The current application is generally related to coil tubing connectors for use in the field of oil and gas exploration or production, although embodiments disclosed herein may be applicable in other fields as well.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
For many coiled tubing operations performed in a wellbore penetrating a subterranean formation, a coiled tubing connector is often used to connect a string of coiled tubing to a subsequent downhole device such as a bottom hole assembly (BHA), a downhole tool (e.g. a jet nozzle, a drilling bit, a valve, etc.), or an additional string of coiled tubing. The downhole device can then be used to perform a variety of oilfield operations to the subterranean formation such as drilling, testing, logging, stimulating, and so on.
Typically, coiled tubing connectors either attach and seal on the external side of a coiled tubing, or attach and seal on the internal side of a coiled tubing. For externally attached and sealed connectors, the outside diameter (OD) of the connector is often undesirably large, precluding the connector from fitting within some wellbore diameters or passing through some wellhead assemblies; for internally attached and sealed connectors, the inner diameter (ID) of the connector is often undesirably small, therefore taking away valuable fluid flow through area from the coiled tubing assembly.
Moreover, seals in traditional coiled tubing connectors are often susceptible to wear and tear due to the axial tensions exerted on the seals by the weight of the downhole devices. By way of “axial tensions”, it is referred to the mechanical and/or frictional forces caused by the weight of the downhole devices on the connector along the longitudinal axis of the coiled tubing-connector-downhole device assembly. An example is shown in
Accordingly, a need exists for a coiled tubing connector provided by the various embodiments of the present application.
According to one aspect, there is provided an assembly which comprises a coiled tubing, a downhole device for performing an operation in a subterranean wellbore, a connector that mechanically connects the coiled tubing to the downhole device; and a sealing device that seals the connection between the coiled tubing and the connector. The sealing device is substantially free of axial tensions caused by the weight of the downhole device. In some cases, the connector mechanically connects to one of the outside and the inside of the coiled tubing and the sealing device is in sealing contact with another of the outside and the inside of the coiled tubing. In one example, the connector mechanically connects to the outside of the coiled tubing and the sealing device is in sealing contact with the inside of the coiled tubing.
In some cases, the connector has a stepped surface extending substantially radially from a side surface (such as the inner side wall) of the connector so that a gap can be formed between the stepped surface and the lower end of the coiled tubing. In one example, the sealing device has a protrusion extending substantially radially from a side surface (such as the outside wall) of the sealing device and lodges into the gap between the stepped surface of the connector and the lower end of the coiled tubing. According to another example of the application, the sealing device is a simple sealing mechanism such as an o-ring or Grayloc type seal ring that is located within the gap between the first stepped surface of the connector and the lower end of the coiled tubing. The separation of the sealing device from the mechanical connector reduces the negative impacts on the O.D. and/or I.D. of the coiled tubing assembly and increases the lifespan of the seal and the assembly.
According to another aspect of the application, there is provided a method of connecting a coiled tubing with a downhole device. The method comprises providing a coiled tubing; mechanically attaching a connector to the coiled tubing; providing a seal between the connector and the coiled tubing, said seal is substantially free of axial tensions caused by a weight of the downhole device; and mechanically attaching the connector with the downhole device.
The downhole device described herein can be an additional string of coiled tubing, a downhole tool such as a drill bit, a bottom hole assembly (BHA), or any other devices that can be connected to the distal end of a coiled tubing assembly for performing an operation in a subterranean wellbore.
These and other features and advantages will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
As used herein, terms such as “up”, “down”, “upper”, “lower”, “top” and “bottom” and other like terms indicate relative positions of the various components of the coiled tubing connector and coiled tubing assembly of the present application with the coiled tubing, connector, and assembly vertically oriented as shown in the drawings. However, it should be borne in mind that the coiled tubing connector and assembly of the present application is designed for employment in wells having wellbore sections that are oriented vertically, that are highly deviated from the vertical, or may be oriented horizontally. Also, the terms “coiled tubing” or “tubing”, as used herein, are intended to mean tubing strings of any character, including coiled tubing or jointed tubing, which are used to convey bottom hole assemblies (BHAs), downhole tools, or other well treatment tools to selected zones or intervals within wells.
As shown in
The upper end 25 of the connector 10 can be mechanical connected to the coiled tubing 12 by any appropriate attachment mechanism such as screws, threads, dimple connection, slips, etc. In the illustrated embodiment in
In one embodiment, a sealing device 20 is provided at an opposite side of the coiled tubing 12 from the connector 10. That is, if the connector 10 mechanically attaches to the outside surface of the coiled tubing 12, the sealing device 20 forms a sealing contact with the inner surface of the coiled tubing 12 (as shown in
In
In
In
Furthermore, when the sealing device 20 is substantially free of the tensile forces created by the weight of the coiled tubing and the bottom hole assembly along the axial direction of the coiled tubing-connector-BHA assembly (“Y” axis in
Alternatives to the above-described sealing device 20 are also possible. For example, the sealing device can be simplified to an o-ring 26 sitting in a groove 26A formed in the first stepped surface 31 of the connector, as shown in
In a further example, as shown in
The initially assembled seal can be further improved during operation. This is because the Grayloc type seal ring is elastically deformable. When fluids are passed through the coiled tubing-connector-tool assembly under high pressure, the seal ring 29 can be further pressed into the gap between the lower end 13 of the coiled tubing 12 and the first stepped surface 31 of the connector 10. This process is facilitated by the first and/or second slanted surfaces 14, 32 formed on the lower end 13 of the coiled tubing 12 and the first stepped surface 31 of the connector 10, respectively.
It should be noted that although embodiments of the present application focus on the connector 10 being mechanically connected to an external surface of a string of coiled tubing 12, and fluidly sealed to an internal surface or a lower end of a coiled tubing, in alternative embodiments the connector may be mechanically connected to an internal surface of the coiled tubing 12, and fluidly sealed to an external surface or a lower end of a string of coiled tubing. Further variations are also possible.
The preceding description has been presented with reference to some illustrative embodiments of the current application. Persons skilled in the art and technology to which this application pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this application. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB10/55199 | 11/16/2010 | WO | 00 | 1/23/2013 |
Number | Date | Country | |
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61261924 | Nov 2009 | US |