PDC (Polycrystalline Diamond Compact) drill bit for preventing coring in complex and difficult-to

Abstract

The invention provides an anti-coring PDC drill bit for a complex and difficult-to-drill stratum, and belongs to the technical field of drilling tools, the anti-coring PDC drill bit comprises a drill bit body, a drill bit joint and PDC cutting teeth, a groove is formed in a main blade of the drill bit, and teeth are distributed on the groove. The blade is characterized in that the position of the groove is determined according to the position of the main blade corresponding to the first cutting tooth of the auxiliary blade. Due to the fact that the number of teeth distributed at the inner cone position of the main blade is small, compared with teeth of a crown-outer cone part, cutting teeth of the inner cone part are large in stress, in a high-abrasiveness or heterogeneity stratum, abrasion of rock at the center of the well bottom to the blade body easily causes falling off of a polycrystalline diamond layer or tooth breakage of the cutting teeth at the center, and the cutting teeth are damaged. And therefore, the inner cone part is easy to have a hollow-out phenomenon. The grooves are formed in the main blades, and the teeth are distributed in the grooves, so that the tooth distribution density can be increased; and in addition, the situation that the cutting teeth at the inner cone position on the main blade are stressed greatly is obviously reduced, and the coring phenomenon is reduced.

Description

Technical Field

[0001] The present invention relates to the technical fields of oil and gas drilling engineering, mining engineering, geological drilling, tunnel engineering, and the like, and in particular to the technical field of PDC drill bits, specifically a PDC drill bit that is anti-coring in complex and difficult-to-drill formations. Background Art

[0002] Polycrystalline Diamond Compact (PDC) drill bits, or PDC drill bits, have developed rapidly since their successful manufacture and use in the early 1970s. They are now widely used in various oil and gas industries, geological industries, and other industries around the world.

[0003] Natural diamonds were first used as a primary tool for geological exploration. Diamond, as we all know, is the hardest material in nature and therefore possesses numerous exceptional properties not found in other materials, such as a low coefficient of expansion, a very high elastic modulus, extremely high chemical stability, great wear resistance, and excellent thermal conductivity. However, the low production and high price of natural diamonds make geological exploration expensive. Furthermore, artificially synthesizing large diamond particles is difficult.

[0004] To address this problem, polycrystalline diamond compacts (PCDs) emerged. They were developed based on the research and theoretical foundations of synthetic diamond and polycrystalline diamond. PCDs are made by sintering diamond powder and a metal or non-metallic binder onto a cemented carbide substrate using a high-temperature, high-pressure synthesis method. PCDs combine the performance advantages of both the carbide substrate and PCD. They possess the exceptionally high wear resistance and hardness of PCD, while also offering the relatively good weldability and fracture toughness of the carbide substrate. Cobalt (Co), as an important catalyst and binder, significantly impacts the performance of PDC teeth during the synthesis process. During the synthesis process, Cobalt catalyzes the bonding between diamond particles under high temperature and high pressure. It helps form stable chemical bonds between diamond particles, thereby improving the hardness and durability of the PDC teeth. The cobalt content has a direct impact on the quality of the PDC sintered compact. An appropriate amount of Cobalt promotes uniform distribution and tight bonding of diamond particles, resulting in a high-quality sintered compact. However, too much or too little cobalt content may lead to a decrease in the quality of the sintered body and affect the performance of the PDC tooth.

[0005] As global oil and gas exploration and development expands into deeper, unconventional reservoirs, the formations in these areas are characterized by poor drillability, high abrasiveness, and strong heterogeneity. PDC drill bits in these formations have low average rotational speeds, low footage, and short lifespans, requiring frequent bit tripping and untripping, which severely restricts the development of oil and gas exploration. Furthermore, field applications have shown that many drill bits, especially larger ones, are prone to polycrystalline diamond (PCD) layer shedding or chipping at the inner cone, and in severe cases, even cutting tooth loss. Once cutting tooth loss occurs, blade sharpening begins. If this is not detected and continued use occurs, the blades on the inner cone section of the drill bit will be worn away.

[0006] In highly abrasive formations, the PDC cutters on drill bits typically reach high temperatures. Because cobalt acts as a catalyst for diamond, it accelerates the transformation of diamond into graphite at atmospheric pressure and high temperatures, disrupting the diamond-diamond bond and causing a sharp decline in PDC performance. Furthermore, the significant difference in thermal expansion coefficients between cobalt and diamond creates thermal stress and microcracks in the PDC's diamond layer at high temperatures. This can lead to the PDC cutter becoming susceptible to shedding of the polycrystalline diamond layer or chipping under external forces.

[0007] Radial tooth arrangement is the first step in designing a PDC drill bit, which determines the rock breaking efficiency and service life of the PDC drill bit. Figure 2 As shown in the figure, in the inner cone section, because the cutters in the center of the drill bit experience less wear, only a small number of cutters are typically required to ensure that the cutter marks in the center completely cover the bottomhole. The crown-to-outer cone section is the primary wear zone, requiring a higher cutter density. In this case, cutters are placed on each blade. Compared to the crown-to-outer cone section, which has more cutters, the inner cone section has only a small number of main cutters to withstand the same cutting forces. Therefore, in highly abrasive and heterogeneous formations, tooth chipping or loss is more likely to occur. Once tooth loss occurs in the inner cone, the blades will be worn. In particular, drill bit coring can occur. This occurs when the rock-breaking capacity of the drill bit's center is unbalanced with that of the outer ring. This results in difficulty breaking rock in the center of the drill bit, while rock around the wellbore is more easily broken. This creates a columnar area of unbroken rock at the bottomhole, resembling a "heart" carved out of the rock. This can cause greater damage to the drill bit. Once the drill bit is damaged, it needs to be lifted and replaced, which has an adverse impact on the construction period and cost. Therefore, in order to reduce the wear of the drill bit and improve the drilling efficiency, the above-mentioned problem needs to be solved. Summary of the Invention

[0008] Based on the above engineering background, the present invention addresses the deficiencies in the prior art and provides a PDC drill bit that is anti-coring in complex and difficult-to-drill formations.

[0009] A PDC drill bit for preventing core-cutting in complex and difficult-to-drill formations comprises a drill bit body and a drill bit joint. The drill bit body is evenly distributed with multiple blades, a gauge surface is provided below the blades, and water holes are provided between the blades; grooves are opened on the main blades, and teeth are arranged in the grooves.

[0010] Furthermore, the size and shape of the groove are calculated according to Formula 1

[0011] Where, R represents the radial position of the groove, H represents the circumferential position of the groove; a , b is a constant that determines the size and shape of the groove. a and b Grooves (6) or bumps (8) of different sizes and shapes can be obtained; The spacing between the cutting teeth on the same blade determines the tooth density. r c The size of the teeth and d It is the straight-line distance from the center of the groove to the drill body.

[0012] Furthermore, the position of the groove is not fixed and is determined by the size of the drill bit and the position of the primary blade corresponding to the first cutting tooth of the secondary blade; Furthermore, the number of grooves is determined according to the number of main blades.

[0013] Furthermore, the size of the teeth in the groove can be consistent with the size of the cutting teeth of the main blade, or small-sized cutting teeth can be used to increase the tooth density in the groove; The type of cutting teeth in the groove can use conventional cylindrical teeth or special-shaped teeth.

[0014] Furthermore, in order to improve the rock breaking efficiency, double or multiple rows of teeth can be arranged on the basis of single row teeth.

[0015] Furthermore, in order to reduce the stress on the cutting teeth at the inner cone position, not only a groove can be opened, but also a convex block of the same size as the groove can be protruded here, and the teeth can be arranged on the convex block; Furthermore, the size and shape of the bump are also calculated according to Formula 1. The position is similar to the groove. The size and type of the teeth on the bump can be determined according to the on-site usage.

[0016] The present invention has the following advantages: For hard formations or those with sandwiched hard formations, conventional cutting teeth are prone to polycrystalline diamond layer shedding or tooth collapse, and in severe cases, the cutting teeth may fall off. By cutting grooves on the main blade, the stress of the cutting teeth on the inner cone part of the main blade is reduced, and the teeth can be arranged in the grooves, increasing the tooth arrangement density and reducing the occurrence of core-cutting.

[0017] In highly abrasive formations, compared to conventional tooth arrangement, grooves are opened on the main blade, and the cutting teeth that should be on the crown curve are distributed in the grooves, which increases the surface area of the blade, thereby increasing the contact and heat dissipation area, which can effectively alleviate the impact of temperature on the PDC cutting teeth in the inner cone part, greatly improving the service life of the drill bit and reducing the cost of use.

[0018] When facing heterogeneous formations with alternating soft and hard formations, grooves on the main blades can be stuck in the rock, which can suppress the lateral vibration and vortex of the drill bit, reduce the drilling pressure or the adverse effects of the rock during the cutting process, and improve the stability of the drill bit.

[0019] By creating grooves, the stress on the cutting teeth that should be on the crown curve is staggered, which improves the stress on the cutting teeth in the inner cone part and avoids the situation where some cutting teeth are subjected to greater stress and are easily damaged.

[0020] Compared with the groove, the bump can also withstand more cutting force, and at the same time distribute the cutting force from the crown curve to the bump, forming a staggered form, avoiding concentrated force on the inner cone part, and also avoiding the occurrence of core-out phenomenon; the protruding part can just be stuck in the rock, which can also prevent the drill bit from vibrating laterally. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention; Figure 2 This is a schematic diagram of radial tooth arrangement of a conventional PDC drill bit; Figure 3 This is a radial tooth arrangement diagram of the grooves on the three main blades of the present invention; Figure 4 Schematic diagram of radial tooth arrangement of the main blades of the present invention, in the order of the first main blade, the third main blade, and the fifth main blade; Figure 5 Schematic diagram of grooves of different sizes and shapes according to the present invention; Figure 6 This is a schematic diagram of the drill bit body structure of the present invention; Figure 7 A schematic diagram of assembling a small-sized cutting tooth according to the present invention; Figure 8 A schematic diagram of the three-dimensional structure of the special-shaped cutting teeth assembled in the present invention; Figure 9 Schematic diagram of the three-dimensional structure of multiple rows of cutting teeth of the present invention; Figure 10 This is a schematic diagram of the radial tooth arrangement on a main blade of the multi-row cutting teeth of the present invention.

[0022] Figure 11 It is a structural schematic diagram of another embodiment of the present invention.

[0023] Figure 12 This is a schematic diagram of the radial tooth arrangement of the main blade in another embodiment of the present invention.

[0024] In the picture: 1- Main cutting tooth anisotropic tooth; 11- Main cutting tooth conventional tooth; 2- Rear row anisotropic tooth; 21- Rear row conical tooth; 3- Gauge guard tooth; 31- Rear row gauge guard tooth; 4- Drill bit joint; 5- Drill bit body; 6- Groove; 7- Water hole; 8- Bump. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the embodiments. It should be noted that, in this document, words such as "upper" and "lower" are merely used to facilitate the description of the drawings and do not limit the directions in actual use, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0026] The specific description of the present invention is described below with reference to the accompanying drawings.

[0027] Example 1:

[0028] like Figure 1 As shown, a PDC drill bit for preventing core-cutting in complex and difficult-to-drill formations comprises a drill bit body 5 and a drill bit joint 4. The drill bit body is uniformly provided with a plurality of blades, each blade having a gauge surface, and water holes 7 are provided between the blades. Specifically, it is preferred to use 6 blades, including 3 main blades and 3 auxiliary blades, and the main blades and auxiliary blades are installed alternately. The main blades refer to the blades including the inner cone, crown top, outer cone, chamfer, diameter protection and other parts. They extend from the core of the drill bit to the diameter protection position. The tooth layout range includes the overall crown curve and is responsible for the main rock breaking and drilling work; the auxiliary blades play the role of assisting rock breaking and stabilizing the drill bit.

[0029] Example 2:

[0030] On the basis of embodiment 1, a groove 6 is opened at the inner cone position on the main blade, and teeth are arranged in the groove 6.

[0031] like Figures 2 to 4 As shown, in Figure 2 In conventional radial tooth arrangement, the position where the auxiliary blade cutting teeth begin to enter (i.e. Figure 2 The number of cutting teeth increases suddenly, which can easily cause the cutting teeth in the inner cone to bear greater cutting force, resulting in the shedding of the polycrystalline diamond layer or tooth collapse, and the occurrence of core hollowing. Therefore, the radial position of the groove is set at the position on the main blade corresponding to the start of the tooth arrangement of the auxiliary blade. Figure 3 A groove is opened on the main blade. However, since the position of the cutting teeth of each blade is arranged according to a certain principle, and in order to avoid the situation where the mounting grooves of the teeth on both sides of the groove on the main blade are cut off, which causes the cutting teeth to be unstable and easy to fall off, the position of the grooves 6 on different main blades is not fixed, such as Figure 3 As shown, in Figure 3 In the example, the teeth staggered distance between adjacent main blades is 6.66mm. In order to clearly see the distribution of the grooves on the main blade, the teeth on the main blade are extracted, as shown in the figure. Figure 4 shown.

[0032] The size and shape of the groove 6 or the convex ring 8 need to be calculated according to the following formula:

[0033] Where, R represents the radial position of the groove, H represents the circumferential position of the groove; a , b is a constant that determines the size and shape of the groove. a and b Grooves (6) or bumps (8) of different sizes and shapes can be obtained; The spacing between the cutting teeth on the same blade is preferably 3-6 mm. The formation hardness is proportional to the tooth density. r c The size of the teeth and r is the radius of the crown arc.

[0034] Position the groove between the cutting teeth. After determining the approximate position of the groove, one of the parameters a and b is fixed. You only need to adjust the other parameter to get different shapes, such as Figure 5 The size and shape of the groove are determined according to the above formula and , the size of the cutting teeth r c The straight-line distance from the center of the groove to the drill bodyd The cutting teeth are now commonly available in sizes of 11, 13.44, 15.88, 19, and 25.4. The straight-line distance from the center of the groove to the drill body is d- It is generally related to the drill bit design and is generally between 20 and 35 mm. In the present invention, d The value is 25mm. The size and depth of the grooves or bumps determine the tooth density within the grooves or bumps. When working in hard formations, the groove or bump size can be increased to increase the tooth density and extend the drill bit's service life. When working in soft formations, the groove or bump size can be decreased to reduce the tooth density and improve rock breaking efficiency.

[0035] In this embodiment, the size of the main cutting teeth is 15.88 mm, which is rounded to 16 mm. The spacing between the teeth is 4 mm. Combined with the radius of the crown arc, r , parameters a and b are selected to be the same size, that is, the size of the main cutting teeth plus the tooth spacing, which is , so the diameter of the groove is rounded to 40mm, and the size of the cutting teeth in the groove is 15.88mm.

[0036] Figure 4 The radial tooth layout diagrams correspond to the 1st, 3rd, and 5th main blades, respectively. With conventional radial tooth layout, only two cutting teeth can be placed at this location. However, after the grooves are added, the blade area is increased, allowing for three cutting teeth to be placed at this location. Three main blades can accommodate three more cutting teeth, increasing the tooth density and reducing the stress on the cutting teeth in the inner cone section.

[0037] Example 3:

[0038] The size of the cutting teeth in the groove can be the same as that of the cutting teeth on the main blade. In order to increase the drilling efficiency or the service life of the drill bit, different sizes of cutting teeth can be selected to increase or decrease the number of teeth in the groove, such as Figure 7 shown. Figure 7 In the embodiment, 11 mm conventional cylindrical teeth are used. On the basis of embodiment 1, one more cutting tooth can be arranged on each main blade, and three more cutting teeth are added to the entire drill bit.

[0039] For hard formations or highly abrasive formations, the cutting teeth are prone to polycrystalline diamond layer shedding or tooth collapse. At the same time, in order to improve the rock breaking efficiency, based on Example 1, the conventional cylindrical cutting teeth are replaced with special-shaped teeth, such as Figure 8As shown, this embodiment uses three-plane profiled teeth. The cutting teeth are the same size as the main cutting teeth, measuring 15.88 mm, and the tooth arrangement is the same as in Example 1. Profiled teeth are more suitable for hard rock, highly abrasive formations, or complex geological conditions (such as directional wells and highly deviated wells), significantly improving drilling efficiency and drill bit life. In extremely soft or plastic formations, the sharp cutting edges of the profiled teeth may produce a large amount of rock cuttings due to over-cutting, making chip removal more difficult and even causing drill bit balling.

[0040] Example 4:

[0041] At the same time, in order to increase the service life of the drill bit and adapt to complex formations, multiple rows of teeth can be arranged in the groove based on Example 1, such as Figure 9 As shown, two three-plane special-shaped teeth are arranged on the rear row. In this embodiment, the arrangement of the rear row teeth is as follows Figure 9 For simplicity, only the radial tooth arrangement of the first main blade is shown. The tooth arrangement of the rear rows of the other two main blades is similar. Using double rows of teeth can better improve rock breaking efficiency and cutting stability.

[0042] Figure 10 The rear row of teeth is 2mm lower than the front row and radially positioned between the two front row teeth. This allows them to participate in rock breaking even after the front row teeth wear. The rear row teeth are the same size as those on the main blade, measuring 15.88mm. Conventional cylindrical cutting teeth can also be used, and smaller sizes can be used. This increases the tooth density and increases the drill bit's lifespan, but this will reduce rock breaking efficiency. Therefore, the type and size of cutting teeth should be selected based on information such as the formation and the construction period.

[0043] Example 5:

[0044] On the basis of embodiment 1, not only a groove can be opened on the main blade of the inner cone section, but the groove can also be changed into a convex block, such as Figure 11 As shown, the bump can also withstand more cutting force, and at the same time distribute the cutting force from the crown curve to the bump, forming a staggered form, avoiding concentrated force on the inner cone part, and also avoiding the occurrence of core-out phenomenon; the protruding part can just be stuck in the rock, and can also avoid lateral vibration of the drill bit.

[0045] Tooth arrangement method Figure 12 As shown, the size and position of the protrusion are the same as the groove in Example 1, the size and spacing of the cutting teeth are the same as in Example 1, three 15.88 mm cutting teeth are used, the diameter of the protrusion is 40 mm, and the position of the protrusion on each main blade is different. In this embodiment, since the cutting tooth diameter d = 15.88 mm, it is rounded to 16 mm. =4mm, (d+ ) / 3 gives 6.66, so the offset distance is 6.66 mm. Similarly, to improve rock breaking efficiency, a special-shaped tooth structure can be used, as in Example 2. Alternatively, to increase the service life of the drill bit, a double-row tooth structure can be used, as in Example 3.

[0046] The size and shape of the bumps are calculated using Formula 1. Their placement is similar to that of the grooves. The size and type of teeth on the bumps can be determined based on field conditions. The teeth within the bumps can be arranged using smaller cutting teeth to increase their density. The calculation method is the same as for the grooves above: add the diameter d of the main cutting teeth to the tooth spacing. Simulation and experimental results show that using grooves increases service life by an average of 30% when using 15.88mm teeth. While bumps offer superior results, they are more expensive to manufacture and are more suitable for harder formations. The two have different application scenarios.

[0047] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A PDC drill bit for preventing core-cutting in complex and difficult-to-drill formations, comprising a drill bit body (5) and a drill bit joint (4), wherein a plurality of blades are evenly distributed on the drill bit body, the blades are provided with gauge surfaces, and water holes (7) are provided between the blades; the characteristics are: A groove (6) or a convex block (8) is provided at the inner cone position of some of the main blades, and teeth are arranged in the groove (6) or the convex ring (8), and the blade used for arranging teeth is a main blade, which is combined at the top end of the drill bit and covers the top of the drill bit; the main blades are separated by auxiliary blades so that the main blades are evenly distributed axially on the drill bit.

2. The PDC drill bit for preventing core-cutting in complex and difficult-to-drill formations according to claim 1, characterized in that: The size and shape of the groove (6) or the convex ring (8) are calculated according to the following formula 1: , where R represents the radial position of the groove, H represents the circumferential position of the groove; a , b is a constant, selected from the range of results obtained from formula 2, which determines the size and shape of the groove. a and b Grooves (6) or bumps (8) of different sizes and shapes can be obtained; The spacing between the cutting teeth on the same blade determines the tooth density. r c The size of the teeth and d is the straight-line distance from the center of the groove to the drill body; .

3. The PDC drill bit for preventing hollowing in complex and difficult-to-drill formations according to claim 2, characterized in that: The position of the groove (6) or the bump (8) on each main blade is not fixed and is determined according to the size of the drill bit and the position of the main blade corresponding to the first cutting tooth of the auxiliary blade.

4. The PDC drill bit for preventing core-cutting in complex and difficult-to-drill formations according to claim 3, characterized in that: The number of grooves (6) or protrusions (8) is determined according to the number of main blades, and only one groove (6) or protrusion (8) is provided on each main blade, and the positions of the grooves (6) or protrusions (8) provided on each main blade are staggered.

5. The PDC drill bit for preventing hollowing in complex and difficult-to-drill formations according to claim 4, characterized in that: The size of the teeth in the groove (6) or the protrusion (8) is consistent with the size of the conventional cutting teeth of the main blade, or small-sized cutting teeth are used, thereby increasing the tooth density in the groove.

6. The PDC drill bit for preventing hollowing in complex and difficult-to-drill formations according to claim 5, characterized in that: The cutting teeth in the groove (6) or the projection (8) use conventional cylindrical teeth or special-shaped teeth.

7. The PDC drill bit for preventing hollowing in complex and difficult-to-drill formations according to claim 5, characterized in that: In order to improve the rock breaking efficiency, double or multiple rows of teeth can be arranged on the basis of single row teeth.

8. The PDC drill bit for preventing hollowing in complex and difficult-to-drill formations according to claim 5, characterized in that: The main cutting teeth used are 15.88mm, the spacing between adjacent teeth is 4mm, and the straight line distance from the center of the groove to the drill body is d = 25 mm, parameters a and b are selected as 4mm, so the calculated radius of the groove is 20mm.

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