Strong deflecting PDC (Polycrystalline Diamond Compact) drill bit capable of changing inner cone angle of short-radius well and well drilling method

Abstract

The invention relates to a strong deflecting PDC drill bit capable of changing the inner cone angle of a short-radius well and a well drilling method, the strong deflecting PDC drill bit comprises a drill bit body, the drill bit body comprises a drill bit cylinder and a blade structure, the inner cone angle of the blade structure is a negative inner cone angle, and the blade structure comprises a plurality of first blades; the stretching mechanism can be axially and movably arranged in the drill bit barrel and is connected with the blade structure through a shear pin; the inner cone angle of the blade mechanism is a positive inner cone angle, and the blade mechanism comprises a plurality of second blades; when the shear pin is not sheared off, the bottom of each second blade is positioned above the bottom of the first blade; when the shear pin is in a shearing state, the stretching mechanism can move downwards in the axial direction of the drill bit barrel to drive the second cutter wings to move downwards so that the second cutter wings can stretch out of the first cutter wings. According to the drill bit, the inner cone angle of the drill bit can be converted from negative to positive so as to adapt to drill bit functional switching of different construction steps of deflecting / horizontal drilling in the well completion operation of a short-radius well.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well drilling technology, and in particular to a high-angle drilling PDC bit and drilling method for short-radius wells with adjustable inner cone angle. Background Technology

[0002] Currently, most oilfield development has entered the mid-to-late stages, generally facing problems such as low recovery rates and poor permeability. Sidetracking, as an important means of tapping remaining oil and gas reservoirs, improving recovery rates, and reducing costs and increasing efficiency, is widely used in the stimulation of old wells and potential areas. Conventional sidetracking uses conventional drilling tools, and the build-up radius usually exceeds 180 meters, which presents problems such as difficulty in hitting the target in thin oil layers, low trajectory control accuracy, easy penetration of non-reservoir areas in the wellbore, high downhole risks, strict equipment requirements, and high costs. To overcome these limitations, short-radius radial horizontal well technology has gradually gained attention. This technology can drill radially distributed horizontal holes in a vertical wellbore at one or more layers, penetrating the near-wellbore contamination zone, significantly expanding the drainage area, and improving single-well production and recovery rates. Among them, flexible drill string radial horizontal well technology, through the matching of special flexible drill string and window-opening build-up tools, can continuously complete window opening, build-up, and horizontal drilling in the same oil layer, achieving short-radius drilling operations with a build-up radius of only 3-5m, a build-up rate of >300° / 30m, and a horizontal section length of >50m. This technology uses a flexible drill pipe to transmit the drilling pressure and torque required for rock breaking to the drill bit, offering advantages such as short construction cycles and small target distance. It enables three-dimensional stimulation and development of remaining oil reservoirs in a single well, involving multiple layers, single layers, and multiple branches.

[0003] This construction process typically involves three drilling techniques: window drilling, directional drilling, and horizontal drilling. Each technique requires a different set of tools. It primarily relies on specially designed flexible drill pipes, which connect 0.1-0.2m sections via hinges. The hinged structure allows adjacent sections to form a certain angle. Combined with appropriate drill bits and window drilling tools, this flexible drilling tool possesses extremely high directional drilling performance. The positive or negative value of the inner cone angle of the PDC drill bit crown significantly affects the load distribution of the drill bit, thus influencing its stability and guiding performance. Figure 1 This is a schematic diagram showing the case where the inner cone angle of the crown of drill bit 01 is a negative inner cone angle. Figure 2 This diagram illustrates the case where the crown inner cone angle of drill bit 01 is a positive inner cone angle. A positive inner cone angle allows for easier release of principal stress along the wellbore perimeter, resulting in more efficient rock breaking at the center; it also improves wellbore support and directional stability. Horizontal drilling bits should resist lateral forces to prevent lateral movement and possess more efficient rock breaking capabilities; a positive inner cone angle is preferable. A negative inner cone angle results in a more prominent cutting surface, making lateral cutting easier and providing a faster response. For directional drilling bits, a negative inner cone shape is preferable, while increasing the crown height enhances directional drilling capability.

[0004] However, in short-radius well operations, the build-up operation requires the use of a strong build-up bit to improve the drilling tool's build-up capability, and the build-up footage in short-radius wells is generally 3-5m. After the build-up is completed, the drill string needs to be pulled out and replaced with a more stable horizontal drilling bit, a complex and cumbersome process with low bit utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a strong directional drilling PDC bit and drilling method for short-radius wells with adjustable inner cone angle, which can switch the inner cone angle of the bit from negative to positive to adapt to the functional switching of the bit during different construction steps of directional / horizontal drilling in short-radius well completion operations.

[0006] The objective of this invention can be achieved using the following technical solutions: This invention provides a forced directional drilling (PDC) bit for short-radius wells with adjustable inner cone angle, comprising: a drill bit body, including a drill bit barrel and a cutter wing structure, wherein the inner cone angle of the cutter wing structure is a negative inner cone angle, the cutter wing structure includes a plurality of circumferentially spaced first cutter wings, the upper end of each first cutter wing being connected to the lower part of the drill bit body, the lower ends of each first cutter wing being connected to each other, and a spacer groove being formed between adjacent two first cutter wings that can communicate with the drill bit body; an extension mechanism, axially movable within the drill bit barrel and connected to the cutter wing structure via a shear pin; and a cutter wing mechanism, having a positive inner cone angle, including a plurality of circumferentially spaced second cutter wings, each second cutter wing being disposed in a corresponding spacer groove and connected to the extension mechanism; in the state where the shear pin is not sheared, the bottom of each second cutter wing is located above the bottom of the first cutter wing; in the state where the shear pin is sheared, the extension mechanism can move downward along the axial direction of the drill bit barrel, driving each second cutter wing downward so that the bottom of each second cutter wing extends beyond the bottom of each first cutter wing.

[0007] This invention also provides a drilling method using the aforementioned short-radius well-changeable internal cone angle PDC drill bit for drilling. The drilling method includes: With the shear pin not cut off, the blade structure is used as the main cutting blade for directional drilling; By throwing a ball to apply pressure, the shear pin is cut off, and the extension mechanism is pushed downward, which in turn drives each second cutter blade to move downward and extend each first cutter blade, so that the effective contact area between the second cutter blade and the bottom of the well is greater than the effective contact area between the first cutter blade and the bottom of the well; the extended cutter blade mechanism is used as the main cutting blade for horizontal drilling.

[0008] As described above, the short-radius well-drilling PDC drill bit and drilling method with adjustable inner cone angle of the present invention utilizes a blade structure with a negative inner cone angle for directional drilling operations. After the directional drilling is completed, the drill bit crown shape is changed from a negative inner cone angle to a positive inner cone angle by cutting the shear pin, improving the drill bit stability and allowing direct horizontal drilling operations. After the shear pin is cut, the extension mechanism drives each second blade to extend relative to the drill bit axis, which allows for controllable changes in the inner cone angle of the drill bit, thereby changing the contact area and stress state between the drill bit and the well wall. This achieves functional adjustment during the directional and horizontal drilling sections of short-radius wells, ensuring that the drill bit completes both directional and horizontal drilling operations in one run, reducing the number of tripping operations on-site, lowering mining costs, and reducing the workload of the drilling team. Attached Figure Description

[0009] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the structure when the inner cone angle of the drill bit crown is negative.

[0010] Figure 2 This is a schematic diagram of the structure when the inner cone angle of the drill bit's crown is a positive inner cone angle.

[0011] Figure 3 The explosion of the short-radius well-setting PDC drill bit with adjustable inner cone angle provided by this invention Figure 1 .

[0012] Figure 4 The explosion of the short-radius well-setting PDC drill bit with adjustable inner cone angle provided by this invention Figure 2 .

[0013] Figure 5 This is a schematic diagram of the structure of the drill bit skirt provided by the present invention.

[0014] Figure 6 Schematic diagram of the body ring and blade structure provided by the present invention Figure 1 .

[0015] Figure 7 Schematic diagram of the body ring and blade structure provided by the present invention Figure 2 .

[0016] Figure 8 Schematic diagram of the body ring and blade structure provided by the present invention Figure 3 .

[0017] Figure 9 Schematic diagram of the extension mechanism provided by the present invention Figure 1 .

[0018] Figure 10Schematic diagram of the extension mechanism provided by the present invention Figure 2 .

[0019] Figure 11 A cross-sectional schematic diagram of the extension mechanism provided by the present invention.

[0020] Figure 12 This is a top view of the extension mechanism provided by the present invention.

[0021] Figure 13 This is a schematic diagram of the blade mechanism provided by the present invention.

[0022] Figure 14 Schematic diagram of the short-radius well-adjustable internal cone angle PDC drill bit provided by the present invention when the shear pin is not sheared off. Figure 1 .

[0023] Figure 15 Schematic diagram of the short-radius well-adjustable internal cone angle PDC drill bit provided by the present invention when the shear pin is not sheared off. Figure 2 .

[0024] Figure 16 A schematic diagram of the structure of the short-radius well-adjustable internal cone angle-modifying PDC drill bit provided by the present invention after the second cutter blades extend after the shear pin is cut off.

[0025] Explanation of icon numbers: 01. Drill bit; 1. Drill bit barrel; 11. Drill bit skirt; 111. Annular step; 112. Drainage groove; 12. Body ring; 2. Blade structure; 21. First blade; 211. Vertical plate; 212. Horizontal plate; 213. Pin placement slot; 214. First cutting tooth; 22. Spacing groove; 23. Hollowed-out receiving cavity; 3. Extension mechanism; 31. Extension block; 311. Arc-shaped side plate; 3111. Pin fixing groove; 3112. Positioning connecting block; 312. Arc-shaped bottom plate; 3121. Spray hole; 313. Empty groove; 32. Slot; 33. Stop boss; 331. Notch; 34. Limiting ring; 341. Ball receiving seat; 342. Liquid inlet channel; 35. Guide block; 4. Blade mechanism; 41. Second blade; 411. Vertical plate; 4111. Connecting groove; 412. Horizontal plate; 42. Double row of cutting teeth. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0027] like Figures 3 to 16As shown, this application provides a forced directional drilling (PDC) bit for short-radius wells with adjustable inner cone angle, comprising: The drill bit body includes a drill bit cylinder 1 and a cutter wing structure 2. The inner cone angle of the cutter wing structure 2 is a negative inner cone angle. The cutter wing structure 2 includes a plurality of first cutter wings 21 arranged circumferentially. The upper end of each first cutter wing 21 is connected to the lower part of the drill bit body. The lower ends of each first cutter wing 21 are connected to each other. An interval groove 22 that can communicate with the drill bit body is formed between two adjacent first cutter wings 21. The extension mechanism 3 is axially movable inside the drill bit body 1 and can be connected to the cutter wing structure 2 via shear pins. The cutter wing mechanism 4 has a positive inner cone angle. The cutter wing mechanism 4 includes a plurality of second cutter wings 41 arranged circumferentially. Each second cutter wing 41 is located in a corresponding spacer groove 22 and can be connected to the extension mechanism 3. When the shear pin is not cut off, the bottom of each second cutter wing 41 is located above the bottom of the first cutter wing 21. When the shear pin is cut off, the extension mechanism 3 can move downward along the axial direction of the drill bit body 1, driving each second cutter wing 41 to move downward so that the bottom of each second cutter wing 41 extends out of the bottom of each first cutter wing 21, so that the effective contact area between the second cutter wing 41 and the bottom of the well is greater than the effective contact area between the first cutter wing 21 and the bottom of the well, and the drill bit completes the switch from a negative inner cone angle to a positive inner cone angle.

[0028] In use, the upper end of the drill bit body is used to connect the flexible drill pipe. When the shear pin is not cut off, the cutter wing mechanism 4 does not extend the first cutter wings 21. The cutter wing structure 2 with a negative inner cone angle is used as the main cutting cutter wing, and directional drilling operations can be performed. After the directional drilling operation is completed, the shear pin is cut off, and the extension mechanism 3 is pushed to move downward, which will drive the second cutter wings 41 to move downward and extend from the bottom of the first cutter wings 21. At this time, the cutter wing mechanism 4 with a positive inner cone angle is used as the main cutting cutter wing, and horizontal drilling operations can be performed.

[0029] Therefore, the PCD drill bit for directional drilling of this application can perform directional drilling operations using the blade structure 2 with a negative inner cone angle. After the directional drilling is completed, the shape of the drill bit crown is changed from a negative inner cone angle to a positive inner cone angle by cutting the shear pin, which improves the stability of the drill bit and allows for direct horizontal drilling operations. After the shear pin is cut, the extension mechanism 3 drives each second blade 41 to extend relative to the drill bit axis, which allows for a controllable change in the inner cone angle of the drill bit. This changes the contact area and stress state between the drill bit and the well wall, enabling functional adjustment during the directional drilling and horizontal drilling sections of short-radius wells. This ensures that the drill bit can complete both the directional and horizontal drilling operations in one trip, reducing the number of tripping operations on site and lowering mining costs and the workload of the drilling team.

[0030] It should be noted that the terms "upper" and "lower" used in this article refer only to... Figure 3The "left" and "right" directions shown are for illustrative purposes only and do not represent the only possible implementation.

[0031] In the specific implementation method, refer to Figures 6 to 12 The extension mechanism 3 includes a plurality of extension blocks 31 spaced apart circumferentially. A slot 32 is formed between two adjacent extension blocks 31, and the plurality of extension blocks 31 are connected by a connecting component to form a whole, which is used to prevent each extension block 31 from coming out of each slot 22. Each extension block 31 can be axially movably inserted into the corresponding slot 22. Each first blade 21 can be inserted into the corresponding slot 32 and connected to the corresponding extension block 31 by a shear pin. Each second blade 41 can be fixedly connected to the corresponding extension block 31.

[0032] Multiple first cutter wings 21 are evenly spaced along the circumference of the drill bit, multiple second cutter wings 41 are evenly spaced along the circumference of the drill bit, and multiple extension blocks 31 are evenly spaced along the circumference of the drill bit. The number of first cutter wings 21, the number of spacer slots 22, the number of second cutter wings 41, and the number of extension blocks 31 are all the same, and the specific number is determined according to actual needs. For example, in this embodiment, the number of extension blocks 31, first cutter wings 21, and second cutter wings 41 are all four. The aforementioned spacer slots 22 are formed between the adjacent two sides of two adjacent first cutter wings 21. The spacer slots 22 are connected to the interior of the drill bit body. The lower part of each extension block 31 can be inserted into each spacer slot 22, and each second cutter wing 41 is also provided in each spacer slot 22 and is fixed to the outside of the corresponding extension block 31. The cross-sectional shape of the extension block 31 matches the cross-sectional shape of the spacer groove 22. Each first blade 21 is also provided with a sealing strip on its sidewall. The sidewall of the extension block 31 can slide in sealed contact with the sidewall of the first blade 21 to ensure the sealing of the drill bit.

[0033] Optional, refer to Figure 9 and Figure 13 Each extension block 31 has a positioning connecting block 3112 on its lower outer wall, and each second blade 41 has a connecting groove 4111 on its inner wall. The positioning connecting block 3112 can be inserted and fixed in the corresponding connecting groove 4111. The blade mechanism 4 can be connected to the extension mechanism 3 by welding. Multiple positioning connecting blocks 3112 are arranged equidistantly in the circumferential direction, and multiple second blades 41 are arranged equidistantly in the circumferential direction. Each second blade 41 is fixedly connected to the positioning connecting block 3112 of the corresponding extension block 31 by welding to form an integral telescopic blade. The positioning connecting block 3112 cooperates with the corresponding connecting groove 4111 to transmit the radial or axial displacement of the extension mechanism 3 to the blade mechanism 4, thereby realizing the telescopic deformation of the second blade 41.

[0034] Further optional, see Figure 7 and Figure 9Each extension block 31 has a pin fixing groove 3111 on its upper side wall for inserting and fixing shearing pins; each second blade 41 has a pin placement groove 213 on its top side wall that connects to its top surface, which is used to cooperate with the pin fixing groove 3111 on the extension block 31 to achieve a limiting and stable connection between the drill bit body and the extension mechanism 3; the head of the shearing pin can be inserted into the pin placement groove 213 from the top surface of the corresponding second blade 41.

[0035] During installation, first insert and fix the shear pin in the pin slot 32 with the head of the shear pin protruding from the pin mounting groove, and then insert the head of the shear pin into the pin placement groove 213 to complete the connection of the shear pins between each second blade 41 and each extension block 31.

[0036] By connecting each second cutter wing 41 to each extension mechanism 3 via shear pins, a first limiting structure can be formed, which can axially limit the extension mechanism 3. After the shear pins are sheared and dislodged by hydraulic energy during drilling, the extension mechanism 3 is released and axial displacement is allowed. In addition, multiple first cutter wings 21 are inserted into each slot 32. The multiple first cutter wings 21 and multiple extension blocks 31 are arranged in a staggered manner along the circumference. The surface contact between the first cutter wings 21 and the extension blocks 31 can also effectively prevent the circumferential relative rotation between the extension mechanism 3 and the drill bit body.

[0037] Further optional, see Figure 7 as well as Figures 9 to 11 The connecting assembly includes multiple stop bosses 33, which are connected between the upper sidewalls of two adjacent extension blocks 31. When the shear pin is not cut off, there is a gap between the top surface of the first blade 21 and the corresponding stop boss 33. When the shear pin is cut off, the stop boss 33 can abut against the top surface of the corresponding first blade 21.

[0038] The number of stop protrusions 33 is the same as the number of extension blocks 31. Each stop protrusion 33 is located at the top of each slot 32. The two sides of each stop protrusion 33 are connected to the opposite sidewalls of two adjacent extension blocks 31. The top surface of each stop protrusion 33 is flush with the top surface of each extension block 31. The stop protrusion 33 is located above the pin fixing slot 3111. After the shear pin is cut, each extension block 31 drives each second blade 41 to move downward until the bottom surface of each stop protrusion 33 abuts against the top surface of each first blade 21. At this time, each second blade 41 extends beyond the first blade 21. The stop protrusions 33 serve two purposes: firstly, they connect each extension block 31 to form a whole; secondly, after the downward extension displacement of the extension mechanism 3 reaches the predetermined stroke, the stop protrusions 33 can abut against the top surface of the first blade 21, forming a second limiting structure to prevent structural instability caused by excessive stroke.

[0039] Further optional, see Figure 7 as well as Figures 9 to 11 Each extension block 31 has a slot 313 on its upper inner side, and each slot 313 is connected to each slot 32. The upper center of the blade structure 2 also has a hollow receiving cavity 23 with a top opening, which is connected to each interval slot 22. The connecting assembly also includes a limiting ring 34, which is located in each slot 313 and connected to the slot wall of each slot 313. Each stop boss 33 is located outside the limiting ring 34, and the bottom surface of the limiting ring 34 is located below the bottom surface of the stop boss 33. When the shear pin is cut off, the bottom surface of the limiting ring 34 can abut against the bottom surface of the hollow receiving cavity 23 after the stop boss 33 fails.

[0040] Reference Figure 6 The first blade 21 is generally L-shaped with an obtuse angle. Each first blade 21 includes a vertical plate 211 and a horizontal plate 212 connected vertically. The upper outer wall of the vertical plate 211 is fixed to the upper inner wall of the drill bit body. The inner surface of the vertical plate 211 is a vertical surface. The outer end of the horizontal plate 212 is connected to the lower end of the vertical plate 211. The inner ends of the horizontal plates 212 of the multiple first blades 21 are connected to each other. The top surface of the horizontal plate 212 is an inclined surface and forms an obtuse angle with the vertical surface, so that the inner cone angle of the blade structure 2 formed by the multiple first blades 21 is a negative inner cone angle. The inner surface of the vertical plate 211 of the multiple first blades 21 and the top surface of the horizontal plate 212 enclose the aforementioned hollow receiving cavity 23. The pin placement groove 213 is provided on the top of the vertical plate 211. The bottom surface of the limiting ring 34 is generally located below the pin fixing groove 3111. When the shear pin is not cut off, part of the limiting ring 34 can be accommodated in the hollowed-out receiving cavity 23. When the shear pin is cut off and the extension mechanism 3 moves downward, after the stop boss 33 fails, the extension mechanism 3 can move downward until the top surface of the limiting ring 34 abuts against the top surface of each horizontal plate 212.

[0041] By using the limiting ring 34 located on the upper part of the extension mechanism 3, on the one hand, the extension blocks 31 can be connected to form a whole; on the other hand, under extreme working conditions, when the axially limiting stop boss 33 fails, the bottom surface of the limiting ring 34 can abut against the bottom surface of the hollow receiving cavity 23, forming a third limiting structure; the contact surface between the limiting ring 34 and each horizontal plate provides the final safety limiting function, preventing the extension mechanism 3 from being completely dislodged from the drill bit body.

[0042] Optionally, the outer wall of the stop boss 33 in the radial direction of the drill bit is located on the inner wall of the outer wall of the extension block 31, forming a notch 331; a gap is left between the stop boss 33 and the outer wall of the limiting ring 34; this can facilitate the installation of the shear pin.

[0043] The entire extension mechanism 3 is equipped with a three-level limiting structure: the first-level limiting is fixed by a shear pin to ensure that the drill bit maintains a negative inner cone angle in the directional section; the second-level limiting is abutted by a stop boss 33 to ensure that the extension mechanism 3 extends stably within a set stroke after the shear pin is cut, so that the drill bit changes to a positive inner cone angle; the third-level limiting is provided by the end face of the limiting ring 34, which prevents the extension mechanism 3 from coming off as a whole when the second-level limiting fails, and provides a final safety limiting, thereby ensuring the safety and reliability of the drill bit.

[0044] Further optional, see Figure 10 and Figure 11 Each slot 313 has an inner bottom that extends upward to form a guide block 35. When the extension mechanism 3 moves downward, the guide block 35 can slide along the side of the corresponding first blade 21.

[0045] The number of guide blocks 35 is the same as the number of extension blocks 31. Two adjacent sides of the guide block 35 can slide along two adjacent sides of the corresponding two adjacent first blade wings 21, which can be used to guide the extension mechanism 3 along a predetermined route, thus providing a straightening effect. Specifically, refer to... Figure 11 The extension block 31 includes a hollow structure formed by an arc-shaped side plate 311 and an arc-shaped bottom plate 312 connected vertically. The arc-shaped bottom plate 312 is a fan-shaped plate. The guide block 35 extends upward from the inner tip of the arc-shaped bottom plate 312. The sidewalls of the arc-shaped side plate 311 and the arc-shaped bottom plate 312 of the extension block 31 form slots 32 with the sidewalls of the arc-shaped side plate 311 and the arc-shaped bottom plate 312 of the adjacent extension block 31. The slots 32 are interconnected. The positioning connecting block 3112 is provided on the lower outer wall of the arc-shaped side plate 311. The upper outer wall of the extension block 31 protrudes radially from the lower outer wall of the extension block 31, and the step between them can be used to axially limit the upper end of the second cutter wing 41.

[0046] Furthermore, each extension block 31 is provided with a liquid passage that runs vertically through it. The extension mechanism 3 also includes a ball receiving seat 341 connected to the upper part of each extension block 31, which is used to support the ball after it is thrown. The ball can block part of each liquid passage after it sits on the ball receiving seat 341, thereby forming a pressure difference and shearing the pin.

[0047] The top surface of the aforementioned limiting ring 34 can be flush with the top surface of the extension block 31. The upper part of the limiting ring 34 can form a ball receiving seat 341. The top surface of the limiting ring 34 has a conical surface surrounding its inner hole, and the diameter of the conical surface gradually decreases from top to bottom. The ball receiving seat 341 is provided to create a hydraulically closed environment after the ball is thrown and seated, and the shearing release of the shear pin is achieved by increasing the pump pressure.

[0048] Optionally, the ball receiving seat 341 is connected to the upper part of each arc-shaped side plate 311. The ball receiving seat 341 is provided with liquid inlet channel 342 corresponding to the position of each arc-shaped bottom plate 312. Multiple spray holes 3121 are provided on each arc-shaped bottom plate 312. The liquid inlet channel 342 corresponding to the arc-shaped bottom plate 312, the cavity of the hollow structure, and the spray holes 3121 on the corresponding arc-shaped bottom plate 312 constitute the liquid passage on the extension block 31.

[0049] The liquid inlet channel 342 extends vertically through the limiting ring 34 along the axial direction. The specific number and diameter of the liquid inlet channel 342 and the spray hole 3121 can be determined according to actual needs. For example, in this embodiment, refer to... Figure 11 Each arc-shaped base plate 312 on the limiting ring 34 is provided with a fluid inlet channel 342, and two nozzles 3121 are provided on the arc-shaped base plate 312. Generally, the diameter of the fluid inlet channel 342 is larger than the diameter of the nozzle 3121. For example, there are four extension blocks 31 and four fluid inlet channels 342, which are evenly distributed along the circumference of the limiting ring 34. The diameter of the fluid inlet channel 342 is 8-12 mm, which ensures that the drilling fluid velocity and flow rate are sufficient to establish a sufficient pressure difference to shear the shear pin after the ball seat 341 is seated. Eight nozzles 3121 are evenly distributed along the circumference at the lower part of the extension mechanism 3. The diameter of the nozzles 3121 is 4-6 mm, so as to realize local jetting at the nozzles 3121 for bottom hole cleaning and cuttings removal. The inlet channel 342 and the nozzle 3121 together form a series fluid passage. The diameter configuration of this fluid passage has been optimized through numerical simulation. Together with the sealing structure on the inner wall of the drill bit body, it can reliably allow the shear pin to be sheared and released by the extension mechanism 3, and ensure that the nozzle 3121 has sufficient kinetic energy to remove rock cuttings at the bottom of the well and cool the cutting teeth during continuous operation, while controlling the overall pressure drop and flow loss within an acceptable range.

[0050] The entire drill bit is centered around a switchable "negative-positive inner cone angle" cutter wing system. The extension mechanism 3, located within the drill bit body, enables segmented control of the directional drilling and horizontal drilling phases, allowing for a controllable transition from a negative to a positive inner cone angle. During the directional drilling phase, the extension mechanism 3 is locked by a first-stage limiting shear pin structure. Upon entering the horizontal section, the ball seat 341 forms a hydraulic seal and shears the shear pin. Under the action of the second-stage limiting stop boss 33, the extension mechanism 3 extends outwards by a predetermined stroke, driving the cutter wing mechanism 4 to extend, thus switching the entire drill bit from a negative to a positive inner cone angle working state. In this working state, the first cutter wing 21 employs a double-row tooth arrangement with larger diameter cutting teeth to improve rock penetration and wear resistance, while simultaneously increasing wellbore contact coverage to meet the demands of continuous and efficient drilling in the horizontal section. The extension mechanism 3 has four inlet channels 342 at the top and eight nozzles 3121 at the bottom, forming a series fluid passage. The orifice diameters are numerically matched to simultaneously meet the differential pressure requirements of the shear pins and the cleaning requirements of the cuttings at the bottom of the well.

[0051] Furthermore, in order to install the extension mechanism 3, refer to Figure 3 and Figure 4 The drill bit body includes a drill bit skirt 11 and a body ring 12 that are detachably connected vertically, and the upper end of each first cutter wing 21 is connected to the lower part of the body ring 12.

[0052] The drill skirt 11 has a cylindrical structure. The upper inner wall of the drill skirt 11 has internal threads for connection with the flexible drill rod. The lower inner wall of the drill skirt 11 also has internal threads, and the upper outer wall of the body ring 12 has external threads. The body ring 12 and the drill skirt 11 are axially concentrically connected, and the two are detachably fixed via a threaded connection. Multiple first cutter wings 21 extend downwards from the lower part of the body ring 12, and these first cutter wings 21 can be integrally formed with the body ring 12.

[0053] Furthermore, refer to Figure 5 An annular step 111 is provided on the lower inner wall of the drill bit skirt 11, and the top surface of the extension mechanism 3 can abut against the annular step 111.

[0054] The annular step 111 is located above the internal thread at the lower end of the drill skirt 11 and can be set close to the internal thread to limit the insertion depth of the telescopic mechanism and form a stable end face support. During installation, the upper part of each extension block 31 in the extension mechanism 3 is inserted into each spacer slot 22, and the extension block 31 is connected to each first cutter wing 21 by shear pins. The top surface of the extension block 31 can be flush with the top surface of the body ring 12. The upper outer wall of the body ring 12 is threadedly connected to the lower inner wall of the drill skirt 11 until the top surfaces of the body ring 12 and the extension block 31 abut against the annular step 111, forming a limit.

[0055] Further optional, see Figure 5 The drill bit skirt 11 has multiple drainage grooves 112 spaced circumferentially on its outer wall. These drainage grooves 112 extend vertically through the top and bottom surfaces of the drill bit skirt 11. The specific number depends on the needs; for example, eight deep drainage grooves 112 can be evenly distributed circumferentially on the outer wall of the drill bit skirt 11. The drainage grooves 112 can enhance the discharge capacity of drilling fluid and cuttings, while reducing annular pressure differential and improving cuttings carrying efficiency during drilling.

[0056] Alternatively, the outer diameter of the drill bit skirt 11 gradually decreases from bottom to top. The drill bit skirt 11 has an overall conical structure, gradually tapering from bottom to top, with a small transition angle on the conical outer wall. The overall drill bit forms a near-full-hole drill string assembly mechanism; it has a high degree of fit with the well wall, enhancing drill bit stability; this structure improves well bottom cleaning capability and reduces cuttings accumulation.

[0057] Further optionally, the negative inner cone angle is -5° to -15°, and the positive inner cone angle is 12° to 24°. Multiple first cutting teeth 214 are longitudinally arranged on the outer surface of the first blade 21, and multiple sets of double-row cutting teeth 42 are longitudinally arranged on the outer surface of the second blade 41. Each set of double-row cutting teeth 42 includes two second cutting teeth arranged side-by-side, and the diameter of the first cutting teeth 214 is smaller than the diameter of the second cutting teeth.

[0058] The inner cone angle of the multiple first blades 21 of the drill bit body is negative (-5° to –15°), forming a projectile-shaped blade profile. This gives the first blades 21 an outward tilt angle relative to the drill bit axis in the radial direction, enhancing the first blades 21's ability to adhere to and guide the well wall in the directional drilling section and increasing lateral cutting force. Each first blade 21 surface has several first cutting teeth 214 arranged longitudinally. The distribution of the first cutting teeth 214 can be staggered. Optionally, the diameter of the first cutting teeth 214 is 8mm. The smaller size of the first cutting teeth 214 results in higher aggression due to the smaller cutting contact area, which will enhance the drill bit's response and lateral cutting force in the well wall direction, improve the guidance and drilling efficiency in short-radius well directional drilling operations, and the dense arrangement of smaller teeth can refine the rock cuttings at the bottom of the well, reduce the force on a single tooth, and reduce the wear of the cutting teeth.

[0059] The blade mechanism 4 consists of multiple second blades 41, evenly arranged circumferentially. Each second blade 41 is engaged with a connecting groove 4111 on the second blade 41 via a positioning connecting block 3112 on the extension mechanism 3, and is fixed by welding to enhance its connection strength and overall stability. (Refer to...) Figure 13 The second blade 41 is generally L-shaped with an acute angle. Each second blade 41 includes a vertical plate 411 and a horizontal plate 412 connected vertically. The inner sidewall of the vertical plate 411 is a vertical surface. A connecting groove 4111 is opened on the vertical plate 411. The top surface of the horizontal plate 412 is an inclined surface and forms an acute angle with the vertical surface, so that the inner cone angle of the blade mechanism 4 composed of multiple second blades 41 is a positive inner cone angle.

[0060] Each second cutter wing 41 has an overall arc-shaped outward-spreading structure, serving as the main cutting wing of the drill bit in its extended state. Its inner cone angle is set to a positive inner cone angle, with a shallow conical structure of 12°–24° to ensure high stability and cutting performance during horizontal well drilling. Several double-row cutting teeth 42 are arranged longitudinally on the surface of each second cutter wing 41 of the cutter wing mechanism 4. This double-row arrangement significantly increases the number of cutting points, enabling multi-point contact and staggered breaking of the bottom rock within the same cutter wing area, thus enhancing the rock-breaking effect. Optionally, the diameter of the second cutting teeth is approximately 12mm. The larger cutting teeth, under the synergistic effect of the double rows, possess strong rock penetration capability and excellent wear resistance. The distributed force also extends the service life of the cutting teeth.

[0061] When the extension mechanism 3 is not extended, the cutter wing mechanism 4 works together with the negative inner cone angle cutter wing of the drill bit body to give the drill bit strong guidance and directional drilling capabilities. When the shear pin is sheared and the extension mechanism 3 is released, the cutter wing mechanism 4 extends and becomes the main cutting cutter wing, and the drill bit as a whole changes to a positive inner cone angle shape, completing the working condition switch from the directional drilling section to the horizontal section, ensuring that the drill bit has both directional drilling capability and long-distance horizontal drilling performance.

[0062] Furthermore, the working principle of this application is as follows: This directional drilling bit, capable of changing its inner cone angle, achieves segmented control of operating conditions by switching the inner cone angle from negative to positive. A negative inner cone angle enhances guidance and lateral cutting capabilities, rapidly establishing well inclination; switching to a positive inner cone angle suppresses lateral deflection and improves bit stability. Taking an example where both the first cutter wing 21 and the second cutter wing 41 have four blades, the details are as follows: During the directional drilling operation, the integrated four blades of the drill bit body serve as the main cutting blades, maintaining a negative inner cone angle under the first-level limiting action of the shear pin; combined with the near-full conical shape of the drill bit skirt 11 and the deep drainage groove 112 on the outer wall, it achieves high lateral cutting capability and high chip carrying capacity.

[0063] When transitioning to the horizontal section, a ball is dropped into the ball receiving seat 341. After the ball sits in the ball receiving seat 341, it blocks the main flow channel. The pump pressure in the well establishes itself in the upstream cavity of the extension mechanism 3 and applies a shear load to the shear pin, thereby shearing the shear pin and releasing the axial degree of freedom of the extension mechanism 3. The circumferential fluid inlet channel 342 of the ball receiving seat 341 is used to maintain circulation and supply fluid to the inner cavity of the extension mechanism 3 after the ball sits in place, so as to ensure the subsequent nozzle jet and cooling and chip removal. Under the stroke limitation of the stop boss 33 of the second-stage limit, the extension mechanism 3 extends outward along the axial direction in a fixed stroke. The positioning connecting block 3112 on its outer wall cooperates with the connecting groove 4111 on the cutter wing mechanism 4 to reliably transmit the axial displacement of the extension mechanism 3 to the cutter wing mechanism 4, so that the cutter wing mechanism 4 undergoes synchronous outward displacement relative to the drill bit body and turns into the main cutting blade, realizing the overall working state of the drill bit from negative inner cone angle to positive inner cone angle. After the ball is dropped, the drilling fluid passes through the inlet channel 342, the inner cavity of the extension mechanism 3, and the lower nozzle 3121 to form a series fluid passage. A high-speed jet is formed at the nozzle 3121 to cool the cutting teeth and flush the bottom of the well to ensure cuttings are carried.

[0064] To ensure safety, the extension mechanism 3 is equipped with three levels of limiting: shear pin limiting, stop boss 33 limiting, and limiting ring 34 end face safety limiting; under extreme working conditions, the limiting ring 34 end face provides the final termination capability. This application controls the contact area between the drill bit and the well wall and the anisotropy of the drill bit by switching the inner cone angle. By switching the positive and negative inner cone angle, it can first complete the short-radius well directional drilling operation in one drilling run, and then complete the stable and efficient horizontal section drilling. This significantly reduces the number of tripping operations and lowers the overall construction cost, while ensuring well bottom cleanliness and structural reliability.

[0065] Furthermore, this application also provides a drilling method using the aforementioned short-radius well-changeable internal cone angle forced directional drilling PDC drill bit. The drilling method includes: With the shear pin not cut off, the blade structure 2 is used as the main cutting blade for skew drilling; By throwing a ball to press down, the shear pin is cut off, and the extension mechanism 3 is pushed downward, so that each second cutter wing 41 moves downward and extends each first cutter wing 21, so that the effective contact area between the second cutter wing 41 and the bottom of the well is greater than the effective contact area between the first cutter wing 21 and the bottom of the well; the extended cutter wing mechanism 4 is used as the main cutting cutter wing for horizontal drilling.

[0066] This drilling method uses the aforementioned short-radius well-adjustable internal cone angle-controlled PDC drill bit. By changing the internal cone angle of the drill bit, the contact area between the drill bit and the well wall can be altered, thereby changing the working performance of the drill bit. This ensures that the drill bit can complete the directional drilling and horizontal drilling operations in one trip, reducing the number of trips and lowering construction costs.

[0067] In summary, the high-inclination PDC drill bit and drilling method of this application are particularly suitable for short-radius wells (inclination radius of only 3-5m, inclination rate > 300° / 30m, horizontal section length > 50m), and have the following advantages: (1) Extensibility of the blade mechanism 4: The blade mechanism 4, through the outward extension action of the extension mechanism 3, enables the drill bit to have different inner cone angles in the directional drilling stage and the horizontal drilling stage.

[0068] (2) Controllable switching mechanism of inner cone angle: By switching from negative inner cone angle to positive inner cone angle in a one-way phase, the contact area between the drill bit and the well wall can be effectively adjusted, the different working effects of the drill bit in the process of directional drilling and horizontal drilling can be optimized, and the seamless switching between the strong directional drilling stage and the horizontal drilling stage can be achieved, reducing the number of tripping and running, and improving the utilization rate of the drill bit.

[0069] (3) Three-level limit protection of extension mechanism 3: The extension mechanism 3 adopts a three-level limit structure (shear pin limit, stop boss 33 limit, limit ring 34 end face limit) to ensure the stability and safety of extension mechanism 3 under different working conditions and avoid excessive displacement and structural instability during the extension process.

[0070] (4) Anisotropy of cutting teeth: During directional drilling, small-diameter cutting teeth are used on the main blade of the drill bit body to enhance rock intrusion ability and guidance; during horizontal drilling, the blade mechanism 4 uses larger diameter cutting teeth to improve wear resistance and bottom hole coverage effect, and adopts double-row tooth arrangement, and improves the cutting efficiency and bottom hole coverage by radial staggered arrangement.

[0071] (5) Hydraulic drive and shear control: The combination of hydraulic drive triggering and shearing mechanism ensures that the drill bit can switch the inner cone angle as needed and achieve stable extension during operation, thereby improving the automation and accuracy of the operation.

[0072] The above are merely illustrative embodiments of the present invention and are not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A forced directional drilling (PDC) bit for short-radius wells with adjustable inner cone angle, characterized in that, include: The drill bit body includes a drill bit cylinder and a cutter wing structure. The inner cone angle of the cutter wing structure is a negative inner cone angle. The cutter wing structure includes a plurality of first cutter wings arranged circumferentially. The upper end of each first cutter wing is connected to the lower part of the drill bit body. The lower ends of each first cutter wing are connected to each other. An interval groove that can communicate with the drill bit body is formed between two adjacent first cutter wings. An extension mechanism is axially movable within the drill bit barrel and can be connected to the cutter wing structure via a shear pin. The cutter wing mechanism has an inner cone angle that is positive. The cutter wing mechanism includes a plurality of second cutter wings arranged circumferentially at intervals. Each second cutter wing is disposed in a corresponding interval groove and can be connected to the extension mechanism. When the shear pin is not cut, the bottom of each second cutter wing is located above the bottom of the first cutter wing. When the shear pin is cut, the extension mechanism can move downward along the axial direction of the drill bit body, causing each second cutter wing to move downward so that the bottom of each second cutter wing extends out of the bottom of each first cutter wing.

2. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 1, characterized in that, The extension mechanism includes a plurality of extension blocks spaced circumferentially, with slots formed between adjacent extension blocks, and the plurality of extension blocks are connected by a connecting component to form a whole; each extension block can be axially movably inserted into a corresponding slot, each first blade can be inserted into a corresponding slot and connected to the corresponding extension block through the shear pin, and each second blade can be fixedly connected to the corresponding extension block.

3. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 2, characterized in that, Each of the extension blocks has a positioning connecting block on its lower outer wall, and each of the second blades has a connecting groove on its inner wall. The positioning connecting block can be inserted and fixed in the corresponding connecting groove.

4. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 2, characterized in that, Each of the extension blocks has a pin fixing groove on its upper sidewall for inserting and fixing the shearing pin; each of the second blades has a pin placement groove on its top sidewall that connects to its top surface, and the head of the shearing pin can be inserted into the pin placement groove from the top surface of the corresponding second blade.

5. The short-radius well-adjustable inner cone angle-modifying PDC drill bit as described in claim 2, characterized in that, The connecting assembly includes multiple stop bosses, which are connected between the upper sidewalls of two adjacent extension blocks; when the shear pin is not cut, there is a gap between the top surface of the first blade and the corresponding stop boss; when the shear pin is cut, the stop boss can abut against the top surface of the corresponding first blade.

6. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 5, characterized in that, Each of the extension blocks has a slot on its upper inner side, and each slot is interconnected with each slot. The upper center of the blade structure also has a hollow receiving cavity with a top opening, and the hollow receiving cavity is connected to each of the interval slots. The connecting assembly also includes a limiting ring, which is disposed in each of the slots and connected to the slot wall of each slot. Each stop boss is located outside the limiting ring, and the bottom surface of the limiting ring is located below the bottom surface of the stop boss. When the shear pin is cut off, the bottom surface of the limiting ring can abut against the bottom surface of the hollowed-out receiving cavity after the stop boss fails.

7. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 6, characterized in that, Each of the empty slots has an inner bottom that extends upward to form a guide block. When the extension mechanism is in a downward state, the guide block can slide along the side of the corresponding first blade.

8. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 2, characterized in that, Each extension block is also provided with a liquid passage that runs vertically through it. The extension mechanism also includes a ball receiving seat connected to the upper part of each extension block for supporting the ball after it is thrown. The ball can block part of each liquid passage after it sits on the ball receiving seat.

9. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 8, characterized in that, The extension block includes a hollow structure formed by arc-shaped side plates and arc-shaped bottom plates connected vertically from top to bottom. The ball receiving seat is connected to the upper part of each arc-shaped side plate. The ball receiving seat has a liquid inlet channel corresponding to the position of each arc-shaped bottom plate. Multiple spray holes are formed on each arc-shaped bottom plate. The liquid inlet channel corresponding to the arc-shaped bottom plate, the cavity of the hollow structure, and the spray holes corresponding to the arc-shaped bottom plate constitute the liquid passage on the extension block.

10. The short-radius well-adjustable inner cone angle-modifying PDC drill bit as described in claim 9, characterized in that, The diameter of the liquid inlet channel is larger than the diameter of the spray nozzle.

11. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 1, characterized in that, The drill bit body includes a drill bit skirt and a body ring that are detachably connected vertically, and the upper end of each of the first cutter wings is connected to the lower part of the body ring.

12. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 11, characterized in that, An annular step is provided on the lower inner wall of the drill bit skirt, and the top surface of the extension mechanism can abut against the annular step.

13. The short-radius well-adjustable inner cone angle-modifying PDC drill bit as described in claim 11, characterized in that, The outer wall of the drill bit skirt is provided with multiple drainage grooves spaced apart circumferentially.

14. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 11, characterized in that, The outer diameter of the drill bit skirt gradually decreases from bottom to top.

15. The short-radius well-adjustable inner cone angle-modifying PDC drill bit as described in claim 1, characterized in that, The negative inner cone angle is -5° to -15°, and the positive inner cone angle is 12° to 24°.

16. The short-radius well-adjustable inner cone angle PDC drill bit as described in claim 1, characterized in that, The outer surface of the first blade has a plurality of first cutting teeth arranged longitudinally, and the outer surface of the second blade has a plurality of sets of double-row cutting teeth arranged longitudinally. Each set of double-row cutting teeth includes two second cutting teeth arranged side by side, and the diameter of the first cutting teeth is smaller than the diameter of the second cutting teeth.

17. A drilling method, characterized in that, Drilling is performed using the short-radius well-adjustable internal cone angle-modifying PDC drill bit as described in claim 16, the drilling method comprising: With the shear pin not cut off, the blade structure is used as the main cutting blade for skew drilling; The shear pin is cut by throwing a ball to press down, and the extension mechanism is pushed to move downward, so that each of the second cutter wings moves downward and extends each of the first cutter wings, so that the effective contact area between the second cutter wings and the bottom of the well is greater than the effective contact area between the first cutter wings and the bottom of the well; the extended cutter wing mechanism is used as the main cutting cutter wing for horizontal drilling.

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