U.S. patent application number 09/735963 was filed with the patent office on 2001-05-24 for apparatus and method for perforating and stimulating a subterranean formation.
Invention is credited to Wesson, David S..
Application Number | 20010001418 09/735963 |
Document ID | / |
Family ID | 22334597 |
Filed Date | 2001-05-24 |
United States Patent
Application |
20010001418 |
Kind Code |
A1 |
Wesson, David S. |
May 24, 2001 |
Apparatus and method for perforating and stimulating a subterranean
formation
Abstract
A method and apparatus for perforating and stimulating a
subterranean formation which is penetrated by a well bore having
casing positioned therein so as to establish fluid communication
between the formation and the well bore. Substantially rigid,
flexible, or liquid propellant is interposed between the casing and
at least one shaped charge in a subterranean well bore and is
ignited due to the shock, heat and/or pressure generated from the
detonated charge. Upon burning, the propellant material generates
gases which clean perforations formed in the formation by
detonation of the shaped charge(s) and which extend fluid
communication between the formation and the well bore.
Inventors: |
Wesson, David S.; (DeSoto,
TX) |
Correspondence
Address: |
JACK E. EBEL
PATENT DEPARTMENT
MARATHON OIL COMPANY
P.O. BOX 269
Littleton
CO
80160
US
|
Family ID: |
22334597 |
Appl. No.: |
09/735963 |
Filed: |
December 12, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09735963 |
Dec 12, 2000 |
|
|
|
09110728 |
Jul 6, 1998 |
|
|
|
09110728 |
Jul 6, 1998 |
|
|
|
08711188 |
Sep 9, 1996 |
|
|
|
5775426 |
|
|
|
|
Current U.S.
Class: |
166/297 ;
166/308.1; 166/55.1 |
Current CPC
Class: |
E21B 43/11852 20130101;
E21B 43/263 20130101; E21B 37/08 20130101; E21B 43/267 20130101;
E21B 43/117 20130101 |
Class at
Publication: |
166/297 ;
166/308; 166/55.1 |
International
Class: |
E21B 043/17 |
Claims
I claim:
1. An apparatus for perforating and stimulating a subterranean
formation which is penetrated by a well bore having casing
positioned therein so as to establish fluid communication between
the formation and the well bore, said apparatus comprising: one or
more explosive charges; propellant interposed said casing and at
least one of said one or more explosive charges; and a detonator
ballistically connected to said one or more charges.
2. The apparatus of claim 1 wherein said propellant is a
substantially rigid.
3. The apparatus of claim 1 wherein said propellant is generally
flexible.
4. The apparatus of claim 1 wherein said propellant has a generally
helical configuration.
5. The apparatus of claim 1 wherein said propellant is one or more
strips.
6. The apparatus of claim 5 wherein said one or more strips are
linear.
7. The apparatus of claim 5 wherein said one or more strips are
arcuate.
8. The apparatus of claim 1 wherein said propellant has an annular
band configuration.
9. The apparatus of claim 1 wherein said propellant has a polygonal
configuration.
10. The apparatus of claim 1 wherein said propellant has a closed
plane curve configuration.
11. The apparatus of claim 1 wherein said propellant is a
llquid.
12. The apparatus of claim 1 wherein said propellant is interposed
said casing and all of said one or more explosive charges.
13. An apparatus for perforating and stimulating a subterranean
formation which is penetrated by a well bore having casing
positioned therein so as to establish fluid communication between
the formation and the well bore, said apparatus comprising: a tube
having one or more apertures therethrough; one or more shaped
charges positioned within said tube, each of said one or more
shaped charges being aligned with one of said one or more
apertures; and propellant interposed said casing and at least one
of said one or more shaped charges.
14. The apparatus of claim 13 wherein said propellant is a
substantially rigid.
15. The apparatus of claim 13 wherein said propellant is generally
flexible.
16. The apparatus of claim 13 wherein said propellant has a
generally helical configuration.
17. The apparatus of claim 13 wherein said propellant is one or
more strips.
18. The apparatus of claim 17 wherein said one or more strips are
linear.
19. The apparatus of claim 17 wherein said one or more strips are
arcuate.
20. The apparatus of claim 13 wherein said propellant has an
annular band configuration.
21. The apparatus of claim 13 wherein said propellant has a
polygonal configuration.
22. The apparatus of claim 13 wherein said propellant has a closed
plane curve configuration.
23. The apparatus of claim 13 wherein said propellant is a
liquid.
24. The apparatus of claim 13 wherein said propellant is interposed
said casing and all of said one or more explosive charges.
25. The apparatus of claim 13 wherein said propellant is secured to
the outer surface of said tube.
26. The apparatus of claim 13 wherein said propellant is water
repellant or water proof, is not physically effected by hydrostatic
pressures encountered in said subterranean formation and is
unreactive or inert to fluids which may be encountered in a well
penetrating and in fluid communication with said subterranean
formation.
29. The apparatus of claim 13 wherein said propellant is a cured
epoxy or plastic having an oxidizer incorporated therein.
30. A method of perforating and stimulating a subterranean
formation which is penetrated by a well bore having casing
positioned therein so as to establish fluid communication between
the formation and the well bore, said method comprising: placing a
liquid propellant between at least one perforating charge in said
well bore and said casing; and detonating said at least one
perforating charge so as to form perforations through said casing
and into said formation, said detonation of said perforating charge
igniting said liquid propellant thereby forming gases which clean
said perforations and which extend fluid communication between said
formation and said well bore.
31. The method of claim 30 wherein said step of placing comprises
injecting liquid propellant into said well bore before said at
least one perforating charge is positioned within the well
bore.
32. The method of claim 30 wherein said step of placing comprises
injecting liquid propellant into said well bore simultaneous with
positioning said at least one perforating charge within the well
bore.
33. A kit for an apparatus for perforating and stimulating a
subterranean formation which is penetrated by a well bore having
casing positioned therein so as to establish fluid communication
between the formation and the well bore, said kit comprising: an
apparatus for perforating a subterranean formation which has one or
more shaped charges; and propellant adapted to be interposed a
casing which is positioned within a well bore penetrating a
subterranean formation and at least one of said one or more shaped
charges when said apparatus is placed within said well bore.
34. The kit of claim 33 wherein said propellant is a substantially
rigid.
35. The kit of claim 33 wherein said propellant is generally
flexible.
36. The kit of claim 33 wherein said propellant has a generally
helical configuration.
37. The kit of claim 33 wherein said propellant is one or more
strips.
38. The kit of claim 37 wherein said one or more strips are
linear.
39. The kit of claim 37 wherein said one or more strips are
arcuate.
40. The kit of claim 33 wherein said propellant has an annular band
configuration.
41. The kit of claim 33 wherein said propellant has a polygonal
configuration.
42. The kit of claim 33 wherein said propellant has a closed plane
curve configuration.
43. The kit of claim 33 wherein said propellant is a liquid.
44. All inventions described herein.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of copending U.S.
patent application Ser. No. 08/711,188, filed Sep. 9, 1996.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to an apparatus and method for
perforating well casing and/or a subterranean formation(s), and
more particularly, to such an apparatus and process wherein a
propellant is employed to substantially simultaneously enhance the
effectiveness of such perforations and to stimulate the
subterranean formation(s).
[0004] 2. Description of Related Art
[0005] Individual lengths of relatively large diameter metal
tubulars are secured together to form a casing string which is
positioned within a subterranean well bore to increase the
integrity of the well bore and provide a path for producing fluids
to the surface. Conventionally, the casing is cemented to the well
bore face and subsequently perforated by detonating shaped
explosive charges. These perforations extend through the casing and
cement a short distance into the formation. In certain instances,
it is desirable to conduct such perforating operations with the
pressure in the well being overbalanced with respect to the
formation pressure. Under overbalanced conditions, the well
pressure exceeds the pressure at which the formation will fracture,
and therefor, hydraulic fracturing occurs in the vicinity of the
perforations. As an example, the perforations may penetrate several
inches into the formation, and the fracture network may extend
several feet into the formation. Thus, an enlarged conduit can be
created for fluid flow between the formation and the well, and well
productivity may be significantly increased by deliberately
inducing fractures at the perforations.
[0006] When the perforating process is complete, the pressure
within the well is allowed to decrease to the desired operating
pressure for fluid production or injection. As the pressure
decreases, the newly created fractures tend to close under the
overburden pressure. To ensure that fractures and perforations
remain open conduits for fluids flowing from the formation into to
the well or from the well into the formation, particulate material
or proppants are conventionally injected into the perforations so
as to prop the fractures open. In addition, the particulate
material or proppant may scour the surface of the perforations
and/or the fractures, thereby enlarging the conduits created for
enhanced fluid flow. The proppant can be emplaced either
simultaneously with formation of the perforations or at a later
time by any of a variety of methods. For example, the lower portion
of the wellbore can be filled with a sand slurry prior to
perforation. The sand is subsequently driven into the perforations
and fractures by the pressured fluid in the wellbore during
conventional overbalanced perforating operations.
[0007] As the high pressure pumps necessary to achieve an
overbalanced condition in a well bore are relatively expensive and
time consuming to operate, gas propellants have been utilized in
conjunction with perforating techniques as a less expensive
alternative to hydraulic fracturing. Shaped explosive charges are
detonated to form perforations which extend through the casing and
into the subterranean formation and a propellant is ignited to
pressurize the perforated subterranean interval and propagate
fractures therein. U.S. Pat. Nos. 4,633,951, 4,683,943 and
4,823,875 to Hill et al. describe a method of fracturing
subterranean oil and gas producing formations wherein one or more
gas generating and perforating devices are positioned at a selected
depth in a wellbore by means of by a section of wireline which may
also be a consumable electrical signal transmitting cable or an
ignition cord type fuse. The gas generating and perforating device
is comprised of a plurality of generator sections. The center
section includes a plurality of axially spaced and radially
directed perforating shaped charges which are interconnected by a
fast burning fuse. Each gas generator section includes a
cylindrical thin walled outer canister member. Each gas generator
section is provided with a substantially solid mass of gas
generating propellant which may include, if necessary, a fast burn
ri20 ng disposed adjacent to the canister member and a relatively
slow burn core portion within the confines of ring. An elongated
bore is also provided through which the wireline, electrical
conductor wire or fuse which leads to the center or perforating
charge section may be extended. Primacord fuses or similar igniters
are disposed near the circumference of the canister members. Each
gas generator section is simultaneously ignited to generate
combustion gasses and perforate the well casing. The casing is
perforated to form apertures while generation of gas commences
virtually simultaneously. Detonation of the perforating shaped
charges occurs at approximately 110 milliseconds after ignition of
gas generating unit and that from a period of about 110
milliseconds to 200 milliseconds a substantial portion of the total
flow through the perforations is gas generated by gas generating
unit.
[0008] U.S. Pat. No. 4,391,337 to Ford et al. discloses an
integrated jet perforation and controlled propellant fracture
device and method for enhancing production in oil or gas wells. A
canister contains a plurality of shaped charge grenades around
which is packed a gas propellant material so as to form a solid
fuel pack.
[0009] U.S. Pat. No. 5,355,802 to Petijean describes a method and
apparatus for perforating a formation surrounding a wellbore and
initiating and propagating a fracture in the formation to stimulate
hydrocarbon production from the wellbore. A tool includes at least
one oriented shaped charge which is connected to detonator via a
firing cord. At least one propellant generating cartridge is also
positioned within tool and is connected to wireline cable through
delay box via wires and cord.
[0010] U.S. Pat. No. 4,253,523 to Ibsen discloses a method and
apparatus for well perforations and fracturing operations. A
perforating gun assembly is comprised of a plurality of shaped
charges positioned in spaced-apart relationship to each other in an
elongated cylindrical carrier. The spaces in the carrier between
the shaped charges are filled with a secondary explosive, such as
an activated ammonium nitrate.
[0011] U.S. Pat. No. 5,005,641 to Mohaupt discloses a gas
generating tool for generate a large quantity of high pressure
gases to stimulate a subterranean formation. The tool comprises a
carrier or frame having a series of staggered openings spaced
longitudinally along the tubular member. Carrier receives a charge
of propellant material which has a passage through which an
ignition tube is inserted.
[0012] However, none of these prior art devices which utilized
propellants in conjunction with perforating devices have proved to
provide completely satisfactory results. Thus, a need exists for an
apparatus and method for perforating and stimulating a subterranean
formation which provides for improved communication between the
wellbore and the subterranean formation penetrated thereby.
[0013] Thus, it is an object of the present invention to provide an
apparatus and method for perforating and stimulating a subterranean
formation which provides for improved communication between the
wellbore and the subterranean formation penetrated thereby.
[0014] It is also object of the present invention to provide an
apparatus for perforating and stimulating a subterranean formation
which is relatively simple in design and can be readily employed
with a variety of perforating gun designs.
[0015] It is a further object of the present invention to provide
an apparatus for perforating and stimulating a subterranean
formation which provides repeatable burns of the propellant
component of the apparatus.
[0016] It is still a further object of the present invention to
provide an apparatus for perforating and stimulating a subterranean
formation which uses perforating charges of lesser energy than
previously employed.
[0017] It is a still further object of the present invention to
provide an apparatus and method for perforating and stimulating a
subterranean formation wherein propellant is positioned between a
perforating charge and the casing of a well bore.
SUMMARY OF THE INVENTION
[0018] To achieve the foregoing and other objects, and in
accordance with the purposes of the present invention, as embodied
and broadly described herein, one characterization of the present
invention comprises an apparatus for perforating and stimulating a
subterranean formation which is penetrated by a well bore having
casing positioned therein so as to establish fluid communication
between the formation and the well bore. The apparatus comprises
one or more explosive charges, propellant interposed between the
casing and at least one of the one or more explosive charges, and a
detonator ballistically connected to the one or more charges..
[0019] Another characterization of the present invention comprises
an apparatus for perforating a subterranean formation comprising an
apparatus for perforating and stimulating a subterranean formation
which is penetrated by a well bore having casing positioned therein
so as to establish fluid communication between the formation and
the well bore. The apparatus comprises a tube having one or more
apertures therethrough, one or more shaped charges positioned
within the tube, and propellant interposed between the casing and
at least one of the one or more shaped charges. Each of the one or
more shaped charges is aligned with one of the one or more
apertures.
[0020] Yet another characterization of the present invention
comprises a method of a method of perforating and stimulating a
subterranean formation which is penetrated by a well bore having
casing positioned therein so as to establish fluid communication
between the formation and the well bore. In accordance with the
method, a liquid propellant is positioned between at least one
perforating charge in the well bore and the casing. The at least
one perforating charge is detonated so as to form perforations
through the casing and into the formation. Detonation of the
perforating charge ignites the liquid propellant thereby forming
gases which clean the perforations and extend fluid communication
between the formation and the well bore.
[0021] A further characterization of the present invention is a kit
for an apparatus for perforating and stimulating a subterranean
formation which is penetrated by a well bore having casing
positioned therein so as to establish fluid communication between
the formation and the well bore. The kit comprises an apparatus for
perforating a subterranean formation which has one or more shaped
charges and a propellant adapted to interposed at least one of the
shaped charges and the casing when the apparatus is positioned
within the well bore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate the embodiments of the
present invention and, together with the description, serve to
explain the principles of the invention.
[0023] In the drawings:
[0024] FIG. 1 is a cross sectional view of the apparatus of the
present invention as positioned within a well penetrating a
subterranean formation;
[0025] FIG. 2 is a cross sectional view of the apparatus of one
embodiment of the present invention;
[0026] FIG. 3 is a cross sectional view illustrating the spatial
relationships between the certain component parts of the apparatus
of the present invention taken along line 3-3 of FIG. 2;
[0027] FIG. 4 is a partial cross sectional view of a perforating
charge as connected to a detonating cord;
[0028] FIG. 5 is a perspective view of one embodiment of the
propellant sleeve of the apparatus of the present invention which
is illustrated in FIG. 2;
[0029] FIG. 6 is a cross section of a portion of a detonating
system suitable for use in the present invention;
[0030] FIG. 7 is a perspective view of another embodiment of the
propellant sleeve of the apparatus of the present invention which
is illustrated in FIG. 2;
[0031] FIG. 8 is a cross sectional view of the propellant sleeve
taken along line 8-8 of FIG. 7;
[0032] FIG. 9 is a cross sectional view of another embodiment of a
propellant sleeve utilized in the apparatus of the present
invention which is illustrated in FIG. 2;
[0033] FIG. 10 is a cutaway view of the propellant sleeve
embodiment depicted in FIG. 9 which illustrates the interior wall
of the sleeve;
[0034] FIG. 11 is a cross sectional view of another embodiment of
the apparatus of the present invention;
[0035] FIG. 12 is a cross sectional view of the another embodiment
of the propellant as utilized in conjunction with the apparatus of
the present invention;
[0036] FIG. 13 is a perspective view of the embodiment of
propellant utilized in conjunction with the apparatus of the
present invention which is also illustrated in FIG. 12;
[0037] FIG. 14 is a schematic view of another embodiment of the
present invention in which liquid propellant is introduced into a
subterranean well bore; and
[0038] FIG. 15 is a schematic view of the embodiment illustrated in
FIG. 15 further illustrating a perforating gun being positioned
within the liquid propellant in a subterranean well bore.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] As illustrated in FIG. 1, a well 10 having a casing 12 which
is secured therein by means of cement 13 extends from the surface
of the earth 14 at least into a subterranean formation 16. One or
more perforating and propellant apparatus 20 of the present
invention are secured to the lower end of tubing string 18 and
lowered into well 10. The upper most apparatus 20 as positioned
within well 10 may be secured directly to the end of tubing string
18. A tandem sub 60 may be utilized to secure apparatus 20 together
while a bull plug 66 may be secured to the terminal end of the
lowermost apparatus 20. Any suitable means, such as a packer 21,
may be employed to isolate the portion of well 10 adjacent interval
16, if desired. A tubing string may be utilized to position and
support the apparatus of the present invention within a well bore.
Tubing will preferably be employed to convey several apparatus 20
into the same well bore. Alternatively, a wireline, slick line,
coil tubing or any other suitable means as will be evident to a
skilled artisan may be used to position and support one or more
apparatus 20 within a well bore.
[0040] Referring now to FIG. 2, the perforating and propellant
apparatus of the present invention is illustrated generally as 20
and has one end thereof secured to a tandem sub 60 while the other
end thereof is secured to a bull plug 66. A perforating charge
carrier 22 is positioned between tandem sub 60 and bull plug 66 and
is secured thereto by any suitable means, such as by mating screw
threads 23 and 24 which are provided in the internal surface of
carrier 22 adjacent each end thereof with corresponding threads 61
and 67 of tandem sub 60 and bull plug 66, respectively. O-rings 70
provide a fluid tight seal between carrier 22 and tandem sub 60
while O-rings 74 provide a fluid tight seal between carrier 22 and
bull plug 66. Carrier 22 may be a commercially available carrier
for perforating charges and contains at least one conventional
perforating charge 40 capable of creating an aperture in the
carrier wall 30, well casing 12, and a portion of the adjacent
subterranean formation 16. A perforating charge tube 34 is
positioned within carrier 22 and has at least one relatively large
aperture or opening 35 and a plurality of smaller apertures or
openings 36 therein. Openings 35 in the wall of charge tube 34 may
be spaced both vertically along and angularly about the axis of the
tube. Charge carrier 22 and perforating charge tube 34 have
generally elongated tubular configurations. A lined perforating
charge 40 has a small end 46 secured in an aperture or opening 36
in perforating charge tube 34, as described below, and a large end
48 aligned with and protruding through opening or aperture 35 in
tube 34. At least one lined perforating charge 40 is mounted in
perforating charge tube 34. A detonating cord 86 is connected to a
detonator above tandem sub 60, to the small end 46 of each
perforating charge 40, and to end cap 68 in bull plug 66. One or
more additional combinations of a perforating charge carrier,
booster transfer and a tandem sub could be mounted above carrier
22. Tube alignment end plates 50 function to align charge tube 34
within carrier 22 so that the front of each charge is adjacent a
scallop 27 in the wall of carrier 22.
[0041] If multiple charges are present, they may be spaced
vertically along and angularly about the axis of the carrier. The
charge density is an appropriate density determined by methods
known to those skilled in the art. Common charge densities range
between two and twenty four per foot. Detonating cord 86 connects a
booster transfer (not illustrated) in tandem sub 60 above carrier
22, all charges 40, and end cap 68 in bull plug 66.
[0042] As illustrated in FIG. 3, brackets 80 on the small end 46 of
lined perforating charge 40 extend through opening 36 in charge
tube 34. A clip 82 secures punch charge 40 to charge tube 34.
Detonating cord 86 is threaded through a space 84 between brackets
80 and clip 82. Charge tube 34 is mounted in carrier 22 so that the
small end 46 of charge 40 is adjacent scallop 27 in carrier 22.
[0043] Referring to FIG. 4, a typical perforating charge is
illustrated generally as 40. A highly compressed explosive 41
partially fills perforating charge case 42. Liner 43 covers the
exposed surface of the explosive. The liner 43 is commonly metallic
and serves to focus the energy of the charge and enable the charge
to perforate a well casing.
[0044] In accordance with the present invention, a sleeve 90 which
has a generally tubular configuration (FIG. 5) is positioned around
perforating charge carrier 22 during manufacture of the perforating
and propellant apparatus 20 of the present invention or during
final assembly thereof which may take place at the well site. As
assembled (FIG. 2), sleeve 90 is secured in positioned around
perforating charge carrier 22 at one end by tandem sub 60 and by
bull plug 66 at the other end. Tandem sub 60 and bull plug 66 may
be sized to have an external diameter greater than sleeve 90 so as
to inhibit damage to sleeve 90 during positioning within a well
bore. Alternatively, protective rings or the like (not illustrated)
which have a larger external diameter than sleeve 90 may be
inserted between tandem sub 60, bull plug 66 and sleeve 90 during
manufacture or final assembly of the apparatus of the present
invention so as to inhibit damage to sleeve 90. Sleeve 90 may
extend the entire distance between tandem sub 60 and bull plug 66
or a portion thereof. Sleeve 90 is constructed of a water repellant
or water proof propellant material which is not physically effected
by hydrostatic pressures commonly observed during perforation of a
subterranean formation(s) and is unreactive or inert to almost all
fluids, in particular those fluids encountered in a subterranean
well bore. Preferably, the propellant is a cured epoxy or plastic
having an oxidizer incorporated therein such as that commercially
available from HTH Technical Services, Inc. of Coeur d'Alene,
Id.
[0045] Any suitable detonating system may be used in conjunction
with the perforating and propellant apparatus 20 of the present
invention as will be evident to a skilled artisan. An example of
such a suitable detonating system suitable is illustrated in FIG.
6. Vent housing 210 is capable of attachment to the end of a tubing
string 211 or wireline (not shown). A vent 212 is attached to
connecting rod 214 inside vent housing 210 and seals fluid passage
216. Rod 214 is in contact with a piston 218. An annular chamber
220 between piston 218 and the interior wall of housing 210 is
filled with air at atmospheric pressure. Adjacent the bottom of
piston 218, shear pins 222 are mounted in shear set 224, and a
firing pin 226 extends downward from the bottom of piston 218.
Retainer 228 joins vent housing 200 and tandem sub 60. Percussion
detonator 230 is mounted in retainer 228 in firing head 236 which
is attached to vent housing 210 and capable of attachment to tandem
sub 60. Sub 60 is attached to perforating charge carrier 22. An
ignition transfer 232 at the top of sub 60 is in contact with
detonating cord 86 passing through central channel 234 and charge
carrier 22, as described above. A booster transfer is located in
each tandem sub 60, linking the detonating cords in the charge
carriers above and below the tandem sub.
[0046] Upon application of sufficient hydraulic pressure to the top
of piston 218, vent 212 and piston 218 simultaneously move
downward, opening fluid passage 214 and causing firing pin 226 to
contact percussion detonator 230. The ignition of percussion
detonator 230 causes a secondary detonation in ignition transfer
232, which in turn ignites detonating cord 86. Detonating cord 86
comprises an explosive and runs between the ends of each charge
carrier, passing between the backs of the charges and the charge
clips holding the charges in the carrier. Cord 86 ignites the
shaped charges 40 in charge carrier 22 and booster transfer, which
contains a higher grade explosive than detonating cord 86.
[0047] As described above and shown in FIG. 6, an impact detonator
provides a primary detonation. If the perforating apparatus is run
on a wireline, the primary detonator could, alternatively, be an
electrical detonator. The primary detonator ignites a
pressure-sensitive chemical in ignition transfer 232, which in turn
ignites detonating cord. The detonating cord then ignites the one
or more charges 40 in the carrier 22 simultaneously. Each transfer
booster also contains an explosive for detonating the cord 86 in
the adjacent carrier. The system may be detonated from the top, the
bottom, or both.
[0048] In operation, the desired number of perforating charge
carriers 22 are loaded with charges 40 and are connected with a
detonating means, such as detonating cord 86. A string of apparatus
20 separated by tandem subs 60 is assembled at the well site as the
units are lowered into well 10 at the end of a tubing string,
wireline, slick line, coil tubing or any other suitable means as
will be evident to a skilled artisan. Propellant sleeve 90 may be
cut from a length of propellant tubular and positioned around
perforating charge carrier 22 at the well site. The apparatus 20 is
then located in the well with the perforating charges adjacent the
formation interval 16 to be perforated. The perforating charges 40
are then detonated. Upon detonation, each perforating charge 40
blasts through a scallop 27 in carrier 32, penetrates propellant
sleeve 90, creates an opening in casing 12 and penetrates formation
16 forming perforations therein. Propellant sleeve 90 breaks apart
and ignites due to the shock, heat, and pressure of the detonated
shaped charge 40. When one or more perforating charges penetrate
the formation, pressurized gas generated from the burning of
propellant sleeve 90 enters formation 16 through the recently
formed perforations thereby cleaning such perforations of debris.
These propellant gases also stimulate formation 16 by extending the
connectivity of formation 16 with well 10 by means of the pressure
of the propellant gases fracturing the formation.
[0049] A proppant, such as sand, may be introduced into well 10
almost simultaneously with the ignition of the perforation and
propellant apparatus 20 of the present invention by any of a
variety of suitable means, such as a conventional perforating
charge carrier which is equipped with punch charges, filled with
sand and connected in series to detonating cord 86, as is
commercially available under the trademark POWR*PERF from
Halliburton Energy Services or Advance Completion Technologies Inc.
As such gases generated by burning propellant sleeve 90 escape from
the well and enter the perforations formed in formation 16, the
sand which is carried into the fractures by the propellant gases
abrades or scours the walls of the perforations and fractures,
thereby enlarging the conduits for fluid flow between the formation
and the well 10. Some of the sand may remain in the fractures as a
proppant, thereby preventing the fractures from closing when the
fluid pressure is relieved.
[0050] To assist in ignition, sleeve 90 may be provided with one or
more grooves or slits 92 which may extend through the entire
thickness of sleeve 90 (FIG. 7) and which may extend substantially
the entire length thereof. The slit(s) is positioned adjacent a
shaped charge 40 such that upon ignition shaped charge 40 impacts
slit 92 which provides a greater surface area for sleeve 90 to
ignite and burn. Preferably, slit(s) 92 is tapered (FIG. 8) such
that the slit is wider at the internal surface of sleeve 90 than
the external surface thereof. To achieve a uniform and repeatable
burn, the internal surface of sleeve 90 may be provided with
grooves or channels 94 (FIGS. 9 and 10) to assist in propellant
sleeve 90 uniformly breaking upon being impacted by shaped charge
40. Grooves or channels 94 may have a varied or a uniform thickness
or depth and may be formed in a uniform or random pattern.
[0051] Referring now to FIG. 11, another embodiment of the
perforating and propellant apparatus of the present invention is
illustrated generally as 120 and has a perforating charge carrier
122 is located between two tandem subs 160 or between a tandem sub
160 and bull plug 166. In this embodiment, carrier 122 is
constructed of a water repellant or proof propellant material which
is not physically effected by hydrostatic pressures commonly
observed during perforation or subterranean formations and is
unreactive or inert to almost all fluids, in particular those
fluids encountered in a subterranean well bore. Preferably, the
propellant is a cured epoxy, carbon fiber composite having an
oxidizer incorporated therein such as that commercially available
from HTH Technical Services, Inc. of Coeur d'Alene, Id. Carrier 122
contains at least one conventional perforating charge 140 capable
of creating an aperture in the carrier wall 130, well casing 12,
and a portion of the interval 16 in the adjacent subterranean
formation. Each perforating charge 140 is secured in an opening 136
in perforating charge tube 134 with a clip. Preferably, tandem sub
160, bull plug 166 and charge tube 134 are constructed of a
material which substantially entirely breaks up or decomposes, for
example thin walled steel, a material which substantially
disintegrates, for example a carbon fiber, epoxy composite, upon
detonation of charges 140, or a material which is completely
burnable, such as a epoxy, oxidizer propellant similar to that used
for sleeve 90.. If more than one shaped charges is utilized, they
may be spaced vertically along and angularly about the axis of the
carrier. The charge density is an appropriate density determined by
methods known to those skilled in the art. Common charge densities
range between six and twelve per foot. Detonating cord 186 connects
a booster transfer in tandem sub 160 above carrier 122, all charges
40, and end cap 168 in bull plug 166, As previously discussed with
respect to the embodiment illustrated in FIG. 2, one or more
combinations of an additional tandem sub and an additional
perforating charge carrier could be mounted below carrier 122. The
detonating cord 186 would then be connected to a booster transfer
in the tandem sub 160 below each additional perforating charge
carrier. In this embodiment, removal of any portion of the gun from
well 10 after detonation is obviated since the carrier is ignited
and the charge tube decomposed and/or disintegrated upon detonation
of charge(s) 140. This advantage is especially pronounced in
instances where a very small amount of space, if any, exists below
the interval of formation 16 which is perforated.
[0052] Although the propellant as utilized in the present invention
is described above as being a sleeve, shell or sheath which is
generally rigid, the propellant may utilized in different shapes,
configurations and/or forms so long as propellant is interposed
casing which is positioned within a subterranean well bore and at
least one perforating charge which is positioned within the casing.
For example, propellant 190 as illustrated in FIG. 13 may be
substantially helical or spiral in form and is positioned around
perforating charge carrier 22 during manufacture of the perforating
and propellant apparatus 20 of the present invention or during
final assembly thereof which may take place at the well site. As
assembled (FIG. 12), propellant 190 is secured in positioned around
perforating charge carrier 22 at one end by tandem sub 60 and by
bull plug 66 at the other end. Tandem sub 60 and bull plug 66 may
be sized to have an external diameter greater than sleeve 90 so as
to inhibit damage to propellant 190 during positioning within a
well bore. Alternatively, protective rings or the like (not
illustrated) which have a larger external diameter than propellant
190 may be inserted between tandem sub 60, bull plug 66 and
propellant 190 during manufacture or final assembly of the
apparatus of the present invention so as to inhibit damage to
propellant 190. Propellant 190 may extend the entire distance
between tandem sub 60 and bull plug 66 or a portion thereof. As
with sleeve 90, propellant 190 is constructed of a water repellant
or water proof propellant material which is not physically effected
by hydrostatic pressures commonly observed during perforation of a
subterranean formation(s) and is unreactive or inert to almost all
fluids, in particular those fluids encountered in a subterranean
well bore. Preferably, the propellant is a cured epoxy or plastic
having an oxidizer incorporated therein such as that commercially
available from HTH Technical Services, Inc. of Coeur d'Alene, Id.
Alternatively, propellant 190 may be in the form of one or more
bands or in the form of one or more generally linear or generally
arcuate strips which are positioned about charge carrier 22 so as
to be interposed at least one perforating charge 40 and casing 12.
The bands of propellant 190 may be generally annular and may have
gap therein so as to be U-shaped or C-shaped in cross section. As
another example, propellant 190 may be flexible and wrapped about
all or a portion of charge carrier 22 in any shape or pattern so as
to be interposed at least one perforating charge 40 and casing 12.
In both of these embodiments, propellant 190 may be secured to
charge carrier by any suitable means as will be evident to a
skilled artisan, such as a commercially available adhesive.
Pursuant to a further alternative, propellant 190 is a relatively
thin, discrete shape having any suitable peripheral configuration,
for example polygonal or a closed plane curve such as a circle, and
is secured to the outer surface of charge carrier 22 by any
suitable means, for example adhesive or screw threads, so as to be
interposed at least one perforating charge 40 and casing 12.
[0053] In yet another embodiment of the present invention, a liquid
propellant 290, such as that manufactured under the trade name
designation Re-flo 403 by Hercules, Inc. of Wilmington, Del., is
injected into well 10 via casing 12 and forms a first upper liquid
surface 291 within well 10. One or more conventional perforating
guns 320 are then lowered into well 10 at the end of a tubing
string, wireline, slick line, coil tubing or any other suitable
means as will be evident to a skilled artisan. The perforating guns
are positioned adjacent the subterranean formation of interest
which is formation 16 as illustrated in FIG. 14. As thus
positioned, the liquid propellant previously injected into well 10
is displaced by the perforating gun(s) 320 such that the liquid
propellant is interposed at least the lowermost perforating charge
322 present in the lowermost perforating gun 320. Preferably, the
volume of liquid propellant 290 previously injected into well 10 is
sufficient to cover all of the perforating charges in every
perforating gun 320 lowered into well 10. As displaced about the
perforating gun(s) 320, the liquid propellant forms a second upper
liquid surface 292 within well 10 which is above the previous
surface 291. The perforating charges 322 are then detonated by
means of a suitable detonating system as previously described. Upon
detonation, each perforating charge 322 penetrates liquid
propellant 290, creates an opening in casing 12 and penetrates
formation 16 forming perforations therein. The liquid propellant
290 ignites due to the shock, heat, and pressure of the detonated
shaped charge(s) 322. When one or more perforating charges
penetrate the formation, pressurized gas generated from the burning
of liquid propellant 290 enters formation 16 through the recently
formed perforations thereby cleaning such perforations of debris.
These gases also stimulate formation 16 by extending the
connectivity of formation 16 with well 10 by means of the pressure
of the gases fracturing the formation. Alternatively, the liquid
propellant may be injected into well 10 simultaneously with
lowering of perforating gun 320 into the well or after perforating
gun 320 is positioned within well 10.
[0054] The perforating and propellant apparatus of the present
invention can be utilized with tubing or wireline. The increased
strength of the tubing over wireline allows the use of a longer
perforating and propellant apparatus, thereby allowing a longer
interval to be perforated and stimulated in a single trip into a
well. A tubing-conveyed apparatus is also compatible with the use
of packers to isolate one or more portions of the well adjacent one
or more intervals of the formation. Thus, the method may be used
where it is desired for some other reason to limit the pressure to
which another portion of the well is subjected, for example, in a
well where one or more other zones have already been completed.
Further, if the well has a high deviation angle from vertical or is
horizontal, the tubing may be used to push the perforating and
propellant apparatus into the well.
[0055] Multiple intervals of a subterranean formation can be
perforated and fractured in a single operation by combining two or
more perforating and propellant apparatus 20 and/or 120 of the
present invention with a single tubing string in a spaced apart
manner as will be evident to a skilled artisan. In using the
perforating and propellant apparatus of the present invention,
shaped charges containing a smaller amount of highly compressed
explosive than conventional charges may be employed since the
shaped charge need only perforate casing 12 as gases which are
generated by burning propellant extend the perforation and
fractures into the subterranean formation. Accordingly, a greater
number of shaped charges may be employed in the apparatus of the
present invention than in a conventional perforating apparatus
and/or shaped charges which produce larger diameter perforations
than those produced by conventional shaped charges may be employed
in the apparatus of the present invention. Further, propellant
sleeve 90 or carrier 122 may have proppant dispersed throughout or
embedded upon the outer surface thereof. This proppant may also
contain a radioactive tag to assist in determining the dispersion
of the proppant into the perforations in the subterranean
formation(s).
[0056] Although the various embodiments of the apparatus of the
present invention have been described and illustrated as being
comprised of several component parts which are secured together in
a fluid tight relationship, it is within the scope of the present
invention to construct the apparatus 20 or 120 of an integral piece
of propellant material which is open to flow of fluids from the
well bore and in which shaped charges are secured.
[0057] As discussed above, the ignition means may be a detonating
material, such as detonating cord 28. Alternatively, the ignition
means may be a deflagrating material or cord. For example, a tube
containing black powder may be utilized as the ignition system to
ignite the propellant in the apparatus and method of the present
invention.
[0058] While the foregoing preferred embodiments of the invention
have been described and shown, it is understood that the
alternatives and modifications, such as those suggested and others,
may be made thereto and fall within the scope of the invention.
* * * * *