Patent Application
20220268111
This present application claims benefit of European Patent Application No. 21158969.2 filed Feb. 24, 2021 and entitled “Elevator for Heavy Load Pipe Lifting, Pipe for Such Elevator and Pipe Handler Assembly Comprising Such Elevator”, which is incorporated herein by reference in its entirety for all purposes.
Not applicable.
The disclosure relates to an elevator for holding an end portion of a pipe in a drill tower. The disclosure further relates to a pipe configured for use with the elevator. The disclosure also relates to a pipe handler assembly comprising such elevator and pipe BACKGROUND OF THE DISCLOSURE
Drill towers generally comprise a pipe handler assembly for handling drill pipes or other tubular structures. An important part of the pipe handler assembly is the elevator, which basically comprises a passive mechanical part that comprises a hole from which the pipe is suspended. The pipe conventionally has a thickened end portion having a diameter that is larger than a minimum diameter of the hole of the elevator. The hole is conventionally provided with an elevator bushing in order to be able to adapt the elevator to different diameters of the pipe. This bushing is suspended from the hole of the elevator and the end portion of the pipe is suspended from the elevator bushing. The hole in the elevator bushing conventionally comprises sidewalls that define a frustoconical shape, which matched a frustoconical part of the end portion between the thick end portion and the cylindrical middle part of the pipe. When a traditional pipe is suspended from the elevator bushing it forms an interface between the elevator and the pipe (i.e., drill pipe).
A traditional drill pipe-elevator interface features an 18-degree angle. The detailed description further illustrates this. This traditional design works very well for standard drill pipe sizes, i.e., 2⅜″ (60.3 mm) through 6⅝″ (168.3 mm), with standard wall thicknesses. However, for completion work over riser (CWOR) and Landing String (LS) applications, where the pipe is typically larger (6⅝″ (168.3 mm) and larger) and wall thickness is greater (up to and, in some cases, over 1″) the 18 degree angle induces excessive tangential (hoop) stresses in the pipe when the string weight nears the axial strength of the pipe. In view of this problem, there is a need to devise solutions that will not induce such stresses.
A solution that has been reported is an increased interface angle. A finite element analysis showed that a 45-degree angle is optimal in reducing the tangential stress component and balancing it with the axial stress.
The inventor of this patent application, however realized that this reported solution incorporating the 45-degree angle suffers from different problems.
Hence there is a need to further develop elevators and pipes.
The inventor of this patent application realized that the interface having an increased angle, such as 45 degrees, reduces the available contact area resulting in excessive bearing stresses between the drill pipe elevator shoulder and the elevator bushing. This is explained in the detailed description below. Reducing the transition radius R between the axial pipe body and the pipe lifting shoulder (typically 1.5″ (38.1 mm) would help, however it would increase the stress concentration in that transition radius which may adversely affect fatigue life of the pipe. An increased outside diameter (OD) of the tool joint is another consideration, however most power tongs (including Iron Roughnecks (IRN)) currently used in the field would not be able to handle such a large tool joint OD.
The present disclosure is intended to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.
In a first aspect, the disclosure relates to an elevator for holding an end portion of a pipe in a drill tower. The elevator has a hole from which, in operational use, the pipe is suspended with an end portion. A minimum diameter of the end portion of the pipe is selected larger than the minimum diameter of the hole. Furthermore, sidewalls of the hole are shaped with a receiving surface for receiving correspondingly-shaped sidewalls of the end portion of the pipe. In an embodiment, the receiving surface comprises a first part and a second part neighbouring the first part, the first part defining a frustoconical shape having a first conicity, the second part defining a shape having at least partially a second conicity lower than the first conicity.
The effects of the features of such elevator in accordance with the disclosure include the following. First of all, a key feature of the elevator is that the receiving surface comprises two parts having different shapes. The first part is still frustoconical, however the second part may be frustoconical, but does not need to be, as long as it at least partially has a conicity lower than the first part. An advantage of this configuration is that the first part may be designed for providing a large upward directed force with larger conicity, while the second part may be designed with a lower conicity to reduce stresses in the transition region. It must be stressed that, even though there are different shapes disclosed, this does not mean that the respective parts as mentioned in the claims are necessarily multiple objects connected together. On the contrary, both the elevator and the matching pipe are most likely made of one-piece to make it very strong.
In order to facilitate understanding of the disclosure one or more expressions are further defined hereinafter.
The wording “elevator” must be interpreted as a mechanical part, from which a pipe is suspended. The elevator function is in many applications provided by a system from which the elevator is suspended, such as a hoisting system in a drill tower.
The wording “pipe” must be interpreted as a tubular structure. In conventional drill tower applications in the petrochemical industry, these pipes are often drill pipes. However, the disclosure is not necessarily limited to drill pipes and elevators for those. The disclosure equally applies to other tubular structures (like casing and tubing), which suffer from similar problems as presented in this specification. Tubulars may be defined by the application. For example, if a drill pipe or casing is used for landing a liner or any other equipment in the well, it is usually called Landing String. Another example is Risers, (CWOR, etc.). The current disclosure covers all oil & gas tubulars irrespective of the specification they are manufactured to (drill pipe, casing, tubing) or the application (landing string, riser, etc.).
In an embodiment of the elevator according to the disclosure, the first conicity is such that sidewalls, in operational use, make an angle with a centreline of the pipe between 30 degrees and 60 degrees, preferably between 35 degrees and 55 degrees, even more preferably between 40 degrees and 50 degrees, and yet even more preferably about 45 degrees. The narrowing ranges in this group of embodiments indicate that the disclosure is not limited to a specific conicity, yet the optimal conicity may very well turn out to be around 45 degrees, which seems to balance the requirements the best in many cases.
In an embodiment of the elevator according to the disclosure, the second part of the receiving surface defines a thoroïde shape which transitions from the first conicity at a side facing the first part to the second conicity at an opposite side. The thoroïde shape which transitions from the first conicity to a lower conicity further reduces the stresses in the second part of the receiving surface of the elevator, but also in the second part of the engaging surface of the pipe.
In an embodiment of the elevator according to the disclosure, the second part of the receiving surface defines a further frustoconical shape. This embodiment forms an alternative to the thoroïde shape of the previous mentioned embodiment. Instead of a transitioning conicity in the second part, one might choose a constant second conicity yet being lower than the first conicity. This embodiment will be discussed in more detail with reference to
In an embodiment of the elevator according to the disclosure, the second conicity is such that sidewalls, in operational use, at least locally make an angle with a centreline of the pipe between 14 degrees and 30 degrees, preferably between 15 degrees and 25 degrees, even more preferably between 16 degrees and 20 degrees, and yet even more preferably about 18 degrees. The narrowing ranges in this group of embodiments have shown to be best for preventing the pipe from becoming stuck in the elevator. In fact, a minimum angle of 14 degrees was calculated and the optimum second conicity has an angle of about 18 degrees according to the calculations.
In a second aspect, the disclosure relates to a pipe configured for use with the elevator described herein, wherein the pipe comprises the end portion, wherein, in operational use, the minimum diameter of the end portion of the pipe is selected larger than the minimum diameter of the hole of the elevator. Furthermore, sidewalls of the end portion are shaped with an engagement surface for engagement with correspondingly-shaped sidewalls of the hole. In at least some embodiments, the engagement surface comprises a first part and a second part neighbouring the first part, the first part defining a frustoconical shape having a first conicity, the second part defining a shape having at least partially a second conicity lower than the first conicity. The pipe of the second aspect matches the elevator of the first aspect. It must be stressed that the elevator and the pipe according to the disclosure belong together as a plug belongs to a socket. Both entities may be sold independently from each other and are therefore claimed as such in certain of the claims set out below.
In an embodiment of the pipe according to the disclosure, the first conicity is such that sidewalls make an angle with a centreline of the pipe between 30 degrees and 60 degrees, preferably between 35 degrees and 55 degrees, even more preferably between 40 degrees and 50 degrees, and yet even more preferably about 45 degrees. The narrowing ranges in this group of embodiments indicate that the disclosure is not limited to a specific conicity yet the optimal conicity may very well turn out to be around 45 degrees, which seems to balance the requirements the best in many cases.
In an embodiment of the pipe according to the disclosure, the second part of the engagement surface defines a thoroïde shape which transitions from the first conicity at a side facing the first part to the second conicity at an opposite side. The thoroïde shape which transitions from the first conicity to a lower conicity further reduces the stresses in the second part of the receiving surface of the elevator, but also in the second part of the engaging surface of the pipe.
In an embodiment of the pipe according to the disclosure, the second part of the engagement surface defines a further frustoconical shape. This embodiment forms an alternative to the thoroïde shape of the previous mentioned embodiment. Instead of a transitioning conicity in the second part, one might choose a constant second conicity yet being lower than the first conicity. This embodiment will be discussed in more detail with reference to
In an embodiment of the pipe according to the disclosure, the second conicity is such that sidewalls at least locally make an angle with a centreline of the pipe between 14 degrees and 30 degrees, preferably between 15 degrees and 25 degrees, even more preferably between 16 degrees and 20 degrees, and yet even more preferably about 18 degrees. The narrowing ranges in this group of embodiments have shown to be best for preventing the pipe from becoming stuck in the elevator. In fact, a minimum angle of 14 degrees was calculated and the optimum second conicity has an angle of about 18 degrees according to the calculations.
An embodiment of the pipe according to the disclosure further comprises a transition part in between the second part and a cylindrical middle part of the pipe. The transition part may be designed as a thoroïde shape as well transitioning between an angle of 0 degrees (no conicity) at a side facing the cylindrical middle part of the pipe and the second conicity of the second part neighbouring the transition part.
In a third aspect the disclosure relates to a pipe handler assembly comprising an elevator in according to the disclosure, and further optionally comprising the pipe in accordance with the disclosure.
In a fourth aspect the disclosure relates to a drill tower comprising the pipe handler assembly according to the disclosure.
In the following is described examples of embodiments illustrated in the accompanying figures, wherein:
Various illustrative embodiments of the present subject matter are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various systems, structures and devices are schematically depicted in the figures for purposes of explanation only and to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached figures are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
The disclosure will be discussed in more detail with reference to the figures.
During drilling operations, a drill pipe 99 is typically suspended from the pipe handler assembly 20, which runs down to a power slip 50 in the drill floor, as illustrated. The power slip 50 serves for holding the drill pipe 99 while drill pipe segments are being mounted or demounted from the drill pipe 99.
It must be noted that there are many variations possible in the set-up and configuration of drill towers. The drill tower 1 presented in
A severe disadvantage, however, is that a contact force F2 applied under this low angle of 18 degrees becomes very large. In fact, if the desired upward-directed force F1 is as illustrated, the contact force F2 is a 1/sin 18°=3.24 times the upward-directed force F1. Consequently, a radially-inward directed crushing force F3 is 1/tan 18°=3.14 times the upward-directed force F1. These crushing forces F3 may cause hoop stresses in the drill pipe.
This disclosure in the example of
The elevator bushing 101 would follow the shape of the radius until it reaches the point where a tangent line forms an angle of 18° with the main axis of the pipe. This minimum contact angle of 18° is provided to prevent the pipe 99 from becoming stuck in the elevator 100 due to friction between the contact surface of the pipe 99 and the contact surface on the elevator.
The amount of friction depends on various operating conditions such as the presence of drilling mud or pipe dope on the contact surfaces. The magnitude of the friction is determined by the so-called coefficient of friction (COF). The typical COF for drill pipe contact surfaces typically lies between 0.08 (for well lubricated surfaces) and 0.25 for dry metal conditions.
The COF can be translated to a so-called friction angle (Af) through the formula: Af=arctan(COF). In the worst-case scenario of a COF=0.25, the friction angle is 14°. As long as the above-described minimum pipe contact angle of 18° is larger than this 14° friction angle, so the pipe will not get stuck in the elevator due to friction.
Thus, the required elevator capacity for CWOR and LS applications can be reached by (1) reducing the hoop stresses in drill pipe and balancing them with the axial stresses, (2) extending the contact area between the drill pipe elevator shoulder and the elevator bushing, (3) and keeping the 1.5″ radius and the tool joint OD unchanged.
The particular embodiments disclosed above are illustrative only, as the disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. The disclosure may be applied in drilling, intervention operations, landing string operations, riser operations, and completion operations. As mentioned earlier, the elevator bushing is not an essential feature of the disclosure, the elevator may also go without such bushing and be shaped according to the drawing.
The disclosure covers all these variants as long as they are covered by the independent claims. No limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the disclosure. Accordingly, the protection sought herein is as set forth in the claims below.
It should be noted that the above-mentioned embodiments illustrate rather than limit the claimed invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The claimed invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claims enumerating several means, several of these means may be embodied by one and the same item of hardware.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21158969.2 | Feb 2021 | EP | regional |
