U.S. patent application number 11/115610 was filed with the patent office on 2006-11-02 for tubing connector.
Invention is credited to L. Michael McKee.
Application Number | 20060243453 11/115610 |
Document ID | / |
Family ID | 37193940 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060243453 |
Kind Code |
A1 |
McKee; L. Michael |
November 2, 2006 |
Tubing connector
Abstract
An apparatus for connecting a first and a second section of
tubing is provided. It comprise a body having a bore therethrough,
a first end, a stiff section, and an exterior surface adapted for
connection to the first and second sections of tubing. A first
tapered section may be provided on the first end of the body, and
the first end of the body may be adapted to be disposed within the
first section of coiled tubing. A second tapered section may be
provided on the second end of the body, and the second end of the
body may be adapted to be disposed within the second section of
coiled tubing. The first and second tapered sections may be
provided with outer and inner tapered surfaces. By connecting two
coiled tubings using a connector as disclosed herein, the result is
cost savings through an improved joint between two coiled tubings
that will withstand bending forces applied proximate the joint in a
manner believed to be superior to joints formed by previous coiled
tubing connectors. Related methods are also provided.
Inventors: |
McKee; L. Michael;
(Friendswood, TX) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION
IP DEPT., WELL STIMULATION
110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
37193940 |
Appl. No.: |
11/115610 |
Filed: |
April 27, 2005 |
Current U.S.
Class: |
166/380 ;
166/242.6; 166/77.2 |
Current CPC
Class: |
E21B 17/04 20130101;
E21B 19/22 20130101; E21B 19/16 20130101 |
Class at
Publication: |
166/380 ;
166/077.2; 166/242.6 |
International
Class: |
E21B 19/22 20060101
E21B019/22 |
Claims
1. A method of connecting a first tubing and a second tubing
comprising: providing a tubing connector having a body with a
longitudinal bore therethrough, the tubing connector having a first
end section and a stiff section, wherein the first end section has
a tapered outer surface; disposing the first end section of the
connector within a first tubing; and securing the stiff section of
the connector to the first tubing and a second tubing within the
inner diameter of the first and second tubings.
2. The method of claim 1 wherein further comprising an internal
tapered surface on the bore.
3. The method of claim 1, wherein the connector further comprises a
second end section, the stiff section being disposed between the
first and the second end sections, and further comprising:
disposing the second end section of the connector within a second
tubing; and securing the stiff section of the connector to the
second tubing; wherein the second end section has a tapered outer
surface.
4. The method of claim 1, wherein the first tubing is coiled
tubing.
5. The method of claim 3, wherein each of the first and the second
tubing is coiled tubing.
6. The method of claim 5, wherein at least one of the first and the
second coiled tubing is spooled on a reel.
7. The method of claim 5, wherein the connector is provided as a
repair between the first and second tubing.
8. An apparatus for connecting a first and a second section of
tubing comprising: a body with a longitudinal bore therethrough, a
first end section, and a stiff section; the first end section of
the connector having a tapered outer surface; and the exterior of
the stiff section adapted to be connected to the inner diameter of
a first and a second tubing.
9. The apparatus of claim 8, wherein the body further comprises a
second end section, the second end section having a tapered outer
surface and the stiff section being disposed between the first and
the second end sections.
10. The apparatus of claim 9, wherein at least one of the first and
the second end section further comprises a tapered internal
surface.
11. The apparatus of claim 7, further comprising an annular lip
disposed about the body and adapted to be disposed between ends of
the first and second sections of tubing.
12. The apparatus of claim 7, further comprising a plurality of
indentations disposed in the exterior surface of the stiff section
of the body adapted for engagement with at least one of the first
and second tubings.
13. The apparatus of claim 12, further wherein the indentations are
varied.
14. The apparatus of claim 8, further comprising a seal disposed
between the body and at least one of the first section and the
second section of tubing.
15. The apparatus of claim 8, further comprising at least one
barrier to prevent debris from entering between the end section of
the body and the tubing.
16. The apparatus of claim 8, further comprising a flow control
device disposed therein.
17. A method of deploying coiled tubing in a wellbore comprising:
providing a coiled tubing connector having a body with a
longitudinal bore therethrough, the body having a first and a
second end sections, each end section having a tapered external
surface, and a stiff section disposed between the first and the
second end sections; disposing the first end section within a first
coiled tubing; disposing the second end section within a second
coiled tubing; securing the stiff section to the inner diameter of
each of a first and a second coiled tubings, thereby forming a
connected tubing; and lowering the connected tubing into a
wellbore.
18. The method of claim 17, wherein the connector further comprises
an annular lip disposed about the body and adapted to be disposed
between ends of the first and second sections of coiled tubing.
19. The method of claim 17, further comprising at least one barrier
disposed adjacent to at least one of the first and the second end
section, thereby preventing debris from entering between the end
section and the coiled tubing.
20. The method of claim 17, wherein at least one of the first and
the second coiled tubing is disposed on a reel.
21. The method of claim 17, wherein the connected coiled tubing is
retrieved from the wellbore.
22. The method of claim 21, wherein the connected coiled tubing is
spooled onto a reel.
23. The method of claim 17, further comprising providing at flow
control device within at least one of the connector, the first
coiled tubing, or the second coiled tubing.
24. A method of deploying coiled tubing in a wellbore comprising:
providing a first tubing connector having a body with a
longitudinal bore therethrough, the first tubing connector having a
first end section and a stiff section, wherein the first end
section has a tapered outer surface; disposing the first end
section of the first tubing connector within a first coiled tubing;
securing the stiff section of the first tubing connector to the
inner diameter of each the first coiled tubing; providing a second
tubing connector having a body with a longitudinal bore
therethrough, the second tubing connector having a first end
section and a stiff section, wherein the first end section has a
tapered outer surface; disposing the first end section of the
second tubing connector within a second coiled tubing; securing the
stiff section of the second tubing connector within the second
coiled tubing; disposing a tool string between the first tubing
connector and the second tubing connector, thereby forming a
connected tubing; and lowering the connected tubing into a
wellbore.
25. The method of claim 23, wherein at least one of the first and
the second coiled tubing is disposed on a reel.
26. The method of claim 23, further comprising providing at flow
control device within at least one of the connector, the first
coiled tubing, or the second coiled tubing.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally pertains to oilfield
equipment, and more particularly to a device and method for
connecting tubing for downhole use.
[0003] 2. Description of the Related Art
[0004] Coiled tubing is used in a broad array of applications in
oilfield operations such as drilling and completing oil and gas
wells, conveying equipment, and performing maintenance on completed
oil and gas wells. To deploy coiled tubing into a wellbore, the
coiled tubing string is unreeled or unspooled from a coiled tubing
reel, run over an injector gooseneck and inserted into a wellhead
system for injecting the coiled tubing into the wellbore. To
retract coiled tubing from a wellbore, the coiled tubing is reeled
or spooled back out of the wellbore through the wellhead system
over the gooseneck and onto the coiled tubing reel. It is known
that bending and straightening the coiled tubing in wellsite
operations and spooling the coiled tubing on a reel causes low
cycle fatigue in the coiled tubing, which if left unchecked can
lead to failure of the coiled tubing. The ability to unreel and
reel coiled tubing as a continuous tubing string nevertheless
offers attractive operational advantages over jointed pipe that
requires connections at each length of pipe.
[0005] There are occasions however when connections are required
between coiled tubing strings, for example, in situations when the
length of coiled tubing required for an operation exceeds the
capacity of the coiled tubing reel; when the capacity of handling
equipment limits the permissible weight of the coiled tubing reel,
thereby limiting the length of coiled tubing permitted to be
spooled thereon; when a repair is required in coiled tubing; or
when retrieving a length of coiled tubing from a well.
[0006] The problem of making coiled tubing connections between two
coiled tubing strings or between coiled tubing and a tool or
completion string has been addressed typically in one of three
ways, those being by field welding, by using stiff connectors or by
using flexible connectors.
[0007] To connect coiled tubing string in the field, butt-welding
is commonly used. Such a weld is made by placing together the ends
of two segments of tubing, each segment having an end cut
perpendicular to its axis, the ends being placed in line which each
other ("butted" together), and a making circumferential weld placed
around the juncture of the cut ends. Welding in field conditions is
more challenging and less robust than the bias-type welding that is
used under controlled conditions in coiled tubing manufacturing.
Butt welded sections of coiled tubing usually are weaker and have
much shorter low cycle fatigue life than the sections of coiled
tubing without welding: typically a butt weld has a low cycle
fatigue life in the order of 50% to 60% of the low cycle fatigue
life of the coiled tubing. As failure of coiled tubing welds can
lead to unsafe working conditions, verification testing using
methods such as X-ray, tensile testing, or pressure testing of the
butt weld performance is required prior to deployment of the welded
coiled tubing in a wellbore. In addition, often connections are
required in areas where explosive conditions may be present which
lead to the need to take additional safety precautions in field
welding. In sum, field welding is a time-consuming and
operationally undesirable method for connecting two segments of
coiled tubing together.
[0008] Stiff connectors are used typically for connecting tools and
devices to the end of coiled tubing such as for connecting a tool
string to the end of unreeled coiled tubing prior to insertion into
the wellbore. Stiff connectors may be used during wellbore
deployment to connect between one or more unreeled coiled tubing
strings. Stiff connectors however are not spooled with the coiled
tubing on the coiled tubing reel as they lack the requisite
flexibility to bend around the coiled tubing reel and deployment
equipment. As a result, stiff connectors present a number of
drawbacks. Like field welding, the use of stiff connectors in
wellbore deployment requires stopping the unreeling of the coil
tubing, installing the stiff connector into the coiled tubing,
making the connection, and then restarting the unreeling of the
coiled tubing string to deploy the connected coiled tubing string
into the wellbore. Furthermore, stiff connectors are often larger
in diameter than the coiled tubing and are fitted externally about
the coiled tubing. As such, they cause operational difficulties
because they do not pass through the wellhead equipment.
[0009] Stiff connectors are known that are designed to be the same
diameter as the coiled tubing or to have an end that can be
inserted into the interior diameter of the coiled tubing; such
connectors are referred to herein as internal connectors. Internal
connectors offer operational advantages over externally placed
connectors as the internal connectors do not cause an increased
outer diameter over the connected portion of the tubing string.
Although operational difficulties are reduced by the use of
internal connectors, the use of stiff internal connectors in coiled
tubing nevertheless poses difficulties. Use of a stiff connector
with flexible coiled tubing creates an abrupt transition between
the connector and the tubing. As the coiled tubing is bent in
routine activities, the end of the coiled tubing adjacent to the
end of the stiff connector flexes to an undesirable degree. This
area is commonly called the hinge point as the bending can be so
severe as to resemble a hinged connection. Such straining of the
coiled tubing at a stiff connection can quickly make the coiled
tubing unsuitable or unsafe for use. It is common that tubing used
with a connector becomes unsuitable for use or fails after only a
few bending/straightening cycles.
[0010] In general, stiff connectors lack the flexibility to permit
them to be spooled onto the coiled tubing reel. On occasion, in
those situations where one end of a stiff connector is connected to
the terminal end of the coiled tubing and the connector is
relatively short, it may be possible to spool coiled tubing onto a
reel with a stiff connector attached, provided that the opposite
end of the connector is not connected to anything. One such
internal connector for connecting one coiled tubing string to
another coiled tubing string or to a completion string (a fixture
for permanent installation in a well) to a coiled tubing string is
described in U.S. Pat. No. 6,474,701 issued on Nov. 5, 2002 to
Bowles et al.
[0011] Flexible connectors are known to provide a spoolable
connection for coiled tubing strings. One method for making a
spoolable flexible connection for connecting tool strings to a
coiled tubing string is described in U.S. Pat. No. 6,561,278 issued
on May 13, 2003 issued to Restarick et al. and related U.S. Pat.
No. 6,766,858 issued on Jul. 27, 2004 to Restarick et al. The
external connectors described therein are particularly applicable
for use with coiled tubing made of composite materials and coiled
tubing having a line embedded within a sidewall. In these patents,
a pair of connectors comprising a first connector disposed about a
first end of a severed tubing string and a second connector
disposed about a second end of a severed tubing string is used to
connect one or more well tool assemblies to the coiled tubing.
[0012] Another type of internal flexible connector for use with
coiled tubing is described in SPE 89527, Luft, H. B., et al.,
entitled Development of a New Spoolable Mechanical Coiled Tubing
Connector, March 2004. As described therein, this flexible
connector uses composite materials, including an elastomeric middle
section to provide flexibility, and entails a construction having
composite materials and using both super alloy steels and
elastomers backfilled into the outer diameter of the connector. The
flexible connector described in SPE 89527 has transition sections
on either end of the connector where the coiled tubing overlaps the
connector. According to Luft et al, testing of this connector
indicated that the low cycle fatigue performance of the
connector/coiled tubing combination provided a life span for the
combination of 39% to 69% of the life span for the coiled tubing
alone.
[0013] Testing required for confirming that the materials from
which a connector is made are compatible for use in a downhole
environment and for oilfield operations also is discussed in SPE
89527. Coiled tubing connectors, like the coiled tubing itself,
need to be compatible with the environment in which they will be
used. Testing is required to demonstrate that significant
degradation to or failure of the coiled tubing connector will not
result from exposure to wellbore environments. For example, coiled
tubing may used for delivering acid treatments to subterranean
formations, or in environments in which elevated levels of H2S are
present. The acid testing reported in SPE 89527 on various
connector materials shows this compatibility can vary. To avoid the
cost and time required for compatibility testing, it would be
advantageous to construct an internal flexible connector from
materials having the same or similar chemical resistance as the
coiled tubing. As a general matter, it would be more cost effective
to construct an internal coiled tubing connector from readily
available commercial materials rather than specialty products such
as those used in the connector described in SPE 89537.
[0014] A particular challenge to using a flexible connector and
coiled tubing made of conventional materials is the varying range
of material properties generally accepted in materials such as
commercial grade steel used to make coiled tubing. These materials
normally are produced with a 10-20% tolerance for yield strength.
For example, 4140 (18-22 Rc) steel is known to have a yield
strength between 80,000 psi and 95,000 psi. This variation in yield
strength is the foundation for design limitations between the
connector and the coiled tubing. For example, if one of the
components has a yield strength near the minimum allowed ("low
yield component") and the other component has a yield strength near
the maximum allowed ("high yield component"), the strain in the
components under the same conditions would differ, leading to
differing low cycle fatigue lives. In such situations, when the low
yield component reaches the yield point, the low yield component
begins to deform plastically but the high yield component remains
in its elastic range and does not yield. By the point at which the
yield point of the high yield component is reached and the high
yield component begins to deform plastically, the low yield
component already has deformed significantly. For example, for a
conventional material such as 4140 steel having minimum and maximum
yield curves as shown in FIG. 1, at a stress of 100 ksi, low yield
component would have as much as 4% strain while the high yield
component would have a strain of about 0.5%. Since low cycle
fatigue life is closely related to the amount of cyclic strain, the
low yield component will fail significantly sooner than the high
yield component.
[0015] The flexible connectors that are known, such as that
disclosed in SPE 89527, have a flexible section in the center of
the connector. This middle flexible section is designed to have a
bending stiffness similar to that of the coiled tubing. The end
sections on either side of the flexible center section are much
stiffer than the coiled tubing. The design theory behind such a
configuration is to provide a flexible center section of the coiled
tubing connector that deforms similarly to the coiled tubing itself
under the same amount of strain. The low cycle fatigue performance
of these flexible connectors depend both on the stiff end
connections providing a gradual transition between the flexible
coiled tubing and the flexible center section of the connector and
on the flexible centers section having similar stiffness and
fatigue life to the coiled tubing. Therefore it is crucial to the
performance of these flexible connectors designed with flexible
center sections that both flexible center section of the connector
and the coiled tubing strain equally. This is not easily achieved
given the variation of material properties and the varying
stress/strain conditions along the bend distance between the
flexible section of the connector and the length of the coiled
tubing string beyond the influence of the connector end section. It
has been observed that coiled tubing connectors that use a flexible
section between two stiff end connections often have inconsistent
performance and periodically fail much sooner than expected.
[0016] Therefore, there exists a need for improved methods and
apparatus for connecting coiled tubing. In carrying out the
principles of the present invention and embodiments thereof,
methods and apparatus are provided which solve the problems in the
prior art.
SUMMARY OF THE INVENTION
[0017] The present invention provides a method of connecting a
first tubing and a second tubing using an internal tubing connector
having a bore, the connector having a first end section having a
tapered outer surface and stiff section wherein the stiff section
of the connector is secured to the first and second tubings. In
some embodiments, the internal surface of the connector along the
bore is also tapered. In some embodiments, a second end section
having a tapered external surface is also provided and disposed
within the second tubing. In preferred embodiments, at least one of
the first tubing or second tubing is coiled tubing, and in
particular embodiments, both of the tubings are coiled tubing. In
the methods of the present invention, at least one of the first or
second tubings may be spooled on a reel. The connector and method
of connecting of the present invention is useful particularly in
making repairs in coiled tubing, wherein a section of coiled tubing
is damaged or removed and the apparatus and method of the present
invention is used to repair, patch or generally connect the two
sections of coiled tubing between which a portion of tubing has
been damaged or removed.
[0018] The connector apparatus of the present invention useful for
connecting a first and a second section of tubing comprises a body
with a longitudinal bore therethrough, a first end section, and a
stiff section; the first end section of the connector having a
tapered outer surface; and the exterior of the stiff section
adapted to be connected to the inner diameter of a first and a
second tubing. In some embodiments, the connector may further
comprise a second end section, the second end section having a
tapered outer surface and the stiff section being disposed between
the first and the second end sections. The first or second end
section may further comprise a tapered internal surface along the
bore. An annular lip may be provided about the body and adapted to
be disposed between ends of the first and second sections of
tubing. One or more seals may be disposed between the connector
body and the first or the second, or both, tubings. The stiff
section of the connector of the present invention may be secured
within the first and second tubings by engaging the exterior
surface of the body with the inner surface of the tubing using a
plurality of indentations, grooves, ridges, punch hole, or other
connective means. In some embodiments, a debris barrier is provided
between at least one end section of the connector and the
tubing.
[0019] The present invention in specific embodiments relates to a
method of deploying coiled tubing in a wellbore comprising
providing a coiled tubing connector having a body with a bore
throughout, the body having first and second end sections with
tapered external surfaces and a stiff section disposed between the
first and the second end sections; placing one end section into a
first coiled tubing section, placing the second end section into a
second coiled tubing, securing the stiff section to the inner
diameter of the first and second coiled tubings to form a connected
tubing and lowering the connected tubing into a wellbore. The
method may further comprise retrieving the coiled tubing from the
wellbore. The first or second coiled tubing may be disposed on a
reel. Similarly, the connected coiled tubing may be disposed on a
reel. In some embodiments, the connector may comprise an annular
lip disposed about the body and adapted to be disposed between ends
of the first and second sections of coiled tubing and in some
embodiments, the connector may comprise at least one barrier to
prevent debris from entering between the end section and the coiled
tubing.
[0020] Other features, aspects and advantages of the present
invention will become apparent from the following discussion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a representative stress/strain curve for a grade
of steel.
[0022] FIG. 2 is side view of a specific embodiment of a coiled
tubing connector constructed in accordance with the present
invention and in use to connect a section of coiled tubing to a
tool string.
[0023] FIG. 3A is a side view of another specific embodiment of a
coiled tubing connector constructed in accordance with the present
invention similar to the one shown in FIG. 2 but shown not
connected to any coiled tubings.
[0024] FIG. 3B is a side view of another specific embodiment of a
coiled tubing connector constructed in accordance with the present
invention.
[0025] FIG. 3C is a side view of another specific embodiment of a
coiled tubing connector constructed in accordance with the present
invention.
[0026] FIG. 4 is side view of two coiled tubing connectors
constructed in accordance with the present invention, and in use to
connect coiled tubing to a tool string.
[0027] FIG. 5 is a side view of a specific embodiment of a coiled
tubing connector constructed in accordance with the present
invention, and in use to connect two sections of coiled tubing to a
tool string.
[0028] FIG. 6A is a strain diagram from a finite element model of a
prior art internal coiled tubing connector having a flexible center
section.
[0029] FIG. 6B is a strain diagram from a finite element model of
an embodiment of a coiled tubing connector according to the present
invention.
[0030] FIG. 7 is side view of another specific embodiment of a
coiled tubing connector constructed in accordance with the present
invention, and in use to connect two sections of coiled tubing.
[0031] While the invention will be described in connection with the
preferred embodiments, it will be understood that it is not
intended to limit the invention to those embodiments. On the
contrary, it is intended to cover all alternatives, modifications,
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Referring to the drawings in detail, wherein like numerals
denote identical elements throughout the several views, there is
shown in FIG. 2 a coiled tubing connector 10 constructed in
accordance with the present invention and in use to connect a first
section of coiled tubing 12 and a second section of coiled tubing
14. The connector 10, having a body 16 having a longitudinal bore
18 therethrough, comprises a stiff section 27 and at least one end
section 28. Often stiff section 27 is provided between two end
sections 28, as is shown FIG. 2. In some embodiments, body 16 of
connector 10 may be discontinuous, and in further embodiments,
stiff section 27 is separable from one or more end sections 28. It
is preferred for embodiments for connecting two sections of coiled
tubing such as that shown in FIG. 2 that body 16 of connector 10 is
a continuous body in which one region of connector body 16 is stiff
section 27 and other region or regions of connector body 16 are end
section or sections 28. Such an embodiment is particularly useful
to be placed between a first section of coiled tubing 12 and a
second section of coiled tubing 14 to form a repair between the two
section, for example when an area has been damaged, stressed, or is
of inferior quality.
[0033] The stiffsection 27 of connector 10 has an outer diameter
that it will fits snugly within the inner diameter of first and
second sections of coiled tubing 12 and 14. The exterior diameter
of body 16 remains essentially constant throughout stiff section
27, excepting in localized areas where a means, such as a groove or
indentation, to effect a connection with coiled tubing 12 and 14
are present.
[0034] In end sections 28 of body 16, external diameter 29 of body
16 gradually decreases from the end 31 of the end section 28
proximate to the stiff section 27 towards the distal end 33 of the
body 16, such that the external diameter of end section 28 of body
16 is not engaged snuggly within the interior diameter of coiled
tubing 12 or 14. When coiled tubing 12 and 14 is straight, end
section 28 is not in contact with the inner diameter of the coiled
tubing 12 or 14 owing to the decreasing external diameter 29 of end
section 28. This decreasing external diameter, referred to herein
as tapered, may be constructed in any variety of ways that provides
a smaller external diameter at the distal end 33 of end section 28;
examples of ways by which a taper may be formed include but are not
limited to a single angle, a series of short angle sectors, a
constant radius, or a compound radius.
[0035] As coiled tubing 12 is connected to connector 10 in stiff
section 27 and coiled tubing 12 bends as is routine in coiled
tubing deployment and operation, only a limited area of end section
28 will be in contact with the interior diameter of coiled tubing
12 as it bends owing to the decreasing exterior diameter 29 of end
section 28. In this way, there is a limited area of contact between
coiled tubing 12/14 as it bends over the length of end section 28
and that limited area of contact translates along the length of end
section 28 as coiled tubing 12 bends. As such, the stress point
occurring at the point of contact translates along the end section
28 and overlapping coiled tubing 12, thereby avoiding the formation
of a specific point of stress concentration or hinge point. This
characteristic of the present invention is referred to herein as
the restrictive bend feature.
[0036] The restrictive bend feature avoids the formation of a hinge
point resulting from stress repeatedly concentrating in areas. It
is known that such hinge points create a week point in coiled
tubing connectors. By design, this restrictive bend feature
provides a transition between the stiff section 27 of connector 10
and the coiled tubing 12 or 14 and distributes the strain in the
coiled tubing over the length of end section 28 rather than in a
localized hinge point. By such a strain distribution, the maximum
stress imposed on any particular point of coiled tubing 12 or 14
overlapping end section 28 and the duration of time at which any
particular point is subjected to that stress is reduced. This
serves to improve the low cycle fatigue performance of the overall
coiled tubing and connector configuration. Such a configuration is
notably different from known flexible internal connectors and is
counter to the conventional approach of providing a flexible middle
section with stiffer section on either side. Thus the coiled tubing
connector of the present invention is useful to provide a
connection that is flexible on both ends and stiff in the
middle.
[0037] In various embodiments, the diameter of the internal surface
of body 16 along longitudinal bore 18 in end section 28 may
decrease in a similar manner to external diameter 29, may remain
the same throughout end section 28, or may increase to form an
internal tapered surface 30. In embodiments in which the diameter
of the internal surface of body 16 along longitudinal bore 18 in
end section 28 remains the same or increases, the cross sectional
wall thickness of body 16 in end section 28 decreases toward distal
end 33 as a result of decreasing external diameter 29. This
decreasing wall thickness makes end section 28 more flexible at
distal end 33 and increasingly less flexible along the length of
end section 28 extending to the end of stiff section 27. In this
way, connector 10 is most flexible at the distal end 33 of end
section 28 and has diminishing flexibility traversing toward stiff
section 27 along the length of end section 28 such that the
stiffest area of end section 28 is at end 31 adjacent to stiff
section 27.
[0038] Connector 10 may be secured to the coiled tubing 12 and 14
in stiff section 27 by techniques suitable for use with internal
connectors such as roll-on connectors, screws, crimping, and
dimpling. In FIG. 2, the connection between stiff section 27 and
coiled tubing 12 and 14 is shown made by indentations 22 on the
outer surface of stiff section 27 receiving protuberances 20 on the
coiled tubing 12 and 14. Such indentations may be made a variety of
ways such as surrounding the coiled tubing with a mold and pressing
the mold to form indentations, using a push or screw to form the
indentations, or using a pre-pattern of weaker points in stiff
section 27 into which coiled tubing 12 or 14 may be easily pressed.
In some embodiments, the exterior surface of stiff section 27 may
be patterned in a manner to facilitate this connection with coiled
tubing 12 and 14. For example, indentations in the exterior surface
of stiff section 27 may spread uniformly about the circumference in
a localized area or along the length of stiff section 27.
Alternatively, depressions for receiving screws holes may be
provided in the exterior surface of stiff section 27; such
depressions may similarly be in a localized area or along the
length of stiff section 27.
[0039] In addition, the pattern, shape, or depth of such
indentations may be varied and in particular, be varied in such a
manner that the stress during bending of the connection is
distributed across the indentations and not concentrated in a
limited localized area. Moreover this variation may be done in such
a manner as to vary the relative snugness of the connection between
connector 10 and coiled tubing 12 or 14 across stiff section 27 of
connector 10 such that the connection between connector 10 and
coiled tubing 12 or 14 is relatively snug near the ends of coiled
tubing 12 or 14 and the connection is less snug in other areas of
stiff section 27 of connector 10. For example, dimple screws
closest to the ends of coiled tubing 12 or 14 of the tubing can be
tightened to a different depth compared to those screws furthest
from the ends of coiled tubing 12 or 14.
[0040] Alternatively or in addition to indentations along the
external surface of stiff section 27, indentations may be provided
on the internal surface of body 16 along longitudinal bore 18. In
this manner, a thinner wall section of body 16 is provided in
desired locations at which coiled tubing 12 or 14 maybe pressed or
crimped to secure contact between connector 10 and coiled tubing 12
or 14. In another embodiment, a groove may be provided around the
circumference of stiff section 27 or a series of circumferential or
partially circumferential grooves may be placed or staggered along
the length of stiff section 27. Various combinations of these
techniques may also be used and are considered within the scope of
the present invention.
[0041] Connector 10 may preferably be provided with one or more
seals 24 to prevent fluid leakage between the connector 10 and each
of either or both of the coiled tubing 12/14. These seals 24 may be
of any known type, including but not limited to O-rings, chevron
seals, T-seals, dynamic seals such as PolyPak.TM., and various
other elastomeric devices.
[0042] In specific embodiments, the present connector 10 may
include an annular lip 26 disposed about the body 16 in the stiff
section 27 and positioned such that it is disposed between the
respective ends of the coiled tubings 12 and 14. The diameter of
annular lip 26 is the same or essentially equivalent to the outer
diameter of coiled tubing 12 and 14. As such, annular lip 26 does
not preclude connector 10 from passing through the wellhead
equipment. Annular lip 26 provides support for the end of the
coiled tubing 12 or 14 or to reduce forces that cause flaring of
tubing ends and also to contain and protect the tubing ends. As
will be appreciated by those of skill in this art, the annular lip
26 functions to reduce deformation or "egging" of the ends of the
coiled tubing 12 or 14 during use.
[0043] In some embodiments, a flow control device, such as a check
valve, may be used in conjunction with connector 10. The flow
control device permits fluid flow through in one configuration and
restricts fluid flow through in another configuration. Methods of
switching such flow control devices from one configuration to
another configuration are well known and include, for example,
exerting an axial external pressure on the connector, dropping a
ball, or providing a control signal. Such embodiments are of
particular use when the coiled tubing is under pressure, such as
well pressure or fluid pressure. The flow control device may be
placed within stiff section 27 of connector 10 or within coiled
tubing 12 or 14 adjacent to connector 10. A combination of internal
and external flow control devices may be also used.
[0044] As shown in FIGS. 3A through 3C, the decreasing exterior
diameter 29 of end section 28 can be constructed on the external
surface of body 16 in a variety of ways, including but not limited
to with a single angle, a series of short angle sectors, a constant
radius or a compound radius. In some embodiments, the diameter of
the internal surface of body 16 along longitudinal bore 18 may
increase in end section 28 to form an internal tapered surface 30.
For example, in the specific embodiments shown in FIG. 2, end
section 28 is shown having an outer tapered surface 29 and a
tapered internal surface 30 in longitudinal bore 18. This internal
tapered surface 30 similarly maybe constructed in a variety of
ways, including but not limited to with a single angle, a series of
short angle sectors, a constant radius, or a compound radius. In
some embodiments, the manner in which decreasing exterior diameter
29 and internal tapered surface 30 are constructed may be the same
and in some embodiments, the manner in which they are formed may be
different. In the specific embodiment shown in FIG. 3A, end section
28 includes an internal tapered surface 30 and a tapered outer
surface of body 29. In the embodiment shown in FIG. 3B, end section
28 includes a plurality of outer tapered surfaces, or short angle
sectors, 29A, 29B and 29C, and internal surface 30 is not tapered.
In the embodiment shown in FIG. 3C, end section 28 includes a
tapered outer surface 29 formed by a constant radius and internal
surface 30 in the longitudinal bore 18 is not tapered.
[0045] There is shown in FIG. 4 a coiled tubing connector 10
constructed in accordance with the present invention and in use to
connect a first section of coiled tubing 12 and a tool string 13.
Connector 10 has a body 16 having a longitudinal bore 18
therethrough and comprises a stiff section 27 and an end section
28. In some embodiments, connector 10 may disassembled by
separating stiff section 27 may be separated from end section 28
and assembled by attached stiff section 27 to end section 28 by
using any number of connection methods known for connecting while
maintaining a flush exterior surface such as threading, patterned
jointing, or lock and key.
[0046] Stiff section 27 of connector 10 has an outer diameter that
fits snugly within the inner diameter of coiled tubing 12. The
other end 41 of stiff section 27 connects to tool string 13. Such a
connection to tool string 13 may be made by any number of
connection methods known for connecting while maintaining a flush
exterior surface such as threading, patterned jointing, or lock and
key. In end section 28, the external diameter 29 of body 16
gradually decreases from end of the end section 28 proximate to the
stiff section 27 towards the distal end 33 of the body 16, such
that the external diameter 29 of end section 28 at the distal end
33 of body 16 is not engaged snuggly within the interior diameter
of coiled tubing 12. When coiled tubing 12 is straight, end section
28 is not in contact with the inner diameter of the coiled tubing
owing to its decreasing external diameter 29. In this way, there is
a limited area of contact between coiled tubing 12/14 as it bends
over the length of end section 28 and that limited area of contact
translates along the length of end section 28 as coiled tubing 12
bends. As such, the stress point occurring at the point of contact
translates along the end section 28 and overlapping coiled tubing
12, thereby avoiding the formation of a specific point of stress
concentration or hinge point. The restrictive bend feature of end
section 28 previously described is present in the embodiment shown
in FIG. 4.
[0047] A specific embodiment is shown in FIG. 5 in which two coiled
tubing connectors 10 constructed in accord with the present
invention are shown to connect a first section of coiled tubing 12,
a tool string 13, and a second section of coiled tubing 14. Each
coiled tubing connector 10 has a body 16 having a longitudinal bore
18 therethrough and comprises a stiff section 27 and an end section
28. Each tubing connector 10 is connected to coiled tubing 12 or 14
at stiff section 27 and to tool string 13 at one end 41. The first
tubing connector 10 is connected at stiff section 27 to coiled
tubing 12 and the second tubing connector 10 likewise is connected
at stiff section 27 to coiled tubing 14. Stiff sections 27 have an
outer diameter that fits snugly within the inner diameter of coiled
tubing 12. End section 28 of each of the first and the second
tubing connector 10 has an external diameter 29 that gradually
decreases from the end 40 of the end section 28 proximate to the
stiff section 27 towards the distal end 33 of the body 16, such
that the external diameter 29 of end section 28 at the distal end
33 of body 16 is not engaged within the interior diameter of coiled
tubing 12 or 14 respectively when the coiled tubing is not
bent.
[0048] In some embodiments, first or second connector 10, or both,
may comprise a body 16 in which one region of the body 16 is stiff
section 27 and another region of body 16 is end section 28. In
other embodiments, body 16 of the first or second connector 10, or
both, may disassembled by separating stiff section 27 from end
section 28 and assembled by attached stiff section 27 to end
section 28 using any number of connection methods known for
connecting while maintaining a flush exterior surface such as
threading, patterned jointing.
[0049] Stiff section 27 of each the first and second connectors 10
have an outer diameter that fits snugly within respectively the
inner diameter of coiled tubing 12 or 14. End section 28 of each of
the first and the second tubing connector 10 has an external
diameter 29 that gradually decreases from the end 31 of the end
section 28 proximate to the stiff section 27 towards the distal end
33 of the body 16, such that the external diameter 29 of end
section 28 at the distal end 33 of body 16 is not engaged within
the interior diameter of coiled tubing 12 or 14 respectively when
the coiled tubing is not bent. This restrictive bend feature of end
section 28 previously described is included in the embodiment shown
in FIG. 5.
[0050] Each of the embodiments described has a reduction in the
exterior diameter of end section 28. When bending occurs in routine
use, coiled tubing 12/14 bends until it contacts end section 28. As
bending continues, the contact point between coiled tubing 12/14
and end section 28 translates along the length of end section 28,
thereby avoiding a localized hinge point. In this way, connector 10
of the present invention undergoes lower strain during bending and
as a result, suffers lower fatigue and has a longer useful
life.
[0051] Advantages of the present invention may be seen by referring
to FIGS. 6A and 6B in which output from finite element modeling is
shown. FIG. 6A illustrates the output of finite element modeling of
a known internal coiled tubing connector having a flexible center
section and stiff end sections; numerous areas of high strain
concentration 50 are shown including an extended area of high
strain concentration 50 in the flexible center section. FIG. 6B
illustrates the output of finite element modeling having the same
inputs as FIG. 6B, except that the connector is modeled is of the
present invention; few areas of high strain concentration 50 are
shown for the present invention connector. As high strain
concentration leads to diminished usage life or to greater risk of
failure, the advantages of the connector of the present invention
are apparent from a comparison of FIG. 6B to FIG. 6A from which is
can be seen that connector 10 of the present invention undergoes
less strain than the coiled tubing connector having a flexible
center section.
[0052] As shown in FIG. 7, in another specific embodiment,
connector 10 may further be provided with a flow guide/debris
barrier 32 disposed at each end of the connector 10. The barrier 32
may include a body 34 with a tubular section 36 extending therefrom
and adapted to fit within the bore 18 of the connector 10. The body
34 may include a shoulder 38 designed to engage the tip of end
section 28 of connector 10. Body 34 may include an annular recess
44 for receiving an annular seal 42. The body 34 may further
include a tapered inner bore 40. The debris barrier 32 functions to
keep debris and solids, which could impede controlled bending, out
of the restrictive bend area between external diameter 29 of end
sections 28 and internal surface 30 of the coiled tubings 12/14.
Barrier 32 may be separate from the connector 10, as shown, or it
may be integral with the connector 10. In various embodiments,
barrier 32 maybe rigid or flexible. An example of an integral
flexible embodiment is an elastomeric cone molded to the end of
connector 10. Any combination of these techniques may be used. If
barrier 32 is separate from connector 10 instead of integral with
it, it may be held in position by a coiled tubing weld bead 46 on
one side and connector 10 on the other side. FIG. 7 further
illustrates that connector 10 may include an anti-extrusion ring 48
adjacent seal 24.
[0053] It can be seen in light of the above description of the
tubing connector of the present invention and related methods that
the present invention represents an improvement over prior coiled
tubing connectors and methods. Advantages of the present invention
include a tensile strength similar to the tensile strength of the
coiled tubing; the capability of bending around a coiled tubing
reel and an injector gooseneck during operation; have a low cycle
fatigue life similar to the coiled tubing; providing a pressure
tight seal both from internal and external sources; and passing
through a wellhead assembly.
[0054] Although the embodiments herein have been described with
respect to coiled tubing, one skilled in the art would understand
that although the present invention is useful in application for
connecting any tubing, notwithstanding its particular usefulness in
coiled tubing applications.
[0055] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents, but also equivalent structures. Thus,
although a nail and a screw may not be structural equivalents in
that a nail employs a cylindrical surface to secure wooden parts
together, whereas a screw employs a helical surface, in the
environment of fastening wooden parts, a nail and a screw may be
equivalent structures. It is the express intention of the applicant
not to invoke 35 U.S.C. .sctn.112, paragraph 6 for any limitations
of any of the claims herein, except for those in which the claim
expressly uses the words `means for` together with an associated
function.
* * * * *