Double-shoulder drill rod joint

Abstract

The utility model discloses a double-shoulder drill rod joint which comprises a male threaded joint, and the male threaded joint is provided with an external thread axially extending between a radially outward outer shoulder and a radially inward male threaded joint surface; the male threaded joint includes a base portion extending axially between the outer shoulder and the external thread and a forward end portion extending axially between the male threaded joint surface and the external thread. According to the stress dispersion groove structure, the stress dispersion range borne by the threaded connector in the working state is enlarged, and failure fracture is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a joint, particularly to a double shoulder drill pipe joint. BACKGROUND

[0002] Drill pipe joint is the basic component of drill string, mainly used for transmitting torque, conveying drilling fluid, and connecting drill pipe in the process of drilling to deepen the wellbore. With the development of world economy, the demand for oil and gas is growing, but large oil and gas development projects are concentrated in deep well, deep sea well, high corrosion well and other fields, and the exploitation difficulty is obviously increased. The API recommended series of drill string components and downhole tools cannot meet the increasingly demanding drilling operation requirements, and new drilling technologies have been continuously emerging in recent years. The double shoulder drill pipe joint of Grant Prideco in the United States is one of the best, and its patent application in China is ZL98806866.4 "Oilfield pipe thread connection device and method of forming thread connection". With the increasingly harsh oil drilling environment, the drill pipe joint bears greater torque and tension, and the thread and sealing surface are more prone to wear, which leads to the following problems: first, the thread joint in working condition is prone to fatigue and cracking due to stress concentration in local area; second, when restoring the original performance by repairing the thread, the original thread and sealing surface are damaged, and it is difficult to find the original reference axis, so special tools are needed to find the center line of the original thread, which increases the time of repairing the thread for customers; third, the thread nose end usually adopts straight face design, and for 1:16 commonly used thread joint with taper, the male joint nose end sharp corner is easy to collide with the female joint thread during make-up and running-in, which damages the thread and leads to thread sticking. SUMMARY

[0003] The technical problem to be solved by the utility model is to provide a double shoulder drill pipe joint to solve the problems in the background art.

[0004] The double shoulder drill pipe joint of the utility model is realized by the following technical scheme, comprising: a male thread joint and a female thread joint connected by threads; the male thread joint has an outer shoulder extending axially between an outer thread and a male thread joint surface radially outward; the male thread joint comprises a base extending axially between the outer shoulder and the outer thread, and a front end part extending axially between the male thread joint surface and the outer thread, the female thread joint has an inner thread extending axially between an inner shoulder radially inward and a female thread joint surface radially outward, and the female thread joint comprises a counterbore part between the inner thread and the female thread joint surface; characterized in that,

[0005] The front end part of the male thread joint has a taper of 5:48.

[0006] The counter-bore portion of the pin is a straight surface;

[0007] The pin and the box are designed with a 1:1 cross-sectional area ratio.

[0008] As a preferred technical solution, a reference step is arranged between the outer shoulder and the base of the pin, the axial center line of the reference step coincides with the axial center line of the external thread, and the diameter of the reference step is slightly larger than the diameter of the base.

[0009] As a preferred technical solution, a first stress dispersion groove is arranged on the outer shoulder at the intersection of the pin and the reference step, the first stress dispersion groove is a groove with a circular arc-shaped radial cross section, one end of the first stress dispersion groove is tangent to the plane of the reference step, and the other end of the first stress dispersion groove is connected to the outer shoulder.

[0010] As a preferred technical solution, the connecting portion of the reference step and the base is a second stress dispersion groove, the second stress dispersion groove is a groove with a circular arc-shaped radial cross section, one end of the second stress dispersion groove is tangent to the plane of the base, and the other end of the second stress dispersion groove is connected to the reference step.

[0011] As a preferred technical solution, the front end portion of the pin has the same taper as the external thread;

[0012] As a preferred technical solution, the radial cross-sectional arc radius of the first stress dispersion groove and the second stress dispersion groove is 0.6-1.0 mm;

[0013] As a preferred technical solution, the radial cross-sectional arc radius of the first stress dispersion groove and the second stress dispersion groove is 0.8 mm.

[0014] The beneficial effects of the utility model are:

[0015] Compared with the original right-angle structure at the intersection of the outer shoulder and the base, the stress dispersion groove structure of the utility model expands the stress dispersion range of the threaded joint in the working state and reduces failure and fracture;

[0016] The reference step of the utility model is arranged at the weakest stress-affected part, is generally not damaged in the working state, and is used as a reference datum when the thread is repaired, so that the center axis of the original thread is found to be accurate and fast.

[0017] The front end portion of the pin of the utility model is designed as a taper surface instead of a straight surface, can effectively avoid nose tip corner collision, is suitable for complex drilling environments, and is especially suitable for offshore drilling.

[0018] The straight face design of the reaming part of the female threaded joint can avoid the collision of the nose end sharp corner, and facilitates the inspection; and the performance of the original double shoulder drill rod joint is improved as a whole. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, obviously, the drawings in the following description are only some embodiments of the present utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0020] Figure 1 It is a cross-sectional view of one end of the male threaded joint of the present utility model;

[0021] Figure 2 It is a cross-sectional view of one end of the female threaded joint of the present utility model;

[0022] Figure 3 It is a connection schematic diagram of the prior art;

[0023] Figure 4 It is a connection schematic diagram of the present utility model;

[0024] Figure 5 It is a VME stress distribution condition diagram of the present utility model;

[0025] Figure 6 It is a VME stress distribution condition diagram of the prior art. DETAILED DESCRIPTION

[0026] All features disclosed in this specification, and all methods or processes disclosed in this specification, can be combined in any manner, except where features or steps are mutually exclusive.

[0027] As Figures 1-2 shown, the double shoulder drill rod joint of the present utility model is provided with a tubular male threaded joint 10 at one end and a tubular female threaded joint 20 at the other end, the tubular male threaded joint 10 of the upper double shoulder drill rod joint is connected with the tubular female threaded joint 20 of the lower double shoulder drill rod joint.

[0028] The tubular male threaded joint 10 has an outer thread 16 extending axially between an outer shoulder 12 radially outward and a male threaded joint surface 14 radially inward, the male threaded joint 10 further comprises a base 19 extending axially between the outer shoulder 12 and the outer thread 16, and a front end portion 18 extending axially between the male threaded joint surface 14 and the outer thread 16.

[0029] The tubular pin 20 is used to threadedly connect with the box 10; the tubular pin 20 has an internal thread 26 extending axially between an inner radial shoulder 22 and an outer radial pin surface 24, and the tubular pin 20 includes a counterbore 28 between the internal thread 26 and the pin surface 24.

[0030] When the pin 10 and the box 20 are connected, the pin surface 24 and the outer shoulder 12 are in a flatly-engaged mating condition so as to exert a pre-load stress on both the pin 10 and the box 20 in the region radially adjacent to the last pin thread 11 before the pin surface 14 and the inner shoulder 22 are flatly engaged.

[0031] In this embodiment, a reference step 13 is provided between the outer shoulder 12 and the base 19 of the pin 10, the reference step 13 has an axis of symmetry coinciding with the axis of symmetry of the external thread 16, and the reference step 13 has a diameter slightly larger than the diameter of the base 19 so as to form a cylindrical surface on which the axis of symmetry can be measured. A first stress dispersion groove 15 is formed in the outer shoulder 12 of the pin at the intersection with the reference step 13, the first stress dispersion groove 15 is a circular-arc-shaped groove in radial cross-section, one end of the circular-arc-shaped first stress dispersion groove 15 is tangent to the plane of the reference step 13, and the other end is connected to the outer shoulder 12; a second stress dispersion groove 17 is formed at the connection between the reference step 13 and the base 19, the second stress dispersion groove 17 is a circular-arc-shaped groove in radial cross-section, one end of the circular-arc-shaped second stress dispersion groove 17 is arranged to be tangent to the plane of the base 19, and the other end is connected to the reference step 13. The circular-arc-shaped first stress dispersion groove 15 and the circular-arc-shaped second stress dispersion groove 17 have a radial cross-sectional arc radius of 0.6-1.0 mm, and the optimal value is 0.8 mm.

[0032] As shown in Figure 4 the stress groove structure disperses the stress of the threaded joint, and can reduce the probability of failure and fracture; the reference step in this embodiment is provided for the convenience of the user to repair the threads, and is provided at the position adjacent to the outer shoulder 12 of the base 19 because this position will not be deformed or damaged even if the threads are damaged, and is an ideal reference point, but is not the only reference point.

[0033] To avoid the nose corner collision, reduce the material loss when repairing and shorten the make-up time, the front end part 18 of the pin connection 10 has the same taper as the external thread 16, which is preferably 5:48; the counter-bore part 28 of the box connection 20 adopts the straight face design, which can avoid the nose corner collision and facilitate the inspection; the taper of the OPTiMA thread is 5:48, compared with the taper 1:16 of the ST thread, the material loss of the OPTiMA thread is reduced when repairing; for example, the material loss of the ST54 thread is 2 inches, and the material loss of the OPTiMA54 thread is 1.14 inches; the OPTiMA54 thread reduces the material loss by 43%; with the same length of the connection, the OPTiMA connection can have more repairing opportunities, and the repairing times are 2:1, which means the prolongation of the service life of the drilling tool; because of the taper design of the OPTiMA thread, the make-up and break-out time of the OPTiMA is reduced by half compared with the make-up and break-out time of the ST; the ST thread needs to rotate thirteen times, while the OPTiMA only needs to rotate seven times; each make-up and break-out can save about 50% of the time; the saving reduces the tripping time, which helps to produce the first batch of oil; in the inspection, if the counter-bore part of the box connection adopts the inclined face design, more time is needed for the alignment of the measuring device, and there will be more measurement errors, which leads to more unqualified products; the box connection of the OPTiMA adopts the straight face design, which can reduce the measurement error in the inspection, thereby reducing the unqualified products and the need for repairing; the reduction of unqualified products can bring great savings to the customers. The inspector can save at least 80% of the time when measuring the straight face counter-bore part and the inclined face counter-bore part.

[0034] Thread OPTiMA 54 OPTiMA 57 Threaded repair material loss 1.14” 1.14” Available repair opportunities (15" box joint length) 3.509 3.509 Thread ST 54 ST 57 Threaded repair material loss 2” 2.26” Available repair opportunities (15" box joint length) 1.750 1.549 Savings 0.86” 1.12” Material loss reduction % 43.00% 98.25% Repair opportunity ratio OPTiMA : ST 2.005 2.266

[0035] Compared with the thread designed without the 1:1 ratio of cross-sectional area, the stress dispersion range of the utility model is expanded, the fatigue resistance is improved, and the service life of the thread is also improved in use. It is suitable for complex drilling environments, especially marine drilling and horizontal drilling, and can cope with large-angle dog legs.

[0036] Compared with the dog leg of 4.8° / 30m, the fatigue cycle number of the thread part of the prior art is 1.012 x 10 9 The fatigue cycle number of the thread part of the utility model is 8.126 x 10 21 ; it can be seen that the fatigue resistance of the OPTiMA is more than 100 times higher than that of the existing thread; in the normal drilling condition, the service life of the utility model is longer.

[0037]

[0038]

[0039] Old thread design, the female thread will be weaker than the male thread; OPTiMA male and female thread design with 1:1 ratio of cross-sectional area, increasing the female thread cross-sectional area, which also enhances the yield strength of the female thread. In deep wells, generally use large diameter drill pipe and need to have high torque values. With the same joint outer diameter and inner diameter size, the theoretical torque value of OPTiMA54 is 82,910 ft-lbs and the theoretical torque value of ST54 is 79,700 ft-lbs. The theoretical torque value of OPTiMA54 is 4% more than the theoretical torque value of ST54. Looking at the theoretical torque value of OPTiMA57 and ST57, the theoretical torque value of OPTiMA57 is 99,013 ft-lbs and the theoretical torque value of ST57 is 87,462 ft-lbs. Here, the theoretical torque value of OPTiMA57 is 13% more than the theoretical torque value of ST57. That is, the larger the size, the more obvious the effect of this design to improve the torque value.

[0040] The above merely illustrates the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any change or replacement without creative labor should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be limited by the protection scope defined in the claims.

Claims

1. A double shoulder drill pipe connection comprising a pin connection and a box connection connected by a threaded connection; the pin connection having an outer shoulder extending axially between a radially outward outer shoulder and an radially inward pin connection surface; the pin connection comprising a base extending axially between the outer shoulder and the outer thread and a nose portion extending axially between the pin connection surface and the outer thread, the box connection having an inner thread extending axially between a radially inward inner shoulder and a radially outward box connection surface, the box connection comprising a counterbore between the inner thread and the box connection surface; characterized in that, the nose portion of the pin connection has a 5:48 taper; the counterbore of the box connection is straight; the pin connection and the box connection are designed with a 1:1 ratio of cross-sectional area.

2. The double shoulder drill pipe joint of claim 1 characterized by: a reference shoulder is provided between the outer shoulder and the base of the pin connection, the reference shoulder having an axis of the reference shoulder coinciding with the axis of the outer thread, the reference shoulder having a diameter larger than the diameter of the base.

3. The double shoulder drill pipe joint of claim 2, wherein: a first stress dispersion groove is provided in the outer shoulder at the intersection of the reference shoulder and the pin connection, the first stress dispersion groove being a radially cross-sectioned circular arc groove, the first stress dispersion groove having one end tangential to the plane of the reference shoulder and the other end connected to the outer shoulder.

4. The double shoulder drill pipe joint of claim 3, wherein: the connection between the reference shoulder and the base is a second stress dispersion groove, the second stress dispersion groove being a radially cross-sectioned circular arc groove, the second stress dispersion groove having one end tangential to the plane of the base and the other end connected to the reference shoulder.

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