Gas control method during TBM tunneling period of hydrocarbon source rock roadway

Abstract

The invention belongs to the technical field of coal mine gas control. The method comprises the steps that a drill site is arranged outside a TBM equipment section, a directional long drill hole is constructed in a pressure relief area outside a roadway contour line, an underground extraction system is used for providing high extraction negative pressure, a negative pressure ring is formed, gas is intercepted, and the gas is prevented from rushing into an operation space. In-hole geological radar is adopted to detect geological structures and the like in the drilling construction period, and a basis is provided for tunneling. The pressure relief area is determined through a distributed optical fiber and a BOTDA demodulator. Layered shotcreting is adopted in a tunneled roadway to construct a supporting isolation shell, hydrocarbon gas is prevented from inrush, and surrounding rock is supported. The problems that the TBM tunneling space is limited and the extraction efficiency is low are solved, the method is suitable for hydrocarbon source rock roadway tunneling, and safe production is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine gas prevention and control, and particularly to a gas prevention and control method during the tunneling of a hydrocarbon source rock roadway by a TBM, which is applicable to preventing gas from surging into the working space and ensuring safe production when tunneling with a full-face rock tunneling machine (TBM) in a hydrocarbon source rock roadway rich in organic matter. Background Art

[0002] A hydrocarbon source rock refers to a rock rich in organic matter that can generate or has generated hydrocarbons (such as methane, ethane, ethylene, acetylene, etc.), including sandstone, shale, carbonaceous mudstone, etc. According to the sedimentary environment and the source of organic matter, hydrocarbon source rocks can be divided into lacustrine hydrocarbon source rocks, marine hydrocarbon source rocks, and coal-measure hydrocarbon source rocks, and their typical products are petroleum and associated gas, petroleum and natural gas, and natural gas respectively. The thickness of hydrocarbon source rocks varies greatly, and the thickness in some areas can reach hundreds to thousands of meters, with a high gas generation intensity, showing significant resource potential. The mining value of hydrocarbon source rocks is jointly determined by their gas content, geological conditions, technical feasibility, and economy. For example, shale gas requires a gas content ≥ 2 m 3 / t and the proportion of adsorbed gas < 30%, coalbed methane requires a gas content ≥ 8 m 3 / t and a permeability ≥ 0.1 mD, tight sandstone gas requires a porosity ≥ 5%, a permeability ≥ 0.01 mD, a gas saturation > 50%, and a gas content ≥ 1.5 m 3 / t to have economic mining value.

[0003] Traditional gas prevention and control methods include arranging the main production roadways in the rock strata of the coal seam roof and floor to reduce the impact of coal seam gas on tunneling, or constructing cross-measure extraction boreholes in the roof and floor rock strata to reduce the coal seam gas content. However, the rock strata of the coal seam roof and floor or interlayers in many mining areas belong to hydrocarbon source rocks, contain a certain amount of organic matter, and are mostly in the gas generation stage, resulting in increased difficulty in gas prevention and control. Although the content of hydrocarbon gases such as methane in hydrocarbon source rocks is lower than that in coal seams, their continuous release still poses a threat to the safety of roadway tunneling.

[0004] In recent years, the level of coal mine mechanization and intelligentization has been continuously improved. The full-face rock tunneling machine (TBM) has been widely used in underground rock roadway tunneling due to its fast tunneling speed (the daily footage can exceed 15 m), especially showing high efficiency in hydrocarbon source rock roadways.

[0005] However, when a TBM tunnels a hydrocarbon source rock roadway, the following technical problems are faced:

[0006] The total length of the TBM equipment is nearly 100 m, and the space in the tunneling face and the equipment layout area is limited, making it difficult to construct dense ordinary extraction boreholes at the tunneling face to control gas outburst;

[0007] When arranging a drill site behind the TBM equipment section for ordinary dense borehole drainage, a relatively long borehole length is required, resulting in a large amount of engineering work, low construction accuracy, and low construction efficiency.

[0008] The permeability of the source rock is low. Under high drainage negative pressure, the load of the drainage system increases, but the drainage efficiency is relatively low, making it difficult to effectively control gas.

[0009] The gas content of the source rock is relatively low (usually < 2 m 3 / t, and the methane proportion is > 85%). Direct drainage is less economical. However, if not drained, hydrocarbon gases continuously pour into the working space from the driving face and roadway wall, easily triggering safety accidents such as gas overrun, asphyxiation, or deflagration.

[0010] In the existing technology, the methods for drainage and prevention of coal seam gas are relatively mature, but there is a lack of a systematic solution specifically for gas prevention during TBM tunneling in source rock roadways. The ordinary drainage borehole method cannot adapt to the space limitation of TBM tunneling and the low permeability characteristics of the source rock. There is an urgent need for an efficient and applicable gas prevention technology to effectively control gas emission while tunneling rapidly and ensure safe production. Summary of the Invention

[0011] In view of this, the purpose of the present invention is to solve the problem of difficult gas prevention during TBM tunneling in source rock roadways in the existing technology, and propose a gas prevention method during TBM tunneling in source rock roadways. By setting up a drill site in the area outside the TBM equipment section, constructing directional long boreholes, and using the underground drainage system for interception drainage, while constructing a support isolation shell in the already tunneled roadway section, effectively preventing gas from pouring into the working space and reducing the risk of gas overrun and related accidents.

[0012] To achieve the above purpose, the present invention provides the following technical solutions:

[0013] A gas prevention method during TBM tunneling in source rock roadways. By setting up a drill site in the area outside the TBM equipment section, constructing multiple directional long boreholes following the trend of the rock roadway in the pressure-relief area outside the contour line of the rock roadway, using the underground drainage system to provide high drainage negative pressure to form a negative pressure circle, and intercepting and draining the pressure-relief area outside the contour line of the rock roadway to prevent a large amount of surrounding rock gas from pouring into the production working space during TBM tunneling;

[0014] In the already tunneled rock roadway section, a support isolation shell is constructed by spraying concrete, which not only plays a supporting role for the roadway surrounding rock but also forms an isolation shell to prevent hydrocarbon gases released from the source rock from pouring into the roadway.

[0015] Furthermore, during the construction of the directional long boreholes, a borehole geological radar is used to detect the geological occurrence along the directional long boreholes, providing a basis for gas prevention during subsequent TBM tunneling.

[0016] Furthermore, geological radar in boreholes is used to detect the geological structures, carbonaceous mudstone, mudstone, coal seams and water-rich areas in the roadway area.

[0017] Furthermore, a gas drainage pump station is built in the stable and hard rock strata near the opening of the roadway driven close to the hydrocarbon source rock. The pump station is set in a chamber or an intake airway, avoiding faults, aquifers, soft rock strata and coal and gas outburst coal seams, and the underground gas drainage system is constructed in accordance with the "Design Standard for Coal Mine Gas Drainage Engineering".

[0018] Furthermore, the pressure-relief area outside the outline of the rock roadway is determined by the following method:

[0019] At a position 10 m behind the driving face, a borehole with a length of 60 m is drilled into the rock mass on one side of the roadway to be driven. The angle between the borehole and the roadway is 45°. Distributed optical fibers are placed in the borehole and the whole borehole section is sealed with cement slurry. After the cement has solidified for 7 days, the deformation along the distributed optical fiber is measured by a BOTDA demodulator, and the area with a deformation rate greater than 3‰ is determined as the pressure-relief area.

[0020] Furthermore, the hydrocarbon source rock is a rock rich in organic matter that can generate or has generated hydrocarbons, including sandstone, shale or carbonaceous mudstone, but not including coal seams.

[0021] Furthermore, a drill site is set every 700 m along the roadway direction, and the horizontal position of the drill site is not higher than the upper outline of the roadway.

[0022] Furthermore, three directional long boreholes are constructed in the pressure-relief area outside the outline of the roadway. The openings of the directional long boreholes are all set in the drill site on the left side of the roadway. Through trajectory adjustment, the end holes are respectively located 7 m outside the left outline of the roadway, 7 m outside the top outline of the roadway, and 7 m outside the right outline of the roadway. The boreholes are connected to the gas drainage pipeline through steel wire hoses and are connected to the gas drainage system for gas drainage.

[0023] Furthermore, the support isolation shell is constructed by the layered shotcrete process to form a dense isolation layer with a total thickness of 100 mm, an initial shotcrete thickness of 50 mm, and a re-shotcrete thickness of 50 mm after initial setting. The grade of the shotcrete is not lower than C20, the surface is flat, and the deviation of convexity and concavity within each square meter is ≤ 30 mm.

[0024] Furthermore, the concrete materials for spraying the support isolation shell are proportioned by weight as cement: water: sand: gravel: accelerator = 1: 0.5: 2: 2: 0.05. Among them, the cement is ordinary Portland cement, the sand particle size is 0.3 - 3 mm, the gravel particle size is 5 - 10 mm, the mud content of both is ≤ 3%, and the accelerator dosage is 5% of the cement weight.

[0025] Furthermore, the shotcrete construction of the support isolation shell is carried out closely behind the TBM equipment, and the re-shotcrete is carried out after the concrete has initially set after the initial shotcrete.

[0026] The present invention has the following beneficial effects compared with the prior art:

[0027] 1. Drill fields are set in areas outside the TBM equipment section, and multiple directional long boreholes following the rock roadway trend are constructed into the pressure relief area outside the rock roadway contour line, solving the problems of limited headspace in the TBM full-face tunneling and inconvenience in taking measures of dense drainage boreholes.

[0028] 2. The directional long borehole drainage method is adopted. Compared with the ordinary dense borehole drainage, the amount of borehole engineering is reduced, and the construction accuracy and efficiency are improved; at the same time, during the borehole construction, borehole geological radar is used to detect the geological structure, carbonaceous mudstone, mudstone, coal seam and water-rich area in the roadway area, providing a basis for determining the subsequent TBM tunneling speed and formulating gas management measures.

[0029] 3. The directional long borehole drainage method has the following advantages: (1) In the area not affected by tunneling disturbance, the gas in the source rock is pre-drained in the long borehole section to reduce the gas content in advance; (2) During the roadway tunneling process, the TBM cutting and rock fragmentation cause the deformation of the surrounding rock, and the rock layer permeability is greatly improved, thus improving the gas drainage efficiency; (3) Due to the increase in permeability, a large amount of gas in the source rock is desorbed, and a negative pressure circle is formed through the high drainage negative pressure of the directional long borehole to intercept the desorbed gas from entering the drainage system, reducing the amount of gas flowing into the tunneling operation space and reducing the risks of gas overrun, asphyxiation and deflagration accidents; (4) The underground mobile drainage system shortens the pipeline distance between the drainage pump station and the drainage point, reduces the pipeline resistance, is conducive to increasing the drainage negative pressure, and improving the drainage effect.

[0030] 4. In the already tunneled rock roadway section, a support isolation shell is constructed by the method of layered shotcrete, which plays a supporting role for the roadway surrounding rock, and at the same time forms a dense isolation shell to prevent hydrocarbon gases such as methane released from the source rock from flowing into the roadway.

[0031] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, wherein:

[0033] Figure 1 It is a construction schematic diagram of the gas prevention and control method during the TBM tunneling of the source rock roadway in the present invention.

[0034] Figure 2 isFigure 1 Cross-sectional view A-A in

[0035] Figure 3 Schematic diagram of the surrounding rock deformation investigation borehole and distributed optical fiber arrangement in the present invention.

[0036] Figure 4 Schematic diagram for determining the area of the directional long borehole arrangement in the present invention. Specific implementation manners

[0037] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0038] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0039] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] Embodiment 1

[0041] Please refer to Figures 1 to 4 , which is a gas prevention and control method during the TBM tunneling of a hydrocarbon source rock roadway, applicable to the TBM tunneling process of rock roadways (such as sandstone, shale or carbonaceous mudstone, but not including coal seams) rich in organic matter and capable of generating or having generated hydrocarbons (such as methane, ethane, ethylene, acetylene, etc.). The specific implementation steps are as follows:

[0042] Step 1: Construction of the underground drainage system

[0043] Build a gas drainage pump station in the stable and hard rock strata near the opening of the roadway driving towards the hydrocarbon source rock. The pump station is set in a chamber or an intake airway, avoiding faults, aquifers, soft rock strata and coal and gas outburst coal seams to ensure stable geological conditions. The location of the pump station is selected to facilitate the transportation, installation, layout of the process system and maintenance of the equipment. The selection of the pump station, pipeline and the gas drainage scale shall be carried out in accordance with the "Design Standard for Coal Mine Gas Drainage Engineering" (GB 50471-2018) to ensure the efficient operation of the gas drainage system and provide a high gas drainage negative pressure.

[0044] Step 2: Investigation of the surrounding rock deformation rate

[0045] At a distance of 10 m behind the driving heading face, construct a borehole with a length of 60 m in the rock mass on one side of the roadway to be driven. The borehole is located in the roadway waistline plane and the included angle with the roadway is 45°. After the borehole construction is completed, place distributed optical fiber in the hole and seal the whole hole section with cement slurry. After the cement solidifies for 7 days, connect a BOTDA demodulator at the hole mouth to measure the deformation along the distributed optical fiber. According to the measurement results, determine the area with a deformation rate greater than 3‰ as the pressure relief area for the subsequent layout of directional long boreholes.

[0046] Under the influence of driving disturbance, the deformations generated at different positions of the borehole are also different. The closer to the roadway, the greater the deformation. These deformations will be sensed and measured by the distributed optical fiber, so as to obtain the deformation of the rock mass at different positions from the roadway contour line. The area with a deformation rate greater than 3‰ is the effective pressure relief area, and the area from the broken zone of the roadway surrounding rock to the area with a deformation rate greater than 3‰ is the area where the directional long borehole can be arranged, that is Figure 4 the ab circular ring area (pressure relief ring) in

[0047] Step 3: Drill site setting

[0048] Set a drill site every 700 m along the roadway direction. The horizontal position of the drill site is not higher than the upper contour line of the roadway to adapt to the space limitation of the full-face tunneling of the TBM. The drill site is set on the left side of the roadway to facilitate the opening construction of the directional long borehole and the connection of the gas drainage pipeline.

[0049] Step 4: Construction of directional long boreholes and geological radar detection

[0050] In the drill site on the left side of the roadway, three directional long boreholes are constructed in the pressure-relief area outside the roadway contour line. The borehole depth is 700 m, the diameter is 153 mm, and the ZYWL-13000DS drill rig is used for construction. Through trajectory adjustment, the end holes of the boreholes are controlled to be located 7 m outside the left contour line of the roadway, 7 m outside the top contour line, and 7 m outside the right contour line respectively. During the construction period, borehole geological radar is used to detect the geological structure, carbonaceous mudstone, mudstone, coal line and water-rich area in the roadway area, providing a basis for adjusting the TBM tunneling speed and formulating gas management measures. After the borehole construction is completed, the extraction pipeline is connected through a steel wire hose and connected to the extraction system, and a negative pressure circle is formed by using high extraction negative pressure for gas interception and extraction.

[0051] After the directional long borehole construction, a steel wire hose is used to connect with the extraction pipeline and connected to the extraction system for extraction. It has the following obvious advantages: (1) The long borehole section in the area not affected by disturbance is for pre-extracting the gas from the source rock, which can reduce the gas in the source rock to a certain extent in advance; (2) More importantly, when the roadway is tunneling, as the TBM continuously cuts and breaks the rock, the surrounding rock deforms, and the rock layer permeability is greatly improved, which greatly improves the gas extraction efficiency; (3) A large amount of gas in the source rock desorbs due to the increase in permeability. At the same time, due to the extraction of the directional long borehole, a negative pressure circle is formed around the roadway, and a large amount of gas desorbed from the source rock will be immediately extracted by the directional long borehole and enter the extraction system, thus greatly reducing the gas flowing into the tunneling space and greatly reducing the risk of accidents such as gas overrun, asphyxiation, and gas deflagration. (4) The establishment of the underground mobile extraction system shortens the pipeline distance between the extraction pump station and the extraction point, reduces the pipeline resistance, is conducive to increasing the extraction negative pressure at the extraction site, and improving the extraction effect.

[0052] Step 5: Construction of the support isolation shell

[0053] During the TBM tunneling period, the support isolation shell is constructed by using the layered shotcrete technology closely behind the TBM equipment. The initial shotcrete thickness is 50 mm. After the concrete begins to set, re-shotcreting is carried out, and the re-shotcrete thickness is 50 mm, and the total thickness reaches 100 mm. The grade of the shotcrete is not lower than C20, the surface is flat, and the uneven deviation within each square meter is ≤ 30 mm. The concrete material is proportioned by weight as cement: water: sand: stone: accelerator = 1: 0.5: 2: 2: 0.05. Among them, ordinary Portland cement (such as P.O 32.5 or 42.5) is used for cement, the sand particle size is 0.3 - 3 mm, the stone particle size is 5 - 10 mm, the mud content of both is ≤ 3%, and the accelerator dosage is 5% of the cement weight.

[0054] After the construction of the support isolation shell, on the one hand, the support isolation shell is closely combined with the exposed rock surface of the roadway to form an "active support", which shares the surrounding rock pressure through its own compressive and shear resistance capabilities and improves the stability of the surrounding rock. On the other hand, the support isolation shell can quickly fill the fissures and cracks on the surface of the exposed source rock, forming a dense isolation layer between the source rock and the roadway space, preventing gases such as gas in the source rock from flowing into the tunneling operation space.

[0055] Through the above steps, the present invention can intercept gas through directional long boreholes and a drainage system during the tunneling of the source rock roadway by TBM, and combine with the support isolation shell to prevent gas from flowing in, effectively ensuring the safety of tunneling operations.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A gas prevention and control method during the tunneling of a hydrocarbon source rock roadway by a TBM, characterized in that: By setting up a drilling site outside the TBM equipment section, multiple directional long boreholes following the direction of the rock tunnel are constructed in the drilling site to the pressure relief area outside the rock tunnel contour line, and using the underground extraction system to provide high extraction negative pressure to form a negative pressure circle, the pressure relief area outside the rock tunnel contour line is intercepted and extracted to prevent a large amount of surrounding rock gas from flowing into the production operation space during TBM excavation; In the excavated rock tunnel section, the support isolation shell is constructed by shotcrete, which not only supports the surrounding rock of the tunnel, but also forms an isolation shell to prevent the hydrocarbon gas released by the source rock from flowing into the tunnel.

2. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: During the construction of directional long drilling, in-hole geological radar is used to explore the geological conditions along the directional long drilling line, providing a basis for gas prevention and control during subsequent TBM excavation.

3. The gas control method during the TBM tunneling of hydrocarbon source rock roadway according to claim 1, characterized in that: The geological structure, carbonaceous mudstone, mudstone, coal line and water-rich area in the tunnel area are detected by in-hole geological radar.

4. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: An extraction pump station is constructed in the stable and hard rock strata near the opening of the source rock tunnel. The pump station is set up in the chamber or air intake tunnel, avoiding faults, aquifers, soft rock strata and coal and gas outburst coal seams. The underground extraction system is constructed in accordance with the "Design Standards for Coal Mine Gas Extraction Engineering".

5. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that, The decompression area outside the rock roadway outline is determined by the following method: 10m back from the front of the tunnel, a 60m-long borehole was constructed towards the rock mass on one side of the tunnel to be excavated. The angle between the borehole and the tunnel was 45°. Distributed optical fiber was inserted into the hole and the entire hole was sealed with cement slurry. After the cement solidified for 7 days, the deformation along the distributed optical fiber was measured by a BOTDA demodulator, and the area with a deformation rate greater than 3‰ was determined as the pressure relief zone.

6. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: The source rock is a rock rich in organic matter that can produce or has produced hydrocarbons, including sandstone, shale or carbonaceous mudstone, but excluding coal seams.

7. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: A drilling site is set up every 700m along the tunnel direction, and the horizontal position of the drilling site is not higher than the upper contour line of the tunnel.

8. The gas control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: Three directional long boreholes were constructed in the pressure relief area outside the tunnel contour line. The directional long boreholes were all set in the drilling site on the left side of the tunnel. Through trajectory adjustment, the final holes were located 7m outside the left contour line of the tunnel, 7m outside the top contour line of the tunnel, and 7m outside the right contour line of the tunnel. The boreholes were connected to the extraction pipeline through a steel wire hose and connected to the extraction system for gas extraction.

9. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 1, characterized in that: The support isolation shell is constructed by layered shotcrete technology to form a dense isolation layer with a total thickness of 100mm, an initial shotcrete thickness of 50mm, and a re-shotcrete thickness of 50mm after initial setting. The shotcrete grade is not less than C20, the surface is flat, and the concave-convex deviation per square meter is ≤30mm.

10. The gas prevention and control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 9, characterized in that: The concrete materials for the support isolation shell spraying are mixed in the following weight ratio: cement: water: sand: gravel: accelerator = 1:0.5:2:2:0.05, wherein the cement is ordinary Portland cement, the sand particle size is 0.3-3mm, the gravel particle size is 5-10mm, the mud content is ≤3%, and the accelerator dosage is 5% of the cement weight.

11. The gas control method during the tunneling of hydrocarbon source rock roadway by TBM according to claim 9, characterized in that: The shotcrete construction of the support isolation shell is carried out closely behind the TBM equipment, and after the initial shotcrete is sprayed, it is re-sprayed after the concrete has initially set.

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