Solid lubricating film forming agent, oil well pipe, oil well pipe threaded joint, and method for manufacturing oil well pipe

Abstract

The present application can provide a solid lubricating film which can impart good lubricity and corrosion resistance to an oil well pipe thread even if graphite is used as a solid lubricant. Two or more kinds of solid lubricants are dispersed in a binder resin, as one of the two or more kinds of solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricants, the graphite has a scale shape and an average particle diameter of 10.0 μm or less, and as the other solid lubricant among the two or more kinds of solid lubricants, a solid lubricant composed of one or more kinds of materials selected from the group consisting of BN, mica, talc, MCA, MoS2, PTFE, PFA, and FEP is contained, the binder resin has a PEEK resin having an average particle diameter of 20 μm or less as a main component, and the PEEK resin is contained in an amount of 70% or more of the total weight of the binder resin.

Description

TECHNICAL FIELD

[0001] The present application relates to a technology of lubrication and corrosion resistance of an oil well pipe threaded joint. The present application relates to a technology of an oil well pipe and an oil well pipe threaded joint in which a solid lubricating coating film is formed on a fastening surface of a threaded portion including a metal seal surface instead of a wet type lubricating compound. In the present specification, the fastening surface of the face of the threaded portion includes the metal seal surface.

[0002] Here, the solid lubricating coating film refers to a coating film composed of a binder resin as a base component and a solid lubricant dispersed and distributed in the binder resin, and an additive added as necessary. The present application aims to improve lubrication by realizing a solid lubricating coating film of an oil well pipe thread, and has corrosion resistance.

[0003] In addition, in the present specification, the phenomenon explained with the terms such as "lubricity" and "high lubricity" refers to a phenomenon of easily sliding with low friction in a broad sense. In addition, high lubricity refers to the number of times of tightening / loosening (also referred to as the number of tightening / loosening) being able to be the prescribed number of times or more in a narrow sense. For example, regarding the burn resistance (anti-burn property) of an oil well pipe threaded joint (described in API 5C5 standard. In the API 5C5 standard, it is required to be able to tighten up to 3 times in the case of a casing size. In addition, in the case of a tubing size, it is required to be able to tighten up to 10 times.

[0004] Note that, in the present specification, a pipe having an internal thread is sometimes collectively referred to as a casing. That is, a coupling is also referred to as one type of casing. BACKGROUND

[0005] In an oil well pipe threaded joint, in lubrication of a threaded portion, a coating film is formed on a fastening surface (seal surface) of a threaded portion of a member of at least one of an external thread side and an internal thread side by surface treatment using a Mn phosphate chemical conversion treatment film, plating using Cu or the like in the past. Then, a lubricating compound containing Pb, Zn or the like is applied on the coating film to seek lubrication.

[0006] Note that, in the present specification, in the case where a coating film is formed on a fastening surface (seal surface) of a threaded portion, the fastening surface including the coating film is referred to as a fastening surface.

[0007] On the contrary, in recent years, a non-wet type lubrication technology based on "dry / no doping" has been attracting attention. "Dry / no doping" includes the meaning that the film itself is not an API-mod compound which is a viscous liquid and the meaning that it does not contain harmful heavy metals. As such a "dry / no doping" lubrication, there is a technology of forming a solid lubricating coating film on a fastening surface to seek lubrication. The present application relates to a technology of lubrication in the case of "dry / no doping".

[0008] In the past, in the patent literature, there are inventions relating to various solid lubricating films. The solid lubricating film is composed of a lubricant component responsible for lubrication and a solid film as a base component that holds the lubricant component in the film. The solid film refers to a film that does not have tackiness, is not a liquid film, and itself has the meaning of completing lubrication when tightening and loosening a threaded fastener. The Mn phosphate film and the electroplated Cu film since the past are solid films. However, since lubrication is sought by coating a grease-like compound as a premise, they are not included in the solid lubricating film. In the present invention, lubrication is achieved in the form of a solid film, and an organic resin film is envisaged as the solid film. Therefore, in the following description, the solid film is also described as an adhesive resin.

[0009] In the present invention, the main component of the solid lubricant is graphite, and the main component of the adhesive resin is a PEEK resin.

[0010] In the field of lubrication of oil well pipe threads and other lubrication fields, there are almost no cases where the main component of the solid lubricant is graphite. In addition, the use of a PEEK resin in the adhesive resin component is widely seen. However, considering the special lubrication conditions like oil well pipe thread joints (harsh lubrication conditions where a large load and an eccentric load are applied), it is believed that there are no past patent literatures that control the PEEK resin within an appropriate range.

[0011] As similar technologies, for example, there are patent literatures 1 to 6.

[0012] Patent literatures 1 to 3 are inventions relating to solid lubricating films of oil well pipe threads. In patent literatures 1 to 3, graphite is exemplified as an example of a substance considered to be a solid lubricant. In patent literature 3, it is also described that, among the candidate materials for the solid lubricant, graphite is the best.

[0013] Patent literature 4 is not an invention of oil well pipe threads. In patent literature 4, graphite is described as one of the constituent elements in the lubrication of bearing parts. In addition, patent literature 5 is a document relating to an aqueous agent, and graphite is exemplified as a solid lubricant.

[0014] Here, the idea widely understood about graphite is that it has the feature of not changing the lubrication condition even at high temperatures and not changing the lubrication even at high loads. In addition, graphite has the property of not exploding even as a fine powder, but only burning. Therefore, graphite is also widely used for the lubrication of mandrels and billets in the piercing process for manufacturing seamless steel pipes, and the understanding of such a stable lubricant has been widely established.

[0015] In addition, PEEK resin (also simply referred to as PEEK) is a thermoplastic resin that is stable even at high temperatures and is known as a hard plastic. PEEK is an acronym from the initials of Poly Ether Ether Ketone. PEEK is a very hard material. In addition, there are commercially available materials in which glass fibers are added to PEEK in order to strengthen the strength, and the strength and rigidity are improved, and materials in which PTFE, graphite, carbon fibers, and the like are mixed in order to improve lubrication. Note that PEEK resin is a resin in which a monomer is sold in a granular form.

[0016] In addition, in the past technology related to the lubrication of oil well pipe threads, although the number of technologies using PEEK resin is very limited, it is described in Patent Literature 6, for example. In Patent Literature 6, a material in which PTFE is dispersed in PEEK resin is exemplified.

[0017] Prior Art Documents

[0018] Patent Literature

[0019] Patent Literature 1: International Publication No. 2014 / 024755

[0020] Patent Literature 2: Japanese Patent Application Laid-Open No. 2008-527249

[0021] Patent Literature 3: Japanese Patent Application Laid-Open No. 2013-545940

[0022] Patent Literature 4: Japanese Patent No. 6776485

[0023] Patent Literature 5: International Publication No. 2019 / 021794

[0024] Patent Literature 6: Japanese Patent Application Laid-Open No. 2015-506445 SUMMARY

[0025] PROBLEMS TO BE SOLVED BY THE INVENTION

[0026] However, in Patent Literatures 1 to 3, although graphite is exemplified, the content of graphite is not explicitly described. That is, the description of Patent Literatures 1 to 3 contains the total amount in the solid lubricant to not containing, and in particular, it is presumed that the content is not conscious.

[0027] In addition, the Knoop hardness of the PEEK resin described in Patent Literature 6 is Hk80. Patent Literature 6 is an example of a special PEEK resin that is significantly soft. Here, the standard hardness of PEEK resin is R120 in Rockwell hardness and HK963 in Knoop hardness, and the hardness of the PEEK resin of Patent Literature 6 is much lower than this standard. Therefore, Patent Literature 6 is an example in which a heterogeneous PEEK resin is used, and is not suitable as the PEEK resin assumed in the present application.

[0028] Furthermore, the lubrication of the oil well pipe thread targeted by this invention is in a special sliding condition.

[0029] That is, on-site (in the actual well), a pin with an actual length of approximately 8m or more but less than approximately 15m is tightened / loosened relative to a sleeve positioned below. At this time, the pin is in a state where, although tightening and loosening are performed using power pliers while the pin is being lifted by a crane, the full load of the pin may be applied to the sleeve thread. In this specification, this is referred to as lubrication under heavy load conditions.

[0030] Furthermore, the pin may not be tightened and loosened in an ideal state at this time. That is, during tightening, the pin thread is inserted into the sleeve thread, or it is set in a state of slight manual tightening. However, the pin is not set upright and stationary relative to the sleeve thread. In addition, the pin is not set in a state of being straight (without deflection) while tilting slightly to one side. That is, the lower part of the pin is constrained by the sleeve thread, and the upper end side, i.e., the front end side opposite to the tightening side, becomes slightly deflected depending on the elastic modulus (Young's modulus) of the material and the actual pin length. Especially in the case of pins with a length of 8m or more, when viewed from below, the pin is set straight in the sleeve and appears to be bent. From this state, the pin is tightened and loosened, so the sleeve thread and the pin thread are not tightened and loosened under a state of uniform and symmetrical load application. Therefore, the tightening and loosening is a situation where a part of the thread surface is strongly impacted locally (lubrication under unbalanced load). In addition, the location of the strong local impact also changes depending on the tightening and loosening.

[0031] In conventional lubrication techniques using grease-like compounds, the compound moves along with the fastener during tightening and loosening. Therefore, even with variations in lubrication conditions, the lubricant (lubricating compound) functions to guide the tightening and loosening in a favorable direction. Consequently, in evaluation tests (also known as laboratory tests) of the tightening and loosening of threaded joints using grease-like compound lubrication techniques, the lubrication condition of the actual-sized pins can be determined by evaluating them using short pins, without relying on evaluations using actual-sized pins.

[0032] On the other hand, according to the inventors' research, in the lubrication technology of oil well pipe threads using solid lubricating films, the solid lubricating film is inevitably ground down to some extent. Moreover, it is necessary to find a way to prevent the grinding debris from clogging the thread clearance. In addition, at this time, the secondary formations from the ground-off solid lubricating film do not necessarily move in conjunction with the tightening and loosening and always follow the movement.

[0033] This happens in actual wells, which is quite different from lubrication using wet lubrication compounds.

[0034] In addition, the following was found in the oil well pipe threaded joint: by the same evaluation as the lubrication technology using the grease-like compound in the past, the lubrication technology of the oil well pipe thread using the solid lubricating film could not be evaluated, and became a loose evaluation. That is, in the past patent literature, the evaluation of the tightening and loosening of the oil well pipe threaded joint was mostly the evaluation using the lubrication using the wet-type lubricating compound (tightening and loosening test using a short pin) even if it was the evaluation of the solid lubricating film. Therefore, the following was found: the conditions (suitable range of components, etc.) of the lubrication of the solid lubricating film described in the past patent literature could not be directly adopted.

[0035] That is, in the case of evaluating the solid lubricating film by the laboratory test, in the evaluation using the short pin as in the case of the lubrication using the lubricating compound, due to the reasons as described above, the influence of the large load / uneven load could not necessarily be simulated. In the evaluation using the short pin shorter than the actual condition in the well, it was found that the solid lubricating film was not easily ground, and the condition that could simulate the burning behavior in the actual well could not be formed.

[0036] Thus, in the past evaluation using the short pin, the secondary product formed by the grinding chips of the solid lubricating film was clogged and burned, or the secondary product was pressed again on the tightening surface, and the condition that the effect of maintaining the lubricating film could not be simulated. That is, in the past evaluation using the short pin alone, the evaluation of the solid lubricating film became loose regardless of the circumstances. Moreover, in the determination of the physical property parameters of the solid lubricating film, there was a problem that the region that was originally unqualified could be erroneously evaluated as a suitable range.

[0037] For such reasons, the inventors found the following: in the past literature, the actual situation was that the suitable range was described based on the loose evaluation as described above.

[0038] In addition, the following was found: in the severe conditions such as the tightening and loosening conditions of the oil well pipe threaded joint, in which the large load is applied and the uneven load is also applied, even if the simple use of graphite as a lubricant was assumed as in Patent Literatures 1 to 5, it could not be smoothly performed.

[0039] One example thereof is listed below.

[0040] The example listed here is the evaluation of the 3.5" size oil well pipe thread JFE BEAR TMExample of the test. The test agent in which the adhesive resin was used only with the epoxy resin, the solid lubricant was used only with the graphite, was fired to form a solid lubricating film on the sleeve thread side. In addition, for the pin thread side, the test agent in which the adhesive resin was used with the fluororesin, the solid lubricant was used with PMSQ (polymethylsilsesquioxane) was used to form a solid lubricating film. Then, a tightening and loosening test was performed using a horizontal power wrench, and as a result, slight burning occurred after one tightening and loosening, and it was determined to be unqualified. At this time, the threads were rubbed with or without gloves to the extent of labor, and heat was generated. From this, it was also clear that the lubrication was not good.

[0041] In addition, at this time, if the threads were observed after loosening, the sealing part was completely intact, but a band-shaped secondary formation from the graphite was formed. It can be inferred that they (the slag) clogged to become the cause of burning on the thread part. During tightening, the band-shaped object (the slag) was formed in the gap between the groove of the sleeve thread and the tooth of the pin thread at the position opposite thereto, and the like. In addition, the object (the slag) was also formed in the gap of the penetration tooth side and the gap of the load tooth side. The band-shaped object was poor in "fluidity", that is, it could not move in conjunction with the tightening speed, and was stored in a part of the part. It is presumed that this became a direct cause of burning, or caused damage to the solid lubricating film, and became a cause of burning in the next tightening and loosening. It was observed that the following state: the band-shaped object was partially destroyed by reverse rotation at the time of loosening, and a powder-shaped substance was included from the band-shaped object.

[0042] This is one example, but if the solid lubricant is made to be only graphite, and film formation is performed after being mixed with the adhesive resin, it is inferred that almost all of them are like this regardless of which adhesive resin is selected.

[0043] Thus, the following insight was obtained: even if graphite, which is explicitly described as effective in the past literature, is actually applied and imitated to perform experiments, almost all of them are burned. This is puzzling. In the case where only graphite is used as the solid lubricant, more or less, a band-shaped secondary formation from the graphite is formed at the time of one tightening and loosening, and it clogs. In addition, the clogged substance further becomes powder-shaped, and the thread gap is closed, and burning occurs in the thread tooth part. Or, it is damaged and is prone to burning after the second time. Furthermore, the present inventors obtained the following insight: in the case where the solid lubricant is composed of 100% graphite, a band-shaped secondary formation from the graphite is firmly formed, and it clogs in the thread gap to become the main cause of burning.

[0044] Thus, the following insight was obtained: there is a common sense that graphite has been considered to be a solid lubricant in history, but it cannot be directly applied in the field of the threads of oil well pipes. That is, there is a problem that if graphite is not used on the basis of determining the appropriate range of graphite, burning cannot be suppressed.

[0045] Moreover, the optimal range in which the lubrication improving effect by graphite is expected needs to be explicitly shown to achieve lubrication. Furthermore, the combination of the binder resin needs to be appropriately selected. However, in the past literature, no explicit indication is made.

[0046] In addition, the lubrication of the oil well pipe thread has a point different from other lubrication behaviors, and thus there is a problem that the provisions made based on the evaluation performed using other lubrication conditions cannot be applied.

[0047] Generally, if the lubrication behavior between two objects of friction is mentioned, a situation in which one is fixed and the other moves is assumed. Also, for the moving object, lubrication is assumed to start from a state in which it is tightly adhered to the fixed object. Even in the case where both objects move, lubrication always starts from a state in which they are in close contact with each other.

[0048] On the other hand, in the lubrication of the oil well pipe thread, at the initial stage of tightening, the pin thread (external thread) starts from a state in which there is a play amount of the thread with respect to the box thread (internal thread). Thus, before the threads are engaged with each other to a certain extent, the threads are not always stably in contact with each other. That is, in the lubrication of the oil well pipe thread, the situation in which strong collision occurs is not uniform with the situation in which almost no collision occurs. Also, at the time of strong collision, there is a high concern that the lubrication film is damaged. Furthermore, in the lubrication after the threads are engaged, the sliding is affected by the lubrication condition at that place.

[0049] In particular, in the case of the solid lubrication film in the state in which there is "play" before the threads are engaged, there is a problem that the solid lubrication film is easily damaged by being directly affected by the eccentric load from the play.

[0050] In addition, in an actual well, at the time of tightening release, there is an effect caused by the total weight of the pin thread being applied to the box thread. In addition, since there is play as described above, the load is not uniformly applied, and before the threads are engaged, there is a tendency that the pin rotates eccentrically. Thus, the solid lubrication film must be a film in which lubrication is resistant to a large load applied as an eccentric load. It cannot be dealt with a film that is peeled off without fail or a film that is almost destroyed and disappears. In an actual well, the oil well pipe is mostly used in a length of Range-3 or Range-2 in the API-5CT standard. If it is the former standard, it is mostly used in a length of about 12 m to about 16 m. For example, the oil well pipe of a length of about 12 m (about 40 feet) has a self weight of about 1 t load in the case of an outer diameter of 9-5 / 8". In a marine drilling rig, the pin thread connected with three pins in advance is mostly used for tightening. Thus, if the oil well pipe of an outer diameter of 9-5 / 8" is used, it becomes a severe condition in which about 3 tons are applied to the box side.

[0051] In the lubrication of oil well pipe threads, it is necessary to assume lubrication that can withstand such large loads and eccentric loads. Thus, the inventors conducted various studies, and as a result, obtained the following insight: it is important to consider how to suppress damage to the solid lubricant film in the presence of a "loose" condition before thread engagement under a large load, and as such, the solid lubricant and the binder resin were studied.

[0052] On the other hand, in past literature, it is difficult to say that the solid lubricant film was designed based on such a viewpoint.

[0053] Incidentally, the above example is a result of using a short pin and not loading a large load, and testing with a horizontal tong. Thus, problems arise in the past condition where evaluation is not performed under conditions close to the application of actual well conditions. Thus, it is shown that in the case where the solid lubricant uses only graphite, the improvement effect cannot be expected as described in the past literature.

[0054] In addition, as described above, the solid lubricant in which the solid lubricant is composed of 100% graphite cannot be applied, and the solid lubricant needs to be newly studied, and the optimization of the composition of the solid lubricant is necessary. In addition, at the same time, the binder resin also needs to be studied.

[0055] In addition, while taking advantage of the lubrication of oil well pipe threads, the viewpoint of corrosion resistance also needs to be considered. Oil well pipe materials are sometimes stored in a field for about 1 to about 2 years over a long period of time, and thus need to be a film that can withstand corrosion even under a rainy condition.

[0056] The present application was completed with a view to the above aspects, and aims to provide a solid lubricant film that can impart good lubricity and corrosion resistance to oil well pipe threads even when graphite is used as a solid lubricant.

[0057] Method for solving the problem

[0058] The present application is a solid lubricant film and reagent in which the main component of the solid lubricant is graphite, and the main component of the binder resin is PEEK resin. Furthermore, for severe conditions where a large load is applied and an eccentric load is also applied, such as tightening and loosening of an oil well pipe thread joint, an appropriate range where stable lubrication and corrosion resistance can be balanced was clarified. Thus, the present application ensures lubricity that can withstand tightening and loosening of actual wells, while also balancing corrosion resistance.

[0059] As described above, in the case where the solid lubricating coating film is formed using only graphite as the solid lubricant, the solid lubricating coating film is damaged in many cases at the time of tightening and loosening. In addition, in the case where only graphite is used, the peeled-off substance is pressed against the thread surface in conjunction with tightening and loosening. Thus, a secondary product is formed, which has been a black band in the past. Moreover, it has been found that this secondary product clogs the gap between the threads and frequently causes burning.

[0060] In particular, it has been found that, in the case where the solid lubricant is graphite 100%, a black band-shaped secondary product from the graphite is firmly formed, which clogs the gap between the threads and becomes a main cause of burning. In addition, it has been found that, by using graphite of a specific shape (scale shape) as the main component and adding a specific other solid lubricant, it is possible to hinder the firm formation of the black band-shaped secondary product from the graphite.

[0061] The present inventors have conducted research on improving the conditions for improvement, including the optimum range of graphite and the optimum range of the binder resin and their blending ratio, in view of this fact, and have found an optimum ratio. For example, when only the "use of simple graphite" described in the past literature is used, burning frequently occurs. Stable lubrication cannot be achieved by simply adding graphite. In order to associate with the improvement of lubrication, it is important to note the optimization of graphite and the hardness control of the component in which the binder resin is the PEEK main body.

[0062] In addition, as described above, if a black band-shaped secondary product is firmly formed based on graphite, it clogs the gap between the threads and directly causes burning. Therefore, it has been found that, for graphite, it is necessary to select the type of graphite, the blending ratio, and the particle diameter, and to select after excluding the range of graphite that becomes a cause of burning.

[0063] In addition, the selection of the binder resin is also important. For the lubrication of the oil well pipe thread, as described above, before the threads are sufficiently engaged with each other, it is exposed to harsh conditions in which a large load and an eccentric load are applied. At this time, it cannot be said that the damage to the solid lubricating coating film is zero, but it is easy to peel off from the hardness and the contact surface. Moreover, the above-described black band-shaped secondary product is peeled off at the time of tightening and loosening and appears in the gap between the threads. It has been found that this is a substance from graphite and the binder resin, and thus the above-described regulation of graphite and the limitation of the binder resin are required, the black band-shaped secondary product is reduced, and even if graphite and the binder resin are peeled off, a black band is not formed but a powder-like to slightly small block-shaped is formed, moves in conjunction with tightening and loosening, and does not occlude a specific portion to cause burning.

[0064] According to the results of the research by the inventor, the following ranges are significantly superior. Although ensuring a certain amount of graphite as a solid lubricant, it is important to mix other kinds of solid lubricants without 100% graphite occupying the solid lubricant. Specifically, it is important to adjust the graphite to 50 to 90%. Further, as the selection of graphite itself, it is important to select small graphite that is in a scale form and has an average particle diameter of 0.1 to 10.0 μm. At the same time, it is important that the binder resin selects PEEK resin as a main component, and selects a resin having an average particle diameter of 20 μm or less by 70% or more. It is also known that, as the weight balance of graphite, it is important to suppress to an appropriate range of 20% or more and 50% or less with respect to the total coating component (= total weight of solid lubricant + total weight of binder resin).

[0065] These provisions reduce "black band-shaped secondary products" formed on the basis of graphite and binder resin that are inevitably shaved (peeled) under load conditions based on large load, eccentric load in the fastening loosening process that is the main cause of burn. Also, the purpose of these provisions is to change the shape to a powder-like to slightly smaller block shape, not a black band shape, move in conjunction with the fastening loosening, and avoid accumulation in a certain specific part to become the cause of burn. At the same time, these provisions are provisions considering that corrosion resistance can also be ensured.

[0066] As conditions of other optimal ranges, research was conducted including the formulation provision including a solvent, the provision of a solid lubricant other than graphite, the pencil hardness or film thickness of the solid lubrication coating, the base layer of the solid lubrication coating, and the like. Also, including the reagent for making the solid lubrication coating, the coating itself, and the oil well pipe thread joint formed with the solid lubrication coating, and the metal material formed with the solid lubrication coating by expanding the invention, the film making method, the invention was constructed as follows.

[0067] Further, one embodiment of the present application is an agent for forming a solid lubricating coating on a threaded portion of an oil well pipe, the gist of which is that two or more solid lubricants are dispersed in a binder resin, as one of the two or more solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricants, the graphite has a scale-like shape and an average particle diameter of 10.0 μm or less, and as the other solid lubricant of the two or more solid lubricants, a solid lubricant composed of one or more materials selected from the group consisting of BN (boron nitride), mica, talc, MCA (melamine cyanurate), MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane; tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), and FEP (fluorinated ethylene propylene; tetrafluoroethylene-hexafluoropropylene copolymer) is contained, and the binder resin contains a PEEK resin having an average particle diameter of 20 μm or less as a main component in an amount of 70% or more of the total weight of the binder resin.

[0068] Further, one embodiment of the present application is an agent for forming a solid lubricating coating on a threaded portion of an oil well pipe, the gist of which is that two or more solid lubricants are dispersed in a binder resin, as one of the two or more solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricants, the graphite has a scale-like shape and an average particle diameter of 10.0 μm or less, and as the other solid lubricant of the two or more solid lubricants, a solid lubricant composed of one or more materials selected from the group consisting of BN (boron nitride), mica, talc, MCA (melamine cyanurate), MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane; tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), and FEP (fluorinated ethylene propylene; tetrafluoroethylene-hexafluoropropylene copolymer) is contained, and the binder resin contains a PEEK resin having an average particle diameter of 20 μm or less as a main component in an amount of 70% or more of the total weight of the binder resin.

[0069] Effects of the Invention

[0070] According to the embodiment of the present application, it is possible to provide a solid lubricating coating which imparts good lubricity and corrosion resistance to a threaded portion of an oil well pipe even when graphite is used as a solid lubricant.

[0071] For example, according to the embodiment of the present application, it is possible to obtain an oil well pipe threaded joint having lubricity at the time of fastening and corrosion resistance, which takes into consideration conditions equivalent to actual wells that can occur in actual well environments. Note that the conditions equivalent to actual wells refer to conditions in which a pin weight is applied to a box from above, a load is applied obliquely due to axial misalignment, a load is applied unevenly and locally, and the like. Attached Figure Description

[0072] Figure 1 This is a diagram showing the oil well tubing and the oil well tubing threaded joint.

[0073] Figure 2 Figure (a) shows the actual fastening diagram in the well, and Figure (b) shows the initial setup position at this time.

[0074] Figure 3 Figure (a) shows the fastening diagram from previous laboratory tests, and Figure (b) shows the initial setup position at this time.

[0075] Figure 4 This is a schematic diagram of the fastening system. (a) shows the actual well conditions, and (b) shows the conditions of previous laboratory tests.

[0076] Figure 5 This is a diagram illustrating the new laboratory test (the hammer clamp test).

[0077] Figure 6 This is a diagram showing an example of the setup of the weight in a new laboratory test (weight clamp test).

[0078] Figure 7 This is a diagram illustrating the structure of the membrane. Detailed Implementation

[0079] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0080] Here, the inventors conducted repeated research and found that the tightening and loosening of the solid lubricating film is divided into two stages, and the conditions that occur in each stage need to be considered.

[0081] <About Figure 2 >

[0082] Figure 2 (a) is an example of fastening that occurs in an actual well.

[0083] Figure 2 (a) is a torque rotation diagram (tightening diagram) simulating a tightening test in an actual well using a pin of actual length 40 feet (≈12 m). In actual oil / gas fields, tightening often begins with the threads not fully engaged. Given this situation, in Figure 2 In (a), the initial setting position is as follows: Figure 2 (b) shows an example where the pin thread is tightened starting with approximately half of the sleeve thread exposed at the initial tightening stage. It should be noted that a 9-5 / 8” 53.5# Q125 JFELION thread is used as the pin. TM The thread, based on the perspective of simulating a real well, uses a pin that is over 40 feet long.

[0084] in addition, Figure 2 (a) is a diagram showing the process of lifting the pin from above the drilling rig using a crane while simultaneously securing it with vertical clamps.

[0085] Should Figure 2 (a) can be considered as a situation that often occurs in actual wells.

[0086] Figure 2 In (a), the focus should be on the period before the point where the torque increases continuously, i.e. Figure 2 In stage 1 of (a), where the rotational speed is below 6.3 rpm, the torque should theoretically not increase. However, in practice, a tendency for the torque to rise irregularly and frequently in a spike-like pattern can be observed in stage 1.

[0087] This suggests that the pin thread makes irregular and localized contact with the sleeve thread as it rotates. This is a situation that actually occurs during fastening in a well.

[0088] Furthermore, in Phase 1, the design and optimization of the solid lubricant film inevitably means that, to some extent, damage and peeling of the solid lubricant film are unavoidable. It is important to emphasize here that... Figure 2 (a) is not an intentional worst-case scenario, but rather a very ordinary torque rotation diagram of a sample with a solid lubricating film.

[0089] <About Figure 3 >

[0090] on the other hand, Figure 3 (a) is used with Figure 2 Torque rotation diagram under the condition of the same solid lubricating film and tightening using a vertical power clamp.

[0091] Figure 3 In, it adopted the same as Figure 2 The pins have the same outer diameter, wall thickness, and thread type, but a short pin about 1m long was used as the pin.

[0092] in addition, Figure 3 (a) is a tightening diagram (torque rotation diagram) showing the tightening process starting from a state where the threads are fully engaged. That is, as shown... Figure 3 (b) shows the tightening diagram (torque rotation diagram) when approximately 1 to 3 threads of the pin are exposed at the start of the initial tightening.

[0093] Should Figure 3 The condition in (a) is also a condition frequently used in previous laboratory tests for tightening, and is an example of manually tightening the thread until it engages.

[0094] Figure 3(a), it is noted that Figure 2 (a) the unit of the horizontal axis is different.

[0095] Figure 3 (a), the state from the state of manual fastening to the state of thread engagement is started to be fastened using pliers, and therefore, the torque in the form of a peak as seen in Figure 2 (a) is not observed.

[0096] From Figure 3 it is known that, in the conventional laboratory test, in stage 1, the solid lubricating film is not broken, and the threads on both sides are fastened from the region where the threads start to contact.

[0097] <Concerning Figure 4 >

[0098] Figure 4 is a graph in which Figure 2 (a) and Figure 3 (a) are illustrated in a state that is easy to compare.

[0099] Figure 4 (a) is an example of Figure 2 (a), and Figure 4 (b) is an example of Figure 3 (a).

[0100] According to the research of the inventor, if the use in an actual well is taken into consideration, the ideal solid lubricating film is preferably one in which the solid lubricating film is not broken, and the worry of breakage or peeling is minimized in the region of (x) of Figure 4 (a). Alternatively, it is preferable to be designed in such a manner that, although the peak can rise slightly (a condition in which the solid lubricating film is damaged), the secondary product from the solid lubricating film that is broken or peeled off does not clog the thread gap during the fastening and loosening process, but rather, is well attached to the threads, assisting in lubrication.

[0101] Here, many of the past documents consider that, when judged from the results of the fastening and loosening test, the lubrication after the thread engagement Figure 4 (b), Figure 3(a) ) as an object. The merits and demerits of the lubrication of the screw threads after the engagement of the screw threads with each other, i.e., the lubrication characteristics of the solid lubricating film itself were considered. Therefore, it was presumed that, using a short pin, using a horizontal tong, a vertical tong, and performing the tightening and loosening after the portion to be engaged by the screw threads was set by hand. Note that, in the patent literature in which the number of times of tightening and loosening is explicitly described, there is also a description that, in the actual well tightening, 10 times can be performed if it is a small diameter size. However, both the evaluation of the short pin and the evaluation of the actual well seem to be the number of times that can be performed. On the other hand, in the case of a large diameter size of 9-5 / 8", 13-3 / 8", there are also scattered descriptions that the number of times of tightening and loosening can be performed to 15-20 times in the tightening and loosening based on the solid lubricating film. However, this number of times is almost impossible in the case of the large diameter using the solid lubricating film in the actual well tightening and loosening.

[0102] In addition, in the case of the oil well pipe thread of the large diameter size, the tightening torque value is probably higher, and the play (looseness) of the sleeve thread and the pin thread is more. Accordingly, before the screw threads are sufficiently engaged, the solid lubricating film is inevitably destroyed and peeled to some extent. In addition, at the beginning of the test, at the stage of setting the pin thread to the sleeve thread, the weight is heavy, and accordingly the operation is difficult, and sometimes the pin thread and the sleeve thread collide unintentionally at a certain frequency. This also becomes a cause of destroying and peeling the solid lubricating film.

[0103] Furthermore, in the present embodiment, the actual well tightening and loosening conditions were taken into account. In addition, when graphite, which is described as being well lubricated in many documents, is used, burning often actually occurs, and in view of this fact, in order to achieve the maximum use of the lubrication using graphite in the actual well conditions, research was conducted in the present invention.

[0104] (Configuration)

[0105] The present embodiment is an invention relating to a film structure formed on a tightening surface in an oil well pipe thread used in an actual oil / gas and a threaded joint having the film structure as a lubricating film. In the present embodiment, the lubricating film having a solid lubricating film formed on the tightening surface of the threaded joint has a feature, and the threaded structure of the threaded joint itself is not particularly limited. The threaded structure of the threaded joint can adopt a known or new threaded structure.

[0106] <Oil well pipe and oil well pipe threaded joint>

[0107] The oil well pipe is constituted by a sleeve 2, a pin 1, and the like, as shown in Figure 1 .

[0108] As shown in Figure 1As shown, the oil well pipe threaded joint is composed of a sleeve 2 such as a coupling or the like having an internal thread 2a and a pin 1 having an external thread 1a. Moreover, a contact surface (fastening surface 10) of the threaded portion in the member of at least one of the sleeve 2 and the pin 1 is formed with a lubricating film having a solid lubricating film.

[0109] <Reagent for forming solid lubricating film>

[0110] Hereinafter, the reagent for forming a solid lubricating film in the present embodiment will be described.

[0111] The reagent of the present embodiment is constituted by dispersing two or more solid lubricants in a binder resin as a base component.

[0112] In the present embodiment, as one of the two or more solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricant. The graphite has a scale-like shape and an average particle diameter of 10.0 μm or less. Herein, in the present embodiment, the scale-like shape means that the crystallinity is preferably the best and the graphite purity is high.

[0113] Further, as the other solid lubricant of the two or more solid lubricants, a solid lubricant composed of one or more materials selected from the first group solid lubricant material and the second group solid lubricant material described below is contained.

[0114] [First group solid lubricant material]

[0115] BN (boron nitride)

[0116] Mica

[0117] Talc

[0118] MCA (melamine cyanurate)

[0119] MoS2 (molybdenum disulfide)

[0120] [Second group solid lubricant material]

[0121] PTFE (polytetrafluoroethylene)

[0122] PFA (perfluoroalkoxy alkane; tetrafluoroethylene-perfluoroalkoxy ethylene copolymer resin)

[0123] FEP (perfluoroethylene propylene copolymer; tetrafluoroethylene-hexafluoropropylene copolymer)

[0124] Herein, the lubrication mechanisms of the first group solid lubricant material and the second group solid lubricant material are different.

[0125] The first group of solid lubricant materials is a lubricant in which a two-dimensional layered compound is bound in the Z direction by intermolecular forces, and when a force is applied in the direction of lubrication, the two-dimensional firm molecular structure slides to seek lubrication. The second group of solid lubricant materials is a lubricant in which one-dimensional straight-chain structure firm-formed molecules are bound to each other by intermolecular forces, and when a force is applied in the direction of lubrication, lubrication is achieved by the mutual sliding of each straight-chain structure unit in the one-dimensional direction.

[0126] The reason for mixing the materials selected from the first group of solid lubricant materials and the second group of solid lubricant materials is described below. If only graphite is used to constitute the lubricant, in the case of lubricating the threads of the oil well pipe, a secondary "black band-shaped secondary product" formed of ground graphite together with ground PEEK resin is formed. Moreover, it is sometimes formed too firmly. Therefore, the "black band-shaped secondary product" can possibly increase the risk of causing a burn by clogging the gap of the thread. In view of such a problem, in the present embodiment, by mixing a solid lubricant of a different kind from graphite, the formation of the secondary product can be reduced, and the risk of a burn can be reduced while maintaining high lubrication.

[0127] Here, as the other solid lubricant, it is preferable to contain at least PTFE. The reason is because PTFE is a solid lubricant kind based on a different mechanism from graphite, and at the same time, PTFE itself is a solid lubricant that can be expected to have high lubrication.

[0128] In addition, the average particle diameter of the other solid lubricant is preferably in the range of 0.1 μm or more and 5 μm or less.

[0129] In addition, in the present embodiment, the binder resin contains, as a main component, PEEK resin having an average particle diameter of 20 μm or less, and the PEEK resin accounts for 70% or more of the total weight of the binder resin.

[0130] The total weight of the solid lubricant is preferably 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0131] The content of graphite as the solid lubricant is preferably 20% or more and 50% or less of the weight of the sum of the total weight of the solid lubricant and the total weight of the binder resin.

[0132] The agent contains a solvent for adjusting the dryness and the liquid viscosity not to remain on the coating. The weight ratio of the solvent is preferably 30% or more and 80% or less with respect to the weight of the sum of the total weight of the solid lubricant and the total weight of the binder resin.

[0133] <Coating structure of the threads of the oil well pipe>

[0134] Hereinafter, the coating structure of the threads of the oil well pipe in the present embodiment will be described.

[0135] A lubricating film having a solid lubricating film is formed on a fastening surface of a threaded portion of a member of at least one of the sleeve and the pin.

[0136] The solid lubricating film is constituted by dispersing a solid lubricant in a binder resin as a base component.

[0137] In the present embodiment, as one of the two or more kinds of solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricants. The graphite has a scale-like shape and an average particle diameter of 10.0 μm or less. Here, in the present embodiment, the scale-like shape means that the crystallinity is preferably the best and the graphite purity is high.

[0138] Further, as the other solid lubricant of the two or more kinds of solid lubricants, a solid lubricant composed of one or more kinds of materials selected from the first group of solid lubricant materials and the second group of solid lubricant materials is contained.

[0139] Here, as the other solid lubricant, PTFE is preferably contained at least.

[0140] In addition, the average particle diameter of the other solid lubricant is preferably in a range of 0.1 μm or more and 5 μm or less.

[0141] In addition, in the present embodiment, the binder resin contains the PEEK resin as a main component having an average particle diameter of 20 μm or less in an amount of 70% or more of the total weight of the binder resin.

[0142] The total weight of the solid lubricants is preferably 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0143] The content of the graphite as the solid lubricant is preferably 20% or more and 50% or less of the weight of the sum of the total weight of the solid lubricants and the total weight of the binder resin.

[0144] The solid lubricating film is formed, for example, to a region including the thread of the threaded portion and adjacent thereto.

[0145] The hardness of the solid lubricating film is preferably 3H or more in terms of pencil hardness.

[0146] The solid lubricating film is preferably, for example, 10 μm or more and 150 μm or less in film thickness.

[0147] In the case where the materials of the sleeve and the pin are carbon steel or low alloy steel, the lubricating film can have a base layer 10B between the fastening surface of the threaded portion and the solid lubricating film 10A (refer to Figure 7 ). The base layer 10B is composed of, for example, an electroplated film or a chemical conversion treatment film.

[0148] In the case where the sleeve and the pin are made of stainless steel, Ni-based alloy or Ti alloy, the lubricating film can have a base layer 10B between the fastening surface of the threaded portion and the solid lubricating film. The base layer 10B is composed of, for example, an electroplated film.

[0149] In addition, the oil well pipe threaded joint can be structured such that a lubricating film having a solid lubricating film is formed on the fastening surface of the threaded portion of one of the sleeve and the pin, and a film softer than the solid lubricating film is formed on the fastening surface of the threaded portion of the other of the sleeve and the pin. The film softer than the solid lubricating film is preferably also a solid lubricating film.

[0150] <About Black Ribbon-shaped Secondary Product>

[0151] As described above, when graphite is selected as the solid lubricant, the generation of "black ribbon-shaped secondary product" is often observed.

[0152] In the field of lubrication of oil well pipe threads, the "black ribbon-shaped secondary product" is the main cause of galling in the case where graphite is used as the main component of the solid lubricant. The "black ribbon-shaped secondary product" is formed secondarily based on the component of the solid resin film (solid lubricant + binder resin component) that is inevitably shaved off during the fastening and loosening process. It is known that if it is clogged in the minute gap between the threads, it becomes the cause of galling. In the case of lubrication of threaded structures, the metals are completely in contact with each other due to the threaded structure. To be exact, the condition from the presence of a very thin gap to the presence of a minute gap is generated, but in any case, there is a gap in the contact surface of the threads. In the case of fastening and loosening of the threads, in conjunction with the action of the threads, the lubricant smoothly and without stagnation, which is the basis for maintaining low friction, i.e., high lubrication.

[0153] The same mechanism is also true in the case of a lubricating film that is not a solid lubricating film. For example, if it is a general-purpose grease-like compound, in order not to run out of oil, uniform application before tightening is critical, and the compound follows the tightening and loosening of the threads. Even if it is this compound, if it is clogged in a place in the thread gap, it becomes a cause of scorching. However, the compound is a viscous liquid, and has a tendency to easily move along the gap. On the other hand, in the case of using graphite as the main component of the solid lubricant, graphite is a layered substance in which the layers are weakly bound to each other by intermolecular forces. Therefore, if graphite is subjected to a large force from a certain direction, it peels off in layers, and low friction (= high lubrication) is achieved on the spot. As described above, graphite makes the plate-like structure strong due to its physical structure, and accordingly the graphite easily connects to each other to become a band regardless of anything. In addition, the organic resin that constitutes the adhesive resin functions as a paste, and has a high tendency to form a strong and slightly thick black band in a manner of completely filling the thread teeth / thread grooves. Therefore, the solid lubricating film is inevitably shaved to some extent by itself when the threads are tightened and loosened, and this is unavoidable. These peeled substances (slag) form the black band-like secondary products as described above. Also, the layered stack is weak due to the intermolecular force level, and moves in the direction of easy sliding under the load applied when tightening and loosening, but the plate-like structure itself is extremely strong, and is not much damaged under the load level applied when tightening and loosening. Therefore, the black band-like secondary products only increase in thickness, and do not have the mobility of moving in conjunction with tightening and loosening. In addition, in reality, tightening and loosening of the threads cannot be uniformly performed, and are not left-right symmetrical. At the initial stage of tightening and at the final stage of loosening, they are performed almost eccentrically to some extent. Therefore, in the solid lubrication using graphite, it is important to take measures to not form the black band-like objects from graphite, or to reduce such formation, or to not be a strong band, but to be easily torn or to form a powdery shape, and to easily follow the tightening and loosening.

[0154] In the present embodiment, in order to achieve the above-mentioned object, the specifications of each material were studied and set.

[0155] Hereinafter, the specifications of each material are further described.

[0156] <Main Component of Solid Lubricant>

[0157] As described above, in the present embodiment, graphite is used as the main component and two or more kinds of solid lubricants are used.

[0158] That is, as one of the two or more kinds of solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricant. The graphite has a scale-like shape and an average particle diameter of 10.0 μm or less.

[0159] Further, as the other solid lubricant among the two or more kinds of solid lubricants, a solid lubricant composed of one or more kinds of materials selected from the first group of solid lubricant materials and the second group of solid lubricant materials is contained.

[0160] In the present embodiment, graphite, which is called high lubricating substance, is utilized, with the improvement in the lubrication field of oil well pipe threads and the application field thereof as the object. There are many application examples in other fields. However, in the lubrication field of oil well pipe threads and the like, if only graphite is selected as a solid lubricant to be implemented as described in the past documents, burn frequently occurs.

[0161] On the contrary, in the present embodiment, the upper and lower limits of each solid lubricant are set from the viewpoint of avoiding the above-mentioned "black band-shaped secondary product" from graphite, that is, not forming the above-mentioned "black band-shaped secondary product" from graphite or reducing the amount thereof even if it is formed. Further, the upper and lower limits of each solid lubricant are set from the viewpoint of not being a band-shaped substance which is firm but being a substance which is divided and cut.

[0162] The lower limit of graphite as the substance contained in the solid lubricant is set to 50% as the minimum amount required for obtaining the lubrication improvement effect by graphite. This is because, when it is less than the lower limit, no improvement in lubrication is observed or the improvement in lubrication is weak.

[0163] The upper limit is set to 90% because, if it exceeds the upper limit, the band-shaped secondary product from graphite is likely to clog the gap of the threads and burn.

[0164] In the present embodiment, graphite is used as the main component of the solid lubricant, and the properties of the band-shaped secondary product from graphite are easily destroyed. Further, a substance which is thick and firm is not formed. The fact that the band-shaped secondary product is generated in a state of short division or powder as much as possible becomes an important point in the improvement in lubrication in the case where graphite is used as the main component of the solid lubricant.

[0165] For this reason, one of the features of the present embodiment is that other kinds of solid lubricants are mixed in graphite to form a solid lubrication film. If it is a solid lubricant other than graphite, even if MoS2, BN, or the like of the layered solid lubricant is mixed as a subcomponent, it is possible to change the properties of the firm (long) band-shaped secondary product, shorten the length of the band shape, or make it powder. As a result, it is possible to avoid the secondary product from graphite from clogging the gap of the pin threads and the box threads and burning. In particular, by mixing a solid lubricant of a kind other than the layered solid lubricant, for example, PTFE, as the other kind of solid lubricant, it is possible to make the properties of the secondary product powder, a band shape which is easily destroyed.

[0166] In the present embodiment, as the kind of graphite, flaky is selected. Natural graphite-based graphite such as earthy graphite, expanded graphite, and artificial graphite are not selected. The reason for selecting flaky is because graphitization is most easily performed, that is, the network of carbon forming a two-dimensional layer structure and the layers thereof are combined in a form of intermolecular force, and thus lubrication is facilitated.

[0167] The particle diameter of the selected graphite is 0.1 to 10.0 μm. This is because, in order to effectively utilize the lubrication of graphite, if the size exceeds 10 μm, the graphite itself becomes too large, and itself becomes the basis of scorching. The lower limit is not particularly limited, and includes the minimum size of graphite. For example, it is considered that the lower limit is 0.1 μm.

[0168] <Concerning the secondary component of the solid lubricant>

[0169] The main component of the solid lubricant of the solid lubricating film is graphite which is 50% or more and 90% or less of the solid lubricant, and the main component of the binder resin is PEEK resin.

[0170] In the present embodiment, the solid lubricant means that, as a broad solid lubricant, additives other than the binder resin component are also included as the solid lubricant.

[0171] The secondary mixed solid lubricating component is a solid lubricant composed of one or more materials selected from the first group of solid lubricant materials and the second group of solid lubricant materials.

[0172] Here, graphite has a strong structure in a two-dimensional plane, and they are in a state of being weakly combined in a layered form by intermolecular force, and when a force is applied, the stacked poker mountain slides like slip, thereby maintaining lubrication. In the case where graphite is used at random, "black band-shaped secondary products" are often formed, which clog the thread gap and cause scorching. It is necessary to avoid these problems by optimization of graphite and optimization of PEEK resin. From such a viewpoint, it is preferable to select the secondary component according to the main structure of the present invention.

[0173] That is, compared with a lubricant using the sliding of a two-dimensional plane based on the same mechanism as graphite, the secondary mixed solid lubricating component is more preferably a lubricating additive of a mechanism in which long-chain molecular chains slide in the direction in which forces are applied to each other.

[0174] From such a viewpoint, the secondary mixed solid lubricating component preferably uses, for example, PTFE. As a preferable condition at this time, it is prescribed that the average particle diameter of 0.1 to 5 μm is good. When it is more than 5 μm, the PTFE itself is entangled, and the improvement effect of lubrication is small. When it is less than 0.1 μm, when this graphite-based component is contained as a secondary component, the lubricating effect of the PTFE is buried, and it cannot be observed that it exhibits particularly good lubrication.

[0175] For other secondary mixed solid lubricating components, for example, the average particle diameter is preferably 0.1 to 5 μm.

[0176] In addition to this, PFA, FEP are also examples following the same mechanism. They are structures having side chains on the molecular structure of PTFE, and lubricity is achieved based on the sliding of the molecular chains with each other. However, since there are side chains, PTFE has more excellent features, and thus it is selected as an appropriate range.

[0177] In addition, the secondary mixed solid lubricating component can also be selected from the viewpoint of improving lubrication by making the film quality hard. Including glass fiber powder, carbon fiber powder, the addition is also included in the present application.

[0178] <Main component of the binder resin and secondary component of the binder resin>

[0179] The binder resin is composed of one or two or more resin components. The binder resin of the present embodiment uses PEEK resin having an average particle diameter of 20 μm or less as a main component. The PEEK resin is contained in 70% or more and 100% or less of the total weight of the binder resin.

[0180] In the field of lubrication of oil well pipe threads, in the case where graphite is used as a solid lubricant for the main component, the main cause of burn is "black band-shaped secondary product" which is secondarily formed based on the solid resin film component (solid lubricant + binder resin component) which is inevitably shaved off in the fastening and loosening process.

[0181] The PEEK resin is prescribed to be 70% or more of the total weight of the binder resin in order to make the solid lubricating film itself hard in the lubrication of oil well pipe threads. That is, it is in order to reduce the amount shaved off from the film, and to reduce graphite and the binder resin component which are the basis of "black band-shaped secondary product".

[0182] In the case where the film is hard, the peeling / grinding amount is reduced, and thus it is preferable. However, instead of simply selecting a hard resin, the PEEK resin (polyether ether ketone) is selected as the main component of the binder resin from the viewpoint that it can be mixed with graphite without problems and the viewpoint of the hardness of the film quality. Thereby, it is avoided to simply become a hard resin.

[0183] Here, as the hard resin, for example, there are polyetherimide (PEI), polyphenylene sulfide (PPS), polyamide-imide (PAI), polybenzimidazole (PBI), phenol formaldehyde resin (PF), and the like. However, they are simply hard resins and cannot be used.

[0184] For example, in the case of polyetherimide (PEI), it is sometimes an amorphous resin and has poor wear resistance. Therefore, in the fastening and loosening process of the threads, the solid lubricating film has a tendency to be shaved off. Polyphenylene sulfide (PPS) has poor toughness and poor usability depending on the use temperature, and promotes burns. In the case of polyamide-imide (PAI), there is no particular problem when PTFE is used as the main component and graphite is mixed as a second component, but when graphite is used as the main component, it is not possible to avoid the "black band-shaped secondary product" from clogging the thread gap and causing burns. Polybenzimidazole (PBI) is too hard and is not suitable for lubrication use itself. In the oil / gas field, substances containing S, such as those containing inhibitors, bactericides, MoS2, are often pointed out as a cause of H2S generation through microbial corrosion. Therefore, polyphenylene sulfide (PPS) cannot be applied. In the lubrication of oil well pipe threads, heat generation cannot be avoided to some extent. The heat resistance of phenol formaldehyde resin (PF) is about 150°C, and therefore, the heat resistance is low and is NG.

[0185] However, there are no particular problems in the use of these in the present application in which PEEK resin is used as the main component at 70% or more.

[0186] The particle diameter of the PEEK resin needs to be 20 μm or less. This is because, as with graphite, in the case where the particle diameter of the PEEK resin is too large, it itself becomes a basis for burns. At the time of fastening and loosening of the threads of the oil well pipe, it is in a state of sliding while being pressed by a large load and the threads are in a state of moving from a narrow gap to a substantially tight fit with each other. Both the binder resin and the solid lubricant are crushed and do not maintain the original size. However, if the initial size is 20 μm, the probability of becoming a cause of burns is high. Therefore, the maximum size of the average particle diameter of the PEEK resin is specified to be 20 μm or less.

[0187] <Dispensing ratio of solid lubricant and binder resin and dispensing ratio of graphite>

[0188] In the state of the film, the content weight of the solid lubricant is set to be 0.1 times or more and 2 times or less of the weight of the binder resin. In addition, the weight fraction of graphite is set to be 20% or more and 50% or less. This specification is also specified from the viewpoint of minimizing the above-mentioned "black band-shaped secondary product" and effectively utilizing the solid lubricating effect of graphite.

[0189] For the solid lubricant of the graphite main body, the total solid lubricant is formulated to be 0.1 to 2.0 times the weight of the binder resin for the following reasons.

[0190] The lower limit is set to 0.1 times because, when less than the lower limit, although "black band-shaped secondary products" do not easily occur to become a range without problems, the solid lubricant itself is small and the lubricating effect cannot be maintained. The upper limit is set to 2.0 times because, when more than the upper limit, "black band-shaped secondary products" are formed more than necessary and burn injuries frequently occur.

[0191] Further, the reason for selecting the PEEK resin and the graphite is also in the water repellency. In the present embodiment, a commodity is mostly required to have lubricity and corrosion resistance under the premise that it is left until use in a state where an oil well pipe thread is provided with a protector and is exposed to the outdoors for about 1 to about 2 years. Therefore, when a component that is contained secondarily is added, the water repellency of the PEEK resin and the graphite also maintains the corrosion resistance at the same time. Further, the hard film also enables reduction of minute cracks, and thus, it is possible to achieve the corrosion resistance while maintaining the lubricity.

[0192] <Composition of the agent>

[0193] The agent contains a solvent in order to adjust the dryness and the liquid viscosity not to remain on the film. The component weight ratio of the solvent can be 30 to 80% with respect to the sum of the solid lubricant component weight and the binder resin component weight.

[0194] The components that constitute the solid lubricating film are prepared in a state of being dissolved in the solvent. The agent is applied, the solvent is volatilized, fired, or subjected to irradiation of far infrared, ultraviolet rays, or the like, thereby being dried, and film formation is performed.

[0195] In the present application, the solvent component weight ratio with respect to the sum of the solid lubricant component weight and the binder resin component weight is set to 30 to 80%. The material of the solvent is not particularly limited. It can be a polar solvent or a non-polar solvent.

[0196] The PEEK resin needs to be fired at more than 350°C, and thus, these solvents need to be volatilized or evaporated in the range of this temperature. The lower limit is set to 30% in order to avoid the liquid viscosity of the agent being high and not being able to be applied well when less than 30%.

[0197] The lower limit is set to 30% in order to avoid the liquid viscosity of the agent being high and not being able to be applied well when less than 30%.

[0198] Examples of polar solvents include DMF (N,N-dimethylformamide), NMP (N-methyl-2-pyrrolidone), DMSO (dimethyl sulfoxide), methanol, and ethanol. Examples of non-polar solvents include n-hexane, toluene, xylene, dioxane, and THF (tetrahydrofuran).

[0199] Regarding organic solvents, examples of ketones include MEK (methyl ethyl ketone) and MIBK (methyl isobutyl ketone); examples of esters include ethyl acetate and butyl acetate; and examples of alcohols include methanol, ethanol, and IPA (isopropanol).

[0200] Then, a film is formed by evaporating the solvent, firing, or irradiating with far-infrared or ultraviolet light. By using solvent dispersion and film formation, lubrication and corrosion resistance can be achieved simultaneously.

[0201] <Regarding the characteristics of the solid lubricating film>

[0202] By coating the reagent of this embodiment, the solvent components are dispersed to form a solid lubricating film, thereby using the solid lubricating film as a film that combines lubrication and corrosion protection.

[0203] The concept and structure of this invention are based on achieving lubrication of the solid lubricating film on the oil well pipe thread.

[0204] If used Figures 2 to 4 As shown, during the tightening and loosening of oil well pipe threads, especially in the initial tightening and final loosening stages, the solid lubricating film is damaged due to the loosening before the threads mesh together. Furthermore, when graphite is used as the main component of the solid lubricant, a often-occurring "black, ribbon-like secondary product" appears. As a means to reduce these effects, the present invention specifies an optimal range.

[0205] However, this idea is not limited to the lubrication of oil well pipe threads and can be widely applied to improve lubrication. Therefore, it is envisioned that its application be extended to solid lubricating films formed on a wide range of metallic materials.

[0206] <Suitable range of membrane hardness and thickness>

[0207] The resulting films are preferably 3H or higher on a pencil hardness tester, and the film thickness is preferably 10 μm or more and 150 μm or less. There is no upper limit to the hardness of the film; the harder the better.

[0208] When the membrane is relatively stiff, it can reduce the "black band-like secondary products" that often appear. If the membrane has a hardness of 3H or higher than pencil hardness, the effect is high, resulting in more than the target number of tightening and loosening cycles.

[0209] In this case, the PEEK resin monomer has a pencil hardness of approximately 3H to approximately 5H, therefore, adding solid lubricants will not reduce the hardness. Furthermore, as mentioned above, glass fibers or carbon fibers can be added to actively increase the hardness of the PEEK resin.

[0210] Regarding film thickness, a minimum film thickness of 10 μm is required to maintain lubrication and corrosion resistance. Regarding the upper limit of film thickness, the clearance between sleeve threads and pin threads varies depending on the type and design of the oil well pipe thread. Therefore, it is difficult to generalize and set 150 μm as the upper limit. For most oil well pipe threads, a clearance between the thread teeth of 100 μm to 150 μm is designed as the upper limit; therefore, 150 μm is specified as the upper limit. More preferably, the film thickness is 10 to 50 μm.

[0211] Here, the clearance between the teeth and grooves of the external and internal threads can be 100–150 μm as described above. However, the clearance between the penetration teeth and the bearing teeth of the external and internal threads varies during tightening and loosening. When the clearance narrows, it becomes approximately tight. Therefore, 10 μm to 50 μm is a preferred range for film thickness. During tightening and loosening, the adhesive resin is actually abraded. In addition, the film thickness coated at room temperature is actually flattened into a thin film. Therefore, even a size larger than the envisioned clearance will not cause a problem.

[0212] It should be noted that the pencil hardness of the aforementioned solid lubricating film was determined according to the method specified in JISK 5600-5-4 (1999). This standard is translated as "ISO / DIS15184, Paints and varnishes - Determination of film hardness by pencil test," and is clearly described in the JIS standard. However, the pencil hardness test method itself is evaluated based on the provisions in the JIS standard. Furthermore, the reason for using pencil hardness to evaluate film hardness is to utilize the "scratch" effect of a pencil. This is a film hardness evaluation method caused by "scratch," similar to the behavior of solid lubricating film peeling off in the external and internal threads of oil well pipe threads. Regarding film hardness determination methods sometimes used in coatings, etc., caused by indentation, Rockwell hardness, Vickers hardness, and Knoop hardness, the coating is thin and affected by the substrate; therefore, pencil hardness is used in this invention.

[0213] <Regarding the base layer beneath the solid lubricating film>

[0214] When the metal material or well pipe is made of carbon steel or low alloy steel, it is preferable that there is a base layer consisting of an electroplated film or a chemically converted film between the metal material or well pipe and the solid lubricating film.

[0215] Here, in the case where the metal material or the oil well pipe is a stainless steel material, a Ni-based alloy, or a Ti alloy, it is preferable that the plating film be present as a base layer. This is to improve the adhesion of the solid lubricating film.

[0216] <Method for manufacturing solid lubricating film>

[0217] The desired film thickness can be coated at one time and the film can be formed by firing or the like.

[0218] However, it is preferable that the film be formed in multiple stages. Furthermore, compared to the case where firing is performed each time the film is formed, it is preferable that the method described below be used.

[0219] That is, the solid lubricating film thickness formed at one time is set to 50 μm or less, and a temporary drying process is interposed approximately once every two times or each time between the film formation and the film formation, and the film formation is repeated multiple times, and the film is formed with the films of 50 μm or less overlapped. Then, the temporary drying is stopped in the final film formation, and drying is performed in a main drying process. As the main drying process, firing, or a drying means such as infrared radiation, ultraviolet radiation, hot air, or a means such as atmospheric standing, natural drying, or the like is used.

[0220] For the solid lubricating film formed, it is preferable that the final total film thickness be adjusted to 10 to 150 μm.

[0221] In the present embodiment, a reagent in which a solid lubricant with graphite as the main component and a binder resin with PEEK resin as the main component are dissolved in a solvent is used to form the film.

[0222] The reagent of the present embodiment is a reagent in which the film components are high with respect to the solvent, and the viscosity is high. Therefore, if the film is formed at one time to the target film thickness, along the oil well pipe thread structure, under the influence of the surface tension, the liquid spreads and the thickness becomes less at the corners of the thread teeth, and the tendency for the liquid to accumulate is high at the corners of the thread grooves. Therefore, it is preferable that the film be formed in multiple stages and fired. However, if the main firing is performed multiple times, the adhesion between the films is slightly weakened, and there is a tendency for the films to easily peel between the layers. Therefore, the temporary firing is performed in a state in which a portion of the components of the solvent is scattered. Then, the operation of coating and temporary firing is repeated again. In this way, it is preferable that the film be formed while being connected to the desired film thickness by the temporary firing, and then the main firing be performed. This is because the film quality and the uniformity of the film thickness are effectively improved. The temporary drying process refers to drying in which only a portion (for example, 30 to 70%) of the solvent is scattered.

[0223] In addition, from the viewpoint of corrosion resistance, in the case where the film is formed multiple times, it is difficult to form a pinhole in a manner that penetrates the entire film, and therefore an effect is also obtained in this regard.

[0224] <surface on which solid lubricating film is formed>

[0225] The solid lubricating film of the present embodiment is used in that the above-mentioned solid lubricating film is formed in either or both of the pin side (external thread side) or the box side (internal thread side) in an oil well pipe thread.

[0226] Alternatively, it is preferable that the solid lubricating film of the present embodiment is formed in either of the pin side (external thread side) or the box side (internal thread side), and a film of a different kind and softer than the above-mentioned solid lubricating film is formed on the fastening surface of the other side.

[0227] In the latter case, it is more preferable that the film of a different kind and softer formed on the side on which the solid lubricating film of the present embodiment is not formed has a hardness of 4B or less in pencil hardness. The latter is a method capable of further improving the lubricating properties.

[0228] Compared with the case in which films having good lubricating properties are opposed to each other to achieve lubrication, in the case in which the hardness of one is softer than the film of the present embodiment and they are opposed to each other, further improvement of the lubricating properties can be expected.

[0229] In the latter case, at the time of fastening release (stage 1: Figure 4 of (x) of the region), in the case of a peak-like torque rise, the soft film itself deforms, and reduction of the surface pressure can be expected. In addition, with the hard film of the present embodiment mainly composed of graphite and PEEK, high lubrication in the entire region of the fastening release of the thread can be expected.

[0230] The soft film having a film hardness of 4B or less in pencil hardness can employ, for example, a film described below.

[0231] <soft film>

[0232] In the present invention, a soft film is used as the solid lubricating film. The soft film does not include a grease-like compound, a liquid-like, semi-solid-like or viscoelastic film similar thereto as the object. That is, in the present invention, a soft film that falls off when touched by hand is excluded.

[0233] In addition, the soft film having a pencil hardness of 4B or less (refers to 4B, 5B, 6B,...) includes, for example, a binder resin composed of organic, inorganic, and the like. Alternatively, the soft film can be composed of a dried alkaline soap layer (the uppermost layer of the extruded lubricant film), and the like.

[0234] In the case of making a soft film from a resin-based film, for example, it can be a film composed of any kind of resin such as an epoxy resin, an acrylate resin, a polyester resin, a polyether resin, a polycarbonate resin, a fluororesin, a water-based acrylic resin, and the like. However, in order to be a soft film hardness, the interval of crosslinking points can be enlarged so that these resins do not become hard, and in addition, the film design can be performed in such a manner that it does not have complex crosslinking points in three dimensions. In addition, in the case of a simple crosslinking structure, compared to the case of having complex crosslinking points in three dimensions, it is possible to make a soft film. If it is described in other parameters, it is preferable that the monomers that constitute the soft film are monomers in which the number of functional groups and the number of epoxy groups are small, respectively. That is, monomers in which the functional group equivalent and the epoxy equivalent are large can be selected. Note that the epoxy equivalent refers to a value obtained by dividing the molecular weight of each monomer by the number of functional groups in the monomer that contribute to the crosslinking reaction. That is, it is synonymous with reducing the crosslinking points. In addition, it is preferable that no additives that make the film hard, such as carbon fibers and glass fibers, are contained. Alternatively, there is a method in which the film is softened by containing a solid lubricant in a little more amount.

[0235] Note that the lower limit of the hardness of the soft film is not particularly specified, but it is defined as the lower limit of the measurement up to 6B in terms of the standard of pencil hardness, and thus up to "≤ 6B (meaning that it cannot be measured)" is targeted. However, as long as it is a level of a film that is recognized as a solid lubricating film other than a liquid, a semi-solid, and a viscoelastic, 8B in terms of pencil hardness can be set as the lower limit value. That is, in the case where the measurement is performed using a pencil up to 7B to 10B on purpose, although it is outside the standard of pencil hardness, 8B or so can be specified as the lower limit.

[0236] <Method for evaluating lubricating properties>

[0237] From the viewpoint of achieving lubricating properties that can withstand the environment that can occur in an actual well, the present embodiment specifies each material. In addition, when the upper and lower limits are specified, it is confirmed (tested) under conditions that conform to the tightening and loosening conditions in an actual well and decided.

[0238] In a method based on a horizontal and vertical power tong using a short pin, which is performed like a usual laboratory test, the tightening and loosening conditions do not follow the actual well conditions, and in the case of a solid lubricating film, it becomes a loose evaluation condition. Therefore, it is meaningless to specify the upper and lower limits of each material by evaluating it by a usual laboratory test. As long as it is not a very strict condition, the number of tightening and loosening is determined to be acceptable. In the present invention, a new laboratory test that can simulate the conditions in an actual well is designed, and evaluation is performed under conditions in accordance with an actual well by the new laboratory test. The new laboratory test is also referred to as a heavy tong test.

[0239] < Test method concerning test under simulated actual well test conditions (new laboratory test (dead load tong test) >

[0240] In the present embodiment, as explained using Figures 2 to 4 the phenomena caused by lubrication of the oil well pipe thread are divided into two stages, before the thread is engaged (stage 1: Figure 4 (x) of the (y), (z) of the area) after the thread is engaged (stage 2: Figure 4 Then, a method of comprehensively evaluating thread lubrication is considered, including lubrication in the second stage (stage 2) on the basis of the tightening and loosening (lubrication) of the initial (stage 1) stage.

[0241] If this evaluation is not performed, the failure frequency in actual wells can be large, although it is OK in the evaluation of the laboratory test. In actual wells, before the threads engage with each other, large loads and eccentric loads are applied, and therefore, sometimes the solid lubricating film is damaged, or peeled off, or in severe cases, peeled off without leaving a trace. On this basis, the upper and lower limits of the appropriate range of the parameters of the present embodiment are selected.

[0242] As explained above, in the case of a solid lubricating film, the film is inevitably damaged by tightening and the like before the thread is engaged. Then, based on the peeled-off substance, a secondary product is formed. If this secondary product clogs the thread gap, burn-on can occur. Therefore, if the lubrication evaluation is not performed under conditions that conform to actual wells, it is possible that a solid lubricating film that is actually a substandard level will be erroneously judged to be a standard. In the case of such a loose evaluation, the limitation of the upper and lower limits of the parameters related to the solid lubricating film, the selection of the appropriate range, becomes meaningless.

[0243] That is, if the secondary product, that is, the reconstituted "secondary product" formed on the premise that the damage and peeling of the solid lubricating film become the basis, does not have an impact on lubrication, it cannot be an accurate solid lubricating film. In the present embodiment, an evaluation based on a new laboratory test that takes into account such insights is performed.

[0244] Note that if the evaluation using a horizontal power tongs with a short pin, the past evaluation using a vertical power tongs with a short pin, the evaluation based on the past laboratory test are relied on, it is meaningless in the evaluation of the solid lubricating coating. In the past patent literature, in the lubrication test based on the solid lubricating coating, for the large diameter size such as 9-5 / 8", 13-3 / 8", there are also scattered expressions that the fastening and loosening is performed 15 to 20 times. This expression is the result of the degree of slightly poor lubrication compared to the grease-like compound, but for the solid lubricating coating, such number of fastening and loosening is substantially impossible. These are considered to be the result obtained based on the evaluation using a short pin with a horizontal or vertical power tongs in the past laboratory test. In the actual well fastening and loosening, in the case of the large diameter using the solid lubricating coating, the case of 15 to 20 times is rare.

[0245] In the present embodiment, based on the above new laboratory test conditions, the test is performed by the device configuration shown in Figure 5

[0246] In the new laboratory test, the evaluation is performed under the condition of the large load at the time of being able to achieve fastening and the eccentric load at the time of fastening and loosening. For example, in the case of the process of the thread fastening with the large load corresponding to the actual size pin, the looseness before the threads engage with each other is considered. In addition, in the case of the process of the thread relaxation, it is reflected that the looseness is generated by the disengagement of the threads from each other.

[0247] In the new laboratory test, the vertical power tongs 4 is used. In addition, as the test pin, the short pin 1 is adopted. However, the load based on the load of the weight 3 and the unloading of the load can be performed at the upper portion of the pin 1.

[0248] Further, the threads of the short pin 1 and the threads of the sleeve 2 are fastened by the pin thread portion la and the sleeve thread portion 2a.

[0249] At this time, in order to simulate the condition that the thread teeth do not engage, the initial temporary fastening position is set so that the pin thread teeth la appear to expose half of the total number of thread teeth from the sleeve 2 (refer to Figure 2 (b)). This becomes one of the causes of looseness. The fastening is started from this state.

[0250] At the time of fastening, the weight 3 is installed in advance at the end portion of the pin 1 on the side opposite to the fastening threads of the sleeve 2.

[0251] The weight of the weight 3 is set to the load corresponding to 1 to 3 actual size pins, and the weight calculated based on the outer diameter and the wall thickness of the actual size pin is placed. If it is 9-5 / 8" 53.5#, it is about 1 t load (2200 Lb) for 1, and it is about 3 tons (6600 Lb) if it corresponds to 3 connections.​

[0252] As Figure 6 illustrated, Figure 5 The weight 3 exemplified in the present embodiment is composed of a weight main body 3A and an insertion rod 13. The insertion rod 13 is joined to the lower surface of the weight main body 3A by welding and is disposed at an axially symmetrical position of the weight 3. By inserting the insertion rod 13 into the pin 1 in a loose state, the weight is installed to the pin. The symbol 1c denotes the inner diameter surface of the pin 1.

[0253] When the weight 3 is installed to the pin 1 in advance as described above, a hole Id, 13a is provided in advance which penetrates the pin 1 and the insertion rod 13. Then, as Figure 6 illustrated, by inserting the penetration rod 12 into the hole Id, 13a, the weight 3 and the pin 1 are integrated.

[0254] At the axially central position of the upper portion of the weight 3, a hook 11 of a swivel type is closely attached by welding and is formed as a structure which is suspended from a suspension device 20 of the ceiling via a sling 21. By this, by adjusting the lifting condition of the weight by the suspension device 20, the magnitude of the load of the weight to the pin can be adjusted.

[0255] Further, at the time of tightening, the state is set in which the sling 21 is loose and the weight load is applied to the sleeve thread and is tightened up to the torque rise (stage 1) at 5 to 20 rpm. This becomes a simulation of loosening. If the torque rises, the rotation speed is lowered to 0.5 to 2 rpm and tightening is performed up to the tightening position (stage 2).

[0256] On the other hand, at the time of loosening (at the time of release), the weight 3 is lifted by the suspension device 20 and release is performed in a state in which the load of the weight 3 is not applied. With respect to the rotation speed, at the time of torque rise, the rotation speed is started to be released at 0.5 to 2 rpm and if the torque reaches about 1 / 10 of the tightening torque value, release is performed at a high speed of 5 to 20 rpm.

[0257] Here, in the case in which the load is not applied at the time of release, a condition close to the environment of an actual well is obtained. This is based on an experimental fact and is based on the insight of data of good lubricating characteristics in the case in which the load of the weight 3 is applied compared to the case in which it is not applied. That is, the inventors actually performed experiments and made observations and as a result, the following insight was obtained: when release is performed in a state in which the weight is applied, the weight becomes an equalizer and the pin is released straight from the tightening end position without loosening. On the other hand, in the case in which the weight is lightened, that is, in the case in which the load is lifted for the purpose of making the weight load zero, including the case in which the load is not completely zero, in the condition in which the joint is released by lightening the load, it is possible to perform tests in a condition in which the loosening of the pin is intense and in which the tendency to cause damage to the solid lubricating film is strong.

[0258] In a new laboratory test based on the above conditions, it is possible to simulate the condition in which the secondary product does not follow the movement of the fastening and relaxation and is clogged in a certain place to cause a burn, or other condition in which the coating itself is peeled off without leaving a trace. Note that the secondary product is a product from the components of the solid lubricating coating released to the thread gap due to inevitable peeling and the like. As a result, it is possible to define the upper and lower limits of the parameters related to the solid lubricating coating as parameters that conform to the actual well conditions. After the relaxation is completed, the pin thread and the sleeve thread are separated, the fragments and the like from the solid lubricating coating are scattered by blowing air on the surface, the surface is inspected, and the fastening is continued again, and evaluation is performed by such a method.

[0259] In the present embodiment, in order to achieve lubricating properties that can withstand the environment that can occur in an actual well, the components and the like are defined. In addition, when defining the upper and lower limits, confirmation is made under conditions that conform to the fastening and relaxation conditions in an actual well, and a decision is made.

[0260] (EFFECTS OF THE PRESENT EMBODIMENT)

[0261] The present embodiment achieves high lubrication that can withstand fastening in an actual well in the field of lubrication using a solid lubricating coating of an oil well pipe thread.

[0262] In the past, there have been many inventions of solid lubricating coatings using graphite. However, the actual situation is that "black band-shaped secondary products" in which graphite and adhesive resin components that are inevitably peeled off during fastening and relaxation are reconstituted almost always cause burns.

[0263] In this regard, in the present embodiment, the amount of graphite and the blending ratio are optimized, and in particular, the solid lubricant is constituted only of graphite. Furthermore, as a suitable adhesive resin, PEEK resin, which has almost no application examples in combination with graphite so far, is selected. In addition, by specifying the weight ratio of graphite in the solid lubricating coating, burns that often occur during solid lubrication with graphite as the main component are avoided.

[0264] As described above, in the present embodiment, high lubrication is achieved. Furthermore, by blending the range of the invention, it is possible to exclude burns or instability of lubrication that have been unavoidable in the past when graphite is selected as a solid lubricating component, and thus it is possible to achieve high lubrication.

[0265] Meanwhile, in the present embodiment, corrosion resistance can also be achieved.

[0266] Furthermore, it is not only applied to lubrication of oil well pipe threads, but can also be expanded to be applied to metal materials. In addition, it is not only a film, but also a reagent for making a film can be targeted.

[0267] (OTHER)

[0268] The present application can also be configured as follows.

[0269] (1) An agent for forming a solid lubricating coating film on a threaded portion of an oil well pipe, wherein two or more solid lubricants are dispersed in a binder resin, as one of the two or more solid lubricants, graphite is contained in an amount of 50% or more and 90% or less of the total weight of the solid lubricants, the graphite has a scale-like shape and an average particle diameter of 10.0 μm or less, and as the other solid lubricant of the two or more solid lubricants, a solid lubricant composed of one or more materials selected from the group consisting of BN (boron nitride), mica, talc, MCA (melamine cyanurate), MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane; tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), and FEP (perfluoroethylene propylene copolymer; tetrafluoroethylene-hexafluoropropylene copolymer) is contained, the binder resin contains PEEK resin having an average particle diameter of 20 μm or less as a main component, and the PEEK resin is contained in an amount of 70% or more of the total weight of the binder resin.

[0270] (2) The total weight of the solid lubricants is 0.1 times or more and 2 times or less of the total weight of the binder resin, and the content of the graphite as the solid lubricant is 20% or more and 50% or less of the total weight of the solid lubricants and the binder resin.

[0271] (3) A solvent is contained, and the weight ratio of the solvent is 30% or more and 80% or less of the total weight of the solid lubricants and the binder resin.

[0272] (4) As the other solid lubricant, at least PTFE is contained, and the average particle diameter of the PTFE is in a range of 0.1 μm or more and 5 μm or less.

[0273] (5) An oil well pipe in which a lubricating coating film having a solid lubricating coating film is formed on a fastening surface of a threaded portion of at least one of a sleeve and a pin, the solid lubricating coating film being formed by dispersing a solid lubricant in a binder resin, the solid lubricating coating film containing graphite in an amount of 50% or more and 90% or less of the total weight of the solid lubricating coating film, the graphite having a scale-like shape and an average particle diameter of 10.0 μm or less, and further, the solid lubricating coating film containing, as the other solid lubricant, a solid lubricant composed of one or more materials selected from the group consisting of BN (boron nitride), mica, talc, MCA (melamine cyanurate), MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane; tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), and FEP (perfluoroethylene-propylene copolymer; tetrafluoroethylene-hexafluoropropylene copolymer), the binder resin containing PEEK resin having an average particle diameter of 20 μm or less as a main component, and the PEEK resin being contained in an amount of 70% or more of the total weight of the binder resin.

[0274] (6) The total weight of the solid lubricating coating film is 0.1 times or more and 2 times or less of the total weight of the binder resin, and the content of the graphite as the solid lubricant is 20% or more and 50% or less of the total weight of the solid lubricating coating film and the binder resin.

[0275] (7) The PTFE as the other solid lubricant has an average particle diameter in the range of 0.1 μm or more and 5 μm or less.

[0276] (8) The solid lubricating coating film is formed in a region including the thread of the threaded portion and adjacent thereto.

[0277] (9) The hardness of the solid lubricating coating film is 3H or more in terms of pencil hardness.

[0278] (10) The film thickness of the solid lubricating coating film is 10 μm or more and 150 μm or less.

[0279] (11) The material of the oil well pipe is carbon steel or low alloy steel, and the lubricating coating film has a base layer between the fastening surface of the threaded portion and the solid lubricating coating film, the base layer being composed of an electroplating film or a chemical conversion treatment film.

[0280] (12) The material of the oil well pipe is stainless steel, Ni-based alloy, or Ti alloy, and the lubricating coating film has a base layer between the fastening surface of the threaded portion and the solid lubricating coating film, the base layer being composed of an electroplating film.

[0281] (13) An oil well pipe threaded joint in which a pin having an external thread is connected to a box having an internal thread, wherein at least one of the oil well pipe of the box and the pin is made of the oil well pipe according to the present application having the lubricating coating.

[0282] (14) The lubricating coating having the solid lubricating coating is formed on the fastening surface of the threaded portion of one of the box and the pin, and a soft film softer than the solid lubricating coating is formed on the fastening surface of the threaded portion of the other of the box and the pin.

[0283] (15) The film hardness of the soft film is 4B or less in terms of pencil hardness.

[0284] (16) The manufacturing method of the oil well pipe according to the present application, wherein the film forming step of coating the agent to form a solid lubricating coating having a film thickness of 50 μm or less is repeated two or more times with a temporary drying step in between until a target total film thickness is reached, and a final drying step is performed after the last film forming step, the final drying step being performed by using a drying means of firing, infrared radiation, ultraviolet radiation or hot air, or an atmospheric standing, natural drying means, and the total film thickness of the solid lubricating coating is adjusted to 10 μm or more and 150 μm or less.

[0285] Example

[0286] Next, an example based on the present embodiment will be described.

[0287] First, the qualification criteria for the lubrication behavior based on the number of fastening and loosening is described. The qualification criteria are as follows. Regarding the casing size, 3 or more fastening and loosening is qualified, and 5 times of qualification is more excellent. Regarding the pipe size, 5 or more is qualified, and 10 or more is evaluated as more excellent. The casing size is regulated according to ISO 13679. On the other hand, for the pipe, 5 or more which is lower than the regulation of ISO 13679 is qualified. This is because, since the solid lubricating film, the tendency of the number of fastening and loosening to deteriorate is significantly higher compared to the conventional lubrication using the grease-like compound, which is gradually recognized in the oil and gas industry. As described above, if the fastening and loosening test is performed from the thread engagement using only the short pin, the regulation of ISO 13679 is a simple target. However, in the present invention, in order to simulate the condition in which the large load and the eccentric load are applied and the thread is not engaged, which is a condition close to the condition that can occur in the actual well, the evaluation is performed by a new laboratory test (heavy weight wrench test). Therefore, it is set as this criteria. The classification of the pipe and the casing is different depending on the design of the well at each site, and in the present invention, the size up to 7" is positioned as the pipe, and the size exceeding that is positioned as the casing. That is, the qualification criteria are different with 7 inches as a boundary.

[0288] The heavy weight is based on the condition in which the load of the plurality of connected loads is applied, and in the manner of 1 ton, 1.5 tons, 2 tons, 3 tons, the heavy weight which conforms to the standard in MKS units is used. Then, the heavy weight is installed at the upper portion of the pin thread and implemented (refer to Figure 5 ).

[0289] The initial fastening position is fastened only to the position in which it seems that half of the total number of pin threads is exposed from the sleeve thread, that is, the fastening is implemented from the state in which the threads are not engaged with each other (the position in which half of the threads are exposed).

[0290] That is, the present embodiment is implemented by the device shown in Figure 5 , Figure 6 .

[0291] In addition, at the time of fastening, the load of the heavy weight is applied. On the other hand, at the time of loosening, the test is implemented in the state designed not to apply the load of the heavy weight. If the test is performed using the load at the time of loosening, in the case of using the pin in which the short pin and the heavy weight are integrated, the behavior is different from the actual size pin of the actual well. Specifically, the short pin integrated with the heavy weight is straightly raised from the fastening position. The heavy weight becomes a balancer, and thus the loosening is not generated. For the pin used in the actual well, since it is long and subtly curved, it is gradually exposed, and the tendency to cause the loosening as the threads are not engaged and to damage the solid lubricating film is high.

[0292] Therefore, in the lubrication evaluation using the heavy hammer wrench, at the time of loosening, the test is performed without applying a load, and when the condition in which the thread teeth become disengaged is approached, loosening caused by the linkage is simulated. Note that not applying a load does not necessarily mean that the load is zero. The test is performed by lifting the heavy hammer by a bridge crane or the like without applying a load. In addition, the test of confirming the number of times of tightening and loosening using the heavy hammer wrench is performed two or more times, and the evaluation is performed by comparing whether the number of times reaches the qualified criteria, and how much the number of times reaches with respect to the number of test points, and whether the parameters can be judged.

[0293] (Example 1)

[0294] In Example 1, the lubrication characteristic evaluation using the heavy hammer wrench is described.

[0295] The conditions and evaluation results of each example are described in Tables 1 to 6. Note that the solid lubrication film is also referred to as a coating film.

[0296]

[0297]

[0298]

[0299]

[0300]

[0301]

[0302] <No. 1 to 11>

[0303] In No. 1 to 11, the test is performed under the conditions in which the steel grade is carbon steel acid-resistant material C110, the thread size is 7"29#, and the thread is JFELION TM In addition, in No. 1 to 11, as the heavy hammer, a 1.5-ton heavy hammer is used, and the evaluation is performed by a new laboratory test under the condition in which three actual length pins are connected.

[0304] On the coupler side, as the lubrication film, a base layer and a solid lubrication film are sequentially formed on the tightening surface. The base layer is provided as a Mn phosphate chemical conversion treatment layer.

[0305] In the solid lubrication film on the coupler side, the main component of the solid lubricant is provided as graphite, and as the graphite, flaky (flaky grade) graphite having an average particle diameter of 5 μm or 10 μm is used. In addition, the binder resin is a PEEK resin, and a resin having an average particle diameter of ≤ 1 μm is used. Furthermore, the film thickness of the solid lubrication film is formed to be 50 μm thick.

[0306] No. 1 is an example in which the fastening surface on the pin threaded side is in a state in which the shot blasted surface is maintained. In Nos. 2 to 11, a solid lubricating film in which the solid lubricant is composed of PTFE and the adhesive resin is composed of fluororesin is formed on the fastening surface on the pin threaded side.

[0307] Further, Nos. 1 to 4, 10 to 11 are examples in which the graphite weight ratio with respect to the entire solid lubricant is comparatively studied.

[0308] No. 1 is an example in which the solid lubricant is composed of only graphite, and in which the fastening and loosening times do not satisfy the qualification level. No. 1 is an example in which "black band-shaped secondary products" from graphite are formed in the gap between the sleeve threaded side and the pin threaded side and clog to cause burning.

[0309] Nos. 2 to 4 and 10 are examples in which graphite is contained within an appropriate range. In all of them, the fastening and loosening times exceed the qualification criteria. Nos. 2 to 4 and 10 are cases in which the graphite content is not 100% but is used in a mixed state with other solid lubricants, and the necessary amount of graphite is contained at 50% or more. As a result, it is observed that high lubrication is achieved and the state in which "black band-shaped secondary products" do not easily clog is achieved.

[0310] No. 11 is an example in which graphite is contained at 40% and is less than the range of the present application. No. 11 is an example in which the lubrication of graphite is not sufficiently utilized and the lubricity is insufficient to cause burning.

[0311] Further, Nos. 4 to 6 are examples in which PTFE is used as a secondary solid lubricant and the particle diameter of the PTFE is changed and studied. According to Nos. 4 to 6, the fastening and loosening times are within the qualification range whether the PTFE particle diameter is 10 μm or 5 μm. However, in the case of 10 μm, compared to 5 μm, a tendency is observed in which the lubricity slightly begins to decline. That is, it is known that the PTFE particle diameter is preferably up to 5 μm.

[0312] Nos. 4, 8, 9 are examples of comparison related to the shape and grade of graphite. They are examples in which graphite of the grades of scale (flaky), scale (vein), and earth (amorphous) are compared respectively. No. 8 has qualified times, but contains fastening and loosening time data of the unqualified level. No. 9 does not reach the qualification level. The lubrication of graphite is greatly affected by the crystallinity of the graphite. Therefore, in the case of graphite of the earth (amorphous) type, the fastening and loosening times do not satisfy the qualification. Further, in the case of graphite of the scale (vein) type, the result is a state of insufficient lubrication.

[0313] No. 7 is an example in which glass fiber is added as another additive to PTFE. No. 7 is an example in which the film becomes harder (pencil hardness: 7H) by the addition of glass fiber, and in particular, the number of times of tightening and loosening is not problematic, but is improved. In No. 7, it is presumed that the amount of film peeling, which is a basis for the "black band-shaped secondary product", is less because the film is harder.

[0314] <No. 12 to 20>

[0315] No. 12 to 20 are examples in which the steel grade is carbon steel acid-resistant material C110, the thread size is 9-5 / 8" 53.5#, and the thread is JFELION TM and examples in which the above are implemented.

[0316] As the weight for the above hammer test, a 3-ton weight was used, and evaluation was performed under the condition in which the actual length pin was connected by three roots.

[0317] On the coupler side, as a lubricating film, a base layer and a solid lubricating film were formed in this order on the tightening surface. The base layer was provided as a Mn phosphate chemical conversion treatment layer.

[0318] In the solid lubricating film on the coupler side, the main component of the solid lubricant was graphite, and as this graphite, flaky (flaky grade) was selected, and as a secondary solid lubricant component, BN was used. In addition, the main component of the binder resin was PEEK resin.

[0319] The tightening surface on the pin side was a shot blasted surface on which a solid lubricating film composed of a metal soap (Ca stearate) dispersed in a fluororesin as a binder resin was formed.

[0320] No. 12 to 20 are examples in which the average particle diameter of graphite, the particle diameter of PEEK resin, and the possibility of a secondary resin component mixed in the PEEK resin were observed.

[0321] No. 13 and 16 are examples in which the average particle diameter of graphite was 20 μm and 25 μm, respectively, and are examples in which the upper limit of the present application of 10 μm was exceeded. No. 13 and 16 are examples in which the number of times of tightening and loosening did not satisfy the qualification. In No. 13 and 16, the "black band-shaped secondary product" easily occurred, and burns were caused. In addition, damage caused by the burns accumulated, and burns were caused earlier.

[0322] Nos. 14 to 17 are studies on conditions of mixing a secondary resin component in the PEEK resin. According to Nos. 14 to 17, if 70% or more of the PEEK resin is contained, even if the solid lubricating film is constituted by a composite resin film containing, for example, an epoxy resin, a PEKK resin, a PAEK resin, or the like, if the other prescribed items are within the target prescribed range, the tightening-loosening frequency can be made to be acceptable.

[0323] No. 15 is a comparative example, which is an example of a condition of mixing 60% of the PEEK resin, 40% of the PE resin (polypropylene), and the PE resin (polyethylene). In No. 15, the PEEK resin content does not satisfy the prescribed amount, and a soft resin is added. Therefore, in No. 15, the pencil hardness of the solid lubricating film is also lower than the prescribed amount, and the tightening-loosening frequency is not acceptable.

[0324] In Nos. 14 to 17, No. 17 is an example in which carbon fibers are used for reinforcement, and is an example in which the tightening-loosening frequency is more excellent. In No. 17, it is presumed that since the film quality is hardened, the peeling of the solid lubricating film itself is also reduced, and as a result, this is a factor in that the "black band-shaped secondary product" is less.

[0325] No. 19 is an example in which the average particle diameter of the PEEK resin exceeds 25 μm, which is the range of the present application, and is a comparative example. The tightening-loosening frequency of No. 19 does not satisfy the acceptable criteria. No. 19 shows that when the particle diameter of the PEEK resin is too large, the lubrication is also deteriorated.

[0326] No. 20 is an example in which the graphite weight is set to 25%, which is 50% lower than the lower limit of the present application, and is an example in which the graphite is not the main component of the solid lubricant. No. 20 is an example in which the proportion of the graphite weight with respect to the total solid lubricating film weight (= the total solid lubricant weight + the total binder resin weight) is also 19%, which is 20% lower than the lower limit of the present application. In No. 20, it is considered that the "black band-shaped secondary product" is less because the graphite is less. In addition, even if not, a burn is caused. The fact that this burn occurs suggests that there is a necessary amount in which the lubricating effect of the graphite is properly exerted, and there is an optimal range of the graphite in order to avoid the adverse effects caused by the graphite peeling from the solid lubricating film at the time of tightening-loosening to become the "black band-shaped secondary product".

[0327] <No. 21 to 29>

[0328] The examples of Nos. 21 to 29 are examples in which the steel material grade is carbon steel material Q125, the thread size is 5.5" 23#, and the thread is JFELION TMExamples of the conditions under which the test was performed are shown in Table 1. For the heavy hammer test, a 1-ton hammer was used, and the evaluation was performed under the condition in which the actual length of the pin was assumed to be 3 times the length of the pin.

[0329] On the coupling side, a base layer and a solid lubricating film were formed in this order as lubricating films on the fastening surface. The base layer was provided as a Mn phosphate chemical conversion treatment layer.

[0330] On the coupling side, as the main component of graphite in the solid lubricating film, flaky graphite (a flaky grade) was selected, and as the secondary solid lubricating component, PTFE was selected. In addition, the main component of the binder resin was PEEK resin.

[0331] On the fastening surface on the pin side, a solid lubricating film using a fluororesin as the binder resin and PMSQ (polymethylsilsesquioxane) as the solid lubricant was formed on the shot blasted surface.

[0332] Examples No. 21 to 27 are examples in which the film thickness of the solid lubricating film was investigated.

[0333] As is clear from No. 21 to 27, in the range of a film thickness of 10 to 150 μm, excellent fastening and loosening times were shown. In the examples of No. 21 (5 μm) and No. 27 (180 μm) outside the range of the present application, the fastening and loosening times did not satisfy the qualification criteria.

[0334] As is clear from No. 21 to 27, particularly excellent lubrication (fastening and loosening times) was shown in the range of a film thickness of 10 to 75 μm.

[0335] In addition, No. 24, 28, and 29 are examples in which the effects of forming a solid lubricating film on either or both of the coupling side and the pin side were compared. In No. 21 to 27, the examples other than these three examples are examples in which a solid lubricating film using a combination of graphite and PEEK resin as the main component was formed on the coupling side, and a soft film or no film was formed on the pin side.

[0336] As is clear from No. 21 to 27, in general, it is meant that in the case in which the solid lubricating film of the present application is provided on the coupling side, sufficient lubrication can be maintained by the film structure of the present application.

[0337] On the other hand, the example of No. 28 is an example in which the solid lubricating film on the pin side and the solid lubricating film on the coupling side were exchanged. As is clear from the comparison of No. 28 and No. 24, even if the solid lubricating films were exchanged, the lubrication hardly changed, and was good.

[0338] No. 29 is an example in which a solid lubricating film with a combination of graphite and PEEK resin as a main body is formed on both the pin side and the coupling side. The number of fastening loosening times of No. 29 is slightly deteriorated compared to No. 24 and No. 28, but it sufficiently shows the pass judgment value.

[0339] <No. 30 to 34>

[0340] Examples of No. 30 to No. 34 are examples implemented under the conditions that the steel grade is carbon steel material Q125, the thread size is 9-5 / 8" 47#, and the thread is JFELION TM In No. 30 to No. 34, as the weight, a 3-ton weight is used, and evaluation is performed by a new laboratory test under the condition that the actual length of the pin is connected by three.

[0341] On the coupling side, as a lubricating film, a base layer and a solid lubricating film are sequentially formed on the fastening surface. The base layer is provided as a Mn phosphate chemical conversion treatment layer.

[0342] In the solid lubricating film on the coupling side, the main component of the solid lubricant is graphite, as the shape of the graphite, a scale shape (a flake shape level) is selected, and as a secondary solid lubricating component, PTFE is selected. In addition, the main component of the adhesive resin is PEEK resin.

[0343] On the fastening surface of the pin side, an example in which an adhesive resin composed of a water-based acrylic resin and a solid lubricant composed of aluminum powder are formed on a shot blasted surface.

[0344] In the examples of No. 30 to No. 33, the weight % of the solvent weight with respect to the film component weight (= solid lubricant weight + adhesive resin) is investigated.

[0345] In the examples of No. 30 in which the solvent weight is lower than the lower limit of the suitable range of the present application and No. 34 in which the solvent weight exceeds the upper limit of the suitable range of the present application, the number of fastening loosening times is about 3 times, which is the limit level, and only a pass.

[0346] In a state in which the solvent is concentrated, for example, in No. 30, the mixing of graphite and PTFE is not sufficient, and there is a local concentration. As a result thereof, the graphite in the solid lubricating film is uneven. Therefore, the formation mode of "black band-shaped secondary products" is highly likely to be uneven, and the possibility of burning increases.

[0347] In No. 34, the graphite and the PTFE are mixed sufficiently. However, in No. 34, since the solvent is thin, when the film is made and gradually dried in the atmosphere, the graphite floats to the surface and gathers among the graphite and the PTFE. Therefore, after the film is made by firing, the concern that the graphite is biased to the surface side of the solid lubricating film becomes high. As a result, it can be assumed that the possibility of scorching increases as a mechanism. Thus, it is understood that the solvent weight needs to be set in a stable range.

[0348] <No. 35 to 34, No. 35 to 36>

[0349] The examples of No. 35 to 36 are examples implemented under the conditions that the steel material is a stainless steel material L80-13CR, the thread size is 7" 38#, and the thread is JFEBEAR TM In No. 35 to 36, as the weight, a 2-ton weight is used, and evaluation is performed by a new laboratory test under the condition that the actual length pin is connected by 3 pieces.

[0350] On the coupler side, as the lubricating film, a base layer and a solid lubricating film are sequentially formed on the fastening surface. The base layer is provided as an electroplated layer of a binary system of Cu and Sn.

[0351] In the solid lubricating film on the coupler side, the main component of the solid lubricant is graphite, and as the graphite, a scale-like (flaky grade) is selected, and the secondary solid lubricating component is PTFE. Note that in No. 35, glass fibers are also contained. In addition, the main component of the adhesive resin is PEEK resin.

[0352] On the pin side, a solid lubricating film composed of an adhesive resin composed of a fluororesin and a solid lubricant composed of a metal soap (Ba stearate) is formed on the shot blasted surface.

[0353] No. 35 to 36 relate to examples applied to a stainless steel material. In particular, No. 35 is also an example in which glass fibers are added and the film hardness is listed. It is understood that both No. 35 to 36 show excellent lubricating properties.

[0354] Here, the above-described examples are exemplified using oil well pipe threads. In lubrication, not only the lubrication behavior from the mutual contact of the two objects of the frictional object, but also the case where the threads are not engaged, the example of a severe lubrication condition in which the lubricating film is peeled off due to the material of the frictional object, and a part is damaged, is shown. Therefore, the present application can also be applied to lubrication from the mutual contact of the two objects of the frictional object, and in addition, as long as the structure of the lubricating film is used, it can be applied to materials other than oil well pipe thread materials, application fields without limitation.

[0355] (Example 2)

[0356] Example 2 is an example of evaluation of corrosion resistance by a salt spray test.

[0357] In the examples shown in Tables 1 to 6, the salt spray test was performed for the No. 3, 10, and 22 configurations. These examples are examples based on the oil well pipe thread conditions of carbon steel.

[0358] In Example 2, for the salt spray test, a new coupling sample was prepared with a solid lubricating coating film.

[0359] In addition, as a comparative example, a material having a thickness of 0.8 mm t of SPCC (thin steel sheet of general mild steel / cold-rolled annealed sheet) was also used.

[0360] Furthermore, the evaluation was performed by once tightening and loosening the protector for both ends of the coupling thread. Then, the salt spray test was performed for the case where the state was maintained and the case where the protector was installed again (equivalent to the second tightening), and the evaluation was performed only in the horizontal arrangement (meaning not vertical) for a prescribed time.

[0361] Note that the outer side of the coupling material was protected by a stretch imide tape.

[0362] The detailed conditions are described below.

[0363] < Salt spray conditions >

[0364] Spray conditions: JIS K 5600-7-1

[0365] Salt concentration: 5 ± 0.5 wt%

[0366] Temperature: 35°C

[0367] Humidity: 98 to 99%

[0368] Spray amount: 1 to 2 ml / hour / 80 cm 2

[0369] pH: 6.5 to 7.2

[0370] Time: 24 hours

[0371] Here, in the comparative example, a material cut to a size of 75 mm x 150 mm for the SPCC sheet was used as a sample, and the same film as No. 3 was formed on the surface. That is, after the Mn phosphate treatment, a reagent was applied, firing was performed, and a solid lubricating coating film was formed. In addition, two samples were prepared, and one side was protected with an imide tape. Furthermore, a material in which the imide tape was also attached to the back side (test object side) of the entire protective film from the end by 1 mm was used as a sample. One of the two was crosscut with a cutting knife (No. A), and the other was directly used as a sample (No. B).

[0372] For No. 3, 10, 22, the conditions of salt water spraying after 1 tightening and loosening with the protector and installation of the protector (No. 3-2, 10-2, 22-2) and the conditions of salt water spraying directly after 1 tightening and loosening with the protector (No. 3-3, 10-3, 22-3) were evaluated.

[0373] Note that No. 3-4 is an example of a salt water spraying test directly without tightening and loosening with the protector.

[0374] The significance of this test method is as follows. This is because oil well pipe threads are mostly shipped after tightening the end portion with the protector and are directly stored in the field near the well. Therefore, the condition after spraying salt water becomes an environment close to the actual use conditions.

[0375] The condition without installation of the protector means a more severe condition when the protector is removed. No. 3-4 is an example of tightening and loosening without the protector, and the corrosion resistance of the film itself is observed in terms of the thread shape.

[0376] The results are shown in Table 7.

[0377]

[0378] Comparative example No. A is an example in which No. 3 is formed on an SPCC thin steel sheet, and the film is provided with a flaw in a manner that the film is cut across to reach the base. In comparative example No. A, rust is observed at the cut portion. On the other hand, the corrosion resistance of the film itself without cutting is excellent, and no corrosion is observed.

[0379] No. 3-2 to 3-4, No. 10-2 to 10-3, and No. 22-2 to 22-3 are all in a sound state, and no corrosion is confirmed. Thus, it is shown that the corrosion resistance of the solid lubricating film of the present application is also excellent.

[0380] Note that graphite itself and PEEK resin itself have water repellency, and the corrosion resistance is excellent. Also, the solid lubricating film is a relatively hard film that is not damaged under the condition of tightening and loosening with the protector. Therefore, it is considered that a minute crack is not formed, and thus such corrosion resistance is shown. In summary, the condition of No. A in which the film is cut with a cutting knife is an excessively severe condition for the solid lubricating film, and under the level of tightening and loosening with the protector, it is shown that the film is not damaged. It is also known that if the solid lubricating film of this composition is formed, good corrosion resistance is shown.

[0381] As described above, it can be demonstrated that by defining the prescribed range of the present application, the solid lubricating coating using the agent can ensure lubricity and corrosion resistance. For the lubrication of the threaded fastening and loosening using the solid lubricating coating consistently described in the present application, it is important that the trace amount of soap component is utilized to slide so that the solid lubricating coating is not damaged when the "play" exists before the thread engagement. In addition, after the thread engagement, the lubrication from the close state is good, and the two lubrication processes can be well controlled.

[0382] Herein, the entire contents of Japanese Patent Application 2021-91462 (filed on May 31, 2021) for which priority is claimed in the present application are incorporated by reference as part of the present application. Herein, a limited number of embodiments are described by way of illustration, but the scope of the right is not limited thereto, and changes based on the above-described disclosed embodiments will be apparent to those skilled in the art.

[0383] Explanation of symbols

[0384] 1 pin

[0385] 1a external thread

[0386] 2 sleeve (coupler)

[0387] 2a internal thread

[0388] 3 weight

[0389] 3A weight body

[0390] 4 power tongs

[0391] 10A solid lubricating coating

[0392] 10B base layer

[0393] 12 through rod

[0394] 13 insertion rod

[0395] 20 hoisting device (crane)

[0396] 21 chain (sling)

Claims

1. A reagent for forming a solid lubricating film, which is used to form a solid lubricating film on the threaded portion of an oil well pipe, characterized in that, Compared to adhesive resins that disperse two or more solid lubricants, As one of the two or more solid lubricants, the solid lubricant contains graphite comprising 50% to 90% of its total weight, wherein the graphite is in the form of flakes and has an average particle size of 10.0 μm or less. The graphite content of the solid lubricant is 20% to 50% of the sum of the total weight of the solid lubricant and the total weight of the binder resin. Furthermore, the other solid lubricant among the two or more solid lubricants mentioned above contains a solid lubricant composed of one or more materials selected from BN (boron nitride), mica, talc, MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and FEP (tetrafluoroethylene-hexafluoropropylene copolymer). The adhesive resin uses PEEK resin with an average particle size of less than 20 μm as the main component, and contains more than 70% of this PEEK resin by weight of the total adhesive resin. The thickness of the solid lubricating film is greater than 10 μm and less than 150 μm.

2. The reagent for forming a solid lubricating film according to claim 1, characterized in that, The total weight of the solid lubricant is more than 0.1 times and less than 2 times the total weight of the adhesive resin.

3. The reagent for forming a solid lubricating film according to claim 1 or claim 2, characterized in that, It contains a solvent, wherein the weight ratio of the solvent is more than 30% and less than 80% relative to the sum of the total weight of the solid lubricant and the total weight of the adhesive resin.

4. The reagent for forming a solid lubricating film according to claim 1 or claim 2, characterized in that, As one of the other solid lubricants, it contains at least PTFE. The average particle size of the PTFE is in the range of 0.1 μm or more and 5 μm or less.

5. An oil well pipe, characterized in that a lubricating film with a solid lubricating film is formed on the threaded portion, wherein... The solid lubricating film is formed by dispersing two or more solid lubricants relative to a binder resin. As one of the two or more solid lubricants, the solid lubricant contains graphite comprising 50% to 90% of its total weight, wherein the graphite is in the form of flakes and has an average particle size of 10.0 μm or less. The graphite content of the solid lubricant is 20% to 50% of the sum of the total weight of the solid lubricant and the total weight of the binder resin. Furthermore, the other solid lubricant among the two or more solid lubricants mentioned above contains a solid lubricant composed of one or more materials selected from BN (boron nitride), mica, talc, MoS2 (molybdenum disulfide), PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and FEP (tetrafluoroethylene-hexafluoropropylene copolymer). The adhesive resin uses PEEK resin with an average particle size of less than 20 μm as the main component, and contains more than 70% of this PEEK resin by weight of the total adhesive resin. The thickness of the solid lubricating film is greater than 10 μm and less than 150 μm.

6. The oil well tubing according to claim 5, characterized in that, The total weight of the solid lubricant is more than 0.1 times and less than 2 times the total weight of the adhesive resin.

7. The oil well tubing according to claim 5 or claim 6, characterized in that, As one of the other solid lubricants, it contains at least PTFE. The average particle size of the PTFE is in the range of 0.1 μm or more and 5 μm or less.

8. The oil well tubing according to claim 5 or claim 6, characterized in that, The solid lubricating film is formed in the area including the thread teeth of the threaded portion and adjacent to them.

9. The oil well tubing according to claim 5 or claim 6, characterized in that, The hardness of the solid lubricating film is 3H or higher on a pencil hardness tester.

10. The oil well tubing according to claim 5 or claim 6, characterized in that, The oil well casing is made of carbon steel or low-alloy steel. The lubricating film has a base layer between the fastening surface of the threaded portion and the solid lubricating film, the base layer comprising an electroplated film or a chemically converted film.

11. The oil well tubing according to claim 5 or claim 6, characterized in that, The oil well casing is made of stainless steel, Ni-based alloy, or Ti alloy. The lubricating film has a base layer between the threaded portion and the solid lubricating film, the base layer comprising an electroplated film.

12. A well pipe threaded connector, characterized in that, a well pipe threaded connector is formed by connecting a sleeve with an internal thread and a pin with an external thread, wherein, At least one of the sleeve and the pin is made of the well tubing according to any one of claims 5 to 11.

13. The oil well pipe threaded joint according to claim 12, characterized in that, A lubricating film containing the solid lubricating film is formed on the fastening surface of the threaded portion of one of the components, the sleeve and the pin. A film softer than the solid lubricating film is formed on the fastening surface of the threaded portion of the other component of the sleeve and the pin.

14. The oil well pipe threaded joint according to claim 13, characterized in that, The membrane hardness of the soft membrane is 4B or less on a pencil hardness tester.

15. A method for manufacturing an oil well pipe, comprising the method for manufacturing an oil well pipe according to any one of claims 5 to 11, characterized in that, Using the reagent according to any one of claims 1 to 4, The film-forming process, which involves coating the agent to form a solid lubricant film with a thickness of less than 50 μm, is interspersed with a temporary drying process and repeated more than twice until the target total film thickness is achieved. The formal drying process is performed after the final film-forming process. The formal drying process is carried out using drying methods such as firing, infrared irradiation, ultraviolet irradiation, or hot air drying, or by atmospheric placement and natural drying. The total thickness of the solid lubricating film is adjusted to be above 10 μm and below 150 μm.

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