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

Abstract

The present invention can provide a solid lubricating coating film that imparts lubricity and excellent corrosion resistance to an oil well pipe thread even if solid lubricating coating film is used for lubrication. An agent for forming a solid lubricating coating film on a threaded portion of an oil well pipe, wherein a binder resin contains a prepolymer and a curing agent, the prepolymer contains one or more than two kinds of epoxy resins, 70 parts by weight or more of the prepolymer is contained relative to 100 parts by weight of the binder resin, the epoxy equivalent weight of the epoxy resins constituting the prepolymer is in a range of 100 or more and 500 or less, 80% by weight or more of a solid lubricant is BN (boron nitride), the average particle diameter of the BN is 10 μm or less, and the total weight of the solid lubricant is 0.1 times or more and 2 times or less 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 and 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 face of a threaded portion including a metal seal face in place of a wet type lubricating compound. In the present specification, a fastening face of a threaded portion includes a metal seal face.

[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. In addition, the present application aims to improve lubrication by achieving a solid lubricating coating film of an oil well pipe thread and to have corrosion resistance.

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

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

[0005] In an oil well pipe threaded joint, in lubrication of a threaded portion, a surface treatment is performed on a face of a threaded portion, that is, a fastening face (a seal face) (hereinafter, also simply referred to as a "fastening face") of a member of at least one of an external thread side and an internal thread side using a Mn phosphate chemical conversion treatment film, plating using Cu or the like, and 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 face (a seal face) of a threaded portion, the fastening face including the coating film is referred to as a fastening face.

[0007] On the other hand, 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 face to seek lubrication. The present application relates to a technology of lubrication in the case of "dry / no doping".

[0008] Herein, in the past patent literature, there are inventions regarding 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 also means that the lubrication at the time of tightening and loosening of the threads is completed. The Mn phosphate film and the electroplated Cu film since the past are solid films. However, since lubrication is sought as a premise by coating a grease-like compound, 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] The past lubricating film used in the oil well pipe threaded joint is described, for example, in Patent Literature 1 to Patent Literature 9.

[0010] Herein, in the field of oil well pipe threads, BN is widely exemplified as one of the candidate groups of solid lubricants in many patent literatures. For example, in Patent Literature 1 and 2, there are examples in which BN is exemplified as a solid lubricant present in a solid lubricating film.

[0011] In addition, epoxy resins are exemplified in the past patent literature. However, in the past patent literature, the epoxy resin is explicitly defined, but there are few cases where the composition of the agent is defined. In addition, in the past patent literature, there are many cases where the technology is intended to be determined, but it cannot be completely determined.

[0012] The definition of the epoxy resin is very broad. The epoxy resin is generally a general term for thermosetting resins composed of a chemical substance having an epoxy group as a prepolymer (a precursor to an epoxy resin) and a curing agent crosslinked and combined with each other. However, both in academia and in commerce, when expressed as an epoxy resin on the face of the patent literature, there are cases where it refers to the chemical substance having an epoxy group of the prepolymer itself, and cases where it refers to the epoxy resin that can be produced by copolymerization of the prepolymer and the curing agent. However, they are almost all used without distinction. In the past patent literature, the epoxy resin is referred to as the latter. In any case, in the past patent literature, the epoxy resin is used only broadly (see Patent Literature 3 to 8).

[0013] Note that, in the following description, in explaining the present invention, the epoxy resin agent as a raw material (prepolymer) for producing an epoxy resin film is referred to as a "prepolymer" or a "narrowly defined epoxy resin". In addition, the epoxy resin (film) finally produced by polymerization of the prepolymer and the curing agent is distinguished as an "epoxy resin film".

[0014] Next, Patent Literature 3 to 9 will be described.

[0015] Patent Document 3 is an invention of forming a solid lubricating film on a Cu-Sn-Zn plated layer substrate. In Patent Document 3, as an adhesive resin of the solid lubricating film, a resin selected from one or both of an epoxy resin and a polyamide-imide resin is selected.

[0016] In Patent Documents 4 to 6, an epoxy resin is exemplified as a component of a solid lubricating film excellent in heat resistance and lubricity. In Patent Documents 4 to 6, as for the heat resistance of the epoxy resin, no material having how many degrees is explicitly described, and it is difficult to grasp the characteristics of the epoxy resin used.

[0017] In Patent Document 7, a two-liquid mixed type of epoxy resin is explicitly shown on a Zr-based plated layer substrate. However, the two-liquid mixed type of epoxy resin is not new, and as described above, the epoxy resin is composed of a narrow sense of an epoxy resin curing agent of a prepolymer. The two-liquid mixed type only means a type of mixing two liquids on the spot. Even if it is a one-liquid type, since it contains a prepolymer and a curing agent therein, it is not new itself.

[0018] Patent Document 8 is an invention of forming an acrylic silicone resin on an ultraviolet curing type resin. In Patent Document 8, an acrylic-modified epoxy resin is exemplified as one of the candidate groups, and a substance obtained by acrylating the terminal of an epoxy resin as a main chain skeleton is described.

[0019] In Patent Document 9, a photocurable acrylic resin film is described. Patent Document 9 describes a photocurable (meth)acrylate resin, and a film obtained by copolymerizing a (meth)acrylate monomer group based on the trigger of a photopolymerization initiator or the like is specified, and as a main chain structure forming an acrylate side chain, an epoxy resin is exemplified together with a polyester, a polyether, and a polyurethane in the candidate group.

[0020] In addition, although it is not an evaluation example of a solid lubricating film, in Non-Patent Document 1, as a tightening test method using a vertical power wrench using a short pin, a method of performing tightening and loosening while always loading a weight (510 kg weight) of 5 kN on the upper end surface of the short pin is described. However, in Non-Patent Document 1, as a means for judging whether a new thread design is possible or not, a conventional grease-like compound is used for evaluation.

[0021] Prior Art Documents

[0022] Patent Documents

[0023] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-110686

[0024] Patent Document 2: WO 2017-110685

[0025] Patent Literature 3: Japanese Patent Application Laid-Open No. 2018-216497

[0026] Patent Literature 4: Japanese Patent Application Laid-Open No. 2015-501906

[0027] Patent Literature 5: Japanese Patent Application Laid-Open No. 2015-198557

[0028] Patent Literature 6: Japanese Patent Application Laid-Open No. 2017-110685

[0029] Patent Literature 7: Japanese Patent Application Laid-Open No. 2017-71844

[0030] Patent Literature 8: Japanese Patent Application Laid-Open No. 2013-183634

[0031] Patent Literature 9: Japanese Patent Application Laid-Open No. 2011-12251

[0032] Non-Patent Literature

[0033] Non-Patent Literature 1: Tsutsui et al., Journal of the Society of Oil Technology, Vol. 61, No. 6 (1996) PP. 527-536. SUMMARY

[0034] PROBLEMS TO BE SOLVED BY THE INVENTION

[0035] The lubrication of the oil well pipe thread targeted in the present invention is in a special sliding condition.

[0036] That is, in the field (actual well), a pin of which actual length is about 8 m or more and less than about 15 m is fastened / loosened with respect to a sleeve provided below. At this time, the pin is in a condition where, although fastening and loosening are performed using a power tong in a state of being hoisted by a crane, the entire load of the pin is applied to the sleeve thread. That is, lubrication in a large load application state is performed.

[0037] Furthermore, at this point, the pin may not be tightened and loosened in an ideal state. 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. Also, the pin is not set in a state where it is tilted slightly to one side and straight, i.e., upright without bending. That is, the pin is constrained by the sleeve thread at the lower part, and the upper end (the front end opposite the tightening side) becomes slightly bent 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, if viewed from below, the pin is set straight inside the sleeve and appears bent. From this state, the pin is tightened and loosened, therefore, 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 occurs under a state of strong localized impact on a part of the thread surface. That is, it becomes lubrication under an off-center load state. Furthermore, the location of the strong localized impact also changes depending on the tightening and loosening.

[0038] 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 loosening of the fastener in a favorable direction. Consequently, in evaluation tests of threaded joint tightening and loosening (also known as laboratory tests), the lubrication condition of the actual-sized pin can be assessed using the evaluation of a short pin, without relying on evaluation using the actual-sized pin.

[0039] 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 products from the ground-off solid lubricating film do not necessarily move in conjunction with the tightening and loosening and always follow the movement.

[0040] The above points illustrate the significant differences between solid lubrication films and lubrication using lubrication compounds in actual well operations.

[0041] When evaluating solid lubricating films through laboratory tests, in evaluations using short pins in the same manner as those using lubricating compounds, the effects of large / eccentric loads may not be simulated for the reasons stated above. In evaluations using short pins shorter than those used in actual wells, it was found that the solid lubricating film is difficult to grind away, and conditions that can simulate the burning behavior in actual wells cannot be formed.

[0042] Thus, in the past evaluation using a short pin, it was not possible to simulate a situation in which a secondary product formed of grinding chips of the solid lubricating film clogs and burns, or a secondary product is pressed again against the fastening surface to have the effect of a lubricating film, and the like. That is, in the past evaluation using a short pin alone, the evaluation of the solid lubricating film becomes loose regardless of the circumstances, and when deciding the physical property parameters of the solid lubricating film, a region that is not qualified in the first place is erroneously evaluated as a suitable range.

[0043] For this reason, the inventors have come to the understanding that in the past existing literature, the actual situation is that a suitable range is described based on the loose evaluation as described above.

[0044] Furthermore, the inventors have come to the understanding that it is necessary to perform evaluation on the premise that the fastening and loosening is performed under the same conditions as those exposed to the actual well pipe thread, that is, under a large load / uneven load, and to make a provision of a parameter group relating to the solid lubricating film. Thus, the inventors have come to the understanding that it is necessary to set each provision on the basis of the meaning of the provision of the upper and lower limits of the parameters, which is clear in terms of the guarantee of lubricity in accordance with the actual conditions of use in the well, and the like. That is, the inventors have come to the understanding that in the evaluation that conforms to the conditions of the actual well, it is important to make a provision of the upper and lower limits of the parameters.

[0045] Here, as described above, in the evaluation of the lubricating behavior that should be confirmed in the lubrication of the well pipe thread, in the past, the fastening and loosening behavior using a power tong, the number of fastening and loosening, using a short pin, has been taken as the evaluation target.

[0046] At this time, in the case where a grease-like compound is used as the lubricant, the compound also moves in conjunction with the fastening and loosening. Thus, in the evaluation of the lubrication, there is no particular problem whether the evaluation is performed using a short pin in a horizontal tong or in a vertical tong, and the lubricating behavior can be evaluated. That is, for the past grease-like compound, including the design of the thread, the possibility of a base layer such as a chemical conversion treatment layer or an electroplated layer, comparative evaluation of the compound itself, and the like, laboratory testing using a short pin can also be performed.

[0047] On the other hand, in the case of lubrication of the solid lubricating film, there is a problem in the evaluation as described above. That is, in the evaluation based on the laboratory testing using a short pin alone, a simulation of the behavior in the actual well is not performed, and the evaluation of the lubrication becomes quite loose. Thus, in the past laboratory testing, there is a problem in that even if the evaluation using a short pin is "qualified", it does not necessarily mean that the evaluation is "qualified" in the fastening and loosening in the actual well.

[0048] In addition, the lubrication of the well pipe thread is different from other lubricating behaviors, and thus, there is a problem in that the provision of the evaluation based on the other lubrication conditions cannot be applied.

[0049] Generally, if the lubrication behavior between two objects that are rubbed is considered, a situation in which one is fixed and the other moves is assumed. Also, for the moving object, it is assumed that lubrication starts from a state in which it is tightly fitted to the fixed object. Even in the case where both objects move, lubrication often starts from a state in which they are in close contact with each other.

[0050] On the other hand, in the lubrication of oil well pipe threads, 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). Therefore, before the threads are engaged with each other to a certain extent, the threads do not always stably contact each other. That is, in the lubrication of oil well pipe threads, the cases of strong collision and the cases of almost no collision are uneven, and the risk of damage to the lubricating film is high at the time of strong collision. Furthermore, in the lubrication after the threads are engaged, sliding is affected by the lubrication conditions on the spot.

[0051] Particularly in the case where there is "play" until the threads are engaged, in the conventional method using a grease-like compound, at the initial stage of tightening and at the final stage of loosening where there is play in the threads, the compound moves in conjunction with the tightening of the threads. Therefore, the influence of this play is small. On the other hand, in the case of a solid lubricating film, there is a difference in that it is directly affected by the eccentric load caused by the play, and the solid lubricating film is easily damaged.

[0052] In addition, in actual wells, at the time of tightening and loosening, there is an influence 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 for the pin to rotate eccentrically. Therefore, the solid lubricating film must be a film that is resistant to lubrication under a large load applied as an eccentric load. A film that falls off without fail, or a film that almost disappears due to damage, cannot be dealt with. In actual wells, oil well pipes are mostly used at a length of about 12 m to about 16 m. For example, an oil well pipe of a length of about 12 m (about 40 feet) becomes a dead weight of about 1 t load under an outer diameter of 9-5 / 8". In offshore drilling rigs, a pin thread that is connected to three in advance is mostly used for tightening, and therefore, if an 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.

[0053] In the lubrication of oil well pipe threads, lubrication that can withstand such a large load and an eccentric load needs to be assumed. Also, as a result of various studies by the inventors, the following insight was obtained: It is important to consider how to suppress damage to the solid lubricating film in the case where there is "play" before the threads are engaged under a large load, and research was conducted on solid lubricants and binder resins with this point in mind.

[0054] On the other hand, in the past literature, it is difficult to say that the design of the solid lubricating film is made based on such a viewpoint.

[0055] Here, the inventors have obtained such an insight that the above insight is peculiar to the solid lubricating film.

[0056] In the past lubrication of the grease-like compound, in conjunction with the tightening and loosening, the viscous liquid-like grease-like compound also moves in conjunction, and thus, the influence of the large load and the eccentric load is considerably mitigated. Therefore, with reference to the past literature, whether the evaluation is made using a short pin with a horizontal clamp or using a short pin with a vertical clamp, the lubrication behavior can be evaluated without any particular problem.

[0057] On the other hand, in the case of the lubrication behavior of the oil well pipe thread using the solid lubricating film as in the present application, in the tightening before the thread engagement and the tightening after the engagement, the solid lubricating film is also damaged and peeled or inevitably thinned gradually. The debris of the peeled solid lubricating film does not necessarily move in conjunction with the tightening and loosening unlike the grease-like compound. Moreover, the inventors have obtained the insight that the influence of the secondary product (debris) from the thinned solid lubricating film released to the gap between the pin thread and the sleeve thread has a large influence on the lubrication. That is, if the gap is clogged with the grinding debris, it sometimes directly leads to the burn. On the other hand, there is a case where the debris is reconstituted by being pressed with a large load, and then attached to either of the threads in the form of a film again, thereby improving the lubrication.

[0058] Moreover, the inventors have obtained the insight that in the evaluation using a short pin in the laboratory test, the conditions of the large load and the eccentric load occurring in the actual well cannot be simulated. That is, in the evaluation using only the short pin, the generation of the secondary product from the solid lubricating film itself is small. Therefore, the lubrication behavior is erroneously determined to be acceptable in most cases, and the poor design of the solid lubricating film is noticed after the application to the actual well in most cases.

[0059] Moreover, in the laboratory test, if the condition of the presence of "looseness" before the thread engagement is not intentionally made, the occurrence in the actual well cannot be simulated. On the other hand, the use of the actual size pin and the test in the actual well and the simulation well (experimental field in which the actual size pin is erected and tightened and loosened) each time is also unrealistic. That is, the experimental cost becomes enormous, and it is unrealistic. For example, the latter costs a rental fee of about 10 million yen or more per day, and in the solid lubricating test, the maximum number of times of tightening and loosening is estimated to be 20 to 30 times, and a huge cost is incurred.

[0060] Moreover, in the past literature, the evaluation of the solid lubricating film has hardly been considered in this way. That is, the evaluation of the lubrication of the thread is not particularly specified, but there are many cases of application of a vertical clamp using a short pin alone, which is common in laboratory tests. In the past evaluation, the evaluation is made excluding the influence of the above-mentioned large load / eccentric load, and thus, basically, most of them show good evaluation results. Therefore, even if the appropriate upper and lower limits of the lubrication using the solid lubricating film are specified by these evaluation methods, it does not mean the appropriate range in the true sense. Thus, even the conditions selected by the short pin evaluation in the past laboratory tests include conditions that cannot be called good lubrication in the actual well, and it cannot be said that the technology is determined.

[0061] Here, although it is not an investigation of the lubrication behavior of the solid lubricating film, it is described in Non-Patent Literature 1 that a load of 510 kg weight is continuously applied to the upper end of the pin at all times at the time of tightening and loosening of the thread. The application of a load of 510 kg weight can have the intention of applying a weight equivalent to one pin of the actual size of the 7" size. As described above, in the evaluation of the solid lubricating film, it is important to simulate the large load and the eccentric load that occur in the actual well. This is because the secondary phenomena caused by the secondary products from the solid lubricating film have a great influence on the lubrication.

[0062] However, in the case of applying the method disclosed in Non-Patent Literature 1 to the laboratory test, there are two problems.

[0063] The first problem is that a load equivalent to one to three connections of the actual size pin in the actual well is applied in the actual well, but the application of 510 kg weight can only cope with a specific case where the pin is light. That is, depending on the size of the pin, the large load is not necessarily simulated.

[0064] The second problem is that the eccentric load cannot be simulated. If judged from the Figure 5 and the like, the intention of Non-Patent Literature 1 is to test the lubrication that starts from the state in which the threads are engaged with each other at the initial tightening position (tightening start point) based on manual tightening, especially at the premium joint, without one rotation before tightening. In addition, although it is difficult to notice, at the time of loosening, if the loosening is continued in the state in which the load of the weight is applied, there is also a problem as follows.

[0065] That is, when loosened, the weight becomes a balancer, and the threads are straightly relaxed from the tightened position without causing slackening. Thus, the pin does not swing, and the burn-on generation at the time of loosening occurring in the actual well cannot be properly simulated. Therefore, depending on the situation, a situation that is misinterpreted as a good lubricating property can occur. Thus, the following insight is also obtained: for the condition parameters related to the solid lubricating film, it is necessary to take into account the lubricating state of the state in which the threads are not sufficiently engaged and the lubrication after engagement to simulate, and it is proven that the lubricating property is excellent.

[0066] Here, as described above, in the field targeted by the present application, as an example of the candidate group of solid lubricants, BN is widely exemplified in many patent documents. For example, in Patent Documents 1 and 2, there are examples in which BN is exemplified as a solid lubricant present in a solid lubricating film. However, from the viewpoint of being able to guarantee the lubricity of the lubricating behavior tolerable in the actual well as described above, defining it as BN only as a broad summary cannot maintain lubrication.

[0067] In addition, although there are examples in which epoxy resin is exemplified as an adhesive resin in the past patent documents, there are few cases in which the adhesive resin can be clearly defined depending on the quality of the epoxy resin.

[0068] In Patent Documents 3 to 8, a substance in which a prepolymer and a curing agent are mixed is referred to as an epoxy resin, or an epoxy resin film produced by them is referred to as an epoxy resin, and only one of the candidate materials is exemplified. Moreover, the epoxy resin is broadly defined, and it is not clear what is determined.

[0069] Here, the epoxy group refers to a three-membered ring having an oxygen group of an oxirane (oxirane), and in order to form a resin, an appropriate curing agent is selected to perform a cross-linking reaction. This means ring-opening polymerization of the three-membered ring. In summary, the epoxy group does not exist in a state of an epoxy resin, and becomes a final form of a polyether (containing R-O-R'), a polyester (containing R-COO-R'), a polyhydroxy ether (containing an -OH group and an ether group), a polyhydroxy amine (containing an -OH group and an amine group), and the like.

[0070] The film properties also inherit the properties of the narrow-sense epoxy resin and the properties of the curing agent. Therefore, even with the broad-sense epoxy resin, it is not possible to determine any technology. The properties of the epoxy resin film also depend on the combination of the "narrow-sense epoxy resin" reagent as the prepolymer and the curing agent, and even if only the narrow-sense epoxy resin reagent is described, it is not possible to determine the properties of the epoxy resin film. If the past patent documents are read, it can be interpreted that any epoxy group can be widely applied, but this is not necessarily the case. It is almost impossible to ensure the high lubricity targeted by the present application. In order to achieve the purpose, as the final form, it is also necessary to select an epoxy resin film with excellent high lubricity.

[0071] In addition, in the past patent literature, the expression "epoxy resin (approximately an epoxy resin film as a final film composed of an epoxy resin and a curing agent) of OO% is also ambiguous. As described above, in the combination of the narrow sense of an epoxy resin and a curing agent, if the epoxy resin is set as A and the curing agent is set as B, they are polymerized in the manner of ABABA... The addition of the equivalent of the epoxy group of the narrow sense of the epoxy resin, the equivalent of the amine when the curing agent is an amine type, or the equivalent of the active hydrogen when it is another curing agent containing an amine is the general blending rule of the epoxy resin. Therefore, even the expression of the weight of the epoxy resin coating film, depending on the selection of the prepolymer and the curing agent, becomes a value with considerable deviation. In the expression of "epoxy resin of OO% only, it cannot be said that the epoxy resin can be clearly indicated, and the technology is not certain.

[0072] That is, even if simply expressed as an epoxy resin, only using an epoxy resin reagent as a raw material (prepolymer), by the selection of the curing agent, it becomes a high molecular body with a completely different structure. Therefore, as long as the range of the parameter that does not clearly regulate the physical properties of the "epoxy resin" as the final cured object, or the physical properties of the reagent containing the epoxy group of the prepolymer, or the curing agent, or the secondary regulation of them, the technology is not regulated.

[0073] In addition, in Patent Literature 3, as a material formed on a Cu-Sn-Zn plated layer substrate, a material selected from one or both of an epoxy resin and a polyamide-imide resin is selected. It is unknown what the epoxy resin described here means. That is, it also widely includes an epoxy resin whose lubricity is not necessarily good.

[0074] In Patent Literatures 4 to 7, for a solid lubricating coating film, only an epoxy resin is exemplified, which is also difficult to determine.

[0075] Patent Literature 8 is an invention of forming an acrylic silicone resin on an ultraviolet curable resin. As for the binder resin of the ultraviolet curable resin, an acrylic-modified epoxy resin is exemplified as one of the candidate groups among organic resins and inorganic resins. In addition, the main chain skeleton is an epoxy resin, and the end thereof is acrylated. Only the epoxy resin coating film is exemplified, and there is no specific information on the curing agent or the characteristics of the epoxy resin.

[0076] On the other hand, Patent Literature 9 describes a photocurable acrylic resin coating film. In the photocurable (meth)acrylate resin, a (meth)acrylate monomer group is copolymerized with a trigger such as a photopolymerization initiator to form a film. Furthermore, in the main chain structure in which an acrylate side chain is formed, an epoxy resin is exemplified in the candidate group together with a polyester, a polyether, and a polyurethane. This invention uses a unit system of PHR (per hundred resin) to express the acrylate (corresponding to the prepolymer of the present invention) and the polymer (corresponding to the curing agent of the present invention), and in the case where the epoxy resin is the main chain structure, the proportion and the weight of the epoxy resin can be accurately expressed. The description of Patent Literature 9 is more explicit than the definitions in Patent Literatures 3 to 7. However, on the other hand, the present invention is not a photopolymerization resin but a film to be made by curing, and therefore the technology of Patent Literature 9 is different from the present invention.

[0077] The present invention has been accomplished in consideration of the above, and aims to provide a solid lubricating coating film which can impart lubricity and excellent corrosion resistance to an oil well pipe thread even when a solid lubricating coating film is used in lubrication.

[0078] Method for solving the problem

[0079] In the past, in view of the above-described situation in which a lubricating material is selected by loose evaluation, the inventors have taken as an object an oil well pipe, an oil well pipe thread joint, and a reagent for producing them, which have both excellent lubricity and rust prevention properties. In an adhesive resin in which an epoxy resin is the main component, BN is contained as a solid lubricating component in an appropriate proportion, and other additives are appropriately added, and such a composition is taken as an object. These films are constructed with prescribed parameters so as to be able to withstand under strict lubrication conditions in the lubrication of an actual oil well pipe thread under a large load and an eccentric load as described above.

[0080] That is, one embodiment of the present invention is a reagent for forming a solid lubricating coating film on a threaded portion of an oil well pipe, the gist of which is that a solid lubricant is dispersed in an adhesive resin, the adhesive resin including a prepolymer and a curing agent, the prepolymer including one or two or more kinds of epoxy resins, 70 parts by weight or more of the prepolymer being contained with respect to 100 parts by weight of the adhesive resin, the epoxy equivalent weight of the epoxy resins constituting the prepolymer being in a range of 100 or more and 500 or less, 80% by weight or more of the solid lubricant being BN (boron nitride), the average particle diameter of the BN being 10 μm or less, and the total weight of the solid lubricant being 0.1 times or more and 2 times or less of the total weight of the adhesive resin.

[0081] Further, the oil well pipe of the present application is an oil well pipe in which a lubricating coating having a solid lubricating coating is formed on a threaded portion, and the main point of the present application is that the solid lubricating coating is formed by dispersing a solid lubricant in a binder resin, the binder resin contains an epoxy resin cured by a curing agent, the binder resin contains 70 parts by weight or more of the epoxy resin with respect to 100 parts by weight of the binder resin, the epoxy equivalent of the epoxy resin is in a range of 100 or more and 500 or less, 80% by weight or more of the solid lubricant is BN (boron nitride), the average particle diameter of the BN is 10 μm or less, and the total weight of the solid lubricant is 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0082] Effects of the Invention

[0083] According to one embodiment of the present application, the specifications (physical property parameters) of the binder resin (main component: epoxy resin) and the solid lubricant (main component: BN) that constitute the solid lubricating coating are comprehensively defined, with reference to the evaluation based on the newly designed laboratory test that can reproduce the behavior in the actual well. As a result, according to one embodiment of the present application, a reagent that can form a solid lubricating coating (lubricating coating) can be provided, in which even when the solid lubricating coating is used in lubrication, it is possible to impart lubricity that is equal to or higher than the lubricating grease-like composite that has been used conventionally, and lubricating properties and corrosion resistance that match the storage rust-preventive grease-like composite and the oil-like rust-preventive material.

[0084] For example, according to the embodiment of the present application, an oil well pipe threaded joint having lubricating properties at the time of fastening and corrosion resistance that take into account conditions equivalent to the actual well that can occur in the actual well environment can be obtained. Note that the conditions equivalent to the actual well refer to conditions such as a situation in which a pin weight is applied to a box from above, a situation in which a load is applied obliquely due to axial misalignment, a situation in which a load is applied unevenly and locally, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 FIG. 1 is a view showing an oil well pipe and an oil well pipe threaded joint.

[0086] Figure 2 FIG. 2 is a view (a) of a fastening diagram in an actual well and a view (b) showing an initial setting position at that time.

[0087] Figure 3 FIG. 3 is a view (a) of a fastening diagram in a conventional laboratory test and a view (b) showing an initial setting position at that time.

[0088] Figure 4 FIG. 4 is a fastening diagram schematic view, (a) is the case of an actual well, and (b) is the case of a conventional laboratory test.

[0089] Figure 5 is a graph showing a new laboratory test (the weight hammer test).

[0090] Figure 6 is a graph showing an example of the setting of the weight in the new laboratory test (the weight hammer test).

[0091] Figure 7 is a graph illustrating a coating structure. DETAILED DESCRIPTION

[0092] Next, an embodiment of the present application will be described with reference to the accompanying drawings.

[0093] Conventionally, for the purposes of lubrication and rust prevention during storage, in order to achieve both purposes, the lubrication of fastening and loosening and the long-term outdoor storage (rust prevention) are addressed by using different kinds or the same kind of grease-like compounds.

[0094] In contrast, in the threaded structure of the present embodiment, in one or both of the portions in which the metal of the outer thread side of the threaded base material and the metal of the inner thread side contact each other, or a part thereof, an epoxy resin coating in which parameters are appropriately specified is used as an adhesive resin. Furthermore, a solid lubricating coating in which BN, which is a solid lubricant, is dispersed in the coating is used. Thus, the present embodiment aims to improve lubrication and impart corrosion resistance.

[0095] In addition, the reagent used to form the solid lubricating coating is also an object. In addition, a lubricating coating in which the coating of the present embodiment is combined with a base layer, and a coating structure in which the hardness of the coating including the other side of the unformed side is suitable for oil well pipe thread lubrication are also objects. In addition, as another use, the present embodiment can be applied to the range in which the lubricating coating can be widely expanded to the improvement of lubrication and rust prevention of metal materials.

[0096] In view of the above problems, the inventors have conducted research, and as a result, by the formulation of the reagent, the development of the solid lubricating coating of the oil well pipe thread, and the confirmation method thereof, the above problems can be solved.

[0097] The solid lubricating coating of the present embodiment is researched with the main component of the adhesive resin being an epoxy resin after curing by a curing agent, and the main component of the solid lubricant being BN (boron nitride).

[0098] (CONSTITUTION)

[0099] The present embodiment is an invention relating to a coating film structure formed on a fastening surface of a threaded portion of an oil well pipe and a structure having the coating film structure as a lubricating coating film in an oil well pipe and an oil well pipe threaded joint used in actual oil / gas. In the present embodiment, the lubricating coating film having a solid lubricating coating film formed on the threaded portion of the oil well pipe has characteristics, and the threaded structure of the oil well pipe and the threaded joint thereof is not particularly limited. The threaded structure of the oil well pipe and the threaded joint thereof can adopt a known or new threaded structure.

[0100] <Oil well pipe and oil well pipe threaded joint>

[0101] The oil well pipe, for example, includes Figure 1 The sleeve 2, the pin 1, and the like.

[0102] As shown in Figure 1 The oil well pipe threaded joint includes a sleeve 2 such as a coupling having an internal thread 2a and a pin 1 having an external thread 1a. Moreover, a lubricating coating film having a solid lubricating coating film is formed on a contact surface (fastening surface 10) of a threaded portion of a member of at least one of the sleeve 2 and the pin 1.

[0103] <Reagent>

[0104] Hereinafter, a reagent for forming a solid lubricating coating film in the present embodiment will be described.

[0105] The reagent of the present embodiment is constituted by dispersing a solid lubricant in a binder resin as a base component.

[0106] The reagent includes a binder resin, a solid lubricant, and a solvent component.

[0107] The binder resin includes a prepolymer and a curing agent.

[0108] The prepolymer is constituted by one or two or more kinds of epoxy resins. The prepolymer is included in the binder resin at 70 parts by weight or more with respect to 100 parts by weight of the binder resin.

[0109] The epoxy equivalent weight of the epoxy resin constituting the prepolymer is in a range of 100 or more and 500 or less.

[0110] The glass transition temperature Tg of the epoxy resin constituting the prepolymer is preferably 100°C or more.

[0111] 80% by weight or more of the solid lubricant is BN (boron nitride). The average particle diameter of the BN is 10 μm or less.

[0112] The total weight of the solid lubricant is 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0113] The solvent component preferably contains 30 parts by weight or more and 80 parts by weight or less relative to 100 parts by weight of the total weight of the solid lubricant and the total weight of the binder resin excluding the curing agent.

[0114] In addition, the agent contains 0 parts by weight or more and 10 parts by weight or less of a curing accelerator relative to 100 parts by weight of the total weight of the epoxy resin constituting the prepolymer.

[0115] The curing agent can be, for example, a curing agent that cures an epoxy resin, including an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent.

[0116] At this time, the epoxy resin constituting the prepolymer preferably has more than 2 epoxy groups (a multifunctional epoxy resin). The epoxy resin constituting the prepolymer preferably has 6 or fewer epoxy groups. More preferably, the epoxy resin constituting the prepolymer has 4 or fewer epoxy groups.

[0117] The viscosity of the agent including the above-described components is preferably 20 mPa-sec or more and 2000 mPa-sec or less.

[0118] The agent of the present embodiment is applied to a threaded fastening surface and dried to form a solid lubricating film 10A (see FIG. 1). Figure 7 (a)).

[0119] <Lubricating Film Having Solid Lubricating Film 10A>

[0120] The solid lubricating film 10A is constituted by dispersing a solid lubricant in a binder resin as a base component.

[0121] The binder resin includes a prepolymer and a curing agent, and the prepolymer and the curing agent undergo polymerization and curing.

[0122] The prepolymer includes one or two or more kinds of epoxy resins. The prepolymer is included in an amount of 70 parts by weight or more relative to 100 parts by weight of the above-described binder resin.

[0123] The epoxy resin constituting the prepolymer has an epoxy equivalent weight in the range of 100 or more and 500 or less.

[0124] The epoxy resin constituting the prepolymer preferably has a glass transition temperature Tg of 100°C or more.

[0125] 80% by weight or more of the solid lubricant is BN (boron nitride). The average particle diameter of this BN is 10 μm or less.

[0126] The total weight of the solid lubricant is 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0127] The curing agent is, for example, a curing agent for curing an epoxy resin, and includes an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent.

[0128] At this time, the epoxy resin constituting the prepolymer preferably has more than 2 epoxy groups (a multifunctional epoxy resin). The epoxy resin constituting the prepolymer preferably has 6 or less epoxy groups. More preferably, the epoxy resin constituting the prepolymer has 4 or less epoxy groups.

[0129] The solid lubricating film 10A of the present embodiment has, for example, a hardness of 3H or more.

[0130] The thickness of the solid lubricating film 10A is, for example, 10 μm or more and 150 μm or less.

[0131] The lubricating film of the present embodiment can have a base layer 10B (refer to Figure 7 (b)) between the fastening surface of the threaded portion of the sleeve and the above-described solid lubricating film 10A.

[0132] The above-described lubricating film is formed on the fastening surface of the threaded portion of at least one of the sleeve and the pin.

[0133] <Decisions on Each Provision>

[0134] The inventors have reached the following four points (a) to (d) and related matters concerning them are important in order to solve the above-described problems.

[0135] (a) Designing an appropriate new laboratory test that simulates the fastening and loosening in an actual well, and by the method of the new laboratory test, defining the upper and lower limits of each parameter for the solid lubricating film, and specifying the appropriate range thereof;

[0136] (b) Referring to the evaluation of the laboratory test of (a), defining the optimum range of BN;

[0137] (c) Using the provision of (b) to define the optimum range of the physical property values of the epoxy resin;

[0138] (d) Further, defining the appropriate range related thereto.

[0139] Here, the appropriate method that simulates the fastening and loosening in an actual well means a method that simulates the fastening behavior that occurs when the oil well pipe threads are fastened in an actual well. Using this method, the upper and lower limits of the parameters of the present embodiment are confirmed, and the appropriate range is determined.

[0140] The state of lubrication of the threads of oil well pipes is divided into two stages, either in a laboratory test or in an actual well. Stage 1 is lubrication at the time of tightening and loosening when the threads are not engaged with each other, and stage 2 is lubrication at the time of tightening and loosening when the threads are engaged with each other. Stage 1 corresponds to the region of (x) in the torque rotation diagram of Figure 4 , for example. Stage 2 corresponds to the region of (y) (z) of Figure 4 , for example.

[0141] As to the former (stage 1), if the portion to be engaged with the threads is tightened by hand or the like at the start of tightening of the threads, this stage disappears (Example: Figure 3 ). However, in many actual wells, only the insertion of the pin into the sleeve provided as the start position of tightening is performed. Or, after this, only a few turns are tightened to be fixed slowly in a manner not to cause cross-threading as the start position of tightening. That is, in many actual wells, tightening and loosening is generally performed from the condition where the threads are not engaged (Example: Figure 2 ). Note that cross-threading means the condition where the threads are tightened in a state of different heights, or the threads slide to the formal thread position during closing.

[0142] Further, in stage 1, tightening and loosening is performed at a high speed of 5 to 20 rpm using a wrench. On the other hand, if the threads are continued to be tightened, the threads start to be engaged and shift to stage 2. By this shift, the torque slightly rises, and thus, from this point, tightening is performed slowly at a speed of approximately 0.5 to 2.0 rpm. At the time of loosening, the reverse procedure is taken.

[0143] These procedures are the same when the conventional grease-like compound is used as lubrication, or when the solid lubricating film of the present embodiment is additionally used. Also, as to the condition of the setting of the threads at the initial position, the behavior at the time of loosening is important. As to the setting position, at the time of initial tightening of the pin threads, the thread is exposed by approximately 1 to 3 teeth or so with respect to the sleeve threads, which is important in studying the behavior of the joint.

[0144] <Concerning Figure 2 >

[0145] Figure 2 is an example of simulating an actual well as it is. That is, Figure 2 is a tightening diagram (torque rotation diagram) at the time of tightening test using a pin of an actual length of 40 feet (≈ 12 m) as the pin and using the solid lubricating film in lubrication.

[0146] The test conditions of Figure 2 (a) are described.

[0147] As an example, as the solid lubricating coating, a solid lubricating coating obtained by dispersing MoS2 as a solid lubricant in a binder resin of PAI (polyamide imide) is used.

[0148] In addition, Figure 2 is an example simulating the situation that is mostly performed in actual oil / gas fields. That is, it is an example in which the initial setting position at the start of fastening, such as Figure 2 (b) is an example in which fastening is started from a situation in which the threads are not sufficiently engaged with each other. That is, as shown in Figure 2 (b), it is an example in which fastening is started from a situation in which the pin threads are exposed by about half or so from the start of initial fastening. The threads are not engaged with each other and this is not caused by intentionally stopping the manual fastening. Even if the pin threads are desired to be set to the box threads by manual fastening, it is inevitably stopped halfway. Above all, fastening by manual fastening is not possible. As theoretically depicted, for a long and heavy actual length pin, it is not that the pin is strictly upright with respect to the box threads. If seen from below to above, it is slightly bent, and above all, fastening by manual fastening is not possible, which is generally occurring.

[0149] The pin used is a 9-5 / 8" 53.5# Q125 JFELION TM threaded and about 40 feet long. Also, Figure 2 (a) is a graph at the time of fastening of the joint while the pin is hoisted by a crane in a form in which the pin is hoisted from above the drilling rig with the full length. Figure 2 The example of the torque rotation graph of (a) can be considered as a situation that often occurs in actual wells.

[0150] In Figure 2 (a), attention should be paid to the region before the point at which the torque continuously increases (zero to about 6.3 revolutions: corresponding to Stage 1). In this region, the torque should not rise in principle, but actually, as shown in Figure 2 (a), it can be confirmed that there is a tendency that the peak-shaped torque irregularly frequently rises. This indicates that the pin threads are irregularly and locally in contact with the box threads while rotating. This is a situation that occurs in actual fastening.

[0151] This means that, due to the design, optimization of the solid lubricating coating, it is unavoidable to some extent that the solid lubricating coating is damaged, peeled off.

[0152] Here, attention is paid to the fact that Figure 3 (a) is a torque rotation graph of a sample with a solid lubricating coating as a condition, not intentionally formed in the worst state, but very commonly.

[0153] <About Figure 3 >

[0154] Figure 2 (a) is a torque rotation chart in the case where the same solid lubricating coating is used and fastening is performed with a vertical power wrench. Figure 3

[0155] In (a), the same outer diameter, wall thickness, and screw type are used as in (b), but a short pin of about 1 m in length is used as the pin. Figure 2 Figure 3 In (a), the same outer diameter, wall thickness, and screw type are used as in (b), but a short pin of about 1 m in length is used as the pin.

[0156] In addition, Figure 3 (a) is a fastening-time chart (torque rotation chart) when fastening is started from a state in which the threads are sufficiently engaged with each other. That is, as shown in (b), it is a fastening-time chart (torque rotation chart) when the number of pin thread teeth exposed at the start of initial fastening is 1 to 3 teeth. Figure 3 (b) is a fastening-time chart (torque rotation chart) when the number of pin thread teeth exposed at the start of initial fastening is 1 to 3 teeth.

[0157] The Figure 3 conditions of (a) are also conditions that are frequently used at the time of fastening in the past laboratory test, and are cases in which fastening tests are performed after manual fastening is performed to a thread engagement state.

[0158] In (a), the unit of the horizontal axis is different from that in (b). Figure 2 Figure 3 In (a), since fastening with a wrench is performed from a state in which manual fastening is performed to a thread engagement state, the sharp peak of torque shown in (a) is not seen. That is, it is understood that the lubricating properties of the solid lubricating coating are examined only in stage 2 without passing through stage 1, which corresponds to the past laboratory test.

[0159] In (a), since fastening with a wrench is performed from a state in which manual fastening is performed to a thread engagement state, the sharp peak of torque shown in (a) is not seen. That is, it is understood that the lubricating properties of the solid lubricating coating are examined only in stage 2 without passing through stage 1, which corresponds to the past laboratory test. Figure 2 Figure 3 In (a), since fastening with a wrench is performed from a state in which manual fastening is performed to a thread engagement state, the sharp peak of torque shown in (a) is not seen. That is, it is understood that the lubricating properties of the solid lubricating coating are examined only in stage 2 without passing through stage 1, which corresponds to the past laboratory test.

[0160] In (a), since fastening with a wrench is performed from a state in which manual fastening is performed to a thread engagement state, the sharp peak of torque shown in (a) is not seen. That is, it is understood that the lubricating properties of the solid lubricating coating are examined only in stage 2 without passing through stage 1, which corresponds to the past laboratory test. Figure 4 <About

[0161] > Figure 4

[0162] Figure 2 is a chart in which (a) and (a) are set to a state that is easy to compare. Figure 3 Figure 4 (a) is an example of

[0163] (b) is an example of Figure 2 Figure 4 Figure 3 Figure 4

[0164] ​​​​​​​​​According to the inventors' research, considering the actual use in a well, the ideal solid lubricating film is preferably one that is not damaged, will not be damaged, or peeled off in the region of (x) of (a) Figure 4 The region of (x) of (a) is one in which the solid lubricating film is not damaged, will not be damaged, or peeled off. Alternatively, it can also be allowed if the peak rises slightly. In addition, it is preferable to be designed in such a way that, even in the case where the solid lubricating film is damaged, the secondary products from the solid lubricating film that are peeled off do not clog the thread gap during the tightening and loosening process, but rather, adhere well to the threads, assisting in lubrication.

[0165] To this end, it is important to control the film quality of the solid lubricating film to be hard to a prescribed hardness or more. As an evaluation method for this hardness, the pencil hardness, which is an index for scratch resistance, can be exemplified. However, as a reagent for the solid lubricating film, it is preferable to suppress the viscosity to a degree that enables spray coating, brush / brush coating when forming the lubricating film, and to be able to coat without film thickness unevenness. Furthermore, at the time of the firing process (Curing process), it is preferable to make the constituent components of the solid lubricating film behave like rubber to liquid and become a single film and a smooth film with each other under the surface tension.

[0166] In addition, in the research evaluation method of the laboratory test of the present embodiment, for the purpose of simulating the tightening and loosening behavior in an actual well, it is preferable to evaluate by a new laboratory test having the conditions of (1) to (6) described below. Note that an example of the device configuration for the actual laboratory test will be described later.

[0167] (1) Set to a state in which a weight corresponding to the weight of 1 to 3 actual size pins is provided on the upper portion of the short pin.

[0168] (2) Stop the initial set position of the short pin thread and the sleeve thread at about half of the pin thread teeth, for example, set so that half is exposed, that is, stop at a degree at which the short pin thread is weakly hooked, and start the tightening and loosening test.

[0169] (3) Start tightening at a high speed of 15 rpm from the state of "(2)", and continue tightening until a prescribed or greater torque is detected.

[0170] (4) If the torque rises, temporarily stop, and tighten at a low speed of 1 rpm (end of tightening).

[0171] (5) Loosening is performed using the reverse procedure.

[0172] (6) If the short pin thread is completely removed, observe the pin thread tooth surface and the sleeve thread surface (blow air to observe according to the situation), and determine whether or not abnormality such as burning has occurred. If there is no problem, repeat from "(2)" onward.

[0173] If the minor burn is on the threaded part (burns on the sealing part are not related to the degree of burns and are all NG), then make corrections, apply a repair solid lubricant as needed, and repeat the steps after “(2)”.

[0174] In this embodiment, based on this evaluation method, a new evaluation of the lubrication characteristics of the solid lubricating film is performed, and suitable conditions related to the solid lubricating film are screened (see embodiment).

[0175] Here, if we judge based on the results of many tightening and loosening tests (laboratory tests) in the past literature, it is considered that the previous laboratory tests focused on the lubrication after thread engagement. Figure 2 The object is the condition of regions (y) and (z) of (a)(b). The quality of lubrication is considered based on the condition of region (x) in previous laboratory tests, i.e., the condition where the torque rises in a peak-like manner, and the condition of a healthy solid lubricating film. That is, in previous laboratory tests, using short pins and evaluation with horizontal or vertical pliers, starting from the position where the threads are fully engaged by manual tightening, it appears as if a tightening and loosening process has been performed. In patent literature that explicitly records the number of tightening and loosening cycles, there are statements that in actual well tightening, if it is a small-diameter size, up to 10 cycles can be performed. However, whether based on the evaluation of short pins or the evaluation of actual wells, if the initial setting position (tightening start position) starts from the position where the threads are fully engaged, it appears to be a possible number of cycles.

[0176] On the other hand, in past literature, for large diameter sizes such as 9-5 / 8” and 13-3 / 8”, there are scattered statements indicating that the number of tightening and loosening operations based on solid lubricating films can reach 15-20 times. However, in actual well tightening and loosening, that is, when the actual size pin has its own weight and the threads are not engaged, it is considered to be almost non-existent in cases involving large diameters using solid lubricating films.

[0177] Of course, simulating actual tightening and loosening conditions is important for evaluating the lubricity of the solid lubricant film. When looseness exists before thread engagement, the evaluation needs to be based on the state of peeling or damage to the solid lubricant film. In this embodiment, various specifications have been made with reference to the results of new laboratory tests that can be evaluated under such conditions.

[0178] The solid lubricating film of this embodiment is based on the premise that a solid lubricating film is formed by dispersing BN, which is the main component of solid lubricant, in an adhesive resin in which epoxy resin film is the main component, and the conditions are specified with reference to the results of new laboratory tests.

[0179] Further, each of the provisions will be described in detail.

[0180] <Basic configuration, film thickness and film structure of solid lubricating film>

[0181] In the present embodiment, the solid lubricating film is configured by dispersing a solid lubricant with BN as the main component in an epoxy resin cured film. It is particularly preferable to obtain a hardness of 3H or more in terms of pencil hardness.

[0182] In the present embodiment, BN is selected as the main component as the solid lubricant in order to make a film that can obtain high lubrication, and in order to make a film that can maintain high lubrication even at high temperatures. That is, at the time of tightening and loosening, the threads of the pin and the threads of the box are rubbed against each other to generate frictional heat. This is in order to sufficiently maintain lubrication at that time as well.

[0183] In the present embodiment, the adhesive resin is an epoxy resin film. The epoxy resin film is set because it is easy to handle, and is low in price compared to other agents. Further, this is because, in addition to being a balanced material, by appropriate selection of a "narrowly defined epoxy resin agent" and a curing agent, a hard film, a film excellent in heat resistance, which is the main focus of the present embodiment, is easily obtained. In addition, the adhesion / bonding of the epoxy resin film is excellent, and it is possible to be established even without a base layer (Mn phosphate chemical conversion treatment film, plating film, etc.), and has many advantages such as no significant shrinkage at the time of curing.

[0184] Regarding the film thickness of the film, in order to maintain the lubrication properties and to maintain the corrosion resistance, a film thickness of 10 μm is the minimum required for film formation. The clearance of the threads of the pin and the threads of the box differs depending on the type and design of the oil well pipe thread, and thus it is difficult to generalize the upper limit, but 150 μm is set as the upper limit.

[0185] Here, most oil well pipe threads are designed so that the clearance of the threads to each other is about 100 μm to about 200 μm, and thus 150 μm or less is specified as the upper limit. The film thickness is more preferably 10 to 50 μm. The clearance of the crest and the root of the external thread and the internal thread can be 100 to 200 μm as described above. However, the clearance between the penetrating teeth side of the external thread and the internal thread, and the clearance between the load teeth side of the external thread and the internal thread change at the time of tightening and loosening. When the clearance narrows, it becomes a substantially close state. Therefore, the smaller the film thickness, the better, and the preferable range of the film thickness is 10 to 50 μm.

[0186] However, these film thicknesses are film thicknesses in the As-formed state before the first fastening. At the time of fastening and loosening, the adhesive resin is slightly ground, and the film thickness of the film coated at room temperature actually has the actual situation in which the film is crushed and becomes thin. Therefore, even if the thickness of the thread surface is above the thickness of the gap assumed, the problem of causing a burn due to this is not caused.

[0187] In addition, the epoxy resin can be formed directly on the thread surface, or a base layer can be formed between the thread surface and the epoxy resin. The base layer can be exemplified by a Mn phosphate chemical conversion treatment layer, a metal plating layer represented by a Cu plating layer, for example. Among various statements, although it is difficult to say that it is certain in theory, the OH group in the epoxy resin forms a hydrogen bond with the metal surface or the like, and a film with strong adhesion can be formed. The above OH group is an OH group present in an epoxy resin film like a polyhydroxy ether, a polyhydroxy amine. Therefore, even without the surface treatment layer of the base, and even in the case where there is a surface treatment layer (sometimes an anchor effect or the like can be expected to be utilized), there are few problems regarding adhesion.

[0188] <Regarding the solid lubricant>

[0189] In the present embodiment, a structure in which a solid lubricant using BN (boron nitride) as a main component is dispersed in an adhesive resin is taken as an object.

[0190] [The solid lubricant]

[0191] Regarding the BN of the solid lubricant, the range in which a significant lubrication improvement effect is obtained was clarified using the above new laboratory test method. That is, regarding various lubrication films in which BN is dispersed in an epoxy resin as an adhesive resin, by conducting a study using the above new laboratory test method, the range in which the BN has a significant lubrication improvement effect was clarified.

[0192] Here, if BN (boron nitride) is used as the solid lubricant, a high-lubrication state is not always formed.

[0193] Regarding the BN, when the total weight of the solid lubricant is taken as the denominator, a composition system containing 80% or more of the BN main component was made, and when the BN having an average particle diameter of 0.1 to 10 μm was selected, a significant effect improvement was known.

[0194] The finer the BN, the better, and the lower limit of the average particle diameter of the commercially available one is 0.1 μm, so the lower limit is set to this value. The upper limit is experimentally determined, and it was confirmed that the range up to 10 μm shows a good effect of lubricity.

[0195] For the firm crystal structure of the two-dimensional plane of BN, in the case of a lubricant formed by overlapping in a plate shape, in the case where the average particle diameter is as large as more than 10 μm, the crystal structure of the plate shape slides to achieve lubrication. At this time, the plate-shaped structures close to each other are elongated in a manner of overlapping each other. As a result thereof, a white band-shaped secondary product is formed. Moreover, since they are formed thick, the tendency to clog the thread gap is high accordingly, and thus the concern of burn-on is high. It is generally considered that in the case where the average particle diameter is small, the overlapping is also small, and the formation of the white band-shaped secondary product can be suppressed, and thus high lubrication can be achieved.

[0196] Thus, when the total weight of the solid lubricant is taken as the denominator, the fact that BN is more than 80% by weight and the average particle diameter of BN is 10 μm or less is taken as a constitutional element of the application.

[0197] The meanings of these provisions are as follows. Among a wide range of BN (boron nitride), it is not always possible to form a state of high lubrication. In the use environment of oil well pipe threads, and BN dispersed in the epoxy resin as the binder resin in the present embodiment, if it is used within the range in order to achieve high lubricity, it is most suitable and remarkable, meaning that high lubricity can be expected.

[0198] Here, BN, like MoS2 and graphite, takes a firm crystal structure in the two-dimensional plate surface direction, and the two-dimensional plate surfaces are in a state of being connected to each other with weak intermolecular forces in the Z-axis direction. When a force is applied, the plate surfaces of BN slide with respect to each other, and thus lubrication is achieved.

[0199] In the present embodiment, more than 80% of BN means that BN is the main component of the solid lubricant. The provision that BN is more than 80% means that even if other solid lubricants are contained in a proportion of 20% or less, there is no adverse effect in the design of the BN main body.

[0200] In the present embodiment, the more BN that is included as a material constituting the solid lubricant, the better. By mixing other components, sometimes the lubricity also becomes poor, and thus as a range to be treated with the BN main body, it is set to be more than 80%. It is preferably more than 90%.

[0201] The finer the average particle diameter of BN, the better. Note that the average particle diameter is a parameter indicating the particle diameter at which the cumulative value in the particle size distribution calculated by a laser diffraction scattering method or the like is 50%.

[0202] The upper limit of the average particle diameter of BN is set to 10 μm because, when it exceeds 10 μm, there is a high concern that the adhesive resin film will be damaged, resulting in the triggering of the peeling without leaving anything. That is, the substance peeled from the solid lubricating film is pressed at the tightening and loosening, and a secondary product is formed. However, when the respective plate-like structures of BN are deformed in a manner of sliding on the plate surface, the plate-like structures of BN that are close to each other are formed in a manner of overlapping, and finally, a firm white band-shaped secondary product is formed. Moreover, they are formed thick, and accordingly, cannot follow the movement at the tightening and loosening, and the concern of the burn is high. Generally, the overlapping is also less when the average particle diameter of BN is small, and the formation of the white band-shaped secondary product can be suppressed. It is considered that as a result, high lubrication can be achieved. At present, the lower limit of the average particle diameter of the commercially available BN is 0.1 μm, and thus it is considered to be around there. However, with the development of technology, BN having an average particle diameter of 0.1 μm or less is also included in the present embodiment.

[0203] In addition, as the industrial classification of BN, there are a flaky BN and a particulate BN. In the present embodiment, either of them can be used. It is preferable to make the BN fine.

[0204] Other solid lubricants than BN can be mixed as long as they are 20% or less, as described above. The kind of the other solid lubricants can be any kind, and PTFE (Teflon (registered trademark): polytetrafluoroethylene), graphite, fluorinated graphite, MoS2, WS2, MCA (melamine cyanurate), mica, talc, and the like can be exemplified. In addition, an oil substance can be mixed as one of the solid lubricants as long as it is 20% or less of the solid lubricant. For example, carnauba wax, PFPE oil (perfluoropolyether), CTFE oil (oligomer of trifluorochloroethylene), and the like can be mixed. It is possible to maintain or improve the lubrication of BN.

[0205] <About the Epoxy Resin Constituting the Adhesive Resin>

[0206] In the present embodiment, an epoxy resin is selected as the adhesive resin.

[0207] In the present embodiment, when the total of the other resins than the epoxy resin constituting the adhesive resin and the epoxy resin as the prepolymer is 100 parts by weight, an epoxy resin containing 70 parts by weight or more is selected. Further, as the epoxy resin, an epoxy resin having an epoxy equivalent of 100 or more and 500 or less is selected.

[0208] Further, the present embodiment preferably makes the solid lubricating film a hard film. To achieve this, the curing agent is selected so as to form an epoxy resin film that becomes a firm three-dimensional network structure. For example, the epoxy resin as the prepolymer is selected to have more than two epoxy groups (polyfunctional epoxy groups), or the curing agent has more than two functional groups, or both have more than two. Thus, a three-dimensionally copolymerized film can be produced, and heat resistance can be achieved.

[0209] The heat resistance described herein refers to the fact that, in the case of slight burning during threaded fastening, the portion where friction is strongly generated sometimes generates heat, and the epoxy resin is not destroyed by this heat.

[0210] The epoxy equivalent is selected to be in the range of 100 to 500 in order to make the film hard by increasing the crosslinking density. In addition, this means increasing the concentration of epoxy groups, which is described elsewhere in order to suppress the epoxy equivalent to be low.

[0211] Here, when the epoxy equivalent exceeds 500, the film quality becomes soft regardless of anything. In addition, it is difficult to have heat resistance that can be dealt with during fastening and loosening. In addition, the lower limit value of the epoxy equivalent is set to 100, which is the approximate limit value of the epoxy resin in circulation. In the case of a smaller epoxy equivalent, not limited to 100, an epoxy material with a lower epoxy equivalent is also included in the present embodiment.

[0212] In addition, the epoxy resin described herein refers to an epoxy resin as a film that is copolymerized with a curing agent as a prepolymer. The reason for selecting the epoxy resin is because of excellent adhesion / adhesiveness, water resistance / humidity resistance, heat resistance, and no significant shrinkage during curing, etc. In addition, this is because the epoxy resin is a material that is easy to handle, and is balanced in terms of price compared to other reagents.

[0213] In particular, in the adhesive resin, the present embodiment targets a hard film, and selects an appropriate curing agent to screen a hard epoxy resin film of 3H or more in pencil hardness. The adhesive resin is a matrix that holds the solid lubricant of the BN main body, and constitutes the main component of the solid lubricating film together with the BN.

[0214] If the epoxy resin film is hard, the reason why the lubricity (fastening and loosening characteristics) is good is as follows.

[0215] In the lubrication of the threaded connection of the oil well pipe with the solid lubricating coating, the solid lubricating coating tends to be damaged when the threaded connection is loose before the threads are engaged with each other. However, the solid lubricating coating tends to be able to withstand the damage. In addition, the weight of the conventional oil well pipe threaded connection having a length of about 8 m to about 12 m is fastened while being loaded. Therefore, a structure in which the solid lubricating coating is ground, although slightly, and lubrication is maintained can be cited. Therefore, if the pencil hardness is not set to be 3H or more in advance, the damage is large, and there is a realistic situation in which the fastening and loosening can be maintained only for zero to several times.

[0216] According to the above, in the present embodiment, the "narrow sense epoxy resin" is set as follows: when the sum of the "narrow sense epoxy resin" other than the weight of the curing agent component and other lubricant components is set to be 100 parts by weight in the reagent for forming the adhesive resin, the epoxy resin is made to be 70 parts by weight or more, thereby making the component with the epoxy resin as the main body. In addition, an epoxy resin having an epoxy equivalent of 100 or more and 500 or less is selected. This is to increase the crosslinking points (to increase the crosslinking density) and to make a firm coating.

[0217] The "narrow sense epoxy resin" of the prepolymer can form a three-dimensional structure even if the number of epoxy groups is two. However, as a further preferable range, a multifunctional epoxy resin having more than two epoxy groups is preferable. The "multifunctional" epoxy resin means that the number of epoxy groups in one molecule is more than two on average. This means that the number of epoxy groups is more than that of the "conventional epoxy resin" having two epoxy groups. The multifunctional epoxy resin further forms a three-dimensional crosslinking in the reaction with the curing agent, and thus the crosslinking network becomes firm at the time of (co)polymerization, and accordingly the film quality can also be hardened (the pencil hardness can also be hardened).

[0218] Meanwhile, the heat resistance is excellent because the Tg (glass transition temperature) is high. Note that, as a preferable range, it is preferable to make the Tg more than 100°C so as to make the heat resistance excellent. The number of epoxy groups is preferably two or more to six or less in one molecule, and a more preferable range is more than two to four or less. This is because, by making the solid lubricating coating hard, peeling is reduced at the initial stage of fastening and at the final stage of loosening, and a little bit of damage is eliminated. The initial stage of fastening and the final stage of loosening are conditions in which the threads are not engaged with each other, that is, there is looseness, and the solid lubricating coating is easily damaged. When the number of epoxy groups is more than six, there is a high concern that steric hindrance will occur in the reaction of the epoxy group with the curing agent. In this case, it is also possible that a hard film is not necessarily obtained in the case where the copolymerization of the epoxy resin with the curing agent takes too much time. Therefore, it is set to be six or less. On the other hand, in the difunctional epoxy resin, a three-dimensional network structure is formed even in the case where the number of functional groups of the curing agent is more than two, and thus the film quality can be hardened. If both the epoxy resin and the curing agent are multifunctional, a harder three-dimensional network is formed, and thus this is preferable.

[0219] Further, the epoxy equivalent is preferably 100 or more and 500 or less. The epoxy equivalent is a value obtained by dividing the molecular weight of the epoxy resin in the strict sense used as the prepolymer by the number of epoxy groups. The epoxy equivalent can be regarded as the molecular weight of the molecule bound at the crosslinking point. The range is defined as described above because the smaller the epoxy equivalent, the higher the crosslinking density, and the harder the film becomes.

[0220] Examples of the prepolymer. As the difunctional epoxy resin of the prepolymer, there are, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol C type epoxy resin, and the like. As the polyfunctional epoxy resin other than the difunctional one, there are, for example, phenol novolak type compound, cresol novolak type epoxy compound, aliphatic type epoxy compound, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, polyfunctional phenol type epoxy resin compound, and the like. These can be used alone or in combination.

[0221] In the present embodiment, the "epoxy resin in the strict sense" means that the epoxy resin accounts for 70% by weight or more when the sum of the "epoxy resin in the strict sense" and other lubricant components other than the curing agent component is 100% by weight. That is, the component is made with the epoxy resin as the main component. As a further preferred range, when the total of the "epoxy resin in the strict sense" is 100% by weight, the polyfunctional epoxy resin is preferably 70% by weight or more.

[0222] The "70% by weight or more of the epoxy resin" in the former means the following. In the present embodiment, as described above, the hard film with a pencil hardness of 3H or more is the object. However, when the epoxy resin is selected and the film is hard, the film often becomes brittle at the same time. Therefore, it means that the other adhesive resin component can be added under the condition of less than 30% by weight. In order to obtain a hard film, it is preferable to make the three-dimensional network structure firm. Therefore, the polyfunctional (more than two epoxy groups) epoxy resin is defined as 70% by weight or more. Under the condition of less than 30% by weight, as the other adhesive resin component, in order to avoid the adhesive resin formed of the epoxy resin from becoming too hard and brittle, a thermoplastic resin can be selected.

[0223] An epoxy resin film as a final material constituted by (co) polymerization of a prepolymer and a curing agent has a property of becoming brittle regardless of the hardness when adjusted. In order to avoid the brittleness, as a monomer of the epoxy resin, a reagent suitable for the case is prepared. Alternatively, a resin in which a strong skeleton such as a benzene ring or a molecular chain is introduced into a main chain of the epoxy resin can be used. At this time, depending on the case, the epoxy resin itself can be rubber-modified, fluorene-modified, urethane-modified, or the like to introduce a soft chain. This is to improve the toughness by introducing a point that reduces internal stress inside the epoxy resin film. Alternatively, a thermoplastic polymer can be added in an amount of less than 30 parts by weight for adjustment. The thermoplastic polymer is intended to improve the toughness by cavitation effect or the like by adding the thermoplastic polymer to the epoxy resin film. The thermoplastic polymer described here is not particularly limited. As the thermoplastic polymer, it is allowed to contain, for example, POM (polyacetal), PC (polycarbonate), PPS (polyphenylene sulfide), PTFE (Teflon (registered trademark): polytetrafluoroethylene), or the like.

[0224] Note that the weight blending amount of the epoxy resin is expressed in parts by weight instead of weight % or the like for the following reason. Basically, for each reagent of the epoxy resin of the prepolymer, one active hydrogen reacts with one epoxy group. Note that one active hydrogen substantially corresponds to the amine equivalent when the curing agent is an amine. Therefore, the weight blending ratio is determined from the epoxy equivalent of each prepolymer and the active hydrogen equivalent of the curing agent. Therefore, the combination of the epoxy resin and the curing agent is infinite. In contrast, the weight blending amount of the epoxy resin is proportional to the amount of the cured epoxy resin. Therefore, if it is not expressed in the weight blending amount of the epoxy resin of the prepolymer, the blending ratio is not clear. Therefore, it is defined using parts by weight.

[0225] However, in the case of a latent curing agent, the curing agent itself is not necessarily required in the true sense. For example, in the case of self-polymerization of the epoxy resin of the prepolymer by anionic polymerization catalytic reaction of the latent curing reagent. As the latent curing agent, imidazole, tertiary amine, dicyandiamide, low-temperature rapid-curing polythiol, or the like can be exemplified. In the case of using these latent curing agents, polymerization is not necessarily performed at 1:1. However, in the present specification, as a parameter that defines the characteristics of the epoxy resin, the weight parts of the epoxy resin of the prepolymer are used for the definition.

[0226] Here, the film is preferably formed by brushing or mechanically applying the reagent at room temperature. Therefore, the reagent needs to be in a liquid state in the room temperature region. In addition, if convenience is considered, the reagent is preferably a single-liquid type instead of a two-liquid type. Also, the reagent is preferably not immediately solidified after being applied to the thread surface, but is filmized by being copolymerized by heat treatment.

[0227] As for the viscosity of the agent, if the viscosity is too low, the agent drips down on the thread from the front end where the agent is applied to the thread. In the case of the internal thread, the agent gathers and accumulates at the 6 o'clock position, and the concern that the film thickness becomes thick only in this portion becomes high. In the case of the external thread, a droplet can also be formed at the 6 o'clock position and fall, and it is difficult to become uniform in the state before the heat treatment. On the other hand, if the viscosity of the agent is too high, the agent cannot be applied by brush coating. In addition, even in the case of spray coating, clogging and the like can occur and it is not suitable. Therefore, the preferable range of the viscosity of the agent is 200 cps or more and 900 cps or less (0.2 Pa-sec or more and 0.9 Pa-sec or less). However, even in the case where the agent itself exceeds this range and the viscosity is too high, the agent is made to be low viscosity by adding a reactive diluent, which is also included in the present embodiment.

[0228] <About the Curing Agent of the Epoxy Resin>

[0229] In the present embodiment, the curing agent refers to an agent that contributes to the cross-linking reaction between the cross-linking groups of the "narrowly defined epoxy resin" of the prepolymer.

[0230] As the curing agent, there is no particular limitation, and all of the curing agents known as the curing agent of the epoxy resin can be used. As long as the condition that the hard epoxy resin film having the pencil hardness exceeding 3H can be achieved by the selection of the narrowly defined epoxy resin and the selection of the curing agent, there is no particular specification as the curing agent.

[0231] As the curing agent, for example, as the amine-based curing agent, aliphatic amine, polyether amine, alicyclic amine, aromatic amine, and the like can be exemplified. The epoxy resin based on these curing agents becomes polyhydroxy amine. As the acid anhydride-based curing agent, dodecenyl succinic anhydride, polyadipic anhydride, tetrahydrophthalic anhydride, trialkyl tetrahydrophthalic anhydride, phthalic anhydride, and the like can be exemplified. The epoxy resin based on these curing agents becomes polyester. As the phenol-based curing agent, dihydroxyphenyl-based and the like can be exemplified, and the epoxy resin based on these curing agents becomes polyhydroxy ether. In addition, as the latent curing agent, amine-based curing agents such as tertiary amine or aromatic amine, imidazole, halogenated boron amine complex, and the like can be listed, and the epoxy resin can be exemplified by polyether.

[0232] As for the amount of the curing agent, in addition to the latent curing agent, it is implemented on the basis of mixing the amount defined by the active hydrogen equivalent of each curing agent and the epoxy equivalent of the narrowly defined epoxy agent. Note that the active hydrogen equivalent of each curing agent is approximately equivalent to the amine equivalent when the curing agent is amine. On the other hand, the amount of addition of the latent curing agent is linked to the reaction speed, and therefore, it is implemented by appropriately determining the amount of blending each time.

[0233] The present embodiment basically forms a hard film of 3H or more in pencil hardness. Therefore, a heat-curing type curing agent is preferably used instead of a room-temperature curing type curing agent. For the former curing agent, the glass transition temperature Tg is low, and the film quality becomes soft. For the latter curing agent, the glass transition temperature Tg is high in many cases, and the heat resistance and mechanical strength are excellent.

[0234] <About a Curing Accelerator for the Epoxy Resin>

[0235] A curing accelerator can be used when the epoxy resin in a narrow sense reacts with the curing agent.

[0236] Although there are exceptions, in the case where the curing agent is an aromatic amine, the curing reaction proceeds if heating is performed, but in the case of many curing agents, the reaction does not proceed even if heating is performed. In such a case, a curing accelerator can be used.

[0237] In the case where an acid anhydride curing agent, a phenol curing agent, or a latent curing agent such as dicyandiamine is selected as the curing agent, curing is hardly performed if a curing accelerator is not used.

[0238] As the curing accelerator, tertiary amines and tertiary amine-based DBU (diazabicyclononene), DBN (diazabicycloundecene), and the like, imidazole-based reagents, phosphines, phosphine salts, and the like, TPP (triphenylphosphine) can be exemplified. For example, when the epoxy resin in a narrow sense (the epoxy resin constituting the prepolymer) is 100 parts by weight, the addition amount of these curing accelerators is 0.01 to 10 parts by weight. However, the addition amount needs to be corrected depending on the situation. It is preferably 0.1 to 3 parts by weight.

[0239] <About Other Additives>

[0240] In the present embodiment, the film is constituted by dispersing a solid lubricant in which BN is the main component in the epoxy resin cured film. However, it is preferable to obtain a hard film (3H or more in pencil hardness). Therefore, obtaining a hard film with the epoxy resin film is the main purpose. In addition, in order to make the film quality hard, glass fibers or carbon fibers can be added. In addition, the resin composition of the present embodiment can also contain a surfactant, an emulsifier, an elastomer, a diluent, an antifoaming agent, an ion capturing agent, and the like.

[0241] <About an Analysis Method for Film Hardness>

[0242] In the present embodiment, pencil hardness evaluation is performed on the hard film. Specifically, the measurement is performed by the method prescribed in JIS K 5600-5-4 (1999). This standard is a translation of "ISO / DIS 15184, Paints and varnishes - Determination of film hardness by pencil test" standard, which is clearly described in the JIS standard. However, the test method of pencil hardness itself is evaluated based on the prescription in the JIS standard. In addition, the reason for evaluating the film hardness by pencil hardness is because it is an "scratch" evaluation using a pencil, which is a film hardness evaluation method similar to the behavior of peeling off the solid lubricating film in the pin and box threads of the oil well pipe threads, which is caused by "scratch". The film hardness measurement method caused by indentation, Rockwell hardness, Vickers hardness, Shore hardness, Knoop hardness, which are sometimes used in the coated film and the like, are not suitable for the case where the coated film is thin, and are affected by the substrate, and thus the pencil hardness is used in the present embodiment.

[0243] <Face on which the solid lubricating film is formed>

[0244] The solid lubricating film of the present embodiment is used in either one or both of the coupling side (the pin thread side) and the pin side (the box thread side) of the oil well pipe threads by forming the above-described coated film. Alternatively, it is preferable to form the solid lubricating film of the present embodiment in either one of the coupling side (the pin thread side) and the pin side (the box thread side), and to form a softer film of a different kind from the above-described coated film in the other side.

[0245] In the latter case, it is more preferable that the hardness of the film of a different kind formed on the side on which the coated film of the present embodiment is not formed is 4B or less in pencil hardness. The epoxy resin film of the present embodiment is a hard film with a pencil hardness of 3H or more, and thus the hardness of the film of a different kind brings about a preferable lubricating property of the film structure with a difference in hardness.

[0246] The former is a use method of the lubricating property of the solid lubricating film as originally intended by the present embodiment. The latter is a method of further improving the lubricating property.

[0247] Compared to the case where the films with good lubricating properties are opposed to each other to achieve lubrication, in the case where the hardness of one is hard or soft compared to the film of the present embodiment, further improvement of the lubricating property can be expected. In the case where the film of a different kind is formed on the side on which the coated film of the present embodiment is not formed, the film of a different kind is preferably a film with a hardness of 4B or less in pencil hardness. Figures 2-4 In the case of tightening and loosening in the condition where there is play before the thread engagement, in the condition of a sharp torque rise (stage 1), it is possible to expect that the soft film itself deforms to reduce the face pressure. In addition, by the hard film of the present embodiment, which is mainly the BN and the epoxy resin film, it is possible to expect high lubrication of the threads in the entire region of tightening and loosening.

[0248] <Method for manufacturing solid lubricating coating film>

[0249] The film can be formed by coating the agent once in the desired thickness of the film to be formed and performing filmization by firing or the like.

[0250] Preferably, instead of performing the film formation by the method of dividing into a plurality of times and performing the main firing a plurality of times, a temporary heat treatment (temporary drying) is preferably performed once or more at a temperature lower than the temperature of the main firing, and then the main firing is performed to form the film. In this case, the solid lubricating coating film thickness based on one coating is set to 50 μm or less, and the film is formed by overlapping the films with the temporary drying process in between. These processes, including the initial film formation, are performed for two or more processes, and in the final film formation, the temporary drying is stopped and the main drying process is performed. As the main drying process, firing, or drying means such as infrared radiation, ultraviolet radiation, hot air, or atmospheric standing, natural drying, or the like can be exemplified. The coating film formed is preferably adjusted to a final total film thickness of 10 to 150 μm. The temporary drying refers to drying in which, for example, only a portion (for example, 30 to 70%) of the solvent is allowed to evaporate.

[0251] This embodiment utilizes an agent based on a substance in which a solid lubricant with BN as the main body and an adhesive resin with an epoxy resin as the main body are dissolved in a solvent to form a film. The agent is preferably an agent in which the film component is increased with respect to the solvent and the viscosity is high. In this case, when the film is formed once, according to the oil well pipe thread structure, due to the influence of the surface tension, at the corner portion at the top of the thread, the liquid is stretched and stored with less thickness, and at the corner portion at the bottom of the thread, the liquid is stored with a higher tendency. Therefore, it is preferable to divide the firing into a plurality of times.

[0252] However, if the main firing is performed a plurality of times, the adhesion between the films is slightly weak, and there is a tendency for peeling to easily occur between the layers. Therefore, it is preferable to perform the temporary firing in a state in which a portion of the components of the solvent evaporates, and then to repeatedly perform the coating and the temporary firing again, and to perform the main firing after the film is formed to the necessary film thickness by the temporary firing. This is because the uniformity of the film quality and the uniformity of the film thickness function effectively. In addition, from the viewpoint of the corrosion resistance, the film formation based on the coating a plurality of times is more difficult to form in a manner in which a pinhole penetrates the entire film. This also has an effect in this regard.

[0253] In addition, performing the main firing by two-stage heat treatment is preferable in order to make the cross-linking structure of the epoxy resin firm. When the first curing treatment is performed to gel at a temperature below the Tg temperature and the second curing is performed at a temperature above the Tg temperature, it is expected that a complete cross-linking structure can be formed.

[0254] Note that detailed explanations of the solid lubricant of the present embodiment in which BN is used as the main component, the adhesive resin in which epoxy resin is used as the main component, other additives, and the method of simulating actual well conditions as the evaluation method are given, and appropriate ranges are defined. In addition, the present embodiment is not limited to the solid lubricating film formed on the threaded joint of the oil well pipe, but can also be applied to the reagent for producing the film and lubrication other than the threaded joint of the oil well pipe. In the following, the sleeve thread (internal thread side) and the pin thread (external thread side) are taken as the center of the explanation. However, the joint of the T&C (Threaded & Coupled) type of the oil well pipe also includes the joint of the integral type.

[0255] <Experiment method simulating actual well test conditions (new laboratory test)>

[0256] In the present embodiment, as used in the following Figure 5 As explained above, the phenomenon caused by the lubrication of the threaded joint of the oil well pipe is divided into two stages, before the thread engagement (stage 1) and after the threads are sufficiently engaged with each other (stage 2). Furthermore, based on the tightening and loosening (lubrication) of the initial stage (stage 1), the lubrication of the threads is comprehensively evaluated including the lubrication of the second stage (stage 2).

[0257] If this evaluation is not performed, the failure can occur frequently in the actual well even though it is OK in the evaluation of the laboratory test. In the actual well, before the threads are engaged with each other, a large load and an eccentric load are applied, and thus the solid lubricating film is damaged or peeled off. In a severe case, it is sometimes peeled off without leaving a trace. Based on this, the upper and lower limits of the appropriate range of the parameters of the present embodiment are selected.

[0258] As explained above, in the case of the solid lubricating film, the damage to the film by the tightening before the thread engagement cannot be avoided. Furthermore, based on the peeled product, the secondary product can be formed. If it clogs the gap between the threads, the burn occurs. Therefore, if the lubrication evaluation is not performed under the conditions conforming to the actual well, the solid lubricating film that is actually a failure level can be erroneously determined as a pass. 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 are meaningless.

[0259] That is, if the secondary product, that is, the reconstituted "secondary product" manufactured based on the damage and the peeling of the solid lubricating film is not considered to affect the lubrication, the accurate regulation of the solid lubricating film cannot be made. In the present embodiment, the evaluation is performed by the new laboratory test in which such an insight is considered.

[0260] Note that, if the evaluation using a horizontal power tongs with a short pin, the evaluation using a vertical power tongs with a short pin (evaluation based on the past laboratory test) is relied on, it is meaningless in the evaluation of the solid lubricating film. In the past patent literature, in the lubrication test based on the solid lubricating film, even for a large diameter size such as 9-5 / 8", 13-3 / 8", there are scattered expressions that the number of times of fastening and loosening is performed to 15-20 times. That is, even for the solid lubricating film, the result is not inferior to that of the grease-like compound, but for the solid lubricating film, it is substantially impossible. For the solid lubricating film, the solid lubricating film as the main body of lubrication is inevitably abraded. On the other hand, the grease-like compound makes the surface clean every time the fastening and loosening is performed, and re-coats the compound, so that the heavy metal such as Pb, Zn as the main body of lubrication is newly supplied every time. Therefore, in the actual well fastening and loosening, in the case of using the solid lubricating film for a large diameter, the case of 15-20 times is rare. In addition, regarding the lubrication of the solid lubricating film, it is considered that the expression that the number of times of fastening and loosening is also possible for about 15 times to about 20 times is a case where the lubrication of the thread is evaluated only in stage 2 after the threads are sufficiently engaged with each other, not in stage 1 before the threads are engaged with each other. That is, it is considered that this is a result obtained by using a short pin based on the evaluation using a horizontal or vertical power tongs, which is often observed in the past laboratory test.

[0261] In the present embodiment, based on the conditions of the above new laboratory test, the test is performed by the device configuration shown in Figure 2

[0262] In the new laboratory test, the evaluation is performed under the condition that the large load loadable at the time of fastening and the partial load condition at the time of fastening and loosening are achieved as a basis. In the new laboratory test, for example, in the case of a process in which the load corresponding to the large load of the actual size pin, the thread fastening, the looseness before the threads are engaged with each other is considered. In addition, in the case of the thread loosening process, it is reflected that the looseness is generated by the disengagement of the engagement of the threads with each other.

[0263] In the new laboratory test, a vertical power tongs 4 is used. In addition, a short pin 1 is used as a test pin. However, the load load and the unloading of the load using a weight 3 can be performed on the upper portion of the pin 1.

[0264] Furthermore, the short pin 1 and the sleeve thread 2 are fastened by the pin thread portion la and the sleeve thread portion 2a.

[0265] At this time, in order to simulate the condition that the thread teeth are not engaged, the initial temporary fastening position is set so that the pin thread tooth la exposes half of the total number of thread teeth from the sleeve thread 2 (refer to Figure 6 ​(b). This is one of the causes of loosening. Tighten from this state.

[0266] When tightening, a counterweight 3 is pre-installed on the upper end of pin 1, which is opposite to the tightening thread of sleeve thread 2.

[0267] The weight of counterweight 3 is set to be equivalent to the load of 1 to 3 actual-sized pins, calculated based on the actual-sized pins' outer diameter and wall thickness. Regarding the weight, if it is 9-5 / 8” 53.5#, then one pin will have a load of approximately 1 t (2200Lb), and if it is equivalent to 3 pins connected together, then it will have a load of approximately 3 tons (6600Lb).

[0268] like Figure 5 As shown, Figure 6 The illustrated weight 3 consists of a weight body 3A and an insert rod 13. The insert rod 13 is welded to the lower surface of the weight body 3A and is positioned in an axisymmetric position on the weight 3. The weight is mounted on the pin 1 by inserting the insert rod 13 into the pin in a sliding position. The symbol 1c represents the inner diameter surface of the pin 1.

[0269] When the counterweight 3 is pre-installed on the insertion rod 13 and pin 1 as described above, holes 1d and 13a are pre-drilled to pass through the pin 1 and insertion rod 13. Then, as... Figures 2-4 As shown, the hammer 3 and pin 1 are integrated by inserting the through rod 12 into the holes 1d and 13a.

[0270] At the center of the upper shaft of the counterweight 3, a swivel-type hook 11 is welded to it, forming a suspension device 20 that is suspended from the ceiling via a chain 21. Thus, by adjusting the lifting position of the counterweight using the suspension device 20, the load on the pin from the counterweight can be adjusted.

[0271] Furthermore, during tightening, the chain 21 is set to a slack state so that the counterweight load is applied to the sleeve thread, and tightening is performed at 5 to 20 rpm until the torque increases (stage 1). Here, a simulation of loosening is formed. If the torque increases, the rotation speed is reduced to 0.5 to 2 rpm, and tightening is performed to the tightened position (stage 2).

[0272] On the other hand, during relaxation, the weight 3 is suspended by the suspension device 20, and relaxation is carried out without applying a load to the weight 3. The rotational speed is set to 0.5 to 2 rpm when the torque increases to begin relaxation, and if the torque reaches about 1 / 10 of the tightening torque value, relaxation is carried out at a high speed of 5 to 20 rpm.

[0273] Here, the condition becomes close to the actual well environment without applying the load based on the weight 3 at the time of relaxation. This is based on the experimental fact, the insight based on the data that the evaluation of the lubrication characteristics is good in the case of applying the load of the weight 3 compared to the case of not applying the load of the weight 3. That is, the inventor actually observed the experiment, and as a result, obtained the insight that if relaxed in the state where the weight is applied, the weight becomes a balancer, and the pin is relaxed straight without looseness from the fastening end position. On the other hand, it was obtained that in the case of relaxing the joint with the load reduced, that is, in the case of conducting the test by hoisting the load in order to make the weight load zero, including the case where the load is not completely zero, the pin is loose drastically, and it is possible to conduct the test in the condition where the tendency to cause damage to the solid lubrication film is strong.

[0274] In the new laboratory test based on the above condition, it is possible to simulate the condition where the secondary product from the component of the solid lubrication film released into the thread gap by peeling off and the like does not move following the fastening relaxation, thereby clogging a certain site to cause a burn, and other conditions where the film itself peels off without leaving anything. As a result, it is possible to define the upper and lower limits of the parameters related to the solid lubrication film as parameters that conform to the actual well conditions. If the relaxation ends, the pin thread and the sleeve thread are separated, and after the fragments and the like from the solid lubrication film existing on the surface of the thread are scattered by blowing, the surface is inspected, and the fastening is continued again, and the evaluation is conducted by such a method.

[0275] The present embodiment defines the components and the like in order to realize the lubrication characteristics that can tolerate the environment that can occur in the actual well. In addition, when defining the upper and lower limits, it is confirmed under the condition that conforms to the fastening relaxation condition in the actual well, and it is decided.

[0276] Hereinafter, the new laboratory test of the above condition is also described as a weight wrench test.

[0277] In the present embodiment, as used in the weight wrench test, the weight 3 is a weight that is used in the actual well, and the weight 3 is a weight that is used in the actual well. Figure 4As explained, it is important to evaluate the thread lubrication based on the tightening and loosening (lubrication) of the initial stage, considering that the phenomena occurring in the lubrication of the oil well pipe threads are divided into two. If this evaluation is not performed, it can often occur that OK in the laboratory test evaluation but frequent failure in the actual well. In the actual well, there are the tightening and loosening in which the lubrication in the state of looseness before the threads are engaged with each other is the main point and the tightening and loosening in which the lubrication after the threads are sufficiently engaged is the main point. In the actual well, the weight of an actual size pin by itself, the weight of three connections according to the situation are applied to the internal thread side of the receiving side. In addition, the pin is not tightened vertically and straightly ideally. In the actual situation, the pin thread is flexed in the elastic region, has a tendency to be provided slightly curved, and the loosened portion is necessarily eccentrically tightened at the initial stage of tightening and the final stage of loosening. In the case of the horizontal and vertical power tongs in which the above short pin is used, it is necessary to provide the solid lubricating film which can also tolerate the condition of the torque instability, sometimes the peak torque rise before the engagement of the threads like (x) of (a). Figure 5 (a) the solid lubricating film of the torque instability, sometimes the peak torque rise before the engagement of the threads like (x) of (a).

[0278] (Other)

[0279] The present application can also be configured as follows.

[0280] (1) An agent for forming a solid lubricating film on a threaded portion of an oil well pipe, wherein the agent is configured by dispersing a solid lubricant in a binder resin, the binder resin includes a prepolymer and a curing agent, the prepolymer includes one or more than two kinds of epoxy resins, 70 parts by weight or more of the prepolymer is included with respect to 100 parts by weight of the binder resin, the epoxy equivalent weight of the epoxy resins configuring the prepolymer is in the range of 100 or more and 500 or less, 80% by weight or more of the solid lubricant is BN (boron nitride), the average particle diameter of the BN is 10 μm or less, and the total weight of the solid lubricant is 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0281] (2) 30 parts by weight or more and 80 parts by weight or less of a solvent component are included with respect to 100 parts by weight of the sum of the total weight of the solid lubricant and the total weight of the binder resin except the curing agent.

[0282] (3) 0 parts by weight or more and 10 parts by weight or less of a curing accelerator are included with respect to 100 parts by weight of the total weight of the agent.

[0283] (4) The epoxy resins configuring the prepolymer have more than 2 epoxy groups (polyfunctional epoxy resins).

[0284] (5) The epoxy resins configuring the prepolymer have 6 or less epoxy groups.

[0285] (6) The epoxy resin constituting the prepolymer has 4 or less epoxy groups.

[0286] (7) The curing agent is a curing agent for curing the epoxy resin, and includes an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent.

[0287] (8) The glass transition temperature Tg of the epoxy resin constituting the prepolymer is 100°C or higher.

[0288] (9) The viscosity of the agent is 20 mPa-s or higher and 2000 mPa-s or lower.

[0289] (10) An oil well pipe in which a lubricating coating film having a solid lubricating coating film is formed on a threaded portion, wherein the solid lubricating coating film is constituted by dispersing a solid lubricant in a binder resin, the binder resin includes an epoxy resin cured by a curing agent, 70 parts by weight or more of the epoxy resin is included with respect to 100 parts by weight of the binder resin, the epoxy equivalent of the epoxy resin is in a range of 100 or more and 500 or less, 80% by weight or more of the solid lubricant is BN (boron nitride), the average particle diameter of the BN is 10 μm or less, and the total weight of the solid lubricant is 0.1 times or more and 2 times or less of the total weight of the binder resin.

[0290] (11) The epoxy resin has more than 2 epoxy groups (a multifunctional epoxy resin).

[0291] (12) The epoxy resin has 6 or less epoxy groups.

[0292] (13) The epoxy resin has 4 or less epoxy groups.

[0293] (14) The curing agent is a curing agent for curing the epoxy resin, and includes an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent.

[0294] (15) The glass transition temperature Tg of the epoxy resin is 100°C or higher.

[0295] (16) The solid lubricating coating film has a hardness of 3H or more in terms of pencil hardness.

[0296] (17) The thickness of the solid lubricating coating film is 10 μm or more and 150 μm or less.

[0297] (18) The lubricating coating film is formed on a fastening surface of a threaded portion of at least one of the sleeve and the pin.

[0298] (19) The lubricating coating film has a base layer between the fastening surface of the threaded portion and the solid lubricating coating film, and the base layer includes a chemical conversion treatment layer or an electroplated layer.

[0299] (20) An oil well pipe threaded joint is an oil well pipe threaded joint connecting a sleeve having an internal thread with a pin having an external thread, and the oil well pipe of at least one of the sleeve and the pin is composed of an oil well pipe formed with the above lubricating film of the present application.

[0300] Embodiment

[0301] Next, an embodiment based on the present embodiment will be described.

[0302] <Regarding the Pass Criteria>

[0303] First, the pass criteria for the lubrication behavior based on the number of fastening and loosening will be described.

[0304] Regarding the criteria, in the case of the casing size, 3 or more times of fastening and loosening is regarded as a pass, and the case where 5 times or more can be performed is judged to be more excellent. In the case of the pipe size, 5 times or more is judged as a pass, and the case where 10 times or more is evaluated to be more excellent. The regulation of the casing size is in accordance with the regulation of ISO 13679. On the other hand, in the case of the pipe, 5 times or more, which is lower than the regulation of ISO 13679, is regarded as a pass.

[0305] Since it is a solid lubricating film, the tendency of the M / B number to deteriorate is significantly reduced compared to the lubrication using the conventional grease-like compound. This is also recognized in the oil and gas industry.

[0306] As described above, if only the short pin is used to perform the fastening and loosening test from the thread engagement, the regulation of ISO 13679 can be used as a simple target. However, in the present embodiment, in order to simulate the condition in which the loosening of the thread engagement occurs under a large load and an eccentric load, which is a condition close to the actual condition that can occur in the well, the evaluation is performed by the "heavy weight wrench test (new laboratory test)".

[0307] In the following description, 9-5 / 8" 53.5#, 9-5 / 8" 43.5#, and 7" 29# are used. In most cases, it is a size for casing application, and therefore, 3 or more times of fastening and loosening described above is regarded as a pass, and the case where 5 times or more can be performed is judged to be more excellent.

[0308] As the condition of the load connecting three pins, in the case of 9-5 / 8" 53.5#, a heavy weight of 3 t was used. In the case of 9-5 / 8" 43.5# and 7" 29#, heavy weights of 2.5 tons and 1 ton, respectively, were used.

[0309] The initial fastening position is fastened only to a position where the total number of pin thread teeth that appear from the sleeve thread is half, that is, the fastening is performed from a state where the thread teeth are not engaged with each other. That is, the device shown in FIGS. 1 to 3 is used. Figure 6 , Figure 5 The test is performed in a state designed to load a load at the time of fastening and, on the other hand, not to load a load at the time of loosening.

[0310] If the test is performed under a load condition based on a weight hammer at the time of loosening, in the case of using a pin that integrates a short pin and a weight hammer, unlike an actual size pin of an actual well, the short pin integrated with the weight hammer is raised straight from the fastening position. The weight hammer becomes a balancer, and thus loosening does not occur. The actual size pin is slightly bent because it is longer, and thus the thread teeth are no longer engaged as the exposure gradually progresses, loosening occurs, and the tendency to damage the solid lubrication film becomes high. Therefore, in the lubrication evaluation using the weight hammer tong, the test is performed without applying a load at the time of loosening, and loosening that occurs in conjunction when the condition in which the thread teeth are not engaged is approached is simulated. In addition, not applying a load does not necessarily mean that the load is zero. The test is performed by lifting the weight hammer with a bridge crane or the like so that the load of the weight hammer is not applied. Note that the test for confirming the number of times of fastening and loosening using the weight hammer tong is performed two or more times, and a comparative evaluation is performed on whether the number of times of each reaches a qualified criterion and how many the number of times of reaching is with respect to the number of test points, and whether the parameters can be determined.

[0311] "Example 1"

[0312] Next, Example 1 based on the present embodiment is described with reference to the table.

[0313] This example is an example in which the lubrication film provided with the solid lubrication film is set to the fastening surface 10 of the oil well pipe thread joint, and whether the lubrication film provided with the solid lubrication film can be determined is evaluated. In this example, under the conditions shown in Tables 1 to 4, a fastening and loosening test is performed, and whether the lubrication film can be determined.

[0314]

[0315]

[0316]

[0317]

[0318] In the table, Nos. 1 to 4 are examples performed under the conditions where the steel grade is a carbon steel high-strength material Q125, the thread size is 9-5 / 8" 53.5#, and the thread is JFELION TM .

[0319] In No. 1 to 4, a solid lubricating film is provided on the coupling side thread by forming an epoxy resin with BN main body. Also, it is an example in which the pin side is maintained in a shot blasted state or formed with a soft lubricating / rust preventing paint.

[0320] The epoxy resin is a cresol novolac type epoxy resin, the number of epoxy groups is 6, and the epoxy equivalent is 200. As the curing agent, a phenol novolac type curing agent is used, and the functional group equivalent of the curing agent, i.e., the active hydrogen equivalent is 195. As the curing aid, TPP (triphenylphosphine) is used, and when the total weight of the epoxy resin + curing agent is set to 100 parts by weight, 2 parts by weight (2 pbr) of the curing aid is mixed, and curing is performed. As the heat treatment, 2 hours at 160°C + 4 hours at 180°C are performed. Note that this epoxy resin is an epoxy resin in which the film hardness is 3H in terms of pencil hardness.

[0321] Note that in the table, the coupling thread is described as CPLG thread, and the pin thread is described as PIN thread.

[0322] No. 1 is an example in which the BN size of the solid lubricant exceeds the prescribed 10 μm and is 20 μm, and the film thickness is 45 μm. No. 1 is an example in which the tightening and loosening test of the oil well pipe thread was performed using a horizontal tong. The weight of the pin was not applied to the coupling, and the shaft was adjusted, and thus No. 1 is an ideal condition in which tightening is performed in a symmetrical position. No. 1 is an example in which the tightening and loosening test can be performed without particular problems. However, compared with the tightening and loosening condition in an actual well, the test evaluation is a loose condition, and thus although the BN is outside the standard, the number of times of tightening and loosening of 5 times or more can be achieved.

[0323] On the other hand, No. 2 is an example in which an acrylate fluorine-based paint was applied to the pin thread side under the same coupling film condition as No. 1. It is an example in which the tightening and loosening test was performed using a vertical tong as shown in the drawing under a condition in which a load weight of 3 t load was applied, i.e., a new laboratory test condition. As described at the beginning of the examples, the load was applied at the time of tightening, and the load was removed (including allowing the load to relax) at the time of loosening, and the tightening and loosening was performed. Note that the 3 t load refers to a condition in which three actual length pins of this size were connected. ​

[0324] In No. 2, the number of times of tightening and loosening does not satisfy the necessary number of times. In an actual well, the weight of the pin is applied to the coupling thread, and the pin is not disposed in a symmetrical position with respect to the coupling center, and is disposed straight, and the shaft of the pin is disposed flexibly. Also, before the threads engage with each other, there is "play", and thus it is a condition in which a large load and an eccentric load are applied to the coupling thread. Under such a condition close to an actual well, in the case where the average particle diameter of the BN of the solid lubricant exceeds the upper limit of 10 μm, the number of times of tightening and loosening does not satisfy the standard.​

[0325] No. 3 is an example in which the average particle diameter of BN in the solid lubricating film on the coupling side was changed from No. 2. Specifically, it is an example in which the average particle diameter of BN was 5 μm, which is within the standard range. The other parameters were also adjusted to be within the range of the present application. This satisfied the standard even in the number of times of fastening and loosening in the heavy hammer tong test. In an actual well, it was also shown that sufficient lubrication could be maintained.

[0326] No. 4 is an example in which the same conditions as No. 3 were set except that a fastening test was performed in a simulated well. In No. 4, three actual length pins were used, and the design was such that no impact was applied to the sleeve thread side when the pin thread was set by a stabbing guide. Also, the design was such that a compensator was used so that the pin thread would not swing more than necessary. This is a result of simulating the conditions in an actual well. No. 4 showed good lubricity, and was the same result as the example of No. 3. From this result, it was known that the heavy hammer tong test, which is a new laboratory test method, could simulate the conditions in an actual well.

[0327] No. 5 is an example in which the film thickness was 8 μm, which is less than the lower limit value of 10 μm, with respect to No. 3, 4. No. 5 is an example in which fastening and loosening could not be performed, and was judged to be NG.

[0328] No. 6 is an example in which the film of the conditions of No. 1 to 5 was formed on the short pin side, rather than the coupling thread side, with a film thickness of 10 μm. The tong was a simple vertical tong, and no hammer was applied to the upper part of the coupling in terms of structure. It was known that even if the film relationship of the coupling thread and the pin thread was reversed, as long as it was within the standard of the present application, sufficient number of times of fastening and loosening could be ensured.

[0329] As can be seen in No. 3 and No. 6, both the example in which there was an epoxy resin film of BN main body on the coupling side, and a soft paint was applied on the pin side, and the example in which the epoxy resin film of BN main body was on the pin side, and a soft paint was applied on the coupling side, showed good lubricating behavior.

[0330] No. 7 is an example in which the steel grade was carbon steel acid-resistant material C110, the thread size was 9-5 / 8" 53.5#, and the thread was JFELION TMExample. The solid lubricating film is provided by forming an epoxy resin on the BN base on the coupling side thread. The pin side is an example in which a soft lubricating / rustproof paint is formed on a shot blasted surface. The example of the solid lubricating film of only the thread of the coupling side is a two-liquid mixed system. The epoxy resin is a bisphenol A type epoxy resin, the number of epoxy groups is four, and the epoxy equivalent is 220. A modified aliphatic polyamine and a polyamide amine are dissolved in a solvent in a weight ratio of 4:6 as a curing agent. The functional group equivalent, i.e., active hydrogen equivalent, of the curing agent as a whole is 95. Therefore, the formulation is performed in a manner to react in the case where the epoxy equivalent of the bisphenol A type epoxy resin is 185. The film hardness is 3B, which is an example of a softness lower than the lower limit of the standard. Furthermore, since it is a two-liquid system, there is a tendency to immediately solidify upon mixing, and it is in a state of a water slurry. The film thickness target is 50 μm. However, it is a state that cannot be called homogeneous. It is an example in which the number of fastening and loosening is not good (comparative example).

[0331] No. 8 to 10 are examples implemented under the conditions where 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 Example. The solid lubricating film is provided by forming an epoxy resin on the BN base on the coupling side thread. The pin side is an example in which a soft lubricating / rustproof paint is formed on a shot blasted surface. The example of the solid lubricating film of only the thread of the coupling side is a two-liquid mixed system. The epoxy resin is a bisphenol A type epoxy resin, the number of epoxy groups is four, and the epoxy equivalent is 220. A modified aliphatic polyamine and a polyamide amine are dissolved in a solvent in a weight ratio of 4:6 as a curing agent. The functional group equivalent, i.e., active hydrogen equivalent, of the curing agent as a whole is 95. Therefore, the formulation is performed in a manner to react in the case where the epoxy equivalent of the bisphenol A type epoxy resin is 185. The film hardness is 3B, which is an example of a softness lower than the lower limit of the standard. Furthermore, since it is a two-liquid system, there is a tendency to immediately solidify upon mixing, and it is in a state of a water slurry. The film thickness target is 50 μm. However, it is a state that cannot be called homogeneous. It is an example in which the number of fastening and loosening is not good (comparative example).

[0332] No. 9 is an example in which an epoxy resin film is provided not only on the coupling thread side but also on the pin thread side, and this example is also an example in which the prescribed number of times or more can be performed.

[0333] When No. 8 and No. 9 are compared, in the case of No. 8, the number of fastening and loosening is good. In the case where the thread of one side has a hard epoxy resin film of 3H or more containing BN as prescribed in the invention, and the other side is a soft film, lubrication is shown to be good.

[0334] No. 10 is an example in which shot blasting is performed on the pin side without a film. It is clear that the BN, which is added in a range prescribed in the present embodiment, has excellent lubricating properties of an epoxy resin film.

[0335] No. 11~No. 13 are examples implemented under the conditions that 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 On the basis of changing the conditions of the solid lubricant BN, an epoxy resin is formed on the coupling side thread to provide a solid lubricating coating. The pin side is an example in which a soft lubricating / rust-preventing paint is formed by shot blasting. The epoxy resin is a tetraphenyl ethane type epoxy resin, the number of epoxy groups is 4, and the epoxy equivalent is 165. The curing agent is a phenol novolak type curing agent, the functional group equivalent of the curing agent, i.e., the active hydrogen equivalent is 206. It is an example in which triphenylphosphine (TPP) is used as a curing auxiliary agent. It is an example in which an epoxy resin is formed on the coupling side thread on the basis of changing the conditions of the solid lubricant BN.

[0336] No. 11, 12 are examples in which shot blasting is implemented only on the pin side. No. 13 is an example in which an acrylic ester-based F paint containing a metal soap is applied. No. 11, 12 differ in film thickness and mixing ratio of solvents, and are both examples in which lubrication is good.

[0337] No. 13 is an example in which BN is not added, and since the solid lubricant is not added, it is an example in which the number of fastening and loosening times does not satisfy the qualification criteria.

[0338] No. 14 is an example implemented under the conditions that the steel grade is carbon steel acid-resistant material C110, the thread size is 7" 29 #, and the thread is JFELION TM On the basis of changing the conditions of the solid lubricant BN, an epoxy resin is formed on the coupling side thread to provide a solid lubricating coating. The pin side is an example in which a soft lubricating / rust-preventing paint is formed by shot blasting. The epoxy resin is a tetraphenyl ethane type epoxy resin, the number of epoxy groups is 4, and the epoxy equivalent is 165. The curing agent is a phenol novolak type curing agent, the functional group equivalent of the curing agent, i.e., the active hydrogen equivalent is 206. It is an example in which triphenylphosphine (TPP) is used as a curing auxiliary agent. It is an example in which an epoxy resin is formed on the coupling side thread on the basis of changing the conditions of the solid lubricant BN.

[0339] No. 15, 16 are examples in which the viscosity of the reagent is outside the appropriate range. No. 15, 16 are both examples in which the steel grade is carbon steel acid-resistant material C110, the thread size is 9-5 / 8" 43.5 #, and the thread is JFELION TM On the basis of changing the conditions of the solid lubricant BN, an epoxy resin is formed on the coupling side thread to provide a solid lubricating coating. The pin side is an example in which a soft lubricating / rust-preventing paint is formed by shot blasting. The epoxy resin is a tetraphenyl ethane type epoxy resin, the number of epoxy groups is 4, and the epoxy equivalent is 165. The curing agent is a phenol novolak type curing agent, the functional group equivalent of the curing agent, i.e., the active hydrogen equivalent is 206. It is an example in which triphenylphosphine (TPP) is used as a curing auxiliary agent. It is an example in which an epoxy resin is formed on the coupling side thread on the basis of changing the conditions of the solid lubricant BN.

[0340] No. 15 used a material in which polyglycerol polyglycidyl ether and polyglycerol polyglycidyl ether were mixed at 1 : 1 in an epoxy resin. The curing agent was phthalic anhydride. When the total weight of the solid lubricant and the total weight of the epoxy resin were set to 100 parts by weight, 5 parts by weight of DMP-30, which is 2,4,6-tris(dimethylaminomethyl)phenol, was added as a curing auxiliary agent. It was a case in which the viscosity of the epoxy resin was as high as to greatly exceed the upper limit standard, 3500 mPa-s. Since the viscosity was too high, there was a disadvantage that it was difficult to coat in a paste shape and homogeneously. However, in the case where coating was performed, the number of times of fastening and loosening was able to be performed three times, and thus it was an example to be judged as an example of the present application.

[0341] No. 16 was a case in which the epoxy resin used cyclohexane dimethanol diglycidyl ether, the curing agent used dicyandiamide, and imidazole was used as a curing auxiliary agent. This example was a case in which the viscosity of the epoxy resin was as low as to greatly exceed the lower limit standard, 25 mPa-s. In No. 16, even if coating was performed with a viscosity like edible oil, it did not stop there, and there was a tendency to accumulate at the 6 o'clock position. Even if coating was attempted while rotating the pipe, it would accumulate at the 6 o'clock position before firing, and as a result, the film thickness was as thin as 25 um, and it was not possible to become a homogeneous film. Therefore, it could be judged that the lubrication was not good. In addition, it was a case in which the Tg of the epoxy resin film was also outside the appropriate range. Therefore, the fastening and loosening test was attempted three times, but in No. 16, the results were two times, one time, and three times, and it was difficult to say that it was good. No. 16 corresponds to a comparative example.

[0342] “Example 2”

[0343] Example 2 is an evaluation of corrosion resistance based on a salt spray test.

[0344] In the examples shown in Example 1, salt spray was performed by picking up from the carbon steel-based oil well pipe thread conditions of No. 3, 8, 11, and 14.

[0345] Regarding the material, a coupling sample was newly made for this salt spray test.

[0346] As a comparative example, a steel sheet having a thickness of 0.8 mmt of SPCC (thin steel sheet of a general soft steel, cold-rolled annealed sheet) was implemented (Condition A).

[0347] As for the oil well pipe thread material, one fastening and loosening was performed with a protector with respect to both ends of the coupling thread. Then, salt water spraying was performed for the case where the state was maintained (No. 3-2, 8-2, 11-2, 14-2) and the case where the protector was installed again and fastening was performed (equivalent to second fastening: No. 3-3, 8-3, 11-3, 14-3). Then, the samples were arranged laterally, that is, corrosion tests were performed under the condition where the samples were observed side by side without being erected.

[0348] As for the pin thread, a sample having only a thread was prepared, and one fastening and loosening was performed with a protector on the side having a thread. An imide tape was spread on the outside where the protector was not installed again, and protection was performed so as not to allow water to enter the inside of the pipe.

[0349] The detailed conditions are described below.

[0350] The conditions of the solid lubricating film of No. 3-2, 3-3, No. 8-2, 8-3, No. 11-2, 11-3, No. 14-2, 14-3 were equivalent to those of No. 3, 8, 11, 14 of Example 1.

[0351] < Salt water spraying conditions >

[0352] The salt water spraying conditions are described below.

[0353] Spraying condition: JIS K 5600-7-1

[0354] Salt water concentration: 5 ± 0.5% by weight

[0355] Temperature: 35°C

[0356] Humidity: 98 to 99%

[0357] Spraying amount: 1 to 2 mL / hour / 80 cm 2

[0358] pH: 6.5 to 7.2

[0359] Time: 24 hours

[0360] The meaning of this test method is described below. This is because the oil well pipe thread is mostly shipped after the end portions are fastened with a protector, and is directly stored in the site near the well. Therefore, the state after spraying salt water is an environment close to the actual use condition. The condition where the protector is not installed refers to a more severe condition at the time of removing the protector. The case of SPCC sheet is a case where fastening and loosening are not performed with a protector, and the corrosion resistance of the film itself is observed in terms of the thread shape.

[0361] The results are shown in Table 5.

[0362]

[0363] As shown in Table 5, No. 3-2, 3-3, No. 8-2, 8-3, No. 11-2, 11-3, No. 14-2, 14-3, including No. A of the comparative example, were not corroded in the salt spray and had sufficient corrosion resistance.

[0364] It is presumed that the film is as hard as 3H, and even if fastening and loosening are performed using a protector, it will not be fatally damaged, and since BN itself is water-repellent, water will not be introduced in most cases.

[0365] Herein, the entire contents of Japanese Patent Application No. 2021-91463 (filed on May 31, 2021) on which this application claims priority are incorporated by reference as part of the present disclosure. Herein, a limited number of embodiments are described by way of illustration, but the scope of the right is not limited thereto, and modifications based on the above-described disclosed embodiments will be apparent to those skilled in the art.

[0366] Explanation of symbols

[0367] 1 Test pin

[0368] 1a External thread

[0369] 1c Inner diameter surface

[0370] 1d Through hole

[0371] 2 Sleeve (coupling)

[0372] 2a Internal thread

[0373] 3 Weight

[0374] 4 Power tongs

[0375] 10A Solid lubricating coating

[0376] 10B Base layer

[0377] 11 Hook metal piece (Swivel type)

[0378] 12 Penetrating rod

[0379] 13 Insertion rod

[0380] 20 Hoisting device (crane)

[0381] 21 Chain (sling)

Claims

1. A solid lubricating film forming agent for forming a solid lubricating film on a threaded portion of an oil well pipe, characterized in that a solid lubricant is dispersed in a binder resin, the binder resin contains a prepolymer and a curing agent, the prepolymer contains one or more kinds of epoxy resins, the prepolymer is contained in an amount of 70 parts by weight or more relative to 100 parts by weight of the binder resin, an epoxy equivalent weight of the epoxy resins constituting the prepolymer is in a range of 100 or more and 500 or less, the solid lubricant contains 80% by weight or more of BN (boron nitride) having an average particle diameter of 10 μm or less, a total weight of the solid lubricant is in a range of 0.1 times or more and 2 times or less of a total weight of the binder resin, a thickness of the solid lubricating film is in a range of 10 μm or more and 150 μm or less, the solid lubricating film has a hardness of 3H or more in terms of pencil hardness, and a viscosity of the agent is in a range of 200 mPa-sec or more and 2000 mPa-sec or less. The agent contains 30 parts by weight or more and 80 parts by weight or less of a solvent component relative to 100 parts by weight of a total of the solid lubricant and the binder resin excluding the curing agent. The agent contains 0 parts by weight or more and 10 parts by weight or less of a curing accelerator relative to 100 parts by weight of a total of the epoxy resins constituting the prepolymer. The epoxy resins constituting the prepolymer are multifunctional epoxy resins having more than 2 epoxy groups. The epoxy resins constituting the prepolymer have 6 or less epoxy groups. The epoxy resins constituting the prepolymer have 4 or less epoxy groups. The curing agent is a curing agent for curing the epoxy resins, and contains an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent. A glass transition temperature Tg of the epoxy resins constituting the prepolymer is 100°C or more.

9. An oil well pipe having a lubricating film with a solid lubricating film formed on a threaded portion, characterized in that the solid lubricating film is formed by dispersing a solid lubricant in a binder resin, the binder resin contains an epoxy resin cured by a curing agent, the epoxy resin is contained in an amount of 70 parts by weight or more relative to 100 parts by weight of the binder resin, an epoxy equivalent weight of the epoxy resin is in a range of 100 or more and 500 or less, the solid lubricant contains 80% by weight or more of BN (boron nitride) having an average particle diameter of 10 μm or less, a total weight of the solid lubricant is in a range of 0.1 times or more and 2 times or less of a total weight of the binder resin, a thickness of the solid lubricating film is in a range of 10 μm or more and 150 μm or less, and the solid lubricating film has a hardness of 3H or more in terms of pencil hardness. The epoxy resin is a multifunctional epoxy resin having more than 2 epoxy groups.

2. The solid lubricating film forming agent according to claim 1, characterized by The epoxy resin has 6 or less epoxy groups.

3. The solid lubricating coating forming agent according to claim 1 or claim 2, characterized by, The epoxy resin has 4 or less epoxy groups.

4. The solid lubricating coating forming agent according to claim 1 or claim 2, characterized by, The curing agent is a curing agent for curing the epoxy resins, and contains an amine-based curing agent, an acid anhydride-based curing agent, a phenol-based curing agent, or a latent curing agent.

5. The solid lubricating coating forming agent according to claim 4, characterized by A glass transition temperature Tg of the epoxy resin is 100°C or more.

6. The solid lubricant coating forming agent according to claim 4, characterized by ​ 7. The solid lubricating coating forming agent according to claim 1 or claim 2, characterized by, ​ 8. The solid lubricating coating forming agent according to claim 7, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. The oil well pipe according to claim 9, characterized in that, ​ 11. The oil well pipe according to claim 10, characterized by ​ 12. The oil well pipe according to claim 10, characterized by ​ 13. The oil well pipe according to any one of claims 9 to 12, characterized by ​ 14. The oil well pipe according to claim 13, characterized by ​ 15. The oil well pipe according to any one of claims 9 to 12, characterized in that, the lubricating coating has a base layer between a surface of the threaded portion and the solid lubricating coating, the base layer comprises a chemical conversion treatment layer or an electroplated layer.

16. An oil well pipe threaded joint which is an oil well pipe threaded joint in which a pin having an external thread is connected to a box having an internal thread, characterized in that, the oil well pipe of at least one of the box and the pin is made of the oil well pipe according to any one of claims 9 to 15.

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