Downhole tool

Details Downhole tool Downhole tool

2002-03-19

2003-12-09

Neuder, William (Department: 3672)

Wells

Conduit wall or specific conduit end structure

Shoe detail

C175S323000, C175S402000

Reexamination Certificate

active

06659173

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a downhole tool, and in particular to a casing or liner shoe.
BACKGROUND OF THE INVENTION
In oil and gas exploration and production operations, bores are drilled to gain access to subsurface hydrocarbon-bearing formations. The bores are typically lined with steel tubing, known as tubing, casing and liner, depending upon diameter, location and function. Bores may also be lined with a filtration medium, such as slotted pipe or tube, or filtration media comprising a combination of two or more of slotted pipe or tubing, slotted screens or membranes and sand-filled screens. Embodiments of the present invention may be useful in some or all of these applications, and for brevity reference will generally made to “tubing”. The tubing is run into the drilled bore from the surface and suspended or secured in the bore by appropriate means, such as a casing or liner hanger. For casing, cement may then be introduced into the annulus between the tubing and the bore wall.
As the tubing is run into the bore the tubing end will encounter irregularities and restrictions in the bore wall, for example ledges formed where the bore passes between different formations and areas where the bore diameter decreases due to swelling of the surrounding formation. Further, debris may collect in the bore, particularly in highly deviated or horizontal bores. Accordingly, the tubing end may be subject to wear and damage as the tubing is lowered into the bore.
These difficulties may be alleviated by providing a “shoe” on the tubing end. Proposals for casing shoes of various forms are described in Canadian Patent No. 1,222,448, U.S. Pat. Nos. 2,334,788 and 4,825,947 and International Patent Application WO96\28635.
SUMMARY OF THE INVENTION
It is among the objectives of embodiments of the present invention to provide an improved tubing shoe.
According to the present invention there is provided a tubing shoe comprising a body for mounting on the lower end of rotatable tubing, and a rigid reaming portion comprising reaming members extending helically around the body towards the leading end thereof in an opposite direction to the intended direction of rotation of the tubing.
According to another aspect of the present invention there is provided a method of reaming a bore in preparation for receiving tubing, the method comprising the steps of:
mounting a tubing shoe on the lower end of tubing, the tubing shoe comprising a body and reaming members extending helically around the body towards the leading end thereof in one direction; and
running the tubing into a bore while rotating the tubing in the opposite direction to said one direction.
In use, these aspects of the present invention facilitate running in of tubing such as casing or liner which is supported or mounted such that it may be rotated as it is run into a bore: liner is typically run in on drill pipe, which may be rotated from surface as necessary; casing may be rotated using a top drive. In the interest of brevity, reference will be made herein primarily to liner. By providing reaming members which extend helically around the body in the opposite direction to the rotation of the liner, the reaming members do not tend to “bite” into obstructions in the bore wall; in conventional shoes provided with helical blades or flutes which extend in the same direction as the rotation of the liner the blades tend to engage obstructions, in a similar manner to a screw. In contrast, in the present invention, the members will tend to ride on or over any obstruction as the members ream the bore to the desired diameter to allow the liner to pass. This minimises the possibility of the shoe and liner becoming stuck fast in the bore due to the shoe becoming locked with a bore obstruction.
While the body and reaming portion are preferably substantially cylindrical, the leading end of each reaming member may define a pilot reaming portion defining a smaller diameter than a subsequent reaming portion. Most preferably, the reaming portions include a cutting or rasping surface or inserts on an outer surface of the portions, such as blocks or inserts of tungsten carbide, diamond or other hard material welded or otherwise fixed to the body or reaming members. The pilot and subsequent reaming portions of each reaming member may be helically aligned, or may be staggered. In a preferred embodiment, the reaming members are provided with inserts of hard material, such as tungsten carbide; testing has shown that such inserts provide more effective cutting and members provided with such inserts are harder wearing. It is believed that the ability to press the inserts into interference fit holes or slots avoids the stresses and other material property changes induced by welding blocks of tungsten carbide in place, and the inserts are spaced apart on the reaming members and are effectively self-cleaning, unlike traditional welded tungsten carbide blocks which require cleaning and often become “clogged”.
Each reaming member may include a stabilising portion, which may extend rearwardly of a reaming portion. Most preferably, the stabilising portion has a relatively smooth and hard wearing outer surface, for example of machined tungsten carbide. Alternatively, or in addition, a torque reducing sleeve or centraliser may be provided on the body rearwardly of the reaming portion. Preferably, the centraliser is spaced rearwardly of the reaming portion. Most preferably, the centraliser is rotatable relative to the body. In the preferred embodiment, the centraliser defines a bushing or sleeve, and one or more fluid conduits may carry fluid to provide lubrication between the bushing and the shoe body. In other embodiments the fluid conduits may be omitted. The centraliser may define raised helical flutes or blades. Preferably, the blades extend in the same direction as the intended direction of rotation of the shoe, that is in the opposite direction to the reaming members. In other embodiments the centraliser blades may extend in the same direction as the reaming members. The centraliser blades may include one or both of axial lead in and lead out portions, the portions facilitating relative axial movement of the centraliser relative to the bore wall. In other embodiments, the centraliser blades may be “straight”, that is extend solely axially.
Alternatively, or in addition, further torque reducing sleeves or centralisers may be provided rearwardly of the shoe or on the liner itself.
The trailing edge of each reaming member may define a back reaming portion, which back reaming portions may include a cutting or rasping surface, such as blocks or inserts of tungsten carbide or other hard material welded, located in bores, or otherwise fixed to the body. This feature is useful in shoes having a reduced diameter portion in which material may gather or become trapped, hindering retraction or withdrawal of the shoe. In the preferred embodiment of the invention there is little or no reduction in shoe body diameter following the reaming members, such that it is not necessary to provide the back reaming feature. Most conveniently, the shoe tapers towards the leading end thereof.
The body may define a fluid transmitting conduit in communication with fluid outlets located between the reaming members; due to the orientation of the members, the rotation of the shoe will not tend to clear cuttings and other material from the channels or flutes between the members, and passing fluid into the channels facilitates maintaining the channels clear of cuttings and the like. Most preferably, the fluid outlets are arranged to direct fluid rearwardly of the leading end of the shoe. Conveniently, at least adjacent fluid outlets are longitudinally offset, to minimise weakening of the shoe body. In other embodiments, such fluid outlets may be provided on a nose portion on the body, the outlets being arranged to direct fluid rearwardly towards or between the reaming members.
Preferably also, the body includes a nose portion, preferably an eccentric nose portion, that is the lea

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