Method for evaluating the loosening of threaded connections of oil well pipes

Abstract

Provided is a fastening loosening evaluation method capable of evaluating the burn-on resistance of an oil well pipe threaded joint with high precision even without performing a test using a full-length threaded joint. For an oil well pipe threaded joint in which a pin is attached to the lower portion of a box having the axis oriented vertically, when performing a test of fastening loosening, a test pin (1) composed of a pin shorter than the pin serving as the evaluation target is used as the pin used in the test, a weight (3) is attached to the upper portion of the test pin (1), the mass of the weight (3) is set to a mass obtained by subtracting the mass of the test pin (1) from the mass of the pin serving as the evaluation target, the initial set position before fastening the test pin (1) is set to a state in which the pin thread of the test pin (1) protrudes from the upper end surface of the box (2) by 5 or more than 1 / 4 of the total number of threads of the test pin (1), whichever is greater.

Description

Technical Field

[0001] This disclosure relates to a technique for evaluating the fastening loosening of oil well pipe threaded joints during the evaluation of the resistance to burning adhesion.

[0002] It should be noted that in this specification, pipes with internal threads are sometimes referred to as "box" in general. That is, couplings are also referred to as a type of box. Background Technology

[0003] For oil well pipe threaded joints, the design and burn-resistant adhesion of the threaded joints are evaluated using a make & break test conducted with power pliers. Regarding burn-resistant adhesion, the appropriateness of the surface treatment and lubrication conditions of the threaded joints is assessed.

[0004] The API 5C5 standard specifies the burn-resistant adhesion of well tubing thread fittings. For casing sizes, the standard requires two tightening / loosening cycles followed by a final tightening (three tightening cycles). For tubing sizes, the standard requires nine tightening / loosening cycles followed by a final tightening (ten tightening cycles). Hereinafter, "tightening / loosening" will be referred to as "Make & Break".

[0005] It should be noted that, for example, the surface treatment and lubrication of the joint during the tightening of the oil well pipe threaded joint are evaluated in the following manner. Specifically, in the case of a T&C (Threaded and Coupled) type threaded joint, for the above evaluation, if the blank pipe is made of carbon steel, a manganese phosphate chemical conversion film is formed on the coupling side (female thread side), and the male thread side is kept in the state after thread cutting, or shot peening is performed on the surface. Then, in the evaluation, a compound is applied to at least one of the coupling side and the male thread side, and a tightening loosening test is performed to evaluate whether burning or sticking occurs. Alternatively, if the blank pipe is made of stainless steel, nickel-based alloys, or other high-alloy materials, in the evaluation, for example, a plating layer is formed on the coupling (female thread), and a compound is applied in the same manner as above, and a tightening loosening test is performed for evaluation. The plating layer consists, for example, of copper plating or other metal plating layers.

[0006] Furthermore, in the above evaluation, when the threaded joint is an integral threaded joint, a chemical conversion film treatment or plating for lubrication is performed on at least one of the threaded joints, and a compound is applied to one or both threaded joints. Then, a fastening / loosening test is performed and evaluated. Here, an integral threaded joint refers to a threaded joint, such as a semi-embedded threaded joint or an embedded threaded joint, that does not use a coupling and connects with an external thread on one side and an internal thread on the other.

[0007] Regarding the actual length of the male thread, for example, if it is a casing, then for Range-2 it is 25-34 feet (7.62m-10.36m), and for Range-3 it is 34-48 feet (10.36m-14.63m). Regarding the actual length of the male thread, for example, if it is a tubing, then for Range-2 it is 28-32 feet (8.53m-9.75m), and for Range-3 it is 38-42 feet (11.58m-12.80m).

[0008] If a male thread of this actual length is used and a tightening / loosening test is performed, the evaluation of the design, surface treatment, and lubrication of the threaded joint becomes a more realistic assessment, closer to actual usage conditions. However, in this case, there is a limitation on the equipment available for conducting the test. Furthermore, longer male threads increase cost and time. Additionally, in reality, there are no cases where new thread developments (male threads, etc.) are used in actual wells without laboratory reliability testing.

[0009] Therefore, sometimes a so-called short male joint (PupJoint) is made by machining the male joint to a length of about 1m. The fastening and loosening test is conducted using the short male joint to evaluate whether the male joint meets the above-mentioned heat resistance adhesion standard.

[0010] Here, as a fastening loosening test, there are horizontal tests performed with the axis of the pipe being tested horizontal, and vertical tests performed with the axis of the pipe being tested vertical.

[0011] The aforementioned horizontal type test is a test that purely evaluates the heat resistance of internal threads (e.g., the threaded portion of a coupling) and external threads (e.g., the threaded portion of a male thread). The horizontal type test is a test that evaluates the heat resistance under ideal conditions where there is essentially no axial misalignment (misalignment of the XY plane) between the internal and external threads.

[0012] On the other hand, in the longitudinal test, the weight of the short male thread is applied to the internal thread (e.g., the threaded portion of the coupling). For example, in the case of a 1m short male thread consisting of 9-5 / 8″ × 53.5#, a tightening and loosening test is conducted with a load of approximately 80kg applied to the lower internal thread (e.g., the threaded portion of the coupling). In the longitudinal test, the initial setting position is such that the male thread is positioned on top of the coupling from above. Therefore, the axial center positions of the coupling and the male thread may not be aligned. That is, as... Figure 14(As shown in (b), in the vertical test, at the initial setting, the male thread produces an offset of the axis in the horizontal plane and is in a state of being obliquely set in the direction of the thread entry, and there is a tendency for the central axis of the short male thread 40 to be offset with respect to the female thread 41. It should be noted that Figure 14 (a) shows the state where the central axes of the female thread 41 and the short male thread 40 are aligned. Therefore, starting from the eccentric state and tightening, it becomes a tightening that converges in the direction of aligning the axis centers. In this case, it is inevitable that the threads are tightened gradually while making local strong contact.

[0013] In addition, as Figure 13 (a) shows, the longer the short male thread 40 is, the higher the tendency for the axis of the short male thread 40 to be obliquely set with respect to the female thread 41 at a specified angle θ. In addition, as Figure 13 (b) shows, there is also a tendency for the longer the short male thread 40 is, the more the axis of the short male thread 40 deflects.

[0014] Therefore, in the vertical test, including the case where the self-weight of the short male thread acts locally on the internal thread, a relatively high load acts on the internal thread of the female thread 41. Therefore, it becomes a severe test. Thus, it is generally considered that the evaluation using the vertical test is important.

[0015] However, there is a problem as follows: Even if it is judged as qualified in the vertical test using the short male thread, when conducting a tightening and loosening test with a male thread of the actual length used or when applying it in an actual well (field), burning adhesion often occurs at the joint. Especially in the tests (evaluations) of new thread designs, new surface treatment coatings, new lubricating coatings, etc., this problem is significant.

[0016] Here, Patent Document 1 describes that core offset (angular misalignment) is likely to occur during the first tightening, and describes an evaluation of burn resistance on the premise of this situation. That is, Patent Document 1 describes an evaluation on the premise of a core offset of about 10 degrees of inclination, for example. This is also a kind of harsh test condition.

[0017] However, regarding the case where the axis of the male thread is inclined by as much as 10 degrees, even considering the taper of the oil well pipe thread, it is impossible to exist in the state where the thread teeth of the joint are engaged. Such an inclination degree of the axis can only be achieved in a state of local contact where the male thread is inclined without correctly engaging the thread part. And this condition is far from the actual well conditions, for example, it may cause cross threading. Cross threading means the situation where tightening occurs with an offset from the original position of the thread.

[0018] Therefore, the test described in Patent Document 1 is a test that deviates from actual use in a well. Alternatively, the test described in Patent Document 1 is a test conducted in a partially abutting state before the threads engage during the first tightening.

[0019] Furthermore, after the initial significant tilt and tightening test, the male thread engaged with the coupling thread on one side, while the shaft stood upright in its normal position on the other. Therefore, a 10-degree tilt at the initial tightening stage would not have been conceivable under meaningful test conditions.

[0020] On the other hand, there is also a method where multiple short male threads are connected together, ensuring a length equivalent to the actual length of the male thread being evaluated, and a tightening / loosening test is performed. This can be exemplified by connecting 3-4 short male threads of 3 meters (approximately 10 feet) longitudinally while conducting the test. By tightening each thread individually while ensuring a length equivalent to a single male thread (equivalent to <12 meters; <40 feet), the difficulty of suspending the male threads is eliminated. However, whether the test can reproduce a state where a mass equivalent to that of a single male thread is applied is limited by the ceiling height of the test area. Furthermore, since the coupling connecting the short male threads is located in the middle axial direction, the rigidity of the male threads used in the test increases accordingly. Consequently, there is a tendency for the connected short male threads to be set vertically relative to the female thread. Therefore, in this case, it cannot be said that it is possible to simulate the situation where the male thread's own weight is inevitably locally applied to the internal thread of the female thread, taking into account the tendency for slight deflection in the actual male thread's axis.

[0021] Non-Patent Document 2 describes an example where, to study the effect of the sleeve's self-load on the torque action of the upper thread, a 5kN (510kg) weight was placed directly above the male thread as a deadweight, and a loosening test was conducted. In this example, a 9-5 / 8″×53.5# male thread and a corresponding coupling were prepared to confirm the effectiveness of the experiment. The inventors simulated this situation, preparing a male thread made of carbon steel, applying a manganese phosphate chemical conversion treatment film as a surface treatment for the coupling, and shot-peened the surface of the male thread. They attempted to conduct the test using a device simulating the technology of Non-Patent Document 2. At this time, after applying a general compound to the threaded joints on both sides of the male thread, it was manually tightened to a stop position as the initial setting position before tightening (the setting position before tightening with power pliers). That is, from tightening to the male thread teeth... A fastening loosening test is performed starting from a state where 1-3 threads remain on the end face of the coupling. The result of this test is considered acceptable if three Make & Break tests are performed. Next, after evaluation in a prior laboratory test using a male thread of actual length, burn-sticking occurred on the thread. Therefore, even if the conditions for obtaining a pass are found in the evaluation test based on the prior art, burn-sticking may still occur with a male thread of actual length. Thus, according to the inventor's research, the prior art cannot clearly define a method for evaluating burn-sticking resistance when using a male thread of actual length.

[0022] Here, the fastening loosening test, conducted outside of typical drilling equipment tests, is performed indoors where ceiling height is limited. Therefore, in the past, tests using longitudinal clamps have used male threads much shorter than those used in actual wells. Furthermore, when testing with male threads of the length used in actual wells, horizontal clamps are more commonly used.

[0023] In these evaluation methods, short male threads are used. Before tightening with power pliers, the threads are temporarily fixed to a state where they correctly mesh, by manually rotating several times within a range that can be rotated by hand, before tightening. That is, conventionally, tightening with power pliers is performed after actual shaft matching. On the other hand, in actual well sites, pipes longer than the short male threads used in the laboratory, such as 12m, are used. And in the most demanding cases, where manual tightening is performed by rotating slightly several times, manual tightening is often omitted. Therefore, in actual well sites, it is conceivable that meshing errors or initial positional misalignment become significant, resulting in stringent tightening conditions. However, in reality, the causal relationship of tightening actions is more complex. In the past, in order to evaluate in the laboratory, the only acceptable method was to set a high number of loosening cycles. Moreover, in practice, the method of rigorous testing through laboratory tests is not usually used.

[0024] Existing technical documents

[0025] Patent documents

[0026] Patent Document 1: Japanese Patent Application Publication No. 2002-327874

[0027] Non-patent literature

[0028] Non-Patent Literature 1: API RP 5C5 Latest Version (Fourth Edition, January 2017): Procedures for Testing Casing and Tubing Connections

[0029] Non-patent literature 2: Tsuyu et al.: Journal of Petroleum Technology Association, Vol. 61, No. 6 (1996), pp. 527-536 Summary of the Invention

[0030] The problem that the invention aims to solve

[0031] This disclosure is made in view of the above points, and its purpose is to provide a method for evaluating the fastening loosening of oil well pipe threaded joints that can accurately evaluate the resistance to burning adhesion even without using threaded fittings of actual length to test the resistance to burning adhesion.

[0032] Methods for solving problems

[0033] To address this issue, the main point of this disclosure is a method for evaluating the tightening and loosening of oil well pipe threaded joints. This method uses power pliers to evaluate the tightening and loosening of oil well pipe threaded joints. The oil well pipe threaded joint includes a female thread with internal threads and a male thread with external threads. In the evaluation method, when testing the tightening and loosening of an oil well pipe threaded joint formed by installing a male thread at the lower part of a female thread with its shaft facing upwards and downwards, a test male thread formed by a male thread shorter than the male thread being evaluated is used as the male thread used in the test. A weight is installed on the upper part of the test male thread. The mass of the weight is set to be greater than or equal to the mass of the test male thread obtained by subtracting the mass of the test male thread from the mass of the male thread being evaluated. As for the initial setting position, which is the starting position for tightening the test male thread before tightening with power pliers, the initial setting position is set to the following state: the test male thread has more than 5 threads or 1 / 4 of the total number of threads of the test male thread protruding from the upper end face of the female thread.

[0034] It should be noted that the common thread used as the evaluation object refers to the length of the common thread actually used in the actual well.

[0035] The effects of the invention

[0036] According to this disclosure, even when using a test male thread that is shorter than the actual length (the male thread being evaluated) to conduct the test, the burn-resistant adhesion of the oil well pipe thread joint can be evaluated more accurately and effectively. Attached Figure Description

[0037] Figure 1 This is a schematic diagram showing the structure of an apparatus for conducting a fastening loosening test based on an embodiment of the present disclosure.

[0038] Figure 2 This is a diagram illustrating the backlash corresponding to the initial setting position.

[0039] Figure 3 It is a diagram illustrating the wobble between the external and internal threads.

[0040] Figure 4 This diagram illustrates an example of installing a counterweight on the upper part of the male buckle.

[0041] Figure 5 This diagram illustrates an example of installing a counterweight on the upper part of the male buckle.

[0042] Figure 6 This diagram illustrates an example of installing a counterweight on the upper part of the male buckle.

[0043] Figure 7 This is a diagram showing the relationship between the insertion rod, the through rod, and the male thread.

[0044] Figure 8 This is a diagram showing the relationship between the through rod and the through hole.

[0045] Figure 9 This is a schematic diagram of the actual thread tightening in a well.

[0046] Figure 10 This is a schematic diagram of the actual thread tightening in a well.

[0047] Figure 11 This is a diagram illustrating the action of the public fastener.

[0048] Figure 12 This is a diagram showing the male buckle in the experiment.

[0049] Figure 13 This is a diagram illustrating an example of male buckle deflection caused by core offset.

[0050] Figure 14 This is a diagram showing the relationship between the central axes of the male and female threads in the initial setup of a threaded connector.

[0051] Figure 15 This is a diagram illustrating an example of the relationship between rotation and torque when using a power clamp for fastening in an evaluation method based on this disclosure.

[0052] Figure 16 This is a diagram illustrating an example of the relationship between rotation and torque when using a power clamp for fastening, a common practice in conventional laboratory evaluation methods. Detailed Implementation

[0053] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0054] Here, the same reference numerals are used and described for the same constituent elements unless there is a convenient reason. Furthermore, the thickness and proportions of each constituent element are sometimes exaggerated in the drawings, and the number of constituent elements is sometimes shown differently from the embodiments. Moreover, this disclosure is not limited to the following embodiments; any form that can be embodied through appropriate combinations or modifications without departing from its spirit may also be included in this disclosure.

[0055] Previously, regarding new thread shape designs, surface treatments (electroplation, chemical conversion treatment), and lubrication methods (compounds, solid lubricants) for oil well pipe threaded fittings, the following facts existed: before a new product was introduced to the market, its feasibility could not be confirmed unless its heat resistance was verified through tests using the actual length of the male thread. However, according to the inventors' research, as mentioned above, the method of evaluation using stringent tests is also inadequate for evaluating existing technologies using short male threads.

[0056] Here, the method described in Non-Patent Document 2 is merely a method of simply placing a weight on the upper end of the male thread. Therefore, the method described in Non-Patent Document 2 cannot simulate the strict tightening and loosening conditions along an actual well as desired by this disclosure. It should be noted that the tightening and loosening treatment in the tightening and loosening test is performed using power pliers from the screw-in starting position (initial setting position) after manual tightening.

[0057] The reasons why the above simulation cannot be performed are as follows.

[0058] (a) First, in the load test using a 510 kg weight described in Non-Patent Document 2, the load is too light to be suitable for a rigorous test when using a short male thread. This tendency is particularly pronounced when the male thread has a large diameter.

[0059] (b) Next, Non-Patent Document 2 does not explicitly describe the initial setting position (tightening start position) for each tightening step. However, in previous tightening and loosening tests, after tightening to the point where it could be tightened manually, the tightening and loosening were repeated using power pliers. That is, conventionally, the initial setting position before each tightening step was the position where it could be tightened manually. However, in this case, the phenomenon of male thread oscillation and rotation, which is commonly seen in actual wells due to the loose setting of the male thread, cannot be simulated. In recent actual wells, mechanical methods are often used without contact, and the male thread is set into the female thread remotely. Then, for the male thread, it is often tightened using power pliers from a position where it is basically only inserted from above. Therefore, the method in Non-Patent Document 2 is quite far removed from the tightening conditions of actual wells.

[0060] In contrast, in this embodiment, the initial setting position before screwing in when tightening with a power clamp is intentionally set to be relatively loose. Thus, tightening is performed while the male thread oscillates and rotates, achieving tightening using a power clamp under conditions close to actual well conditions.

[0061] Here, use Figure 15 and Figure 16 This section details the action of torque during the clamping of a longitudinal power clamp. Figure 15 This is a torque / rotation diagram example based on the present disclosure, performed under a tightened condition starting from an initially loose setting. On the other hand, Figure 16 This is a torque / rotation chart example from previous longitudinal tests.

[0062] Based on the use of power clamps for fastening according to this disclosure, such as Figure 15 As shown, the male thread is gradually tightened sequentially through regions (x), (y), and (z) (stages). On the other hand, in previous laboratory tightening tests, the male thread was not tightened through region (x), but rather sequentially through regions (y) and (z) (stages). It should be noted that the inventors have confirmed the following: the relationship between rotation and torque during actual well tightening using power clamps becomes... Figure 15 The graph shown approximates the relationship between rotation and torque.

[0063] Figure 15 The region (x) shown represents the phenomenon observed when the male thread is loosely tightened relative to the female thread. The ideal state in region (x) is a tight fit between the male and female threads that engages without interference. That is, in region (x), the tightening should ideally occur without generating torque, but after conducting various experiments, the inventors have obtained the following insights: Figure 15In the tightening of region (x), numerous spike-like torques were generated. This is presumed to be due to the localized contact between the male and female threads in region (x) as the male thread offsets relative to the female thread and tightens. Furthermore, it is anticipated that in actual wells, various conditions such as wind and rain, ocean, desert, and cold regions will affect the tightening. Therefore, it is believed that in the tightening of region (x), such as… Figure 15 The state of generating more spike-like torque simulates the actual state in a well.

[0064] Furthermore, the inventors have also observed that in tests using the longitudinal type of short male thread, when a male thread weight equivalent to the actual length is applied to the short male thread and tightened, the occurrence of the aforementioned spike-like torque during tightening in the aforementioned (x) region increases.

[0065] After region (x), the thread passes through region (y), that is, through the lubrication state until it reaches complete contact with the seal (see reference). Figure 15 Although it is also based on the design of oil well pipe threads, the (y) region is equivalent to about 1 to 2 turns. Then, after fully contacting the shoulder, from the (z) region, that is, from the state of contact with the shoulder, the male thread rotates, the torque suddenly increases, and the thread is finally tightened.

[0066] As mentioned above, Figure 15 The fastening in region (x) shown may occur in actual wells. In region (x), according to the above insights, it can cause thread deformation or damage, damage to the manganese phosphate layer or metal plating of the substrate, or uneven spread of the coating compound, leading to uneven compound distribution. Furthermore, in region (x), in the case of a solid lubricant coating, it can cause damage and peeling of the coating. Therefore, it is known that concerns about damage to both the male and female threads are increasing. Based on the above insights, this disclosure provides a simulated test by applying a load to a short male thread and setting the initial fastening starting position to be relatively loose.

[0067] On the other hand, when manually tightened to the limit that can be tightened manually, such as... Figure 16 As shown, there is no tightening in region (x), only in regions (y) and (z). Therefore, lubrication was only simulated up to the point of complete contact with the shoulder, and it is difficult to say that it completely simulates what actually happens. In this state, when a load is applied to the male thread, the male thread's shaft is tightened perpendicularly to the female thread. Therefore, lubrication is more stable when a load is applied to the male thread. As a result, in the evaluation of the test, the lubrication characteristics were more stable, and the number of M / B cycles was higher, that is, the evaluation was overly good.

[0068] Based on the above research, the inventors have concluded that even without using the longer male thread (the male thread being evaluated) used in actual wells, it is generally possible to reproduce the stringent tightening conditions, which are typically only present in actual wells, by improving the initial state of thread tightening without measuring torque, and the hammer conditions for tightening and loosening. Furthermore, it has been concluded that by adjusting the load of the hammer applied to the male thread, it can be shown that disturbances in the initial torque of the tightening are related to disturbances in subsequent torque or defects in the thread surface.

[0069] Here, the torque-turn graph is the simplest method for judging the characteristics of a loosening tightening. Even if the graph looks normal at first glance, defects can sometimes appear on the threads through repeated tightening. On the other hand, when the value starts to rise in the looser stage of the tightening compared to normal, it can be determined that the tightening cannot be completed properly.

[0070] (c) The third issue in Non-Patent Document 2 is the load conditions of the weight during loosening.

[0071] Furthermore, the inventors have obtained the following insights through various experiments: by intentionally loosening the initial setting position and tightening the male thread so that it can easily swing and rotate during tightening, when the thread is loosened, and when no counterweight is placed or the load from the male thread and the counterweight to the internal thread is low, it is possible to simulate a more stringent condition than that of a real well.

[0072] That is, in the method described in Non-Patent Document 2, when the thread is loosened (when the tightening is loosened), the load of the counterweight is symmetrically and evenly distributed on the axial center of the short male thread. Therefore, the engagement state of the thread is relatively stable. Then, the thread is loosened straight from the tightened position without any wobble. As a result, in the method described in Non-Patent Document 2, the male thread is difficult to swing and rotate, and it cannot properly simulate the burning and sticking that occurs during loosening in actual wells. Depending on the situation, it may be mistaken for a situation with good lubrication characteristics. Therefore, the inventors have realized that in actual wells, when the male thread frequently swings and rotates during loosening, it is preferable to intentionally reduce the load applied to the male thread, and to set it to a state in which the male thread is easy to swing and rotate, in order to more accurately simulate actual well conditions.

[0073] Therefore, in this embodiment, considering this situation, a weight is applied to the test male thread using a counterweight during tightening. Furthermore, the weight is reduced during loosening. The counterweight applied during tightening is a component that intentionally applies the actual weight of the male thread in a well to the female thread (internal thread). On the other hand, the weight of the counterweight during loosening reduces the wobbling of the male thread that would occur due to loosening in an actual well.

[0074] Of course, this disclosure also includes cases where the load on the counterweight is not reduced during loosening. Even in this case, this embodiment can provide a higher accuracy evaluation than before. However, even without removal during loosening, by using the counterweight during tightening, the load on the threaded surface of the long pipe body in an actual well can be reproduced. Therefore, this disclosure provides an evaluation closer to that of an actual well compared to conventional tightening methods.

[0075] In the horizontal test using a short male thread, the weight of the male thread itself has no effect on the threaded joint. Even in the vertical test using a short male thread, without the use of a counterweight, only about 1 / 10 of the actual length of the male thread (the male thread being evaluated) is applied to the internal thread of the female thread. It should be noted that when the actual male thread is set to about 8-12m, the short male thread is often about 1m.

[0076] On the other hand, in actual wells, under the most stringent conditions, such as make and break using a three-connected male thread, it is preferable to anticipate the weight of the actual male thread and conduct tests, taking into account the load of this three-connection configuration (see [reference]). Figure 11 (b); Example of two connections). That is, preferably, it is designed to simulate loads applied to the insert tooth flank surface that range from those used in actual well applications to severe loads. The insert tooth flank surface refers to the surface of the internal and external threads that abuts against the longitudinal wall when the thread is arbitrarily tightened. This surface is not the thread tooth surface or the thread valley surface, but rather the inclined surface of the thread that is in contact with the thread when arbitrarily tightened.

[0077] Furthermore, as mentioned above, it is important to consider the effect of swaying in addition to the simple load. That is, by simulating the initial swaying that occurs in an actual well (refer to...). Figure 2 and Figure 3 This allows for a proper evaluation of heat resistance and stickiness.

[0078] Here, as Figure 2 (a) If the male thread 1 is placed only on top of the female thread 2 (only inserted), approximately half of the threads in the external thread 1a of the male thread 1 will be exposed from the female thread. Therefore, the male thread is prone to wobbling when tightened with power pliers. In contrast, as Figure 2 (b) The tighter the fastener, the less the male buckle 1 wobbles during tightening. Additionally, as... Figure 3 As shown, due to the taper of the male thread teeth, there will inevitably be some wobble in the joint.

[0079] Considering the above, in this embodiment, a shorter male buckle than the male buckle being evaluated is used as the test male buckle 1. A longitudinally type (a type that tightens the male and female buckles vertically) power clamp 4 is also used, and the initial setting position before tightening is specified as being looser than before. Furthermore, in this embodiment, a weight 3 is applied to the male buckle 1. Thus, in this embodiment, a more suitable method for evaluating burn-resistant adhesion is achieved, taking into account both the issue of the weight load of the weight 3 and the problem of "initial setting wobbling."

[0080] exist Figure 1 The diagram shows a schematic of the device structure for the fastening loosening test in this embodiment.

[0081] In this embodiment, a tightening / loosening test is conducted on an oil well pipe threaded joint formed by attaching a male thread to the upper part of a female thread 2 with its shaft facing upwards and downwards. During this test, a test male thread 1 is used as the male thread, which is shorter than the male thread to be evaluated in the test. It should be noted that the external thread of the test male thread 1 is designed to be the same as the external thread of the male thread to be evaluated.

[0082] In addition, a weight 3 is installed on the upper part of the male buckle 1 used for testing. The mass of the weight 3 is set to be greater than or equal to the mass of the male buckle being evaluated, obtained by subtracting the mass of the male buckle 1 used for testing from the mass of the male buckle being evaluated. For simplicity, it is set to be greater than or equal to the mass of the male buckle being evaluated.

[0083] The initial setting position is set to a state in which the male thread of the test male thread 1 has more than 5 threads or 1 / 4 of the total number of threads of the test male thread 1, and the threads of the male thread 1 are exposed from the upper end face of the female thread 2.

[0084] The initial setting position is the starting position before tightening the test male buckle 1 using the power clamp 4.

[0085] Furthermore, in this embodiment, the weight 3 can be suspended by a suspension device 20 (heavy machinery) such as a crane. Reference numeral 21 indicates the chain used as a sling for the crane. By enabling the weight 3 to be suspended, the load on the internal thread 2a of the female thread 2 via the male thread 1 using the weight 3 can be adjusted.

[0086] At this point, the counterweight 3 can be pre-connected to the male thread 1. In this case, by suspending the counterweight 3, the load on the internal thread 2a of the female thread 2 using the mass of the male thread 1 can also be adjusted.

[0087] in addition, Figure 1An example is shown where the female buckle 2 is used as the lower part of the power clamp 4 for fixation. In this case, the manually tightened male buckle 28 is fixed to the lower part of the female buckle 2, and the female buckle 2 does not shift when the power clamp 4 grips the female buckle 2. On the other hand, depending on the method of power clamping, sometimes the manually tightened male buckle 28 is used as the lower part of the power clamp 4 for fixation. This disclosure does not limit the method of fixing the lower part of the power clamp 4.

[0088] In this embodiment, when the power clamp 4 is tightened, the chain 21 is set to be loosened (not suspended), and the weights of the counterweight 3 and the male fastener 1 are not loaded on the internal thread 2a. Furthermore, when the power clamp 4 is loosened, the weight 3 is suspended by the chain 21, thereby reducing the load on the internal thread 2a from the weight 3. At this time, even when the weight 3 is connected to the male fastener 1, the load on the internal thread 2a from the male fastener 1 can also be reduced. For example, the suspension state of the crane 20 is controlled such that the weights of the weight 3 and the male fastener 1 are not loaded on the internal thread 2a. The reduction of the load is not limited to controlling the load using the weight 3 and the male fastener 1 to be zero. For example, the weight corresponding to the weight can be reduced as described above, or the suspension can be controlled to be less than half the total load of the weight 3 and the male fastener 1.

[0089] Furthermore, even if only the crane 20 is used to suspend the device to reduce the load, the posture of the male buckle 1 may become unstable when it comes loose. Therefore, the load reduction amount can be set to be relatively small.

[0090] This disclosure also includes tests conducted without the weight 3 during the detachment process.

[0091] (Regarding the initial settings location)

[0092] In general, during a tightening and loosening test using a short male thread, since the offset between the axial centers of the external thread 1a and the internal thread 2a can be reduced and tightened, it is possible to manually tighten the thread until about 1 to 3 threads of the male thread 1 are exposed. When the tightening and loosening test is performed from this position using a power clamp 4, even if the male thread 1 has a large diameter of 9-5 / 8″ or 13-3 / 8″, it is difficult for it to burn and stick. However, in this embodiment, if the tightening is stopped by manual tightening just before the external thread 1a and the internal thread 2a are fully engaged, and the initial state before tightening is set as a wobbly state, then when tightening with the power clamp 4, the short male thread 1 can reproduce the oscillation and rotation of the long male thread, which becomes a condition that easily leads to burning and sticking. That is, it can be set to a harsh test that simulates the actual tightening state in a well.

[0093] Regarding the engagement and initial setup of the female and male threads, in actual wells, the male thread is not set perfectly straight. The male thread tends to be set at a slight angle (see [reference]). Figure 13 Therefore, in actual wells, the male thread cannot be set to the extent that is often seen in laboratories (test sites), with about 1 to 3 threads protruding from the female thread 2. In actual wells, the initial setting position is mostly a state where more than 1 to 3 threads are exposed, resulting in the male thread being exposed.

[0094] The relationship between rotation (speed) and torque when using a power clamp for fastening is, for example, as described above. Figure 15 In this way, the torque increases sharply due to the rotation near the tightening point. Therefore, even when tightened to a position that can be manually tightened, in actual wells, it is common to see about 7-9 teeth exposed. It is rare to see a tightening of about 1-3 teeth after manual tightening.

[0095] Furthermore, in actual wells, when observing the male thread as a whole, it does not tighten gradually in a straight line. The male thread is manually tightened onto the female thread, becoming suspended by a rope from the opposite side of the tightened side. From this state, the male thread is tightened or loosened by rotating it with power pliers. At this time, as the male thread moves away from the tightened female thread, the end of the male thread gradually tightens or loosens while flexing and wobbling. Importantly, it is in a state where the tightening is not uniform, with some areas of strong contact or weak contact in the threaded portion, that is, there is "wobbling," while tightening and loosening. This situation is not easy to see when observing from a distance when using a male thread of actual length, but it is clearly visible when observing the rotation of the male thread during screwing in from above with power pliers. Figure 11 (b) In practice, it was observed that when the female buckle 30c is used as the bending point, the male buckles 30a and 30b on both sides achieve balance while rotating and being tightened.

[0096] In this embodiment, the intention of this disclosure is that, for this situation, instead of testing with the actual length male thread in the laboratory (testing range), a suitable simulation test is conducted using a short male thread that is shorter than the actual length male thread. Therefore, by improving the combination of the applied load, the load application method, the length of the short male thread, and the fastening setting method (initial setting position) to a more optimized state, it is possible to achieve a more accurate evaluation.

[0097] In this embodiment, for example, during a fastening / loosening test, the weight 3 is suspended from above using heavy machinery (suspension device 20) such as a crane. Then, based on the lifting of the weight 3 using the heavy machinery 20, the load applied to the female buckle 2 side (internal thread 2a side) via the upper part of the test male buckle 1 is adjusted. For example, during fastening, the suspended chain 21 is loosened, and the weight 3 is applied to the female buckle 2 side (internal thread side) via the male buckle 1. On the other hand, tension can be applied to the suspended chain 21 without applying or reducing the load on the weight 3. Thus, the load on the male buckle 1 can be adjusted using the weight 3. After conducting various studies, the inventors have reached the following conclusions: When tightening, applying a load to the internal thread 2a side of the female thread 2 becomes a stringent condition; when loosening, assuming the weight 3 is suspended while the mass of the external thread 1a (male thread 1), including the weight 3, is not applied to the internal thread 2a side, resulting in a oscillating rotation of the male thread accompanied by shaking, which also becomes a stringent condition. In this embodiment, this state can be simulated.

[0098] (Test buckle 1)

[0099] Furthermore, in this embodiment, the combination of the length of the short male thread 1 and the load applied to the internal thread using the counterweight 3 is also important. For example, when the length of the short male thread 1 is 3000mm to 5000mm, by applying a load equivalent to or greater than that of an 8m male thread blank pipe during tightening, and also applying a load during loosening, it is possible to simulate the tightening and loosening conditions of using a full-length male thread in an actual well. However, with short male threads of this length, the setup during experiments often becomes slightly difficult.

[0100] On the other hand, when using short male threads with a length of 600mm to 2000mm, similarly, by applying a load equivalent to or greater than the weight of an 8m male thread blank pipe during tightening, and conversely setting it to a state where no load is applied during loosening, it is easier to simulate the tightening and loosening conditions of using actual-length male threads in a well.

[0101] As described above, in this embodiment, the aim is to simulate, with higher precision than ever before, the potential for lubrication and burning of the oil well pipe threads during operation using actual length male threads in real oil / gas fields.

[0102] In actual installation of male fasteners, each 8-12 meter (25-40 foot) component is individually fastened, or components consisting of 2-3 connected components are fastened using power clamps 4. During installation, the male fastener 30 is simultaneously suspended from above by a crane 32 using ropes and fastened (see reference). Figure 9 , Figure 10However, due to its construction, it is impossible for the load on the internal thread to be completely zero. Because the male thread needs to gradually shift downwards as it is tightened with the external thread, in the most stringent case, the entire load of the male thread is applied to the lower female thread side. Furthermore, in actual installation, when loosening the fastener, the load on the male thread 30 is slightly reduced towards the female thread 31 because the male thread is suspended from above by ropes while being loosened. However, in the most stringent case, the entire weight of the male thread 30 is applied to the female thread 31 side.

[0103] The following describes this embodiment in more detail.

[0104] (Evaluation Method)

[0105] This embodiment describes a method for evaluating the fastening loosening of an oil well pipe threaded joint with a female thread 2 having an internal thread 2a and a male thread 1a having an external thread. It is a longitudinal method where the joint's shaft is positioned vertically. Specifically, a fastening loosening test is performed using a power clamp 4 on an oil well pipe threaded joint where the male thread is installed from the upper part (threaded portion) of the female thread 2, which is positioned vertically. This is based on the actual well operation where the internal thread 2a is located at the bottom and the external thread 1a is located at the top. In the case of a T&C type threaded joint, the lower side abuts against the coupling (female thread 2), and the upper side abuts against the male thread. In the case of an integrated threaded joint, the lower side becomes the female thread 2, and the upper side becomes the male thread.

[0106] (Test buckle 1)

[0107] In this embodiment, the test male thread 1 is a short male thread that is shorter than the male thread to be evaluated and has the same thread structure as the male thread to be evaluated. The test male thread 1 is manufactured, for example, by cutting off the male thread to be evaluated.

[0108] The length of the male buckle 1 used in the test is, for example, between 600mm and 5000mm, preferably between 600mm and 2000mm.

[0109] The setting of 600mm or more is based on the minimum length required to ensure the gripping part of the power clamp 4. Furthermore, the setting of 5000mm or less, preferably 2000mm or less, is based on the limit of length for easy operation. Additionally, the upper limit of 5000mm is determined because the actual length of the male thread is mostly in the 8-12 meter range (25-40 foot range), so it is determined based on approximately half of that. The longer it is, the closer it is to the actual length of the male thread. In this case, especially even without the application of the counterweight 3, it becomes the tightening itself within the actual length of the male thread, thus also implying the limit length for arrangement during laboratory experiments.

[0110] In practice, it is convenient to use, for example, a male thread of about 1m (e.g., 600mm to 1500mm) as the male thread 1 for testing. The length of this male thread 1 for testing is selected based on the ease of handling, and it is also an appropriate length from the viewpoint of the ease of fixing the counterweight 3 shown below. The male thread 1 for testing can also be a male thread with a structure formed by connecting multiple oil casing short sections.

[0111] It should be noted that there are no specific regulations regarding the length of the two sides of the female thread; in practice, the female thread used in the well can be used. Furthermore, when gripping with pliers, it is preferable to loosen the male thread 1 in a manner that does not damage the opposite threaded surface of the evaluation object, and then manually tighten it for testing.

[0112] However, when the load on the counterweight 3 is not reduced during release, the length of the test thread 1 is preferably set to, for example, 3000 mm to 5000 mm. This is because the optimal length of the test thread 1 varies depending on the combination of load application methods described later. It should be noted that when the load on the counterweight 3 is not reduced during release, i.e., when the load is maintained during the release process, a length of 3000 mm or more is preferred. This is because, if the length is less than 3000 mm, when the counterweight 3 is suspended during release without load reduction, it may not be possible to accurately simulate the actual well conditions.

[0113] (Load of the third hammer)

[0114] In this embodiment, a weight 3 is installed on the upper part of the test male buckle 1, and a fastening loosening test is conducted under load.

[0115] The mass of the weight 3 is, for example, set to be (the mass of the male thread (actual male thread) being evaluated - the mass of the male thread 1 used in the test) or more. Alternatively, the mass of the weight 3 is, for example, set to be the mass of the male thread being evaluated, which has a length of 8m or more. Furthermore, the upper limit of the mass of the weight 3 is, for example, set to be 3 times the mass of the male thread (actual male thread) being evaluated. Currently, applying these or more tightening conditions does not reflect the actual conditions in the well. However, this method is included in this application when a new idea is proposed to connect four or more male threads, moving beyond the maximum of three.

[0116] As mentioned above, the mass of the weight 3, for example, the load applied to the internal thread 2a, will be a lower limit equivalent to the mass of the male thread being evaluated, and an upper limit equivalent to the mass of the three male threads being evaluated. The reason for adding a weight 3 equivalent to the actual length of the male thread or equivalent to the mass of three connected threads is as follows: That is, during actual make and break operations in actual wells, in onshore wells (onshore drilling equipment), due to the tightening and operation of each thread individually, the maximum applied weight is the weight of one male thread. Three threads are considered because in offshore wells (offshore drilling equipment), components pre-connected in threes are often transported to the drilling equipment and tightened in units of three on the drilling equipment.

[0117] However, in actual well Make & Break, such as Figure 9 , Figure 10 Because the male thread is suspended and secured using a boom crane, not all of the male thread 30's weight is applied to the female thread 31. Specifically, in actual well operations, as the male thread is gradually lowered while tightening the threads, it is theoretically impossible to completely suspend it to achieve zero load due to its own weight. Therefore, the mass of the counterweight 3 used in the test is preferably a mass that can simulate the maximum possible load. However, if it is necessary to consider tests under harsh conditions, it is technically possible to increase the mass of the counterweight 3 to the desired level. The weight of the counterweight 3 is only technically specified based on the crane (heavy machinery) used to suspend the male thread 1 for the test and set it on the female thread 2 along with the counterweight 3. It should be noted that the counterweight 3 can also be configured to be suspended by another crane.

[0118] (How to set up Hammer 3 and the shape of Hammer 3)

[0119] A counterweight 3 is installed on the upper part of the male thread 1 on the reverse tightening side, which serves as the test thread. This is to simulate a condition close to the actual use of the thread by applying a load during tightening. It should be noted that the upper part of the male thread 1 refers to, for example, the position of the threaded portion formed on the upper side or the area before and after it.

[0120] Furthermore, the method of installing the counterweight 3 on the upper part of the test buckle 1 is not particularly limited.

[0121] Next, examples of installing the counterweight 3 will be explained (Installation Examples 1 to 3).

[0122] <Installation Example 1>

[0123] In installation example 1, such as Figure 4 As shown, a clamp 5 is used to fix the weight 3 to the upper side of the test male buckle 1. Figure 4In the example, a hook rod is shown as the clamp 5. Then, the clamp 5 is set to a state in which the weight 3 is suspended by a sling 6 such as a rope or chain, thereby installing the weight 3 on the upper part of the male buckle 1.

[0124] exist Figure 4 In the illustration, a plate-shaped block is shown as the shape of the hammer 3, but the shape of the hammer 3 can also be other shapes. In addition, it is preferable to pre-install a clamp 5 on the hammer 3 that can be suspended by the crane 20.

[0125] In this case, when the male buckle 1 swings, the weight 3 also moves in a swinging rotation manner.

[0126] It should be noted that, in this case, the actual height of the counterweight 3 is not located above the male buckle 1. However, the load-bearing position of the counterweight 3 on the male buckle 1 (the support position of the counterweight 3) is located above the male buckle 1.

[0127] <Installation Example 2>

[0128] In installation example 2, such as Figure 5 As shown, the weight 3 is a cylindrical shape resembling a steel billet, with its lower surface diameter larger than that of the test male buckle 1. The upper end of the insertion rod 10 is pre-fixed to the lower surface of the weight 3 by welding or other means. The diameter of the insertion rod 10 is set to be smaller than the diameter of the inner diameter surface 1c of the test male buckle 1. Preferably, an accessory 11 capable of being suspended by a crane 20 is pre-installed on the upper part of the weight 3.

[0129] Then, in installation example 2, it is set that the weight 3 is placed on the upper end of the test male buckle 1 while the insertion rod 10 is inserted into the upper opening of the test male buckle 1 from the top.

[0130] In this case, in response to the lateral oscillation of the male buckle 1, the center of gravity of the weight 3 is eccentric and displaced laterally. Furthermore, the insertion rod 10 makes it difficult for the weight 3 to detach from the upper part of the male buckle 1. The length of the insertion rod 10 is preferably more than half the length of the male buckle 1 used in the test.

[0131] <Installation Example 3>

[0132] In installation example 3, such as Figure 6 The image shows an example where the insertion rod 10 is positioned on the lower surface of the counterweight 3, which is made of a disc-shaped plate. The other structures are the same as in installation example 2.

[0133] The weight 3 can be installed using any method. The weight 3 of the required mass can be installed on the upper part of the male buckle 1 for testing. Other known methods can be used to install it on the upper part of the male buckle 1.

[0134] At this time, it is preferable to install it on the upper part of the male buckle 1 as in installation examples 1 to 3, so that in response to the swinging rotation of the male buckle 1, at least the position of the counterweight 3 is also displaced (swung) in the lateral (radial) direction relative to the male buckle 1.

[0135] Thus, in this example, it is safe and simple, and can respond to the oscillation and rotation of the male thread 1, allowing the load on the internal thread 2a to change using the counterweight 3. Thus, in order to enable a rigorous evaluation of the burning and sticking caused by the swaying of the several counterweights 3, the following conditions are preferably met.

[0136] (1) The hammer 3 is symmetrical in the left, right and front and back.

[0137] (2) In the form of the male buckle 3-way insertion type (installation example 2, 3, etc.), there is a margin of more than 20mm (the margin between the outer diameter of the insertion rod 10 and the inner side of the male buckle).

[0138] Here, as an example of the installation method of the counterweight 3, the case of installation using the insertion rod 10, as in Installation Example 2, will be listed and explained in detail.

[0139] In order to achieve the actual weight of the male thread (the male thread being evaluated) using the counterweight 3, a cylindrical iron block is pre-cut into a component with a load capacity equivalent to that required, which serves as the counterweight 3. The cylindrical iron block can be, for example, a steel billet before seamless rolling.

[0140] Additionally, as the insertion rod 10, a component is prepared by cutting a small-diameter cylindrical iron block to a length of 70-80% of the length of the test male thread 1. The insertion rod 10 can also be in a tubular form (steel pipe). The small-diameter cylindrical iron block can be, for example, a fine steel billet before seamless rolling.

[0141] Then, the upper end face of the insertion rod 10 is joined to the center of the lower surface (bottom surface) of the cylindrical weight 3 by welding. The joining method of the insertion rod 10 to the lower surface of the weight 3 is not limited to welding, and other known joining methods may also be used.

[0142] It should be noted that the hanging accessories are fixed by welding at the center of the upper surface of the hammer 3.

[0143] In order to evaluate threaded joints of different sizes, it is preferable to prepare weights 3 with various outer diameters and masses in advance.

[0144] In this embodiment, such as Figure 7As shown, a through hole 10a is formed in the radial (lateral) direction for the insertion rod 10. This through hole 10a is set to a diameter sufficient to allow the through rod 12 to pass through. Additionally, a through hole 1d is pre-formed in the test male buckle 1. The through hole 1d is positioned such that, when the insertion rod 10 is inserted from the upper side of the male buckle 1 and the counterweight 3 is placed on the upper end of the male buckle 1, the through hole 10a opening in the insertion rod 10 is visible laterally. Two through holes 1d are formed symmetrically about the male buckle 1. Then, during the test, the through rod 12 is passed through the through hole 10a from the outside, from one through hole 1d to the other. The through rod 12 is set to a length at both ends protruding outwards only from each through hole 1d.

[0145] like Figure 7 and Figure 8 As shown, the through hole 1d allows the inserted through rod 12 to move vertically. The through hole 1d can be circular, or it can be an elongated hole with its major axis pointing vertically, etc. Figure 7 In this configuration, with the counterweight 3 placed on top of the male buckle 1, the through rod 12 is positioned at the center of the through hole 1d, but this is not a limitation. For example, it could be... Figure 8 (b) State. It should be noted that the chain 21 used for suspending the counterweight itself and the other sling 23 suspended from the through bar are set to be independently hooked to the hook 29 of the crane, and the state of tension is set as the initial position.

[0146] Alternatively, a large-diameter component, such as a nut component with a larger diameter than the small diameter of the through hole 1d, can be installed at both ends or one end of the through rod to prevent the through rod 12 from coming off.

[0147] In this way, when the insert rod 10 is inserted through the through hole 1d by the through rod 12, the installation of the counterweight 3 is more stable.

[0148] Furthermore, the through rod 12 can move vertically within the through hole 1d. This vertical displacement is, for example, set to be greater than or equal to the downward displacement of the male thread 1 caused by fastening. The displacement is, for example, 10mm to 50mm.

[0149] Furthermore, the mass of the hammer 3 can be adjusted (increased) by adding weights to one side of the hanging accessories of the hammer 3 through several mass adjustments (increasing the direction of the weight). There are no restrictions on the method of adding weights; it can be a hook-type or a ring-shaped component.

[0150] (Methods for applying the third weight and methods for reducing the load)

[0151] In reality, to prevent excessive imbalance of the load relative to the male buckle 1, the method of applying the counterweight 3 is to suspend the hanging accessory 11 set on the counterweight 3 itself together with the through rod 12 through which the insertion rod 10 passes through the counterweight 3 (see reference). Figure 7 For example, for both ends of the suspension fitting 11 and the through bar 12, slings 21 and 23, such as slings or chains, which are mounted on the crane at their upper ends, are pre-suspended. By pre-releasing these slings 21 and 23, a state is set in which a load is applied to the internal thread 2a side. Anticipating the worst-case scenario of a breakdown in equilibrium, it is preferable to improve the situation so that the counterweight 3 itself does not fall downwards.

[0152] For example, such as Figure 7 As shown, a hanging accessory 11, serving as a hook, is installed at the center of the upper end face of the counterweight 3 by welding or the like. The hanging accessory 11 is preferably a swivel that can rotate to eliminate torsion. A chain or similar suspension cable 21 is suspended from this hanging accessory 11, and the suspension cable 21 is further attached to, for example, a hook 29 of a crane 20. The tension of this chain or similar suspension cable 21 (hereinafter also referred to as chain 21) allows for easy determination of whether a load is applied to the counterweight 3 based on its slack.

[0153] From this state, the power clamp 4 is driven to perform a tightening test on the threaded joint. Therefore, when the external thread 1a moves in the tightening direction, the position of the external thread 1a (the position of the male thread 1) moves downwards, causing tension to be applied to the chain 21 or sling 23 suspended on the counterweight 3. Since the load from the male thread 1 may become lighter when the tension is applied, it is preferable to apply the load from the male thread 1, including the counterweight 3, to the internal thread 2a side while the sling 23 is suspended on the through bar 12 to prevent the counterweight 3 from falling, and while confirming that the sling 23 is relaxed (confirming applied stress).

[0154] In this embodiment, when using an insert-type counterweight 3 with an insert rod 10 inserted, to prevent accidents such as the counterweight 3 falling, the sling connected to the counterweight 3 is suspended without tension in the crane 20 as a precaution. Furthermore, a test is conducted with the sling 23 suspended at both ends of the through rod 12. The sling 23, installed on the through rod 12, is, for example, suspended under tension and pre-hooked onto the overhead crane. In this case, when the hoisting device (winch) is pre-clamped and suspended on the overhead crane in a manner that allows tension to be applied to the sling 23 independently of the crane 20, tension can be easily applied.

[0155] It should be noted that the preferred configuration is as follows: the chain 21 for suspending the front end of the counterweight 3 and the front end of the sling 23 for suspending the through bar 12 are each independently suspended from the hook on the upper part of the crane. When tightening or loosening the threads from this state, by monitoring the vertical positional relationship between the through hole 1d and the through bar 12, it is possible to determine whether (the mass of the male thread + the mass of the counterweight 3) is applied to the internal thread of the female thread 2.

[0156] Slack in chain 21 means that the load tends to be applied to the internal thread side of the female buckle 2 located below. To apply the full load (mass of male buckle 1 + mass of counterweight 3), as... Figure 8 While monitoring the positional relationship between the through rod 12 and the through hole 1d, the experiment was conducted by slightly raising and lowering the crane 20. For example, Figure 8 (a) shows the state in which the load is applied to the crane (the state in which no load is applied to the internal thread of the female thread). Figure 8 (b) shows the state where no load is applied to the crane (the state where all load is applied to the internal thread of the female thread).

[0157] like Figure 7 As shown, the suspension position in the crane 20 is fixed and the threads are tightened. It should be noted that this is assumed that the through rod 12 is not in contact with the upper and lower openings of the through hole 1d, and the sling 23 installed on the through rod 12 is not slack. As the threads are gradually tightened from this state, the position of the male thread 1 decreases, the position of the through hole 1d shifts downwards, but the position of the through rod 12 remains unchanged. Therefore, relative to the position of the through hole 1d, the position of the through rod 12 gradually moves upwards. Then, it can be seen that after the through rod 12 contacts the 12 o'clock position (the upper end of the opening) of the through hole 1d (refer to...), Figure 8 (a) The stress of the counterweight 3 is not applied to the internal thread side at all. Then, it is possible to know the position where the integrated counterweight 3 needs to be lowered. The position (tension) of the chain 21 will also change slightly, but when the position of the through hole 1d and the through rod 12 is monitored, it is possible to maintain strict conditions for the load applied to the internal thread 2a. In addition, the position of the crane can also be lowered by contacting the through rod 12 with the 6 o'clock position (lower end of the opening) of the through hole 1d (see reference). Figure 8 (b) This is confirmed by ensuring that the sling suspending the through bar 12 is not slack. When applying a load while tightening the threads, the position of the through bar 12 relative to the through hole 1d can be monitored to ensure that the desired load can always be carried safely and reliably.

[0158] Here, further explanation is provided regarding the correct conditions of load ON / OFF (load ON: load applied, load OFF: load removed) during tightening / loosening, which are the subjects of this disclosure. When chain 21 is slack, the full weight of the test male buckle 1 and the weight of the counterweight 3 are applied to the female buckle 2 (clamp) located at the lower part. More precisely, this includes the overall weight of the through bar 12, the overall weight of the suspension fitting 11, and the weight of the chain 21 and other suspension cables placed above the counterweight 3 in the slack state. In this disclosure, the weight is described as the main component of the weight of the test male buckle 1 and the weight of the counterweight 3, etc., occupying a short distance. This refers to the applied load.

[0159] On the other hand, the "unloaded state" mentioned in this disclosure, caused by the tension of chain 21, ideally refers to a state in which the overall weight, including the weight of the test male buckle 1 and the weight of the counterweight 3, is not applied to the lower female buckle 2 (clamp). That is, it refers to a state with zero applied load. However, maintaining this state throughout the test is difficult. This is because the position of the test male buckle 1 gradually rises as it loosens.

[0160] Therefore, in this disclosure, the "removed state" is defined as follows: that is, the range from the state where the applied load is zero to the application of a weight equivalent to 2m to the male buckle 1 used for the test is defined as the "removed state". 2m means that when the length of the male buckle 1 used for the test is set to the range of 600mm to 2m, as described in the following embodiments, the upper limit of the effective length used for loosening in the "removed state" is specified.

[0161] like Figure 8 As shown, this judgment can be easily made based on the positional relationship between the through rod 12 and the through hole 1d. This can be achieved by ensuring that the through rod 12 does not contact the hole at the 6 o'clock position, and if it does contact the hole, immediately returning it to the 12 o'clock position while conducting the test.

[0162] Additionally, monitoring can be performed using a crane weight gauge. The crane weight gauge is hooked onto the overhead crane, with chain 21 positioned below it. For components where the counterweight and the short test male buckle 1 are integrated, the weight is measured using this crane weight gauge before the test. In the relaxed state, the difference between the weight measured by the crane weight gauge and the actual weight is equivalent to the full weight applied to the lower female buckle (coupling). Even when chain 21 is taut, it does not mean that the full weight of the counterweight and the full weight of the test male buckle 1 are suspended. Since even when only a portion is suspended, the chain is under tension, the "unloaded state" can be determined using the above method.

[0163] Thus, "unloading the load" refers to adjusting (controlling) the load so that the weight of the male buckle 1 and the weight of the counterweight 3 used for testing are not applied to the female buckle 2 side. In this example, the control of unloading the load also includes the state in which the load applied to the female buckle 2 side is not actually zero.

[0164] (Initial setting location for public buckle)

[0165] In this embodiment, it is also important to position the external thread 1a of the test male thread 1 relative to the internal thread 2a of the female thread 2.

[0166] In this embodiment, the initial setting position (tightening start position) before tightening is defined as a state in which the threaded portion is intentionally wobbled while a load is applied to the upper part of the test male thread 1 using a weight 3. By tightening the thread from this position using a power pliers 4, the actual thread tightening conditions can be simulated. That is, in this embodiment, the male thread is intentionally set in a position where it is not tightened to the manual tightening position.

[0167] It should be noted that during this stage, sometimes a component that integrates the counterweight 3 and the male buckle 1 is used. Additionally, sometimes the counterweight 3 is installed laterally. In the former case, as shown in the following setup, the integrated counterweight and male buckle type is suspended using a crane or similar device, and the counterweight is installed without applying any load. In the latter case, the male buckle 1 is inserted into the female buckle 2 until it reaches the following position. Furthermore, a stabbing guide can be used for initial tightening.

[0168] In this embodiment, the initial setting position during the tightening and loosening test using the power clamp 4 is set such that the external thread 1a is inserted into the internal thread 2a in a manner that will not cause an engagement error, and the threads are tightened manually. The threads are engaged to some extent, and cannot be pulled out even if pulled (even if the male thread 1 is lifted upwards). Specifically, the initial setting position is set to a position where the number of remaining threads of the male thread from the upper end face (coupling end face) of the female thread 2 is greater than or equal to the number of threads remaining in the male thread, which is either 5 or 1 / 4 of the total number of threads of the male thread.

[0169] The initial setting position with this looser tightening is used to simulate strict conditions to achieve the shaking during Make & Break.

[0170] Here, when manually tightened to the position with 1-3 threads remaining, it is impossible to simulate shaking. After another 1-3 cycles to achieve a tight fit, the male thread simply tightens while descending directly downwards. In this case, since it is difficult for the male thread to partially abut against the coupling thread (internal thread 2a of the female thread 2) during tightening, which might occur in actual wells, it gradually tightens while uniformly abutting against the coupling thread (internal thread 2a of the female thread 2).

[0171] Conversely, if only the external thread 1a is inserted into the internal thread 2a, thread misalignment (tightening with misaligned threads) may occur during Make & Break. Therefore, there is a risk that the intended tightening loosening test cannot be performed. If the dry film formed on the thread surface due to thread misalignment is destroyed or the thread teeth themselves are damaged, the lubricating properties of the dry film cannot be evaluated. Therefore, the number of remaining threads at the initial setting position before tightening is preferably less than 2 / 3 of the total number of threads. The evaluation can also include concerns about thread misalignment, and the condition of inserting only the external thread 1a into the internal thread 2a is also included in this application.

[0172] (Method of applying a heavy hammer while conducting a fastening loosening test)

[0173] In this embodiment, by taking into account not only the load of the counterweight 3, but also the shaking when the male buckle 1 is tightened / loosened, it is possible to ideally simulate the actual Make & Break.

[0174] This describes the state of compaction in a simulated actual well.

[0175] Figure 9 This is a schematic diagram simulating the Make & Break in a male thread. In this case, as is often the case in actual wells, the compensator 33 and male thread 30 are usually suspended by a crane 32 and the male thread 30 is set up, and attention is paid to the fact that the male thread 30 is straight toward the internal thread of the female thread 31.

[0176] In addition, such as Figure 10 As shown, without the compensator, the Make / Break condition becomes severe because the male thread 30 tends to be angled relative to the female thread 31. During the initial tightening and later loosening stages, the external and internal threads partially abut or do not abut, resulting in uneven load application and only a stronger load applied to a portion, thus creating a severe condition.

[0177] When the coupling 31 (female) and male 30 are tightened to the temporary tightened position by hand, it is rare for the male 30 to stand upright from that position. When viewed from below, it can be visually confirmed that the male 30 appears to be bent (see exaggerated illustration). Figure 11(a)). In the case of fastening two or more male threads 30, most are configured such that the inclination direction changes at the coupling 30c position between male threads 30a and 30b, and several bends are complementary and opposite to each other (see exaggerated illustration). Figure 11 (b)). As a result, there is often wobbling when tightening the actual male thread. It should be noted that the terms "oblique setting" and "bending" used here do not mean that the axis of the male thread is tilted by as much as 5 to 10 degrees, but rather that the male thread is flexing in the elastic area. The angle is small, referring to the appearance of a gradually bending appearance when viewed from below.

[0178] Therefore, in the initial tightening and later loosening stages, the external and internal threads partially engage or disengage. Consequently, a uniform load is not applied to the external thread; instead, a stronger load is applied to only a portion, creating a tight condition. Wobble leads to a larger load being applied from the male thread, and due to uneven tightening and localized contact rotation, an offset load is applied. Figure 12 As shown, in simulating this situation with a counterweight 3 attached to the short male thread 1, the simulation is performed in this embodiment by loosely setting the fastening position of the male thread 1 in a manner that is not fully manually tightened. When considering the condition of imposing a large load as expected in an actual well, it is rare for the load to be applied evenly to the threaded joint when the fastener comes loose; it is necessary to anticipate the condition of applying an offset load due to local contact. This disclosure intentionally creates and simulates this harsh application condition.

[0179] Here, when the length of the test male thread 1 is between 3000mm and 5000mm, a heavy hammer load can be applied under load both during tightening (make-up) and loosening (break-out). This loading method is very similar to the conditions implemented in actual wells, but with slight differences. The effect of large load and offset load is achieved by setting a heavy hammer 3 at the end of the male thread with a weight equivalent to or greater than that of an 8m male thread blank pipe, and setting the initial setting position within a specified range.

[0180] On the other hand, in order to simplify the setup for the test, when using a shorter male thread with a length of 600mm or more up to 2000mm as the male thread 1 for the test, by applying a heavy hammer load when tightening (make-up) but not applying or reducing the load when loosening (break-out), it is possible to achieve the effect of large load and offset load.

[0181] When breaking out, the method of applying the offset load, with the weight 3 suspended in the direction without the weight 3, is related to the length of the male thread. Although it tends to be related to the length of the male thread, when breaking out with a load applied to the male thread with the weight 3, when the male thread is short, it tends to rise straight upwards gradually without wobbling. That is, it is presumed that this is because the weight 3 acts as a counterweight, allowing the thread to loosen without wobbling. In this case, the offset load cannot be simulated. On the other hand, when the male thread is long, it tends to bend due to its length, so even when the thread is loosened with the load of the weight 3 applied, the conditions of wobbling and offset load can be simulated.

[0182] In shorter male threads, to generate a wobble when male thread 1 is released, this can be achieved by suspending a weight 3 from above and releasing it. Testing was conducted with the weight 3 suspended completely without any load applied as a zero-load condition (ideal zero-load condition), and with the weight 3 slightly suspended as a maximum load condition. When released within these ranges, wobble can be simulated. In fact, when confirmed by touch, the entire male thread including the weight 3 becomes hotter when suspended and broken out compared to the state where the full load of the male thread including the weight 3 is applied to the internal thread 2a. Based on this fact, the change in slippage due to wobble inevitably has an adverse effect on the film, compounds, etc., that contribute to lubrication.

[0183] Here, as Figure 1 As shown, the position where the torque is applied to the male thread 1 using the power clamp 4 is below the load position of the male thread 1 using the counterweight 3. Additionally, the tightening and loosening of the joint in the well pipe thread joint tightening and loosening test is performed using a longitudinal power clamp 4. The power clamp 4 is often driven, for example, by computer control similar to that used in actual wells. Manual tightening methods are also included in this disclosure.

[0184] (other)

[0185] In this embodiment, the following structure can also be adopted.

[0186] (1) This embodiment is a method for evaluating the tightening and loosening of oil well pipe threaded joints. It is a method for evaluating the tightening and loosening of oil well pipe threaded joints consisting of a female thread with internal threads and a male thread with external threads using power pliers. When testing the tightening and loosening of an oil well pipe threaded joint consisting of a female thread with its shaft facing upward and downward, a test male thread consisting of a male thread shorter than the male thread being evaluated is used as the male thread used in the test. A weight is installed on the upper part of the test male thread. The mass of the weight is set to be greater than or equal to the mass of the male thread being evaluated minus the mass of the test male thread. The initial setting position is set to a state in which the number of threads of the test male thread, which is greater than 5 or 1 / 4 of the total number of threads of the test male thread, is exposed from the upper end face of the female thread. The initial setting position is the tightening start position before tightening the test male thread with power pliers.

[0187] For example, the mass of the hammer is set to be the mass of the male buckle, which is the object of evaluation, with a length of 8m or more.

[0188] Alternatively, for example, the length of the male buckle used in the above-mentioned test can be set to a range of 600mm to 5m.

[0189] Based on this structure, a fastening loosening evaluation method can be provided that can accurately evaluate the burn-resistant adhesion of oil well pipe threaded joints even without testing with threaded joints of actual length.

[0190] That is, even if a male thread shorter than the male thread to be evaluated is used as the test male thread, the initial setting position before tightening is intentionally set loosely compared to the past by applying a load on the upper part of the male thread that is equivalent to the male thread to be evaluated. Thus, in this embodiment, the thread is tightened while it is oscillating and rotating, and tightening is performed under conditions close to the actual well conditions.

[0191] As a result, one aspect of the present invention improves upon conventional laboratory-level equipment, focusing on an evaluation method for assessing and estimating the presence or absence of burn-in and lubrication characteristics in actual wells. Another aspect of the present invention relates to an evaluation method for determining whether the design, surface treatment, and lubrication of threaded joints are suitable for actual well operating conditions. This method can determine that, under conditions deemed satisfactory in tests based on one aspect of the present invention, no burn-in incidents occur in actual wells, sufficient lubrication is provided, and the joint is suitable for application.

[0192] (2) In this embodiment, the loosening is performed by reducing the load applied to the internal thread of the female thread from at least the weight of the male thread and the test thread.

[0193] For example, the load applied from the weight and the test male thread to the internal thread of the female thread is set to a removed state (e.g., adjusted (controlled) to zero), while loosening is performed.

[0194] According to this structure, by intentionally reducing the load when using the power clamp to loosen the connection, setting it to a state where the load is essentially not applied and the male thread is easy to swing and rotate, it is possible to simulate more realistic well conditions.

[0195] As a result, based on this structure, the burn resistance of oil well pipe thread joints can be evaluated more accurately and effectively.

[0196] In this case, for example, even if the length of the male thread used for testing is shortened to, for example, a range of 600mm to 2m, it is still possible to evaluate it with high accuracy.

[0197] In addition, when loosening, without reducing the load applied to the internal thread of the female thread, it is preferable to obtain the length of the male thread for testing, which is 3m or more and 5m or less.

[0198] (3) In this embodiment, a suspension device is provided, which is capable of suspending at least the weight of the hammer and the test male thread, and adjusting (controlling) the load applied from the hammer and the test male thread to the internal thread of the female thread by means of the suspension device.

[0199] According to this structure, for example, it is possible to adjust the load state applied from the counterweight to the internal thread via the male thread.

[0200] It should be noted that the suspension male buckle itself contributes to the instability of the male buckle.

[0201] (4) In this embodiment, the weight is placed on the upper end of the test male buckle and includes: an insertion rod that extends downward from the lower surface of the weight and is loosely inserted into the test male buckle; and a through rod that protrudes laterally from the insertion rod and protrudes outward through a through hole formed in the test male buckle, the diameter of the through hole being larger than the diameter of the through rod.

[0202] According to this structure, by oscillatingly mounting a counterweight on the upper part of the male thread and suspending the counterweight, the male thread can also be suspended. That is, it can be configured to reduce the load applied to the internal thread by the male thread.

[0203] (5) Further, this embodiment is a manufacturing method of an oil well pipe thread joint, where the oil well pipe thread joint includes a female thread with an internal thread and a male thread with an external thread. Among them, for the candidate male thread as the evaluation object adopted, a make-and-break test using the make-and-break evaluation method described above is performed, and the structure of the oil well pipe thread joint is determined according to the evaluation based on this test.

[0204] At this time, for example, the evaluation is at least one of at least the oil well pipe thread shape design and the lubrication conditions (conditions such as the lubrication physical properties, lubricating substances, surface treatment, lubricants, etc.) used in the oil well pipe thread joint.

[0205] According to this structure, even if a short male thread is used in the test, an evaluation equivalent to the test using the male thread as the evaluation object can be obtained. As a result, the oil well pipe thread joint can be manufactured with better precision.

[0206] Example

[0207] Next, the example of this embodiment will be described.

[0208] (Judgment criteria for make-and-break test, pass / fail judgment criteria based on the number of M / B times)

[0209] The number of M / B times is the number of Make&Break times, which is expressed by the number of fastening times here.

[0210] First, the judgment criteria for the make-and-break test and the pass / fail judgment criteria based on the number of M / B times in this example will be described.

[0211] In the laboratory lubrication test of the oil well pipe thread in this example, there are two judgment criteria. It is the pass / fail judgment based on the number of M / B times accompanied by the judgment of the surface state, and the judgment based on the test using the male thread of the actual length as the reference.

[0212] For the former, according to the API-5C5 standard, based on the number of Make&Break times, in casing applications, achieving 3 or more times is a pass judgment. In pipeline applications, it is achieving 10 or more times, and at the same time, there is no galling and no defects in the metal parts of the coupling and the male thread surface. It should be noted that casing applications and pipeline applications are designed according to the wells drilled by oil manufacturers, and cannot be strictly distinguished by outer diameter size uniformly. Therefore, in this disclosure, 7″ and below are regarded as pipeline sizes, and those exceeding 7″ are regarded as casings, and the discussion will be carried out below.

[0213] "No burning or sticking, no defects" refers to the so-called "no galling." The solid lubricant coating itself will erode; the eroded parts will re-adhere and re-form during fastening and loosening, thus achieving lubrication. Therefore, partial peeling and erosion of the solid lubricant coating are unavoidable, and peeling of the solid lubricant film does not affect the acceptance / failure determination. For couplings (female or male), visual inspection revealing defects, fuzzing, or surface deformation due to metal flattening; even if these can be made / broken, they are considered unacceptable. Furthermore, after visual inspection, palpation with bare hands or gloves reveals defects indicating cuts; these are also considered unacceptable. Additionally, since a burnished (reflective) finish on the sealing part is a sign of good lubrication, it should not be considered unacceptable. It is considered acceptable.

[0214] The latter is judged based on the deviation between the results of the fastening loosening test using the full-length male thread and the evaluation of the laboratory test using the short-length male thread. The smaller the deviation, the higher the accuracy of the evaluation of the laboratory test using the short-length male thread.

[0215] (Example 1)

[0216] Example 1 illustrates an example of how, based on this disclosure, a tightening and loosening test can simulate the Make & Break in a real-length male thread when the mass of a counterweight is applied to the internal thread under male thread load. Here, the counterweight is installed using... Figure 7 The installation method shown in "Example 2" is the same in other embodiments.

[0217] Table 1 shows the test conditions and evaluation results for each sample (C-1 to C-4) in Example 1.

[0218] Table 1 lists the number of Make / Break cycles as the criterion for judgment, and no samples are specifically deemed NG based solely on wear assessment. That is, no sample is deemed NG based on wear assessment even if Make / Break cycles are achieved in conjunction with the number of Make / Break cycles. Therefore, in the following embodiments, only the number of Make / Break cycles is used for judgment.

[0219] Here, “(Total Load)” in Table 1 corresponds to the load applied to the internal thread of the coupling. The same applies to the other tables.

[0220] [Table 1]

[0221]

[0222] In Example 1, JFELION is used in C-1 to C-4 as shown in Table 1. TMThe evaluation of heat resistance and adhesion of L80 carbon steel materials of size 9-5 / 8″ 43.5# (registered trademark) is conducted. Here, the thread design for each condition is assumed to be of the same construction, i.e., the same thread construction.

[0223] The specific thread design in Example 1 is summarized below.

[0224] (1) Male thread: In cross-section, it is a rotary shape of a compound R-convex curve.

[0225] (2) Coupling: A straight line shape with a 4.7-degree tapered shape in cross-section.

[0226] (3) Sealing point location: The length ratio of the male thread front end to the male thread front end is 0.31.

[0227] (4) Thread count: 5 TPI (TPI: number of threads per inch), 20 threads

[0228] Then, in Example 1, there is an example of a fastening loosening test performed to evaluate the developed solid lubricant.

[0229] Here, as lubrication on the coupling side, a solid lubricant coating is formed on the chemically converted manganese phosphate film. The solid lubricant coating is formed by spreading a binder resin composed of a multifunctional epoxy resin and a solid lubricant mainly composed of polyethylene into a solvent, and then firing it at a temperature of 200-300°C after coating. It should be noted that on the male thread side of the external thread, an F-type resin film is coated after shot peening.

[0230] <c-4>

[0231] C-4 uses a full-length male thread. The tightening loosening test was performed under conventional conditions, without using a counterweight, with the initial setting position (tightening start position) set to a completely manual tightening state (hereinafter referred to as the conventional position). C-4 achieved 3 M / B cycles, which is considered a passing example (burning and sticking occurred on the 4th cycle). This is used as the judgment criterion in Example 1. Here, the mass of the full-length male thread is approximately 1.0 ton (metric ton). It should be noted that the short male thread is 1m long and weighs approximately 110kg.

[0232] <C-1~C-3>

[0233] Examples C-1 to C-3 are based on the present disclosure where the initial setting position (tightening start position) is set to a relatively loose state and tightened manually (hereinafter referred to as the loose position), and the power clamp 4 is used to tighten and loosen the clamp under the condition of applying a test load with a counterweight.

[0234] It should be noted that in each table, the initial setting position (tightening start position) is recorded as "pre-tightening male thread setting position".

[0235] Any one of C-1 to C-3 shall be subject to the same qualification criteria as C-4.

[0236] However, C-1 is a case where the length of the test male thread is as short as 2000mm, and the weight of the counterweight is also as light as approximately 0.5 tons. In this case of C-1, upon release, the counterweight acts as a counterweight, and the short test male thread rises gradually and straight without oscillating or rotating. Therefore, compared to the actual situation, it becomes a less rigorous evaluation. Thus, it is an example where the M / B count reached 7 times, exceeding the expected number of times. In addition, C-1 is an example where the combined mass of the test male thread and the counterweight is lighter than the mass of the actual length male thread. Thus, the evaluation of C-1 deviates significantly from the evaluation of C-4.

[0237] In contrast, C-2 and C-3 are examples of test male buckles 1 with lengths of 3000mm and 5000mm, respectively, and examples of hammers 3 with a weight of about 1 ton applied during both Make-up and Break-Out.

[0238] In C-2 and C-3, the M / B number becomes the same as the number of times in C-4 in the case of actual length.

[0239] Examples C-2 and C-3 illustrate cases where the length of the male thread used in the test is 3000 mm or more. Furthermore, C-2 and C-3 represent cases where the mass of the counterweight 3 is equivalent to the mass of the actual length male thread.

[0240] As can be seen from the examples C-1 to C-3, by performing tightening and loosening under a load equivalent to the mass of the actual length male thread with a weighted hammer, and by setting the initial setting position to a relatively loose position, it is possible to obtain an evaluation equivalent to that in the test using the actual length male thread.

[0241] In contrast, it can be seen that when the mass of the counterweight is set to be less than that of the actual length male thread, the evaluation becomes less rigorous compared to the evaluation in the test using the actual length male thread.

[0242] (Example 2)

[0243] Example 2 compares horizontal and vertical tests, and illustrates the Make / Break action caused by the presence or absence of a counterweight. It should be noted that Example 2 includes cases where the male thread length is set to the actual length and cases with a length of 1000mm or less.

[0244] Table 2 shows the test conditions and evaluation results for each sample (A-1 to A-6) in Example 2.

[0245] Table 2 lists the number of Make / Break cycles as the criterion, and no samples were specifically deemed NG based solely on wear assessment. That is, no sample was deemed NG based on wear assessment even if Make / Break cycles were achieved in conjunction with the number of Make / Break cycles.

[0246] [Table 2]

[0247]

[0248] Table 2 shows examples A-1 to A-6, which were obtained by evaluating the heat resistance and adhesion of Q125 carbon steel of size 13-3 / 8″ 72.0# for the construction of newly designed threaded joints. The thread design of each sample was set to be the same, that is, the same thread construction.

[0249] The specific thread design in Example 2 is summarized below.

[0250] (1) Male thread: The shape of rotation of a 2″R convex curve in cross section.

[0251] (2) Coupling: A straight line shape that is 3 degrees tapered in cross-section.

[0252] (3) Sealing point location: The length ratio of the male thread front end to the male thread front end is 0.25.

[0253] (4) Thread size: 4TPI, 18 threads

[0254] <a-4>

[0255] A-4 uses a full-length male thread. This is a case where the fastening and loosening test is carried out under the previous condition that the initial setting position (tightening start position) is set to the previous position without using a drop hammer.

[0256] That is, A-4 is an example obtained by preparing a full-length male thread and testing the burn resistance of this new thread design. It becomes a judgment benchmark and the conditions of an actual well. In A-4, burn sticking occurs after the third loosening. It should be noted that the initial tightening setting position is the position where 10 threads of the male thread of the coupling are exposed, which is a common position in an actual well and is considered a reasonable position as a realistic tightening position. Regarding the full-length male thread, since it is sometimes inserted slightly obliquely in structure no matter how it is improved, in this example, it is 10 threads at the manual tightening limit.

[0257] That is, in A-4, burn sticking occurs at the 3rd M / B, and the evaluation is unqualified. It is used as the judgment benchmark in Example 2.

[0258] <A-1 to A-3>

[0259] The examples shown in A-1 to A-3 are cases where a short male thread is used as the test male thread, and the initial setting position before tightening is set to the previous position tightened completely by manual tightening and the test is carried out. In this example, the axial adjustment of the coupling / male thread is well done with a horizontal vice. In addition, since a short male thread is used together with a horizontal and a vertical vice, the operation is relatively easy, so it can be tightened to a place where it seems to be tightened manually to about 2 to 3 threads of the male thread exposed. Then, the tightening using the power vice 4 is carried out from this position.

[0260] A-1 is a horizontal type test, which is a case where the test is carried out without applying load to the thread teeth during tightening and loosening, and 6 Make&Break can be carried out. It should be noted that in A-1, the test is intentionally completed at the 6th Make&Break.

[0261] In the ISO13679 standard, since the casing material is a qualified level as long as it can carry out 3 M / B, it can be known that it is far beyond this level. That is, the deviation from the evaluation of A-4 is relatively large.

[0262] A-2 is an example simulating the previous vertical type test. Compared with the situation in A-1 where the self-weight of the short male thread does not load on the coupling thread, in A-2, the male thread is erected and the test is carried out. Correspondingly, it is a situation where the self-weight of the short male thread is applied to the thread teeth of the coupling. For this size, even for a short male thread, there is a self-weight of about 110KG, which means the situation where it is applied to the thread teeth of the coupling.

[0263] In case A-2, the number of M / B tests for evaluation was reduced to 5 (sticking on the 6th burn), but it still became a passable evaluation. Then, the difference from the evaluation in A-4 was significant.

[0264] A-3 is an example simulating Non-Patent Document 2, where a 510KG weight is placed on the upper part of the male buckle and a fastening loosening test is conducted. In case A-3, the number of M / B tests for evaluation is reduced to 4 (sticking on the 5th burn test), but it is still considered a pass evaluation and is judged to have burn-stick resistance that meets the requirements of API 5C5:2017.

[0265] As mentioned above, in the tests under conditions A-1 to A-3, simulating actual wells, the load was presumed to be too light, and therefore it could be judged as qualified. That is to say, it can be seen that in the tests under conditions A-1 to A-3, the test conditions for evaluating the resistance to burning and sticking are less stringent than the test conditions using actual length male threads. Therefore, even if the appropriateness of the new thread design can be screened, it does not guarantee that burning and sticking will not occur during the loosening of the fastener using actual length.

[0266] <a-5>

[0267] A-5 uses a 600mm short male thread as the test male thread. Then, based on this disclosure, a loosening test was conducted under the condition that the initial setting position (tightening start position) was set to a relatively loose position and 7 threads were exposed, and a load equivalent to 1 ton (equivalent to 9-10m) as a single male thread length was applied with a weight. However, during loosening, the male thread and weight were suspended by a crane, and the load from the weight 3 and the internal threads of the male thread during loosening was controlled to near zero.

[0268] It was confirmed that in the test under the conditions of A-5, the number of M / B tests was 2 (the third test resulted in sticking), which was deemed unqualified and thus equivalent to the actual well conditions of A-4.

[0269] That is, it can be seen that the evaluation conducted under the conditions of A-5 can be equivalent to the evaluation conducted under the rigorous fastening and loosening test with actual length.

[0270] <a-6>

[0271] The conditions for A-6 are the same as those for A-5. It is an example of setting the initial position (tightening start position) to the previous position and starting tightening with one tooth exposed.

[0272] For example, in case A-6, with the initial setting position (tightening start position) set to the previous position, the M / B count was 3 (sticking on the 4th attempt), and the evaluation was considered satisfactory. That is to say, it can be seen that when the initial setting position is set to the state of complete tightening by manual tightening before tightening and testing, it is evaluated well, but cannot simulate the actual well conditions.

[0273] As can be seen above, by performing tightening and loosening under a load equivalent to the mass of the actual length male thread with a heavy hammer, and by setting the initial setting position to a relatively loose position, it is possible to obtain an evaluation equivalent to that in the test using the actual length male thread.

[0274] It can be seen that even if the length of the male thread used in the test is set to a relatively short length of 600 mm as in A-5, by applying the load of the weight of the hammer when screwing in and reducing the load on the internal thread when loosening, it can be evaluated in the same way as the rigorous fastening loosening test using the actual length.

[0275] (Example 3)

[0276] Example 3 illustrates an example of how, based on this disclosure, a fastening loosening test in which the load of a weight is applied to the internal thread via the male thread can simulate the Make & Break in the actual length of the male thread.

[0277] Table 3 shows the test conditions and evaluation results for each sample (B-1 to B-6) in Example 3.

[0278] Table 3 lists the number of Make / Break cycles as the criterion, and no samples were specifically deemed NG based solely on wear assessment. That is, no sample was deemed NG based on wear assessment even if Make / Break cycles were achieved in conjunction with the number of Make / Break cycles.

[0279] [Table 3]

[0280]

[0281] In Example 3, JFELION was used for each sample (B-1 to B-6) shown in Table 3. TM The burning resistance of L80-13Cr chromium steel material of size 9-5 / 8″53.5# (registered trademark) was evaluated. The thread design of each sample was set to be the same, that is, the same thread construction.

[0282] The specific thread design in Example 3 is summarized below.

[0283] (1) Male thread: In cross-section, it is a rotary shape of a compound R-convex curve.

[0284] (2) Coupling: A straight line shape with a 4.7-degree tapered shape in cross-section.

[0285] (3) Sealing point location: The length ratio of the male thread front end to the male thread front end is 0.31.

[0286] (4) Thread count: 5 TPI, 20 threads

[0287] Then, in Example 3, the evaluation of the developed solid lubricant was carried out using a fastening loosening test.

[0288] As a lubricant for the coupling side, a solid lubricant coating is formed on the Cu-Sn alloy plating. This solid lubricant coating is formed by using a substance that spreads Teflon (registered trademark) in a mixture of polyamide-imide and polyimide as the main component, and then firing it at a temperature of 200-300°C. It should be noted that on the male external thread side, after shot peening, a water-based acrylic coating is applied and dried with far-infrared light to form a film.

[0289] <b-4>

[0290] B-4 uses a male thread of actual length and is tested under conventional conditions where the initial setting position (tightening start position) is set to the previous position without using a counterweight. The M / B test for B-4 was 2 times, which is considered a failure (burning and sticking occurred on the 3rd test). This will be used as the judgment criterion in Example 3.

[0291] <b-1>

[0292] In B-1, the load is applied using a counterweight, which is the case where the initial setting position before tightening is set to the previous position of fully manual tightening.

[0293] In the test under the conditions of B-1, the number of M / B tests was 5 (burning and sticking occurred on the 6th test), which was judged as passing the evaluation, which is a large deviation from the evaluation of B-4.

[0294] <b-2>

[0295] B-2 is an example where the initial setting position before tightening is set to the same condition as B-1, except that the initial setting position before tightening is set to a looser position.

[0296] In B-2, by setting the initial setting position before tightening to a looser position, the M / B count is 3 (burning occurs on the 4th time), which is a slightly less stringent evaluation compared to the actual B-4. However, it is an evaluation that is closer to the actual B-4 evaluation compared to B-1.

[0297] <b-3>

[0298] For B-3, compared with B-2, the male buckle for the test is set to 2000 mm and the load is reduced when it loosens.

[0299] In B-3, a heavy hammer 3 of sufficient weight is applied and a severe test of applying shaking when tightening and loosening is carried out. The tightening and loosening test fails due to sticking during the third occurrence. That is, it can be seen that the evaluation is equivalent to that of B-4 with an M / B number of 2 times, and an evaluation equivalent to that in the test using the actual length male buckle can be obtained.

[0300] It should be noted that although the evaluation in B-2 is qualified, compared with B-1 with the initial setting position being the previous position, the evaluation of B-2 is similar to that of B-4. Then, it can be seen that by applying a load with the heavy hammer 3 and setting the initial setting position to a looser position, the evaluation accuracy is improved.

[0301] <B-6, B-5>

[0302] B-6 is an example in which a tightening and loosening test is carried out under the same conditions as B-4, except that a solid lubricant obtained by further improving the solid lubricant determined to be unqualified in the evaluation of B-4 is used. In the evaluation based on the conditions of B-6, the M / B number is 5 or more, and the evaluation is determined to be qualified. In addition, as B-5, after the test is carried out under the conditions of B-3 except using the solid lubricant used in B-6, the M / B number is 5, and the evaluation is determined to be qualified.

[0303] As described above, it can be seen that even if a male buckle shorter than the actual length is used as the male buckle for the test, by conducting the test based on the present disclosure, the burn resistance can be evaluated with higher accuracy than in the past.

[0304] It should be noted that in the above embodiments, the case where the example on the large diameter side is constituted is illustrated, but it is presumed that the present disclosure can obtain the same effect regardless of conditions such as the outer diameter, wall thickness dimension, and steel type.

[0305] Here, the entire content of the US provisional application 63 / 161122 (filed on March 15, 2021) to which this application claims priority is incorporated into this disclosure by reference. Here, a limited number of embodiments are described for illustration, but the scope of protection is not limited thereto, and changes based on the above-described embodiments are obvious to those skilled in the art.

[0306] Explanation of reference numerals

[0307] 1 Male buckle for the test

[0308] 1a External thread

[0309] 1c inner diameter surface

[0310] 1d through hole

[0311] 2. Female coupling (joint)

[0312] 2a Internal thread

[0313] 3 heavy hammers

[0314] 4 Power Clamp

[0315] 10 Insertion rods

[0316] 10a Through Hole

[0317] 12 Penetrating Rods

[0318] 20. Suspension device (crane)

[0319] 21 Chain (Suspension Cable)

[0320] 23. Slings (suspending cables)

Claims

1. A method for evaluating the tightness and loosening of oil well pipe threaded joints, which is a method for evaluating the tightness and loosening of oil well pipe threaded joints using power pliers. The oil well pipe threaded joint includes a female thread with internal threads and a male thread with external threads. In the method for evaluating the tightness and loosening, When conducting a tightening and loosening test on an oil well pipe threaded joint formed by installing a male thread on the upper part of a female thread with the shaft facing upwards and downwards, The test buckle, made from a buckle shorter than the buckle being evaluated, is used as the test buckle. A weight is mounted on the upper part of the male buckle used in the test, and the mass of the weight is set to be greater than or equal to the mass obtained by subtracting the mass of the test male buckle from the mass of the male buckle being evaluated. For the initial setting position, which is the starting position for tightening the test male thread before tightening with power clamps, the initial setting position is set to the state where more than one of the following thread numbers is exposed from the upper end face of the female thread: either five or one-quarter of the total number of threads of the test male thread.

2. The method for evaluating the loosening of oil well pipe thread joints according to claim 1, wherein, The mass of the hammer is set to be at least 8m long as the length of the male buckle being evaluated.

3. The method for evaluating the loosening of oil well pipe thread joints according to claim 1 or claim 2, wherein, The length of the male buckle used in the test is set to be between 600mm and 5m.

4. The method for evaluating the loosening of oil well pipe thread joints according to any one of claims 1 to 3, wherein, The loosening is performed by reducing the load applied to the internal thread of the female thread from at least one of the weights and the male thread used for testing.

5. The method for evaluating the loosening of oil well pipe thread joints according to claim 4, wherein, It is equipped with a suspension device capable of suspending the weight and at least the weight of the male buckle used for testing. By using the suspension device, the load applied from the weight and the test male thread to the internal thread of the female thread is adjusted.

6. The method for evaluating the loosening of oil well pipe thread joints according to claim 4 or 5, wherein, Upon release, the load applied from the counterweight and the test male thread to the female thread is removed.

7. The method for evaluating the loosening of oil well pipe thread joints according to any one of claims 4 to 6, wherein, The weight is placed on the upper end of the male buckle used for testing. It also includes: an insertion rod that extends downward from the lower surface of the weight and is loosely inserted into the test male thread; and a through rod that protrudes laterally from the insertion rod and protrudes outward through a through hole formed in the test male thread. The diameter of the through hole is larger than the diameter of the through rod.

8. The method for evaluating the loosening of oil well pipe thread joints according to any one of claims 4 to 7, wherein, The length of the male buckle used in the test is set to be between 600mm and 2m.

9. A method for manufacturing an oil well pipe threaded connector, the oil well pipe threaded connector comprising a female thread with internal threads and a male thread with external threads, wherein in the method for manufacturing the oil well pipe threaded connector, A fastening loosening test is performed using the fastening loosening evaluation method for oil well pipe threaded joints according to any one of claims 1 to 8, and the construction of the oil well pipe threaded joint is determined based on the evaluation based on the test.

10. The method for manufacturing an oil well pipe threaded joint according to claim 9, wherein, The evaluation is at least one of the oil well pipe thread shape design and the lubrication conditions used in the oil well pipe thread joint.

Images