JPS6115351Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a threaded joint for oil country tubular goods, and aims to improve the sealing performance of the joint and provide a joint that is easy to manufacture.

It is well known that when drilling oil and gas wells, tubing pipes are used to pump out oil and the like, and casing pipes are used to form the walls of oil wells. However, recently, the drilling depth of oil and gas wells has increased, and the drilling environment has become H ₂ S,
Because it is a corrosive environment where CO ₂ gas exists,
Tubing pipes and casing pipes used for this require sufficient strength and corrosion resistance not only for the pipe body but also for the joints, and in the case of threaded joints in particular, high sealing performance for the threads is required. There is.

By the way, as a joint of this type, the first
EL casing (Extreme Line
Casing) joint structure is known. That is, in this case, the male thread side tube end 1 and the female thread side tube end 2 are screwed together at the threaded portion 3, and the distal end 4 of the female thread side tube end 2 and the shoulder portion 5 of the male thread side tube end 1 are screwed together. The structure is such that the outer tip surface 6 of the male thread side tube end 1 and the inner inner surface 7 of the female thread side tube end 2 are brought into sealing contact as a so-called metal touch.

In such a joint structure, the pipe end is thickened to about twice the pipe wall thickness in order to obtain strength of the joint part, and a shoulder part 5 is provided to butt against the end of the female thread side pipe end 2. However, since the shape of the tube end is complicated, it takes a lot of time to process and manufacture.

In addition, oil country tubular goods, especially tubing pipes, are generally used repeatedly and the joints are attached and detached many times, so in the structure described above, the sealing surface of the metal touch seal may become deformed due to repeated attachment and detachment, or the sealing surface may become damaged due to flaws. The disadvantage is that the sealing performance deteriorates. Furthermore, since a gap 8 is created between the distal end of the male-threaded tube end 1 and the shoulder 9 formed on the inner surface of the female-threaded tube end 2, when equipment such as tubing or pipes passes through, This is the gap 8
This often caused damage to the inner surface of the tube.

The present invention has been devised to solve these conventional drawbacks, and therefore, the present invention consists of a combination of the following two structures. In other words, (1) Regarding the structure of the sleeve joint, a female thread is formed on the inner surface of the sleeve joint except for both ends and the center, seal packings are attached to the open sides of both ends, and a protrusion is provided in the center. This protrusion is formed with an inwardly inclined taper, and a smooth surface is further formed on the inner surface of the inner part leading to the protrusion.

(2) Regarding the structure of the tube end, the ratio of increase in thickness at the tube end is suppressed, the outer peripheral surface of the outer end of the increase in thickness is formed flat, and the position corresponding to the female thread of the sleeve joint is At the same time, the outer periphery of the tip of the tube end is formed into a smooth surface so that it comes into airtight contact with the smooth surface of the sleeve joint, and the tube end is aligned with the protrusion of the sleeve joint. The structure is such that a taper is formed at the end and the protrusion is brought into contact with the end.

An embodiment of the present invention will be described below with reference to FIG. 2. First, in the figure, 10 is a sleeve joint, and the inner surface open side of this sleeve joint 10 (only one side is shown in FIG. 2) is A seal packing 11 made of , fluorine-based, polyimide resin, etc. is attached, and a female threaded part 12 is formed in the middle part, and a protrusion part 13 is provided in the circumferential direction at the center part of the inner surface of the sleeve joint 10. The inner surface of the inner part extending to the protrusion 13 forms a smooth surface 14 in the circumferential direction. Further, in this embodiment, the threaded portion 12 is different from the conventional one.
It uses the same modified dome thread as the EL casing, which prevents galling and improves fitting efficiency.

On the other hand, the reference numeral 20 in FIG. 2 is the tube end to be connected, and the tube end 20 has a thickened portion 21 formed therein. However, in this embodiment, this thickened portion 21
The thickening ratio (t ₁ /to) is set to about 1.5, and the conventional shoulder part 5 (see Fig. 1) is eliminated, and the outer end 21 of the thickened part is
The outer peripheral surface of a is formed flat, a male threaded portion 22 is formed at a position corresponding to the female threaded portion 12 of the sleeve joint 10, and a smooth surface 23 is formed on the outer periphery of the tip. Further, in the present invention, as shown in FIG. 3, a taper (α=0 to 15° in this embodiment) is formed at the tube terminal end 24, and correspondingly, the sleeve joint protrusion 13 is also tapered. The seal area is increased.

According to the present invention as described above, when the male threaded part 22 of the pipe end 20 and the female threaded part 12 of the sleeve joint 10 are screwed together to connect both pipe ends, the sleeve joint 1
The smooth surface 14 of the tube end 20 and the smooth surface 23 of the tube end 20 are in airtight contact, and the tapered surface of the tube end 24 is firmly abutted against the tapered side surface of the protrusion 13. The sealed seal packing 11 comes into close contact with the outer end portion 21a of the thickened portion at the tube end. Therefore, according to the present invention, the threaded portion 1 is
2, 22 is ensured, the corrosion resistance of the threaded portion is improved, and the tapered surface of the pipe end portion 24,
Since the tapered sides of the protrusion 13 are butted against each other, there is no risk of damage to the inner surface even if pipe equipment passes inside the pipe as in the past, and during repeated use, metal touches on the smooth surfaces 14 and 23 will not occur. Even if the parts are worn, a seal will be maintained between the abutting part of the tube end part 24 and the packing 11. In addition, by reducing the wall thickness increase ratio at the tube end, the number of upset operations can be reduced.
This reduces the occurrence of flaws (circumferential wrinkle flaws), and since there is no need to cut male and female screws with complex shapes, the amount of cutting can be reduced to approximately 2/3, resulting in a reduction in machining time. It is possible to reduce the overall labor and time, and even if the thickness increase ratio is reduced, the sleeve joint method is used, so there are various advantages such as ensuring sufficient strength of the joint part. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional threaded joint structure, FIG. 2 is a schematic diagram showing an example of the threaded joint structure according to the present invention, and FIG. 3 is an enlarged view of the end portion of the pipe in FIG. 2. In the figure, 10 is a sleeve joint, 11 is a seal packing, 12 is a female thread, 19 is a protrusion, 14 is a smooth surface, 20 is a tube end, 21 is a thickened part, 21a is an outer end of the thickened part, and 22 is a Male thread part, 23 is smooth surface, 24
indicates the end of the tube.

Claims (1)

[Scope of utility model registration request] A threaded joint for oil country tubular goods that connects opposing ends of pipes using a sleeve joint, in which a female thread is formed on the inner surface of the sleeve joint except for both ends and the center, and a seal packing is provided on the open side of both ends. When installed, a protrusion is formed in the central part, and this protrusion is formed with an inwardly inclined taper, and a smooth surface is formed on the inner surface of the inner part leading to the protrusion. The outer peripheral surface of the outer end of the increased thickness portion is formed flat by suppressing the increase in thickness, and a female threaded portion is formed at a position corresponding to the female threaded portion of the sleeve joint, and the outer circumference of the tip of the pipe end is is formed into a smooth surface so as to be in airtight contact with the smooth surface of the sleeve joint, and the pipe terminal end is tapered to match the projection of the sleeve joint, and this end and the projection are abutted. A threaded joint for oil country tubular goods characterized by the following.