Wells – Processes – Assembling well part
Reexamination Certificate
2001-10-24
2003-09-23
Bagnell, David (Department: 3672)
Wells
Processes
Assembling well part
C166S207000, C166S217000
Reexamination Certificate
active
06622797
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
This invention relates generally to a device and method adapted for use with oilfield pipe (“tubulars”). More specifically, the invention relates to a device and method used to plastically radially expand downhole tubular members in a wellbore.
2. Background Art
Casing joints, liners, and other oilfield tubulars are often used in drilling, completing, and producing a well. Casing joints, for example, may be emplaced in a wellbore to stabilize a formation, to protect a formation against elevated wellbore pressures (e.g., wellbore pressures that exceed a formation pressure), and the like. Casing joints may be coupled in an end-to-end manner by threaded connections, welded connections, and other connections known in the art. The connections may be designed so as to form a seal between an interior of the coupled casing joints and an annular space formed between exterior walls of the casing joints and walls of the wellbore. The seal may be, for example, an elastomer seal (e.g., an o-ring seal), a metal-to-metal seal formed proximate the connection, or similar seals known in the art.
In some well construction operations, it is advantageous to radially plastically expand threaded pipe or casing joints in a drilled (“open”) hole or inside a cased wellbore. In a cased wellbore, radially expandable casing can be used to reinforce worn or damaged casing so as to, for example, increase a burst rating of the old casing, thereby preventing premature abandonment of the hole. In open hole sections of the wellbore, the use of radially expandable casing may reduce a required diameter of a drilled hole for a desired final cased hole diameter, and may also reduce a required volume of cement required to fix the casing in wellbore.
In conventional oilfield drilling, casing strings are installed at regular intervals whereby the casing for the next interval is installed through the casing for the previous interval. This means that the outer diameter of a casing string is limited by the inner diameter of the previously installed casing string. Thus the casing strings in a conventional wellbore are nested relative to each other, with casing diameters decreasing in a downward direction.
Conventionally, an annular space is provided between each string of casing and the wellbore so that cement may be pumped into the annular space or annulus to seal between the casing and the wellbore.
Because of the nested arrangement of the casing strings in a conventional wellbore, and the annular space required around the casing strings for cement, the hole diameter required at the top of the wellbore is relatively large. This large initial wellbore diameter may lead to increased costs due to the expense of large diameter casing, the expense of drilling large diameter holes, and the added expense of cementing a large casing string.
In addition, the nested arrangement of the casing strings in a conventional wellbore can severely limit the inner diameter of the final casing string at the bottom of the wellbore, which restricts the potential production rate of the well.
It is desirable that a casing string can be radially expanded in situ after it has been run into the wellbore through the previous casing string, so as to minimize the reduction of inner diameter of the final casing string at the bottom of the wellbore. Radially expanding a casing string in the wellbore has the added benefit of reducing the annular space between the drilled wellbore and the casing string, which reduces the amount of cement required to effect a seal between the casing and the wellbore.
When a cold-forming expansion process is used (e.g., when a cold-forming expansion tool or “pig’ is moved through a casing string so as to radially plastically expand the casing string), the casing string is usually run into the hole “box-down” (e.g., the “box” or female threaded connection is run into the hole facing downhole so that the expansion tool (“pig”) does not deform the “pin” nose or male threaded connection when the expansion tool is forced upward through the casing string). Note that tubular strings such as drill pipe, casing, or similar tubular members are normally run into the hole “pin-down” because it is easier to make up the threaded connections in the tubular string.
Various expandable casing techniques have already been developed. An expansion tool is typically used to plastically radially expand a string of casing or tubing disposed inside a wellbore from an initial condition (e.g., from an initial diameter) to an expanded condition (e.g., with a larger diameter). One common prior-art expansion process uses a conically tapered, cold-forming expansion tool (commonly referred to as a “pig”) to expand casing in a wellbore. The expansion tool is generally attached to a lower end of a casing string that is run into the wellbore. A leading mandrel of the expansion tool generally comprises a cylinder with an external diameter that is less than a “drift” diameter of the made-up casing or tubing that is to be radially expanded. The expansion tool includes a tapered section having a taper angle that is generally between 5 degrees and 45 degrees. The expansion tool is generally symmetric about a longitudinal axis thereof. The expansion tool also includes a cylindrical section having a diameter typically corresponding to a desired expanded inner diameter of a casing string. The cylindrical section is followed by a tapered section.
After the casing string is set in place in the hole, usually by hanging-off the casing string from a casing hanger, a working string of drillpipe or tubing is run into the wellbore and attached to the expansion tool (e.g., the working string is generally attached to the leading mandrel). The expansion tool may also comprise an axial bore therethrough (not shown) so that pressurized fluid (e.g., drilling fluid) may be pumped through the working string, through the expansion tool, and in to the wellbore so as to hydraulically pressurize the wellbore. Hydraulic pressure acts on a piston surface defined by a lower end of the expansion tool, and the hydraulic pressure is combined with an axial upward lifting force on the working string to force the expansion tool upward through the casing string so as to outwardly radial displace the casing string to a desired expanded diameter. In this expansion process, a rate of radial expansion is determined by, for example, a total plastic strain required to expand the casing string, the taper angle, and a rate of axial displacement of the expansion tool through the casing string. Consistency of the expansion process is controlled by transitions along the expansion tool and a cross-sectional area of, for example, lengths of casing that form the casing string, threaded connections that couple the length of casing, and the like.
The expansion tool may be inserted into the casing string at either the bottom or the top, depending on the tool design and the application. Radial expansion may be performed at rates of, for example, 25 to 60 feet per minute. Other expansion processes, such as expansion under localized hydrostatic pressure, or “hydroforming,” are known in the art, but are generally not used as much as the aforementioned cold-forming expansion process.
U.S. Pat. No. 5,348,095, issued to Worrall et al, discloses a method of creating a wellbore in an underground formation. A borehole is drilled in the underground formation, whereafter a casing of a ductile material is lowered into the borehole. The casing is selected to have a smaller elastic radial deformation than the surrounding formation when the casing is radially expanded against the borehole wall by application of a radial force to the casing. The radial force is applied to the casing so as to radially expand the casing against the borehole wall thereby inducing a plastic radial deformation of the casing and an elastic radial deformation of the surrounding underground formation, whereafter the radial force is removed from the casing.
U.S. Pat. No. 5,667,011, issued to Gill et al,
Bagnell David
Dougherty Jennifer
Hydril Company
Rosenthal & Osha L.L.P.
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