Metal pipes for oil wells

Abstract

The present invention provides a metal pipe for oil wells, the metal pipe being able to be fastened with high torque. A metal pipe (1) for oil wells according to the present disclosure is provided with a resin film (100) on or above at least one of a pin contact surface (400) and a box contact surface (500). The resin film (100) contains, in mass%, 40.0% to 97.0% of an epoxy resin, 3.0% to 50.0% of a hydrated magnesium silicate powder, 0% to 10.0% of TiO2, 0% to 10.0% of a wax, 0% to 20.0% of a fluorine-based additive and 0% to 10.0% of graphite, while satisfying formula (1).　(1): (CW + CF + CG) / (CMg + CTiO2 + CSi) ≤ 0.28 In formula (1), the content of the wax expressed in mass% is assigned to CW; the content of the fluorine-based additive expressed in mass% is assigned to CF; the content of the graphite expressed in mass% is assigned to CG; the content of the hydrated magnesium silicate powder expressed in mass% is assigned to CMg; the content of TiO2 expressed in mass% is assigned to CTiO2; and the content of a silane coupling agent expressed in mass% is assigned to CSi.

Description

[Technical Field]

[0001] The present disclosure relates to metal tubing, and more particularly to metal tubing for oil wells. [Background technology]

[0002] Metallic oil well pipes are used in oil wells and gas wells (hereinafter, oil wells and gas wells will be collectively referred to simply as "oil wells"). Metallic oil well pipes have threaded joints. Specifically, in oil well drilling sites, multiple metallic oil well pipes are connected according to the depth of the oil well to form a connected oil well pipe assembly, typically casing or tubing. A connected oil well pipe assembly is formed by screwing together the threaded joints. Inspection may be performed on the connected oil well pipe assembly. When inspection is performed, the connected oil well pipe assembly is pulled up and unscrewed. Then, the metallic oil well pipe is removed from the connected oil well pipe assembly by unscrewing, and inspected. After inspection, the threaded joints of the metallic oil well pipes are screwed together again, and the metallic oil well pipes are reused as part of a connected oil well pipe assembly.

[0003] The metal oil well pipe includes a pin and a box. The pin has a pin contact surface including a male thread portion on the outer peripheral surface of the end of the metal oil well pipe. The box has a box contact surface including a female thread portion on the inner peripheral surface of the end of the metal oil well pipe. In this specification, the male thread portion and the female thread portion are collectively referred to as "thread portion." Note that the pin contact surface may further include a pin-unthreaded metal contact portion including a pin seal surface and a pin shoulder surface. Similarly, the box contact surface may further include a box-unthreaded metal contact portion including a box seal surface and a box shoulder surface.

[0004] The pin contact surface and the box contact surface of an oil well metal pipe are repeatedly subjected to strong friction when the pipe is screwed in and out. Therefore, the pin contact surface and the box contact surface are prone to galling (irreparable seizure) when the pipe is screwed in and out repeatedly. Therefore, oil well metal pipe is required to have sufficient durability against friction, i.e., excellent seizure resistance.

[0005] Conventionally, compound grease containing heavy metal powder, called dope, has been used to improve the seizure resistance of oil well metal pipes. The application of compound grease to the pin contact surface and / or box contact surface can improve the seizure resistance of oil well metal pipes. However, the heavy metal powders, such as Pb, Zn, and Cu, contained in the compound grease may have an adverse effect on the environment. Therefore, there is a need to develop oil well metal pipes that have excellent seizure resistance without the use of compound grease.

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

[0007] Patent Document 1 discloses a metal oil well pipe having a threaded joint and comprising a pin and a box, each having a contact surface including a threaded portion and an unthreaded metal contact portion. This metal oil well pipe has a solid lubricant coating composed of a solid lubricant and a binder on the contact surface of at least one of the pin and box. In a cross section in the thickness direction of the solid lubricant coating, secondary particles of the solid lubricant with an equivalent area diameter of 15 to 60 μm account for 5 to 90% of the area. Patent Document 1 states that this allows for the production of a metal oil well pipe that can reliably ensure seizure resistance and airtightness without the application of compound grease.

[0008] The oil well metal pipe disclosed in Patent Document 2 has a threaded joint and is composed of a pin and a box, each having a contact surface with a threaded portion and an unthreaded metal contact portion. The contact surface of at least one of the pin and box has a viscous liquid or semi-solid lubricating coating and a dry solid coating formed thereon. Patent Document 2 states that this makes it possible to obtain an oil well metal pipe that suppresses rust formation and exhibits excellent seizure resistance and airtightness without using compound grease. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-021278 [Patent Document 2] International Publication No. 2006 / 104251 Summary of the Invention [Problem to be solved by the invention]

[0010] In oil and natural gas drilling, vertical wells, which are drilled vertically, and directional wells, which are drilled at an angle, are typically used. On the other hand, horizontal drilling is another method of drilling oil and natural gas. Horizontal drilling involves drilling a vertically drilled oil well, gradually bending it horizontally, and finally drilling it horizontally along the oil and natural gas reservoir. Compared to conventional vertical wells and directional wells, horizontal wells allow for greater contact with the oil and natural gas reservoir, thereby increasing the amount of oil and natural gas produced per well. In recent years, the use of horizontal drilling has been increasing in oil and natural gas drilling. Therefore, there is a demand for metal oil well tubular structures that can be used in oil well tubular structure assemblies designed for horizontal drilling.

[0011] In horizontal drilling, when the drilling direction changes from vertical to horizontal, the OCTG connected body bends. In the bent portion of horizontal drilling, the OCTG connected body is rotated circumferentially while drilling to reach the target oil and natural gas reservoir. Therefore, particularly in the bent portion of the OCTG connected body, torsion is applied to the OCTG connected body due to the bending and circumferential rotation of the OCTG connected body. When torsion is applied under a high load, the OCTG is likely to loosen. When the drilling direction is vertical, the OCTG is primarily subjected to torsion in the circumferential direction of the OCTG. However, in horizontal drilling, in addition to the torsion in the circumferential direction of the OCTG, torsion due to bending of the OCTG is also applied to the OCTG. Therefore, compared to vertical drilling, even more excessive torsion is applied to the OCTG in horizontal drilling. Therefore, the OCTG is even more likely to loosen.

[0012] Oil well tubular goods connectors used in horizontal drilling require metal tubular goods that can be fastened with a higher torque than conventional ones. If metal tubular goods can be fastened with a higher torque than conventional ones, the threaded joints will be less likely to loosen. Therefore, the threaded joints will be less likely to loosen even at the bent parts of the oil well tubular goods connectors during horizontal drilling.

[0013] An object of the present disclosure is to provide a metal oil well pipe that can be fastened with a high torque. [Means for solving the problem]

[0014] The metal pipe for oil well use according to the present disclosure comprises: a tube body including a first end and a second end; The tube body is a pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box a box contact surface including an internal thread; The oil well metal pipe further comprises: a resin coating on or above at least one of the pin contact surface and the box contact surface; The resin coating is Epoxy resin: 40.0 to 97.0 mass% Hydrous magnesium silicate powder: 3.0 to 50.0 mass%, TiO2: 0~10.0% by mass, Wax: 0 to 10.0 mass% Fluorine-based additives: 0 to 20.0 mass% Graphite: 0~10.0% by mass, Anti-rust pigment: 0 to 30.0 mass%, Color pigment: 0 to 10.0% by mass, and Silane coupling agent: contained in an amount of 0 to 10.0 mass % and satisfying formula (1). (C W +C F +C G ) / (C Mg +CTiO2 +C Si )≦0.28 (1) Here, C in formula (1) W The wax content is in mass %, and C F The content of the fluorine-based additive is in mass %, and C G The graphite content is in mass %, and C Mg The content of the hydrous magnesium silicate powder is in mass %, and C TiO2 The content of TiO2 is in mass %, and C Si The content of the silane coupling agent in mass % is substituted for each of the above. [Effects of the Invention]

[0015] The metal oil well pipe according to the present disclosure can be fastened with a high torque. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a graph showing the relationship between the coefficient of friction of a resin coating containing an epoxy resin and the yield torque. [Figure 2] FIG. 2 is a graph showing the relationship between the storage modulus and yield torque of a resin coating containing an epoxy resin. [Figure 3] FIG. 3 is a graph showing the relationship between the ratio (F1) of the sum of the wax content (mass%), the fluorine-based additive content (mass%), and the graphite content (mass%) to the sum of the hydrous magnesium silicate powder content (mass%) and the TiO content in a resin coating containing an epoxy resin, and the storage modulus of the resin coating. [Figure 4] FIG. 4 is a structural view showing an example of the metallic oil well pipe according to this embodiment. [Figure 5] 5 is a partial cross-sectional view showing a cross section (longitudinal cross section) parallel to the pipe axis direction of the coupling for the metal pipe for oil well use shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view of a portion of the metallic oil well pipe shown in FIG. 5 near a pin, taken along a line parallel to the axial direction of the metallic oil well pipe. [Figure 7]FIG. 7 is a cross-sectional view of a portion of the metallic oil well pipe shown in FIG. 5 near the box, taken along a line parallel to the axial direction of the metallic oil well pipe. [Figure 8] FIG. 8 is a diagram showing an example of a metal oil well pipe in which the pin includes a male thread portion but does not include a pin seal surface or a pin shoulder surface, and the box includes a female thread portion but does not include a box seal surface or a box shoulder surface. [Figure 9] FIG. 9 is a diagram showing the configuration of an integral type metallic oil well pipe according to this embodiment. [Figure 10] FIG. 10 is an enlarged view of the pin contact surface shown in FIG. [Figure 11] FIG. 11 is an enlarged view of the box contact surface shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present embodiment will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0018] The present inventors have conducted research into a metal oil well pipe that can be fastened with a high torque, and have obtained the following findings.

[0019] Increasing the friction coefficient of the resin coating has been proposed as a method for increasing the make-up torque. If resin coatings with high friction coefficients come into contact and slide against each other when a threaded joint is made to be tightened, it is expected that the tightening torque will increase. If the tightening torque increases, the yield torque also increases. In other words, the yield torque can be used as an indicator of whether or not metal oil well pipes can be tightened with a high torque. The inventors adjusted the friction coefficient of the resin coating by incorporating a solid powder, hydrated magnesium silicate powder, into a resin coating containing an epoxy resin, and investigated the relationship between the friction coefficient and the yield torque.

[0020] Figure 1 is a graph showing the relationship between the coefficient of friction of a resin coating containing epoxy resin and yield torque. The horizontal axis of Figure 1 shows the coefficient of friction (μ) of the resin coating containing epoxy resin. The vertical axis of Figure 1 shows the yield torque (ft.lbs) when a metal oil well pipe coated with a resin coating containing epoxy resin is screwed together. Here, yield torque refers to the torque at which a threaded joint yields when screwed together. The higher the yield torque, the higher the torque that can be used for screwing together.

[0021] Referring to Figure 1, the correlation coefficient R between the friction coefficient of the resin coating containing epoxy resin and the yield torque is 2 The coefficient of friction of the resin coating containing epoxy resin was 0.144. This means that there is almost no correlation between the friction coefficient of the resin coating and the yield torque. Contrary to the expectations of the inventors, it was found that the correlation between the friction coefficient and the yield torque is low. In other words, it was found that the yield torque cannot be increased simply by increasing the friction coefficient of the resin coating.

[0022] Therefore, the present inventors conducted further studies on metal oil well pipes that can be fastened with high torque. The present inventors focused on the behavior of the resin coating in the final stage of screw tightening. In the final stage of screw tightening, two resin coatings come into contact with each other at high surface pressure and slide against each other. At this time, an external force is applied to the resin coating, and energy generated by torsion is also applied. If the resin coating has high resistance to the energy generated by the external force and torsion, the resin coating will resist and try to maintain its shape even in the final stage of screw tightening. In this case, it is thought that the screw tightening torque will increase. Here, the present inventors considered that increasing the dynamic viscoelasticity of the resin coating would be effective in increasing resistance to the energy generated by the external force and torsion.

[0023] Dynamic viscoelasticity is divided into storage modulus and loss modulus. The storage modulus is the component of energy generated in an object due to external force and strain that is stored inside the object. The loss modulus is the component of energy generated in an object due to external force and strain that is diffused to the outside. The inventors believed that the yield torque is affected by the storage modulus of the resin coating, rather than the loss modulus of the resin coating. Therefore, the inventors investigated the relationship between the storage modulus of the resin coating and the yield torque for resin coatings containing epoxy resins.

[0024] Figure 2 is a graph showing the relationship between the storage modulus of a resin coating containing an epoxy resin and the yield torque. The horizontal axis of Figure 2 shows the storage modulus (MPa) of the resin coating containing an epoxy resin. The vertical axis of Figure 2 shows the yield torque (ft.lbs) when a metal oil well pipe coated with a resin coating containing an epoxy resin is screwed together.

[0025] Referring to Figure 2, the correlation coefficient R between the storage modulus of the resin coating containing epoxy resin and the yield torque 2 The yield torque of metal oil well pipes was 0.7082. This means that there is a correlation between the storage modulus of resin coatings containing epoxy resins and the yield torque. In other words, it was found that increasing the storage modulus of the resin coating can increase the yield torque of metal oil well pipes.

[0026] In other words, contrary to conventional knowledge, it was found that the yield torque cannot be increased simply by increasing the friction coefficient of the resin coating, but that the yield torque can be increased only by increasing the storage modulus of the resin coating.

[0027] The present inventors have investigated methods for increasing the storage modulus of resin coatings containing epoxy resins. As a result, they have concluded that the storage modulus of resin coatings can be increased by using epoxy resin as the base material for the resin coating and adding hydrous magnesium silicate powder, which is a solid powder. Therefore, the present inventors prepared resin coatings containing 40.0 to 97.0 mass% of epoxy resin and 3.0 to 50.0 mass% of hydrous magnesium silicate, and investigated their storage moduli. As a result, they found that even resin coatings with the above composition can sometimes have a decreased storage modulus. In other words, simply adding hydrous magnesium silicate powder to a resin coating does not increase the storage modulus of the resin coating.

[0028] Further investigation into methods for increasing the storage modulus of a resin coating containing an epoxy resin revealed that the storage modulus of the resin coating can be increased if the composition satisfies the following formula (1). (C W +C F +C G ) / (C Mg +C TiO2 +C Si )≦0.28 (1) Here, C in formula (1) W The wax content is in mass %, and C F The content of the fluorine-based additive is in mass %, and C G The graphite content is in mass %, and C Mg The content of the hydrous magnesium silicate powder is in mass %, and C TiO2 The content of TiO2 is in mass %, and C Si The content of the silane coupling agent in mass % is substituted for each of the above.

[0029] where (C W +C F +C G ) / (C Mg +C TiO2 +C Si)=F1. Figure 3 is a graph showing the relationship between F1 in a resin coating containing an epoxy resin and the storage modulus of the resin coating. Figure 3 shows an excerpt from the results of an example described below. The horizontal axis of Figure 3 represents F1. The vertical axis of Figure 3 represents the storage modulus (MPa) of the resin coating.

[0030] Referring to FIG. 3, if F1 is 0.28 or less, the storage modulus of the resin coating is 1.50 MPa or more. While the reason for this is unclear, it is presumed to be as follows: Epoxy resin has a moderate hardness and contains a large amount of oxygen (O) and hydrogen (H) inside. Furthermore, hydrated magnesium silicate powder and TiO2 have hydroxyl groups and metals such as magnesium and titanium exposed on the surface of the powder, resulting in polarity on the powder surface. Therefore, the hydroxyl groups and metals on the surface of the hydrated magnesium silicate powder and TiO2 form hydrogen bonds with the oxygen (O) and hydrogen (H) contained in the epoxy resin. This increases the storage modulus of the resin coating. Furthermore, the silane coupling agent has an alkoxysilyl group and an organic reactive group. The alkoxysilyl group and the organic reactive group each chemically bond with the epoxy resin. Therefore, the silane coupling agent crosslinks epoxy resins together. This increases the storage modulus of the resin coating.

[0031] Wax, fluorine-based additives, and graphite do not contain large amounts of polar moieties such as oxygen (O), and therefore have poor adhesion to epoxy resins. Therefore, if the amount of hydrous magnesium silicate powder, TiO2, and silane coupling agent is excessive relative to the amount of wax, fluorine-based additives, and graphite, the storage modulus of the resin coating is increased. Specifically, the ratio of the total amount of wax (mass%), fluorine-based additives (mass%), and graphite (mass%) to the total amount of hydrous magnesium silicate powder (mass%), TiO2 (mass%), and silane coupling agent (mass%) is set to 0.28 or less. This increases the storage modulus of the resin coating.

[0032] From the above, it has been found that, contrary to conventional knowledge, simply increasing the friction coefficient of the resin coating does not increase the yield torque, but that it can only be increased by increasing the storage modulus of the resin coating. It has also been found that the storage modulus of the resin coating can only be increased by adjusting the contents of each component in the resin coating so as to satisfy the above-mentioned formula (1). By increasing the storage modulus of the resin coating and thereby increasing the yield torque, a metal oil well pipe that can also be used for horizontal drilling can be obtained. The metal oil well pipe of the present disclosure has been completed based on the above-mentioned knowledge and has the following configuration.

[0033] [1] A metal pipe for oil wells, a tube body including a first end and a second end; The tube body is a pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box a box contact surface including an internal thread; The oil well metal pipe further comprises: a resin coating on or above at least one of the pin contact surface and the box contact surface; The resin coating is Epoxy resin: 40.0 to 97.0 mass% Hydrous magnesium silicate powder: 3.0 to 50.0 mass%, TiO2: 0~10.0% by mass, Wax: 0 to 10.0 mass% Fluorine-based additives: 0 to 20.0 mass% Graphite: 0~10.0% by mass, Anti-rust pigment: 0 to 30.0 mass%, Color pigment: 0 to 10.0% by mass, and Silane coupling agent: 0 to 10.0 mass % and satisfying formula (1), Metal pipes for oil wells. (C W +CF +C G ) / (C Mg +C TiO2 +C Si )≦0.28 (1) Here, C in formula (1) W The wax content is in mass %, and C F The content of the fluorine-based additive is in mass %, and C G The graphite content is in mass %, and C Mg The content of the hydrous magnesium silicate powder is in mass %, and C TiO2 The content of TiO2 is in mass %, and C Si The content of the silane coupling agent in mass % is substituted for each of the above.

[0034] [2] The metal pipe for oil well use according to [1], the pin contact surface further includes a pin seal surface and a pin shoulder surface; The box contact surface further includes a box seal surface and a box shoulder surface. Metal pipes for oil wells.

[0035] The metallic oil well pipe according to this embodiment will be described in detail below.

[0036] [Configuration of metal pipe for oil wells] First, the configuration of the oil well metallic pipe of this embodiment will be described. The oil well metallic pipe has a well-known configuration. There are two types of oil well metallic pipe: T&C type oil well metallic pipe and integral type oil well metallic pipe. Each type of oil well metallic pipe will be described in detail below.

[0037] [When oil well metal pipe 1 is T&C type] Fig. 4 is a structural view showing an example of a metal oil well pipe 1 according to this embodiment. Fig. 4 is a structural view of a so-called T&C (Threaded and Coupled) metal oil well pipe 1. Referring to Fig. 4, the metal oil well pipe 1 includes a pipe main body 10.

[0038] The pipe body 10 extends in the pipe axis direction. A cross section of the pipe body 10 perpendicular to the pipe axis direction is circular. The pipe body 10 includes a first end portion 10A and a second end portion 10B. The first end portion 10A is the end portion opposite the second end portion 10B. In the T&C type metal pipe for oil well use 1 shown in FIG. 4, 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 a screw.

[0039] Fig. 5 is a partial cross-sectional view showing a cross section (longitudinal cross section) parallel to the pipe axis direction of the coupling 12 of the metal oil well pipe 1 shown in Fig. 4. With reference to Figs. 4 and 5, the pipe body 10 includes a pin 40 and a box 50. The pin 40 is formed at a first end 10A of the pipe body 10. At the time of fastening, the pin 40 is inserted into the box 50 of another metal oil well pipe 1 (not shown) and fastened to the box 50 of the other metal oil well pipe 1 by a screw.

[0040] The box 50 is formed at the second end 10B of the pipe body 10. At the time of fastening, the pin 40 of another metal pipe for oil well use 1 is inserted into the box 50, and the box 50 is fastened to the pin 40 of the other metal pipe for oil well use 1 by a screw.

[0041] [About the configuration of pin 40] Fig. 6 is a cross-sectional view parallel to the pipe axis direction of the metal oil well pipe 1 of a portion near a pin 40 of the metal oil well pipe 1 shown in Fig. 5. The dashed line portion in Fig. 6 shows the configuration of a box 50 of another metal oil well pipe 1 when fastening to another metal oil well pipe 1. Referring to Fig. 6, the pin 40 has a pin contact surface 400 on the outer circumferential surface of the first end 10A of the pipe body 10. When fastening to another metal oil well pipe 1, the pin contact surface 400 is screwed into the box 50 of the other metal oil well pipe 1 and comes into contact with a box contact surface 500 (described later) of the box 50.

[0042] The pin contact surface 400 includes at least a male thread portion 41 formed on the outer circumferential surface of the first end portion 10A. The pin contact surface 400 may further include a pin seal surface 42 and a pin shoulder surface 43. In FIG. 6, the pin shoulder surface 43 is located on the tip surface of the first end portion 10A, and the pin seal surface 42 is located on the outer circumferential surface of the first end portion 10A closer to the tip of the first end portion 10A than the male thread portion 41. In other words, the pin seal surface 42 is located between the male thread portion 41 and the pin shoulder surface 43. The pin seal surface 42 is tapered. Specifically, the outer diameter of the pin seal surface 42 gradually decreases from the male thread portion 41 to the pin shoulder surface 43 in the longitudinal direction (pipe axis direction) of the first end portion 10A.

[0043] When fastening another oil well metal pipe 1, the pin seal surface 42 comes into contact with a box seal surface 52 (described later) of the box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other oil well metal pipe 1, so that the pin seal surface 42 comes into contact with the box seal surface 52. Then, when the pin 40 is further screwed into the box 50 of the other oil well metal pipe 1, the pin seal surface 42 comes into close contact with the box seal surface 52. As a result, when fastening, the pin seal surface 42 comes into close contact with the box seal surface 52, forming a seal based on metal-metal contact. Therefore, the airtightness of the oil well metal pipes 1 fastened to each other can be improved.

[0044] In Fig. 6, the pin shoulder surface 43 is disposed on the tip surface of the first end portion 10A. That is, in the pin 40 shown in Fig. 6, the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43 are disposed in this order from the center of the pipe body 10 toward the first end portion 10A. When fastening with another oil well metal pipe 1, the pin shoulder surface 43 faces and contacts a box shoulder surface 53 (described later) of a box 50 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other oil well metal pipe 1, so that the pin shoulder surface 43 contacts the box shoulder surface 53. This allows a high torque to be obtained when fastening. Furthermore, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0045] The pin contact surface 400 of the pin 40 includes at least the male thread portion 41. In other words, the pin contact surface 400 may include the male thread portion 41, but not the pin seal surface 42 or the pin shoulder surface 43. The pin contact surface 400 may include the male thread portion 41 and the pin shoulder surface 43, but not the pin seal surface 42. The pin contact surface 400 may include the male thread portion 41 and the pin seal surface 42, but not the pin shoulder surface 43.

[0046] [About the composition of Box 50] 7 is a cross-sectional view parallel to the pipe axis direction of the metal oil well pipe 1 of a portion near the box 50 of the metal oil well pipe 1 shown in FIG. 5. The dashed line portion in FIG. 7 shows the configuration of the pin 40 of another metal oil well pipe 1 when fastening to another metal oil well pipe 1. Referring to FIG. 7, the box 50 has a box contact surface 500 on the inner circumferential surface of the second end 10B of the pipe body 10. When fastening to another metal oil well pipe 1, the pin 40 of the other metal oil well pipe 1 is screwed into the box contact surface 500, and the box contact surface 500 comes into contact with the pin contact surface 400 of the pin 40.

[0047] The box contact surface 500 includes at least a female thread portion 51 formed on the inner circumferential surface of the second end portion 10B. During fastening, the female thread portion 51 meshes with the male thread portion 41 of the pin 40 of another metal oil well pipe 1.

[0048] The box contact surface 500 may further include a box seal surface 52 and a box shoulder surface 53. In FIG. 7, the box seal surface 52 is located on the inner circumferential surface of the second end portion 10B, closer to the pipe body 10 than the female thread portion 51. In other words, the box seal surface 52 is located between the female thread portion 51 and the box shoulder surface 53. The box seal surface 52 is tapered. Specifically, the inner diameter of the box seal surface 52 gradually decreases from the female thread portion 51 toward the box shoulder surface 53 in the longitudinal direction (pipe axial direction) of the second end portion 10B.

[0049] When fastening another metal oil well pipe 1, the box seal surface 52 comes into contact with the pin seal surface 42 of the pin 40 of the other metal oil well pipe 1. More specifically, when fastening, the pin 40 of the other metal oil well pipe 1 is screwed into the box 50, so that the box seal surface 52 comes into contact with the pin seal surface 42, and when further screwed, the box seal surface 52 comes into close contact with the pin seal surface 42. As a result, when fastening, the box seal surface 52 comes into close contact with the pin seal surface 42, forming a seal based on metal-metal contact. Therefore, the airtightness of the metal oil well pipes 1 fastened together can be improved.

[0050] The box shoulder surface 53 is located closer to the pipe body 10 than the box seal surface 52. That is, in the box 50, the box shoulder surface 53, the box seal surface 52, and the female thread portion 51 are located in this order from the center of the pipe body 10 toward the tip of the second end 10B. When fastening another oil well metal pipe 1, the box shoulder surface 53 faces and contacts the pin shoulder surface 43 of the pin 40 of the other oil well metal pipe 1. More specifically, when fastening, the pin 40 of the other oil well metal pipe 1 is inserted into the box 50, so that the box shoulder surface 53 contacts the pin shoulder surface 43. This allows a high torque to be obtained when fastening. Furthermore, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0051] The box contact surface 500 includes at least an internal thread portion 51. During fastening, 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 seal surface 52 corresponds to and contacts the pin seal surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0052] When the pin contact surface 400 includes the male thread portion 41 but does not include the pin seal surface 42 or the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 but does not include the box seal surface 52 or the box shoulder surface 53. When the pin contact surface 400 includes the male thread portion 41 and the pin shoulder surface 43 but does not include the pin seal surface 42, the box contact surface 500 includes the female thread portion 51 and the box shoulder surface 53 but does not include the box seal surface 52. When the pin contact surface 400 includes the male thread portion 41 and the pin seal surface 42 but does not include the pin shoulder surface 43, the box contact surface 500 includes the female thread portion 51 and the box seal surface 52 but does not include the box shoulder surface 53.

[0053] The pin contact surface 400 may include multiple male thread portions 41, multiple pin seal surfaces 42, or multiple pin shoulder surfaces 43. For example, on the pin contact surface 400 of the pin 40, the pin shoulder surface 43, the pin seal surface 42, the male thread portion 41, the pin seal surface 42, the pin shoulder surface 43, the pin seal surface 42, and the male thread portion 41 may be arranged in this order from the tip of the first end 10A toward the center of the pipe body 10. In this case, on the box contact surface 500 of the box 50, the female thread portion 51, the box seal surface 52, the box shoulder surface 53, the box seal surface 52, the female thread portion 51, the box seal surface 52, and the box shoulder surface 53 are arranged in this order from the tip of the second end 10B toward the center of the pipe body 10.

[0054] 6 and 7 illustrate a so-called premium joint in which the pin 40 includes a male thread portion 41, a pin seal surface 42, and a pin shoulder surface 43, and the box 50 includes a female thread portion 51, a box seal surface 52, and a box shoulder surface 53. However, as described above, the pin 40 may include the male thread portion 41 but not the pin seal surface 42 or the pin shoulder surface 43. In this case, the box 50 includes the female thread portion 51 but not the box seal surface 52 or the box shoulder surface 53. FIG. 8 illustrates an example of a metal oil well pipe 1 in which the pin 40 includes the male thread portion 41 but not the pin seal surface 42 or the pin shoulder surface 43, and the box 50 includes the female thread portion 51 but not the box seal surface 52 or the box shoulder surface 53.

[0055] [When the oil well metal pipe 1 is an integral type] The oil well metal pipe 1 shown in Figures 4, 5 and 8 is a so-called T&C type oil well metal pipe 1 in which a pipe body 10 includes a pin pipe body 11 and a coupling 12. However, the oil well metal pipe 1 of this embodiment may be an integral type instead of a T&C type.

[0056] FIG. 9 is a structural diagram of an integral-type metal oil well pipe 1 according to this embodiment. Referring to FIG. 9, the integral-type metal oil well pipe 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 located on the opposite side to the second end portion 10B. As described above, in the T&C type metal oil well pipe 1, the pipe body 10 includes a pin pipe body 11 and a coupling 12. That is, in the T&C type metal oil well pipe 1, the pipe body 10 is formed by fastening two separate members (the pin pipe body 11 and the coupling 12). In contrast, in the integral-type metal oil well pipe 1, the pipe body 10 is integrally formed.

[0057] The pin 40 is formed at a first end 10A of the pipe body 10. When fastening, the pin 40 is inserted into and screwed into a box 50 of another integral type metallic pipe for oil well use 1, and is fastened to the box 50 of another integral type metallic pipe for oil well use 1. The box 50 is formed at a second end 10B of the pipe body 10. When fastening, the pin 40 of another integral type metallic pipe for oil well use 1 is inserted into and screwed into the box 50, and is fastened to the pin 40 of another integral type metallic pipe for oil well use 1.

[0058] The configuration of the pin 40 of the integral type metal oil well pipe 1 is the same as the configuration of the pin 40 of the T&C type metal oil well pipe 1 shown in Fig. 6. Similarly, the configuration of the box 50 of the integral type metal oil well pipe 1 is the same as the configuration of the box 50 of the T&C type metal oil well pipe 1 shown in Fig. 7. In Figs. 6 and 7, in the pin 40, the pin shoulder surface 43, the pin seal surface 42, and the male thread portion 41 are arranged in this order from the tip of the first end 10A toward the center of the pipe body 10. Therefore, in the box 50, the female thread portion 51, the box seal surface 52, and the box shoulder surface 53 are arranged in this order from the tip of the second end 10B toward the center of the pipe body 10. However, like the pin contact surface 400 of the pin 40 of the T&C type metal oil well pipe 1, the pin contact surface 400 of the pin 40 of the integral type metal oil well pipe 1 only needs to include at least the male thread portion 41. Furthermore, like the box contact surface 500 of the box 50 of the T&C type metal pipe for oil well use 1, the box contact surface 500 of the box 50 of the integral type metal pipe for oil well use 1 may include at least the female thread portion 51.

[0059] In short, the metal oil well pipe 1 of this embodiment may be of the T&C type or the integral type.

[0060] [Resin coating] The oil well metal pipe 1 of this embodiment has a resin coating 100 on or above at least one of the pin contact surface 400 and the box contact surface 500. FIG. 10 is an enlarged view of the pin contact surface 400 shown in FIG. 6. FIG. 11 is an enlarged view of the box contact surface 500 shown in FIG. 7. As shown in FIGS. 10 and 11, the oil well metal pipe 1 of this embodiment may have the resin coating 100 on both the pin contact surface 400 and the box contact surface 500. However, the oil well metal pipe 1 of this embodiment may have the resin coating 100 on only one of the pin contact surface 400 or the box contact surface 500. For example, as shown in FIG. 10, when the resin coating 100 is provided on the pin contact surface 400, the resin coating 100 does not have to be provided on the box contact surface 500. Furthermore, as shown in FIG. 11, when the resin coating 100 is provided on the box contact surface 500, the resin coating 100 does not have to be provided on the pin contact surface 400. In other words, the metal oil well pipe 1 according to this embodiment has the resin coating 100 on the pin contact surface 400 and / or the box contact surface 500 .

[0061] [Resin coating composition] The resin coating 100 has the following composition:

[0062] Epoxy resin: 40.0 to 97.0% by mass The epoxy resin is the base material of the resin coating 100. Here, the base material refers to the component contained in the resin coating 100 in the largest amount. The epoxy resin has appropriate hardness and contains a large amount of oxygen (O) and hydrogen (H) inside. Therefore, the epoxy resin easily forms hydrogen bonds with the hydroxyl groups exposed on the surface of the magnesium silicate hydrate powder and TiO2, and with metals such as magnesium and titanium. The epoxy resin also chemically bonds with the silane coupling agent. If the epoxy resin content is less than 40.0% by mass, the hardness of the resin coating 100 decreases, making the resin coating 100 more likely to peel off when repeatedly tightened and loosened. On the other hand, if the epoxy resin content exceeds 97.0% by mass, the other components, including the magnesium silicate hydrate powder, cannot be contained in sufficient amounts, which may result in a decrease in the seizure resistance and yield torque of the metal oil well pipe 1. Therefore, the epoxy resin content is 40.0 to 97.0% by mass. The lower limit of the epoxy resin content is preferably 43.0% by mass, more preferably 45.0% by mass, and even more preferably 50.0% by mass, and the upper limit of the epoxy resin content is preferably 95.0% by mass, more preferably 90.0% by mass, and even more preferably 89.0% by mass.

[0063] Hydrous magnesium silicate powder: 3.0 to 50.0% by mass The hydrous magnesium silicate powder increases the storage modulus of the resin coating 100. Hydroxyl groups and polar groups containing magnesium are exposed on the surface of the hydrous magnesium silicate powder. Therefore, the hydrous magnesium silicate powder easily forms hydrogen bonds with oxygen (O) and hydrogen (H) inside the epoxy resin. It is believed that the formation of hydrogen bonds by the hydrous magnesium silicate powder within the epoxy resin increases the storage modulus of the resin coating 100. If the content of the hydrous magnesium silicate powder is less than 3.0 mass%, the above effect cannot be obtained. On the other hand, if the content of the hydrous magnesium silicate powder exceeds 50.0 mass%, the resin coating 100 will not be formed properly. Therefore, the content of the hydrous magnesium silicate powder is 3.0 to 50.0 mass%. The lower limit of the content of the hydrous magnesium silicate powder is preferably 5.0 mass%, more preferably 7.0 mass%, and even more preferably 10.0 mass%. The upper limit of the content of the hydrous magnesium silicate powder is preferably 45.0% by mass, more preferably 40.0% by mass, and even more preferably 35.0% by mass.

[0064] TiO2:0~10.0% by mass TiO2 is an optional component and does not necessarily need to be included. When included, TiO2 increases the storage modulus of the resin coating 100. TiO2 is in the form of powder. Hydroxyl groups and titanium-containing polar groups are exposed on the surface of the TiO2 powder. Therefore, TiO2 easily forms hydrogen bonds with oxygen (O) and hydrogen (H) inside the epoxy resin. It is believed that the formation of hydrogen bonds by TiO2 within the epoxy resin increases the storage modulus of the resin coating 100. However, if the TiO2 content exceeds 10.0 mass%, abrasive wear may be promoted, potentially reducing the seizure resistance of the metal oil well pipe 1. Therefore, the TiO2 content is 0 to 10.0 mass%. When included, the lower limit of the TiO2 content is preferably 0.1 mass%, more preferably 0.2 mass%, and even more preferably 0.5 mass%. When TiO2 is contained, the upper limit of the TiO2 content is preferably 5.0 mass %, more preferably 4.0 mass %, and even more preferably 3.0 mass %.

[0065] Wax: 0 to 10.0% by mass Wax is an optional component and does not necessarily have to be included. When included, wax enhances the lubricity of the resin coating 100. However, if the wax content exceeds 10.0% by mass, the hardness of the resin coating 100 decreases, and the resin coating 100 becomes more likely to peel off when repeatedly tightening and loosening the screw. Therefore, the wax content is 0 to 10.0% by mass. When included, the lower limit of the wax content is preferably 1.0% by mass, more preferably 2.0% by mass, and even more preferably 3.0% by mass. When included, the upper limit of the wax content is preferably 9.0% by mass, more preferably 8.0% by mass, and even more preferably 5.0% by mass.

[0066] The wax may be, for example, one or more selected from the group consisting of animal wax, vegetable wax, mineral wax, and synthetic wax. More specifically, the wax may be one or more selected from the group consisting of beeswax, spermaceti (all animal-based), Japan wax, carnauba wax, candelilla wax, rice wax (all vegetable-based), paraffin wax, microcrystalline wax, petrolatum, montan wax, ozokerite, ceresin (all mineral-based), oxidized wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, amide wax, and hydrogenated castor oil (castor wax) (all synthetic wax). More preferably, the wax may be one or more selected from the group consisting of polyethylene wax and polypropylene wax. The resin coating 100 may contain multiple types of wax. When multiple types of wax are contained, the wax content refers to the total content of the multiple types of wax.

[0067] Fluorine-based additives: 0 to 20.0 mass% The fluorine-based additive is an optional component and does not necessarily have to be included. When included, the fluorine-based additive enhances the lubricity of the resin coating 100. However, if the content of the fluorine-based additive exceeds 20.0 mass%, the hardness of the resin coating 100 decreases, and the resin coating 100 becomes more likely to peel off when repeatedly tightening and loosening the screw. Therefore, the content of the fluorine-based additive is 0 to 20.0 mass%. When included, the lower limit of the content of the fluorine-based additive is preferably 1.0 mass%, more preferably 5.0 mass%, and even more preferably 8.0 mass%. When included, the upper limit of the content of the fluorine-based additive is preferably 18.0 mass%, more preferably 15.0 mass%, and even more preferably 10.0 mass%.

[0068] Fluorine-based additives are a general term for additives containing fluorine. Examples of fluorine-based additives include one or more selected from the group consisting of perfluoropolyether (PFPE) and polytetrafluoroethylene (PTFE). The resin coating 100 may contain multiple types of fluorine-based additives. When multiple types of fluorine-based additives are contained, the content of the fluorine-based additives refers to the total content of the multiple types of fluorine-based additives.

[0069] Graphite: 0~10.0% by mass Graphite is an optional component and does not necessarily have to be included. When included, graphite enhances the lubricity of the resin coating 100. However, if the graphite content exceeds 10.0% by mass, the hardness of the resin coating 100 decreases, and the resin coating 100 becomes more likely to peel off when repeatedly tightening and loosening the screw. Therefore, the graphite content is 0 to 10.0% by mass. When included, the lower limit of the graphite content is preferably 1.0% by mass, more preferably 3.0% by mass, and even more preferably 5.0% by mass. When included, the upper limit of the graphite content is preferably 9.0% by mass, more preferably 8.0% by mass, and even more preferably 7.0% by mass.

[0070] Anti-rust pigment: 0 to 30.0 mass% The anti-rust pigment is an optional component and does not necessarily have to be included. When included, the anti-rust pigment enhances the anti-rust properties of the resin coating 100. However, if the content of the anti-rust pigment exceeds 30.0 mass%, the resin coating 100 will not form properly. Therefore, the content of the anti-rust pigment is 0 to 30.0 mass%. When included, the lower limit of the content of the anti-rust pigment is preferably 1.0 mass%, more preferably 2.0 mass%, and even more preferably 4.0 mass%. When included, the upper limit of the content of the anti-rust pigment is preferably 25.0 mass%, more preferably 20.0 mass%, and even more preferably 10.0 mass%.

[0071] The anti-rust pigment is not particularly limited as long as it is a well-known pigment that enhances the anti-rust properties of the resin coating 100. The anti-rust pigment is, for example, one or more selected from the group consisting of zinc phosphate, aluminum tripolyphosphate, aluminum phosphite, metal carboxylic acid soap, and sulfonate. The resin coating 100 may contain multiple types of anti-rust pigments. When multiple types of anti-rust pigments are contained, the content of the anti-rust pigments refers to the total content of the multiple types of anti-rust pigments.

[0072] Colored pigment: 0~10.0% by mass The color pigment is an optional component and does not necessarily have to be included. When included, the color pigment colors the resin coating 100, making damage to the resin coating 100 easier to visually recognize. However, if the content of the color pigment exceeds 10.0 mass%, the resin coating 100 will be poorly formed. Therefore, the content of the color pigment is 0 to 10.0 mass%. When included, the lower limit of the color pigment content is preferably 0.1 mass%, more preferably 0.2 mass%, and even more preferably 0.5 mass%. When included, the upper limit of the color pigment content is preferably 8.0 mass%, more preferably 5.0 mass%, and even more preferably 3.0 mass%.

[0073] The color pigment is not particularly limited as long as it is a well-known pigment that can color the resin coating 100. For example, the color pigment is one or more selected from the group consisting of copper phthalocyanine, zinc oxide, carbon black, yellow iron oxide, iron oxide, and chromium hydroxide. The resin coating 100 may contain multiple types of color pigments. When multiple types of color pigments are contained, the content of the color pigments refers to the total content of the multiple types of color pigments.

[0074] Silane coupling agent: 0 to 10.0 mass% The silane coupling agent is an optional component and does not necessarily have to be included. When included, the silane coupling agent enhances the adhesion of the resin coating 100. This prevents peeling of the resin coating 100 when the metal oil well pipe 1 is repeatedly screwed and unscrewed. The silane coupling agent also crosslinks the epoxy resin to increase the storage modulus of the resin coating 100. However, if the content of the silane coupling agent exceeds 10.0 mass%, the resin coating 100 will not form properly. Therefore, the content of the silane coupling agent is 0 to 10.0 mass%. When included, the lower limit of the content of the silane coupling agent is preferably 0.1 mass%, more preferably 0.2 mass%, and even more preferably 0.5 mass%. When included, the upper limit of the content of the silane coupling agent is preferably 8.0 mass%, more preferably 6.0 mass%, and even more preferably 4.0 mass%.

[0075] Other ingredients: 0 to 10.0% by mass Other components are optionally contained, and may not be contained. Examples of other components include one or more selected from the group consisting of preservatives and antioxidants. When other components are contained, the total content of the other components is 10.0 mass% or less. In other words, the total content of the other components is 0 to 10.0 mass%.

[0076] The resin coating 100 may be a resin coating 100 consisting of 40.0 to 97.0 mass% epoxy resin, 3.0 to 50.0 mass% hydrous magnesium silicate powder, 0 to 10.0 mass% TiO2, 0 to 10.0 mass% wax, 0 to 20.0 mass% fluorine-based additive, 0 to 10.0 mass% graphite, 0 to 30.0 mass% anti-rust pigment, 0 to 10.0 mass% color pigment, 0 to 10.0 mass% silane coupling agent, and 0 to 10.0 mass% other components.

[0077] [Formula (1)] The resin coating 100 satisfies formula (1). (C W +C F +C G ) / (C Mg +C TiO2 +C Si )≦0.28 (1) Here, C in formula (1) W The wax content is in mass %, and C F The content of the fluorine-based additive is in mass %, and C G The graphite content is in mass %, and C Mg The content of the hydrous magnesium silicate powder is in mass %, and C TiO2 The content of TiO2 is in mass %, and C Si The content of the silane coupling agent in mass % is substituted for each of the above.

[0078] where (C W +C F +C G ) / (C Mg +C TiO2 +C Si) = F1. If F1 exceeds 0.28, the content of wax, fluorine-based additives, and graphite, which do not easily form hydrogen bonds with epoxy resins, is too high compared to the content of hydrous magnesium silicate powder and TiO2, which easily form hydrogen bonds with epoxy resins, and the content of silane coupling agent, which crosslinks epoxy resins. In this case, the storage modulus of the resin coating 100 decreases. Therefore, F1≦0.28. The upper limit of F1 is preferably 0.25, more preferably 0.20, even more preferably 0.15, and even more preferably 0.10. F1 may be 0.

[0079] When the composition of the resin coating 100 satisfies formula (1), the storage modulus of the resin coating 100 increases. As a result, the yield torque of the metal oil well pipe 1 provided with the resin coating 100 increases.

[0080] [Storage modulus of resin film] The storage modulus of the resin coating 100 is not particularly limited, but a higher value is preferable. If the storage modulus of the resin coating 100 is 1.50 MPa or greater, the yield torque of the metal oil well pipe 1 provided with the resin coating 100 can be significantly increased. Therefore, the storage modulus of the resin coating 100 is preferably 1.50 MPa or greater. The lower limit of the storage modulus of the resin coating 100 is more preferably 1.55 MPa, even more preferably 1.70 MPa, and even more preferably 2.00 MPa. The upper limit of the storage modulus of the resin coating 100 is not particularly limited, but is, for example, 10.00 MPa.

[0081] [Method for measuring storage modulus] The storage modulus of the resin coating 100 is measured by the following method. The composition for forming the resin coating 100 is sandwiched between the hot plate and geometry of a rotational rheometer. The storage modulus is measured when the geometry is rotated in one direction at a constant speed. The test specimen is set at room temperature, rapidly heated to 210°C, and held at 210°C for 20 minutes, after which the storage modulus is measured. The measurement conditions are as follows: measurement temperature: 210°C, timing for measuring storage modulus: 20 minutes after the start of measurement, frequency: 1 Hz, environment: nitrogen gas.

[0082] [Resin coating thickness] 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 metal oil well pipe 1 can be more stably increased. The lower limit of the thickness of the resin coating 100 is preferably 2 μm, more preferably 5 μm, and even more preferably 10 μm. The upper limit of the thickness of the resin coating 100 is preferably 50 μm, more preferably 40 μm, and even more preferably 30 μm.

[0083] [Method for measuring the thickness of resin coating] The thickness of the resin coating 100 is measured by the following method. A probe of an electromagnetic induction type film thickness measuring instrument is brought into contact with the pin contact surface 400 or box contact surface 500 on which the resin coating 100 is formed. The probe has an electromagnet, and when a magnetic body is brought close, electromagnetic induction occurs, and the voltage changes depending on the distance between the probe and the magnetic body. The thickness of the resin coating 100 is determined from the change in voltage. The measurement points are 12 points around the circumferential direction of the metal oil well pipe 1 (12 points at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°). The arithmetic average of the measurement results at the 12 points is taken as the thickness of the resin coating 100.

[0084] [Chemical composition of the tube body] The chemical composition of the pipe body 10 of the oil well metal pipe 1 according to this embodiment is not particularly limited. That is, in this embodiment, the steel type of the pipe body 10 of the oil well metal pipe 1 is not particularly limited. The pipe body 10 may be formed of, for example, carbon steel, stainless steel, alloy, or the like. That is, the oil well metal pipe 1 may be a steel pipe made of an Fe-based alloy, or an alloy pipe typified by a Ni-based alloy pipe. Here, the steel pipe may be, for example, a low-alloy steel pipe, a martensitic stainless steel pipe, a duplex stainless steel pipe, or the like. On the other hand, among alloy steels, high-alloy steels such as Ni-based alloys and duplex stainless steels containing alloy elements such as Cr, Ni, and Mo have high corrosion resistance. Therefore, when these high-alloy steels are used as the pipe body 10, excellent corrosion resistance can be obtained in corrosive environments containing hydrogen sulfide, carbon dioxide, and the like.

[0085] [Manufacturing method] A method for manufacturing the metal oil well pipe 1 according to this embodiment will be described below.

[0086] The method for manufacturing the metal oil well pipe 1 according to this embodiment includes a preparation step, a coating step, and a hardening step. The hardening step is carried out after the coating step.

[0087] [Preparation process] In the preparation step, a metal oil well pipe 1 is prepared, which includes a pipe body 10 including a pin 40 having a pin contact surface 400 including a male thread portion 41, and a box 50 having a box contact surface 500 including a female thread portion 51. As described above, the metal oil well pipe 1 according to this embodiment has a well-known configuration. That is, in the preparation step, it is sufficient to prepare a metal oil well pipe 1 having a well-known configuration.

[0088] [Coating process] In the application step, a composition is applied to at least one of the pin contact surface 400 and the box contact surface 500. The composition is a composition for forming the resin coating 100 described above. The composition contains 40.0 to 97.0 mass% of epoxy resin, 3.0 to 50.0 mass% of hydrous magnesium silicate powder, 0 to 10.0 mass% of TiO2, 0 to 10.0 mass% of wax, 0 to 20.0 mass% of fluorine-based additive, 0 to 10.0 mass% of graphite, 0 to 30.0 mass% of rust-preventive pigment, 0 to 10.0 mass% of color pigment, and 0 to 10.0 mass% of silane coupling agent, and satisfies formula (1). The composition further contains a solvent. The composition for forming the resin coating 100, excluding the solvent, is the same as the composition of the resin coating 100 described above.

[0089] The composition can be produced, for example, by dissolving or dispersing an epoxy resin, a hydrous magnesium silicate powder, and, if necessary, other components in a solvent and mixing them. The solvent is, for example, one or more selected from the group consisting of water, alcohol, and organic solvents. The solvent may contain a trace amount of a surfactant. The proportion of the solvent is not particularly limited. The proportion of the solvent may be adjusted so that the composition has an appropriate viscosity depending on the application method. The proportion of the solvent is, for example, 40 to 60% by mass, where the total of all components other than the solvent is 100% by mass.

[0090] The method for applying the composition to the pin contact surface 400 and / or the box contact surface 500 is not particularly limited, and may be any known method. For example, the composition in a solution state is applied to the pin contact surface 400 and / or the box contact surface 500 by spraying. In this case, the viscosity of the composition is adjusted so that it can be spray-applied under an environment of normal temperature and pressure. The method for applying the composition to the pin contact surface 400 and / or the box contact surface 500 may be brushing, dipping, or the like, instead of spraying.

[0091] [Curing process] In the curing step, the applied composition is cured to form the resin coating 100. By heating the composition applied to at least one of the pin contact surface 400 and the box contact surface 500, the composition is thermally cured to form the solid resin coating 100. The heating method is not particularly limited and may be a well-known method. For example, the heating method is a method in which the metal oil well pipe 1 to which the composition has been applied is placed in a well-known heating furnace and heated. The heating temperature is, for example, 200 to 250°C, and the heating time is, for example, 5 to 30 minutes.

[0092] Through the above steps, the metal oil well pipe 1 according to this embodiment is manufactured.

[0093] [Surface preparation process] The method for manufacturing the metal oil well pipe 1 according to this embodiment may further include a surface treatment step before the coating step. The surface treatment step may include, for example, one or more treatments selected from the group consisting of pickling treatment, blasting treatment, and alkaline degreasing treatment.

[0094] When performing pickling, the pin contact surface 400 and / or the box 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 increase the surface roughness of the pin contact surface 400 and / or the box contact surface 500. When performing blasting, for example, sandblasting is performed in which a blasting material (abrasive) is mixed with compressed air and projected onto the pin contact surface 400 and / or the box contact surface 500. In this case, the surface roughness of the pin contact surface 400 and / or the box contact surface 500 is increased.

[0095] In the surface preparation step, the same treatment may be performed on the pin contact surface 400 and the box contact surface 500, or different treatments may be performed on the pin contact surface 400 and the box contact surface 500. In addition, the surface preparation step may be performed only on the pin contact surface 400, or only on the box contact surface 500.

[0096] The metal oil well pipe 1 according to this embodiment is manufactured by the above steps. However, the above-described manufacturing method is only one example of the manufacturing method of the metal oil well pipe 1 according to this embodiment, and the manufacturing method is not limited to this. The metal oil well pipe 1 according to this embodiment may be manufactured by other methods. [Example]

[0097] The effects of the metallic oil well pipe of this embodiment will be described in more detail below with reference to examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the metallic oil well pipe of this embodiment. Therefore, the metallic oil well pipe of this embodiment is not limited to this one example of conditions.

[0098] In the examples, compositions for forming resin films were prepared, and the storage modulus of the resin films was evaluated. Specifically, the following procedures were carried out.

[0099] [Storage modulus evaluation test] A composition having the composition shown in Table 1 was prepared. In addition to the components listed in Table 1, the composition contained a solvent. The solvent was a mixed solution of water, alcohol, and a surfactant. The composition was applied to the hot plate of a rotational rheometer (Anton Paar Japan, Model MCR302). The composition was sandwiched between the hot plate and the geometry, and the geometry was rotated in one direction at a constant speed to measure the storage modulus. The test specimen was set at room temperature, rapidly heated to 210°C, and held at 210°C for 20 minutes, after which the storage modulus was measured. The measurement conditions were as follows: measurement temperature: 210°C, timing of measuring storage modulus: 20 minutes after the start of measurement, frequency: 1 Hz, environment: nitrogen gas. The composition was applied so that the resin coating thickness was 30 to 40 μm.

[0100] [Table 1]

[0101] [Evaluation results] Referring to Table 1, the resin coatings of test numbers 4 to 8 and 12 to 18 had appropriate contents of each component and further satisfied formula (1). Therefore, the storage modulus was 1.50 MPa or more. The resin coatings of test numbers 4 to 8 and 12 to 18 were able to increase the yield torque of the metal oil well pipes.

[0102] On the other hand, the resin coatings of test numbers 1 and 2 did not contain hydrous magnesium silicate powder. As a result, the storage modulus was less than 1.50 MPa. In other words, the resin coatings of test numbers 1 and 2 could not increase the yield torque of the metal oil well pipes.

[0103] The resin coatings of test numbers 3 and 9 had too little content of hydrous magnesium silicate powder. Furthermore, they did not satisfy formula (1). As a result, the storage modulus was less than 1.50 MPa. In other words, the resin coatings of test numbers 3 and 9 could not increase the yield torque of the metal oil well pipe.

[0104] Although the resin coatings of test numbers 10 and 11 had appropriate contents of each component, they did not satisfy formula (1). As a result, the storage modulus was less than 1.50 MPa. In other words, the resin coatings of test numbers 10 and 11 could not increase the yield torque of the metal oil well pipe.

[0105] The resin coating of test number 19 contained too much wax and did not satisfy formula (1). Therefore, the storage modulus was less than 1.50 MPa. In other words, the resin coating of test number 19 could not increase the yield torque of the metal oil well pipe.

[0106] The resin coating of test number 20 had an excessively low content of hydrous magnesium silicate powder, resulting in a storage modulus of less than 1.50 MPa. In other words, the resin coating of test number 20 was unable to increase the yield torque of the metal oil well pipe.

[0107] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure. [Explanation of symbols]

[0108] 1 Metal pipe for oil well 10 Tube body 10A 1st end 10B 2nd end 11-pin body 12 Coupling 40-pin 41 Male thread 42 Pin seal surface 43 Pin shoulder surface 50 boxes 51 Female thread 52 Box seal surface 53 Box shoulder surface 100 Resin coating 400 pin contact surface 500 Box Contact Surface

Claims

1. A metal pipe for oil wells, a tube body including a first end and a second end; The tube body is a pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box a box contact surface including an internal thread; The oil well metal pipe further comprises: a resin coating on or above at least one of the pin contact surface and the box contact surface; The resin coating is Epoxy resin: 40.0 to 97.0% by mass, Hydrous magnesium silicate powder: 3.0 to 50.0 mass%, TiO 2 : 0-10.0% by mass Wax: 0 to 10.0% by mass, Fluorine-based additives: 0 to 20.0 mass% Graphite: 0 to 10.0% by mass, Anti-rust pigment: 0 to 30.0 mass% Color pigment: 0 to 10.0% by mass, and Silane coupling agent: 0 to 10.0 mass % is contained, and formula (1) is satisfied. Metal pipes for oil wells. (C W +C F +C G ) / (C Mg +C TiO2 +C Si )≦0.28 (1) Here, C in formula (1) W The wax content is in mass %, and C F The content of the fluorine-based additive is, in mass %, G The graphite content is in mass %, and C Mg The content of the hydrous magnesium silicate powder is, in mass %, TiO2 The TiO 2 The content of C is in mass%. Si The content of the silane coupling agent in mass % is substituted for each of the above.

2. The metal pipe for oil well use according to claim 1, the pin contact surface further includes a pin seal surface and a pin shoulder surface; The box contact surface further includes a box seal surface and a box shoulder surface. Metal pipes for oil wells.

Images