MX2011005424A

MX2011005424A - Oilfield threaded connections.

Info

Publication number: MX2011005424A
Application number: MX2011005424A
Authority: MX
Inventors: Gregory Andyle Bailey; Steven C Langford
Original assignee: Vam Usa Llc
Priority date: 2008-11-24
Filing date: 2008-11-24
Publication date: 2011-06-21
Also published as: CA2744396A1; CN102224368A; JP2012510009A; WO2010059145A1; EP2359043A1; CN102224368B; BRPI0823334A2; JP5538418B2; EP2359043A4; CA2744396C

Abstract

A threaded oilfield tubular connection includes a box connector 12 having internal threads 16, 18, and a pin connector 14 having external threads 22, 24 for mating with the internal threads. Each of a box torque shoulder 20 and a pin torque shoulder 26 may be negative angle shoulders, and the thread flanks on the internal and external threads may also be negative angle load flanks. The connector substantially maintains a desired preload when dope is trapped between the threads during makeup. Another embodiment provides positive angle torque shoulders and positive angle load flanks.

Description

THREADED CONNECTIONS FOR OIL FIELDS FIELD OF THE INVENTION The present invention relates to threaded connections for oil fields of the type having a coupling torque support. More particularly, the present invention relates to a threaded connection for oilfields in which the load flank of the thread is at a slightly negative angle, and the torque support is at a similar negative angle. This combination minimizes the preload loss when a high pressure due to the imprisoned thread compound develops at the connection.

DESCRIPTION OF THE RELATED TECHNIQUE Offshore drilling using automated handling systems and makeup systems has led to connections that are prepared with a thread compound, either in the coastal facilities (on the mainland), or in the drill tower, before you take them to the drilling lathes to pass the strip of tubes down the well. While the aforementioned techniques make personnel out of the risk zone, which is desirable, these techniques exclude the ability to apply a "human touch" in terms of proper application of the compound to the threads. Therefore, the sensitivity of the connection in terms of a possible excess of compound applied to the threads, is significantly higher with modern solutions to pass the pipe.

Threaded connections with seals adjacent to each end, both for internal and external sealing against pressure, tend to trap the thread compound between the seals. Seals are desirable to obtain the necessary capabilities for pressure inversion scenarios. However, these seals also inadvertently confine the pressure of the thread compound that is trying to escape from the connection during work to complete. In addition, the expanded integral box and interior liner connections, which commonly have this configuration, are often less robust than threaded and coupled connections, due to the limited material available, imposed by slack problems that are mandatory in their use.

In the market there are integral, tapered connections, two steps (two step), with negative load flank, dual seal. An example is the Grant Prideco ANJO connection that has a thread shape with negative load flank, a two step thread (discontinuous thread), a 15 ° torque support near the axial center of the connector, and both inner seals as outside. Another connection is the Hydrill SLX connection which also has a thread shape with negative load flank, two step threads, a 15 ° torque support near the axial center of the connector, and inner and outer seals. For this last case, the outer seal is also a medium connector. A third connection with a thread shape with negative load flank and two-step threads, is the VAM SLIJII connection, which has a torque support near the axial center of the connector, substantially perpendicular to the axis of the connection , and also has inner and outer seals. In the market there are integral, tapered, single-step connections, with a negative-charge, dual-seal flank. One example is the Hunting Seal Lock SF, which has a thread shape with negative load flank, single step threads, a 15 ° torque support on the outer face of the connector, and inner and outer seals. There are also other similar connectors with an outer diameter flush or almost flush.

One of the potential significant adverse effects of an excess of thread compound, which generates high pressures within the connector, is the loss of connection preload and stored torque when the compound pressure is dissipated. The loss of stored torque is a significant concern in off-shore drilling applications, in which the connector presents the possibility of unscrewing and uncoupling during the process of introduction (of the strip into the well). The completion. { making up) of a connection with a capacity of up to 20157 meters-kilograms and observing how it collapses to 3359.5 meters-kilograms, is particularly disconcerting for the operators that drill wells of one hundred million dollars in waters with a depth of 830 meters. If the completion torque (makeup torque) and preload is substantially maintained, it is possible to significantly improve the reliability of the connection.

US Patent No. 4,753,460 discloses a threaded connection with a negative load flank on two-step threads, a torque support on the pin connector, and the box connector . { box connector) for a high torque coupling. In United States Publication 2002/0033603 a threaded connection is disclosed with conventional threads with rounded roots and with a loading shoulder between the end of the box and a matching surface located on the pin. It is also possible for an end surface of the box member to engage with a matching surface located on the pin member.

The present invention overcomes the disadvantages of the prior art, and hereinafter an improved tubular connection for oilfields is disclosed.

BRIEF DESCRIPTION OF THE INVENTION In one embodiment, the threaded tubular oilfield connection includes a box connector having internal threads, and a box torque support and a matching pin connector, which has external threads and a carrier support. Torque in the pin, for its coupling with the torque support of the box. Each of the external threads and internal threads has a thread loading flank, which is at a negative angle with respect to a central axis of the connection. Both the torque support of the box and the pin torque support have a similarly negative angle. The variations include a torsion support angle, with a magnitude greater than that of the load flank angle. When an excess of excess dope is imprisoned between the threads, a pressure of the thread compound is generated, which may result in some radial separation of the pin and box member. In the case where this pressure dissipates, this radial separation is reduced. If the angles of the load flank of the threads and of the torque support are substantially parallel, the axial component of the contact force between the pin and box members remains constant, and the stored torque remains substantially unaffected. If the axial distance between the load flank and the torque support increases as the radial spacing between the pin and box members decreases due to a disparity in these angles, the axial component of the contact force could be increased to as the potential energy of the pressure of the imprinted varnish is translated into additional mechanical preload, the result being an additional stored twist.

In another embodiment, a threaded connection for fields Petroleum includes a box connector with internal threads and a box torque support, and a pin connector with external threads and a pin torque support. Each of the external and internal threads has a thread loading flank, which is perpendicular to, or which forms a positive angle with respect to, a central axis of the connection; and, each of the following: the torque support, the case, and the torque support of the pin, is also at a similar angle with respect to the central axis of the connection. Variations include a torque support angle with a magnitude less than that of the load-side angle. A maximum variance between the angle of the load flank of the pin, and the angle of support of torque of the pin, or between the angle of load flank of the box, and the angle of support of torque of the box, it should be generally less than 5o or less.

These aspects and advantages, and others, of the present invention will become more evident from the following specification, in which reference is made to the Figures in the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an embodiment of a threaded connection according to the invention.

Figure 2 is an enlarged view of a portion of the threads and torque supports, shown in Figure 1.

Figure 3 is an enlarged view of the threads and torque supports shown in Figure 2, when the connection is exposed to an internal pressure trapped between the threads.

Figure 4 is a partial cross-sectional view of another embodiment of a threaded connection in accordance with the present invention, with positive flank-loading threads and a positive torque support for torque.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, it can be seen that a threaded tubular oilfield connection, 10, comprises a box connector 14 having tapered internal threads, with two steps, 16, 18, and a torque support. 20. A matching pin connector 12 has external threads, tapered two-step threads 22, 24 and a torque support 26 to match the torque support 20. Both in the pin and in the pin connectors. In this case, the torque support is provided axially between thread steps, which have been preferably provided on a slight taper and which have a significant radial spacing between the two steps of the threads. Figure 1 also discloses a frustoconical sealing surface 28 on the box connector 14, which forms a metal-to-metal seal with the matching surface 30 on the connector of the pin 12 thereby preventing internal pressure pass the threads 18, 24. The pin connector 12, has a similar frusto-conical surface 32, which matches the surface 34 on the box connector 14, to similarly seal the threads 16, 22 against external fluids. Once the connection 10 is completed, the inner and outer seals trap the fluid pressure between the seals and therefore between the threads. When this trapped cavity is filled with lubricant or thread compound, which is commonly referred to as pipe varnish, the pressure increases as the cavity is reduced during completion or final completion of the connection, resulting in radial separation of the threads.

Still with reference to Figure 1, it must therefore be understood that if a high pressure develops within the connection due to the hydraulic behavior of the trapped thread compound, there may be a significant loss of preload when said hydraulic pressure "bleeds" ( bleeds off). By using the aspects disclosed herein, it is possible to substantially maintain the final preload once the fluid pressure due to the excess varnish condition dissipates. These aspects are particularly advantageous, but not by way of limitation, for an integral two-step tapered connection, in which a torque support is spaced between the two screw steps of both the box connector and the pin connector, and that incorporates a thread shape with negative load flank. As it reveals in what follows, a key aspect is that the negative torque support and the negative load flank angle of the threads are parallel or have a slight angle disparity that prevents the loss of preload and therefore maintains substantially and effectively the high initial preload while the radial separation of the pin and case due to the high pressure of the varnish becomes support interference as the varnish pressure dissipates. In addition, it is possible to control the relative angle between a positive load flank and a torque support, in order to prevent axial decoupling during radial deflection, as shown in Figure 4 and discussed below.

Referring now to Figure 2, each of the two step threads both on the pin connector and on the box connector have a negative load flank with an angle 36, preferably its magnitude may vary between approximately 1o. and approximately 15 °. A negative flank, or a hook thread, minimizes radial separation of the pin and housing under tension and pressure loading, in a manner well known for coupling connectors. The torque supports, between the pin and box connectors, similarly have a negative angle, as shown by the angle 38 in Figure 2. The magnitude of the angle 38 for the torque supports may vary from preferably between about and about 20 °, depending on the angle of the load flank. A small difference between these angles allows the connection to be energized axially due to the reaction forces of the supports that are energized as the axial distance between the load flank and the torque supports increases as the radial clearance decreases in response to reduced fluid pressure (varnish) between the pin connector and the box connector. For many embodiments, the variance between the negative angle on the load flanks of the threads and the negative angles for the support of box and pin torque will be less than 5o, and in most applications the magnitude of the The negative angle of the torque support is substantially the same, or slightly higher than the negative angle of the load flanks of the threads that can provide greater axial overlap at the torque support interface after the bleeding of the varnish pressure , so that the breaking torque can be increased, which is desirable. It is preferable that each of the following: the torque support of the box and the torque support of the pin have a negative angle within 1 or the negative load flank of the connector thread of the box and the pin connector. For many embodiments, the load flanks of the threads of the box connector and the pin connector are a negative angle between about 3o and about 12 °, and the torque support of the box and the torque support The torque of the pin has a negative angle between about 3o and about 13 °, such that the angular disparity between the torque support and the load flanks is essentially equal to 1o. Each of the flanks of effort on the internal threads and the External threads are preferably at a positive angle, but according to the invention it is possible to use several desired stress flank angles. According to the present invention, the angles of the stress flanks can be positive, negative or neutral.

According to some connections of the prior art, a dovetail is effectively developed between the flanks of the load and the torque supports. This dovetail is de-energized when the radial deflection induced by the compound pressure for the threads decreases. The existence of this pressure increase and the subsequent pressure drop inside the connection during and after the completion, of up to 703 Kg / cm2 have been measured. In the "over varnish" condition, the pin and housing separate radially, and when the fluid pressure is reduced, there is a significant loss in the initial preload. According to the present invention, an "over varnish" condition continues to result in radial separation between the pin connector and the box connector, as shown in Figure 3. However, in this case, when relieves fluid pressure, separation decreases and the connection reverts down the torque supports and flanks of the load, with the result that the connector has an equal or higher preload, instead of the significant reduction of the preload which takes place in many connections of the prior art. By providing a torque support with a negative angle, when coupled with load flanks that also have a negative angle, the connection is much less sensitive toa reduced preload when, between the threads, there is an excess of thread compound. As used herein, the term "negative" angle means that the surface on the box connector, which conventionally consists of a pin connector above the box connector, has a slightly downward slope as compared to the box connector. a line that is perpendicular to the central axis of the connection, instead of having an upward slope that is conventional in public domain American Petroleum Institute connectors with positively charged flanks, such as trapezoidal and 8-turn threads. Similarly, a negative surface on the connector of the pin is slightly tapered downwards for a matching coupling with the respective surface on the connector of the box. Both load flanks are at a slightly downward angle and remain within a fairly close tolerance of less than one degree. Furthermore, it is preferable that both the load flanks on the pin connector and the load flanks on the box connector each have a substantially flat coupling when the connection has been fully established, although there could be slight disparities between these flank angles, or the surfaces of the flanks on the threads as such may have slightly different lengths. Similarly, a substantially flat coupling between the torque support on the box member and the torque support on the pin member is desired, although, again, there could be a slight variance between these angles, for example, typically less than 1 degree, due to machining tolerances. It is not necessary that the load supports have the same radial length.

If the angle of the torque support has a higher magnitude, a wedge is formed between the load flank and the torque support, which can convert the radial preload of the varnish pressure to an additional axial preload on the Torque support. If the angle of the torque support is of a lower magnitude, a dovetail configuration is created which is solved by the present invention. If the angle of the torque support is parallel or close to being parallel to the load flank of the threads, the preload should be substantially maintained. By providing the aspects disclosed herein, the tubular connection for oilfields is able to maintain a relatively high breakout value even if an excess of varnish is trapped between the seals. The imprinted varnish increases the circumferential tension and the radial separation of the connectors can take place, even if the pressure of the excess varnish is relieved, it is desirable that the connection returns substantially to its original shape without a significant reduction in the initial preload. This is not possible when the flanks of the load on the connection and the torque supports on the connection are effectively at significantly different angles, and which effectively create a dovetail condition. According to one embodiment of the invention, the angle of the load flank of the threads and the torque supports are both at a negative angle, preferably with a slight difference, which allows the connection to be energized axially as the distance between the load flanks and the torque support increases as the radial spacing between pin and housing decreases in response to a lower compound pressure for the threads.

Another potential advantage of the torsional torsional support, which only applies to the "negative" support option, is that of allowing the radial deflection of the connector under a high axial compression load that allows the stress flank clearances to close. This in turn will help the support area carry the compression load and prevent deformation of the shoulder. By giving less rigidity to the support, the stress flank clearances have the ability to close and participate in the transport of the compression load before the carrier area of the torque support yields. This radial deflection to allow this axial advance owes its capacity to the radial component of the reaction force acting on the torque support. This radial force is the result of the torque support, formed at an angle.

In another embodiment of the invention, as shown in Figure 4, the threaded connection 10 includes a pin member 14 and a box member, 12, with a torque support formed by the engagement of the surfaces 20 of the member. pin and surface 26 of the box member. The connection shown in Figure 4 has threads of two steps, but the invention of Figures 1-3 or Figure 4 can also be used in a tapered single-step thread.

Figure 4 illustrates that the threads have a load flank 42 that is positive; and that the torque support, formed by surfaces 26 and 28 is also positive. According to the present invention, these surfaces are controlled in such a way that any variance between the load flank in one of the following: the pin member or the box member, and the torque support in the same pin member or member box is less than 5o, for example the angle of the load flank can be a positive 10 0, and the torque support can be a positive 9th. Each of the surfaces 26, 28, for this embodiment is at an angle of perpendicular to positive of 0 to 15 ° and preferably less than 15 °. Figure 4 shows the torque support separated between the threads of two steps, although alternatively the torque support can be provided at either end of the connection. With the exception of the differences in the load flanks and the torque supports, otherwise the connection may be as set forth in the foregoing for the negative angle embodiment. The principles described herein could be applied to threaded and coupled connectors, single-step connectors or connectors with only a single seal. The pressure of the thread compound can take place due to the inner seal in combination with a torque support or restriction in the threads, independently of the existence of an outer seal. Other connections with aspects of internal and external seals are susceptible to an excess of varnish and would also benefit from the present invention.

While specific embodiments of the invention have been described in some detail herein, this was done solely for the purpose of explaining the various aspects of the invention and is not intended to limit the scope of the invention as defined in the drawings. following claims. Those skilled in the art will understand that the embodiment shown and described is given by way of example, and that in the practice of the invention it is possible to make various other substitutions, alterations and modifications, including but not limited to alternative designs specifically set forth herein; this, without departing from the scope of the present invention. While the present invention has been described in particular with reference to the drawings appended thereto, it should be understood that within the scope and spirit of the present invention it is possible to make other additional modifications, in addition to those shown or suggested herein.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. A threaded tubular connection for oil fields, comprising: a box connector, having internal threads and a box torque support; a pin connector, having matching external threads for a coupling, with the internal threads and a pin torque support, for coupling with the box torque support, when the connection is completed; each of the external threads and the internal threads having a load flank of the thread that is at a negative angle with respect to a central axis of the connection; and each of the torque supports of the box and the torque supports of the pin, is at a negative angle with respect to a central axis of the connection.

2. The threaded tubular connection for oilfields according to claim 1, further characterized in that each of the connectors of the box and the connectors of the pin, includes two-step tapered threads, and each of the two-step tapered threads has the side of negative charge.

3. The threaded tubular connection for oil fields according to claim 2, further characterized in that the torque support of the box and the torque support of the pin, are axially separated between the threads of two steps in each of the connectors of the box and the connectors of the pin.

4. The threaded tubular oilfield connection according to claim 1, further characterized in that it additionally comprises: a seal surface of the pin, adjacent to one end of the pin of the pin connector for a sealing engagement with the box connector when complete the connection; and a seal surface of the box, adjacent to one end of the box connector housing, for a sealing engagement with the connector when the connection is complete.

5. The threaded tubular connection for oil fields according to claim 1, further characterized by each of the following, the load flank of the thread on the connector of the box and the connector of the pin, the torque support of the The housing and the torque support of the pin are at a negative angle to the central axis of the connection with a variance of less than 5o between the load flank and the torque support on the respective pin connector or box connector.

6. The threaded tubular connection for oilfields according to claim 5, further characterized in that the flanks of the threads are at an angle of 1 ° to 15 °, and the torque support of the box and the torque support of the pin are each at an angle of 1 ° to 20 °, the angle of the torque support being substantially equal to or greater than the angle of the load flank.

7. The threaded connection for oilfields according to claim 1, further characterized in that each of the torque supports of the box and the support of torque of the pin have a negative angle within the 5o of the flank of negative charge of the threads on the connector of the box and on the connector of the pin.

8. The threaded tubular connection for oil fields according to claim 1, further characterized in that each of the load flanks of the threads in the connector of the box and the connector of the pin, is at a negative angle less than 15 °, and each of the box's torque brackets and the pin's torque brackets have a negative angle of less than 20 °.

9. The threaded tubular connection for oilfields according to claim 1, further characterized in that each of the stress flanks of the internal threads and of the external threads is at a positive angle.

10. A threaded tubular connection for oilfields, comprising: a box connector having internal threads and a box torque support; a pin connector that has external threads for a matching coupling with the internal thread; and a pin torque support for coupling with the box torque support when the connection is completed; including each of the external threads and the internal threads, two-step tapered threads having a thread loading flank that is at an angle to a central axis of the connection; the torque support of the box and the torque support of the pin being axially spaced between the threads of two steps on each of the box connectors and the pin connectors; and each of the torque supports of the box and the torque supports of the pin being at an angle with respect to a central axis of the connection with a variance of less than 5o between the load flank and the torque support on the respective connector of the pin or connector of the box.

1. The threaded tubular oilfield connection according to claim 10, further characterized in that it additionally comprises: a seal surface of the pin, adjacent to a pin end of the pin connector, for a sealing coupling, which matches, with the connector of the box when the connection is completed; and a seal surface of the box, adjacent to one end of the box connector housing, for a sealing coupling, which matches, with the connector when the connection is completed.

12. The threaded tubular connection for oil fields according to claim 10, further characterized by each of the load flank of the thread on the connector of the box and on the connector of the pin, the load flank of the box, torque support The torsion of the box and the support of torque of the pin are at an angle with a variance of less than 5o between any two of the angles.

13. The threaded tubular connection for oilfields according to claim 12, further characterized in that the load flanks of the threads are at an angle with a negative value of 1 or 15 °, and the torque support of the box and the The torque support of the pin are each at a negative angle of 1 to 20 °, the angle of the torque support being substantially equal to or greater than the angle of the load flank.

14. The threaded connection for oil fields according to claim 10, further characterized in that each of the torque support of the box and the support of the torque of the pin have a negative angle within 5o of the load flank of the negative threads, on the connector of the box and on the connector of the pin.

15. The threaded tubular connection for oil fields according to claim 1, further characterized in that each of the load flanks of the threads on the connector of the box and on the connector of the pin, is a positive angle less than 15 °, and each of the torque support of the box and the pin torque support have a positive angle of less than 15 °.

16. A method for forming a tubular connection for oil fields, comprising: providing a box connector with internal threads and a torque support of the box; provide a pin connector with external threads for a matching coupling with the threads internal and a pin torque support for a coupling with the torque support of the box when the connection is completed; forming each of the external threads and of the internal threads, with a load flank of the threads that are at an angle with respect to a central axis of the connection; forming each of the torque support of the box and the torque support of the pin with a negative angle with respect to a central axis of the connection; and complete the connector of the box and the pin connector, to form the threaded connection.

17. The method according to claim 16, further characterized in that each of the connector of the box and the connector of the pin, are formed with tapered threads of two steps; and separating the torque support from the box and the pin torque support axially between the threads of two steps on each of the box connector and the pin connector.

18. The method according to claim 16, further characterized by additionally comprising: forming a seal surface of the pin, adjacent to a pin end of the pin connector for a sealing engagement with the box connector when the connection is completed; and forming a seal surface of the box, adjacent to a box end of the box connector for a sealing engagement with the connector when the connection is completed.

19. The method according to claim 16, further characterized in that each of the following, the load flank of the thread on the connector of the box and the pin connector, the torque support of the box and the pin torque support are formed with a An angle with a variance less than 5o between the load flank and the torque support on a respective pin connector or box connector.

20. The method according to claim 19, further characterized in that the flanks of the threads are at a negative angle of 1 or 15o, and the torque support of the box and the torque support of the pin are, each of them, with a negative angle of 1 or 15 °, the angle of the torque support being substantially equal to or greater than the angle of the load flank.

21. A threaded tubular connection for oil fields, comprising: a box connector having internal threads and a box torque support; a pin connector having external threads for a coupling, which matches, with the internal threads and a pin torque holder for a coupling with the box torque support when the connection is completed; each of the external threads and the internal threads having a load flank of the threads which is at a positive angle with respect to a central axis of the connection; each of the following, the torque support of the box and the torque support of the pin are at a positive angle with respect to the central axis of the connection; and each of the Following, the load flank of the threads on the housing connector and the pin connector, the box torque support and the pin torque support are at a positive angle with respect to an axis Central geometry of the connection, there being a variance less than 5o between the load flank and the torque support on the respective box connector or pin connector.

22. The threaded tubular connection for oilfields according to claim 21, further characterized in that each of the following, the box connector and the pin connector includes two-step tapered threads, and each of the two-step tapered threads has the flank of positive charge.

23. The threaded tubular connection for oil fields according to claim 22, further characterized in that the torque support of the box and the torque support of the pin are axially separated between the threads of two steps on each of the following : the connector of the box and the connector of the pin.