Wells – Packers or plugs – With expanding anchor
Reexamination Certificate
2002-06-10
2004-02-24
Bagnell, David (Department: 3672)
Wells
Packers or plugs
With expanding anchor
Reexamination Certificate
active
06695050
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to downhole tools for use in wellbores and methods of drilling such apparatus out of wellbores, and more specifically, to such tools having drillable components made at least partially of composite or non-metallic materials, such as engineering grade plastics, composites, and resins. This invention relates particularly to improvements in preventing undesired extrusion of packer seal elements between segmented non-metallic packer element shoes, alternatively referred to as back-up shoes, back-up rings, retaining shoes, packer shoes, or retaining rings, used to provide support to expandable packer elements used in drillable, essentially nonmetallic packer and bridge plug type tools. This invention is especially suitable for use with such segmented non-metallic packer element retaining shoes used in extreme temperature and differential pressure environments which tend to make expandable packer element seals more prone to extrusion, related damage, and possibly failure.
BACKGROUND OF THE INVENTION
In the drilling or reworking of oil wells, a great variety of downhole tools are used. For example, but not by way of limitation, it is often desirable to seal tubing or other pipe in the casing of the well, such as when it is desired to pump cement or other slurry down the tubing and force the cement or slurry around the annulus of the tubing or out into a formation. It then becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well or for otherwise isolating specific zones in a well. Downhole tools referred to as packers and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas.
When it is desired to remove many of these downhole tools from a wellbore, it is frequently simpler and less expensive to mill or drill them out rather than to implement a complex retrieving operation. In milling, a milling cutter is used to grind the packer or plug, for example, or at least the outer components thereof, out of the wellbore. Milling is a relatively slow process, but milling with conventional tubular strings can be used to remove packers or bridge plugs having relative hard components such as erosion-resistant hard steel. One such packer is disclosed in U.S. Pat. No. 4,151,875 to Sullaway, assigned to the assignee of the present invention and sold under the trademark EZ Disposal® packer.
In drilling, a drill bit is used to cut and grind up the components of the downhole tool to remove it from the wellbore. This is a much faster operation than milling, but requires the tool to be made out of materials which can be accommodated by the drill bit. Typically, soft and medium hardness cast iron are used on the pressure bearing components, along with some brass and aluminum items. Packers of this type include the Halliburton EZ Drill® and EZ Drill® SV squeeze packers.
The EZ Drill® SV squeeze packer, for example, includes a lock ring housing, upper slip wedge, lower slip wedge, and lower slip support made of soft cast iron. These components are mounted on a mandrel made of medium hardness cast iron. The EZ Drill® bridge plug is also similar, except that it does not provide for fluid flow therethrough.
All of the above-mentioned packers are disclosed in Halliburton Services—Sales and Service Catalog No. 43, pages 2561-2562, and the bridge plug is disclosed in the same catalog on pages 2556-2557.
The EZ Drill® packer and bridge plug and the EZ Drill® SV packer are designed for fast removal from the wellbore by either rotary or cable tool drilling methods. Many of the components in these drillable packing devices are locked together to prevent their spinning while being drilled, and the harder slips are grooved so that they will be broken up in small pieces. Typically, standard “tri-cone” rotary drill bits are used which are rotated at speeds of about 75 to about 120 rpm. A load of about 5,000 to about 7,000 pounds of weight is applied to the bit for initial drilling and increased as necessary to drill out the remainder of the packer or bridge plug, depending upon its size. Drill collars may be used as required for weight and bit stabilization.
Such drillable devices have worked well and provide improved operating performance at relatively high temperatures and pressures. The packers and bridge plugs mentioned above are designed to withstand pressures of about 10,000 psi (700 kg/cm
2
) and temperatures of about 425° F. (220° C.) after being set in the wellbore. Such pressures and temperatures require using the cast iron components previously discussed.
However, drilling out cast iron components requires certain techniques. Ideally, the operator employs variations in rotary speed and bit weight to help break up the metal parts and re-establish bit penetration should bit penetration cease while drilling. A phenomenon known as “bit tracking” can occur, wherein the drill bit stays on one path and no longer cuts into the downhole tool. When this happens, it is necessary to pick up the bit above the drilling surface and rapidly recontact the bit with the packer or bridge plug and apply weight while continuing rotation. This aids in breaking up the established bit pattern and helps to re-establish bit penetration. If this procedure is used, there are rarely problems. However, operators may not apply these techniques or even recognize when bit tracking has occurred. The result is that drilling times are greatly increased because the bit merely wears against the surface of the downhole tool rather than cutting into it to break it up.
In order to overcome the above long-standing problems, the assignee of the present invention introduced to the industry a line of drillable packers and bridge plugs currently marketed by the assignee under the trademark FAS DRILL®. The FAS DRILL® line of tools has a majority of the components made of non-metallic engineering grade plastics to greatly improve the drillability of such downhole tools. The FAS DRILL® line of tools has been very successful and a number of U.S. patents have been issued to the assignee of the present invention, including U.S. Pat. No. 5,271,468 to Streich et al., U.S. Pat. No. 5,224,540 to Streich et al., and U.S. Pat. No. 5,390,737 to Jacobi et al, all of which are incorporated herein by reference.
Notwithstanding the success of the FAS DRILL® line of drillable downhole packers and bridge plugs, the assignee of the present invention discovered that certain metallic components still used within the FAS DRILL® line of packers and bridge plugs at the time of issuance of the above patents were preventing even quicker drill-out times under certain conditions or when using certain equipment. Exemplary situations include milling with conventional jointed tubulars and in conditions in which normal bit weight or bit speed could not be obtained. Other exemplary situations include drilling or milling with non-conventional drilling techniques such as milling or drilling with relatively flexible coiled tubing.
When milling or drilling with coiled tubing, which does not provide a significant amount of weight on the tool being used, even components made of relatively soft steel, or other metals considered to be low strength, create problems and increase the amount of time required to mill out or drill out a downhole tool, including such tools as the assignee's FAS DRILL® line of drillable non-metallic downhole tools.
Furthermore, packer shoes and optional back-up rings made of a metallic material are employed not so much as a first choice but due to the metallic shoes and back-up rings being able to withstand the temperatures and pressures typically encountered by a downhole tool deployed in a borehole.
To address the preceding shortcomings, the assignee hereof filed a U.S. patent application on May 5, 1995, Ser. No. 08/442,448, which issued on May 30, 1996, as U.S. Pat. No. 5,540,279 (the '279 patent), describing and claiming an improved downhole tool appa
Crockford Lloyd A.
Smith Donald R.
Winslow Donald W.
Bagnell David
Halford Brian
Halliburton Energy Service,s Inc.
Rahhal Anthony L.
Wusterberg John W.
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