Wells – Processes – Cleaning or unloading well
Reexamination Certificate
1998-09-11
2001-05-08
Bagnell, David (Department: 3673)
Wells
Processes
Cleaning or unloading well
C166S173000, C015S104040
Reexamination Certificate
active
06227297
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to techniques for cleaning a tube disposed in a well. The invention particularly relates to scraping mud and the like from the outside of a tubular member in an oil or gas well before or during a cementing operation, thereby to improve the bond between the cement and the tubular member.
In drilling and completing oil or gas wells, casing is often installed to line at least part of the wellbore. Sometimes a liner is also installed. The liner usually has a smaller diameter than the casing and is often of a flush-joint construction (i.e., there are no outwardly protruding collars at the joints of the liner) so that the liner can be readily lowered into the bore through the casing after the casing has been set. In this configuration, the liner partially overlaps with the casing, but otherwise it extends below the casing into a deeper region of the well.
To fix the casing or the liner in the wellbore, cement is pumped down the central opening through the tubular string defining the casing or liner and back up the annulus between the outside of the string and the wall of the wellbore. To space the string from the wellbore wall and to scrape the wall to ensure the annulus is open around the entire string, centralizer apparatus are attached to the string prior to lowering it into the well. It is important to have the annulus open so that the cement does not channel along only part of the outside of the string, which channeling results in an improper bond whereby leaks between the bore and the string can occur. Such leaks can allow fluid to uncontrollably escape to the surface, thereby possibly creating a hazardous situation; or the leaks can allow communication of fluids between geological zones, thereby possibly detrimentally contaminating one zone with fluid from another. In addition to, or in lieu of, the use of centralizers, sometimes a liner is rotated or reciprocated during a cementing job to prevent channeling.
Despite the possible benefits of centralizers and reciprocation, drilling mud or other materials may be on the tubular member to be cemented in the well. Such materials can adversely affect or prevent good bonding between the cement and the tubular member. It would be desirable to have some type of article or apparatus or method to reliably clean such materials from the tubular member before or during the cementing process.
A product directed to this need has been advertised by Turbeco Inc. under the term “D-MUDDER.” This is described as including a wiper element that seals against the tubular member to wipe a mud film from the outer surface of the tubular member. It is believed that such a wiper seal would rapidly deteriorate in the harsh downhole environment of an oil or gas well; therefore, although this advertised “D-MUDDER” product contemplates the problem addressed by the present invention, there is still the need for an improvement in the technique for cleaning a tubular member in a well.
SUMMARY OF THE INVENTION
The present invention overcomes the above-noted and other shortcomings of the prior art by providing a novel and improved tube cleaning article and related apparatus and method. As used throughout this specification, and in the claims, “tube” refers to any tubular member, or string of such members, with which the present invention can be used. Examples include pipe, tubing, casing, and liners of the type used in oil or gas wells.
The tube cleaning article of the present invention removes material from the outside of a tube in a well. This tube cleaning article comprises a resilient member configured to define an encompassing path around a portion of the outer surface of the tube. The resilient member has a metallic inner surface biased toward the tube when the member is mounted on the tube such that the metallic inner surface scrapes material from the outer surface of the tube in response to reciprocating the tube relative to the resilient member. In a preferred embodiment, the metallic inner surface presents more than two metallic edges along a longitudinal path of the outer surface of the tube.
In a particular aspect of the present invention, an apparatus to scrape material from the outside of a tube in a well comprises a split metallic ring to mount on the outside surface of the tube such that the ring compresses toward the outside surface of the tube but permits relative reciprocation between the tube and the ring. In a preferred embodiment, the split in the ring includes a gap in the circumference of the ring, which gap extends at a transverse angle to the axial length of the ring. The apparatus can further comprise a spacer adapted to mount on the tube such that the ring, when mounted on the tube, is between upper and lower portions of the spacer when the spacer is also mounted on the tube.
A method of cleaning a tube in a well in accordance with the present invention comprises reciprocating the tube in the well and scraping the tube with a metal body, disposed around the outer perimeter of the tube, in response to reciprocating the tube. Scraping the tube with a metal body preferably includes engaging the tube with more than two scraping edges along every longitudinal path around the perimeter of the tube. Scraping the tube with a metal body also preferably includes housing the metal body within a spacer slidably mounted on the tube and engaged within the well outside the tube.
Advantages of the foregoing include that the article and apparatus are relatively easy and inexpensive to make and maintain. They are durable and can withstand the harsh materials, pressures and temperatures encountered in the downhole environment of a well. The present invention readily and reliably removes material, including mill coating and deposits on top of the mill coating, from the outer surfaces of tubes thereby enabling good bonds to form between cement and the tube.
Therefore, from the foregoing, it is a general object of the present invention to provide a novel and improved tube cleaning article and related apparatus and method. Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art when the following description of the preferred embodiments is read in conjunction with the accompanying drawings.
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Publication entitled “New From BJ Turbeco—D-Mudder ‘A Turbeco Inc. Product,’” Davis-Lynch, Inc.
One page entitled “CO-Axial Spiral,” Halliburton Oil Well Cementing Co. (published or in use before Sep. 1, 1997). (Ex. A).
One page entitled “Hall's Spiral Casing Guide,” Houston Pipe Appliance Company (published or in use before Sep. 1, 1997). (Ex. B).
One page Larkin Packer Company, Inc. (published or in use before Sep
Bagnell David
Kreck John
McAfee & Taft
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