U.S. patent application number 13/334847 was filed with the patent office on 2013-06-27 for pulse detonation tool, method and system for formation fracturing.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Anthony John DEAN, Imdad IMAM, Roderick Mark LUSTED, Adam RASHEED, Christopher Edward WOLFE. Invention is credited to Anthony John DEAN, Imdad IMAM, Roderick Mark LUSTED, Adam RASHEED, Christopher Edward WOLFE.
Application Number | 20130161007 13/334847 |
Document ID | / |
Family ID | 48653425 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130161007 |
Kind Code |
A1 |
WOLFE; Christopher Edward ;
et al. |
June 27, 2013 |
PULSE DETONATION TOOL, METHOD AND SYSTEM FOR FORMATION
FRACTURING
Abstract
According to one aspect of the invention, a pulse detonation
tool is provided for fracturing subterranean formations. The pulse
detonation tool includes a pulse detonation combustor and creates
an isolated zone within a wellbore. The tool generate a series of
repeating supersonic shock waves that are directed into the
subterranean formation to cause propagation of multiple fractures
into the formation. According to another aspect of the invention, a
method and system for fracturing a subterranean formation using
pulse detonation is provided.
Inventors: |
WOLFE; Christopher Edward;
(Niskayuna, NY) ; DEAN; Anthony John; (Scotia,
NY) ; IMAM; Imdad; (Schenectady, NY) ; LUSTED;
Roderick Mark; (Niskayuna, NY) ; RASHEED; Adam;
(Glenville, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WOLFE; Christopher Edward
DEAN; Anthony John
IMAM; Imdad
LUSTED; Roderick Mark
RASHEED; Adam |
Niskayuna
Scotia
Schenectady
Niskayuna
Glenville |
NY
NY
NY
NY
NY |
US
US
US
US
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
48653425 |
Appl. No.: |
13/334847 |
Filed: |
December 22, 2011 |
Current U.S.
Class: |
166/297 ;
166/63 |
Current CPC
Class: |
E21B 43/263 20130101;
E21B 43/11857 20130101 |
Class at
Publication: |
166/297 ;
166/63 |
International
Class: |
E21B 43/263 20060101
E21B043/263; E21B 29/02 20060101 E21B029/02 |
Claims
1. A pulse detonation tool for fracturing subterranean formations,
adapted to be lowered into production tubing within a wellbore, and
comprising: a first sealing mechanism and a second sealing
mechanism configured to create an isolated zone having an axis
parallel to and extending through the production tubing, wherein
the first sealing mechanism has at least one inlet port configured
to allow a fuel and an oxidizer to flow into a pulse detonation
combustor disposed within the isolated zone and wherein the first
sealing mechanism is further configured to connect to an oxidizer
and fuel source by way of a fluid injection line extending from the
surface through the tubing; at least one valve assembly to achieve
controlled delivery of the fuel and oxidizer to the pulse
detonation combustor, the pulse detonation combustor comprising: a
combustion region defining a fluid flow path; a mixing region for
producing a flammable mixture comprising a controlled volume of
fuel and oxidizer, wherein the mixing region is in fluid
communication with the at least one inlet port and the combustion
region; an ignition device configured to periodically ignite the
flammable mixture; and means for initiating a series of repeating
detonations that generate a series of repeating supersonic shock
waves, wherein the shock waves are directed into the subterranean
formation to cause propagation of multiple fractures into the
formation.
2. The apparatus of claim 1 wherein the first sealing mechanism and
second sealing mechanism are positioned to align the isolated zone
with perforations in the production tubing, a well casing, or
both.
3. The apparatus of claim 1 wherein the shock waves are about 10 to
about 16 times the initial pressure in the wellbore.
4. The apparatus of claim 3 wherein the shock waves are in the
range of about 10,000 psi to 24,000 psi, and preferably 15,000
psi.
5. The apparatus of claim 1 wherein the frequency of operation of
the pulse detonation combustor is at a frequency in the range from
about 0.1 millihertz to 100 hertz, preferably 0.2 millihertz to 5
hertz, and more preferably 0.01-0.2 Hertz.
6. The apparatus of claim 1 wherein the means for initiating a
series of repeating detonations comprise a series of obstacles
disposed along the fluid flow path of the combustion region.
7. The apparatus of claim 1 wherein the at least one inlet port
comprises a fuel inlet port and an oxidizer inlet port.
8. The apparatus of claim 1 wherein the at least one inlet port and
the at least one valve assembly are further configured to introduce
a buffer into the pulse detonation combustor after each detonation
to purge the combustor of combustion products.
9. The apparatus of claim 8 wherein the buffer is non-flammable and
selected from the group consisting of the oxidant, the fuel or air
.
10. The apparatus of claim 8 wherein the at least one inlet port
further comprises a buffer inlet port.
11. The apparatus of claim 1 wherein the at least one valve
assembly comprises a plurality of valves and valve-actuating
means.
12. The apparatus of claim 1 wherein the at least one valve
assembly comprises a fuel valve disposed between the fuel source
and inlet port, the fuel valve configured to only allow fuel to
flow into the combustion chamber periodically.
13. The apparatus of claim 1 further comprising means for
preventing backflow of the fuel or flammable mixture towards the
surface within the tubing.
14. The apparatus of claim 1 wherein the pulse detonation combustor
comprises a tubular housing having a first end and a second end and
a circular side wall.
15. The apparatus of claim 14 wherein the tubular housing is formed
by an elongated, cylindrical shock tube closed at both ends and
disposed within the production tubing, wherein the shock tube has
an outside diameter smaller than the inside diameter of the
production tubing and is adapted to be lowered into and
subsequently removed from the wellbore.
16. The apparatus of claim 15 wherein the shock tube contains and
isolates the flammable mixture from the production tubing
surrounding the shock tube so as to confine combustion waves
generated by the repeating detonations to within the shock
tube.
17. The apparatus of claim 15 wherein the shock tube further
comprises a plurality of spaced nozzles along the length of the
circular side wall, each nozzle extending radially outward and
configured to aim the shock waves in a substantially axial
direction into the formation.
18. The apparatus of claim 17 wherein the nozzles are adapted so
that the shock tube can be lowered into and subsequently removed
from the wellbore.
19. The apparatus of claim 14 wherein the circular side wall of the
tubular housing is formed by the production tubing.
20. The apparatus of claim 19 wherein the first and second end of
the tubular housing are formed by the first and second sealing
mechanisms, respectively.
21. The apparatus of claim 20 wherein the flammable mixture is
contained within the production tubing so as to confine combustion
waves generated by the repeating detonations to the production
tubing.
22. The apparatus of claim 20 further comprising a cylindrical tube
with an outside wall, wherein the outside wall has a diameter
smaller than the diameter of the production tubing, and wherein the
first and second sealing mechanisms are adapted to be mounted to
each end of the cylindrical tube to form an annular combustion
region between the outside wall of the cylindrical tube and the
production tubing.
23. The apparatus of claim 22 wherein the mixing region is disposed
in fluid communication with the at least one inlet port and the
annular combustion region, and wherein the annular combustion
region is aligned with the perforations in the well casing to
provide direct flow of the flammable mixture into the fractures of
the subterranean formation.
24. The apparatus of claim 23 wherein the combustion wave generated
by the repeating detonations extends into the fractures of the
formation.
25. The apparatus of claim 1 wherein the structural components of
the pulse detonation combustor are made of materials sufficient to
withstand repeated shock waves and thermal deformations from the
repeated detonations and to resist fluid pressure in the
wellbore.
26. The apparatus of claim 1 wherein the ignition device comprises
at least one ignition point.
27. The apparatus of claim 1 wherein the ignition device comprises
multiple ignition points.
28. The apparatus of claim 1 wherein the ignition device comprises
electrical ignition means or chemical ignition means.
29. The apparatus of claim 1 wherein the ignition device comprises
a remote signaler to remotely ignite the flammable mixture.
30. The apparatus of claim 1 wherein the fuel is a liquid fuel or a
gaseous fuel.
31. The apparatus of claim 1 adapted to be lowered into a wellbore
on a wireline, production tubing, coiled tubing, or any combination
thereof.
32. The apparatus of claim 1 wherein the at least one inlet port is
configured to provide a continuous supply of air to the pulse
detonation combustor during the operation of the combustor.
33. The apparatus of claim 1 wherein the first and second sealing
mechanisms comprise a pair of expandable packers.
34. The apparatus of claim 1 further comprising means to introduce
a proppant into the fractures.
35. A method of fracturing subterranean formations comprising the
steps of: (a) deploying at least one pulse detonation combustor
into production tubing disposed within a wellbore; (b) positioning
the pulse detonation combustor in an isolated zone within the
wellbore, wherein the isolated zone is adjacent to a portion of the
formation to be fractured; (c) commencing a pulse detonation cycle
by, (i) creating a flammable mixture comprised of a fuel and
oxidant mixture in the pulse detonation combustor by injecting a
controlled amount of fuel from a fuel source and controlled amount
of oxidant from an oxidant source into the pulse detonation
combustor, wherein both the fuel source and oxidant source are
located at the surface; (ii) igniting the fuel and oxidant mixture
to cause a detonation, wherein the detonation within the pulse
detonation combustor generates a supersonic shockwave; and (iii)
purging combustion products of the detonation from the pulse
detonation combustor; (d) directing the shockwave into the
subterranean formation; and (e) repeating steps (i)-(iii) at a
selected time and frequency sufficient to generate a series of
repeating supersonic shock waves, thereby causing propagation of
multiple fractures in the formation.
36. The method according to claim 35 wherein the isolated zone is
formed by a first and second sealing mechanism secured within the
wellbore.
37. The method according to claim 35 wherein the isolated zone is
aligned with perforations in the production tubing, well casing, or
both.
38. The method according to claim 35 wherein the pulse detonation
combustor comprises: a combustion region defining a fluid flow
path; a mixing region for producing the flammable mixture
comprising a controlled volume of fuel and oxidizer, wherein the
mixing region is in fluid communication with the at least one inlet
port and the combustion region; an ignition device configured to
periodically ignite the flammable mixture; and means for initiating
a series of repeating detonations.
39. The method of claim 35 wherein the step of purging the pulse
detonation combustor comprises introducing a buffer into the pulse
detonation combustor after igniting a fuel and oxidant mixture from
a previous cycle and before commencing a next pulse detonation
cycle.
40. The method of claim 35 further comprising the step of
introducing a proppant into the fractures.
41. The method according to claim 35 further comprising the step of
controlling the time and frequency of the pulse detonation cycle by
a programmable digital signal processor.
42. The method according to claim 35 wherein the pulse detonation
combustor provides shockwaves at a frequency in the range from
about 0.1 millihertz to 100 hertz, preferably 0.2 millihertz to 5
hertz, and more preferably 0.01-0.2 Hertz.
43. The method according to claim 35 wherein two or more pulse
detonation combustors are connected in series.
44. A method of fracturing subterranean formations comprising the
steps of: establishing a wellbore extending to the subterranean
formation; and deploying a pulse detonation apparatus for
generating repeating, supersonic shockwaves within the interior of
the wellbore at a selected time and frequency sufficient to produce
multiple fractures in the subterranean formation without causing
damage to the wellbore and to further extend the fractures until at
least one hydrocarbon fluid fracture is intersected.
45. A system for fracturing a subterranean/subterranean/geologic
formation, comprising: means for establishing a wellbore extending
to the subterranean formation; and a pulse detonation apparatus for
generating repeating, supersonic pulses within the interior of the
wellbore with a total number of pulses sufficient to produce
multiple fractures in the subterranean formation and further extend
the fractures until at least one hydrocarbon fluid fracture is
intersected.
Description
BACKGROUND
[0001] Formation fracturing is becoming an important tool for
hydrocarbon production. There is an increasing need to produce
hydrocarbons from wells in subterranean formations that contain a
sufficient volume of hydrocarbon fluids, but have low permeability
or restricted flow near the wellbore so that production is slow or
difficult and, thus, not economical. In addition to oil and/or gas
producing wells, formation fracturing is also an important tool for
injection wells, storage wells, brine or water production wells,
and disposal wells.
[0002] Flow of a fluid, such as oil or gas, through a porous
medium, i.e. a subterranean formation, is directly related to the
permeability of the formation. A formation with low permeability
can occur naturally due to the geological conditions of the
formation. Low permeability can also be caused by damage to the
formation from drilling, cementing and perforating operations.
Further, mature wells can incur damage from the buildup of fine
particulates and contaminants. If permeability can be increased in
these formations, more fluid can be recovered.
[0003] It is known that one way to increase production and
permeability within a formation is artificial stimulation through
"well fracturing." Various fracturing procedures have been
introduced and used, including: (1) hydraulic fracturing; (2)
explosive fracturing; (3) various chemical treatments (usually
acids); (4) high energy gas fracturing or controlled pulse
fracturing; and (5) combinations of the above.
[0004] Originally, devices and materials such as nitroglycerin,
dynamite or other high energy materials that produce "explosive"
events were used to increase fluid flow around the wellbore of an
oil or gas production well. This method of formation fracturing is
called explosive fracturing and is associated with a rapid pressure
rise over a short time period. The success of this method has been
limited, however, due to safety hazards and because frequently the
explosive compaction of the formation opposite to the explosion
fracture causes formation and wellbore damage, which results in a
decrease rather than increase of permeability.
[0005] Currently, the most common method of formation fracturing is
hydraulic fracturing. Hydraulic fracturing increases formation
permeability by slowly pumping a fluid into the formation, which in
turn creates a slow pressure rise in the formation. Fluid pressure
is steadily increased until the tensile strength of the rock
formation is exceeded. At that point, a fracture will be initiated
that propagates from opposite sides of the wellbore into the
formation. Because the increased fluid pressure flows to the point
of least resistance, a single bidirectional fracture typically is
formed. Although this method is successful, the equipment and labor
involved in hydraulic fracturing is extensive and expensive. There
are also growing concerns regarding the environmental consequences
associated with hydraulic fracturing due, in part, to the huge
amounts of water that are required and the variety of chemicals
that are used in connection with hydraulic fracturing.
[0006] The third type of well fracturing used in lieu of hydraulic
fracturing or explosive fracturing is called "high energy gas
fracturing" or "propellant fracturing." This method employs
propellant deflagration technology to create a more rapid pressure
rise than that seen in hydraulic fracturing, but less rapid than
during an explosive fracturing regime. "Deflagration" refers to the
rapid burning of a material at faster rate than normal combustion,
but at a rate slower than detonation. Propellant deflagration
produces a good distribution of radial fractures around a wellbore
and can be employed in lieu of hydraulic fracturing techniques as a
more cost effective manner to create and propagate fractures. The
resulting radial fractures, however, do not penetrate deep enough
into the formation (i.e only 50-75 feet) and thus it is often
necessary to combine them with, for example, hydraulic fracturing
or chemical treatments.
[0007] Each of the current methods of formation fracturing thus
have drawbacks. Pulse detonation devices, in general, are known and
have been considered for use in jet aircrafts for propulsion, coal
gasification, impulsive cleaning systems and medical cleaning
devices. A pulse detonation device is an apparatus which produces
high pressure exhaust from a series of repetitive detonations
within a detonation chamber. The process is a constant volume heat
addition process. The gaseous fuel is detonated within a chamber,
causing a pulse detonation wave which propagates at supersonic
speeds. The detonation wave compresses the fluid within the
chamber, increasing its pressure, temperature and density, and
producing a series of high-intensity, high-decibel blasts.
[0008] In pulse detonation combustors, a mixture of fuel and
oxidizer, such as air, is ignited and either transitioned from
deflagration to detonation, or detonated via direction initiation
(DI), so as to produce detonation waves. The deflagration to
detonation transition (DDT) or DI of detonation typically occurs in
a tube or pipe structure.
BRIEF DESCRIPTION OF THE INVENTION
[0009] In one aspect of the invention, a pulse detonation tool for
fracturing subterranean formations is adapted to be lowered into a
production tubing disposed within a wellbore and comprises a first
and second sealing mechanism configured to create an isolated zone
having an axis parallel to and extending through the production
tubing, wherein the first sealing mechanism has at least one inlet
port configured to allow a fuel and an oxidizer to flow into a
pulse detonation combustor disposed within the isolated zone and
wherein the first sealing mechanism is further configured to
connect to an oxidizer and a fuel source by way of a fluid
injection line extending from the surface through the tubing; at
least one valve assembly to achieve controlled delivery of the fuel
and oxidizer to the pulse detonation tool; the pulse detonation
combustor comprising: a combustion region defining a fluid flow
path; a mixing region for producing a flammable mixture comprising
a controlled volume of fuel and oxidizer, wherein the mixing region
is in fluid communication with the at least one inlet port and the
combustion region; an ignition device configured to periodically
ignite the flammable mixture; and means for initiating a series of
repeating detonations that generate a series of repeating
supersonic shock waves, wherein the shock waves are directed into
the subterranean formation to cause propagation of multiple
fractures into the formation.
[0010] Another aspect of the invention includes a method of
fracturing subterranean formations comprising the steps of: (a)
deploying at least one pulse detonation combustor into production
tubing disposed within a wellbore; (b) positioning the pulse
detonation combustor in an isolated zone within the wellbore,
wherein the isolated zone is adjacent to a portion of the formation
to be fractured; (c) commencing a pulse detonation cycle by, (i)
creating a flammable mixture comprised of a fuel and oxidant
mixture in the pulse detonation combustor by injecting a controlled
amount of fuel from a fuel source and controlled amount of oxidant
from an oxidant source into the pulse detonation combustor, wherein
both the fuel source and oxidant source are located at the surface;
(ii) igniting the fuel and oxidant mixture to cause a detonation,
wherein the detonation within the pulse detonation combustor
generates a supersonic shockwave; and (iii) purging combustion
products of the detonation from the pulse detonation combustor; (d)
directing the shockwave into the subterranean formation; and (e)
repeating steps (i)-(iii) at a selected time and frequency
sufficient to generate a series of repeating supersonic shock
waves, thereby causing propagation of multiple fractures in the
formation.
[0011] In another aspect of the invention, a method of fracturing
subterranean formations comprises the steps of establishing a
wellbore extending to the subterranean formation; and deploying a
pulse detonation apparatus for generating repeating, supersonic
shockwaves within the interior of the wellbore at a selected time
and frequency sufficient to produce multiple fractures in the
subterranean formation without causing damage to the wellbore and
further extend the fractures until at least one hydrocarbon fluid
fracture is intersected.
[0012] Another aspect of the invention includes a system for
fracturing a subterranean/subterranean/geologic formation,
comprising: means for establishing a wellbore extending to the
subterranean formation; and a pulse detonation apparatus for
generating repeated, supersonic pulses within the interior of the
wellbore with a total number of pulses to produce multiple
fractures in the subterranean formation and further extend the
fractures until at least one hydrocarbon fluid fracture is
intersected.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The nature and various additional features of the invention
will appear more fully upon consideration of the illustrative
embodiments of the invention which are schematically set forth in
the figures. Like reference numerals represent corresponding
parts.
[0014] FIG. 1 illustrates a cross-sectional view of a pulse
detonation combustor according to an exemplary embodiment of the
present invention;
[0015] FIG. 2 is a schematic illustration of a pulse detonation
tool disposed within a wellbore according to an exemplary
embodiment of the present invention as shown in FIG. 1;
[0016] FIG. 3 illustrates a cross-sectional view of a pulse
detonation combustor according to yet another exemplary embodiment
of the present invention;
[0017] FIG. 4 is a schematic illustration of a pulse detonation
tool disposed within a wellbore according to the exemplary
embodiment of the present invention as shown in FIG. 3;
[0018] FIG. 5 illustrates a cross-sectional view of a pulse
detonation combustor according to yet another exemplary embodiment
of the present invention.
DETAILED DESCRIPTION
[0019] Embodiments of the present invention will be explained in
further detail by making reference to the accompanying drawings,
which do not limit the scope of the invention in any way.
[0020] FIG. 1 depicts a cross-sectional side view of an
illustrative pulse detonation tool 100, hereinafter referred to as
"tool 100," for formation fracturing according to various exemplary
embodiments of the present invention. In FIG. 2, tool 100 is shown
suspended within a wellbore 304 that should be understood as
extending from ground level into a subterranean formation 305.
[0021] Turning now to FIG. 1 in which an embodiment of the present
invention is depicted. In one or more embodiments, tool 100
contains at least one pulse detonation combustor 101. As used
herein, a "pulse detonation combustor" PDC is understood to mean
any device or system that produces both a pressure rise and
velocity increase from a series of repeated detonations or
quasi-detonations within the device. A "quasi-detonation" is a
supersonic turbulent combustion process that produces a pressure
rise and velocity increase higher than the pressure rise and
velocity increase produced by a deflagration wave. As used herein,
"detonation" includes both detonations and quasi-detonations.
[0022] Embodiments of PDCs include a means of igniting a
fuel/oxidizer mixture, for example a fuel/air mixture, and a
detonation chamber, in which pressure wave fronts initiated by the
ignition process coalesce to produce a detonation wave. Each
detonation or quasi-detonation is initiated either by external
ignition, such as spark discharge or laser pulse, or by gas dynamic
processes, such as shock focusing, autoignition or by another
detonation (i.e. cross-fire). Pulse detonation may be accomplished
in a number of types of chambers including detonation tubes, shock
tubes, resonating detonation cavities and annular detonation
chambers, for example. In addition, a PDC can include one or more
detonation chambers. The structure and construction of the pulse
detonation combustor 101 is that of any known pulse detonation
combustor type device, and the present invention is not limited in
this regard.
[0023] In one or more embodiments, pulse detonation combustor 101
includes an ignition chamber 110 and a combustion region, or
detonation chamber, 120. The ignition chamber 110 and the
detonation chamber 120 can be formed as a contiguous region, as in
FIG. 1, or discrete chambers (not illustrated).
[0024] In the embodiment shown in FIGS. 1-2, pulse detonation
combustor 101 includes a tubular housing 102, an ignition device 10
disposed within ignition chamber 110, detonation chamber 120 formed
within tubular housing 102, a fuel/oxidizer mixing region or
chamber 130, at least one fuel inlet port 50 that supplies oxidizer
and fuel to pulse detonator combustor 101, and at least one valve
assembly 80. The diameter of tubular housing 102 can be varied to
fit and preferably generally fills up the diameter of production
tubing 300 or wellbore 304.
[0025] As used herein, "wellbore", "borehole" and "well" are used
interchangeably and should not be considered of varying scope.
[0026] Tubular housing 102 is preferably fabricated from a steel or
like material having sufficient wall thickness and strength that it
will not be destroyed during the pulse detonation cycle. Similarly,
each of the components of tool 100 described herein should be
formed from strong, durable materials and securely mounted so as to
withstand the high pressures, repeated shock waves and thermal
deformations from the repeated detonations and to resist fluid
pressure in the wellbore during the pulse detonation cycle.
[0027] In the embodiment shown in FIGS. 1-2, tubular housing 102
has a first end 103 and a second end 104 and a circular side wall
105. For example, and as shown in FIG. 2, tubular housing 102 is an
elongated, cylindrical shock tube closed at both ends (103/104).
Circular side wall 105 of tubular housing 102 has an outside
diameter smaller than the inside diameter of the production tubing
300, and is adapted to be lowered into and subsequently removed
from a wellbore 304. In the embodiment shown here, tubular housing
102 also has discharge port 70 for venting combustion products or
excess fuel or oxidant. One of ordinary skill in the art would
recognize that port 70 could be eliminated or modified if the
fuel/oxidizer mixture results in combustion products that condense
into water or can readily dissolve into the water within the
wellbore , or that other means for venting known in the art could
be used to vent combustion products back to the surface or
downhole.
[0028] Configured as a shock tube, tubular housing 102 contains and
isolates the flammable mixture from production tubing 300 so as to
confine combustion, or detonation, waves 20 generated by the
repeating detonations to within tubular housing 102. Tubular
housing 102 further comprises a plurality of spaced nozzles 80
along the length of the circular side wall 105. Nozzles 80 are
located at spaced intervals. Each nozzle 80 extends radially
outward and is configured to direct or aim the shock waves 30
generated by the repeating detonations in a substantially axial
direction into the subterranean formation 305. Nozzles 80 are
adapted so that tubular housing 102 can be lowered into and
subsequently removed from wellbore 304. For example, in one
embodiment, nozzles 80 can be telescoping.
[0029] In the embodiment shown here, fuel inlet port 50 is also
configured to supply a buffer to pulse detonator combustor 101,
wherein the buffer is any nonflammable fluid. In this embodiment,
the buffer is different from the fuel and oxidant and introduced
separately. One of ordinary skill in the art would recognize,
however, that a buffer and buffer inlet is not required if there is
sufficient time between detonation cycles to allow the combustion
products remaining in the pulse detonation combustor 101 to cool
below autoignition temperature of the fuel-oxidizer mixture for the
next detonation cycle. Furthermore, even if a buffer is required,
one of ordinary skill in the art would recognize that either the
fuel or oxidizer could be used as the buffer by configuring and
adjusting valve assembly 80, thereby eliminating the need for a
separate buffer and buffer inlet.
[0030] Referring now to FIG. 2, tool 100 also includes a first
sealing mechanism 200 and a second sealing mechanism 201. Sealing
mechanisms 200/201 are configured to create an isolated zone 210
having an axis parallel to and extending through wellbore 304.
Sealing mechanisms 200/201 comprise any suitable means for sealing,
such as an expandable packer shown in FIG. 2 or tubing (not
illustrated). First sealing mechanism 200 is located uphole of
tubular housing 102 and second sealing mechanism 201 is located
downhole of tubular housing 102. First and second sealing
mechanisms 200/201 are positioned to align isolated zone 210 with
perforations 306 in the production tubing 300, well casing (not
shown), or both.
[0031] First sealing mechanism 200 has at least one first inlet
port 50 configured to allow a fuel, an oxidizer and a buffer to
flow into pulse detonation combustor 101 disposed within isolated
zone 210. In the embodiment shown in FIG. 2, the at least one first
inlet port 50 comprises fuel inlet port 50a, oxidizer inlet port
50b, and buffer inlet port 50c. First inlet ports 50a-c are
configured in accordance with technology known to a skilled artisan
in pulse detonation technology. Furthermore, one of ordinary skill
in the art could configure a single inlet port 50 to achieve flow
communication with the fuel source 302, oxidizer source 301 and/or
buffer source 303 (not shown). Although not shown in FIGS. 1-2, in
certain embodiments, oxidizer source 301 is the same as buffer
source 303. For example, in practicing the invention, one skilled
in the art could utilize air as both the oxidant and the buffer.
Accordingly, in certain embodiments oxidizer inlet 50b and buffer
inlet 50c are one and the same.
[0032] Additionally, in the embodiment shown in FIGS. 1-2, tubular
housing 102 has at least one second inlet, or injection, port 51
configured to allow a fuel, an oxidizer and a buffer to flow into
combustor 101. As shown in FIG. 1, the at least one second inlet
port 51 comprises multiple inlet ports, more specifically fuel
inlet port 51a, oxidizer inlet port 51b, and buffer inlet port 51c.
Second inlet ports 51a-c are configured in accordance with
technology known to a skilled artisan in pulse detonation
technology. For example, in other embodiments, fuel is introduced
co-axially through fuel inlet port 50a (see FIG. 3), or oxidizer is
supplied to combustor 101 downstream of the fuel injection via
inlets 50b (not shown). As used herein, "downstream" refers to a
direction of flow of at least one of fuel, or oxidizer or buffer.
Accordingly, the inlet ports, or injectors, can be arranged in
various other locations such as perpendicular to the flow, at a
tangential angle to the flow (to induce swirl), or at an angle in
conjunction with a suitably shaped wall to help promote mixing. Any
known mechanism for injection can be used such as air-blast
atomization, pressure-atomization, etc. By way of further example,
one of ordinary skill in the art could configure a single inlet
port to achieve injection of the fuel, oxidizer and/or buffer into
combustor 101. Additionally, as discussed above, in certain
embodiments wherein oxidizer source 301 is the same as buffer
source 303, oxidizer inlet 51b and buffer inlet 51c are the same
inlet port.
[0033] Referring again to FIG. 2, tool 100 is further configured to
connect to an oxidizer source 301, fuel source 302 and buffer
source 303 by way of multiple fluid injection lines 307, 308, 309
extending from the surface through the wellbore 304 or production
tubing 300. In practicing the invention, fuel source 302 can be a
liquid fuel or a gaseous fuel. Furthermore, tool 100 is operable
with a plurality of different fuels including, but not limited to,
gaseous fuels, such as, hydrogen, ethylene, natural gas, or
propane, liquid fuels, such as, gasoline, kerosene, or aviation
fuels, and a plurality of oxidizers including, but not limited to,
air. Examples of suitable fuel/oxidizer combinations, or flammable
mixtures, would include hydrogen/oxygen or methane/oxygen, both of
which would be delivered in gaseous form only. Another example of a
suitable flammable mixture would be propane/oxygen, wherein the
propane would be in liquid form. Liquid rocket propellants using
nitrous oxide or liquid oxygen as an oxidizer can also be used.
Likewise, liquid explosives could be used as a fuel source, such as
nitromethane mixed with dietylenetriamine or ethylenediamine. It
should be noted, however, that the specific fuel/oxidizer
combination selected will be dictated by operational parameters and
characteristics within the wellbore 304 and subterranean formation
305, as well as the desired characteristics of fractures 400 within
the formation, in order to optimize performance and limit damage
within the formation or wellbore. The invention is not limited to
the use of the above-identified fuel/oxidizer combinations and any
suitable flammable mixture known to those skilled in the art of
pulse detonation technology can be used in order to achieve the
desired shock waves and resulting fracture geometry within the
formation.
[0034] Tool 100 also comprises at least one valve assembly disposed
within tubular housing 102. The at least one valve assembly is
configured to achieve controlled delivery of the fuel, oxidizer and
buffer to tool 100. In the embodiment shown in FIG. 1, the at least
one valve assembly comprises fuel valve 80a, oxidizer valve 80b,
and buffer valve 80c.
[0035] As used herein, the term "valve" or "valve assembly" is
intended to describe any device that turns on and off a flow at a
high frequency, namely, faster than or equal to the time scale of
one pulse detonation combustion cycle. Valves 80a-c are configured
in accordance with pulse detonation technology known to one of
ordinary skill in the art, and may be either a passive check valve
or active valve, or a combination of both. Furthermore, one of
ordinary skill in the art could configure a single valve to achieve
controlled delivery of the fuel, oxidizer and/or buffer. As shown
in FIG. 1, fuel valve 80a and oxidizer valve 51b are positioned
within tubular housing 102 downstream of fuel inlet port 51a and
oxidizer port 51b, and both are configured to only allow fuel and
oxidizer to flow into the mixing chamber 130 periodically.
[0036] Although not shown, in other embodiments, the valve assembly
is located outside of tubular housing 102 but within isolated zone
210. In still further embodiments, the valve assembly is located
upstream of the isolated zone 210 defined by sealing mechanisms
200/201. For example, in these embodiments, fuel valve 51 a is
disposed between the fuel source and inlet port 51a, and oxidizer
valve 51b is disposed between the oxidizer source and inlet port
51b. In exemplary embodiments, tool 100 also comprises means for
preventing backflow of the fuel or flammable mixture towards the
surface within the production tubing 300.
[0037] Pulse detonation combustor 101 is detonated by suitable
detonation means connected to ignition device 10. In this
embodiment, ignition device 10 is located within ignition chamber
110 and is arranged downstream from the fuel and oxidizer inlets.
Ignition device 10 comprises at least one ignition point, as shown
in FIG. 1, or may comprise multiple ignition points (as shown in
FIG. 3). Ignition device 10 can be, but is not limited to being, a
spark plug, a plasma igniter, and/or a laser source, or any
suitable device. Ignition device 10 is configured to periodically
ignite the flammable mixture and, as such, is fabricated from
suitable materials to allow device 10 to achieve multiple ignition
events without being destroyed or consumed during the repeating
detonation cycles.
[0038] In further embodiments, ignition device 10 comprises an
external power source, timing device and remote signaler configured
to remotely ignite the flammable mixture exiting mixing chamber
130, wherein the timing of ignition is predetermined and controlled
via one of ordinary by one skill in the art. In an embodiment where
there is no separate mixing chamber, the location of the ignition
device 10 is arranged based upon the optimum ignition location for
fuel-oxidizer mixing. For example, the ignition device 10 can be
placed downstream of the fuel inlet port to provide time for the
fuel to mix with the oxidizer. Ignition device 10 should also be
placed upstream of any detonation-creating obstacles that may be
located in the detonation chamber.
[0039] Ignition chamber 110 and detonation chamber, or combustion
region, 120 define a fluid flow path in flow communication with
mixing chamber 130, as illustrated in FIG. 1. Mixing chamber 130 is
also in fluid communication with the at least one inlet port and
the detonation chamber 120. Mixing chamber 130 is configured to
produce a flammable mixture comprising a controlled volume of fuel
and oxidizer and to promote uniform flow into the ignition chamber
110. For example, the geometry of mixing chamber 130 can be a
cylindrical chamber wherein the fuel and oxidizer mix as a result
of turbulence created by the fuel and oxidant jet inlet
interaction. Mixing chamber 130 can also comprise a perforated
plate or a geometry to induce swirl or other turbulence for
example. In practicing the invention, any suitable flow mixing
element can be used to promote the uniform flow of the fuel/oxidant
mixture into the ignition chamber 110 and additional geometry known
to those skilled in the art can function to enhance mixing and
uniform flow if desired.
[0040] Pulse detonator combustor 101 also comprises means for
initiating a series of repeating detonations that in turn generate
a series of repeating supersonic, high impulse shock waves 30. In
one embodiment, as shown in FIG. 1, the means for initiating a
series of repeating detonations comprise a series of obstacles
disposed along the fluid flow path within detonation chamber 120.
More specifically, in the embodiments shown herein, detonation
chamber 120 includes an obstacle field or center body 90 to promote
turbulence within the detonation chamber 120. The center body 90 is
often referred to as deflagration to detonation transition (DDT)
geometry. DDT geometry enhances the deflagration to detonation
transition process by increasing turbulence in the detonation
chamber 120. There are a variety of DDT geometries. The overall
length and diameter of the center body 90 will be dictated by
operational parameters and characteristics within the wellbore 304
and subterranean formation 305, as well as the desired
characteristics of fractures 400 within the formation, in order to
optimize performance.
[0041] It is to be noted that the invention is not limited to the
use of a particular DDT geometry. Any suitable DDT geometry can be
used to increase turbulence. Similarly, detonation chamber 120 can
be arranged without DDT geometry or with other means for initiating
a series of repeating supersonic shock waves known to those skilled
in the art. For example, in alternate embodiments, the means for
initiating a series of repeating detonations comprises direct
initiation (DI) detonation methods, such as a high energy laser,
spark, or other shock-to-detonation methods suitable for achieving
direction initiation (DI) of detonation. In practicing the
invention, one of ordinary skill in the art would recognize that DI
of detonation is preferable over DDT if circumstances allow for
lower frequency requirements, high pressure in the well bore, and
the appropriate fuel-oxidizer mixtures. In addition, the
fuel-oxidizer ratio can be supplied so that there is a slightly
fuel-rich mixture in the ignition chamber 110 to improve the
selected means for initiating a series of repeating detonations .
This can be accomplished by controlling the flow of fuel and
oxidizer into the ignition chamber 110 via valve assembly 80.
[0042] Referring to FIG. 2, the resulting shock waves 30 are
directed into the subterranean formation 305 and create propagation
of multiple fractures 400 (not shown) into formation 305 without
causing damage to the surrounding wellbore 304. In the embodiment
shown here, combustion or detonation waves 20 are confined to
tubular housing 102. In practicing the invention, the resulting
shock waves 30 are in the range of about 10 to 16-times the initial
pressure in the formation. For example, in one embodiment with an
initial pressure of 100,000 psi-160,000 psi. If the initial
pressure in the wellbore is lower, the shock waves could be
approximately in the range of about 10,000 psi to 24,000 psi, and
preferably 15,000 psi. The frequency of operation of the particular
embodiment of pulse detonation combustor 101 shown in FIGS. 1-2 is
in the range from about 0.1 millihertz to 100 Hertz. It should be
noted, however, that the firing frequency, in part, is determined
by the time required to purge and refill the volume within pulse
detonation combustor 101 with the fuel/oxidant flammable mixture.
As such, in certain embodiments (see, for example, see FIGS. 3-5),
the firing frequency will be in the range of about 0.1 millihertz
to 5 Hz, preferably 0.01-0.2 Hz. After the requisite number of
firing cycles, multiple fractures 400 will extend into formation
305 at a distance in the range of about 50 meters to about 300
meters, and in certain embodiments a distance of about 100
meters.
[0043] In practice, and referring again to FIG. 2, to fracture a
subterranean formation and recover hydrocarbons, a wellbore 304 is
drilled vertically and/or horizontally into subterranean formation
305 to some depth below the surface. The wellbore 304 can be lined
with production tubing or casing, to strengthen the walls of the
well, or not. For example, individual lengths of metal tubing can
be secured together to form a casing string which is positioned
within a well bore, thus increasing the integrity of the wellbore
and providing a path for hydrocarbons to flow to the surface. If
casing is used, and to further strengthen the walls of the wellbore
304, the annular area formed between the casing and the borehole
304 can be filled with cement to permanently set the casing in the
wellbore. The casing can then be perforated at a location where
fracturing is to take place using a perforation tool that is
lowered into the wellbore from the surface.
[0044] Tool 100, which includes sealing mechanism 200/201, is then
lowered into the wellbore 304 to a depth adjacent to the particular
section of subterranean formation 305 to be fractured. In the
example shown in FIG. 2, tool 100 is positioned adjacent to
perforations 306. Tool 100 can be lowered and positioned into a
wellbore 304 by conventional means, such as on a wireline,
slickline, production tubing, pipe tubing, coiled tubing, or any
combination thereof, or any other technique known or yet to be
discovered by a skilled artisan.
[0045] Prior to lowering the tool 100 into the wellbore 304, the
location, distance and direction of the at least one natural
hydrocarbonaceous fluid fracture is determined. Furthermore, the
characteristics of the subterranean formation 305 are determined
and used to construct a pulse detonation combustor 101 with the
desired pulse detonation characteristics for the particular
formation such that optimum radial fractures can be achieved within
the subterranean formation 305. These determinations can be made by
geologists and others skilled in the art.
[0046] Once tool 100 is properly positioned within the well to
create an isolated zone 210 adjacent to both the perforations 306
and the portion of the formation to be fractured, the pulse
detonation cycle is commenced. A controlled amount of fuel from
fuel source 302 located on the surface, and a controlled amount of
oxidizer from oxidizer source 303 located on the surface, are
injected into mixing chamber 130 via fuel supply line 308, oxidizer
supply line 309, and the respective inlet ports, to create a
flammable mixture comprised of a predetermined fuel and oxidant
mixture in the pulse detonation combustor 101.
[0047] The flammable mixture flows from the mixing chamber 130 to
the ignition chamber 110 and is ignited. The flame then propagates
into the detonation chamber and detonates within the detonation
chamber 120, which in turn generates a supersonic shockwave. In the
embodiment shown in FIGS. 1-2, the shockwave is then directed
radially into the subterranean formation via nozzles 80 that are
aligned with perforations 306. Following the first detonation
cycle, the combustion products of the detonation are then purged
from detonation chamber 120 and, if necessary, a buffer is
introduced into the pulse detonation combustor 101 before
commencing the next pulse detonation cycle.
[0048] As illustrated in FIG. 2, the generated shock waves 30
resulting from pulse detonation are at supersonic velocities (for
example, approximately 2000 m/s), and high pressure in the range of
about 10 to 16 times the initial pressure of the formation. The
shock waves 30 are directed radially into the formation through
nozzles 80 formed in tubular housing 102. The generated shock waves
30 pass through perforations 306 formed in the well casing to open
and extend existing fractures. The shock waves also may clear out
blockages of materials that have been deposited in existing
fractures.
[0049] These same steps are repeated at a predetermined, calculated
time and frequency sufficient to generate a series of repeating,
high impulse supersonic shock waves that cause propagation of
multiple fractures 400 to extend further and further into the
formation with each cycle. In practice, the precise number of
repeated detonation "pulses", or cycles, required to reach the
desired fracture length will depend on the nature and
characteristics of the formation. More specifically, in one example
rock formation, the propagation of a fracture 1 cm in length
requires 1000 detonation cycles. Therefore, in order to extend the
fracture out 100 m into the formation, the pulse detonation cycle
will require 10,000,000 pulses or cycles.
[0050] The repeating, high impulse shock waves have a pressure
above the maximum fracture extension pressure but below that which
would cause casing, wellbore or formation damage. In other words,
the shock waves create a pressure loading rate sufficient to
fracture the rock and create multiple radial fractures at the
wellbore and extending into the formation, but low enough to avoid
crushing the formation or casing adjacent to the wellbore. As such,
the repeated "pulses" will allow fractures to continue their
extension into the formation to obtain the required distances to
reach the hydrocarbons in the formation.
[0051] In another embodiment, shown in FIGS. 3-4, circular side
wall 105 of tubular housing 102 is formed by the production tubing
300, and the first and second end of the tubular housing (103/104)
are formed by the first sealing mechanism 200 and second sealing
mechanism 201, located uphole and downhole respectively. As further
shown in FIG. 3, concentric liner 115 is positioned within tubular
housing 102 with an outside wall that has a diameter smaller than
the diameter of production tubing 300, and wherein the uphole and
downhole seal 200/201 are adapted to be mounted to each end of the
cylindrical tube to form an annular combustion region 120 between
the outside wall of concentric liner 115 and production tubing 300.
In this embodiment, mixing region 130 is disposed in fluid
communication with the at least one inlet port 50 and annular
combustion region 120. Furthermore, annular combustion region 120
is aligned with the perforations 306 to provide direct flow of the
flammable mixture into the fractures of the subterranean formation
305. Pulse detonation combustor 101, according to this exemplary
embodiment, includes multiple ignition sources 10.
[0052] In this embodiment, both the combustion waves 20 and shock
waves 30 generated by the repeating detonations extend into the
fractures 400. More specifically, the flammable mixture is pushed
into perforations 306 and thus into the subterranean formation. In
one embodiment (not shown), combustion can be initiated in the
production tubing and then transition into the fueled perforations
or fractures within the formation. Alternatively, and as shown in
FIG. 3, multiple ignition devices 10 can be positioned so that
combustion is initiated directly into the formation. With this
embodiment, both the detonation waves and shock waves will occur
directly in the rock formation, resulting in a higher pressure
loading.
[0053] FIG. 5 illustrates another exemplary embodiment of tool 100.
In this embodiment, circular side wall 105 of tubular housing 102
is once again formed by the production tubing 300, and the first
and second end of the tubular housing (103/104) are formed by the
first sealing mechanism 200 and second sealing mechanism 201,
located uphole and downhole respectively.
[0054] As shown in FIG. 5, isolated zone 210 within the production
tubing forms the detonation, or combustion, region 120 of pulse
detonation combustor 101 and the entire volume between the first
and second sealing mechanisms 200/201 will be filled with the
flammable mixture. In contrast to the embodiment shown in FIGS.
3-4, because the flammable mixture is contained within production
tubing 300, combustion waves 20 will be confined to production
tubing 300 and will not extend into the formation. Shock waves 30
extend radially into the formation. The arrangement of the ignition
device 10 and fuel and oxidizer inlet ports and valve assembly are
similar to those in the previous embodiments, and a mixing region
is provided to promote uniform flow. Even more significantly than
the other embodiments, the firing frequency will largely be
determined by the time required to purge and refill the volume
within tubular housing.
[0055] As used herein, the terms "tubular housing" and "concentric
liner" include tubes having a circular or alternatively
non-circular cross-section. Exemplary hollow carriers or concentric
liners include cylindrical tubes and tubes having polygonal
cross-sections, such as, for example, hexagonal tubes. Each of the
circular and non-circular cross-sections identified above may have
a continuous cross sectional area, or the cross sectional area may
vary. For example, in the exemplary embodiments shown in FIGS. 1-2,
the cross-section of the ignition chamber 110 can be larger than
the cross section of the detonation chamber 120. Likewise, the
volume of the detonation chamber 120 can be larger than that of the
ignition chamber 110, wherein the specific ratio is set to optimize
the performance based upon the characteristics of the subterranean
formation or wellbore. Cross-sectional area variations in the
ignition chamber 110 and the detonation chamber 120 allow for
control of the bulk flow velocity, which in turn enhances fuel-air
mixing, initial flame growth, DDT turbulence, minimizes loads on
the upstream components in tool 100, and can reduce the requisite
length of pulse detonator combustor 101, for example. By reducing
the length of the combustor, the run-up time for DDT will be
reduced, which will then enable combustor 101 to operate at higher
frequencies. Higher frequency will generate more pressure rise and
increase the usable output of tool 100 in the subterranean
formation.
[0056] In further embodiments, tool 100 comprises means to
introduce a proppant into the fractures. Fractures have a tendency
to close or collapse once the pressure in the formation is
relieved. To prevent such closing when the fracturing pressure is
relieved, fracturing techniques often employ a granular or
particulate material, referred to as a "proppant," that is left
behind in the fractures. The proppant is used to keep the fracture
open and thus provide a flow path through which hydrocarbons can
flow. In one or more of the embodiments disclosed herein, the means
to introduce proppants include mixing the proppant with the fuel,
the oxidizer or both and the introduction of the proppant would
start with the deflagration event pushing the proppant into the
formation. In other embodiments, proppants could be entrained with
the fracturing fluid or introduced via other means as is known in
the art. A variety of proppants can be used depending on the
geological conditions of the formation, including particulate
materials, such as sand, glass beads and ceramic pellets, which
create a porous structure.
[0057] It is noted that the above embodiments have been shown with
respect to a single pulse detonation combustor. However, the
concept of the present invention is not limited to single pulse
detonation combustor. Furthermore, it should be expressly
understood that any desired number of pulse detonation combustors
could be employed in series, and that the dimensions,
configurations, and compositions of tool 100 is within the
discretion of the skilled artisan to meet the needs of a particular
well.
[0058] Finally, in exemplary embodiments, a computer program can be
used to model the pulse detonation cycle to predict the resulting
generation of fracture propagation, and thereby determine a
suitable configuration of tool 100 for fracture propagation in the
surrounding formation. Tool 100 may also be equipped with remote
pressure and temperature sensors, transducers, acoustic sensors,
accelerometers (vibration sensors), chemical sensors such as oxygen
sensor to confirm presence or absence of oxidizer] or other means
known in the art to accurately monitor the pulse denotation cycle
within the wellbore.
[0059] Although the apparatus and method of the invention is
disclosed with examples that incorporate a cased well with
production tubing that has been perforated, the apparatus and
method of the invention are equally applicable to an open hold
completion of a well.
[0060] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *