A method for strengthening the anti - breakage of the casing of a surface vertical well in a coal - mined area

Abstract

A method for strengthening the anti - breakage of the casing of a surface vertical well in a coal - mining subsidence area, specifically including the following steps: (1) Determine the position for installing the anti - breakage strengthening device; (2) According to the design of the wellbore structure of the surface vertical well in the subsidence area, determine the dimensions and model parameters of each component of the anti - breakage strengthening device; (3) Assemble each component of the anti - breakage strengthening device together; (4) Install the assembled anti - breakage strengthening device onto the casing and correspond to the position determined in step (1); (5) Lower the casing into the surface vertical well in the coal - mining subsidence area according to the design, so that the anti - breakage strengthening device is just located at the position determined in step (1) to provide overall protection for the casing. The present invention can quickly determine the optimal installation position of the anti - breakage strengthening device, effectively protect the casing, reduce the casing protection cost, reduce the self - weight of the anti - breakage strengthening device, and also increase the fixing ability of the anti - breakage strengthening device, making it not easy to fall off.

Description

Technical Field

[0001] The present invention relates to the technical field of ground vertical well casing protection in coal mining areas. Specifically, it relates to a method for strengthening the anti-breakage of ground vertical well casings in coal mining areas. Background Art

[0002] The prevention and control of coal mine gas disasters is a major safety issue faced in the process of coal mine production in China. Conducting ground drilling to extract gas in the upper part of the coal mining area is one of the commonly used means for coal mine gas control. However, during the coal seam mining process, the overlying rock strata are affected by mining and undergo rock movement and deformation, which often causes damage to the casings of the mining wells, such as stretching, extrusion, fracture, and deformation, reducing the gas extraction efficiency of the mining wells. In severe cases, it will even lead to the failure of the mining wells, greatly shortening the service life of the coal mine mining wells, causing a large waste of manpower and material resources, and also severely restricting the process of coal mine gas control. If the casings of the mining wells can be protected to reduce the damage effect of the overlying rock strata on the casings, it can effectively ensure the safety production in the coal mine underground.

[0003] Currently, common casing protection measures mainly include: weak coal seam roof reinforcement technology, wellbore annulus technology, new material reinforcement technology, reinforcement member reinforcement technology, etc. The weak coal seam roof reinforcement technology uses a mixed method of bolt + cable + anchor net to reinforce the weak coal seam roof, and protects the casing by reducing the downward movement amplitude of the overlying rock strata. This technology is cumbersome and complex in construction, costly, and will affect the coal mine production progress during underground construction. The wellbore annulus technology protects the casing by reserving annular cement in the wellbore and reserving the lateral displacement space of the rock strata. When the rock strata displacement exceeds the annular distance, the stability enhancement effect is poor. The new material reinforcement technology is to optimize the selection of materials with certain strength and elasticity to make the casing, and at the same time select new materials with certain fluid-plasticity to replace the traditional mud cementing to improve the anti-extrusion deformation ability of the casing. The material cost has a greater impact on its application. Compared with other casing protection technologies, the reinforcement member reinforcement technology has the advantages of simple construction, low protection cost, not affecting underground production, and being applicable to various terrains, and has a broad application prospect. However, there are still problems such as unclear effective protection positions, easy detachment during the production process, and large casing loads caused by the excessive self-weight of the reinforcement members. Therefore, there is an urgent need for a method for strengthening the anti-breakage of ground vertical well casings in coal mining areas to provide more effective protection for the ground vertical well casings in the on-site coal mining area. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for strengthening the anti-breakage of ground vertical well casings in coal mining areas. The present invention can quickly determine the optimal installation position of the anti-breakage reinforcement device, effectively protect the casing, reduce the casing protection cost, reduce the self-weight of the anti-breakage reinforcement device, and also increase the fixing ability of the anti-breakage reinforcement device, making it not easy to fall off.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for strengthening the anti-breakage of the surface vertical well casing in the coal mining area, specifically including the following steps:

[0007] (1). Determine the position for installing the anti-breakage strengthening device;

[0008] (2). According to the design of the surface vertical well casing structure in the mining area, determine the dimensions and model parameters of each component of the anti-breakage strengthening device;

[0009] (3). Assemble each component of the anti-breakage strengthening device together;

[0010] (4). Install the assembled anti-breakage strengthening device on the casing and correspond to the position determined in step (1);

[0011] (5). Lower the casing into the surface vertical well in the coal mining area according to the design, so that the anti-breakage strengthening device is just located at the position determined in step (1), and conduct overall protection on the casing.

[0012] The anti-breakage strengthening device includes a strengthening main body and a reinforcing cylinder. The strengthening main body is composed of at least one pressure-bearing cylinder spliced together. The pressure-bearing cylinder and the reinforcing cylinder are both concentrically sleeved outside the casing. The inner diameter and outer diameter of the pressure-bearing cylinder and the reinforcing cylinder are the same. The inner diameter of the pressure-bearing cylinder is larger than the outer diameter of the casing. There are two reinforcing cylinders arranged at intervals up and down. The lower end of the upper reinforcing cylinder is connected to the upper end of the uppermost pressure-bearing cylinder, and the upper end of the lower reinforcing cylinder is connected to the lower end of the lowermost pressure-bearing cylinder. A clamping assembly that hugs the casing is fixedly arranged on the inner circumference of the reinforcing cylinder. A number of protective assemblies are fixedly connected in a circumferential array on the outer circumference of each pressure-bearing cylinder.

[0013] External male threads are integrally formed on the outer circles of the upper ends of the pressure-bearing cylinder and the reinforcing cylinder, and internal female threads that are threadedly matched with the external male threads are integrally formed on the inner circles of the lower ends of the pressure-bearing cylinder and the reinforcing cylinder. The internal female thread of the upper reinforcing cylinder is threadedly connected to the external male thread of the uppermost pressure-bearing cylinder, and the external male thread of the lower reinforcing cylinder is threadedly connected to the internal female thread of the lowermost pressure-bearing cylinder. The corresponding external male threads and internal female threads between two adjacent pressure-bearing cylinders are threadedly connected. A number of groups of side threaded interfaces that are arranged in a circumferential array and are internally and externally permeable are fixedly installed on the cylinder wall of each pressure-bearing cylinder. Each group of side threaded interfaces includes a number of side threaded interfaces arranged at intervals up and down.

[0014] The protection component includes an outer rubber gasket and an inner metal gasket. Both the outer rubber gasket and the inner metal gasket are in the structure of arc-shaped plates. The outer rubber gasket and the inner metal gasket have the same height and equal circular arc angles. The inner circumference of the outer rubber gasket is bonded to the outer circumference of the inner metal gasket. A number of T-shaped threaded through holes that are vertically spaced and internally and externally corresponding and permeable are provided in the middle of the upper parts of the outer rubber gasket and the inner metal gasket. Each of the T-shaped threaded through holes corresponds to each of the corresponding sets of side threaded interfaces on the pressure-bearing cylinder one by one internally and externally. Along the radial direction, a buffer damping pipe column is fixedly provided at the position corresponding to each T-shaped threaded through hole on the inner circumference of the inner metal gasket. A compression spring is fixedly connected to the inner end edge of each buffer damping pipe column. The center line of the compression spring coincides with the center line of the buffer damping pipe column. The inner hole inner diameters of the T-shaped threaded through holes, the inner diameters of the side threaded interfaces, the inner diameters of the buffer damping pipe columns, and the inner diameters of the compression springs are all the same. The lower side edges of the outer rubber gasket and the inner metal gasket are flush with the lower end of the pressure-bearing cylinder. The upper side edges of the outer rubber gasket and the inner metal gasket are flush with the lower side edge of the external thread male head of the pressure-bearing cylinder. A first fixing screw passing through the corresponding buffer damping pipe column and compression spring is provided in each of the T-shaped threaded through holes of the outer rubber gasket and the inner metal gasket. The inner ends of the first fixing screws are respectively threadedly connected to each of the corresponding sets of side threaded interfaces on the pressure-bearing cylinder. The inner ends of the compression springs are all pressed against the outer circumference of the pressure-bearing cylinder.

[0015] The clamping component includes two inner connecting bases. The two inner connecting bases are radially symmetrically and fixedly connected in the inner circumference of the reinforcement cylinder. Threaded blind holes with open inner sides are provided in the middle of the inner sides of the two inner connecting bases. A second fixing screw is connected in each of the two threaded blind holes. One end of the second fixing screw extending out of the threaded blind hole is connected with a fixed steel bracket. The two fixed steel brackets are radially symmetrically arranged. The fixed steel bracket is in the structure of a semi-circular arc-shaped plate with the open side facing inwards. The inner circumference of the fixed steel bracket is in tight pressure contact with the outer circumference of the sleeve. The two fixed steel brackets enclose a whole cylindrical structure that holds the sleeve. One end of the second fixing screw extending out of the threaded blind hole is rotatably connected to the outer circumference of the fixed steel bracket.

[0016] Step (1) is specifically as follows: Due to differences in coal seam mining height, lithology and thickness of overlying strata, and mining distance, etc., during the mining process, there are differences in the position, stress, and displacement distribution characteristics of the separated layer section, and the fracture positions of the mining well casing are also different. Therefore, the position of installing the anti-fracture strengthening device is determined according to the following method:

[0017] (1) Determine the key strata according to the lithology combination of the surrounding rock in the coal mining area and the key stratum discrimination method;

[0018] (2) Using the stress monitoring data of the separated layer section of the overlying strata on the approximate geological working surface in the coal mining area, fit to obtain stress functions applicable to different coal seam mining heights and different overlying rock combinations in the coal mining area;

[0019] (3) Based on the stress function obtained by fitting and combined with the mechanical parameters of different types of casing, the position of the anti - breakage reinforcement device can be quickly determined.

[0020] The specific steps of step (III) are as follows: First, according to the requirement of the casing protection length, adjust the length of the main body of the reinforcement. Connect several required pressure - bearing cylinders up and down, and thread - connect the corresponding external male threads and internal female threads between adjacent two pressure - bearing cylinders, so as to assemble the main body of the reinforcement. Then, according to the length of the assembled main body of the reinforcement, select several protection components. Use several first fixing screws to sequentially pass through the respective T - shaped threaded through - holes of the outer rubber gaskets, the respective T - shaped threaded through - holes of the inner metal gaskets, each buffer damping pipe column and each compression spring in the corresponding protection components and thread - connect them to the respective side threaded interfaces in a corresponding group on the pressure - bearing cylinder, so that the inner ends of each compression spring are all pressed against the outer circumference of the pressure - bearing cylinder. Then, use the second fixing screws to connect the corresponding fixing steel brackets to the corresponding inner connecting bases inside the reinforcement cylinder, and assemble the clamping components. Then, thread - connect the internal female thread of the upper reinforcement cylinder to the external male thread of the uppermost pressure - bearing cylinder, and thread - connect the external male thread of the lower reinforcement cylinder to the internal female thread of the lowermost pressure - bearing cylinder. In this way, the assembly work of each component of the anti - breakage reinforcement device is completed.

[0021] The specific steps of step (IV) are as follows: Sleeve the assembled anti - breakage reinforcement device on the outside of the casing and move it correspondingly to the position determined in step (I). Adjust each second fixing screw to increase the length of the second fixing screw extending out of the threaded blind hole, so that the inner circumferences of each fixing steel bracket and the outer circumference of the casing are tightly pressed and in contact. In this way, the two fixing steel brackets in each reinforcement cylinder together enclose a complete cylindrical structure that clamps the casing, and the two reinforcement cylinders are fixed on the casing, thereby fixing the assembled anti - breakage reinforcement device at the predetermined position to be protected on the casing.

[0022] The present invention has prominent substantial features and remarkable progress compared with the prior art. Specifically, the pressure-bearing cylinder is sleeved outside the sleeve to evenly share the stress of the overlying strata affected by mining disturbances and provide overall protection for the casing. A number of protective components are circumferentially arrayed on the outer circumference of the pressure-bearing cylinder to increase the buffering capacity of the anti-breaking reinforcement device against the extrusion stress of the surrounding rock. The outer rubber gasket is used to reduce the extrusion stress of the external rock strata and provide overall protection for the pressure-bearing cylinder. The inner metal gasket is used to connect the outer rubber gasket, prevent the outer rubber gasket from deforming during the process of lowering the casing, and provide secondary protection for the overall pressure-bearing cylinder. The buffer damping pipe string plays a buffering role to prevent the compression spring from deforming too quickly and being damaged. The compression spring further absorbs the extrusion stress of the external rock strata through compression. The outer rubber gasket, buffer damping pipe string, and compression spring are light in weight. In this way, while the protective component increases the buffering capacity of the anti-breaking reinforcement device against the extrusion stress of the surrounding rock, it can also reduce the self-weight of the anti-breaking reinforcement device;

[0023] The pressure-bearing cylinder of the present invention is designed to be separated from the reinforcement cylinder, and the length of the reinforcement main body can be adjusted according to the protection length requirements. A number of required pressure-bearing cylinders are butt-jointed up and down. The corresponding external thread male head and internal thread female head between adjacent pressure-bearing cylinders are thread-connected. The internal thread female head of the upper reinforcement cylinder is thread-connected to the external thread male head of the uppermost pressure-bearing cylinder, and the external thread male head of the lower reinforcement cylinder is thread-connected to the internal thread female head of the lowermost pressure-bearing cylinder. Adjust each second fixing screw to increase the length of the second fixing screw extending out of the threaded blind hole, so that the inner circumference of each fixing steel bracket is tightly pressed against the outer circumference of the casing. In this way, the two fixing steel brackets in each reinforcement cylinder jointly enclose a complete cylindrical structure around the casing, fixing the two reinforcement cylinders on the casing, and thus fixing the assembled anti-breaking reinforcement device at the predetermined position to be protected on the casing, increasing the fixing ability of the anti-breaking reinforcement device and making it not easy to fall off;

[0024] The present invention also proposes a method for quickly determining the optimal installation position of the anti-breaking reinforcement device, which can reduce the casing protection cost and avoid the burden on the casing load caused by installing redundant reinforcement.

[0025] In summary, the present invention can quickly determine the optimal installation position of the anti-breaking reinforcement device, effectively protect the casing, reduce the casing protection cost, reduce the self-weight of the anti-breaking reinforcement device, and also increase the fixing ability of the anti-breaking reinforcement device, making it not easy to fall off. Description of the Drawings

[0026] Figure 1 is the installation and use schematic diagram of the present invention.

[0027] Figure 2 is the structural schematic diagram of the pressure-bearing cylinder of the present invention.

[0028] Figure 3 It is a top view of the pressure-bearing cylinder of the present invention.

[0029] Figure 4 It is a top view of the protection component of the present invention.

[0030] Figure 5 It is a front view of the protection component of the present invention.

[0031] Figure 6 It is a right view of the protection component of the present invention.

[0032] Figure 7 It is a schematic assembly diagram of the reinforcement cylinder and the clamping component of the present invention from a top view angle. Specific Embodiments

[0033] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0034] As Figure 1-7 shown, a method for preventing breakage and strengthening the surface vertical well casing in the coal mining affected area specifically includes the following steps:

[0035] (1) Determine the position for installing the breakage prevention and strengthening device.

[0036] (2) According to the design of the surface vertical well casing structure in the mining affected area, determine the dimensions and model parameters of each component of the breakage prevention and strengthening device.

[0037] (3) Assemble each component of the breakage prevention and strengthening device together.

[0038] (4) Install the assembled breakage prevention and strengthening device on the casing 1 and correspond to the position determined in step (1).

[0039] (5) Lower the casing 1 into the surface vertical well in the coal mining affected area according to the design, so that the breakage prevention and strengthening device is just located at the position determined in step (1) to provide overall protection for the casing 1.

[0040] The breakage prevention and strengthening device includes a strengthening member main body and a reinforcement cylinder 2. The strengthening member main body is composed of at least one pressure-bearing cylinder 3 spliced together. Both the pressure-bearing cylinder 3 and the reinforcement cylinder 2 are concentrically sleeved outside the casing 1. The inner diameter and outer diameter of the pressure-bearing cylinder 3 and the reinforcement cylinder 2 are the same. The inner diameter of the pressure-bearing cylinder 3 is greater than the outer diameter of the casing 1. There are two reinforcement cylinders 2 arranged at intervals up and down. The lower end of the upper reinforcement cylinder 2 is connected to the upper end of the uppermost pressure-bearing cylinder 3, and the upper end of the lower reinforcement cylinder 2 is connected to the lower end of the lowermost pressure-bearing cylinder 3. A clamping component that clamps on the casing 1 is fixedly provided on the inner circumference of the reinforcement cylinder 2. A plurality of protection components are fixedly connected in a circumferential array on the outer circumference of each pressure-bearing cylinder 3.

[0041] The outer circles of the upper ends of the pressure-bearing cylinder 3 and the reinforcement cylinder 2 are integrally formed with external thread male heads 4. The inner circles of the lower ends of the pressure-bearing cylinder 3 and the reinforcement cylinder 2 are integrally formed with internal thread female heads that are threadedly matched with the external thread male heads 4. The internal thread female head of the upper reinforcement cylinder 2 is threadedly connected to the external thread male head 4 of the uppermost pressure-bearing cylinder 3. The external thread male head 4 of the lower reinforcement cylinder 2 is threadedly connected to the internal thread female head of the lowermost pressure-bearing cylinder 3. The corresponding external thread male heads 4 and internal thread female heads between two adjacent pressure-bearing cylinders 3 are threadedly connected. A plurality of groups of side thread interfaces 5 that are arranged in a circumferential array and are internally and externally permeable are fixedly installed on the cylinder wall of each pressure-bearing cylinder 3. Each group of side thread interfaces 5 includes a plurality of side thread interfaces 5 that are arranged at intervals up and down.

[0042] The protection component includes an outer rubber gasket 6 and an inner metal gasket 7. Both the outer rubber gasket 6 and the inner metal gasket 7 are arc-shaped plate structures. The outer rubber gasket 6 and the inner metal gasket 7 have the same height and equal arc angles. The inner circumference of the outer rubber gasket 6 is bonded to the outer circumference of the inner metal gasket 7. A plurality of T-shaped threaded through holes 8 that are arranged at intervals up and down and are internally and externally corresponding and permeable are opened in the middle of the outer rubber gasket 6 and the inner metal gasket 7. Each of the T-shaped threaded through holes 8 corresponds to each of the corresponding group of side thread interfaces 5 on the pressure-bearing cylinder 3 one by one internally and externally. A buffer damping pipe column 9 is fixedly provided along the radial direction at the position corresponding to each T-shaped threaded through hole 8 on the inner circumference of the inner metal gasket 7. A compression spring 10 is fixedly connected to the inner end edge of each buffer damping pipe column 9. The center line of the compression spring 10 coincides with the center line of the buffer damping pipe column 9. The T-shaped threaded through hole 8 is large on the outside and small on the inside. The inner hole inner diameter of the T-shaped threaded through hole 8, the inner diameter of the side thread interface 5, the inner diameter of the buffer damping pipe column 9, and the inner diameter of the compression spring 10 are all the same. The lower sides of the outer rubber gasket 6 and the inner metal gasket 7 are flush with the lower end of the pressure-bearing cylinder 3. The upper sides of the outer rubber gasket 6 and the inner metal gasket 7 are flush with the lower side of the external thread male head 4 of the pressure-bearing cylinder 3. A first fixing screw that passes through the corresponding buffer damping pipe column 9 and compression spring 10 is provided in each of the T-shaped threaded through holes 8 of the outer rubber gasket 6 and the inner metal gasket 7. The inner ends of each first fixing screw are respectively threadedly connected to each of the corresponding group of side thread interfaces 5 on the pressure-bearing cylinder 3. The inner ends of each compression spring 10 are all pressed against the outer circumference of the pressure-bearing cylinder 3.

[0043] The clamping assembly includes two inner connecting bases 11, which are radially symmetrically and fixedly connected to the inner circumference of the reinforcement cylinder 2. In the middle of the inner side surfaces of the two inner connecting bases 11, there are internally open threaded blind holes. A second fixing screw 12 is connected in each of the two threaded blind holes. One end of the second fixing screw 12 extending out of the threaded blind hole is connected to a fixing steel bracket 13. The two fixing steel brackets 13 are radially symmetrically arranged. The fixing steel bracket 13 is a semi-circular arc plate structure with the open side facing inwards. The inner circumference of the fixing steel bracket 13 is in tight pressure contact with the outer circumference of the casing 1. The two fixing steel brackets 13 are combined to form a whole cylindrical structure that hugs the casing 1. One end of the second fixing screw 12 extending out of the threaded blind hole is rotatably connected to the outer circumference of the fixing steel bracket 13.

[0044] Step (1) is specifically as follows: Due to differences in coal seam mining height, lithology and thickness of overlying strata, and mining distance, etc., during the mining process, there are differences in the position, stress and displacement distribution characteristics of the separated layer section, and the fracture positions of the mining well casing 1 are also different. Therefore, the position of installing the anti-fracture strengthening device is determined according to the following method:

[0045] (1) Determine the key strata according to the surrounding rock lithology combination and key strata discrimination method in the coal mining area;

[0046] (2) Using the stress monitoring data of the separated layer section of the overlying strata on the approximate geological working surface in the coal mining area, fit the stress functions applicable to different coal seam mining heights and different overlying rock combinations in the coal mining area;

[0047] (3) According to the fitted stress function and combined with the mechanical parameters of different types of casings 1, the position of installing the anti-fracture strengthening device can be quickly determined.

[0048] Step (III) is specifically as follows: First, according to the requirement of the protective length of the casing 1, the length of the reinforcing member body is adjusted. A number of pressure-bearing cylinders 3 required are butt-jointed up and down. The corresponding external thread male heads 4 and internal thread female heads between two adjacent pressure-bearing cylinders 3 are thread-connected, so as to assemble the reinforcing member body. Then, according to the length of the assembled reinforcing member body, a number of protective components are selected. A number of first fixing screws are respectively passed through the respective T-shaped threaded through holes 8 of the outer rubber gaskets 6, the respective T-shaped threaded through holes 8 of the inner metal gaskets 7, the respective buffer damping pipe columns 9 and the respective compression springs 10 in the corresponding protective components and are respectively thread-connected to the respective side threaded interfaces 5 on the pressure-bearing cylinder 3 in a corresponding group, so that the inner ends of the respective compression springs 10 are all pressed against the outer circumference of the pressure-bearing cylinder 3. Then, the corresponding fixing steel brackets 13 are connected to the corresponding inner side connection bases 11 inside the reinforcing cylinder 2 by using the second fixing screws 12, and the clamping components are assembled. Then, the internal thread female head of the upper reinforcing cylinder 2 is thread-connected to the external thread male head 4 of the uppermost pressure-bearing cylinder 3, and the external thread male head 4 of the lower reinforcing cylinder 2 is thread-connected to the internal thread female head of the lowermost pressure-bearing cylinder 3. In this way, the assembly work of each component of the anti-breakage reinforcing device is completed.

[0049] Step (IV) is specifically as follows: The assembled anti-breakage reinforcing device is sleeved on the outside of the casing 1 and is correspondingly moved to the position determined in Step (I). The respective second fixing screws 12 are adjusted to increase the length of the second fixing screws 12 extending out of the threaded blind holes, so that the inner circumferences of the respective fixing steel brackets 13 are all tightly pressed against the outer circumference of the casing 1. In this way, the two fixing steel brackets 13 in each reinforcing cylinder 2 together enclose a complete cylindrical structure that holds the casing 1, and the two reinforcing cylinders 2 are fixed on the casing 1, so as to fix the assembled anti-breakage reinforcing device at the predetermined position to be protected on the casing 1.

[0050] The mechanical parameters of different models of casings in Step (I) are shown in Table 1:

[0051] Table 1. Mechanical parameters of different models of casings

[0052] ;

[0054] Taking a coal mine working face as an example, the buried depth of the main coal seam in this coal mine is 160.87 - 1003.85 m, the coal thickness is 0.34 - 7.80 m, with an average of 5.81 m, the coal seam structure is simple, and the position of the key stratum is 57 - 130 m above the coal seam. The method in Step (I) is used to determine the best position of the anti-breakage reinforcing device as shown in Table 2:

[0055] Table 2. Determination of the best position of the anti-breakage reinforcing device under different coal seam mining heights and different overlying rock combinations

[0056]

[0057] Three pressure-bearing cylinders 3 of the present invention are sleeved outside the sleeve to evenly share the stress of the overlying strata affected by mining disturbances and provide overall protection for the casing 1. A number of protection components are installed in a circumferential array on the outer circumference of the pressure-bearing cylinder 3 to increase the buffering capacity of the anti-breaking reinforcement device against the extrusion stress of the surrounding rock. The outer rubber gasket 6 is used to reduce the extrusion stress of the external rock strata and provide overall protection for the pressure-bearing cylinder 3. The inner metal gasket 7 is used to connect the outer rubber gasket 6 to prevent the outer rubber gasket 6 from deforming during the lowering process of the casing 1 and provide secondary protection for the pressure-bearing cylinder 3 as a whole. The buffer damping pipe string 9 plays a buffering role to prevent the compression spring 10 from being damaged due to too fast deformation. The compression spring 10 further absorbs the extrusion stress of the external rock strata through compression. The outer rubber gasket 6, the buffer damping pipe string 9 and the compression spring 10 are light in weight. In this way, while the protection component increases the buffering capacity of the anti-breaking reinforcement device against the extrusion stress of the surrounding rock, it can also reduce the self-weight of the anti-breaking reinforcement device;

[0058] The pressure-bearing cylinder 3 of the present invention is designed to be separated from the reinforcement cylinder 2, and the length of the reinforcement main body can be adjusted according to the protection length requirements. A number of required pressure-bearing cylinders 3 are butt-jointed up and down. The corresponding external male thread 4 and internal female thread on adjacent two pressure-bearing cylinders 3 are thread-connected. The internal female thread of the upper reinforcement cylinder 2 is thread-connected to the external male thread 4 of the uppermost pressure-bearing cylinder 3, and the external male thread 4 of the lower reinforcement cylinder 2 is thread-connected to the internal female thread of the lowermost pressure-bearing cylinder 3. Adjust each second fixing screw 12 to increase the length of the second fixing screw 12 extending out of the threaded blind hole, so that the inner circumferences of each fixing steel bracket 13 are tightly pressed against the outer circumference of the casing 1. In this way, the two fixing steel brackets 13 in each reinforcement cylinder 2 jointly enclose a whole cylindrical structure that holds the casing 1, fixing the two reinforcement cylinders 2 on the casing 1, thereby fixing the assembled anti-breaking reinforcement device at the predetermined position to be protected on the casing 1, increasing the fixing ability of the anti-breaking reinforcement device and making it not easy to fall off;

[0059] The present invention also proposes a method for quickly determining the best installation position of the anti-breaking reinforcement device, which can reduce the protection cost of the casing 1 and avoid the burden on the load-bearing of the casing 1 caused by installing redundant reinforcement parts.

[0060] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that; still modifications or equivalent replacements can be made to the present invention, and any modification or partial replacement without departing from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A method for strengthening the anti-breakage of the casing of a surface vertical well in a coal mining area affected by mining, characterized in that: Specifically, it includes the following steps: (1) Determine the position for installing the anti-breakage strengthening device; (2) According to the design of the vertical wellbore structure on the ground in the mining area, determine the dimensions and model parameters of each component of the anti-breakage strengthening device; (3) Assemble each component of the anti-breakage strengthening device together; (4) Install the assembled anti-breakage strengthening device on the casing and correspond to the position determined in step (1); (5) Lower the casing into the vertical well on the ground in the coal mining area according to the design, so that the anti-breakage strengthening device is just located at the position determined in step (1) to provide overall protection for the casing; The anti-breakage strengthening device includes a strengthening main body and a reinforcement cylinder. The strengthening main body is composed of at least one pressure-bearing cylinder spliced together. The pressure-bearing cylinder and the reinforcement cylinder are both concentrically sleeved outside the casing. The inner diameter and outer diameter of the pressure-bearing cylinder and the reinforcement cylinder are the same. The inner diameter of the pressure-bearing cylinder is larger than the outer diameter of the casing. There are two reinforcement cylinders arranged at intervals up and down. The lower end of the upper reinforcement cylinder is connected to the upper end of the uppermost pressure-bearing cylinder, and the upper end of the lower reinforcement cylinder is connected to the lower end of the lowermost pressure-bearing cylinder. A clamping assembly that clamps on the casing is fixedly arranged on the inner circumference of the reinforcement cylinder. A number of protection components are fixedly connected in a circumferential array on the outer circumference of each pressure-bearing cylinder; On the outer circle of the upper end parts of the pressure-bearing cylinder and the reinforcement cylinder, external thread male heads are integrally formed. On the inner circle of the lower end parts of the pressure-bearing cylinder and the reinforcement cylinder, internal thread female heads that are thread-matched with the external thread male heads are integrally formed. The internal thread female head of the upper reinforcement cylinder is thread-connected to the external thread male head of the uppermost pressure-bearing cylinder, and the external thread male head of the lower reinforcement cylinder is thread-connected to the internal thread female head of the lowermost pressure-bearing cylinder. The corresponding external thread male heads and internal thread female heads between two adjacent pressure-bearing cylinders are thread-connected. A number of groups of side thread interfaces that are arranged in a circumferential array and are internally and externally transparent are fixedly installed on the cylinder wall of each pressure-bearing cylinder. Each group of side thread interfaces includes a number of side thread interfaces arranged at intervals up and down; The protection component includes an outer rubber gasket and an inner metal gasket. Both the outer rubber gasket and the inner metal gasket are arc-shaped plate structures. The outer rubber gasket and the inner metal gasket have the same height and equal arc angles. The inner circumference of the outer rubber gasket is bonded to the outer circumference of the inner metal gasket. A number of T-shaped threaded through holes that are vertically spaced and internally and externally corresponding and transparent are provided in the middle of the upper part of the outer rubber gasket and the inner metal gasket. Each of the T-shaped threaded through holes corresponds to each side threaded interface of a corresponding group on the pressure-bearing cylinder one by one internally and externally. A buffer damping pipe column is fixedly provided radially at each position corresponding to each T-shaped threaded through hole on the inner circumference of the inner metal gasket. A compression spring is fixedly connected to the inner end edge of each buffer damping pipe column. The center line of the compression spring coincides with the center line of the buffer damping pipe column. The inner hole inner diameter of the T-shaped threaded through hole, the inner diameter of the side threaded interface, the inner diameter of the buffer damping pipe column, and the inner diameter of the compression spring are all the same. The lower side edges of the outer rubber gasket and the inner metal gasket are flush with the lower end of the pressure-bearing cylinder. The upper side edges of the outer rubber gasket and the inner metal gasket are flush with the lower side edge of the external thread male head of the pressure-bearing cylinder. A first fixing screw passing through the corresponding buffer damping pipe column and compression spring is provided in each of the T-shaped threaded through holes of the outer rubber gasket and the inner metal gasket. The inner ends of the first fixing screws are respectively threadedly connected to each side threaded interface of a corresponding group on the pressure-bearing cylinder. The inner ends of each compression spring are all pressed against the outer circumference of the pressure-bearing cylinder; The clamping component includes two inner connecting bases. The two inner connecting bases are radially symmetrically and fixedly connected in the inner circumference of the reinforcement cylinder. Threaded blind holes with inner openings are provided in the middle of the inner sides of the two inner connecting bases. A second fixing screw is connected in each of the two threaded blind holes. One end of the second fixing screw extending out of the threaded blind hole is connected to a fixed steel bracket. The two fixed steel brackets are radially symmetrically arranged. The fixed steel bracket is a semi-circular arc-shaped plate structure with the open side facing inwards. The inner circumference of the fixed steel bracket is in tight pressure contact with the outer circumference of the sleeve. The two fixed steel brackets enclose a whole cylindrical structure that clamps the sleeve. One end of the second fixing screw extending out of the threaded blind hole is rotatably connected to the outer circumference of the fixed steel bracket.

2. The method for strengthening the prevention of breakage of the surface vertical well casing in the coal mining area according to claim 1, wherein: Step (1) is specifically as follows: Due to differences in coal seam mining height, lithology and thickness of overlying strata, and mining distance, etc., during the mining process, there are differences in the position, stress, and displacement distribution characteristics of the separated layer section, and the fracture positions of the mining well casing are also different. Therefore, the position of installing the anti-fracture reinforcement device is determined according to the following method: (1) Determine the key strata according to the surrounding rock lithology combination and key strata discrimination method in the coal mining area; (2) Using the stress monitoring data of the separated layer section of the overlying strata on the approximate geological working surface in the coal mining area, fit to obtain stress functions applicable to different coal seam mining heights and different overlying rock combinations in the coal mining area; (3) According to the fitted stress function and combined with the mechanical parameters of different types of casings, the position of installing the anti-fracture reinforcement device can be quickly determined.

3. The method for strengthening the prevention of breakage of the surface vertical well casing in the coal mining area according to claim 2, characterized in that: Step (iii) is specifically as follows: First, according to the requirement of the protective length of the casing, the length of the main body of the reinforcement is adjusted. A number of required pressure-bearing cylinders are butt-jointed up and down, and the corresponding external thread male heads and internal thread female heads between two adjacent pressure-bearing cylinders are thread-connected, so as to assemble the main body of the reinforcement. Then, according to the length of the assembled main body of the reinforcement, a number of protective components are selected. A number of first fixing screws are respectively passed through the respective T-shaped threaded through-holes of the outer rubber gaskets, the respective T-shaped threaded through-holes of the inner metal gaskets, the respective buffer damping pipe columns and the respective compression springs in the corresponding protective components and are respectively thread-connected to the respective side threaded interfaces in a corresponding group on the pressure-bearing cylinder, so that the inner ends of the respective compression springs are all pressed against the outer circumference of the pressure-bearing cylinder. Then, the corresponding fixing steel brackets are connected to the corresponding inner side connection bases inside the reinforcement cylinder by using second fixing screws, and the clamping components are assembled. Then, the internal thread female head of the upper reinforcement cylinder is thread-connected to the external thread male head of the uppermost pressure-bearing cylinder, and the external thread male head of the lower reinforcement cylinder is thread-connected to the internal thread female head of the lowermost pressure-bearing cylinder. Thus, the assembly work of each component of the anti-breakage reinforcement device is completed.

4. The method for strengthening the anti-breakage of the surface vertical well casing in the coal mining disturbed area according to claim 3, characterized in that: Step (iv) is specifically as follows: The assembled anti-breakage reinforcement device is sleeved on the outside of the casing and correspondingly moved to the position determined in step (i). The respective second fixing screws are adjusted so that the length of the second fixing screws extending out of the threaded blind holes is increased, and the inner circumferences of the respective fixing steel brackets and the outer circumference of the casing are all tightly pressed in contact. Thus, the two fixing steel brackets in each reinforcement cylinder are combined to form a complete cylindrical structure that clamps on the casing, and the two reinforcement cylinders are fixed on the casing, so as to fix the assembled anti-breakage reinforcement device at the predetermined position to be protected on the casing.

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