Note: Descriptions are shown in the official language in which they were submitted.
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SUBSURFACE LUBRICATOR AND METHOD OF USE
FIELD OF THE INVENTION
This invention generally relates to hydrocarbon well
completion, recompletion and workover and, in particular,
to a subsurface lubricator and a method of using same to
facilitate well completion, re-completion and workover.
BACKGROUND OF THE INVENTION
Significant advances in facilitating well completion,
re-competition and workover using long downhole tool
strings have been described in applicant's co-pending
Canadian patent applications 2,451,748 and 2,451,750,
respectively filed on April 4, 2006 and respectively
entitled: A Casing Transition Nipple And Method Of Casing A
Well To Facilitate Well Completion, Re-Completion And
Workover; and Method Of Subsurface Lubrication To
Facilitate Well Completion, Re-Completion And Workover.
In view of these advances there exists a need for a
subsurface lubricator that permits a long tool string to be
lubricated into a well cased for subsurface lubrication.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide
a subsurface lubricator and method of using same to permit
a long tool string to be lubricated into a cased wellbore.
The invention therefore provides a subsurface
lubricator for lubricating a long tool string into a cased
wellbore, comprising: a lubricator tube for housing the
long tool string, the lubricator tube having a top end and
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a bottom end; a bidirectional packoff tool connected to the
bottom end of the lubricator tube; and a mechanism that
induces controlled linear motion of the lubricator tube to
lubricate the lubricator tube through a wellhead of the
cased wellbore so that the bidirectional packoff tool is
located in a top of a casing of the cased wellbore, in
which location pressurized fluid can be supplied through a
port of the wellhead to lubricate the lubricator tube
further into the casing by applying fluid pressure to a top
of the bidirectional packoff tool.
The invention further provides a method of lubricating
a downhole tool string into a cased wellbore, comprising:
mounting a subsurface lubricator with a lubricator tube
that houses the downhole tool string above a pressure
control gate mounted to a wellhead of the cased wellbore;
opening the pressure control gate and lubricating a
lubricator tube of the subsurface lubricator through the
wellhead until a bidirectional packoff tool connected to a
bottom end of the lubricator tube is located in a top of a
casing of the cased wellbore; and injecting pressurized
fluid through the wellhead into an annulus above the
bidirectional packoff tool to lubricate the lubricator tube
further into the casing.
The invention yet further provides a subsurface
lubricator for lubricating a long tool string into a cased
wellbore, comprising: a lubricator tube for housing the
long tool string, the lubricator tube having a top end and
a bottom end; a bidirectional packoff tool connected to the
bottom end of the lubricator tube; and hydraulic cylinders
for lubricating the lubricator tube through a wellhead of
the cased wellbore so that the bidirectional packoff tool
is located in a top of a casing of the cased wellbore, in
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which location pressurized fluid can be supplied through a
port of the wellhead to an annulus above the bidirectional
packoff tool to lubricate the lubricator tube further into
the casing.
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 diagram of an embodiment of a
subsurface lubricator in accordance with the invention;
FIG. 2 is a schematic diagram of the subsurface
lubricator shown in FIG. 1 mounted to a well cased for
subsurface lubrication;
FIG. 3 is a schematic diagram of the subsurface
lubricator shown in FIG. 2 after a lubricator tube of the
subsurface lubricator has been lubricated into the cased
well until a bi-directional packoff tool connected to a
bottom end of the lubricator tube is in a top of a casing
of the cased well;
FIG. 4 is a schematic diagram of the subsurface
lubricator shown in FIG. 3 with hydraulic cylinders
removed;
FIG. 5 is a schematic diagram of the subsurface
lubricator shown in FIG. 4 in a fully lubricated-in
position;
FIG. 6 is a schematic diagram of the subsurface
lubricator after a well completion, re-competition or
workover operation is completed and the subsurface
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lubricator has been partially lubricated out of the cased
well;
FIG. 7 is a schematic diagram of the subsurface
lubricator shown in FIG. 6 with the hydraulic cylinders re-
connected to permit the lubricator tube to be completely
lubricated out of the cased well;
FIG. 8 is a schematic diagram of the subsurface
lubricator shown in FIG. 4 in a completely lubricated-out
position;
FIG. 9 is a cross-sectional schematic diagram of one
embodiment of a bi-directional packoff tool in accordance
with the invention; and
FIG. 10 is a cross-sectional schematic diagram of
another embodiment of the bi-directional packoff tool in
accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention provides a subsurface lubricator that
facilitates well competition, re-completion and workover.
The subsurface lubricator is lubricated down through a
wellhead of a well and into an upper section of a
production casing supported by the wellhead. The subsurface
lubricator permits long tool strings to be lubricated into
the well while significantly reducing a distance that an
injector for controlling the tool string is located above
the ground after the tool string has been lubricated into
the well. Expense is therefore reduced and safety is
improved by lowering working height and reducing mechanical
stress on the wellhead.
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FIG. 1 is a schematic diagram, partially in cross-
section, showing an embodiment of a subsurface lubricator
20 in accordance with the invention. The subsurface
lubricator 20 includes a lubricator tube 22 having a
plurality of lubricator joints 22a, 22b, 22c, ... 22n. The
number of lubricator joints in the lubricator tube 22
depends on a length of the respective joints (generally 8'-
10'(2.44m-3.05m)) and the length of the downhole tool
string to be lubricated into a well. The lubricator joints
22a-22n are threadedly interconnected end-to-end, so that
the lubricator tube 22 is a hollow cylinder with smooth
cylindrical inner and outer walls. A bidirectional packoff
tool 24 is connected to a bottom end of the lubricator tube
22. The bidirectional packoff tool 24 will be described in
detail with reference to FIGs. 9 and 10.
The lubricator tube 22 reciprocates through a central
passage in an anchor plate 32. Quick-release connectors at
connection points 33 connect hydraulic cylinders 46a, 46b
to the anchor plate 32. The function of the hydraulic
cylinders 46a, 46b will be described with reference to
FIGs. 2-8. Affixed to the top of the anchor plate 32 is an
anchor pin 34. Pin threads 35 are cut into an outer
periphery of the anchor pin 34. The pin threads 35 are
engaged by box threads of an anchor nut 42 to lock the
lubricator tube 22 in the fully lubricated-in position, as
will also be explained below with reference to FIG. 5.
Threadedly connected to a top end of the lubricator
tube 22 is a lubricator tube adaptor 38. The lubricator
tube adaptor has a central passage that communicates with
an interior of the lubricator tube 22 and has a diameter at
least as large as a diameter of the lubricator tube 22. A
top end of the lubricator tube adaptor 38 supports an
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adaptor flange 40. The adaptor flange 40 permits any
compatible flanged component to be mounted to a top of the
subsurface lubricator 20, such as: a high pressure valve; a
blowout preventer (BOP); a frac stack; a coil tubing
injector; a wireline grease injector; a coil tubing BOP; a
wireline BOP; or any other appropriate equipment. A bottom
end of the lubricator tube adaptor 38 includes an annular
shoulder (not shown) that rotatably supports the anchor nut
42. The anchor nut 42 may be a spanner nut, or a hammer
union having two or more hammer lugs 44, which are well
known in the art. An injector plate 36 is connected to the
adaptor 38 in a radial orientation. The injector plate 36
includes at least two connection points for respectively
connecting top ends of hydraulic cylinder extension rods
52a and 52b. The extension rods 52a and 52b are connected
to cylinder rods 48a and 48b by quick-release connectors
50a and 50b. The top end of each extension rod 52a, 52b is
connected at the connection points of the injector plate 36
by a respective fastener 54a and 54b, such as a spanner nut
or a quick-release connector.
The anchor pin 34 and the anchor plate 32 are shown
partially in cross-section to illustrate part of an annular
packing cavity 56 that surrounds the lubricator tube 22.
The packing cavity 56 accepts a high-pressure packing 57,
such as chevron packing, which is well known in the art.
The high-pressure packing 57 is retained in the packing
cavity 56 by packing nut 58. A packing wedge 59 is a V-
shaped steel ring that compresses the high-pressure packing
57 in the packing cavity 56 when the packing nut 58 is
tightened.
FIG. 2 is a schematic diagram of the subsurface
lubricator 20 mounted to a wellhead 21 of a well cased as
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described in applicant's above-referenced Canadian patent
application assigned serial number 2,541,478. The wellhead
includes a casing head 60 supported by a conductor 62. The
casing head 60 supports a surface casing 64. A tubing head
spool 65 is mounted to the casing head 60. The tubing head
spool 65 supports a production casing 66 of a first
diameter, which extends downwardly to a casing transition
nipple 68. The casing transition nipple supports a
production casing 70 of a second, smaller diameter. The
production casing 70 extends downwardly through the
production zone(s) of the well. As will be understood by
those skilled in the art, the subsurface lubricator 20 and
the long tool string that it houses is generally made up on
the ground and then hoisted into place using a rig or a
crane (not shown). As will also be understood by those
skilled in the art, mounted to a top of the subsurface
lubricator 20 will be at least a coil tubing injector or a
wireline grease injector (neither of which is shown) for
suspending and manipulating the downhole tool string.
Reference may be made to applicant's above-identified co-
pending patent applications for a more detailed
explanation.
Generally, the subsurface lubricator 20 is mounted to
a top of a pressure control gate, such as to the top of a
blowout preventer 72 using flange bolts 74 and a metal ring
gasket (not shown), which is well known in the art. If the
well is a live well, blind rams 76 of the blowout preventer
72 are closed to prevent any escape of hydrocarbons from
the well while the subsurface lubricator 20 is mounted to
the blowout preventer 72.
FIG. 3 is a schematic diagram illustrating a first
stage of a process of lubricating the lubricator tube 22
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into the cased well. In the first stage, the blind rams 76
(see FIG. 2) of the BOP 72 are opened after appropriate
pressure balancing, and the hydraulic cylinders 46a, 46b
are operated to draw in the cylinder rods 48a, 48b. This
lubricates the lubricator tube partially into the well so
that the bidirectional packoff tool 24 passes through the
BOP 72, the tubing head spool 65 and into a top of the
casing 66. If the BOP is equipped with appropriately sized
tubing rams, the tubing rams 77 may then be closed to
provide a fluid seal around the lubricator tube 22.
However, a high-pressure fluid seal is provided by the
high-pressure packing 57 in the packing cavity 56 of the
anchor plate 32, as described above with reference to FIG.
1.
FIG. 4 is a schematic diagram illustrating a second
stage in the process of lubricating the lubricator tube 22
into the cased well. After the lubricator tube 22 has been
lubricated into the well using the hydraulic cylinders 46a,
46b so that the bidirectional packoff tool 24 is in a top
of the casing 66, a high pressure fluid source 80 is
connected to a side port 67 of the tubing head spool 65,
and high-pressure fluid is pumped or otherwise injected
into an annulus above the bidirectional packoff tool 24
until the natural well pressure is overburdened and the
hydraulic cylinders 46a and 46b as well as the hydraulic
cylinder extensions 52a and 52b can be removed from the
subsurface lubricator 20. The high-pressure fluid may be
water, hydraulic fluid, compressed air, a compressed gas,
or any other fluid that meets performance requirements as
well as safety and environmental regulations. As will be
understood by those skilled in the art, high-pressure fluid
is trapped in the annulus between an upper sealing element
of the bidirectional packoff tool 24 and the tubing rams 77
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or the high-pressure packing 57. Once sufficient fluid
pressure is injected, the trapped high-pressure fluid
overbears well pressure and lubricates the lubricator tube
22 downwards into the casing.
After the hydraulic cylinders 46a, 46b and the
cylinder extension rods a 52a, 52b have been removed, the
high-pressure fluid from the fluid source 80 is again
pumped into the annulus above the bidirectional packoff
tool 24 until of the lubricator tube 22 is fully lubricated
into the cased well, as shown in FIG. 5. In this position
the anchor nut 42 is threaded onto the anchor pin 34 (see
FIG. 1) to lock the subsurface lubricator in the fully
lubricated-in position. A valve on the side port 65 may
then be closed and the downhole tool string housed in the
lubricator tube 22 can be lowered into the cased well and
manipulated to perform any of the functions for which it
was designed.
Since the internal diameter of the lubricator tube 22
is at least as large as an internal diameter of the
production casing 70, the subsurface lubricator 20 provides
full-bore access to the cased wellbore. Well stimulation
fluids can also be pumped down a coil tubing string (not
shown) supporting the downhole tubing string, or "down the
backside" through the lubricator tube 22. As will be
explained below with reference to FIGs. 10 and 11, the
bidirectional packoff tool 24 completely isolates the
wellhead from high-pressure well stimulation fluids.
After the downhole tool string has been used as
planned, it is pulled back up into the lubricator tube by
operating the coil tubing injector or the wireline grease
injector (neither of which is shown), and the lubricator
tube 22 is lubricated out of the cased well. FIG. 6
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illustrates a first stage of lubricating the lubricator
tube 22 out of the cased well. The process begins by
connecting a line from a side port 69 of the tubing head
spool 65 to a drain pit 90, or to any other suitable
collection container, if required, so that the pressurized
fluid used to lubricate in the lubricator tube 22 can be
drained from the annulus above the bidirectional packoff
tool 24. The anchor nut 42 is then rotated to release it
from the anchor pin 34. A valve on the side port 69 is
slowly opened to begin draining the pressurized fluid from
the annulus. Assuming that the natural well pressure
overbears the combined weight of the lubricator tube 22,
the downhole tool string, and any equipment mounted to the
adaptor 38, which is frequently the case, the lubricator
tube 22 will begin to lubricate out of the well as soon as
the side port 69 valve is opened. If that is not the case,
a rig or a crane is connected to the injector plate 36 and
the lubricator tube 22 is hoisted up to lubricate it out of
the cased well.
This lubrication of the lubricator tube 22 out of the
cased well is permitted to continue until the lubricator
tube 22 is returned to a position where the hydraulic
cylinders 46a and 46b and the extension rods 52a and 52b
can be reconnected, as shown in FIG. 7. The valve on the
side port 69 is then closed until the hydraulic cylinders
46a, 46b and the extension rods 52a, 52b are re-connected.
The valve on the side port 69 is then reopened and the
hydraulic cylinders 46a, 46b are operated to lubricate out
the lubricator tube 22 until a top the bidirectional
packoff tool 24 is just below the side port 69. Any
remaining high-pressure fluid is permitted to drain from
the annulus and the valve on the side port 69 is then
closed before the hydraulic cylinders 46a, 46b are used to
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lubricate the lubricator tube 22 to the position shown in
FIG. 8. The blind rams 76 of the BOP 72 can then be closed
and a rig or crane connected to a top of the subsurface
lubricator 10 to support it while the flange bolts 74 are
removed after pressure trapped above the blind rams 76 has
been released in a manner well understood in the art. The
subsurface lubricator 20 with the enclosed downhole tool
string is then hoisted off of the wellhead by the rig or
the crane, and preparations for production from the well
can commence.
FIG. 9 is a schematic cross-sectional view of one
embodiment of the bidirectional packoff tool 24 shown in
FIGS. 1-8. In this embodiment, the bidirectional packoff
tool 24 is made up using cup tool mandrels 100a and 100b.
The cup tool mandrels 100a, 100b can be interconnected in
any orientation and in any sequence using threaded collars
102. The cup tool mandrels 100a and 100b have an internal
diameter that is the same as that of the lubricator tube
22. Each cup tool mandrel 100a and 100b slidably supports
an elastomeric cup 104a and 104b, which packs off in the
casing 66 to provide required pressure isolation. Each
elastomeric cup 104a and 104b includes a depending
skirt 106a, 106b, which extends downwardly from a cup
body 108a, 108b and is formed integrally therewith. The
depending skirt 106a, 106b has an outer diameter that is
slightly larger than the inner diameter of the casing 66.
The depending skirt 106a, 106b is open at its bottom end,
and forms a sealed cavity around the cup tool mandrels
100a, 100b that is closed at a top end by an inwardly
biased lip 110a, 110b, so that when the elastomeric cup
104a, 104b is exposed to fluid pressure it is forced to
slide away from the pressure on the respective cup tool
mandrel 100a, 100b.
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Movement of the elastomeric cups 104a, 104b on the
respective cup tool mandrels 100a, 100b is constrained by a
square step 112a, 112b which inhibits packoff of the
elastomeric cups 104a, 104b when the bidirectional packoff
tool is being lubricated through the wellhead and into the
casing 66. The elastomeric cups 104a, 104b pack off against
a respective gauge ring 114a, 114b to provide a high
pressure fluid seal in a manner well known in the art.
As can be seen, the elastomeric cup 104a is oriented
upwardly and provides the upper sealing element of the
bidirectional packoff tool 24. It is the elastomeric cup
104a that traps the high pressure fluid from high-pressure
fluid source 80 to lubricate the lubricator tube 22 down
the casing 66. As can also be seen, the elastomeric cup
104b is oriented downwardly and packs off to isolate the
wellhead 21 from well pressure as well as any high pressure
fluids pumped into the casing 70 to stimulate production
from the well.
A bullnose 116 guides the bidirectional packoff tool
24 through the wellhead and the casing 66 and protects the
elastomeric cup 104b when the lubricator tube 22 is
lubricated into or out of the well. An adapter sleeve 118
threadedly connected to a top of the cup tool mandrel 100a
is similarly configured to protect the elastomeric cup
104a, and to provide a pin thread 120 for connecting the
bidirectional packoff tool 24 to a box thread in a bottom
end of the lubricator tube 22.
FIG. 10 is a schematic diagram of another embodiment
of the bidirectional packoff tool 24 shown in FIGs. 1-8.
This embodiment permits the lubricator tube to be locked in
the casing to reduce lifting stress on the wellhead 21 when
high pressure fluids are pumped through coil tubing or down
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the backside through the lubricator tube 22 to stimulate
production from the well.
As shown in FIG. 11, a top half of the bidirectional
packoff tool 24 is identical to that described above with
reference to FIG. 10, and will not be redundantly
described. A bottom half of the bidirectional packoff tool
24 is a casing packer 150, many configurations of which are
well known in the art. The casing packer 150 includes an
annular packer element 152, which when activated by
internal mechanisms 154 (schematically shown) packs off
against the casing 66 to provide a high pressure fluid
seal. There are many different packer elements known in the
art and many types of internal mechanism for controlling
them.
The casing packer 150 also includes casing-engaging
slips 156, which are extended to a casing-engaging position
in which they bite into the casing 66 to prevent upward
movement of the bidirectional packoff tool 24 when the
casing packer 150 is set. Internal mechanisms 158
(schematically shown), many configurations of which are
also well known in the art, move the casing-engaging slips
150 from the casing-engaging position to an unset position
in which the lubricator tube 22 can be withdrawn from the
casing 66.
It should be understood that the bidirectional packoff
tool 24 can be constructed using any known cup tool,
packoff nipple or casing packer technology and that the
invention is not limited to the two embodiments described
with reference to FIGs. 9 and 10.
It should also be understood that the hydraulic
cylinders 46a, 46b described with reference to FIGs. 1-8
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could be replaced with pneumatic cylinders, ball jacks,
screw jacks, or any other robust mechanism for inducing
controlled linear movement that can be used to lubricate
the lubricator tube 22 into the well until the
bidirectional packoff tool 24 is lubricated into a top of
the casing 66.
The embodiments of the invention described above are
therefore intended to be exemplary only, and the scope of
the invention is intended to be limited solely by the scope
of the appended claims.
