U.S. patent application number 10/782336 was filed with the patent office on 2007-05-03 for reactive stimulation of oil and gas wells.
Invention is credited to Glenn Bob Barnett, Lesley O. Bond, Ercill Ray Hunt.
Application Number | 20070095529 10/782336 |
Document ID | / |
Family ID | 37994756 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070095529 |
Kind Code |
A1 |
Bond; Lesley O. ; et
al. |
May 3, 2007 |
REACTIVE STIMULATION OF OIL AND GAS WELLS
Abstract
A method and apparatus for stimulating producing strata in oil
or gas wells. The formation is penetrated using existing shaped
charges, and an oxygen-rich material then is introduced into the
producing formation. Thus, oxygen is available within the formation
to sustain an explosive reaction with the existing formation
hydrocarbons acting as fuel. This explosive reaction will cause
fracturing of the formation and will counteract plugging that often
results from the use of conventional shaped charges. In one
embodiment, a container encloses shaped charges surrounded by
oxygen-rich material. The shaped charges are ignited first,
perforating the well casing and any surrounding cement. Additional
explosive charges at each end of the container then are ignited.
This forces the oxygen-rich material into the perforation tunnels.
Alternately, the oxygen can be a part of the shaped charge and
projected into the formation with the shaped charge to accomplish
the same results.
Inventors: |
Bond; Lesley O.; (Neosho,
MO) ; Hunt; Ercill Ray; (Point Blank, TX) ;
Barnett; Glenn Bob; (Owasso, OK) |
Correspondence
Address: |
MARY M LEE, P.C.
1300 E. NINTH STREET
SUITE 4
EDMOND
OK
73034-5760
US
|
Family ID: |
37994756 |
Appl. No.: |
10/782336 |
Filed: |
February 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60502703 |
Sep 12, 2003 |
|
|
|
Current U.S.
Class: |
166/259 ;
166/260; 175/4.6 |
Current CPC
Class: |
E21B 43/117 20130101;
E21B 43/248 20130101 |
Class at
Publication: |
166/259 ;
166/260; 175/004.6 |
International
Class: |
E21B 43/24 20060101
E21B043/24 |
Claims
1. An apparatus for stimulating production from a
hydrocarbon-containing formation in an oil or gas well, the
apparatus comprising: a container sized to be received and
supported in the well at a level adjacent the formation; at least
one shaped charge supported within the container, the shaped charge
adapted when ignited to perforate the formation; a supply of
oxygen-rich material in each of the shaped charges and adapted to
be propelled into the formation by the explosion of the shaped
charge, wherein the oxygen-rich material is not explosively
reactive with water and is capable of fueling the burning of
hydrocarbons in the formation regardless of the presence of water
in the well when the shaped charge is ignited; and at least one
igniter for detonating the shaped charge.
2. The apparatus of claim 1 wherein the container is elongated
having first and second ends.
3. The apparatus of claim 2 wherein the apparatus further comprises
a high order primer cord in contact with each of the at least one
shaped charge and adapted to be ignited by the igniter.
4. The apparatus of claim 3 wherein the igniter is an electric
igniter.
5. The apparatus of claim 2 wherein the at least one shaped charge
comprises a plurality of shaped charges positioned to perforate
different locations in the formation.
6. The apparatus of claim 5 wherein the apparatus further comprises
a high order primer cord in contact with each of the at least one
shaped charge and adapted to be ignited by the igniter.
7. The apparatus of claim 1 wherein the oxygen-rich material is
potassium nitrate.
8. The apparatus of claim 1 wherein the at least one shaped charge
comprises a plurality of shaped charges positioned to perforate
different locations in the formation.
9. The apparatus of claim 8 wherein the apparatus further comprises
a high order primer cord in contact with each of the at least one
shaped charge and adapted to be ignited by the igniter.
10. The apparatus of claim 1 wherein the igniter is an electric
igniter.
11. The apparatus of claim 8 wherein the apparatus further
comprises a primer cord in contact with each of the at least one
shaped charge.
12. (canceled)
13. (canceled)
14. The apparatus of claim 1 wherein each of the at least one
shaped charge comprises: a body of explosive formed to have a
conical frontal recess; a detonator adapted to ignite the body of
explosive; a liner shaped to line the frontal recess in the body of
explosive; and wherein the oxygen-rich material forms a layer
between the liner and the frontal recess of the body of
explosive.
15. The apparatus of claim 1 wherein each of the at least one
shaped charge comprises: a body of fast burning explosive formed to
have a conical frontal recess; a detonator adapted to ignite the
body of fast burning explosive; an insert shaped to conform to and
be received in the frontal recess in the body of explosive and to
have a planar front, the insert formed of a slow burning explosive;
and a disc-shaped layer of fast burning explosive having a front
and a rear, the rear positioned on the planar front of the insert;
wherein the oxygen-rich material forms a layer on the front of the
layer of fast burning explosive.
16. The apparatus of claim 1 wherein each of the at least one
shaped charge comprises: a first body of fast burning explosive
formed to have a frontal recess; a body of oxygen-rich material
formed to be received in frontal recess of the first body of
explosive and to have a frontal recess with a cylindrical center
and a frusto-conical forward portion; a second body of fast burning
explosive shaped to conform to and be received in the cylindrical
center of the recess in the body of oxygen-rich material and to
have a conical front recess continuous with the frusto-conical
forward portion of the frontal recess in the body of oxygen-rich
material so that the frontal recess of the second body of explosive
and the frusto-conical portion of the frontal recess in the
oxygen-rich material form a complete cone; detonators adapted to
ignite the first body of fast burning explosive and the second body
of fast burning explosive; and a conically shaped metal liner
positioned inside the complete cone formed by the frontal recess of
the second body of explosive and the frusto-conical portion of the
frontal recess in the oxygen-rich material.
17. The apparatus of claim 1 wherein each of the at least one
shaped charge comprises: a body of fast burning explosive formed to
have a stepped frontal recess with a conical center portion and a
frusto-conical forward portion having a narrowest diameter to form
a step between the center portion and the forward portion; a body
of oxygen-rich material formed to be received in frusto-conical
forward portion of the frontal recess of the body of explosive and
having a narrowest diameter substantially the same as the widest
diameter of the center portion of the frontal recess of the body of
fast burning explosive, so that the conical center portion of the
frontal recess of the body of explosive and the body of oxygen-rich
material form a complete cone; a detonator adapted to ignite the
body of fast burning explosive; and a conically shaped liner
positioned inside the conical center portion of the frontal recess
in the body of fast burning explosive.
18. A method for stimulating hydrocarbon containing strata in an
oil or gas well, the method comprising: perforating the formation
using a shaped charge; and explosively introducing an oxygen-rich
material into the formation, wherein the oxygen-rich material is
introduced into the formation by the explosive force of the shaped
charge, and wherein the oxygen-rich material is not explosively
reactive with water and is capable of fueling the burning of
hydrocarbons in the formation regardless of the presence of water
in the well when the shaped charge is ignited.
19. The method of claim 18 wherein the oxygen-rich material is
potassium nitrate.
20. The method of claim 19 wherein the oxygen-rich material is
introduced into the formation ahead of the jet from the shaped
charge.
21. The method of claim 19 wherein the oxygen-rich material is
introduced into the formation behind the jet from the shaped
charge.
22. (canceled)
23. (canceled)
24. The method of claim 18 wherein the oxygen-rich material is
introduced into the formation behind the jet from the shaped
charge.
25. The method of claim 18 wherein the oxygen-rich material is
introduced into the formation ahead of the jet from the shaped
charge.
26. An apparatus for stimulating production from a
hydrocarbon-containing formation in an oil or gas well, the
apparatus comprising: a container sized to be received and
supported in the well at a level adjacent the formation, wherein
the container is elongated having first and second ends; two end
charges of low order explosive material, one positioned at each of
the first and second ends of the container; at least one shaped
charge supported within the container between the two end charges,
the shaped charge adapted when ignited to perforate the formation;
a supply of oxygen-rich material supported within the container
around the shaped charge and adapted to be introduced explosively
into the formation with the shaped charge, wherein the oxygen-rich
material is not explosively reactive with water and is capable of
fueling the burning of hydrocarbons in the formation regardless of
the presence of water in the well when the shaped charge is
ignited; and at least one igniter for detonating the shaped charge
and the end charges.
27. The apparatus of claim 26 wherein the apparatus further
comprises a high order primer cord in contact with each of the at
least one shaped charges and both the end charges and adapted to be
ignited by the igniter.
28. The apparatus of claim 27 wherein the igniter is an electric
igniter.
29. The apparatus of claim 26 wherein the at least one shaped
charge comprises a plurality of shaped charges positioned to
perforate different locations in the formation.
30. The apparatus of claim 29 wherein the apparatus further
comprises a high order primer cord in contact with each of the at
least one shaped charges and both the end charges and adapted to be
ignited by the igniter.
31. The apparatus of claim 29 wherein the oxygen-rich material is
potassium nitrate.
32. The apparatus of claim 26 wherein the oxygen-rich material is
potassium nitrate.
33. The apparatus of claim 32 wherein the apparatus further
comprises a high order primer cord in contact with each of the at
least one shaped charges and both the end charges and adapted to be
ignited by the igniter.
34. The apparatus of claim 26 wherein the igniter is an electric
igniter.
35. The apparatus of claim 34 wherein the at least one shaped
charge comprises a plurality of shaped charges positioned to
perforate different locations in the formation.
36. The apparatus of claim 34 wherein the oxygen-rich material is
potassium nitrate.
37. A shaped charge for use in perforating hydrocarbon-containing
formations in oil and gas wells, the shaped charge comprising: a
housing; a body of fast burning explosive in the housing, the front
of the body of explosive defining a rearwardly pointing conical
recess; a detonator adapted to ignite the body of fast burning
explosive; a body of oxygen-rich material in the housing, wherein
the oxygen-rich material is not explosively reactive with water and
is capable of fueling the burning of hydrocarbons in the formation;
and whereby the shaped charge is adapted to perforate the formation
and the body of oxygen-rich material is adapted to be introduced
explosively into the formation with the shaped charge whereby
burning of hydrocarbons therein is promoted regardless of the
presence of water in the well when the explosive is ignited.
38. The shaped charge of claim 37 further comprising a liner shaped
to line the conical recess in the body of explosive and wherein the
oxygen-rich material forms a conically shaped layer between the
liner and the body of explosive.
39. The shaped charge of claim 37 further comprising an insert
shaped to conform to and be received in the frontal recess in the
body of explosive and to have a planar front, the insert formed of
a slow burning explosive; and a disc-shaped layer of fast burning
explosive having a front and a rear, the rear positioned on the
planar front of the insert; wherein the oxygen-rich material forms
a layer on the front of the layer of fast burning explosive.
40. The shaped charge of claim 37 wherein the oxygen-rich material
is formed to be received in conical recess of the first body of
explosive and is shaped to have a frontal recess with a cylindrical
center and a frusto-conical forward portion, and wherein the shaped
charge further comprises: a second body of fast burning explosive
shaped to conform to and be received in the cylindrical center of
the recess in the body of oxygen-rich material and to have a
conical front recess continuous with the frusto-conical forward
portion of the frontal recess in the body of oxygen-rich material
so that the frontal recess of the second body of explosive and the
frusto-conical portion of the frontal recess in the oxygen-rich
material form a complete cone; a detonator adapted to ignite the
second body of fast burning explosive; and a liner is positioned
inside the complete cone formed by the frontal recess of the second
body of explosive and the frusto-conical portion of the frontal
recess in the oxygen-rich material.
41. The shaped charge of claim 37 wherein the conical recess in the
body of fast burning explosive has a conical center portion and a
frusto-conical forward portion, wherein the narrowest diameter of
the forward portion is greater than the widest diameter of the
center portion to form a step therebetween, where in the shaped
charge further comprises a conical liner inside the center portion,
and wherein the oxygen-rich material is a frusto-conically shaped
layer received in forward portion so that exposed forward surfaces
of the liner and the oxygen-rich material form a complete
cone-shaped recess.
Description
[0001] This application claims the benefit of the filing date of
provisional application Ser. No. 60/502,703, entitled "Reactive
Stimulation of Oil and Gas Wells," filed Sep. 12, 2003, the
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and devices for
stimulating producing formations in oil and gas wells to increase
production.
BACKGROUND OF THE INVENTION
[0003] The quantity of oil and gas production from a hydrocarbon
bearing strata into a borehole is influenced by many physical
factors. Darcey's flow equation, which defines flow in a well,
takes into account the reservoir constants of temperature,
viscosity, permeability, reservoir pressure, pressure in the
borehole, thickness of the producing strata, and the area exposed
to flow.
[0004] It has long been known that increasing the exposed flow area
in a producing well increases production. For example, it is known
that drilling a larger diameter hole exposes more of the producing
strata and thus increases production.
[0005] Enlarging the flow areas, in open hole intervals, has been
accomplished by using both explosives and chemicals. However, use
of these agents is somewhat limited where the producing strata are
cemented behind steel casing. In cased applications, the well is
"perforated" to create small holes that extend through the steel
casing, the annulus cement and the adjacent formation.
[0006] Prior to the invention of the shaped charge, wells were
perforated with multiple, short-barreled guns. The bullets
penetrated the casing, the annulus cement, and the producing
strata. The shaped charge, with its greater penetration and
reliability, though, has largely replaced the so-called "bullet
guns."
[0007] A shaped charge makes a hole through the casing and into the
strata by forming a high speed stream of particles that are
concentrated in a small diameter jet. As the high energy particles
hit solid material, the solid material is pulverized. Thus, shaped
charges can be used to place numerous small perforations where
desired in a well. However, the fine material from the pulverized
rock and the shaped charge particles can have a detrimental effect
on fluid flow in the area around the perforation. Debris from the
spent charge as well as fragments and particles from the pulverized
formation tend to plug the perforations and obstruct passages in
the fractured formation.
[0008] The formation pressure acts on the small oil droplets in the
formation to force the hydrocarbons from the connected pore spaces
into the well bore. The magnitude of the area in the formation
exposed by the perforations directly affects the amount of flow
and/or work required for that production. Accordingly, increasing
the exposed flow area by perforation does two favorable things: it
increases the flow rate directly, and, it reduces the amount of
work required to maintain a given production rate. Increasing the
flow area in a well increases the ultimate recovery from the
well/reservoir by conserving formation pressure or reservoir
energy.
[0009] The present invention provides a method and apparatus
capable of increasing the exposed surface area in a formation when
using shaped charges to perforate a well. This apparatus and method
augment the use of shaped charges by including the introduction of
oxygen rich material into the formation with the explosive. The
delivery of an oxygen source to the hydrocarbon-containing
formation, in the presence of the explosive reaction, provides
sustained explosive burning of the hydrocarbons in the vicinity of
the perforation. The burning in the formation continues until the
oxygen-rich material is depleted, when the burning
self-extinguishes. Thus, the extent of the burning can be
controlled by selecting the amount of oxygen-rich material to be
introduced into the formation.
[0010] This significant secondary reaction in the strata has two
beneficial effects. In the first place, the reaction will cause a
cleaning effect on the fine particles that might otherwise plug the
perforation. The cleaning effect occurs when the explosive burning
causes high pressure gases to be generated, and these pressurized
gases are discharged rapidly back into the borehole or casing.
Secondly, the extended burning or explosion in the treated statum
causes further fracturing of the formation. This results in further
expansion of the exposed flow areas in the formation beyond the
initial shaped charge perforation. In addition, in the event the
strata being perforated are water bearing, the explosive reaction
will not occur; rather, only oil or gas bearing formations will be
stimulated.
SUMMARY OF THE INVENTION
[0011] The present invention is directed to apparatus for
stimulating production from a hydrocarbon-containing formation in
an oil or gas well. The apparatus comprises a container sized to be
received and supported in the well at a level adjacent the
formation. At least one shaped charge is supported within the
container. The shaped charge is adapted, when ignited, to perforate
the formation and to initiate a burn of hydrocarbons therein. The
apparatus includes a supply of oxygen-rich material supported
within the container and adapted to be introduced explosively into
the formation with the shaped charge. In this way, the burn of
hydrocarbons therein is extendable. The apparatus further includes
at least one igniter for detonating the shaped charge.
[0012] Still further, the present invention comprises a method for
stimulating production from a hydrocarbon-containing formation in
an oil or gas well. The method comprises perforating the formation
using a shaped charge and introducing an oxygen-rich material to
the formation. Thus, the burn of the hydrocarbons is enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a longitudinal section view of an apparatus in
accordance with a first embodiment of the present invention. The
apparatus is shown positioned at the level of a target formation in
an oil or gas well.
[0014] FIG. 2 is a schematic diagram illustrating the timing of the
sequence of events produced by the apparatus of FIG. 1.
[0015] FIG. 3 is a fragmented sectional view of the target
formation shown in FIG. 1 after completion of the stimulation
treatment.
[0016] FIG. 4 is a longitudinal sectional view of an apparatus in
accordance with a second embodiment of the present invention
positioned at the level of a target formation in an oil or gas
well.
[0017] FIG. 5 is a section view of a shaped charge made in
accordance with one embodiment of the present invention.
[0018] FIG. 6 is a section view of a shaped charge made in
accordance with another embodiment of the present invention.
[0019] FIG. 7 is a section view of a shaped charge made in
accordance with another embodiment of the present invention.
[0020] FIG. 8 is a section view of a shaped charge made in
accordance with another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The Embodiment of FIGS. 1-3
[0021] With reference now to the drawings in general and to FIG. 1
in particularly, there is shown therein an apparatus constructed in
accordance with a first preferred embodiment of the present
invention and designated generally by the reference numeral 10. The
apparatus 10 is adapted to stimulate production from a
hydrocarbon-containing formation or strata 12 in an oil or gas well
14.
[0022] An illustrative well environment is shown in FIG. 1 and
comprises shale zones 16 and 18 above and below the formation 12.
In most instances, the apparatus 10 will be used in a cased
interval of the well 14, and the casing of the well 14 is indicated
at 20 with the cement in the annulus designated at 22.
[0023] The apparatus 10 comprises a container 24 sized to be
received and supported in the well 14 at a level adjacent the
formation 12. Preferably, the container 24 is elongated having
first and second ends 26 and 28.
[0024] The apparatus 10 further comprises at least one shaped
charge supported within the container 24. The shaped charge is
adapted, when ignited, to perforate the formation. Preferably,
there is a plurality of shaped charges that can be positioned to
perforate different locations in the formation 12. More preferably,
there are three shaped charges, such as the charges 30. This
embodiment may use conventional shaped charges. Accordingly, no
detailed description of the shaped charges 30 is provided
herein.
[0025] With continuing reference to FIG. 1, an igniter of some sort
is provided to detonate the shaped charges 30. In the preferred
embodiment of FIG. 1, the igniter comprises an electrical igniter
32 disposed within container 24. The igniter 32 is electrically
connected to a conductor wire 34 which extends from the apparatus
10 to the well head (not shown). As shown here, the conductor wire
34 may be used to suspend the apparatus 10 in the well 14.
[0026] Extending from the igniter 32 is a primer cord 38.
Preferably, the primer cord comprises a high order explosive, and
is crimped into and made a part of the igniter 32. The primer cord
38 connects to the shaped charges 30 in series. Thus, when the
igniter 32 is initiated by a signal from the surface through the
conductor wire 34, the shaped charges 30 will be ignited by the
fast burning primer cord 38, which runs from the igniter 32 to the
uppermost shaped charge 30 in the plurality of charges.
[0027] Referring still to FIG. 1, the apparatus 10 preferably also
includes a supply of oxygen-rich material supported within the
container 24 and adapted to be introduced explosively into the
formation 12 with the shaped charges, such as the charges 30. This
will provide a source of oxygen to support explosive burning of the
hydrocarbons in the formation.
[0028] In the embodiment of FIG. 1, the oxygen-rich material 40 in
the container 24 is external to and surrounds the shaped charges
30. Preferably, the oxygen-rich material 40 is potassium nitrate.
However, the other materials such as ammonium nitrate may be
utilized in addition to or instead of potassium nitrate. As used
herein, "oxygen-rich material" denotes any material capable of
releasing oxygen when activated.
[0029] To propel the oxygen-rich material 40 through the
perforations behind the shaped charges 30, the apparatus is
provided with separate delivery explosives in the form of end
charges 44 and 46. The end charges 44 and 46 preferably are
composed of a slow burning (low order) explosive and may be
positioned at the first and second ends 26 and 28, respectively, of
the container 24. When thus arranged, it is convenient to attach
the primer cord 38 to the end charges 44 and 46, as shown in FIG.
1. Thus, a single signal on the conductor wire 34 to the igniter 32
will ignite the end charges 44 and 46 as well as the shaped charges
30 via the primer cord 34.
[0030] The end charges 44 and 46, positioned at each end of the
supply of oxygen-rich material 40, will create very high pressures
momentarily inside the container 24 and the well casing 20. This
pressure will force the oxygen-rich material 40 out through the
perforations in the casing 20, the annulus cement 22, and into the
surrounding formation 12 immediately behind the shaped charges.
This in turns causes explosive burning of the hydrocarbons in the
formation 12 that is supported by the oxygen being released by the
oxygen-rich material 40.
[0031] The operation of the apparatus of FIG. 1 is explained with
reference to the diagram in FIG. 2. At Time Zero, the signal from
the conductor wire 34 triggers the igniter 32 (FIG. 1), which in
turn initiates the explosive reaction in the fast burning primer
cord 38 that runs the length of the container 24. The reaction time
of the igniter 32 is shown at 50 on the time graph in FIG. 2. The
spike has a duration of about 0.0500 milliseconds, and the total
reaction time of the igniter is about 0.200 milliseconds.
[0032] The igniter 32 initiates the reaction in the fast burning
primer cord 38. Being a fast burning explosive, the cord 38 burns
from the igniter to the cord end very rapidly, for a duration of
about 0.500 milliseconds indicated at 52 in FIG. 2. The preferred
primer cord 38 burns at about 20,000 feet per second. Thus, the
primer cord 38 could travel a 10-foot string of 40 shaped charges,
for example, in only about 0.500 milliseconds.
[0033] The primer cord 38 ignites the shaped charges 30, the
oxygen-rich material 40, and the low order explosives in the end
charges 44 and 46. Due to fast burning (high order) explosives in
the shaped charges 30, the shaped charges burn rapidly for about
0.100 milliseconds as indicated at 54. However, the much slower
burning oxygen-rich material 40 and the end charges 44 and 46 burn
for a much longer duration, about 4.000 milliseconds and about
5.000 milliseconds at 56 and 58, respectively.
[0034] Referring still to FIG. 2, the secondary reaction in the
formation comprising the sustained burning of the hydrocarbons
lasts until the oxygen-rich material 40 is depleted, as indicated
at 60. The total duration of the reactive explosion of hydrocarbons
and oxygen in the formation, therefore, begins shortly after the
introduction of oxygen in the perforated hole and into the
formation and expires as the pyrotechnic reactions stop for lack of
oxygen or other reagents.
[0035] The effect of the operation of the apparatus 10 is
illustrated in FIG. 3, to which attention now is directed. This
drawing illustrates the condition of the well after ignition of the
apparatus 10. The container 24 and its components are substantially
destroyed, leaving perforations 62 corresponding to the positions
of the shaped charges 30. The sustained, explosive burn of the
hydrocarbons in the formation surrounding the perforations 62 has
substantially increased the surface area for production by
fracturing and cleaning the formation.
The Embodiment of FIGS. 4-6
[0036] Shown in FIG. 4 is another preferred embodiment of the
apparatus of the present invention. In this embodiment, the
apparatus 10A comprises an elongated container 24A having first and
second ends 26A and 28A. The container 24A is suspended by a
conductor wire 34A similar to the corresponding components of the
apparatus 10 of FIG. 1. An electrical igniter 32A, which may be
similar to the igniter 32 of the previous embodiment, is supported
near the first end 26A of the container 24A.
[0037] At least one and preferably three shaped charges 70 are
supported inside the container 24A. As in the previous embodiment,
the shaped charges 70 preferably are connected in series to a
primer cord 38A, which is connected to the igniter 32A. Generally,
it is desirable to average about four shaped charges per foot.
[0038] The apparatus 10A also includes a supply of oxygen-rich
material. However, in this embodiment, the oxygen-rich material is
contained in the shaped charges 70.
[0039] One preferred embodiment for the "oxygenated" shaped charge
70 of this invention is shown in FIG. 5 and designated as 70A. The
shaped charge 70A comprises a body of high explosive 72 formed to
have a conically shaped frontal recess 74.
[0040] A detonator is included in the shaped charge 70A to ignite
the body of explosive 72. The detonator may be the primer cord 38A
running therethrough.
[0041] A liner 76, usually of copper, is included. The liner 76 is
shaped to line the frontal recess 74 in the body of explosive 72.
Thus, the liner 76 in this configuration is conical.
[0042] Still further, a layer of oxygen-rich material 78 is
included in the shaped charge 70A. In the preferred form, the
oxygen-rich layer 78 is positioned between the conical copper liner
76 and the conical frontal recess 74 of the body of explosive 72.
The conically shaped oxygen-rich material 78 and the conically
shaped copper liner 76 thus form a bimetallic liner for the shaped
charge 70.
[0043] After the primer cord 38A ignites the high explosive 72, the
rapid burning of explosive 72 will convert the conically shaped
copper liner into a rapidly moving jet that will perforate the
casing and the formation (neither shown in this Figure). At the
same time, the conically shaped oxygen-rich layer 78 will also be
converted into a slower moving slug of oxygen-rich material. This
slower moving slug follows the rapidly moving jet into the
formation where, in the presence of the jet and the hydrocarbons in
the formation, the oxygen-rich slug will support an extended burn
of the hydrocarbons.
[0044] Shown in FIG. 6 is another embodiment of a shaped charge in
accordance with the present invention designated as 70B. In this
embodiment, the shaped charge 70B comprises a conically shaped body
of fast burning explosive 80. The recess 82 is also conical in
shape. A detonator is included, such as the primer cord 38A, to
ignite the fast burning explosive 80.
[0045] The shaped charge 70B further comprises a conically shaped
insert 84 of slower burning (lower order) explosive. The insert 84
is shaped to conform to and be received in the frontal recess 82 of
the body 80. Thus, the insert 84 in the embodiment shown is
conically shaped. Further, the insert 84 is shaped to have a planar
front 86.
[0046] Referring still to FIG. 6, the shaped charge 70B comprises a
disc shaped layer 88 of fast burning explosive. The fast burning
layer 88 has a front 90 and a rear 92. The rear 92 is fixed to the
planar front 86 of the insert 84.
[0047] Still further, the shaped charge 70B includes a disc shaped
layer 98 of elastic material molded at high pressure to contain an
oxygen-rich material, such as potassium nitrate fixed on the front
of the fast burning layer 88.
[0048] It is now seen that, when the shaped charge 70B is
detonated, the oxygen-rich disk 98 will be propelled through the
casing 20 and cement annulus 22. The initial movement of the disc
of oxygen-rich material 98 will be ahead of the shaped charge jet.
However, the shaped charge jet will quickly pierce the disc of
oxygen-rich material 98 and will proceed to make the perforation
through the casing 20 and cement annulus 22. The solid oxygen-rich
disk 98 becomes a projectile that follows the jet into the
perforation tunnel. The disk 98 supports the combustion of
hydrocarbons in the formation ignited by the jet for the selected
duration.
[0049] Turning now to FIG. 7, another embodiment of the
"oxygen-loaded" shaped charge will be described. This embodiment,
designated generally by the reference numeral 70C, comprises a
first body 100 of fast burning explosive formed to have a frontal
recess 102. Preferably, the frontal recess 102 is generally conical
in shape and the apex is curved or domed instead of pointed.
[0050] Also included is a body of oxygen-rich material 104, such as
potassium nitrate, formed to be received in the frontal recess 102
of the first body of explosive 100 and to have a frontal recess
106. The frontal recess 106 has a cylindrical center portion 108
and a frusto-conical forward portion 110.
[0051] Still further, the shaped charge 70C comprises a second body
112 of fast burning explosive shaped to conform to and be received
in the cylindrical center 108 of the recess 102 in the body of
oxygen-rich material 104. The second body 112 is also shaped to
have a conical front recess 114 continuous with the frusto-conical
forward portion 110 of the frontal recess 106 in the body of
oxygen-rich material 104. In this way, the frontal recess 114 of
the second body of explosive 112 and the frusto-conical portion 110
of the frontal recess 106 in the oxygen-rich material 104 form a
complete cone.
[0052] The charge 70C includes detonators, such as the primer cords
38A and 38B, adapted to ignite the first body of fast burning
explosive 100 and the second body of fast burning explosive 112. A
conically shaped metal liner 118 is positioned inside the complete
cone formed by the frontal recess 114 of the second body of
explosive 104 and the frusto-conical portion 110 of the frontal
recess 106 in the oxygen-rich material 104.
[0053] The primer cords 38A and 38B ignite the first and second
bodies of fast burning explosives 100 and 112. Then, second body of
high order explosive 112 will collapse the liner 118 to form a high
velocity jet which will penetrate the casing, cement, and
formation. Concurrently, the first body of high order explosive 100
propels the oxygen rich material 104 into the perforation tunnel in
time to support the reaction of the jet and the hydrocarbons in the
formation.
[0054] With reference now to FIG. 8, yet another embodiment of a
shaped charge will be described. This shaped charge, designated
generally as 70D, comprises a body of fast burning explosive 120.
The body of explosive 120 is formed to have a stepped frontal
recess 122 with a conical center portion 124 and a frusto-conical
forward portion 126. The narrowest diameter of the forward portion
126 forms a step 128 between the center portion 124 and the forward
portion 126.
[0055] The charge 70D further comprises a body of oxygen-rich
material 130 formed to be received in frusto-conical forward
portion 126 of the frontal recess 122 of the body of explosive 120.
The narrowest diameter of the body of oxygen-rich material 130 is
substantially the same as the widest diameter of the center portion
124 of the frontal recess 122 of the body of fast burning explosive
120. Thus, the conical center portion 124 of the frontal recess 122
of the body of explosive 120 and the body of oxygen-rich material
130 form a complete cone.
[0056] A detonator, such as the primer cord 38A is adapted to
ignite the body of fast burning explosive 120. Also, included is a
conically shaped liner 132 positioned inside the conical center
portion 124 of the frontal recess 122 in the body of fast burning
explosive 120.
[0057] The primer cord 38A ignites the body of fast burning
explosives 120. Then, the liner 132 and a small part of the oxygen
rich material 126 will collapse into a high velocity jet that will
penetrate the casing, cement, and formation. The remaining oxygen
rich material 126 will form a slower moving slug that will enter
the perforation tunnel in time to support the reaction of the jet
and the hydrocarbons in the formation.
[0058] In accordance with the method of the present invention,
there is provided a method for stimulating the hydro-carbon
containing strata in an oil and gas well. First, preferably using
one of the above described apparatus, the formation is perforated
using a shaped charge. An oxygen-rich material, such a potassium
nitrate, is introduced into the formation to support a sustained
burn of the hydrocarbons therein.
[0059] Whether the apparatus 10A with the shaped charge 70B is
employed or the shaped charge 70A is utilized or the apparatus 10
of FIG. 1 is used, the oxygen-rich material is forced into the
formation following the shaped charge jets. In all cases, though, a
supply of oxygen-rich material is dispersed through the altered
formation in the presence of ignited hydrocarbons so that a
sustained burn can occur. This effectively increases the exposed
surface area and enhances production from the altered
formation.
[0060] Changes can be made in the combination and arrangement of
the various parts and elements described herein without departing
from the spirit and scope of the invention as defined in the
following claims.
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