Patent Application
20120217004
The field of the invention is expandable open hole packers and more particularly those that use the expansion process for increasing sealing contact pressure and using applied pressure differential to enhance the sealing force.
Packers are mounted on tubular strings and have to pass through close clearances in existing tubulars to get to the location where the packer is to be deployed. In some cases the dimensional difference between the drift diameter of the existing tubular that the packer needs to pass and the set dimension is so great as to create problems in getting a reliable seal. The limits of the tubular in expansion can be reached in situations where the mandrel is expanded. Some examples of packers set by expansion can be seen in U.S. Pat. Nos. 6,959,759; 6,986,390; 7,051,805 and 7,493,945.
Some designs rely on the element to swell in the presence of well fluids such as water or hydrocarbons, such as: U.S. Pat. Nos. 7,387,158; 7,478,679; 7,730,940; 7,681,653; 7,552,768; 7,441,596; 7,562,704; 7,661,471. In some of these designs the reduction in stiffness and resulting contact pressure is offset with applied axial compressive forces triggered with the swelling as shown in U.S. Pat. No. 7,552,768 or thereafter as a result of pressure differentials such as U.S. Pat. No. 7,392,841. Swelling to make a seal is a time consuming process which can mean significant additional operator cost if the swelling has to conclude to a sealing condition before other steps can be undertaken in a well completion.
Some designs rely on axial mandrel shrinkage to apply an axial boost force to ends of a sealing element that is being radially expanded as illustrated in U.S. Pat. No. 7,431,078.
Other designs involved the use of packer cups that could be run through another tubular and then spring outwardly in the larger wellbore to obtain a seal. These designs suffered from potential damage during run in that could destroy their ability to seal. Their inherent design limited the speed that they could be run into or removed from a wellbore without swabbing the well coming out or pressurizing the formation on the trip into the well.
Some designs used tubular expansion combined with exterior rings that moved relatively to each other to extend the reach of a packer in the wellbore as illustrated in U.S. Pat. No. 7,661,473. This design also had an option for using a swelling material 44 as the sealing element. The expansion enhancing mechanism went the length of the seal element and due to the ramp structure it employed to enlarge wound up adding to the initial dimension while providing only a limited amount of enhancement in the radial direction to the underlying mechanical expansion of the mandrel.
US Publication 20050000697 illustrates a technique of corrugating pipe downhole to make it more flexible for subsequent expansion. US Publication 2010 0314130 illustrates using internal spacers and driving a swage through them to expand a seal into a wellbore wall.
What is needed and provided by the present invention, among other features, is the ability to parlay the expansion force of the mandrel into a rotational movement of fingers attached to a ring. The fingers bend outwardly to move the sealing element toward a wellbore wall to enhance the sealing contact. The fingers can bend independently so as to make the pushing out of the seal conform to a surrounding borehole wall that is not necessarily round and can be oval or irregular. The mandrel features an external ring that due to shrinkage of the mandrel as it is expanded winds up under the bent fingers to further hold out the fingers against the sealing element to maintain the seal. The ring and finger structure permits fluid to get under an end of the sealing element and to further aid in pushing the element against the borehole wall which can be open hole. Another ring from the mandrel exterior extends into the element to retain it against sliding force from pressure differentials. Various options are possible such as orienting the rings with fingers in mirror image orientations to enhance seal against differential pressures from above or below the set seal. The ring itself can be an extrusion barrier and as another option the seal can extend the length of the fingers and their base ring. Those skilled in the art will better appreciate the various aspects of the present invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
An open hole packer uses mandrel expansion and a surrounding sealing element that can optionally have a swelling feature and further a seal enhancing feature of a ring with an internal taper to match an undercut on the mandrel exterior. As a swage progresses to the taper at the transition between the ring and the extending flat fingers, the fingers get plastically deformed in an outward radial direction to push out the sealing element. Shrinkage of the mandrel axially due to radial expansion brings a ring on the mandrel outer surface under the fingers to act as a support for the fingers against the seal which is pushed against the open hole. Mirror image orientations are envisioned to aid in retaining pressure differentials in opposed directions. Another external mandrel ring extends into the seal to keep its position during differential pressure loading.
The drift dimension of ring 18 is at least as large as the sealing element 30 for run in to provide protection to the sealing element 30
As can be seen in
The support ring 18 can be initially split so that it can be fit over the mandrel 12 and axially fixated by having a groove 19 that fits over a key 21. The location of the key and the groove can be reversed. When there is differential pressure as indicated by arrow 52 is will more likely communicate past ring 18 in any clearance gap after expansion around ring 18 and within tubular wall 48.
What is shown is an assembly that has a low protected profile for run in due to the sealing element being retracted and in an undercut and protected by a ring structure with extending fingers that define gaps between them. The gaps are closed at the cantilevered ends as alternating fingers overlap ends of adjacent fingers. The tapered transition in the ring and finger structure makes the fingers turn out in plastic deformation against a surrounding sealing element to hold the sealing element out against the borehole wall. Such support can be enhanced with a ring that positions itself under the fingers to hold their ends out against the sealing element. The seal enhancing assemblies when mounted on the ends of a sealing element also allow well fluids to reach the underside at the ends of the sealing element. In situations where such element is a swelling element, the end swelling is enhanced as the actuating fluid such as water or hydrocarbons fully surrounds the end of the sealing element for enhanced swelling and thus sealing. The gaps between the fingers that enlarge during expansion also promote such fluid exposure not only to enhance swelling but also to enhance the sealing force from pressure delivered between the mandrel and the sealing element to give the sealing element the operating characteristics of a packer cup without the downsides of such seals such as low pressure differential tolerance, damage on run in and swabbing the well on the way out. The illustrated designs allow for a seal to form rapidly without having to delay other procedures waiting for swelling only to make the seal as in previous designs. The boost sealing force occurs from under the sealing element as opposed to axially oriented spring systems as used in the past. The expansion process and configuration of the finger ring creates packer cup like behavior in an annularly shaped element. The use of an undercut allows the sealing element to be protected for run in by the ring of the finger ring assembly. The undercut dovetails with a taper on the transition between the ring and the fingers to create the pivoting plastic deformation of the fingers that presses out the sealing element. The plastic pivoting movement can be further bolstered by a support ring that moves into position due to axial shrinkage that results from expansion especially with the mandrel in compression. Mirror image assemblies are contemplates as well as sealing elements that end at the end of the fingers that can have the support that moves into position due to axial shrinkage during expansion or that support can be optionally omitted. Retention devices can also extend from the mandrel into the sealing element to assist in axial fixation and minimizing of leak paths between the sealing element and the mandrel. The sealing element ends that overlap the fingers are not bonded to the fingers or the mandrel so as to facilitate fluid entry under the sealing element for a boost force. The sealing element can optionally swell to enhance the seal. Multiple assemblies in the same orientation are also envisioned for backup purposes. The entire string that delivers the mandrel does not need to be expanded but rather just the mandrel itself is sufficient for expansion to get the desired sealing benefit of the present invention. Alternatively portions of the delivering string or the entire string can be expanded into the borehole wall with the expandable packer segments. Any tubular joints that are under the sealing element need not still seal after the expansion as the sealing element against the borehole wall will cover such joints.
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.
