U.S. patent application number 11/567633 was filed with the patent office on 2008-06-12 for thermally activated well perforating safety system.
Invention is credited to John D. Burleson, Flint R. George, Antony F. Grattan, John H. Hales, Ryan A. Harrison.
Application Number | 20080134922 11/567633 |
Document ID | / |
Family ID | 39111869 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080134922 |
Kind Code |
A1 |
Grattan; Antony F. ; et
al. |
June 12, 2008 |
Thermally Activated Well Perforating Safety System
Abstract
An explosives safety system includes an explosive component, a
blocking member displaceable to selectively permit and prevent
detonation of the explosive component, and a thermal actuator
responsive to temperature change and configured to displace the
member in response to the temperature change. Another explosives
safety system includes a thermal actuator with a material having a
volume variable in response to the temperature change, and
detonation of the explosive component being selectively permitted
and prevented by the actuator when the material volume changes. A
method of preventing undesired detonation of an explosive component
includes the steps of: providing a material having a volume
variable in response to a change in a temperature; positioning the
material and the explosive component in a well, thereby increasing
the material temperature; increasing the material volume in
response to the increasing temperature; and permitting detonation
of the explosive component in response to the increasing
volume.
Inventors: |
Grattan; Antony F.;
(Aberdeen, GB) ; Burleson; John D.; (Denton,
TX) ; George; Flint R.; (Flower Mound, TX) ;
Hales; John H.; (Frisco, TX) ; Harrison; Ryan A.;
(Flower Mound, TX) |
Correspondence
Address: |
SMITH IP SERVICES, P.C.
P.O. Box 997
Rockwall
TX
75087
US
|
Family ID: |
39111869 |
Appl. No.: |
11/567633 |
Filed: |
December 6, 2006 |
Current U.S.
Class: |
102/206 |
Current CPC
Class: |
E21B 43/1185 20130101;
F42C 15/44 20130101; F42C 15/34 20130101; F42C 15/36 20130101; F42C
15/005 20130101 |
Class at
Publication: |
102/206 |
International
Class: |
C06C 5/06 20060101
C06C005/06 |
Claims
1. A thermally activated explosives safety system, comprising: an
explosive component; a blocking member displaceable to selectively
permit and prevent detonation of the explosive component; and a
thermal actuator responsive to temperature change, the actuator
being configured to displace the blocking member in response to the
temperature change.
2. The system of claim 1, wherein the actuator includes a material,
a volume of the material being variable in response to the
temperature change.
3. The system of claim 2, wherein the material volume increases in
response to a temperature increase, and wherein the material volume
decreases in response to a temperature decrease.
4. The system of claim 2, wherein the blocking member displaces to
a position preventing detonation of the explosive component in
response to an increase in the material volume.
5. The system of claim 2, wherein the blocking member displaces to
a position permitting detonation of the explosive component in
response to an increase in the material volume.
6. The system of claim 1, wherein the actuator displaces the
blocking member to a position preventing detonation of the
explosive component in response to a temperature decrease.
7. The system of claim 1, wherein the actuator displaces the
blocking member to a position permitting detonation of the
explosive component in response to a temperature increase.
8. The system of claim 1, wherein the blocking member is positioned
between a firing head and a perforating gun.
9. The system of claim 1, wherein the blocking member is positioned
between perforating guns.
10. The system of claim 1, wherein the blocking member is
positioned between a firing pin and the explosive component.
11. The system of claim 1, wherein the system includes at least two
explosive components, and wherein the blocking member is positioned
between the explosive components.
12. The system of claim 1, wherein the blocking member is displaced
laterally relative to a passage by the actuator in response to the
temperature change.
13. The system of claim 1, wherein the blocking member is rotated
by the actuator about an axis parallel to a passage in response to
the temperature change.
14. The system of claim 1, wherein the blocking member is rotated
by the actuator about an axis orthogonal to a passage in response
to the temperature change.
15. The system of claim 1, wherein the blocking member blocks a
passage to prevent detonation of the explosive component.
16. The system of claim 1, wherein the blocking member has an
opening which is aligned with a passage to permit detonation of the
explosive component.
17. The system of claim 1, further comprising a biasing device
which biases the blocking member in a direction to prevent
detonation of the explosive component.
18. The system of claim 1, wherein the system includes at least two
of the thermal actuators, and wherein the actuators are
cooperatively operable to displace the blocking member.
19. The system of claim 1, wherein the actuator includes a
bimetallic structure which changes shape in response to the
temperature change.
20. The system of claim 1, wherein the actuator includes a shape
memory alloy material which changes shape in response to the
temperature change.
21. The system of claim 1, wherein the blocking member engages a
firing pin to prevent displacement of the firing pin and thereby
prevent detonation of the explosive component.
22. A thermally activated explosives safety system, comprising: an
explosive component; a thermal actuator responsive to temperature
change, the actuator including a material having a volume which is
variable in response to the temperature change; and wherein
detonation of the explosive component is selectively permitted and
prevented by the actuator when the material volume changes.
23. The system of claim 22, wherein detonation of the explosive
component is prevented when the material volume increases.
24. The system of claim 22, wherein detonation of the explosive
component is prevented when the material volume decreases.
25. The system of claim 22, wherein the material volume increases
in response to a temperature increase, and wherein the material
volume decreases in response to a temperature decrease.
26. The system of claim 22, wherein a blocking member displaces to
a position preventing detonation of the explosive component in
response to an increase in the material volume.
27. The system of claim 22, wherein a blocking member displaces to
a position permitting detonation of the explosive component in
response to an increase in the material volume.
28. The system of claim 22, wherein the actuator displaces a
blocking member to a position preventing detonation of the
explosive component in response to a temperature decrease.
29. The system of claim 22, wherein the actuator displaces a
blocking member to a position permitting detonation of the
explosive component in response to a temperature increase.
30. The system of claim 22, wherein a blocking member displaceable
by the actuator blocks a passage to prevent detonation of the
explosive component.
31. The system of claim 22, wherein the actuator includes a
bimetallic structure which changes shape in response to the
temperature change.
32. The system of claim 22, wherein the actuator includes a shape
memory alloy material which changes shape in response to the
temperature change.
33. The system of claim 22, wherein the actuator reduces a gap
between elements of the system to thereby permit detonation of the
explosive component.
34. The system of claim 22, wherein the actuator extends a firing
pin outwardly to thereby permit detonation of the explosive
component.
35. The system of claim 22, wherein the actuator aligns multiple
elements of an explosive train to thereby permit detonation of the
explosive component.
36. The system of claim 22, wherein the actuator displaces a
blocking member to thereby permit detonation of the explosive
component.
37. The system of claim 22, wherein the actuator aligns an opening
with a passage to thereby permit detonation of the explosive
component.
38. The system of claim 22, wherein the actuator rotates a blocking
member to thereby permit detonation of the explosive component.
39. A method of preventing undesired detonation of an explosive
component, the method comprising the steps of: providing a material
having a volume which is variable in response to a change in a
temperature of the material; positioning the material and the
explosive component in a subterranean well, thereby increasing the
temperature of the material; increasing the volume of the material
in response to the temperature increasing step; and permitting
detonation of the explosive component in response to the volume
increasing step.
40. The method of claim 39, further comprising the steps of
decreasing the volume of the material in response to decreasing the
temperature of the material, and preventing detonation of the
explosive component in response to the volume decreasing step.
41. The method of claim 40, wherein the volume decreasing and
detonation preventing steps are performed after the volume
increasing and detonation permitting steps.
42. The method of claim 39, further comprising the step of
preventing detonation of the explosive component, and wherein the
detonation preventing step is performed prior to the volume
increasing and detonation permitting steps.
43. The method of claim 39, further comprising the step of
containing the material in an enclosure, thereby forming an
assembly which becomes increasingly rigid as the volume of the
material increases.
44. The method of claim 43, further comprising the step of
transmitting a force through the assembly when the assembly has an
increased rigidity to thereby detonate the explosive component.
45. The method of claim 43, further comprising the step of
preventing detonation of the explosive component by preventing
effective transmission of a force through the assembly when the
assembly has a reduced rigidity.
46. The method of claim 39, wherein the providing step further
comprises providing the material as part of a thermal actuator.
47. The method of claim 46, wherein the detonation permitting step
further comprises the actuator displacing a blocking member in
response to the volume increasing step.
48. The method of claim 46, wherein the detonation permitting step
further comprises the actuator rotating a blocking member in
response to the volume increasing step.
49. The method of claim 46, wherein the detonation permitting step
further comprises the actuator extending a firing pin outward in
response to the volume increasing step.
50. The method of claim 46, wherein the detonation permitting step
further comprises the actuator decreasing a gap in response to the
volume increasing step.
51. The method of claim 46, wherein the detonation permitting step
further comprises the actuator aligning multiple explosive
components in response to the volume increasing step.
Description
BACKGROUND
[0001] The present invention relates generally to equipment used
and operations conducted in conjunction with a subterranean well
and, in an embodiment described herein, more particularly provides
a thermally activated explosives safety system.
[0002] In well perforating operations, it is vitally important to
prevent undesired detonations of explosive components. Injury or
even death of personnel can result from untimely detonations, as
well as damage to the well, surface equipment and other
property.
[0003] Various safety systems have been used in the past, but these
have not been entirely successful. Some safety systems rely on
pressure to provide an actuating force, with the pressure being
present only downhole. Other systems rely on temperature downhole
to melt a substance, such as a eutectic material, thereby
permitting detonation of an explosive component.
[0004] Unfortunately, in some such systems the substance cannot be
reformed or "un-melted" in the event that the explosive component
has to be retrieved from the well, so that the substance again
prevents detonation of the explosive component. Those systems which
do permit reforming of the melted substance have a relatively large
operating envelope. This re-arming of the safety system is
important if, for example, a perforating gun or firing head
mis-fires downhole and has to be retrieved to the surface with
undetonated explosive components therein.
[0005] Therefore, it may be seen that improvements are needed in
the art of thermally activated explosives safety systems.
SUMMARY
[0006] In carrying out the principles of the present invention,
explosives safety systems and associated methods are provided which
solve at least one problem in the art. One example is described
below in which a thermal actuator is used to alternately permit and
prevent detonation of an explosive component. Another example is
described below in which a material has a volume which varies in
response to a temperature change, and the variable material volume
is used to alternately permit and prevent detonation of an
explosive component.
[0007] In one aspect of the invention, a thermally activated
explosives safety system is provided. The system includes an
explosive component and a blocking member displaceable to
selectively permit and prevent detonation of the explosive
component. A thermal actuator of the system is responsive to
temperature change. The actuator is configured to displace the
blocking member in response to the temperature change.
[0008] In another aspect of the invention, a thermally activated
explosives safety system includes a thermal actuator responsive to
temperature change, the actuator including a material having a
volume which is variable in response to the temperature change.
Detonation of the explosive component is selectively permitted and
prevented by the actuator when the material volume changes.
[0009] In yet another aspect of the invention, a method of
preventing undesired detonation of an explosive component includes
the steps of: providing a material having a volume which is
variable in response to a change in a temperature of the material;
positioning the material and the explosive component in a
subterranean well, thereby increasing the temperature of the
material; increasing the volume of the material in response to the
temperature increasing step; and permitting detonation of the
explosive component in response to the volume increasing step.
[0010] These and other features, advantages, benefits and objects
of the present invention will become apparent to one of ordinary
skill in the art upon careful consideration of the detailed
description of representative embodiments of the invention
hereinbelow and the accompanying drawings, in which similar
elements are indicated in the various figures using the same
reference numbers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic partially cross-sectional view of a
well system and associated method embodying principles of the
present invention;
[0012] FIG. 2 is an enlarged scale schematic cross-sectional view
through a thermally activated explosives safety system in the well
system of FIG. 1;
[0013] FIG. 3 is a schematic cross-sectional view of a first
alternate configuration of the explosives safety system;
[0014] FIG. 4 is a schematic cross-sectional view of the first
alternate configuration of the explosives safety system, taken
along line 4-4 of FIG. 3, wherein detonation of an explosive
component is prevented;
[0015] FIG. 5 is a schematic cross-sectional view of the first
alternate construction of the explosives safety system, wherein
detonation of the explosive component is permitted;
[0016] FIG. 6 is a schematic cross-sectional view of a second
alternate configuration of the explosives safety system, wherein
detonation of an explosive component is prevented;
[0017] FIG. 7 is a schematic cross-sectional view of the second
alternate configuration of the explosives safety system, wherein
detonation of the explosive component is permitted;
[0018] FIG. 8 is a schematic cross-sectional view of a third
alternate configuration of the explosives safety system;
[0019] FIG. 9 is a schematic cross-sectional view of a fourth
alternate configuration of the explosives safety system;
[0020] FIG. 10 is a schematic cross-sectional view of a fifth
alternate configuration of the explosives safety system, wherein
detonation of an explosive component is prevented;
[0021] FIG. 11 is a schematic cross-sectional view of the fifth
alternate configuration of the explosives safety system, wherein
detonation of the explosive component is permitted;
[0022] FIGS. 12 & 13 are schematic side elevational views of
multiple thermal actuators usable in the various configurations of
the explosives safety system, the actuators being depicted in a
retracted condition in FIG. 12, and in an extended condition in
FIG. 13;
[0023] FIG. 14 is a schematic cross-sectional view of a sixth
alternate configuration of the explosives safety system;
[0024] FIG. 15 is a schematic cross-sectional view of a seventh
alternate configuration of the explosives safety system;
[0025] FIG. 16 is a schematic cross-sectional view of a eighth
alternate configuration of the explosives safety system, wherein
detonation of an explosive component is prevented;
[0026] FIG. 17 is a schematic cross-sectional view of the eighth
alternate configuration of the explosives safety system, wherein
detonation of the explosive component is permitted;
[0027] FIG. 18 is a schematic cross-sectional view of a ninth
alternate configuration of the explosives safety system;
[0028] FIG. 19 is a schematic cross-sectional view of a tenth
alternate configuration of the explosives safety system;
[0029] FIG. 20 is a schematic cross-sectional view of an eleventh
alternate configuration of the explosives safety system;
[0030] FIG. 21 is a schematic cross-sectional view of a twelfth
alternate configuration of the explosives safety system;
[0031] FIG. 22 is a schematic cross-sectional view of a thirteenth
alternate configuration of the explosives safety system;
[0032] FIG. 23 is a schematic cross-sectional view of a fourteenth
alternate configuration of the explosives safety system; and
[0033] FIG. 24 is a schematic cross-sectional view of a fifteenth
alternate configuration of the explosives safety system.
DETAILED DESCRIPTION
[0034] It is to be understood that the various embodiments of the
present invention described herein may be utilized in various
orientations, such as inclined, inverted, horizontal, vertical,
etc., and in various configurations, without departing from the
principles of the present invention. The embodiments are described
merely as examples of useful applications of the principles of the
invention, which is not limited to any specific details of these
embodiments.
[0035] In the following description of the representative
embodiments of the invention, directional terms, such as "above",
"below", "upper", "lower", etc., are used for convenience in
referring to the accompanying drawings. In general, "above",
"upper", "upward" and similar terms refer to a direction toward the
earth's surface along a wellbore, and "below", "lower", "downward"
and similar terms refer to a direction away from the earth's
surface along the wellbore.
[0036] Representatively illustrated in FIG. 1 is a well system 10
and associated method which embody principles of the present
invention. A tubular string 12 is installed in a wellbore 14 lined
with casing 16. Suspended from the tubular string 12 is a
perforating assembly 18 which is used to form perforations 20
through the casing 16, through cement 22 surrounding the casing,
and into one or more subterranean formations or zones 24.
[0037] Although the perforating assembly 18 is depicted in FIG. 1
as being of the type known to those skilled in the art as a "tubing
conveyed" perforating assembly, other types of perforating
assemblies may be used in keeping with the principles of the
invention. For example, the perforating assembly 18 could be
conveyed by wireline, slickline or any other form of
conveyance.
[0038] Furthermore, although the perforating assembly 18 is used as
an example of an assembly which utilizes explosive components,
other types of assemblies may be used in keeping with the
principles of the invention. For example, casing cutters, setting
tools and other types of well tools and equipment are known which
include explosive components, and which can benefit from the
principles of the present invention to enhance the safety of their
operation.
[0039] Therefore, it should be clearly understood that the
invention is not limited in any manner to the specific well
systems, methods, explosives safety systems, etc. described herein.
Instead, the principles of the invention are applicable to a wide
variety of well tools, equipment and operations which utilize
explosive components.
[0040] The perforating assembly 18 depicted in FIG. 1 includes a
firing head 26 for initiating detonation of explosive perforating
charges (not visible in FIG. 1) of perforating guns 28. The firing
head 26 may be actuated in any manner to initiate detonation of the
perforating charges. For example, pressure, telemetry (such as
acoustic, pressure pulse, electromagnetic or other form of
telemetry), mechanical force, electrical signal, or other stimulus
may be used.
[0041] Although one firing head 26 above the perforating guns 28 is
illustrated in FIG. 1, there may be multiple firing heads, a firing
head may be attached at a lower end of the perforating assembly 18
below the perforating guns, and different types of firing heads may
be used, in keeping with the principles of the invention.
[0042] In an important feature of the well system 10, the
perforating assembly 18 also includes thermally activated
explosives safety systems 30, 32. The safety system 30 is depicted
in FIG. 1 as being interconnected between the firing head 26 and
the upper perforating gun 28, in order to prevent the firing head
from undesirably initiating detonation of the perforating guns, and
the safety system 32 is depicted in FIG. 1 as being interconnected
between the perforating guns, in order to prevent undesirable
transfer of detonation between the perforating guns.
[0043] However, it should be clearly understood that these
positions of the safety systems 30, 32 are merely examples of a
variety of different positions in which the safety systems can have
beneficial use. For example, it is known practice to include a
shearable safety joint in a perforating assembly to allow safer
connection and disconnection of a firing head while the safety
joint is positioned in a blowout preventer stack.
[0044] An example of such a shearable safety joint is described in
U.S. Pat. No. 6,675,896, the entire disclosure of which is
incorporated herein by this reference. An explosives safety system
(such as one of the safety systems 30, 32) could be interconnected
between the safety joint and the perforating guns, or incorporated
as part of the safety joint, to thereby provide an increased
measure of safety while the firing head is being connected or
disconnected.
[0045] Referring additionally now to FIG. 2, a schematic
cross-sectional view of a thermally activated explosives safety
system 40 is representatively illustrated. The safety system 40 may
be used for the safety systems 30, 32 in the well system 10 of FIG.
1. The safety system 40 may also be used in other well systems in
keeping with the principles of the invention.
[0046] As depicted in FIG. 2, the safety system 40 includes an
assembly 42 positioned between a firing pin 44 and an explosive
component. The details of the assembly 42 are not visible in FIG.
2, but examples of the assembly will be described in detail
below.
[0047] The assembly 42 selectively prevents the firing pin 44 from
contacting the explosive component 46 to thereby prevent detonation
of the explosive component. The assembly 42 may prevent such
contact between the firing pin 44 and the explosive component 46 in
various ways, for example, by blocking a passage 48 between the
firing pin and the explosive component. The assembly 42 may prevent
contact between the firing pin 44 and the explosive component 46 in
any manner (some of which are described in detail below) in keeping
with the principles of the invention.
[0048] The firing pin 44 may be a part of the firing head 26, or it
may be part of another portion of the perforating assembly 18 (such
as a detonation transfer sub). The firing pin 44 may be displaced
in response to any type of stimulus, such as mechanical force,
pressure, detonation of another explosive component adjacent the
firing pin, etc.
[0049] The explosive component 46 is depicted in FIG. 2 as being of
the type known to those skilled in the art as an initiator.
Detonation of the initiator is transferred to another explosive
component 50 of the type known to those skilled in the art as a
booster, and detonation of the booster is transferred to yet
another explosive component 52 of the type known to those skilled
in the art as a detonating cord.
[0050] The explosive components 46, 50, 52 described above are
merely examples of the wide variety of explosive components for
which detonation may be selectively permitted and prevented using
the safety system 40. Other types include, but are not limited to,
perforating charges, cutting charges, strip charges, linear
charges, setting charges, etc.
[0051] Referring additionally now to FIG. 3, an alternate
configuration of the safety system 40 is representatively
illustrated. In this configuration, the assembly 42 is used to
selectively permit and prevent transfer of detonation between
multiple boosters (explosive components 50) connected to multiple
lengths of detonating cord (explosive components 52).
[0052] The assembly 42 may prevent such detonation transfer by, for
example, blocking the passage 48 between the explosive components
50. However, the assembly 42 may prevent detonation transfer
between the explosive components 50 in any manner (some of which
are described in detail below) in keeping with the principles of
the invention.
[0053] Referring additionally now to FIG. 4, a schematic
cross-sectional view of the safety system 40 is representatively
illustrated. In this view it may be seen that this configuration of
the assembly 42 includes a blocking member 54 in the form of a
plate which blocks the passage 48 to prevent detonation of an
explosive component (for example, by preventing contact between the
firing pin 44 and the explosive component 46, by preventing
detonation transfer between the explosive components 50, etc.).
[0054] The assembly 42 further includes a thermal actuator 56 for
displacing the blocking member 54 relative to the passage 48. The
thermal actuator 56 is preferably of the type which includes a
material having a volume which varies in response to temperature
change.
[0055] Suitable thermal actuators are manufactured by
Therm-Omega-Tech, Inc. (which actuators include a material that
changes phase at a predetermined temperature), Caltherm
Corporation, Rostra Vernatherm LLC, and others. Thermal actuators
are available which extend or lengthen upon a temperature increase
and retract upon a temperature decrease, which retract upon a
temperature increase and extend or lengthen upon a temperature
decrease, and others which rotate in response to a temperature
change.
[0056] As depicted in FIG. 4, the thermal actuator 56 is of the
type which extends upon a temperature increase, but the actuator is
shown in its retraced configuration. A rod 58 of the actuator 56 is
connected to the blocking member 54.
[0057] The actuator 56 may be assisted in maintaining the blocking
member 54 in its position blocking the passage 48 by means of
biasing devices 60 (such as springs, etc.). Alternatively, the
actuator 56 may be capable of exerting sufficient force to displace
the member 54 to this position, and to maintain the member in this
position, without use of the biasing devices 60.
[0058] Referring additionally now to FIG. 5, the safety system 40
is representatively illustrated after a temperature increase has
caused the actuator 56 to extend the rod 58 further outward and
thereby displace the blocking member 54 so that it no longer blocks
the passage 48. Detonation of the explosive components 46, 50, 52
in either of the configurations of FIGS. 2 & 3 is now permitted
by the safety system 40.
[0059] The temperature increase is preferably due to installation
of the safety system 40 in the well. Of course, the local
geothermal gradient and the depth at which the safety system 40 is
to be installed are factors which will influence the available
temperature increase and, thus, the design of the thermal actuator
56, so that reliable operation of the assembly 42 in a particular
well system is assured.
[0060] In an important feature of the safety system 40, the
displacement of the blocking member 54 by the thermal actuator 56
is reversible, and may be reversible multiple times. That is, the
thermal actuator 56 may displace the blocking member 54 to its
positions depicted in FIGS. 4 & 5 in response to any number of
respective temperature increases and decreases.
[0061] For example, when used in the well system 10 of FIG. 1, the
safety system 40 may be used to prevent detonation of the explosive
components 46, 50, 52 while the perforating assembly 18 is near the
surface (i.e., at a relatively low temperature). When the
perforating assembly 18 (including the safety system 40) is
installed in the wellbore 14, the resulting temperature increase
will cause the actuator 56 to displace the blocking member 54, so
that detonation of the explosive components 46, 50, 52 is permitted
(as depicted in FIG. 5). Upon retrieval of the perforating assembly
18 to the surface (such as due to a misfire of the firing head 26,
or another circumstance resulting in undetonated explosive
components possibly being brought back to the surface), the
resulting temperature decrease will cause the actuator 56 to
displace the blocking member 54 back to its position blocking the
passage 48 and preventing detonation of the explosive components
46, 50, 52.
[0062] Referring additionally now to FIGS. 6 & 7, schematic
cross-sectional views of an alternate configuration of the safety
system 40 are representatively illustrated. In this configuration,
the blocking member 54 is pivoted or rotated about a pivot 62 by
the actuator 56, instead of being displaced laterally relative to
the passage 48 as in the configuration of FIGS. 4 & 5.
[0063] In FIG. 6, the member 54 blocks the passage 48, and
detonation of the explosive components 46, 50, 52 is thereby
prevented at a corresponding relatively low temperature. In FIG. 7,
the member 54 does not block the passage 48, and detonation of the
explosive components 46, 50, 52 is thereby permitted at a
corresponding relatively high temperature.
[0064] As with the configuration of FIGS. 4 & 5 (and the other
alternate configurations of the safety system 40 described below),
the displacement of the blocking member 54 is reversible. Thus, the
safety system 40 always prevents detonation of the explosive
components 46, 50, 52 at any time the safety system is at a
sufficiently low temperature (such as near the surface or at a
depth relatively shallow in the well).
[0065] Referring additionally now to FIG. 8, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the blocking member 54 is displaced laterally by the
actuator 56 in a recess 64 which intersects the passage 48.
[0066] The blocking member 54 has an opening 66 formed therein
which may be aligned with the passage 48 when it is desired to
permit detonation of the explosive components 46, 50, 52. As
depicted in FIG. 8, the member 54 is in a position in which the
opening 66 is not aligned with the passage 48, and so detonation of
the explosive components 46, 50, 52 is prevented. The actuator 56
will displace the member 54 to align the opening 66 and passage 48
in response to a sufficient increase in temperature.
[0067] In the configuration as shown in FIG. 8, the firing pin 44
is propelled through the passage 48 in response to detonation of a
detonating cord (explosive component 52) and booster (explosive
component 50) above the firing pin. Until such detonation occurs,
the firing pin 44 is secured in place by shear pins 68 or other
suitable fasteners. A vent passage 70 prevents undesirable pressure
increase in the passage 48 below the firing pin 44 when the firing
pin is propelled downward through the passage.
[0068] Referring additionally now to FIG. 9, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. This
configuration is similar in many respects to the configuration of
FIG. 8.
[0069] However, in this configuration the blocking member 54 does
not include the opening 66. Instead, the blocking member 54 is
displaced by the actuator 56 to a position in which it no longer
blocks the passage 48 in response to a sufficient temperature
increase.
[0070] For this purpose, the actuator 56 is of the type in which
the rod 58 is retracted (to thereby laterally displace the member
54 so that it no longer blocks the passage 48) in response to a
temperature increase. The actuator 56 will extend the rod 58 (to
thereby laterally displace the member 54 so that it again blocks
the passage 48) in response to a subsequent temperature
decrease.
[0071] Thus, the actuator 56 is preferably of the type which is
known to those skilled in the art as a "reverse" thermal actuator.
Such actuators still include a material having a volume which
varies in response to a temperature change, but the actuators are
constructed in a manner causing the actuators to lengthen or extend
in response to a temperature decrease, and causing the actuators to
retract in response to a temperature increase.
[0072] As will be readily appreciated from the above descriptions
of various configurations of the safety system 40, detonation of an
explosive component may be prevented by blocking a passage (for
example, to block displacement of a firing pin through the passage,
or to prevent detonation transfer between explosive components,
etc.), and detonation of the explosive component may be permitted
by unblocking the passage. Referring additionally now to FIGS. 10
& 11, schematic cross-sectional views of another alternate
configuration of the safety system 40 is representatively
illustrated, in which another manner of blocking and unblocking the
passage 48 may be accomplished.
[0073] In this configuration, the blocking member 54 is in the form
of a shaft which is rotated in the recess 64 intersecting the
passage 48. This rotation of the shaft is caused by the actuator 56
which extends or retracts the rod 58 in response to corresponding
increases or decreases in temperature.
[0074] The rod 58 is connected to the blocking member 54 by means
of a yoke 72 and arm 74. The yoke 72 and arm 74 transfer linear
displacement of the rod 58 into rotational displacement of the
blocking member 54.
[0075] As depicted in FIG. 10, the opening 66 is rotated so that it
is not aligned with the passage 48, and the passage is thus
blocked, preventing detonation of the explosive components 46, 50,
52. As depicted in FIG. 11, the opening is rotated so that it is
aligned with the passage 48, and the passage is thus unblocked,
permitting detonation of the explosive components 46, 50, 52.
[0076] The blocking member 54 is rotated to the position shown in
FIG. 10 in response to a temperature decrease, and the blocking
member is rotated to the position shown in FIG. 11 in response to a
temperature increase. As with the other configurations of the
safety system 40 described herein, these displacements of the
blocking member 54 are reversible and repeatable.
[0077] Note that, in the configuration of FIGS. 10 & 11, the
blocking member 54 is rotated about an axis (defined by the recess
64) which is orthogonal to the passage 48. In contrast, in the
configuration of FIGS. 6 & 7, the blocking member 54 is rotated
about an axis (defined by the pivot 62) which is parallel to the
passage 48.
[0078] In some embodiments of the safety system 40, greater
displacement may be desired than can conveniently be obtained from
a single thermal actuator 56. In those circumstances, multiple
thermal actuators 56 may be used, with the actuators being
connected in series.
[0079] Similarly, in some embodiments of the safety system 40,
greater force may be desired than can conveniently be obtained from
a single thermal actuator 56. In those circumstances, multiple
thermal actuators 56 may be used, with the actuators being
connected in parallel.
[0080] In FIGS. 12 & 13, an example is representatively
illustrated of multiple actuators 56 connected in series. Although
only two actuators 56 are depicted, any number of actuators may be
connected in series (and/or in parallel).
[0081] In FIG. 12, the actuators 56 are in their retracted
configurations. In FIG. 13, the actuators 56 are in their extended
configurations. It will be readily appreciated that the actuators
56 connected in series can produce greater displacement than a
single one of the actuators can produce.
[0082] Referring additionally now to FIG. 14, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, multiple actuators 56 are used to produce sufficient
displacement to rotate the blocking member 54 relative to the
passage 48.
[0083] In addition, the displacement produced by the actuators 56
is transmitted to the arm 74 connected to the blocking member 54
via a rod 76, and the yoke 72 is integrally formed with the arm 74.
The biasing device 60 biases the rod 76 downward, i.e., so that the
blocking member 54 is rotated to its position blocking the passage
48 when the actuators 56 are in their retracted configurations. As
discussed above, the biasing device 60 may not be used if the
actuators 56 produce sufficient retracting force to rotate the
blocking member 54 without assistance from the biasing device.
[0084] Referring additionally now to FIG. 15, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the safety system 40 does not selectively block and
unblock the passage 48 to thereby respectively prevent and permit
detonation of the explosive components 46, 50, 52.
[0085] Instead, additional explosive components 50, 52 contained in
a shuttle 80 are displaced by a material 78 having a volume which
varies in response to changes in temperature. This material 78 may
be the same as the material used in the actuators 56 described
above.
[0086] The material 78 may be a solid, a liquid, a gas, a gel, a
plastic, a combination thereof, or any other type of material. The
material 78 may change phase to produce relatively large changes in
volume.
[0087] For example, a material known as THERMOLOID.TM. is used in
the thermal actuators available from Therm-Omega-Tech, Inc. This
material (as well as other materials) may be suitable for use as
the material 78 in the safety system 40 of FIG. 15. Indeed, the
combination of the shuttle 80 and the material 78 in a chamber 82
of the assembly 42 may be considered as the thermal actuator 56 in
this embodiment of the safety system 40.
[0088] The material 78 increases in volume in response to a
temperature increase. When the material 78 increases in volume, the
shuttle 80 is displaced laterally relative to the passage 48.
Eventually, the explosive components 50, 52 contained in the
shuttle 80 are aligned with the explosive components 50 in the
passage 48, and detonation transfer through the passage is
permitted.
[0089] The biasing device 60 biases the shuttle 80 toward the
chamber 82 so that, when the temperature decreases and the volume
of the material 78 correspondingly decreases, the shuttle will
displace laterally and the explosive components 50, 52 in the
shuttle will no longer be aligned with the explosive components in
the passage 48. Detonation transfer through the passage 48 will
thereby be prevented.
[0090] Other types of thermal actuators, such as the thermal
actuators 56 described above and depicted in FIGS. 2-14, may be
used in place of the material 78 in the chamber 82 to displace the
shuttle 80, if desired.
[0091] Referring additionally now to FIGS. 16 & 17, schematic
cross-sectional views of another alternate configuration of the
safety system 40 are representatively illustrated. In this
configuration, the thermal actuator 56 includes an arm 84 made of a
material which changes shape in response to changes in
temperature.
[0092] The arm 84 is connected to the blocking member 54. At
relatively low temperature, the arm 84 has a shape which positions
the blocking member 54 so that it blocks the passage 48, thereby
preventing detonation of explosive components 50, 52 on one side of
the member, as depicted in FIG. 16.
[0093] However, at a relatively high temperature, the arm 84 has
another shape which positions the blocking member 54 so that it
does not block the passage 48, thereby permitting detonation of the
explosive components 50, 52 on either side of the recess 64, as
depicted in FIG. 17.
[0094] The arm 84 could be constructed of various different
materials. Examples of suitable materials include, but are not
limited to, bimetallics, shape memory alloys, etc.
[0095] Referring additionally now to FIG. 18, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the assembly 42 includes the variable volume
material 78 contained within an enclosure 86 positioned between a
rod 88 and the firing pin 44 in the passage 48.
[0096] The rod 88 is propelled downward in response to detonation
of explosive components 50, 52 above a piston 90 at an upper end of
the rod. The enclosure 86 is preferably somewhat flexible, so that
if the material 78 is at a relatively low temperature (and the
material thus has a reduced volume), insufficient force will be
transmitted from the rod 88 to the firing pin 44 to shear the shear
pin 68 retaining the firing pin in the position shown in FIG.
18.
[0097] However, when the material 78 is at a relatively high
temperature, the increase in volume of the material causes the
combined material and enclosure 86 in the assembly 42 to become
more rigid. In this condition, the material 78 and enclosure 86 in
the assembly 42 can transmit sufficient force from the rod 88 to
the firing pin 44 to shear the shear pins 68 and propel the firing
pin into contact with the explosive component 46, thereby
detonating the explosive components 46, 50, 52.
[0098] Referring additionally now to FIG. 19, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. This
configuration is similar in many respects to the configuration of
FIG. 18. However, the rod 88, piston 90 and associated biasing
device 60 and shear pins 68 are not used in the configuration of
FIG. 19.
[0099] Instead, detonation of the explosive components 50, 52 above
the assembly 42 (which includes the material 78 and the enclosure
86) applies a downwardly directed force to the assembly. If the
material 78 is at a relatively high temperature (and thus has an
increased volume), then the assembly 42 will have increased
rigidity and sufficient force will be transmitted through the
assembly to the firing pin 44 to propel the firing pin into contact
with the explosive component 46. If, however, the material 78 is at
a relatively low temperature (and thus has a reduced volume), then
the assembly 42 will have a correspondingly reduced rigidity and
sufficient force will not be transmitted through the assembly to
the firing pin 44 to cause detonation of the explosive component
46.
[0100] In the configurations of FIGS. 18 & 19, the enclosure 86
may be made of any material suitable to contain the material 78
when it has increased volume, and to withstand the resulting stress
caused by the expansion of the material 78, while being
sufficiently flexible to reduce force transmission through the
assembly 42 when the material 78 has a reduced volume. For example,
the enclosure 86 could be made of high strength polymers,
relatively thin metals, etc.
[0101] Referring additionally now to FIG. 20, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the actuator 56 is used to extend and retract the
firing pin 44 in response to corresponding increases and decreases
in temperature of the material 78 in the actuator.
[0102] In contrast to the other embodiments of the safety system 40
described above, the firing pin 44 is a part of the actuator 56 in
the configuration of FIG. 20. For example, the firing pin 44 may be
formed on an end of the rod 58.
[0103] When a sufficient force 92 is applied to the upper end of
the actuator 56, shear pins 68 will shear and the actuator will be
propelled downward through the passage 48 toward the explosive
component 46. The force 92 may be applied mechanically, by
pressure, such as detonation of explosive components above the
actuator 56, or by other means.
[0104] If the firing pin 44 extends outwardly from the actuator 56
a sufficient distance, then the firing pin will contact the
explosive component 46 and cause detonation of the explosive
components 46, 50, 52. If, however, the firing pin 44 is retracted
into the actuator 56 (as depicted in FIG. 20), then the firing pin
will not contact the explosive component 46.
[0105] The firing pin 44 extends outwardly from the actuator 56 in
response to a temperature increase, which causes the volume of the
material 78 to increase. A piston 94 at an upper end of the rod 58
is displaced downward when the material 78 volume increases,
thereby downwardly displacing and outwardly extending the firing
pin.
[0106] Similarly, the firing pin 44 is retracted when the material
78 is at a relatively low temperature and has a corresponding
reduced volume. The biasing device 60 may assist in upwardly
displacing the piston 94, rod 58 and firing pin 44 if the decreased
volume of the material 78 does not produce sufficient force to do
this without the aid of the biasing device.
[0107] Referring additionally now to FIG. 21, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the actuator 56 is used to alternately increase and
decrease a gap G between the actuator and explosive components 50,
52 above the actuator.
[0108] When the gap G is sufficiently large, detonation of the
explosive components 50, 52 above the actuator 56 will not generate
sufficient downward force on the actuator to cause the shear pins
68 to shear and propel the firing pin 44 into contact with the
explosive component 46. However, when the gap G is sufficiently
small, the force applied to the actuator 56 will be great enough to
cause the shear pins 68 to shear and propel the firing pin 44 into
contact with the explosive component 46, thereby causing detonation
of the explosive components 46, 50, 52.
[0109] The size of the gap G is determined by the volume of the
material 78, which is positioned between a piston 96 connected to
the firing pin 44 and an outer housing 98 of the actuator 56. When
the material 78 volume increases in response to increased
temperature, the housing 98 is displaced upward, thereby reducing
the gap G.
[0110] When the material 78 volume decreases in response to reduced
temperature, the housing 98 is displaced downward, thereby
increasing the gap G. The biasing device 60 may assist in
displacing the housing 98 downward, if desired.
[0111] Referring additionally now to FIG. 22, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the thermal actuator 56 is used to rotate the
blocking member 54 relative to the passage 48.
[0112] The blocking member 54 rotates about a pivot 100. The pivot
100 defines an axis of rotation of the blocking member 54 which is
orthogonal to the passage 48.
[0113] As depicted in FIG. 22, the actuator 56 has rotated the
blocking member 54 to a position in which the passage 48 is
unblocked, and so detonation of the explosive components 46, 50, 52
below the assembly 42 is permitted. The actuator 56 rotates the
blocking member 54 to this position in response to increased
temperature.
[0114] However, when the temperature is sufficiently low, the
actuator 56 will rotate the blocking member 54 (clockwise as viewed
in FIG. 22) to a position in which the member blocks the passage 48
and detonation of the explosive components 46, 50, 52 below the
assembly 42 is prevented.
[0115] Referring additionally now to FIG. 23, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the blocking member 54 is displaced laterally by the
actuator 56 in the recess 64 which intersects the passage 48.
[0116] The blocking member 54 has the opening 66 formed therein
which may be aligned with the passage 48 when it is desired to
permit detonation of the explosive components 46, 50, 52 below the
assembly 42. As depicted in FIG. 23, the member 54 is in a position
in which the opening 66 is not aligned with the passage 48, and so
detonation of the explosive components 46, 50, 52 below the
assembly 42 is prevented. The actuator 56 will displace the member
54 to align the opening 66 and passage 48 in response to a
sufficient increase in temperature.
[0117] The member 54 is displaced laterally in response to
extension and retraction of the rod 58 by the actuator 56.
Specifically, a rounded end of the rod 58 engages a rounded end of
the member 54 to thereby cause lateral displacement of the member,
similar to a cam and follower arrangement.
[0118] In the configuration as shown in FIG. 23, the firing pin 44
is propelled through the passage 48 in response to detonation of
the detonating cord (explosive component 52) and booster (explosive
component 50) above the firing pin. Until such detonation occurs,
the firing pin 44 is secured in place by the shear pins 68 or other
suitable fasteners.
[0119] Referring additionally now to FIG. 24, a schematic
cross-sectional view of another alternate configuration of the
safety system 40 is representatively illustrated. In this
configuration, the actuator 56 rod 58 engages a recess 102 formed
in the firing pin 44 to thereby prevent detonation of the explosive
components 46, 50, 52 below the assembly 42.
[0120] When the temperature is increased sufficiently, the actuator
56 will retract the rod 58 from the recess 102, thereby permitting
the firing pin 44 to be propelled downward through the passage 48
in response to detonation of the explosive components 50, 52 above
the firing pin. However, when the actuator 56 is at a relatively
low temperature, engagement between the rod 58 and the recess 102
prevents displacement of the firing pin 44, even though detonation
of the explosive components 50, 52 above the firing pin might
produce sufficient force to shear the shear pins 68.
[0121] It may now be fully appreciated that the various
configurations of the thermally activated explosives safety system
40 described above provide greatly improved safety in well
operations utilizing explosive components.
[0122] Although some of the configurations of the safety system 40
have been described above as if the configuration is used to
selectively permit and prevent detonation transfer between
explosive components, and other configurations of the safety system
have been described above as if the configuration is used to
selectively permit and prevent contact between a firing pin and an
explosive component, it should be clearly understood that any of
the configurations may be used for either purpose with appropriate
modifications.
[0123] For convenience and clarity of description, the various
configurations of the safety system 40 have been described above
with each configuration oriented as if detonation transfer occurs
in a downward direction through the safety system. It will be
appreciated, however, that detonation transfer can occur in an
upward direction (for example, if a firing head initiates
detonation from the bottom of a perforating assembly, etc.) or
horizontally, or at any inclination. Accordingly, it should be
understood that the various configurations of the safety system 40
may be used in any orientation in keeping with the principles of
the invention.
[0124] Of course, a person skilled in the art would, upon a careful
consideration of the above description of representative
embodiments of the invention, readily appreciate that many
modifications, additions, substitutions, deletions, and other
changes may be made to these specific embodiments, and such changes
are within the scope of the principles of the present invention.
Accordingly, the foregoing detailed description is to be clearly
understood as being given by way of illustration and example only,
the spirit and scope of the present invention being limited solely
by the appended claims and their equivalents.
* * * * *