Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Advancing subterranean length of pipe or cable
Reexamination Certificate
1998-11-04
2001-11-13
Pezzuto, Robert E. (Department: 3673)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Advancing subterranean length of pipe or cable
C405S154100, C166S383000
Reexamination Certificate
active
06315498
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to an apparatus for injecting tubing down a pipe or open hole. In particular, the instant invention relates to an apparatus for injecting coiled tubing down a pipe in deep water to provide servicing of the pipe to remove paraffinic blockages, hydrates, scale, or solid debris from the pipe. More particularly, the instant invention relates to an apparatus for injecting tubing into a pipe, wherein a substantial portion of the pipe is horizontal.
BACKGROUND OF THE INVENTION
In the development and production of subterranean hydrocarbon deposits and other energy sources there are many occasions when it is necessary to insert an elongated tube from the surface deep into a pipe or open hole. Such pipes or holes may be vertical, horizontal, curved or combinations thereof and may be part of, for example, a well, pipe line, production line, or drill pipe. The inserted tube has an outer diameter that is smaller than the inner diameter of the pipe or open hole. The insertion of the tube may be for such purposes as, for example, removing blockages or general servicing.
Often during repair or servicing of a pipe a rig capable of handling long lengths of straight screw-type pipes is not available. In many cases the strength of larger diameter straight screwed tubing is not needed, so the cost of running this type of tube is not justifiable. In these cases it is often advantageous to use a long, continuous, injected tubing called coiled tubing. Many apparatuses have been developed to insert or inject a continuous length of relatively thin walled steel tubing into a pipe or open hole from a large reel or spool on the surface.
Large forces are often necessary to insert and withdraw thousands of feet or more of steel tubing into a pipe or open hole which may be filled with hydrocarbons or other materials. Most apparatuses focus on the injector head located where the smaller tubing is injected into the larger tubing. The injector head grips the tubing along its length and, in conjunction with a motor, guides and forces the tubing into the pipe via, for example, a dual, opposed conveyor belt on the surface of the well. Typical injector heads are described in, for example, U.S. Pat. Nos. 3,827,487; 5,309,990; 4,585,061; 5,566,764; and 5,188,174 which are incorporated herein by reference.
Unfortunately, the apparatuses of these patents are problematic in many respects. One such problem is that the tubing may be bent or kinked, i.e., the tubing becomes helical, down the well due to the large forces pushing against it and the weight of the tubing itself. This is especially problematic when the pipe is deviated from vertical. As the pipe becomes more horizontal, the weight of the coiled tubing itself no longer acts as a force pulling the tubing along, and instead acts against the wall of the pipe, creating friction. In addition, the weight of the tube no longer acts to straighten the coiled tubing, and the coil encourages coiling in the pipe. Such a coil, coupled with friction, results in increased force between the coiled tube and the inner diameter of the pipe, and this effectively binds the tubing. As a result of this and other problems, such prior art devices cannot effectively insert more than about 3,000 to about 5,000 feet (900 to 1500 meters) of tubing in substantially horizontal pipe.
Another typical problem with prior art devices is that the injector equipment associated with such devices is often relatively heavy, difficult to move, and complex due to a large chain assembly machinery which serves as a conveyor belt to force the tubing into the pipe.
Other methods have been employed to increase the length to which tubing can be injected. U.S. Pat. No. 5,704,393 describes an apparatus that can be set in the well at the end of the coiled tubing string at a determinable location. The apparatus is a valve apparatus, a packer apparatus, and a connector. Seals are provided that allow the coiled tubing, but not fluid, to move in a centrally located bore through the packer apparatus. The apparatus is immobile against the outer pipeline, and has the ability restrict or prevent fluid flow. Once the packer is set, the annular pressure, i.e., the pressure differential between the pipeline and the interior of the coiled tubing, is increased by injecting fluid into the annular volume. This increased pressure stiffens and straightens the coiled tubing, allowing for increased distance of injection of coiled tubing into the pipeline.
It is apparent that what is needed in the art is an apparatus that allows one to readily insert and withdraw tubing from a pipe for long distances, i.e., greater than about 6,000 feet (1830 meters), without bending or kinking the tubing. It would be beneficial if such an apparatus could be employed to insert and withdraw tubing from a substantially horizontal pipe of extended length of greater than 6,000 feet (1830 meters), and that the tubing can extend past turns. Moreover, it would be of great benefit if such an apparatus was portable, easily handled, and could be adapted to handle tubing of differing diameters.
SUMMARY OF THE INVENTION
A new apparatus has been developed that inserts and withdraws tubing from pipes or open holes. Beneficially, the new apparatus may be employed to insert and withdraw tubing to lengths of over 6000 feet (1830 meters), preferably greater than 26,000 feet (9900 meters), and more preferably greater than 60,000 feet (18,300 meters). Advantageously, the apparatus is portable, easily handled, and adaptable to handle tubing of differing diameters.
The instant invention comprises a thruster pig that utilizes a pressure differential across the thruster pig to generate force needed to inject tubing down a pipe or well. The thruster pig is a device that firmly attaches to or is integral with the tubing to be inserted in the pipe. The body of the thruster pig has an outer diameter greater than the outer diameter of the injected tubing and equal to or smaller than the inner diameter of the pipe.
The attachment of the thruster pig to the tubing may be by any conventional method. One preferred method is to use standard releasing subs, known in the art, that allow the thruster pig to be released by pumping a ball down the injected tubing. The attachment point may also contain a hinge, ball joint, or swivel joint that allows the thruster pig to more easily orient itself in the pipe. The seal between the injected tubing and the thruster pig can be a metal weld, a screw type seal, a compression type seal, or any other seal known to the art.
The thruster pig has a sealing apparatus, for example one or more chevrons, to impede fluid migration between the body of the thruster pig and the inner surface of the pipe. This effectively creates an annulus between the injected tubing and the pipe so that pressure can be applied to the rear of the thruster pig. The shape of the thruster pig is not important, so long as the thruster pig makes essentially a fluid-tight seal between the injected tubing and pipe.
The thruster pig has an opening that allows fluids pumped down the center of the injected tubing to pass to the front of the thruster pig. The opening may contain the injected tube, or it may be a continuation of that flow path. When the thruster pig is moving forward, fluid may also be withdrawn from the volume ahead of the pig through the opening.
The thruster pig has a means for allowing fluids to flow from the annulus through the device as the thruster pig is being withdrawn. This means consists of one or more valves, in series or in parallel, that allow the user to pumped fluids to pass through the thruster pig to the annulus behind the thruster pig. These valves are often check valves. The check valves are designed to let the fluids injected down the tubing to circulate through the annulus and out of the pipe.
Finally, the thruster pig has a second set of valves or check valves allows fluids under some conditions to flow from the annulus between the tubing and the interior surface of the pipe to the front of the
Baugh Benton F.
Crawford James R.
Garvey, Smith, Nehrbass & Doody LLC
Lee Jong-Suk
Pezzuto Robert E.
Superior Energy Services, LLC
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