresponding to the second protective layer working face. The diameter of the in-layer drilling holes is not less than 94mm, and the protective casing is installed throughout the in-layer drilling holes; the spacing of the in-layer drilling holes is 10-40m.

7. The method for extracting gas from protected layers by drilling holes in the layer according to claim 1, characterized in that: In step 2, if the gas pressure of the protected layer exceeds 3 MPa or the length of the working face of the second protective layer is relatively large, short boreholes along the layer are constructed first to intercept and extract the gas from the coal seam of the protected layer and flow into the gas tunnel.

8. The method for extracting gas from a protected layer by drilling holes in the layer according to claim 1, characterized in that: In step 2, compressed air is used for slag removal during the layer drilling construction, and the air pressure is not less than 0.8 MPa; if the rock is exposed for more than 30m at the end of the layer drilling and the coal is not exposed as expected, additional layer drilling is constructed nearby.

9. The method for extracting gas from a protected layer by drilling holes in the layer according to claim 1, characterized in that: In the step 3, during the mining process of the second protective layer working face, the protected coal seam is extracted to relieve pressure. If the in-layer drill holes designed in the gas tunnel for extracting the second protective layer working face are completed before the mining of the second protective layer working face, the gas tunnel is closed before the mining of the second protective layer working face after taking measures to prevent flooding of the gas tunnel. Before closing, all the extraction drill holes are opened, and extraction pipelines are buried in the closed wall of the gas tunnel. The extraction pipelines pre-buried in the closed wall of the gas tunnel are used to extract the gas from the in-layer drill holes and the gas tunnel. If the gas tunnel is not closed during the mining of the second protective layer working face, an extraction pipeline is laid in the gas tunnel, and each in-layer drill hole is tightly connected to the extraction pipeline.

10. The method for extracting gas from protected layers by drilling holes in the layer according to claim 1, characterized in that: The ventilation volume of the gas tunnel shall not be less than 1000m 3 / min.

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