Coal mine drilling continuous pipe lowering anti-blocking device and method

Abstract

The present application belongs to the technical field of continuous pipe in coal mine, and relates to a coal mine drilling continuous pipe lowering anti-blocking device and method, which utilizes the anti-blocking device to lower the continuous pipe in the open hole drilling in the coal mine, and specifically comprises the following steps: selecting the corresponding specification of the anti-blocking device according to the inner diameter of the drilling and the outer diameter of the continuous pipe, and calculating the specified distance between the installation of the adjacent two anti-blocking devices; when lowering the continuous pipe into the drilling, the anti-blocking device is installed on the continuous pipe at the specified distance in sequence. The present application establishes a mathematical model for the reasonable arrangement of the anti-blocking device, controls the clearance coefficient of the anti-blocking device in combination with the inner diameter of the drilling, the outer diameter of the continuous pipe and the stress characteristics in the coal mine, and provides a method for selecting the appropriate specification of the anti-blocking device and the distance between the two anti-blocking devices, thereby avoiding the serious eccentricity caused by the excessively large distance or the structural redundancy caused by the excessively small distance.

Description

Technical Field

[0001] This invention belongs to the field of continuous tubing technology in coal mines, and relates to a device and method for preventing obstruction when lowering continuous tubing in coal mine boreholes. Background Technology

[0002] Coiled tubing technology in coal mines, as a novel technology that can effectively replace traditional drill pipes, offers advantages such as eliminating the need for individual drill pipe loading and unloading, high operational efficiency, and ease of automation and intelligentization. However, during the lowering of coiled tubing, resistance is often encountered due to factors such as rock friction and irregular borehole walls, leading to difficulties in lowering and even damage to the coiled tubing. Therefore, there is an urgent need to develop effective anti-resistance methods to improve operational safety and efficiency.

[0003] Currently, coiled tubing resistance reduction technology mainly draws on experience from surface wells in the oil industry, such as reducing frictional resistance through lubricants. However, the underground environment of coal mines has unique characteristics such as high temperature, high pressure, and soft coal seams. When traditional technologies are directly applied, they are prone to failure due to material degradation and insufficient adaptability. At the same time, the limited space underground further increases the difficulty of operation, necessitating the exploration of new resistance reduction methods tailored to coal mine conditions.

[0004] Centralizers (i.e., anti-collision devices) are tools used in oil drilling to keep tubing centered, reducing frictional resistance by minimizing contact with the wellbore. However, their application in coal mines faces multiple challenges: first, the high-temperature, high-pressure environment may affect the mechanical properties of the centralizer material; second, soft coal seams easily increase the adhesion resistance between the centralizer and the wellbore wall; and third, existing anti-collision devices do not fully consider the space limitations and rapid disassembly / reassembly requirements in coal mines. Therefore, innovative optimization of the structural design, material selection, and layout strategy of centralizers is necessary. Specifically, the shortcomings of existing centralizer technologies include: first, excessively large contact areas may increase local friction; second, the spacing arrangement lacks theoretical basis, easily leading to coiled tubing eccentricity or redundant contact; and third, complex connection structures are not conducive to rapid installation and maintenance underground. To solve these problems, it is necessary to design low-resistance anti-collision devices based on the stress characteristics of the tubing string in coal mines, improve centering accuracy by optimizing the spacing, and develop simple connection mechanisms to adapt to narrow working spaces.

[0005] In summary, developing a continuous tubing lowering anti-obstruction device and method for special conditions in coal mines requires comprehensive improvement of centralizer design, drag-reducing materials, and layout processes to overcome bottlenecks such as poor environmental adaptability and low operational efficiency, and to provide technical support for efficient and safe underground coal mine operations. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a device and method for preventing obstruction when lowering continuous tubing in coal mine boreholes, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preventing obstruction during continuous drilling in coal mines involves lowering continuous drilling into an open borehole using an obstruction prevention device, specifically including the following steps: Step 1: Select the corresponding anti-blocking device according to the inner diameter of the open hole and the outer diameter of the continuous pipe in the coal mine, and calculate the specified distance between two adjacent anti-blocking devices. Step 2: When running the continuous tube into the borehole, install anti-blocking devices at specified intervals on the continuous tube in sequence; The method for selecting the anti-blocking device in step 1 includes: Calculate the gap coefficient of the anti-blocking device :

[0008] Wherein, R1 is the inner radius of the borehole, R2 is the outer radius of the anti-blocking device, and it is controlled to be less than 80%. 90%.

[0009] =R2-D Wherein, D is the outer radius of the continuous tube, i.e. the inner radius of the anti-blocking device, and H is the difference between the inner and outer radii of the anti-blocking device; Calculate the outer and inner radii of the anti-blocking device, and then select an anti-blocking device of the corresponding specifications.

[0010] Furthermore, the method for calculating the specified distance L for installing the anti-blocking device in step 1 is as follows:

[0011] in, The calculated spacing of the anti-blocking devices. This is the continuous tube temperature correction factor. Let θ be the angle between the borehole centerline and the horizontal plane, and q be the weight per unit length. 0 represents the elastic modulus of the continuous tube material at a reference temperature of 20℃. Moment of inertia of cross section 1-K

[0012]

[0013] Wherein, K is the relative temperature coefficient. This represents the change in elastic modulus. This represents the change in temperature.

[0014] Furthermore, when running the continuous tube into the borehole, a blocking device is first installed at the end of the continuous tube, and then the blocking devices are installed sequentially at specified intervals.

[0015] On the other hand, the present invention also provides a device for preventing obstruction during the lowering of continuous tubing in coal mine drilling. The device includes a straightening ring device and a straightening structure device. The straightening ring device is used to be sleeved on the continuous tubing and includes an outer ring and an inner ring fixedly installed inside the outer ring. Both the outer ring and the inner ring are designed as separate units. The straightening structure device includes multiple support structures fixedly installed at intervals on the outer ring.

[0016] Furthermore, the support structure is made of rigid metal material, and different support structures are spaced at a certain angle to be evenly distributed on the outer ring.

[0017] Furthermore, the axial ends of the support structure are designed with slopes, which are directed toward the midpoint of the support structure.

[0018] Furthermore, the support structure features a hollow design in the middle to facilitate the flow of cement slurry and coal slag, thereby reducing weight and friction.

[0019] Furthermore, the outer ring is made of rigid metal material and is used for fixed connection with the support structure; the inner ring is made of elastic material, which generates greater friction when in contact with the continuous tube, thereby increasing the friction between the continuous tube and the straightening collar device.

[0020] Furthermore, one side of the outer ring is provided with an opening and closing shaft, so that the two parts of the split outer ring are hinged together, and a protruding ring is provided on the other side, which is connected by a connector to realize the installation of the split outer ring.

[0021] Furthermore, the outer ring is a split circular tube, and the connector is a screw and nut structure.

[0022] Furthermore, the support structure is provided in six parts, and is arranged in a centrally symmetrical manner on the outer ring.

[0023] The beneficial effects of this invention are as follows: This invention establishes a mathematical model for the rational arrangement of anti-blocking devices, and calculates the optimal installation spacing by combining the borehole inner diameter, the coiled tubing outer diameter, and downhole stress characteristics. This model, in conjunction with the anti-blocking device gap coefficient, utilizes a mathematical model... Control (80% < (<90%), providing a method for selecting appropriate anti-blocking devices to ensure the stability and centering effect of the coiled tubing downhole, and clarifying the calculation method for the specified distance L between two adjacent anti-blocking devices, avoiding severe eccentricity caused by excessive spacing or structural redundancy caused by insufficient spacing. This scientific arrangement not only reduces frictional resistance but also simplifies the construction process. For example, installing one device at the end of the coiled tubing first and then arranging them sequentially at intervals reduces the difficulty of downhole operations and improves the overall safety of the operation. Finally, by introducing the influence coefficients of downhole temperature, pressure, and formation deformation, the critical buckling load of the coiled tubing is corrected, forming a calculation model and mechanical equilibrium equations adapted to complex well conditions. This innovation provides accurate stability prediction, laying a theoretical foundation for spacing optimization and descent speed control, and preventing stuck pipe or fracture accidents caused by buckling instability.

[0024] Furthermore, the anti-obstruction device for continuous tubing lowering in coal mines provided by this invention is specifically designed for the complex environments of coal mines, such as high temperature, high pressure, and soft coal seams. By introducing an anti-obstruction device (centralizer) made of high-temperature and high-pressure resistant composite materials, the lowering efficiency and safety of the continuous tubing are significantly improved. This technology effectively solves the problem of insufficient adaptability of traditional oilfield drag reduction methods in coal mine applications, such as material performance degradation and increased operational difficulty. The core advantage lies in reducing the frictional resistance between the continuous tubing and the borehole wall, preventing jamming or damage during lowering, and facilitating rapid installation and maintenance in confined underground spaces, thereby improving the overall reliability and economy of the operation.

[0025] Secondly, the device employs high-temperature and high-pressure resistant composite materials to manufacture the anti-blocking device, and optimizes the shape and distribution of the blades (support structure) to reduce the contact area with the borehole wall. This not only improves the centering of the coiled tubing and significantly reduces frictional resistance during lowering, but also ensures the stability and durability of the anti-blocking device in harsh environments. For example, the slope and hollow design of the support structure further promote the flow of coal slurry and slag, reducing the weight of the device and additional resistance. Compared with traditional centralizers, this optimization reduces friction, greatly improving the service life and operational efficiency of the anti-blocking device. Furthermore, this invention utilizes a modular quick-installation design with a split-type centralizing collar and opening / closing shaft, facilitating rapid on-site installation and replacement, thus improving operational efficiency. In summary, this invention not only possesses significant technical advantages, such as reduced frictional resistance and increased efficiency, but also has high practical value and promising prospects for widespread application, which will drive the intelligent development of coiled tubing technology in coal mines.

[0026] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a side view of a coal mine drilling continuous pipe lowering anti-blocking device in the embodiment. Figure 2 This is a schematic diagram of the main structure of a coal mine drilling continuous pipe lowering anti-blocking device in the embodiment. Figure 3 This is an isometric view of a coal mine borehole continuous pipe lowering anti-blocking device in the embodiment; Figure 4 This is a schematic diagram illustrating the application of a coal mine borehole continuous pipe lowering anti-blockage device in the embodiment. Figure 5 This is a flowchart illustrating the process of selecting the specifications of the anti-blocking device for lowering continuous borehole pipe in coal mines in this embodiment.

[0028] Reference numerals in the attached drawings: 1. Support structure; 2. Outer ring; 3. Inner ring; 4. Connector; 5. Opening and closing shaft. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0031] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] Please see Figures 1-4 This invention presents a device and method for preventing obstruction during the lowering of continuous drilling tubing in coal mines. The device is manufactured from high-temperature and high-pressure resistant composite materials, possessing excellent wear resistance and deformation resistance, effectively adapting to the harsh environment of underground coal mines. By optimizing the shape and distribution of the blades, the device reduces the contact area with the borehole wall, thereby lowering frictional resistance. Simultaneously, its modular quick-installation design facilitates rapid on-site installation and replacement, improving operational efficiency.

[0033] Furthermore, to address the issue of uneven stress during the lowering of the continuous tube, this method proposes a mathematical model for the rational arrangement of anti-obstruction devices. By combining the orifice trajectory and the stress characteristics of the tube string, the optimal installation spacing is determined, thereby maximizing the centering effect and stability of the continuous tube.

[0034] Previous researchers have conducted extensive theoretical studies on coiled tubing buckling. This invention posits that the critical load borne by the coiled tubing during downhole operations is closely related to the critical force of the pressure rod instability, thus establishing a mechanical equilibrium equation for the coiled tubing under complex well conditions. Furthermore, by introducing influencing factors such as downhole temperature, pressure, and formation deformation, the critical load is corrected. Based on this, the lowering speed of the coiled tubing and the spacing of the anti-blocking devices are optimized to ensure that the coiled tubing remains stable throughout operations, preventing accidents such as stuck pipe and breakage caused by buckling instability.

[0035] Example 1 like Figures 1-4 As shown, the anti-obstruction device for lowering continuous pipe in coal mine drilling designed in this embodiment includes a straightening collar device and a straightening structure device; wherein the straightening collar device is used to be sleeved on the continuous pipe and is designed with inner and outer cooperation, including an outer ring 2 and an inner ring 3 fixedly installed in the outer ring 2, and the outer ring 2 and the inner ring are both designed separately to facilitate quick assembly and disassembly.

[0036] The straightening structure device includes multiple support structures 1 fixedly installed at intervals on the outer ring 2, which are made of rigid metal material; specifically, the different support structures 1 are spaced at a certain angle to ensure uniform arrangement. The support structure 1 has a certain slope at both ends along its axis, with the slope pointing towards the midpoint of the support structure 1. The support structure 1 also has a hollow design in the middle to facilitate the flow of cement slurry and coal slag, thereby reducing weight and friction.

[0037] Specifically, the outer ring 2 is made of rigid metal material and is used to fix it to the support structure 1 so as to connect the split outer ring 2 into a whole and to be sleeved on the connecting pipe by the inner ring 3; The inner ring 3 is made of a material with a certain degree of elasticity and a large frictional force when in contact with the continuous tube inside it, in order to increase the frictional force between the continuous tube and the straightening collar device.

[0038] Furthermore, one side of the outer ring 2 is provided with an opening and closing shaft 5 so that the two parts of the split outer ring 2 are hinged together, and a protruding ring 6 is provided on the other side and connected by a connector 4 to realize the installation of the split outer ring 2.

[0039] Specifically, the outer ring 2 is a split circular tube, the connector 4 is a screw and nut structure; the support structure 1 consists of six parts, which are arranged symmetrically on the outer ring 2.

[0040] When installing the anti-blocking device on the continuous pipe, first open the outer ring 2 and the inner ring 3 fixedly connected to the outer ring 2 from one end of the protruding ring 6, and then fit it radially onto the continuous pipe. Then, use the connector 4 to lock the outer ring 2 with the protruding ring 6 to install the anti-blocking device on the continuous pipe.

[0041] Example 2 like Figure 5 As shown, based on Example 1, this example provides a method for preventing obstruction when lowering continuous borehole tubing in a coal mine. Currently, there is an open-hole drill in a coal mine, and the drill is a horizontal borehole. The borehole diameter is 20cm, the inner diameter of the continuous tubing used is 42.88mm, and the wall thickness is 3.96mm. The continuous tubing is lowered into an open-hole borehole in a coal mine using an anti-blocking device. The specific steps include: Step 1: Calculate the gap coefficient of the anti-blocking device according to Formula 1. :

[0042] Wherein, R1 is the inner radius of the borehole, R2 is the outer radius of the anti-blocking device, and is controlled to be ≤ 80%. 90%.

[0043] 0.08m≤ 0.9m The outer radius of the anti-blocking device is determined to be within the range of 0.08m to 0.09m, which is equivalent to 80mm to 90mm. according to H=R2-D Wherein, D is the outer radius of the continuous tube, i.e., the inner diameter of the anti-blocking device; H is the difference between the inner and outer radii of the centralizer. The range of values ​​for the height of support structure 1 plus the thickness of the straightening collar device (outer ring 2 + inner ring 3) should be: 54.6mm≤ 64.6mm In this embodiment, an anti-blocking device with an inner radius of 50.8 mm and a height of 1 plus a straightening collar device (outer ring 2 + inner ring 3) thickness of 64 mm was selected for field use, which meets the requirements.

[0044] Step Two: After selecting the appropriate anti-blocking device specifications, calculate the spacing between the anti-blocking devices.

[0045] According to the formula

[0046] in, The calculated spacing of the anti-blocking devices. Here, q is the temperature correction factor for the continuous tube, and q is the gravity per unit length. 0 represents the elastic modulus of the continuous tube material at a reference temperature of 20℃. Moment of inertia of cross section 1-K

[0047] K is the relative temperature coefficient.

[0048] The elastic modulus is taken at a reference temperature of 20°C. This represents the change in elastic modulus. Temperature change

[0049] Where D is the outer radius of the continuous tube and d is the inner radius of the continuous tube. In practical applications, assuming the temperature inside the underground coal seam borehole is 30℃, then take... The value is 0.99. Referring to the paper "Mechanical Analysis of Coiled Tubing String in Coiled Tubing Operations," the properties of the coiled tubing material are known as follows: EI is 1.29 × 10⁻⁶. 4 Nm2 D is 25.4 mm, and q is 45.69 N / m.

[0050] Substitute into calculation L L≈10m Calculations show that one of these anti-blocking devices (centralizers) should be used every 10m.

[0051] This invention proposes an anti-obstruction device and method for running continuous tubing in coal mine boreholes, and provides specific selection methods and principles for the anti-obstruction device. The two control requirements cover complementary areas without affecting each other. The operation steps and design methods are highly relevant to the actual conditions in coal mines, making them easy to operate. The design and spacing of the anti-obstruction device fully consider practical problems, ensuring the stability and centering effect of the continuous tubing underground. This innovation not only avoids increased frictional resistance due to severe eccentricity of the continuous tubing, but also prevents structural redundancy and increased construction difficulty caused by excessively small spacing.

[0052] It should be noted that, in other embodiments, those skilled in the art can also combine the method for preventing obstruction during the lowering of continuous drilling pipe in coal mines in Embodiment 2 with the centralizer (obstruction prevention device) in the prior art for lowering continuous drilling pipe in coal mines.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of preventing a coal mine drill hole continuous pipe from being blocked during lowering, characterized in that, The process of lowering continuous tubing into an open-hole borehole in a coal mine using a barrier device includes the following steps: Step 1: Select the corresponding anti-blocking device according to the inner diameter of the open hole and the outer diameter of the continuous pipe in the coal mine, and calculate the specified distance between two adjacent anti-blocking devices. Step 2: When running the continuous tube into the borehole, install anti-blocking devices at specified intervals on the continuous tube in sequence; The method for selecting the anti-blocking device in step 1 includes: Computing a chock clearance coefficient : Wherein, R1 is the inner radius of the borehole, R2 is the outer radius of the anti-blocking device, and it is controlled to be less than 80%. 90%. =R2-D Wherein, D is the outer radius of the continuous tube, i.e. the inner radius of the anti-blocking device, and H is the difference between the inner and outer radii of the anti-blocking device; Calculate the outer and inner radii of the anti-blocking device, and then select an anti-blocking device of the corresponding specifications.

2. The method for preventing obstruction during continuous drilling in coal mines according to claim 1, characterized in that, The method for calculating the specified distance L for installing the anti-blocking device in step 1 is as follows: in, The calculated spacing of the anti-blocking devices. This is the continuous tube temperature correction factor. Let θ be the angle between the borehole centerline and the horizontal plane, and q be the weight per unit length. 0 represents the elastic modulus of the continuous tube material at a reference temperature of 20℃. Moment of inertia of cross section 1-K Wherein, K is the relative temperature coefficient. This represents the change in elastic modulus. This represents the change in temperature.

3. The method for preventing obstruction during continuous drilling in coal mines according to claim 1, characterized in that, When running the continuous tubing into the borehole, a blocking device is first installed at the end of the continuous tubing, and then the blocking devices are installed at specified intervals.

4. A device for preventing obstruction during the lowering of continuous drilling tubing in coal mines, characterized in that, The anti-blocking device is applicable to the anti-blocking device according to any one of claims 1 to 3, wherein the anti-blocking device includes a straightening collar device and a straightening structure device; the straightening collar device is used to be sleeved on the continuous pipe, including an outer ring and an inner ring fixedly installed in the outer ring, wherein the outer ring and the inner ring are both of a separate design; the straightening structure device includes a plurality of support structures fixedly installed at intervals on the outer ring.

5. The anti-blocking device according to claim 4, characterized in that, The support structure is made of rigid metal material, and different support structures are spaced at a certain angle to be evenly distributed on the outer ring.

6. The anti-blocking device according to claim 4, characterized in that, The support structure is designed with slopes at both ends along its axial direction, with the slopes pointing toward the midpoint of the support structure.

7. The anti-blocking device according to claim 4, characterized in that, The support structure features a hollow design in the middle to facilitate the flow of cement slurry and coal slag, thereby reducing weight and friction.

8. The anti-blocking device according to claim 4, characterized in that, The outer ring is made of rigid metal material and is used for fixed connection with the support structure; the inner ring is made of elastic material, which generates a large frictional force when in contact with the continuous tube, thereby increasing the frictional force between the continuous tube and the straightening collar device.

9. The anti-blocking device according to claim 7, characterized in that, The outer ring has an opening and closing shaft on one side, which allows the two parts of the split outer ring to be hinged together, and a protruding ring on the other side, which is connected by a connector to realize the installation of the split outer ring.

10. The anti-blocking device according to claim 9, characterized in that, The outer ring is a split circular tube, and the connector is a screw and nut structure.

11. The anti-blocking device according to claim 9, characterized in that, The support structure consists of six parts, which are arranged symmetrically on the outer ring.

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