Pipe joints or couplings – Nonmetal to metal – Internal member
Reexamination Certificate
1999-10-20
2002-04-02
Dayoan, B. (Department: 3627)
Pipe joints or couplings
Nonmetal to metal
Internal member
C285S334500
Reexamination Certificate
active
06364368
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to couplings for use with coiled tubing and, more specifically, to couplings and adapters for connecting composite coiled tubing to other tools or tubing.
BACKGROUND OF THE INVENTION
Coiled tubing has been used successfully in the oil and gas industry for many years. The development of new technology has expanded its role in completion, workover, drilling and production applications. The vast majority of technology and applications have focused on metallic coiled tubing and a variety of connections and adapters have been developed. Connectors for coupling consecutive strings of tubing have been developed, as have connectors for attaching a variety of well service and production tools or components to coiled tubing.
Although uses for metallic coiled tubulars have significantly increased in the past twenty years, limitations are experienced on occasion with metallic tubulars, including tensile strength limitations due to string weight and corrosion susceptibility from inhospitable conditions. Technology advancements in non-metallic, composite based coiled tubing products have facilitated solutions to many of the limitations encountered with metallic coiled tubing. Composite tubing is commonly composed of a combined resinous-fibrous outer tube concentrically encompassing a plastic inner tube, with the inner tube substantially providing sealing and flow properties and the outer tube substantially providing the strength and protective properties. When manufactured, the inner tube becomes an integral part of the outer tube. As compared to steel tubulars of like size, composite tubulars tend to have lower weight, superior burst properties, improved flow coefficients and increased fatigue resistance, while steel tends to exhibit more favorable collapse, compressive and tensile properties. Thus, in certain applications, composite tubulars are a direct alternative to steel while in other applications composites are the highly preferred option.
The physical properties of composite coiled tubing pose challenges and opportunities for the development of new technology to exploit the advantages of composite tubulars. One such opportunity relates to coupling composite coiled tubing strings either consecutively, to metallic coiled tubing or to service and/or production tools. Terminals (splices or joints) for composites tubulars are different from terminals for steel tubulars.
Technological advancements in tubular connections have been introduced over the years with a variety of couplings for connecting rigid non-metallic and flexible tubing and hoses. The prior art demonstrates a diversity of compression type couplings (e.g. Schmidt U.S. Pat. No. 3,685,860; Burge U.S. Pat. No. 3,907,335; and Anderson U.S. Pat. No. 4,032,177) grapple type couplings (e.g. Sampa 4,936,618) and wedge-style or slip- type couplings (e.g. Cox U.S. Pat. No. 5,156,206). However, the prior art fails to simultaneously achieve a combination of coupling characteristics, which are preferred for use with composite coiled tubing when used in subterranean wells. For example, prior art connections fail to provide a satisfactory mechanism for attaching threaded components to composite coiled tubing without a reduction in tensile strength or loss of positive sealing ability. In addition, otherwise desirable prior art connections fail to achieve an internally flush connection. For connecting flexible or composite tubulars, the prior art often makes use of internal cylindrical nipples supporting the connection, thereby resulting in a reduction of internal diameter. Also, threaded connections with mated positive-angle bearing threads tend to unzip or progressively shear under tensile loading.
Common grapple-type connections also frequently tend to be rather bulky, having relatively large external diameters, thus restricting the range of useful applications of larger sizes of coiled tubing to relatively larger outer tubing or casing strings. In addition, grapple and slip type couplings, which have been used successfully on metallic coiled tubing, commonly rely on compressive friction engagement to provide tensile strength in the connection. However, composite tubulars typically have a relatively lower hoop stress and crush resistance compared to steel tubulars. Therefore, grapple and slip type couplings do not provide adequate tensile strength when used with composite tubing. It is desirable, therefore, to have an improved coupling for use with composite coiled tubing to connect the tubing to other composite tubing or to metallic components without a reduction in internal diameter and with a joint efficiency exceeding 100% of the tensile strength of the tube body, while maintaining a leak-free, positive seal.
In order for tubing to be commonly accepted by operators for use as production tubing, it is highly desirable to provide a full ID joint in order to minimize pressure drops and facilitate unrestricted passage of the largest possible OD tools through the tubing. Not only will it normally be necessary to join lengths of tubing (splices), but also the tubing will have to be joined to various downhole completion tools and instruments which will be run in production wells, including, for example, landing nipples, safety valves, packers, instrumentation telemetry packages and items related to “smart” well completions.
SUMMARY OF THE INVENTION
A typical system for a coiled tubing operation involves a rather long length of coiled tubing, either steel, composite or other material, wound onto a relatively large reel. This invention pertains primarily to composite, plastic or resinous-based coiled tubulars. Typically, the tubing is fitted with a tool or instrument on the extended end, which is then mechanically deployed and/or retracted down a wellbore for either permanent or temporary application by winding the coiled tubing reel. Most applications necessitate coupling tools or consecutive strings of tubing together to effect the desired operations.
The present invention provides a coupling and method for connecting composite coiled tubing and affords solutions to some of the challenges of coupling composite coiled tubing to either another string of tubing or any other connection. This invention offers advantages over the prior art in that it better exploits composite coiled tubing's advantages by offering a coupling which may have a high tensile holding strength and a full-bore, unrestricted, internal flush joint connection with a relatively small external upset coupling. The coupling may provide tensile strength and pressure rating properties equal to those properties of the coiled tubing body. The coupling may fully protect the tip-end of the composite tubing and in provides a fluid tight seal with the coiled tubing. In addition, the coupling is relatively simple in design and operation. The coupling may be applied in the field using common hand tools and conventional tools to effect the proper taper on the tubing.
One primary object of this invention is to provide a coupling that offers a joint efficiency equal to or greater than the coiled tubing body such that the coupling is not the limiting component of tensile strength. Two embodiments are disclosed in detail which afford this characteristic. The first embodiment preferably utilizes a specially designed thread profile in the threaded female adapter, which provides full body strength in the joint. A second embodiment bonds the coiled tubing to an unthreaded female adapter.
In the first embodiment, the female adapter may be comprised of a generally cylindrical, metallic coupling with two sets of inner threads; one for engaging the composite coiled tubing and one for engaging a male adapter or other male connecting component. Threads for engaging the coiled tubing preferably have a negative flank with a load-bearing angle that encourages deeper engagement into the outer layer of composite material with an increase in tension. The threads taper radially inward along the center axis of the adapter, running toward the axial
Dayoan B.
Helmreich Loren G.
Kilgore Marion D.
Lugo Carlos
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