U.S. patent application number 11/957757 was filed with the patent office on 2009-06-18 for explosive shock dissipater.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Larry Grigar, Steven W. Henderson.
Application Number | 20090151589 11/957757 |
Document ID | / |
Family ID | 40133734 |
Filed Date | 2009-06-18 |
United States Patent
Application |
20090151589 |
Kind Code |
A1 |
Henderson; Steven W. ; et
al. |
June 18, 2009 |
EXPLOSIVE SHOCK DISSIPATER
Abstract
A method of dampening stress waves propagated from the
detonation of an explosive device in a wellbore to protect a device
positioned downhole including the steps of positioning a shock
dissipater between an explosive device and a package; detonating
the explosive device propagating a stress wave toward the shock
dissipater and the package; and reflecting a portion of the stress
wave in the shock dissipater. The shock dissipater may have one or
more interface formed between materials of dissimilar acoustic
impedances. The shock dissipater may reflect a compressive portion
of the stress wave at one interface and a tensile portion of the
stress wave at another interface.
Inventors: |
Henderson; Steven W.; (Katy,
TX) ; Grigar; Larry; (East Bernard, TX) |
Correspondence
Address: |
SCHLUMBERGER RESERVOIR COMPLETIONS
14910 AIRLINE ROAD
ROSHARON
TX
77583
US
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
40133734 |
Appl. No.: |
11/957757 |
Filed: |
December 17, 2007 |
Current U.S.
Class: |
102/333 |
Current CPC
Class: |
E21B 17/07 20130101;
F42D 3/04 20130101; F42D 5/045 20130101; G01V 1/52 20130101 |
Class at
Publication: |
102/333 |
International
Class: |
F42D 1/00 20060101
F42D001/00 |
Claims
1. An apparatus for dampening a stress wave, the apparatus
comprising a first interface formed between a first layer of
material and a second layer of material, the first and second
layers of material having dissimilar acoustic impedances.
2. The apparatus of the claim 1, further including a third layer of
material positioned in contact with the second layer of material to
form a second interface, the second and third layers of material
having dissimilar acoustic impedances.
3. The apparatus of claim 2, wherein the acoustic impedance of the
first layer of material and the acoustic impedance of the third
layer of material are dissimilar.
4. The apparatus of claim 2, wherein the acoustic impedance of the
first layer is less than the acoustic impedance of the second
impedance layer and the second acoustic impedance is greater than
the acoustic impedance of the third layer of material.
5. The apparatus of claim 4, wherein the acoustic impedance of the
first layer of material and the acoustic impedance of the third
layer of material are dissimilar.
6. The apparatus of claim 2, wherein the acoustic impedance of the
first layer is greater than the acoustic impedance of the second
impedance and the second acoustic impedance is greater than the
acoustic impedance of the third layer of material.
7. A wellbore tool string, the tool string comprising: an explosive
device, a package; and a shock dissipater positioned between the
explosive device and the package, the shock dissipater including a
first interface formed between a first layer of material and a
second layer of material, the first and second layers of material
having dissimilar acoustic impedances.
8. The tool string of claim 7, wherein the shock dissipater is a
sub assembly.
9. The tool string of claim 7, further including a housing having
an axial bore and a longitudinal axis, wherein the shock dissipater
is positioned across the axial bore such that the first interface
is oriented substantially perpendicular to the longitudinal
axis.
10. The tool string of claim 7, further including a conduit formed
through the shock dissipater, the conduit being oriented
substantially parallel to the longitudinal axis of the housing.
11. The tool string of claim 7, further including a third layer of
material positioned in contact with the second layer of material to
form a second interface, the second and third layers of material
having dissimilar acoustic impedances.
12. The tool string of claim 11, wherein one of the layers of
material is a metal, another one of the layers of material is an
elastomeric material, and another one of the layers of material is
foam.
13. The tool string of claim 11, wherein the acoustic impedance of
the first layer of material and the acoustic impedance of the third
layer of material are dissimilar.
14. The tool string of claim 11, wherein the acoustic impedance of
the first layer is less than the acoustic impedance of the second
impedance and the second acoustic impedance is greater than the
acoustic impedance of the third layer of material.
15. The tool string of claim 14, wherein the acoustic impedance of
the first layer of material and the acoustic impedance of the third
layer of material are dissimilar.
16. The tool string of claim 11, wherein the acoustic impedance of
the first layer is greater than the acoustic impedance of the
second impedance and the second acoustic impedance is greater than
the acoustic impedance of the third layer of material.
17. The tool string of claim 11, further including a housing having
an axial bore and a longitudinal axis, wherein the shock dissipater
is positioned across the axial bore such that the first interface
is oriented substantially perpendicular to the longitudinal
axis.
18. The tool string of claim 17, further including a conduit formed
through the shock dissipater, the conduit being oriented
substantially parallel to the longitudinal axis of the housing.
19. A method of dampening stress waves propagated from the
detonation of an explosive device in a wellbore to protect a device
positioned downhole, the method comprising the steps of:
positioning a shock dissipater between an explosive device and a
package; detonating the explosive device propagating a stress wave
toward the shock dissipater and the package; and reflecting a
portion of the stress wave in the shock dissipater.
20. The method of claim 19, wherein the step of reflecting
includes: reflecting a tensile wave portion of the stress wave at
one interface between layers of material; and reflecting a
compressive wave portion of the stress wave at another interface
between layers of material.
21. The apparatus of claim 2, wherein the acoustic impedance of the
first layer of material and the acoustic impedance of the third
layer of material are similar.
Description
TECHNICAL FIELD
[0001] The present invention relates in general to explosive
devices and more particular to devices and systems for shielding
devices from the stress energy propagated from explosions by
dissipating the propagated stress energy.
BACKGROUND
[0002] It is often necessary to use explosives during wellbore
operations, in particular during the drilling of a well. For
example, it may be desired to obtain a sidewall core before the
well is completed. To obtain a core, an explosive charge may be
detonated to propel a coring device into the wall to obtain a
sample. It is also commonly required to provide communication
between the wellbore and the surrounding formation after the well
is completed with a casing. To provide the necessary communication,
perforations are created through the casing, cement and into the
formation. The perforations are commonly created with shaped
explosive charges.
[0003] These explosive devices may be lowered and positioned at the
desired location in various manners. In the simplest of operations
the explosive charge may be positioned by measuring the length of
the conveyance, carrying the explosive charge, that is run into the
well until it is believed that the explosive charges are properly
positioned.
[0004] In many instances it is desired or necessary to include
electronic instrumentation or other mechanical packages in close
proximity to the explosive charges or other working packages that
may be sensitive to the explosive shock waves. For example, in
high-angle wells and horizontal wells it may be necessary to
include locating electronics with the conveyance and explosive
device for proper positioning. Electronic equipment and the like
are also desirable for locating thin zones and positioning of the
explosive device. Further, in deep wells the stretch of conveyance
(wireline or pipe) alone may necessitate the use of locating
equipment for positioning. Additionally, it is often desired to
perform multiple operations in a well without running into and then
out of the well between operations, in these cases it is desirable
to include electronic equipment in the tool string.
[0005] The firing of the explosive charges produces a large shock
wave that propagates through the wellbore and perforating assembly.
These shock waves can exert massive forces upon the electronic
instrumentation and other downhole equipment, often resulting in
damage to or failure of the equipment. It may be desired to shield
any number of various devices, or packages, from the shock waves
propagated from the explosive device. Packages to be shield from
the explosive shock waves may include, without limitation to,
sensors, gauges, logging instruments, telemetry devices, additional
explosives, and valves.
SUMMARY
[0006] Examples of apparatus, devices, systems and method for
dissipating a stress wave to shield a package such as, without
limitation, an electronic system or working member from the stress
wave. In one example, an apparatus for dampening a stress wave
includes a first interface formed between a first layer of material
and a second layer of material, the first and second layers of
material having dissimilar acoustic impedances.
[0007] In another example, a wellbore tool string includes an
explosive device, a package, and a shock dissipater positioned
between the explosive device and the package, the shock dissipater
includes a first interface formed between a first layer of material
and a second layer of material, the first and second layers of
material having dissimilar acoustic impedances. Additional layer of
alternating acoustic impedance material can be add to further
reduce the shock.
[0008] In another example, a method of dampening stress waves
propagated from the detonation of an explosive device in a wellbore
to protect a device positioned downhole includes the steps of
positioning a shock dissipater between an explosive device and a
package; detonating the explosive device propagating a stress wave
toward the shock dissipater and the package; and reflecting a
portion of the stress wave in the shock dissipater back to the
originating device and propagating a smaller portion of the shock
wave through the device.
[0009] The foregoing has outlined some of the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The foregoing and other features and aspects of the present
invention will be best understood with reference to the following
detailed description of a specific embodiment of the invention,
when read in conjunction with the accompanying drawings,
wherein:
[0011] FIG. 1 is a wellbore schematic illustrating an example of a
tool string incorporating a shock dissipating system of the present
invention;
[0012] FIG. 2 is partial cross-sectional view of an example of a
shock dissipater incorporated into a sub assembly; and
[0013] FIG. 3 is an illustration of a shock dissipater in
isolation.
DETAILED DESCRIPTION
[0014] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0015] As used herein, the terms "up" and "down"; "upper" and
"lower"; and other like terms indicating relative positions to a
given point or element are utilized to more clearly describe some
elements of the embodiments of the invention. Commonly, these terms
relate to a reference point at the surface from which drilling
operations are initiated as being the top point and the total depth
of the well being the lowest point.
[0016] FIG. 1 is a schematic illustration of an example of a system
for dissipating the shock from an explosion, generally denoted by
the numeral 10. System 10 includes a tool string, generally denoted
by the numeral 12, suspended by a conveyance 14 in a well or
wellbore 16. Conveyance 14 may include without limitation wireline,
slickline, coiled tubing, jointed tubing and the like for carrying
and suspending tool string 12 in wellbore 16. It is recognized that
conveyance 14 may be included in whole or in part with tool string
12.
[0017] In the illustrated example, tool string 12 includes an
explosive device 18, a shock dissipater 20, and a package 22.
Explosive device 18 is illustrated as a perforating gun; however
explosive device 18 may be without limitation a coring device, a
cutting tool or other device that includes an explosive charge or
other element that produces a shock wave upon activation.
[0018] Package 22 may be any device, tool or system that it is
desired to be protected from the shock waves propagated from the
detonation or activation of explosive device 18. For purposes of
description herein, package 22 is often referred to generally as an
electronics package. For example, package 22 may include
electronics and instrumentation for sensing pressure or
temperature. Package 22 may be an electronics package such as,
without limitation, logging instruments, telemetry equipment, and
positioning instruments. However, it is recognized that package 22
may include any other device that may need to be shielded from the
shock waves of the explosive device, including without limitation,
valves and explosive devices.
[0019] Shock dissipater 20 is provided for dampening shock energy
generated by downhole explosive device 18, thus providing a means
for running packages 22 in tool string 12. In FIG. 1, dissipation
device 20 is illustrated as a sub assembly that is positioned
within tool string 12 between perforating gun 18 and package 22.
However, in other examples dissipating device 20 may be formed for
example as part of package 22 or within explosive device 18.
[0020] Refer now to FIG. 2 wherein an example of shock dissipater
20 is illustrated. Dissipater 20 of the present example is
illustrated incorporated into an assembly that is adapted for
threadably connecting within tool string. Dissipater 20 includes a
body or housing 24, which in the illustrated example is a tubular
collar having a longitudinal axis 26. In this example, housing 24
forms an axial bore 28 that, may or may not, extend the full length
of housing 24, as will be further explained below.
[0021] Dissipater 20, which will be described in more detail below
with reference to FIG. 3, includes two dissimilar members 30a and
30b that form an interface 32 therebetween. Dissipater 20 is
connected within housing 24 so that interface 32 is positioned
approximately perpendicular to longitudinal axis 26. A conduit 34,
indicated by the dashed lines, may be formed through shock
dissipater 20. In this example, conduit 34 is oriented
substantially parallel to longitudinal axis 26 and bore 28. Conduit
34 may be provided, for example, for passing wiring (not shown) to
perforating gun 18 (FIG. 1) or other electronics, or for passing a
drop bar for detonating explosive device 18.
[0022] Referring now to FIG. 3, wherein an example of shock
dissipater 20 is shown in isolation. In the illustrated example,
dissipater 20 is constructed of three members or layers denoted by
the numeral 30a, 30b, and 30c. Although the Figures only
illustrated examples having either two layers 30, one interface 32,
or three layers 30, two interfaces 32, more than three layers 30
may be utilized. Each layer 30 is constructed of a material having
acoustic impedance (I), which is defined generally as the acoustic
sound speed (c) in the material multiplied by the density (.rho.)
of the material of construction.
[0023] Layers 30 are positioned in contact with one another to form
interfaces 32. Adjacent layers 30 have dissimilar acoustic
impedance, and are referred to herein as dissimilar layer or
members. Thus, layer 30a has an impedance I.sub.a and layer 30b has
an impedance of I.sub.b. Similarly, 30c has an impedance I.sub.c,
which is different from and therefore dissimilar to its adjacent
layer 30b. Layer 30c has an impedance that is dissimilar to layer
30b, and that may be the same as or different from the impedance of
layer 30a.
[0024] Upon detonation of explosive device 18, shock or stress
waves, illustrated by arrows 36, propagate through the first
dissipating layer 30a encountered. Stress waves 36 include a
tensile portion and a compressive portion. When shock waves 36
encounter interface 32ab, a portion of the stress energy is
transmitted into the adjacent layer 30b, illustrated by the arrow
36t, and a portion is reflected, illustrated by the arrow 36r. When
stress energy 36t encounters interface 36bc a portion is
transmitted and a portion is reflected. Any of the interfaces could
be angled so as to deflect shock or stress waves coming from any
potential direction as necessary.
[0025] At each interface 32, provided the adjacent acoustic
impedances are different, a portion of the stress wave is
transmitted and a portion of the stress wave is reflected. When the
impedance of the first layer encountered is less than the impedance
of the second layer encountered (I.sub.a<I.sub.b) a tensile
stress wave is reflected. When the impedance of the first layer
encountered is greater than the impedance of the second layer
encountered (I.sub.a>I.sub.b) a compressive stress wave is
reflected.
[0026] A coefficient of reflection, KR, and a coefficient of
transmission, K.sub.T, is provided below wherein I.sub.1 is the
impedance of the first layer encountered by the stress wave and
I.sub.2 is the impedance of the layer across the interface from the
first layer.
K T = 2 I 2 I 2 + I 1 ##EQU00001## K R = I 2 - I 1 I 2 + I 1
##EQU00001.2##
[0027] With reference to FIGS. 1-3, dissipater 20 may be
constructed in various forms and positioned in different positions
to protect a package 22 as desired or needed. For example, package
22 may be an electronics package 22 that is positioned proximate to
explosive device 18 and therefore need a substantial amount of
protection from the shock wave encountered upon detonation. Shock
dissipater 20 may be positioned between package 22 and explosive
device 18 for example in a sub assembly, or positioned within the
housing incorporating package 22. Due to the high degree of shock,
or stress, wave dissipation required dissipater 20 may be formed
with more than one interface 32. A few examples of materials that
may be used for layers 30 include elastomeric materials, rubber,
plastic, various grades of metals, steel, iron, encapsulated water,
cement and air. If more than two layers 30 are utilized, the
materials of construction may be alternated, for example
rubber-steel-rubber, or may include more than two materials of
construction, for example rubber-steel-cement-steel. It is further
noted that the same type of material may be utilized in adjacent
layers, provided that the materials have dissimilar impedances.
Also, the same material may be used in non-adjacent layers along
the lines noted above.
[0028] From the foregoing detailed description of specific
embodiments of the invention, it should be apparent that a system
for dissipating impulse stress energy propagated from an explosive
device to shield a device from the stress energy that is novel has
been disclosed. Although specific embodiments of the invention have
been disclosed herein in some detail, this has been done solely for
the purposes of describing various features and aspects of the
invention, and is not intended to be limiting with respect to the
scope of the invention. It is contemplated that various
substitutions, alterations, and/or modifications, including but not
limited to those implementation variations which may have been
suggested herein, may be made to the disclosed embodiments without
departing from the spirit and scope of the invention as defined by
the appended claims which follow.
* * * * *