Drill string joint design
By optimizing the size design and material processing of the casing and sleeve sections, the reliability and lifespan issues of the drill string under bending and fatigue were solved, achieving high reliability and long lifespan for the drill string.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SANDVIK MINING & CONSTR TOOLS AB
- Filing Date
- 2021-09-16
- Publication Date
- 2026-07-21
AI Technical Summary
Existing drill pipes suffer from reduced reliability and lifespan due to bending and fatigue during use, especially when encountering hard rock formations or rock fissures, where material failure is likely to occur.
By optimizing the dimensional design of the casing and sleeve sections to correlate their maximum bending stress with that of the center rod section, and employing specific diameter ratios (C_sleeve > 2.0, C_casing > 0.6) to enhance the stiffness and bending resistance of the drill string, combined with appropriate materials and hardening treatments, effective flushing of drill cuttings is ensured.
It improves the reliability and lifespan of drill pipes, effectively copes with mechanical stress during drilling, and extends the service life of drill pipes.
Smart Images
Figure CN115989357B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to drill strings for use with drill bits used in percussion rock drilling. Specifically, this invention relates to improving the reliability and lifespan of such drill strings. Background Technology
[0002] Percussion drilling is used to form long boreholes via multiple elongated drill strings, which are joined end-to-end by interconnected male and female threaded ends. Established technology breaks rock through hammering impacts transmitted from a rock drill bit mounted at one end of the drill string towards the rock at the bottom of the borehole. Typically, the energy required to break the rock is generated by a hydraulically driven piston that contacts the end of the drill string (via a shank adapter) to generate a stress (or shock) wave that propagates through the drill string and ultimately to the rock. Conventional male and female threaded connections are described in US 4,332,502, US 4,398,756, US 4,687,368, and DE 2800887.
[0003] The male and female threaded ends of adjacent drill pipes are joined to form a drill string, and the joint typically withstands significant forces during drilling. These forces cause fatigue in the joint and lead to wear and breakage within the threaded portion of the joint. Typically, it is the threaded male spigot that fails, which determines the service life of the joint. US 6,767,156 discloses a threaded joint between two impact drill pipes having tapered guide surfaces located at the axially frontal ends of the male and female portions to attempt to achieve a secure connection and prevent damage to the threads.
[0004] The applicant's EP2845992B1 aims to mitigate the aforementioned disadvantages.
[0005] One known problem with drill string joint design is failure due to bending originating from non-straight holes. This can lead to breakage within the casing or sleeve section, thus reducing the reliability and lifespan of the drill string.
[0006] Therefore, a drill string joint design is needed that reduces stress and increases bending resistance, thereby improving the reliability and lifespan of the drill string. Summary of the Invention
[0007] The object of the present invention is to provide a drill string that has improved reliability and lifespan. According to a first aspect of the invention, this object is achieved by a drill string as defined in the appended independent claim 1, with alternative embodiments defined in the dependent claims. The drill string will form part of an assembly consisting of such connected drill strings. The drill string includes an elongated central rod portion extending axially between a male end and a female end. The central rod portion is a hollow cylinder, which is formed by an internal first diameter (d) 杆 ) and the outer second diameter (D 杆 The male end includes a casing, wherein the casing includes a base that projects axially from a shoulder that axially separates the casing and the center rod portion. The female end includes a sleeve portion configured for fitting into the casing. Similarly, the base has external threads, and the sleeve portion has internal threads, wherein the internal threads correspond to the external threads, such that the internal threads of the sleeve portion can attach to the external threads of the base of the casing of another drill string in the assembly. In the radial plane of the longitudinal axis of the drill string, the base of the casing is defined by an external third diameter (D). 套管 ) and the inner fourth diameter (d 套管 The sleeve portion is defined by the outer fifth diameter (D). 套筒 ) and the sixth internal diameter (d 套筒 This invention is limited to the outer second diameter (D). 杆 Drill string with a diameter between 30 mm and 60 mm, preferably between 40 mm and 60 mm. 套筒 and C 套管 Related to the diameter of the drill string, as defined by the following formula:
[0008]
[0009]
[0010] C 套筒 It should be greater than 2.0, or C. 套管 It should be greater than 0.6.
[0011] Technicians understand that diameters cannot be freely chosen. For example, the outer diameter of the casing is naturally limited by the inner diameter of the sleeve portion. Furthermore, the outer diameter of the sleeve portion is typically limited by the size of the drilled hole and the need for sufficient space between the sleeve portion and the inner wall of the hole to flush away drill cuttings that have passed through the sleeve portion. Similarly, the inner diameter of the casing limits the rate at which flushing fluid can be pumped through the drill string and therefore should not be too small. Drill string design is clearly a difficult balancing act, and this invention guides technicians in selecting combinations of parameters that reduce the risk of material failure in the drill string while maintaining consistent flushing performance. Solving this problem is far more difficult than it appears.
[0012] The inventors of this invention have recognized that drill string failure is due to a combination of increased stiffness in the central section and forced bending of the drill string caused by harder rock layers or cracks in the rock. The bending of the drill string occurs simultaneously with its rotation, resulting in additional stress due to the bending, and fatigue due to the continuous change in the bending axis caused by the rotation of the string in its bent state within the hole.
[0013] The proposed solution involves setting the dimensions of the sleeve and bushing portions such that the calculated maximum bending stress in the sleeve and bushing portions is related to the calculated maximum bending stress in the center rod portion, respectively. However, the inventors have recognized that the calculated maximum stresses in the bushing and bushing portions should not be equal to the calculated maximum bending stress in the center rod portion, but rather should be multiplied by a coefficient C by the calculated maximum bending stress in the center rod portion, respectively. 套筒 Or C 套管 This is relevant in order to account for common strength differences, such as those that may arise from localized material variations due to uneven hardening and / or processing during drill string manufacturing.
[0014] In some embodiments, C 套筒 > 2.0 and C 套管 > 0.6. This balance of the first, second, third, fourth, fifth, and sixth diameters involved provides high reliability and long service life for the drill string.
[0015] In some embodiments, the base of the sleeve is tapered.
[0016] In some embodiments, the base of the sleeve is cylindrical.
[0017] In some embodiments, the first diameter (d) 杆 The diameter is 30 mm, of which the second diameter (D) 杆 The diameter is 57 mm, of which the third diameter (D) 套管 The diameter is 48 mm, of which the fourth diameter (d) 套管 The diameter is 21 mm, of which the fifth diameter (D) 套筒 The diameter is 76 mm, and the sixth diameter (d) is 76 mm. 套筒 The value is 51 mm.
[0018] In some embodiments, the drill string is adapted for use with an outer seventh diameter (D) 孔 ( ) drill bits, where the fifth diameter < 0.90 Seventh diameter (D) 孔 ).
[0019] On the other hand, it relates to a system comprising a plurality of drill rods according to the first aspect described above.
[0020] In some embodiments, the drill string of the system is of the type described above, suitable for use with a seventh outer diameter (D). 孔 Used together with drill bits where the fifth diameter is < 0.90 Seventh diameter (D) 孔 ), and the system also includes a drill bit.
[0021] The difference in diameter between the outer diameters of the bore and the sleeve section allows for efficient flushing of drill cuttings through the sleeve section, while providing a robust and durable drill string capable of withstanding the forces involved.
[0022] In some embodiments, the seventh diameter is > 89 mm. The drill string has a second diameter between 30 mm and 60 mm, preferably between 40 mm and 60 mm, wherein the diameter is determined by C. 套筒 and C 套管 The specific limitations on the relevant diameter of the controlled drill string provide a robust and durable drilling system.
[0023] In some embodiments, the threads on the base and the threads on the sleeve portion are both straight.
[0024] In some embodiments, the threads on the base and the threads on the sleeve portion are both arc-shaped. Attached Figure Description
[0025] Figure 1 This shows a perspective view of two identical drill string rods connected together.
[0026] Figure 2 It shows, as Figure 1 The enlarged perspective view A shows the male end of the drill string.
[0027] Figure 3 It shows, as Figure 1 The diagram shows an enlarged perspective view B of the female end of a drill string, which is connected to the male end of another drill string.
[0028] Figure 4 It was also shown Figure 1 The image shows a cross-sectional side view of the sleeve portion and casing of the two connected drill string sections, the cross-section being cut in a plane passing through the longitudinal central axis of the drill string.
[0029] Figure 5 This shows the neutral point at the center of the hollow circle in the section modulus.
[0030] Detailed Implementation
[0031] Figures 1-4 A first embodiment of the invention is shown. As shown, multiple identical drill string rods 1, 1b can be connected to form a system / assembly 10. The drill string rod 1 includes an elongated central rod portion 2 extending axially between a male end 3 and a female end 4. Figure 4 As shown, the central rod portion 2 is a hollow cylinder, which consists of an internal first diameter d 杆 and the outer second diameter D 杆 Limited. The male end 3 includes a sleeve 5, and the sleeve 5 includes a base 6 projecting axially from a shoulder 7 that axially separates the sleeve 5 and the center rod portion 2. The female end 4 includes a sleeve / sleeve portion 8 configured to be fitted onto the sleeve 5. The base 6 is provided with external threads, and the sleeve portion 8 is provided with internal threads, wherein the internal threads correspond to the external threads, such that the internal threads of the sleeve portion 8 can be attached to the external threads of the base 6 of the sleeve 5 of another drill string of the assembly. In the radial plane P of the longitudinal axis of the drill string, the base 6 of the sleeve 5 is defined by an outer third diameter (D). 套管 ) and the inner fourth diameter (d 套管 The sleeve portion 8 is defined by the outer fifth diameter (D). 套筒 ) and the sixth internal diameter (d 套筒 (This is a limitation.) It should be noted that in... Figure 4 In the middle, D 套管 and d 套筒 They are all mentioned in conjunction with the same arrow, but their actual diameters are slightly different, with d being one of them. 套筒 Greater than D 套管 The scale of the attached diagram makes the difference in diameter appear... Figure 4 A single arrow cannot be used to show this. Although the diameter can vary along the lengths of the casing and sleeve portions separately, a radial plane P passing through both the casing and sleeve portions is used to define the relationship between the diameters in a clear manner, as needed. This invention is limited to drill strings with an outer diameter between 30 mm and 60 mm, preferably between 40 mm and 60 mm, such as drill bits with diameters of 54 mm to 127 mm. Therefore, the second diameter (D) 杆 The diameter is between 30 mm and 60 mm, preferably between 40 mm and 60 mm. 套筒 and C 套管 It can be derived from the diameter of the drill string and is related to the diameter of the drill string using the following formula.
[0032] These formulas are derived from the calculation of the section modulus of hollow cylindrical beams / structures, which provide a good approximation of the currently discussed cross-sectional shapes. Specifically, the equation for the section modulus of a hollow cylindrical cross-section is:
[0033]
[0034]
[0035]
[0036] Figure 5 This shows the neutral point at the center of the hollow circle in the section modulus.
[0037] We assume:
[0038] S 套管 = C 套管 S 杆
[0039]
[0040] And similarly, S 套筒 =C 套筒 S 杆
[0041]
[0042]
[0043] In this embodiment, the first diameter d 杆 It is 30 mm, of which the second diameter D 杆 It is 57 mm, of which the third diameter D 套管 It is 48 mm, of which the fourth diameter d 套管 It is 21 mm, of which the fifth diameter D 套筒 It is 76 mm, and the sixth diameter d 套筒 It is 51mm.
[0044] This embodiment of drill rods 1 and 1b is suitable for use with drill bits (not shown) having a specific diameter of 54 mm, 57 mm, 64 mm, 70 mm, 76 mm, 89 mm, 102 mm, 115 mm, or 127 mm (excluding drill bits). Because the drill bit protrudes radially, the actual diameter of the drilled hole is slightly larger. In other embodiments, the first to sixth diameters can be selected differently, as long as the second diameter D defines the outer diameter of the central rod portion 2. 杆 It meets the above-mentioned limit between 30 mm and 60 mm, and other diameters meet C. 套筒 Greater than 2.0 or C 套管 A limit greater than 0.6. Preferably, C 套筒 Greater than 2.0 and C 套管 Greater than 0.6.
[0045] The drill string is made of a suitable material (such as steel) and is hardened as needed.
[0046] The drill string 1, 1b is sized based on the size of the drill bit to which it will be used. However, sufficient space must be provided around the sleeve portion 8 to allow drill cuttings to be flushed through it. For this purpose, in some embodiments, the drill string 1, 1b can be adapted to be used with a drill bit having an outer seventh diameter D. 孔 The drill bit is used together, wherein the outer fifth diameter D of the sleeve portion 8. 套筒 Less than 0.90 Seventh diameter D 孔 .
[0047] Multiple identical drill strings 1, 1b can be supplied together as part of a system / assembly 10 consisting of drill strings 1, 1b. Alternatively, system 10 may include a drill bit. The drill strings 1, 1b of system 10 may have an outer seventh diameter D. 孔 The fifth diameter is < 0.90. Seventh diameter D 孔 The system also includes a drill bit.
[0048] The outer fifth diameter D of the hole and sleeve part 8 套筒 The difference in diameter between them allows for the effective flushing of drill cuttings through the sleeve section 8, while providing a robust and durable drill string 1, 1b capable of withstanding the forces involved.
[0049] In some embodiments, the seventh diameter D 孔 It can be 54 mm - 127 mm. As described above, the drill string of the present invention has a second diameter between 30 mm and 60 mm, preferably between 40 mm and 60 mm. (By C) 套筒 and C 套管 The specific limitations on the relevant diameters provided provide for a robust and durable system / component 10.
Claims
1. A drill string (1) for forming part of an assembly (10) consisting of such drill string (1, 1b) connected together, the drill string (1) comprising: The elongated central rod portion (2) extends axially between the male end (3) and the female end (4). The central rod portion (2) is a hollow cylinder, consisting of an inner first diameter d. 杆 and the outer second diameter D 杆 limited, The male end (3) includes a sleeve (5). The sleeve (5) includes a base (6) that protrudes axially from a shoulder (7) that axially separates the sleeve (5) from the central rod portion (2). The female end (4) includes a sleeve portion (8) configured to be fitted into the sleeve (5). The base (6) is provided with external threads, and the sleeve portion (8) is provided with internal threads. The internal thread corresponds to the external thread, such that the internal thread of the sleeve portion (8) can be attached to the external thread of the base (6) of the casing (5) of the other drill rod (1b) of the assembly (10). In the radial plane (P) of the longitudinal axis (9) of the drill string (1), the base (6) of the casing (5) is formed by an external third diameter D. 套管 and the fourth internal diameter d 套管 Limited, and the sleeve portion (8) is defined by an outer fifth diameter D 套筒 and the sixth internal diameter d 套筒 The second diameter D is defined as follows: 杆 Between 30 mm and 60 mm, where: in, And C 套筒 > 2.0 or C 套管 > 0.
6.
2. The drill string (1) according to claim 1, wherein, C 套筒 > 2.0 and C 套管 > 0.
6.
3. The drill string (1) according to any one of claims 1 to 2, wherein, The base (6) of the sleeve (5) is tapered.
4. The drill string (2) according to any one of claims 1 to 2, wherein, The base (6) of the sleeve (5) is cylindrical.
5. The drill string (1) according to claim 1 or 4, wherein, The first diameter d 杆 The second diameter D is 30 mm. 杆 It is 57 mm, wherein the third diameter D 套管 It is 48 mm, wherein the fourth diameter d 套管 It is 21 mm, wherein the fifth diameter D 套筒 It is 76 mm, and the sixth diameter d is mentioned. 套筒 It is 51 mm.
6. The drill string (1) according to any one of claims 1 to 2, wherein, The drill string (1) is suitable for use with an external seventh diameter D 孔 The drill bit is used together, wherein the fifth diameter D 套筒 < 0.90 The seventh diameter D 孔 .
7. A drilling system (10) comprising a plurality of drill rods (1, 1b) according to any one of the preceding claims.
8. The drilling system (10) according to claim 7, wherein, The drill string (1) is suitable for use with an external seventh diameter D 孔 The drill bit is used together, wherein the fifth diameter D 套筒 < 0.90 The seventh diameter D 孔 The system (10) includes the drill bit.
9. The drilling system (10) according to claim 8, wherein, The seventh diameter (D) 孔 The value is 54 mm-127 mm or greater than 127 mm.
10. The drilling system (10) according to any one of claims 7-9, wherein, The second diameter (D) 杆 The diameter is between 40mm and 60mm.
11. The drilling system (10) according to any one of claims 7-9, wherein, The threads on the base (6) and the threads on the sleeve portion (8) are both straight.
12. The drilling system (10) according to any one of claims 7 to 9, wherein, The threads on the base (6) and the threads on the sleeve portion (8) are both arc-shaped.
13. The drilling system (10) according to claim 9, wherein, The seventh diameter D 孔 Available in 54 mm, 57 mm, 64 mm, 70 mm, 76 mm, 89 mm, 102 mm, 115 mm or 127 mm.