U.S. patent application number 16/088580 was filed with the patent office on 2019-04-18 for processes for producing hydrocarbons from a reservoir.
The applicant listed for this patent is NEXEN ENERGY ULC. Invention is credited to Thomas HARDING.
Application Number | 20190112907 16/088580 |
Document ID | / |
Family ID | 58646035 |
Filed Date | 2019-04-18 |
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United States Patent
Application |
20190112907 |
Kind Code |
A1 |
HARDING; Thomas |
April 18, 2019 |
PROCESSES FOR PRODUCING HYDROCARBONS FROM A RESERVOIR
Abstract
In one aspect, there is provided a process for producing
hydrocarbons from a reservoir, comprising: within the reservoir,
electrically heating a liquid heating fluid such that the liquid
heating fluid is evaporated to produce a gaseous heating fluid that
heats the liquid hydrocarbon material within the reservoir such
that the heated liquid hydrocarbon material is mobilized and such
that the gaseous heating fluid is condensed to produce a condensed
heating fluid, wherein the liquid heating fluid includes at least a
fraction of the condensed heating fluid such that at least a
fraction of the condensed heating fluid is refluxed; and producing
a fluid including the mobilized hydrocarbon material; wherein the
hydrocarbon reservoir is spaced apart from the earth's surface by a
minimum distance of less than 75 metres.
Inventors: |
HARDING; Thomas; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEXEN ENERGY ULC |
Calgary |
|
CA |
|
|
Family ID: |
58646035 |
Appl. No.: |
16/088580 |
Filed: |
May 13, 2016 |
PCT Filed: |
May 13, 2016 |
PCT NO: |
PCT/CA2016/000142 |
371 Date: |
September 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 43/2401 20130101;
E21B 36/04 20130101; E21B 43/168 20130101 |
International
Class: |
E21B 43/24 20060101
E21B043/24; E21B 43/16 20060101 E21B043/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2016 |
CA |
2,929,924 |
Claims
1. A process for producing hydrocarbon material from a hydrocarbon
reservoir comprising: within the reservoir, electrically heating a
liquid heating fluid such that the liquid heating fluid is
evaporated to produce a gaseous heating fluid that heats the liquid
hydrocarbon material within the reservoir such that the heated
liquid hydrocarbon material is mobilized and such that the gaseous
heating fluid is condensed to produce a condensed heating fluid,
wherein the liquid heating fluid includes at least a fraction of
the condensed heating fluid such that at least a fraction of the
condensed heating fluid is refluxed; and producing a fluid
including the mobilized hydrocarbon material; wherein the
hydrocarbon reservoir is spaced apart from the earth's surface by a
minimum distance of less than 75 metres.
2. A process for producing hydrocarbon material from a hydrocarbon
reservoir comprising: within the reservoir, electrically heating a
liquid heating fluid such that the liquid heating fluid is
evaporated to produce a gaseous heating fluid; heating hydrocarbon
material with the gaseous heating fluid such that the heated
hydrocarbon material is mobilized and such that the gaseous heating
fluid is condensed to produce a condensed heating fluid; wherein
the liquid heating fluid includes at least a fraction of the
condensed heating fluid such that at least a fraction of the
condensed heating fluid is refluxed; and producing a produced fluid
including at least the mobilized hydrocarbon material; wherein the
hydrocarbon reservoir is spaced apart from the earth's surface by a
minimum distance of less than 75 metres
3. A process for producing hydrocarbon material from a hydrocarbon
reservoir comprising a high pressure phrase and a low pressure
phase, wherein the low pressure phase follows the high pressure
phase; wherein: the low pressure phase includes, while the
reservoir is disposed below a predetermined low pressure: within
the reservoir, electrically heating a liquid heating fluid such
that the liquid heating fluid is evaporated to produce a gaseous
heating fluid that heats the liquid hydrocarbon material within the
reservoir such that the heated liquid hydrocarbon material is
mobilized and such that the gaseous heating fluid is condensed to
produce a condensed heating fluid, wherein the liquid heating fluid
being evaporated includes at least a fraction of the condensed
heating fluid such that at least a fraction of the condensed
heating fluid is refluxed; and producing a production fluid
including the mobilized hydrocarbon material; and the high pressure
phase includes, while the reservoir is disposed above a
predetermined high pressure: within the reservoir, electrically
heating a liquid heating fluid such that the liquid heating fluid
is evaporated to produce a gaseous heating fluid that heats the
liquid hydrocarbon material within the reservoir such that the
heated liquid hydrocarbon material is mobilized and such that the
gaseous heating fluid is condensed to produce a condensed heating
fluid, wherein the liquid heating fluid being evaporated includes
at least a fraction of the condensed heating fluid such that at
least a fraction of the condensed heating fluid is refluxed; and
producing a production fluid including the mobilized hydrocarbon
material.
4. (canceled)
5. The process as claimed in claim 3: wherein, during the low
pressure phase, the predetermined low pressure is less than 1500
kPa.
6. The process as claimed in claim 3: wherein, during the low
pressure phase, the predetermined low pressure is less than 1000
kPa.
7. The process as claimed in claim 3: wherein, during the high
pressure phase, the predetermined high pressure is greater than
1750 kPa.
8. The process as claimed in claim 3: wherein, during the high
pressure phase, the predetermined high pressure is greater than
2000 kPa.
9. The process as claimed in claim 3; wherein the ratio of the
predetermined high pressure to the predetermined low pressure is
greater than 1.5.
10. The process as claimed in claim 3; wherein the ratio of the
predetermined high pressure to the predetermined low pressure is
greater than 2.
11. The process as claimed in claim 3; wherein the ratio of the
predetermined high pressure to the predetermined low pressure is
greater than 3.
12. The process as claimed in claim 3; wherein the duration of the
low pressure phase is at least one (1) month.
13. The process as claimed in claim 3; wherein the duration of the
high pressure phase is at least one (1) month.
14. The process as claimed in claim 3; wherein the high pressure
phase and the low pressure phase define a cycle, and the cycle is
repeated at least once.
15. The process as claimed in claim 3; wherein the high pressure
phase and the low pressure phase define a cycle, and the cycle is
repeated at least twice.
16. The process as claimed in claim 3; further comprising: during
at least a fraction of the duration of the low pressure phase,
supplying supplemental liquid heating fluid to the reservoir from a
source at the surface, such that the liquid heating fluid being
evaporated includes the supplemental liquid heating fluid.
17. The process as claimed in claim 3, further comprising: during
at least a fraction of the duration of the high pressure phase,
supplying supplemental liquid heating fluid to the reservoir from a
source at the surface, such that the liquid heating fluid being
evaporated includes the supplemental liquid heating fluid.
18. The process as claimed in claim 3, further comprising: during a
fraction of the duration of the low pressure phase, suspending the
producing of the production fluid.
19. The process as claimed in claim 3, further comprising: during a
fraction of the duration of the high pressure phase, suspending the
producing of the production fluid.
20. The process as claimed in claim 3, further comprising: during a
fraction of the duration of the low pressure phase, suspending the
producing of the production fluid; and during at least a fraction
of the time period while the producing is suspended, supplying
supplemental liquid heating fluid to the reservoir from a source at
the surface, such that the liquid heating fluid being evaporated
includes the supplemental liquid heating fluid.
21. The process as claimed in claim 3, further comprising: during a
fraction of the duration of the high pressure phase, suspending the
producing of the production fluid; and during at least a fraction
of the time period while the producing is suspended, supplying
supplemental liquid heating fluid to the reservoir from a source at
the surface, such that the liquid heating fluid being evaporated
includes the supplemental liquid heating fluid.
Description
FIELD
[0001] The present disclosures relates to improvements in
production of hydrocarbon material from hydrocarbon-bearing
reservoirs.
BACKGROUND
[0002] Thermal enhanced oil recovery methods are used to recover
bitumen and heavy oil from hydrocarbon reservoirs. Petroleum
reservoirs contain solid matrix, oil and water and all thermal
recovery processes used for heavy oil recovery employ heat to raise
the temperature of the oils to reduce their viscosity. In the
process, all of the materials present in the reservoir must be
heated in order to achieve heating of the oil. In the present
disclosure, the water present in the formation is used as the
primary heat transfer medium, supplemented with a minimal amount of
injected fluid. The most dominant of the thermal recovery methods
is steam-assisted gravity drainage ("SAGD"). SAGD operations are
impaired by energy losses and hydraulic pressure losses suffered by
fluids being conducted through the injection and production wells.
As well, SAGD operations are particularly susceptible to fluid
incursions from active water zones, which may disrupt the SAGD
process. The SAGD process also suffers from high capital and
operating costs making SAGD project economics marginal and
susceptible to changes in commodity price. SAGD involves the use of
large amounts of water and consumes significant quantities of fuel
for steam generation causing large carbon dioxide emissions.
SUMMARY
[0003] In one aspect, there is provided a process for producing
hydrocarbons from a reservoir, comprising: within the reservoir,
electrically heating a liquid heating fluid such that the liquid
heating fluid is evaporated to produce a gaseous heating fluid that
heats the liquid hydrocarbon material within the reservoir such
that the heated liquid hydrocarbon material is mobilized and such
that the gaseous heating fluid is condensed to produce a condensed
heating fluid, wherein the liquid heating fluid includes at least a
fraction of the condensed heating fluid such that at least a
fraction of the condensed heating fluid is refluxed; and producing
a fluid including the mobilized hydrocarbon material; wherein the
hydrocarbon reservoir is spaced apart from the earth's surface by a
minimum distance of less than 75 metres.
[0004] In another aspect, there is provided a process for producing
hydrocarbon material from a hydrocarbon reservoir comprising:
within the reservoir, electrically heating a liquid heating fluid
such that the liquid heating fluid is evaporated to produce a
gaseous heating fluid; heating hydrocarbon material with the
gaseous heating fluid such that the heated hydrocarbon material is
mobilized and such that the gaseous heating fluid is condensed to
produce a condensed heating fluid; wherein the liquid heating fluid
includes at least a fraction of the condensed heating fluid such
that at least a fraction of the condensed heating fluid is
refluxed; and producing a produced fluid including at least the
mobilized hydrocarbon material; wherein the hydrocarbon reservoir
is spaced apart from the earth's surface by a minimum distance of
less than 75 metres.
[0005] In another aspect, there is provided a process for producing
hydrocarbon material from a hydrocarbon reservoir comprising a high
pressure phrase and a low pressure phase, wherein the low pressure
phase follows the high pressure phase;
wherein:
[0006] the low pressure phase includes, while the reservoir is
disposed below a predetermined low pressure: [0007] within the
reservoir, electrically heating a liquid heating fluid such that
the liquid heating fluid is evaporated to produce a gaseous heating
fluid that heats the liquid hydrocarbon material within the
reservoir such that the heated liquid hydrocarbon material is
mobilized and such that the gaseous heating fluid is condensed to
produce a condensed heating fluid, wherein the liquid heating fluid
being evaporated includes at least a fraction of the condensed
heating fluid such that at least a fraction of the condensed
heating fluid is refluxed; and [0008] producing a production fluid
including the mobilized hydrocarbon material;
[0009] and
[0010] the high pressure phase includes, while the reservoir is
disposed above a predetermined high pressure: [0011] within the
reservoir, electrically heating a liquid heating fluid such that
the liquid heating fluid is evaporated to produce a gaseous heating
fluid that heats the liquid hydrocarbon material within the
reservoir such that the heated liquid hydrocarbon material is
mobilized and such that the gaseous heating fluid is condensed to
produce a condensed heating fluid, wherein the liquid heating fluid
being evaporated includes at least a fraction of the condensed
heating fluid such that at least a fraction of the condensed
heating fluid is refluxed; and [0012] producing a production fluid
including the mobilized hydrocarbon material.
[0013] In another aspect, there is provided
A process for producing hydrocarbon material from a hydrocarbon
reservoir comprising a high pressure phrase of the process and a
low pressure phase of the process, wherein the low pressure phase
follows the high pressure phase; wherein:
[0014] the low pressure phase includes, while the reservoir is
disposed below a predetermined low pressure: [0015] within the
reservoir, electrically heating a liquid heating fluid such that
the liquid heating fluid is evaporated to produce a gaseous heating
fluid; [0016] heating hydrocarbon material with the gaseous heating
fluid such that the heated hydrocarbon material is mobilized and
such that the gaseous heating fluid is condensed to produce a
condensed heating fluid; [0017] wherein the liquid heating fluid
being evaporated includes at least a fraction of the condensed
heating fluid such that at least a fraction of the condensed
heating fluid is refluxed; and [0018] producing a production fluid
including at least the mobilized hydrocarbon material;
[0019] and
[0020] the high pressure phase includes, while the reservoir is
disposed above a predetermined high pressure: [0021] within the
reservoir, electrically heating a liquid heating fluid such that
the liquid heating fluid is evaporated to produce a gaseous heating
fluid; [0022] heating hydrocarbon material with the gaseous heating
fluid such that the heated hydrocarbon material is mobilized and
such that the gaseous heating fluid is condensed to produce a
condensed heating fluid; [0023] wherein the liquid heating fluid
being evaporated includes at least a fraction of the condensed
heating fluid such that at least a fraction of the condensed
heating fluid is refluxed; and [0024] producing a production fluid
including at least the mobilized hydrocarbon material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the drawings, embodiments of the invention are
illustrated by way of example. It is to be expressly understood
that the description and drawings are only for the purpose of
illustration and as an aid to understanding, and are not intended
as a definition of the limits of the invention.
[0026] Embodiments will now be described, by way of example only,
with reference to the attached figures, wherein:
[0027] FIG. 1 is a schematic illustration of a system, with a
single well, used to implement an embodiment of the process;
[0028] FIG. 2 is a schematic illustration of a system, with a
non-production well and a production well, used to implement an
embodiment of the process; and
[0029] FIG. 3 is a sectional elevation view of a heating assembly
of a system used to implement an embodiment of the process.
DETAILED DESCRIPTION
[0030] There is provided a process for producing liquid hydrocarbon
material from a hydrocarbon reservoir 1000. Liquid hydrocarbon
material is liquid material that consists of a least one
hydrocarbon compound.
[0031] In some embodiments, for example, the liquid hydrocarbon
material includes bitumen. In some of these embodiments, for
example, the bitumen is a liquid hydrocarbon material with an API
gravity less than, or equal to, 10, and with an in situ viscosity
of greater than 10,000 centipoise. In some embodiments, for
example, the liquid hydrocarbon material includes heavy oil.
[0032] In some embodiments, for example, the hydrocarbon reservoir
1000 is an oil sands reservoir. In some embodiments, for example,
the hydrocarbon reservoir is a heavy oil reservoir. In some
embodiments, for example, the hydrocarbon reservoir is disposed
subsea.
[0033] In some embodiments, for example, the process includes:
within the reservoir 1000, electrically heating a liquid heating
fluid such that the liquid heating fluid is evaporated to produce a
gaseous heating fluid that heats the liquid hydrocarbon material
within the reservoir such that the heated liquid hydrocarbon
material is mobilized and such that the gaseous heating fluid is
condensed to produce a condensed heating fluid, wherein the liquid
heating fluid includes at least a fraction of the condensed heating
fluid such that at least a fraction of the condensed heating fluid
is refluxed; producing a fluid including the mobilized hydrocarbon
material.
[0034] In some embodiments, for example, the process includes:
[0035] within the reservoir 1000, electrically heating a liquid
heating fluid such that the liquid heating fluid is evaporated to
produce a gaseous heating fluid;
[0036] heating hydrocarbon material with the gaseous heating fluid
such that the heated hydrocarbon material is mobilized and such
that the gaseous heating fluid is condensed to produce a condensed
heating fluid;
[0037] wherein the liquid heating fluid includes at least a
fraction of the condensed heating fluid such that at least a
fraction of the condensed heating fluid is refluxed;
[0038] producing a produced fluid including at least the mobilized
hydrocarbon material.
[0039] In some embodiments, for example, the produced fluid may
also include some heating fluid.
[0040] In some embodiments, for example, the liquid heating fluid
is comprised mainly of the refluxing condensed heating fluid, and
is, occasionally, supplemented by additional liquid heating fluid
that is supplied downhole into the reservoir from a source of
liquid heating fluid disposed at the surface.
[0041] In some embodiments, for example, the liquid heating fluid
includes formation water that is resident within the hydrocarbon
reservoir, or may include liquid heating fluid (for example, water)
that is supplied into the hydrocarbon reservoir from a source at
the surface, or may include both of the formation water and the
injected heating fluid.
[0042] By refluxing the liquid heating fluid within the reservoir,
heat losses are avoided, when compared to conducting a heating
fluid, such as steam, from the surface and into the reservoir, such
as during a steam-assisted gravity drainage ("SAGD) operation. Heat
losses are attributable to the production of the condensed heating
fluid (i.e. steam condensate) along with the heated and mobilized
bitumen through the production well to the surface. The steam
condensate is at or near saturated steam temperature as it is
produced into the well, and heat losses occur as the produced fluid
are conducted from the reservoir to the surface facilities. In the
process of separating the oil from the water at the surface,
additional heat is lost. In many SAGD operations, the produced
water is further cooled to allow for treatment to render it
suitable for recycling as boiler feedwater. Thus, if the water is
"refluxed" within the reservoir, instead of being produced, the
heat losses associated with the production and recycling of
produced water are avoided.
[0043] In those embodiments where at least a fraction of the liquid
heating fluid is being supplied from above the surface, in some of
these embodiments, for example, the ratio of the volumetric rate at
which the supplied liquid heating fluid is being supplied to the
rate at which heat energy is being delivered by the electric heater
is less than 25 cubic metres per day per megawatt, such as, for
example, less than 10 cubic metres per day per megawatt.
[0044] In some embodiments, for example, the liquid heating fluid
includes water, such that, upon evaporation, steam is produced. The
steam is conducted to the hydrocarbon material within the
reservoir, and heats the hydrocarbon material, thereby effecting
mobilization of the hydrocarbon material, while also effecting the
condensation of the steam. In some embodiments, for example, at
least some of the condensed steam then drains into a collection
reservoir, where it is re-evaporated by an electric heater disposed
within the collection reservoir.
[0045] In some embodiments, for example, the liquid heating fluid
may include any combination of an anti-foaming chemical, a
corrosion inhibitor, a scale inhibitor, and solvent material that
is soluble within the hydrocarbon material. In some embodiments,
for example, the solvent material includes at least one hydrocarbon
compound, wherein the at least one hydrocarbon compound includes a
total number of carbon atoms of between three (3) and ten (10),
such as between five (5) and seven (7).
[0046] For oil sands formations, and where the liquid heating
fluid, in the evaporated state, is steam, or is substantially
steam, the cycle of evaporation, condensing and re-evaporation
results in the creation of a steam chamber.
[0047] In some embodiments, for example, at least a fraction of the
reflux is effected by an electric heater that is disposed within
the hydrocarbon reservoir. In some embodiments, for example,
electric heater includes an electrically resistive heater. In some
embodiments, for example, the term "electric heater" covers heaters
that effect electromagnetic heating.
[0048] In some embodiments, for example, the electric heater is
disposed in indirect heat transfer communication with at least a
fraction of the condensed heating fluid.
[0049] In some embodiments, for example, the electric heater is
disposed within a collection reservoir, and the collection
reservoir receives reservoir fluid from the hydrocarbon reservoir.
The reservoir fluid includes the mobilized hydrocarbon material and
condensed heating fluid. In some embodiments, for example, the
collected reservoir fluid is free, or substantially free, of the
liquid heating fluid. In this respect, the electrical heating by
the electric heater is such that the collected reservoir fluid is
free, or substantially free, of the liquid heating fluid. In some
embodiments, for example, the collected reservoir fluid consists
of, or substantially consists of, the mobilized hydrocarbon
material. In this respect, the electrical heating by the electric
heater is such that the collected reservoir fluid the collected
reservoir fluid consists of, or substantially consists of, the
mobilized hydrocarbon material. The collected reservoir fluid,
consisting of, or substantially consisting of, the mobilized
hydrocarbon material, is disposed in heat transfer fluid
communication with the condensed heating fluid that is disposed
externally of the collection reservoir. In this respect, upon
heating by the electric heater, the collected reservoir fluid
concomitantly effects the transfer of such heat imparted by the
electric heater to the condensed heating fluid, thereby effecting
evaporation of the condensed heating fluid. In some of these
embodiments, for example, the heating of the collected reservoir
fluid, consisting of, or substantially consisting of, the mobilized
hydrocarbon material (and, in some embodiments, for example, being
free, or substantially free of heating fluid), is such that the
collected reservoir fluid is disposed at a temperature of less than
350 degrees Celsius, such as, for example, less than 300 degrees
Celsius, such as, for example, less than 275 degrees Celsius, such
as, for example less than 250 degrees Celsius.
[0050] Referring to FIG. 1, in some embodiments, for example, the
process is effected with a single well 102. In this respect, a
system 100 is provided for effecting the process, and includes the
well 102 which is used for both production of the produced fluid as
well as for effecting the entirety of the reflux of the liquid
heating fluid that is effecting mobilization of the hydrocarbon
material (i.e. a second well is not being used to contain an
electric heater to effect the refluxing).
[0051] The produced fluid is produced through the well 102. In some
embodiments, for example, production is effected by artificial
lift, such as by a downhole pump (such as, for example, an electric
submersible pump) and/or by gas lift.
[0052] The well 102 extends into the hydrocarbon reservoir 1000
from the surface. The well 102 includes a collection reservoir 108
for collecting reservoir fluids. The reservoir fluids include
mobilized hydrocarbon material and condensed heating fluid. In some
embodiments, for example, the reservoir fluid being collected
within the well 102 is free, or substantially free, of heating
fluid. In some embodiments, for example, the reservoir fluid being
collected within the production well consists of, or substantially
consists of, mobilized hydrocarbon material Such collected
reservoir fluid 110 may be in heat transfer communication with the
condensed heating fluid, such as, for example, condensed heating
fluid that is disposed externally of the production well 102. In
some embodiments, for example, the collected reservoir fluid 110
may include the mobilized hydrocarbon material and condensed
heating fluid.
[0053] An electric heater 104 is disposed within the well 102 and,
more specifically, within the collection reservoir 108 of the well
102. The collection reservoir includes reservoir fluid that has
collected therein. As mentioned above, the reservoir fluid includes
mobilized hydrocarbon material, and may also include condensed
heating fluid.
[0054] The electric heater 104 is configured for effecting heating
of the collected reservoir fluid 110. In some embodiments, for
example, the electric heater 104 is disposed in direct heat
transfer communication with the collected reservoir fluid 110.
Heating of any condensed heating fluid, whether disposed as part of
the collected reservoir fluid 110, or disposed in heat transfer
communication with the collected reservoir fluid 110, externally of
the well 102, is, therefore, effected by the electric heater 104,
when the electric heater is heating the collected reservoir fluid
110. In some embodiments, for example, the electrical heating by
the electric heater 104 is such that the collected reservoir fluid
consists is free, or substantially free, of the liquid heating
fluid. In some embodiments, for example, the electrical heating by
the electric heater is such that the collected reservoir fluid
consists of, or substantially consists of, the mobilized
hydrocarbon material, and, in this respect, is free, or
substantially free, of the liquid heating fluid.
[0055] Referring to FIG. 3, in some embodiments, for example, the
electric heater 104 is part of a heating assembly 700, such that
the electric heater is in indirect heat transfer communication with
the reservoir fluid via a liquid heat transfer medium 704. An
example of a suitable liquid heat transfer medium 704 is glycerin.
In this respect, a heating assembly 700 is provided, and includes a
housing 702, the electric heater, and the liquid heat transfer
medium 704. The electric heater is disposed within a housing 702,
with the space between the electric heater and the housing 702
being occupied with the liquid heat transfer medium 704. The liquid
heat transfer medium 704 has a higher boiling point than that of
the heating fluid at the pressure of the hydrocarbon reservoir
portion from which the mobilized hydrocarbon material is being
produced, such as by at least 10 degrees Celsius, such as, for
example, by at least 20 degrees Celsius, such as, for example, by
at least 50 degrees Celsius, such as, for example, by at least 100
degrees Celsius. The collection reservoir 108 is defined by a space
within the production well 102, between the housing 702 and the
wellbore string (such as, for example, casing) of the production
well. Because the heater assembly is disposed within the collection
reservoir, the liquid heat transfer medium 704 is disposed in heat
transfer communication with the collected reservoir fluid, through
the wall of the housing 702. In this respect, heat is transferred
from the electric heater to the collected reservoir fluid via the
liquid heat transfer medium 704 and through the wall of the housing
702. By virtue of this configuration, any evaporated heating fluid
may become disposed at a relatively higher temperature, owing to
the fact that the liquid heat transfer medium 704 can be heated to
higher temperatures by the electric heater, and transfer this
higher quality heat to the reservoir fluids (and, therefore, to the
condensed heating fluid), versus direct heating of the reservoir
fluids by the electric heater (without any intervening liquid heat
transfer medium 704). This also facilitates production of a "drier"
hydrocarbon material.
[0056] In some embodiments, for example, the electric heater 104 is
disposed within a laterally extending section 102a of the well 102,
that extends from a vertically extending section 102b, at the heel
102c of the well 102. In some embodiments, for example, the
laterally extending section 102a is disposed along a horizontal, or
substantially horizontal, axis.
[0057] In some embodiments, for example, the electric heater 104
includes a plurality of heater segments, and each one of the heater
segments may be controllable independently from the other heater
segments in terms of the rate of energy being produced. By
providing a plurality of heater segments that are independently
controllable, improved control of heating fluid conformance is made
possible.
[0058] In some embodiments, for example, the electrical heating
provides for more uniform heating of the hydrocarbon reservoir
versus heating of the hydrocarbon reservoir with steam.
[0059] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 110 is such that the temperature of
the collected reservoir fluid is greater than or equal to at least
the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. In this respect, both of
(i) evaporation of the heating fluid that is disposed in heat
transfer communication with the collected reservoir fluid, but
externally of the collection reservoir 108, and (ii) evaporation of
any heating fluid that is present within the collected reservoir
fluid, is promoted, so as to return the heating fluid to the
reservoir for effecting mobilization of the hydrocarbon material
within the reservoir 1000, and thereby contribute to the refluxing.
As well, by promoting the evaporation, the produced fluid 118
contains less heating fluid, thereby reducing energy requirements
to transport the produced fluid to the surface 1002 (as there is
less fluid volume to produce), and also reducing demands on
separation processes for removal of heating fluid from the produced
fluids.
[0060] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 110 is effected in response to
sensing of a temperature, of the collected reservoir fluid, that is
at or below a predetermined temperature that is based upon the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, prior to the
electrical heating of the collected reservoir fluid, a temperature
of the collected reservoir fluid is sensed that is at or below a
predetermined temperature that is based upon the boiling point of
the liquid heating fluid at the pressure of the hydrocarbon
reservoir portion from which the mobilized hydrocarbon material is
being produced. In some embodiments, for example, the predetermined
temperature is at or above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced. The
purpose of having the predetermined temperature being at the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, is for evaporating liquid heating fluid
that has collected within the well. Liquid heating fluid that has
collected within the well would be disposed at or below the boiling
point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced (where the heating fluid, in the liquid
state, is water, this would be the saturated steam temperature
within the reservoir). By effecting electrical heating while the
collected reservoir fluid is disposed at or below the boiling point
of the liquid heating fluid at the pressure of the hydrocarbon
reservoir portion from which the mobilized hydrocarbon material is
being produced, the intention is to vaporize the liquid heating
fluid that has collected within the well as part of the collected
reservoir fluid. In some embodiments, for example, it may be
intended to vaporize the heating fluid that is disposed externally
of the well 102, in which case the predetermined temperature may be
above the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced, for purposes of precluding
collection of the heating fluid within the well 102.
[0061] In some embodiments, for example, the well 102 includes the
heel 102c. In this respect, the electrical heating of the collected
reservoir fluid by the electric heater 104 is such that the
temperature of the collected reservoir fluid, disposed at the heel
102c of the production well 102, is greater than or equal to the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. Similar to the above, both of (i)
evaporation of the heating fluid that is disposed in heat transfer
communication with the collected reservoir fluid, but externally of
the collection reservoir, and (ii) evaporation of any heating fluid
that is present within the collected reservoir fluid, is promoted,
so as to return the heating fluid to the reservoir for effecting
mobilization of the hydrocarbon material within the reservoir, and
thereby contribute to the refluxing. As well, by promoting the
evaporation, the produced fluid that is being produced contains
less heating fluid, thereby reducing energy requirements to
transport the produced fluid to the surface (as there is less fluid
volume to produce), and also reducing demands on separation
processes for removal of heating fluid from the produced
fluids.
[0062] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 110 by the electric heater 104 is
effected in response to sensing of a temperature, of the collected
reservoir fluid 110 disposed at the heel 102c of the well 102, that
is at or below a predetermined temperature that is based upon the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, for example, prior
to the electrical heating of the collected reservoir fluid 110 by
the electric heater 104, a temperature, of the collected reservoir
fluid that is disposed at the heel 102c of the well 102, is sensed
that is at or below a predetermined temperature that is based upon
the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. In some embodiments, for
example, the predetermined temperature is at or above the boiling
point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. The purpose of having the predetermined
temperature being at the boiling point of the liquid heating fluid
at the pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced, is for
evaporating liquid heating fluid that has collected within the
well. Liquid heating fluid that has collected within the well would
be disposed at or below the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced (where
the heating fluid, in the liquid state, is water, this would be the
saturated steam temperature within the reservoir). By effecting
electrical heating while the collected reservoir fluid is disposed
at or below the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced, the intention is
to vaporize the liquid heating fluid that has collected within the
well as part of the collected reservoir fluid. In some embodiments,
for example, it may be intended to vaporize the heating fluid that
is disposed externally of the well, in which case the predetermined
temperature may be above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced, for
purposes of precluding collection of the heating fluid within the
well.
[0063] In some embodiments, for example, during a first time
interval, the collected reservoir fluid 110, within the well 102,
is not being produced (such as, for example, when the production of
the collected reservoir fluid is suspended), liquid heating fluid
is being supplied to the hydrocarbon reservoir via the well 102,
and the electrical heating is such that the liquid heating fluid is
evaporated and such that the hydrocarbon reservoir surrounding the
well 102 becomes disposed above a predetermined temperature that is
above the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced (such as, for example, above
350 degrees Celsius). Both of the supplying of the liquid heating
fluid and the electrical heating is then suspended. Subsequently,
during a second time interval, and while the rate at which heat
energy is being delivered by the electric heater is less than 50%
of the rate at which heat energy is being delivered by the electric
heater during the first time interval, the collected reservoir
fluid 110 may be produced. In some of these embodiments, for
example, during the second time interval, the rate at which heat
energy is being delivered by the electric heater is less than 25%
of the rate at which heat energy is being delivered by the electric
heater during the first time interval. In some of these
embodiments, for example, during the second time interval, the
electrical heating by the electrical heater is suspended.
[0064] During the first time interval, the electrical heating is
such that the hydrocarbon reservoir surrounding the well 102
becomes dry, or substantially dry, in that any heating fluid within
this portion of the hydrocarbon reservoir, has become evaporated,
and is being applied to effect heating and mobilization of
hydrocarbon material within the reservoir. Further, in some
embodiments, for example, the electrical heating during the first
time interval may be sufficient to effect heating of liquid heating
fluid being supplied to the hydrocarbon reservoir, via the well
102, to relatively high temperatures, including those which would
otherwise promote coking of hydrocarbon material that is collected
within collection reservoir of the well 102, so long as collection
of the mobilized hydrocarbon material within the collection
reservoir is avoided. During the first time interval, draining of
the mobilized hydrocarbon material into the collection reservoir
may be precluded by the high pressure conditions existing at the
collection reservoir owing to the evaporation of the liquid heating
fluid. During the second time interval, the mobilized hydrocarbon
material is draining and collecting within the well 102, and is
then subsequently produced. The electrical heating of the
hydrocarbon reservoir during the first time interval, in
combination with any electrical heating of the hydrocarbon
reservoir during the second time interval, is sufficient to
maintain, during the second time interval, the hydrocarbon
reservoir portion, that is surrounding the well 102, above the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. Because the temperature is so
maintained, during the second time interval, condensed heating
fluid may be re-evaporated, or substantially re-evaporated, prior
to becoming disposed within the well 102, such that the collected
reservoir fluid 110, which is being produced, is free, or
substantially free, of any heating fluid. As well, because the
production is being effected, pressure within the hydrocarbon
reservoir is being reduced, such that the heating fluid is more
likely to remain in a vapour state, as opposed to being condensed.
In some embodiments, for example, the collected reservoir fluid 110
being collected within the well 102, and which is being produced,
consists of, or substantially consists of, the mobilized
hydrocarbon material. In parallel, because the electrical heating
is suspended while the collected reservoir fluid 110 is being so
produced, coking of the collected hydrocarbon material is
mitigated. In this respect, the process includes:
(a) during a first time interval, while supplying a liquid heating
fluid to the hydrocarbon reservoir through a well 102, electrically
heating, within the well 102, with an electrical heater, a combined
heating fluid including the supplied liquid heating fluid and a
condensed heating fluid, such that the combined heating fluid is
evaporated to produce a gaseous heating fluid that is conducted
into the reservoir and then condensed upon heating of hydrocarbon
material to produce the condensed heating fluid; (b) suspending the
supplying of the liquid heating fluid; (c) after the suspending,
and during a second time interval, reducing the rate at which heat
energy is being delivered by the electric heater such that the rate
at which heat energy is being delivered by the electric heater is
less than 50% of the rate at which heat energy is being delivered
by the electric heater during the first time interval, and while
the electric heater is delivering the heat energy at the reduced
rate, collecting reservoir fluid within the well 102, and producing
the collected reservoir fluid 110, wherein the collected reservoir
fluid 110 includes the hydrocarbon material that has become
mobilized and drained into the well 102; and (d) suspending of the
producing.
[0065] The electrical heating of the hydrocarbon reservoir during
the first time interval, in combination with any electrical heating
of the hydrocarbon reservoir during the second time interval, is
sufficient to, during the second time interval, effect evaporation
of condensed heating fluid, that has condensed after effecting
heating and mobilization of the hydrocarbon material, wherein the
evaporation of the condensed heating fluid is effected prior to the
condensed heating fluid being received by the well 102.
[0066] In some embodiments, for example, the electrical heating of
the hydrocarbon reservoir during the first time interval, in
combination with any electrical heating of the hydrocarbon
reservoir during the second time interval, is sufficient to effect
evaporation of condensed heating fluid that has condensed after
effecting heating and mobilization of the hydrocarbon material,
prior to the condensed heating fluid being received by the well
102, such that the collected reservoir fluid is free, or
substantially free, of heating fluid. In some embodiments, for
example, the collected reservoir fluid consists of, or
substantially consists of, the mobilized hydrocarbon material.
[0067] In some of these embodiments, for example, during the second
time interval, the rate at which heat energy is being delivered by
the electric heater is less than 25% of the rate at which heat
energy is being delivered by the electric heater during the first
time interval. In some of these embodiments, for example, during
the second time interval, the electrical heating by the electrical
heater is suspended.
[0068] In some embodiments, for example, the steps (a) to (d) are
repeated at least once, such as, for example, at least twice, such
as, for example, at least three (3) times, such as, for example, at
least five (5) times. In this respect, in some embodiments, for
example, the process is a cyclic process including steps (a) to
(d), and the cyclic process is repeated at least once, such as, for
example, at least twice, such as, for example, at least three (3)
times, such as, for example, at least five (5) times.
[0069] In some embodiments, for example, during a first time
interval when the collected reservoir fluid, within the well 102,
is not being produced (such as, for example, when the production of
the collected reservoir fluid is suspended), the electrical heating
is such that the hydrocarbon reservoir becomes disposed above a
predetermined temperature that is above the boiling point of the
liquid heating fluid at the pressure of the hydrocarbon reservoir
portion from which the mobilized hydrocarbon material is being
produced (such as, for example, above 350 degrees Celsius).
Subsequently, during a second time interval, the collected
reservoir fluid 110 may be produced, and during such production,
the electrical heating of the collected reservoir fluid may be
continued but modulated such that the collected reservoir fluid 110
is disposed below 300 degrees Celsius, thereby mitigating coking of
the collected reservoir fluid 110. In this respect, during the
first time interval, the electrical heating is such that the
hydrocarbon reservoir surrounding the well 102 becomes dry, or
substantially dry, in that any heating fluid within this portion of
the hydrocarbon reservoir, has become evaporated, and is being
applied to effect heating and mobilization of hydrocarbon material
within the reservoir. Further, in some embodiments, for example,
the electrical heating during the first time interval may be
sufficient to effect heating of liquid heating fluid being supplied
to the hydrocarbon reservoir, via the well 102, to relatively high
temperatures, including those which would otherwise promote coking
of hydrocarbon material that is collected within collection
reservoir of the well 102, so long as collection of the mobilized
hydrocarbon material within the collection reservoir is avoided.
During the first time interval, draining of the mobilized
hydrocarbon material into the collection reservoir may be precluded
by the high pressure conditions existing at the collection
reservoir owing to the evaporation of the liquid heating fluid.
During the second time interval, reservoir fluid, including the
mobilized hydrocarbon material is draining and collecting within
the production well 102, and is then subsequently produced. The
electrical heating during the first time interval, in combination
with any electrical heating during the second time interval, is
sufficient to maintain, during the second time interval, the
hydrocarbon reservoir portion, that is surrounding the well 102,
above the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. Because the temperature is
so maintained, condensed heating fluid is evaporated prior to
becoming disposed within the well 102, such that the collected
reservoir fluid 110 being collected within the well 102, and which
is being produced, is free, or substantially free, of the heating
fluid. As well, because the production is being effected, pressure
within the hydrocarbon reservoir is being reduced, such that the
heating fluid is more likely to remain in a vapour state, as
opposed to being condensed. In some embodiments, for example, the
collected reservoir fluid 100 consists of, or substantially
consists of, the mobilized hydrocarbon material. In parallel,
because the electrical heating is modulated such that such that the
collected reservoir fluid 110 is disposed below 350 degrees
Celsius, as described above, while the collected reservoir fluid
110 is being so produced, coking of the collected hydrocarbon
material is mitigated. In this respect, the process includes:
(a) during a first time interval, while supplying a liquid heating
fluid to the hydrocarbon reservoir through a well 102, electrically
heating, within the well 102, a combined heating fluid including
the supplied liquid heating fluid and a condensed heating fluid,
such that the combined heating fluid is evaporated to produce a
gaseous heating fluid that is conducted into the reservoir, and
then condensed upon heating of hydrocarbon material to produce the
condensed heating fluid; (b) suspending the supplying of the liquid
heating fluid; (c) after the suspending of the supplying of the
liquid heating fluid, during a second time interval, modulating the
electrical heating such that the electrical heating of reservoir
fluid (including the mobilized hydrocarbon material, and, in some
embodiments, for example, consisting, or substantially consisting
of the mobilized hydrocarbon material) that is being collected
within the well 102 is such that the temperature of the collected
reservoir fluid 110 is less than 350 degrees Celsius (such as, for
example, less than 350 degrees Celsius, such as, for example, less
than 300 degrees Celsius, such as, for example, less than 250
degrees Celsius, such as, for example, less than 220 degrees
Celsius), and, while the modulated electrical heating of collected
reservoir fluid is being effected, producing the collected
reservoir fluid 110 from the well 102; and (c) suspending the
producing.
[0070] The electrical heating of the hydrocarbon reservoir during
the first time interval, in combination with any electrical heating
of the hydrocarbon reservoir during the second time interval, is
sufficient to, during the second time interval, effect evaporation
of condensed heating fluid, that has condensed after effecting
heating and mobilization of the hydrocarbon material, prior to the
condensed heating fluid being received by the well 102.
[0071] In some embodiments, for example, the electrical heating of
the hydrocarbon reservoir during the first time interval, in
combination with any electrical heating of the hydrocarbon
reservoir during the second time interval, is sufficient to, during
the second time interval, effect evaporation of condensed heating
fluid, that has condensed after effecting heating and mobilization
of the hydrocarbon material, prior to the condensed heating fluid
being received by the well 102, such that the collected reservoir
fluid 110 is free, or substantially free, of the heating fluid. In
some embodiments, for example, the collected reservoir fluid 110
consists of, or substantially consists of, the mobilized
hydrocarbon material.
[0072] In some embodiments, for example, the modulating of the
electrical heating includes suspending of the electrical
heating.
[0073] In some embodiments, for example, the steps (a) to (d) are
repeated at least once, such as, for example, at least twice, such
as, for example, at least three (3) times, such as, for example, at
least five (5) times. In this respect, in some embodiments, for
example, the process is a cyclic process including steps (a) to
(d), and the cyclic process is repeated at least once, such as, for
example, at least twice, such as, for example, at least three (3)
times, such as, for example, at least five (5) times.
[0074] In some embodiments, for example, during the first time
interval, the evaporated combined heating fluid is superheated such
that the temperature of the hydrocarbon reservoir becomes disposed
above the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. In this respect, in some
embodiments, for example, the predetermined temperature is above
300 degrees Celsius, such as, for example, above 350 degrees
Celsius, such as, for example, above 400 degrees Celsius.
[0075] By effecting heating of the hydrocarbon reservoir to above
the predetermined temperature, the reservoir fluid, that is being
collected within the well and then produced, is free, or
substantially free, of the condensed heating fluid. In some
embodiments, for example, consists of, or substantially consists
of, the mobilized hydrocarbon material.
[0076] As discussed above, in some embodiments, for example, the
collected reservoir fluid 110 consists of, or substantially
consists of, the mobilized hydrocarbon material, and, in this
respect, is free, or substantially free, of the heating fluid. In
those embodiments where the electric heater 104 is disposed in
direct heat transfer communication with the collected reservoir
fluid, by having the collected reservoir fluid consisting of, or
substantially consisting of, the mobilized hydrocarbon material,
evaporation of condensed heating fluid disposed in heat transfer
communication with the collected reservoir fluid, may produce
evaporated heating fluid having a relatively higher temperature,
owing to the fact that the mobilized hydrocarbon material can be
heated to higher temperatures by the electric heater, and transfer
this higher quality heat to any condensed heating fluid disposed in
heat transfer communication with the collected reservoir fluid,
versus direct heating of the condensed heating fluid by the
electric heater (without any intervening liquid heat transfer
medium 704).
[0077] Also, by having the collected reservoir fluid 110 be free,
or substantially free, of the heating fluid, scale formation within
the production well 102 may be mitigated. Where the heating fluid,
in its liquid state, includes water, it is preferable that water
does not become disposed in contact structures within the
production well, including the electric heater 104, as evaporation
of water in this context may result in precipitation of dissolved
scale-forming solids within the production well 102, including onto
the electric heater or other structures, resulting in scale
formation. This may be particularly relevant where the water
includes connate water (and is, therefore, not possible to subject
to pre-treatment for removal of scale-forming solids), and is most
likely to occur during initial start-up. Accordingly, in such
embodiments, by ensuring that the collected reservoir fluid is
free, or substantially free, of the heating fluid, the collected
heating fluid is fluidically isolated, or substantially fluidically
isolated, from the production well, thereby mitigating potential
scale formation within the production well (including scale
formation on the electric heater).
[0078] Further, as a necessary incident, by having the collected
reservoir fluid 110 be free, or substantially free, of the heating
fluid, production of a "drier" hydrocarbon material is facilitated.
This reduces energy requirements to transport the produced fluid to
the surface (as there is less fluid volume to produce) and also
reduces demands on separation processes for removal of heating
fluid from the produced fluids.
[0079] In this respect, in some embodiments, for example, the rate
of heating of the collected reservoir fluid 110 by the electric
heater 104 is modulated such that the collected reservoir fluid is
free, or substantially free, of the heating fluid. In some
embodiments, for example, the rate of heating of the collected
reservoir fluid 110 by the electric heater 104 is modulated such
that the collected reservoir fluid consists of, or substantially
consists of, the mobilized hydrocarbon material.
[0080] In some embodiments, for example, the composition of the
collected reservoir fluid 110 may be sensed by a densitometer. In
this respect, the rate of heating effected by the electric heater
104 may be modulated based on sensing of the density of the
collected reservoir fluid by the densitometer. In response to
sensing of a density of the collected reservoir fluid that is
characteristic of a collected reservoir fluid having excessive
non-hydrocarbon fluid (such as the heating fluid), the rate of
heating by the electric heater may be increased to effect
evaporation of the fluid. This will promote the maintenance of a
collected reservoir fluid that consists of hydrocarbon material, or
substantially hydrocarbon material, and, in this respect, free, or
substantially free, of the heating fluid. This promotes reflux of
the condensed heating fluid (as above-described), higher quality
heat transfer to effect the evaporation of the condensed heating
fluid, mitigates scale formation, and production of "drier"
hydrocarbon material.
[0081] Alternatively, the amount of water within the produced
reservoir fluid can be detected by measuring electrical resistance
of the produced reservoir fluid, capacitance of the produced
reservoir fluid, or both of electrical resistance and capacitance
of the produced reservoir fluid, and the rate of heating by the
electric heater may be modulated in response to this
measurement.
[0082] In some embodiments, for example, the electric heater 104 is
submerged within the collected reservoir fluid 110 (in some
embodiments, for example, free of, substantially free of the
heating fluid, and in some embodiments, for example, consisting of
hydrocarbon material, or substantially hydrocarbon material), and
the producing is modulated such that sufficient collected reservoir
fluid is maintained within the production well 102 such that the
electric heater is submerged within collected reservoir fluid.
[0083] In those embodiments where the temperature of the collected
reservoir fluid is above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced, the
collected reservoir fluid is produced, such that the collected
reservoir fluid is conducted to above the surface of the earth. In
some embodiments, for example, the temperature of the collected
reservoir fluid is between: (i) a temperature that is 10 degrees
Celsius above the steam saturation temperature at the pressure
within the hydrocarbon reservoir, and (ii) 350 degrees Celsius. In
some embodiments, for example, the collected reservoir fluid 110 is
free, or substantially free, of the heating fluid. In some
embodiments, for example, the collected reservoir fluid 110
consists of, or substantially consists of, mobilized hydrocarbon
material. Once disposed above the surface of the earth (such as,
for example, within the surface facilities), the produced reservoir
fluid becomes disposed in indirect heat exchange communication with
a heat transfer fluid such that heat is indirectly transferred to
the heat transfer fluid. The transferring of heat to the heat
transfer fluid is such that the heat transfer fluid is evaporated.
The evaporated heat transfer fluid is communicated to a turbine
such that rotation of the turbine is effected, such that
electricity is generated.
[0084] In some embodiments, for example, the laterally, or
substantially laterally, extending section 102a of the production
well 102 is co-operatively configured with the electric heater 104
such that while the reservoir fluid is being conducted towards the
well 102, the laterally, or substantially laterally, extending
section 102a of the production well 102 is disposed to receive and
collect the reservoir fluid across (but not necessarily
continuously across) a reservoir fluid-receiving portion of the
laterally, or substantially laterally, extending section of the
production well 102, and the length of the reservoir
fluid-receiving portion, measured along the axis of the operative
portion, is at least 1000 metres. Because the heating fluid is not
supplied from the surface, heat losses, associated with longer
wells, is not concerning, as it is for SAGD operations. Also,
because the volumetric flow of produced fluid is relatively less
than for SAGD production, hydraulic pressure losses are also not a
material factor for well design. In combination, this enables the
use of longer wells in in-situ reflux operations to effect
production of hydrocarbon material, although shorter wells (i.e.
those less than 1000 metres) could also be used.
[0085] In some embodiments, for example, the vertically, or
substantially vertically, extending section 102b of the production
well 102 has a length, measured along the axis of the vertically,
or substantially vertically, extending section, of at least 1000
metres, so as to allow for production from deeper resources. Again,
heat losses and hydraulic pressure losses, with in-situ reflux are
not concerning, as it is for SAGD operations, and it is, possible
to, therefore, use longer wells, although shorter wells (i.e. those
less than 1000 metres in depth) could also be used.
[0086] Liquid heating fluid may be supplied from a source disposed
above the surface 1002. In some embodiments, for example, the
supplying of liquid heating fluid is effected via an injector
string 114 disposed within the production well 102. In some
embodiments, for example, the injector string includes a "spaghetti
string".
[0087] Supplying of liquid heating fluid may be suspended, when
sufficient refluxing of the condensed heating fluid is being
effected such that the desirable production of reservoir fluid is
effected (for example, the produced reservoir fluid is free, or
substantially free, of heating fluid, and/or, for example, the
produced reservoir fluid consists of, or substantially consists of,
hydrocarbon material). In some cases, after the supplying has been
suspended, periodic make-up of heating fluid may be required. For
example, liquid heating fluid may be lost to the reservoir 1000,
and make-up heating fluid may be required. In this respect, while
the heating of a liquid heating fluid is being effected,
supplemental liquid heating fluid 116 may be supplied from a source
disposed above the surface 1002. In this respect, the liquid
heating fluid includes the supplemental liquid heating fluid 116.
In some embodiments, for example, the supplying of supplemental
liquid heating fluid 116 is effected via an injector string 114
disposed within the production well 102. In some embodiments, for
example, the injector string includes a "spaghetti string". In some
embodiments, for example, the supplying of the supplemental liquid
heating fluid is effected in response to sensing of a pressure,
within the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced, that is less than a
predetermined pressure. The predetermined pressure is based on,
amongst other things, the desirability of operating at higher
pressures in order to provide a greater driving force for
production, balanced versus the recognition that heat transfer
efficiency is greater at lower pressures and that cap rock
integrity may limit the maximum possible operating pressure.
[0088] In operation, during start-up, the hydrocarbon reservoir is
heated by heat generated by the electric heater, such that
hydrocarbon material is mobilized by the heating of the hydrocarbon
reservoir. The mobilized hydrocarbon material drains into the well
102. The heating is effected by conduction, convection, or a
combination of conduction and convection. In some embodiments, for
example, the convective heating is effected by evaporated formation
water, such that the heating fluid includes evaporated formation
water. Subsequently, or, in parallel, heating fluid is supplied
from the surface facilities and is injected into the reservoir.
Evaporation of the injected heating fluid is effected by the heat
generated by the electric heater 104. The evaporated heating fluid
is conducted to the hydrocarbon reservoir and transfers heat energy
to the hydrocarbon material such that the hydrocarbon material is
mobilized and the heating fluid is condensed. Reservoir fluid 110
enters the well 102 via ports 106, collects within the collection
reservoir 108 and is electrically heated by the electric heater 104
(either directly or via the heater assembly 106). Heating is
controlled such that the reservoir fluid is, primarily, collected
mobilized hydrocarbon material. The heated reservoir fluid
transfers heat to condensed heating fluid that is disposed in heat
transfer communication with the reservoir fluid, thereby effecting
re-evaporation of the condensed heating fluid, and thereby
effecting the reflux 112. Eventually, after sufficient hydrocarbon
material has been mobilized and drained into the well 102 (such as,
for example, as described above), an evaporated fluid chamber
develops (where the heating fluid, in the liquid state, is water,
then a steam chamber would be developed). In parallel, reservoir
fluid collected within the production well 104 is continuously
produced, such as by a downhole pump and/or artificial lift, or by
reservoir pressure.
[0089] Referring to FIG. 2, in some embodiments, for example, the
process is effected by a system 200 including a non-production well
202 and a production well 204. A first electric heater 206 is
disposed within the non-production well 202. At least a fraction of
the reflux is effected by a first electric heater 206. The
producing of the produced fluid 224 is effected via the production
well 204. The production well 204 is disposed below the
non-production well 202. The non-production well 202 does not
produce produced fluid 224. The non-production well is provided
for, amongst other things, to effect reflux of the condensed
heating fluid. In comparison to the embodiment illustrated in FIG.
1, this configuration may enable recovery and production of
hydrocarbon material that is disposed closer to the bottom of the
hydrocarbon reservoir, with less energy losses to the formation
below the hydrocarbon reservoir without any hydrocarbon
reserves.
[0090] The non-production well 202 extends into the hydrocarbon
reservoir 2000 from the surface. In some embodiments, for example,
the first electric heater 206 is disposed within a laterally
extending section 202a of the non-production well 202, that extends
from a vertically extending section 202b, at the heel 202c of the
non-production well 202. In some embodiments, for example, the
laterally extending section 202a is disposed along a horizontal, or
substantially horizontal, axis.
[0091] In some embodiments, for example, the first electric heater
206 is disposed within the collection reservoir 210 of the
non-production well 202. The collection reservoir 210 includes
reservoir fluid 212 that has collected therein. In some
embodiments, for example, the collected reservoir fluids 212 is
free, or substantially free, of the heating fluid. In some
embodiments, for example, the collected reservoir fluids 212
consists of, or substantially consists of, the mobilized
hydrocarbon material. The collected mobilized hydrocarbon material
is disposed in heat transfer communication with at least a fraction
of the condensed heating fluid, such as condensed heating fluid
that is disposed externally of the non-production well 202. In some
embodiments, for example, the collected reservoir fluid may also
include the condensed heating fluid.
[0092] The first electric heater 206 is configured for effecting
heating of the collected reservoir fluid 212. In some embodiments,
for example, the first electric heater is disposed in direct heat
transfer communication with the collected reservoir fluid. Heating
of any condensed heating fluid, whether disposed as part of the
collected reservoir fluid, or disposed in heat transfer
communication with the collected reservoir fluid, externally of the
production well, is, therefore, effected by the first electric
heater, when the first electric heater is heating the collected
reservoir fluid. In some embodiments, for example, the electrical
heating by the first electric heater 206 is such that the collected
reservoir fluid is free, or substantially free, of heating fluid.
In some embodiments, for example, the electrical heating by the
first electric heater 206 is such that the collected reservoir
fluid consists of, or substantially consists of, the mobilized
hydrocarbon material.
[0093] Referring to FIG. 3, in some embodiments, for example, the
first electric heater 206 is part of a heating assembly 700, such
that the electric heater is in indirect heat transfer communication
with the collected reservoir fluid via a liquid heat transfer
medium 704. An example of a suitable liquid heat transfer medium
704 is glycerin. In this respect, a heating assembly 700 is
provided, and includes a housing 702, the electric heater, and the
liquid heat transfer medium 704. The electric heater is disposed
within a housing 702, with the space between the electric heater
and the housing 702 being occupied with the liquid heat transfer
medium 704. The liquid heat transfer medium 704 has a higher
boiling point than that of the heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, such as by at least 10 degrees Celsius,
such as, for example, by at least 20 degrees Celsius, such as, for
example, by at least 50 degrees Celsius, such as, for example, by
at least 100 degrees Celsius. The collection reservoir 210 is
defined by a space within the non-production well 202, between the
housing 702 and the wellbore string (such as, for example, casing)
of the non-production well 202. Because the heater assembly is
disposed within the collection reservoir, the liquid heat transfer
medium 704 is disposed in heat transfer communication with the
collected reservoir fluid 212, through the wall of the housing 702.
In this respect, heat is transferred from the first electric heater
to the collected reservoir fluid via the liquid heat transfer
medium 704 and through the wall of the housing 702. By virtue of
this configuration, any evaporated heating fluid may become
disposed at a relatively higher temperature, owing to the fact that
the liquid heat transfer medium 704 can be heated to higher
temperatures by the first electric heater, and transfer this higher
quality heat to the reservoir fluids (and, therefore, to the
condensed heating fluid), versus direct heating of the reservoir
fluids by the first electric heater (without any intervening liquid
heat transfer medium 704).
[0094] In some embodiments, for example, the first electric heater
206 is disposed within a laterally extending section 202a of the
non-production well 202, that extends from a vertically extending
section 202b, at the heel 202c of the non-production well 202. In
some embodiments, for example, the laterally extending section 202a
is disposed along a horizontal, or substantially horizontal,
axis.
[0095] In some embodiments, for example, the first electric heater
206 includes a plurality of heater segments, and each one of the
heater segments may be controllable independently from the other
heater segments in terms of the rate of energy being produced. By
providing a plurality of heater segments that are independently
controllable, improved control of heating fluid conformance is made
possible.
[0096] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 212 is such that the temperature of
the collected reservoir fluid is greater than or equal to at least
the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. In this respect, both of
(i) evaporation of the heating fluid that is disposed in heat
transfer communication with the collected reservoir fluid, but
externally of the collection reservoir 210, and (ii) evaporation of
any heating fluid that is present within the collected reservoir
fluid, is promoted, so as to return the heating fluid to the
reservoir for effecting mobilization of the hydrocarbon material
within the reservoir 2000, and thereby contribute to the
refluxing.
[0097] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 212 is effected in response to
sensing of a temperature, of the collected reservoir fluid, that is
at or below a predetermined temperature that is based upon the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, prior to the
electrical heating of the collected reservoir fluid, a temperature
of the collected reservoir fluid is sensed that is at or below a
predetermined temperature that is based upon the boiling point of
the liquid heating fluid at the pressure of the hydrocarbon
reservoir portion from which the mobilized hydrocarbon material is
being produced. In some embodiments, for example, the predetermined
temperature is at or above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced. The
purpose of having the predetermined temperature being at the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, is for evaporating liquid heating fluid
that has collected within the well or is in close proximity to the
well. Liquid heating fluid that has collected within the well would
be disposed at or below the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced (where
the heating fluid, in the liquid state, is water, this would be the
saturated steam temperature within the reservoir). By effecting
electrical heating while the collected reservoir fluid is disposed
at or below the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced, the intention is
to vaporize the liquid heating fluid that has collected within the
well as part of the collected reservoir fluid. In some embodiments,
for example, it may be intended to vaporize the heating fluid that
is disposed externally of the well, in which case the predetermined
temperature may be above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced, for
purposes of precluding collection of the heating fluid within the
well.
[0098] In some embodiments, for example, the non-production well
202 includes the heel 202c. In this respect, the electrical heating
of the collected reservoir fluid by the electric heater 206 is such
that the temperature of the collected reservoir fluid, disposed at
the heel 202c of the non-production well 202, is greater than or
equal to the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced. Similar to the
above, both of (i) evaporation of the heating fluid that is
disposed in heat transfer communication with the collected
reservoir fluid, but externally of the collection reservoir, and
(ii) evaporation of any heating fluid that is present within the
collected reservoir fluid, is promoted, so as to return the heating
fluid to the reservoir for effecting mobilization of the
hydrocarbon material within the reservoir, and thereby contribute
to the refluxing.
[0099] In some embodiments, for example, the electrical heating of
the collected reservoir fluid by the first electric heater 206 is
effected in response to sensing of a temperature, of the collected
reservoir fluid disposed at the heel 202c of the non-production
well 202, that is at or below a predetermined temperature that is
based upon the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced. In some
embodiments, for example, prior to the electrical heating of the
collected reservoir fluid by the first electric heater 206, a
temperature, of the collected reservoir fluid that is disposed at
the heel 202c of the non-production well 202, is sensed that is at
or below a predetermined temperature that is based upon the boiling
point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, for example, the
predetermined temperature is at or above the boiling point of the
liquid heating fluid at the pressure of the hydrocarbon reservoir
portion from which the mobilized hydrocarbon material is being
produced. The purpose of having the predetermined temperature being
at the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced, is for evaporating liquid
heating fluid that has collected within the well. Liquid heating
fluid that has collected within the well would be disposed at or
below the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced (where the heating fluid, in
the liquid state, is water, this would be the saturated steam
temperature within the reservoir). By effecting electrical heating
while the collected reservoir fluid is disposed at or below the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, the intention is to vaporize the liquid
heating fluid that has collected within the well as part of the
collected reservoir fluid. In some embodiments, for example, it may
be intended to vaporize the heating fluid that is disposed
externally of the well, in which case the predetermined temperature
may be above the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced, for purposes of
precluding collection of the heating fluid within the well.
[0100] As discussed above, in some embodiments, for example, the
collected reservoir fluid 212 consists of, or substantially
consists of, the mobilized hydrocarbon material, and, in this
respect, is free, or substantially free, of the heating fluid. In
those embodiments where the first electric heater is disposed in
direct heat transfer communication with the collected reservoir
fluid, by having the collected reservoir fluid consisting of, or
substantially consisting of, the mobilized hydrocarbon material
(and, in this respect, free, or substantially free, of the heating
fluid) evaporation of condensed heating fluid disposed in heat
transfer communication with the collected reservoir fluid, may
produce evaporated heating fluid having a relatively higher
temperature, owing to the fact that the mobilized hydrocarbon
material can be heated to higher temperatures by the first electric
heater 206, and transfer this higher quality heat to any condensed
heating fluid disposed in heat transfer communication with the
collected reservoir fluid, versus direct heating of the condensed
heating fluid by the first electric heater (without any intervening
liquid heat transfer medium 704).
[0101] Also, by having the collected reservoir fluid 212 be free,
or substantially free, of the heating fluid, scale formation within
the non-production well 202 may be mitigated. Where the heating
fluid, in its liquid state, includes water, it is preferable that
water does not become disposed in contact structures within the
non-production well 202, including the first electric heater 206,
as evaporation of water in this context may result in precipitation
of dissolved scale-forming solids within the non-production well,
including onto the first electric heater or other structures,
resulting in scale formation. Accordingly, in such embodiments, by
ensuring that the collected reservoir fluid be free, or
substantially free, of the heating fluid, the collected heating
fluid is fluidically isolated, or substantially fluidically
isolated, from the non-production well, thereby mitigating
potential scale formation within the non-production well (including
scale formation on the second electric heater 220).
[0102] In this respect, in some embodiments, for example, the rate
of heating of the collected reservoir fluid 212 by the first
electric heater 206 is modulated such that the collected reservoir
fluid is free, or substantially free, of the heating fluid. In some
embodiments, for example, the rate of heating of the collected
reservoir fluid 212 by the first electric heater 206 is modulated
such that the collected reservoir fluid consists of, or
substantially consists of, the mobilized hydrocarbon material.
[0103] In some embodiments, for example, the composition of the
collected reservoir fluid 212 may be sensed by a densitometer. In
this respect, the rate of heating effected by the first electric
heater 206 may be modulated based on sensing of the density of the
collected reservoir fluid by the densitometer. In response to
sensing of a density of the collected reservoir fluid that is
characteristic of a collected reservoir fluid having excessive
non-hydrocarbon fluid (such as the heating fluid), the rate of
heating by the second electric heater 220 may be increased to
effect evaporation of the fluid. This will promote the maintenance
of a collected reservoir fluid that consists of hydrocarbon
material, or substantially hydrocarbon material, and, in this
respect, is free, or substantially free, of the heating fluid.
Amongst other things, this promotes reflux of the condensed heating
fluid (as above-described), higher quality heat transfer to effect
the evaporation of the condensed heating fluid, and mitigates scale
formation.
[0104] Alternatively, the amount of water within the produced
reservoir fluid can be detected by measuring electrical resistance
of the produced reservoir fluid, capacitance of the produced
reservoir fluid, or both of electrical resistance and capacitance
of the produced reservoir fluid, and the rate of heating by the
electric heater may be modulated in response to this
measurement.
[0105] The produced fluid 224 is produced through the production
well 204. In some embodiments, for example, production is effected
by artificial lift, such as by a downhole pump and/or by gas
lift.
[0106] The production well 204 extends into the hydrocarbon
reservoir from the surface. The production well 204 includes a
collection reservoir 224 for collecting reservoir fluids 226. The
reservoir fluids include mobilized hydrocarbon material and
condensed heating fluid. In some embodiments, for example, the
reservoir fluid being collected within the production well is free,
or substantially free, of the heating fluid. In some embodiments,
for example, the reservoir fluid being collected within the
production well consists of, or substantially consists of,
mobilized hydrocarbon material. Such collected reservoir fluid may
be in heat transfer communication with condensed heating fluid that
has bypassed the non-production well 202. In some embodiments, for
example, the collected reservoir fluid may include the mobilized
hydrocarbon material and condensed heating fluid that has bypassed
the non-production well 202. The condensed heating fluids are more
likely to be disposed in such relationships with the collected
reservoir fluid in later-stage in-situ reflux processes being
practised within oil sands. In more mature operations, the steam
chamber tends to laterally grow, resulting in condensed heating
fluid bypassing the non-production well 202 while draining within
the reservoir.
[0107] In some embodiments, for example, it may be desirable to
remove condensed heating fluid from the reservoir fluid 224 being
collected within the production well 204, prior to production of
the reservoir fluid, as well as to reflux such condensed heating
fluid that has bypassed the non-production well 202.
[0108] In this respect, a second electric heater 220 is disposed
within the production well and, more specifically, within the
collection reservoir 224 of the production well 204. The collection
reservoir includes reservoir fluid that has collected therein.
[0109] The second electric heater 220 is configured for effecting
heating of the collected reservoir fluid 226. In some embodiments,
for example, the second electric heater is disposed in direct heat
transfer communication with the collected reservoir fluid. Heating
of any condensed heating fluid, whether disposed as part of the
collected reservoir fluid, or disposed in heat transfer
communication with the collected reservoir fluid, externally of the
production well 204, is, therefore, effected by the second electric
heater, when the second electric heater is heating the collected
reservoir fluid. In some embodiments, for example, the electrical
heating by the second electric heater 220 is such that the
collected reservoir fluid is free, or substantially free, of
heating fluid. In some embodiments, for example, the electrical
heating by the second electric heater 220 is such that the
collected reservoir fluid consists of, or substantially consists
of, the mobilized hydrocarbon material.
[0110] Referring to FIG. 3, in some embodiments, for example, the
second electric heater 220 is part of a heating assembly 700, such
that the second electric heater is in indirect heat transfer
communication with the collected reservoir fluid 226 via a liquid
heat transfer medium 704. An example of a suitable liquid heat
transfer medium 704 is glycerin. In this respect, a heating
assembly 700 is provided, and includes a housing 702, second the
electric heater, and the liquid heat transfer medium 704. The
second electric heater is disposed within a housing 702, with the
space between the second electric heater and the housing 702 being
occupied with the liquid heat transfer medium 704. The liquid heat
transfer medium 704 has a higher boiling point than that of the
heating fluid at the pressure of the hydrocarbon reservoir portion
from which the mobilized hydrocarbon material is being produced,
such as by at least 10 degrees Celsius, such as, for example, by at
least 20 degrees Celsius, such as, for example, by at least 50
degrees Celsius, such as, for example, by at least 100 degrees
Celsius. The collection reservoir 224 is defined by a space within
the production well, between the housing 702 and the casing of the
production well 204. Because the heater assembly is disposed within
the collection reservoir, the liquid heat transfer medium 704 is
disposed in heat transfer communication with the collected
reservoir fluid, through the wall of the housing 702. In this
respect, heat is transferred from the second electric heater to the
collected reservoir fluid via the liquid heat transfer medium 704
and through the wall of the housing 702. By virtue of this
configuration, any evaporated heating fluid may become disposed at
a relatively higher temperature, owing to the fact that the liquid
heat transfer medium 704 can be heated to higher temperatures by
the second electric heater, and transfer this higher quality heat
to the reservoir fluids (and, therefore, to the condensed heating
fluid), versus direct heating of the reservoir fluids by the second
electric heater (without any intervening liquid heat transfer
medium 704). This also facilitates production of a "drier"
hydrocarbon material.
[0111] In some embodiments, for example, the second electric heater
220 is disposed within a laterally extending section 204a of the
production well 204, that extends from a vertically extending
section 204b, at the heel 204c of the production well 204. In some
embodiments, for example, the laterally extending section 204a is
disposed along a horizontal, or substantially horizontal, axis.
[0112] In some embodiments, for example, the second electric heater
220 includes a plurality of heater segments, and each one of the
heater segments may be controllable independently from the other
heater segments in terms of the rate of energy being produced. By
providing a plurality of heater segments that are independently
controllable, improved control of heating fluid conformance is made
possible.
[0113] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 226 is such that the temperature of
the collected reservoir fluid is greater than or equal to at least
the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced. In this respect, both of
(i) evaporation of the heating fluid that is disposed in heat
transfer communication with the collected reservoir fluid, but
externally of the collection reservoir, and (ii) evaporation of any
heating fluid that is present within the collected reservoir fluid,
is promoted, so as to return the heating fluid to the reservoir for
effecting mobilization of the hydrocarbon material within the
reservoir, and thereby contribute to the refluxing. As well, by
promoting the evaporation, the produced fluid 224 that is being
produced contains less heating fluid, thereby reducing energy
requirements to transport the produced fluid to the surface (as
there is less fluid volume to produce), and also reducing demands
on separation processes for removal of heating fluid from the
produced fluids.
[0114] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 226 is effected in response to
sensing of a temperature, of the collected reservoir fluid, that is
at or below a predetermined temperature that is based upon the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, prior to the
electrical heating of the collected reservoir fluid, a temperature
of the collected reservoir fluid is sensed that is at or below a
predetermined temperature that is based upon the boiling point of
the liquid heating fluid at the pressure of the hydrocarbon
reservoir portion from which the mobilized hydrocarbon material is
being produced. In some embodiments, for example, the predetermined
temperature is at or above the boiling point of the liquid heating
fluid at the pressure of the hydrocarbon reservoir portion from
which the mobilized hydrocarbon material is being produced. The
purpose of having the predetermined temperature being at the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, is for evaporating liquid heating fluid
that has collected within the well. Liquid heating fluid that has
collected within the well would be disposed at or below the boiling
point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced (where the heating fluid, in the liquid
state, is water, this would be the saturated steam temperature
within the reservoir). By effecting electrical heating while the
collected reservoir fluid is disposed at or below the boiling point
of the liquid heating fluid at the pressure of the hydrocarbon
reservoir portion from which the mobilized hydrocarbon material is
being produced, the intention is to vaporize the liquid heating
fluid that has collected within the well as part of the collected
reservoir fluid. In some embodiments, for example, it may be
intended to vaporize the heating fluid that is disposed externally
of the well, in which case the predetermined temperature may be
above the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced, for purposes of precluding
collection of the heating fluid within the well.
[0115] In some embodiments, for example, the production well 204
includes the heel 204c. In this respect, the electrical heating of
the collected reservoir fluid 226 by the second electric heater 220
is such that the temperature of the collected reservoir fluid,
disposed at the heel 204c of the production well 204, is greater
than or equal to the boiling point of the liquid heating fluid at
the pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced. Similar to the
above, both of (i) evaporation of the heating fluid that is
disposed in heat transfer communication with the collected
reservoir fluid, but externally of the collection reservoir, and
(ii) evaporation of any heating fluid that is present within the
collected reservoir fluid, is promoted, so as to return the heating
fluid to the reservoir for effecting mobilization of the
hydrocarbon material within the reservoir, and thereby contribute
to the refluxing. As well, by promoting the evaporation, the
produced fluid 224 that is being produced contains less heating
fluid, thereby reducing energy requirements to transport the
produced fluid to the surface (as there is less fluid volume to
produce), and also reducing demands on separation processes for
removal of heating fluid from the produced fluids.
[0116] In some embodiments, for example, the electrical heating of
the collected reservoir fluid 226 by the second electric heater 220
is effected in response to sensing of a temperature, of the
collected reservoir fluid disposed at the heel 204c of the
production well 204, that is at or below a predetermined
temperature that is based upon the boiling point of the liquid
heating fluid at the pressure of the hydrocarbon reservoir portion
from which the mobilized hydrocarbon material is being produced. In
some embodiments, for example, prior to the electrical heating of
the collected reservoir fluid by the second electric heater, a
temperature, of the collected reservoir fluid that is disposed at
the heel 204c of the production well 204, is sensed that is at or
below a predetermined temperature that is based upon the boiling
point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced. In some embodiments, for example, the
predetermined temperature is at or above the boiling point of the
liquid heating fluid at the pressure of the hydrocarbon reservoir
portion from which the mobilized hydrocarbon material is being
produced. The purpose of having the predetermined temperature being
at the boiling point of the liquid heating fluid at the pressure of
the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced, is for evaporating liquid
heating fluid that has collected within the well. Liquid heating
fluid that has collected within the well would be disposed at or
below the boiling point of the liquid heating fluid at the pressure
of the hydrocarbon reservoir portion from which the mobilized
hydrocarbon material is being produced (where the heating fluid, in
the liquid state, is water, this would be the saturated steam
temperature within the reservoir). By effecting electrical heating
while the collected reservoir fluid is disposed at or below the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, the intention is to vaporize the liquid
heating fluid that has collected within the well as part of the
collected reservoir fluid. In some embodiments, for example, it may
be intended to vaporize the heating fluid that is disposed
externally of the well, in which case the predetermined temperature
may be above the boiling point of the liquid heating fluid at the
pressure of the hydrocarbon reservoir portion from which the
mobilized hydrocarbon material is being produced, for purposes of
precluding collection of the heating fluid within the well.
[0117] As discussed above, in some embodiments, for example, the
collected reservoir fluid 226 consists of, or substantially
consists of, the mobilized hydrocarbon material. In those
embodiments where the second electric heater 206 is disposed in
direct heat transfer communication with the collected reservoir
fluid, by having the collected reservoir fluid consisting of, or
substantially consisting of, the mobilized hydrocarbon material,
evaporation of condensed heating fluid, disposed in heat transfer
communication with the collected reservoir fluid, may produce
evaporated heating fluid having a relatively higher temperature,
owing to the fact that the mobilized hydrocarbon material can be
heated to higher temperatures by the second electric heater, and
transfer this higher quality heat to any condensed heating fluid
disposed in heat transfer communication with the collected
reservoir fluid, versus direct heating of the condensed heating
fluid by the second electric heater (without any intervening liquid
heat transfer medium 704).
[0118] Also, by having the collected reservoir fluid 226 be free,
or substantially free, of the heating fluid, scale formation within
the production well 204 may be mitigated. Where the heating fluid,
in its liquid state, includes water, it is preferable that water
does not become disposed with structures within the production
well, including the second electric heater 206, as evaporation of
water in this context may result in precipitation of dissolved
scale-forming solids within the production well, including onto the
second electric heater or other structures, resulting in scale
formation. Accordingly, in such embodiments, by ensuring that the
collected reservoir fluid is free, or substantially free, of the
heating fluid, the collected heating fluid is fluidically isolated,
or substantially fluidically isolated, from the production well,
thereby mitigating potential scale formation within the production
well (including scale formation on the second electric heater).
[0119] Further, as a necessary incident, by having the collected
reservoir fluid 226 be free, or substantially free, of the heating
fluid, production of a "drier" hydrocarbon material is facilitated.
This reduces energy requirements to transport the produced fluid
224 to the surface 2006 (as there is less fluid volume to produce)
and also reduces demands on separation processes for removal of
heating fluid from the produced fluids.
[0120] In this respect, in some embodiments, for example, the rate
of heating of the collected reservoir fluid by the second electric
heater 220 is modulated such that the collected reservoir fluid 226
consists of, or substantially consists of, the mobilized
hydrocarbon material, and, in this respect, is free, or
substantially free, of the heating fluid.
[0121] In some embodiments, for example, the composition of the
collected reservoir fluid 226 may be sensed by a densitometer. In
this respect, the rate of heating effected by the electric heater
220 may be modulated based on sensing of the density of the
collected reservoir fluid by the densitometer. In response to
sensing of a density of the collected reservoir fluid that is
characteristic of a collected reservoir fluid having excessive
non-hydrocarbon fluid (such as the heating fluid), the rate of
heating by the electric heater 220 may be increased to effect
evaporation of the fluid. This will promote the maintenance of a
collected reservoir fluid that consists of hydrocarbon material, or
substantially hydrocarbon material, and, in this respect, is free,
or substantially free, of the heating fluid. This promotes reflux
of the condensed heating fluid (as above-described), higher quality
heat transfer to effect the evaporation of the condensed heating
fluid, mitigates scale formation, and production of "drier"
hydrocarbon material.
[0122] In some embodiments, for example, the electric heater 220 is
submerged within the collected reservoir fluid 226 (consisting of
hydrocarbon material, or substantially hydrocarbon material, and,
in this respect, being free, or substantially free, of the heating
fluid), and the producing is modulated such that sufficient
collected reservoir fluid is maintained within the production well
204 such that the electric heater is submerged within collected
reservoir fluid.
[0123] In those embodiments where the temperature of the collected
reservoir fluid 226, within the production well 204, is above the
boiling point of the liquid heating fluid at the pressure of the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, the collected reservoir fluid is
produced, such that the produced collected reservoir fluid 224 is
conducted to above the surface of the earth. In some embodiments,
for example, the temperature of the collected reservoir fluid is
between: (i) a temperature that is 10 degrees Celsius above the
steam saturation temperature at the pressure within the hydrocarbon
reservoir, and (ii) 350 degrees Celsius. In some embodiments, for
example, the collected reservoir fluid 226 consists of, or
substantially consists of, mobilized hydrocarbon material, and, in
some embodiments, for example, is free, or substantially free, of
the heating fluid. Once disposed above the surface of the earth
(such as, for example, within the surface facilities), the
collected reservoir fluid becomes disposed in indirect heat
exchange communication with a heat transfer fluid such that heat is
indirectly transferred to the heat transfer fluid. The transferring
of heat to the heat transfer fluid is such that the heat transfer
fluid is evaporated. The evaporated heat transfer fluid is
communicated to a turbine such that rotation of the turbine is
effected, such that electricity is generated.
[0124] In some embodiments, for example, the laterally extending
section 204a of the production well 204 is disposed below that of
the laterally extending section of the non-production well 202. In
some of these embodiments, for example, the laterally extending
section of the production well 204 is disposed in alignment, or
substantially alignment, with the laterally extending section of
the non-production well 202.
[0125] In some embodiments, for example, the laterally, or
substantially laterally, extending section 204a of the production
well 204 is co-operatively configured with the electric heater 220
such that while the reservoir fluid is being conducted towards the
well 204, the laterally, or substantially laterally, extending
section of the production well is disposed to receive and collect
the reservoir fluid across (but not necessarily continuously
across) a reservoir fluid-receiving of the laterally, or
substantially laterally, extending section of the production well,
and the length of the operative portion, measured along the axis of
the reservoir fluid-receiving portion, is at least 1000 metres.
Because significant heating fluid is not supplied from the surface,
heat losses, associated with longer wells, is not concerning, as it
is for SAGD operations. Also, because the volumetric flow of
produced fluid is relatively less than for SAGD production,
hydraulic pressure losses are also not a material factor for well
design. In combination, this enables the use of longer wells in
in-situ reflux operations to effect production of hydrocarbon
material, although shorter wells (i.e. those less than 1000 metres)
could also be used.
[0126] In some embodiments, for example, the vertically, or
substantially vertically, extending section 204b of the production
well 204 has a length, measured along the axis of the vertically,
or substantially vertically, extending section, of at least 1000
metres, so as to allow production from deeper resources. Again,
heat losses and hydraulic pressure losses, with in-situ reflux are
not concerning, as it is for SAGD operations, and it is, possible
to, therefore, use longer wells, although shorter wells (i.e. those
less than 1000 metres in depth) could also be used.
[0127] In some embodiments, for example, where the hydrocarbon
reservoir contains relatively less viscous hydrocarbon material
that is targeted for production, the non-production and production
wells 202, 204 may be spaced apart a relatively greater distance
than SAGD well pairs, such as by a spacing distance that is greater
than five (5) metres, such as ten (10) metres.
[0128] In some embodiments, for example, the heating fluid being
electrically heated within the non-production well 202, in its
liquid state, may include formation water that is resident within
the hydrocarbon reservoir, or may include heating fluid (for
example, water) that is injected into the hydrocarbon reservoir and
supplied from above the surface, or may include both of the
formation water and the injected heating fluid. In some
embodiments, for example, the supplying of supplied liquid heating
fluid 118 is effected via an injector string 216 disposed within
the non-production well 202. In some embodiments, for example, the
injector string includes a "spaghetti string". In those embodiments
where at least a fraction of the liquid heating fluid is being
supplied from above the surface, in some of these embodiments, for
example, the ratio of the volumetric rate at which the supplied
liquid heating fluid is being supplied to the rate at which heat
energy is being delivered by the electric heater is less than 25
cubic metres per day per megawatt, such as, for example, less than
10 cubic metres per day per megawatt.
[0129] In some embodiments, for example, heating fluid may be lost
to the reservoir, and make-up heating fluid may be required. In
this respect, while the heating of a liquid heating fluid is being
effected, supplemental liquid heating fluid may be supplied from a
source disposed above the surface 2002, such as via the injection
string 216. In this respect, the liquid heating fluid includes the
supplemental liquid heating fluid. In some embodiments, for
example, the supplying of the supplemental liquid heating fluid is
effected in response to sensing of a pressure, within the
hydrocarbon reservoir portion from which the mobilized hydrocarbon
material is being produced, that is less than a predetermined
pressure. The predetermined pressure is based on, amongst other
things, the desirability of operating at higher pressures in order
to provide a greater driving force for production, balanced versus
the recognition that heat transfer efficiency is more efficient at
lower pressures and that cap rock integrity may limit the maximum
possible operating pressure. The injector string 216 may be
disposed outside of the well, and could also be used to inject
heating fluid during start-up.
[0130] In operation, during start-up, the hydrocarbon reservoir is
heated by heat generated by the first and second electric heaters
206, 220 (either directly or via the heater assembly), such that
hydrocarbon material is mobilized by the heating of the hydrocarbon
reservoir. The mobilized hydrocarbon material drains and enters the
non-production well 202 via ports 208. The heating is effected by
conduction, convection, or a combination of conduction and
convection. In some embodiments, for example, the convective
heating is effected by evaporated formation water, such that the
heating fluid includes evaporated formation water. Subsequently,
or, in parallel, heating fluid is supplied from the surface
facilities and is injected into the hydrocarbon reservoir.
Evaporation of the injected heating fluid is effected by the heat
generated by the electric heater 206. The evaporated heating fluid
is conducted to the hydrocarbon reservoir and transfers heat energy
to the hydrocarbon material such that the hydrocarbon material is
mobilized and the heating fluid is condensed.
[0131] Reservoir fluid enters the non-production well 202 via ports
208, collects within the collection reservoir 210 and is heated by
the first electric heater 206 (either directly or via the heater
assembly). The heating is controlled such that the collected
reservoir fluid is free, or substantially free, of heating fluid,
and, in some embodiments, for example, consists of, or
substantially consists of, the mobilized hydrocarbon material. The
heated reservoir fluid transfers heat to condensed heating fluid
that is disposed in heat transfer communication with the reservoir
fluid, thereby effect re-evaporation of the condensed heating
fluid, and thereby effect the reflux 214.
[0132] Reservoir fluid 226 also drains, by gravity, and enters the
production well 204 through ports 222, and is collected within the
collection reservoir defined within the production well 204, and is
heated by the second electric heater. The heating is controlled
such that the collected reservoir fluid is free, or substantially
free, of heating fluid, and, in some embodiments, for example,
consists of, or substantially consists of, the mobilized
hydrocarbon material. The heated reservoir fluid transfers heat to
any condensed heating fluid that is disposed in heat transfer
communication with the reservoir fluid, thereby effect
re-evaporation of the condensed heating fluid, and thereby effect
the reflux 228, and also thereby providing a drier hydrocarbon
material for production.
[0133] Eventually, after sufficient hydrocarbon material has been
mobilized and drained into the non-production and production wells
202, 204 (such as, for example, as described above), an evaporated
heating fluid chamber develops (where the heating fluid, in the
liquid state, is water, then a steam chamber would be developed).
The developed evaporated heating fluid chamber enables evaporated
heating fluid to be conducted to hydrocarbon material within the
hydrocarbon reservoir (and, more specifically, at the edge of the
chamber) so as to heat, mobilize and then drive drainage of the
hydrocarbon material towards the production well 204. In parallel,
the drained hydrocarbon material may be produced from the
production well 204 using reservoir pressure or with assistance of
artificial lift, such as with a downhole pump or gas lift.
[0134] In some embodiments, for example, it may be desirable, after
the hydrocarbon reservoir has been sufficiently heated in the
region surrounding the production well 204, to reduce the rate at
which heat is generated by the second electric heater, or suspend
the generation of heat by the second electric heater, thereby
reducing operating costs and also mitigating coking. In this
respect, the process includes:
[0135] during a first time interval, effecting electrical heating
of the hydrocarbon reservoir with both of the first and second
electric heaters (in some embodiments, for example, liquid heating
fluid is supplied through the non-production well 202 and is
heating by the first electric heater, and, in some embodiments, for
example, liquid heating fluid may also be supplied through the
production well 204 and be heated by the second electric heater);
and after the first time interval, and during a second time
interval, while either one of:
[0136] (a) the second electrical heater is delivering heat energy
at a rate that is less than 50% of the rate at which heat energy is
being delivered by the second electrical heater during the first
time interval, or
[0137] (b) the electrical heating being effected by the second
electrical heater has become suspended;
[0138] and while continuing to effect the electrical heating with
the first electric heater: (a) supplying a liquid heating fluid to
the hydrocarbon reservoir through the non-production well 202, such
that a combined heating fluid, including the supplied liquid
heating fluid and a condensed heating fluid, is evaporated to
produce a gaseous heating fluid that is conducted into the
reservoir and then condensed upon heating of hydrocarbon material
to produce the condensed heating fluid; and [0139] (b) producing,
via the production well 204, reservoir fluid that has collected
within the production well 204, wherein the collected reservoir
fluid includes hydrocarbon material that has been mobilized by the
electrical heating.
[0140] The electrical heating of the hydrocarbon reservoir during
the first time interval, in combination with the electrical heating
of the hydrocarbon reservoir during the second time interval by the
first electric heater and any electrical heating of the hydrocarbon
reservoir during the second time interval by the second electrical
heater, is sufficient to, during the second time interval, effect
evaporation of the condensed heating fluid, that has been condensed
after having effected heating and mobilization of the hydrocarbon
material, prior to the condensed heating fluid being received by
the production well 204.
[0141] In some embodiments, for example, the electrical heating of
the hydrocarbon reservoir during the first time interval, in
combination with the electrical heating of the hydrocarbon
reservoir during the second time interval by the first electric
heater and any electrical heating of the hydrocarbon reservoir
during the second time interval by the second electrical heater, is
sufficient to, during the second time interval, effect evaporation
of the condensed heating fluid, that has been condensed after
having effected heating and mobilization of the hydrocarbon
material, prior to the condensed heating fluid being received by
the production well 204, such that the collected reservoir fluid
consists of, or substantially consists of, the mobilized
hydrocarbon material and, in this respect, is free, or
substantially free, of heating fluid.
[0142] Reducing the rate at which heat energy is being delivered by
the electrical heater to the reservoir fluid that has collected
within the production well 204, after sufficient electrical heating
of the hydrocarbon reservoir during the first time interval,
mitigates coking while also enabling the production of reservoir
fluid, collecting within the production well, that is free, or
substantially free, of the heating fluid. In some embodiments, for
example, the collected reservoir fluid consists of, or
substantially consists of, hydrocarbon material. It is believed
that, after sufficient time, continued heating, at the same rate,
by the second electric heater becomes unnecessary to effect
evaporation of the condensed heating fluid, that has been condensed
after effecting heating and mobilization of the hydrocarbon
material, prior to the condensed heating fluid being received by
the production well 204, and that the rate at which such heat
energy is being delivered can be reduced.
[0143] In some embodiments, for example, during the first time
interval, supplying of a liquid heating fluid is also being
effected via the non-production well 202, such that a combined
heating fluid, including the supplied liquid heating fluid and a
condensed heating fluid, is evaporated to produce a gaseous heating
fluid that is conducted into the reservoir and then condensed upon
heating of hydrocarbon material to produce the condensed heating
fluid.
[0144] In some embodiments, for example, during the first time
interval, the heat being generated by the first electric heater
effects heating of the reservoir fluid that has collected within
the non-production well such that the collected reservoir fluid is
free, or substantially free, of heating fluid. In some embodiments,
for example, the collected reservoir fluid consists of, or
substantially consists of, hydrocarbon material that has been
heated and mobilized by the gaseous heating fluid and drained to
the non-production well. In this respect, the hydrocarbon material,
that has been collected within the non-production well function as
a heat transfer medium, transferring heat generated by the first
electric heater to the condensed heating fluid disposed externally
of the non-production well. As well, during the first time
interval, reservoir fluid, including hydrocarbon material that has
been heated and mobilized by the gaseous heating fluid, that has
been collected within the production well 204, is produced via the
production well 204. In some of these embodiments, for example,
during the first time interval, the electrical heating by the
second electrical heater is such that the temperature of the
collected reservoir fluid is less than 350 degrees Celsius (such
as, for example, less than 350 degrees Celsius, such as, for
example, less than 250 degrees Celsius, such as, for example, less
than 220 degrees Celsius), thereby mitigating coking within the
production well 204 during the first time interval.
[0145] In one aspect, the hydrocarbon reservoir 1000 is spaced
apart from the earth's surface 1002 by a minimum distance of less
than 75 metres, such as, for example, less than 50 metres. Because
the subject process can be operated at relatively low pressures (as
compared to, for example, SAGD), implementation of the process in
relatively shallow reservoirs is made possible, as the risk of
adversely affecting the environment at or near the earth'' s
surface, including risk of contaminating ground water, is
mitigated.
[0146] In another aspect, the process includes a lower pressure
phase and a higher pressure phase.
[0147] During the lower pressure phase, the pressure within the
reservoir is disposed below a predetermined low pressure. In some
embodiments, for example, the pressure within the reservoir 1000 is
maintained below the predetermine low pressure by co-operatively
controlling the rate at which supplemental liquid heating fluid is
supply into the reservoir 1000 (such as, for example, from the
surface) for heating by the electrical heater with the rate at
which the produced fluid is being produced. In some embodiments,
for example, the predetermined low pressure is less than 1500 kPa,
such as, for example, less than 1000 kPa, such as, for example, 750
kPa. In some embodiments, for example, the predetermined low
pressure is 500 kPa.
[0148] After having operated the lower pressure phase, the low
pressure phase is suspended and pressure within the reservoir 1000
is then increased to above the predetermined high pressure. In some
embodiments, for example, the pressure increase is effected at a
rate of increase in pressure within the reservoir 1000 of at least
about 3 kPa per day, such as, for example, at least 5 kPa per day,
such as, for example, at least 1 kPa per day.
[0149] In some embodiments, for example, at the time of suspension
of the low pressure phase, supplemental liquid heating fluid is
being supplied into the reservoir 100, for heating by the
electrical heater, while the produced fluid is being produced. In
some of these embodiments, for example, the increase in pressure is
effected by decreasing the rate of production of the produced
fluid, while continuing supplying of the supplemental liquid
heating fluid into the reservoir, for heating by the electrical
heater, at the same or substantially the same rate. In other ones
of these embodiments, for example, the increase in pressure is
effected by continuing production of the produced fluid at the same
or substantially the same rate, while increasing the rate at which
supplemental liquid heating fluid is being supplied into the
reservoir 1000 for heating by the electrical heater. In this
respect, in those embodiments where supplemental liquid heating
fluid is being supplied into the reservoir 100, for heating by the
electrical heater, while the produced fluid is being produced, the
pressure within the reservoir is increased by co-operatively
modulating the rate at which the supplemental liquid heating fluid
is being supplied to the reservoir 1000 for heating by the
electrical heater with modulating of the rate at which the produced
fluid is produced from the reservoir 1000.
[0150] In some embodiments, for example, at the time of suspension
of the low pressure phase, there is an absence of supplying of
supplemental liquid heating fluid into the reservoir 100, for
heating by the electrical heater, while the produced fluid is being
produced. In some of these embodiments, for example the increase in
pressure is effected by decreasing the rate of production of the
produced fluid.
[0151] During the higher pressure phase, the pressure within the
reservoir is disposed above a predetermined high pressure. In some
embodiments, for example, the pressure within the reservoir 1000 is
maintained above the predetermine high pressure by co-operatively
controlling the rate at which supplemental liquid heating fluid is
supply into the reservoir 1000 (such as, for example, from the
surface) for heating by the electrical heater with the rate at
which the produced fluid is being produced. In some embodiments,
for example, the predetermined high pressure is greater than 1750
kPa, such as, for example, greater than 2000 kPa, such as, for
example, greater than 2250 kPa. In some embodiments, for example,
the predetermined high pressure is 2500 kPa.
[0152] In some embodiments, for example, the high pressure phase is
then suspended, and pressure within the reservoir 1000 is then
reduced to below the predetermined low pressure. In some
embodiments, for example, the pressure reduction is effected at a
rate of decrease in pressure within the reservoir 1000 of at least
about 3 kPa per day, such as, for example, at least 5 kPa per day,
such as, for example, at least 1 kPa per day.
[0153] In some embodiments, for example, at the time of suspension
of the high pressure phase, supplemental liquid heating fluid is
being supplied into the reservoir 100, for heating by the
electrical heater, while the produced fluid is being produced. In
some of these embodiments, for example, the reduction in pressure
is effected by suspending supplying of the supplemental liquid
heating fluid into the reservoir for heating by the electrical
heater. In other ones of these embodiments, for example, the
reduction in pressure is effected by increasing the rate of
production of the produced fluid, while continuing supplying of the
supplemental liquid heating fluid into the reservoir, for heating
by the electrical heater, at the same or substantially the same
rate. In other ones of these embodiments, for example, the decrease
in pressure is effected by continuing production of the produced
fluid at the same or substantially the same rate, while decreasing
the rate at which supplemental liquid heating fluid is being
supplied into the reservoir 1000 for heating by the electrical
heater. In this respect, in those embodiments where supplemental
liquid heating fluid is being supplied into the reservoir 100, for
heating by the electrical heater, while the produced fluid is being
produced, the pressure within the reservoir is decreased by
co-operatively modulating the rate at which the supplemental liquid
heating fluid is being supplied to the reservoir 1000 for heating
by the electrical heater with modulating of the rate at which the
produced fluid is produced from the reservoir 1000.
[0154] In some embodiments, for example, at the time of suspension
of the high pressure phase, there is an absence of supplying of
supplemental liquid heating fluid into the reservoir 100, for
heating by the electrical heater, while the produced fluid is being
produced. In some of these embodiments, for example the reduction
in pressure is effected by increasing the rate of production of the
produced fluid.
[0155] In some embodiments, for example, the ratio of the
predetermined high pressure to the predetermined low pressure is
greater than 1.5, such as, for example, greater than 2, such as,
for example, greater than 3.
[0156] In some embodiments, for example, the duration of the high
pressure phase is at least one (1) month, such as, for example, at
least three (3) months. In some embodiments, for example, the
duration of the low pressure phase is at least one (1) month, such
as, for example, at least three (3) months. In some embodiments,
for example, the ratio of the time duration of the high pressure
phase to the time duration of the low pressure phase is between
1.5:1 and 1:1.5, such as, for example, 1.2:1 to 1:1.2, such as, for
example, 1.1:1 to 1:1.1. In some embodiments, for example, the
ratio is 1:1.
[0157] In some embodiments, for example, the high pressure phase
and the low pressure phase define a cycle, and the cycle is
repeated at least once, such as, for example, at least twice, such
as, for example, at least three (3) times, such as, for example, at
least five (5) times.
[0158] During the increase in pressure, the rate of production is
reduced, but the produced gaseous heating fluid is driven into the
formation and has a greater tendency to condense and fill pore
spaces within the reservoir to improve thermal conductivity.
[0159] During the reduction in pressure, the rate of production
increases.
[0160] In the above description, for purposes of explanation,
numerous details are set forth in order to provide a thorough
understanding of the present disclosure. However, it will be
apparent to one skilled in the art that these specific details are
not required in order to practice the present disclosure. Although
certain dimensions and materials are described for implementing the
disclosed example embodiments, other suitable dimensions and/or
materials may be used within the scope of this disclosure. All such
modifications and variations, including all suitable current and
future changes in technology, are believed to be within the sphere
and scope of the present disclosure. All references mentioned are
hereby incorporated by reference in their entirety.
* * * * *