U.S. patent application number 13/768516 was filed with the patent office on 2013-08-22 for microwave system and method for intrinsic permeability enhancement and extraction of hydrocarbons and/or gas from subsurface deposits.
The applicant listed for this patent is Peter M. Kearl. Invention is credited to Peter M. Kearl.
Application Number | 20130213637 13/768516 |
Document ID | / |
Family ID | 48981390 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130213637 |
Kind Code |
A1 |
Kearl; Peter M. |
August 22, 2013 |
MICROWAVE SYSTEM AND METHOD FOR INTRINSIC PERMEABILITY ENHANCEMENT
AND EXTRACTION OF HYDROCARBONS AND/OR GAS FROM SUBSURFACE
DEPOSITS
Abstract
A system of a radiating antenna and a sheet beam klystron, as a
microwave source, coupled to the antenna by a short waveguide and
the method of locating the antenna downhole in a well at a selected
target zone by use of a dual chamber flexible tube and applying
power to the source to heat and fracture the rock in the target
zone and created a migrating phase boundary that radiates out from
the antenna 25 meters or more to release the hydrocarbons in the
rock.
Inventors: |
Kearl; Peter M.; (Grand
Junction, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kearl; Peter M. |
Grand Junction |
CO |
US |
|
|
Family ID: |
48981390 |
Appl. No.: |
13/768516 |
Filed: |
February 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61633730 |
Feb 17, 2012 |
|
|
|
Current U.S.
Class: |
166/248 ;
166/57 |
Current CPC
Class: |
E21B 43/2405 20130101;
E21B 43/2401 20130101 |
Class at
Publication: |
166/248 ;
166/57 |
International
Class: |
E21B 43/24 20060101
E21B043/24 |
Claims
1. A method of inducing increased permeability at a selected target
area downhole in a well comprising lowering to the target area a
system including a sheet beam klystron as the source of microwave
energy, a recirculator, a dummy load, and a directional
antenna.
2. The method in accordance with claim 1 further comprising
positioning the antenna in the target area and pointing it in a
selected direction to cover a selected sector.
3. The method in accordance with claim 2, further comprising
applying DC power to the klystron through a power cable from a
generator on the surface.
4. The method in accordance with claim 3, further comprising
applying the DC voltage at a selected low level and then increasing
the voltage to an operating level in response to a measured
parameter downhole or on a set schedule.
5. The method in accordance with claim 3, further comprising
employing a dual chamber flexible tube for lowering the system to
the target area and recirculating a coolant from the surface
through one chamber, downhole in contact with the source of
microwave energy, recirculator, dummy load and antenna and back to
the surface through the second chamber in the flexible tubing.
6. A method of intrinsic permeability enhancement at a selected
subsurface level to release hydrocarbon liquids and gases at the
selected subsurface level by employing a sheet beam klystron as the
source of microwave energy coupled to a directional antenna, the
method comprising positioning the source downhole near the
directional antenna and positioning the directional antenna at the
selected subsurface level and applying power to the source of
microwave energy.
7. The method of intrinsic permeability enhancement at a selected
subsurface level in accordance with claim 6, further comprising
fracturing the rock at the selected level and increasing the rock
permeability by increasing the interconnected porosity resulting in
increased hydrocarbon delivery efficiency.
8. The method of intrinsic permeability enhancement at a selected
subsurface level in accordance with claim 6, further comprising the
further steps of fracturing the rock at the selected level and
separating during fracturing selected hydrocarbons.
9. The method in accordance with claim 6, wherein a well has been
drilled to a depth to reach the selected level, the method further
comprising vaporizing a portion of the material at the selected
subsurface level and creating a sufficient pressure differential
between the area where the material is vaporized and the drilled
well to push the hydrocarbons into and up the well.
10. The method in accordance with claim 6, further comprising
applying microwave energy to form a phase boundary extending away
from the antenna.
11. The method in accordance with claim 10, further comprising
extending the phase boundary 25 meters or more from the
antenna.
12. The method in accordance with claim 10, further comprising
applying microwave energy at a sufficient density to vaporize a
portion of the material in the phase boundary to create a pressure
differential between the area in the phase boundary and the drilled
well.
13. The method in accordance with claim 6, further comprising
applying power from the surface through a cable to the source and
circulating a coolant from the surface to the source and
antenna.
14. The method in accordance with claim 6, further comprising
positioning the antenna to cover a selected sector and rotating the
antenna a selected number of degrees to cover another sector and
applying power to the source.
15. The method in accordance with claim 6, further comprising
closing the casing at the surface and controlling the temperature
in the selected level.
16. The method in accordance with claim 6, further comprising
closing the casing at the surface and controlling the pressure in
the casing.
17. The method in accordance with claim 6, further comprising the
producing superheated steam or other critical or super critical
fluids in the target formation to enhance hydrocarbon removal
rates.
18. A system for in-situ extraction of hydrocarbons from a target
formation in a well comprising: a casing in the well, a well screen
of low dielectric material at the lower end of the casing in the
target formation, a source of microwave energy and a radiating
antenna positioned in the casing at the target formation, and a
short waveguide coupling the source of microwave energy to the
antenna.
19. A system for creating a subsurface permeable cylinder by
fracturing an unfractured rock at selected depths comprising a
radiating antenna and a source of microwave energy near the antenna
to expose a large surface area of unfractured rock to allow low
hydrocarbon desorption rates that are compensated with large cross
sectional areas for efficient and productive gas wells.
20. A method of creating a subsurface permeable cylinder as a
reservoir comprising fracturing the rock at selected depths by a
downhole system including a radiating antenna and a source near the
antenna to expose a large surface area of unfractured rock to
provide a reservoir and sequestering carbon in the reservoir.
21. The method of sequestering carbon in accordance with claim 20,
further comprising pressurizing the reservoir and locating one or
more hydrocarbon producing wells near the reservoir to enhance
hydrocarbon production.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application claims priority to and benefits of U.S.
Provisional Application No. 61/633,730 filed Feb. 17, 2012, the
entire contents of which is hereby expressly incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a downhole High Power
Microwave (HPM) System and methods of using the System, which are
capable of fracturing rock and increasing primary permeability in
rock at depths (subsurface "Target Area") consistent with
hydrocarbon production by utilizing in-situ water and hydrocarbon
contents to selectively heat and remove hydrocarbons, including
gas, from fractured rock. "Hydrocarbons", as used herein, include
gas and liquids.
BACKGROUND
[0003] This application expressly incorporates by this reference,
as though set forth in full, U.S. Pat. No. 7,828,057 assigned to
Peter M. Kearl (inventor herein) dba Geoscience Service and United
States Patent Application Publication Number 2008/0265654.
[0004] Oil shale, tar sands, oil sands and subsurface media in
specific areas contain useful recoverable hydrocarbons. For
example, it has been reported that there are vast oil shale
deposits in the United States, and in particular, in the States of
Colorado, Utah and Wyoming; with over 1.5 trillion barrels of oil
in the oil shale in these States. Recently, there has been interest
expressed in recovering the hydrocarbons from shale in numerous
geologic basins throughout the United States and the world. There
have been many attempts to extract the hydrocarbons from this type
of subsurface deposits.
[0005] Some of these applications involve removal of the subsurface
media to above ground and the use of a retort to remove the oil. To
avoid the step of excavating or mining, a number of in-situ
processes have been proposed.
[0006] One proposal employs relatively low power at low frequencies
supplied by a magnetron. The microwave generator is a mixer
apparatus similar to those used in microwave ovens and is
relatively ineffective for controlled heating and removing of
hydrocarbons. This downhole magnetron is disclosed in U.S. Pat. No.
4,193,448 issued Mar. 18, 1980 to Calhoun G. Jeambey, as inventor,
and the use of this generator is disclosed in detail in U.S. Pat.
No. 4,817,711 issued Apr. 4, 1989 to Calhoun G. Jeambey, as
inventor. The proposal by Jeambey uses low frequencies and relies
on ionic heating, pulse power that allows conductive heat losses
and relative low power levels. This system will not produce an
expanding phase boundary by dielectric heating and will not apply
sufficient power to reach significant distances into the rock. This
is not an effective approach.
[0007] Microwave heating has significant advantages over low
frequency heating (generally less than 1.0 gigahertz) for the
extraction of subsurface hydrocarbons. The imaginary part of the
permittivity .epsilon..sub.r'' (the loss tangent
.epsilon..sub.r''/.epsilon..sub.r) is a measure of how dissipative
a medium is and gives the rate of attenuation to a propagating
wave. In the lower RF frequency ranges, .epsilon..sub.r'' is
dominated by ion conductivity. As rock is heated by a low frequency
RF source, ions in groundwater will act as a charge carrier until
approximately 100 degrees centigrade is achieved, depending on the
system pressure, at which time the water will vaporize, terminating
the charge carrier pathway. Further heating of the rock will rely
on conduction that requires large energy inputs over substantial
time periods to achieve desirable results. For example, kerogen
locked in oil shale requires temperatures in the range of 450 to
500 degrees centigrade in order to liquify for removal. This
requires an additional 350 to 400 degrees centigrade heating by
conduction for RF frequency heating applications.
[0008] Although not designed for commercially recovering
hydrocarbons from oil shale or other subterranean locations, a high
power microwave system is disclosed in U.S. Pat. No. 5,299,887
issued Apr. 5, 1994 to Donald L. Ensley. This system is disclosed
for the removal of contaminant from a sub-surface soil matrix. It
is taught in this patent that the application of high power
microwave energy to chlorinated hydrocarbons contaminated (CHC)
soil causes micro-fractionation of various soil aggregates,
including clay and rock formations. This effect increases the local
permeability and resulting diffusion rates for egress of both
liquid and vapor phase CHC.
[0009] The teachings of the Ensley U.S. Pat. No. 5,299,887 patent
were included in U.S. Pat. No. 6,012,520 by Andrew Yu and Peter
Tsou as an alternative to the use of high-pressure water jet
drilling to create a high-permeability web in a hydrocarbon
reservoir.
[0010] These systems of Ensley, Yu and Tsou and the system
disclosed in the U.S. Pat. No. 7,828,057 and the application
Publication Number 2008/0265654 involve a microwave source and its
attendant components located on the surface near the well or near
the contaminates to be removed from the soil. The equipment is too
large to fit downhole and does not have the components necessary to
function downhole.
[0011] However, while not using the above technology, advances in
the extraction of hydrocarbons from low permeable reservoir rocks
have greatly expanded energy options for a number of countries.
Common practice for increasing subsurface permeabilities for
petroleum and other hydrocarbon reservoir rocks, especially shale
formations, involves hydrofracturing where liquids and sometimes
hazardous chemicals are injected into subsurface rock formations
under high pressures to fracture the rock and provide a pathway for
the extraction of hydrocarbons. This practice has raised concerns
of potentially toxic chemicals contaminating groundwater, well
failures resulting in surface spills, and leakage from surface
impoundments resulting in the pollution of local water supplies.
Nevertheless, technologies capable of in-situ extraction of
hydrocarbons with minimal environmental impacts have a bright
future in the global economy.
SUMMARY
[0012] In some embodiments, the present invention is a method of
inducing increased permeability at a selected target area downhole
in a well comprising lowering to the target area a system including
a sheet beam klystron as the source of microwave energy, a
recirculator, a dummy load, and a directional antenna.
[0013] The method may further include positioning the antenna in
the target area and pointing it in a selected direction, applying
DC power to the klystron through a power cable from a generator on
the surface or applying the DC voltage at a selected low level and
then increasing the voltage to an operating level in response to a
measured parameter downhole or on a set schedule, employing a dual
chamber flexible tube for lowering the system to the target area,
and recirculating a coolant from the surface through one chamber,
downhole in contact with the source of microwave energy,
recirculator, dummy load and antenna and back to the surface
through the second chamber in the flexible tubing.
[0014] In some embodiments, the present invention is a method of
intrinsic permeability enhancement at a selected subsurface level
to release hydrocarbons at the selected subsurface level by
employing a sheet beam klystron as the source of microwave energy
coupled to a directional antenna, the method comprising positioning
the source downhole near the directional antenna and positioning
the directional antenna at the selected subsurface level and
applying power to the source of microwave energy. The rock may then
be fractured at the selected level and increasing the rock
permeability by increasing the interconnected porosity resulting in
increased hydrocarbon delivery efficiency.
[0015] In some embodiments, the directional antenna covers a
sector, such as 30 degrees or 60 degrees, and is rotated to cover a
new sector when the enhancement is determined to be sufficient or
complete.
[0016] In some embodiments, the present invention is a system for
in-situ extraction of hydrocarbons from a target formation in a
well comprising: a casing in the well, a well screen of low
dielectric material at the lower end of the casing in the target
formation, a source of microwave energy and a radiating antenna
positioned in the casing at the target formation, and a short
waveguide coupling the source of microwave energy to the
antenna.
[0017] In some embodiments, the present invention is a system for
creating a subsurface permeable cylinder by fracturing an
unfractured rock at selected depths comprising a radiating antenna
and a source of microwave energy near the antenna to expose a large
surface area of unfractured rock to allow low hydrocarbon
desorption rates that are compensated with large cross sectional
areas for efficient and productive gas wells.
[0018] In some embodiments, the present invention is a method of
creating a subsurface permeable cylinder as a reservoir comprising
fracturing the rock at selected depths by a downhole system
including a radiating antenna and a source near the antenna to
expose a large surface area of unfractured rock and sequestering
carbon in the cylinder. The reservoir may be pressurized and
located near hydrocarbon producing wells to enhance the hydrocarbon
production.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagram of the surface components of the High
Power Microwave System, in accordance with some embodiments of the
present invention.
[0020] FIG. 2 is a front elevation view of the downhole components
of the High Power Microwave System with the cylindrical casing and
cylindrical sleeve shown in cross-section and the well bore not
shown, in accordance with some embodiments of the present
invention.
[0021] FIG. 3 is a cross sectional diagram of the flexible tubing
with reinforced power cables and cooling tubes, in accordance with
some embodiments of the present invention.
[0022] FIG. 4 is a left side elevation view of components of the
System shown in FIG. 2, in accordance with some embodiments of the
present invention.
[0023] FIG. 5 is a front elevation view of the carriage used for
the insertion and positioning of the System, in accordance with
some embodiments of the present invention.
DETAILED DESCRIPTION
[0024] The downhole high power microwave system and proposed
methods disclosed in this application provide an alternative to
hydrofracturing that is environmentally sensitive and has the
potential to improve fracturing efficiencies. One potential
improvement of significance is that the released hydrocarbons can
be extracted from the well while the microwave fracturing by a
sheet beam klystron is taking place. Another improvement is that
chemicals, which are objected to by some, are not needed.
[0025] The microwave fracturing is accomplished by the high power
microwave system and the method of placing the system at the
selected level (the target area) and controlling the fracturing
from the surface. The surface components of the proposed downhole
system include a 400 cycle turbine generator, or similar source,
which supplies electrical power for the system. The output of the
electrical generator is applied to an electrical control unit that
contains, but is not limited to, a crowbar, a transformer, a filter
and a power supply to provide DC power to the subsurface or
downhole high power microwave system. A reinforced flexible tube,
which is compartmentalized, carries electrical wire to power the
downhole microwave system, has a pair of chambers to carry coolant
to and from the system downhole and carries a selected number of
wires for monitoring the downhole conditions, such as temperature
and pressure, and for control signals for various functions
downhole, such as moving the system up, down or rotational. A high
capacity cooling system is connected to the flexible tube through a
pump to maintain an adequate supply of coolant for the downhole
high power microwave system. This coolant may be a typical coolant,
and a particularly good coolant is water, for example. The system
is deployed downhole by using a large motorized dram capable of
holding substantial lengths of flexible tubing and interchangeable
with additional drums depending on the depths to be treated. A
pulley, connected to the well head manifold, directs the system
into the well. A blow out preventer, common to oil and gas wells,
is employed. A compression assembly secures the tube and provides
an air tight seal during operation of the system.
[0026] The well head manifold directs vapors from the well to a
condenser that collects hydrocarbon vapors or directs them to the
power generator as a fuel source. A valve is used to control
downhole pressure for development of superheated fluids from
in-situ water or other in-situ fluids to aid in the extraction of
hydrocarbons. The well may be encased, with the casing extending
from the surface and almost to the subsurface target area. Also the
well may not have the usual casing, but may be encased over a
selected length from the lower end up the selected distance with a
low dielectric loss sleeve or casing.
[0027] The major system components placed downhole are the
termination of the components in the flexible tube, a high power
microwave source, preferably a sheet beam klystron, a directional
antenna, a dummy load and a recirculator to direct the microwave
beam to the antenna and reflected waves to the dummy load. The
system further includes an orientation tool, which may be a carrier
having flexible positioning arms and motorized wheels, that allows
surface operators to place the antenna at the desired depth and
radiation direction. Commonly used well field tools such as, but
not limited to, gyroscopes or flux gate compasses provide the
information for orientation of the system in various directions.
The flexible tube, with power and instrument cables, is attached to
a manifold near the microwave source which directs power and the
cooling system to the sheet beam klystron tube and other
components. The sheet beam klystron tube provides, but is not
limited to, 1 megawatt (MW) of power at a frequency of, but not
limited to, 6 to 8 GHz. Microwave power is emitted from the
klystron tube via a short wave guide, with an arc detector, to the
recirculator. A purpose of the recirculator is to protect the
klystron tube by shifting the phase of reflected power to a
separate output wave guide connected with the water or coolant
cooled dummy load where reflected power is coupled into coolant,
such as water, to prevent damage to the klystron tube. The antenna
is preferably cooled by the coolant and may be a phased array
antenna, for example. The antenna is capable of radiating a
directional beam in various radiation patterns depending on the
proposed fracture patterns. The antenna radiates in a selected
pattern and is directed to cover sectors, such as 30 degrees or 60
degrees, for example. The coolant for the system components is
directed by coolant tubes along the klystron, recirculator, dummy
load and antenna. The system components listed above are major
equipment items. Other components which may be included are
additional arc detectors and monitoring equipment.
[0028] Several different applications are possible for emitting
microwave radiation into the subsurface while protecting the
downhole microwave system. Thus, another component of the system is
a low dielectric loss sleeve or a low dielectric loss permeable
well casing. Where the hole or bore is encased with casing material
like steel, the sleeve is comprised of, but not limited to, a
perforated fused quartz or a ceramic cylinder that seats into a
shoe at the base of the steel casing. Numerous holes in the fused
quartz or ceramic cylinder can be used as a sleeve that will
protect the equipment while radiating in a subsurface target area.
Using well logging and geophysical data to select target zones,
high power microwave energy will be emitted from the antenna in
specific patterns to create migrating phase boundaries that will
fracture the rock and create specified zones of increased
permeability. As a selected zone is completed, the sleeve and the
system are pulled back to another target area and the process
repeated. The other option is to case a selected length of the well
with a permeable low-loss well casing and radiate either selected
target zones or the entire target formation through the low loss
dielectric sleeve.
[0029] The high power microwave system is designed to either
produce hydrocarbons from subsurface target areas or to increase
the permeability surrounding the well by increasing interconnected
porosity and fracturing the rock by dielectric heating of in-situ
water and hydrocarbons. For dielectric heating to efficiently heat
the rock, frequencies must be high enough to exclude ionic
heating-generally greater than 1 GHz. Efficient dielectric heating
for purposes of hydrocarbon removal occurs in the 2 to 10 GHz
range, but is not limited to the upper frequency range.
[0030] In use, the system is lowered into the well using the
flexible tubing system that contains duel cooling chambers or
tubes, reinforced power cable, and instrument cables. The system
can be used in either vertical or horizontal wells. The high power
microwave system of a sheet beam klystron, antenna, recirculator,
dummy load and ancillary components can be lowered into a vertical
shaft or a vertical shaft which curves and becomes a horizontal
shaft. A carriage, having preferably motorized wheels and
tensioning arms pressing against the inside of the casing and
attached to some of the components of the high power microwave
system, guides the system down and along the casing. The carriage
preferably positions the system in the center of the casing.
[0031] In some embodiments, the method of inducing increased
permeability at a selected target area downhole in a bare well or
an encased well comprises the steps of lowering a system comprising
a sheet beam klystron as the source of microwave energy, a
directional antenna, a dummy load and a recirculator coupled
between the source and the antenna to direct reflected energy from
the antenna to the dummy load. The system is then positioned with
the antenna in the target area and pointing in the selected
direction. DC power is applied to the klystron through a power
cable from a generator on the surface. The DC voltage may be
started at a selected lower level and increased to an operating
level in response to a measured parameter downhole or on a set
schedule.
[0032] In some embodiments, a coolant is sent from the surface
through one chamber in the flexible tubing to cool the source,
recirculator, dummy load and antenna and then back to the surface
through the second chamber in the flexible tubing.
[0033] The temperature of the various components, the pressure of
an enclosed well, the frequency of the source and flow rates and
other parameters may be measured and controlled during and after
fracturing.
[0034] If a sector is covered by the radiation of the antenna, upon
completion of the fracturing in this sector the antenna is rotated
to cover the next sector. To rotate the antenna the flexible tubing
may be twisted clockwise or counterclockwise as needed. Otherwise
the tubing may be terminated in a manifold above the klystron and
the wires, cable and tubes distributed as required so that
individual components or groups may be selectively rotated.
[0035] In some embodiments, unlike conventional hydrofracturing
operations, it is unnecessary to introduce water into the formation
to create permeability enhancements. A focused beam is used to
direct microwave energy in any direction to remove water and
hydrocarbons plus increase permeability. Issues with injecting
water that dissolves tight shale and decreases permeability are
eliminated.
[0036] Several operational methodologies are possible using the HPM
system depending on the type of well, the direct production of
hydrocarbons, or the development of permeability zones surrounding
the well to increase long term production. Relatively shallow
vertical wells, down to about 2000 feet, in oil shale deposits of
the Western United States and other locations can be drilled and
the HPM system used to produce a very high percent of the
hydrocarbons in a radial distance of 25 meters or more. Kerogen can
be liquefied and pumped to the surface using submersible pumps.
Gases collected at the surface can be either sold and/or used to
power on site generators.
[0037] For deep shale deposits, microwaves can produce hydrocarbons
or be used to increase the permeability surrounding hydrocarbon
wells for future production. The HPM system can be used in a
similar manner as multistage hydrofracturing where selected areas
of the well are radiated to increase permeability in selected
subsurface regions. Using the HPM system, it is possible to
increase the permeability of a cylinder 50 meters or more in
diameter surrounding the well, to provide a large surface area
interface between permeable rock created by microwave heating and
the ambient hydrocarbon producing rock. The ability to direct
microwave energy to any location in the subsurface provides
flexibility in developing optimal production from various
hydrocarbons subsurface reservoirs.
[0038] The apparatus and method of this invention provide an
enhanced zone of intrinsic permeability surrounding bore holes that
increases production rates for new or existing wells located in
subsurface gas or petroleum reservoirs. A permeable skin region is
created around the well bore that extends several meters radially
from the well bore.
[0039] The system for extracting and recovering hydrocarbons from
subsurface target formations may be a closed system downhole with
pressure control to most effectively extract hydrocarbons from
rock, such as oil shale. Oil shale typically contains a minimum of
2% to 4% of water. If there is insufficient water in the target
formation, water may be added through an encased bore hole.
[0040] The water and/or other fluids, such as kerogen, in the
target formation is superheated and causes fracturing of the rock.
Further, the superheated fluid[s], from the target formation or
added, causes the pressure to increase to push the liquified or
volatized hydrocarbon to the surface. These hydrocarbons are
collected in a tank and recovered.
[0041] Critical or superheated fluids, such as water which has a
critical temperature of 647.3 degrees K. and a critical pressure of
218.3 atm. or methane which has a critical temperature of 190.4
degrees K at 45.4 atm. can be created either in-situ or added to
the system to act as organic solvents to enhance hydrocarbon
removal. The microwave recovery system controls downhole pressure
and temperature necessary for the enhanced recovery of hydrocarbons
via critical fluids.
[0042] The pressure created by the superheated water or steam may
be controlled by controlling the microwave power applied to the
antenna positioned in the target formation. Further, the frequency
of the output of the microwave source may advantageously be 2.45
Gigahertz, which is the closest frequency to the resonance of
water.
[0043] The above and other features, objects and advantages of this
invention will become apparent from a consideration of the
foregoing and the following description, the appended claims and
the accompanying drawings.
[0044] Some embodiments of the downhole microwave system are
illustrated in the drawings and will be described in detail herein.
FIG. 1 illustrates the surface components of the downhole HPM
system. A turbine generator 1, or similar source, at the surface of
the well supplies electrical power for the system. The output of
the electrical generator 1 is applied to an electrical control unit
2 that contains, but is not limited to, a crowbar, transformer,
filter and power supply to provide DC power to the subsurface HPM
system. DC power is connected to the downhole system through a
flexible tube 3 via a coupler 4.
[0045] FIG. 3 illustrates a cross sectional view of the dual
chamber flexible tube 3 that is used to lower the HPM system into
the well and to retrieve the system out of the well, according to
some embodiments of the present invention. The flexible tube 3
includes reinforced flexible tubing 25 capable of supporting the
weight of the HPM system at depths consistent with conventional oil
and gas wells. The interior of the flexible tubing 3 is divided by
a septum 26 that creates dual chambers 27 and 28. Tension cables
can be added in the septum 26 if necessary to support the weight of
the HPM system. One chamber 27 is used to input coolant, such as
water, from the surface to the HPM system while the other chamber
28 is used for the return flow of heated water that is sent to a
high capacity cooling system 6. An insulated DC power cable 29 is
located in the center of the septum 26 to provide power to the
klystron tube. Instrument cables 30, not limited to two, are also
contained within the septum 26. The instrument cables provide
information from, but not limited to, downhole instruments that
monitor HPM location, arcing, temperature, and pressure, as well as
a way of controlling downhole environment, operating conditions and
components, like a carriage for up/down movement and rotation.
[0046] A pump 5 is connected to the dual chamber 27, 28 of tube 3
with the high capacity cooling system 6 to maintain an adequate
supply of coolant, such as water, for the downhole HPM system.
[0047] FIG. 1 illustrates the HPM system is deployed downhole using
a large motorized drum 7 capable of holding substantial lengths of
flexible tubing and interchangeable with additional drums depending
on the depths to be treated. A pulley 8 is connected to a well head
manifold 9 and directs the HPM system into the well. A blow out
preventer, common to oil and gas wells, is not shown. A compression
assembly 10 secures the flexible tube 3 and provides an air tight
seal during operation of the system.
[0048] The well head manifold 9 directs vapors from the well to a
condenser 11 that collects hydrocarbon vapors or directs them to
the power generator as a fuel source and/or to a separator for
collection. A valve 12 is used to control downhole pressure for
development of superheated fluids from in-situ water, or other
in-situ fluids, to aid in the extraction of hydrocarbons. The
system is attached to the well casing 13 that extends to the
subsurface target area.
[0049] FIGS. 2 and 4 illustrate the major system components placed
in the well, according to some embodiments of the present
invention. An orientation tool 14 allows surface operators to place
the radiating antenna 22 of the system at the desired depth within
the target zone or area and to direct the antenna in the desired
radiation direction. Alternatively, other positioning tools may be
employed, such as the carriage shown in FIG. 5, or the like.
Commonly used well field tools such as, but not limited to,
gyroscopes or flux gate compasses provide the information for
orientation of the system in various directions. The flexible tube
3 with dual coolant chambers and power and instrument cables is
attached to a manifold 15 that directs power and the cooling system
to the sheet beam klystron tube 16.
[0050] FIG. 5 illustrates one type of orientation tool, according
to some embodiments of the present invention. A carriage 25 has
three or more flexible arms 31 spaced at intervals around one or
more of the components of the system. The intervals are preferably
130 degrees or 90 degrees. The carriage is shown attached to the
klystron tube 16 in FIG. 5. Motorized rollers or wheels 32 engage
the inner surface of the casing or low dielectric loss sleeve to
move the system in the desired direction. The flexible arms 31 keep
the wheels 32 in contact with the inner surface.
[0051] The size of the "down-hole" sheet beam klystron is limited
by the size of the bore. For example, for an assumed bore diameter
of 23 cm a sheet beam klystron can deliver a maximum power of 1
megawatt continuous wave (CW), which is more than twice the power
of a conventional klystron. This is because the cylindrical beam of
a conventional klystron, at the same beam voltage (125 kV) could
not be operated at the same current (17 Amps) because the
dimensions of its beam would result in more current density than
magnetic confinement of the beam could make possible. The sheet
beam klystron tube 16 may be, but is not limited to, a 1 MW or
greater sheet beam klystron tube at a frequency of, but not limited
to, 6 to 8 GHz. The sheet beam klystron tube may be similar to one
disclosed in U.S. Provisional Patent Application No.
61/633,730.
[0052] The typical steel casing in which the system of this
application is used has a diameter of 9 inches. Other useful and
relatively common casing sizes in which the system may be used have
a 6 inch diameter or a 20 inch diameter.
[0053] Microwave power is emitted from the klystron tube 16 via a
wave guide 17, with an arc detector 18, directly to a recirculator
19. The waveguide 17 is a short waveguide that only has to be long
enough to accommodate a dummy load 21 and connectors between the
recirculator 19 and the klystron 16. This places the source 16 near
the antenna 22, which is in the target zone. The main purpose of
the recirculator 19 is to protect the klystron tube 16 by shifting
the phase of reflected power to a separate output wave guide 20
connected with a water cooled dummy load 21. Reflected power from
the antenna 22 is coupled into cooling water to prevent damage to
the klystron tube. Another major component of the downhole
equipment is the directional antenna or applicator 22. The antenna
22 is an applicator that is capable of radiating a directional beam
in various radiation patterns to accomplish the desired fracture
patterns. A water cooled phased array antenna provides the desired
radiation pattern. Water tubes 23 provide coolant for the downhole
system components. Other components which may be included are mode
converters, additional arc detectors and monitoring equipment, for
example.
[0054] FIGS. 4 and 2 illustrate one type of connection between the
downhole components of the system. The waveguide 17 may be
rectangular or some other appropriate configuration. Also, the
dummy load 21 may be between the antenna 22 and the recirculator 19
and the waveguide 17 could then be shorter to couple the klystron
tube 16 to the recirculator 19.
[0055] In some embodiments, arc detectors are strategically placed
in the waveguide to detect potential arcing problems and to
immediately shut down the system if there is an arcing problem. The
arc detectors and down hole sensors are integrated into the central
control system 2 that monitors, but not limited to, electrical
arcs, cooling water temperatures, off-gas temperatures, off-gas
concentrations, and power conditions for the power supply and the
klystron, and provides safety controls for the operation of the
system.
[0056] Another component of the downhole system is a low dielectric
loss sleeve 24 attached to the end of the well casing or steel pipe
13. If the well bore is not encased, a low dielectric loss
permeable sleeve 24 extends up the well and functions as the well
casing to protect the system components in the open well bore not
cased with steel pipe 13. The sleeve may be comprised of, but not
limited to, a perforated fused quartz or a ceramic cylinder that
seats into a shoe at the base of the steel casing 13. Several
different applications are possible for emitting microwave
radiation into the subsurface while protecting the downhole
microwave system. Numerous holes in a fused quartz or ceramic
cylinder can be used to form the low dielectric loss sleeve that
protects the equipment while radiating a subsurface target
area.
[0057] Using well logging and geophysical data to select target
zones, high power microwave energy is emitted from the antenna 22
in specific patterns to create migrating phase boundaries to
fracture the rock and create specified zones of increased
permeability. As a selected zone is completed, the sleeve 24 and
the HPM system are pulled back to another target zone and the
process repeated. An alternative to encasing the well down to the
target area in steel, is to encase an extended portion or the whole
well with a permeable low-loss well casing and to radiate either
selected target zones or the entire target formation without moving
the sleeve or casing.
[0058] Each sector to be radiated is selected to most efficiently
extract the desired hydrocarbons from the target formation. The
smaller the angle of the sector radiated the greater the energy in
the sector. An angle of 30.degree. is useful for most target
formations. The angle of the sector may be increased or decreased
when appropriate. The process is continued until the majority of
the region at a selected depth has been radiated in all directions.
The antenna 22 is either raised or lowered, or moved to the right
or left in a horizontal well, in the casing 13 and sleeve 24 to
another region in the target formation and the process of launching
phase boundaries in sequenced sectors repeated. This process is
continued until the distance of the phase boundary from the antenna
22 results in diminishing hydrocarbon recovery rates which will
dictate cessation of the process in that sector and eventually at
the operating depth of the antenna and in the particular bore
hole.
[0059] The downhole microwave system is capable of removing nearly
100 percent of the water and volatile hydrocarbons. Careful
laboratory measurement of the loss tangent for rock material that
has been previously placed in a microwave field has shown that it
is possible to effectively microwave and remove water and
hydrocarbons in a cylinder conservatively predicted to be 50 meters
in diameter and the length of the production zone. In horizontal
wells, distances of one or two thousand meters for the production
zone are not uncommon.
[0060] An important advantage of not introducing water into the
well over hydraulic fracturing is the residual moisture left alter
hydrofracturing. Water introduced into a shale formation will cause
some liquefaction or smearing of the shale reducing permeability at
the fracture/shale interface. Once drilling fluids are removed from
the well and the casing placed in the well to the depth of the
target zone, no water is introduced into the well for the microwave
process of this invention. Permeability enhancements remain
constant during the life of the well since all water is removed in
microwaved zones. Depletion in production rates will be reduced
resulting in gas wells that produce high volumes of gas for longer
durations.
[0061] In some embodiments, the method of inducing increased
permeability at a selected target area downhole in an open well or
an encased well comprises the steps lowering a system comprising
the sheet beam klystron 16, as the source of microwave energy, a
directional antenna 22, a recirculator 19 between the source and
the antenna and a dummy load 21. The recirculator directs reflected
energy from the antenna 22 to the dummy load 21. The system is
lowered to a selected depth, in either a vertical or a vertical and
horizontal well, and is then positioned with the antenna 22 in the
target area and pointing in the selected direction. A low
dielectric loss sleeve or well casing around the antenna and source
protect these components during and after fracturing. DC power is
applied to the klystron 16 through a power cable 29 from the
generator 1 on the surface. The DC voltage may be started at a
selected lower level and increased to an operating level of 17 amps
at 125 kilovolts. The increase may be in response to a measured
parameter downhole or on a set schedule. Upon completion of the
fracturing in the sector covered by the antenna, the antenna 22 is
rotated to cover the next sector.
[0062] A coolant is recirculated from the surface through one
chamber 27 in the flexible tubing 3, downhole in contact with the
source 22, recirculator 19, dummy load 21 and antenna 22 by way of
coolant tubes 23 and then back to the surface through the second
chamber 28 in the flexible tubing 3.
[0063] The temperature of various components, the pressure of an
enclosed well, the frequency of the source and flow rates and other
parameters may be measured during and after fracturing.
[0064] There are several options for producing hydrocarbons from
vertical or horizontal wells using the HPM microwave system. In
vertical wells, microwave heating can begin at the bottom of the
target zone and moved upwards. As hydrocarbons, such as kerogen in
oil shale deposits are heated, liquid kerogen will flow downward
and toward the bottom of the well where it can be collected and
pumped to the surface. Once the kerogen is removed, the well can be
completed as a conventional gas well. For horizontal wells, there
are several options available to produce hydrocarbons. Multi-stage
fracturing at selected intervals, similar to hydrofracturing, can
be achieved using the microwave system. It is also possible to
remove nearly 100 percent of the hydrocarbons in a cylinder
surrounding a horizontal well for the entire length of the well
within the target zone. The depth of the target area may be in
excess of 10,000 feet with the antenna and the system being
positioned at this depth.
[0065] The system does not require the use of large volumes of
water or chemicals that could potentially impact the environment,
or large quantities of sand, ail of which are necessary for a
conventional hydrofracturing operation. The oil and gas industry
relies on competent well construction to prevent potentially toxic
chemicals used in hydrofracturing from contaminating valuable
groundwater supplies. Effective disposal of water and chemicals
used in hydrofracturing relies on cooperation between industry and
the regulatory community. A breakdown in this process could result
in a catastrophic release to the environment and large remediation
costs. The high power microwave system relies on in-situ water and
hydrocarbons to achieve fracturing of the rock. Outside sources of
water or chemicals are not necessary for the performance of the
high power microwave system. The costs of transport and disposal of
hydrofracturing fluids is avoided and is a savings added in
comparisons of technology efficiencies.
[0066] The presence of in-situ water provides another physical
mechanism to improve hydrocarbon removal efficiencies. It is
possible to control downhole temperatures and pressures with this
microwave system. With the presence of water, super-heated steam
can be created within the rock formations that will assist in
stripping hydrocarbons from shale rocks.
[0067] The physical process of efficiently heating subsurface
hydrocarbon deposits is based on launching a phase boundary in the
subsurface using directed microwave energy, thereby heating the
hydrocarbon to temperatures where liquification or vaporization
occurs. As hydrocarbons are removed, the remaining rock absorbs
limited amounts of energy allowing the phase boundary to continue
to migrate radially from the access well. This phase boundary may
radiate out 25 meters or more.
[0068] The pressure and temperature may be controlled to provide
the pressure and temperature at which selected fluids become
critical or super critical fluids. For example, methane is often
present in the subsurface area and the pressure may be established
at or above 45.4 atmospheres with a temperature at or above 190.4
degrees K. to create a critical or super critical fluid of the
methane which acts as an organic solvent to enhance hydrocarbon
removal. The pressure and temperature may also be controlled to
create a critical or super critical fluid of the water in the
target area.
[0069] As an alternative to or in addition to pressure in the well,
a sump near the bottom of the well with piping to the exterior of
the well (not shown) may be used to recover the hydrocarbons and
other liquids or gases from the bottom of the well.
[0070] The microwave system will produce significant fracture
densities and wall cause solid blocks of shale to experience
enhanced porous permeabilities from the radiation which will result
in an increase of hydrocarbon production. Some photomicrographs of
low permeable clay subjected to microwave heating show tracks or
tunnels created by escaping gases. The effect of microwave heating
results in solid blocks of shale showing significant increases in
primary permeability in addition to increases in permeability due
to fractures.
[0071] Microwave heating will result in hydrocarbons being
liquefied and vaporized, and transported from deep within the earth
via a permeable pathway created by microwave heating and under an
enhanced gradient from high pressures deep within the earth to
atmospheric pressure at the earth's surface. Throughout this
journey, some of the vapor will be kept within the microwave field.
However, this vapor absorbs very little energy and allows the bulk
of the energy to heat rock. Primary separation of various
hydrocarbons within the microwave field during transport from the
rock and during vapor collection on the surface is possible with
the microwave system. Separated or partially separated hydrocarbon
compounds will significantly reduce refining costs further
increasing the economic value of the High Power Microwave
System.
[0072] Once downhole microwave treatment has been completed, there
will be a large surface area interface between the permeable
microwaved rock and hydrocarbon producing ambient or country rock.
The high power microwave system has increased permeability and
increased the surface area interface beyond the capabilities of
hydrofracturing. More of hydrocarbon producing rock is exposed to
permeable pathways allowing for the increased production from wells
as compared to conventional hydrofracturing. Low permeable country
rock that exhibits low hydrocarbon desorption rates have a large
cross sectional area for hydrocarbons to flow through permeable
rock to the well. A natural gas well capable of producing large
volumes of gas for long periods of time will be the ultimate result
after the microwave removal of hydrocarbons and permeability
enhancement is completed. No toxic chemicals are injected into the
ground. There are no requirements for precious water resources or
expensive disposal practices for the waste water and chemical.
[0073] Eventually, the highly permeable subsurface zones created by
microwave treatment provide a reservoir for carbon sequestering.
Carbon dioxide and other greenhouse gases can be sequestered in the
same well that produced hydrocarbons by injecting these gases in
liquid form back into the earth. This process may also be
advantageous during active production where post-processed
microwaved subsurface reservoirs are pressurized during carbon
sequestering, thereby increasing the pressure gradient for active
zones and forcing hydrocarbons into producing wells.
[0074] While the description above contains specificity, this
should not be construed as limiting the scope of the invention; but
merely as providing illustrations of the presently preferred
embodiment of the invention. Although some embodiments and methods
for extracting subsurface hydrocarbons have been described above,
the inventions are not limited to the specific embodiments, but
rather the scope of the inventions are to be determined as
claimed.
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