Patent Application
20110315373
The field of this invention is subterranean plugs or annular seals that experience pressure differential and more particularly mandrel adaptations designed to retain a material such as a shape memory or swelling material in position against such pressure differentials through mechanical retention.
Swelling members have been secured to mandrels in a variety of way. One way is to mount the swelling member on a longitudinally split base and secure the base to the mandrel by closing the split base around the mandrel and inserting a long tapered pin. The swelling material itself is secured to the base with adhesives or other chemical bonding techniques. Illustrative of this design is U.S. Pat. No. 7,730,940.
Another technique is to use rigid rings secured to the mandrel on either end of the sealing element to hold it in position as shown in US Publications 2010/0116496 and 2009/0229816. Yet another way is to shrink fit or create tension in the element adjacent the mandrel in an effort to hold it in position and prevent leak paths along the mandrel and element interface. These concepts are illustrated in U.S. Pat. Nos. 7,441,596 and 7,681,653.
Other designs couple end retention with booster devices to enhance the radial seal force applied beyond the swelling such as by sliding a wedge under the swelling element from at least one end. An example of this design is U.S. Pat. No. 7,552,768. Flexible stacks of notched rings have been disposed at opposed ends of a swelling element with a through bolt extending through the element to pull the end ring stacks toward each other. This is shown in US Publication 2010/0038074. Sometimes the swelling material is located in an inflatable to assist the inflatable in holding a seal as shown in U.S. Pat. No. 7,597,152. Other multi-layered designs of swelling sealing systems are shown in U.S. Pat. No. 7,422,071 and US Publication 2009/0178800.
This design uses a single or series of undercut profiles, slots or retentive groove in the mandrel ID or OD depending on where the material is to be retained. The undercut profile allows for greater mechanical retention of the plug material resisting displacement while experiencing a pressure differential.
The present invention addresses the issue of annular seal or tubular plug retention against pressure differentials in a simplified manner using features of the mandrel or the surrounding tubular and positioning the material adjacent to the mandrel surface formation which can be in the form of a projection or depression or a combination so that the material is better retained against pressure differentials when sealing at a subterranean location. The materials can be shape memory materials or swelling materials. These and other aspects of the present invention will be more readily understood by those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be found in the appended claims.
A mandrel is formed with a projection, depression or a surface irregularity to retain the seal material sealing a passage in the mandrel or an annular space around it against differential pressure. The material can be a shape memory or swelling material.
The plug 16 can be a shape memory polymer that tends to get softer when swelling to a larger dimension and needs fixation assistance that the projection 14 can provide. Other materials that swell can also be used. Other alternatives are swelling rubber or foams or retained mineral clays such as bentonite. While two surfaces 18 and 20 that intersect have been illustrated, either surface can be omitted so that fixation boost occurs in a single preferred direction rather than opposed directions. While surfaces 18 and 20 are shown flat they can be rounded or irregular and can also feature a surface roughness to aid retention of the plug 16.
Instead of the projection 14 the inside wall 12 can be surface roughened to enhance the grip of the plug 16 on the inside diameter or wall 12. Alternatively, the projection 14 can be flipped so it is a recess while still being subject to the alternatives described above when it is in the form of a recess. Depending on the length of the plug 16 and the surfaces 18 and 20 more than one protrusion 14 or its described variations can underlie a single plug. Alternatively, the single plug 16 that is illustrated can be a stack of plugs to seal the interior of the tubular 10.
All variants discuss for
Those skilled in the art will appreciate that the various embodiments are simple voids or projections or surface textures designed to enhance grip against pressure differential in an environment where a tubular is plugged or an annular space around a tubular is to be sealed. Different shape configurations are employed with an eye toward enhancing the security of the grip against a differential pressure. While the surfaces can be optionally adhesive coated or the plug itself can be placed in position with an exterior adhesive coat, the use of adhesives is totally optional. Mechanical fasteners are not required. The shape can be machined or otherwise formed to the inside or outside of the mandrel, depending on the configuration used.
In another alternative the seal 32 can be used as shown in
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
