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 OF INVENTOR:
Ross Arthur Blimke
FIELD OF THE INVENTION
The present invention relates to a perforating gun brake
and, in particular, a perforating gun brake used when the well
is underbalanced.
R~7ROUND OF THE INVENTION
20Perforating guns are used to create perforations in a well
casing so that oil and gas can flow from an underground
formation into a well bore. A common type of perforating gun
is lowered into a well on a wireline and then triggered
electrically via the wireline.
A well is said to be "underbalanced" when the pressure
within the formation is greater than the pressure within the
well. When the well casing is perforated in an underbalanced
well, there is a rapid influx of fluids into the well bore.
This is viewed as desirable as it provides a good clean out of
drilling mud, formation sand, cement residue and other matter
which may otherwise clog the formation and retard the flow of
gas and oil. However, as fluids enter the well casing they
tend to drive the perforating gun up the well bore. When this
occurs the wireline often gets tangled around the perforating
gun or damaged. A damaged wireline is prone to breakage when
pulling the perforating gun to surface, especially if the
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perforating gun becomes temporarily stuck in the well bore as
a result of being pulled to surface at an angle due to tangles
in the wireline. The wireline is a braided line. As strands
of wire break, a mass of wire strands is created. The
perforating gun is inserted into the well bore through a
lubricator which is positioned above the blind rams of the Blow
out Preventer. The lubricator has a rubber pressure fitting
through which the wireline extends. The pressure fitting
tightly engages the rubber to squeeze and deform it to maintain
some pressure containment notwithstAn~ing the fact that the
wireline extends through it. When strands of the wireline are
broken and tangled forming a mass, it is difficult, and
sometimes impossible, to pull the perforating gun through the
blow out preventer to a position where the blind rams can be
closed and the perforating gun removed. In such cases, there
is no alternative than to cut the wireline and use a fishing
tool to subsequently remove the perforating gun from the well.
SU~ARY OF THE INVENTION
What is required is a perforating gun brake that will hold
the perforating gun in position until the initial surge of
fluids into the well bore passes and the pressure in the
wellbore is substantially equal to formation pressure.
According to the present invention there is provided a
perforating gun brake which includes a tubular housing, an
annular piston and a mandrel. The tubular housing has an
exterior surface, a first end, a second end, and an interior
surface that defines an interior bore that extends from the
first end to the second end. The first end of the tubular
housing includes coupling means for coupling with a perforating
gun. The annular piston has an exterior surface, a first end,
a second end, and an interior bore that extends between the
first end and the second end. The first end of the annular
piston is telescopically received in the interior bore at the
second end of the tubular housing. The mandrel has an exterior
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surface, a first end, a second end, and a wire conduit that
extends between the first end and the second end. The mandrel
extends through the interior bore of the annular piston into
the interior bore of the tubular housing. The mandrel serves
as a guide for the telescopic movement of the annular piston.
An annular hydraulic fluid chamber is formed in the interior
bore of the tubular housing between the exterior surface of the
mandrel and the interior surface of the tubular housing. The
hydraulic fluid chamber has a first end and a second end.
First sealing means are positioned at the first end of the
hydraulic fluid chamber between the exterior surface at the
first end of the mandrel, and the interior surface of the
tubular housing. Second sealing means are positioned at the
second end of the hydraulic fluid chamber between the exterior
surface of the annular piston and the interior surface of the
tubular housing. Piston biasing means are provided on the
mandrel, exerting a biasing force urging the annular piston
toward the first end of the mandrel. The movement of the
piston along the mandrel is resisted by hydraulic fluid in the
hydraulic fluid chamber. An electrically actuatable flow means
is positioned on the first sealing means. Several gripping
members are pivotally mounted to the exterior surface of the
annular piston spaced from the first end. The gripping members
are movable between a retracted position substantially parallel
to the exterior surface and a deployed position extending
outwardly at an angle from the exterior surface. Gripping
members deploying means are mounted to the exterior surface of
the mandrel. The gripping members deploying means are pressure
responsive, such that the gripping members deploying means
exerts a biasing force to move the gripping members to the
deployed position in response to pressure exerted upon
detonation of the perforating gun. A pair of wires extend
through the wire conduit from the second end to the first end
of the mandrel. One wire of the pair of wires is connected to
the electrically actuatable flow means. A direct current
positive/negative firing module is connected to the pair of
wires. A positive electric pulse or a negative electric pulse
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can be sent through one wire of the pair of wires to trigger
the perforating gun. The other form of electric pulse can be
sent through another wire of the pair of wires to trigger the
electrically actuatable flow means positioned on the first
sealing means. Upon detonation of the perforating gun the
pressure responsive biasing means moves the gripping members
to the deployed position. The gripping members remain in the
deployed position until the electrically actuatable flow means
is triggered to allow hydraulic fluid to escape from the
hydraulic chamber. As the hydraulic chamber is emptied of
hydraulic fluid the annular piston moves telescopically into
the tubular housing and is urged by the piston biasing means
toward the first end of the mandrel. The movement of the
annular piston along the mandrel moves the gripping members
away from the gripping members deploying means allowing the
gripping members to return to the retracted position.
The perforating gun brake, as described above, deploys
gripping members to maintain its position during the initial
surge of fluids into the well bore. The gripping members are
maintained in their deployed position the pressure in the well
bore is substantially equal to formation pressure. The time
for this to occur varies with the application. Once pressure
equalization has occurred, the flow means can be electrically
actuated to allow sufficient hydraulic fluid to escape to cause
the gripping members to return to the retracted position. The
preferred form of electrically actuated flow means is a charge
which can be detonated to remove an aluminum pin. The preferred
means for deploying the gripping members includes a collar
biased by a spring. The collar is secured to the exterior
surface of the mandrel by screw-form shear pins with the spring
in compression. The force associated with the detonation of
the perforating gun serves to shear the shear pins whereby the
collar is pushed into engagement with the gripping members by
the spring and moves the gripping members to the deployed
position. The deploying collar holds the gripping members in
their deployed position until the annular piston moves along
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the mandrel; positioning the gripping members out of reach of
the deploying collar. This can only occur when hydraulic fluid
has been released from the hydraulic chamber by the removal by
detonation of all or part of the first seal assembly. It is
preferred that biasing means be provided to urge the gripping
members back into the retracted position.
BRIEF D~PTPTION 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.
FIGURE 2 is a side elevation view, in section, of the
perforating gun brake illustrated in FIGURE 1, secured to a
perforating gun and with gripping members in a deployed
position.
FIGURE 3 is a side elevation view, in section, of the
perforating gun brake illustrated in FIGURE 1, secured to a
perforating gun and with gripping members back in a retracted
position after deployment.
DET~JT-~n D--CPTPTION OF THE rK~nK~v 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 1, perforating gun brake 10 includes
a tubular housing 12, an annular piston 14 and a mandrel 16.
The tubular housing 12 having an exterior surface 18, a first
end 20, a second end 22, and an interior surface 24 that
defines an interior bore 26 that extends from first end 20 to
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second end 22. First end of tubular housing 12 includes a
coupling 28 for coupling with a perforating gun (not shown in
FIGURE 1). In order to facilitate assembly, tubular housing
12 is fabricated from three threadedly connected components
12a, 12b, 12c. Components 12a, 12b, 12c, are connected at
threaded connections 13. Each threaded connection is sealed
by O ring seals 15. Piston 14 has an exterior surface 30, a
first end 32, a second end 34, and an interior surface 36 which
defines an interior bore 38 that extends between first end 32
and second end 34. First end 32 of annular piston 14 is
telescopically received in interior bore 26 at second end 22
of tubular housing 12. Mandrel 16 has an exterior surface 40,
a first end 42, a second end 44, and a wire conduit 46 that
extends between first end 42 and second end 44. Mandrel 16
extending through interior bore 38 of annular piston 14 into
interior bore 26 of tubular housing 12. Mandrel 16 serves as
a guide for the telescopic movement of annular piston 14, as
will be hereinafter further described. In order to facilitate
assembly, mandrel 16 is fabricated from three threadedly
connected components 16a, 16b, and 16c. Components 16a, 16b,
16c, are connected at threaded connections 17. Each threaded
connection is sealed by O ring seals 19. An annular hydraulic
fluid chamber 48 is formed in interior bore 26 of tubular
housing 12 between exterior surface 40 of mandrel 16 and
interior surface 24 of tubular housing 12. Hydraulic fluid
chamber 48 has a first end 50 and a second end 52. A first
sealing assembly, generally indicated by reference numeral 54,
is positioned at first end 50 of hydraulic fluid chamber 48
between exterior surface 40 at first end 42 of mandrel 16, and
interior surface 24 of tubular housing 12. In FIGURE 1, first
sealing assembly 54 includes a fitting 56 to which is secured
a hollow aluminum pin-like closure 58. A one way valve 60 is
provided in order to fill hydraulic fluid chamber 48 with
hydraulic fluid. A second sealing assembly, generally
indicated by reference numeral 62, is positioned at second end
52 of hydraulic fluid chamber 48 between exterior surface 30
of annular piston 14 and interior surface 26 of tubular housing
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12. In FIGURE 1, sealing assembly 62 includes a pair of O ring
seals 64. A further pair of O ring seals 65 provide a seal
between interior surface 36 of annular piston 14 and exterior
surface 40 of mandrel 16. A raised shoulder 66 is provided on
exterior surface 40 of mandrel 16. A piston biasing spring 68
is provided which encircles mandrel 16. Piston biasing spring
68 has a first end 70 and a second end 72. First end 70
engages second end 34 of annular piston 14. Second end 72
engages shoulder 66. Piston biasing spring 68 exerting a
biasing force which urges annular piston 14 toward first end
42 of mandrel 16. This movement is resisted, however, by the
presence of hydraulic fluid in hydraulic fluid chamber 48. An
electrically detonatable explosive charge 74 is positioned on
first sealing assembly 54 and serves an electrically actuatable
means for permitting flow of hydraulic fluid from hydraulic
fluid chamber 48. Upon detonation of explosive charge 74,
hollow aluminum pin-like closure 58 is removed. Several
gripping members 76 are pivotally mounted to exterior surface
30 at second end 34 of annular piston 14. Gripping members 76
are movable between a retracted position and a deployed
position. In the retracted position, gripping members 76 are
positioned substantially parallel to exterior surface 30, as
illustrated in FIGURE 1. In the deployed position, gripping
members 76 extend outwardly at an angle from exterior surface
30, as illustrated in FIGURE 2. Referring to FIGURE 1, each
of gripping members 76 has a first end 78 and a second end 80.
Gripping feet 82 are positioned at second end 80. A pivot pin
84 is spaced from first end 78. A retracting spring 86 is
provided having a first end 88 and a second end 90. Retracting
spring 86 is placed in compression with first end 88 engaging
exterior surface 30 of annular piston 14 and second end 90
engaging first end 78 of gripping member 76. Retracting spring
86 provides a force which pivots gripping member 76 to the
retracted position. A gripping members deploying collar 92 is
slidably mounted to exterior surface 40 of mandrel 16.
Deploying collar 92 is biased by a spring 94. Spring 94 has
a first end 96 and a second end 98. First end 96 exerts a
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force upon deploying collar 92. Second end 98 exerts a force
upon a fixed ret~ining collar 100 on exterior surface 40 of
mandrel 16. Deploying collar 92 is secured to exterior surface
40 of mandrel 16 by screw-form shear pins 102, with spring 94
placed in a compressed state so that it will release its stored
energy upon shear pins 102 being sheared. An insulated pair
of wires 104 and 106 extend through wire conduit 46 from second
end 44 to first end 42 of mandrel 16. Wires 104 and 106 are
connected to a diode 108 which serves as a direct current
positive/negative firing module. Wire 104 serves as a D.C.
positive electric wire. Wire 106 serves as a D.C. negative
electric wire. Diode 108 is connected to an electrical contact
pigtail 110 at second end 44 of mandrel 16, which that permits
connection to a wireline extending to surface (not shown).
D.C. positive electric wire 104 is adapted to be connected to
a perforating gun, as will hereinafter be further described.
D.C. negative electric wire 106 is connected to electrically
detonatable explosive charge 74. A port plug 107 is provided
to allow access for the purpose of making this connection.
Referring to FIGURES 2 and 3, perforating gun brake 10 is
illustrated connected to a perforating gun assembly, generally
indicated by reference numeral 112. Perforating gun assembly
112 includes a quick change connection 114 with a quick change
electric terminal 116, a perforating gun top sub 118, and a
perforating gun 120.
The use and operation of perforating gun brake 10 will now
be described with reference to FIGURES 1 through 3. Referring
to FIGURES 2 and 3, coupling 28 is used to connect perforating
gun brake 10 to quick change connection 114 of perforating gun
assembly 112. D.C. Positive electric wire 104 is connected to
electric terminal 116 of perforating gun assembly 112.
Perforating gun brake is then lowered on a wireline (not shown)
to the position within a well casing where perforation is
desired. Once perforating gun 120 is in position, a positive
electric pulse is sent through the wireline. Once the electric
pulse reaches diode 108 it is routed along D.C. positive
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electric wire 104 and used to trigger perforating gun 120. The
detonation of perforating gun 120 provides a jarring impact to
perforating gun brake 10 which serves to shear pins 102. The
shearing of shear pins 102 leaves deploying collar 92 free to
travel along mandrel 16 and releases the stored energy in
spring 94. Spring 94 pushes deploying collar 92 along mandrel
16. Deploying collar 92, in turn, pushes gripping members 76
outwardly to the deployed position, illustrated in FIGURE 2.
Gripping members 76 remain held in the deployed position by
deploying collar 92. When it is intended that gripping members
76 should be released, a negative electric pulse is sent
through the wireline. When the electric pulse reaches diode
108 it is routed through D.C. negative electric wire 106 to
trigger the electrically detonatable explosive charge 74,
positioned on first sealing assembly 54. Hollow aluminum pin-
like closure 58 is blown out of position upon explosive charge
74 being detonated, allowing hydraulic fluid to escape from
hydraulic chamber 48. As hydraulic chamber 48 is emptied of
hydraulic fluid, piston 14 is free to move telescopically into
interior bore 26 of tubular housing 12. Piston 14 is urged by
piston biasing spring 68 toward first end 42 of mandrel 16;
this movement, which was formerly resisted by hydraulic fluid
in hydraulic chamber 48, is unopposed. Referring to FIGURE 3,
movement of annular piston 14 along mandrel 16, moves gripping
members 76 away from deploying collar 92, which was holding
them in the deployed position. Once free of deploying collar
92, the force exerted by retracting spring 86 is able to pivot
gripping members 76 back to the retracted position.
It will be apparent to one skilled in the art the braking
action provided by perforating gun brake 10. In particular,
it will be apparent that perforating gun brake 10 prevents a
premature release of gripping members 76, as gripping members
76 are held in the deployed position until an appropriate
signal is sent to detonate explosive charge 74. It will finally
be apparent to one skilled in the art that modifications may
be made to the illustrated embodiment without departing from
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the spirit and scope of the invention as hereinafter defined
in the Claims.
