JP3225779B2 - Oil well pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casing oil country tubular good which is not destroyed by land subsidence.

[0002]

2. Description of the Related Art An oil well for pumping crude oil from an oil reservoir to the ground is composed of an oil well pipe.
It comprises a tubing oil well pipe for pumping crude oil and a casing oil well pipe for protecting the tubing oil well pipe from the outside.

[0003] Since the above-mentioned oil well is generally dug vertically, in particular, an oil well pipe for a casing (hereinafter, referred to as an oil well pipe).
(Referred to simply as an oil well pipe), downward frictional force generated by the surrounding land subsidence acts.

However, in most of the conventional oil wells, the frictional force acting on the oil well pipe as described above is not always large, and thus the probability that the oil well pipe is broken by the frictional force is low. No mitigation measures have been taken.

[0005]

However, in recent years, with the deterioration of the conditions for extracting crude oil, the depth of oil wells has tended to increase, and the problem of destruction due to land subsidence of oil well pipes constituting oil wells has been increasing. Began to be noticeable. In other words, a large pressure is applied to the oil country tubular goods as the depth increases, and the frictional force acting as a result increases, and the situation that the oil country tubular goods are destroyed cannot be ignored. Therefore, recently, there has been a demand for an oil country tubular good capable of reducing a frictional force generated by land subsidence, which has not existed conventionally.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problematic store of the prior art. Since the frictional force acting on the oil well pipe can be reduced, the oil well is hardly destroyed even by land subsidence. It is intended to provide tubes.

[0007]

The oil country tubular goods according to the present invention have a density of 0.930 g / cm ³ outside the oil country tubular goods main body.
A stiffness coefficient S (t) after one year in a temperature range of 130 ° C. or more where an oil country tubular good is used.
An oil country tubular good characterized by having a sliding layer made of a material in the range of ^-5 N / m ² to 10 ³ N / m ² .

Further, the stiffness coefficient S (t) after one year has passed in a temperature range of 130 ° C. or more where the oil country tubular goods are used outside the oil country tubular goods main body is 10 ⁻⁵ N / m ² to 10 ³ N / m. ^Two
An oil country tubular good characterized by having a sliding layer made of a material mainly composed of an ethylene propylene block copolymer within the range of (1).

Particularly preferable results are obtained by using maleic acid-modified polyethylene as the polyethylene, maleic acid-modified polypropylene as the polypropylene, and maleic acid-modified ethylene propylene block copolymer as the ethylene propylene block copolymer.

Further, it is preferable that a protective layer is provided outside the sliding layer.

[0011]

When a frictional force due to land subsidence acts on an oil well pipe buried vertically in the ground, a viscous slip layer covering the outside of the oil well pipe is deformed while being dragged downward by the frictional force. Most of the frictional force acting on the OCTG is
Since the slip layer is used for deformation, the frictional force acting on the oil country tubular good is reduced.

The following is a description of such a phenomenon in the schematic diagram shown in FIG. That is, when a constant shear stress (residual negative friction force) τ due to land subsidence acts on the upper surface of the slip layer 21 having the thickness h exhibiting the viscous behavior, after t seconds, the shear deformation (shown by a broken line in the figure) occurs. Viscous behavior) occurs.

The relationship between the shear deformation d (t) after t seconds and the residual negative friction force τ is based on the stiffness coefficient S of the slip layer.
Using (t) and the thickness h of the slip layer, it can be expressed as in equation (1).

Τ = S (t) · d (t) / 3h (1) From equation (1), if a material having a small stiffness coefficient S (t) is used for the slip layer, the residual negative frictional force τ Can be reduced.

The present inventors have conducted a model experiment, and in order to reduce the possibility that an oil country tubular good will be destroyed by land subsidence,
It has been found that the frictional force τ should be 2 × 10 ³ N / m ² or less. Furthermore, it has been found that by setting the frictional force τ to 2 × 10 ³ N / m ² or less, it is possible to almost completely prevent breakage.

From these results, when the frictional force of 2 × 10 ³ N / m ² continues to act on the slip layer having a thickness h of 2 mm, the displacement d (t) of the slip layer after one year is reduced. 20mm
Stiffness coefficient, that is, the stiffness coefficient S (t) after one year of the slip layer where the oil country tubular good does not break down
Was found to be 10 ³ N / m ² . That is,
After one year, the stiffness coefficient S (t) is 10 ³ N / m ²
Then, the oil country tubular good is hardly broken, and the stiffness coefficient S (t) after one year corresponding to the case where the frictional force acting on the sliding layer is 2 × 10 ³ N / m ² is 10 ³ N / m
If it was ² , it was found that there was virtually no destruction of the OCTG.

In other words, a material having a stiffness coefficient S (t) of more than 10 ³ N / m ² after a lapse of one year does not have a sufficient slip layer deformability, cannot reduce the frictional force, and cannot be used for an oil country tubular good. Has a high probability of being destroyed.

Further, the stiffness coefficient S after one year of use
It was also found that when (t) was less than 10 ^-5 N / m ² , the slip layer softened and eluted.

The stiffness coefficient S (t) of the material according to the present invention gradually decreases during less than one year, but after one year, it is the same as that at one year and hardly changes. The range of the stiffness coefficient S (t) is the same after one year has passed.

As described above, the oil country tubular goods according to the present invention reduce the frictional force between the submerged ground and the oil country tubular goods main body by viscous behavior of the sliding layer, and prevent the oil country pipes from breaking. Yes, the material of the sliding layer is selected according to the temperature at which the oil country tubular goods are used.

That is, as a matter of course, it is necessary that the material used for the sliding layer has a desired viscous behavior in the intended temperature range.

Therefore, for example, when used in a temperature range of 130 to 160 ° C., in which destruction of an oil country tubular good is a problem, the stiffness coefficient S (t) after one year has passed as a material for the slip layer is as follows: 1 in the temperature range of 130 to 160 ° C
By selecting a material within a range of 0 ^-5 to 10 ³ N / m ² , more preferably a material within a range of 10 ^-5 to 10 ² N / m ² , the destruction of the oil country tubular good can be prevented. Become.

Of course, even outside this temperature range,
It is desirable to satisfy this condition. That is, it is needless to say that a material that satisfies the above range of the stiffness coefficient S (t) in a temperature range as wide as possible is preferable.

At present, the temperature to which the OCTG is exposed is 1
As a result of various investigations on materials having a temperature of 60 ° C. or less but satisfying the above conditions, it was found that some materials could be used as the slip layer.

[0025] That is, as the material of the sliding layer, the polyethylene having a density greater than 0.930 g / cm ^3, maleic acid modified polyethylene having a density greater than 0.930 g / cm ^3, ethylene-propylene block copolymer, maleic acid-modified ethylene-propylene block copolymer , Polypropylene or maleic acid-modified polypropylene, the value of the stiffness coefficient S (t) after one year in this temperature range is 10 ⁻⁵ to 10 ³ N / m ^2.
Thus, the condition that the oil country tubular good is not broken can be satisfied.

In the case of using polyethylene or polyethylene maleate, if the density becomes 0.930 g / cm ³ or less, the stiffness coefficient S after one year at a high temperature is increased.
The value of (t) becomes 10 ⁻⁵ N / m ² or less, and a slip layer cannot be formed due to elution.

A slip layer made of a material mainly composed of polyethylene or a maleic acid-modified ethylene-propylene block copolymer other than polyethylene or maleic acid-modified polyethylene, maleic acid-modified ethylene propylene block copolymer, polypropylene or maleic acid-modified polypropylene also shows similar characteristics. The condition that is not destroyed can be satisfied.

It is to be noted that additives and the like can be mixed with the above-mentioned resin as required. And such a slip layer can be formed on the outer surface of the oil country tubular good by, for example, extrusion coating.

Next, the reason for providing the protective layer will be described. The protective layer has a function of preventing the slip layer and the oil country tubular goods main body from being damaged when the oil country tubular goods are transported or buried. In the present invention, a case having a protective layer is included as necessary.

For the protective layer, a material that does not soften under the environment where the oil country tubular goods are used is used. That is, when the upper limit of the use temperature is 160 ° C., a material having a softening point exceeding 160 ° C. may be used.

As such a material, polypropylene or an ethylene propylene block copolymer is preferred.

As in the case of the slipping layer, additives and the like can be mixed in the protective layer as required.

The protective layer made of resin can also be formed on the outer peripheral surface of the sliding layer, for example, by extrusion coating. On the other hand, a metal such as mild steel is also useful as a protective layer. For example,
A mild steel strip can be wound spirally to form a protective layer. Of course, the presence or absence of the protective layer does not affect the frictional force acting on the OCTG.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An oil country tubular good according to an embodiment of the present invention will be described with reference to FIGS. Fig. 1 is a sectional view of this oil country tubular good.
1 is an oil country tubular good, 2 is a slip layer, and 3 is a protective layer.

FIG. 2 is an explanatory view showing one method of manufacturing an oil country tubular good. This oil country tubular good has a sliding layer extruder 4 on the outer peripheral surface of the oil country tubular good 1 for extrusion coating of the slip layer 2, and a protective layer extruder 5 for extrusion coating of the outer peripheral surface of the slip layer 2 with the protective layer 3. It is manufactured by

Example 1 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
This is a 12,000 mm long oil country tubular goods, and is formed by extrusion coating the outer peripheral surface with polyethylene having a softening temperature of 125 ° C. and a density of 0.938 g / cm ³ , which is heated and melted by a slide layer extruder 4, and a 3 mm thick slide layer. 2 was manufactured.

Example 2 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
It is a 12,000 mm long oil country tubular good, and its outer peripheral surface is extruded with a maleic acid-modified polyethylene having a softening temperature of 130 ° C. and a density of 0.945 g / cm ³ , which is heated and melted by a slide layer extruder 4, and has a thickness of 3 mm. An oil country tubular good having a slip layer 2 was manufactured.

Example 3 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
An oil country tubular good having a length of 12,000 mm, the outer peripheral surface of which is extruded and coated with an ethylene propylene block copolymer having a softening temperature of 135 ° C., which has been heated and melted by a slide layer extruder 4, and
An oil country tubular good having the slip layer 2 having a thickness of mm was manufactured.

Example 4 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
An oil country tubular good having a length of 12,000 mm, the outer peripheral surface of which was heated and melted by a slide layer extruder 4 and coated with polypropylene having a softening temperature of 140 ° C., was extruded to produce an oil country tubular good having a slide layer 2 having a thickness of 3 mm.

Example 5 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
It is a 12,000 mm long oil country tubular good, and the outer peripheral surface is extruded with a maleic acid-modified polypropylene having a softening temperature of 140 ° C., which has been heated and melted by a sliding layer extruder 4 to form a sliding layer 2 having a thickness of 2 mm. The protective layer extruder 5 heats and melts the softened temperature of 1 on the outer peripheral surface of the lever sliding layer 2.
An oil country tubular good in which a protective layer 3 having a thickness of 3 mm was formed by extrusion coating with 65 ° C. polypropylene was manufactured.

Example 6 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
This is a 12,000 mm long oil country tubular good, and its outer peripheral surface is extruded with a maleic acid-modified polyethylene having a softening temperature of 125 ° C. and a density of 0.938 g / cm ³ , which is heated and melted by a slide layer extruder 4, and has a thickness of 2 mm. Is formed on the outer peripheral surface of the sliding layer 2 by extrusion coating with an ethylene propylene block copolymer having a softening temperature of 155 ° C., which is heated and melted, by a protective layer extruder 5 to form a protective layer having a thickness of 3 mm. The oil country tubular goods having formed No. 3 were manufactured.

Example 7 The used steel pipe had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
It is a 12,000 mm long oil well tube, and the outer peripheral surface is extruded and coated with a maleic acid-modified ethylene propylene block copolymer having a softening temperature of 135 ° C., which is heated and melted by a sliding layer extruder 4 to form a 2 mm thick sliding layer 2. Then, on the outer peripheral surface of the sliding layer 2, a thickness of 0.3 mm and a width of 200 mm
A steel strip having a thickness of 2 mm was spirally wound to produce an oil country tubular good having the protective layer 3 formed thereon.

Comparative Example 1 The steel tube used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
It is a 12,000 mm long oil country tubular good, and its outer peripheral surface is extrusion-coated with polyethylene having a softening temperature of 100 ° C. and a density of 0.928 g / cm ³ , which is heated and melted by a slide layer extruder 4, and a 2 mm thick slide layer. 2 was manufactured.

Comparative Example 2 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
This is a 12,000 mm long oil country tubular goods, and its outer peripheral surface is extruded with a maleic acid-modified polyethylene having a softening temperature of 100 ° C. and a density of 0.928 g / cm ³ , which is heated and melted by a slide layer extruder 4, and has a thickness of 2 mm. An oil country tubular good having a slip layer 2 was manufactured.

Comparative Example 3 The steel pipe used had an outer diameter of 177.8 mm, a wall thickness of 23.8 mm,
It is a 12,000 mm long oil well tube, and the outer peripheral surface is extruded and coated with an ethylene vinyl acetate copolymer resin having a softening temperature of 80 ° C., which is heated and melted by a slide layer extruder 4 to form a 2 mm thick slip layer 2. Subsequently, the softening temperature, which was heated and melted, by the protective layer extruder 5 on the outer peripheral surface of the sliding layer 2 was 1
3 mm thick protective layer 3 made of polypropylene at 55 ° C.
An oil country tubular good was formed.

The above Examples 1 to 7 and Comparative Examples 1 to 3
About 130 ° C, 135 ° C, 140 ° C, 1
1 at 45 ° C, 150 ° C, 155 ° C and 160 ° C
The stiffness coefficient S (t) of the slip layer after a lapse of one year and 15
The stability of the protective layer after standing in a furnace at 0 ° C. and 160 ° C. for 1 hour was investigated. Table 1 shows the results.

[0047]

[Table 1]

For the oil country tubular goods of Examples 1 to 7, the stiffness coefficient S (t) after one year has passed is 10 ⁻⁵ to 10 ³ N / m.
^It can be used in the temperature range (circle ○ in the table) in the range of 2. In this temperature range, there is little possibility that the oil country tubular goods will be destroyed by land subsidence. In addition, it is extremely safe when used in a temperature range (marked by ◎ in the table) in which the stiffness coefficient S (t) is in the range of 10 ⁻⁵ to 10 ² N / m ² .

On the contrary, Comparative Examples 1 and 2 can be used only at 130 ° C. or lower, and at 135 ° C. or higher, the stiffness coefficient S (t) after one year has passed is 10 ⁻⁵ N / m ² or less. In Comparative Example 3, the stiffness coefficient S (t) after one year had passed in any temperature range was 10 ⁻⁵ N / m ² or less.
It can be seen that the slip layer elutes and the oil country tubular goods are easily destroyed by land subsidence.

Although the protective layer of the oil country tubular good of Example 6 is slightly deformed on the high temperature side, it is expected that the protective layer sufficiently plays the role of the protective layer during transportation and burial construction. Of course, the protective layer of mild steel of Example 7 is stable regardless of the temperature.

Thus, an oil country tubular good having a slip layer made of a material mainly composed of polyethylene, maleic acid-modified polyethylene, ethylene propylene block copolymer, maleic acid-modified ethylene propylene block copolymer, polypropylene or maleic acid-modified polypropylene, or a mixture thereof. Is extremely safe against destruction from land subsidence when used in a temperature range from room temperature to 160 ° C.

[0052]

According to the present invention, the oil well pipe can be prevented from being destroyed due to land subsidence, and the slip layer and the oil well pipe main body can be prevented from being damaged not only when the oil well pipe is transported but also when the oil well pipe is buried.

[Brief description of the drawings]

FIG. 1 is a sectional view of an oil country tubular good according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a method of manufacturing an oil country tubular good according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating the viscous behavior of a slip layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oil well pipe main body 2 Slip layer 3 Protective layer 4 Slip layer extruder 5 Protective layer extruder

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-24211 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16L 9/14 B32B 1/08 B32B 13 / 06 E21B 17/00

Claims (6)

(57) [Claims] 1. A density of 0.930 outside the oil country tubular good main body.
polyethylene or polypropylene exceeding g / cm ³ a material mainly, 130 ° C. or more, which oil well pipes are used
Stiffness coefficient S after one year in the upper temperature range
(T) An oil country tubular good characterized by having a sliding layer made of a material in the range of 10 ⁻⁵ N / m ² to 10 ³ N / m ² . 2. The oil country tubular good according to claim 1, wherein the polyethylene is a maleic acid-modified polyethylene. 3. The oil country tubular good according to claim 1, wherein the polypropylene is maleic acid-modified polypropylene. 4. A stiffness coefficient S (t) after one year in a temperature range of 130 ° C. or more in which the oil country tubular goods are used, outside the oil country tubular goods main body, is 10 ⁻⁵ N / m ² to 10 ³ N / s. An oil country tubular good having a sliding layer made of a material mainly containing an ethylene propylene block copolymer having a range of m ² . 5. The oil country tubular good according to claim 4, wherein the ethylene propylene block copolymer is a maleic acid-modified ethylene propylene block copolymer. 6. The oil country tubular good according to claim 1, further comprising a protective layer outside the sliding layer.