Wells – Means for guiding insertable element laterally of well axis – Secured in operative position by movable means engaging well...
Reexamination Certificate
1999-08-09
2001-11-20
Bagnell, David (Department: 3672)
Wells
Means for guiding insertable element laterally of well axis
Secured in operative position by movable means engaging well...
C166S382000, C166S217000
Reexamination Certificate
active
06318459
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to anchoring devices for use in oil wells, and in particular an anchoring device for releasably securing an oil well tubing string within an oil well casing.
BACKGROUND OF THE INVENTION
Production oil wells typically contain a well casing into which is inserted a production tubing string. The production tubing string serves as both a means to insert and remove a downhole pump and pump rod, and provides a conduit for the extraction of oil and fluids from the well. The upper end of the production tubing string is held within the well casing through the use of a variety of flanges, hangers, rotating heads, or similar devices. Attached at or near the lower end of the tubing string is a downhole pump that is most commonly either a reciprocating or a progressive cavity pump. Reciprocating pumps are traditional oil well pumps wherein the pump rod is reciprocated within the production tubing string by means of a pump jack or similar device. In progressive cavity pumps the pump rod is attached to a downhole rotor that is confined within a pump housing such that rotation of the pump rod causes the rotor to rotate and pump or drive oil and other fluids to the surface.
Regardless of the form or type of downhole pump utilized within the oil well, it is necessary to securely anchor the lower end of the production tubing string to the well casing. Anchoring the lower portion of the tubing string serves to hold it in place so that downhole equipment and the interior surface of the well casing are not damaged during operation as will be the case if the production tubing string were merely allowed to be suspended freely within the well casing. In addition, the downhole anchoring device serves to prevent the production tubing string from moving upwardly or downwardly, in the case of reciprocating pump, or from rotating, in the case of a progressive cavity pump, during pumping.
While others have proposed downhole anchoring devices having a variety of different configurations and methods of operation, existing anchors all suffer from a number of common limitations. First, many are mechanically complex and involve complicated and expensive mechanical structures in order to “set” them and anchor the production tubing string to the well casing. Many other current downhole anchors are severely limited in terms of their application in oil wells having a high sand content. In cases where oil is contained in sand formations, during production sand can often become tightly packed around the anchor making it difficult, and in some cases impossible, to release the anchor and remove it from the well when desired. Where the anchor fails to release, laborious and expensive flushing procedures must be employed in order to wash compacted sand from around the anchor allowing it to release. High pressure or sour gas wells add additional complications under such circumstances. Finally, prior downhole anchors have herebefore not provided a mechanism by which the production tubing string can be released from the anchor in the event that the anchor becomes jammed or sanded in while in its deployed state.
SUMMARY OF THE INVENTION
The invention therefore provides a device for anchoring an oil well tubing string within an oil well casing that is mechanically simple, inexpensive to construct, less prone to becoming jammed or immobilized when it becomes sanded in, and that in one embodiment further provides a means to separate the production tubing string from the anchoring mechanism in the event that the anchor should become jammed in its deployed configuration.
Accordingly, in one of its aspects the invention provides an anchoring device for anchoring an oil well tubing string within an oil well casing, the device comprising; a drive mandrel having an upper end and a lower end, said upper end releasably securable to an oil well tubing string; and, an anchor mandrel having an upper end that is releasably securable to said drive mandrel, and means for selectively engaging and disengaging the interior surface of an oil well casing, wherein said means for selectively engaging and disengaging the interior surface of an oil well casing comprises a plurality of rotatable slips, said slips having a gripping surface to contact and adhere to the interior surface of an oil well casing such that when said anchor mandrel is rotated in a first direction said slips are rotatably deployed to an engaged position with said gripping surfaces in contact with the interior surface of the oil well casing thereby anchoring said device to the casing and limiting further rotational movement in said first direction and limiting longitudinal movement of said device, and rotation of said anchor mandrel in a second opposite direction causes said slips to be rotatably retracted from said engaged position to a disengaged position such that said gripping surfaces of said slips are withdrawn from contact with the interior surface of the oil well casing.
In a further aspect the invention provides an anchoring device for anchoring an oil well tubing string within an oil well casing, the device comprising: an anchor mandrel having attached thereto anchoring means for selectively engaging and disengaging the interior surface of an oil well casing; a drive mandrel, said drive mandrel having an upper end releasably securable to an oil well tubing string and a lower end releasably securable to said anchor mandrel; and, a shear ring having an upper end, a lower end and a shear zone of reduced tensile strength located between said upper and said lower ends, said shear ring assisting in releasably securing said drive mandrel to said anchor mandrel such that when said drive mandrel is secured to said anchor mandrel tensile load applied between said drive mandrel and said anchor mandrel in excess of the yielding strength of said shear zone causes breakage of said shear ring along said shear zone and separation of said drive mandrel from said anchor mandrel.
Further objects and advantages of the invention will become apparent from the following description taken together with the accompanying drawings.
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patent: 4883121 (1989-11-01), Zwart
patent: 5197546 (1993-03-01), Murray
patent: 5636690 (1997-06-01), Garay
patent: 5829531 (1998-11-01), Hebert et al.
patent: 6062309 (2000-05-01), Gosse
patent: 6073693 (2000-06-01), Aldridge
Wawrzynowski Michael
Wright Andrew J.
Bagnell David
Dougherty Jennifer R.
Gadu, Inc.
Merek & Voorhees
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