Impact-resistant support structure for wellbore instability and impact damage and its construction method

Abstract

This invention discloses a borehole buffer impact support structure for preventing instability and impact damage in gas extraction boreholes. The borehole buffer impact support structure unit includes an annular groove on the inner wall of the extraction pipe, support rods arranged radially along the extraction pipe, and connecting rods. Each support rod includes a rod body with inner and outer large ends, respectively. The radial inner surface of the annular groove has an annular opening. The connecting rod connects adjacent large ends of two support rods, and a strain sensor is mounted on the connecting rod. The detection data from each strain sensor serves as the basis for adjusting the number and position of the borehole buffer impact support structure units. This invention also discloses a corresponding construction method. Using this invention ensures that each borehole buffer impact support structure unit is appropriately positioned after grouting and sealing, avoiding both excessive use that leads to cost waste and reduced efficiency, and insufficient use that could cause damage to the extraction pipe, thus ensuring the smooth operation of gas extraction and reducing costs while increasing efficiency.

Description

Technical Field

[0001] This invention relates to the field of coal mine operation technology, and in particular to the technology of protecting extraction holes. Background Technology

[0002] Pre-drainage of gas through boreholes is currently the main measure for preventing coal and gas outburst accidents. In soft coal seams with low coal hardness, the drainage boreholes are prone to collapse and deformation during drilling and drainage. When the coal body has a high firmness coefficient, the borehole is also prone to collapse during drainage due to changes in mining stress.

[0003] Low strength of the sealing pipe leads to frequent fracturing of the sealing pipe during the sealing period, resulting in low and rapid decay of the borehole extraction concentration. This makes it impossible to guarantee the effective extraction time of the extraction borehole, seriously affecting the extraction efficiency and directly impacting the safe production of the mine.

[0004] Currently, the main measures to prevent borehole collapse in coal seam gas drainage boreholes are grouting and sealing, and pipeline support for borehole protection. Patents with publication numbers CN102200024A, CN110130852A, and CN110541726A all describe related grouting and sealing devices, which can effectively seal the borehole, but they have the following problems: 1. The extraction device has multiple connection ports, which can easily create leakage channels and reduce the extraction concentration.

[0005] 2. A high-stress zone is formed at the borehole. This high-stress zone will exert a great squeezing effect on the extraction pipe, which may cause the extraction pipe to deform or crack, seriously affecting the gas extraction operation.

[0006] To prevent the extraction pipe from being deformed by pressure, patent publication number CN103850699A utilizes a herringbone or cross-shaped internal support structure to protect the extraction hole. This type of strong support provides point-to-surface support to the pipe wall. When the pipe wall is subjected to external pressure, stress concentration inevitably occurs, making the extraction pipe prone to damage. In the event of an unstable impact failure of the extraction hole, the sudden increase in impact stress further exacerbates the damage to the extraction pipe.

[0007] 3. The support placement is not correlated with the deformation of the extraction pipe, resulting in a mismatch and incoordination between the support location and the instability impact stress. The extraction pipe section between the support and the pressure point will be subjected to tensile force. Because the support location did not take into account the matching with the instability impact stress, the support effect is unstable. Unless the supports are densely installed, it will increase material and installation costs and reduce construction efficiency.

[0008] 4. The existing extraction pipe support structure cannot monitor stress and strain while effectively supporting the extraction pipe.

[0009] 5. When the extraction pipe is subjected to stress, the existing extraction pipe support structure may experience axial displacement, which may cause changes in the support and protection parts or even cause it to lose its support and protection function.

[0010] Therefore, it is evident that existing devices are insufficient to effectively protect gas extraction pipes from instability and impact damage in loose and easily collapsing coal seams, and related devices and technologies require further improvement and development.

[0011] The design concept of this invention is as follows: Based on traditional grouting and sealing for gas extraction, the extraction pipe is replaced with a direct-connection integral structure. A borehole buffer support structure capable of monitoring stress and strain is added. This structure is designed to monitor stress and strain; by monitoring stress and strain, the number and position of the borehole buffer support structures are adjusted to match the needs of resisting stress and strain, ensuring that the deformation of each support structure under stress is within a safe range. This prevents collapse and excessive deformation of the extraction pipe caused by borehole instability and impact damage in the extraction area, thereby increasing the concentration of extracted gas and extending the effective extraction period. Furthermore, it avoids the increased costs and decreased efficiency caused by setting too many supports. Summary of the Invention

[0012] The purpose of this invention is to provide a protective buffer support structure for the extraction pipe in the event of instability and impact damage, which can not only effectively support the extraction pipe, but also facilitate the monitoring of stress and strain.

[0013] To achieve the above objectives, the borehole buffer support structure for preventing instability and impact damage of the extraction borehole of the present invention includes a borehole buffer support structure unit. The borehole buffer support structure unit includes an annular groove disposed on the inner wall of the extraction pipe, support rods arranged radially along the extraction pipe, and connecting rods. Multiple support rods are evenly spaced along the circumferential direction of the extraction pipe. The support rod includes a rod body, with an outer large end at the outer end that matches the annular groove, and an inner large end at the inner end for pressing against other support rods when the extraction pipe deforms. The annular groove has an annular opening on its radial inner surface. The width of the outer large end in the section perpendicular to the extraction pipe axis is smaller than the annular opening, while the width of the outer large end in the section passing through the extraction pipe axis is larger than the annular opening. When the extraction pipe does not deform, there is a deformation gap between the inner large ends of the multiple support rods, which allows the extraction pipe to deform safely. The connecting rod is connected between the outer large ends of two adjacent support rods. The connecting rod is equipped with a strain sensor. The lines of each strain sensor extend to the outside of the borehole through the extraction pipe and are connected to an electrical control device. The electrical control device is connected to a display screen. The connecting rod is used to transmit stress and strain to the corresponding strain sensor when the extraction pipe deforms. The detection data of each strain sensor serves as the basis for adjusting the number and position of the protective hole buffer support structure unit.

[0014] The outer surface of the outer large end is provided with an outer rubber pad, and the inner surface of the inner large end is provided with an inner rubber pad.

[0015] This invention also discloses a construction method for the borehole buffer support structure to prevent instability and impact damage of the above-mentioned extraction borehole. The borehole buffer support structure unit is used to support the extraction pipe, which is used to extract gas. The extraction pipe is installed inside the borehole and is carried out according to the following steps: The first step is to drill test holes for construction. The second step is to prepare the structure for grouting before drilling the first test borehole; The third step is grouting and sealing the holes; The fourth step is to optimize and adjust the installation position and spacing of the protective hole buffer impact support structure unit based on the detection data of each strain sensor of each protective hole buffer impact support structure unit, so as to form an optimized installation position and spacing scheme for the protective hole buffer impact support structure unit. The second to fourth steps form a regulatory cycle; The fifth step is to change to the next test borehole and perform the adjustment cycle until the installation position and spacing of the optimized borehole protection buffer impact support structure unit in the fourth step has not changed the original installation position and spacing of the borehole protection buffer impact support structure unit. The installation position and spacing of the borehole protection buffer impact support structure unit at this time is taken as the final solution. The sixth step is to construct a predetermined number of gas extraction holes in the gas extraction area, and to install a protective buffer support structure unit for each gas extraction hole according to the final plan.

[0016] The first step is to drill holes in the center of the predetermined gas extraction area as test holes. At least three test holes are set up, namely, hole number one, hole number two, and hole number three. The borehole stress state is initially determined, and the installation position and spacing of the initial borehole protection buffer support structure unit are determined based on the initially determined borehole stress state. The second step is to install inner and outer grouting bags at intervals on the extraction pipe, with sealing gaskets installed between the axial ends of the inner and outer grouting bags and the extraction pipe; to install the hole protection buffer support structure unit in the extraction pipe between the inner and outer grouting bags according to the installation position and installation interval determined in the first step; to connect the inner and outer grouting bags using grouting bags pipes, and to extend the hole sealing grouting pipe between the inner and outer grouting bags. The integral structure consisting of the grouting bag, the sealing grouting pipe, the extraction pipe, the inner grouting bag, the outer grouting bag, and the various hole protection buffer support structures inside the extraction pipe is extended into the No. 1 borehole to the predetermined position. Install the electrical control device and display screen outside the test borehole, and extend the lines of each strain sensor of each borehole buffer support structure unit to the outside of the borehole through the extraction pipe and connect them to the electrical control device. Multiple through holes for gas extraction are evenly distributed on the pipe wall of the extraction pipe facing inward from the inner grouting bag. The No. 1 borehole space facing inward from the inner grouting bag serves as the extraction section; the No. 1 borehole between the inner and outer grouting bags serves as the predetermined sealing section. The third step is to first inject grout into the bladder, and then seal the grout holes. The process of grouting a grouting bag involves connecting the outer end of the grouting bag pipe to an external grouting pump, which is connected to a container filled with well-mixed grouting liquid. The grouting pump is then turned on, and grout is injected into the inner and outer grouting bags to a predetermined pressure. At this point, the inner and outer grouting bags expand and seal the No. 1 borehole. Grouting and sealing are performed as follows: After the bag grouting is completed, the grouting pump is turned off, the bag grouting pipe is disconnected from the grouting pump, the outer end of the sealing grouting pipe is connected to the external grouting pump, the grouting pump is turned on, and grouting liquid is injected into the sealing section to the predetermined sealing pressure; after the grouting liquid solidifies, the grouting and sealing are completed; during the grouting and sealing process, the staff monitors the actual detection data SC of each strain sensor of each protective hole buffer impact support structure unit through the display screen; Staff members determined in advance, based on the pressure test, the detection data of the strain sensor corresponding to the maximum deformation state of the extraction pipe at the location of the protective hole buffer impact support structure unit, and used this detection data as the maximum strain data MAX. The fourth step is as follows: The protective hole buffer support structure unit is divided into three categories: appropriate, dangerous, and overly safe. When the actual measured data of all strain sensors of a hole buffer impact support structure unit fall within the range of SC≤80%, and the actual measured data of at least one strain sensor of the hole buffer impact support structure unit is ≥40%, the hole buffer impact support structure unit is classified into the appropriate category. When the actual detection data of at least one strain sensor of a hole buffer impact support structure unit falls within the range of SC > 80%, the hole buffer impact support structure unit is classified as a dangerous class. When the actual detection data of all strain sensors of a protective hole buffer impact support structure unit fall within SC < 40%, the protective hole buffer impact support structure unit is classified as over-safe. The position of the appropriate type of protective hole buffer support structure unit is not adjusted; For a dangerous type of borehole buffer impact support structure unit, if neither of its two adjacent borehole buffer impact support structure units belongs to the dangerous type, then the borehole buffer impact support structure unit is cancelled, and two borehole buffer impact support structure units are evenly spaced in the extraction pipe between the two adjacent borehole buffer impact support structure units. For a dangerous type of borehole buffer impact support structure unit, if there is a dangerous type of borehole buffer impact support structure unit among its adjacent borehole buffer impact support structure units, then the area of ​​the extraction pipe where the consecutive adjacent dangerous type of borehole buffer impact support structure units are located is called the doubled area. All borehole buffer impact support structure units within the doubled area are cancelled, and twice the original number of borehole buffer impact support structure units are set in this area at intervals. For the over-safety type of borehole buffer impact support structure unit; the area of ​​the extraction pipe where consecutive adjacent borehole buffer impact support structure units belonging to the over-safety type are located is called the over-safety area; the number of consecutive adjacent borehole buffer impact support structure units belonging to the over-safety type in the over-safety area is N, where N is a natural number; all borehole buffer impact support structure units in the over-safety area are cancelled, and borehole buffer impact support structure units are set at intervals of 0.5N in this area; when 0.5N is not an integer, the number of newly set borehole buffer impact support structure units in the over-safety area is taken as a natural number greater than 0.5N and adjacent to 0.5N.

[0017] The present invention has the following advantages: When the extraction pipe deforms, the existence of the deformation gap allows the extraction pipe to deform to a certain extent under impact or compression. When the deformation of the extraction pipe under pressure is large, the inner large ends of multiple support rods will press against each other to form an effective support for the extraction pipe, preventing further deformation and damage. When the extraction pipe deforms, the connecting rods deform accordingly, allowing each strain sensor to monitor the stress and strain. Workers can observe the detection data of each strain sensor in the protective hole buffer support structure for each extraction hole instability impact failure on the display screen, providing a basis for adjusting the number and position of the protective hole buffer support structure units.

[0018] The width of the outer large end on the cross section perpendicular to the extraction pipe axis is smaller than that of the annular opening, while the width of the outer large end on the cross section passing through the extraction pipe axis is larger than that of the annular opening. This design makes it convenient to hang the outer large end at the annular opening of the annular groove by rotating it 90 degrees after passing through the annular opening without it coming off.

[0019] The annular groove can prevent the support rod from moving axially when the extraction pipe is subjected to external force, ensuring that the position of the support pipe does not change and that the function of the support pipe is not reduced due to the axial movement of the support rod.

[0020] The outer rubber pad is used to form a buffer between the outer large end and the inner wall of the extraction pipe, and the inner rubber pad is used to form a buffer between the inner large ends to weaken the impact force and prevent structural damage.

[0021] By employing the construction method of this invention, and through adjusting the cycle of the test borehole, the optimal distribution scheme of the borehole protection buffer impact support structure unit can be obtained for the boreholes in the same gas extraction area. This ensures that the actual stress and strain of each borehole protection buffer impact support structure unit after grouting and sealing is appropriate, avoiding both excessive use of borehole protection buffer impact support structure units that would lead to cost waste and reduced efficiency, and insufficient use of borehole protection buffer impact support structure units that would cause potential damage to the extraction pipe. This guarantees the smooth progress of gas extraction work and reduces costs while increasing efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a gas extraction borehole using the present invention; Figure 2 yes Figure 1 AA view; Figure 3 yes Figure 2 BB cross-section diagram; Figure 4 This is a structural diagram of the support rod and connecting rod of the protective hole buffer support structure unit; Figure 5 This is a structural diagram of the support rod. Detailed Implementation

[0023] like Figures 1 to 5 As shown, the hole buffer support structure for the instability and impact damage of the extraction hole of the present invention includes a hole buffer support structure unit 7. The hole buffer support structure unit 7 includes an annular groove 2 disposed on the inner wall of the extraction pipe 1 (referring to the gas extraction pipe), a support rod and a connecting rod 10 disposed radially along the extraction pipe 1, and multiple support rods (preferably three) are evenly spaced in the circumferential direction of the extraction pipe 1.

[0024] The support rod includes a rod body 3, with an outer large end 4 at the outer end of the rod body 3 that matches the annular groove 2, and an inner large end 5 at the inner end of the rod body 3 for pressing against other support rods when the extraction pipe 1 deforms; the annular groove 2 has an annular opening 6 on its radial inner surface, such as... Figure 2 As shown, the width of the outer large end 4 in the cross-section perpendicular to the axis of the extraction pipe 1 is smaller than that of the annular opening 6. For example... Figure 3As shown, the width of the outer large end 4 in the cross section passing through the axis of the extraction pipe 1 is greater than that of the annular opening 6 (when the outer large end 4 is inserted into the annular groove 2 through the annular opening 6, the outer large end 4 is rotated to insert into the annular groove 2 using its thinner side, and after insertion, the rod body 3 is rotated, specifically 90 degrees. At this time, the outer large end 4 will hang on the radial inner surface of the annular groove 2 using its wider side and will not come out); when the extraction pipe 1 is not deformed, there is a deformation gap 8 between the inner large ends 5 of the multiple support rods. The deformation gap 8 is used to allow the extraction pipe 1 to undergo safe deformation (deformation that will not cause the extraction pipe 1 to break); when the inner large ends 5 of each support rod of the same protective hole buffer impact support structure unit are pressed together, each support rod supports the extraction pipe 1 to resist further deformation.

[0025] In the same borehole buffer support structure unit, the connecting rod 10 is connected between the outer large end 4 of two adjacent support rods. The connecting rod 10 is equipped with a strain sensor 9. The line of each strain sensor 9 extends to the outside of the borehole through the extraction pipe 1 and is connected to an electrical control device. The electrical control device is connected to a display screen. The electrical control device adopts a single-chip microcomputer, an industrial control computer, or an integrated circuit. The electrical control device and the display screen are all conventional technologies and are not shown in the figure.

[0026] The connecting rod 10 is used to transmit stress and strain to the corresponding strain sensor 9 when the extraction pipe 1 deforms. The detection data of each strain sensor 9 serves as the basis for adjusting the number and position of the protective hole buffer support structure unit 7.

[0027] When the extraction pipe 1 deforms, the deformation gap 8 allows the extraction pipe 1 to deform to a certain extent under impact or compression. When the deformation of the extraction pipe 1 under pressure is large, the inner large ends 5 of multiple support rods will press against each other to form an effective support for the extraction pipe 1, preventing further deformation and damage. When the extraction pipe 1 deforms, the connecting rod 10 deforms accordingly, causing each strain sensor 9 to monitor stress and strain. The staff can observe the detection data of each strain sensor 9 of the protective hole buffer support structure for the unstable impact damage of each extraction hole on the display screen, providing a basis for adjusting the number and position of the protective hole buffer support structure unit 7.

[0028] The width of the outer large end 4 on the cross section perpendicular to the axis of the extraction pipe 1 is smaller than that of the annular opening 6, while the width of the outer large end 4 on the cross section passing through the axis of the extraction pipe 1 is larger than that of the annular opening 6. This arrangement makes it convenient to hang the outer large end 4 at the annular opening 6 of the annular groove 2 by rotating it 90 degrees after passing through the annular opening 6 without it coming off.

[0029] The annular groove 2 can prevent the support rod from moving axially when the extraction pipe 1 is subjected to external force, ensuring that the position of the support pipe does not change and that the function of the support pipe is not reduced due to the axial movement of the support rod.

[0030] The outer surface of the outer large end 4 is provided with an outer rubber pad 11, and the inner surface of the inner large end 5 is provided with an inner rubber pad 12. The outer rubber pad 11 is used to form a buffer between the outer large end 4 and the inner wall of the extraction tube 1, and the inner rubber pad 12 is used to form a buffer between the inner large ends 5, thereby weakening the impact force and preventing structural damage.

[0031] This invention also discloses a construction method for the borehole buffer support structure to prevent instability and impact damage of the above-mentioned extraction borehole. The borehole buffer support structure unit 7 is used to support the extraction pipe 1, which is used to extract gas. The extraction pipe 1 is installed inside the borehole (gas extraction borehole) and is carried out according to the following steps: The first step is to drill multiple test boreholes; The second step is to prepare the structure before grouting for the first test borehole (i.e., borehole number one). The third step is grouting and sealing the holes; The fourth step is to optimize and adjust the installation position and installation spacing of the protective hole buffer impact support structure unit 7 based on the detection data of each strain sensor 9 of each protective hole buffer impact support structure unit 7, so as to form an optimized installation position and installation spacing scheme for the protective hole buffer impact support structure unit 7. The second to fourth steps form a regulatory cycle; The fifth step is to replace the next test borehole (such as borehole number 2) and perform the adjustment cycle until the installation position and spacing of the optimized borehole buffer impact support structure unit 7 in the fourth step have not changed the original installation position and spacing of the borehole buffer impact support structure unit 7. The installation position and spacing of the borehole buffer impact support structure unit 7 at this time is taken as the final scheme. The sixth step is to construct a predetermined number of gas extraction holes in the gas extraction area, and to install a protective buffer support structure unit 7 for each gas extraction hole in accordance with the final plan.

[0032] The first step is to drill holes in the center of the predetermined gas extraction area as test holes. At least three test holes are set up, namely Hole No. 1, Hole No. 2 and Hole No. 3; more test holes can be drilled as needed.

[0033] The borehole stress state was initially determined, and based on this, the installation positions and spacing of the preliminary borehole protection and impact support structure units 7 were determined. The principle was that in areas with high borehole stress, the borehole protection and impact support structure units 7 were arranged relatively densely, while in areas with low borehole stress, no borehole protection and impact support structure units 7 were installed, or the spacing was larger. The goal was to ensure that the borehole protection and impact support structure units 7 could support the extraction pipe 1 under the corresponding borehole stress with a certain degree of redundancy (e.g., if a certain area required a 2-meter interval for a borehole protection and impact support structure unit 7 based on the borehole stress state, a 1.7-meter interval could be used to provide redundancy). In areas where the stress was less than the compressive strength of the extraction pipe 1, there was no need to install borehole protection and impact support structure units 7. The compressive strength of the extraction pipe 1 was determined experimentally in advance.

[0034] Preliminary determination of borehole stress state can be achieved using existing measurement methods such as stress measurement or pore pressure method. For example, a strain gauge or a pressure measuring instrument can be installed inside the test borehole (to measure the stress state in the formation and infer the magnitude and direction of the stress) to obtain a preliminary understanding of the borehole stress state. Both stress measurement and pore pressure methods for measuring borehole stress are existing technologies, and there are also existing patented technologies specifically for measuring borehole stress, which will not be detailed here.

[0035] Because of the adjustment cycle, there are no requirements for the accuracy of the installation position and spacing of the initial borehole buffer impact support structure unit 7. Even if two different schemes are determined for the initial borehole buffer impact support structure unit 7, the same optimal distribution scheme of the borehole buffer impact support structure unit 7 will be obtained after the adjustment cycle is completed. This ensures that neither too many borehole buffer impact support structure units 7 are set up, resulting in cost waste and efficiency reduction, nor too few borehole buffer impact support structure units 7 are set up, resulting in the hidden danger of damage to the extraction pipe 1.

[0036] The second step is to install inner grouting bags 14 and outer grouting bags 15 at intervals on the extraction pipe 1. Sealing gaskets 16 are installed between the inner grouting bags 14 and outer grouting bags 15 and the extraction pipe 1 at both ends of the axial direction (axial direction of the extraction pipe 1). The hole protection buffer support structure unit 7 is installed in the extraction pipe 1 between the inner grouting bags 14 and outer grouting bags 15 according to the installation position and installation interval determined in the first step. The inner grouting bags 14 and outer grouting bags 15 are connected by the bag grouting pipe 17, and the hole sealing grouting pipe 18 is extended between the inner grouting bags 14 and outer grouting bags 15. The integral structure consisting of the grouting bag 17, the sealing grouting pipe 18, the extraction pipe 1, the inner grouting bag 14, the outer grouting bag 15, and the various hole protection buffer support structure units 7 inside the extraction pipe 1 is extended into the No. 1 borehole to the predetermined position. Install the electrical control device and display screen outside the test borehole, and extend the lines of each strain sensor 9 of each borehole buffer impact support structure unit 7 to the outside of the borehole through the extraction pipe 1 and connect them to the electrical control device. Multiple through holes for gas extraction are evenly distributed on the pipe wall of the extraction pipe 1 inside the grouting bag 14 (i.e., this section of the extraction pipe is a perforated pipe). The test borehole space inside the grouting bag 14, such as the No. 1 borehole space, serves as the extraction section 19. The test borehole space between the inner grouting bag 14 and the outer grouting bag 15, such as the No. 1 borehole space, serves as the predetermined sealing section 20. The third step is to first inject grout into the bladder, and then seal the grout holes. The process of grouting using grouting bags involves connecting the outer end of the grouting pipe 17 (located outside the No. 1 borehole) to an external grouting pump, which is connected to a container filled with well-mixed grouting fluid. The pump is then turned on, and grout is injected into the inner grouting bag 14 and the outer grouting bag 15 to a predetermined pressure. At this pressure, the inner and outer grouting bags 14 and 15 expand and seal the No. 1 borehole. The degree of expansion of the inner and outer grouting bags 14 and 15 corresponds to the grouting pressure, and those skilled in the art can easily determine the grouting pressure required to seal the test borehole. The grouting equipment used is conventional; the grouting pump and grouting fluid container are not shown in the figure.

[0037] Grouting and sealing are performed as follows: After the bag grouting is completed, the grouting pump is turned off, the bag grouting pipe 17 is disconnected from the grouting pump, the outer end of the sealing grouting pipe 18 (located outside the No. 1 borehole) is connected to the external grouting pump, the grouting pump is turned on, and grouting fluid is injected into the sealing section 20 to the predetermined sealing pressure; after the grouting fluid solidifies, the grouting and sealing are completed; during the grouting and sealing process, the staff monitors the actual detection data SC (actual measurement) of each strain sensor 9 of each protective hole buffer impact support structure unit 7 through the display screen. Staff members determined in advance, based on the pressure test, the detection data of strain sensor 9 at the location of the protective hole buffer impact support structure unit 7 when the extraction pipe 1 reaches the maximum deformation state (i.e., the detection data of strain sensor 9 before the extraction pipe 1 is damaged due to pressure deformation), and used this detection data as the maximum strain data MAX; when SC>MAX, it indicates that the extraction pipe 1 at this location will suffer structural damage and may break. The fourth step is as follows: The protective hole buffer support structure unit 7 is divided into three categories: appropriate, dangerous, and overly safe. When the actual detection data of all strain sensors 9 of a hole protection buffer impact support structure unit 7 fall within the range of SC≤80%, and the actual detection data of at least one strain sensor 9 of the hole protection buffer impact support structure unit 7 is ≥40%, the hole protection buffer impact support structure unit 7 is classified into the appropriate category; at this time, the position and spacing of the hole protection buffer impact support structure unit 7 just meet the requirements of pipe protection.

[0038] When the actual detection data of at least one strain sensor 9 of a borehole buffer impact support structure unit 7 falls within the range of SC > 80%, it means that the extraction pipe 1 at that location is more likely to break due to stress data fluctuations (i.e., SC > MAX); the borehole buffer impact support structure unit 7 is classified as a dangerous category. When the actual detection data of all strain sensors 9 of a hole buffer impact support structure unit 7 fall within SC < 40%, the hole buffer impact support structure unit 7 is classified as over-safe (i.e., the hole buffer impact support structure unit 7 at this location needs to be too dense relative to the protective tube). The position of the appropriate type of protective hole buffer support structure unit 7 is not adjusted; For a dangerous type of borehole buffer impact support structure unit 7, if neither of its two adjacent borehole buffer impact support structure units 7 belongs to the dangerous type, then the borehole buffer impact support structure unit 7 is cancelled, and two borehole buffer impact support structure units 7 are evenly spaced in the extraction pipe 1 between the two adjacent borehole buffer impact support structure units 7, that is, the support is doubled.

[0039] For a dangerous type of borehole buffer impact support structure unit 7, if there is a dangerous type of borehole buffer impact support structure unit 7 among its adjacent borehole buffer impact support structure units 7, then the area of ​​the extraction pipe 1 where the consecutive adjacent dangerous type of borehole buffer impact support structure units 7 are located is called the doubled area. All borehole buffer impact support structure units 7 within the doubled area are cancelled, and twice the original number of borehole buffer impact support structure units 7 are set in this area at intervals. For the over-safety type of borehole buffer impact support structure unit 7; the area of ​​the extraction pipe 1 where consecutive adjacent borehole buffer impact support structure units 7 of the over-safety type are located is called the over-safety area; the number of consecutive adjacent borehole buffer impact support structure units 7 of the over-safety type in the over-safety area is N, where N is a natural number; all borehole buffer impact support structure units 7 in the over-safety area are cancelled, and borehole buffer impact support structure units 7 are set at intervals of 0.5N in this area; when 0.5N is not an integer, the number of newly set borehole buffer impact support structure units 7 in the over-safety area is taken as a natural number greater than 0.5N and adjacent to 0.5N.

[0040] By employing the construction method of this invention, and through adjusting the cycle of the test borehole, the optimal distribution scheme of the borehole protection buffer impact support structure unit 7 can be obtained for the boreholes in the same gas extraction area. This ensures that the actual stress and strain of each borehole protection buffer impact support structure unit 7 after grouting and sealing is appropriate, avoiding both excessive use of borehole protection buffer impact support structure unit 7 which would lead to cost waste and reduced efficiency, and insufficient use of borehole protection buffer impact support structure unit 7 which would cause the risk of damage to the extraction pipe 1. This ensures the smooth progress of gas extraction work and reduces costs while increasing efficiency.

[0041] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A borehole buffer support structure for impact damage due to borehole instability, comprising a borehole buffer support structure unit, characterized in that: The borehole buffer support structure unit includes an annular groove on the inner wall of the extraction pipe, support rods and connecting rods arranged radially along the extraction pipe, with multiple support rods evenly spaced along the circumferential direction of the extraction pipe. The support rod includes a rod body, with an outer large end at the outer end that matches the annular groove, and an inner large end at the inner end for pressing against other support rods when the extraction pipe deforms. The annular groove has an annular opening on its radial inner surface. The width of the outer large end in the section perpendicular to the extraction pipe axis is smaller than the annular opening, while the width of the outer large end in the section passing through the extraction pipe axis is larger than the annular opening. When the extraction pipe does not deform, there is a deformation gap between the inner large ends of the multiple support rods, which allows the extraction pipe to deform safely. The connecting rod is connected between the outer large ends of two adjacent support rods. The connecting rod is equipped with a strain sensor. The lines of each strain sensor extend to the outside of the borehole through the extraction pipe and are connected to an electrical control device. The electrical control device is connected to a display screen. The connecting rod is used to transmit stress and strain to the corresponding strain sensor when the extraction pipe deforms. The detection data of each strain sensor serves as the basis for adjusting the number and position of the protective hole buffer support structure unit.

2. The borehole buffer support structure for impact damage due to instability of the extraction borehole according to claim 1, characterized in that: The outer surface of the outer large end is provided with an outer rubber pad, and the inner surface of the inner large end is provided with an inner rubber pad.

3. A construction method for the borehole buffer support structure for impact damage due to borehole instability as described in claim 1, wherein the borehole buffer support structure unit is used to support the extraction pipe, the extraction pipe is used to extract gas, and the extraction pipe is installed inside the borehole, characterized in that... Follow these steps: The first step is to drill test holes for construction. The second step is to prepare the structure for grouting before drilling the first test borehole; The third step is grouting and sealing the holes; The fourth step is to optimize and adjust the installation position and spacing of the protective hole buffer impact support structure unit based on the detection data of each strain sensor of each protective hole buffer impact support structure unit, so as to form an optimized installation position and spacing scheme for the protective hole buffer impact support structure unit. The second to fourth steps form a regulatory cycle; The fifth step is to change to the next test borehole and perform the adjustment cycle until the installation position and spacing of the optimized borehole protection buffer impact support structure unit in the fourth step has not changed the original installation position and spacing of the borehole protection buffer impact support structure unit. The installation position and spacing of the borehole protection buffer impact support structure unit at this time is taken as the final solution. The sixth step is to construct a predetermined number of gas extraction holes in the gas extraction area, and to install a protective buffer support structure unit for each gas extraction hole according to the final plan.

4. The construction method according to claim 3, characterized in that: The first step is to drill holes in the center of the predetermined gas extraction area as test holes. At least three test holes are set up, namely, hole number one, hole number two, and hole number three. The borehole stress state is initially determined, and the installation position and spacing of the initial borehole protection buffer support structure unit are determined based on the initially determined borehole stress state. The second step is to install inner and outer grouting bags at intervals on the extraction pipe. Sealing gaskets are installed between the axial ends of the inner and outer grouting bags and the extraction pipe. The hole protection buffer support structure unit is installed in the extraction pipe between the inner and outer grouting bags according to the installation position and installation interval determined in the first step. Use a grouting tube to connect the inner grouting bladder and the outer grouting bladder, and use a sealing grouting tube to extend between the inner grouting bladder and the outer grouting bladder; The integral structure consisting of the grouting bag, the sealing grouting pipe, the extraction pipe, the inner grouting bag, the outer grouting bag, and the various hole protection buffer support structures inside the extraction pipe is extended into the No. 1 borehole to the predetermined position. Install the electrical control device and display screen outside the test borehole, and extend the lines of each strain sensor of each borehole buffer support structure unit to the outside of the borehole through the extraction pipe and connect them to the electrical control device. Multiple through holes for gas extraction are evenly distributed on the pipe wall of the extraction pipe facing inward from the inner grouting bag. The No. 1 borehole space facing inward from the inner grouting bag serves as the extraction section; the No. 1 borehole between the inner and outer grouting bags serves as the predetermined sealing section. The third step is to first inject grout into the bladder, and then seal the grout holes. Bag grouting involves connecting the outer end of the bag grouting pipe to an external grouting pump, which is then connected to a container filled with well-mixed grouting liquid. Turn on the grouting pump and inject grout into the inner and outer grouting bags to the predetermined pressure. At this time, the inner and outer grouting bags expand and seal the No. 1 borehole. Grouting and sealing are performed as follows: After the bag grouting is completed, the grouting pump is turned off, the bag grouting pipe is disconnected from the grouting pump, the outer end of the sealing grouting pipe is connected to the external grouting pump, the grouting pump is turned on, and grouting liquid is injected into the sealing section to the predetermined sealing pressure; after the grouting liquid solidifies, the grouting and sealing are completed; during the grouting and sealing process, the staff monitors the actual detection data SC of each strain sensor of each protective hole buffer impact support structure unit through the display screen; Staff members determined in advance, based on the pressure test, the detection data of the strain sensor corresponding to the maximum deformation state of the extraction pipe at the location of the protective hole buffer impact support structure unit, and used this detection data as the maximum strain data MAX. The fourth step is as follows: The protective hole buffer support structure unit is divided into three categories: appropriate, dangerous, and overly safe. When the actual measured data of all strain sensors of a hole buffer impact support structure unit fall within the range of SC≤80%, and the actual measured data of at least one strain sensor of the hole buffer impact support structure unit is ≥40%, the hole buffer impact support structure unit is classified into the appropriate category. When the actual detection data of at least one strain sensor of a hole buffer impact support structure unit falls within the range of SC > 80%, the hole buffer impact support structure unit is classified as a dangerous class. When the actual detection data of all strain sensors of a protective hole buffer impact support structure unit fall within SC < 40%, the protective hole buffer impact support structure unit is classified as over-safe. The position of the appropriate type of protective hole buffer support structure unit is not adjusted; For a dangerous type of borehole buffer impact support structure unit, if neither of its two adjacent borehole buffer impact support structure units belongs to the dangerous type, then the borehole buffer impact support structure unit is cancelled, and two borehole buffer impact support structure units are evenly spaced in the extraction pipe between the two adjacent borehole buffer impact support structure units. For a dangerous type of borehole buffer impact support structure unit, if there is a dangerous type of borehole buffer impact support structure unit among its adjacent borehole buffer impact support structure units, then the area of ​​the extraction pipe where the consecutive adjacent dangerous type of borehole buffer impact support structure units are located is called the doubled area. All borehole buffer impact support structure units within the doubled area are cancelled, and twice the original number of borehole buffer impact support structure units are set in this area at intervals. For the over-safety type of borehole buffer impact support structure unit; the area of ​​the extraction pipe where consecutive adjacent borehole buffer impact support structure units belonging to the over-safety type are located is called the over-safety area; the number of consecutive adjacent borehole buffer impact support structure units belonging to the over-safety type in the over-safety area is N, where N is a natural number; All protective hole buffer support structure units within the safety zone are removed, and protective hole buffer support structure units are installed at intervals of 0.5N within this zone; When 0.5N is not an integer, the number of newly installed protective hole buffer support structure units in the safe zone shall be a natural number greater than 0.5N and adjacent to 0.5N.

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