U.S. patent application number 13/979818 was filed with the patent office on 2015-08-13 for methods of increasing the volume of a perforation tunnel using a shaped charge.
This patent application is currently assigned to HALLIBURTON ENERGY SERVICES, INC.. The applicant listed for this patent is HALLIBURTON ENERGY SERVICES, INC.. Invention is credited to Tony Grattan.
Application Number | 20150226533 13/979818 |
Document ID | / |
Family ID | 50388778 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150226533 |
Kind Code |
A1 |
Grattan; Tony |
August 13, 2015 |
METHODS OF INCREASING THE VOLUME OF A PERFORATION TUNNEL USING A
SHAPED CHARGE
Abstract
A method of increasing the volume of a perforation tunnel in a
subterranean formation comprises: positioning a shaped charge in a
well, wherein the shaped charge comprises a main explosive load,
wherein the main explosive load comprises a substance, wherein the
substance is capable of increasing the volume of the perforation
tunnel whereas a substantially identical shaped charge without the
substance is not capable of increasing the volume of the
perforation tunnel.
Inventors: |
Grattan; Tony; (Alvarado,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HALLIBURTON ENERGY SERVICES, INC. |
Houston |
TX |
US |
|
|
Assignee: |
HALLIBURTON ENERGY SERVICES,
INC.
Houston
TX
|
Family ID: |
50388778 |
Appl. No.: |
13/979818 |
Filed: |
September 27, 2012 |
PCT Filed: |
September 27, 2012 |
PCT NO: |
PCT/US12/57494 |
371 Date: |
July 15, 2013 |
Current U.S.
Class: |
102/313 |
Current CPC
Class: |
F42D 1/04 20130101; F42B
12/207 20130101; F42B 1/02 20130101; F42D 1/08 20130101; E21B
43/117 20130101 |
International
Class: |
F42D 1/08 20060101
F42D001/08; F42D 1/04 20060101 F42D001/04 |
Claims
1. A method of increasing the volume of a perforation tunnel in a
subterranean formation comprising: positioning a shaped charge in a
well, wherein the shaped charge comprises a main explosive load,
wherein the main explosive load comprises a substance, wherein the
substance is capable of increasing the volume of the perforation
tunnel whereas a substantially identical shaped charge without the
substance is not capable of increasing the volume of the
perforation tunnel.
2. The method according to claim 1, wherein the step of positioning
comprises inserting the shaped charge into the well.
3. The method according to claim 1, wherein the main explosive load
comprises an explosive material.
4. The method according to claim 3, wherein the explosive material
is selected from the group consisting of:
[3-Nitrooxy-2,2-bis(nitrooxymethyl)propyl]nitrate "PETN";
1,3,5-Trinitroperhydro-1,3,5-triazine "RDX";
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine "HMX";
1,3,5-Trinitro-2-[2-(2,4,6-trinitrophenyl)ethenyl]benzene "HNS";
2,6-bis,bis(picrylamino)-3,5-dinitropyridine "PYX";
1,3,5-trinitro-2,4,6-tripicrylbenzene "BRX";
2,2',2'',4,4',4'',6,6',6''-nonanitro-m-terphenyl "NONA"; and
combinations thereof.
5. The method according to claim 1, wherein the increase in volume
of the perforation tunnel is an increase in at least one dimension
of the perforation tunnel.
6. The method according to claim 1, wherein the substance is
capable of increasing the volume of the perforation tunnel via an
increase in the amount of heat of explosion of the main explosive
load.
7. The method according to claim 6, wherein the substance is any
substance that is capable of increasing the heat of explosion of
the main explosive load.
8. The method according to claim 6, wherein the increase in the
heat of explosion is predetermined.
9. The method according to claim 8, wherein the concentration of
the substance is selected such that the predetermined heat of
explosion is achieved.
10. The method according to claim 8, wherein the substance is
selected such that a predetermined heat of explosion is
achieved.
11. The method according to claim 1, wherein the main explosive
load comprises more than one substance.
12. The method according to claim 1, wherein the substance is
selected from the group consisting of metals, metal alloys,
plastics, thermoplastics, fluoropolymers, and combinations
thereof.
13. The method according to claim 10, wherein the metal or metal
alloy is selected from the group consisting of aluminum, zinc,
magnesium, titanium, tantalum, and combinations thereof.
14. The method according to claim 1, wherein the concentration of
the substance is selected such that a desired increase in volume of
the perforation tunnel is achieved.
15. The method according to claim 1, wherein the substance is in a
concentration in the range of about 0.05% to about 40% by weight of
the main explosive load.
16. The method according to claim 1, wherein the main explosive
load has a positive or zero oxygen balance.
17. The method according to claim 1, wherein a sufficient amount of
oxygen is available to cause complete combustion of the main
explosive load.
18. The method according to claim 1, wherein the substance is
selected such that at least a sufficient amount of oxygen is
available in order to achieve a desired increase in volume of the
perforation tunnel.
19. The method according to claim 1, wherein the concentration of
the substance is selected such that at least a sufficient amount of
oxygen is available in order to achieve a desired increase in
volume of the perforation tunnel.
20. The method according to claim 1, further comprising the step of
detonating the main explosive load, wherein the step of detonating
is performed after the step of positioning.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to PCT Application No.
PCT/US12/57494, filed on Sep. 27, 2012.
TECHNICAL FIELD
[0002] The present invention relates to an improved shaped charge
for use in perforating a subterranean formation. Specifically, the
shaped charge includes a main explosive load, which includes a
substance that is capable of increasing the volume of the
perforation tunnel. The increase in volume can be achieved via an
increase in the heat of explosion of the explosive load. The
increase in heat of the explosion can be caused by the
substance.
SUMMARY
[0003] According to an embodiment, a method of increasing the
volume of a perforation tunnel in a subterranean formation
comprises: positioning a shaped charge in a well, wherein the
shaped charge comprises a main explosive load, wherein the main
explosive load comprises a substance, wherein the substance is
capable of increasing the volume of the perforation tunnel whereas
a substantially identical shaped charge without the substance is
not capable of increasing the volume of the perforation tunnel.
BRIEF DESCRIPTION OF THE FIGURES
[0004] The features and advantages of certain embodiments will be
more readily appreciated when considered in conjunction with the
accompanying figures. The figures are not to be construed as
limiting any of the preferred embodiments.
[0005] FIG. 1 depicts a wellbore comprising a shaped charge.
[0006] FIG. 2 depicts the shaped charge.
[0007] FIG. 3 depicts a perforation tunnel of FIG. 1.
DETAILED DESCRIPTION
[0008] As used herein, the words "comprise," "have," "include," and
all grammatical variations thereof are each intended to have an
open, non-limiting meaning that does not exclude additional
elements or steps.
[0009] As used herein, the word "substance" means elements,
compositions or mixtures having a definite composition and
properties. A substance is intended to include, for example, pure
elements, alloys, metals, polymers, compounds, mixtures, and
combinations thereof. No compound, mixture, or other material is
intended to be excluded by the use of the word "substance."
[0010] Shaped charges are used in a variety of applications, such
as military and non-military applications. In non-military
applications, shaped charges are used: in the demolition of
buildings and structures; for cutting through metal piles, columns
and beams; for boring holes; and in steelmaking, quarrying,
breaking up ice, breaking log jams, felling trees, and drilling
post holes. Another common non-military application is the oil and
gas industry.
[0011] Oil and gas hydrocarbons are naturally occurring in some
subterranean formations. A subterranean formation containing oil or
gas is sometimes referred to as a reservoir. A reservoir may be
located under land or off shore. Reservoirs are typically located
in the range of a few hundred feet (shallow reservoirs) to a few
tens of thousands of feet (ultra-deep reservoirs). In order to
produce oil or gas, a wellbore is drilled into a reservoir or
adjacent to a reservoir.
[0012] A well can include, without limitation, an oil, gas, or
water production well, or an injection well. As used herein, a
"well" includes at least one wellbore. A wellbore can include
vertical, inclined, and horizontal portions, and it can be
straight, curved, or branched. As used herein, the term "wellbore"
includes any cased, and any uncased, open-hole portion of the
wellbore. A near-wellbore region is the subterranean material and
rock of the subterranean formation surrounding the wellbore. As
used herein, a "well" also includes the near-wellbore region. The
near-wellbore region is generally considered to be the region
within approximately 100 feet of the wellbore. As used herein,
"into a well" means and includes into any portion of the well,
including into the wellbore or into the near-wellbore region via
the wellbore.
[0013] A portion of a wellbore may be an open hole or cased hole.
In an open-hole wellbore portion, a tubing string may be placed
into the wellbore. The tubing string allows fluids to be introduced
into or flowed from a remote portion of the wellbore. In a
cased-hole wellbore portion, a casing is placed into the wellbore
that can also contain a tubing string. A wellbore can contain an
annulus. Examples of an annulus include, but are not limited to:
the space between the wellbore and the outside of a tubing string
in an open-hole wellbore; the space between the wellbore and the
outside of a casing in a cased-hole wellbore; and the space between
the inside of a casing and the outside of a tubing string in a
cased-hole wellbore.
[0014] Stimulation techniques can be used to help increase or
restore oil, gas, or water production of a well. One example of a
stimulation technique is a perforation of a well by using shaped
charges. The shaped charges can be detonated, thereby creating a
void that extends into the formation. The void is called a
perforation tunnel. The perforation tunnel increases the
permeability of the formation. Permeability refers to how easily
fluids flow through a material. This increase in permeability means
that fluids will flow more easily into or from the wellbore;
thereby increasing the overall production of the well and recovery
over time. The perforation tunnels may also allow fracturing fluids
to access the formation more easily.
[0015] In hydraulic fracturing, a fracturing fluid is pumped at a
sufficiently high flow rate and high pressure through the wellbore
and into the near wellbore region to create or enhance a fracture
in the subterranean formation. Creating a fracture means making a
new fracture in the formation. Enhancing a fracture means enlarging
a pre-existing fracture or fissure in the formation. A frac pump is
used to pump the fracturing fluid into the wellbore and formation
at high rates and pressures, for example, at a flow rate in excess
of 10 barrels per minute (4,200 U.S. gallons per minute) at a
pressure in excess of 5,000 pounds per square inch ("psi"). The
pressurized fluid enters the wellbore and formation, through the
perforation tunnels. The pressure that is created causes the
formation to fracture or crack beyond the perforation tunnels. The
fractures create new channels in the formation which may increase
the extraction rate of a well.
[0016] Perforation tunnels are often created with the use of shaped
charges. A shaped charge generally includes a conically-shaped
charge case, a solid explosive load, a liner, a central booster,
array of boosters, or detonation wave guide, and a hollow cavity
forming the shaped charge. If the hollow cavity is lined with a
thin layer of metal, plastic, ceramic, or similar materials, the
liner forms a jet when the explosive charge is detonated. Upon
initiation, a spherical wave propagates outward from the point of
initiation in the basic case of a single point initiated charge,
initiated along the axis of symmetry. This high pressure wave moves
at a very high velocity, typically around 8 kilometers per second
(km/s). As the detonation wave engulfs the lined cavity, the liner
material is accelerated under the high detonation pressure,
collapsing the liner. During this process, for a typical conical
liner, the liner material is driven to very violent distortions
over very short time intervals (microseconds) at strain rates of
104 to 107/s. Maximum strains greater than 10 can be readily
achieved since superimposed on the deformation are very large
hydrostatic pressures (peak pressures of approximately 200
gigapascals "GPa" (30 million pounds force per square inch "psi"),
decaying to an average of approximately 20 GPa). The collapse of
the liner material on the centerline forces a portion of the liner
to flow in the form of a jet where the jet tip velocity can travel
in excess of 10 km/s. The conical liner collapses progressively
from apex to base under point initiation of the high explosive. A
portion of the liner flows into a compact slug (sometimes called a
carrot), which is the large massive portion at the rear of the
jet.
[0017] Liners can be made from a variety of materials, including
various metals and glass. Common metals include copper, aluminum,
tungsten, tantalum, depleted uranium, lead, tin, cadmium, cobalt,
magnesium, titanium, zinc, zirconium, molybdenum, beryllium,
nickel, silver, gold, platinum, and pseudo-alloys of tungsten
filler and copper binder. The selection of the material depends on
many factors including economic drivers as well as performance
requirements. For example, a copper and lead powdered matrix
pressed into a final geometric form has been found to work well for
the oil and gas industry, historically with higher performance
embodiments comprising increasing amounts of tungsten powder within
the metal matrix.
[0018] Shaped charges are generally positioned in the wellbore and
can be included in a perforating gun. The perforating gun can be
used to hold the charges. The perforating gun may be placed inside
a casing and is lowered into the well on either tubing or a wire
line until it is at the desired location within the well. The
perforating gun assembly generally includes a charge holder that
holds the shaped charges, a detonation cord that links each charge
located in the charge holder, and a detonator. When the charges are
detonated, particles are expelled, forming a high-velocity jet that
creates a pressure wave that exerts pressure on the formation and
possibly the casing for a cased-hole portion. The detonation
creates the perforation tunnel by forcing material radially away
from the jet axis.
[0019] It has been discovered that the volume of a perforation
tunnel can be increased by using a shaped charge including a
substance within the main explosive load. The substance increases
the overall heat produced by the detonation or explosion of the
charge. The increased heat of explosion will result in an increase
in volume of the perforation tunnel.
[0020] According to an embodiment, a method of increasing the
volume of a perforation tunnel in a subterranean formation
comprises: positioning a shaped charge in a well, wherein the
shaped charge comprises a main explosive load, wherein the main
explosive load comprises a substance, wherein the substance is
capable of increasing the volume of the perforation tunnel whereas
a substantially identical shaped charge without the substance is
not capable of increasing the volume of the perforation tunnel.
[0021] Any discussion of the embodiments regarding the shaped
charge is intended to apply to all of the method embodiments. Any
discussion of a particular component of an embodiment (e.g., a
shaped charge or a substance) is meant to include the singular form
of the component and also the plural form of the component, without
the need to continually refer to the component in both the singular
and plural form throughout. For example, if a discussion involves
"the shaped charge 100," it is to be understood that the discussion
pertains to one shaped charge (singular) and two or more shaped
charges (plural).
[0022] Turning to the Figures, FIG. 1 depicts a well system 10
containing multiple shaped charges 100 located within multiple
zones of the well system. The well system 10 can include at least
one wellbore 11. The wellbore 11 can penetrate a subterranean
formation 20. The subterranean formation 20 can be a portion of a
reservoir or adjacent to a reservoir. The wellbore 11 can have a
generally vertical cased or uncased section 14 extending downwardly
from a casing 15, as well as a generally horizontal cased or
uncased section extending through the subterranean formation 20.
The wellbore 11 can include only a generally vertical wellbore
section or can include only a generally horizontal wellbore
section.
[0023] A tubing string 24 (such as a stimulation tubing string or
coiled tubing) can be installed in the wellbore 11. The well system
10 can comprise at least a first zone 16 and a second zone 17. The
well system 10 can also include more than two zones, for example,
the well system 10 can further include a third zone 18, a fourth
zone 19, and so on. The methods include the step of positioning a
shaped charge 100 in a well. More than one shaped charge 100 can be
positioned in the well. According to an embodiment, a first shaped
charge can be positioned within the first zone 16, a second shaped
charge can be positioned within the second zone 17, and so on. It
is to be understood that more than one shaped charge can be
positioned within a given zone (e.g., the first zone or second
zone). According to an embodiment, the well system 10 includes
anywhere from 2 to hundreds or thousands of zones. The zones can be
isolated from one another in a variety of ways known to those
skilled in the art. For example, the zones can be isolated via
multiple packers 26. The packers 26 can seal off an annulus located
between the outside of the tubing string 24 and the wall of
wellbore 11.
[0024] It should be noted that the well system 10 is illustrated in
the drawings and is described herein as merely one example of a
wide variety of well systems in which the principles of this
disclosure can be utilized. It should be clearly understood that
the principles of this disclosure are not limited to any of the
details of the well system 10, or components thereof, depicted in
the drawings or described herein. Furthermore, the well system 10
can include other components not depicted in the drawing. For
example, the well system 10 can further include a well screen. By
way of another example, cement may be used instead of packers 26 to
isolate different zones. Cement may also be used in addition to
packers 26.
[0025] The well system 10 does not need to include a packer 26.
Also, it is not necessary for one well screen and one shaped charge
100 to be positioned between each adjacent pair of the packers 26.
It is also not necessary for a single shaped charge 100 to be used
in conjunction with a single well screen. Any number, arrangement
and/or combination of these components may be used.
[0026] The step of positioning can comprise inserting the shaped
charge 100 into the well. The shaped charge 100 can be positioned
in the well at a desired location. According to an embodiment, the
desired location is the location at which the perforation tunnel 22
is to be created. The shaped charge 100 can be included in a
carrier (not shown). More than one shaped charge 100 can be
included in the carrier. The carrier can be any carrier capable of
holding the shaped charge 100, for example, the carrier can be a
perforating gun. The step of positioning can further comprise
inserting the carrier into the well. The methods can further
include the step of inserting the shaped charge 100 into the
carrier, wherein the step of inserting is performed prior to the
step of positioning.
[0027] As can be seen in FIG. 2, the shaped charge 100 includes a
main explosive load 102. The shaped charge 100 can further include
a charge case 101, wherein the charge case 101 is positioned
adjacent to the main explosive load 102. The charge case 101 can
comprise a metal or metal alloy. As used herein, the term "metal
alloy" means a mixture of two or more elements, wherein at least
one of the elements is a metal. The other element(s) can be a
non-metal or a different metal. An example of a metal and non-metal
alloy is steel, comprising the metal element iron and the non-metal
element carbon. An example of a metal and metal alloy is bronze,
comprising the metallic elements copper and tin. The metal or metal
alloy of the charge case 101 can be selected from the group
consisting of aluminum, zinc, magnesium, titanium, tantalum, and
combinations thereof.
[0028] The shaped charge 100 can further comprise a liner 103,
wherein the liner 103 is positioned adjacent to the main explosive
load 102. As can be seen in FIG. 2, the shaped charge 100 can
include a liner 103, the main explosive load 102, and a charge case
101, wherein the liner 103 is positioned adjacent to the main
explosive load 102 and the charge case 101 is positioned adjacent
to the other side of the main explosive load 102. The liner 103 can
be made from a variety of materials, including various metals and
glass. Common metals include copper, aluminum, tungsten, tantalum,
depleted uranium, lead, tin, cadmium, cobalt, magnesium, titanium,
zinc, zirconium, molybdenum, beryllium, nickel, silver, gold,
platinum, and pseudo-alloys of tungsten filler and copper binder.
The liner 103 can have a thickness of at least 0.025 inches (in).
According to another embodiment, the liner 103 has a thickness in
the range of about 0.025 to about 0.250 in, preferably of about
0.050 to about 0.100 in.
[0029] The shaped charge 100 can further comprise a central
booster, array of boosters, or detonation wave guide (shown in FIG.
2 as a central booster 106). According to an embodiment, the
central booster, array of boosters, or detonation wave guide is
capable of detonating the main explosive load 102. Detonation means
a supersonic exothermic front accelerating through a medium that
eventually drives a shock front or wave that propagates directly in
front of the explosive load. The shaped charge 100 can further
include a seal disc 105 and a detonation cord 104. According to an
embodiment, the detonation cord 104 is capable of initiating the
central booster, array of boosters, detonation wave guide, or the
main explosive load 102. If more than one shaped charge 100 is
positioned in the well, then the detonation cord 104 can be
connected to and link two or more of the shaped charges 100
together. The detonation cord 104 can be part of a carrier (not
shown).
[0030] The shaped charge 100 comprises the main explosive load 102.
According to an embodiment, the main explosive load 102 comprises
an explosive material. The explosive material can be selected from
commercially-available materials. For example, the explosive
material can be selected from the group consisting of
[3-Nitrooxy-2,2-bis(nitrooxymethyl)propyl]nitrate "PETN";
1,3,5-Trinitroperhydro-1,3,5-triazine "RDX";
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine "HMX";
1,3,5-Trinitro-2-[2-(2,4,6-trinitrophenyl)ethenyl]benzene "HNS";
2,6-bis,bis(picrylamino)-3,5-dinitropyridine "PYX";
1,3,5-trinitro-2,4,6-tripicrylbenzene "BRX";
2,2',2'',4,4',4'',6,6',6''-nonanitro-m-terphenyl "NONA"; and
combinations thereof. According to an embodiment, the main
explosive load 102 further comprises a de-sensitizing material. The
de-sensitizing material can be capable of binding the main
explosive load 102 together. The de-sensitizing material can also
help the main explosive load 102 retain its shape. The
de-sensitizing material can be selected from the group consisting
of a wax, graphite, plastics, thermoplastics, fluoropolymers (e.g.,
polytetrafluoroethylene), other non-energetic (inert) binders, and
combinations thereof.
[0031] The substance is capable of increasing the volume of the
perforation tunnel 22; whereas, a substantially identical shaped
charge without the substance is not capable of increasing the
volume of the perforation tunnel. As used herein, the phrase
"substantially identical" means the device contains the same
components, materials, concentrations of materials, etc. with the
exception of the component or material specifically excluded. As
can be seen in FIG. 3, the perforation tunnel 22 can be, but is not
limited to being, conical in shape. The increase in volume can be
an increase in at least one dimension of the perforation tunnel.
According to an embodiment, the increase in the at least one
dimension can be an increase in the diameter of the base of the
perforation tunnel b, the length of the perforation tunnel l, an
increase in both the diameter of the base b and the length l, or an
increase in a diameter at any interval along the length l. The
increase in the volume can vary depending on the specifics of the
oil or gas operation. The increase in the volume can be a desired
value.
[0032] According to an embodiment, the substance is capable of
increasing the volume of the perforation tunnel 22 via an increase
in the amount of heat of explosion of the main explosive load 102
(i.e., the amount of heat produced during detonation of the main
explosive load). The generation of heat in large quantities
accompanies most explosive chemical reactions. It is the rapid
liberation of heat that causes the gaseous products of most
explosive reactions to expand and generate high pressures. This
rapid generation of high pressures of the released gas constitutes
the explosion. The strength, or potential, of an explosive is the
total work that can be performed by the gas resulting from its
explosion, when expanded adiabatically from its original volume,
until its pressure is reduced to atmospheric pressure and its
temperature to 15.degree. C. The potential is therefore the total
quantity of heat given off at constant volume when expressed in
equivalent work units and is a measure of the strength of the
explosive. Each product and reactant making up the explosive load
will have a specific heat of formation. The standard heat of
formation of a compound is the change of enthalpy that accompanies
the formation of 1 mole of the compound from its elements, with all
substances being in their standard states. The heat released by the
explosive material at a constant pressure and 25.degree. C. can be
calculated as follows:
HEX=.DELTA.U=|U.sub.prod1-U.sub.react1|+|U.sub.prod2-U.sub.react2|
. . . ,
where HEX refers to the heat of explosion in units of calories per
gram (cal/g); .DELTA.U is the change in energy at a constant volume
for the calorimetric reaction; and U.sub.prod and U.sub.react are
the internal energies of the products and reactants (1, 2, and so
on), respectively, at room temperature (i.e., 25.degree. C. (298.15
K)). The heat released can be referred to as the "heat of
explosion." With an increase in HEX, the explosive load has an
increased ability to do work. This increased ability to do work
means that the overall volume of the perforation tunnel can be
increased compared to an explosive load without the increase in
HEX. According to an embodiment, the increase in the heat of
explosion is predetermined. The predetermined heat of explosion
can, in part, be calculated based on the desired increase in the
volume of the perforation tunnel 22, but may also be derived from
experimental results.
[0033] According to an embodiment, the substance is any substance
that is capable of increasing the overall heat of explosion of the
main explosive load 102, thereby resulting in an overall increase
in the ability to perform work, thereby increasing the perforation
tunnel geometry. The main explosive load 102 can also comprise more
than one substance. The substance can be selected from the group
consisting of metals, metal alloys, plastics, thermoplastics,
fluoropolymers (e.g., polytetrafluoroethylene), and combinations
thereof. The metal or metal alloy can be selected from (but not
limited to) the group consisting of aluminum, zinc, magnesium,
titanium, tantalum, and combinations thereof. The quantity of the
heat of explosion and overall higher work energy can vary and will
depend on the heat for formation of the specific substance(s)
chosen. For example, the heat of formation of aluminum oxide
(Al.sub.2O) is 163 kilojoules per mole (kJ/mol) and the heat of
formation of aluminum III oxide (Al.sub.2O.sub.3) is 1,590 kJ/mol.
According to an embodiment, the one or more substances are chosen
such that a desired heat of explosion is achieved.
[0034] The quantity of the heat of explosion can also depend on the
concentration of the one or more substances. Generally, the greater
the concentration of the substance, the greater the heat of
explosion. According to an embodiment, the concentration of the one
or more substances is selected such that the desired heat of
explosion is achieved. According to another embodiment, the
concentration of the one or more substances is selected such that
the desired increase in volume of the perforation tunnel is
achieved. According to yet another embodiment, the substance is in
a concentration of at least 0.05% by weight of the main explosive
load 102. According to yet another embodiment, the substance is in
a concentration in the range of about 0.05% to about 40%,
preferably about 1% to about 25%, by weight of the main explosive
load 102.
[0035] The heat of explosion can be limited by the oxygen balance
of the explosive. Oxygen balance (OB or OB %) indicates the degree
to which an explosive can be oxidized. If an explosive molecule
contains just enough oxygen to form carbon dioxide from carbon,
water from hydrogen molecules, all of its sulfur dioxide from
sulfur, and all metal oxides from metals with no excess molecules,
then the explosive has a zero oxygen balance. An explosive has a
positive oxygen balance if the explosive contains more oxygen than
needed, and an explosive has a negative oxygen balance if the
explosive contains less oxygen than needed. If the explosive has a
negative oxygen balance, then the combustion of the explosive
molecules will be incomplete, and large amounts of toxic gases such
as carbon monoxide will be present. Generally, when a positive or
zero OB is present, the heat of explosion will be the greatest;
whereas, the heat of explosion will be less when a negative OB is
present. According to an embodiment, the main explosive load 102
has a positive or zero OB. According to another embodiment, a
sufficient amount of oxygen (O.sub.2) is available to cause
complete combustion of the main explosive load 102. The available
O.sub.2 can come from the substance, part of another material
(e.g., the booster), and/or the area surrounding the shaped
charge.
[0036] The substance can be selected such that at least a
sufficient amount of oxygen is available in order to achieve
complete combustion of the main explosive load 102. The substance
can also be selected such that at least a sufficient amount of
oxygen is available in order to achieve the predetermined heat of
explosion. The substance can also be selected such that at least a
sufficient amount of oxygen is available in order to achieve the
desired increase in volume of the perforation tunnel 22. The
concentration of the substance can also be selected such that at
least a sufficient amount of oxygen is available in order to
achieve complete combustion of the main explosive load;
alternatively, such that at least a sufficient amount of oxygen is
available in order to achieve the predetermined heat of explosion;
alternatively, such that the desired increase in volume of the
perforation tunnel is achieved. By way of example, Al.sub.2O.sub.3
can provide more available oxygen compared to Al.sub.2O. The
substance and/or the concentration of the substance can also be
selected based on the quantity of available oxygen present in the
area surrounding the positioned shaped charge.
[0037] The substance can also form available oxygen by reacting
with other unoxidized elements or compounds present in the system.
The substance can also increase the heat of explosion by reacting
with other unoxidized elements or compounds present in the system.
By way of example, if the substance is Al.sub.2O and a negative OB
is present, then the formation of Al.sub.2O.sub.3 via a reaction of
the Al.sub.2O and other unoxidized compounds or elements can occur.
The formation of Al.sub.2O.sub.3 is a highly exothermic chemical
reaction and can increase the overall heat of explosion.
[0038] The methods can further comprise the step of detonating the
main explosive load 102, wherein the step of detonating is
performed after the step of positioning. The step of detonating can
comprise causing initiation of the main explosive load 102. The
initiation of the main explosive load 102 can include initiating
the booster 106, booster array, or detonation wave guide. According
to an embodiment, the detonation of the main explosive load 102,
and the jet produced by the liner material 103, creates the
resulting perforation tunnel 22. More than one main explosive load
102 can be detonated. As can be seen in FIG. 1, a first main
explosive load 102 located in the first zone 16 can be detonated;
thereby creating a first perforation tunnel 22, a second main
explosive load shown located in the third zone 18 can be detonated;
thereby creating a second perforation tunnel, and so on. Of course
more than one main explosive load can be detonated within a given
zone. Moreover, not every zone need include a shaped charge and the
exact zones that contain a shaped charge and the total number of
shaped charges positioned within those zones can vary depending on
the specifics of the particular oil or gas operation.
[0039] The methods can further comprise the step of fracturing at
least a portion of the subterranean formation 20, wherein the step
of fracturing is performed after the step of positioning or after
the step of detonating. The step of fracturing can include placing
a fracturing fluid into at least one of the perforation tunnels 22.
The methods can further include the step of performing an acidizing
treatment in at least a portion of the subterranean formation 20,
wherein the step of performing an acidizing treatment is performed
after the step of positioning or after the step of detonating. The
step of performing an acidizing treatment can include introducing
an acidizing fluid into at least one of the perforation tunnels
22.
[0040] Therefore, the present invention is well adapted to attain
the ends and advantages mentioned as well as those that are
inherent therein. The particular embodiments disclosed above are
illustrative only, as the present invention may be modified and
practiced in different but equivalent manners apparent to those
skilled in the art having the benefit of the teachings herein.
Furthermore, no limitations are intended to the details of
construction or design herein shown, other than as described in the
claims below. It is, therefore, evident that the particular
illustrative embodiments disclosed above may be altered or modified
and all such variations are considered within the scope and spirit
of the present invention. While compositions and methods are
described in terms of "comprising," "containing," or "including"
various components or steps, the compositions and methods also can
"consist essentially of" or "consist of" the various components and
steps. Whenever a numerical range with a lower limit and an upper
limit is disclosed, any number and any included range falling
within the range is specifically disclosed. In particular, every
range of values (of the form, "from about a to about b," or,
equivalently, "from approximately a to b,") disclosed herein is to
be understood to set forth every number and range encompassed
within the broader range of values. Also, the terms in the claims
have their plain, ordinary meaning unless otherwise explicitly and
clearly defined by the patentee. Moreover, the indefinite articles
"a" or "an", as used in the claims, are defined herein to mean one
or more than one of the element that it introduces. If there is any
conflict in the usages of a word or term in this specification and
one or more patent(s) or other documents that may be incorporated
herein by reference, the definitions that are consistent with this
specification should be adopted.
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