JPS6026878A - Steel pipe joint for oil well - 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 (1) Field of Industrial Application The present invention relates to a joint for oil well steel pipes used in oil fields, and particularly to a joint used in places where airtightness is required.

(2) Prior art In recent years, due to the deterioration of the global oil situation, oil well drilling has become active in various countries, but the environment is becoming increasingly harsh, with deepening, high temperature and high pressure, and cooling. Drilling also targeted oil fields containing hydrogen sulfide (H2S), which were heading toward the ocean floor and had not been seen since.

The characteristics of the joint required here include not only the strength required to withstand high stress, but also resistance to erosion caused by fine particles such as rocks contained in oil that rises at high speed. There is no leakage of gas, especially H2S, and since the joint itself is expensive, it can be used again and again in the next oil field after extraction from one oil field without being used up.

By the way, hydrogen sulfide (H2S) is not only harmful to the human body, but also has the property of rapidly corroding the parts and inducing cracks when it enters a pan under high stress. Therefore, in oil fields where hydrogen sulfide (Has) exists, long oil wells)
If hydrogen sulfide (H2S) infiltrates the threaded part of the joint where the stress is greatest within the J-song string, the joint will break during use, causing major economic damage due to interruptions in oil extraction. This would cause serious disaster to the farmers and nearby residents.

Currently commonly used American Petroleum Institute (API)
) The standard joint has the shape shown in Figure 1, but it is structured so that gas can easily leak through the helical gap formed by the top of the male thread 3 of bottle 1 and the bottom of the female thread 4 of box 2. Therefore, API standard fittings are not used in hydrogen sulfide (H2S) oil fields.

Also, since the inner surface of the IJ song with the API standard joint has discontinuous steps at the joint, the upward flow of crude oil becomes turbulent. It cannot be used in high-pressure oil fields because the flow velocity is high in high-pressure oil fields, and turbulent flow occurs due to hard objects such as rocks contained in the crude oil.

Therefore, a joint that has both airtightness and smooth inner surface,
A so-called premium joint is used.

Premium joints currently in use are roughly divided into two types.

One type is a machined part 2 (hereinafter referred to as a box) with a female thread on the inner surface of the end of the steel pipe, as shown in Figure 2.
If you cut out a part of the thread, make a groove, fit a Teflon ring T there, and then screw together the machined part 1 (hereinafter referred to as the bottle) that has a male thread on the outer surface of the end of the steel pipe, the comparative terms and conditions will be met. This is a joint in which the Teflon ring T deforms and fits closely along the male thread 3, creating an airtight structure.

However, the Teflon ring T, which was previously fitted into box 2 at the joint processing factory, fell off due to vibration during transportation.
Alternatively, it is often the case that the bottle 1 is pushed out by the male screw 3 while being rotated and screwed together at the site. There is a drawback that it causes a decrease in strength.

Another type is shown in FIG. Screw the bottle into the box 2 to make metal contact between the pin nose tip face 5 and the box end face 7, or between the bottle nose flank 6 and the box flank 8, and then use a machine to rotate it strongly and push it into the metal contact area. This is a joint that causes plastic deformation to create a more completely airtight structure. Although the contact parts are zinc-plated, tin-plated, or chemically treated, the coating often breaks down and comes into contact with the pieces, causing seizure and making it impossible to reuse1. There are two methods: the integral method, in which a bottle is machined at one end of the tube and a box at the other end, and the tubes are connected to each other, and the two are connected by a coupling consisting of two boxes and a tube with a bottle machined at both ends. There are various cambling methods, both of which use a Teflon ring seal or a metal contact seal.

(3) Purpose of the Invention In view of the above-mentioned drawbacks, the purpose of the present invention is to provide a highly airtight oil well/line steel pipe screw joint that does not use a Teflon ring that easily falls off and can be used repeatedly without baking. Our goal is to provide the following.

(4) Constituent Function of the Invention The gist of the invention is to provide a steel pipe joint in which a pin having a male thread on the outer surface of one end of one pipe and a box having a female thread on the inner surface of the other end are screwed together.
A smooth groove is provided on the end face, the bottle nose flank, the second end face of the bottle nose, and the inner diameter surface of the bottle nose part, and a smooth groove is provided on the box first end, the box second end, and the inner diameter surface near the box first end face. , the bottle nose flank makes an included angle of 15° or less with respect to the tube axis, the first end surface of the bottle nose makes an included angle of 60° or more with the tube axis, and the box flank makes an included angle of 15° or less with the tube axis. None, the first end of the box is 60 mm with respect to the tube axis.
The included angle is greater than or equal to °, and each point on the outer diameter of the bottle nose flank is smaller than the inner diameter of the corresponding point on the box flank;
For use in oil wells, the pin nose is longer than the box flank, and the first end surface of the bottle nose is in contact with the first end surface of the box, and the second end surface of the bottle nose is in contact with the second end surface of the box. For steel pipe joints, the thickness of the pin nose is made thinner to prevent elastic deformation, and when screwed together, the first end face of the bottle nose and the first end face of the box are brought into close contact to create an airtight S structure, so that the pin nose is not screwed in excessively. The second end surface of the bottle nose is brought into contact with the second end of the box to prevent buckling or breaking, and serves as a stopper, and at the same time, the bottle nose flank is elastically deformed and brought into close contact with the box flank, creating a 2N airtight structure. Smooth concave grooves are created on the inner diameter surface to prevent turbulence and erosion. On the other hand, once removed and the pin nose is free from stress, it will return to its original state due to elastic force, making it reusable. It is a joint.

The present invention will be described in detail below using the drawings. 4 to 6 show a joint for oil country tubular goods showing one embodiment of the present invention,
Figure 4 shows an integral type pin in a threaded joint.
FIG. 5 shows an integral type box, and FIG. 6 shows cross sections of the bottle and box screwed together. In FIG. 4, the bottle nose flank 14 consists of a straight line forming an included angle of θ with respect to the tube axis. When the bottle nose flank 14 is arcuate, the maximum angle among the included angles between the tangent at each point and the tube axis is defined as 01.

The first end face 12 of the bottle nose is a straight line that forms an included angle of θ2 with respect to the tube axis. When the bottle nose first end surface 12 is arcuate, the maximum angle among the included angles between the tangent at each point and the tube axis is defined as 02.

The bottle groove 15 has a smooth curved surface made of a combination of curved lines. When n15 is made of an arcuate curved surface, the included angle between the tangent at each point and the tube axis is θ3.

Extension line of bottle nose first end face 12 (hereinafter referred to as A'PI) Extension line of toppin nose flank 14 (hereinafter referred to as 1pF)
) is the intersection of A1 and the second end face of the bottle nose (E.

If we define the intersection of the extension line of B") 13 and IPF as B1, the intersection of the extension line of smooth groove 15 (hereinafter referred to as IPG) and Ilp+ as 011'pa, and the intersection of the inner diameter surface DPI as D, we can obtain the bottle nose tip thickness. (The vertical distance between A-0) is TP+ 1 The length of the bottle nose flank i" The distance parallel to the tube axis between B) is LPF, the groove depth is DPI
and 0) is HPG, the groove length C-D
The distance parallel to the tube axis) is 1 Lpc.

3 indicates a male thread, and API standard round threads or buntless threads are also acceptable and have nothing to do with airtightness.0 In Figure 5, the box flank U stands out from a straight line that forms an included angle to the pipe axis. .

When the box flank shape is a circular arc, the definition is the same as 01 when the bottle nose flank 14 is circular.

The first box end 22 is formed by a straight line forming an included angle of θ5 with respect to the tube axis. When the box first end face 22 is an arc, the definition is the same as 02 when the first end face of the bottle nose is an arc.

The groove 5 of the box consists of a combination of curved lines, and the included angle between the tangent at point D' and the tube axis is 06.

If the length 5 is made of an arc shape, the definition is the same as θ3.

The intersection of the extension line of the box flank (hereinafter referred to as 6Bp) and the first end of the box flank is A'l box second end face (B" B/
//) The intersection of the extension line of O (hereinafter referred to as lB2) and 7BF is B', and the intersection of the extension line of the smooth groove δ (hereinafter referred to as lBG) and AB+ is C' + lBG and the box inner diameter surface DBI. If the intersection point is D', then the vertical distance of the first end of the box) is TB+ 1 The box flank length (A
The distance parallel to the tube axis between ' and B' is IJBF *
HB. , groove length C'~D
the distance parallel to the tube axis) is LBG.

Reference numeral 4 indicates a female thread, which may be screwed into the male thread 3 of the bottle.

The reason why the first end surface n of the box in FIG.
This is because when an attempt is made to push the bottle into the box 20, a force is exerted to push up the bottle nose 11.

Each point of the outer diameter of the bottle nose flank 14 is smaller than the inner diameter of each corresponding point of the box flank, the bottle nose flank length LPF is longer than the box flank length LBF, and the inclination angle θ2 of the first end face 12 of the bottle nose is smaller than the inner diameter of the corresponding point of the box flank. 1st
The reason why the inclination angle θ of the end face 22 is large and the reason why the second end face 13 of the bottle nose and the second end face of the box are provided will be explained with reference to FIG.

When screwing together the bottle 10 shown in FIG. 4 and the box shown in FIG.
The lower end of the end surface 22 abuts geometrically, that is, in a state where the bottle nose 11 is not elastically deformed.

The maximum value of the gap between the bottle nose flank 14 and the box flank at this time is defined as HPB.

In this state, there is a fan-shaped gap above point C (C'), and there is also a gap of maximum HPB between the bottle nose flank 14 surface and the box flank road surface. Next, when the bottle 10 is rotated using a machine and moved further to the right, the box first end face 22
Since the advancement of the bottle nose 11 is suppressed by
The box rotates clockwise around the first end of the box and stops when θ2-θ5 is reached.

The bin north flank 14 is elastically bent upwards to point E.
In contact with the box flank, the bottle nose length is LPF
C < LPF).

At this point, the second end face 13 of the bottle nose comes into contact with the second end face Z3 of the box, and when the torque rapidly increases and reaches a predetermined value, the screwing operation is completed.1 A double airtight structure is obtained.

The position of the second end surface 13 of the bottle nose is determined so that the pin nose 11 portion contacts the bottle nose flank surface U within elastic deformation.

In this case, Lpc + Lna = L + Lpc
≦50mm.

LBG≦5011m, L≦100mm, L
pc > LBa, Lpa = LBG + Lp
c < LEG.

Fig. 7 shows another embodiment of the joint of the present invention screwed together, in which the first end face 12 of the bottle nose and the first end face n of the box are curved surfaces with the same curvature, and the groove 15 of the bottle nose and the bamboo 5 of the box is a combination of straight lines.

When the screwing of the pin 10 with the honks mark is completed, the first end surface 12 of the bottle nose and the first end surface 22 of the box are in full contact with each other, and the bottle nose portion is slightly elastically deformed upward and comes into contact at the E' portion.
It has a double airtight structure.

Next, the reason for the numerical limitation is described.

The included angle θ8 of the bottle nose flank 14 with respect to the tube axis is 15
The reason why the angle is within 15 degrees is because if the angle is larger than 15 degrees, the bottle nose thickness Tp+ cannot be made much thicker, the length of the bottle nose is short, and the amount of elastic deformation is also small.

If the included angle θ of the first end surface of the bottle nose with respect to the tube axis is 6 times 0 or more, if it is less than this, the tip of the bottle nose (A
This is because the meat (near the point) is tingling and deforms during processing, making it impossible to obtain sufficient processing accuracy.

The included angle θ4 to the tube axis of the box flank is 15.

Below and the bottle nose first end face 12 is the box first end face 22
This is because if the inclination angle of the bottle nose flank 14 is greater than the maximum value of θ1≦15° when it comes into geometric contact with the bottle nose flank 14, the gap between the top and flanks of the bottle nose flank 14 will become large and the bottle nose flank 14 will no longer deform and contact. be.

The reason why the included angle θ at the first end of the box is set to 60° or more is because if the angle is less than this angle, the first end of the box easily deforms and a sufficient processing grain size cannot be obtained.

Next, the groove lengths LPG and LEG should be within 5Q1+α.If they exceed 5Qmm, the joint strength will decrease and the length of the tool holder will become too long, causing chatter during groove machining, resulting in a smooth surface. This is because it will not happen. The included angle θ1 of the groove slope with respect to the pipe axis. θ6 is 45° or less.
This is because if the bottle nose is exceeded, stress will be concentrated in the deepest part of the bottle, making the bottle nose more likely to break.

(5) Examples Next, the effects of the present invention will be explained in more detail using examples of the present invention.

Example 1 A pipe to be joined (oil well steel pipe API standard N-80, outer diameter 177.8 m, wall thickness 11.5111 m f) was used.

The integral type joint is made from a thickened steel pipe with absent at both ends. Two sets of test specimens were manufactured for both the integral method and the compacting method, and two sets of API standard joints were used as comparison materials.

Display the specifications of the test piece.

Six test specimens were assembled with joints coated with API 5A2 modified compound grease with a tightening torque of 1100 kg-m.
Maintained at atmospheric pressure and tensile force of 135 tons, 66℃ to 163℃
Although the four joints of the present invention were subjected to a temperature cycle of 100 times, all of them were perfect with no leakage from the joints, but A, P
Both of the I-standard units had nitrogen gas leaks.

Implementation Reli 2 Tighten one set of each type of Honreimei that had no gas leak in Example 1 with a torque of 1100/l; I repeated this several times, but no burning occurred.

(6) Effects of the Invention As detailed above, the present invention has the advantage of preventing loss of airtightness due to the Teflon ring falling off, unlike conventional premium joints.
Furthermore, there was no problem that the product could not be reused due to seizure caused by fully bent plastic deformation contact.

Furthermore, since the groove machined on the inner surface of the tip of the bottle nose has a smooth surface, stress concentration does not occur, and deformation is within the elastic limit, so the stress is low and there is no stress corrosion due to H2S, and the upper fluid can flow through the groove. This is an excellent joint that can prevent erosion caused by turbulent flow, and is extremely useful industrially.

[Brief explanation of the drawings] Fig. 1 is a cross-sectional view of an APi standard oil well pipe joint, Fig. 2 is a cross-sectional view of a premium joint using a Teflon ring, and Fig. 3 1 is a cross-sectional view of a metal contact type premium joint. Figure 4 is a cross-sectional view of one aspect of the bottle of the present invention, Figure 5 is a cross-sectional view of one aspect of the box of the present invention, and Figure 6 is a contact portion when the bottle and box of the present invention are screwed together. Detailed view: FIG. 7 is a detailed view of the abutment part when the bottle and box are screwed together according to another embodiment of the present invention. ■...Bin, 2 Box, 3...Male thread, 4...Female thread, 5...Bin nose tip surface, 6...Bin nose flank, 7. Box end surface, 8...Box flank, 10... Bottle, 11... Bottle nose, 12. Bottle nose first end surface, 13... Bottle nose second end surface, 14... Bottle nose flank, 15... Smooth groove on the bottle side, Input... Box, 21. ...Near the first end of the box, n...First end face of the box, Ru...Second end face of the box, 24...Box flank, 5...Smooth groove on the box side. Patent applicant: Nippon Steel Corporation representative Patent attorney: Fuku Kumagai 1.

Claims (1)

[Scope of Claims] fil In a steel pipe joint in which a pin having a male thread on the outer surface of the end of one steel pipe is screwed together with a box having a female thread on the inner surface of the end of the other steel pipe, the pin has a pin nose first end surface and a pin nose flank. A smooth groove is provided on the second end face of the pin nose and the inner diameter surface of the bottle nose portion, and a smooth groove is provided on the box first end face, the box flank, the second end face of the box, and the inner diameter surface near the first end of the box. makes an included angle of 10° or less with respect to the tube axis, the first end face of the bottle nose makes an included angle of 60° or more with the tube axis, the box flank makes an included angle of 10° or less with the tube axis, and the box nose Each point of the outer diameter of the first end bottle nose flank is smaller than the inner diameter of each corresponding point of the box flank, the length of the bottle nose is longer than the length of the box flank, and the first end surface of the bottle nose is thicker than the first end surface of the box. having an angle, the bottle nose first
A steel pipe joint for oil wells having an end face and a box first end face, and a pin nose second end face and a box second end face. (2) A patent claim characterized by having a smooth port consisting of a combination of straight lines and/or circular arcs within 50 points toward the inner depth from the inner diameter tip of the pin nose and the inner diameter tip of the first end face of the box. Steel pipe joints for oil wells as described in Scope 1. (3) Claim 1, characterized in that the included angle between the tangent line and the tube axis at each point of the smooth groove on the inner diameter surface of the pin nose portion and the inner diameter surface near the first end of the box is within 45 degrees. Pot pipe fittings for oil wells.