U.S. patent application number 10/656913 was filed with the patent office on 2006-01-19 for main body of explosive composition.
This patent application is currently assigned to BAKER HUGHES, INCORPORATED. Invention is credited to Robert R. Green, Hooshang Rezaie.
Application Number | 20060011278 10/656913 |
Document ID | / |
Family ID | 34465047 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060011278 |
Kind Code |
A1 |
Rezaie; Hooshang ; et
al. |
January 19, 2006 |
Main body of explosive composition
Abstract
One embodiment of the present invention discloses an explosive
material comprising a mix of a first quantity of explosive and a
second quantity of explosive. The first quantity of explosive
consists of a large particulate size explosive. The second quantity
of explosive consists of a small particulate size explosive. The
combination of the first and second quantity of explosives results
in an explosive mixture having a density greater than either the
first or second quantity of explosive. The explosive material is
encapsulated within a bonding agent to form a pelletized explosive.
The explosive material can be comprised of approximately 50% by
weight of the first quantity of explosive and approximately 50% by
weight of the second quantity of explosive.
Inventors: |
Rezaie; Hooshang; (Katy,
TX) ; Green; Robert R.; (Aransas Pass, TX) |
Correspondence
Address: |
Keith R Derrington;Simmons & Derrington LLP
Frost Bank Building
6750 West Loop South Suite 920
Bellaire
TX
77401
US
|
Assignee: |
BAKER HUGHES, INCORPORATED
|
Family ID: |
34465047 |
Appl. No.: |
10/656913 |
Filed: |
September 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60408242 |
Sep 5, 2002 |
|
|
|
Current U.S.
Class: |
149/92 |
Current CPC
Class: |
F42B 1/02 20130101; C06B
21/0083 20130101; C06B 45/22 20130101; C06B 45/02 20130101; C06B
21/0041 20130101 |
Class at
Publication: |
149/092 |
International
Class: |
C06B 25/34 20060101
C06B025/34 |
Claims
1. An explosive material comprising: a first quantity of explosive
admixed with a second quantity of explosive, said first quantity of
explosive comprising particles having a larger diameter than the
particles of said second quantity of explosive.
2. The explosive material of claim 1, wherein the combination of
said explosives produces an explosive mixture whose fixed volume
has a density greater than 90% of the theoretical mean density of
the explosive material.
3. The explosive material of claim 1 encapsulated within a bonding
agent to form a pelletized explosive.
4. The explosive material of claim 1 whose pressed density is from
approximately 96% to approximately 98% of its theoretical mean
density.
5. The explosive material of claim 1, wherein said first quantity
of explosive is selected from the group consisting of HMX, PBX,
TATB, PYX, HNS or DATB.
6. The explosive material of claim 1, wherein said second quantity
of explosive is selected from the group consisting of HMX, PBX,
TATB, PYX, HNS or DATB.
7. The explosive material of claim 1, where said first quantity of
explosive consists of particles having a diameter that ranges from
approximately 300 microns to approximately 45 microns.
8. The explosive material of claim 1, where said first quantity of
explosive consists of Class I explosive.
9. The explosive material of claim 1, where said second quantity of
explosive consists of particles having a diameter that ranges from
approximately 5 microns to approximately 7 microns.
10. The explosive material of claim 1, where said second quantity
of explosive consists of Class V explosive.
11. The explosive material of claim 1, where said second quantity
of explosive has a distribution of particles such that 90% of the
particles have a diameter of less than 10 microns.
12. The explosive material of claim 1 comprising approximately 50%
by weight of said first quantity of explosive and approximately 50%
by weight of said second quantity of explosive.
13. The explosive material of claim 1 comprising from approximately
25% to 75% by weight of said first quantity of explosive and from
approximately 25% to 75% by weight of said second quantity of
explosive.
14. A shaped charge comprising: a housing; a liner; and an
explosive material positioned between said housing and said liner,
said explosive material comprising a first quantity of explosive
consisting of a large particulate size explosive admixed with a
second quantity of explosive consisting of a small particulate size
explosive such that the combination of said explosives produces an
explosive mixture whose fixed volume has a density greater than
said first quantity of explosive or said second quantity of
explosive.
15. The explosive material of claim 14 encapsulated within a
bonding agent to form a pelletized explosive.
16. The explosive material of claim 14 whose bulk density is from
approximately 96% to approximately 98% of its theoretical mean
density.
17. The explosive material of claim 14, wherein said first quantity
of explosive is selected from the group consisting of HMX, PBX,
TATB, PYX, HNS or DATB.
18. The explosive material of claim 14, wherein said second
quantity of explosive is selected from the group consisting of HMX,
PBX, TATB, PYX, HNS or DATB.
19. The explosive material of claim 14, where said first quantity
of explosive consists of particles having a diameter that ranges
from approximately 300 microns to approximately 45 microns.
20. The explosive material of claim 14, where said first quantity
of explosive consists of Class I explosive.
21. The explosive material of claim 14, where said second quantity
of explosive consists of particles having a diameter that ranges
from approximately 5 microns to approximately 7 microns.
22. The explosive material of claim 14, where said second quantity
of explosive consists of Class V explosive.
23. The explosive material of claim 14, where said second quantity
of explosive has a distribution of particles such that 90% of the
particles have a diameter of less than 10 microns.
24. The explosive material of claim 14 comprising approximately 50%
by weight of said first quantity of explosive and approximately 50%
by weight of said second quantity of explosive.
25. The explosive material of claim 14 comprising from
approximately 25% to 75% by weight of said first quantity of
explosive and from approximately 25% to 75% by weight of said
second quantity of explosive.
26. A method of forming an explosive material comprising the steps
of: blending a first quantity of explosive of a large particulate
size with a second quantity of explosive of a small particulate
size to produce a blended explosive material whose fixed volume has
a density greater than 90% of the theoretical mean density of the
explosive material.
27. The method of claim 26 further comprising mixing said blended
explosive material with a fluid in a vessel to produce a slurry,
heating the slurry to initiate an encapsulation process, adding an
encapsulation agent to the slurry, mixing the slurry and
encapsulation agent together, and terminating the nucleation
process when granulated explosive pellets are formed whose diameter
are approximately 1000 microns to approximately 2000 microns.
28. The method of claim 26 further comprising blending said
explosive material to produce a pressed density of from
approximately 96% to approximately 98% of its theoretical mean
density.
29. The method of claim 26 further comprising blending 50% by
weight of said first quantity of explosive and blending 50% by
weight of said second quantity of explosive.
30. The method of claim 29 where said first quantity of explosive
consists of Class I explosive having particle sizes of
approximately 45 to 300 microns and said second quantity of
explosive consists of Class V explosives having particle sizes of
approximately 5 to 7 microns.
Description
RELATED APPLICATIONS
[0001] This application claims priority from co-pending U.S.
Provisional Application No. 60/408,242, filed Sep. 5, 2002, the
full disclosure of which is hereby incorporated by reference
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to the field of explosive
compositions. More specifically, the present invention relates to a
combination of explosive where the combination possesses operating
characteristics that are superior to the constituent components of
the combination.
[0004] 2. Description of Related Art
[0005] Explosive compositions, also known as high explosives, are
used in a variety of industrial applications including mining,
military ordinance, car safety bags, general pyrotechnic
applications, and in the production of hydrocarbons. One of the
predominate uses of high explosives in some ordinance applications
and in hydrocarbon production is in conjunction with shaped charge
perforating devices. With respect to hydrocarbon production, shaped
charges are used to perforate the casing circumscribing the oil/gas
well bore, the cement around the casing, and the surrounding
formation. The resulting perforation produces a pathway for
hydrocarbons contained within geological formations to travel into
the well bore and ultimately to the well head.
[0006] Shaped charges used for well bore perforating are generally
affixed within a cylindrical gun tube which is then inserted within
a gun body. Often many gun tubes are axially connected to form a
perforating string. Depending on the particular application, each
gun tube typically contains multiple shaped charges within its
circumference that are aligned to discharge radially outward from
the gun body. The outer diameter of the gun tubes can range from
less than 1.5 inches to almost 5 inches. The combination of gun
tube within a gun body is generally referred to as a perforating
gun. In use, the perforating gun is attached to a wireline and
inserted into the well bore. The wireline generally provides a
tethering support for the perforating gun while it is within the
well bore; it also is a conduit for electrical signals to be
provided from the surface to the perforating gun to detonate the
shaped charges.
[0007] An individual shaped charge usually comprises a housing, a
liner, and explosive positioned between the liner and the housing.
The housing is typically formed from high strength metals, such as
steel, and has a generally cylindrically cavity formed within which
extends from inside of the housing through one of its ends. As is
known in the art, explosive material is packed into the cavity and
a liner is pressed into the housing with the liner's outer
circumference abutting the inner circumference of the housing
cavity. This configuration confines the explosive between the liner
and the housing cavity. When the explosive within the shaped charge
is detonated, the force of the detonation collapses the liner and
ejects it from one end of the charge at very high velocity in a
pattern called a "jet". The jet penetrates the casing, the cement
and a quantity of the formation.
[0008] During packaging of the shaped charge, the explosives are
pressed into the housing under pressure under a liner. The
compressive forces generally range from about 20,000 to about
40,000 pounds force. Typical explosives used include HMX, RDX, TEX,
TATB, PYX, HNS, DATB, and PETN. The pressing of the explosive under
pressure not only positions the explosive into the housing, but
also compacts the explosive into a more dense form. While physical
constraints, such as yield strength of the housing, possible
desensitization of the booster charge, or inadvertent detonation of
the explosive, limit how much compaction can be applied to the
explosives; the explosives are compacted as much as is
possible.
[0009] Pressure compacting of most explosives into shaped charges
results in the pressed density of the explosive being at 85%-90% of
the theoretical mean density of the explosive. Generally pressed
density defines the density of a fixed quantity of explosive in
particulate form after the explosive has been pressed or compacted.
The bulk density of the explosive generally defines the density of
the explosive in loose form without the explosive first being
subjected to external mechanical forces, such as compaction.
Whereas the theoretical mean density of the explosive is the
density of explosive in solid form. The magnitudes of the bulk
density and press density are always less than the magnitude of the
theoretical mean density. This is due to the interstices that exist
between the individual particles of explosives, even when the
explosive is pressed or compacted. The presence of these
interstices, which have a lower density than the explosive, causes
the density of the volume of explosive particulate to be lower than
the density of a solid piece of explosive.
[0010] Explosive particles can be categorized based on their size.
One standard for this categorization is found in military standard
MIL-DTL-45444C. This standard allocates the particles into a
particular class depending on what weight percentage of the
particles can pass through specified sieve sizes. The
MIL-DTL-45444C classification system is illustrated in Table 1.
TABLE-US-00001 TABLE 1 MIL-DTL-45444C Explosive Particle
Classification Through U.S. Class I Class II Class III Class IV
Class V Class VI Standard Sieve Weight Weight Weight Weight Weight
Weight No. Percent Percent Percent Percent Percent Percent 8 -- --
-- 100 -- -- 12 -- -- 99 min 85 min -- 99 min 35 -- -- -- 25 +/- 15
-- -- 50 90 +/- 6 100 .sup. 40 +/- 15 -- -- 90 min 100 .sup. 50 +/-
10 -- .sup. 20 +/- 10 15 max -- .sup. 65 +/- 15 120 -- 98 min -- --
-- -- 200 20 +/- 6 -- .sup. 10 +/- 10 -- -- .sup. 30 +/- 15 325
.sup. 8 +/- 5 75 min -- -- 98 min .sup. 15 +/- 10
[0011] The classification system of Table 1 is not limited to a
single type of explosive, but includes explosives having different
chemical compositions. As such, particles of Class 1 HMX have the
same size or same size distribution as particles of Class 1
PETN.
[0012] As is well understood, increasing the kinetic energy of the
jet will in turn result in a larger diameter perforation, or a
deeper penetration. Many factors can affect the kinetic energy of
the jet, such as the size and type of liner, the size of the shaped
charge, the amount of explosive used, or the type of explosive.
Often, it is desired to maximize the jet energy in order to obtain
either a large diameter perforation or a deep penetration.
Increasing the amount of high explosive can in turn increase the
jet energy. However, physical dimensional constraints exist that
limit the housing capacity, which in turn limits the maximum amount
of explosive that can be packed within the housing.
[0013] Other physical factors of the explosive can also increase
the energy it can impart to the liner upon detonation. It is well
known that the dynamic velocity of an explosive is directly
proportional to the density of the explosive. It is also known that
the dynamic pressure produced during detonation by an explosive is
proportional to the square of the explosive density. Accordingly
increasing the density of an explosive, or a quantity of explosive
particulate, increases the velocity and pressure produced by the
explosive during detonation.
[0014] Therefore, there exists a need for an explosive whose
detonation produces jets having a kinetic energy that is greater
than the kinetic energy of jets produced by explosive that is
compacted into a shaped charge.
BRIEF SUMMARY OF THE INVENTION
[0015] One embodiment of the present invention discloses an
explosive material comprising a mix of a first quantity of
explosive and a second quantity of explosive. The first quantity of
explosive consists of a large particulate size explosive. The
second quantity of explosive consists of a small particulate size
explosive. The combination of the first and second quantity of
explosives results in an explosive mixture having a density greater
than either the first or second quantity of explosive. The
explosive material is encapsulated within a bonding agent to form a
pelletized explosive. The explosive material can be comprised of
approximately 25% to 75% by weight of the first quantity of
explosive and approximately 25% to 75% by weight of the second
quantity of explosive.
[0016] One form of the explosive material has a pressed density
that is from approximately 96% to approximately 98% of theoretical
mean density of the solid explosive. The first or second quantity
of explosive can be selected from the group consisting of HMX, PBX,
TATB, PYX, HNS or DATB. With respect to the explosive material, the
first quantity of explosive can consists of particles whose
diameter ranges from approximately 300 microns to approximately 45
microns. Alternatively, the first quantity of explosive can consist
of Class I explosive.
[0017] The second quantity of explosive can consist of particles
whose diameter ranges from approximately 5 microns to approximately
7 microns. Alternatively, it too can consist of Class V explosive,
or can be comprised of a distribution of particles such that 90% of
the particles have a diameter of less than 10 microns.
[0018] The explosive of the present invention can also be used in
combination with a shaped charge, in mining, military ordinance,
car safety bags, general pyrotechnic applications, and in the
production of hydrocarbons.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0019] FIG. 1 illustrates a cross sectional view of a shaped charge
having a housing, a liner, and a quantity of high explosive.
DETAILED DESCRIPTION OF THE INVENTION
[0020] With reference to the drawing herein, a shaped charge 10
according to one embodiment of the invention is shown in FIG. 1.
The shaped charge 10 typically includes a generally cylindrically
shaped housing 1, which can be formed from steel, ceramic or other
material known in the art. A quantity of explosive powder, also
known as the main body of explosive 2, is inserted into the
interior of the housing 1. A recess 4 formed at the bottom of the
housing 1 can contain a booster explosive (not shown) such as pure
RDX. The booster explosive, as is understood by those skilled in
the art, provides efficient transfer to the main body of explosive
2 of a detonating signal provided by a detonating cord (not shown)
that is typically placed in contact with the exterior of the recess
4. The recess 4 can be externally covered with a seal, shown
generally at 3.
[0021] One embodiment of the present invention considers an
explosive formed by mixing two different quantities of explosive,
where the particles that make up each of the two different
quantities have different diameters. It has been discovered that
the pressed density of a quantity of explosive can be increased
when the explosive is produced by combining two quantities of
explosives, where the particles that make up each of the quantities
have different diameters. More specifically, it has been found that
a mixture of 50% by weight of Class 1 HMX with 50% by weight of
Class 5 HMX results in a body of explosive with a resulting pressed
density that is 96% to 98% of the theoretical mean density. This
increased pressed density is a vast improvement over the pressed
density of traditionally compacted explosives. Further, a range of
mass percentages of a mixture of 25% to 75% of Class I explosive
and 25% to 75% of Class V explosive has been found to produce
advantageous results. The novel explosive of the present invention
possesses a pressed density having a magnitude greater than prior
art explosives. Accordingly the explosive of the present invention
is capable of producing detonations that have a higher detonation
velocity and pressure than explosives having a lower pressed
density. Higher detonation velocities and pressures result in the
explosive transmitting a greater kinetic energy upon
detonation.
[0022] One such application of the explosive of the present
invention is its use with shaped charges. As such, when the
explosive of the present invention is used in conjunction with
shaped charges, the liner will exit the shaped charge with more
energy to produce larger and deeper penetrations. In turn these
larger and deeper penetrations can result in enhanced hydrocarbon
production. An added advantage of the present invention is that
improved performance can be realized without increasing the amount
of explosive within the shaped charge. Accordingly the size of the
shaped charges can remain the same while attaining these improved
results.
[0023] One preferred embodiment of the present invention is a 50%
by weight mix of Class I explosive with a 50% by weight of finely
divided Class V explosive. Class I explosive has a general range of
particles of from approximately 45 microns to approximately 300
microns. Finely divided Class V explosive has a median particle
diameter of 5 microns and an average particle size of 5 to 7
microns in diameter. Further, 90% of the particles of the finely
divided Class V explosive are less than 10 microns in diameter. The
choice of sizes of differing explosive sizes is important in
reaching the desired pressed densities. The smaller particles must
be able to occupy the interstices that exist between the larger
particles. Other embodiments of the present invention exist as
well, such as an explosive comprised of a mix of Class I, Class V,
and Class VI and a mix of Class I with Class VI.
[0024] While the explosive of the present invention can be used in
its particulate or crystalline form, for safety concerns, it is
preferred that the explosive be granulated or pelletized prior to
its packaging for use. The granulation or pelletizing methods
employed can be any that are known in the art, but the methods
should involve encapsulating the explosive within a polymeric
covering. The preferred method of granulation involves mixing the
quantities of explosive having different particle diameters with a
fluid (generally de-ionized water) inside of a vessel. The mix of
explosive and fluid creates a slurry inside of the vessel.
[0025] The explosive particles and fluid are mixed as they are
added to the vessel. Generally a mixer is included with the vessel,
where the mixer consists of mixing blades, a shaft, and a motor. As
is well known, the motor provides rotational energy to the shaft,
and rotates the mixing blades within the vessel. With respect to
the present invention, the mixing blades work to mix the fluid and
explosive particles to create a homogenous slurry. The explosive
particles of different class sizes are blended together prior to
being added to the vessel. The blending process generally does not
involve an agitator, like a mixing blade, but instead is some type
of container in which the mix is added and the container is rotated
thus mixing together the container contents.
[0026] While the slurry is being mixed, it is also being heated to
about 70.degree. C. (160.degree. F.) to about 77.degree. C.
(170.degree. F.). The preferred heating technique employs routing
pipes inside of the mixing vessel through which a heated fluid
passes. The heated fluid, such as low pressure steam, transfers
thermal energy into the slurry. When the explosive mixture reaches
the proper temperature set point, as determined by one skilled in
the art, a solvent/polymer lacquer is added to the slurry. As is
well known, the lacquer will encapsulate amounts of explosive to
form beads that are approximately 1000 microns to approximately
2000 microns in diameter. Encapsulating the explosive works to
desensitize the explosive, thereby reducing the likelihood of an
unintentional detonation of the explosive. After encapsulation the
pelletized explosive can be transported or packaged in its usual
manner.
[0027] In more detail, the encapsulation process first requires a
nucleation step. Nucleation occurs when the explosive particles are
drawn together by small attractive forces; where the attractive
forces include Van der Walls forces, electromagnetic forces,
molecular, and magnetic forces. It is important that the correct
ratio of fluid and explosive particle be present in the vessel
because if the fluid portion is too large, then the explosive
particles will be too far apart and nucleation cannot occur.
Conversely, if too much explosive is present, mixing will be
hindered and the explosive particles cannot move freely. Many
factors determine the proper fluid/explosive ratio, such as
particle size, the range and ratio of particle size, and the type
of fluid. It is believed that one skilled in the art can determine
the proper ration without undue experimentation.
[0028] As noted above, when the proper temperature set point is
reached, a lacquer is added to the slurry mix. The lacquer is a mix
of a polymer (such as VITON.RTM.) and a solvent, such as butyl
acetate. When the lacquer combines with the slurry mix the polymer
separates from the solvent and forms into tiny sheet like members.
The sheet like members "float" in the slurry/lacquer mix until they
encounter the nucleated explosive particles and wrap around and
encapsulate the nucleated particles. This produces an initial
granule of from about 5 to 600 microns. These initial granules will
in turn be further encapsulated inside of another polymer sheet to
create larger granules. This process will perpetuate as long as the
temperature inside of the vessel is held at the proper temperature.
Lowering the temperature inside of the vessel can terminate the
encapsulation process. The nucleation step is generally terminated
by an operator who monitors the nucleation process. Some indicators
signaling the nucleation should be terminated are that the outer
surface, or skin of the granules be shiny and not tacky. Other
indicators are that the fluid is fully separated from the granules
and is clear, and that no particle dust be present above the fluid
surface. Cooling of the vessel can be achieved by switching the
fluid in the heating tubes from steam to cool water.
EXAMPLE
[0029] In an exemplary embodiment of the present invention,
specific manufacturing equipment was selected in the production of
one embodiment of the explosive of the present invention. That
equipment includes a minimum 1000 gallon jacketed stainless steel
reactor with a vapor tight accessible opening, a glass window, and
two openings--one opening for lacquer addition and one opening for
process flow addition. It is preferred that the reactor be heated
via a hot water supply system instead of being electrically heated.
Further, the jacketing system should accommodate cooling as well.
The vessel should be designed such that the heat transfer rate is
2.0.degree. C., this applies to heating and cooling of what is
contained in the vessel. The reactor should be equipped with a 4.0
inch shaft having a single radial impeller and a single axial
impeller. The impeller diameter should not be less than one third
of the inside diameter of the reactor. The motor provided to rotate
the shaft have a horse power of at least 40 and be able to deliver
an impeller tip speed of at least 800 ft/minute. A separation
system should be employed to receive the slurry exiting the reactor
and separate the solid damp product from the liquid.
[0030] After the solid damp product is removed from the slurry
mixture it should be dried in a drying room capable of drying over
1000 pounds of product within 24 hours. The drying temperature
should not exceed 80.degree. C. Once dried, the product should be
desensitized by the addition of graphite and blended to ensure it
is homogenous. The preferable amount of graphite addition is
approximately 0.25 percent by weight.
[0031] Explosives of smaller particle size require a smaller
ignition force to induce combustion. Thus the novel combination of
the present invention, due to the dispersion of smaller particles
disposed between the larger particles, presents a main body of
explosive that is more sensitive to external forces and is more
easily detonated than known explosives. This is true even though
the combination is encapsulated. To make the explosive safe for
transportation purposes, it is desensitized which increases the
force necessary to cause detonation. As is well known in the art,
the explosive of the present invention can be desensitized with the
addition of graphite or other desensitizing agents.
[0032] The present invention described herein, therefore, is well
adapted to carry out the objects and attain the ends and advantages
mentioned, as well as others inherent therein. While a presently
preferred embodiment of the invention has been given for purposes
of disclosure, numerous changes can be made in the details of
procedures for accomplishing the desired results. Such as using
methylene chloride or acetone as a lacquer solvent. These and other
similar modifications will readily suggest themselves to those
skilled in the art, and are intended to be encompassed within the
spirit of the present invention disclosed herein and the scope of
the appended claims.
* * * * *