Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] Hydraulically-Actuated Explosive Downhole Tool
CROSS-REFERENCES TO RELATED APPLICATIONS
[0002] This continuation-in-part application claims the benefit of the
filing date of
U.S. application serial no. 13/777,134, filed February 26, 2013, which is a
continuation
application claiming the benefit of the priority date of U.S. Application Ser.
No. 12/637,255
(now U.S. Patent No. 8,381,807), filed December 14, 2009, each of which are
incorporated by
reference as a part of this application.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR
DEVELOPMENT
[0003] Not applicable.
BACKGROUND
[0004] The present disclosure relates to a well stimulation tool for
oil and/or gas
production. The embodiments described herein generally relate to an explosive
stimulation
downhole tool that may be hydraulically actuated and is for use in a
hydrocarbon well.
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1. Description of the Related Art.
[0005] In hydrocarbon wells, fracturing (or "fracing") is a technique
used to create
and/or extend a fracture from the wellbore deeper into the surrounding
formation, thus increasing
the surface area for flow of formation fluids into the well. Fracing may be
done by either
injecting fluids at pressures sufficient to overcome the compressive and
cohesive forces on the
formation of interest (hydraulic fracturing), by using explosives to generate
sufficient pressure
and gas flow (e.g. TNT or PETN at up to 1,900,000 psi), and or by using
propellant stimulation.
Fluids used in hydraulic fracturing may carry proppants, which are typically
granular material
such as sand or ceramic particles. . Further, fracturing may be performed
using a combination
of these techniques.
[0006] Gas generating propellants have been utilized in combination
with, in addition
to, or in lieu of other fracturing techniques as a more cost effective manner
to create and
propagate fractures in a subterranean formation. In accordance with
conventional propellant
stimulation techniques, a propellant is ignited to pressurize a perforated
subterranean interval
either simultaneous with or after the perforating step so as to propagate
fractures therein.
[0007] For example, U.S. Patent No. 5,775,426 (issued July 7, 1998, the
'426
Patent"), which is incorporated by reference herein, describes a perforating
apparatus wherein a
shell of propellant material is positioned to substantially encircle a shaped
charge. The
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propellant material is ignited due to shock, heat, and/or pressure generated
from a detonated
charge. Upon burning, the propellant material of the '426 Patent generates
gases that clean
perforations formed in the formation by detonation of the shaped charge and
which extend fluid
communication between the formation and the well bore.
BRIEF SUMMARY
[0008] One embodiment of the downhole tool has a flowpath therethrough and
includes a first section having an internal sidewall, an outer sidewall, and
at least a portion of an
explosive volume, such as a propellant volume, within the first section. At
least one chamber
may be disposed, such as in an annular portion, between the outer surface of
the tool and the
flowpath, with a first end of each chamber positioned adjacent to the
propellant, or other
explosive, volume. A detonator assembly may be positioned in one or more
chambers proximal
to the propellant, or other explosive, volume to, when actuated, ignite or
cause ignition of the
propellant or other explosive. Actuation of the detonator assembly is caused
by impact of a
primer by a firing pin, which is caused to move by the pressure differential
between the flowpath
and a portion of the chamber. Ignition of the propellant causes pressure waves
to be directed
radially away from the tool and into the surrounding formation.
[0009] Also
according to one embodiment, a plurality of flow ports may be disposed
through the exterior surface to provide for fluid flow into and out of the
flowpath. A moveable
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sleeve assembly operates to prevent and permit fluid flow through the flow
ports, depending on
its position. In a first position, a sleeve substantially prevents fluid flow
through the flow ports,
while in a second position fluid flow is substantially permitted. The moveable
sleeve also
prevents or allows pressure communication between the flowpath and each
chamber to cause
application of a hydraulic force to the firing pin. The moveable sleeve may,
in some
embodiments, be a sleeve assembly comprising two, or more, sleeves joined by a
connector such
that the sleeves may move together. In some embodiments, the sleeve assembly
may comprise
two or more sleeves that are disengageable, such that, at a defined point in
the sleeve assembly's
movements, the sleeve's separate, allowing at least a first sleeve of the
sleeve assembly to
continue its movement while a second sleeve of the sleeve assembly remains
stationary or,
possibly, moves in a different direction than the first sleeve.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] FIG. I is a partial sectional elevation of the preferred
embodiment of the
present invention.
[0011] FIG. 2 is a sectional elevation of a portion of the preferred
embodiment more
fully disclosing the middle sub and piston sleeve.
[0012] FIG. 3 is a sectional elevation through section line 3-3 of FIG.
2.
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[0013] FIG. 4 is a sectional elevation through section line 4-4 of FIG.
2
[0014] FIG. 5 is a sectional elevation of a pressure chamber and firing
pin of the
preferred embodiment.
[0015] FIG. 6 is a sectional elevation of a portion of the preferred
embodiment
wherein the sleeve assembly is in a disengaged state in a second position.
[0016] FIG. 7 is a sectional elevation of the firing assembly and
pressure chamber
shown in FIG. 5 wherein the firing pin has been released and has impacted the
primer.
[0017] FIGS. 8A-8B are a partial sectional elevation of an alternative
embodiment of
the present invention.
[0018] FIG. 8C is an enlarged view of window 8C in FIG. 8A.
[0019] FIG. 9 is an isometric view of the mandrel of FIG. 8.
[0020] FIG. 10 is a sectional elevation though section line 10-10 of
FIG. 8.
[0021] FIG. 11 is an enlarged view of a pressure chamber and firing pin
of the
alternative embodiment as shown in FIG. 8A.
[0022] FIG. 12 is a sectional elevation of a portion of the alternative
embodiment
wherein the sleeve assembly is in a disengaged state in a second position.
[0023] FIG. 12A is an enlarged view of window 12A in FIG. 12.
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[0024] FIG. 13 is an enlarged view of the pressure chamber and firing
pin as shown in
FIG. 12.
DETAILED DESCRIPTION
[0025] When used with reference to the figures, unless otherwise
specified, the terms
"upwell," "above," "top," "downwell," "below," and "bottom," and like terms
are used relative
to the direction of normal production through the tool and wellbore. Thus,
normal production of
hydrocarbons migrates through the wellbore and production string from the
downwell to upwell
direction without regard to whether the tubing string is disposed in a
vertical wellbore, a
horizontal wellbore, or some combination of both. In the figures, the arrow
depicting flowpath
30 is pointing in the "downwell" direction (i.e., opposite the normal
direction of fluid flow in the
well during production).
[0026] FIG. 1 depicts a partial sectional elevation of one embodiment of
the invention
downhole tool, which comprises a first section 20 having a mandrel 22 with an
internal sidewall
24 and a ported sleeve 26 having a ported outer sidewall 28. A flowpath 30
through the tool is
partially defined by the substantially cylindrical internal sidewalls of the
mandrel 22, a top
connection 32, a middle sub 34, a ported housing 36, and a bottom connection
38. The mandrel
22 is threadedly attached to the top connection 32 and the middle sub 34 at
its upper and lower
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ends, respectively. A cylindrical propellant volume 46 is adjacent to and
between the mandrel
22 and the ported sleeve 26.
[0027] The ported sleeve 26 has a plurality of circular ports 40 spaced
equally radially
around the outer sidewall 28, and is attached to the top connection 32 with a
plurality of low
head cap screws 42. The bottom end of the ported sleeve 26 is attached to the
upper end of the
middle sub 34 with a series of interlaced tabs 44 positioned in slots 45
disposed in the outer
surface of the middle sub 34.
[0028] A second section 48 of the tool includes a plurality of oblong
flow ports 50 that
define a fluid communication path between the flowpath 30 and the exterior of
the tool. The
flow ports 50 may be spaced around, and disposed through, the cylindrical
ported housing 36,
which has an upper end connected to the lower end of the middle sub 34 with a
plurality of
circumferentially-aligned grub screws 52, and a lower end threadedly attached
to the bottom
connection 38. Sealing rings 60 are positioned throughout the embodiment to
prevent undesired
fluid communication between the various elements, except through the flowpath
30 and through
the plurality of flow ports 50.
[0029] A pressure chamber 54, such as a cylindrical pressure chamber, is
disposed
longitudinally through a chamber, such as annular portion 56, of the middle
sub 34. A detonator
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assembly 58 and firing pin 90 are located within the pressure chamber 54, with
the detonator
assembly 58 located proximal to the upper end of the pressure chamber 54.
[0030] The middle sub 34 and ported housing 36 enclose a moveable sleeve
assembly
62 having an attached ball seat 64, or other plug seat, for selectively
allowing communication
through the flow ports 50 to the surrounding formation, as will be described
infra. The sleeve
assembly 62 is, in the embodiment of Fig. 1, anchored in a first position by a
plurality of
circumferentially-aligned shear pins 66.
[0031] FIG. 2 is a sectional view of a portion of an embodiment
including the middle
sub 34 and sleeve assembly 62, which comprises a piston sleeve 68 coupled to
an insert sleeve
70. The sleeve assembly 62 is moveable between a first position and a second
position, wherein
in the first position the sleeve assembly 62 prevents fluid communication
between the flowpath
30 and the exterior of the tool through the flow ports 50. For example, in the
first position, the
upper end of the piston sleeve 68 abuts a bottom profile 72 of the middle sub
34 to define a
portion of the flowpath 30. A first plurality of ports 74 provides a fluid
communication path to
the exterior of the piston sleeve 68. A radially contractible firing pin
locking key 76 is disposed
circumferentially around the piston sleeve 68.
[0032] A lower section of the piston sleeve 68 has a larger interior
diameter than an
upper section. In the first position, the upper end of the insert sleeve 70
initially abuts the
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shoulder 78 defining the top end of the second portion, and is coupled thereto
with a
circumferentially-positioned expandable piston locking key 80 or other
bridging element. The
insert sleeve 70 is initially secured to the ported housing 36 with shear
screws 66. Upper and
lower sealing rings 84, 86 are circumferentially disposed around the insert
sleeve 70 to isolate
the flow ports 50 from the flowpath 30, thus substantially preventing
communication between
the flowpath 30 and the exterior of the tool.
[0033] FIG. 3 is a sectional view through section line 3-3 of FIG. 2
more fully
disclosing the positioning of the three pressure chambers 54 disposed
longitudinally within the
portion 56 of the middle sub 34, and showing first ends 88 of firing pins 90
(see Fig. 2), which,
in Figs 2 and. 3, are orientated in the upwell direction.
[0034] FIG. 4 more fully discloses the positioning of the shear screws
66 to secure the
insert sleeve 70 to the ported housing 36. The flow ports 50 are spaced
equally radially around
the ported housing 36. The ball seat 64 defines an orifice 65 composing a
portion of the
flowpath 30.
[0035] FIG. 5 is a sectional view of the detonator assembly 58 and
firing pin 90. The
firing pin 90 is within pressure chamber 54 proximal to an inlet 55, and is
retained in position by
the firing pin locking key 76 engaged with a retention groove 100
circumferentially disposed
around the firing pin 90. The first end 88 of the firing pin 90 is pressure
isolated from the second
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end 89 with a sealing ring 102. The inlet 55 of each chamber 54 provides a
fluid communication
path to the flowpath 30.
[0036] The detonator assembly includes a primer 92, primer case 94,
shaped charge
96, and an isolation bulkhead 98.The primer 92 is spaced above the firing pin
90 within the
primer case 94. The shaped charge 96 is positioned above and adjacent to the
primer case 94.
The isolation bulkhead 98 is positioned adjacent the shaped charge 94 and
proximal to the
propellant volume 46. In this position, detonation of the shaped charge 94
will cause
corresponding ignition of the propellant volume 46.
[0037] FIG. 6 is a sectional elevation of an embodiment wherein the
sleeve assembly
62 comprising the piston sleeve 68 and insert sleeve 70 is in a second
position to allow fluid
communication between the flowpath 30 and the surrounding formation through
the flow ports
50 of the ported housing 36. To shift the sleeve assembly 62 to this second
position from the
first position shown in FIG. 1, an appropriately-sized ball 104 or other plug
is caused to flow
down the wellbore and to engage the ball seat 64. Engagement of ball 104 with
the ball seat 64
seals off the flowpath 30 to prohibit fluid flow in the downwell direction
through the orifice 65.
Thereafter, the well operator can cause the pressure within the flowpath 30 to
exceed the shear
strength of the shear pins 66 attaching (in the first position) the insert
sleeve 70 to the ported
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housing 36, which causes the shear pins 66 to fracture and detach the insert
sleeve 70. In FIG. 6,
the shear pins 66 are shown in a sheared state.
[0038] After shearing the pins 66, increased fluid pressure within the
flowpath 30
causes the insert sleeve 70 and piston sleeve 68 to move downwell until the
lower section of the
piston sleeve 68 contacts an inner shoulder 82 of the piston housing 36. In
this position, the
piston locking key 80 expands into an adjacent flanged section 81 and
decouples the insert sleeve
70 from the piston sleeve 68. The insert sleeve 70 is thereafter allowed to
continue downwell
under the flowpath pressure until it contacts the bottom connection 38 (see
Fig. I). The ported
housing 36 further includes a locking section 106 that engages a ratchet ring
108
circumferentially disposed around the insert sleeve 70 to prevent upwell
movement of the insert
sleeve 70 after moving into the locking section 106.
[0039] Movement of the sleeve assembly 62 to the second position causes
hydraulic
actuation of the firing pin 90 as follows. Engagement of the piston sleeve 68
with the interior
shoulder 86 positions an outer groove 110 to allow the firing pin locking key
76 to radially
contract thereinto. This contraction causes the firing pin locking key 76 to
disengage from the
firing pin 90.
[0040] As shown in FIG. 7, pressure communicated into the pressure
chamber 54
causes the firing pin 90 to move towards the detonator assembly, upwell in
Fig. 6, because of the
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pressure differential above and below the sealing ring 102. In other words,
because pressure on
the detonator assembly side of the sealing element 102 is atmospheric,
hydraulic pressure on the
opposing side of sealing element 102 applies a hydraulic force on the second
end 89 of the firing
pin 90 resulting in movement towards the detonator assembly.
[0041] FIG.
7 shows the detonator assembly 58 with the pressure chamber 54 after the
firing pin locking key 76 has released the firing pin 90 and at the point of
contact of the firing pin
90 with the primer 92. The sealing ring 102 between the first end 88 and
second end 89 of the
firing pin 90 isolates pressure in the pressure chamber 54 on the detonator
assembly side of the
sealing ring 102 from the pressure in the flowpath 30. After ports 74 are
aligned with the inlet
55, pressure within the flowpath 30 is communicated through the ports 74 into
the pressure
chamber 54 at a position below the sealing element 102 (e.g. on the side
opposite of the
detonator assembly), resulting in a pressure differential that moves the
firing pin 90 to contact
and detonate the primer 92. Detonation of the primer 92 is contained by the
case 94 and causes
detonation of the adjacent shaped charge 96, which transfers explosive energy
to the propellant
volume 46, causing ignition thereof. The explosive energy is directed radially
outwardly in the
form of pressure waves through the circular ports 40 (see Fig. 1) and into the
surrounding
formation.
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[0042] FIG.
8A and FIG. 8B together depict an alternative embodiment 112 having an
upper end 114, a lower end 116, and a flowpath 115 extending through the
embodiment 112
between the ends 114, 116. The embodiment 112 comprises a top connection 118,
an outer
sleeve 120 having a cylindrical outer sidewall 121, a middle sub 122, a nozzle
housing 124, a
lower housing 126, and a bottom connection 128. The outer sleeve 120 is
connected to the top
connection 118 with circumferentially-aligned screws 130. An upper end 132 of
the nozzle
housing 124 is connected to the lower end 134 of the middle sub 122 with a
third group of
circumferentially-aligned screws 136. The upper end 140 of the lower housing
126 is connected
to the lower end 138 of nozzle housing 124 with circumferentially aligned
screws 142. The
lower end 144 of the lower housing 126 is connected to the bottom connection
128 with
circumferentially aligned screws 146. The lower housing 126 has a generally
cylindrical inner
surface 147, a portion of which has annular ridges defining a locking section
149. Nozzle
housing 124, as depicted in Figs. 8A and 8B does not contain ports through
which fluid may
flow upon movement of the lower sleeve from a first position to a second
position. However, it
will be appreciated that such ports may be present and are envisioned as
within the scope of
present disclosure.
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[0043] Referring specifically to FIG. 8A, the top connection 118 has an
upper end
surface 148, a lower end surface 150, and interior surfaces partially defining
a flowpath that
intersects with the tool flowpath 115. The interior surfaces may include a
partially conical
surface 152 adjacent to the upper end surface 148 and an adjacent cylindrical
surface 154. An
inner shoulder surface 156 is positioned between the upper and lower end
surfaces 148, 150 and
adjacent to the surface 154.
[0044] The middle sub 122 has an upper end surface 158 and an lower end
surface
160. A cylindrical outer surface 161 extends between the upper end surfaces
158 and a shoulder
surface 163. The middle sub 122 may have a varying inner diameter defined by a
cylindrical
upper inner surface 162, a cylindrical intermediate surface 164, and a
cylindrical lower inner
surface 166. An annular upper intermediate shoulder surface 168 is adjacent to
and between the
intermediate surface 164 and the upper inner surface 162. A lower intermediate
shoulder surface
170 is adjacent to and between the intermediate surface 164 and the lower
inner surface 166. In
the embodiment of Figure 8, the intermediate surface 164 partially defines
flowpath 115.
[0045] Mandrel 172 occupies a portion of the interior of the tool, such
as a portion of
the top connection 118 and the middle sub 122 as shown in Figure 8. The
mandrel 172 may be
fixed relative to top connection 118, middle sub 122, or both. The mandrel 172
has an upper
end surface 174, an lower end surface 176, and a cylindrical internal sidewall
178 adjacent to
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and extending between the upper and lower end surfaces 174, 176 that defines a
portion of the
flowpath 115. A cylindrical outer surface 182 (shown in Figure 9) extends from
the upper end
surface 174 to a shoulder surface 175 near the lower end surface 176.
[0046] The mandrel 172 is inhibited from translational and rotational
movement
relative to the top connection 118 and middle sub 122. For example,
circumferentially-aligned
screws 180 may fix the mandrel 172 to the top sub 118. Further, the upper end
surface 174 may
be in contact with the inner shoulder 156 of the top connection 118,t186he
lower end surface 176
may be in contact with the upper shoulder 168 of the middle sub 122, or both.
A first section
177 of the embodiment 112 includes at least part of the internal sidewall of
the mandrel 172 and
at least part of the outer sidewall.
[0047] FIG. 9 is an isometric view of the mandrel 172, which may be a
generally
tubular body having an outer surface 182. The mandrel 172 may include a
circumferential
groove 184 near the upper end surface 174. Longitudinal grooves 186 may extend
along the
outer surface 182 between the circumferential groove 184 and the shoulder
surface 175. Charge
receptacles, such as cylindrical recesses 188 are placed along and in
communication withthe
longitudinal grooves 186. The number, placement, and spacing of charge
receptacles may vary
based on the results desired by the operator. Explosives, such as shaped
charges 187, occupy
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some or all of the charge receptacles formed in the mandrel 172, with at least
some charges being
positioned within the first section 177.
[0048] A detonator cord 259 is fastened to each of the shaped charges
187 and extends
along one longitudinal groove 186a, into the circumferential groove 184, and
into the next
longitudinal groove 186b, around the shoulder surface 175 and into the next
longitudinal groove
(not shown), and so on. In this manner the detonator cord 259 may occupy one
or more of the
grooves 186. One end of the detonator cord 259 is fastened to the detonator
assembly 258, as
shown in FIG. 8A.
[0049] Referring back to FIG. 8A, a moveable sleeve assembly may be comprised
of
a pin sleeve 190 and a lower sleeve 202 and defines a portion of the flowpath
115. The pin
sleeve 190 has an upper end surface 192, a lower end surface 194, a
cylindrical inner surface 196
adjacent to and extending between the end surfaces 192, 194, and an outer
surface 198 adjacent
to the end surfaces 192, 194. The upper end surface 192 contacts the lower
shoulder surface 170.
In some embodiments, the pin sleeve 190 may comprise a pin sleeve coupler
element, such as
groove 200 shown in Figure 8 circumscribing the sleeve 190 proximal to the
lower end surface
194.
[0050] Referring jointly to FIGS. 8A-8B, the lower sleeve 202 is
adjacent to and in
communication with pin sleeve 190. The lower sleeve 202 has an upper end
surface 204 in
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contact with the lower end surface 194 of the pin sleeve 190, and an annular
lower end surface
206. A cylindrical inner surface 208 and a generally cylindrical outer surface
210 extends
between the upper end surface 204 and lower end surface 206. In some
embodiments, the outer
surface 210 may include a lower sleeve coupler element, such as the groove 212
that
circumscribes the lower sleeve 202 near the upper end surface 204 in the
embodiment illustrated
in Figure 8B. The outer surface 210 also may include shear pin receivers such
as recesses 214
for receiving an end, such as the shearable ends 216, of pins 218.
[0051] In
certain embodiments, the downhole tool may contain a bridge assembly for
connecting the pin sleeve and lower sleeve. In some embodiments, the bridge
assembly
releasably connects the pin sleeve and lower sleeve such that the pin sleeve
and lower sleeve
may be disconnected at a desired time or in response to a predetermined event.
Referring to
Figure 8C, one embodiment of a bridge assembly comprises a collet ring 219
configured to
engage the groove 200 of the pin sleeve 190 and groove 212 of the lower sleeve
202. The collet
ring 219 has a body 221 with a lower end surface 223 and a cylindrical outer
surface 225. In
the embodiment of Figure 8C, a plurality of fingers 227 may extend from the
body 221 and
occupy the groove 200 in the pin sleeve 190, terminating in upper end surfaces
229. The body
221 circumscribes, and occupies the groove 212 defined by, the lower sleeve
202. The lower
end surface 223 is adjacent to the outer surface 225. The body 221 has a
cylindrical inner
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surface 233 and upper and lower partially-conical surfaces 235, 237 adjacent
to the inner surface
233. The lower partially-conical surface 235 is also adjacent to the lower end
surface 223. It
will be appreciated that the configuration of the collet ring 219, when
present, may be modified
in numerous ways, and that the claims are not limited to any particular
configuration of collet
ring 219. Further, bridge assemblies of varying configurations, including
bridge assemblies that
do not include a collet ring, are within the scope of the present disclosure.
One example of such
a bridge assembly may comprise a locking assembly described in United States
Patent
Application No. 13/694,509, incorporated herein by references, modified such
that the ball or
other bolt connects the sleeves and allows the lower sleeve to pull the pin
sleeve until the ball or
bolt reaches the recessed area and the sleeves can disengage.
[0052]
Referring again to FIG. 8B, the lower sleeve 202 is engaged with a seat
carrier
220 that has an upper end surface 222, a lower end surface 224, and a
generally cylindrical outer
surface 226 extending between the upper and lower end surfaces 222, 224. The
carrier 220 has
an upper shoulder surface 228 and a lower shoulder surface 230. In some
embodiments, the
lower sleeve 202, seat carrier 220, or other structure engaged to lower sleeve
202 and/or seat
carrier 220 may include one or more retaining elements. For example, in the
embodiment of
Figure 8B, such retaining element comprises a ratchet ring, shown residing in
a groove 232
circumscribing the seat carrier 220. .
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[0053] A ball seat 236 may be threaded to the seat carrier 220. Plugs
other than balls
are within the scope of the present disclosure and the ball seat 236 may be
substituted with any
seat configured to seal with the desired plug, provided that the plug and plug
seat fit within the
geometry, both size and shape, of the downhole tool, and, in the case of plug,
any structures in
the well through which the plug must pass to reach the plug seat. The ball
seat 236 has an upper
end surface 238 adjacent to the lower end surface 206 of the lower sleeve 202,
and a lower end
surface 240 positioned adjacent to the upper intermediate shoulder surface 228
of the seat carrier
220. The ball seat 236 defines an orifice 242 intersecting the flowpath.
[0054] In some embodiments, a cement sleeve 244 is attached to the seat
carrier 220
below the lower shoulder surface 230. The cement sleeve 244 may be a tubular
body having an
upper end surface 246 and a lower end surface 248. A cylindrical outer surface
252 is positioned
adjacent to the lower end surface 248. A shoulder 254 is adjacent to and
positioned above the
outer surface 252.
[0055] An actuator, such as a detonator assembly 258, for actuating the
charges 187 is
placed adjacent to the grooves 186. For example, and referring back to FIG.
8A, a chamber 256
is disposed longitudinally through a mandrel wal1250 of the middle sub 122
between the upper
inner surface 162 and the outer surface 161. The detonator assembly 258 and a
firing pin 260 are
located within the chamber 256, with the detonator assembly 258 located near
the upper end
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surface of the middle sub 122. The detonator assembly 258 and firing pin 260
are configured to
match the shape and size of the chamber 256, which is cylindrical in certain
embodiments. FIG.
shows one embodiment with three such chambers 256 positioned within the middle
sub 122
in the mandrel wall 250. Alternative embodiments of my have more or fewer
chambers. A
detonator cord 259 is coupled to the detonator assembly 258 and occupies a
longitudinal channel
186 formed in the mandrel 172.
[0056] Referring to embodiment shown in FIG. 11, the firing pin 260
occupies the
chamber 256 near an inlet 262 extending between the lower inner surface 166 of
the middle sub
122 and the chamber 256. The firing pin 260 has a first end 266 isolated from
a second end 268
with a sealing ring 270 such that first end 266 and second end 268 are not in
fluid
communication. The chamber 256 is isolated from the flowpath 115 with a
sealing element 261a
positioned between the pin sleeve 190 and the middle sub 122. A second sealing
element 261b
may also isolate the chamber 256 from fluid in flowpath 115.
[0057] A retaining pin 264 may be connected to the firing pin 260, such
as the
retaining pin 264 shown in FIG. 11 between the sealing ring 270 and the second
end 268. A
portion of the retaining pin may occupy at least a portion of the inlet 262.
In such a
configuration, movement of the firing pin 260 within the chamber 256
substantially away from
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the position shown in FIG. 11 while the retaining pin 264 is intact is
inhibited by the inlet wall
263.
[0058] A detonator assembly 258, such as illustrated in FIG 11, may
include a primer
272, primer case 274, shaped charge 276, and a bulkhead 278. The primer 272 is
within the
primer case 274 and is spaced between the firing pin 260 and at least one
charge 187. The
bulkhead 278 may be an isolation bulkhead positioned adjacent the shaped
charge 276 and
proximal to the mandrel 172. In this position, detonation of the shaped charge
276 will cause
corresponding detonation of the charges 187 positioned in recesses 188 of the
mandrel 172. The
detonator cord 259 is fastened to the detonator assembly 258.
[0059] FIG. 12 is a sectional elevation of a portion of the embodiment
wherein the pin
sleeve 190 is downwell of the sealing element 261, which allows fluid
communication between
the flowpath 115 and the inlet 262. To shift the pin sleeve 190 to this
position from the first
position shown in FIG. 8A, an appropriately-sized ball 280 or other
appropriate plug is caused to
flow down the wellbore and to engage the ball seat 236 or other corresponding
plug seat. In the
embodiment of FIG. 12, engagement of the ball 280 with the ball seat 236 seals
off the flowpath
115 to stop fluid flow through the orifice 242. Thereafter, the well operator
can cause sufficient
pressure to cause the ball seat 236, seat carrier 220, and lower sleeve 202 to
move downwell.
For example, according to the embodiment of FIG 12, the fluid pressure in
flowpath 115 is
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increased such that pressure differential across the ball seat 236, exceeds
the shear strength of the
shear pins 218, causing the shear pins 218 to fracture and detach the lower
sleeve 202 from the
nozzle housing 124.. In FIG. 12, the shear pins 218 are shown in a sheared
state with ends 216
having moved relative to the position shown in FIG. 8A. Because the pin sleeve
190 is joined to
the lower sleeve 202 with the collet ring 219, the pin sleeve 190 is also
moved downwell.
[0060] In some embodiments, a bridge element between the pin sleeve and
lower
sleeve may disengage, break, or other otherwise disconnect such that the pin
sleeve 190 and
lower sleeve 202 no longer move together. For example, in the embodiment of
FIG. 12,
movement of the pin sleeve 190 is limited by contact of the lower end surface
223 of the collet
ring 219 with an annular inner shoulder 127 of the nozzle housing 124. As
pressure is applied
after the collet ring 219 contacts the shoulder 127, the upper partially-
conical surface 235 of the
collet ring 219 allows the upper end surface 204 of the lower sleeve 202 to
disconnect. In this
manner, the lower sleeve 202 is disconnected from the pin sleeve 190 and may
move in
connection with the pressure differential across the ball seat 236. The lower
sleeve 202 may
thereafter move to the position shown in FIG. 12, in which ratchet ring 234
has expanded
against, and engaged, the locking section 149.
[0061] Movement of the pin sleeve 190 to the second position shown in
FIG. 12
allows pressure to thereafter be communicated from the flowpath 115 into the
pressure chamber
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256 through the inlet 262 and act on the second end 260 of the firing pin 260
and create a
pressure differential thereacross. In other words, because pressure within the
chamber on the
detonator assembly 258 side of the sealing ring 270 is atmospheric, pressure
on the opposite side
of the sealing element 270 applies a force on the second end 268, causing
movement of the firing
pin 260 within the chamber 256 toward the detonator assembly 258. In
embodiments having a
retaining pin 264, or other firing pin restraint (for example, firing pin
locking key, 76 in Fig. 2),
the pressure from flowpath 115 must be high enough to apply sufficient force
to the firing pin
260 to shear the retaining pin 264 as it contacts the inlet wall 263, or to
otherwise disable,
overcome, or deactivate a firing pin restraint configured to respond to the
fluid pressure.
[0062] FIG.
13 shows the detonator assembly 258 with the pressure chamber 256 after
the retaining pin 264 has sheared and at the point of contact of the firing
pin 260 with the primer
272. The sealing ring 270 between the first end 266 and second end 268 of the
firing pin 260
isolates pressure in the pressure chamber 256 upwell of the sealing ring 270
from the pressure in
the flowpath 115. Detonation of the primer 272 is contained by the case 274
and causes
detonation of the adjacent shaped charge 276, which ignites the detonator cord
259. Ignition of
the detonator cord 259 detonates the charges 187 fastened thereto, and which
are adjacent to the
mandrel 172. The explosive resultant energy is directed radially outwardly
through the outer
sleeve 120 in the form of pressure waves and, desirably, into the surrounding
formation.
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[0063] In some embodiments, the number of longitudinal channels may
exceed the
number of detonator assembly, as illustrated for the embodiment shown in Fig.
9, showing six
longitudinal channels and Fig. 10, illustrating the use of three detonator
assemblies. During
operation, activation of the primer 272 is followed by ignition of shaped
charge 276, which may
ignite the detonator cord 259 fasted to the charges 187. The detonator cord
may be directed into
multiple channels, such as by wrapping the detonator cord into grooves 184 as
it exits a
longitudinal channel 186, at and end of the mandrel. The detonator cord 259
can then be passed
from groove 184 into a second longitudinal channel 186 and ignite the charges
placed therein. In
this manner, it is possible that a single primer 272 and detonator cord 259,
could be used to
initiate detonation of each of the charges 187 positioned in the mandrel 178.
[0064] The present invention is described above in terms of specific
illustrative
embodiments. Those skilled in the art will recognize that alternative
constructions of such an
apparatus can be used in carrying out the present invention. Other aspects,
features, and
advantages of the present invention may be obtained from a study of this
disclosure and the
drawings, along with the appended claims.
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