1. Field of the Invention
The invention relates generally to devices and methods used to dispose tubewire into a radially surrounding tubing string.
2. Description of the Related Art
Coiled tubing has become a popular means for running a bottom hole assembly (“BHA”) or other tools into a subterranean wellbore. In most cases, it is desirable to be able to transmit electrical power down to the BHA or other tools as well as to permit control signals or sensed data to be transmitted between the surface and the downhole tools. Conventionally, this is done by disposing wireline into the coiled tubing. Wireline is a braided steel cable with layers of armor with conductors inside.
Use of wireline can be problematic. Wireline is prone to damage from acidic fluids in some instances. The slack in wireline must be adjusted over time, which requires time and money.
Tubewire is an alternative to wireline and has many advantages over wireline. Tubewire can be disposed inside coiled tubing to provide electrical power and a signal path from the surface to various downhole tools attached to the end of the coiled tubing. Tubewire is a tube that contains an insulated cable that is used to provide electrical power and/or data to the bottom hole assembly or to transmit data from the BHA to the surface. Tubewire is substantially inflexible relative to its wireline. Tubewire is available commercially from manufacturers such as Draka Cableteq of North Dighton, Mass.
Tubewire can be disposed into coiled tubing at the surface. Systems and methods for injecting and retrieving tubewire into and out of coiled tubing are discussed in U.S. Pat. No. 7,845,419 by Naumann, which is incorporated herein by reference in its entirety. While the coiled tubing is spooled up on a reel at surface, the tubewire is placed into the coiled tubing by pumping fluid through the coiled tubing at high flow rates while an injector is used to feed the tubewire into the coiled tubing by applying a pushing force. The inventors have determined that, occasionally, the tubewire can get stuck or stop moving during injection. As a result, the full motive force of the injector is applied to stationary tubewire, causing the tubewire to buckle and be permanently damaged. When tubewire buckles, it tends to take on a helical shape just prior to failure. The inventors have determined that coiled tubing has a large inside diameter (“ID”) relative to the outside diameter (“OD”) of the tubewire. Therefore, a relatively small axial force can cause the tubewire to buckle, plastically yield and fail inside the coiled tubing. The tubewire injector can easily generate the required axial force.
U.S. Pat. No. 7,845,419 by Naumann discussed the use of a flexible wand to mitigate buckling of tubewire during injection.
The present invention provides devices and methods that can reduce or eliminate the potential for buckling to occur during tubewire injection. An exemplary tubewire injection system is described which includes an injector having a drive mechanism adapted to apply an axial pushing force to the tubewire in order to inject the tubewire into the coiled tubing. In certain embodiments, the injector can also apply an axial pulling force on the tubewire in order to retrieve the tubewire. Also in certain embodiments, the injection system includes a pumping mechanism adapted to pump fluids through the coiled tubing while axial force is being applied to the tubewire. Preferably, the tubewire injector includes a drive mechanism that will drive the tubewire at a preselected speed or rate so that tension is maintained on the tubewire during injection and retrieval. The tubewire injection system can further include a control system to regulate injector forces, such as spool speed, drive mechanism speed and fluid pressure, at levels desirable for injection or removal of the tubewire.
The tubewire injection system of the present invention includes a buckling mitigation assembly. In described embodiments, the buckling mitigation assembly features a first small diameter passage for the tubewire to pass through as it exits the injector. A first tapered transition section is provided between the small diameter passage and an intermediate diameter passage. A second tapered transition section is provided between the intermediate diameter passage and the opening of the coiled tubing into which the tubewire is being injected. In certain embodiments, the second tapered transition section will be connected to a large diameter passage whose interior diameter approximates the interior diameter of the coiled tubing. The large diameter passage is then coupled to the coiled tubing.
In particular embodiments, the intermediate diameter tubing section has an inner diameter that is from about 0.5 inches to about 2.0 inches. Also in particular embodiments, the intermediate diameter tubing section has an axial length of from about less than one foot to about 20 feet.
The buckling mitigation assembly can be incorporated within sections of treating iron which extend between the injector and the coiled tubing. In operation, the intermediate diameter tubing section together with the tapered transition sections provide reduced diameter pathways through which the tubewire must pass and which provide lateral forces that counter buckling.
For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:
The term “tubewire”, as used herein, refers to a tube which may or may not encapsulate a conductor or other communication means, such as, for example, the tubewire manufactured by Draka Cableteq of North Dighton, Massachusetts. Tubewire for example, might consist of a ⅛″ outer diameter by 0.023″ wall of stainless steel or Incoloy 825 tube containing 16-18 gauge stranded copper wire covered by Halar™ or Teflon™ insulator. In this example, the insulator is tight against the tube and the wire. In the alternative, the tubewire may encapsulate one or more fiber optic cables or a mixture of wire(s) and fiber optic cable(s). The tubewire may consist of multiple tubes and may be concentric or may be coated on the outside with plastic or rubber.
Tubewire 28 is wrapped onto another spool 30 and can be fed from spool 30 into injector 26 and then into coiled tubing 12 through the buckling mitigation assembly. Spool 30 may also be hydraulically or electrically controlled and driven at a selected speed.
As described in U.S. Pat. No. 7,845,419 [hereinafter, “the '419 patent], a pump (not shown) is preferably used to apply fluid pressure to help inject the tubewire 28 into the coiled tubing 12 or to retrieve tubewire 28 from within the coiled tubing 12. The '419 patent also describes a control system that is in communication with spool 30, injector 16, and the fluid pump via bi-directional communication links in order to monitor and regulate the injector forces. The '419 patent also describes an exemplary drive mechanism used by the injector 16.
Referring primarily to
In
The interior profile of the insert 48 will be described with reference to both
In preferred embodiments, the intermediate diameter section 58 has a length that is from less than one foot to about 20 feet. In more preferred embodiments, the length is from about 5 feet to about 20 feet. In particularly preferred embodiments, the intermediate diameter section 58 has a length of about 10 feet and provides an interior diameter of about 1.05 inches.
According to further preferred embodiments, the first tapered transition section 56 has a length of about 24 inches. The second tapered transition section 60 has a preferred length of about 12 inches. However, it should be understood that these lengths are exemplary only rather than limiting. Also, it should be understood that the preferred or optimal lengths may change as other dimensions of the tubewire buckling mitigation assembly 18 are changed. For example, the preferred length of the first tapered transition section 56 might be different if the intermediate diameter section 58 had a different internal diameter.
It is noted that the angle of the tapers used for the first and second tapered transition sections 56, 60 is preferably very gentle. In preferred embodiments, the angle of the tapers (as measured from the central axis) for the sections 56, 60 is from about 1 degree to about 5 degrees. In particularly preferred embodiments, the angle of the tapers is approximately 1 degree.
According to exemplary methods of operation in accordance with the present invention, tubewire 28 is injected by the injector 16 through the buckling mitigation assembly 18 and into the coiled tubing 12. At the same time, fluid (normally water) is pumped through the treating iron tee 38 and into the coiled tubing 12. It is this fluid movement which “drags” the tubewire 28 along and into the coiled tubing 12. Significant pressure exists within the treating iron sections 34, 36 to allow for the fluid flow rates necessary to move the tubewire 28. When the tubewire 28 stops moving into the coiled tubing 12 for any reason, a force (Fc) will arise which acts along the tubewire 28 in opposition to the injector force (Fa). This opposing force (Fc) will cause the tubewire 28 to buckle helically, as depicted in
The tapered transition sections 56, 60 and intermediate diameter section 58 are described herein as being defined within an insert 48 that is located within sections of treating iron 34, 36. However, it should be understood that this specific construction is exemplary only and that the described interior profile of the buckling mitigation assembly 18 can be constructed in a number of other ways.
Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.