JPS63106491A - Pipe joint for oil well pipe having stopper function in screw screwing section - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pipe joint for oil country tubular goods (casing pipes, tubing/4'ves) used for well protection and oil extraction of oil (gas) wells. The present invention relates to a joint for oil country tubular goods that is inexpensive to manufacture and has excellent airtight performance.

(Prior Art and Problems) As oil well environments become more and more severe, the required performance of oil well pipe joints is becoming increasingly sophisticated. On the other hand, reflecting the slump in oil prices in recent years, high-performance and inexpensive joints are strongly desired by customers. Oil well pipe joints can be roughly divided into two types: API standard buttress threaded joints, tip threaded joints, and special joints that do not meet API standards.

Traditionally, special joints have been used for high-pressure gas wells and steam injection wells for secondary and tertiary recovery, due to their high-pressure gas-tight performance.

Generally, the cost of oil country tubular goods in oil well development is thought to account for about 10% of the total, and the high cost of oil country tubular goods due to the use of special joints cannot be ignored.

The special joint is generally represented by the shape shown in FIG. 6, and has a non-threaded tapered part 39 at the tip of the male screw, and a central protrusion 40 on the box 32, unlike the normal A shown in FIG.
Different from PI standard buttress threaded joints. In the joint shown in FIG. 6, the pin tip screw taper portion, the box threadless internal chi/tone portion 35 that includes the taper portion, and the protrusion portion 4o have two main effects. The first is the screwless chi 2 part 3
High airtight performance can be obtained by tightly fitting 3.35 into the joint when fitting.

Second, the protrusion 40 of the box serves as a stopper for tightening the male screw, and the screw fitting parts 37 and 38 and the airtight part 33
．． 35 with the specified interference type (male side outer diameter - corresponding female side inner diameter)
t-Can be given. This is an extremely important point in designing the circumferential tensile stress and airtight pressure generated in the box.

On the other hand, API standard buttress joints do not have the above-mentioned threadless taper part and box center protrusion, so they cannot be safely used in high-pressure gas wells or in severe corrosive environments where stress corrosion cracking is at risk, even if they are inexpensive.

From the manufacturer's perspective, there are two reasons for the high cost of the special joint shown in FIG. First, since the box has a central protrusion, the wall thickness of the raw pipe becomes thicker, and the cutting depth due to machining increases significantly compared to an API buttress threaded joint without a central protrusion, reducing productivity. The second is alloying elements Cr and M, which are unnecessary in thin-walled tubes, in order to ensure the hardenability of thick-walled tubes.

This is due to the need to add a village.

In the past, as a special joint, threadless tee 9 shown in Figure 8 was used.
A joint having a central projection and no central projection has been invented (Japanese Unexamined Patent Publication No. 150689/1989). Although it is a low-priced special joint that excludes the central protrusion, it is highly praised for its ability to provide metal-to-metal contact, as it quickly responds to customer needs. If the parts that are not marked are viewed as a reverse item, it is unfinished.

For joints that do not have a central protrusion, such as API joints, a triangle mark is stamped near the incompletely threaded upper part of the male thread, and the positional relationship between the box end and this triangle mark is kept within a certain range. , trying to determine the tightening position.

However, under severe drilling operations such as off-site drilling, drilling, and extremely cold Alaska, it is impossible to measure the tightening allowance for each bolt in advance and then tighten it by controlling the tightening torque value. The method that suits the actual situation is to place the target position within the target range. This unreasonableness is entirely due to the fact that the joint does not have a stopper that determines the tightening position.

The invention shown in FIG. 8 also has the same drawbacks as the API joint in this respect. Furthermore, since the tightening position is not constant, it is difficult to permanently maintain the designed interference type of the metal contact portion provided.

(Objective of the Invention) The object of the present invention is to eliminate the central protrusion, which is the main cause of the high manufacturing cost of special oil country tubular joint boxes, and to provide the joint with an alternative tightening positioning structure, thereby reducing the manufacturing cost. ,
Moreover, it is an object of the present invention to provide an oil country tubular joint with high airtight performance and the ability to control tensile stress in the box circumferential direction.

In addition, the idea of the present invention is that the central protrusion of Metskus called Druksi and Ruder is not used as a stopper for the male screw.
Since other structures attempt to control the fitting position of the male thread, there are also joint structures that do not actively use the central protrusion as a male thread stop. sell. In the latter case, the purpose is to prevent excessive plastic deformation that occurs when the unthreaded portion of the bottle tip comes into contact with the central protrusion.

(Means for Solving the Problems) The present invention solves the conventional problems and advantageously achieves the object of the present invention. A cylinder (box) is provided with a non-threaded arm on its extension, and this male threaded pipe end pin is fastened.
K is a joint structure for oil country tubular goods in which a corresponding female thread is carved, and a threadless inner cylinder teno part 9 corresponding to the part without a pin thread is carved on the inner extension of the female thread. When screwing together, place the male thread end of the pin, the thread at the start point of a complete thread, on the bottom of the screw that rises sharply at the end of the complete thread (or the start point of an incomplete thread) deep inside the female thread of the box. If there is intentional excessive contact, or when the pin and box are screwed together, the incompletely threaded part where the bottom of the screw on the fully threaded extension of the male threaded end of the pin rises up is removed from the inside of the female thread of the box, where the completely threaded end ends. The threaded part has a stopper function, which is characterized by having a structure that intentionally over-contacts the thread at the end and stops tightening by a combination of a relatively complete thread and an incomplete thread on the pin and box side. This is a pipe fitting for oil country tubular goods.

The structure as a stopper function in the present invention is a stop between the screw thread and the screw bottom by intentional engagement of a complete screw and an incomplete screw. Common sense suggests that a structure in which a complete thread and an incomplete thread engage with each other is impossible for a threaded joint, and is considered a basic design error. However, if the position of an incomplete screw formed at the end of a row of screws on a pin or box is precisely and deliberately machined into a tight state, the other complete screw will be able to reach a dead end and will need help from a central protrusion, etc. , the pin can be tightened into place in the box. That is, the essential element for replacing screws with stoppers is the engagement between the incomplete screws and the complete screws at the end of the screw row. Therefore, there are two combinations: a combination with an incomplete thread on the pin side and a complete thread on the box side, and a combination with a complete thread on the bottle side and an incomplete thread on the box side. In the case of husband and wife, the joint structure and the operation at the time of fitting will be explained below using a specific example shown in FIGS. 1 and 2.

(Function) (,) Combination of a fully threaded pin and an incompletely threaded box The right half of Figure 1 (,) shows the relative positions of the thread rows when fitting a joint with threaded pins and boxes using common sense. .

The pin fully threaded end 7 is made so that tightening is completed before the box fully threaded end 8, so that the screws do not force each other. Of course, in this case, unless the tightening allowance is measured before starting tightening, it will not be possible to complete tightening so that the pin tip 10 is exactly in the center of the box as shown in the figure. The left half of Figure 1 (,) is
The screw row positions of the pin and the box are designed so that when the pin fully screwed end reaches the fully threaded end of the box by tb, the pin tip 9 will be in the center of the MEX. Figure 1(b) shows JI
The incomplete threaded part of the S symbol has been rewritten using threads. When machining the box screws, the blade cuts the screw inward from position 5 and escapes, so the bottom of the screw rises inward as it progresses from position 5 to 6 as shown in the figure.

Therefore, when the pin is tightened into this box, the screw threads 2 touch each other at the point where they are about to enter the screw bottom 5, and the pin cannot be tightened any deeper. In this case, the tightening position of the pin tip is controlled by appropriately adjusting the relief position of the box thread cutting blade.

(b) Combination of an incompletely threaded pin and a fully threaded box FIG. 2(b) shows a structure in which, contrary to the previous example, the threaded bottom of the pin rises as it approaches the tip of the pin. In this case, the screw thread of the box will rise and come into contact with the bottom of the pin screw, and the tightening will be completed. In the case of the previous example, it is possible to design a design in which the pin and box screws have some degree of interference with each other and the bottle screw thread contacts the box screw bottom and stops, but in this example, the raised screw bottom of the pin Since it comes into contact with the box thread, tightening ends before the pin and box are fully tightened. So pin freely,
Although there is a drawback that the tightening margin of the box screw cannot be adjusted, it is possible in principle.

(Example) Hereinafter, a pipe joint for oil country tubular goods (hereinafter referred to as the present joint) according to the present invention will be described based on an example joint shown in FIG. 3.

As shown in FIG. 3, the tapered point 9 cylindrical portion 16 at the tip of the tube 11 is usually 1A6
A male thread 17 based on an API standard buttress thread with a tapered diameter is provided. The male thread 17 has a fully threaded portion Ps having a predetermined thread height h and a length Ls (bottle complete thread), and has a threaded portion Ps having a predetermined thread height h, and has a threaded portion Ps having a length Ls (bottle complete thread), and has a tenon thread free from the end of the fully threaded portion PM. Pipe outer circumferential surface 11m
1. Incomplete threaded portion where the thread height does not reach the predetermined thread height h. is formed with a length L4 (bottle incomplete thread).

On the inner periphery of the joint end 18 of the box 12, a female thread 19 is carved in such a way that its diameter decreases toward the inner depth (to the left) in order to obtain a threaded relationship corresponding to the male thread 17. Then, at the innermost part where the female screw 19 is cut and stopped, make a screw thread following the female screw 19 and add a k6 to 1A2 teno gun in the range corresponding to the 4th to 6th threads. There is a threadless part, and the inner peripheral surface of this threadless part is the inner peripheral sealing surface 14m. The inner seal surface 14m is the opposite seal surface 4
Intersects a' at the center of the box. On the other hand, the pipe 11 also has
1716 at the tip of the part where the male screw 17 is cut off
A threadless lip portion 20 of ~1/12 inch is formed. The outer periphery of the lip portion 20 is connected to the inner periphery sealing surface 14.
The outer peripheral sealing surface corresponding to a is 20 m. Boundary 1 between fully threaded part L2 and incompletely threaded part L1 of GEX female thread
5 is formed by quickly releasing the thread cutting tool toward the tube axis while cutting the thread. The degree of the bottom of the box screw is steeper as the speed at which the thread cutting tool escapes inward is faster, and it effectively serves as a stopper. In normal thread cutting, the cutting process is programmed so that the blade is completely removed while feeding the l-pitch tool, but in order to obtain a sharp thread bottom, as shown in Figure 3 (C), It is necessary to devise a way to quickly release the knife during the .25 pitch. On the other hand, the complete thread 19 portion 15 of the bottle 16 ideally has a shape in which the screw thread rises sharply, as shown by the circled portion 21 in FIG. 3(b). When the bottle 16 processed as described above and the box 18 are screwed together, they will be tightened when the pin screw rising portion 21 reaches the incompletely threaded portion of the box. At this time, the pin end surface 22m is designed to be located at the center of the box. Also, the metal-to-metal contact portion 14
m and 20m are provided with a strip margin ΔDI. The screwed state of the male thread and the female thread also has a tightening allowance of 70 threads at the fully tightened position. When the bins 16 and 23 fitted from the left and right sides of the box are tightened, a slight gap is maintained between the tip surfaces 22m + 23m.

Figure 4 shows a prototype tube with an outer diameter of 177.8 mm based on the above specifications.
mw+, wall thickness 11m, box outer diameter 194.46m.

This figure shows the relationship between tightening torque and rotational speed when a pair of bottles and indexes with a tensile strength of 70 kV'wx are screwed together.

For the purpose of lubrication, the inner surface of the box was galvanized with a thickness of approximately 20 μm, and API standard Con/4'und grease was used when tightening. As shown in the figure, the screw-in torque increases as tightening progresses, and increases rapidly just before the end of tightening. At this time, the screw thread at the tip of the bottle has reached the incomplete thread deep inside the box. After the rapid increase in torque, the solder tightening progressed slightly (0 to 0.02 turns), but the final tightening position was within ±0.1■ of the target tightening position. When the male screw was loosened from the box and the male screw and the female screw of the box were examined, no seizure phenomenon was observed. From this experiment, it was confirmed that the screw stopper effect of complete and incomplete screws is sufficiently useful for practical use.

The invention can also be applied to other joint shapes. An example is shown in FIG. Unlike the above embodiment, a protrusion is carved in the center of the box 25. If the bottle to be tightened has a thin wall, aggressively bringing the male screw tip 2 into contact with this protrusion may have an adverse effect on the metal-to-metal airtight surface 27m. Even in such a case, the screw stopper that utilizes the locking effect of the complete screw and the incomplete screw shown in the middle circle 28 in FIG. 5 can be applied. What is the reason for providing a protrusion in the center of the box? This increases the deformation resistance of Tuxus against internal pressure and strengthens the airtightness of the metal contact surface. Also, the inner surface of Pi f29 is Tux 25
Matching the inner surfaces also has the advantage of smoothing the flow within the tube and preventing erosion, which tends to occur at tube expansion and tube contraction sections. In this way, the present invention can be used even when there is a protrusion in the center of the box, but it cannot be used as a stopper.

(Effects of the Invention) As described in detail above, the joint of the present invention exhibits remarkable practical effects that fully achieve the above-mentioned objects of the invention.

Furthermore, in the explanatory diagrams, examples, and application examples of the present invention described above,
Although a tapered threaded joint is used, the effects of the present invention can be similarly obtained with a parallel threaded joint.

[Brief explanation of the drawing]

FIGS. 1 to 5 are diagrams for explaining the pipe joint according to the present invention, and FIG. A joint that has a stopper structure and does not have a protrusion in the center of the box. FIG. 1(b) corresponds to the screw locking portion. male,
Enlarged view of female screw. Fig. 2(a) is a diagram showing a joint having a four-horn structure in which the threaded bottom of an incomplete pin screw comes into contact with the thread of a complete dex thread, and does not have a box central protrusion. Figure (b) is an enlarged view of the male and female screws corresponding to the screw locking part, and Figure 3 (,) is an explanatory diagram showing an embodiment of the present invention, which has the same structure as Figure 1. Preparation, A
Based on the PI padless joint, the center of the box has a metal-to-metal contact airtight part, and the tightening position is designed to be where the male screw tip starts to engage with the incomplete screw deep inside the female screw. Figures 3(b) and 3(e) are enlarged views of the male threaded end and female threaded end corresponding to the stopper part.
The figure shows the relationship between the tightening torque and the tightening rotation speed when the joint shown in Fig. 3 is screwed together, and Fig. 5 shows an application example of the present invention.
An explanatory diagram showing a joint in which a protrusion is carved in the center of the box. Figures 6 to 8 show known joints related to the present invention, and Figure 6 shows the center protrusion of the box as a salt screw tightening stopper. Fig. 7 is an explanatory diagram of the current oil country pipe special threaded joint in use, and Fig. 8 is an explanatory diagram of the API standard buttress threaded joint. It is an explanatory view of a joint without a stopper utilized. 1: Screw thread 2: Screw thread 3: Screw thread 4: Screw bottom 5: Screw bottom 6: Screw bottom 7: Pin complete end end 8: Box fully thread end end 9: Bottle tip 10: Pin tip 11: Tube 12: Male thread 14a: Metal-to-metal contact portion 15: Boundary between fully threaded portion and incompletely threaded portion 16: Tapered tenor arm cylindrical portion 17: Male thread 18: Joint end 19: Female thread 20: Lip end 21: Fully screwed Seat part 22a: Pin tip 23: Pin
25: GEX 28: Boundary area between complete thread and incomplete thread 29: Pipe agent Teruo Taniyama ゛, -〇 Figure 1 (Q) l2 thread 2: thread 3: thread 4: thread bottom 5: Screw bottom 6: Screw bottom 7: Bin complete end 8: Box complete screw end 9: Bottle tip lO: Bottle tip Fig. 2 (Q) 7: Bin complete end 8: Box complete screw end 9: Bottle tip 10: Pin tip tip snoring retraction Iku Fig. 5 25: Box 28: Boundary between completely threaded part and incompletely threaded part 29: Vibrator Fig. 6 Fig. 8M

Claims (1)

[Claims] A male thread is carved into the tip of the pipe, and an unthreaded taper part is provided on the extension thereof, and the cylinder (box) to which this male threaded pipe end pin is fastened has a corresponding one. A female thread is engraved to
It has an oil country tubular joint structure in which a threadless inner cylinder taper part corresponding to the pin threadless part is carved on the inner extension, and when the pin and box are screwed together, the male thread tip of the pin starts to fully thread. Intentionally over-contact the screw thread at the point with the bottom of the screw that rises rapidly at the end of the complete thread (or the start point of the incomplete thread) deep inside the female thread of the box, or do not connect the pin or box screw thread. Sometimes, the incompletely threaded part of the male threaded end of the pin, where the bottom of the screw on the fully threaded extension rises up, is intentionally brought into excessive contact with the thread of the fully threaded end deep inside the female thread of the box.
1. A pipe joint for oil country tubular goods having a stopper function in a threaded part, characterized by having a structure in which tightening is stopped by a combination of relatively complete threads and incomplete threads on the pin and box side.