Note: Descriptions are shown in the official language in which they were submitted.
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AN I MPROVED WELLHEAD ;[ SOLATI ON T~:)OL
Field Of The Invention
This invention relates to wellhead isolation tools
and in particular to the improvement of an existing tool
which utilizes a mandrel with an attached concentric
piston inserted into a wellhead array by the hydraulic
action in a concentric and surrounding hydraulic cylin-
der. The replacing of the surrounding hydraulic cylindsr
by a telescoping surrounding hydraulic cylinder is
proposed.
Background Of The Inven~ion
In oilfield service work, a piece of equipment
referred to in the trade as a "tree saver" or wellhead
isolation tool is often used. ~his apparatus generally
introduces a hollow high pressure mandrel with a sealing
nipple through the low pressure rated valves and fittings
on a wellhead and the resilient sealing material on the
nipple at the lower end of the mandrel seals the mandrel
in the well casing or tubing. (For the remainder of
this description the term "casing" will be used to desig-
nate both casing and tubing). This allows high pressure
fluids to be introduced into the well casing through the
mandrel without their having any communication with these
low pressure valves and fittings. There are a multitude
of different configurations of these wellhead isolation
tools, each with their own drawbacks. One wellhead
isolation tool which was designed and manufactured by
McEvoy circa 1955 is still utilized in well servicing
today. One of the permanent problems with this apparatus
is the overall height when in place on the wellhead and
ready to be utilized. The overall height of the unit is
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such that a scaffold or ladder is required for personnel
to work on the top end where the plug valve and connec-
tion fittings are located. This height also leads to a
great sideways strain on the wellhead from the movement
of the attached steel piping when fluid is being pumped
through it. Replacing the long stroking hydraulic
cylinder with a telescoping cylinder is proposed as a way
of making a low profile wellhead isolation tool from the
existing high profile tool.
SummarY Of The Invention
According to a broad aspect, the invention relates
to a novel method to insert a concentric ma~drel and
sealing nipple through a wellhead and its associated
array of valves and fittings so the sealing nipple and
its resilient sealing material will contact and seal
against the casing in the well. As the mandrel and other
various parts of the tool are the subjects of many lapsed
patents, only the novel idea of using the mandrel as the
first stage of a telescoping cylinder and then adding the
other telescoping stages, sufficient to accomplish the
required travel and give the lowest possible profile, is
the subject of this application.
The usual action of a telescoping cylinder is to
generate force when the cylinder is being extended. The
novel use in this invention uses the force generated by
the cylinder while it is being rstracted. The subject
portion of the apparatus consists of a mandrel with an
attached piston, a sealing nipple and a connection for a
plug valve, (this plug valve being referred to as the top
of the tool), the piston and mandrel sealed and travell-
ing in a cylinder due to hydraulic force, and being
restrained at both ends of the travel in this cylinder.
This cylinder is referred to as the first stage cylinder
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of the telescoping cylinder. This first stage cylinder
is of such shape and finish, that with appropriate
sealing mechanisms, it becomes the piston and rod of a
second concentric cylinder, this second cylinder being
referred to as the second stage cylinder. ~fter hydrau-
lic means have moved the piston and the attached mandrel
and they have travelled down the length allowed in the
first stage cylinder, moving the attached nipple into the
wellhead, and the hydraulic means closed to prevent
movement of the mandrel with respect to this first stage,
hydraulic means are applied in the second stage cylinder
and the first stage cylinder moves away from the top
restraint and towards the lowe.r restraint in the second
stage cylinder. Thus, the mandrel which is~hydraulically
locked in place in the first stage cylinder, is again
moved down through the sealed concentric hole at the end
of the second stage and thus further into the wellhead.
When the travel o~ the first stage cylinder in the second
stage is stopped by the lower restraint, the position of
the mandrel and the second stage cylinder is consolidated
by an appropriate locking mechanism. It is obvious to
those skilled in the art that this second stage cylinder
may also be of such shape and finish that it becomes the
piston and rod of a third stage cylinder, and this
process may be repeated up to a usual maximum of six to
eight stages. For the description in this application,
we shall show two stages, but it is well recognized that
three or more stages could be utilized. It will also be
noted that the movement of the mandrel would be the same
if the hydraulic means were run into the cylinder ports
in a di~ferent sequence or this hydraulic means were run
into both ports at the same time. The second or final
stage of the telescoping cylinder is adapted to the
wellhead in one of the recognized ways. The mandrel and
sealing nipple is thus moved through the wellhead array
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and into the casing. Appropriate piping is now attached
above the plug valve and this valve opened. When
treatment of the well has been completed, the plug valve
is closed, the piping is removecl, the locking mechanism
is unlocked and hydraulic fluid is pumped into the
appropriate port and fluid bled from the other ports.
This causes the mandrel and piston to move in the reverse
direction and the second stage cylinder to move likewiss,
thus moving the sealing nipple e1nd mandrel from the
wellhead array. The apparatus will now be in the
position to be removed from the well.
Brief Description Of The Drawinqs
The invention is illustrated by way of example only
in the accompanying drawings in which:
15 FIG. 1 is an elevation view, partly in section, of
the existing McEvoy type wellhead isolation tool on a
simplified wellhead in the position prior to moving the
mandrel into the wellhead by hydraulic means; and
FIG. 2 is an elevation view, partly in section, of
the improved wellhead isolation tool on a simplified
wellhead in the position prior to moving the mandrel by
hydraulic means; and
FIG. 3 is an elevation view, partly in section, of
the tool in FIG. 2 after hydraulic means have been used
to move the mandrel and the first stage cylinder into the
second stage cylinder. The mandrel and sealing nipple
have been moved into the well.
Description Of The Existinq Embodimen~
Referring to Figure 1, the tool illustrated gener-
ally includes a hollow mandrel 11 with attached piston13, an attached nipple 15 with resilient sealing means 16
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and a plug valve 7, a lockdown flange 4; a matched
lockdown ring 8 on the double ended hydraulic c~linder 33
which utilizes the mandrel as the rod, appropriate
packing and sealing rings, flu:id ports 25 and 26. Travel
stops 14 are spaced inside the cylinder. ~he plug valve
will be designated the top of the tool. The wellhead
valve 12 and gate 18 are not part of the tool. In
operation, the gate of the wel:Lhead valve is opened as
seen in Figure 3, hydraulic fluid is introduced into
port 26 and bled from port 25. The action on the piston
is to move it and the attached mandrel and sealing nipple
in a downward direction until the piston reaches the
lower travel stop. The lockdown flange and thus the plug
valve and sealing nipple are now in the position noted by
the broken lines. The mandrel is locked in place with
bolts at the lockdown plates and is ready for use. When
the well servicing has been completed, the nipple and
mandrel are retracted out of the well by actions in the
reverse of the insertion order. The wellhead valve is
closed and the tool removed. It is shown that the height
of the plug valve above the wellhead valve when in the
operating position i~ equal to the length of the cylinder
plus mandrel connection to the plug valve. This total
height depends on the length of mandrel required in the
tree saver. It i# this overall height which creates
problems for operating personnel and sideways æwaying
movement during well servicing.
Description of the Preferred Embodiment
Referring to Figure 2 and 3, the tool illustrated
generally includes a hollow mandrel 11 with a connection
2 for the plug valve 7, a lockdown flange ~, a piston 13
attached to the mandrel in a set position, and a nipple
15 with its resilient sealing material 16. The mandrsl
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and piston are enclosed by ths concentric first stage
cylinder 3 with upper and lower restraining rings 5
spaced at both ends, the fluid port 26, the appropriate
seals 19, and the shoulder 17 with its seals 19. This
assembly is guided and confined in the second stage
cylinder 1 in a concentric and sliding way by the
shoulder 22 and its seal 19, the aforementioned shoulder
17 and the upper and lower restraining rlngs 14. An
annular space 21 i formed by the fit of cylinder 1 in 3.
This second stage cylinder features a lockdown ring 8
configured to match the lockdown plate 4 with circum-
ferentially sp~ed locking bolts 6, upper fluid port 24,
lower fluid port 25 and the appropriate seal 19. The
second stags cylinder is attached in a remo~eable or
solid way to the mounting adapter 10. The mounting
adapter allows the complete apparatus to be attached to a
wellhead valve 12 with its gate 18 and thus to the
wellhead 20 and the associated casing 23. In the
description of the operation, the plug valve will be
considered the top, the wellhead the bottom of the
Figures. With the tool in the position shown in Figure
2, the wellhead valve gate is opened. Hydraulic fluid is
pumped into ports 26 and 24 with port 25 open to the
hydraulic fluid tank. The piston and mandrel move in a
downward direction until the piston reaches the first
stage lower restraining ring. Simultaneously, the fluid
entering the ~l~ular space 21 will move the piston formed
by the shoulder 17 on the first stage cylinder down until
it reaches th~ lower restraining ring in the second stage
cylinder. The m~ndrel will now be extended into the well
casing as sh~n in Figure 3. The ports 26, 25 and 24 are
now closed. The locking plate is attached to the locking
ring by the lDckiny bolts. The tree saver is now in
position to have fluid pumped through the mandrel and
into the well casing.
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When the well servicing is completed, the tree
saver is removed in the following way. The locking bolts
are removed, hydraulic fluid is introduced into the port
at 25, ports 2~ and 26 are allowed to bleed hydraulic
fluid back to the tank. The mandrel and first stage
cylinder move upwards in relation to the second stage and
thus the sealing nipple on the end of the mandrel is
moved out of the wellhead array. The gate in the
wellhead valve is closed and the tool may then be
removed. During some of these operations, well pressure
and other conditions may dictate different sequences of
operations, but these are a part of the operational
techniques of the tool and not part of the wellhead
isolation tool. I
Those skilled in the art will appreciate that
various features, characteristics and advantages of the
present invention have been set forth herein or are
readily reali7.ahle from the detailed description of the
preferred embodiments. However, the disclosure is
illustrative and various changes may be made while
utilizing the principles of the present invention and
falling within the scope of the invention as expressed in
the appended claims.
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