JPS5983887A - Pipe joint for oil well pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention provides a method for extracting crude oil produced from underground.
This article relates to the joint structure of oil country tubular goods that are sunk underground.

The depth of wells that produce crude oil is several thousand meters, and in recent years the depth has been increasing further to reach 10,000 meters. The oil country pipes that are used to pump crude oil from such wells are made up of an enormous number of single pipes connected to each other by pipe joints.The most important requirements for these pipe joints are The objective is to withstand strong tensile loads and maintain reliable airtightness to prevent internal fluid from leaking. Requirements for such pipe joints for oil country tubular goods have become stricter as the depth of wells has increased, and many proposals have been made to meet these requirements.

For example, Japanese Patent Publication No. 35-76'30, Japanese Patent Publication No. 41-
1742, Japanese Patent Publication No. 45-18096, Japanese Patent Publication No. 52-27367, and US Special Publication No. 290.
7589 specification, US Pat. No. 2,980,451 specification, and US Pat. As shown in the following.

The pipe joint shown in FIG. 1 has a coupling A having a cylindrical appearance and a tube 0. C'ii are screwed together. On the inward side of the coupling A, a buttress-type internal thread is carved in accordance with the A, P, and ■ standards, the inner diameter of which decreases as it goes deeper in the axial direction from both ends with a taper of heat. A shoulder portion B is formed to protrude in the radial direction at the center of the innermost portion. On the other hand, each of the pipes a and C has a male tapered thread, which is the same as the female thread formed on the coupling A, at its end. If the screw-like shape Wt between the coupling A and the pipe C on the left side of FIG. 1 is enlarged, it will be shown in FIG. RIJ (is.

As seen in Fig. 3, there is an unthreaded lip section in the area corresponding to 5 to 3 threads. The outer periphery of this lip [iJK ItJ: A section following the niJ stage external thread.A flat outer peripheral sealing surface D1 of the taper is formed, and its tip has an overhang shape (an angle with respect to the inner wall of the axial rotation of the tube C). Approximately 100') tip sealing surface D2 is shown in shape 1.On the other hand, a non-threaded portion V1 with a taper of 6 is provided near the shoulder 71sB of the coupling A, and the outside of the lip 111 is νd. An inner seal surface B1 corresponding to the ring imD, and an abutting seal surface B corresponding to the tip seal +TnD are formed.Then, the pipe C and the coupling A are screwed together and strongly tightened. In this case, the outer seal surface IID and the inner seal surface, the tip seal direction D2 and the abutting seal surface B!fl, are in contact with each other and the metal +fn
An airtight seal can be obtained between the two metal rings.

However, the hole C and the coupling A, which are sunk in the well, have a tensile charge T (50
~100 (l ton) and the internal pressure P (1000 to 2000 Kg/cm) in the direction of the black arrow is applied, and it is usual that a slight vibration is applied.As a result, the coupling A ( !: Gradual deformation occurs in the threaded part of pipe C, and the contact pressure between the outer seal surface, the inner seal surface, and between the tip seal surface A and the abutting seal curved horse decreases, and finally Fi Fig. 4 is reached. A gap G as shown in the figure appears, causing leakage of the internal fluid.Furthermore, no matter how strongly the coupling A and pipe C were screwed together at the initial stage of recessing, , once you are deep inside the well,
Once again, this will not be treated as an i+i JW,
It is also impossible to completely restore the airtightness. In such a state, it goes without saying that the tensile strength of the pipe joint deteriorates.

Recently, from the viewpoint of cost saving, the use of 1/g
After use, C and cup link A tend to be unscrewed and re-screwed for use in other wells. However, with conventional pipe fittings, the seal is strong for all sets) [1
Excessive tightening was performed to obtain one full pressure, and as a result, a type of seizure damage called galling occurred between the metal seals, making it difficult to reuse them. What's more, this Goring becomes so severe that it is tightened and tightened in an attempt to restore the seal to its original form.

Misfire #J was made with the aim of solving the drawbacks of conventional pipe joints as described in g11, and causes a drop in surface pressure and gaps on the metal sealing surface due to deformation of the pipe joint. Even when external forces such as It provides pipe fittings.

Below, the structure of the present invention will be explained based on the embodiment shown in the drawings. FIG. A buttress-type screw 3a with a predetermined taper is carved on the surface, a lip portion 4 without a thread is formed at the end, and an outer peripheral seal 1...4a is provided on the outer peripheral surface of the lip portion 4. Further, the tip end surface vtX is provided with a tip sealing surface 4b. These points are different from the tube ends in conventional pipe joints.In the present invention, the vf characteristics are as follows.As shown in the figure, the lip portion 4 has a depth along the axial direction of the tube 3. The point is that a slit 5 with a diameter is bored. This slit 5 is C, which is opened approximately at the center of the tip sealing surface 4b with an opening gap di.
When the end surface of the tube 3 is bent, it is annular with a thickness t'4, so the slit 5 also has a tip seal rtii 4
Needless to say, it is provided in an annular manner around the central part of b. Slit 5? 'l [+1 direction depth l
is 1 to 1.5 times the length L of the lip portion 4 (l = 1 to 1.
5L). It is preferable to make the holes by electrical discharge machining. Slit 5 in lip part 4
When a pressing force from the inner gap acts on the 2L circumferential sealing surface 4a due to aJ<, the outer 111! of the lip 1lS4! The prong 4c bends inward, and the thickness t of the lip portion 4 decreases.
(Width of the tip ring surface 4b) is the opening gap d of the slit 5
Reduce the size by the amount corresponding to O11. However, when the pressing force is released, the opening gap d of the slit 5 returns to its original state due to the springback of the outer slit 4c. With the depth l and the size of the opening distance 1δt7d,
Is that an influence? The reception and, by extension, the fate of the unexploded 9J will be affected. That is, the larger the depth l of the slit 5 to the center and the larger the opening gap d, the greater the amount of deflection of the outer prong 4c. l■l The repulsive force becomes weaker at 11'T, making it impossible to obtain a strong surface pressure and weakening the sealing effect.On the other hand, if the depth l and the opening gap d are small, the outer seal 11+14 a Vc becomes weaker. Although a strong surface pressure is obtained on the seal 4a and the sealing effect is increased, the rigidity of the outer IN seal 4C increases, which tends to cause galling on the outer IN seal surface a, and the pipe fitting tit P+
It becomes difficult to put it into use. Depth of slit 5 zll Length of foot 14 L(1)l~l. The reason why it is set to 5 times is because of the use of 11J Koki, and it was taken into consideration that the outside sill 4c (+) should have the appropriate deflection allowance for a deer with a spring back force. The length L is l'f1.5 times the thickness t of the lip 111ζ, and the lip thickness t is 'dgrl after the wall thickness of the tube 3.

As for its specific dimensions C, the yield stress of the paulownia material and the surface pressure value of the sealing surface required for the pipe 3 are never used as a reference. It goes without saying that the outer circumferential sealing surface 4a and the tip sealing surface 4b need to be finished with a B\i1 finish of 6-8 or higher. Coupling 1
The figure shows that the shoulder 2 is formed deep inside the O-coupling 1, and the shoulder 2 is formed deep inside the O-coupling 1. The peripheral seal surface 2a and the abutting seal [(n
2b is provided, and there is no difference from the conventional one. Tightening by the 0th stage Power Tight is performed with a predetermined torque. As the tightening of Power Tight progresses, the external sealing surface 4a of the lip portion 4 is tightly fitted to the inner peripheral sealing surface 2aK of the coupling l, and as the contact area between the mutual sealing surfaces 2a and 4a increases, Kjl [O pressure also increases. Further) (as the tightening of the wartite progresses, the mutual seal ``(I]2a
, 4a gradually approaches the optimum saturation state, and
The outer slit 4C gradually bends inward, and the opening gap d of the slit 5 closes.At the final stage of Power Tight tightening, the tip sealing surface 4b of the lip 4 closes to the shoulder 2 of the coupling 1. Abutment seal 1il provided on
12b, a strong surface pressure is obtained between the mutual seals 1m2b and 4b, and thus the screwing and tightening of the pipe 3 and the cup link 1 is completed. The state after tightening is shown in Figure 7. In the American pipe joint, the main areas where go-links occurred were the outer seal surface 4a of the lip portion 4 and the inner seal σi2 of the coupling 1.
It was a. However, in the pipe joint of the present invention, after the optimum pressure (m) for ensuring an airtight seal is obtained between the outer circumferential sealing surface 4a and the inner circumferential sealing surface 2a, the pressure becomes saturated and the Since the surface pressure is not excessive, it is possible to prevent galling from occurring.

FIG. 8 shows another embodiment of the pipe joint according to the present invention. The difference between the pipe fitting shown above and the above one is that the slit goes around the tip sealing surface and has a downward slope of 5.
' or uphill slope σ 5'' (shown by broken line fc)
K, I, we have established the following. In this way, the tii between the outer circumferential seal curve 4a and the inner circumferential seal curve 2a, and between the tip seal curve 4b and the abutting seal surface 2b are precisely
This is convenient for adjusting the distribution of J pressure and can be used to prevent galling.

FIG. 9 shows yet another embodiment.

1ftl [m] A fitting groove 6 with a tapered depth is bored in the shoulder part 2 of the coupling 1, and the lip part 4 of the tube 3 is fitted into the fitting groove 6. In this case, the lip portion 4 is provided with an inner sealing surface 4d in addition to the outer peripheral sealing surface 4a, and the total iN+ product of the sealing surfaces can be expanded. Additionally, the opening gap of the slit 5 is made larger than that shown in Figures 5 to 8 of Item IJ to increase the total deflection of the lip portion 4 and to adjust the counterpressure of the sealing surface over a wide range. In any of the embodiments in which it is possible to do so, it is not always possible that the deflection of the lip portion 4 will return to its original state due to springback when the screw tightening is completely released.

Next, the 7-hole effect and galling prevention effect of the pipe joint according to the present invention are compared with those of the conventional pipe joint. Table 1 shows A, P and P in the engineering standards.
-11Q, N-80, and C-75 grade 9.1 pipes, the pipe joint of the present invention shown in Figs. 5 to 9 and the conventional pipe fitting shown in Fig. 1 to (04) This figure shows the results of a tensile test conducted with each pipe connected using a pipe fitting and water pressure applied to the inside, as well as the results of an investigation into the occurrence of galling. As shown, the bone thinning and hand 1trJ according to the present invention:
Even if the pipe joint is subjected to axial tension until it breaks,
No water leaked. When it came to the occurrence of goring, it was only by repeating tightening and tightening more than twice as many times as in the conventional method that the occurrence of goring was observed for the first time. Therefore, it is shown that the pipe joint related to misfire 154 is sufficiently durable for reuse.

It is clear from the results in Table 1 that the slit provided in the lip t'+Is plays an important role in the stopper, and from the experimental results it is clear that the slit provided in the lip t' It has been found that the relationship between the length L and the slit depth l (Lll ratio) needs to be set appropriately. Table 2 shows the results of this experiment. This is a steel pipe of C-75 grade of A, P, ■ standard, the outer diameter of the pipe is 88.9 mm, and the wall thickness of the pipe is 6.4 mm.
5 sushi! j Thickness of the tip of the knob part is 5mm, lip part length is 7mm
The depth of the slit is I! 1 shows the results of various changes. Although this size of L/l is originally in a trade-off relationship from the viewpoint of galling prevention and seal leakage, as can be seen from Table 2, L/l! By setting the ratio in the range of 1.0 to 1.5, both can be satisfied. When a slit with a depth along the tube axis is made in the lip part and the tube made in this way is screwed into the coupling, an interference fit is created with appropriate self-pressure on the mutual sealing surfaces. By doing so, it is possible to exhibit a reliable sealing effect, and the pipe joint 1-J: can be reused, which is of great benefit to the crude oil extraction industry.

[Brief explanation of the drawing]

FIGS. 1 to 4 show an example of a conventional pipe joint, and FIG. 1 shows a pipe partially shown in cross section. 41 view of the hand, Figure 2 is an enlarged view of the left side cross section in Figure 1, Figure 3 is an enlarged view of the circled part in Figure 2, and Figure 4 shows a strong axial tension on the pipe joint. 5 to 9 are cross-sectional views showing a state in which the sealing surface is deformed due to the application of internal pressure; The figure is a cross-sectional view showing the state in which the pipe is threaded into the lip of the pipe end. Further, Figures 8 and 9 are partial cross-sectional views showing the state in which they are screwed and tightened with Power Tight, and Figures 8 and 9 are partial cross-sectional views showing other examples. l...Coupling 2...h4 Capital 3...Tube 4
...Lip part 5, 5', 5"...Slit 6
...Pre-mating special d'r applicant Sumitomo Metal Industries Co., Ltd. 1↓1! People Patent attorney Toshihiko Uchida? Storehouse 1 Figure 2 Figure 5 Figure 7 Figure 8 Ingo f'49 Figure 3 544d62

Claims (1)

[Claims] 1. In a threaded joint for oil country tubular goods, a lip portion having a tapered outer circumferential sealing surface and a tip sealing surface is formed at the end of the pipe in which a male thread is carved, and is threadedly engaged with a 0+J marked pipe. A shoulder portion having an inner circumferential sealing surface and an abutting sealing surface which are in close contact with the outer circumferential sealing surface and the tip sealing surface is formed in the inner deep part of the coupling in which a female thread is carved, and the tip sealing surface of the 111 pipe is A pipe joint for oil country tubular goods, characterized in that a slit with a depth extending along the axial direction of the pipe is bored around the entire circumference of the pipe. 2. The pipe joint for oil country tubular goods according to claim 1, wherein the depth of the slit carved in the tip seal curve of the lip portion of the pipe is 1 to 1.5 times the length of the lip portion.