Multi-variable-diameter reaming-while-drilling tool

Abstract

According to the variable-diameter reaming-while-drilling tool, in the tool, a drill collar comprises a main body with a hollow channel for guiding in fluid, the side wall of the main body is provided with a sinking groove recessed towards the hollow channel, and the bottom of the sinking groove is provided with a through hole communicated with the hollow channel; the first-stage cutting block is movably connected with the sinking groove in the direction perpendicular to the hollow channel and comprises a pair of cutting bodies close to or away from each other, and each cutting body comprises a block body with at least one part movably contained in the through hole. The block body comprises a plurality of side inner cavities extending in the direction perpendicular to the hollow channel and a first cutting surface arranged on the outer surface, away from the hollow channel, of the block body. A secondary cutting tooth movably connected to the side inner cavity, the secondary cutting tooth including a second cutting surface on an outer surface remote from the hollow channel; the throttling guide rail piston cylinder is arranged in the hollow channel so as to guide in fluid, and the throttling guide rail piston cylinder covers the through hole. According to the tool, the extension length of the cutting teeth is controlled through the displacement, and the purpose of variable-diameter broaching is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling hole enlargement, and particularly to a variable-diameter hole enlargement tool while drilling. Background Art

[0002] Existing hole enlargement tools while drilling are generally divided into two types for hard formations and loose formations. The hole enlargement tool for hard formations is designed to have fixed and non-retractable cutting teeth to deal with hard formations. The enlarged hole diameter is single. Since the cutting teeth are fixed, to prevent sticking of the drill string, the cutting angle of the cutting teeth is usually relatively smooth, resulting in weak cutting ability and low hole enlargement efficiency. The hole enlargement tool for loose formations is usually designed with retractable cutting teeth, and the enlarged hole diameter can be variable. It is opened by the method of ball plugging and pressure building, and different-sized steel balls are respectively inserted to achieve the retraction and extension of the cutting teeth, and the retraction and extension actions cannot occur repeatedly. In case of sticking of the drill string during the hole enlargement process, only the cutting teeth can be retracted to end the hole enlargement operation in advance. Moreover, the cutting teeth are designed as blade type, with low strength of the cutting tooth support structure and low hole enlargement efficiency. When conducting hole enlargement operation with a large hole diameter and encountering geological interlayers, it is easy to be damaged and accidents such as cutting teeth falling into the bottom of the well are likely to occur. The safety, functionality and application range of the current hole enlargement tools while drilling are difficult to meet the technical requirements of drilling variable-diameter hole enlargement at the present stage.

[0003] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] The object of the present invention is to provide a variable-diameter hole enlargement tool while drilling, which controls the extension length of the cutting teeth by the size of the displacement, avoids sticking of the cutting teeth of the hole enlargement tool caused by changes in formation hardness, can achieve the purpose of long-section variable-diameter hole enlargement in complex formations, and has an anti-sticking design. For the hole enlargement tool while drilling with segmented hole enlargement and different hole diameters, it can achieve the purpose of hole enlargement with different hole diameters in one trip. The strength of the cutting tooth support design meets the technical requirements of hole enlargement in hard and soft formations, improves the problem of low hole enlargement efficiency, and the wellbore after the hole enlargement operation is relatively smooth, avoiding the reaming repair operation required for micro-steps. By controlling the retraction and extension states of multiple-stage cutting teeth through the displacement multiple times, the situation of ending the hole enlargement operation in advance due to sticking of the drill string is effectively avoided, and the segmented hole enlargement and different-hole-diameter hole enlargement operations are completed in one trip.

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

[0006] A variable-diameter hole enlargement tool while drilling of the present invention includes:

[0007] A drill collar, which includes a main body having a hollow channel for introducing fluid. A sink is provided on the side wall of the main body and recessed towards the hollow channel, and a through hole communicating with the hollow channel is provided at the bottom of the sink;

[0008] The first-stage cutting block is movably connected to the sinking groove in a direction perpendicular to the hollow channel. The first-stage cutting block includes a pair of cutting bodies that approach or move away from each other. The cutting body includes a block body that is at least partially movably received in the through hole. The block body includes a plurality of side inner cavities extending in a direction perpendicular to the hollow channel and a first cutting surface provided on the outer surface of the block body away from the hollow channel.

[0009] At least a pair of limiting screw sleeves, which are threadedly connected to the side inner cavities.

[0010] At least a pair of second-stage cutting teeth, which are movably connected to the side inner cavities. The second-stage cutting teeth include a second cutting surface on the outer surface away from the hollow channel.

[0011] At least a pair of cutting tooth springs, which are arranged in the space formed by the limiting screw sleeves and the second-stage cutting teeth to elastically connect the second-stage cutting teeth.

[0012] The throttling guide piston cylinder is arranged in the hollow channel to introduce fluid. The throttling guide piston cylinder covers the through hole.

[0013] The main spring has its top end connected to the bottom end of the throttling guide piston cylinder.

[0014] The spring base is hermetically connected to the bottom of the drill collar at its bottom end, and the spring base supports the main spring.

[0015] In the described variable-diameter hole enlarging tool while drilling, when the fluid passes through a flow rate greater than a predetermined flow rate, the throttling guide piston cylinder moves downward and extrudes the throttling guide piston cylinder to cause the first-stage cutting block to protrude outward. When the fluid passes through a flow rate less than the predetermined flow rate, the elastic force of the main spring causes the throttling guide piston cylinder to move upward.

[0016] In the described variable-diameter hole enlarging tool while drilling, the predetermined flow rate is 20 - 25 L / S.

[0017] In the described variable-diameter hole enlarging tool while drilling, a step is formed at the connection between the through hole and the sinking groove.

[0018] In the described variable-diameter hole enlarging tool while drilling, supporting portions extend out from both ends of the block body, and the supporting portions are movably arranged in the sinking groove in cooperation with the step.

[0019] In the described variable-diameter hole enlarging tool while drilling, a guiding portion protruding from the side wall of the drill collar is provided at the periphery of the sinking groove.

[0020] In the described variable-diameter hole enlarging tool while drilling, the guiding portion has an arc-shaped outer surface.

[0021] In the described variable-diameter hole enlarging tool while drilling, the second outer surface is farther away from the hollow channel than the first outer surface.

[0022] In the described variable-diameter hole reaming tool while drilling, a stepped boss is provided at the bottom end of the throttle guide piston barrel, and the top end of the main spring is sleeved on the stepped boss.

[0023] In the described variable-diameter hole reaming tool while drilling, the central axes of the drill collar and the throttle guide piston barrel are collinear.

[0024] In the above technical solution, the variable-diameter hole reaming tool provided by the present invention has the following beneficial effects: The variable-diameter hole reaming tool realizes the function of hole reaming while drilling through multiple controls of the displacement of the drilling pump for multiple levels and the expansion and contraction of the cutting teeth. The large-size cutting block has high torsional strength and is used as the main force to initially ream the wellbore. The small-size cutting teeth are used to subsequently correct the wellbore to keep it smooth. The design of the cutting block and multiple cutting teeth can achieve the purpose of reaming by segmentally grinding hard and soft formations, and can effectively solve the problems of block falling caused by the instability of the wellbore after reaming by a single cutting method, which in turn induces sticking of the drill string and breakage of the cutting teeth, and greatly improves the downhole safety and reaming quality of the hole reaming operation while drilling. It can realize multiple hole reaming operations during the drilling process. The reaming diameter is controlled according to the displacement, and the reaming diameter range is large and the structural design strength of the cutting teeth is high, avoiding the breakage and falling of the cutting teeth caused by the change of formation hardness during the reaming process. It has a function of releasing stuck drill strings caused by damage and deformation of the cutting blades, and has a function of finely repairing the wellbore, and can meet the technical requirements of time-sharing, segmented, and variable wellbore diameter hole reaming while drilling in one trip. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram of the extended state of a variable-diameter hole reaming tool while drilling provided by an embodiment of the present invention.

[0027] Figure 2 It is a schematic structural diagram of the retracted state of a variable-diameter hole reaming tool while drilling provided by an embodiment of the present invention.

[0028] Figure 3 It is a schematic structural diagram of the first-stage cutting block of a variable-diameter hole reaming tool while drilling provided by an embodiment of the present invention.

[0029] Figure 4 It is a schematic structural diagram of the throttle guide piston barrel of a variable-diameter hole reaming tool while drilling provided by an embodiment of the present invention.

[0030] Figure 5 Structural schematic diagram of the side inner cavity of a first-stage cutting block of a variable-diameter hole reamer while drilling provided by an embodiment of the present invention. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the number of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0036] In the present invention, unless otherwise clearly specified or limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the present invention, unless otherwise clearly specified or limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0038] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0039] See Figures 1-5 As shown, in one embodiment, a variable-diameter hole enlarging tool while drilling according to the present invention includes

[0040] A drill collar 1, which includes a main body having a hollow channel for introducing fluid, and a sink is provided on the side wall of the main body and recessed towards the hollow channel, and a through hole communicating with the hollow channel is provided at the bottom of the sink;

[0041] A first-stage cutting block 2, which is movably connected to the sink in a direction perpendicular to the hollow channel. The first-stage cutting block 2 includes a pair of cutting main bodies approaching or separating from each other. The cutting main body includes a block 9 at least partially movably accommodated in the through hole. The block 9 includes a plurality of side cavities 12 extending in a direction perpendicular to the hollow channel and a first cutting surface 10 provided on the outer surface of the block 9 away from the hollow channel;

[0042] At least a pair of limiting nuts 4, and the limiting nuts 4 are threadedly connected to the side cavities 12;

[0043] At least a pair of second-stage cutting teeth 3, the second-stage cutting teeth 3 are movably connected to the side cavities 12, and the second-stage cutting teeth 3 include a second cutting surface 11 on the outer surface away from the hollow channel;

[0044] At least a pair of cutting tooth springs 5, which are arranged in the space formed by the limit sleeve 4 and the secondary cutting teeth 3 to elastically connect the secondary cutting teeth 3;

[0045] A throttle guide piston cylinder 6, which is arranged in the hollow channel to introduce fluid, and the throttle guide piston cylinder 6 covers the through hole;

[0046] A main spring 7, whose top end is connected to the bottom end of the throttle guide piston cylinder 6;

[0047] A spring base 8, whose bottom end is sealingly connected to the bottom of the drill collar 1, and the spring base 8 supports the main spring 7.

[0048] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, when the fluid passes through a flow rate greater than a predetermined value, the throttle guide piston cylinder 6 moves downward and extrudes the throttle guide piston cylinder 6 to make the first-stage cutting block 2 protrude outward. When the fluid passes through a flow rate less than the predetermined value, the elastic force of the main spring 7 makes the throttle guide piston cylinder 6 move upward.

[0049] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, the predetermined flow rate is 20 - 25 L / S.

[0050] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, a step is formed at the connection of the through hole and the sink.

[0051] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, supporting parts extend from both ends of the block 9, and the supporting parts are movably arranged in the sink in cooperation with the step.

[0052] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, a guiding part protruding from the side wall of the drill collar 1 is provided at the periphery of the sink.

[0053] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, the guiding part has an arc-shaped outer surface.

[0054] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, the second outer surface is farther from the hollow channel than the first outer surface.

[0055] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, a stepped boss is provided at the bottom end of the throttle guide piston cylinder 6, and the top end of the main spring 7 is sleeved on the stepped boss.

[0056] In a preferred embodiment of the variable-diameter hole enlarging tool while drilling, the central axes of the drill collar 1 and the throttle guide piston cylinder 6 are collinear.

[0057] In one embodiment, the variable-diameter hole enlarging tool while drilling includes

[0058] A drill collar 1, which includes a body having a hollow channel for introducing fluid, a sink is provided on the side wall of the body and recessed towards the hollow channel, a through hole communicating with the hollow channel is provided at the bottom of the sink, and a step is formed at the connection of the through hole and the sink;

[0059] A first-stage cutting block 2, which is slidably and sealingly connected to the sink in a direction perpendicular to the hollow channel. The first-stage cutting block 2 includes a pair of cutting bodies approaching or separating from each other. The cutting body includes a block 9 at least partially movably accommodated in the through hole and supporting portions extending at both ends of the block 9. The supporting portions are movably arranged in the sink in cooperation with the step. The block 9 includes a plurality of side inner cavities 12 extending in a direction perpendicular to the hollow channel and a first cutting surface 10 provided on the outer surface of the block 9 away from the hollow channel;

[0060] At least a pair of limiting screw sleeves 4, and the limiting screw sleeves 4 are threadedly connected to the side inner cavities 12;

[0061] At least a pair of second-stage cutting teeth 3, the second-stage cutting teeth 3 are slidably and sealingly connected to the side inner cavities 12, and the second-stage cutting teeth 3 include a second cutting surface 11 on the outer surface away from the hollow channel;

[0062] At least a pair of cutting tooth springs 5, and the cutting tooth springs 5 are arranged in the space formed by the limiting screw sleeves 4 and the second-stage cutting teeth 3 to elastically connect the second-stage cutting teeth 3;

[0063] A throttle guide piston cylinder 6, which is arranged in the hollow channel to introduce fluid, and the throttle guide piston cylinder 6 covers the through hole,

[0064] A main spring 7, the top end of which is connected to the bottom end of the throttle guide piston cylinder 6,

[0065] A spring base 8, the bottom end of which is sealingly connected to the bottom of the drill collar 1, and the spring base 8 supports the main spring 7,

[0066] When the fluid flow rate is greater than a predetermined flow rate, the throttle guide piston cylinder 6 moves downward and extrudes the throttle guide piston cylinder 6 to make the first-stage cutting block 2 protrude outwards. When the fluid flow rate is less than the predetermined flow rate, the elastic force of the main spring 7 makes the throttle guide piston cylinder 6 move upward.

[0067] In one embodiment, the variable-diameter reaming tool while drilling realizes the function of the expansion and contraction of the first-stage cutting block 2 and the second-stage cutting teeth 3 by the size of the mud pump displacement. When the variable-diameter reaming tool assembly is completed and ready to enter the well, under the elastic force of the main spring 7, the throttle guide piston cylinder 6 restricts the step of the first-stage cutting block 2 through the guide rail so that it is in the side inner cavity 12 of the tool body, and the second-stage cutting teeth 3 are in the side inner cavity 12 of the first-stage cutting block 2 under the elastic force of the cutting tooth spring 5.

[0068] During the process of running in hole, the variable-diameter hole enlarging tool with adjustable diameter can always flush the nozzles with a small displacement. When the tool reaches the hole enlarging position, increase the displacement of the mud pump to 20 - 25 L / S. The current displacement can push the throttle guide piston barrel 6 downward, and the guide rail pushes out the first-stage cutting block 2. Then start the rotary table to carry out the initial step-making stage of hole enlarging. Subsequently, carry out the hole enlarging operation with stable drilling pressure and increased speed. When the hole enlarging is completed, turn off the mud pump. The throttle guide piston barrel 6 relies on the elastic force of the main spring 7 to perform the contraction action of the first-stage cutting block 2, thus completing the hole enlarging operation. If it is necessary to increase the hole diameter of the enlarged hole, increase the displacement of the mud pump to 30 - 32 L / S. The current displacement first pushes the throttle guide piston barrel 6 downward, and the guide rail pushes out the first-stage cutting block 2. Then it pushes the second-stage cutting teeth 3 to protrude radially. Start the rotary table to carry out the initial step-making stage of hole enlarging. Subsequently, carry out the hole enlarging operation with stable drilling pressure and increased speed. When the hole enlarging is completed, turn off the mud pump. The throttle guide piston barrel 6 relies on the elastic force of the main spring 7 to perform the contraction action of the first-stage cutting block 2, and the second-stage cutting teeth contract into the side cavity of the first-stage cutting block 2 by the elastic force of the cutting tooth spring 5, thus completing the overall hole enlarging operation.

[0069] As Figure 1 shown, the whole of the first-stage cutting block 2 is slidably and sealingly connected to the short drill collar 1, and its lower step is limited by the throttle guide piston barrel 6. The second-stage cutting teeth 3 are slidably and sealingly connected to the side inner cavity 12 of the first-stage cutting block 2. The limit sleeve 4 is threadedly connected to the side inner cavity 12 of the first-stage cutting block 2. The cutting tooth spring 5 is placed in the space formed by the limit sleeve 4 and the second-stage cutting teeth 3, and elastically connects the second-stage cutting teeth 3. The throttle guide piston barrel 6, the main spring 7, and the spring base 8 are placed in the drill collar 1. The spring base 8 is sealingly connected to the bottom of the drill collar 1. The displacement of the mud pump causes the throttle guide piston barrel 6 to generate a downward position, and the elastic force of the main spring 7 causes the throttle guide piston barrel 6 to generate an upward displacement.

[0070] In one embodiment, during the under-reaming operation, the tool can be circulated with a small displacement at any time during the process of running in the hole. When the tool is lowered to the under-reaming position A, the under-reaming section of well A is 100 m, and the required under-reaming hole diameter is enlarged to 220 mm. The displacement of the mud pump is increased to 20 - 25 L / S. The current displacement can push the throttle guide piston barrel 6 downward, and the guide rail pushes out the first-stage cutting block 2. The under-reaming diameter reaches 220 mm. The rotary table is turned on to 55 - 60 r / min to carry out the initial step-making stage of under-reaming. Subsequently, the under-reaming operation is carried out with a stable drilling pressure to increase the speed. When the under-reaming of section A is completed, the mud pump is turned off. The throttle guide piston barrel 6 relies on the elastic force of the main spring 7 to perform the contraction action of the first-stage cutting block 2, completing the overall under-reaming operation of section A. Subsequently, when the tool is lowered to the under-reaming position B, the required under-reaming hole diameter is enlarged to 310 mm. The displacement of the mud pump is increased to 30 - 32 L / S. The current displacement first pushes the throttle guide piston barrel 6 downward, and the guide rail pushes out the first-stage cutting block 2, and then pushes the second-stage cutting teeth 3 to project radially. The under-reaming diameter reaches 310 mm. The rotary table is turned on to 40 - 50 r / min to carry out the initial step-making stage of under-reaming. Subsequently, the under-reaming operation is carried out with a stable drilling pressure to increase the speed. When the under-reaming of section B is completed, the mud pump is turned off. The throttle guide piston barrel 6 relies on the elastic force of the main spring 7 to perform the contraction action of the first-stage cutting block 2, and the second-stage cutting teeth 3 contract into the side cavity of the first-stage cutting block 2 by the elastic force of the cutting tooth spring 5, completing the overall under-reaming operation of section B.

[0071] As Figure 3 、 5 shown, multiple side inner cavities 12 are arrayed and spaced apart on the block body 9 of the first-stage cutting block 2. The side inner cavities 12 are cavities that are narrow inside and wide outside. The outer wide part of the cavity is provided with threads, and the limit sleeve 4 is threadedly connected to the outer wide part of the side inner cavity 12. The second-stage cutting teeth 3 are movably arranged in the side inner cavity 12. The second-stage cutting teeth 3 are convex block structures that are wide inside and narrow outside. It can be seen that the limit sleeve 4 can resist the wide part inside the second-stage cutting teeth 3 to prevent the second-stage cutting teeth 3 from coming out of the side inner cavity 12. The cutting tooth spring 5 is located between the wide part inside the second-stage cutting teeth 3 and the side inner cavity 12 and is blocked by the limit sleeve 4. The cutting tooth spring 5 elastically presses the second-stage cutting teeth 3 towards the hollow channel direction, so that when the fluid passes through a flow rate less than a predetermined value, the second-stage cutting teeth 3 retract into the first-stage cutting block 2, and when the fluid passes through a flow rate greater than the predetermined value, overcoming the elastic force of the cutting tooth spring 5, the second-stage cutting teeth 3 project out of the first-stage cutting block 2 in the direction away from the hollow channel. Further, the second-stage cutting teeth 3 are provided with a stepped portion for abutting against the cutting tooth spring 5.

[0072] Finally, it should be noted that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0073] Only some exemplary embodiments of the present invention have been described by way of illustration. Without doubt, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A variable-diameter hole enlarging tool while drilling, Characterized in that, It includes, A drill collar, which includes a main body having a hollow channel for introducing fluid. A sunk groove recessed towards the hollow channel is provided on the side wall of the main body, and a through hole communicating with the hollow channel is provided at the bottom of the sunk groove; A primary cutting block, which is movably connected to the sunk groove in a direction perpendicular to the hollow channel. The primary cutting block includes a pair of cutting main bodies approaching or separating from each other. The cutting main body includes a block body at least partially movably accommodated in the through hole. The block body includes a plurality of side inner cavities extending in a direction perpendicular to the hollow channel and a first cutting surface provided on the outer surface of the block body away from the hollow channel; At least a pair of limiting screw sleeves, which are threadedly connected to the side inner cavities; At least a pair of secondary cutting teeth, which are movably connected to the side inner cavities. The secondary cutting teeth include a second cutting surface on the outer surface away from the hollow channel; At least a pair of cutting tooth springs, which are arranged in the space formed by the limiting screw sleeve and the secondary cutting tooth to elastically connect the secondary cutting tooth; A throttle guide piston cylinder, which is arranged in the hollow channel to introduce fluid. The throttle guide piston cylinder covers the through hole, A main spring, whose top end is connected to the bottom end of the throttle guide piston cylinder, A spring base, whose bottom end is hermetically connected to the bottom of the drill collar, and the spring base supports the main spring.

2. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, When the fluid passes through a flow rate greater than a predetermined value, the throttle guide piston cylinder moves downward and extrudes the throttle guide piston cylinder to make the primary cutting block protrude outwards. When the fluid passes through a flow rate less than the predetermined value, the elastic force of the main spring makes the throttle guide piston cylinder move upward.

3. A variable-diameter hole enlarging tool while drilling according to claim 2, Characterized in that, The predetermined flow rate is 20 - 25 L / S.

4. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, A step is formed at the connection of the through hole and the sunk groove.

5. A variable-diameter hole enlarging tool while drilling according to claim 4, Characterized in that, Supporting parts extend out from both ends of the block body, and the supporting parts are movably arranged in the sunk groove in cooperation with the step.

6. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, A guiding part protruding from the side wall of the drill collar is provided at the periphery of the sunk groove.

7. A variable-diameter hole enlarging tool while drilling according to claim 6, Characterized in that, The guiding part has an arc-shaped outer surface.

8. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, The second outer surface is farther from the hollow channel than the first outer surface.

9. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, A stepped boss is provided at the bottom end of the throttle guide piston cylinder, and the top end of the main spring is sleeved on the stepped boss.

10. A variable-diameter hole enlarging tool while drilling according to claim 1, Characterized in that, The central axes of the drill collar and the throttle guide piston cylinder are collinear.

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