Patent Application
20100224373
The present invention relates to subsea wellhead orientation, and more particularly, in certain embodiments, to methods and systems for aligning a Christmas tree with a tubing hanger.
Tubing hangers need a specific orientation with respect to the wellhead because they contain numerous bores, which require alignment with corresponding portions of respective Christmas trees. Conventionally, there are two ways to achieve orientation of a Christmas tree relative to a tubing hanger. The first uses a tubing spool assembly, which latches to the wellhead and provides landing and orientation features. The tubing spool is very expensive and adds height to the overall stack-up. Additionally, the tubing spool is so heavy that very few work class vessels can install it, and it frequently requires installation by expensive drilling vessels. Furthermore, the drilling riser must be removed to install the tubing spool.
The second method of orienting a Christmas tree relative to a tubing hanger involves the use of a blowout preventer (“BOP”) stack hydraulic pin and orientation adapter joint. This method requires detailed knowledge of the particular BOP stack in order to accurately install a hydraulically actuated pin, which protrudes into the BOP stack bore. An orientation helix is attached above the tubing hanger running tool, and, as the tubing hanger lands, the helix engages the hydraulic pin and orientates the tubing bores to a defined direction. This method requires accurate drawings of the BOP stack elevations and spacing between the main bore and the outlet flanges, which may require hours of surveying and multiple trips to make measurements. Tremendous room for error exists with this method, particularly in older rigs. Thus, this method requires significant up front planning. Additionally, setting the lockdown sleeve in the wellhead generally requires a rig because the BOP must remain in place as a reference point for orientation of the tubing hanger and corresponding lockdown sleeve.
The present invention relates to subsea wellhead orientation, and more particularly, in certain embodiments, to methods and systems for aligning a Christmas tree with a tubing hanger.
One embodiment of the present invention provides a method of aligning a Christmas tree with a tubing hanger. The method comprises the step of providing a wellhead with an orientation key on an outer surface and an opening on an inner surface. The method further comprises the step of providing the Christmas tree attached to a guide tube having an orientation profile configured to engage the orientation key and guide the Christmas tree into a desired orientation relative to the wellhead. The method further comprises the step of providing a lockdown sleeve with a mating profile on an inner surface, and a protuberance on an outer surface configured to engage the opening on the inner surface of the wellhead when the lockdown sleeve is in a desired orientation relative to the wellhead. The method further comprises providing the tubing hanger with a mating profile on an outer surface configured to engage the mating profile of the lockdown sleeve and guide the tubing hanger into a desired orientation relative to the lockdown sleeve. The method further comprises moving the lockdown sleeve into engagement with the wellhead. The method further comprises moving the tubing hanger into engagement with the lockdown sleeve. The method further comprises moving the Christmas tree into engagement with the wellhead and the tubing hanger.
Another embodiment provides a system for aligning a Christmas tree with a tubing hanger. The system comprises a wellhead with an orientation key on an outer surface and an opening on an inner surface. The system further comprises the Christmas tree attached to a guide tube having an orientation profile configured to engage the orientation key and guide the Christmas tree into a desired orientation relative to the wellhead. The system further comprises a lockdown sleeve with a mating profile on an inner surface, and a protuberance on an outer surface configured to engage the opening on the inner surface of the wellhead when the lockdown sleeve is in a desired orientation relative to the wellhead. The system further comprises the tubing hanger with a mating profile on an outer surface configured to engage the mating profile of the lockdown sleeve and guide the tubing hanger into a desired orientation relative to the lockdown sleeve.
The features and advantages of the present invention will be readily apparent to those skilled in the art. While those skilled in the art may make numerous changes, such changes are within the spirit of the invention.
Referring to
Referring now to
Lockdown sleeve 113 may fit within wellhead 112. Referring now to
In addition to protuberance 132 on outer surface 134, lockdown sleeve 113 may have mating profile 136 on inner surface 138 for engaging tubing hanger 114 (not shown in
Referring now to
Using the methods of certain embodiments of the present invention, installing Christmas tree 110 on wellhead 112 in alignment with tubing hanger 114 may allow for automatic alignment of Christmas tree 110 with tubing hanger 114. Referring again to
Tubing hanger 114 may move into lockdown sleeve 113 and rotate or otherwise move until mating profile 140 on tubing hanger 114 engages mating profile 136 on lockdown sleeve 113. The two mating profiles 136 and 140 may then cause tubing hanger 114 to move into desired engagement with lockdown sleeve 113. Because the orientation of mating profile 136 may be known relative to orientation key 116, when mating profile 136 engages mating profile 140 on tubing hanger 114, the orientation of mating profile 140 may be known relative to orientation key 116. Thus, tubing hanger 114 may have a known orientation relative to wellhead 112.
Christmas tree 110, with guide tube 124 may move onto wellhead 112 and rotate or otherwise move until orientation profile 126 engages orientation key 116. Orientation key 116 and orientation profile 126 may then cause Christmas tree 110 to move into desired engagement with wellhead 112. Because the orientation of tubing hanger 114 may be known relative to the orientation key 116, when the orientation key 116 and the orientation profile 126 engage, the orientation of tubing hanger 114 may be known relative to Christmas tree 110. Thus, Christmas tree 110 may easily move into desired engagement in a proper orientation with tubing hanger 114.
Known values of orientation key 116, opening 120, orientation profile 126, protuberance 132, mating profile 136, and mating profile 140 may be used to calculate the orientation of tubing hanger 114, allowing Christmas tree 110 to be properly positioned. Alternatively, one or more of orientation key 116, opening 120, orientation profile 126, protuberance 132, mating profile 136, and mating profile 140 may be positioned such that Christmas tree 110 is automatically positioned properly. In yet other embodiments, orientation key 116, opening 120, orientation profile 126, protuberance 132, mating profile 136, and mating profile 140 may all be radially aligned such that Christmas tree 110 is automatically positioned properly.
Thus, alignment of tubing hanger 114, lockdown sleeve 113, wellhead 112, and Christmas tree 110 may be set in a desired orientation without the need for extraneous alignment devices. Rather, modifications of existing tubing hangers, lockdown sleeves, wellheads, and Christmas trees may allow for an improved method of obtaining a desired alignment. For example, a slim bore (13½″ nominal size) tubing hanger may be installed into a standard bore (18¾″ nominal size) wellhead and achieve a defined orientation of all the tubing hanger through bores and downhole control lines with respect to the wellhead. A lockdown sleeve may be installed prior to the tubing hanger and provide a passive orientation helix which uses the weight of the production tubing to align the tubing hanger prior to landing. As noted above, the lockdown sleeve may have a spring-loaded key, which may engage a slot in the bore of the wellhead, and a fixed key on the outside of the wellhead may align and guide the Christmas tree into the correct orientation so that all the Christmas tree stabs engage the tubing hanger bores correctly. In some embodiments, the helix key in the tubing hanger, the spring-loaded key in the lockdown sleeve, and the fixed key on the outside of the wellhead may all be aligned with one another, allowing orientation to be verified visually from outside the subsea wellhead.
Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, many of the features could be moved to different locations on respective parts without departing from the spirit of the invention. Furthermore, no limitations are intended to be limited to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Moreover, the indefinite articles “a” or “an”, as used in the claims, are defined herein to mean one or more than one of the element that it introduces. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.
