JPS6283584A - Oil well pipe joint - 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] r Industrial field of application The present invention relates to an oil country tubular joint that can ensure high airtightness by preventing deformation and flow of a resin ring for maintaining airtightness, and has excellent seizure resistance.

rPrior Art J The depth of oil wells is several thousand meters, and in recent years has reached 10,000 meters. A huge number of oil country tubular goods are installed vertically in such oil wells, and they are all connected in series by pipe joints. Various severe forces act on such pipe fittings, including axial tensile force due to the weight of the pipe and pipe fitting itself, ground pressure exerted on the outer circumferential surface, and pressing force on the inner circumferential surface due to internal fluid. . Needless to say, these forces become more severe as the depth of the oil well increases. In order to be able to use it even under such severe conditions, it is required to be able to withstand an enormous tensile force of 1 load and at the same time to have reliable airtightness. Therefore, in order to meet the above requirements, many proposals have been made for improving pipe joints.

For the above-mentioned tension carts, good results have been obtained by improving the shape, pitch, etc. of the threads in the threaded portion of the joint. On the other hand, regarding airtightness, generally speaking, there is a technique in which a metal-to-metal seal is provided by forming a tapered lip in the non-barrel portion of a male screw member, or a resin ring is formed by forming an annular groove around the female screw member. Techniques for insertion and attachment are known. FIG. 4 shows a conventional oil country tubular joint in which a metal-to-metal seal portion M is provided and a resin ring 4 is inserted and mounted.

The conventional oil well pipe joint described above has a threadless portion 1 of a female thread member L.
1 and the outer surface (metal seal portion) 21 of the lip portion 5 provided at the tip of the male screw member 2 to form a metal-to-metal seal portion M when the joint is tightened.

The metal-to-metal seal part M is designed with a slight difference in diameter between male and female in order to increase surface pressure and ensure sealing performance, and is usually subjected to a high surface pressure of 100 to 150 kg/mJO. There is.

Therefore, if there is insufficient lubrication during fastening, seizure is likely to occur.

Therefore, a metal coating, a chemical conversion coating, a resin coating, or the like is formed on the metal-to-metal seal portion M to ensure high lubricity and prevent seizure.

However, as described above, an excessive tensile force acts on a pipe joint that connects a huge number of oil country tubular goods, and as a result, the surface pressure of the metal-to-metal seal portion M is weakened and the sealing performance is deteriorated. This phenomenon of reduced sealing performance tends to become more pronounced as the depth of oil wells increases in recent years. Furthermore, it is also conceivable that the metal-to-metal seal portion M may seize or develop surface flaws due to repeated use of the pipe joint. Therefore, in order to ensure airtight performance,
As shown in FIG. 4 above, the threaded portion lO of the female threaded member 1
Annular I? An oil country tubular joint is used in which an IJ 3 is provided around the circumference and a resin ring 4 made of Teflon or the like is inserted into the annular groove 3.

FIG. 5 shows a state in which the resin ring 4 is deformed by the threaded portion of the male threaded member 2. As shown in FIG. When the male threaded member 2 is screwed into the female threaded member l and tightened and rotated, the resin ring 4 is simultaneously deformed and compressed by the threaded portion of the male threaded portion 20, and is simultaneously engaged with the female threaded member l. Fills the gap with the male screw member 2. The annular groove 3 of the female screw member 1 is formed by cutting, and its surface roughness is approximately 124R.
It is max. On the other hand, the surface roughness of the male screw portion 20 of the male screw member 2 is approximately 54R+max, which is smaller than the surface roughness of the annular groove 3 surface. Furthermore, a lubricant is applied to the male threaded portion 20 prior to screwing. Therefore, the frictional resistance between the male screw member 2 and the resin ring 4 is smaller than the frictional resistance between the surface of the annular groove 3 and the resin ring 4.
When the joint was fastened, the resin ring 4 did not slip and rotate within the annular groove 3, was smoothly deformed along the shape of the threaded part of the male threaded part 20, and was filled in a good condition.

Therefore, even if the internal fluid leaks from the metal-to-metal seal portion M into the joint joint, the resin ring 4 can prevent the leakage to the outside. Furthermore, in a pipe joint that does not have a metal-to-metal seal portion M, the resin ring 4 is the main sealing member.

"Problems to be Solved by the Invention" Recently, with the deterioration of the oil well environment, high alloy steel with excellent heat resistance and corrosion resistance is increasingly being used for oil country tubular goods. However, high-alloy steel has lower seizure resistance than low-alloy steel and carbon steel grade products that have been used for oil country tubular goods to date. Therefore, as a measure to prevent seizure, the female screw member 1 side is coated with copper and silver.

Plated with soft metals such as gold, lead, and zinc, the male screw member 2
In order to retain a sufficient amount of lubricant on the outer surface, it was necessary to roughen the surface by sandblasting or the like to obtain a surface roughness of approximately 10 mRmax. As a result, the frictional resistance between the male threaded member 2 and the resin ring 4 increases, making it impossible for the resin ring 4 to deform cleanly along the shape of the threaded part, and when the joint is tightened, the male threaded part 20 While sliding and rotating with respect to the annular groove 3, it is pushed into the inner part of the female screw member 1, and when it is tightened back, it is pulled back toward the opening side. Therefore, a portion 4a of the resin ring 4 flows out from within the annular groove into the gap between the male screw member 2 and the female screw member l. When the degree of this outflow is small, it does not affect the sealing performance [Fig. 6 fat
], when the resin ring 4 causes its own flow to both sides of the groove [see Fig. 6 (bl)], or when a gap occurs between the resin ring 4 and the annular groove 3 [see tel of Fig. 6], As can be seen from these drawings, the surface pressure exerted by the resin ring 4 on the male screw member 2 and the female screw member 1 becomes uneven and inappropriate, and the leakage prevention effect is lost. .In addition, when the degree of leakage is severe,
(The M resin ring 4 is bitten into the screw part to be screwed together, and the outflow part 4a of the resin ring 4 is made to contract in diameter with respect to the male screw member 2 and expand with respect to the female screw member 1. As a result, there is a risk that the sole properties of the metal-to-metal seal portion M may be deteriorated and leakage of internal fluid may occur.Furthermore, in such a state, the tightening resistance of the female thread member 1 and the male thread member 2 may be reduced. becomes large, so excessive tightening torque is required.
There was also the drawback that work efficiency deteriorated.

"Means for Solving the Problems" The present invention 8 etc. strives for thorough research to solve the above problems,
As a result, we came to the following findings.

■ Appropriate surface roughening treatment is applied to the metal seal part of the male screw member, and seizure will not occur if 4ffi agent is used.

However, what if the metal seal part is not roughened? I'A? Seizing will occur even if IJPY is applied to the surface. This is held in a metal-to-metal seal /lJ
This is thought to be due to insufficient lubricant 9.

- When the terminal portion of the male screw member is subjected to surface roughening treatment, the airtight performance of the resin ring becomes FM, and at the same time, the sealing performance of the metal-to-metal seal portion also deteriorates. This is because the resin ring causes a counterflow due to an increase in frictional resistance between the male thread and the resin ring.

■ If a soft metal plating such as copper, ia, gold, lead, zinc, etc. is applied to the inner peripheral surface of the female threaded member and a lubricant is applied, roughening treatment can be applied to the threaded part of the male threaded member while leaving it finished by cutting. At least no seizure will occur. The reason is that these soft metal platings themselves undergo plastic flow IJJ.
This is because it demonstrates the

The configuration of the present invention was determined based on the above findings. This will be explained using drawings.

Figures 1 (δ) to (C) show an embodiment of the oil country pipe joint according to the present invention, and Figure 1 (ta) is an enlarged cross-sectional view of the main part of the female screw member 1, and Figure 1 (bl is an enlarged view of the tip of the male screw member 2 (C1 is a partially cutaway view showing the female screw member 1.!: fastened to the male screw member 2).

Both the female thread member 1 and the male thread member 2 contain 1 chromium.
Made of A alloy steel containing 0% or more. On the inner peripheral surface of the female screw member l, copper is applied to both the threaded portion 10 and the non-threaded portion 11.
It is plated with soft metals such as silver, gold, lead, and zinc to reduce frictional resistance. An annular groove 3 is provided around the threaded portion IO of the female screw member 1, and a resin ring 4 made of Teflon or the like is inserted into the annular groove 3. The annular groove 3 is usually formed by cutting, and its dimensions are as follows:
The width is 1.0 to 2.0 times the screw pitch, and the depth is 1.5 to 2.0 times the screw thread height.

A lip portion 5 without a screw is provided at the tip of the male screw member 2. The outer surface of the knob portion 5 is a metal seal portion 21, which comes into close contact with the threadless portion 11 of the female screw member I to form a metal-to-metal seal portion M when the joint is fastened. The metal seal portion 21 is subjected to an appropriate surface roughening treatment by sandblasting or the like, so that the lubricant applied to the threaded joint in advance is easily retained on the surface of the metal seal portion 21. On the other hand, the surface of the terminal portion 20 has been finished by cutting.

FIG. 2 shows an embodiment of the treatment method for roughening only the surface of the metal seal portion 21 described above. This covers only the terminal portion 20 of the male screw member 2 with the taber ring 6,
By performing sandblasting with the knob portion 5 at the tip exposed, only the surface of the metal seal portion 21 is roughened.

"Function" The oil country pipe joint according to the present invention includes copper on the inner circumferential surface of the female thread member.
Plated with soft metals such as silver, gold, lead, and zinc,
Reduces frictional resistance when connecting joints.

On the other hand, since the metal sole at the tip of the male screw member is roughened, a sufficient amount of the A'8 l'h agent is retained in the metal-to-metal seal where seizure is most likely to occur. Seizing can be reliably prevented.

Furthermore, since the threaded portion of the male threaded member is machined and a lubricant is applied to the surface, the frictional resistance between it and the resin ring becomes a very small value. Therefore, the resin ring will not rotate within the annular groove or flow out of the groove, that is, the sealing performance of the resin ring will not be impaired.

rExample J Table 1 shows the results of a comparison of the airtight performance of a coupling type oil well pipe fitting based on the present invention and a conventional product.
It was shown to.

(Margin below) The experimental conditions are as shown below.

・Male thread member material 'R25Cr-5ON i & vi thread height 1. 6 Yomaro screw pitch 5.01 day taper 1/16 ・Male screw member material 25Cr -5ON i SM
Annular groove width 7.6 m Annular groove depth
2.4-Zen/Resin ring material Teflon ring width 7.2 Seal-Ring thickness
1.81 Dragon Compound
API standard product/tightening conditions Rotation speed: 5 rpm Tightening torque: 900 kg-m The experimental method was to apply lubricant to the threaded part of the joint and the metal-to-metal seal part, then repeat tightening and cotton tufting. Inspect the threads and metal-to-metal seals every time, and observe whether or not seizure has occurred.

Tightening and tasseling were performed until seizing occurred, and for those that did not cause seizing, the tightening was repeated 20 times.

In Table 1, the fluidity state and airtightness of the 111 fat ring were determined after tightening the cotton tassel until seizing occurred, or after 20 times for those that did not cause seizing. This is the result of observation after

Cedar (As for the flow state of the fat ring, as shown in Figure 6 (al), part 4a of the fat ring 4 has flowed out,
A state in which there is no gap between the annular groove 3 and the annular groove 3 is defined as a low flow state, and a state in which the ring 4 is self-flowing to both sides of the groove, as shown in the same figure (bl), or a state in which the ring 4 is self-flowing to both sides of the groove (C1 As shown in FIG.
A state in which the fluid flows out into the gap with the T screw member 1 and also has a gap with the annular groove 3 is defined as a large flow.

In addition, the airtight performance was evaluated by measuring the pressure of the nitrogen gas pumped into the internal fluid when it returned to the mountain. Metal Octopus When measuring the pressure at the time of leakage when only the metal seal part M is used, a leak detection hole 7 is drilled with a drill etc. near the metal-to-metal seal part M of one example of the female screw member, and the leak detection hole 7 is drilled in the sealed state of the oil country pipe. Nitrogen gas was pumped to the pipe while increasing the pressure, and the pumping pressure was measured when the nitrogen gas leaked outside the oil country tubular joint.

[See FIG. 3 (lI)] When measuring the pressure at the time of leakage when only the resin ring 1 is used, an internal pressure acting hole 8 is installed in the lip portion 5 of the male screw member 2 in the part where the metal-to-metal seal is not formed. A leakage detection hole 9 was drilled on the side of the male screw member 1 from the mounting position of the lubricant ring 4 to the mouth opening side, and the pumping pressure when nitrogen gas leaked was measured.

[Figure 3 (see BL)] [Experimental results] ■ [Comparison of metal to metal seal parts] Matta (Conventional product without sandblasting (Wipe 2)
, 5.8, seizure occurred in the metal-to-metal seal portion due to the 5 or 7 times of tightening and cotton tassels, and the airtight performance of the metal-to-metal seal portion was extremely low. (Pressure at time of leakage: 90 to 105 kgf/cd) On the other hand, with the product of the present invention, even after 20 tightenings and tassels, there is no seizure of the threads that engage, and the product has the highest quality. It was confirmed that there was no seizure even in the metal-to-metal seal part where seizure is likely to occur, and the airtight performance was significantly improved. Uchi, with the product of this invention,
Even when the pressure of nitrogen gas reaches a pressure high enough to rupture the oil country tubular body, airtightness is still ensured. (Trial number 1.
4 is over 850 kgf/cd, trial number 7 is 830
kgf/ant or more) ■ [Comparison of resin ring parts] Although the conventional product (sample number 3.6.9), in which the entire outer surface of the male screw member was sandblasted, could suppress the occurrence of seizure, the resin ring As a result, the leakage of nitrogen gas at the resin ring part was 380 to 41
It occurs at 0 kgf/cJ.

In contrast, in the product of the present invention, a portion of the resin ring rarely flows out to the threaded portion, and the sealing performance of the resin ring is ensured. That is, in the product of the present invention, even if the pressure of nitrogen gas pumping reaches the bursting pressure of the oil country tubular body, the sealing performance is still maintained. (850 kgf for incense 1 and 4
/- or more, 830 kgf/cj or more for incense 7) ■ [
Effect of resin ring flow on the metal-to-metal seal part) In the conventional products (Fukou 3, 6.9) in which the entire outer surface of the male screw member was sandblasted, the airtight performance of the metal-to-metal seal part was descend. (Pressure at the time of leakage: 800~
(815 kgf/cd) This is because the large flow of the resin ring causes the diameter of the male screw member to be reduced and the diameter of the female screw member to be expanded. On the contrary,
In the product of the present invention, the airtight performance of the metal-to-metal seal portion is not impaired in the slightest.

Note that the type of oil country tubular joint according to the present invention can be either a coupling type or an integral type. In the examples, Teflon was used as the material for the resin ring, but it is not limited to fluorine-based resins, and other synthetic resins with excellent heat resistance and corrosion resistance may also be used.
Furthermore, depending on the degree of airtightness required and the type of oil country tubular goods, a plurality of resin rings may be inserted and mounted.

The surface roughening treatment applied to the metal seal portion of the male screw member is not limited to sandblasting, but may also include shore blasting, grid-plus low-left processing, sandpaper finishing, and the like.

4. Effects of the Invention As described above, the oil country tubular joint according to the present invention does not cause seizure in the metal-to-metal seal portion even when used repeatedly, and the +M fat ring inserted into the annular groove. There is no possibility that a part of the gas will flow out to the ring part, and therefore the sealing performance of the metal-to-metal seal part and the resin ring part will not be impaired in the slightest, resulting in a significant improvement in airtightness. This can be achieved by a simple process of applying soft full bending plating to the inner circumferential surface of the female screw member and roughening the metal seal portion of the R screw member, making it easy to manufacture.

Further, since the resin ring is prevented from being inappropriately deformed, unnecessary stress is not exerted on the male screw member and the female screw member. Furthermore, since the tightening resistance of the male screw member is reduced, excessive tightening torque is not required and work efficiency is improved. Since it is possible to expand the scope of application of oil country tubular goods made of high-alloy steel, it is effective in oil wells with corrosive environments, which have been difficult to mine until now.

[Brief explanation of drawings]

Figures 1 to 1 (C1) show an embodiment of the oil country pipe joint according to the present invention, Figure 1 (3) is an enlarged sectional view of the main part of the female screw member, and Figure 1 (bl is the male screw member). Enlarged view of the tip of the member (C1 is a partially cutaway drawing showing the fastened state of the above female screw member and male screw member. In Figure 2, only the surface of the metal seal part is roughened. Fig. 3 (al and (bl) are drawings for explaining an experimental method for evaluating airtightness performance. Fig. 4 shows an example of a conventional processing method. Figure 5 shows the fastened state of the oil country pipe joint, and Figure 6 shows the deformed state of the male screw member of the resin ring due to the threaded part.
This shows a state in which a part of the resin ring has flowed out from inside the annular groove. 1.-Female screw member 10--Nephew portion 1t--Nephew portion 2--Male screw member 20--Male screw portion 21-Metal seal portion 3-Annular groove
4-Resin ring 5-Lip part M--Metal to metal seal part Patent applicant Sumitomo Metal Industries Co., Ltd. Representative Patent attorney 1) Toshihiko Figure 2 Figure 5

Claims (1)

[Claims] 1. An oil country tubular joint made of high alloy steel containing 10% or more of chromium, in which the inner peripheral surface of the female screw member is plated with a soft metal such as copper, silver, gold, lead, or zinc. A resin ring for maintaining airtightness is inserted into the annular groove provided around the threaded part of the threaded member, and only the metal seal at the tip of the male threaded member is roughened. Oil well pipe fittings featuring: