Wells – Packers or plugs – Expanded by confined fluid from central chamber – pump or...
Reexamination Certificate
1998-11-18
2001-05-15
Bagnell, David (Department: 3672)
Wells
Packers or plugs
Expanded by confined fluid from central chamber, pump or...
C166S122000
Reexamination Certificate
active
06230798
ABSTRACT:
The invention relates to hydraulic anchor packers for use in well bores.
It is well known in the gas and oil drilling industry that hydraulic anchor packers may be used to isolate sections of a well bore and support materials and equipment within a well bore. Conventional hydraulic anchor packers typically comprise a plurality of metallic gripping elements having a serrated surface for engaging the wall of a well bore. The gripping elements are generally mounted on, or operated by, hydraulic pistons which move the gripping elements between a gripping and non-gripping position in response to a hydraulic pressure differential. Although such anchor packers operate very effectively, they are expensive to manufacture and use, and are unsuitable for use in uncased well bores.
It is an object of the present invention to provide an anchor packer which is relatively inexpensive to manufacture and use, and which is suitable for use in both cased and uncased well bores, and which is automatically released from the well bore string used to position it when it is set.
The invention provides a hydraulic anchor packer for use in a well bore comprising: an inflatable packer element incorporating a cylinder and an elastomer sleeve provided on the exterior surface thereof, the elastomer sleeve being retained by retaining means adjacent the cylinder at the end portions of the sleeve but free of the cylinder intermediate the end portions; an aperture defined by the wall of the cylinder for connecting the exterior of the cylinder in a region where the elastomer sleeve is free thereof to the interior of the cylinder; means for releasably connecting the packer element to a well bore string; means for causing fluid from within the cylinder to flow through the aperture and between the elastomer sleeve and exterior surface of the cylinder to radially expand the elastomer sleeve; and means for trapping fluid which has flowed into the chamber between the elastomer sleeve and the cylinder to prevent relaxation of the elastomer sleeve.
A hydraulic anchor packer of this type is shown in U.S. Pat. No. 3,270,814. In this packer anchor, however, no provision is made releasing the anchor from the well bore string used to position it and accordingly if circumstances require release of the anchor packer form the drill string a separate release tool must be provided.
The present invention is characterized in that the means for trapping fluid comprises a piston having a first position in which the aperture is in communication with the interior of the well bore string and the packer element is connected to the well bore string and a second position in which the aperture is isolated from the interior of the well bore string and the packer element is released from the well bore string, and means are provided for shifting the piston from the first position to the second position when the pressure differential across the piston exceeds a predetermined value to trap fluid in the chamber and release the packer element from the well bore string.
The hydraulic anchor packer of the present invention may be run into a well bore by means of a conveying string until a desired depth is achieved. The hydraulic anchor packer may be then set by pumping well bore fluid down the conveying string to the cylinder and activating the means for causing fluid within the cylinder to flow through the aperture. The resulting flow of well bore fluid between the elastomer sleeve and the exterior surface of the cylinder causes the elastomer sleeve to deform radially and press against the neighbouring wall of the well bore. The pressure of the fluid located between the elastomer sleeve and the cylinder is increased until the friction forces between the elastomer sleeve and the wall of the well bore secure the anchor packer in position. The piston moves from its first position to its second position when the pressure differential across it reaches a predetermined value, thereby trapping the fluid which has inflated the packer and releasing the packer from the well bore string. The force exerted on the wall of the well bore by the elastomer sleeve is maintained by preventing the leakage of fluid from the chamber formed between the elastomer sleeve and the cylinder.
The inflatable packer element may incorporate a retaining shoulder provided on the cylinder adjacent each end portion of the elastomer sleeve. Preferably, the retaining shoulders are provided as nuts threadedly engaged with the cylinder.
The retaining means may comprise a bond between the surfaces of the elastomer sleeve and an adjacent retaining shoulder. The retaining means may also comprise a bond between the surfaces of the elastomer sleeve and the cylinder. In each case, the bond may be provided by an adhesive. Furthermore, it is preferable for the retaining means to comprise at least one reinforcing element engaging an adjacent end portion of the elastomer sleeve. The or each reinforcing element is preferably mounted on the cylinder and more preferably attached to a retaining shoulder. It is also desirable for the or each reinforcing element to be embedded in an adjacent end portion of the elastomer sleeve.
The primary function of the retaining means is to retain the end portions of the elastomer sleeve adjacent the cylinder so as to prevent leakage of well bore fluid.
The means for causing fluid to flow through the aperture preferably comprises a drop ball and a seat located within the cylinder for receiving the drop ball. The means is activated by introducing the drop ball into the fluid flow within the conveying string. The drop ball is carried down the string by the fluid flow until it is received by the seat within the cylinder. A seal is formed between the drop ball and the seat preventing the passage of well bore fluid. The fluid flow is thereby diverted through the aperture in the cylinder which is located up-hole of the drop ball and seat.
Furthermore, it is preferable for the inflatable packer element to be mounted on an exterior surface of a mandrel having an inflate port adapted to communicate fluid to the aperture in the cylinder; the means for causing fluid to flow through the aperture and the means for trapping fluid being located within the mandrel. The inflatable packer element may be releaseably mounted on the mandrel. The inflatable packer element may be thereby readily removed from the main body of the hydraulic anchor packer for the purposes of maintenance or replacement.
A serrated metallic gripping element may also be provided on the exterior surface of the elastomer sleeve.
The hydraulic anchor packer of the present invention has the advantage over the traditional anchor packers of being simple and inexpensive to manufacture and use. The invention has the further advantage of being suitable for use in both cased and uncased well bores.
REFERENCES:
patent: 2827965 (1958-03-01), Mounce
patent: 3270814 (1966-09-01), Richardson et al.
patent: 3529665 (1970-09-01), Malone
patent: 4082298 (1978-04-01), Sanford
patent: 4823882 (1989-04-01), Stokley et al.
patent: 4871179 (1989-10-01), Bell et al.
patent: 5375662 (1994-12-01), Echols, III et al.
patent: 5542473 (1996-08-01), Pringle et al.
Bagnell David
Dawelheit Kamal
Dykema Gossett PLLC
Smith International Inc.
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