Pin-actuated lock ring arrangement

In a wellhead near the top of an oil and gas well, a locking ring assembly for locking an inner tubular wellhead member axially relative to an outer tubular wellhead member. The inner tubular member has a circumferential recess that contains a locking ring. After insertion of the inner tubular member into the outer tubular member, actuating pins radially expand the locking ring so that it partially leaves the circumferential recess and engages a corresponding recess in the outer tubular member. The pins may be deployed by a seal inserted above the inner tubular member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to locking rings for securing inner wellhead tubular members to outer wellhead tubular members. More particularly, this invention relates to a locking ring on an inner wellhead tubular member that is actuated by a series of pins that may be compressed by an annulus seal and that, when compressed, pushes the locking ring into engagement with the outer wellhead tubular member.

2. Brief Description of Related Art

Typically, locking mechanisms are used between inner and outer wellhead tubular members to help prevent relative axial movement between the members. In some cases, such locking mechanisms are integrated with seals or packoffs, which are typically used as a pressure barrier in the annular space between the inner and outer tubular members.

For example, U.S. Patent Appln. Pub. No. 2012/0025470 discloses an arrangement that includes a casing hanger inserted in a well bore. An annular seal is inserted so as to seal the space between the casing hanger and the well bore. To accomplish this, the annular seal includes ridges that, when pressed against surfaces of the casing hanger and the wellbore, become embedded in the surfaces. Not only does this arrangement seal the space between the casing hanger and the well bore, but it also locks the casing hanger in place axially relative to the wellbore.

One characteristic of such an integrated sealing/locking arrangement, is that ridges perform both a sealing and a locking function. Such an arrangement is advantageous in certain applications. It is possible, however, that there may be annulus seal designs that would perform the sealing function well, but that do not have the required profile to lock the casing hanger relative to the well bore. Another characteristic of such an integrated sealing/locking arrangement, is that the ridges, which lock the casing hanger in place by engaging the walls of the casing hanger and the well bore, are positioned in the load path for lockdown. Again, this feature is advantageous in certain applications. In some instances, however, it may be desirable to have a locking mechanism that is separate from the annulus seal, and not located in the load path. Such a situation may arise, for example, where there is a need to increase resistance to fatigue and the reliability of the seal.

SUMMARY OF THE INVENTION

Disclosed herein is a wellhead having a locking ring assembly for locking an inner tubular member, such as a casing hanger, axially relative to an outer tubular member, such as a well bore. The assembly includes a radially expandable locking ring that is substantially contained in a recess around the circumference of the inner tubular member. The ring has an unlocked position, in which it is substantially fully seated within the recess, and a locked position, in which it expands at least partially out of the recess and into engagement with a corresponding recess in the outer tubular member. When in the locked position, the ring prevents the inner tubular member from moving axially relative to the outer tubular member.

The ring may be actuated by an actuating mechanism that substantially surrounds the inner tubular member and slides axially between an up position and a down position. When in the up position, the actuating mechanism is substantially disengaged from the locking ring so that the locking ring can remain in its unlocked position within the recess of the inner tubular member. Conversely, when in the down position, the actuating mechanism may at least partially displace the locking ring from the recess, forcing the locking ring to expand into a locked position and engage the recess of the outer tubular member.

In one example embodiment the actuating member may be a series of pins that are substantially vertically oriented around the circumference of the inner tubular member. In another embodiment, the actuating member may be a ring that surrounds the inner tubular member.

Further disclosed herein is a method of locking a casing hanger to a wellhead, where a casing hanger having a recess around its circumference, and a radially expandable locking ring within the recess, is inserted into a well bore. Thereafter, an actuating mechanism may be employed to expand the locking ring so that it engages a recess of the well bore, thereby locking the casing hanger axially relative to the well bore. In an example embodiment, the actuating mechanism may be deployed by an annular seal inserted into the well bore above the casing hanger. As discussed above with respect to the locking ring assembly, the actuating mechanism may be a series of pins surrounding the casing hanger. Alternatively, it may be a ring that surrounds the inner tubular member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The foregoing aspects, features, and advantages of the present invention will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. In describing the preferred embodiments of the invention illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose.

The present technology may be used in oil and gas wells, and in particular in wellheads at the top of the wells. Typical wellheads may serve a number of different functions, including casing suspension, tubing suspension, pressure sealing, and so forth. Some of these functions require an inner well member, such as, for example, a casing hanger, to be inserted into the wellhead and locked axially relative to the wellhead.

Referring toFIG. 1, there is shown a perspective view of an inner tubular member, which is, in the example embodiment shown, a casing hanger2according to one example embodiment of the present technology. As can be seen, the casing hanger2of this embodiment is substantially cylindrical and has a circumferential protrusion6extending from the outer surface thereof. The circumferential protrusion6has an upper portion6aand a lower portion6b, and defines a circumferential recess8and a plurality of holes10. In the embodiment ofFIG. 1, the circumferential recess8is positioned below at least one debris trap48located on the casing hanger2. The holes10are more clearly shown inFIGS. 2-4, where it is apparent that each hole10has a longitudinal axis that is angled radially inward. In some embodiments, the longitudinal axis of each hole may be nearly vertical or vertical. Each hole10extends through an upper portion6aof the circumferential protrusion and intersects the circumferential recess8at a back end thereof.

As further shown inFIG. 1, a locking ring12may be positioned within the recess8, and axially restrained by upper and lower portions6a,6bof the circumferential protrusion6. The locking ring12has an inner surface40and an outer surface42(shown inFIG. 2). In its neutral state, the locking ring12is biased so that it is substantially fully seated within the recess8. However, the locking ring12also has a notch14that allows the ring12to expand radially outwardly from the outer surface of the casing hanger2. Such expansion of the locking ring12may occur, for example, if an outward force is exerted against the inner surface40of the ring12, or if an object enters the recess8inside the inner surface40, thereby displacing the ring12and forcing it to expand radially outward. In addition, the locking ring12may have shoulders16(best shown inFIG. 2). A crush washer18(also shown inFIG. 2) may be positioned between the locking ring12and the lower portion6bof the circumferential protrusion.

In the example embodiment shown inFIG. 1, a plurality of pins20may be inserted at least partially into the holes10. The pins20may be elongate, and, like the holes10, have a longitudinal axis that is angled radially inward. The pins20may be at least partially supported in their vertical position by the holes10, and may further be oriented and retained in position by a dowel pin22that engages a grooved slot24in each pin (shown inFIG. 2), or by similar means. The dowel pin22may have an axis that is substantially perpendicular to the axis of the each pin20, and passes through the grooved slot24in each pin and into the casing hanger2. The grooved slot24is preferably elongate so that the pin may move up and down in an axial direction while the dowel is engaged with the slot24. The pins20are axially moveable relative to the casing hanger2and have at least an up position (shownFIG. 3) and a down position (shown inFIGS. 2 and 4). When in the up position, the pin20does not extend into the lower portion of the hole10, which intersects the recess8. When in the down position, however, the pin20may extend at least partially into the tower portion of the hole10, which causes the pin20to come into contact with, and at least partially displace the locking ring12.

Referring now toFIG. 2, it can be seen that each pin20may have a contoured upper surface. For example, each pin20may have a push surface28, which may slope downward with distance radially outward. In addition, each pin20may have a retrieval tooth30to aid in moving the pin from a down position to an up position, as described in detail below. The tooth30projects upward from the push surface28and includes a notch with a downward facing surface for selectively applying an upward lifting force.

In one non-limiting example, the locking ring of the present technology may lock a casing hanger in place relative to wellhead tubing according to the following method. After the casing hanger2is inserted into a bore32of a wellhead34, the pins20and locking ring12are configured as shown inFIG. 3, with the pins20in the up position, and the locking ring12fully seated within the recess8. The casing hanger2and the wellhead34define a portion of a well head assembly.

Next, as shown inFIG. 4, an annulus seal36is inserted into the bore32to circumscribe in upper end of the casing hanger2. As the annulus seal36is lowered, the lower ends38of the annulus seal36contact the push surfaces28of the pins and begin to push down, or compress, the pins20relative to the casing hanger2. As the pins20are pushed down, the bottom end of each pin20enters the lower portion of its hole10, which intersects the back of the recess8. As the pin20contacts the inner surface40of the locking ring12, it exerts an outward force on the ring12, and displaces the ring12at least partially from the recess8. Accordingly, the ring12expands radially outward, and its outer surface42extends beyond the recess8and into locking engagement with a recess44in the wellhead wall. The recess44is configured to receive the locking ring12and interferes with axial movement of the locking ring12. Thus, with the pins20in the down position, the locking ring12is in a locked position, and the casing hanger2is fixed axially in place relative to the wellbore.

In the event that the casing hanger2needs to be retrieved from the wellbore, the following process may be employed. First, the annulus seal36may be removed from the bore32. Thereafter a running tool (not shown) may be inserted into the bore. The running tool should have means to engage the retrieval teeth30of the pins20. The running tool is lowered over the top of the casing hanger2until it engages each of the retrieval teeth30. Thereafter the running tool is raised, thereby exerting an upward force on the retrieval teeth30and moving the pins20into the up position. As the pins20move into the up position, the ends of the pins20move out of the bottom portions of the holes10and cease to displace the locking ring12. Accordingly, the locking ring12contracts back into the recess8and disengages from the recess44in the wellhead wall. With the locking ring8thus disengaged, the casing hanger2may move axially relative to the wellhead and can be withdrawn from the well. In an alternative embodiment, the annular seal36itself may be equipped with means for engaging the retrieval teeth30and may pull the pins20into the up position, thereby eliminating the need to insert a separate running tool.

Referring toFIG. 5, there is shown an alternate embodiment where the locking ring12has a chamfered surface46at an upper end of the outer surface42. In such an embodiment, the recess44in the wellhead wall may have an angled surface48that corresponds to the chamfered surface46when the locking ring12is extended into its locked position. Such a chamfered surface46may ease the entry of the locking ring12into the recess44in situations where, for example, the locking ring12is not exactly aligned with the recess44when the locking ring expands. In addition, the locking ring12may have a chamfered surface at a bottom end of the outer surface42(not shown). In fact, the locking ring12may have any profile that will allow locking engagement with the recess44of the wellhead.

Although the above example embodiments use pins to displace the locking ring12and expand it into locked engagement with the recess44in the wellhead wall, it is to be understood that other ring actuating mechanisms are also contemplated by the present invention. For example, instead of pins, one example embodiment employs a tapered ring (not shown) that has an up position and a down position. Similar to the pins disclosed above, when the tapered ring is in the down position it is configured to at least partially displace the locking ring12from the recess8and into locked engagement with the wellhead wall. Conversely, when the tapered ring is in the up position, it ceases to displace the ring12from the recess8, and the ring contracts back into the recess8.

One advantage to the pin actuated locking rings is that, unlike some known locking rings, the pin actuated locking rings of the present technology does not share a profile with the back-up seal of an annulus seal. Thus, there is more room for back-up sealing geometry, thereby allowing for more flexibility in the design and location of the back-up seal. In addition, with the above disclosed design, the load path for lockdown need not run through the annulus seal. Accordingly, the reliability and resistance to fatigue of the annulus seal will be improved. Furthermore, the locking rings disclosed herein allow for a secure lockdown of the casing hanger without modification of the annulus seal, thereby eliminating the need for time consuming and costly testing of alternative annulus seal designs.

While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, although the example embodiments have disclosed use of the locking ring with a casing hanger, the inner tubular member could instead be a tubing hanger, plug, safety valve, or other device. Furthermore, it is to be understood that the above disclosed embodiments are merely illustrative of the principles and applications of the present invention. Accordingly, numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.