Metal pipe for oil well

Abstract

The shear strength of the resin coating of the metal pipe for oil wells according to the present disclosure is excellent. This oil well metal pipe is provided with a resin film (100) formed as the uppermost layer of at least one of a pin contact surface (400) and a box contact surface (500). The resin coating (100) contains a base resin in a total amount of 40.0 to 99.4 mass%, a nylon in an amount of 0.1 to 20.0 mass%, TiO2 in an amount of 0.5 to 30.0 mass%, hydrous magnesium silicate in an amount of 0 to 49.4 mass%, wax in an amount of 0 to 10.0 mass%, a fluorine-based additive in an amount of 0 to 30.0 mass%, graphite in an amount of 0 to 10.0 mass%, an anti-rust pigment in an amount of 0 to 10.0 mass%, a coloring pigment in an amount of 0 to 10.0 mass%, and a coupling agent in an amount of 0 to 10.0 mass%. The ratio of the total content of the wax, the fluorine-based additive, and the graphite in mass% in the resin coating (100) to the total content of the TiO2, the hydrous magnesium silicate, and the nylon in mass% is 5.00 or less.

Description

Technical Field

[0001] The present disclosure relates to a metal pipe, and more particularly to a metal pipe for oil wells. Background Art

[0002] Oil well metal pipes are used in oil wells and gas wells (hereinafter collectively referred to as oil wells and gas wells and simply referred to as "oil wells"). Oil well metal pipes have threaded joints (male or female). At the oil well mining site, a plurality of oil well metal pipes are connected according to the depth of the oil well to form an oil well pipe connection body. An oil well pipe connection body is, for example, a casing and an oil pipe. The oil well pipe connection body is formed by threading the oil well metal pipes together. In addition, there are cases where the oil well pipe connection body is inspected. In the case of an inspection, the oil well pipe connection body is pulled up and the threads are loosened. In addition, the oil well metal pipe is removed from the oil well pipe connection body by loosening the threads and inspected. After the inspection, the oil well metal pipes are threaded together again, and the oil well metal pipe is reused as a part of the oil well pipe connection body.

[0003] The metal pipe for oil wells comprises a pin buckle part and a box buckle part. The pin buckle part has a pin buckle part contact surface including an external threaded part on the outer peripheral surface of the end of the metal pipe for oil wells. The box buckle part has a box buckle part contact surface including an internal threaded part on the inner peripheral surface of the end of the metal pipe for oil wells. In the present specification, the external threaded part and the internal threaded part are also collectively referred to as "threaded part". It should be noted that the pin buckle part contact surface also includes a pin buckle part unthreaded metal contact part, and the pin buckle part unthreaded metal contact part includes a pin buckle part sealing surface and a pin buckle part shoulder surface. Similarly, the box buckle part contact surface also includes a box buckle part unthreaded metal contact part, and the box buckle part unthreaded metal contact part includes a box buckle part sealing surface and a box buckle part shoulder surface.

[0004] The pin and box contact surfaces of oil well metal pipes are repeatedly subjected to strong friction when the threads are tightened and loosened. Therefore, the pin and box contact surfaces are prone to galling (irreparable wear) when the threads are repeatedly tightened and loosened. Therefore, sufficient durability against friction, that is, excellent wear resistance, is required for oil well metal pipes.

[0005] In the past, in order to improve the wear resistance of metal pipes for oil wells, compound greases mixed with heavy metal powders called dopants were used. The wear resistance of metal pipes for oil wells can be improved by applying compound grease to the contact surface of the pin part and / or the contact surface of the box part. However, there is a possibility that heavy metal powders such as Pb, Zn and Cu contained in the compound grease will affect the environment. Therefore, it is desired to develop a metal pipe for oil wells that has excellent wear resistance even without using compound grease.

[0006] Techniques for improving the wear resistance of oil well metal pipes are proposed in, for example, Japanese Patent Application Laid-Open No. 2003-021278 (Patent Document 1) and International Publication No. 2006 / 104251 (Patent Document 2).

[0007] The metal pipe for oil wells disclosed in Patent Document 1 has a threaded joint, which is composed of a pin and a box, each of which has a contact surface including a threaded portion and a non-threaded metal contact portion. Furthermore, the contact surface of at least one of the pin and the box has a solid lubricating coating composed of a solid lubricant and a binder. In the cross section in the thickness direction of the solid lubricating coating, the area ratio occupied by secondary particles of the solid lubricant with an equivalent area diameter of 15 to 60 μm is 5 to 90%. Patent Document 1 discloses the following: According to the metal pipe for oil wells, wear resistance and air tightness can be stably ensured without applying a composite grease.

[0008] The oil well metal pipe disclosed in Patent Document 2 has a threaded joint, which is composed of a pin and a box, each of which has a contact surface having a threaded portion and a non-threaded metal contact portion. Furthermore, the contact surface of at least one of the pin and the box has a viscous liquid or semi-solid lubricating film and a dry solid film formed thereon. Patent Document 2 discloses that according to the oil well metal pipe, rust is suppressed without using a compound grease, and excellent wear resistance and airtightness are exhibited.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2003-021278

[0012] Patent Document 2: International Publication No. 2006 / 104251 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] However, in the excavation of oil and gas, vertical drilling for excavating vertically and inclined drilling for excavating in an inclined direction relative to the vertical direction are generally used. On the other hand, one of the methods for excavating oil and gas is horizontal excavation. Horizontal excavation refers to the following method: the oil well excavated vertically is gradually bent in the horizontal direction, and finally excavated horizontally along the oil and gas reservoir. Compared with the usual vertical drilling and inclined drilling, horizontal drilling can contact more oil and gas reservoirs and increase the oil and gas production per unit drilling. In recent years, the use of horizontal excavation has increased in the excavation of oil and gas. Therefore, metal pipes for oil wells that can be used in oil well pipe connections conceived for horizontal excavation are sought.

[0015] In horizontal excavation, when the excavation direction changes from vertical to horizontal, the oil well pipe coupling body bends. In the bent portion of horizontal excavation, the oil well pipe coupling body is rotated in the circumferential direction of the pipe while excavation is performed so that the oil well pipe coupling body reaches the target oil and gas reservoir. Therefore, in the bent portion of the oil well pipe coupling body, in particular, as the oil well pipe coupling body bends and rotates in the circumferential direction, a torsion is applied to the metal pipe for oil wells. If the torsion is applied with a higher load, the metal pipe for oil wells is easy to loosen. In the case of vertical excavation direction, the torsion of the metal pipe for oil wells is mainly applied to the metal pipe for oil wells in the circumferential direction of the pipe. However, in the case of horizontal excavation, in addition to the torsion of the metal pipe for oil wells in the circumferential direction of the pipe, the torsion caused by the bending of the metal pipe for oil wells is also applied. Therefore, compared with the excavation in the vertical direction, in horizontal excavation, excessive torsion is further applied to the metal pipe for oil wells. Therefore, the metal pipe for oil wells is more likely to loosen.

[0016] If the oil well metal pipe can be tightened with a higher torque than before, the oil well metal pipe will not be easily loosened at the bent portion of the oil well pipe coupling during horizontal excavation. Therefore, when used for horizontal excavation, an oil well metal pipe that can be tightened with a higher torque than before is sought.

[0017] An object of the present disclosure is to provide a metal pipe for oil wells having an improved shear strength of a resin coating.

[0018] Solutions for solving problems

[0019] The oil well metal pipe disclosed herein includes a pipe body including a first end portion and a second end portion.

[0020] The pipe body comprises:

[0021] a male buckle portion formed at the first end portion; and

[0022] a female buckle portion formed at the second end portion,

[0023] The pin portion has a pin portion contact surface including an external thread portion,

[0024] The box portion has a box portion contact surface including an internal thread portion,

[0025] The oil well metal pipe further comprises a resin coating formed as the uppermost layer of at least one of the pin portion contact surface and the box portion contact surface,

[0026] The resin coating contains:

[0027] At least one base resin selected from the group consisting of epoxy resins, phenolic resins, acrylic resins, urethane resins, polyester resins, polyamide-imide resins, polyimide resins, and polyetheretherketone resins: 40.0 to 99.4% by mass in total,

[0028] Nylon: 0.1-20.0% by mass,

[0029] TiO2: 0.5-30.0 mass %,

[0030] Hydrous magnesium silicate: 0-49.4% by mass,

[0031] Wax: 0-10.0 mass %,

[0032] Fluorine additives: 0-30.0 mass %,

[0033] Graphite: 0-10.0 mass %,

[0034] Anti-rust pigment: 0-30.0 mass %,

[0035] Coloring pigment: 0 to 10.0% by mass, and

[0036] Coupling agent: 0-10.0% by mass

[0037] The ratio of the total content of the wax, the fluorine-based additive and the graphite in the resin coating in terms of mass % to the total content of the nylon, the TiO 2 and the hydrous magnesium silicate in terms of mass % is 5.00 or less.

[0038] Effects of the Invention

[0039] The resin coating of the oil well metal pipe disclosed herein is excellent in shear strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of a metal pipe for oil wells when the threads are tightened.

[0041] Figure 2 This is a cross-sectional view perpendicular to the pipe axis direction of the oil well metal pipe in the vicinity of the resin coating when the threads are tightened.

[0042] Figure 3 This is a graph showing the relationship between the shear strength and the yield torque of the resin coating.

[0043] Figure 4 This is a graph showing the relationship between the shear material ratio in the resin coating and the shear strength of the resin coating.

[0044] Figure 5This is a structural diagram showing an example of a T&C type (Threaded and Coupled) oil well metal pipe according to the present embodiment.

[0045] Figure 6 Yes means Figure 5 The illustrated partial cross-sectional view is a cross-sectional view of a coupling of a metal pipe for oil wells, taken along a section (longitudinal section) parallel to the pipe axis direction.

[0046] Figure 7 yes Figure 6 A cross-sectional view of a portion near a pin portion of the oil well metal pipe shown in FIG. 1 , parallel to the pipe axis direction of the oil well metal pipe.

[0047] Figure 8 yes Figure 6 A cross-sectional view of a portion near a box portion of the oil well metal pipe shown in FIG. 1 , parallel to the pipe axis direction of the oil well metal pipe.

[0048] Fig. 9 This is a diagram showing an example of an oil well metal pipe in which a pin portion includes an external thread portion but does not include a pin portion sealing surface and a pin portion shoulder surface, and a box portion includes an internal thread portion but does not include a box portion sealing surface and a box portion shoulder surface.

[0049] Fig.10 It is a structural diagram of the integral oil well metal pipe according to the present embodiment.

[0050] Fig.11 yes Figure 7 An enlarged view of the contact surface of the pin portion is shown.

[0051] Fig.12 yes Figure 8 An enlarged view of the contact surface of the female buckle portion is shown. DETAILED DESCRIPTION

[0052] Hereinafter, the present embodiment will be described in detail with reference to the drawings. The same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0053] The present inventors have studied metal pipes for oil wells that can be applied to oil well pipe couplings used in horizontal excavation and that can be fastened with a higher torque than before. As a result, the inventors have obtained the following findings.

[0054] As described above, an oil well pipe connection body is formed by threading the oil well metal pipes together. If the oil well metal pipes are threaded together, the torque increases according to the number of revolutions. In particular, the torque increases sharply in the final stage of thread tightening. On the other hand, if the torque when the threads are tightened becomes too high, the oil well metal pipe may yield. In this specification, the torque when the oil well metal pipe yields when the threads are tightened is also referred to as "yield torque". The higher the yield torque, the higher the torque that can be tightened with the oil well metal pipe. In other words, the yield torque can be used as an indicator of whether the oil well metal pipe can be tightened with a higher torque.

[0055] So far, as a method for improving the tightening torque of metal pipes for oil wells, a method of increasing the friction coefficient of the resin coating formed on the metal pipes for oil wells has been proposed. It is expected that when the metal pipes for oil wells are screwed together, if the resin coatings with a high friction coefficient come into contact and slide with each other, the torque of the screw tightening will increase. Therefore, by increasing the friction coefficient of the resin coating, it is possible to increase the yield torque. Therefore, the inventors of the present invention made the resin coating contain hydrated magnesium silicate powder and / or TiO2 as solid powder, adjusted the friction coefficient of the resin coating, and investigated the relationship between the friction coefficient and the yield torque. However, contrary to the expectations of the inventors of the present invention, it was found that the correlation between the friction coefficient and the yield torque is weak. The results of the investigation by the inventors of the present invention made it clear that the yield torque cannot be effectively increased by only increasing the friction coefficient of the resin coating.

[0056] Therefore, the inventors of the present invention have further studied oil well metal pipes that can be tightened with a higher torque. First, the inventors of the present invention focused on the behavior of the resin coating in the final stage of thread tightening. In the final stage of thread tightening, the resin coatings contact each other with a high surface pressure and slide along the circumferential direction of the oil well metal pipe.

[0057] Figure 1 This is a schematic diagram of a metal pipe for oil wells when the threads are tightened. Figure 1 The screw tightening is performed, for example, in the following manner: Fix the oil well metal pipe 1a. Insert the male buckle portion 40 of the oil well metal pipe 1b into the female buckle portion 50 of the fixed oil well metal pipe 1a. Rotate the inserted oil well metal pipe 1b in the circumferential direction of the oil well metal pipe 1b.

[0058] Figure 2 This is a cross-sectional view perpendicular to the pipe axis direction of the oil well metal pipe near the resin coating when the thread is tightened. It is assumed that the oil well metal pipe 1a is fixed and the oil well metal pipe 1b is rotated in the pipe circumferential direction while the thread is tightened. Here, the surface of the resin coating 100a on the resin coating 100b side is called the front surface. The surface of the resin coating 100a on the oil well metal pipe 1a side is called the back surface. Figure 2When the oil well metal pipe 1b is rotated in the circumferential direction of the pipe to be threaded, a driving force F1 in the same direction as the rotation direction of the oil well metal pipe 1b is generated on the resin coating 100b formed on the oil well metal pipe 1b. In the final stage of threaded tightening, the surface pressure pressing the resin coating 100a and the resin coating 100b in the radial direction of the oil well metal pipes 1a and 1b is high. If the threads are tightened under high surface pressure, the resin coating 100a slides while being strongly pressed on the resin coating 100b. Therefore, a driving force F1 in the same direction as the rotation direction of the oil well metal pipe 1b is also generated in the resin coating 100a. Since the resin coating 100a is fixed to the surface of the oil well metal pipe 1a, a force F2 in the opposite direction to F1 is generated on the back of the resin coating 100a. That is, in the final stage of thread tightening, forces in opposite directions are applied to the front and back surfaces of the resin coating 100a in the circumferential direction of the oil well metal pipe 1. The same is true for the resin coating 100b, and in the final stage of thread tightening, forces in opposite directions are applied to the front and back surfaces of the resin coating 100b in the circumferential direction of the oil well metal pipe 1.

[0059] The force that is equal in size and acts in opposite directions on two parallel surfaces in an object is called shear force. It is believed that if the shear strength of the resin coating 100 is high, even if sliding occurs between the surface and the back of the resin coating 100 due to thread tightening, it is difficult to deform or damage, and the sliding resistance becomes larger. If the resin coating 100 is deformed and damaged under low torque, the torque remains low and the number of revolutions of the metal pipe 1 for oil wells is increased. In this case, the yield torque cannot be increased. On the other hand, it is believed that if the deformation and damage of the resin coating 100 are suppressed when the threads are tightened, and the sliding resistance is high, the resin coating 100 can maintain a shape close to that before the threads are tightened until the final stage of the threads, and the torque can also be increased. In this case, it is believed that a high torque can be obtained relative to the number of revolutions of the metal pipe 1 for oil wells. That is, it is believed that the yield torque is increased by increasing the shear strength of the resin coating 100.

[0060] The present inventors have conducted detailed investigations on the relationship between the shear strength of a resin coating and the yield torque of an oil well metal pipe. Figure 3 This is a graph showing the relationship between the shear strength and the yield torque of the resin coating. Figure 3 The horizontal axis represents the shear strength (MPa) of the resin film. Figure 3 The vertical axis represents the yield torque (ft.lbs) when the oil well metal pipe having the resin coating formed thereon is thread-tightened.

[0061] Reference Figure 3 , the correlation coefficient R between the shear strength and yield torque of the resin coating 2The result shows that the shear strength of the resin coating and the yield torque have a strong positive correlation. That is, the detailed study by the inventors of the present invention has shown that the yield torque of the oil well metal pipe can be effectively increased if the shear strength of the resin coating is increased.

[0062] The present inventors have studied a method for improving the shear strength of the resin coating 100. The present inventors have focused on hydrogen bonding and electrostatic interactions in the resin coating 100. Hereinafter, hydrogen bonding and electrostatic interactions are referred to as gravitational interactions. In the case where there are many gravitational interactions in the resin coating 100, more gravitational interactions need to be cut off in order to deform and damage the resin coating 100. The present inventors believe that by increasing the gravitational interactions in the resin coating 100, the shear strength of the resin coating 100 can be improved.

[0063] The present inventors have studied a method for increasing the attractive interaction in the resin coating 100. As a result, they have found that it is possible to increase the attractive interaction in the resin coating 100 by including nylon in the resin coating 100.

[0064] Nylon is a general term for polymers having a structure in which units containing amide bonds (CONH) and hydrocarbons (CH2) are repeated. The hydrogen (H) contained in the amide bonds forms hydrogen bonds with other elements. Therefore, it is believed that if the resin coating 100 contains a base resin having a functional group that forms hydrogen bonds with the hydrogen contained in the amide bonds and nylon, the hydrogen bonds increase and the gravitational interaction increases. The present inventors have conducted research and believe that if a total of 40.0 to 99.4% by mass of a base resin selected from the group consisting of epoxy resins, phenolic resins, acrylic resins, urethane resins, polyester resins, polyamide-imide resins, polyimide resins, and polyetheretherketone resins is contained, and 0.1 to 20.0% by mass of a nylon resin coating 100, the gravitational interaction of the resin coating 100 can be increased.

[0065] However, the resin coating 100 having the above composition may not necessarily improve the shear strength of the resin coating 100. For this reason, the inventors have further studied the composition of the resin coating 100 in detail. As a result, it was found that if the resin coating 100 has the above composition and the total content of wax, fluorine-based additives and graphite in mass % is less than or equal to 5.00, the shear strength of the resin coating 100 is improved.

[0066] The ratio of the total content of the wax, the fluorine-based additive, and the graphite expressed in mass % to the total content of TiO 2 , the hydrous magnesium silicate, and the nylon expressed in mass % is defined as the "shear material ratio". Figure 43 is a graph showing the relationship between the shear material ratio in the resin coating 100 and the shear strength of the resin coating 100 . Figure 4 This is a partial extract of the results of the examples described later. Figure 4 The horizontal axis represents the shear material ratio. Figure 4 The vertical axis represents the shear strength (MPa) of the resin coating 100. Figure 4 If the shear material ratio is 5.00 or less, the shear strength of the resin coating 100 will be 58.0 MPa or more.

[0067] Wax, fluorine-based additives, and graphite are added for the purpose of reducing the friction coefficient of the resin coating 100. However, wax, fluorine-based additives, and graphite basically do not have a functional group that forms a hydrogen bond with hydrogen in an amide bond. Therefore, it is believed that it will not contribute to the increase in shear force caused by the increase in gravitational interaction. It is believed that if the content of wax, fluorine-based additives and graphite relative to nylon is too much, the gravitational interaction cannot be fully increased, and the shear strength of the resin coating 100 cannot be improved. It is believed that TiO2 and hydrous magnesium silicate themselves have high shear strength. Therefore, it is believed that when the content of nylon, TiO2 and hydrous magnesium silicate is high, the shear strength of the resin coating 100 is improved.

[0068] In summary, it is clear that, unlike previous views, the yield torque cannot be effectively increased by simply increasing the friction coefficient of the resin coating, and the yield torque can only be effectively increased by increasing the shear strength of the resin coating. It is further clarified that the shear strength of the resin coating can only be increased by adjusting the components in the resin coating as described above. By increasing the shear strength of the resin coating to increase the yield torque, a metal pipe for oil wells that can also be used for horizontal excavation can be obtained. The metal pipe for oil wells disclosed in the present invention is completed based on the above view and has the following structure. [1]

[0070] A metal pipe for oil wells,

[0071] It comprises a tube body including a first end and a second end,

[0072] The pipe body comprises:

[0073] a male buckle portion formed at the first end portion; and

[0074] a female buckle portion formed at the second end portion,

[0075] The pin portion has a pin portion contact surface including an external thread portion,

[0076] The box portion has a box portion contact surface including an internal thread portion,

[0077] The oil well metal pipe further comprises a resin coating formed as the uppermost layer of at least one of the pin portion contact surface and the box portion contact surface,

[0078] The resin coating contains:

[0079] At least one base resin selected from the group consisting of epoxy resins, phenolic resins, acrylic resins, urethane resins, polyester resins, polyamide-imide resins, polyimide resins, and polyetheretherketone resins: 40.0 to 99.4% by mass in total,

[0080] Nylon: 0.1-20.0% by mass,

[0081] TiO2: 0.5-30.0 mass %,

[0082] Hydrous magnesium silicate: 0-49.4% by mass,

[0083] Wax: 0-10.0 mass %,

[0084] Fluorine additives: 0-30.0 mass %,

[0085] Graphite: 0-10.0 mass %,

[0086] Anti-rust pigment: 0-30.0 mass %,

[0087] Coloring pigment: 0 to 10.0% by mass, and

[0088] Coupling agent: 0-10.0% by mass

[0089] The ratio of the total content of the wax, the fluorine-based additive and the graphite in the resin coating in terms of mass % to the total content of the nylon, the TiO 2 and the hydrous magnesium silicate in terms of mass % is 5.00 or less.

[0090] [2] The metal pipe for oil wells according to [1], wherein

[0091] The ratio of the content of the nylon expressed in mass % to the total content of the base resin expressed in mass % is 0.30 or less.

[0092] [3] The metal pipe for oil wells according to [1] or [2], wherein

[0093] The male buckle contact surface also includes a male buckle sealing surface and a male buckle shoulder surface.

[0094] The contact surface of the box buckle part also includes a box buckle part sealing surface and a box buckle part shoulder surface.

[0095] Hereinafter, the metal pipe for oil wells according to the present embodiment will be described in detail.

[0096] [Structure of metal pipe for oil wells]

[0097] First, the structure of the metal pipe for oil wells of this embodiment is described. The metal pipe for oil wells has a well-known structure. There are T&C type metal pipe for oil wells and integral type metal pipe for oil wells. Below, each type of metal pipe for oil wells is described in detail.

[0098] [When the metal pipe 1 for oil well is of T&C type]

[0099] Figure 5 It is a structural diagram showing an example of the oil well metal pipe 1 according to the present embodiment. Figure 5 This is a structural diagram of a so-called T&C type oil well metal pipe 1. Figure 5 The oil well metal pipe 1 includes a pipe body 10 .

[0100] The pipe body 10 extends in the pipe axis direction. The cross section of the pipe body 10 perpendicular to the pipe axis direction is circular. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is an end on the opposite side of the second end 10B. Figure 5 In the illustrated T&C type oil well metal pipe 1, the pipe body 10 includes a pin pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin pipe body 11. More specifically, the coupling 12 is fastened to one end of the pin pipe body 11 by means of a thread.

[0101] Figure 6 Yes means Figure 5 The cross-sectional view of the coupling 12 of the oil well metal pipe 1 shown is a partial cross-sectional view of a cross section (longitudinal cross section) parallel to the pipe axis direction. Figure 5 and Figure 6 The pipe body 10 includes a pin part 40 and a box part 50. The pin part 40 is formed at the first end 10A of the pipe body 10. When fastening, the pin part 40 is inserted into the box part 50 of another oil well metal pipe 1 (not shown) and is fastened to the box part 50 of the other oil well metal pipe 1 by threading.

[0102] The box portion 50 is formed at the second end portion 10B of the pipe body 10. During fastening, the pin portion 40 of another oil well metal pipe 1 is inserted into the box portion 50 and fastened to the pin portion 40 of another oil well metal pipe 1 by threads.

[0103] [Regarding the structure of the male buckle portion 40]

[0104] Figure 7 yes Figure 6 The cross-sectional view of the vicinity of the pin portion 40 of the oil well metal pipe 1 is parallel to the pipe axis direction of the oil well metal pipe 1 . Figure 7 The dotted line portion in shows the structure of the box buckle portion 50 of the other oil well metal pipe 1 when fastened with the other oil well metal pipe 1. Figure 7 The pin part 40 has a pin part contact surface 400 on the outer peripheral surface of the first end portion 10A of the pipe body 10. When fastened with another oil well metal pipe 1, the pin part contact surface 400 is screwed into the box part 50 of the other oil well metal pipe 1 and contacts the box part contact surface 500 (described later) of the box part 50.

[0105] The pin contact surface 400 includes at least an external thread portion 41 formed on the outer peripheral surface of the first end portion 10A. The pin contact surface 400 may further include a pin sealing surface 42 and a pin shoulder surface 43. Figure 7 In the embodiment, the male buckle shoulder surface 43 is arranged on the top end surface of the first end portion 10A, and the male buckle sealing surface 42 is arranged on the outer peripheral surface of the first end portion 10A, which is closer to the top end side of the first end portion 10A than the external thread portion 41. That is, the male buckle sealing surface 42 is arranged between the external thread portion 41 and the male buckle shoulder surface 43. The male buckle sealing surface 42 is set to be conical. Specifically, in the male buckle sealing surface 42, in the length direction (tube axis direction) of the first end portion 10A, the outer diameter gradually decreases as it moves from the external thread portion 41 toward the male buckle shoulder surface 43.

[0106] When fastened to other metal pipes 1 for oil wells, the male buckle sealing surface 42 contacts the female buckle sealing surface 52 (as described later) of the female buckle 50 of the other metal pipes 1 for oil wells. More specifically, when fastening, the male buckle 40 is inserted into the female buckle 50 of the other metal pipes 1 for oil wells, and the male buckle sealing surface 42 contacts the female buckle sealing surface 52. Then, the male buckle 40 is further screwed into the female buckle 50 of the other metal pipes 1 for oil wells, and the male buckle sealing surface 42 and the female buckle sealing surface 52 are in close contact. Thus, when fastening, the male buckle sealing surface 42 and the female buckle sealing surface 52 are in close contact to form a seal based on metal-to-metal contact. Therefore, in the metal pipes 1 for oil wells that are fastened to each other, the air tightness can be improved.

[0107] exist Figure 7 In the embodiment, the male buckle shoulder surface 43 is arranged on the top end surface of the first end portion 10A. Figure 7In the male buckle part 40 shown, an external threaded part 41, a male buckle part sealing surface 42, and a male buckle part shoulder surface 43 are sequentially arranged from the center of the pipe body 10 toward the first end 10A. When fastened to other metal pipes 1 for oil wells, the male buckle part shoulder surface 43 is opposite to and in contact with the female buckle part shoulder surface 53 (as described later) of the female buckle part 50 of the other metal pipes 1 for oil wells. More specifically, when fastening, by inserting the male buckle part 40 into the female buckle part 50 of the other metal pipes 1 for oil wells, the male buckle part shoulder surface 43 contacts the female buckle part shoulder surface 53. Thus, high torque can be obtained during fastening. In addition, the positional relationship between the male buckle part 40 and the female buckle part 50 in the fastened state can be stabilized.

[0108] It should be noted that the pin part contact surface 400 of the pin part 40 includes at least the external threaded portion 41. That is, the pin part contact surface 400 may include the external threaded portion 41 and does not include the pin part sealing surface 42 and the pin part shoulder surface 43. The pin part contact surface 400 may include the external threaded portion 41 and the pin part shoulder surface 43 and does not include the pin part sealing surface 42. The pin part contact surface 400 may include the external threaded portion 41 and the pin part sealing surface 42 and does not include the pin part shoulder surface 43.

[0109] [Regarding the structure of the female buckle portion 50]

[0110] Figure 8 yes Figure 6 The cross-sectional view of the portion near the box portion 50 of the oil well metal pipe 1 is parallel to the pipe axis direction of the oil well metal pipe 1 . Figure 8 The dotted line portion in FIG. 4 shows the structure of the male buckle portion 40 of the other oil well metal pipe 1 when fastened to the other oil well metal pipe 1. Figure 8 The box part 50 has a box part contact surface 500 on the inner peripheral surface of the second end 10B of the pipe body 10. When fastened to another oil well metal pipe 1, the box part contact surface 500 is screwed into the pin part 40 of the other oil well metal pipe 1 and contacts the pin part contact surface 400 of the pin part 40.

[0111] The box portion contact surface 500 includes at least an internal thread portion 51 formed on the inner peripheral surface of the second end portion 10B. During fastening, the internal thread portion 51 meshes with the external thread portion 41 of the pin portion 40 of another oil well metal pipe 1.

[0112] The female buckle contact surface 500 may further include a female buckle sealing surface 52 and a female buckle shoulder surface 53. Figure 8In the embodiment, the box buckle portion sealing surface 52 is arranged on the inner peripheral surface of the second end portion 10B, closer to the pipe body 10 than the internal thread portion 51. That is, the box buckle portion sealing surface 52 is arranged between the internal thread portion 51 and the box buckle portion shoulder surface 53. The box buckle portion sealing surface 52 is set to be tapered. Specifically, in the box buckle portion sealing surface 52, the inner diameter gradually decreases from the internal thread portion 51 toward the box buckle portion shoulder surface 53 in the longitudinal direction (tube axis direction) of the second end portion 10B.

[0113] When fastened to other metal pipes 1 for oil wells, the sealing surface 52 of the female buckle part contacts the sealing surface 42 of the male buckle part 40 of the other metal pipes 1 for oil wells. More specifically, when fastened, the male buckle part 40 of the other metal pipes 1 for oil wells is screwed into the female buckle part 50, so that the sealing surface 52 of the female buckle part contacts the sealing surface 42 of the male buckle part, and by further screwing in, the sealing surface 52 of the female buckle part and the sealing surface 42 of the male buckle part are in close contact. Thus, when fastened, the sealing surface 52 of the female buckle part and the sealing surface 42 of the male buckle part are in close contact to form a seal based on metal-metal contact. Therefore, in the metal pipes 1 for oil wells that are fastened to each other, the airtightness can be improved.

[0114] The shoulder surface 53 of the box buckle part is arranged on the side closer to the pipe body 10 than the sealing surface 52 of the box buckle part. That is, in the box buckle part 50, the shoulder surface 53 of the box buckle part, the sealing surface 52 of the box buckle part, and the internal thread part 51 are arranged in order from the center of the pipe body 10 toward the top of the second end 10B. When fastened with other metal pipes 1 for oil wells, the shoulder surface 53 of the box buckle part is opposite to and in contact with the shoulder surface 43 of the male buckle part 40 of the other metal pipes 1 for oil wells. More specifically, when fastening, the shoulder surface 53 of the box buckle part is in contact with the shoulder surface 43 of the male buckle part by inserting the male buckle part 40 of the other metal pipes 1 for oil wells into the box buckle part 50. Thus, high torque can be obtained during fastening. In addition, the positional relationship between the male buckle part 40 and the box buckle part 50 in the fastened state can be stabilized.

[0115] The box contact surface 500 includes at least an internal thread portion 51. When tightened, the internal thread portion 51 of the box contact surface 500 of the box 50 corresponds to and contacts the external thread portion 41 of the pin contact surface 400 of the pin 40. The box sealing surface 52 corresponds to and contacts the pin sealing surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0116] In the case where the pin part contact surface 400 includes the external threaded portion 41 and does not include the pin part sealing surface 42 and the pin part shoulder surface 43, the box part contact surface 500 includes the internal threaded portion 51 and does not include the box part sealing surface 52 and the box part shoulder surface 53. In the case where the pin part contact surface 400 includes the external threaded portion 41 and the pin part shoulder surface 43 and does not include the pin part sealing surface 42, the box part contact surface 500 includes the internal threaded portion 51 and the box part shoulder surface 53 and does not include the box part sealing surface 52. In the case where the pin part contact surface 400 includes the external threaded portion 41 and the pin part sealing surface 42 and does not include the pin part shoulder surface 43, the box part contact surface 500 includes the internal threaded portion 51 and the box part sealing surface 52 and does not include the box part shoulder surface 53.

[0117] The pin contact surface 400 may include a plurality of external threaded portions 41, or may include a plurality of pin sealing surfaces 42, or may include a plurality of pin shoulder surfaces 43. For example, in the pin contact surface 400 of the pin 40, the pin shoulder surface 43, the pin sealing surface 42, the external threaded portion 41, the pin sealing surface 42, the pin shoulder surface 43, the pin sealing surface 42, and the external threaded portion 41 may be sequentially arranged from the top of the first end 10A toward the center of the pipe body 10. In this case, in the box contact surface 500 of the box 50, the internal threaded portion 51, the box sealing surface 52, the box shoulder surface 53, the box sealing surface 52, the internal threaded portion 51, the box sealing surface 52, and the box shoulder surface 53 may be sequentially arranged from the top of the second end 10B toward the center of the pipe body 10.

[0118] exist Figure 7 and Figure 8 , the figure shows a so-called advanced joint in which the pin part 40 includes an external threaded portion 41, a pin part sealing surface 42, and a pin part shoulder surface 43, and the box part 50 includes an internal threaded portion 51, a box part sealing surface 52, and a box part shoulder surface 53. However, as described above, the pin part 40 may include an external threaded portion 41 and not include the pin part sealing surface 42 and the pin part shoulder surface 43. In this case, the box part 50 includes an internal threaded portion 51 and not includes the box part sealing surface 52 and the box part shoulder surface 53. Fig. 9 This is a diagram showing an example of an oil well metal pipe 1 in which a pin portion 40 includes an external thread portion 41 but does not include a pin portion sealing surface 42 and a pin portion shoulder surface 43 , and a box portion 50 includes an internal thread portion 51 but does not include a box portion sealing surface 52 and a box portion shoulder surface 53 .

[0119] [When the metal pipe for oil well 1 is of integral type]

[0120] Figure 5 , Figure 6 and Fig. 9The oil well metal pipe 1 shown is a so-called T&C type oil well metal pipe 1 in which the pipe body 10 includes a pin body 11 and a coupling 12. However, the oil well metal pipe 1 of this embodiment may not be a T&C type but an integral type.

[0121] Fig.10 1 is a structural diagram of an integral oil well metal pipe 1 according to the present embodiment. Fig.10 The integral type metal pipe for oil wells 1 includes a pipe body 10. The pipe body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is arranged on the side opposite to the second end portion 10B. As described above, in the T&C type metal pipe for oil wells 1, the pipe body 10 includes a male buckle portion pipe body 11 and a coupling 12. That is, in the T&C type metal pipe for oil wells 1, the pipe body 10 is formed by fastening two separate components (male buckle portion pipe body 11 and coupling 12). In contrast, in the integral type metal pipe for oil wells 1, the pipe body 10 is formed integrally.

[0122] The male buckle 40 is formed at the first end 10A of the pipe body 10. When fastening, the male buckle 40 is inserted into the female buckle 50 of the other integral oil well metal pipe 1 and screwed in, and fastened with the female buckle 50 of the other integral oil well metal pipe 1. The female buckle 50 is formed at the second end 10B of the pipe body 10. When fastening, the male buckle 40 of the other integral oil well metal pipe 1 is inserted into the female buckle 50 and screwed in, and fastened with the male buckle 40 of the other integral oil well metal pipe 1.

[0123] The structure of the male buckle part 40 of the integral oil well metal pipe 1 is Figure 7 The structure of the male buckle part 40 of the T&C type oil well metal pipe 1 shown in FIG. Figure 8 The structure of the box buckle 50 of the T&C type oil well metal pipe 1 is the same. Figure 7 and Figure 8 In the embodiment, in the pin part 40, the pin part shoulder surface 43, the pin part sealing surface 42, and the external threaded portion 41 are arranged in order from the top end of the first end 10A toward the center of the pipe body 10. Therefore, in the box part 50, the internal threaded portion 51, the box part sealing surface 52, and the box part shoulder surface 53 are arranged in order from the top end of the second end 10B toward the center of the pipe body 10. However, like the pin part contact surface 400 of the pin part 40 of the T&C type oil well metal pipe 1, the pin part contact surface 400 of the pin part 40 of the integral type oil well metal pipe 1 only needs to include at least the external threaded portion 41. Also, like the box part contact surface 500 of the box part 50 of the T&C type oil well metal pipe 1, the box part contact surface 500 of the box part 50 of the integral type oil well metal pipe 1 only needs to include at least the internal threaded portion 51.

[0124] The oil well metal pipe 1 of the present embodiment may be a T&C type or an integral type.

[0125] [Resin coating 100]

[0126] The oil well metal pipe 1 of the present embodiment includes a resin coating 100 formed as the uppermost layer of at least one of the pin portion contact surface 400 and the box portion contact surface 500 . Fig.11 yes Figure 7 An enlarged view of the pin contact surface 400 is shown. Fig.12 yes Figure 8 FIG. 5 is an enlarged view of the female buckle portion contact surface 500. Fig.11 and Fig.12 As shown in FIG. 1 , the oil well metal pipe 1 according to the present embodiment may include the resin coating 100 as the uppermost layer on both the pin part contact surface 400 and the box part contact surface 500. However, the oil well metal pipe 1 according to the present embodiment may include the resin coating 100 as the uppermost layer on only one of the pin part contact surface 400 and the box part contact surface 500. For example, Fig.11 As shown in FIG. 1 , when the male buckle portion contact surface 400 is provided with the resin coating 100, the female buckle portion contact surface 500 may not be provided with the resin coating 100. Fig.12 As shown, when the resin coating 100 is provided on the box part contact surface 500, the resin coating 100 may not be provided on the pin part contact surface 400. In other words, the oil well metal pipe 1 according to the present embodiment includes the resin coating 100 as the uppermost layer on the pin part contact surface 400 and / or the box part contact surface 500.

[0127] [Composition of Resin Film 100]

[0128] The resin coating film 100 has the following composition.

[0129] Base resin: 40.0 to 99.4% by mass in total

[0130] The substrate resin is the substrate of the resin coating 100. The substrate resin is one or more selected from the group consisting of epoxy resin, phenolic resin, acrylic resin, urethane resin, polyester resin, polyamide-imide resin, polyimide resin, and polyetheretherketone resin. These substrate resins have moderate hardness and also contain a large number of functional groups that form hydrogen bonds with hydrogen (H) in nylon. Therefore, these substrate resins increase the gravitational interaction in the resin coating 100 and improve the shear strength of the resin coating 100. When the total content of the substrate resin is less than 40.0% by mass, the hardness of the resin coating 100 is reduced, and the shear strength of the resin coating 100 cannot be improved. On the other hand, when the content of the substrate resin exceeds 99.4% by mass, since it cannot contain a sufficient amount of other components including nylon and TiO2, the wear resistance and yield torque of the metal pipe 1 for oil wells may be reduced. Therefore, the total content of the substrate resin is 40.0 to 99.4% by mass. The total content of the substrate resin refers to the total content of all substrate resins when containing multiple substrate resins.

[0131] The lower limit of the total content of the base resin is preferably 42.0% by mass, more preferably 50.0% by mass, more preferably 55.0% by mass, more preferably 60.0% by mass, more preferably 65.0% by mass, and still more preferably 70.0% by mass.

[0132] The upper limit of the total content of the base resin is preferably 95.0% by mass, more preferably 90.0% by mass, further preferably 88.0% by mass, and further preferably 87.0% by mass.

[0133] Nylon: 0.1-20.0% by mass

[0134] It is believed that nylon helps the hydrogen (H) inside it to form hydrogen bonds with the functional groups in the base resin, thereby improving the shear strength of the resin coating 100. When the nylon content is less than 0.1% by mass, the above effect cannot be obtained. On the other hand, when the nylon content exceeds 20.0% by mass, the content of other components cannot be fully ensured. In this case, it is possible that the formation of the resin coating 100 is poor or the wear resistance and yield torque of the resin coating 100 are reduced. Therefore, the nylon content is 0.1 to 20.0% by mass.

[0135] The lower limit of the nylon content is preferably 0.3% by mass, more preferably 0.5% by mass, more preferably 0.8% by mass, more preferably 1.0% by mass, more preferably 2.0% by mass, more preferably 2.5% by mass, more preferably 3.0% by mass, more preferably 4.0% by mass, and more preferably 5.0% by mass. The upper limit of the nylon content is preferably 19.0% by mass, more preferably 17.0% by mass, and more preferably 15.0% by mass.

[0136] TiO2: 0.5-30.0% by mass

[0137] Titanium dioxide (TiO2) improves the shear strength of the resin coating 100. TiO2 is a powder. Hydroxyl groups and polar groups containing titanium are exposed on the surface of TiO2. Therefore, TiO2 easily forms hydrogen bonds with hydrogen (H) in nylon and functional groups in the base resin. It is believed that the shear strength of the resin coating 100 is improved by the formation of hydrogen bonds between TiO2 and the base resin. When the TiO2 content is less than 0.5% by mass, the above-mentioned effect cannot be obtained. On the other hand, when the TiO2 content exceeds 30.0% by mass, abrasive wear may be promoted, and the wear resistance of the metal pipe 1 for oil wells is reduced. Therefore, the content of TiO2 is 0.5 to 30.0% by mass.

[0138] The lower limit of the content of TiO2 is preferably 0.7% by mass, more preferably 1.0% by mass, and more preferably 1.2% by mass. The upper limit of the content of TiO2 is preferably 28.0% by mass, more preferably 26.0% by mass, more preferably 25.0% by mass, more preferably 23.0% by mass, and more preferably 21.0% by mass.

[0139] Hydrous magnesium silicate: 0-49.4% by mass

[0140] Hydrous magnesium silicate is an optional component and may not be contained. That is, the content of hydrous magnesium silicate may be 0% by mass. Hydrous magnesium silicate is a powder. When contained, that is, when the content of hydrous magnesium silicate exceeds 0% by mass, hydrous magnesium silicate further improves the shear strength of the resin coating 100. Hydroxyl groups and polar groups containing magnesium are exposed on the surface of hydrous magnesium silicate. Therefore, hydrous magnesium silicate easily forms hydrogen bonds or electrostatic interactions with hydrogen (H) in nylon and functional groups in the substrate resin. It is believed that the shear strength of the resin coating 100 is improved by the formation of hydrogen bonds in nylon and the substrate resin by hydrous magnesium silicate. As long as a small amount of hydrous magnesium silicate is contained, the above-mentioned effect can be obtained to a certain extent.

[0141] On the other hand, when the content of the hydrous magnesium silicate exceeds 49.4 mass %, the resin coating 100 is poorly formed. Therefore, the content of the hydrous magnesium silicate is 0 to 49.4 mass %.

[0142] The lower limit of the content of the hydrous magnesium silicate is preferably 0.1% by mass, more preferably 0.3% by mass, more preferably 5.0% by mass, more preferably 7.0% by mass, and still more preferably 10.0% by mass.

[0143] The upper limit of the content of the hydrous magnesium silicate is preferably 45.0% by mass, more preferably 42.0% by mass, more preferably 40.0% by mass, more preferably 35.0% by mass, and still more preferably 30.0% by mass.

[0144] Wax: 0-10.0% by mass

[0145] The type of wax contained in the resin coating 100 of the present embodiment is not particularly limited. The wax is, for example, one or more selected from the group consisting of animal wax, vegetable wax, mineral wax, and synthetic wax. Preferably, the wax is one or more selected from the group consisting of beeswax, spermaceti (the above are animal), wood wax, carnauba wax, candelilla wax, rice bran wax (the above are vegetable), paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokelite, ceresin (the above are mineral), oxidized wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, amide wax, hydrogenated castor oil (Castorwax) (the above are synthetic wax).

[0146] More preferably, the wax is at least one selected from the group consisting of polyethylene wax and polypropylene wax. The resin film 100 may contain multiple types of waxes. When multiple types of waxes are contained, the content of the wax is the total content of the multiple types of waxes.

[0147] Wax is a component that can be contained arbitrarily or not. That is, the content of wax can be 0% by mass. When contained, that is, when the content of wax exceeds 0% by mass, wax improves the lubricity of the resin coating 100. As long as a small amount of wax is contained, the above effect can be obtained to a certain extent.

[0148] On the other hand, when the wax content exceeds 10.0 mass %, the hardness of the resin coating 100 decreases, and the base material ratio decreases, making the resin brittle, and the resin coating 100 is easily peeled off when the screws are repeatedly tightened and loosened. Therefore, the wax content is 0 to 10.0 mass %.

[0149] The lower limit of the wax content is preferably 0.1% by mass, more preferably 0.5% by mass, more preferably 0.8% by mass, more preferably 1.0% by mass, and still more preferably 2.0% by mass.

[0150] The upper limit of the wax content is preferably 9.0% by mass, more preferably 8.0% by mass, and further preferably 7.5% by mass.

[0151] Fluorine additives: 0-30.0 mass%

[0152] In this specification, fluorine-containing additives are also collectively referred to as fluorine-based additives. Fluorine-based additives are, for example, one or two selected from the group consisting of perfluoropolyether (PFPE) and polytetrafluoroethylene (PTFE). The resin coating 100 may also contain multiple fluorine-based additives. In the case of containing multiple fluorine-based additives, the content of the fluorine-based additives is the total content of the multiple fluorine-based additives.

[0153] In the present embodiment, the fluorine additive is a component that can be contained arbitrarily or not. That is, the content of the fluorine additive can be 0% by mass. When contained, that is, when the content of the fluorine additive exceeds 0% by mass, the fluorine additive improves the lubricity of the resin coating 100. As long as a small amount of the fluorine additive is contained, the above-mentioned effect can be obtained to a certain extent.

[0154] On the other hand, when the content of the fluorine-based additive exceeds 30.0% by mass, the hardness of the resin coating 100 decreases and becomes brittle. As a result, when the screws are repeatedly tightened and loosened, the resin coating 100 is easily peeled off. Therefore, the content of the fluorine-based additive is 0 to 30.0% by mass.

[0155] The lower limit of the content of the fluorine-based additive is preferably 0.1 mass %, more preferably 0.5 mass %, more preferably 1.0 mass %, more preferably 2.0 mass %, more preferably 3.0 mass %, more preferably 4.5 mass %, more preferably 5.0 mass %, and more preferably 7.5 mass %.

[0156] The upper limit of the content of the fluorine-based additive is preferably 25.0% by mass, more preferably 20.0% by mass, more preferably 18.0% by mass, more preferably 15.0% by mass, and still more preferably 12.5% ​​by mass.

[0157] Graphite: 0-10.0 mass%

[0158] In the present embodiment, graphite is a component that may be contained arbitrarily or may not be contained. That is, the content of graphite may be 0% by mass. When contained, that is, when the content of graphite exceeds 0% by mass, graphite improves the lubricity of the resin coating 100. As long as a small amount of graphite is contained, the above-mentioned effect can be obtained to a certain extent.

[0159] On the other hand, when the content of graphite exceeds 10.0 mass %, the hardness of the resin coating 100 decreases and becomes brittle. As a result, when the screw is repeatedly tightened and loosened, the resin coating 100 is easily peeled off. Therefore, the content of graphite is 0 to 10.0 mass %.

[0160] The lower limit of the content of graphite is preferably 0.1% by mass, more preferably 0.5% by mass, more preferably 0.8% by mass, more preferably 1.0% by mass, more preferably 2.0% by mass, and still more preferably 3.0% by mass.

[0161] The upper limit of the content of graphite is preferably 9.0% by mass, more preferably 8.0% by mass, further preferably 7.0% by mass, further preferably 6.0% by mass.

[0162] Anti-rust pigment: 0-30.0% by mass

[0163] In the present embodiment, the rust-proof pigment is not particularly limited as long as it is a well-known pigment that improves the rust resistance of the resin coating 100. The rust-proof pigment is, for example, one or more selected from the group consisting of zinc phosphate, aluminum tripolyphosphate, aluminum phosphite, carboxylic acid metal soap, and sulfonate. The resin coating 100 may also contain multiple types of rust-proof pigments. In the case of containing multiple types of rust-proof pigments, the content of the rust-proof pigment refers to the total content of the multiple types of rust-proof pigments.

[0164] In the present embodiment, the rust-proof pigment is a component that can be contained arbitrarily or not. That is, the content of the rust-proof pigment can be 0% by mass. When contained, that is, when the content of the rust-proof pigment exceeds 0% by mass, the rust-proof pigment improves the rust resistance of the resin coating 100. As long as a small amount of the rust-proof pigment is contained, the above-mentioned effect can be obtained to a certain extent.

[0165] On the other hand, when the content of the rust-proof pigment exceeds 30.0 mass %, the resin coating 100 is poorly formed. Therefore, the content of the rust-proof pigment is 0 to 30.0 mass %.

[0166] The lower limit of the content of the rust-proof pigment is preferably 1.0% by mass, more preferably 1.5% by mass, more preferably 2.0% by mass, more preferably 3.0% by mass, and still more preferably 3.5% by mass.

[0167] The upper limit of the content of the rust-proof pigment is preferably 25.0% by mass, more preferably 20.0% by mass, and further preferably 10.0% by mass.

[0168] Coloring pigment: 0-10.0 mass%

[0169] In the present embodiment, the coloring pigment is not particularly limited as long as it is a well-known pigment that can color the resin coating 100. The coloring pigment is, for example, one or more selected from the group consisting of copper phthalocyanine, zinc oxide, yellow iron oxide, iron oxide, and chromium hydroxide. The resin coating 100 may also contain multiple coloring pigments. In the case of containing multiple coloring pigments, the content of the coloring pigment is the total content of the multiple coloring pigments.

[0170] In the present embodiment, the coloring pigment is a component that can be contained arbitrarily or not. That is, the content of the coloring pigment can be 0% by mass. In the case of containing, that is, when the content of the coloring pigment exceeds 0% by mass, the coloring pigment colors the resin film 100. As a result, the damage of the resin film 100 is easy to visually recognize. As long as a small amount of coloring pigment is contained, the above effect can be obtained to a certain extent.

[0171] On the other hand, when the content of the coloring pigment exceeds 10.0% by mass, the resin coating 100 is poorly formed. Therefore, the content of the coloring pigment is 0 to 10.0% by mass.

[0172] The lower limit of the content of the coloring pigment is preferably 0.1% by mass, more preferably 0.2% by mass, further preferably 0.5% by mass, further preferably 0.8% by mass.

[0173] The upper limit of the content of the coloring pigment is preferably 8.0% by mass, more preferably 5.0% by mass, further preferably 3.0% by mass, further preferably 2.0% by mass.

[0174] Coupling agent: 0-10.0 mass%

[0175] In this embodiment, the coupling agent is not particularly limited. The coupling agent is, for example, one or two selected from the group consisting of a silane coupling agent and a titanium coupling agent. The resin coating 100 may also contain multiple coupling agents. In the case of containing multiple coupling agents, the content of the coupling agent is the total content of the multiple coupling agents.

[0176] In the present embodiment, the coupling agent is a component that can be contained arbitrarily or not. That is, the content of the coupling agent can be 0% by mass. When contained, that is, when the content of the coupling agent exceeds 0% by mass, the coupling agent improves the adhesion of the resin coating 100. Therefore, when the thread tightening and thread loosening of the oil well metal pipe 1 are repeatedly performed, the peeling of the resin coating 100 is suppressed. As long as a small amount of coupling agent is contained, the above effect can be obtained to a certain extent.

[0177] On the other hand, when the content of the coupling agent exceeds 10.0 mass %, the resin coating 100 is poorly formed. Therefore, the content of the coupling agent is 0 to 10.0 mass %.

[0178] The lower limit of the content of the coupling agent is preferably 0.1% by mass, more preferably 0.2% by mass, more preferably 0.5% by mass, more preferably 0.7% by mass, and still more preferably 1.0% by mass.

[0179] The upper limit of the content of the coupling agent is preferably 8.0% by mass, more preferably 6.0% by mass, further preferably 5.0% by mass, further preferably 4.0% by mass.

[0180] The resin coating film 100 may consist of the above composition, or may contain the above composition and impurities in a balance of 0 to 1.0 mass %.

[0181] [Shear material ratio]

[0182] In the resin coating 100 of the present embodiment, the ratio of the total content of wax, fluorine-based additives and graphite in mass % to the total content of nylon, TiO2 and hydrous magnesium silicate in mass % is 5.00 or less. Hereinafter, the ratio of the total content of wax, fluorine-based additives and graphite in mass % to the total content of nylon, TiO2 and hydrous magnesium silicate in mass % is also referred to as shear material ratio.

[0183] As described above, it is believed that wax, fluorine-based additives, and graphite do not contribute to the increase in shear force due to the increase in attractive interaction in the resin film 100. If the total content of wax, fluorine-based additives, and graphite is too high relative to the total content of nylon, TiO2, and hydrous magnesium silicate, the attractive interaction cannot be sufficiently increased, and the shear strength of the resin film 100 cannot be improved. Therefore, on the premise of having the above composition, the shear material ratio of the resin film 100 is 5.00 or less.

[0184] The upper limit of the shear material ratio is preferably 4.50, more preferably 4.00, more preferably 3.50, more preferably 3.00, and more preferably 2.90. The lower limit of the shear material ratio is not particularly limited, and is, for example, 0.00, for example, 0.10.

[0185] When the resin coating 100 has the above composition, the shear material ratio is 5.00 or less, and the shear strength is improved. As a result, the yield torque of the oil well metal pipe 1 having the resin coating 100 is improved.

[0186] [Base resin to nylon ratio]

[0187] It is preferred that the ratio of the content of nylon in mass % to the total content of the base resin in mass % is 0.30 or less. As described above, by forming hydrogen bonds between hydrogen (H) in nylon and functional groups in the base resin, the attractive interaction increases, thereby improving the shear strength of the resin coating 100. When the ratio of the content of nylon to the total content of the base resin is 0.30 or less, the number of functional groups increases, further promoting the formation of hydrogen bonds in the resin coating 100. As a result, the shear strength of the resin coating 100 is further improved.

[0188] The upper limit of the ratio of the nylon content to the total content of the base resin is more preferably 0.25, further preferably 0.20, further preferably 0.18, and further preferably 0.15. The lower limit of the ratio of the nylon content to the total content of the base resin is not particularly limited, and is, for example, 0.01. The lower limit of the ratio of the nylon content to the total content of the base resin is preferably 0.02, and further preferably 0.03.

[0189] [Shear strength]

[0190] The shear strength of the resin coating 100 is not particularly limited, and the higher the shear strength, the more preferred. When the shear strength of the resin coating 100 is 58.0 MPa or more, the yield torque of the oil well metal pipe 1 having the resin coating 100 can be further stably improved. Therefore, the shear strength of the resin coating 100 is preferably 58.0 MPa or more. The lower limit of the shear strength of the resin coating 100 is more preferably 58.5 MPa, and more preferably 59.0 MPa. The upper limit of the shear strength of the resin coating 100 is not particularly limited, and is, for example, 70.0 MPa.

[0191] [Measurement method of shear strength]

[0192] The shear strength of the resin coating 100 can be measured by the following method. A test piece is cut out from the oil well metal pipe 1 having the resin coating 100. The size of the test piece is, for example, set to a surface size of 10 mm × 10 mm and a thickness of 10 mm. However, the size of the test piece is not particularly limited, and for example, the surface of the test piece can be 30 mm × 30 mm. The resin coating 100 is formed on the surface of the test piece. This surface corresponds to the contact surface 400 or 500 of the oil well metal pipe 1 on which the resin coating 100 is formed.

[0193] The shear strength of the obtained test piece is determined using a surface and interface property analyzer (e.g., manufactured by DAIPLA WINTESCO., LTD., trade name: SAICAS). Using a cutting knife with a blade width of 1 mm, the surface of the resin coating 100 is cut at a constant speed (horizontal speed 2 μm / sec, vertical speed 0.2 μm / sec) at an angle of 10° to peel off the resin coating 100 from the contact surfaces 400, 500. It should be noted that all tests were carried out at room temperature (25±5°C). In the case where the surface of the test piece is bent, the direction of measuring the shear strength on the surface of the test piece is set to a direction perpendicular to the bending direction of the test piece (i.e., the pipe axis direction of the metal pipe 1 for oil wells). At this time, the shear strength (MPa) of the resin coating 100 is determined based on the horizontal force, vertical force and vertical displacement applied to the cutting knife.

[0194] [Thickness of resin coating film 100]

[0195] In the present embodiment, the thickness of the resin coating 100 is not particularly limited. The thickness of the resin coating 100 is, for example, 1 to 100 μm. In this case, the yield torque of the oil well metal pipe 1 can be more stably improved. The lower limit of the thickness of the resin coating 100 is preferably 2 μm, more preferably 5 μm, and more preferably 10 μm. The upper limit of the thickness of the resin coating 100 is preferably 50 μm, more preferably 40 μm, and more preferably 30 μm.

[0196] [Method for measuring the thickness of the resin coating film 100]

[0197] The thickness of the resin coating 100 can be measured by the following method. The probe of an electromagnetic induction type film thickness measuring device is brought into contact with the male buckle contact surface 400 or the female buckle contact surface 500 on which the resin coating 100 is formed. The probe has an electromagnet, and when it is close to a magnetic body, electromagnetic induction is generated, and its voltage changes according to the distance between the probe and the magnetic body. The thickness of the resin coating 100 is calculated based on the change in the voltage. The measurement locations are 12 locations in the circumferential direction of the metal pipe 1 for oil wells (the 12 locations of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°). The arithmetic mean of the measurement results of the 12 locations is taken as the thickness of the resin coating 100.

[0198] [Other layers]

[0199] The metal pipe for oil wells 1 according to the present embodiment may include another layer between at least one of the pin part contact surface 400 and the box part contact surface 500 and the resin coating 100 as the uppermost layer. For example, the metal pipe for oil wells 1 may include another layer below the resin coating 100 as the uppermost layer, that is, between the pin part contact surface 400 and the resin coating 100. In addition, for example, the metal pipe for oil wells 1 may include another layer between the lower layer of the resin coating 100 as the uppermost layer, that is, between the box part contact surface 500 and the resin coating 100 as the uppermost layer.

[0200] Other layers are, for example, one or more chemical conversion coatings and / or one or more plating layers. More specifically, other layers are, for example, one or more selected from the group consisting of phosphate coatings, plating layers, chromate coatings, and zirconium coatings. Phosphate coatings are, for example, one or more selected from the group consisting of zinc phosphate coatings, manganese phosphate coatings, calcium phosphate coatings, and iron phosphate coatings. Plating layers are, for example, one or more selected from the group consisting of Zn plating, Ni plating, Cu plating, Zn-Ni alloy plating, Zn-Co alloy plating, and Ni-W alloy plating. In the case where the plating is a Zn-Ni alloy plating, the chemical composition of the Zn-Ni alloy plating is, for example, composed of 10 to 20% by mass of Ni, and the remainder of Zn and impurities. In the case where the plating is a Cu plating, the chemical composition of the Cu plating is, for example, composed of Cu and impurities. Multiple other layers can be stacked radially along the metal pipe 1 for oil wells. For example, the plating layer may be disposed on the pin contact surface 400 , the chromate coating may be disposed on the plating layer, and the resin coating 100 as the uppermost layer may be disposed on the chromate coating.

[0201] [Chemical Composition of the Tube Main Body 10]

[0202] The chemical composition of the pipe body 10 of the metal pipe for oil wells 1 involved in the present embodiment is not particularly limited. That is, in the present embodiment, the steel type of the pipe body 10 of the metal pipe for oil wells 1 is not particularly limited. The pipe body 10 can be formed of, for example, carbon steel, stainless steel, and alloys. That is, the metal pipe for oil wells 1 can be a steel pipe formed of an Fe-based alloy, or an alloy pipe represented by a Ni-based alloy pipe. Here, the steel pipe is, for example, a low-alloy steel pipe, a martensitic stainless steel pipe, a duplex stainless steel pipe, etc. On the other hand, among alloys, high alloys such as Ni-based alloys and duplex stainless steels containing alloying elements such as Cr, Ni, and Mo have higher corrosion resistance. Therefore, if these high alloys are used as the pipe body 10, excellent corrosion resistance can be obtained in a corrosive environment containing hydrogen sulfide, carbon dioxide, etc.

[0203] [Manufacturing method]

[0204] Next, a method for manufacturing the oil well metal pipe 1 according to the present embodiment will be described.

[0205] The method for producing the oil well metal pipe 1 according to the present embodiment includes a preparation step, a coating step, and a curing step. The curing step is performed after the coating step.

[0206] [Preparation process]

[0207] In the preparation process, an oil well metal pipe having a pipe body 10 including a pin portion 40 and a box portion 50 is prepared. The pin portion 40 has a pin portion contact surface 400 including an external thread portion 41, and the box portion 50 has a box portion contact surface 500 including an internal thread portion 51. As described above, the oil well metal pipe according to the present embodiment has a well-known structure. That is, in the preparation process, an oil well metal pipe having a well-known structure may be prepared.

[0208] [Coating process]

[0209] In the coating step, the composition is applied to at least one of the pin contact surface 400 and the box contact surface 500 of the prepared oil well metal pipe. The composition is a composition for forming the above-mentioned resin coating 100. The composition contains: a base resin: a total of 40.0 to 99.4 mass%, nylon: 0.1 to 20.0 mass%, TiO2: 0.5 to 30.0 mass%, hydrous magnesium silicate: 0 to 49.4 mass%, wax: 0 to 10.0 mass%, fluorine-based additives: 0 to 30.0 mass%, graphite: 0 to 10.0 mass%, rust-proof pigments: 0 to 30.0 mass%, coloring pigments: 0 to 10.0 mass%, and coupling agents: 0 to 10.0 mass%, and the ratio of the total content of the wax, the fluorine-based additive, and the graphite in mass% to the total content of the nylon, TiO2, and the hydrous magnesium silicate in mass% is 5.00 or less. The composition further contains a solvent. The composition for forming the resin coating film 100 , except for the solvent, is the same as the composition of the above-mentioned resin coating film 100 .

[0210] The composition can be prepared, for example, by dissolving or dispersing the base resin, nylon, TiO2, and other components as needed in a solvent and mixing them. The solvent is, for example, one or more selected from the group consisting of water, alcohol, and an organic solvent. The solvent may contain a trace amount of a surfactant. The proportion of the solvent is not particularly limited. The proportion of the solvent can be adjusted in a manner that makes the composition have an appropriate viscosity according to the coating method. For example, when the sum of all components except the solvent is set to 100% by mass, the proportion of the solvent is 40 to 60% by mass.

[0211] The method of applying the composition on the male buckle contact surface 400 and / or the female buckle contact surface 500 is not particularly limited, and any well-known method may be used. For example, the composition in a solution state is applied to the male buckle contact surface 400 and / or the female buckle contact surface 500 by spraying. In this case, the viscosity of the composition is adjusted in a manner that allows spraying under normal temperature and pressure. The method of applying the composition on the male buckle contact surface 400 and / or the female buckle contact surface 500 may also be brushing and dipping instead of spraying.

[0212] [Curing process]

[0213] In the curing step, the applied composition is cured to form a resin coating 100. By heating the composition applied to at least one of the male buckle contact surface 400 and the female buckle contact surface 500, the composition is thermally cured to form a solid resin coating 100. The heating method is not particularly limited and can be a well-known method. The heating method is, for example, a method of placing the oil well metal pipe 1 coated with the composition into a well-known heating furnace for heating. The heating temperature is, for example, 200 to 250°C, and the heating time is, for example, 5 to 30 minutes.

[0214] The oil well metal pipe 1 according to the present embodiment is manufactured through the above steps. It should be noted that the method for manufacturing the oil well metal pipe 1 according to the present embodiment may include other steps.

[0215] [Substrate treatment process]

[0216] The method for producing the oil well metal pipe 1 according to the present embodiment may further include a base treatment step before the coating step. In the base treatment step, for example, one or more selected from the group consisting of pickling treatment, blasting treatment, and alkali degreasing treatment are performed.

[0217] In the case of pickling treatment, for example, the pin buckle part contact surface 400 and / or the box buckle part contact surface 500 are immersed in a strong acid solution such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, or a mixed acid thereof to improve the surface roughness of the pin buckle part contact surface 400 and / or the box buckle part contact surface 500. In the case of blasting treatment, for example, sandblasting is performed, that is, a blasting material (abrasive) and compressed air are mixed and projected onto the pin buckle part contact surface 400 and / or the box buckle part contact surface 500. In this case, the surface roughness of the pin buckle part contact surface 400 and / or the box buckle part contact surface 500 is improved.

[0218] It should be noted that in the base treatment process, the same treatment may be performed on the male buckle contact surface 400 and the female buckle contact surface 500, or different treatments may be performed. In addition, the base treatment process may be performed only on the male buckle contact surface 400, or only on the female buckle contact surface 500.

[0219] The oil well metal pipe 1 according to the present embodiment is manufactured through the above steps. However, the above manufacturing method is an example of the manufacturing method of the oil well metal pipe 1 according to the present embodiment, and the present invention is not limited to this manufacturing method. The oil well metal pipe 1 according to the present embodiment may also be manufactured by other methods.

[0220] Example

[0221] The effects of the metal pipe for oil wells of the present embodiment will be further specifically described below through examples. The conditions in the following examples are one example of conditions used to confirm the feasibility and effects of the metal pipe for oil wells of the present embodiment. Therefore, the metal pipe for oil wells of the present embodiment is not limited to this one example of conditions.

[0222] In the examples, a composition for forming a resin film was prepared, and the shear strength of the resin film was evaluated. Specifically, the results are as follows.

[0223] Prepare a composition having the composition shown in Table 1. In the composition of each test number, the ratio of the total content of wax, fluorine-based additives and graphite in mass % to the total content of nylon, TiO2 and hydrous magnesium silicate in mass % is calculated. The results are shown in the "Shear Material Ratio" column of Table 1. In the composition of each test number, the ratio of the content of nylon in mass % to the total content of base resin in mass % is calculated. The results are shown in the "Nylon Ratio" column of Table 1. It should be noted that the composition contains a solvent in addition to the composition described in Table 1. A mixed solution of water, alcohol and a surfactant is used as the solvent.

[0224] [Table 1]

[0225] Table 1

[0226]

[0227] As a metal material simulating a metal pipe for an oil well, a cold-rolled steel plate with a length of 30 mm, a width of 30 mm, and a thickness of 2 mm was prepared (chemical composition: C≤0.15%, Mn≤0.60%, P≤0.100%, S≤0.050%, and the remainder: Fe and impurities). The composition of each test number was coated on the cold-rolled steel plate. The target film thickness of the resin coating was 20 μm. The cold-rolled steel plate coated with the composition was heat treated at 210°C for 20 minutes and then cooled to form a resin coating on the cold-rolled steel plate. The shear strength of the resin coating of each test number was measured according to the above-mentioned [Shear Strength Determination Method]. At this time, the surface of the test piece was set to 30 mm×30 mm, and the thickness was set to 2 mm. The results are shown in Table 1.

[0228] [Evaluation results]

[0229] Referring to Table 1, the contents of the components of the resin films of Test Nos. 1 to 24 were appropriate, and the shear material ratio was 5.00 or less. As a result, the shear strength of these resin films was 58.0 MPa or more, which was high.

[0230] The shear strength of the resin films of Test Nos. 1 to 23, in which the ratio of the nylon content by mass % to the total content by mass % of the base resin was 0.30 or less, was 59.0 MPa or more. The resin films of Test Nos. 1 to 23 had higher shear strength than Test No. 24.

[0231] On the other hand, the nylon content of the resin coating of Test No. 25 was too low. As a result, the shear strength of the resin coating of Test No. 25 was less than 58.0 MPa, and did not have high shear strength.

[0232] The nylon content of the resin coating of Test No. 26 was too high. As a result, the shear strength of the resin coating of Test No. 26 was less than 58.0 MPa, and did not have high shear strength.

[0233] The resin films of Test Nos. 27 and 28 had appropriate contents of each component, but the shear material ratio was greater than 5.00. As a result, the shear strength of the resin films of Test Nos. 27 and 28 was less than 58.0 MPa, and did not have high shear strength.

[0234] The content of TiO2 in the resin film of Test No. 29 was too low. As a result, the shear strength of the resin film of Test No. 29 was less than 58.0 MPa, and did not have high shear strength.

[0235] The content of TiO2 in the resin film of Test No. 30 was too high. As a result, the shear strength of the resin film of Test No. 30 was less than 58.0 MPa, and did not have high shear strength.

[0236] The embodiments of the present disclosure have been described above. However, the above embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above embodiments, and the above embodiments can be appropriately modified and implemented within the scope of the present disclosure.

[0237] Description of Reference Numerals

[0238] 1, 1a, 1b: Metal pipes for oil wells

[0239] 10: Tube body

[0240] 10A: 1st end

[0241] 10B: 2nd end

[0242] 11: Male buckle body

[0243] 12: Coupling

[0244] 40: Male buckle

[0245] 41: External thread

[0246] 42: Sealing surface of male buckle

[0247] 43: Shoulder surface of male buckle

[0248] 50: Female buckle

[0249] 51: Internal thread

[0250] 52: Sealing surface of female buckle

[0251] 53: Shoulder surface of the female buckle

[0252] 100, 100a, 100b: Resin coating

[0253] 400: Male buckle contact surface

[0254] 500: Female buckle contact surface

Claims

1. A metal pipe for oil wells, comprising a pipe body including a first end portion and a second end portion, The pipe body comprises: a male buckle portion formed at the first end portion; and a female buckle portion formed at the second end portion, The pin portion has a pin portion contact surface including an external thread portion, The box portion has a box portion contact surface including an internal thread portion, The oil well metal pipe further comprises a resin coating formed as the uppermost layer of at least one of the pin portion contact surface and the box portion contact surface, The resin coating contains: At least one base resin selected from the group consisting of epoxy resins, phenolic resins, acrylic resins, urethane resins, polyester resins, polyamide-imide resins, polyimide resins, and polyetheretherketone resins: 40.0 to 99.4% by mass in total, Nylon: 0.1-20.0% by mass, TiO2: 0.5-30.0 mass %, Hydrous magnesium silicate: 0-49.4% by mass, Wax: 0-10.0 mass %, Fluorine additives: 0-30.0 mass %, Graphite: 0-10.0 mass %, Anti-rust pigment: 0-30.0 mass %, Coloring pigment: 0 to 10.0% by mass, and Coupling agent: 0-10.0% by mass The ratio of the total content of the wax, the fluorine-based additive and the graphite in the resin coating in terms of mass % to the total content of the nylon, the TiO 2 and the hydrous magnesium silicate in terms of mass % is 5.00 or less.

2. The metal pipe for oil wells according to claim 1, wherein: The ratio of the content of the nylon expressed in mass % to the total content of the base resin expressed in mass % is 0.30 or less.

3. The metal pipe for oil wells according to claim 1 or claim 2, wherein: The male buckle part contact surface also includes a male buckle part sealing surface and a male buckle part shoulder surface, The contact surface of the box buckle part also includes a box buckle part sealing surface and a box buckle part shoulder surface.

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