Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: PERFORATING GUN WITH SWITCH CARTRIDGE
INVENTOR(S): LAGRANGE, Timothy E.; WOOD, Jeffrey D.; and
GARTZ, Jeffrey
TECHNICAL FIELD
[0002] The present disclosure relates to devices and method for
perforating a subterranean formation.
BACKGROUND
[0003] Hydrocarbons, such as oil and gas, are produced from cased
wellbores intersecting one or more hydrocarbon reservoirs in a formation.
These
hydrocarbons flow into the wellbore through perforations in the cased
wellbore.
Perforations are usually made using a perforating gun that is generally
comprised of a
steel tube "carrier," a charge tube riding on the inside of the carrier, and
with shaped
charges positioned in the charge tube. The gun is lowered into the wellbore on
electric
wireline, slickline, tubing, coiled tubing, or other conveyance device until
it is adjacent
to the hydrocarbon producing formation. Thereafter, a surface signal actuates
a firing
head associated with the perforating gun, which then detonates the shaped
charges.
Projectiles or jets formed by the explosion of the shaped charges penetrate
the casing
to thereby allow formation fluids to flow through the perforations and into a
production
string.
[0004] In certain instances, it may be desirable to use switches to
selectively fire guns in a perforating tool. The present disclosure addresses
the need
to house or otherwise accommodate such switches in a downhole tool.
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SUMMARY
[0005] In aspects, the present disclosure provides an apparatus for use
in a
wellbore. The apparatus may include a first gun assembly and a second gun
assembly.
The first gun assembly may have: a first charge tube having a longitudinal
axis defined
by an axis that passes through centers of opposing ends of the charge tube; a
first
detonator cord disposed along the first charge tube, a first signal-conveying
wire
disposed along the first charge tube, a first coupler affixed to an end of the
first charge
tube, the first coupler including: a receptacle receiving an end of the
detonator cord,
and a coupler contact electrically connected to the first signal conveying
wire, and a
first cartridge assembly including: a body having a cavity and a cradle, an
input contact
positioned on the body and electrically coupled to the coupler contact, a
throughput
contact positioned on the body, a switch disposed in the cavity, the switch
being
electrically connected to the input contact and the throughput contact, and an
initiating
element disposed in the cradle and electrically connected to the switch, the
initiating
element being energetically coupled to the end of the detonator cord in the
receptacle,
wherein the switch and the initiating element at least partially overlap along
the
longitudinal axis; and a first signal transfer assembly electrically coupled
to the
throughput contact.
[0006] The second gun assembly may have: a second charge tube, a second
detonator cord disposed along the second charge tube, a second signal-
conveying wire
disposed along the second charge tube, the second signal-conveying wire being
electrically coupled to the first contact assembly, a second coupler affixed
to an end of
the second charge tube, the second coupler including: a receptacle receiving
an end of
the second detonator cord, and a coupler contact electrically connected to the
second
signal conveying wire; and a second cartridge assembly including: a body
having a
cavity, an input contact electrically positioned on the body and coupled to
the second
coupler contact, a throughput contact positioned on the body, a switch
disposed in the
cavity, the switch being electrically connected to at least the input contact,
and an
initiating element disposed in the cavity and electrically connected to the
switch, the
initiating element being energetically coupled to the end of the second
detonator cord
in the receptacle.
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100071 In
aspects, the present disclosure also provides an apparatus for use with a
gun assembly having charge tube with a longitudinal axis defined by an axis
that passes
through centers of opposing ends of the charge tube, a detonator cord disposed
along
the first charge tube, and a signal-conveying wire disposed along the first
charge tube.
The apparatus may include: a switch having an initiating element; a coupler
configured
to be received at an end of the first charge tube, the first coupler
including: a receptacle
receiving an end of the detonator cord, and a coupler contact electrically
connected to
the first signal conveying wire; and a cartridge assembly engagable with the
first
coupler, the cartridge assembly including: a body having a cavity configured
to receive
the switch and a cradle configured to receive the initiating element, an input
contact
positioned on the body, and a throughput contact positioned on the body,
wherein
engaging the cartridge assembly with the coupler simultaneously electrically
couples
the input contact to the coupler contact and energetically couples the
initiating element
with the end of the detonator cord, and wherein the switch and the initiating
element
are positioned in a parallel, side-by-side arrangement to at least partially
overlap along
the longitudinal axis.
[0008] In
aspects, the present disclosure provides a perforating gun. The
perforating gun may include a carrier and at least one bulkhead. The carrier
may have
at least two sections connecting to one another at a connection. There are no
sealing
members between the two sections at the connection. The bulkhead is disposed
within
the carrier and has at least one sealing member forming a seal between the
bulkhead
and an inner surface of the carrier.
[0009] It should
be understood that certain features of the invention have been
summarized rather broadly in order that the detailed description thereof that
follows
may be better understood, and in order that the contributions to the art may
be
appreciated. There are, of course, additional features of the invention that
will be
described hereinafter and which will in some cases form the subject of the
claims
appended thereto.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For detailed understanding of the present disclosure,
references
should be made to the following detailed description taken in conjunction with
the
accompanying drawings, in which like elements have been given like numerals
and
wherein:
FIG. 1 schematically illustrates a side sectional view of a perforating gun
with
a switch cartridge according to one embodiment of the present disclosure;
FIG. 2 isometrically illustrates the FIG. 1 embodiment without a carrier;
FIG. 3 schematically illustrates a side sectional view of portion of the FIG.
1
embodiment;
FIGS. 4A-B illustrate a coupler according to one embodiment of the present
disclosure;
FIGS. 5A-B illustrate one embodiment of a cartridge assembly according to
the present disclosure;
FIGS. 6A-B schematically illustrate prior art switches;
FIG. 7 illustrates a side sectional view of an interface between a bulkhead
and
a cartridge assembly according to one embodiment of the present disclosure;
FIG. 8 illustrates a side sectional view of an interface between a coupler and
a
cartridge assembly in accordance with one embodiment of the present
disclosure;
FIG. 9 schematically illustrates a side sectional view of a perforating gun
with
a switch cartridge according to another embodiment of the present disclosure;
FIG. 10 isometrically illustrates the FIG. 9 embodiment without a carrier;
FIG. 11A-C illustrate another coupler according to the present disclosure;
FIGS. 12A-B illustrate another embodiment of a cartridge assembly according
to the present disclosure;
FIG. 13 illustrates a side sectional view of an interface between a bulkhead
and the FIGS. 12A-B cartridge assembly according to one embodiment of the
present
disclosure; and
FIG. 14 illustrates a side view of another arrangement of the FIG. 9
perforating
tool according to one embodiment of the present disclosure.
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DETAILED DESCRIPTION
[0011] The present disclosure relates to devices and methods for
perforating a
formation intersected by a wellbore. The present disclosure is susceptible to
embodiments of different forms. There are shown in the drawings, and herein
will be
described in detail, specific embodiments of the present disclosure with the
understanding that the present disclosure is to be considered an
exemplification of the
principles of the disclosure, and is not intended to limit the disclosure to
that illustrated
and described herein.
[0012] Referring to FIG. 1, there is shown one embodiment of a
perforating
tool 100 in accordance with the present disclosure. The perforating tool 100
may
include a first gun assembly 110 and a second gun assembly 112. Each gun
assembly
110, 112 includes a carrier 111 that is shaped to receive a charge tube 114.
Each gun
assembly 110, 112 also includes one or more shaped charges 116 fixed within
the
charge tube 114. To enable selectively firing the gun assemblies, a select
fire system
may be used in which a cartridge assembly 200a is programmed to only fire the
first
gun assembly 110 and a cartridge assembly 200b is programmed to only fire the
second gun assembly 112. While two gun assemblies 110, 112 are shown, three or
more gun assemblies and associated cartridge assemblies may be used.
[0013] Generally, the perforating tool 100 is lowered into a wellbore
(not
shown) on electric wireline, slickline, tubing, coiled tubing, or other
conveyance
device (not shown) until it is adjacent to the hydrocarbon producing formation
(not
shown). Thereafter, a surface signals are used to actuate the gun assemblies
110, 112,
which then detonate the associated shaped charges. Projectiles or jets formed
by the
explosion of the shaped charges penetrate a casing (now shown) lining a
wellbore (not
shown) to thereby allow formation fluids to flow through the perforations and
into a
production string (not shown). Illustrative arrangements according to the
present
disclosure for enabling select firing of the gun assemblies 110, 112 are
described
below.
[0014] Referring now to FIG. 2, a gun assembly 110 in accordance with
one
embodiment of the present disclosure is shown in an isometric view. For
clarity, the
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carrier 111 (FIG. 1) is not shown. In this embodiment, the charge tube 114 may
be
formed as a tubular member having a first end 118, a second end 120, and an
interior
bore 122. The charge tube 114 provides a receiving structure in which the
shaped
charges 116, a bulkhead 130a, a coupler 160a, and the cartridge assembly 200a
(FIG.
1) are secured. The bulkhead 130a may be fixed to the first end 118 with a
suitable
fastening element 132, such as a screw.
[0015] The charge tube 114 may include a first opening 148 through
which the
shaped charge 116 may be inserted into the interior bore 122 and a second
opening
150 through which the coupler 160a may be inserted into the interior bore 122.
Depending on the configuration of the coupler 160a a third opening 152 (FIG.
3) may
be present through which a portion of the coupler 160a may project out of the
charge
tube 114.
[0016] Referring to FIGS. 1 and 3, the bulkhead 130a acts a structural
barrier
between sections of the perforating tool 100. In embodiments, the bulkhead
130a may
be a disk-like member having an outer circumferential surface 134 (Fig. 3) and
a
passage 136 (Fig. 3). The bulkhead 130a may include an alignment key 143 fixed
on
the outer surface 134 that is complementary to a keyway 145 (FIG. 1) formed
along
an inner surface 147 of the carrier 111. The keyway 145 may be a slot, groove,
or
other similar surface depression that has a specified angular orientation
relative to one
or more features of the perforating gun 110, e.g., a scallop 149 or another
reduced thin
wall section of the carrier 111. Thus, upon the alignment key 143 entering the
keyway
145, the shaped charge 116, which has a fixed angular alignment relative to
the
alignment key 143, can be aligned with the scallop 149.
[0017] As shown in FIG. 1, the charge tube 114 is sealed between the
opposing
bulkheads 130a,b inside the carrier 111. In one arrangement, one or more seals
138
may be disposed on the outer circumferential surface 134. The seals 138
provide an
interior of the carrier 111 that is fluid-tight. The passage 136 of the
bulkhead 130a is
shaped to receive an signal transfer assembly 146a. The signal transfer
assembly 146a
is configured to transmit signals across the bulkhead 130a or other structural
barriers
in the perforating tool 100 (FIG. 1). The signal transfer assembly 146a also
has seals
139 to form a fluid-tight seal in the passage 136. An signal transfer assembly
146b is
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configured to transmit signals across the bulkhead 130b and is generally
similar to the
signal transfer assembly 146a. The bulkhead 130b may have the same
construction as
the bulkhead 130a.
[0018] Referring to Figs. 3 and 4 A,B, there is shown a coupler 160a
in
accordance with one embodiment of the present disclosure. The coupler 160a
provides
two operative connections when engaged with the cartridge assembly 200a (FIG.
1).
The first connection is an energetic connection between a detonator cord 174
and the
cartridge assembly 200a (FIG. 1). As used herein, an "energetic connection" or
"energetic coupling" is a connection or coupling that enables the transmission
of
sufficient energy, such as thermal energy, to detonate the detonator cord 174.
The
second connection transfers power (e.g., electrical power) and / or signals
(e.g., control
signals), hereafter collectively "signals," from the signal transfer assembly
146a to the
cartridge assembly 200a (FIG. 1). The coupler 160b provides similar operative
connections for the cartridge assembly 200b (FIG. 1).
[0019] Referring to Figs. 4A,B, in one embodiment, the coupler 160a
may
include a body 162 on which a coupler contact 167 is positioned. The coupler
contact
167 may include a coupler contact surface 164 and a wiring contact 166. As
illustrated,
the coupler contact surface 164 is formed on a coil spring disposed on a
tubular
receptacle 168 of the body 162. However, other coupler contact surfaces 164
configured for compressive engagement, such as on leaf springs, may be used.
In still
other embodiments, the coupler contact surface 164 may not use a biasing
feature; i.e.,
a feature that provides a biasing force. The wiring contact 166 may be any
type of
fastener, hook, frame, or other member that can be affixed to the body 162 and
has at
least a portion that is electrically conductive. A coupler 160b is generally
of the same
construction as that of the coupler 160a.
[0020] Referring to Figs. 5A-B, there is schematically shown a
cartridge
assembly 200a in accordance with one embodiment of the present disclosure.
Cartridge assembly 200b may use a similar configuration as cartridge assembly
200a.
As will be apparent from the discussion below, the cartridge assembly 200a
acts as a
structural and electrical adaptor that enables switches of various different
configurations and sizes to be used in the perforating tool 100. Exemplary
switches
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180, 181 that may be operatively connected to the cartridge assembly 200a are
shown
in Figs. 6A-B.
[0021] Referring to FIG. 6A, the switch 180 may be any conventionally
constructed electrical device that, in response to a received signal, can
output sufficient
thermal energy to detonate an energetic material such as that used in the
detonator cord
174 (FIG. 3) or the booster 172 (FIG. 3) and / or transmit, re-transmit, or
otherwise
convey an electrical signal. One class of switches are considered "select
fire" switches
because they can be programmed to initiate the firing of one perforating gun
of a
plurality of perforating guns or the firing of a sub-set of perforating guns
of sets of
perforating guns. The switch 180 may include analog and/or digital circuity
configured to receive and interpret signals. Interpreting signals may be as
simple as
recognizing polarity or comparing a received signal with a preprogrammed code
or
pattern. Irrespective of the configuration, the switch 180 either initiates
the firing of
the associated perforating gun or passes the signal to the next switch 180
based on the
received signal.
[0022] A conventional construction may include a body 182 that has an
electrical input 184, an electrical output 186, and an initiating element 188.
The
electrical input 184 may be a wire, terminal, pad, or other structure to which
a wire,
node, pad, or such structure can be electrically connected. The electrical
output 186
may also be a similarly configured wire, terminal, a node, or a pad. The
initiating
element 188 applies activating energy for detonating the detonator cord 174 or
booster
172 in response to an activation signal (e.g., electrical energy). In some
embodiments,
the initiating element 188 may be metal rod or similar member that generates
heat with
the application of electrical energy. Wires 190, 192 connect the initiating
element 188
to the body 182 of the switch 180. Thus, the initiating element 188 may be
positioned
at a location that is different from where the body 182 is positioned. The
switch 180
may also include a ground wire 194.
[0023] Referring to FIG. 6B, another prior art switch 181 may include
a body
183 that has an electrical input 185, an electrical output 187, and an
initiating element
189. The electrical input 185 may be a wire, terminal, pad, or other structure
to which
a wire, node, pad, or such structure can be connected. The electrical output
187 may
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also be a wire, terminal, a node, or a pad. The initiating element 189 applies
activating
energy for detonating the detonator cord 174 or booster 172 in response to an
activation
signal (e.g., electrical energy). In some embodiments, the initiating element
189 may
be metal rod or similar member that generates heat with the application of
electrical
energy. In this embodiment, the initiating element 189 is integral with the
body 183
and, therefore, co-located with the body 183. The switch 181 may also include
a
ground wire 195.
[0024] It is emphasized that the present disclosure is not limited to
any
particular switch design or initiating element. To the contrary, with the
benefit of the
present teachings, one skilled in the art will appreciate that the devices of
the present
disclosure can be readily adapted to accommodate a wide variety of switches
that
employ different electrical and physical configurations. Also, for brevity,
reference to
the switch 180 is inclusive of a reference to the switch 181 (FIG. 6B).
[0025] Referring to FIG. 5A-B, the cartridge assembly 200a includes a
body
202 in which a cavity 204 is formed and an electrical assembly 206 for
communicating
signals to and from the switch 180 (FIG. 6A). The cavity 204 is sized and
shaped to
house the switch 180 (FIG. 6A). In one arrangement, the electrical assembly
206 forms
electrical connections with the switch 180 (FIG. 6A) using a throughput
contact 208
and an input contact 210.
[0026] The input contact 210 conveys a received signal to the switch
180 (FIG.
6A) inside the cartridge assembly 200a. The input contact 210 may include an
external
input contact 222 and a wire 224. The external input contact 222 may be a
screw or
other fastening element that is fixed to a second face 226 of the body 202 and
is
electrically connected to the wire 224. The external input contact 222 may be
sized to
present a suitable contact surface 230 for physically contacting the coupler
contact
surface 164 (FIG. 3). The wire 224 has an end 228 that leads to the cavity
204. The
end 228 may be electrically connected to the electrical input 184 (FIG. 6A) of
the
switch 180 (FIG. 6).
[0027] The throughput contact 208 conveys the signal received by the
cartridge
assembly 200a to another cartridge assembly, here cartridge 200b. The signal
may be
the same as or similar to the received signal or a new signal. The throughput
contact
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208 may include a external throughput contact 212, an eyelet 214, and a wire
216. The
external throughput contact 212, may be a disk or plate that is fixed using
the eyelet
214, or other suitable device, to a first face 218 of the body 202. The eyelet
214 may
be a screw or other fastening element that is also fixed to the first face 218
and is
electrically connected to the external throughput contact 212 and the wire
216. The
wire 216 has an end 220 that terminates within or near the cavity 204. The end
220
may be electrically connected to the electrical output 186 (FIG. 6A) of the
switch 180
(FIG. 6). In certain embodiments, the external throughput contact 212 may be
formed
as a compressive element that acts as a biasing member; e.g., a spring. In
such
embodiments, the external throughput contact 212 applies a compressive force
to the
cartridge 200. Thus, the compressive force applied by the external throughput
contact
212 and / or the coupler contact surface 164 (FIG. 3) may be used to ensure
that the
cartridge assembly 200 compressively engages the coupler 160. This compressive
engagement ensures that signals and activation energy (e.g., thermal energy)
can be
transferred between the cartridge assembly 200 and the coupler 160
[0028] In embodiments, the cartridge assembly 200 may also include an
electrical grounding assembly 240 for grounding the switch 180 (FIG. 6). The
grounding assembly 240 may include a contact element 242 positioned in the
cavity
204, an external ground contact 244, and a wire 245 electrically connecting
the contact
element 242 to the external ground contact 244. The external ground contact
244 may
be electrically connected to a biasing member 246 that is in contact with an
inner
surface of the charge tube 114 (FIG. 2). In one arrangement, the cartridge
assembly
200 may use a metal bow spring as the biasing member 246.
[0029] Referring to Figs. 2 and 5A-B, in embodiments, the cartridge
assembly
200a may be secured in the charge tube 114 with a mechanical interlocking
mechanism. For example, the second end 120 of the charge tube 114 may include
a
"J" slot 250 that is shaped and dimensioned to be complementary to a post 252
that
projects out of the body 202.
[0030] It should be appreciated that the switch 180 (FIG. 6A) may be
pre-
installed in the cartridge assembly 200a prior to assembly of the perforating
tool 100.
This pre-installation may include making electrical connections between the
electrical
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input 184 and electrical output 186 (FIG. 6A) of the switch 180 (FIG. 6A) and
the
wires 224, 220 (FIG. 5B), respectively, of the cartridge assembly 200a (FIG.
5B).
Conventionally, making such electrical connections may require twisting of
wires,
soldering, etc. Advantageously, in embodiments of the present disclosure, such
activity is done beforehand between the switch 180 (FIG. 6A) and the cartridge
assembly 200a. Later installation simply requires sliding or otherwise
positioning the
cartridge assembly 200a inside the perforating tool 100 to engage the coupler
160 and
form the electrical connections. Here, the engagement occurs by positioning
the
cartridge assembly 200a into a side-by-side relative relationship. These
electrical
connections may be formed by electrically conductive surfaces that are in
physical
contact, and possibly in compressive contact, or sufficiently close as to
allow the
transmission of electrical signals. Moreover, the energetic connection that
enables the
transfer of thermal energy may also be formed by the same installation action.
[0031] The gun assembly 112 also includes similar features, e.g., a
cartridge
assembly 200b, a bulkhead 130b, a coupler 160b, etc. and uses the same
construction
as gun assembly 110, although in other embodiments a different construction
may be
used.
[0032] An exemplary use of the perforating tool 110 be described with
reference to FIGS. 1- 8.
[0033] Referring to FIG. 1, the perforating gun 100 has an uphole end
280 and
a downhole end 282. The uphole end 280 connects to a conveyance device such as
a
wireline (not shown), which extends to a surface location. The downhole end
282
points a well bottom (not shown). While two gun assemblies 110, 112 are shown
between the ends 280, 282, three or more gun assemblies, each with one or more
shaped charges 116, may be present. In one exemplary mode of operation, the
perforating gun closest to the downhole end 282, here perforating gun 112, is
fired
first. Thereafter, the next most adjacent perforating gun uphole of the fired
perforating
gun, here perforating gun 110, is fired. To facilitate sequential "bottom up"
firing of
the perforating tool 100, multiple firing signals may be sent. For instance, a
first firing
signal may be sent to fire the perforating gun 112 and a second firing signal
may be
sent to fire the perforating gun 110. As further described below, the
cartridge assembly
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200a is programmed to pass the first firing signal to the cartridge 200b. The
cartridge
200b is programmed to fire the perforating gun 112 upon receiving the first
firing
signal. The cartridge 200a is programmed to fire the perforating gun 110 upon
receiving the second firing signal. If more than two gun assemblies are
present, then
three or more cartridge assemblies and associated firing signals may be
needed.
[0034] Referring to FIG. 1, to initiate firing, the first firing
signal may be
transmitted from a surface location to the perforating gun 100 by a signal
conducting
carrier 290. A signal receiving interface for receiving the first firing
signal is provided
in an end cap 292. The end cap 292 may be a disk-like closure member attached
to
the uphole end 280 of the perforating tool 100. The signal transfer assembly
146a
includes a signal conducting tip 251 on one end and a connection with a wire
176a at
the other end. The wire 176a is in signal communication with the cartridge
assembly
200a via the coupler 160a. Therefore, when the tip 251 electrically engages
the signal
conducting carrier 290, a signal conducting circuit is formed across the
bulkhead 130a
such that the first firing signal can be communicated from the signal
conducting carrier
290 to the coupler 160a.
[0035] The signal transfer from the signal transfer assembly 146a to
the
coupler 160a is illustrated in FIG. 8. In one arrangement, a signal conducting
circuit
is formed by the wire 176a and a coupler contact 167. The wire 176a and the
coupler
contact 167, which includes the wiring contact 166 and the coupler contact
surface
164, are all formed of an electrically conductive material, such as a metal,
and are
electrically connected to one another using suitable known electrical
connections. In
this arrangement, the body 162 is made of an electrically non-conductive
material, e. g. ,
a non-metal such as a plastic. The first firing signal travels via the wire
176a to the
wiring contact 166 and then to the coupler contact surface 164. The electrical
connection between the coupler contact surface 164 and the external input
contact 222
of the input contact 210 transfers the first firing signal to the input
contact 210 of the
cartridge 200a.
[0036] Referring to Figs. 5A,B, the first firing signal travels from
the external
input contact 222 via the wire 224 to the electrical input 184 (FIG. 6A) of
the switch
180 (FIG. 6A). Because the switch 180 (Fig. 6A) is programmed to fire the gun
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assembly 110 (FIG. 1) only after receiving the second firing signal, the
switch 180
(FIG. 6A) passes the first firing signal to the throughput contact 208 via the
electrical
connection to the wire 216. The first firing signal travels via the wire 216
to the eyelet
214 and the external throughput contact 212.
[0037] FIG. 7 illustrates the signal transmission interface and signal
transfer
from the external throughput contact 212 of the cartridge assembly 200a to
contact
assembly 146b in the bulkhead 130b. The contact assembly 146b includes a
signal
conducting tip 251 on one end and a connection with a wire 176b at the other
end. The
wire 176b is in signal communication with the cartridge assembly 200b via a
coupler
160b (FIG. 1). Therefore, when the tip 251 contacts the external throughput
contact
212 of the cartridge assembly 200a, a signal conducting circuit is formed
across the
bulkhead 130b such that the first firing signal can be communicated from the
cartridge
assembly 200a of the perforating gun 110, via the coupler 160b, to the
cartridge
assembly 200b of the perforating gun 112 (Fig. 1).
[0038] The electrical connection between the contact assembly 146b in
the
bulkhead 130b and the coupler 160b and the electrical connection between the
coupler
160b and the cartridge assembly 200b is similar to that already described in
connection
with FIGS. 8 and 7, respectively. The first firing signal travels through
these electrical
connections to the input contact 210 of the cartridge assembly 200b.
[0039] Referring to Figs. 5A,B, the first firing signal is received at
the external
input contact 222 and transmitted by the wire 224 to the electrical input 184
(FIG. 6A)
of the switch 180 (FIG. 6A). Because switch 180 (Fig 6A) is programmed to
recognize
that the first firing signal is for firing the perforating gun 112, the switch
180 initiates
the firing of the perforating gun 112.
[0040] Referring to FIG. 3, the firing of the perforating gun 112 is
performed
by using a detonation-transfer type energetic connection between the cartridge
assembly 200b (FIG. 1) and the coupler 160b, which is the same as coupler 160a
shown in this Figure. In one arrangement, the coupler 160a has a receptacle
168 in
which is formed a bore 170 for receiving an optional booster charge 172 and an
end of
a detonator cord 174. The detonator cord 174 is energetically connected to the
shaped
charge 116. Upon receiving sufficient thermal energy from the cartridge
assembly
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200b (FIG. 1), as described below, the booster charge 172 detonates, which
detonates
the detonator cord 174. The detonation train then detonates the shaped charge
116. It
should be understood that the booster charge 172 is optional and may be
omitted in
embodiments wherein the detonator cord 174 can be directly detonated.
[0041] FIG. 8 illustrates the energetic connection between the
cartridge
assembly 200a and the coupler 160a. A similar energetic connection is present
between the cartridge assembly 200b and the coupler 160b. Referring to FIGS. 8
and
6A, the switch 180 may include an initiating element 188. The initiating
element 188
applies activating energy for detonating the detonator cord 174 or the booster
172 in
response to an activation signal (e.g., electrical energy). In some
embodiments, the
initiating element 188 may be formed of a metal that is resistant to
electrical flow and
generates heat when electrical current is applied. The initiating element 188
may act
directly on and detonate the detonator cord 174. In other embodiments, the
initiating
element 188 may act on the booster charge 172 disposed in the receptacle 170
and
positioned immediately adjacent to the initiating element 188. When fully
assembled,
the booster charge 172 may be in physical contact with or spatially separated
from the
initiating element 188. Nevertheless, the booster charge 172 is sufficiently
close
enough to be detonated by the thermal energy emitted by the initiating element
188.
The booster charge 172 and / or the detonator cord 174 may be formed of
energetic
materials include, but are not limited to, RDX (cyclotrimethylenetrinitramine
or
hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX
(cyclotetramethylenetetranitramine or
1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane), TATB
(triaminotrinitrobenzene), FINS
(hexanitrostilbene), and other similar materials that are formulated to
generate a high
order output (i.e., thermal energy and shock waves). Detonation of the booster
charge
172 thereafter detonates the detonator cord 174, which carries the detonation
to one or
more shaped charges 116 of the perforating gun 112.
[0042] To fire the perforating gun 110, the second firing signal is
transmitted
via the signal conducting carrier 290 to the perforating tool 100. The second
firing
signal is communicated to the cartridge 200a in a manner previously described.
In this
instance, however, the switch 180 (FIG. 6A) recognizes that the second firing
signal
is an instruction to firing the perforating gun 110. Thus, instead of passing
on the
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signal, the switch 180 (FIG. 6A) initiates the firing of the perforating gun
110 in a
manner previously described.
[0043] Referring to Figs. 1 and 7, embodiments of the present
disclosure form
fluid-tight seals between the bulkhead 130a,b and an inner surface 140
defining an
inner bore of the carrier 111. Referring to FIG. 7, two carriers, carriers
111a and 111b,
are shown connected at a threaded connection 252. It should be noted that, in
this
embodiment, at the threaded connection 252, there are no sealing elements
forming a
seal between the surface of carrier 111a and carrier 111b. That is, there is
only metal-
to-metal contact between the carriers 111a,b and there are no interposed
members,
such as o-rings, that forms seals between the contacting surfaces of the
carriers 111a,b.
Additionally, may be metal-to-metal contact between the carriers 111a,b and
the
bulkheads 130a,b. Instead, the sealing elements 138 only form seals between
the
bulkhead 130a,b and the inner surface 140. A similar sealing arrangement is
present
at the uphole end 280 adjacent to the end cap 292. In other embodiments one or
more
seals (not shown) may be at the threaded connection 252.
[0044] Additionally, embodiments of the present disclosure isolate a
perforating gun interior from the shockwaves from the firing of an adjacent
perforating
gun. Referring to FIG. 7, the bulkhead 130 may be formed with sufficient axial
thickness and of a material sufficiently strong to prevent the pressure waves
and shock
from one perforating gun from affecting an adjacent gun. In one arrangement,
the
bulkhead may have a first of seals 138a forming a seal with a first carrier
111a and a
second set of seals 138b forming a seal with a second carrier 111b. The
bulkhead 130
may be fixed between a first interior torque shoulder 254a of the first
carrier 111a and
a second interior torque shoulder 254b of the second carrier 111b. Thus, when
the
carriers 111a,b are threaded together at a threaded connection 256, the
bulkhead 130
is compressed between the torque shoulders 254a,b. In some embodiments, the
toque
shoulder 254a,b may be formed on other locations of the carriers 111a,b. As
noted
previously, seals 139 form a fluid barrier between the contact assemblies
146a,b and
the bulkheads 130a,b respectively.
[0045] Referring to FIG. 9, there is shown another embodiment of a
perforating tool 100 in accordance with the present disclosure. The
perforating tool
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100 may include a first gun assembly 110 and a second gun assembly 112. Each
gun
assembly 110, 112 includes a carrier 111 that is shaped to receive a charge
tube 114.
Each gun assembly 110, 112 also includes one or more shaped charges 116 fixed
within the charge tube 114. To enable selectively firing the gun assemblies
110, 112,
a select fire system may be used in which a cartridge assembly 300a is
programmed
to only fire the first gun assembly 110 and a cartridge assembly 300b is
programmed
to only fire the second gun assembly 112. Illustrative arrangements according
to the
present disclosure for enabling such select firing are described below.
[0046] Referring now to FIG. 10, the gun assembly 110 in accordance
with
one embodiment of the present disclosure is shown in an isometric view. For
clarity,
the carrier 111 (FIG. 9) is not shown. In this embodiment, the charge tube 114
may
be formed as a tubular member having a first end 118, a second end 120, and an
interior
bore 122. The charge tube 114 provides a receiving structure to which the
shaped
charges 116, a bulkhead 130a, and a coupler 400a are secured. The bulkhead
130a
may be fixed to the first end 118 with a suitable fastening element 132, such
as a screw.
[0047] The charge tube 114 may include a first opening 148 through
which the
shaped charge 116 may be inserted into the interior bore 122 and a second
opening
151 through which a detonator cord 174 may be inserted into the interior bore
122.
The charge tube 114 also includes one or more slots 462 for receiving the
coupler
400a.
[0048] The coupler 400a provides a bay into which the cartridge
assembly
300a (FIG. 9) can be inserted during assembly of the perforating tool 100
(FIG. 9).
Upon insertion, the cartridge assembly 300a (FIG. 9) becomes operatively
engaged
with the coupler 400a: i.e., physically connected to the structure of the
perforating tool
100 (FIG. 9), electrically coupled into the signal communication wiring of the
perforating tool 100 (FIG. 9), and energetically coupled to the ballistic
assembly,
which include the detonator cord 174 and optional booster charge (not shown).
As
further described below, the use of sliding surfaces and biased connections
enable the
structural, electrical connections, and energetic connections to be made
principally
during insertion and with minimal additional handling. FIG. 11A is a sectional
isometric view of the cartridge assembly 300a positioned within the coupler
400a.
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FIG. 11B is an isometric view of the coupler 400a. FIG. 11C is an end view of
the
coupler 400a.
[0049] Referring to FIGS. 11A-C, in one embodiment, the coupler 400a
may
include a hollow body 402 having a tubular receptacle 404 that communicates
with an
interior 406 and a coupler contact 408.
[0050] Referring to FIG. 11C, the tubular receptacle 404 extends from
the
body 402 and includes a bore 410. The bore 410 is sized and shaped to receive
an end
412 of the detonator cord 174 (FIG. 10) and optionally a booster charge 414.
The
coupler contact 408 includes a coupler contact surface 416 and a wiring
contact 420.
The coupler contact surface 416 may be formed on a body, such as, plate, a
rod, tube,
fastener, or other electrically conductive member that is exposed to the
interior 406.
The wiring contact 420 may be an eyelet, fastener, hook, frame, or other
member that
is exposed to an exterior of the body 402 and has at least a portion that is
electrically
conductive. The wiring contact 420 is electrically connected to a signal
conducting
carrier, such as a wire 176. Referring to FIGS. 11B and C, wings 422 formed on
an
external surface of the body 402 may be sized and shaped to be closely
received into
complementary slots 462 (FIG. 10) formed at the end 120 (FIG. 10) of the
charge tube
114. The coupler 400b is generally of the same construction as that of the
coupler
400a.
[0051] Referring to FIGS. 12A-B, there is schematically shown a
cartridge
assembly 300a in accordance with one embodiment of the present disclosure that
is
housed at least partially within the interior 406 of the coupler 400a (FIG. 11
B and C).
Cartridge assembly 300b may use a similar configuration as cartridge assembly
300a.
FIG. 12A is a top view of the cartridge assembly 300a that omits an upper
section so
that the interior may be visible. FIG. 12B is an isometric view of the
cartridge
assembly 300a.
[0052] As will be apparent from the discussion below, the cartridge
assembly
300a acts as a structural and electrical adaptor that enables switches of
various
different configurations and sizes to be used in the perforating tool 100
(FIG. 9).
Exemplary switches 180, 181 that may be operatively connected to the cartridge
assembly 300a have already been described in connection with FIGS. 6A-B.
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[0053] In one
embodiment, the cartridge assembly 300a includes a body 302
in which a cavity 304 is formed and electrical contact assemblies for
communicating
signals to and from the switch 180 (FIG. 6A). The body 302 is sized to be
received
into the interior 406 of the coupler 400a (FIG. 11B and C). The cavity 304 is
sized
and shaped to house the switch 180 (FIG. 6A). In one arrangement, the
electrical
assemblies include a throughput contact 308 and an input contact 310 to form
electrical
connections with the switch 180 (FIG. 6A).
[0054] The input
contact 310 conveys a received signal to the switch 180 (FIG.
6A) inside the cartridge assembly 300a. The input contact 310 may include a
resilient
external input contact 322 that projects from an exterior wall 326 of the body
302. The
external input contact 322 may be sized to present a contact surface that is
biased away
from the body 302. The biasing allows the external input contact 322 to
compressively
and physically contact the coupler contact surface 416 (FIG. 11A). The input
contact
310 may have an end 328 positioned within the cavity 304 and that is suitable
to
electrically connect with the electrical input 184 (FIG. 6A) of the switch 180
(FIG.
6). The input contact 310 may be a spring, plate, pad, or other conductive
element. In
one embodiment, the input contact 310 is formed as continuous thin
electrically
conductive plate. In other embodiments, the input contact 310 may be formed of
two
or more elements.
[0055] FIG. 11A
illustrates the signal transmission interface and signal
transfer via the input contact 310 of the cartridge assembly 300a. A signal
communication path is formed when the external input contact 322 of the
cartridge
assembly 300a (FIG. 12A) electrically couples to the coupler contact surface
416 of
the coupler 400a, which is in electrical communication with the wiring contact
420.
Therefore, when the electrical contact surface 322 of the cartridge 200a (FIG.
12A)
contacts the coupler contact surface 416, a signal conducting circuit is
formed between
the wire 176 and the switch 180 (FIG. 6A) inside the cartridge assembly 300a
(FIG.
12A).
[0056] The
throughput contact 308 conveys the signal received by the cartridge
assembly 300a to another cartridge assembly, here the cartridge assembly 300b
(FIG.
9). The signal may be the same as or similar to the received signal or a new
signal.
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The throughput contact 308 may include an external throughput contact 332 and
an
end 334. The external throughput contact 332 may be sized to present a contact
surface
that is biased away from the body 302 to compressively and physically contact
the
conductive tip 251 (FIG. 13) as described later. The end 334 terminates within
or near
the cavity 304 and may be electrically connected to the electrical output 186
(FIG.
6A) of the switch 180 (FIG. 6). In one embodiment, the throughput contact 308
is
formed as continuous thin electrically conductive plate. In other embodiments,
the
throughput contact 308 may be formed of two or more elements.
[0057] In embodiments, the cartridge assembly 300 may also include a
grounding contact 340 for electrically grounding the switch 180 (FIG. 6). The
grounding contact 340 may include an end 342 positioned in the cavity 304 and
an
external ground contact 344. The external ground contact 344 may be in
electrical
contact with an inner surface of the charge tube 114 or bulkhead 130b (FIG.
2). The
end 342 terminates within or near the cavity 304 and may be electrically
connected to
the ground wire 194 (FIG. 6A) of the switch 180 (FIG. 6). In one embodiment,
the
grounding member 340 is formed as continuous thin electrically conductive
plate. In
other embodiments, the grounding member 340 may be formed of two or more
elements.
[0058] The cartridge assembly 300a further includes a cradle 350 for
receiving
the initiating element 188 (FIG. 6A)). Referring to FIGS. 11 A and 12A, the
cradle
350 is sized and shaped to position the initiating element 188 (FIG.11A)
sufficiently
close to detonate the detonating cord end 412 and / or booster 414 in the
tubular
receptacle 404 in a manner already previously described; i.e., form an
energetic
connection. The cradle 350 may communicate with the cavity 304 using suitable
openings (not shown) that can accommodate hardware and wiring.
[0059] Referring to FIG. 11A, 12A and FIG. 6A, it should be noted that
the
cradle 350 and the cavity 304 are oriented to position the switch 180 and the
initiating
element 188 in a parallel, or side-by-side, relative alignment. That is, the
switch 180
and the initiation element 188 at least partially overlap along a longitudinal
axis of the
perforating tool 100 (FIG. 9), the longitudinal axis being an axis that passes
through
centers of the ends 118, 120 of the charge tube 114 (FIG. 9). In some
embodiments,
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the switch 180 and the initiation element 188 may have different radial
offsets or
distances from the longitudinal axis. In further embodiments, an annular space
relative
to the longitudinal axis may separate the switch 180 and the initiation
element 188.
Consequently, when inserted into the perforating tool 100 (FIG. 9), the switch
180 and
the initiation element 188 also at least partially overlap along a
longitudinal axis of the
perforating tool 100 (FIG. 9). As should be appreciated, the parallel, side-by-
side
arrangement occupies less total axial distance along the longitudinal axis
than a serial,
end-to-end arrangement. Additionally, in certain embodiments, the longitudinal
axis
may intersect the initiation element 188. That is, the initiation element 188
may
centrally positioned at or concentric with the longitudinal axis and the
switch 180 may
be radially offset from the initiation element 188 and the longitudinal axis.
Also, as
best seen in FIG. 12B, a lid 360 may be used to enclose the switch 180 (FIG.
6) within
the cavity 304.
[0060] FIG. 13
illustrates the signal transmission interface and signal transfer
via the throughput contact 308 of the cartridge assembly 300a. A signal
communication path is formed when the external throughput contact 332 of the
cartridge assembly 300a electrically couples to the contact assembly 146b in
the
bulkhead 130b. As described previously, the contact assembly 146b includes a
signal
conducting tip 251 on one end and a connection with a wire 176b at the other
end. The
wire 176b is in signal communication with the cartridge assembly 300b (FIG.
9).
Therefore, when the tip 251 contacts the external throughput contact 332 of
the
cartridge assembly 300a, a signal conducting circuit is formed across the
bulkhead
130b such that the first firing signal can be communicated from the cartridge
assembly
300a of the perforating gun 110 to the cartridge assembly 300b of the
perforating gun
112 (FIG. 9).
[0061] Like
embodiments previously described, it should be appreciated that
the switch 180 (FIG. 6A) may be pre-installed in the cartridge assembly 300a
prior to
assembly of the perforating tool 100 (FIG. 9). This pre-installation may
include
making electrical connections between the electrical input 184, electrical
output 186,
and ground 194 (FIG. 6A) of the switch 180 (FIG. 6A) and the ends 328, 334,
342,
respectively, (FIG. 12A). The electrical connections may be made by known
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techniques such as soldering, splicing, etc. Later installation simply
requires sliding
the cartridge assemblies 300a,b (FIG. 9) inside the couplers 400a,b (FIG. 10),
respectively, of the perforating tool 100 (FIG. 9) to form the electrical
connections.
[0062] Referring to FIG. 9, the gun assembly 112 also includes
features
similar to those described in connection with the gun assembly 110, e.g., a
cartridge
assembly 300b, a bulkhead 130b, a coupler 400b, etc. and uses the same
construction
as gun assembly 110, although in other embodiments a different construction
may be
used.
[0063] Referring to FIGS. 9 and 10, in one illustrative mode of
assembly, two
or more perforating guns, e.g., guns 110, 112, may be assembled with wiring
176a,b
and the components required to form a ballistic train (e.g., detonating cord
174, shaped
charges 116, etc) but without the cartridge assembly 300a, which contains the
addressable switch 180 and initiating element 188 (FIG. 6A). The wiring 176
winds
around an outer surface 361 of the charge tube 114 and connects to the
external contact
member 408 (FIG. 11A) which is positioned on wing 422a. While not visible in
FIG.
10, it should be appreciated that the external contact member 408 is
positioned external
to the charge tube 114 such that an electrical connection with the wiring 176
can be
readily made.
[0064] Thereafter, the perforating guns 110, 112 may be shipped to a
rig site.
At the rig site, the cartridge assembly 300a is inserted into the coupler 400a
and the
cartridge assembly 300b engages the coupler 400b upon being inserted into the
coupler
400b. It should be noted that the engagement is accomplished without removing
or
disassembling the charge tube assembly. A similar procedure is used if three
or more
perforating guns are present. Thereafter, the gun assemblies may be connected
sequentially.
[0065] It should be noted that the assembly at the rig site forms
electrical and
energetic connections at the same time that perforating gun 100 is assembled.
For
example, sliding the cartridge assembly 300a into the coupler 400a physically
and
electrically couples the coupler contact surface 416 with the external input
contact 322.
The external input contact 322 may be a spring-like biased body that can
compress
into a biased engagement with the coupler contact surface 416. Sliding the
cartridge
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assembly 300a into the coupler 400a also physically positions the initiating
assembly
188 (FIG. 11A) close enough to the detonator cord end 412 (FIG. 11A) or
booster
414 (FIG. 11A) to form an energetic connection therebetween. Also, installing
the
bulkhead 130b onto the end 118 of the charge tube 114 physically and
electrically
couples the resilient external throughput contact 332 and the conductive tip
251 as well
as the contact 340 and a surface of the charge tube 114 or the bulkhead 130b.
The
external throughput contact 332 may also be a spring-like biased body that can
compresses into a biased engagement with the conductive tip 251. Likewise, the
contact 340 may be a spring-like biased body that can compresses into a biased
engagement with the bulkhead 130b or charge tube 114.
[0066] The operation of the FIGS. 9-13 embodiments is generally
similar to
the perforating guns and assemblies previously described. Referring to FIG. 9,
in one
exemplary mode of operation, the perforating gun closest to the downhole end
282,
here perforating gun 112, is fired first. Thereafter, the next most adjacent
perforating
gun uphole of the fired perforating gun, here perforating gun 110, is fired.
To facilitate
sequential "bottom up" firing of the perforating tool 100, multiple firing
signals may
be sent. For instance, a first firing signal may be sent to fire the
perforating gun 112
and a second firing signal may be sent to fire the perforating gun 110. As
further
described below, the cartridge assembly 300a is programmed to pass the first
firing
signal to the cartridge 300b. The cartridge 300b is programmed to fire the
perforating
gun 112 upon receiving the first firing signal. The cartridge 300a is
programmed to
fire the perforating gun 110 upon receiving the second firing signal. If more
than two
gun assemblies are present, then three or more cartridge assemblies, couplers,
and
associated firing signals may be needed. However, as described in with FIG. 14
later,
the signal direction can be reversed by transmitting the firing signal to
throughput
contacts 308 and passing firing signals through the input contacts 310. That
is, the
cartridges 300a,b are bi-directional.
[0067] To initiate firing, the first firing signal may be transmitted
from a
surface location to the perforating gun 100 by a signal conducting carrier
290. A signal
receiving interface for receiving the first firing signal is provided in the
end cap 292.
The signal transfer assembly 146a includes a signal conducting tip 251 on one
end and
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a connection with a wire 176a at the other end. The wire 176a is in signal
communication with the cartridge assembly 300a via the coupler contact 408
(FIG.
11A). Therefore, when the tip 251 electrically engages the signal conducting
carrier
290, a signal conducting circuit is formed across the bulkhead 130a such that
the first
firing signal can be communicated from the signal conducting carrier 290 via
wire
176a to the coupler contact 408 and then to the switch 180 (FIG. 6A) inside
the
cartridge assembly 300a (FIG. 12A).
[0068] Referring to FIG. 11A, the first firing signal travels from the
coupler
contact 408 to the electrical input 184 (FIG. 6A) of the switch 180 (FIG. 6A).
Because
the switch 180 (FIG. 6A) is programmed to fire the gun assembly 110 (FIG. 1)
only
after receiving the second firing signal, the switch 180 (FIG. 6A) passes the
first firing
signal to the throughput contact 308 (FIG. 12a). Referring to FIG. 13, the
first firing
signal travels via the external throughput contact 332 of the throughput
contact 308
and the signal conducting tip 251 to the wire 176b. Thereafter, the first
firing signal
travels via the wire 176b to the cartridge assembly 300b. Because switch 180
(Fig
6A) in cartridge assembly 300b is programmed to recognize that the first
firing signal
is for firing the perforating gun 112, the switch 180 (FIG. 6A) initiates the
firing of
the perforating gun 112.
[0069] To fire the perforating gun 110, the second firing signal is
transmitted
via the signal conducting carrier 290 to the perforating tool 100. The second
firing
signal is communicated to the cartridge 300a in a manner previously described.
In this
instance, however, the switch 180 (FIG. 6A) recognizes that the second firing
signal
is an instruction to firing the perforating gun 110. Thus, instead of passing
on the
signal, the switch 180 (FIG. 6A) initiates the firing of the perforating gun
110 in a
manner previously described.
[0070] Referring to FIG. 14, there is shown another embodiment of a
perforating tool 100 in accordance with the present disclosure. The
perforating tool
100 may include a first gun assembly 110 and a second gun assembly 112, which
include features previously discussed such as associated bulkheads 130a,b,
respectively. To initiate firing, the first firing signal may be transmitted
from a surface
location to the perforating gun 100 by a signal conducting carrier 290. To
enable
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selectively firing the gun assemblies 110, 112, a select fire system may be
used in
which a cartridge assembly 300a is programmed to only fire the first gun
assembly
110 and a cartridge assembly 300b is programmed to only fire the second gun
assembly 112. The cartridge assembly 300a has an associated coupler 400a. The
cartridge assembly 300b has an associated coupler 400b.
[0071] In the
FIG. 14 arrangements, the firing signals are conveyed in an
opposite direction through the cartridge assemblies 300a,b as compared to the
FIG. 9
arrangement. That is, the firing signals are conveyed by the signal conducting
carrier
290 to the throughput contact 308a. Depending on the firing signal, the firing
signal
either fires the gun assembly 110 or passes the firing signal via the input
contact 310a
to the gun assembly 112. Thus, the throughput contact 308a can receive a
signal to
fire switch 180 inside cartridge 300A or can pass the firing signal to input
contact 310a
to the switch 180 (FIG. 6A) inside the cartridge assembly 300b.
[0072] As used in
this disclosure, the terms "aligned" means co-linear or
concentric. Thus, axes that are aligned are concentric. Axes that are
misaligned or
eccentric are separated by a predetermined distance. As used in this
disclosure, terms
such as "substantially," "about," and "approximately" refer to the standard
engineering
tolerances that one skilled in the art of well tools would readily understand.
[0073] As used
herein, an "electrical connection" or "electrical engagement" is
a connection wherein electrical signals are conveyed between two or more
objects.
Physical contact between the two bodies may or may not be present.
[0074] It is also
reiterated that devices according to the present disclosure may
be used in conjunction with the switch 180, the switch 181 or any other switch
configuration, whether or not addressable.
[0075] The
foregoing description is directed to particular embodiments of the
present invention for the purpose of illustration and explanation. It will be
apparent,
however, to one skilled in the art that many modifications and changes to the
embodiment set forth above are possible without departing from the scope of
the
invention. It is intended that the following claims be interpreted to embrace
all such
modifications and changes.
