Wells – Processes – Placing or shifting well part
Reexamination Certificate
1998-11-04
2002-02-05
Neuder, William (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S384000, C166S241100, C166S241600, C405S184000
Reexamination Certificate
active
06343657
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to a method of injecting tubing down a pipe or open hole. In particular, the instant invention relates to a method of injecting coiled tubing down a pipe in deep water to service the pipeline, i.e., to remove paraffinic blockages, hydrates, scale, or solid debris from the pipe. More particularly, the instant invention relates to a method of injecting tubing into a pipe where a substantial portion of the pipe is horizontal and the total injected length is greater than about 6,000 feet (1,830 meters).
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. These pipes or holes may be vertical, horizontal, curved, or combinations of these 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 purposes of, 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 current 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. These patents are incorporated here by reference.
Unfortunately, the apparatuses of these patents are problematic in many respects. One 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, but 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. This coil, coupled with friction, results in increased force between the coiled tube and the inner diameter of the pipe and 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 of machinery that serves as a conveyor belt to force the tubing into the pipe.
One method of reducing friction in injected tubing is the tubing friction reducer described in U.S. Pat. No. 5,692,563. This patent describes a friction reducer containing multiple bearings set in legs extending outward from a body. The patent specifies that bearings of about 0.2188 inches in diameter can be used. Use of these bearings would give a clearance of about 0.1 inches or less between the tip of the bearing and the holding leg. In addition, this patent describes friction reducing devices with 12 or more rows of wheels. Applicants found that the described friction reducer embodiments were not applicable for larger diameter coiled tubing, in that the designs did not have the mechanical strength needed to support tubing. For example, the patent states that the friction reducer could be made of a metal such as aluminum, plastic, rubber, or other composites, and the ball bearings in one embodiment are of Teflon. Applicants found that molded steel bodies with a minimum number of welds were necessary to circumvent tight turns in a pipe without breaking. Applicants found certain very durable composites, such as polysulfone, could be used as wheel material only for very light service. For normal service, steel wheels are required. Finally, applicants found that sludge and oil in a pipeline would freeze the bearings described in the '563 patent. Conventional testing assumes a relative high contact stress with the oil lubricity assisting, but with the oil viscosity as a non-factor. In the low-loading characteristics of coiled tubing, the viscosity can be a factor several times that of friction. Therefore, the devices described in U.S. Pat. No. 5,692,563 were not deemed operable for heavier coiled tubing or for pipe with obstructions.
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 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 a method for readily inserting and withdrawing 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 a method 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.
BRIEF SUMMARY OF THE INVENTION
A new method has been developed for inserting and withdrawing tubing from pipes or open holes. Beneficially, the new method 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 method uses an apparatus that is portable, easily handled, and adaptable to handle tubing of differing diameters.
The method comprises feeding a coil tubing into a pipe that has a larger diameter than the coil tubing. The injected tubing has a thruster pig located at or near the distal end of the injected tubing. The thruster pig utilizes a pressure differential across the thruster pig to generate force needed to inject tubing down a pipe or well. The thruster pig device is attached to the tubing, and is as a practical matter usually attached near, i.e., within about 2000 feet, preferably within 100 feet, of the distal end of the tubing. The body of the thruster pig has a outer diameter greater than the outer diameter of the injected tubing and equal to or smaller than the inner diameter of
Baugh Benton F.
Crawford James R.
Garvey, Smith, Nehrbass & Doody LLC
Neuder William
Superior Energy Services, LLC.
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