Wells – With electrical means – Magnetic
Reexamination Certificate
2000-01-05
2001-08-07
Tsay, Frank S. (Department: 3672)
Wells
With electrical means
Magnetic
C166S311000, C166S099000
Reexamination Certificate
active
06269877
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetic assembly for downhole use in wells lined with a metal casing, and more particularly to a magnetic assembly for use in collecting metal fragments created by perforation of the metal casing.
BACKGROUND OF THE INVENTION
The use of magnets for fishing out “junk”, i.e. met al fragments, from wells is well-known. For example, U.S. Pat. No. 3,520,359 (Ehrlich) discloses a magnetic tool consisting of a non-magnetic cage which houses a plurality of permanent magnets. A passage is provided in the tool to allow circulation of fluid downwardly through the tool to wash away non-magnetic materials and thus facilitate the retrieval of metal junk by the magnet. A disadvantage of this type of device, however, is that the tool is suited for use in the retrieval of junk after it has fallen down the well rather than capturing the junk while falling.
Another type of device, exemplified in the disclosure of Canadian Patent Application No. 2,232,941 (Owens et al.), is a magnetic retrieval tool for use in a method wherein a section is cut from a metal casing and a plurality of initially-shielded magnets are then used to retrieve the section. The magnets can either be unshielded by a ink mechanism, or pivotally-mounted magnets can be moved toward the cutout section. This type of device, however, requires ongoing user involvement for its operation, and employs a more complicated mechanism than the subject invention.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to facilitate removal of metal junk from a well in a single operation, without the necessity of having to retrieve the perforator tool and then retool for a subsequent junk removal procedure. Another object is to provide a junk removal device which is reliable, requires relatively little maintenance, and is easy to operate.
The invention in one form is a magnetic assembly for use below a perforator tool in a well lined with a metal casing, and including a generally cylindrical magnetic body having a centering means on its distal end and having an attachment means on its proximal end. The centering means on the distal end of the magnetic body maintains the distal end generally centred within the metal casing. The attachment means on the proximal end of the magnetic body supports the magnetic body in use below the perforator tool. The centering means and the attachment means maintain the magnetic body in a generally centred position within the metal casing while allowing fluid to flow past the magnetic body in a generally annular passage created between the metal casing and the magnetic body. After the perforator tool has perforated the metal casing at a location within a resource cavity, the magnetic body collects metal fragments that are carried past it in a resulting fluid flow.
The attachment means may be connected to a central position on a bottom end of the perforator tool in use, such connection providing both support for the magnetic body and centering of the proximal end of the magnetic body. The connection between the attachment means and the perforator tool may be by means of a female threaded portion of the perforator tool engaging with a male threaded portion of the attachment means.
The magnetic assembly may include a tube and at least one magnet positioned within the tube. Preferably, the at least one magnet consists of a plurality of magnets in longitudinally-spaced relation within the tube. The magnetic assembly also includes a plurality of spacers, each extending between a respective adjacent pair of the magnets.
The centering means may include a central body having a rounded tapering nose, and at least three vanes extending generally radially and at equiangular spacing around the central body at a position behind the nose. Each vane extends parallel to the axis of the metal casing, and has an arcuate profile. Preferably, the centering means has four vanes. The centering means may be separable from the magnetic body, and be connected to the magnetic body by means of a female threaded portion of the centering means engaging with a male threaded portion of the magnetic body.
In a more particular form, the invention is a magnetic assembly that includes a pipe section having a threaded distal end and a threaded proximal end, a guide shoe having a first end threadedly mounted on the distal end of the pipe section, and a thread adaptor having a first end threadedly mounted on the proximal end of the pipe section. The pipe section has a series of magnets mounted therewithin in longitudinally-spaced relation. The guide shoe has a rounded tapering nose on a second end and has a central body and a series of equiangularly-spaced vanes extending from the central body. The vanes are sized such that an outer radial extremity of each vane is in use in close proximity to an inside face of the metal casing, and a flow passage extends between adjacent pairs of the vanes. The thread adaptor has a second end adapted to connect to a central position on a bottom face of the perforator tool in use. The pipe section is thereby maintained generally centred within the metal casing such that a generally annular flow passage is created between the pipe section and the metal casing. After the perforator tool has perforated a portion of the metal casing extending through a resource cavity, fragments of the metal casing carried through the annular flow passage by fluid flow resulting from the perforation are magnetically pulled toward, and held on, an outside surface of the pipe section.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will next be more fully described by means of a preferred embodiment utilizing the accompanying drawing s, in which:
FIG. 1
is a side view of a well with a perforator tool and connected magnetic assembly suspended therein;
FIG. 2
is a side view of the magnetic assembly; and,
FIG. 3
is a section al side view of the generally cylindrical magnetic body of the magnetic assembly.
REFERENCES:
patent: 2830663 (1958-10-01), Kirby, II
patent: 2857970 (1958-10-01), Hopkins
patent: 3637033 (1972-01-01), Mayall
patent: 4515212 (1985-05-01), Krugh
patent: 4768597 (1988-09-01), Lavigne et al.
patent: 5327974 (1994-07-01), Donovan et al.
patent: 5960894 (1999-10-01), Lilly et al.
patent: 6170577 (2001-01-01), Noles, Jr. et al.
patent: 2232941 (1998-02-01), None
Borgstrom Dennis V.
Zeer Ian B.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tsay Frank S.
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