Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION:
Perforating gun brake.
NAME ( S ) OF INVENTOR ( S )
Michael Hillyer
FIELD OF THE INVENTION
The present invention relates to a perforating gun brake.
BACKGROUND OF THE INVENTION
Perforating guns are used to create perforations in a well
casing so that a fluid can flow from an underground formation
into the interior of the well casing and thence be withdrawn
from a well. There are several types of perforating gun that
can be lowered into a well on a wireline, detonated
electronically via the wireline, and then withdrawn from the
well.
When the perforating gun is detonated, gases in the
annulus caused by the detonation tend to propel the perforating
gun up the well casing. In addition, upon a well casing being
perforated, fluids (both liquids and gas) from the formation
rapidly enter the well casing through the perforations. As the
fluids enter the well casing they also tend to move the
perforating gun up the well bore. To counter this action, a
perforating gun brake can be used.
Mohaupt in United States Patent 4,852,647 describes a
perforating gun brake including gripping feet that are
maintained in engagement with the well casing by means of
springs . When the charge in the perforating gun is detonated,
shear pins retaining the springs in a compressed position are
sheared, the springs are then freed to expand, and the gripping
feet are thereby deployed. The gripping feet are unable to
retract to the disengaged position against the force of the
springs in the expanded position, and so remain in engagement
with the well casing as the perforating gun brake is withdrawn
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from the well. Blimke in United States Patent 5,700,968 that
issued in 1997 describes a perforating gun brake that also uses
gripping feet to engage a well casing. As with the Mohaupt
reference, when the charge in the perforating gun is detonated,
shear pins retaining springs in a compressed position are
sheared. The springs then expand to deploy gripping feet.
Detonation of a second explosive charge within the perforating
gun brake is required to release a hydraulic retaining collar.
This releases tension on the spring that deploys the gripping
feet and permits the gripping feet to move back into a
retracted position as the perforating gun brake is removed from
the well casing. It will be understood that the perforating
gun brakes described by Mohaupt and Blimkie both must be
refurbished after each use.
SU1~IARY OF THE INVENTION
What is required is a perforating gun brake that is simple
to operate and that does not require replacement or repair of
parts after each use.
According to the present invention there is provided a
perforating gun brake which includes a first body having an
axis. Several gripping feet are provided each having a pivot
end and a remote end. The pivot end is pivotally mounted to
the first body. The gripping feet are movable between a stored
position substantially parallel to the axis of the first body
and an engaging position extending outwardly at an angle in
relation to the first body. A second body is coupled to and
axially movable relative to the first body. A wedge member is
carried by the second body. The wedge member exerts a force
upon the remote end of the gripping feet upon movement of the
second body to force the gripping feet outwardly into the
engaging position.
With the perforating gun brake, as described above, the
force of detonation drives the second body toward the first
body. As the second body moves toward the first body, the
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wedge member forces the gripping feet into the engaging
position. Once the force of the detonation has subsided, the
weight of the perforating gun pulls the second body away from
the first body. This disengages the wedge member to permit the
gripping feet to return to the stored position in preparation
for withdrawing the perforating gun brake from the well casing.
Although beneficial results may be obtained through the
use of the perforating gun brake, as described above, even more
beneficial results may be obtained when a spring is positioned
to exert a biasing force upon the second body to bias the
second body away from the first body. The additional force
of the spring assists the gripping feet to release.
There are various configurations that can accomplish the
above described objectives. Beneficial results have been
obtained by providing the first body with an interior bore and
having the second body telescopically received in the interior
bore of the first body.
There are, similarly, various configurations of wedge
member that can be used. Beneficial results have been obtained
through the use of a conical wedge member.
Although beneficial results may be obtained through the
use of the perforating gun brake, as described above, even more
beneficial results may be obtained when an expandable retainer
is positioned about the gripping feet to exert a biasing force
upon the gripping feet to bias the gripping feet into the
stored position. The force of the expandable retainer
prevents unplanned outward movement of the gripping feet. The
use of the expandable retainer is especially beneficial when
the perforating gun is to be used in a well that is not
vertical, as the force of gravity acting on a freely pivoting
gripping foot may cause it to fall away from the perforating
gun brake toward the well casing as the perforating gun is
lowered in position.
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BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more
apparent from the following description in which reference is
made to the appended drawings, wherein:
FIGURE 1 is a side elevation view, in section, of a
perforating gun brake constructed in accordance with the
teachings of the present invention, prior to detonation.
FIGURE 2 is a side elevation view, in section of the
perforating gun brake illustrated in FIGURE l, upon detonation.
FIGURE 3 is a side elevation view, in section of the
perforating gun brake illustrated in FIGURE 1, after the forces
associated with detonation have subsided.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, a perforating gun brake
generally identified by reference numeral 10, will now be
described with reference to FIGURES 1 through 3.
Referring to FIGURE l, perforating gun brake 10 includes
a first body 12 and a second body 14. First body 12 has an
axis 15, an exterior surface 16, a first end 18, a second end
20, and an interior bore 22 accessible from second end 20 of
first body 12. A wireline attachment 24 is at first end 18 of
first body 12 whereby first body 12 is suspended from a
wireline 26. Each of several gripping feet 28 has a pivot end
and a remote end 32. The several gripping feet 28 are
pivotally mounted at pivot end 30 to second end 20 of first
body 12. Referring to FIGURES 1 and 2, each of the gripping
feet 28 is movable between a stored position substantially
30 parallel to first body 12, illustrated in FIGURE 1, and an
engaging position extending outwardly at an angle in relation
to axis 15 of first body 12, illustrated in FIGURE 2.
Referring to FIGURE 1, an expandable retainer 33 normally
retains gripping feet 28 in the stored position parallel to
first body 12. Expandable retainer 33 can be in the form of
a rubber strap.
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Second body 14 has a first end 34, a second end 36, and
a cylindrical central portion 37. First end 34 and central
portion 37 of second body 14 are telescopically received in
interior bore 22 at second end 18 of first body 12. Gripping
5 feet 28 are retained in position against a surface 39 of
central portion 37 of second body 14 by expandable retainer 33
when in the stored position. Second body 14 is telescopically
movable relative to first body 12 between an extended position,
illustrated in FIGURE 1, and a compressed position, illustrated
in FIGURE 2. A perforating gun attachment 38 is at second end
36 of second body 14, whereby a perforating gun 40 is attached
to second body 14. Electrical wiring extends through a conduit
41 from wireline attachment 24 at first end 18 of first body
12 to perforating gun attachment 38 at second end 36 of second
body 14, whereby an electrical signal to trigger detonation is
transmitted via wireline 26 secured to wireline attachment 24
to perforating gun 40 secured to perforating gun attachment 38.
A conical wedge member 42 is carried by central portion
37 at the end of central portion 37 toward second end 36 of
second body 14. Wedge member 42 engages remote end 32 of
gripping feet 28. Referring to FIGURE 2, when perforating gun
40 detonates, explosive charges 50 explode radially, as shown
by arrows 52, causing perforations 54 in a well casing 56.
Detonation causes movement urging perforating gun brake 10 up
the well. This force is first exerted upon and causes movement
of second body 14 toward first end 18 of first body 12. Upon
movement of second body 14 as result of detonation of
perforating gun 40, wedge member 42 forces gripping feet 28
outwardly, against a retaining force from expandable retainer
33, from the stored position parallel to axis 15 of first body
12 and into the engaging position. An upward force on
perforating gun 40 is caused by gases in the annulus caused by
the detonation, shown by open arrows 58, but the force is
prevented from forcing perforating gun 40 a large distance up
well casing 56 by the gripping action of remote ends 32 of
gripping arms 28 on well casing 56.
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Referring to FIGURES 1 and 3, a spring 44 disposed within
interior bore 22 of first body 12 exerts a biasing force upon
first end 34 of second body 14 to bias second body 14 away from
f first end 18 of f first body 12 . Referring to FIGURE 3 , when the
forces unleashed by detonation of perforating gun 40 subside,
second body 14 is biased away from first end 18 of first body
12, moving wedge member 42 from away from gripping feet 28,
illustrated in FIGURE 2, and permitting gripping feet 28 to be
disengaged from well casing 56 and return to the stored
position, illustrated in FIGURE 3. Expandable retainer 33
exerts a force axially inward upon gripping feet 28, urging
gripping feet 28 back to the stored position.
It will be apparent to one skilled in the art that
modifications may be made to the illustrated embodiment without
departing from the spirit and scope of the invention as
hereinafter defined in the Claims.
