A concave PDC drill bit

Abstract

This invention provides a concave PDC drill bit, comprising: a drill bit body; and concave cutting wings evenly distributed on the drill bit body; wherein the crown portion of the concave cutting wings is constructed as a continuously connected outer cone portion, an arc-shaped crown top, and an inner cone portion, the outline of the outer cone portion is formed as an outwardly convex first curve, and the outline of the inner cone portion is formed as an inwardly concave second curve, the center of the first curve and the center of the outline curve of the arc-shaped crown top are on the same side, and the center of the second curve and the center of the outline curve of the arc-shaped crown top are on opposite sides of the crown outline line of the concave cutting wings.

Description

Technical Field

[0001] This invention belongs to the field of drilling tool technology, and specifically relates to a concave PDC drill bit. Background Technology

[0002] As drilling depth increases, drilling difficulty also increases, placing higher demands on drill bits. In complex and difficult-to-drill formations such as hard formations, mixed hard and soft formations, and gravel formations, PDC drill bits experience low drilling speeds, rapid failures, and limited footage. In high-hardness, highly abrasive formations, the concave cutter wings are prone to wear and damage at their crowns, and the cutting teeth are susceptible to wear and impact damage, resulting in short drill bit life and poor stability during drilling, thus affecting drilling efficiency and effectiveness.

[0003] In practical applications, achieving axial force balance on the cutting teeth of conventional PDC drill bits is difficult. The instantaneous rotation center point of the drill bit, formed by the inner cone end of the concave cutter blade, is prone to lateral displacement, causing the drill bit to spin and resulting in lateral vibration. This leads to rapid wear of the cutting elements. Due to this lateral vibration, the cutting teeth at the crown of the concave cutter blade in conventional PDC drill bits are susceptible to significant impact and breakage. The large load on the crown also causes premature wear and failure of the drill bit. Furthermore, when drilling in steep rock formations or other formations prone to drill bit tilting, maintaining a stable tilt rate and efficiency is not guaranteed. Summary of the Invention

[0004] To address the technical problems described above, this invention aims to provide a concave PDC drill bit. During drilling, this concave PDC drill bit can form a core column in the core area, thereby effectively limiting the lateral vibration and vortex of the concave PDC drill bit, greatly improving its working stability. Furthermore, this concave PDC drill bit can effectively avoid tooth breakage and excessive wear in the core and inner cone areas, which is very beneficial for extending its service life.

[0005] To this end, the present invention provides a concave PDC drill bit, comprising: a drill bit body; and concave cutting wings evenly distributed on the drill bit body; wherein the crown portion of the concave cutting wings is configured as a continuously connected outer cone portion, an arcuate crown top portion, and an inner cone portion, the outline of the outer cone portion is formed as an outwardly convex first curve, the outline of the inner cone portion is formed as an inwardly concave second curve, the center of the first curve is on the same side as the center of the outline curve of the arcuate crown top portion, and the center of the second curve is on both sides of the crown outline line of the concave cutting wings.

[0006] In one embodiment, the radii of curvature of the contour curve at the top of the arc-shaped crown, the second curve, and the first curve increase progressively.

[0007] In one embodiment, the diameter of the inner cone is set to be in the range of one-third to two-thirds of the diameter of the drill bit body, and the axial extension dimension of the inner cone is set to be in the range of one-fifth to one-third of the diameter of the drill bit.

[0008] In one embodiment, a plurality of cutting teeth are provided on the working end face of the concave blade.

[0009] In one embodiment, the diameter-maintaining section of the concave blade and the outer cone are connected by a transitional connection formed by a conical surface.

[0010] In one embodiment, a plurality of the cutting teeth extend along the diameter-maintaining section, the outer cone, the top of the arc-shaped crown, the inner cone, and the arc-shaped transition zone.

[0011] In one embodiment, the apex of each cutting tooth is higher than the corresponding contour line of the concave blade.

[0012] In one embodiment, the cutting teeth are triangular teeth.

[0013] In one embodiment, the recessed portion is provided with a water outlet.

[0014] In one embodiment, a nozzle is provided on the drill bit body and between adjacent concave blades.

[0015] Compared with the prior art, the advantages of this application are:

[0016] During drilling operations, the concave PDC drill bit of the present invention penetrates the formation and forms a core column in the inner conical region of the concave blades. The inward-curving inner conical structure and the core column effectively limit the lateral vibration and vortex of the concave PDC drill bit, significantly improving its operational stability. Simultaneously, the concave PDC drill bit utilizes the concave blade structure to achieve annular pre-fracture of the formation at the bottom of the well, disrupting the bottom-well stress balance and reducing the difficulty of formation fracturing. This enables large-volume fracturing in the core column region, resulting in brittle fracture, effectively reducing the rock-breaking energy and significantly improving the mechanical drilling rate of the concave PDC drill bit. The inner and outer conical sections of the concave blades of the concave PDC drill bit employ a densely spaced triangular PDC tooth design, significantly improving the impact resistance and silica agglomerate fracturing capability of the concave PDC drill bit. In addition, this concave PDC drill bit can effectively avoid tooth breakage and excessive wear in the core and inner cone areas, which is very beneficial to improving its service life. Attached Figure Description

[0017] The invention will now be described with reference to the accompanying drawings.

[0018] Figure 1The structure of the concave PDC drill bit according to the present invention is schematically shown.

[0019] Figure 2 schematically shown Figure 1 The concave blade structure of the concave PDC drill bit is shown.

[0020] Figure 3 The outline shape of the concave blade is schematically shown.

[0021] Figure 4 The distribution structure of the cutting teeth is schematically shown.

[0022] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0023] The invention will now be described with reference to the accompanying drawings.

[0024] For ease of understanding, in this application, the end of the concave PDC drill bit closest to the wellhead during wellbore operation is defined as the upper end, upstream end, or similar terminology, while the end furthest from the wellhead is defined as the lower end, downstream end, or similar terminology. Furthermore, the direction along the length of the concave PDC drill bit is referred to as the longitudinal direction, axial direction, or similar terminology, while the direction perpendicular to it is referred to as the transverse direction, radial direction, or similar terminology.

[0025] Figure 1 The structure of the concave PDC drill bit 100 according to the present invention is schematically shown. For example... Figure 1 As shown, the concave PDC drill bit 100 includes a drill bit body 1 and concave cutter wings 2 evenly distributed on the drill bit body 1. Multiple concave cutter wings 2 are provided and evenly spaced in the circumferential direction. One end of the drill bit body 1 is provided with a connecting joint for connecting other drilling tools. Figure 2 In the illustrated embodiment, there are five concave blades 2. One of the concave blades 2 extends radially inward to the central axis of the drill bit body 1.

[0026] According to the present invention, such as Figure 3 As shown, the crown of the concave blade 2 is constructed as a continuously connected outer cone 21, an arc-shaped crown top 22, and an inner cone 23. The outline of the outer cone 21 is formed as a first curve that convexes outward, and the outline of the inner cone 23 is formed as a second curve that concave inward. The center of the first curve is on the same side as the center of the outline curve of the arc-shaped crown top 22, and the center of the second curve is on both sides of the crown outline of the concave blade 2. Thus, the crown outline of the concave blade 2 is formed as three continuously connected smooth curves.

[0027] The radii of curvature of the contour curve of the top 22 of the arc-shaped crown, the second curve formed by the contour of the inner cone 23, and the first curve formed by the contour of the outer cone 21 increase progressively.

[0028] like Figure 3 As shown, the top 22 of the arc-shaped crown extends downward along the axial direction, which is beneficial for drilling extension and ensures continuous drilling of the drill bit during the drilling process. The outer cone 21 forms a slightly convex arc surface, which facilitates the stability of the drill bit during drilling and makes orientation easier. The inner cone 23 forms a slightly concave arc surface, which not only facilitates the removal of rock debris but also helps to form a core column protrusion in the drill bit core using the concave inner cone structure, thereby helping to limit the lateral vibration of the drill bit and improve the working stability of the drill bit. Figure 3 The dotted line in the text refers to the central axis of the concave PDC drill bit 100.

[0029] According to the present invention, the diameter of the inner cone portion 23 of the concave blade 2 is set within the range of one-third to two-thirds of the diameter of the drill bit body 1. This size range ensures that the drill bit has moderate attack power and stability, and forms a large core column protrusion. The axial extension dimension of the inner cone portion 23 is set within the range of one-fifth to one-third of the drill bit diameter. This size setting ensures both the structural strength of the concave blade of the drill bit and the sufficient height of the core column protrusion to release ground stress. Because the inner cone portion 23 is formed into an inwardly concave structure, during drilling operations, the concave PDC drill bit 100 penetrates the formation and forms a core column in the region of the inner cone portion 23 of the concave blade. On the one hand, the inwardly concave structure of the inner cone portion 23 and the core column can effectively limit the lateral vibration and vortex of the concave PDC drill bit 100, greatly improving the working stability of the concave PDC drill bit 100. On the other hand, the high-stress fracture of the formation at the crown of the concave blade 2 and the release of in-situ stress by the irregular bottom-hole morphology are achieved by utilizing the concave blade structure of the crown to achieve annular early fracture of the formation at the bottom of the well, break the stress balance at the bottom of the well, and reduce the difficulty of formation fracture. This allows the concave PDC bit 100 to achieve large-volume fracture in the core column area, forming a brittle collapse phenomenon, effectively reducing the rock breaking energy and significantly improving the mechanical drilling rate of the concave PDC bit 100.

[0030] Furthermore, the diameter-protecting section 6 of the concave blade 2 and the outer cone portion 21 are connected by a conical surface 7. The outer diameter of the diameter-protecting section 6 is larger than the maximum outer diameter of the outer cone portion 21.

[0031] According to the present invention, such as Figure 2 As shown, multiple cutting teeth 5 are provided on the working end face 20 of the concave blade 2. The working end face 20 here refers to the side wall end face of the concave blade 2 that contacts the formation rock when the concave PDC drill bit 100 is rotating and drilling, that is, the side end face along the rotation direction of the drill bit.

[0032] like Figure 4 As shown, multiple cutting teeth 5 extend and are distributed along the diameter-maintaining section 6, the outer cone portion 21, the arc-shaped crown top 22, the inner cone portion 23, and the arc-shaped transition zone 4. Preferably, the multiple cutting teeth 5 are evenly spaced apart. Furthermore, each cutting tooth 5 is installed pointing towards the rotation direction of the concave PDC drill bit 100. This structure is highly beneficial for improving the working effect and drilling efficiency of the concave PDC drill bit 100.

[0033] The apex of each cutting tooth 5 is set higher than the corresponding contour line of the concave blade 2, which is beneficial for the cutting tooth 5 to cut and break rocks, and at the same time, it is beneficial to protect the contour surface of the concave blade 2.

[0034] According to one embodiment of the present invention, the cutting teeth 5 are triangular teeth. Preferably, the outer cone portion 21 and inner cone portion 23 of the concave blade 2 of the concave PDC drill bit 100 adopt a dense triangular PDC tooth distribution design. Compared with conventional drill bits with the same tooth density design, this structure of the concave PDC drill bit 100 results in a faster mechanical drilling speed and higher rock breaking specific power, which can significantly improve drilling efficiency and is very beneficial to improving the impact resistance and silica agglomeration breaking ability of the concave PDC drill bit 100.

[0035] According to the present invention, the drill body 1 of the concave PDC drill bit 100 is also provided with a water outlet (not shown). Preferably, the water outlet is disposed between adjacent concave blades 2.

[0036] like Figure 2 and Figure 4 As shown, the drill bit body 1 is also equipped with nozzles 8, and multiple nozzles 8 are provided, with each nozzle 8 positioned between adjacent concave cutter wings 2. The nozzles 8 can spray cleaning fluid during drilling to clean the cutting teeth 5 in real time. This helps prevent the drill bit from getting stuck, greatly ensuring the continuous drilling operation and thus guaranteeing drilling efficiency.

[0037] During drilling operations, the concave PDC drill bit 100 of the present invention penetrates the formation and forms a core column in the inner cone region 23 of the concave blade 2. The inwardly concave inner cone structure and the core column effectively limit the lateral vibration and vortex of the concave PDC drill bit 100, greatly improving its operational stability. Simultaneously, the concave PDC drill bit 100 utilizes the crown-protruding concave blade structure to achieve annular pre-fracture of the formation at the bottom of the well, disrupting the bottom-well stress balance and reducing the difficulty of formation fracturing. This results in large-volume fracturing in the core column region, forming a brittle fracture phenomenon, effectively reducing the rock-breaking energy and significantly improving the mechanical drilling rate of the concave PDC drill bit 100. The concave PDC drill bit 100 features a concave blade 2 with a densely packed triangular PDC tooth design in its inner cone 23 and outer cone 21, significantly improving its impact resistance and silica agglomeration breaking ability. Furthermore, this concave PDC drill bit 100 effectively avoids tooth breakage and excessive wear in the core and inner cone areas, greatly extending its service life.

[0038] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] Furthermore, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A concave PDC drill bit, comprising: Drill bit body (1); Concave blades (2) are evenly distributed on the drill bit body; The crown of the concave blade is constructed as a continuously connected outer cone (21), an arc-shaped crown top (22), and an inner cone (23). The outer cone (21) has an outwardly convex first curve, and the inner cone (23) has an inwardly concave second curve. The center of the first curve and the center of the contour curve of the arc-shaped crown top (22) are on the same side of the crown contour line of the concave blade (2). The center of the second curve and the center of the contour curve of the arc-shaped crown top (22) are on opposite sides of the crown contour line of the concave blade (2). The contour curve of the top of the arc-shaped crown (22), the second curve, and the radius of curvature of the first curve increase progressively. The diameter of the inner cone (23) is set to be in the range of one-third to two-thirds of the diameter of the drill body (1). The axial extension dimension of the inner cone (23) is set to be in the range of one-fifth to one-third of the diameter of the drill body (1).

2. The recessed PDC bit of claim 1 wherein, Multiple cutting teeth (5) are provided on the working end face (20) of the concave blade (2).

3. The concave PDC drill bit according to claim 2, characterized in that, The concave blade (2) has a diameter-protecting section (6) and the outer cone (21) connected by a conical surface (7).

4. The concave PDC drill bit according to claim 2, characterized in that, The apex of each of the cutting teeth (5) is higher than the corresponding contour line of the concave blade (2).

5. The concave PDC drill bit according to claim 2, characterized in that, The cutting teeth (5) are triangular teeth.

6. The concave PDC drill bit according to claim 1, characterized in that, Water outlet holes are provided between adjacent concave blades (2).

7. The concave PDC drill bit according to claim 1, characterized in that, A nozzle (8) is provided on the drill bit body (1) and between adjacent concave blades (2).

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