U.S. patent application number 14/043835 was filed with the patent office on 2014-10-09 for electrical isolation of subterranean casing section.
This patent application is currently assigned to ELECTRO-PETROLEUM, INC. The applicant listed for this patent is ELECTRO-PETROLEUM, INC. Invention is credited to Marian Morys.
Application Number | 20140299312 14/043835 |
Document ID | / |
Family ID | 51653650 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140299312 |
Kind Code |
A1 |
Morys; Marian |
October 9, 2014 |
ELECTRICAL ISOLATION OF SUBTERRANEAN CASING SECTION
Abstract
A method and apparatus for electrically-enhanced oil recovery
from an oil-bearing subterranean formation are provided. An
isolation opening extends around the circumference of a casing to
provide a separation of the inflow section from an adjacent section
of the casing. A portion of the oil-bearing formation disposed on
the outside of the isolation opening is removed to form a void in
the oil-bearing formation adjacent the isolation opening. A
material having less electrical conductivity than the casing is
inserted into the void and the isolation opening to form an
insulative barrier.
Inventors: |
Morys; Marian; (Downingtown,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRO-PETROLEUM, INC |
VILLANOVA |
PA |
US |
|
|
Assignee: |
ELECTRO-PETROLEUM, INC
VILLANOVA
PA
|
Family ID: |
51653650 |
Appl. No.: |
14/043835 |
Filed: |
October 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61708235 |
Oct 1, 2012 |
|
|
|
Current U.S.
Class: |
166/65.1 |
Current CPC
Class: |
E21B 43/2401 20130101;
E21B 17/08 20130101 |
Class at
Publication: |
166/65.1 |
International
Class: |
E21B 43/16 20060101
E21B043/16 |
Claims
1. In a recovery apparatus employing electrical enhanced oil
recovery from an oil-bearing formation, the apparatus comprising a
wellhead having a hollow casing extending through at least one
non-oil-bearing formation into the oil bearing formation, the
casing having an inflow section with at least one inflow opening
into the oil-bearing formation for extracting oil using
electrically enhanced oil recovery, the method for improving the
efficiency of the extracting by forming an electrical isolation
barrier within the oil-bearing layer adjacent the inflow opening of
casing, comprising the steps of providing an isolation opening
extending around the circumference of the casing to provide a
separation of the inflow section from an adjacent section of the
casing, removing a portion of the formation disposed on the outside
of the isolation opening to form a void in the oil-forming
formation, providing a quantity of material into the void and the
isolation opening to form an insulative barrier.
2. The method of claim 1 including the steps of providing a second
isolation opening extending around the circumference of the casing
on the opposite side of the inflow opening to provide access
between the formation outside the casing and the interior of the
casing, removing a portion of the formation disposed on the outside
of the isolation opening to form a second void in said formation,
providing a quantity of insulative material sufficient to fill said
second void and the second isolation opening and filling said
second void and said isolation opening with said flowable material,
and treating the flowable material to solidify the flowable
material contained within the second void and the second isolation
opening to form a second isolation barrier.
3. The method of claim 1 wherein said isolation barrier and said
adjacent casing sections have interior surfaces, including the
further step of shaping the interior surface of said isolation
barrier to conform to the interior surfaces of the adjacent casing
sections.
4. The method of claim 1 including the further step of providing a
hollow cylindrical insulating liner formed of an electrical
insulation material, and applying the liner over the inward surface
of said isolation barrier.
5. The method of claim 1 including the further steps of providing
passages on the inner surface of said liner, and closing the
passages by a mandrel positioned within the inner surface.
6. The method clam 1, wherein the casing comprises multiple
sections, each having a hollow cylindrical shell of an electrically
conductive material, wherein the step of providing an isolation
opening is performed by removing a 360 degree ring of the
conductive material of the hollow cylindrical shell.
7. The method of claim 6 wherein said step of removing a 360 degree
ring is performed by cutting away the electrically conductive
material.
8. The method of claim 6 wherein the step of removing a 360 degree
ring is performed by applying a chemical material to the ring to
dissolve the same.
9. In a recovery apparatus employing electrical enhanced oil
recovery from an oil-bearing formation, the apparatus comprising a
wellhead having a hollow casing extending through at least one
non-oil-bearing formation, the casing having an inflow section with
at least one inflow opening into the oil-bearing formation for
extracting oil using electrically enhanced oil recovery, the method
for improving the efficiency of the extracting by forming
electrical isolation barriers within the oil-bearing layer on
opposite sides of the inflow opening of the casing, comprising the
steps of forming isolation openings extending substantially 360
degrees about the circumference of the casing on opposite sides of
said inflow openings to provide access between the oil-bearing
formation and the interior of the casing, removing a portion of the
oil-bearing formation disposed on the outside of each opening of
said casing to form voids in said formation, providing a quantity
of flowable material sufficient to fill said voids and said
isolation openings and injecting said material into said voids and
said isolation openings, and treating said flowable material to
solidify said flowable material contained within said voids and
said isolation openings to form isolation barriers interrupting
electrical communication between the inflow section and the
reminder of said casing.
10. Recovery apparatus for extracting oil using electrical enhanced
oil recovery from an oil-bearing formation comprising a wellhead
having a hollow casing with multiple sections extending through at
least one non-oil-bearing formation into the oil bearing formation,
the casing having an inflow section with at least one inflow
opening in registry with the oil-bearing formation for extracting
oil using electrically enhanced oil recovery, said inflow section
being separated from an adjacent one of said multiple sections by a
ring-shaped opening extending around the circumference of the
casing, and an isolation barrier mounted in said ring-shaped
opening to maintain the physical continuity of the casing and
operable to improve the efficiency of the extracting, the barrier
comprising electrically non-conductive material isolating said
inflow section from the adjacent section, the barrier having an
interior dimension substantially similar to the interior dimension
of the casing sections on both sides of the barrier, and an
exterior dimension extending beyond the exterior circumference of
said casing sections and into the formation surrounding said
ring-shaped opening between said adjacent casings sections.
11. Recovery apparatus according to claim 10 wherein said isolation
barrier material has flowable state when it is first inserted into
said ring-shaped opening and into the formation surrounding said
opening, and is curable into a solid state when the insertion is
complete.
Description
PRIORITY CLAIM
[0001] The present application claims priority under .sctn.119 to
U.S. Provisional Application No. 61/708,235 filed Oct. 1, 2012. The
entire disclosure of the foregoing application is hereby
incorporated herein by reference.
FIELD OF INVENTION
[0002] The present invention relates to a method for enhancing the
production of oil from subterranean oil reservoirs. In particular,
the present invention provides an improved system that uses an
electric current passing through the oil reserves to enhance oil
recovery.
BACKGROUND OF THE INVENTION
[0003] Recovery of heavy oil poses many challenges related to lack
of oil mobility both in the formation and during artificial lift.
Steam assisted gravity drainage is commonly used to improve or
enable heavy oil production.
[0004] Methods for inducing electrical current into oil-bearing
formations to improve recovery of oil reserves are described in
U.S. Pat. Nos. 3,782,465, 4,495,990, 6,877,556, and 7,325,604,
issued Feb. 5, 2008, the entire contents of which are incorporated
herein by reference.
SUMMARY OF THE INVENTION
[0005] In light of the foregoing, the present invention addresses
provides a method and apparatus for overcoming shortcomings of the
prior art. To direct current flow through the oil bearing formation
it is desirable to limit the extent of at least one electrode to
the oil bearing formation. In accordance with one embodiment of
this invention, this is accomplished by placing electrical
isolating barriers projecting into the oil bearing formation from
the casing at the top and the bottom of oil bearing formation. If
the production casing does not extend past the bottom boundary of
the oil bearing formation then only one isolating barrier is needed
on top of the formation.
[0006] According to one aspect, the present invention provides a
method for recovering oil from an oil-bearing subterranean
formation employing a hollow well casing having an inflow section
providing fluid flow from the oil-bearing formation into the
casing. The method includes the step of providing an isolation
opening extending around the circumference of the casing to provide
a separation of the inflow section from an adjacent section of the
casing. A portion of the oil-bearing formation disposed on the
outside of the isolation opening is removed to form a void in the
oil-bearing formation adjacent the isolation opening. A material
having less electrical conductivity than the casing is inserted
into the void and the isolation opening to form an insulative
barrier.
[0007] According to another aspect, the present invention also
provides a recovery apparatus for extracting oil using electrical
enhanced oil recovery from an oil-bearing formation comprising a
wellhead having a hollow casing with multiple sections extending
through at least one non-oil-bearing formation into the oil bearing
formation. The casing has an inflow section with at least one
inflow opening in registry with the oil-bearing formation for
extracting oil using electrically enhanced oil recovery. The inflow
section is separated from an adjacent one of said multiple sections
by a ring-shaped opening extending about the full 360 degree
circumference of the casing, and an isolation barrier mounted in
the ring-shaped opening. The barrier is comprises electrically
non-conductive material isolating the inflow section from the
adjacent section. The barrier has an interior dimension similar to
the interior dimension of the casing sections on both sides of the
barrier, and an exterior dimension extending beyond the exterior
circumference of the casing sections and into the formation
surrounding the ring-shaped opening between said adjacent casings
sections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of an oil-field casing modified
in accordance with the present invention to provide isolating
barriers; within the oil-bearing formation;
[0009] FIG. 2 is a diagrammatic view (not to scale) of the
oil-field casing of FIG. 1, showing the current flow from the
perforated or slotted inflow section of the casing when used with a
remote surface electrode;
[0010] FIG. 3 is a diagrammatic view (not to scale) of the
oil-field casing of FIG. 1, showing the current flow from the
perforated or slotted inflow section of the casing when used with a
two-section casing, having isolated upper and lower casing sections
above and below the perforated or slotted inflow section which
serve as remote electrodes;
[0011] FIG. 4 is a diagrammatic view similar to FIG. 2 (not to
scale), showing the casing terminating at its lower end in a
lateral extension;
[0012] FIG. 5 is a perspective view of an isolating barrier; with a
portion broken away;
[0013] FIG. 6 is a vertical sectional view of an isolating barrier
insulated from the center of the casing by a layer of insulation;
and
[0014] FIG. 7 is an enlarged fragmentary perspective view showing
the components of the isolating barrier when the invention is used
in a bore hole filled with conductive fluids.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] Referring now to FIG. 1 a system for recovering subterranean
oil reserves is illustrated. The system includes a well 10
extending into an oil-bearing formation 46. A production casing 44
extending into the well 10 has a perforated inflow section 45
adjacent the oil-bearing formation that allows fluid flow from the
subterranean formations into the casing. A power source 20 is
operable to induce an electrical current into the oil-bearing
formation and a pump 41 b pumps oil and other fluids from the
casing up to the surface through production tubing 41a.
[0016] The details of the well structure will now be described in
greater detail. The well 10 extends through subterranean layers 47
over the oil-bearing formation 46 and may extend into subterranean
layers below the oil bearing formation, referred to as underburden.
The production casing 44 is an axially elongated conduit extending
into the well. The casing may be comprised of any of variety of
materials, including, but not limited to electrically-conductive
materials, such as metal. In the present instance, the production
casing is formed of steel.
[0017] The production casing 44 is in fluid communication with a
wellhead 41 from which the production casing hangs. An intermediate
casing 13 surrounding the production casing extends into the
overburden 47 and may be retained in place by a cement sheath
surrounding the intermediate casing. A surface casing 12 extending
into the ground adjacent the wellhead 41 surrounds the intermediate
casing 13. The surface casing may be retained in place by a cement
sheath surrounding the surface casing.
[0018] A perforated inflow section 45 in the casing 44 allows fluid
to flow into the casing 45 from the surrounding oil-bearing
formation. The perforations extend around the circumference of the
casing and may be any of a variety of perforations, such as
variously-shaped holes or slots, such as longitudinally-extending
slots.
[0019] A pump 41 b within the casing 44 is operable to pump oil
and/or other fluids through the casing 44 and/or out of the well
10. In particular, an elongated conduit, referred to as production
tubing, may extend into the production casing 44 so that the bottom
edge of the production tubing is positioned adjacent the perforated
inflow section 45. The pump 41 b may be in fluid communication with
the production tubing 41a so that the pump 41 b pumps fluid from
the casing up to the surface through the production tubing. In this
way, the pump 41b may be positioned adjacent the inflow section 45
of the casing 44.
[0020] The system further includes a power source 20 for inducing
an electrical current into the subterranean layers and in
particular into the oil-bearing layer 46. By inducing an electrical
current into the oil bearing formation 46, which enhances oil
production. For instance, the electrical current induced into the
oil may provide one or more of the following affects on the fluid
in the oil-bearing formation: reduction of oil viscosity due to
temperature rise resulting from passage of electrical current;
electro-kinetic processes, and/or electrochemical reactions that
affect the properties of fluid and the medium matrix.
[0021] The power source 20 may provide an AC or DC current and is
connected to two electrically conductive elements that operate as
electrodes. For instance, the production casing 44 may be formed of
metal and may be connected with the power source so that the
production casing operates as one of the electrodes. The second
electrode is located remotely from the casing so that the
oil-bearing formation 46 is between the two electrodes. For
instance, the second electrode may be a metallic plate or other
conductive structure positioned at the surface or the casing of an
adjacent well may be formed of electrically conductive material,
such as metal, so that the adjacent well casing operates as the
second electrode. Regardless of whether the second electrode is on
the surface or subsurface, both electrodes are connected to the
power source 20 to provide a current flow between the two
electrodes.
[0022] In some applications, if the production casing 44 of a well
10 is used as an electrode, the induced current from the power
source 20 may not pass through the oil in the oil-bearing formation
46 for a variety of reasons. One issue that may arise is due to the
differing resistivities of the subterranean layers that cause only
a small portion of the current to flow through the oil-bearing
formation. Specifically, the majority of the induced current may
bypass the oil-bearing formation 46, due to higher electrical
conductivity in the overburden and underburden 47 surrounding the
oil-bearing formations. Additionally, the surface area of the
electrode in contact with the oil-bearing formation 46 is
substantially smaller than that in contact with the rest of the
formation, which can lead to only a small portion of the induced
current passing through the oil in the oil-bearing formation.
[0023] To improve the current flow through the oil-bearing
formation, the system includes one or more electrically-insulative
barriers 49 along the length of the production casing 44. The
barrier 49 operates to substantially isolate electrically one
portion of the production casing from other portion or portions of
the casing. For instance, as shown in FIG. 1, the power source 20
is connected with the inflow section 45 of the production casing
44. The barriers 49 substantially isolate the inflow section 45
electrically from the rest of the production casing. Accordingly,
the induced current will tend to flow through the oil-bearing
formation rather than along the production casing 44.
[0024] The barrier 49 is a radially extending structure that
protrudes into the subterranean layers. Specifically, in the
present instance, an upper barrier extends radially outwardly from
the casing 44 adjacent the upper portion of the oil-bearing
formation 46. If the production casing 44 extends through the
oil-bearing formation, a lower barrier 49 may also be utilized. For
instance, as shown in FIG. 1, a second barrier extends radially
outwardly into the lower portion of the oil-bearing formation. In
this way, a portion of the casing 44 operating as an electrode is
electrically isolated from another portion of the casing, and in
particular, is isolated from the portion of the casing above and
below the barriers 49.
[0025] Although the barrier 49 has been described above as an
element formed of an insulative material, it should be understood
that the barrier may be configured in other manners that
electrically isolate the portion of the casing 44 acting as the
electrode from the rest of the casing. Specifically, a short length
of the casing could be removed from between the electrode portion
of the casing and the reset of the casing. For instance, the casing
could be severed around the entire circumference of the casing so a
gap is formed between the inflow portion 45 of the casing and the
portion of the casing above the inflow portion. In this way, there
is a break in the conductive path of the casing between the inflow
portion 45 and the upper portion of the casing. Similarly, a
section of the casing can be removed from the casing adjacent the
lower portion of the oil-bearing formation 46.
[0026] Although the barriers 49 may be configured so that they are
installed when the production casing 44 is installed into the well,
in the typical scenario, the barriers 49 are installed after the
casing 44 is already installed in the well 10. For instance,
referring to FIGS. 1 and 5-6, a short section of the production
casing may be cut-out. In the present instance, a section of the
production casing approximately one foot long or less is severed
from the production casing so that the production casing is not a
continuous length of conduit. The casing 44 may be severed using
any of a variety of techniques, such as milling, explosive cutting,
jet milling, and/or chemical dissolution of the area of the casing
where the opening or window is desired.
[0027] After severing the casing across the entire cross-section of
the casing, the subterranean formation adjacent the severed section
is also cut away to form a void or cavity 52 extending around the
circumference of the production casing adjacent the opening. The
cavity 52 extends radially outwardly into the subterranean layer,
which in the present instance is the oil-bearing formation 46. For
instance, the cavity may extend approximately 10-20 inches away
from the casing. The cavity 52 also extends axially along the
length of the casing 44 so that the length of the cavity along the
length of the casing is longer than the length of casing that is
severed from the casing.
[0028] After the casing is severed and the cavity is formed,
non-conductive material is inserted into the cavity 52 and into the
window formed in the casing 44. Any of a variety of non-conductive
materials can be used to fill the cavity to form the barrier
element. In the present instance, the non-conductive material is a
readily deformable material, such as a liquid or generally flowable
viscous material that is injected into the cavity 52 and into the
window in the casing. If the non-conductive material is fluid or a
generally flowable material, preferably the material is curable so
that the material forms a generally rigid or stable structure in
the form of the barrier 49. Although the non-conductive material
can be any of a variety of generally insulative materials, such as
plastic or rubber, in the present instance the material is an
insulative epoxy injected into the cavity that cures to form a
generally solid structure that electrically isolates and/or
insulates the portion of the casing between the barriers 49 from
the rest of the casing 44. When installing barriers both above and
below the oil-bearing formation, the first barrier is allowed to
set and solidify, before the second circumferential opening is made
in the casing, so that the casing section between the barriers is
stabilized while the second opening is being formed.
[0029] When the borehole will contain electrically conductive
fluids, the fluid in the casing may provide an electrical pathway
that will dissipate the electric flow from the power source. For
instance, one of the fluids in the well may be salt water that may
provide a conductive path. Therefore, an interior barrier may be
provided to impede the induced current from traveling through the
salt water along the length of the casing rather than through the
oil-bearing formation. The interior barrier insulates the interior
of the borehole, especially in the areas of the isolating barriers
49. FIGS. 6 and 7 illustrate an isolating barrier 52 between
adjacent sections 44a and 44b of the casing 44. An insulating liner
55 covers the interior surface of the barrier 52. The liner 55 has
a plurality of longitudinal passages 56 extending along its length
to allow fluids to travel past the barrier. The passages 56 are
closed by a fiberglass mandrel 57 within the liner 55. The closed
passages may serve as conduits for use during the formation of the
isolating barrier 52.
[0030] Referring now to FIG. 2, an alternate installation is
illustrated in which a well casing 120 is used in conjunction with
a surface electrode 121 and a power supply 122. The well casing 120
has an inflow section with perforations or slots forming an inflow
section similar to the installation illustrated in FIG. 1. The
inflow section in FIG. 2 is positioned in the oil-bearing formation
146 which falls between the adjoining overburden and underburden
147. The current flow is indicated by arrows 123.
[0031] Another alternate installation is illustrated in FIG. 3 in
which a well casing 149 is separated into an upper section 149a,
and a lower section 149c by a perforated or slotted inflow section
149b. Isolating barriers 159a and 159b are mounted above and below
the inflow section 149b having perforations or slots to
electrically isolate the inflow section 149b from the upper and
lower sections 149a and 149c. A power supply 152 has one side 150
connected to the inflow section and the other side connected to the
upper and lower sections. The current flow generated by the power
supply 152 is indicated by the arrows 153.
[0032] FIG. 4 shows an installation where a well casing 160 is used
in conjunction with a surface electrode 161 and a power supply 162.
The well casing 160 terminates in a lateral extension having a
first section 169a, a perforated or slotted inflow section 169b,
and a terminal section 169c in the oil-bearing formation 166 which
falls between the adjoining overburden and underburden 147. The
inflow section 169b is isolated from the sections 169a and 169c by
isolating barriers 179a and 179b. The current flow is indicated by
arrows 163.
[0033] In the embodiments illustrated in FIGS. 2 and 3, two
electrical isolating barriers 159a and 159b are positioned about
the perimeter of the casing on opposite sides of the inflow
section, so as to divert the electric current flow in either
direction. However if the casing terminates beyond the inflow
section within the oil-bearing formation, the second barrier 159b
may be omitted.
[0034] While particular embodiments of the invention have been
illustrated and described, changes or modifications may be made
without departing from the inventive concepts as set forth in the
following claims:
* * * * *