Wells – Conduit wall or specific conduit end structure
Reexamination Certificate
2000-08-02
2002-07-30
Bagnell, David (Department: 3672)
Wells
Conduit wall or specific conduit end structure
C166S241100, C166S177400
Reexamination Certificate
active
06425442
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to drilling and completion techniques for downhole wells, and more particularly, but not exclusively, to drillable, anti-rotation devices for use with plugs, float collars and float shoes.
BACKGROUND OF THE INVENTION
The process of drilling subterranean wells to recover oil and gas from reservoirs, consists of boring a hole in the earth down to the petroleum accumulation and installing a pipe liner from the reservoir to the surface. Casing is the protective pipe liner within the wellbore that is cemented in place to prevent collapse of borehole walls and to insure a pressure-tight connection from the surface to the oil and gas reservoir. Casing is typically run into the hole in sections, one section at a time and then is cemented in place. Drilling may then be continued below the casing until the reservoir is reached.
Typically, primary cementing is performed by running in a steel, non-drillable casing string into the wellbore. The casing string commonly has a float collar positioned one or two joints above the float shoe which is at its lower end. Collars and shoes help prevent the back flow of cement during cementing operations. The collars and shoes are usually equipped with a check-valve to prevent cement from returning up the interior of the casing string. Once the casing is run to the desired depth, the casing remains filled with drilling fluid and the cementing operation may begin.
When it is desired to cement the casing in the wellbore, a bottom plug or wiper plug is launched in the casing between the fluid in the well and the cement slurry. This bottom plug commonly has a fluid passage through it which may be sealed by a diaphragm or membrane. The cement is pumped into the casing on top of the bottom plug, forcing the bottom plug down the well, displacing the mud below the plug out of the well, until the bottom plug seats on the float collar, or shoe, or a shoulder. Once the plug reaches the restriction, pumping pressure is increased. This ruptures the seal in the plug's fluid passage and the cement slurry flows through the plug and through the fluid passage of the shoe or collar. Once the required amount of cement is pumped into the well, a top plug is launched into the casing atop the fluid cement column. Typically, the top plug does not have a fluid passage through it. A fluid such as mud or drilling fluid is then pumped into the casing, forcing the top plug and the fluid cement column down the hole and up into the annulus between the casing and the wellbore. It should be recognized that one or more top or bottom plugs may be utilized in cementing operations.
The plugs are usually constructed of a pliable or elastomeric material, such as plastic, wood, rubber, or aluminum, and commonly have a hollow metal or plastic core. The plugs traditionally also have wiper wings which fit snugly within the steel, non-drillable casing string. All of the plugs are constructed of a drillable material. The plugs have three primary purposes: (1) to separate the wet cement slurry from the fluid it is displacing or the fluid which is being used to pump the cement slurry to the desired level; (2) to wipe off the inner surface of the pipe string as the plug travels down the hole; and (3) to aid in preventing back flow of the cement pumped into the casing/hole annulus as the cement sets.
Once the cement has set up and other desired operations have been performed, the plug(s), collar, shoes, and cement may be drilled out. In order to drill the well out, the drill string is run back into the hole until the drill contacts the top plug and the string and drill bit are rotated. In all too many instances, when the drill bit is rotated the plug and set cement within or about it begins to rotate atop of the plug, cement, collar, or shoe on which it rests. This rotation of the plug wastes valuable time and energy in attempting to drill out the well.
Attempts in the past have been made to prevent the rotation of the plug(s) and associated set cement to aid in the drilling of the plugs. One device is disclosed in U.S. Pat. No. 5,842,517 and assigned to Davis-Lynch, Inc. The '517 patent discloses a combination float collar, cement plug, and wiper plug each having inclined J-slots for interconnecting the pieces.
U.S. Pat. No. 5,390,736 assigned to Weatherford/Lamb, Inc., discloses interconnectable plugs and float collars having a “bunt” design. The '736 teaches forming a male “bunt” shaped end and female “bunt” end for fitting the male end.
U.S. Pat. No. 5,165,474 assigned to Dowell Schlumberger, discloses an anti-rotation device for plugs having deformable lips. The '474 teaches a tubular section having a high coefficient of friction, a divergent internal diameter, and a plurality of horizontal annular teeth opposing axial movement of the cement plug within the casing string.
U.S. Pat. No. 5,095,980 assigned to Halliburton Company, discloses a combination non-rotating plug set. The '980 patent teaches a combination of plugs and a collar having molded inserts or teeth. The teeth are adapted to interconnect when the individual tools are in contact to prevent rotation of the interconnected pieces.
U.S. Pat. No. 4,190,111 to Davis discloses an anti-rotation tool to be used in combination with a plug. The '111 teaches a flat plate having protrusions on both faces of the plate. The protrusions are designed to engage, dent and penetrate a cement surface on the plug. The plate is run below the wiper plug.
To date these prior art anti-rotation devices have failed to consistently and effectively prevent the rotation of the plugs when drilling out. In many cases at least one if not all the engaging surfaces fail to engage, allowing rotation of the plugs. In addition, it is not uncommon to fail to pump the plugs in contact with one another, preventing interconnection of the plugs. Further, in deviated or horizontal wells it is difficult, at best, to interconnect the tools to be drilled out, thereby resulting in failure to limit rotation of the plug. Additionally, it is common for the teeth, slots, hooks, protrusions to slip or fail negating the purpose of the devices. Further, the prior art devices require the purchase of interconnecting pieces, such as, a set of plugs and a corresponding shoe or collar from the same vendor, thereby limiting the choice of an operator to select preferred plugs, collars, and shoes.
It would be a benefit therefor, to have an anti-rotation device which is reliable and inexpensive. It would be a further benefit to have an anti-rotation device which does not require interconnection of the plugs to prevent rotation. It would be a still further benefit which does not require interconnection between the plugs and shoe or collar. It would be an additionally benefit to have an anti-rotation device which is adapted for use in deviated and horizontal wells. It would be a still further benefit to have an anti-rotation device which may be used with collars, shoes, and plugs originating from differing sources.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is an anti-rotational device of the type used for limiting the rotation of plugs and tools when being drilled out. The anti-rotational device includes: a drillable, substantially cylindrical sleeve connectable within a substantially undrillable pipe string, in the preferred embodiment, a steel, non-drillable string of cylindrical oilfield casing. As used herein, “substantially cylindrical” is intended to cover a sleeve which not only is truly cylindrical, but also a sleeve which is at least partially tapered from one of its ends to the other. The sleeve has at least one rib or discontinuous sets of ribs or other sets of protrusions or grooves or other sets of indentations formed within the interior of the sleeve. The sleeve is formed to dispose at least one plug therein limiting the rotation of the plug and associated set cement when drilling out.
The drillable sleeve is a tubular member forming a passageway therethrough. The sleeve may be formed o
Hawkins, III Samuel P.
Latiolais, Jr. Burney
Lutgring Keith T.
Bagnell David
Dougherty Jennifer R
Frank's International, Inc.
Johnson, Jr. William E.
The Matthews Firm
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