Well-through device and construction method thereof

Abstract

This invention belongs to the field of oil and gas extraction technology and discloses a well-clearing device and its construction method. The well-clearing device includes: a milling column, comprising a cutting shaft section and a helical spline shaft section. The outer circumferential surface of the cutting shaft section is provided with multiple centralizing bands distributed along a helical line. Each centralizing band has a first cutting element and a second cutting element at the chamfered ends at opposite ends along the axial direction of the milling column. The first cutting element is used for forward reaming when the well-clearing device is lowered into the well, and the second cutting element is used for reverse reaming when the well-clearing device is raised into the well; a helical spline sleeve, drivenly connected to the outer circumference of the helical spline shaft section and coaxially arranged with the milling column; and a pushing element, connected to the end of the helical spline sleeve axially away from the cutting shaft section. The pushing element can push the helical spline sleeve axially towards the end closer to the cutting shaft section, thereby driving the milling column to rotate downwards. This invention can optimize the well-clearing reaming construction process and improve the efficiency of reaming construction.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a well cleaning device and its construction method. Background Technology

[0002] In the field of oil and gas extraction technology, for gas fields with low pressure and ultra-low permeability, open-hole horizontal wells offer a greater advantage in selective staged fracturing under specific geological conditions, due to limitations such as wellbore trajectory curvature and wellbore size. Currently, the mainstream technology for open-hole horizontal wells utilizes tubing as the completion and fracturing string, running it in a single operation across long horizontal open-hole sections without the need for casing cementing or perforation operations, thus achieving selective staged fracturing of the horizontal section.

[0003] In open-hole fracturing, well cleaning is a fundamental step to ensure the smooth deployment of open-hole fracturing tools, and these tools are the core equipment. Well cleaning processes are mainly divided into two types based on their function: single-end milling and double-end milling, simulating rigid well cleaning with open-hole fracturing tools. Ultimately, different well cleaning techniques are achieved using the right tools. However, in actual well cleaning operations, problems such as mudstone necking, sand bed accumulation, or sand bridge blockage often arise during drilling. To address this, a strategy of "first, clean the well; second, flush; third, reaming" is typically employed repeatedly to resolve the obstruction. The reaming operation often requires rotating the tool using a jib or top drive to achieve well cleaning. This method is not only complex and inefficient but also increases the risk of tool sticking at the bottom of the well, further increasing the complexity and time cost of the operation.

[0004] Therefore, there is an urgent need to propose a well-drainage device and its construction method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a well-clearing device and its construction method, which can optimize the well-clearing and reaming construction process and improve the efficiency of reaming construction.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a well-drainage device, comprising:

[0008] The milling column includes a cutting shaft section and a helical spline shaft section. The outer circumferential surface of the cutting shaft section is provided with multiple straightening bands distributed along a helical line. Each straightening band is provided with a first cutting element and a second cutting element at the chamfers at opposite ends along the axial direction of the milling column. The first cutting element is used to perform forward reaming when the well cleaning device is lowered into the well, and the second cutting element is used to perform reverse reaming when the well cleaning device is raised into the well.

[0009] A spiral spline sleeve is connected to the outer circumference of the spiral spline shaft section and is coaxially arranged with the milling column;

[0010] A pusher is connected to one end of the spiral spline sleeve away from the cutting shaft section along the axial direction. The pusher can push the spiral spline sleeve to move along the axial direction towards the end closer to the cutting shaft section, thereby driving the milling column to rotate downward.

[0011] In some embodiments, each of the straightening belts is provided with a third cutting element on its radial outer surface, the third cutting element being used to trim the window at the opening point.

[0012] In some embodiments, the well-drainage device further includes a connecting shaft, a first sealing joint, and an elastic element. The first sealing joint is connected between the spiral spline sleeve and the pusher. The connecting shaft is disposed in the inner hole of the first sealing joint and is connected between the spiral spline shaft segment and the inner wall of the pusher. The elastic element is fitted onto the outer periphery of the connecting shaft. One end of the elastic element is connected to or abuts against the connecting shaft, and the other end of the elastic element is connected to or abuts against the first sealing joint. The pusher can drive the first sealing joint and the spiral spline sleeve to move synchronously. The movement of the first sealing joint can compress the elastic element. When the pusher stops pushing, the elastic element can return from the compressed state to the initial state after the drill string is lifted.

[0013] In some embodiments, the well-drainage device further includes a second sealing joint, which is fitted around the outer periphery of the helical spline shaft segment and is connected to one end of the helical spline sleeve along the axial direction near the cutting shaft segment via a self-sealing thread. The second sealing joint and the helical spline sleeve are always able to cover the spline block of the helical spline shaft segment.

[0014] In some embodiments, the first sealing joint has a first oil injection hole, and the second sealing joint has a second oil injection hole, wherein the first oil injection hole or the second oil injection hole is used for injecting lubricating oil.

[0015] In some embodiments, a floating piston is movably fitted between the outer peripheral wall of the connecting shaft and the inner bore wall of the first sealing joint. The floating piston is capable of reciprocating along the axial direction. A first sealing element is embedded in the inner bore wall of the floating piston, which abuts against the outer peripheral wall of the connecting shaft. A second sealing element is embedded in the outer peripheral wall of the floating piston, which abuts against the inner bore wall of the first sealing joint. The floating piston is configured to always be located between the first oil injection hole and the pusher along the axial direction.

[0016] In some embodiments, the inner wall of the second sealing joint is fitted with a mudguard ring and a third seal. When the second sealing joint is fitted onto the outer periphery of the spiral spline shaft section, the mudguard ring and the third seal can abut against the outer peripheral wall of the smooth shaft section of the spiral spline shaft section. Along the axial direction, the third seal is located between the mudguard ring and the second oil injection hole, and both the mudguard ring and the third seal are located on the side of the second oil injection hole closer to the cutting shaft section.

[0017] In some embodiments, the inner wall of the second sealing joint is further fitted with a copper tile, and when the second sealing joint is fitted onto the outer periphery of the spiral spline shaft section, the copper tile can abut against the outer peripheral wall of the optical axis section of the spiral spline shaft section.

[0018] In some embodiments, the elastic element is a disc spring assembly.

[0019] Secondly, the present invention provides a method for constructing a well-clearing device, using the well-clearing device described in the first aspect, the method comprising the following steps:

[0020] Drill strings are connected at opposite ends of the wellbore duct to form a tubular structure;

[0021] The tubular structure was lowered into the well.

[0022] If obstruction is encountered during the lowering process, a pushing force is applied to the pusher, causing the pusher to move the spiral spline sleeve axially, which in turn drives the milling column to rotate and descend, so that the first cutting part can perform positive reaming until there is no obstruction in the well.

[0023] Remove the tubing string structure, inspect and measure the outer diameter of the well cleaning device. If the outer diameter is smaller than the original size, replace the well cleaning device and perform well cleaning again.

[0024] The beneficial effects of this invention are:

[0025] The well-clearing device provided by this invention features a multi-head helical spline structure including a helical spline sleeve and a helical spline shaft section, and a first cutting element at the chamfer of the centralizing band. This allows the device to achieve forward reaming simply by applying axial force to the pushing component when encountering resistance during drilling. This well-clearing device requires no additional rotational power input, has a simple structure, is easy to operate, optimizes the well-clearing reaming process, and improves reaming efficiency. Furthermore, the well-clearing device also includes a second cutting element, which enables reverse reaming when the device is lifted, allowing for smooth withdrawal in case of unexpected situations, thereby reducing equipment wear and economic losses.

[0026] The construction method of the well-clearing device provided by the present invention can effectively solve the problem of difficulty in well-clearing and lowering caused by mudstone necking, sand bridges or sand beds. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the well-drainage device provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the transmission structure of the spiral spline shaft segment and the spiral spline sleeve provided in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the unfolded structure of the helical spline shaft segment provided in an embodiment of the present invention.

[0031] In the picture:

[0032] 1. Milling column; 11. Cutting shaft section; 12. Spiral spline shaft section; 13. Straightening belt; 14. First cutting part; 15. Second cutting part; 16. Third cutting part;

[0033] 2. Spiral spline sleeve;

[0034] 3. Pushing component;

[0035] 4. Connecting shaft;

[0036] 5. First sealing joint; 51. First oil injection hole;

[0037] 6. Elastic components;

[0038] 7. Second sealing joint; 71. Second oil injection hole; 72. Mudguard ring; 73. Third sealing element; 74. Copper bearing;

[0039] 8. Floating piston; 81. First seal; 82. Second seal. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0043] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for 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, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0047] like Figures 1-3 As shown, this embodiment provides a well-drainage device, including a milling column 1, a spiral spline sleeve 2, and a pusher 3.

[0048] The milling column 1 includes a cutting shaft section 11 and a helical spline shaft section 12. The outer circumferential surface of the cutting shaft section 11 is provided with multiple centering bands 13 distributed along a helical line. At the chamfered ends of each centering band 13 along the axial direction of the milling column 1, a first cutting element 14 and a second cutting element 15 are provided. The first cutting element 14 is used for forward reaming during drilling with the well cleaning device, and the second cutting element 15 is used for reverse reaming during lifting of the well cleaning device. A helical spline sleeve 2 is driven and connected to the outer circumference of the helical spline shaft section 12 and is coaxially arranged with the milling column 1. A pusher 3 is connected to the end of the helical spline sleeve 2 axially away from the cutting shaft section 11. The pusher 3 can push the helical spline sleeve 2 axially towards the end closer to the cutting shaft section 11, thereby driving the milling column 1 to rotate downwards. The pusher 3 is also coaxially arranged with the milling column 1 and the helical spline sleeve 2, meaning that all components in the well cleaning device share the same central axis.

[0049] In practice, when the well-drilling device encounters obstruction during drilling, only a pushing force needs to be applied to the pusher 3, causing the pusher 3 to push the spiral spline sleeve 2 axially towards one end of the cutting shaft section 11. As the spiral spline sleeve 2 moves axially, due to the transmission between the spiral spline sleeve 2 and the spiral spline shaft section 12, the axial movement of the spiral spline sleeve 2 can be converted into the rotational motion of the spiral spline shaft section 12, thereby causing the milling column 1 to rotate downwards as a whole. During the downward rotation, the first cutting element 14 on the milling column 1 performs forward reaming on the well wall. If obstruction or unexpected formation collapse occurs during the well-drilling process, preventing the well-drilling device from continuing downwards, the top drive equipment can be activated to lift the well-drilling device. During lifting, the second cutting element 15 performs reverse reaming to ensure the well-drilling device can be smoothly withdrawn, reducing economic losses.

[0050] Specifically, such as Figure 2 As shown, the number of spline blocks in the spiral spline shaft segment 12 is 6, but it is not limited to this. The number can be set according to the actual situation.

[0051] The well-clearing device provided in this embodiment features a multi-head helical spline structure including a helical spline sleeve 2 and a helical spline shaft section 12. A first cutting element 14 is provided at the chamfer of the centralizing band. This allows the device to achieve forward reaming simply by applying axial force to the pushing element 3 when encountering resistance during drilling. This well-clearing device requires no additional rotational power input, has a simple structure, is easy to operate, optimizes the well-clearing reaming process, and improves reaming efficiency. Furthermore, the well-clearing device is also equipped with a second cutting element 15, which enables reverse reaming when the device is lifted, allowing the device to be smoothly withdrawn in case of unexpected situations, thereby reducing equipment wear and economic losses.

[0052] Specifically, the well-clearing device provided in this embodiment can improve the efficiency of on-site well-clearing and reaming operations by more than 1 to 2 times, effectively shorten the reaming operation cycle by 1 to 2 days, save 50,000 to 100,000 yuan per well, and complete approximately 50 open-hole segmented fracturing wells annually. The market size is expected to reach 7.5 million to 15 million yuan in the next 3 years.

[0053] Optionally, the first cutting element 14 and the second cutting element 15 are configured as PDC composite sheets. PDC composite sheets are composite materials composed of artificial polycrystalline diamond and a hard substrate (usually tungsten alloy), which have high hardness, high wear resistance and impact resistance.

[0054] Optionally, the first cutting element 14 and the second cutting element 15 can be soldered to the straightening belt 13 by silver soldering.

[0055] like Figure 1 As shown, in some embodiments, a third cutting element 16 is provided on the radial outer surface of each straightening band 13. The third cutting element 16 is used to trim the window at the opening point. This arrangement enriches the functionality of the well-drainage device, enabling it to perform window trimming after casing window opening.

[0056] Optionally, the third cutting component 16 is set to YD cutting alloy, where YD refers to a high-performance cemented carbide material, usually a tungsten-cobalt alloy, which has good cutting performance.

[0057] Optionally, the third cutting element 16 can be brazed to the surface of the straightening belt 13.

[0058] like Figure 1 As shown, in this embodiment of the well-drainage device, two sets of centralizing belt assemblies are axially spaced on the outer circumferential surface of the cutting shaft section 11. Each set of centralizing belt assemblies includes multiple centralizing belts 13 distributed along a spiral line, and each centralizing belt 13 is provided with a first cutting element 14, a second cutting element 15, and a third cutting element 16. Of course, in other embodiments, three or four sets of centralizing belt assemblies can also be provided, depending on the actual situation.

[0059] like Figure 1 As shown, in some embodiments, the well-drainage device further includes a connecting shaft 4, a first sealing joint 5, and an elastic element 6. The first sealing joint 5 is connected between the spiral spline sleeve 2 and the pusher 3. The connecting shaft 4 is disposed in the inner hole of the first sealing joint 5 and is connected between the spiral spline shaft section 12 and the inner wall of the pusher 3. The elastic element 6 is fitted onto the outer periphery of the connecting shaft 4, with one end connected to or abutting against the connecting shaft 4 and the other end connected to or abutting against the first sealing joint 5. The pusher 3 can drive the first sealing joint 5 and the spiral spline sleeve 2 to move synchronously. The movement of the first sealing joint 5 can compress the elastic element 6. When the pusher 3 stops pushing, the elastic element 6 can return from the compressed state to its initial state after the drill string is lifted.

[0060] With this configuration, when force is applied to the pusher 3, the elastic element 6 is compressed to store elastic potential energy. When the pushing force applied to the pusher 3 is removed, the stored elastic potential energy is released, and the elastic element 6 automatically resets after the drill bit is lifted, thus driving the milling column 1 to reset as well. In this way, there is no need to apply a special force to restore the milling column 1 to its original position, making the operation simpler and faster.

[0061] For example, the first sealing joint 5 and the spiral spline sleeve 2, and the first sealing joint 5 and the pusher 3 can be connected by a self-sealing thread. The connecting shaft 4 can be threaded to the spiral spline shaft section 12, and further, an O-ring seal can be provided between the connecting shaft 4 and the spiral spline shaft section 12.

[0062] During the specific assembly, first, the elastic element 6 is fitted onto the connecting shaft 4, then the connecting shaft 4 and the elastic element 6 are fitted together into the inner hole of the first sealing joint 5, and then the two ends of the first sealing joint 5 are connected and fixed.

[0063] Optionally, the elastic element 6 is a disc spring assembly. The disc spring assembly is composed of multiple stacked disc springs. By combining different numbers and arrangements of disc springs, a larger elastic deformation range and a higher elastic potential energy storage capacity can be achieved. Compared with ordinary compression springs, it is more suitable for providing a larger force in a limited space.

[0064] like Figure 1 As shown, in some embodiments, the well-drainage device further includes a second sealing joint 7, which is fitted around the outer periphery of the helical spline shaft section 12 and is connected to the end of the helical spline sleeve 2 axially close to the cutting shaft section 11 via a self-sealing thread. The second sealing joint 7 and the helical spline sleeve 2 are always able to cover the spline block of the helical spline shaft section 12.

[0065] By setting the second sealing joint 7, it can be ensured that the spline block of the spiral spline shaft section 12 is never exposed to the formation, thereby protecting the spiral spline structure. This is beneficial to ensuring smooth transmission between the spiral spline shaft section 12 and the spiral spline sleeve 2, and also helps to extend the service life of the well cleaning device.

[0066] like Figure 1 As shown, in some embodiments, the first sealing joint 5 has a first oil injection hole 51, and the second sealing joint 7 has a second oil injection hole 71. The first oil injection hole 51 or the second oil injection hole 71 is used to inject lubricating oil. That is, the device can be filled with lubricating oil through one of the first oil injection hole 51 or the second oil injection hole 71 to lubricate the mating movement between the helical spline shaft section 12 and the helical spline sleeve 2.

[0067] Furthermore, after the lubricating oil is injected, the plugs can be tightened into the first oil injection hole 51 and the second oil injection hole 71 to seal them.

[0068] like Figure 1 As shown, in some embodiments, a floating piston 8 is movably fitted between the outer peripheral wall of the connecting shaft 4 and the inner bore wall of the first sealing joint 5. The floating piston 8 is capable of reciprocating along the axial direction. A first sealing element 81 is embedded in the inner bore wall of the floating piston 8, and the first sealing element 81 can abut against the outer peripheral wall of the connecting shaft 4. A second sealing element 82 is embedded in the outer peripheral wall of the floating piston 8, and the second sealing element 82 can abut against the inner bore wall of the first sealing joint 5. The floating piston 8 is configured to always be located between the first oil injection hole 51 and the pusher 3 along the axial direction.

[0069] With this configuration, firstly, the floating piston 8 and its first and second seals 81 and 82 can provide a sealing effect, which helps prevent the leakage of lubricating oil inside the device and prevents drilling fluid from entering the device and contaminating the lubricating oil during drilling, thus improving the service life of the elastic element 6. Secondly, when the force applied to the pusher 3 is inconsistent, the floating piston 8 can move back and forth to regulate and balance the pressure.

[0070] Optionally, both the first seal 81 and the second seal 82 can be configured as Y / O combination seals. A Y / O combination seal is a sealing structure that combines the features of a Y-ring and an O-ring, and this combination seal structure can enhance sealing performance under complex working conditions.

[0071] like Figure 1As shown, in some embodiments, the inner wall of the second sealing joint 7 is fitted with a mudguard ring 72 and a third seal 73. When the second sealing joint 7 is fitted onto the outer periphery of the spiral spline shaft section 12, the mudguard ring 72 and the third seal 73 can abut against the outer peripheral wall of the smooth shaft section of the spiral spline shaft section 12. Along the axial direction, the third seal 73 is located between the mudguard ring 72 and the second oil injection hole 71, and both the mudguard ring 72 and the third seal 73 are located on the side of the second oil injection hole 71 closer to the cutting shaft section 11. The smooth shaft section of the spiral spline shaft section 12 refers to the area without spline blocks.

[0072] This configuration further improves the sealing performance of the well-drainage device by using the mud ring 72 and the third seal 73, effectively preventing mud, drilling fluid, and other contaminants from entering the device from one side of the second sealing joint 7, which helps to extend the service life of the device.

[0073] Optionally, the third seal 73 can be configured as a Y / O combination seal.

[0074] like Figure 1 As shown, in some embodiments, the inner wall of the second sealing joint 7 is further fitted with a copper tile 74. When the second sealing joint 7 is fitted onto the outer periphery of the spiral spline shaft section 12, the copper tile 74 can abut against the outer peripheral wall of the smooth shaft section of the spiral spline shaft section 12. The copper tile 74 mainly serves to straighten the shaft and can effectively prevent wear between the spiral spline shaft section 12 and the second sealing joint 7.

[0075] Optionally, the copper tile 74 has a split structure, which can be disassembled and installed into the mounting groove of the second sealing joint 7.

[0076] During the specific assembly, first install the mudguard ring 72, the third seal 73 and the copper tile 74 into the corresponding mounting groove of the second sealing joint 7, and then fit them together onto the outer periphery of the spiral spline shaft section 12.

[0077] Correspondingly, this embodiment also provides a construction method for a well-clearing device. Using the aforementioned well-clearing device, the construction method includes the following steps:

[0078] S1. Connect drill strings at opposite ends of the well-drilling device to form a tubular structure;

[0079] S2. Lower the tubular structure into the well;

[0080] S3. If obstruction is encountered during the lowering process, a pushing force is applied to the pusher 3, causing the pusher 3 to push the spiral spline sleeve 2 to move axially, thereby driving the milling column 1 to rotate downwards, so that the first cutting part 14 can perform positive reaming until there is no obstruction in the well.

[0081] S4. Remove the tubing string structure, check and measure the outer diameter of the well cleaning device. If the outer diameter is smaller than the original size, replace the well cleaning device and clean the well again.

[0082] Specifically, in step S1, the milling column 1 and the pusher 3 at both ends of the well-drilling device are respectively machined with oil drill pipe threads, which, while connecting to the tools or drill strings at both ends, also serve to seal, resist pressure and tension, and transmit torque. For example, the formed pipe string structure can be: roller cone bit + slope drill pipe + well-drilling device + slope drill pipe + slope weighted drill pipe + slope drill pipe, wherein the roller cone bit and slope drill pipe are connected to the milling column 1, and the slope drill pipe + slope weighted drill pipe + slope drill pipe are connected to the pusher 3.

[0083] When executing step S2, when lowering the tubing string into the well, the well cleaning device should be lowered and lowered once to the opening point. If no sticking is detected, continue drilling. During open-hole drilling without sticking, the drilling speed should be 40-50 seconds per tube, maintaining a smooth and uniform speed to prevent formation leakage. Special attention should be paid to sections with high dogleg curvature. The drilling speed should be appropriately slowed, and close monitoring of load changes is crucial. "Dogleg curvature" is a quantitative indicator of the degree of curvature in the wellbore trajectory, used to describe the curvature of a section. Excessive curvature (high dogleg curvature) in a section of the wellbore can cause resistance to the drilling equipment and even the risk of stuck pipe. Therefore, special attention must be paid to operating speed and load changes in such cases. If there is a change in diameter, the passage through the change-diameter section should be slowed down; excessive pressure that could cause stuck pipe is strictly prohibited.

[0084] If obstruction is encountered during drilling, proceed to step S3 to perform forward reaming as the wellbore cleaning equipment descends. Alternatively, in sections with high resistance, the drill string can be repeatedly pulled up and down, performing forward and reverse reaming repeatedly until smooth flow is achieved. Specific procedures will depend on the actual obstruction encountered.

[0085] If repeated pulling of the drill string is used to ream the hole, drilling fluid must be circulated simultaneously. When encountering resistance in the open hole section, the load should be controlled below 8t. After successfully moving the tubing string up and down, pull it at least once more in the obstructed section until there is no sticking, ensuring a smooth wellbore. After drilling to the bottom of the well, first sweep the wellbore with thick slurry, then circulate the original drilling fluid. First, scaffold through with a small displacement, then gradually increase to the normal displacement (circulating drilling fluid should be sieved) until the inlet and outlet drilling fluid properties are consistent (controlling the drilling fluid to have good rheological properties), and record the scaffolding pressure, circulation pump pressure, and displacement. If drilling to the bottom of the well is successful after the short pull, proceed to the next step, S4.

[0086] In step S4, the outer diameter of the well-cleaning device is checked and measured. If the outer diameter is smaller than the original size, it indicates that the well-cleaning device has been worn or damaged during the well-cleaning process. This may mean that there are still minor obstructions or irregularities in some areas of the wellbore, making it impossible to ensure the integrity of the wellbore or the designed diameter. Therefore, a new well-cleaning device needs to be replaced and the well-cleaning process repeated to further ensure the smoothness and unobstructedness of the wellbore and the effectiveness of the well-cleaning process.

[0087] In addition, after the tubing string structure is pulled out, grouting is required in a timely manner. Grouting refers to cleaning the wellbore, removing impurities, protecting the well wall, and ensuring the stability of the construction environment for subsequent fracturing and other operations by injecting drilling fluid or other slurry materials (such as thick slurry).

[0088] The construction method of the well-clearing device provided in this embodiment can effectively solve the problem of difficulty in lowering the well due to mudstone necking, sand bridge or sand bed.

[0089] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A well-clearing device, characterized in that, include: The milling column (1) includes a cutting shaft section (11) and a spiral spline shaft section (12). The outer circumferential surface of the cutting shaft section (11) is provided with a plurality of straightening bands (13) distributed along a spiral line. Each straightening band (13) is provided with a first cutting element (14) and a second cutting element (15) at the chamfers at opposite ends along the axial direction of the milling column (1). The first cutting element (14) is used to perform forward reaming when the well cleaning device is lowered into the well, and the second cutting element (15) is used to perform reverse reaming when the well cleaning device is lifted out of the well. The spiral spline sleeve (2) is connected to the outer periphery of the spiral spline shaft section (12) and is coaxially arranged with the milling column (1); A pusher (3) is connected to one end of the spiral spline sleeve (2) away from the cutting shaft section (11) along the axial direction. The pusher (3) can push the spiral spline sleeve (2) to move along the axial direction toward one end closer to the cutting shaft section (11) so as to drive the milling column (1) to rotate downward.

2. The well-drainage device according to claim 1, characterized in that, Each of the straightening belts (13) is provided with a third cutting element (16) on its radial outer surface, the third cutting element (16) being used to trim the window at the opening point.

3. The well-drainage device according to claim 2, characterized in that, The well-drilling device further includes a connecting shaft (4), a first sealing joint (5), and an elastic element (6). The first sealing joint (5) is connected between the spiral spline sleeve (2) and the pusher (3). The connecting shaft (4) is disposed in the inner hole of the first sealing joint (5) and is connected between the spiral spline shaft section (12) and the inner wall of the pusher (3). The elastic element (6) is fitted on the outer periphery of the connecting shaft (4). One end of the elastic element (6) is connected to or abuts against the connecting shaft (4), and the other end of the elastic element (6) is connected to or abuts against the first sealing joint (5). The pusher (3) can drive the first sealing joint (5) and the spiral spline sleeve (2) to move synchronously. The movement of the first sealing joint (5) can compress the elastic element (6). When the pusher (3) stops pushing, the elastic element (6) can be reset from the compressed state to the initial state after the drill string is lifted.

4. The well-drainage device according to claim 3, characterized in that, The well-drainage device also includes a second sealing joint (7), which is fitted around the outer periphery of the spiral spline shaft section (12) and is connected to the spiral spline sleeve (2) along the axial direction near the cutting shaft section (11) by a self-sealing thread. The second sealing joint (7) and the spiral spline sleeve (2) are always able to cover the spline block of the spiral spline shaft section (12).

5. The well-drainage device according to claim 4, characterized in that, The first sealing joint (5) has a first oil injection hole (51), and the second sealing joint (7) has a second oil injection hole (71). The first oil injection hole (51) or the second oil injection hole (71) is used for injecting lubricating oil.

6. The well-drainage device according to claim 5, characterized in that, A floating piston (8) is movably fitted between the outer peripheral wall of the connecting shaft (4) and the inner wall of the first sealing joint (5). The floating piston (8) is capable of reciprocating along the axial direction. A first sealing element (81) is embedded in the inner wall of the floating piston (8). The first sealing element (81) can abut against the outer peripheral wall of the connecting shaft (4). A second sealing element (82) is embedded in the outer peripheral wall of the floating piston (8). The second sealing element (82) can abut against the inner wall of the first sealing joint (5). The floating piston (8) is configured to always be located between the first oil injection hole (51) and the pusher (3) along the axial direction.

7. The well-drainage device according to claim 5, characterized in that, The inner wall of the second sealing joint (7) is fitted with a mudguard ring (72) and a third sealing element (73). When the second sealing joint (7) is fitted onto the outer periphery of the spiral spline shaft section (12), the mudguard ring (72) and the third sealing element (73) can abut against the outer peripheral wall of the smooth shaft section of the spiral spline shaft section (12). Along the axial direction, the third sealing element (73) is located between the mudguard ring (72) and the second oil injection hole (71), and both the mudguard ring (72) and the third sealing element (73) are located on the side of the second oil injection hole (71) closer to the cutting shaft section (11).

8. The well-drainage device according to claim 7, characterized in that, The inner wall of the second sealing joint (7) is also fitted with a copper tile (74). When the second sealing joint (7) is fitted onto the outer periphery of the spiral spline shaft section (12), the copper tile (74) can abut against the outer periphery wall of the optical axis section of the spiral spline shaft section (12).

9. The well-drainage device according to claim 3, characterized in that, The elastic element (6) is a disc spring assembly.

10. A method for constructing a well-clearing device, using the well-clearing device as described in any one of claims 2 to 9, characterized in that, The construction method of the well-clearing device includes the following steps: Drill strings are connected at opposite ends of the wellbore duct to form a tubular structure; The tubular structure was lowered into the well. If obstruction is encountered during the descent, a pushing force is applied to the pusher (3) to push the spiral spline sleeve (2) to move axially, thereby driving the milling column (1) to rotate downward so that the first cutting part (14) can perform positive reaming until there is no obstruction in the well. Remove the tubing string structure, inspect and measure the outer diameter of the well cleaning device. If the outer diameter is smaller than the original size, replace the well cleaning device and perform well cleaning again.

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