A method for measuring coal seam gas pressure and coordinating investigation of regional extraction effects

Abstract

The present invention relates to a method for measuring coal seam gas pressure and collaborative investigation of regional extraction effects, belonging to the field of coal mining and coal mine safety technology. First, a regional pre-extraction borehole is constructed, and the pre-extraction borehole is integrally grouted to seal the cracks between the bottom rock tunnel and the overlying coal seam. Then, a pressure measuring borehole is constructed, and after the pressure measuring work is completed, coal seam gas pre-extraction work is carried out. The extraction effect is analyzed and the coal seam gas pre-extraction rate is calculated based on the gas pressure drop. The present invention adjusts the construction procedures of the pressure measuring borehole and the extraction borehole, first constructs the extraction borehole as a whole, and forms an integral grouting area around the pressure measuring borehole to be constructed to ensure the accuracy of the gas pressure measurement results, thereby achieving a collaborative investigation of the regional extraction effect of the coal seam gas, improving the extraction effect investigation efficiency, and shortening the gas control construction period.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mining and coal mine safety, and relates to a method for measuring coal seam gas pressure and collaborative investigation of regional extraction effects. Background Art

[0002] In order to investigate the gas parameters and regional gas pre-extraction effects in mining areas of high-gas coal seams or protruding coal seams, the gas pressure drop method or gas content drop method is generally used for investigation. A pressure measurement borehole is constructed in the bottom rock tunnel below the coal seam to measure the original gas pressure, gas content and other parameters of the coal seam in the specified area. Then, a pre-extraction borehole is designed and constructed to extract the coal seam gas in the mining area. After a certain period of extraction, in order to investigate the effect of coal seam gas extraction, it is necessary to drill again to measure the residual gas pressure or gas content data at different extraction times. However, this method has the following disadvantages:

[0003] (1) The gas content reduction method is a commonly used method to examine the effect of coal seam pre-extraction. It has the advantage of a simple measurement method. The disadvantage is that it requires at least two arrangements of personnel and drilling rigs to construct the original gas content test borehole and the residual gas content test borehole respectively, and it is impossible to examine the changes in the residual gas content and the changes in the coal seam gas pre-extraction rate in real time.

[0004] (2) When the gas pressure drop method is used to examine the effect of coal seam pre-extraction, the excavation of the bottom rock roadway will form a certain range of damaged areas and crack development areas around the roadway. Relying solely on the pressure measurement drilling and sealing grouting cannot seal the surrounding cracks tightly, which will lead to inaccurate gas pressure measurement results, thereby affecting the evaluation results of coal seam gas pre-extraction effect. In addition, since the original gas pressure measurement borehole cannot be drilled within 50m around the extraction borehole, it is necessary to wait until the pressure measurement link is completed before constructing the extraction borehole. The pressure test time of low permeability coal seams is generally at least 20 days, which will affect the construction progress of the pre-extraction drilling of the overlying coal seam and cause the extraction time difference coefficient to be high, exacerbating the tension of mining and excavation succession. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a method for measuring coal seam gas pressure and collaborative investigation of regional extraction effects, so as to improve the efficiency of extraction effect investigation and shorten the gas control period.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for measuring coal seam gas pressure and collaboratively investigating regional extraction effects comprises the following steps: first, constructing regional pre-extraction boreholes, grouting the pre-extraction boreholes as a whole to seal the fissures between the bottom rock tunnel and the overlying coal seam, then constructing pressure measurement boreholes, and carrying out coal seam gas pre-extraction after the pressure measurement work is completed. The extraction effect is analyzed and the coal seam gas pre-extraction rate is calculated based on the gas pressure drop.

[0008] Optionally, the method specifically includes the following steps:

[0009] S1: Within a strip of at least 15m on both sides of the roadway contour line of the bottom rock roadway, pre-drainage drilling holes are constructed in the bottom rock roadway. The spacing and row spacing of the pre-drainage drilling holes are arranged according to twice the extraction radius R. After the pre-drainage drilling holes are completed, the extraction screen pipe is inserted into the entire pre-drainage drilling hole, and then grouting is performed to seal the hole. The grouting liquid enters the original rock area and cracks from the pre-drainage drilling hole to form an overall grouting area.

[0010] S2 After the pre-drainage borehole grouting and sealing is completed, a drainage valve is installed at the orifice of the pre-drainage borehole, and the pre-drainage borehole is connected to the main drainage pipeline. The drainage valve is kept closed to ensure the gas pressure balance inside the pre-drainage borehole;

[0011] S3 After all pre-drainage drilling is completed, pressure testing holes are constructed in the overall grouting area. The spacing and row spacing of the pressure testing holes are 30-50m. Pressure testing tubes are inserted into the pressure testing holes and the holes are sealed. The sealing method is the same as that of the pre-drainage drilling holes. After the slurry solidifies, a pressure gauge is installed at the orifice of the pressure testing hole to measure the original gas pressure P of the coal seam until the pressure is stable for more than 7 days.

[0012] After the pressure test in S4 is completed, the extraction valves of all pre-extraction boreholes are opened to start joint extraction, and the dynamic gas pressure P1 of the pressure test borehole is monitored. The real-time pre-extraction rate η of the coal seam is calculated according to the formula (P-P1) / P to evaluate the pre-extraction effect of the coal seam.

[0013] Optionally, the pre-drilled holes are sealed by grouting using the "two blocking and one injection" method.

[0014] Optionally, all rock sections of the extraction borehole are sealed by grouting, and the final grouting hole pressure is not less than 6MPa.

[0015] The beneficial effects of the present invention are as follows: pre-extraction boreholes are first constructed around the pressure measuring boreholes, and the sealing grouting effect of the pre-extraction boreholes forms a fracture closure zone around the pressure measuring boreholes in advance, which can ensure the accuracy of the gas pressure measurement results. At the same time, the gas pressure drop during the pre-extraction process can be measured in real time, and the real-time pre-extraction rate of each stage can be mastered, thereby realizing dynamic evaluation of the gas pre-extraction effect in the area, improving the efficiency of the extraction effect inspection, and shortening the gas control period.

[0016] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0018] Figure 1 It is a plan view schematic diagram of the present invention;

[0019] Figure 2 for Figure 1 A-A' cross-sectional view (along the coal seam strike);

[0020] Figure 3 for Figure 1 BB' cross-sectional view (along the dip of the coal seam).

[0021] Figure numerals: coal seam 1, floor rock roadway 2, pre-extraction borehole 3, extraction screen 4, original rock area 5, fracture 6, fracture overall grouting area 7, extraction valve 8, extraction main pipeline 9, pressure measuring borehole 10, pressure measuring tube 11, pressure gauge 12. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0023] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0024] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0025] See Figures 1 to 3 A method for measuring coal seam gas pressure and collaboratively investigating regional extraction effects involves constructing a regional pre-extraction borehole 3. Grouting is then performed throughout the pre-extraction borehole 3 to seal the fissure between the floor rock tunnel 2 and the overlying coal seam 1. A pressure measurement borehole 10 is then constructed. After the pressure measurement is completed, pre-extraction of coal seam gas is performed. The extraction effect is analyzed based on the gas pressure drop, and the pre-extraction rate of coal seam gas is calculated. The method specifically includes the following steps:

[0026] (1) Within a strip of at least 15 m on both sides of the bottom rock tunnel 2 in the coal seam 1, through-layer pre-drainage boreholes 3 are constructed in the bottom rock tunnel 2. The borehole spacing and row spacing are arranged according to twice the extraction radius R. After the pre-drainage borehole 3 is completed, the extraction screen pipe 4 is lowered into the pre-drainage borehole 3 throughout the entire length. The "two plugging and one injection" method is used for grouting and sealing, that is, a plug is formed at both ends of the sealing section using a sealer, and then the sealing material is injected into the middle section. The grouting liquid penetrates from the pipe wall of the pre-drainage borehole 3 into the original rock area 5 and the fissure 6, forming a fissure overall grouting area 7.

[0027] Grouting is carried out to seal the entire rock section of the extraction borehole, and the final grouting hole pressure is not less than 6MPa.

[0028] (2) After the grouting and sealing of the pre-drainage borehole 3 is completed, an extraction valve 8 is installed at the orifice of the pre-drainage borehole 3, and the pre-drainage borehole 4 is connected to the extraction main pipeline 9, and the extraction valve 8 is kept in a closed state to ensure the gas pressure balance inside the pre-drainage borehole 3.

[0029] (3) After the pre-drainage boreholes 3 are all completed, pressure-testing boreholes 10 are constructed in the overall grouting area 7. The spacing and row spacing of the pressure-testing boreholes 10 are 30 to 50 m. Pressure-testing tubes 11 are inserted into the pressure-testing boreholes 10. The sealing method is the same as that of the pre-drainage boreholes 4. The final grouting pressure is not less than 6 MPa. After the slurry solidifies, a pressure gauge 12 is installed at the orifice of the pressure-testing borehole 10 to measure the original gas pressure P of the coal seam until the pressure remains stable for more than 7 days.

[0030] (4) After the pressure test is completed, the extraction valves 8 of all pre-extraction boreholes 4 are opened to start joint extraction, and the dynamic gas pressure P1 of the pressure test borehole 10 is monitored. The real-time pre-extraction rate η of the coal seam is calculated according to the formula (P-P1) / P to evaluate the pre-extraction effect of the coal seam.

[0031] The present invention adjusts the construction procedures of pressure measuring drilling holes and extraction drilling holes. The extraction drilling holes are first constructed as a whole, and an overall grouting area is formed around the pressure measuring drilling holes to be constructed to ensure the accuracy of the gas pressure measurement results, realize the coordinated investigation of the regional extraction effect of coal seam gas, improve the efficiency of the extraction effect investigation, and shorten the gas control construction period.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for measuring coal seam gas pressure and collaborative investigation of regional extraction effects, characterized by: First, pre-drainage holes are drilled in the construction area. Grouting is then used to seal the cracks between the floor rock tunnel and the overlying coal seam. Pressure testing holes are then drilled. After the pressure testing is completed, coal seam gas pre-drainage is carried out. The extraction effect is analyzed based on the gas pressure drop and the coal seam gas pre-drainage rate is calculated. The specific steps include: S1: Within a strip at least 15m wide on both sides of the roadway contour line of the floor rock roadway, pre-drainage drilling holes are constructed through the layers in the floor rock roadway. The spacing and row spacing of the pre-drainage drilling holes are arranged according to twice the extraction radius R. After the pre-drainage drilling holes are completed, extraction screens are lowered throughout the pre-drainage drilling holes, and then grouting is performed to seal the holes. The grouting liquid enters the original rock mass area and cracks from the pre-drainage drilling holes to form an overall grouting area. S2 After the pre-drainage borehole is grout-sealed, install a drainage valve at the orifice of the pre-drainage borehole, connect the pre-drainage borehole to the main drainage pipeline, and keep the drainage valve closed to ensure the gas pressure balance inside the pre-drainage borehole; S3 After all pre-drainage drilling is completed, pressure-testing boreholes are constructed in the overall grouting area. The spacing and row spacing of the pressure-testing boreholes are 30-50m. Pressure-testing tubes are inserted into the pressure-testing boreholes and the holes are sealed. The sealing method is the same as that for the pre-drainage boreholes. After the slurry solidifies, a pressure gauge is installed at the orifice of the pressure-testing borehole to measure the original gas pressure P of the coal seam until the pressure remains stable for more than 7 days. S4 After the pressure test is completed, the extraction valves of all pre-extraction boreholes are opened to start joint extraction, and the dynamic gas pressure P1 of the pressure test borehole is monitored. The real-time pre-extraction rate η of the coal seam is calculated according to the formula (P-P1) / P to evaluate the pre-extraction effect of the coal seam.

2. The method for measuring coal seam gas pressure and coordinating regional extraction effect assessment according to claim 1 is characterized by: The pre-drilled holes are sealed with grouting using the two-blocking and one-injection pressure sealing method, with both ends sealed first and then grouting.

3. The method for measuring coal seam gas pressure and coordinating regional extraction effect assessment according to claim 1 is characterized by: The entire rock section of the pre-drilled hole is sealed with grouting, and the final grouting hole pressure is not less than 6MPa.

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