Hard coal seam acoustic wave penetration method

Abstract

The application discloses a hard coal seam acoustic wave penetration method, comprising the following steps: sampling coal blocks of a hard coal seam to be penetrated, and obtaining tensile strength and shear strength of the coal blocks; drilling a working borehole in the hard coal seam, and impacting the working borehole at a set working strength, so that the strength of an impact wave generated by the impacting is lower than the strength at which the impact wave generates a crushing zone in the hard coal seam; the impact wave generated by the impacting cracks the hard coal seam around the working borehole, the impact wave attenuates after cracking the hard coal seam, and forms an acoustic wave, and the acoustic wave penetrates the hard coal seam. The application solves the problem that an effective high-strength sound source capable of being loaded to a coal seam is difficult to develop in the prior art. The application cracks the coal seam around the borehole by impacting, and the acoustic wave attenuated by the impact force excites the coal seam. The application can obtain a high-strength acoustic wave directly loaded to the hard coal seam. The application can promote gas desorption, and meets the demand of gas treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coal seam permeability improvement, and particularly relates to a hard coal seam acoustic wave permeability improvement method. BACKGROUND

[0002] China's primary consumption energy mainly relies on coal supply, and the long-term proportion reaches more than 60%, which is the main pillar of China's industrial development. China's coal production has reached a high level of 4 billion tons per year, and about one-third of the national coal production, about 1 billion tons, is produced from high-gas mines, high-gas outburst mines and high-gas emission mines. The gas safety problem in coal production is very serious, and the loss caused by gas control is also very serious.

[0003] In order to solve the gas problem in coal production, the most effective gas control measure at present is intensive drilling and long-term pre-drainage, including bedding drilling and through drilling. The new coal seam permeability improvement technology based on controllable shock wave technology has been applied in many coal mines, and has been proved to be very effective and widely used in the coal industry. However, various active disturbance type coal seam strengthening measures, while strengthening and permeability improving the coal seam, also damage the coal seam, reducing the gas analysis capacity of the coal seam. From the perspective of coexistence of permeability improvement and damage, the existing active disturbance type coal seam permeability improvement theory and practice, only high-strength acoustic wave has the smallest damage to the coal seam, the largest permeability improvement effect and range, and the effect of promoting gas desorption. However, the main reason why the high-strength acoustic wave strengthening coal seam measure cannot be widely applied is that it is difficult to develop an effective high-strength acoustic source that can be loaded into the coal seam, so the existing measures cannot meet the demand of gas control. SUMMARY

[0004] The embodiment of the application provides a hard coal seam acoustic wave permeability improvement method, which solves the problem that an effective high-strength acoustic source that can be loaded into the coal seam is difficult to develop in the prior art.

[0005] In order to achieve the above purpose, the embodiment of the application provides a hard coal seam acoustic wave permeability improvement method, which comprises the following steps:

[0006] Sampling the coal blocks of the hard coal seam to be permeability improved to obtain the tensile strength and shear strength of the coal blocks;

[0007] Drilling a working borehole in the hard coal seam, and implementing impact in the working borehole at a set working strength, so that the strength of the shock wave generated by the impact is lower than the strength at which the shock wave generates a crushing zone in the hard coal seam;

[0008] The shock wave generated by the impact cracks the hard coal seam around the working borehole, and the shock wave that cracks the hard coal seam forms an acoustic wave after attenuation, and the acoustic wave improves the permeability of the hard coal seam.

[0009] In a possible implementation, the following steps are performed before the working borehole is drilled in the hard coal seam:

[0010] A test borehole is drilled in the hard coal seam to be made permeable, and an impact is performed in the test borehole, the impact being such that the intensity of the shock wave generated by the impact is lower than the intensity of the shock wave that generates a crushing zone in the hard coal seam;

[0011] The generated shock wave cracks the hard coal seam around the test borehole, and the shock wave that cracks the hard coal seam forms a sound wave after attenuation; the maximum sound pressure of the sound wave is measured, and the intensity of the shock wave generated by the impact is regulated according to the maximum sound pressure, so that the maximum sound pressure is less than the tensile strength and shear strength of the coal mass, and the intensity of the shock wave at this time is the working intensity.

[0012] In a possible implementation, when the maximum sound pressure is measured, the sound intensity and sound pressure of the sound wave at each place in the hard coal seam are calculated, and the effective action distance of the sound wave is determined according to the tensile strength and shear strength of the coal mass;

[0013] The position of the working borehole and the distance between the working borehole and the hard coal seam are set according to the effective action distance.

[0014] In a possible implementation, the effect of the sound wave on the hard coal seam is observed, and if the effect does not meet the expected setting, the working borehole is impacted again with the same intensity of the shock wave for multiple times.

[0015] In a possible implementation, the sound wave entering the hard coal seam propagates in the hard coal seam under the constraint of the coal seam roof and the coal seam floor, and forms a channel wave, and the hard coal seam in the area where the channel wave converges and strengthens is further made permeable.

[0016] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0017] The embodiment of the present application provides a hard coal seam acoustic wave penetration method, and the present application implements strong impact in a borehole in the hard coal seam, the strong impact first cracks the hard coal seam to form an impact fissure zone, and the borehole and the coal seam are communicated, meanwhile, the hard coal seam is used to attenuate and slow down the impact in the borehole into high-strength acoustic waves and then load the acoustic waves into the coal seam to form an impact desorption zone, and then the hard coal seam is implemented penetration and excitation. The present application cracks the coal seam around the borehole by using the impact, and the acoustic waves attenuated by the impact force excite the coal seam. The present application does not generate a sound field first and then load the sound field into the hard coal seam, but applies impact to the hard coal seam region, evolves into a sound field and then loads the sound field into the hard coal seam, and the method can obtain high-strength acoustic waves directly loaded into the hard coal seam. Therefore, the method does not harm the coal seam, and at the same time, the required acoustic waves can be obtained, the expected penetration effect and penetration range are realized, the gas desorption is promoted, and the gas management demand is met. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0019] Figure 1 The structure schematic diagram of the shock wave disturbance zone provided by the embodiment of the present application.

[0020] Figure 2 The structure schematic diagram of the hard coal seam generating a crushing zone provided by the embodiment of the present application.

[0021] Figure 3 The structure schematic diagram of the controllable impact cracking coal seam provided by the embodiment of the present application.

[0022] Figure 4 The schematic diagram of the slot wave propagating in the coal seam provided by the embodiment of the present application.

[0023] Figure 5 The flow chart of the hard coal seam acoustic wave penetration method provided by the embodiment of the present application.

[0024] The drawings show that: 1-impact wave; 2-compression stress wave; 3-elastic acoustic wave; 4-crushing zone; 5-borehole; 6-coal seam roof; 7-coal seam floor. DETAILED DESCRIPTION

[0025] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0026] In the description of the embodiments of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0027] As shown in Figures 1 to 5 The hard coal seam acoustic wave penetration method provided by the embodiments of the present application comprises the following steps:

[0028] The coal blocks of the hard coal seam to be penetrated are sampled to obtain the tensile strength and shear strength of the coal blocks.

[0029] A working drill hole is drilled in the hard coal seam, and an impact with a set working intensity is carried out in the working drill hole, so that the intensity of the impact wave generated by the impact is lower than the intensity of the impact wave generating the crushing zone in the hard coal seam.

[0030] The impact wave generated by the impact cracks the hard coal seam around the working drill hole, and the impact wave that cracks the hard coal seam forms an acoustic wave after attenuation, and the acoustic wave penetrates the hard coal seam.

[0031] It should be noted that, as shown in Figure 2 The impact wave generated by the impact can form a crushing zone 4, a broken zone, a radial crack and a hoop crack, the broken zone, the radial crack and the hoop crack communicate the drill hole with more coal seams, but the crushing zone 4 consumes a large amount of energy and causes damage to the drill hole 5 and the coal seam, so the impact intensity needs to be controlled to not generate the crushing zone 4, as shown in Figure 3As shown. Therefore, the impact intensity is selected to avoid generating a crushed zone 4 in a hard coal seam. This means that controlled impact is used to generate a controllable shock wave to fracture the coal seam. By measuring the tensile and shear strengths of the coal, we can determine the intensity of the shock wave that creates a crushed zone in the hard coal seam.

[0032] like Figure 1 As shown, shock waves can create a shock wave disturbance zone in a coal seam. In areas where the intensity of shock wave 1 exceeds the coal seam strength, the coal seam fractures in a direct fracture mode. In areas where the intensity decays below the compressive strength but still exceeds the tensile and shear strengths, the coal seam is torn apart in the form of a compression stress wave 2, which ultimately decays into a high-intensity elastic acoustic wave 3 that no longer has the capacity to damage the coal seam's physical parameters. This fractured coal seam creates a shock fracture zone, and the elastic acoustic wave 3 forms a shock desorption zone within the coal seam.

[0033] This method applies a strong impact in a borehole in a hard coal seam. The strong impact first fractures the hard coal seam, forming an impact fracture zone that connects the borehole and the coal seam. Simultaneously, the impact in the borehole is attenuated and slowed down by the hard coal seam, transforming it into a high-intensity acoustic wave. This wave is then applied to the coal seam to form an impact desorption zone, which then enhances and excites the coal seam. Rather than generating an acoustic field first and then applying it to the hard coal seam, this method applies an impact in the hard coal seam, transforming it into an acoustic field, and then applying it to the hard coal seam. This method can produce high-intensity acoustic waves that are directly applied to the hard coal seam.

[0034] In hard coal seams that can be programmably drilled, direct seam drilling can be performed. Whether drilling head-on at the excavation face or drilling along the seam within the working face, regardless of the impact source used, the working length of the drilling can be divided into several operating sections, with impacts applied separately in each section. The impact force fractures the coal seam surrounding the drill hole, and the sound waves, after attenuating the impact force, re-excite the coal seam. Therefore, this method does not damage the coal seam while still generating the desired sound waves, achieving the desired permeability enhancement effect and range, promoting gas desorption, and meeting gas control requirements.

[0035] When a coal seam is strongly impacted, the shock wave in the coal seam is attenuated and evolved into high-intensity sound waves, and the vibration of the coal seam radiates high-intensity sound waves to the coal seam.

[0036] The main reasons why many current active perturbation methods are ineffective in increasing permeability are that they cause significant damage while having little effect on increasing permeability. These factors are: First, these permeability-enhancing measures are typically implemented within coal seams, which is not only inconvenient to implement but also increases the damage to the coal seams. Second, when using high-intensity acoustic waves, which are most effective for increasing permeability in coal seams, attempts are often made to generate the high-intensity acoustic waves first and then inject them into the coal seam. However, due to the principles of acoustic wave generation, this cannot be achieved by generating the high-intensity acoustic waves first.

[0037] In this embodiment, the following steps are performed before drilling a working borehole in a hard coal seam:

[0038] A test borehole is drilled in the hard coal seam to be increased in permeability, and an impact is implemented in the test borehole, so that the intensity of the impact wave generated by the impact is lower than the intensity of the impact wave that generates a crushing zone in the hard coal seam.

[0039] The hard coal seam around the test borehole is cracked by the generated impact wave, and the impact wave that cracks the hard coal seam forms a sound wave after attenuation. The maximum sound pressure of the sound wave is measured, and the intensity of the impact wave generated by the impact is regulated according to the maximum sound pressure, so that the maximum sound pressure is less than the tensile strength and shear strength of the coal block, and the intensity of the impact wave at this time is the working intensity.

[0040] It should be noted that the maximum sound pressure of the sound wave formed by the impact wave is less than the tensile strength and shear strength of the coal block, which can ensure that the strongest sound wave is obtained, and the intensity of the sound wave can also be controlled by controlling the intensity of the impact wave, thereby ensuring that the sound wave will not harm the coal seam, while achieving the best permeability-increasing effect.

[0041] In this embodiment, when measuring the maximum sound pressure, the sound intensity and sound pressure of the sound wave at each place in the hard coal seam are calculated, and the effective action distance of the sound wave is determined according to the tensile strength and shear strength of the coal block.

[0042] The position of the working borehole and the distance between the working borehole and the hard coal seam are set according to the effective action distance.

[0043] It should be noted that the sound intensity and sound pressure of the high-intensity sound wave at each place in the coal seam are calculated, and the effective distance of the high-intensity sound wave tearing the coal seam is determined according to the tensile strength and shear strength of the coal seam, so as to assist the staff to arrange the position of the working borehole, the position and spacing of the impact, and thereby achieve the best permeability-increasing effect and improve the work efficiency.

[0044] In this embodiment, the effect of the sound wave in increasing the permeability of the hard coal seam is observed, and if the effect does not meet the expected setting, the working borehole is impacted again with the same impact wave intensity multiple times.

[0045] It should be noted that the sound wave action time is positively correlated with the increase of the permeability of the coal seam and the gas desorption capacity, and is negatively correlated with the adsorption capacity. Multiple impacts in the borehole can increase the sound wave operation time. When the multiple loading mode is adopted, the expansion effect of multiple impacts also needs to be considered, and specific test research needs to be conducted on various rock layers and coal seams. According to a large number of test results, the sound wave operation time is positively correlated with the permeability, so increasing the number of impacts can increase the action time of the sound wave, and this way can generate more and richer fractures in the coal seam to communicate the borehole with more coal seams.

[0046] The maximum sound pressure of the sound wave generated in the coal seam is the tensile shear strength of the coal seam. If the sound wave action under this strength cannot achieve the purpose of exciting the coal seam, the number of impacts can be increased to increase the sound wave action time, so as to use the fatigue effect to increase the permeability of the coal seam. If the effect still does not meet the expected setting, the impact wave strength can be appropriately increased to impact multiple times again. The present application expands the cracks in the coal seam by means of the fatigue effect of multiple actions, and the distance between the borehole and the coal seam is designed by controlling the number of impacts, and the optimal distance is about 1 meter. Both the strength of the impact wave is saved, and the deep part of the coal seam is not damaged.

[0047] In the embodiment, the sound wave entering the hard coal seam propagates in the hard coal seam under the constraint of the coal seam roof 6 and the coal seam floor 7, and the propagating sound wave forms a channel wave, and the channel wave realizes further permeability of the hard coal seam in the area where the channel wave is gathered and strengthened.

[0048] It should be noted that, as shown in Figure 4 , the sound wave generated in the hard coal seam cannot be transmitted to the outside of the coal seam roof 6 and the coal seam floor 7, but only propagates in the hard coal seam under the constraint of the coal seam roof 6 and the coal seam floor 7, which forms a channel wave. Even if the strength of the channel wave is not enough to excite the hard coal seam, through the reflection of the coal seam roof 6 and the coal seam floor 7, the hard coal seam in a certain area can be strengthened due to the gathering of the channel wave, thereby realizing further permeability of the hard coal seam in the area. The propagation mode of the channel wave in the hard coal seam is shown in Figure 4 .

[0049] Any structure has a natural frequency, and the coal seam roof 6 and the coal seam floor 7 as well as the faults and pore cracks in the coal seam are large and micro structures. When these structures resonate with the external sound wave or the self-excited sound wave, better tearing and excitation effects can be achieved, thereby further promoting the effect of gas desorption.

[0050] In the embodiment, the part between the hole opening of the working borehole and 30 meters inside the hole is a non-working area.

[0051] It should be noted that, at the borehole opening, a non-impact area of more than 30 meters is generally reserved to avoid the cracks caused by the strengthening effect from connecting the borehole and the roadway.

[0052] In the embodiment, the impact is implemented by a controllable impact wave device.

[0053] It should be noted that the process of implementing the impact by the controllable impact wave device is prior art, and the specific steps can be referred to the patent of the method for increasing the permeability of the coal seam in the coal seam roof and floor borehole, with the publication number CN111456801B. The operation steps can meet the purpose of implementing the impact and generating the impact wave with the set strength in the hard coal seam sound wave permeability method of the present application.

[0054] In the embodiment, the shock wave is attenuated to form a low-frequency sound wave.

[0055] It should be noted that the attenuation coefficient of the sound wave propagating in the medium is closely related to the frequency of the sound wave, the absorption attenuation reflects the kinetic ability of the sound wave in the medium, and the scattering attenuation reflects the diffraction trend of the sound wave in the medium. Therefore, the effect of loading the low-frequency sound wave to the coal seam is better, and the effective range is larger.

[0056] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be embraced in the present application.

Claims

1. A method for increasing the acoustic transmittance of hard coal seams, characterized in that: The following steps are involved: Sampling coal lumps from the hard coal seam to be enhanced, and obtaining the tensile strength and shear strength of the coal lumps; drilling a test borehole in the hard coal seam to be enhanced, and performing impact in the test borehole, such that the intensity of the shock wave generated by the impact is lower than the intensity of the crushed zone generated by the shock wave in the hard coal seam; The generated shock wave fractures the hard coal seam surrounding the test borehole, and the shock wave that fractures the hard coal seam attenuates to form an acoustic wave; the maximum sound pressure of the acoustic wave is measured, and the intensity of the shock wave generated by the impact is regulated according to the maximum sound pressure, so that the maximum sound pressure is less than the tensile strength and shear strength of the coal block. The intensity of the shock wave at this time is the working intensity; drilling a working borehole in the hard coal seam, and performing impact in the working borehole at a set working intensity, so that the intensity of the shock wave generated by the impact is lower than the intensity of the shock wave generating a crushing zone in the hard coal seam; The shock wave generated by the impact fractures the hard coal seam around the working borehole. The shock wave that fractures the hard coal seam attenuates to form an acoustic wave, which increases the permeability of the hard coal seam.

2. The method for increasing the acoustic wave transmission of hard coal seams according to claim 1, characterized in that: When measuring the maximum sound pressure, calculating the sound intensity and sound pressure of the sound wave at various locations in the hard coal seam, and determining the effective action distance of the sound wave based on the tensile strength and shear strength of the coal block; The position of the working drill hole and the distance between the working drill hole and the hard coal seam are set according to the effective working distance.

3. The method for increasing the acoustic wave transmission of hard coal seams according to claim 1, characterized in that: The effect of the acoustic wave penetration enhancement on the hard coal seam is observed. If the effect does not meet the expected setting, the working borehole is impacted again multiple times with the same shock wave intensity.

4. The method for increasing the acoustic wave transmission of hard coal seams according to claim 1, characterized in that: The sound waves entering the hard coal seam propagate in the hard coal seam under the constraints of the coal seam roof and coal seam floor. The propagated sound waves form channel waves, and the channel waves converge and strengthen in the area of ​​the hard coal seam to achieve further permeability enhancement of the hard coal seam there.

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