Note: Descriptions are shown in the official language in which they were submitted.
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BLAST JOINT SWIVEL FOR WELLHEAD ISOLATION TOOL
AND METHOD OF USING SAME
FIELD OF THE INVENTION
The present invention relates to equipment for
servicing oil and gas wells and, in particular, to a blast
joint for a wellhead isolation tool used to isolate a
wellhead from exposure to high-pressure, abrasive and
corrosive fracturing fluids used to stimulate a well.
BACKGROUND OF THE INVENTION
Most oil and gas wells require stimulation to enhance
hydrocarbon flow to make or keep them economically viable.
The servicing of oil and gas wells to stimulate production
requires the pumping of fluids into the well under high
pressure. The fluids are generally corrosive and/or
abrasive because they are laden with corrosive acids and/or
abrasive proppants, such as sharp sand or bauxite.
In order to protect components that make up the
wellhead, such as the valves, tubing hanger, casing hanger,
casing head and/or blowout preventer equipment, wellhead
isolation equipment, such as a wellhead isolation tool, a
casing saver or a blowout preventer protector is used
during well fracturing and well stimulation procedures.
The wellhead isolation equipment may include a "blast
joint" that is connected to a production tubing in the well
used as a "dead string" to monitor downhole pressure during
well stimulation and to flow back stimulation fluids after
the well stimulation is complete, or as an additional fluid
path for delivering high pressure stimulation fluids into
the well.
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As shown schematically in FIG. 1, a wellhead isolation
tool 10 includes a sealing assembly 12, e.g. a "cup tool"
or a high pressure fluid seal for a blowout preventer
protector that seals off in a tubing spool above a bit
guide. A blowout preventer protector equipped with a cup
tool is described in U.S. Patent Application Publication
2003/0192698 (Dallas) entitled BLOWOUT PREVENTER PROTECTOR
AND METHOD OF USING SAME which was published on Oct. 16,
2003. An example of a sealing assembly that seals off
above a bit guide is described in U.S. Patent Application
Publication 2003/0221838 (Dallas) entitled WELL STIMULATION
TOOL AND METHOD OF USING SAME which was published on Dec.
4, 2003.
The wellhead isolation tool 10 further includes a
blast joint 20 that has a threaded lower end 22 for
connection to a threaded top end 32 of a tubing string 30
supported by slips 34 on a wellhead 40. The wellhead
isolation --ool 10 is lowered by a rig (not shown) into
contact wit:h the threaded top end 32 of the tubing string
30 and then the entire wellhead isolation tool 10 is
rotated to connect the blast joint to the tubing string.
As can be appreciated by those of ordinary skill in the
art, connecting the blast joint to the tubing string in
this way can be challenging. Precise control of the tool
10 must be exercised to ensure proper engagement of the
threaded ends of the blast joint and the tubing string. If
the tool 10 is a bit too high, the threads will not engage.
If, however, the tool 10 is a bit too low the tool 10 will
tilt as it is rotated and there is a real danger of cross-
threading. The difficulty of connecting wellhead isolation
equipment using this prior-art technique can therefore
result in unwanted delays and/or equipment damage.
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Accordingly, there remains a need for an improved
apparatus and method for connecting a blast joint to a
tubing string.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide
an apparatus and method that facilitates connection of a
blast joint. to a tubing string.
The irivention therefore provides a blast joint swivel
for use in a wellhead isolation tool, comprising: a blast
joint hanger mounted to a top of the wellhead isolation
tool; and a swivel body received within the blast joint
hanger, the swivel body having an axial fluid passage with
bottom threads for connection to a top end of a blast
joint, the blast joint hanger supporting the swivel body
for unconstrained axial rotation relative to the blast
joint hanger.
The invention further provides a method of connecting
a blast joint of a wellhead isolation tool to a tubing
string suspended in a wellbore, the method comprising:
mounting a blast joint swivel to a top end of a wellhead
isolation tool and connecting the blast joint to a bottom
end of the blast joint swivel; hoisting the wellhead
isolation tool over a wellhead of the well and lowering the
wellhead isolation tool until a threaded bottom end of a
blast joint contacts a threaded upper end of the tubing
string; and rotating the blast joint to threadedly connect
the blast joint to the tubing string.
The invention further provides a wellhead isolation
tool for isolating a wellhead from high pressure fluids
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used to stimulate a well, comprising: a fracturing head
through which the high-pressure fluids can be pumped into
the well; a blast joint hanger mounted to a top of the
fracturing head, the fracturing head and blast joint hanger
together defining a central passage in fluid communication
with the side ports; a tubular swivel body received within
the central bore for unconstrained rotational movement
relative to the blast joint hanger; and a tubular blast
joint connected to a bottom end of the swivel body, a
bottom end of the blast joint being threaded for connection
to a top end of a tubing string suspended in the well.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the
invention, reference will now be made to the accompanying
drawings, in which:
FIG. 1 is a schematic cross-sectional view of a method
of conriecting a blast joint to a tubing string in
accordance with the prior art;
FIG. 2 is a schematic cross-sectional view of a method
of connecting a blast joint to a tubing string in
accordance with an embodiment of the invention;
FIG. 3 is a partial cross-sectional view of a wellhead
isolation tool with a blast joint swivel in accordance with
an embodiment of the invention; and
FIG. 4 is a partial cross-sectional view of another
type of wellhead isolation tool with a blast joint swivel
in accordance with another embodiment of the invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In general, and as will be explained below, the
invention provides a blast joint swivel for use with a
wellhead isolation tool. The blast joint swivel includes a
blast -]oint hanger mounted to a top of the wellhead
isolation tool and a swivel body rotatably received in the
blast joint hanger. The swivel body threadedly connects to
a blast joint which, in turn, threadedly connects to a top
end of a tubing string suspended in a well. In one
embodiment the blast joint swivel can also be displaced
vertically over a limited range of movement between upper
and lower abutments to facilitate threading of the blast
joint to the tubing string. The blast joint swivel
facilitates connection of the wellhead isolation tool to
the tubing string, which reduces wellhead isolation tool
setup time.
As shown schematically in FIG. 2, a wellhead isolation
tool 10 includes a sealing assembly 12, e.g. a "cup tool"
or a high pressure fluid seal for a blowout preventer
protector that seals off in a tubing spool above a bit
guide. The wellhead isolation tool 10 also includes a
blast joint 20 which has a threaded lower end 22 for
connection to an upper threaded end 32 of a tubing string
supported by slips 34 on a wellhead 40. The blast joint
25 20 is rotatably received within a mandrel of the wellhead
isolation tool 10, as will be described in greater detail
below. As shown in FIG. 2, the blast joint 20 can be
rotated relative to the wellhead isolation tool 10 so that
the blast joint 20 can be threaded onto the tubing string
30 30 without having to rotate the entire wellhead isolation
tool 10. By rotating the blast joint 20 in lieu of the
entire wellhead isolation tool 10, the connection of the
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wellhead isolation tool 10 to the tubing string 30 is
significantly easier.
FIG. 3 is a partial cross-sectional view of a wellhead
isolation tool 10 with a blast joint swivel 11 in
accordance with an embodiment of the invention. As shown
in FIG. 3, the wellhead isolation tool 10 includes a
fracturi.ng head 50. The fracturing head 50 includes angled
side ports 52 through which high-pressure fracturing fluids
(often laden with proppants) can be pumped in a manner well
known in the art. The fracturing head 50 includes a
generally tubular body defining an axial fluid passage (or
central bore) 54 for conveying the fracturing fluids into
the well.. The fracturing head 50 can include a replaceable
wear-resistant sleeve (or insert) 56 and an associated seal
58 which are provided to protect the fracturing head from
the corrosive and/or abrasive fracturing fluids in order to
prolong the longevity of the fracturing head.
The blast joint swivel 11 further includes a blast
joint hanger 60 connected to a top of the fracturing head
50 by a threaded union, e. g. a hammer union (which is not
shown, but which is well known in the art). The threads of
the hammer union connect to the upper threads 59 of the
fracturing head 50 to secure a lower flange 62 of the blast
joint hanger 60 to the top of the fracturing head.
Furthermore, the blast joint hanger 60 is sealed to the
fracturing head 50 by a metal ring gasket 63 and a pair of
backup annular sealing elements 64 (e.g. elastomeric seals
such as rubber gaskets) which provide a fluid-tight seal
between the blast joint hanger and the fracturing head.
The metal ring gasket 63 is described in Applicant's co-
pending U.S. Patent Application 10/690,142 (Dallas)
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entitled METAL RING GASKET FOR A THREADED UNION filed on
February 21, 2003.
Secured atop the blast joint hanger 60 is an adapter
spool 135 to which is secured a high-pressure fluid flow
control component in a manner well known in the art. In
the embodiment illustrated in FIG. 3, the blast joint
hanger 60 has upper threads 65 for connecting to another
threaded union, e.g. a hammer union (not shown). The
hammer union secures the adapter spool 135 to the top of
the blast joint hanger 60. A metal ring gasket 68 and a
pair of backup annular sealing elements 66 (e.g. rubber
gaskets) provide a fluid-tight seal between the blast joint
hanger 60 and the adapter spool 135.
As shown in FIG. 3, the blast joint hanger 60
rotatably receives a blast joint swivel 11, which can
rotate in an unconstrained manner relative to the blast
joint hanger 60. The blast joint swivel 11 has a swivel
body 70 and a blast joint 80. The blast joint 80 is
threadedly connected to a bottom end 75 of the swivel body
70. To facilitate rotation of the blast joint swivel, a
pair of spaced-apart needle bearings (i.e. a lower needle
bearing 110 and an upper needle bearing 120) are disposed
between the swivel body 70 and the blast joint hanger 60.
The lower needle bearing 110 is supported and restrained by
a lower collar 90 which is threadedly connected to an
inside of the blast joint hanger 60. The lower collar 90
includes a pair of inner annular seal grooves dimensioned
to receive high-performance annular sealing elements 92 for
providing a fluid-tight seal between the lower collar 90
and the swivel body 70. The high-performance annular
sealing elements can be any one or more of quad seals, lip
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seals, or 0-rings with backups. The seals can also be
polypack or V-pack. These seals can be made of any one of
a variety of high-performance sealing materials such as
nitrile rubber, carbon rubber, polyurethane, VitonTM or
TeflonTM having 50-100 durometer and, in some embodiments,
70-90 durometer. Another high-performance annular sealing
element is seated in annular groove 71 at the top end of
the swivel body 70. These seals inhibit penetration of
corrosive and/or abrasive fracturing fluid into the blast
joint swivel.
The lower collar 90 also includes a pair of outer
annular seal grooves dimensioned to receive annular sealing
elements 94, e.g. elastomeric 0-rings, for providing a
fluid-tight seal between the lower collar 90 and the blast
joint hanger 60.
As further shown in FIG. 3, the blast joint swivel 11
can be displaced vertically relative to the blast joint
hanger 60 over a limited range, facilitating the threading
of the blast joint 80 onto the tubing string. The swivel
body 70 includes a lower annular shoulder 72 supported, in
an inoperative or unengaged position (i.e. before the blast
joint contacts the tubing string), by a lower abutment 61
formed by an annular shoulder on the blast joint hanger 60.
The lower abutment 61 limits downward displacement of the
blast joint swivel 11 relative to the blast joint hanger
60. The swivel body 70 also includes an upper annular
shoulder 74 which is spaced a vertical distance D beneath
an upper abutment 104 formed by an annular shoulder in an
upper collar 100. Therefore, the upper abutment and the
lower abutment limit the vertical travel of the blast joint
swivel relative to the blast joint hanger. The blast joint
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swivel can thus be displaced within a vertical range of the
distance D. In one embodiment, the distance D is at least
as great as the vertical displacement of the blast joint
relative to the tubing string when the blast joint is
threadedly connected to the tubing string.
The upper collar 100 is threadedly connected to an
inside of the blast joint hanger 60 to restrain the upper
needle bearing 120 between the upper collar 90 and the
blast joint hanger 60. In one embodiment, the upper collar
100 has two inner annular seal grooves and two outer
annular seal grooves for receiving annular sealing elements
106, e.g. 0-rings, which provide fluid-tight seals between
the swivel body and the upper collar and between the upper
collar and the blast joint hanger, respectively.
In operation, the wellhead isolation tool 10 is
hoisted over the wellhead and lowered until the blast joint
contacts the tubing string. Before the blast joint
contacts the tubing string, the blast joint swivel is
disposed in rest position. When the blast joint contacts
the tubing string, the blast joint and swivel body are
forced upwardly relative to the blast joint hanger as the
wellhead isolation tool is lowered. This upward
displacement is limited by the upper abutment 104 so that
the maximum vertical travel of the swivel body is not more
than the distance D. Once the swivel body has been
displaced upwardly by a distance d where d< D, the swivel
body and blast joint are in an operative or engaged
position. In the operative position, the blast joint can
be threaded onto the tubing string. As the blast joint
threads onto the tubing string, the swivel body is drawn
downwards towards the rest position. Accordingly, the
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distance D should be at least as great as the vertical
displacement of the blast joint relative to the tubing
string when the blast joint is connected to the tubing
string.
FIG. 4 is a partial cross-sectional view of a variant
of the wellhead isolation tool 10 equipped with the blast
joint swivel 11 in accordance with another embodiment of
the invention. For the sake of clarity and brevity, same
or similar components will not be redundantly described.
In this embodiment, a high-pressure valve 140 having a
lower flange 142 is bolted directly to an upper flange 69
of the blast joint hanger 60.
The blast joint swivel 11 includes a swivel body 70
rotatabl.y received within the axial passage (or central
bore) of the blast joint hanger. In other words, the
swivel body and blast joint are free to rotate relative to
the blast joint hanger and fracturing head. A lower needle
bearing 110 and an upper needle bearing 130 are disposed
between the swivel body and the blast joint hanger to
facilitate smooth rotation of the swivel body.
As shown in FIG. 4, a pair of high-performance annular
sealing elements are seated in respective annular seal
grooves 71 in the top end of the swivel body. Likewise,
another pair of high-performance annular sealing elements
are seated in annular seal grooves 92 in a lower collar 90.
These high-performance annular sealing elements inhibit
penetration of corrosive and/or abrasive fracturing fluid
into the blast joint swivel.
The lower collar 90 supports and restrains the first
needle bearing 110 as well as a steel spacer ring 130
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disposed above the first needle bearing 110. The spacer
ring 130 is pressed upwardly into partial abutment with an
annular shoulder of the blast joint hanger. The spacer
ring 130 also supports a second needle bearing 120,
restraining the second needle bearing 120 between the
spacer ring 130 and another annular shoulder of the blast
joint hanger. The swivel body can thus be displaced the
limited distance D between the lower abutment defined by an
annular shoulder 95 of the lower collar 90 and an upper
abutment 124 defined by a bottom surface of the second
needle bearing 120.
The swivel body and blast joint can also be vertically
displaced relative to the blast joint hanger but only over
a limited range as was described above with respect to the
previous embodiment. Vertical displacement of the swivel
body and blast joint relative to the blast joint hanger is
limited by a lower abutment and an upper abutment. In one
embodiment, as shown in FIG. 4, the swivel body includes a
lower annular shoulder 72 which, in a rest position, abuts
a lower abutment 95 formed by an annular shoulder of the
lower collar 90. The swivel body also includes an upper
annular shoulder 74 which is spaced the distance D (again
in the rest position) beneath an upper abutment 124 formed
by a bottom surface of the upper needle bearing 120. When
the blast joint is lowered into contact with the tubing
string, the swivel body and blast joint are displaced
upwardly (by up to a distance D) as the wellhead isolation
tool is lowered. Once the wellhead isolation tool 10 has
been lowered, the blast joint can begin to be threaded onto
the tubing string. As the blast joint is threaded onto the
tubing string, the swivel body and blast joint move back
down toward the rest position. Accordingly, as was
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explained above, the upper and lower abutments should be
spaced apart by the vertical distance D, which is at least
as great as the vertical displacement of the blast joint
relative to the tubing string when the blast joint threads
onto the tubing string.
Modifications and improvements to the above-described
embodiments of the present invention may become apparent to
those skilled in the art. The foregoing description is
intended to be exemplary rather than limiting. The scope
of the invention is therefore intended to be limited solely
by the scope of the appended claims.
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