U.S. patent application number 12/838006 was filed with the patent office on 2012-01-19 for enhanced hydrocarbon recovery using microwave heating.
This patent application is currently assigned to Dennis Tool Company. Invention is credited to Mahlon D. Dennis.
Application Number | 20120012319 12/838006 |
Document ID | / |
Family ID | 45465997 |
Filed Date | 2012-01-19 |
United States Patent
Application |
20120012319 |
Kind Code |
A1 |
Dennis; Mahlon D. |
January 19, 2012 |
ENHANCED HYDROCARBON RECOVERY USING MICROWAVE HEATING
Abstract
A downhole tool utilizing microwave energy for stimulating
production of hydrocarbons from a drilled well. A microwave
generator is disposed within the body of the tool and supplied with
power from the surface. Microwaves generated by the tool are
applied to a refractory dielectric material disposed at a lower end
of the tool or to dielectric material in fluids circulated into the
wellbore, or directly to the formation.
Inventors: |
Dennis; Mahlon D.;
(Kingwood, TX) |
Assignee: |
Dennis Tool Company
Houston
TX
|
Family ID: |
45465997 |
Appl. No.: |
12/838006 |
Filed: |
July 16, 2010 |
Current U.S.
Class: |
166/302 ;
166/66.5 |
Current CPC
Class: |
E21B 43/2401
20130101 |
Class at
Publication: |
166/302 ;
166/66.5 |
International
Class: |
E21B 43/24 20060101
E21B043/24; E21B 36/00 20060101 E21B036/00 |
Claims
1. A downhole tool, comprising: an elongated body having dimensions
for fitting into a wellbore suitable for production of
hydrocarbons, the enclosure having a proximal end adapted for
connection to a means for lowering the enclosure into the wellbore;
a microwave generator generating electromagnetic energy at
predetermined microwave wavelengths, the generator disposed within
the body and operable to receive power through a cable extending
through the proximal end of the enclosure; a transmission line for
transmitting the electromagnetic energy from the microwave
generator to a head of an applicator located near a distal end of
the body, remote from the microwave generator; and a head attached
to the body and forming a distal end of the tool.
2. The downhole tool of claim 1, wherein at least a portion of at
least one wall of the head unit being comprised of a microwave
transparent, refractory material, and wherein the applicator is
located at least partially within the head and radiates microwave
energy through the microwave transparent refractory material.
3. The downhole tool of claim 2, wherein the at least one exterior
wall of the head is comprised of an abrasion-resistant, refractory
material.
4. The downhole tool of claim 1, further comprising at least one
microwave absorbable element disposed within the head for heating
the head in response to absorbing at least a portion of said
microwave energy from the applicator.
5. The downhole tool of claim 3, wherein the at least one microwave
absorbing element material is comprised of one of silicon carbide,
graphite, and silicon-nitride.
6. The downhole tool of claim 1, wherein the transmission line
comprises a waveguide.
7. The downhole tool of claim 1, further comprising thermal
insulation disposed within the body between the microwave generator
and the head.
8. The downhole tool of claim 1, further including means for
cooling the microwave generator.
9. The downhole tool of claim 1, wherein the microwave generator
and the head are separated by a predetermined distance sufficient
to substantially reduce transfer of heat from the head to the
microwave generator.
10. An apparatus for stimulating production in a well drilled
through a hydrocarbon-bearing formation, comprising: a downhole
tool disposed within a wellbore adjacent to a formation to be
heated by the downhole tool comprising, an elongated body having
dimensions for fitting into a wellbore suitable for production of
hydrocarbons, the enclosure having a proximal end adapted for
connection to a means for lowering the enclosure into the wellbore;
a microwave generator generating electromagnetic energy at
predetermined microwave wavelengths, the generator disposed within
the body and operable to receive power through a cable extending
through the proximal end of the enclosure; a transmission line for
transmitting the electromagnetic energy from the microwave
generator to a head of an applicator located near a distal end of
the body, remote from the microwave generator; a head attached to
the body and forming a distal end of the tool; means for lowering
the downhole tool into the wellbore extending from the earth's
surface above the wellbore, into the wellbore and connect to the
downhole tool; a power source located on the earth's surface; and a
cable for coupling the power from the power source to the microwave
generator, the cable running down the wellbore.
11. The apparatus of claim 10, wherein at least a portion of at
least one wall of the head unit is comprised of a microwave
transparent, refractory material.
12. The apparatus of claim 10, wherein the at least one exterior
wall of the head is comprised of an abrasion-resistant, refractory
material.
13. The apparatus of claim 10, further comprising at least one
microwave absorbable element disposed within the head for heating
the head in response to absorbing at least a portion of said
microwave energy from the applicator.
14. The apparatus of claim 10, wherein the at least one microwave
absorbing element material is comprised of one of silicon carbide,
graphite, and silicon-nitride.
15. The apparatus of claim 10, wherein the transmission line
comprises a waveguide.
16. The apparatus of claim 10, further comprising thermal
insulation disposed within the body between the microwave generator
and the head.
17. The apparatus of claim 10, further comprising fluid containing
microwave absorbable material within the borehole adjacent to the
head.
18. A method for stimulating hydrocarbon recovery from a wellbore
comprising: lowering a downhole tool into a wellbore adjacent to a
hydrocarbon bearing formation of interest, the downhole comprising:
an elongated body dimensioned and shaped for fitting into a
wellbore drilled for production of hydrocarbons; a microwave
generator disposed within the body, near a proximal end of the
body, for generating electromagnetic energy at predetermined
microwave wavelengths, the microwave generator adapted for
receiving power through a cable extending from the surface; a
transmission line for transmitting the electromagnetic energy from
the microwave generator to an applicator located near a distal end
of the body, remote from the generator; and a head attached to a
distal end of the body; and applying power to the microwave
generator with a cable extending from a power supply on the surface
to the tool within the wellbore.
19. The method of claim 18, wherein the tool is lowered on
continuous tubing.
20. The method of claim 18, further comprising circulating within
the wellbore near the downhole tool a fluid containing dielectric
material for heating by microwaves generated by the tool.
21. The method of claim 20, wherein at least a portion of at least
one wall of the head unit being comprised of a microwave
transparent, refractory material, and wherein the applicator is
located at least partially within the head and radiates microwave
energy through the microwave transparent refractory material, to
the microwave absorbable material.
22. The method of claim 18, wherein the tool further comprises at
least one microwave absorbable element disposed within the head for
heating the head in response to absorbing at least a portion of
said microwave energy from the applicator.
23. The method of claim 22, wherein the at least one microwave
absorbing element material is comprised of one of silicon carbide,
graphite, and silicon-nitride.
Description
BACKGROUND
[0001] There are a number of techniques used to stimulate or
enhance production of hydrocarbons from wells by increasing the
permeability of the formation outside the wellbore. The most
well-known and widely used approach is hydraulic fracturing of the
formation to increase permeability. In-situ heating of hydrocarbon
bearing formations has also been used to address production
problems relating to fluids in the reservoir rock and the
production equipment, such as deposition of wax and asphaltene
materials, creation of water and oil emulsion, fluid invasion
resulting in clay swelling and fines migration. However, thermal
stimulation of a formation can also be used to fracture the
formation through thermal expansion of materials comprising the
formation, as well as to improve fluid flow characteristics of
near-wellbore porous regions by reducing the viscosity of the oil,
preventing or removing waxes or asphaltenes build-up in the
wellbore and near-wellbore region, preventing formation of hydrates
and dehydrating clay.
SUMMARY
[0002] The invention pertains, generally, to stimulating production
of hydrocarbons from a well by lowering a downhole tool into a
wellbore to generate microwave radiation for heating.
[0003] A first, exemplary embodiment of a downhole tool comprises a
microwave generator positioned for generating microwave radiation
and a transmission line for carrying microwave electromagnetic
energy from the generator towards a microwave absorbable material
disposed within a head portion of the tool. After the tool is
lowered into the borehole using jointed pipe or coiled tubing,
electric energy is supplied to the microwave generator, causing
microwave radiation to be generated. This radiation is directed to,
and absorbed by, the microwave absorbable material causing it to
heat. The thermal energy is transferred to fluids in the borehole
through thermal conduction, and then to the adjoining
formation.
[0004] A second, exemplary embodiment of such a downhole tool
comprises a microwave generator and a transmission line that
carries the microwave electromagnetic energy from the generator
toward a head, at least a portion of which is made from microwave
transparent material. The microwave radiation travels through the
head and then is radiated from an antenna so that microwave
absorbable materials within fluids within the wellbore and/or
surrounding hydrocarbon-bearing formation absorb the microwave
radiation. The microwave radiation absorbed by the well fluid
and/or the microwave absorbable material within the rock formation
results in heating of the rock formation. The head may optionally
include a reflecting element for directing or focusing the
radiation, or for scattering the radiation.
[0005] According a method for using the tool, the tool is lowered
into the borehole to the desired position, and the microwave
generator is turned on to generate microwave electromagnetic energy
that is transmitted toward the head of the tool. Optionally,
drilling fluid to which microwave absorbable material has been
added is circulated into the wellbore so that the microwave
radiation heats the microwave absorbable material. Depending on the
formation and how the downhole is used, the heating stimulates flow
of hydrocarbons by either reducing its viscosity or causing thermal
expansion that leads to fracturing of the formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic illustration of a wellbore into which
is lowered a downhole tool for generating heat within the wellbore
and adjoining formation.
[0007] FIG. 2 is a schematic illustration of a first embodiment of
the downhole tool shown in FIG. 1.
[0008] FIG. 3 is a schematic illustration of a second embodiment of
the downhole tool shown in FIG. 1.
DETAILED DESCRIPTION
[0009] In the following description, like features or elements are
marked throughout the specification and drawings with the same
reference numerals, respectively.
[0010] Referring to FIG. 1, downhole tool 100 is lowered into
wellbore 102 and positioned next to a region of interest 106 in a
hydrocarbon bearing formation 104. The tool 100 is lowered into and
supported within the wellbore at a desired location on the end of,
in this example, continuous or coiled tubing 108. Because the
wellbore has already been drilled and is likely filled with fluid,
lowering the tool using coiled tubing will allow the tool to be
pushed into the wellbore until such time as the weight of the tool
and the tubing overcomes the hydrostatic pressure within the well.
However, a string of jointed pipe or, if the conditions permit, a
wireline could also be used to lower the tool within the wellbore.
The tool is supplied with electricity by an instrumentation cable
110 running through the tubing connected to a power source 112
located on the surface.
[0011] A controller 114 controls operation of the tool. One example
of a controller comprises a circuit that turns power to the tool on
or off, or that changes the voltage and/or current of the
electricity being supplied to the tool. Another example is a
circuit that generates and transmits to the downhole tool control
signals understood by a controller within the downhole tool, which
in turn causes the tool to operate or to stop operation, or to
change an operational characteristic. The signals can be
transmitted, for example, over cable 110, another wire that runs to
the downhole tool from the surface, the continuous tubing or
jointed pipe that lowers the tool into the hole, or using RF
communication methods. The controller may also include logic
implemented using just hardware or a combination of hardware and
software (for example a specially programmed processor) for
performing one or more predetermined or programmed control
processes.
[0012] Drilling fluid from a source 116 on the surface supplies
fluid containing microwave absorbable compounds. The fluid can be
drilling fluid to which such compounds have been added. The fluid
can be pumped down continuous tubing or joined pipe inserted into
the bore hole prior to the tool 100 being lowered into the bore
hole, or while the tool is in the bore hole by, for example,
pumping fluid through the tubing or pipe to which the tool is
connected and having the fluid exit openings into the bore hole
above or in the tool.
[0013] FIGS. 2 and 3 illustrate, respectively, alternative
embodiments 200 and 202 of downhole tool 100 from FIG. 1. Each of
the embodiments 200 and 202 includes a body 204 that forms an
enclosure. The body is comprised, for example, of a hollow,
sleeve-shaped element made of steel, stainless steel, or other
material or combination of materials capable of withstanding the
relatively high temperature and pressure and corrosive environment
of the wellbore. The body can be comprised, for example, of one or
more lengths of metal tubing having a diameter smaller than the
diameter of the borehole 102.
[0014] Enclosed within the body is at least one microwave generator
206 and a waveguide 208 for transmitting microwaves from the
generator to head 210 (for the embodiment of FIG. 2) or head 212
(for the embodiment of FIG. 3). The body protects the microwave
generator. The head attaches to a distal end of the body. A coaxial
cable could be substituted for the waveguide. The microwave
generator is operable to generate microwave energy while the tool
is disposed within the borehole using power supplied from the
surface via, for example, line 110. The microwave energy that is
generated is coupled with a microwave absorbing material disposed
within a head portion 210 of FIG. 2, of the tool or, in the example
of FIG. 3, within fluid circulated into the borehole or in a
portion of the rock formation adjacent to the downhole tool. The
microwave generator is thermally isolated from the head by distance
and/or by use of a thermal insulating material (not shown in the
drawings). Alternately, or additionally, the body may incorporate a
cooling system for the generator. An example of a cooling system
includes the use of fluid, such as drilling fluid, supplied to the
tool through tubing connected to the proximal end of the tool. The
fluid could, for example, enter the top or proximal end of the
tool, and flow past generator 206 and then out openings in the tool
nearer the distal end of the body 204 of the tool or in the head of
the tool. The generator and related equipment and wiring would be
enclosed within a suitable protective housing with heat exchanging
surfaces disposed on it.
[0015] The microwave generator may take the form of, for example, a
magnetron, a klystron or a travelling tube. It could,
alternatively, utilize solid state devices rather than vacuum
tubes. The generator 206 that is schematically illustrated includes
additional elements such as a power supply for rectifying and
stepping up voltage, an adaptor for coupling the generator to the
waveguide, an isolator for preventing reflected microwave energy
from entering the generator, and a controller and other
instrumentation for controlling and/or monitoring the operation of
the generator. The body can also house other auxiliary equipment,
such as instrumentation for reporting the temperature of various
parts of the generator and the head. The generator may be tuned to
operate at standard frequencies set aside for industrial
application or scientific applications, such as 915 MHz, 2.45 GHz,
5.8 GHz and 22.125 GHz. However, it could be tuned to a frequency
within the microwave range of 300 MHz to 300 GHz. The frequency
being chosen depending at least in part on the material that is
intended to be heated by the microwave energy from the
generator.
[0016] In the embodiment of FIG. 2, microwave absorbable material
is placed in head 210 and is heated by microwave energy generated
by the microwave generator. In the embodiment of FIG. 3, microwave
energy generated by the generator is radiated into either drilling
fluid containing microwave absorbable material and/or into the rock
formation adjacent to the tool through a radiating element (i.e. an
antenna) disposed within a microwave transparent head 212 or window
within head 212.
[0017] Referring only to FIG. 2, the head 210 is comprised of a
support structure, for example enclosure 212, for supporting a
plurality of microwave absorbing elements 214 comprised of
microwave absorbing material disposed within the head. The support
structure can include additional elements (not shown) for
positioning and retaining the element within the head. The
microwave absorbing material absorbs microwave energy at the
frequency or range of frequencies at which the generator operates,
thereby causing the material to heat. In this example, the
microwave absorbing material is a refractory, dielectric material.
The material preferably also has a relatively high loss factor.
Examples of a refractory dielectric material particularly suitable
for the downhole tool include silicon nitride (Si3N4), graphite,
and silicon carbide. A microwave absorbing element can be made or
fabricated by sintering a microwave absorbable compound into the
shape of, for example, a rod or pellet.
[0018] In the example of FIG. 2, the support structure is made of a
refractory material, with a melting point above the highest
temperature that the microwave absorbing material is intended to
operate. The supporting structure is machined or fabricated from a
material that is, in one embodiment of this example, transparent to
the microwave radiation. Portions of the structure exposed to the
environment of the wellbore are preferably made from a corrosion
and abrasion resistant material. Examples of corrosion resistant,
microwave-transparent materials suitable for this application
include sialon, an alloy containing silicon nitride and aluminum.
The structure transfers heat from the microwave absorbing material
214 to the environment surrounding the tool, in particular fluid
within the borehole, through conduction. The fluid then transfers
the heat by convection to the surrounding geological formation.
Although shown as enclosing microwave absorbing material, an
alternative embodiment of the head 210 could include openings for
permitting fluid at the bottom of the wellbore to flow through the
head and thereby directly contact the microwave absorbing
material.
[0019] Microwave energy transmitted from the waveguide 208 is
coupled to the microwave absorbable elements 214 by an applicator,
which is generally indicated by reference number 216. Although the
illustrated applicator comprises a feed horn, it is intended only
to be representative. Other types of applicators could be utilized,
including resonant, travelling-wave and near-field applicators.
Near-field applicators include open-ended waveguides, slotted
waveguides and antennas. An applicator may extend into the head,
depending on the type of applicator utilized. In the case of a
resonant applicator, a resonant cavity can be, for example, formed
within the head 210 and coupled with the waveguide. The cavity
could resonate in a single mode or a multi-mode.
[0020] Referring to FIG. 3, the head 212 has at least a window (not
illustrated) formed therein of a material that is transparent to
microwave radiation. The entire head can be made of such material,
or combination of materials. Portions of the structure exposed to
the environment of the wellbore are preferably made from a
corrosion and abrasion resistant material. Examples of materials
that are microwave transparent and resistant to corrosion and
abrasion include sialon. In this example, the waveguide terminates
in a near-field applicator, represented by antenna 218, for
radiating electromagnetic energy transmitted from the microwave
generator into the wellbore and/or surrounding formation. The
illustrated antenna is a dipole. However, other forms of antennae
can be used. Furthermore the radiation can be redirected or focused
to a particular area within formation predetermined patterns using
one or more reflecting surfaces, and can also be scattered using
stationary or dynamic antennae.
[0021] The foregoing description is of an exemplary and preferred
embodiments employing at least in part certain teachings of the
invention. The invention, as defined by the appended claims, is not
limited to the described embodiments. Alterations and modifications
to the disclosed embodiments may be made without departing from the
invention. The meaning of the terms used in this specification are,
unless expressly stated otherwise, intended to have ordinary and
customary meaning and are not intended to be limited to the details
of the illustrated structures or the disclosed embodiments.
* * * * *