Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR RECOVERING BITUMEN FROM A BITUMEN RESERVE
USING ELECTROMAGNETIC HEATING
TECHNICAL FIELD
[0001] The following relates to systems and methods for recovering bitumen
from a bitumen
reserve using electromagnetic heating.
DESCRIPTION OF THE RELATED ART
[0002] Bitumen is known to be considerably viscous and does not flow like
conventional
crude oil, and can be present in an oil sand reservoir. As such, bitumen is
recovered using what
are considered non-conventional methods. For example, bitumen reserves are
typically
extracted from a geographical area using either surface mining techniques,
wherein overburden
is removed to access the underlying pay (e.g., oil sand ore-containing
bitumen) and transported
to an extraction facility; or using in situ techniques, wherein subsurface
formations (containing
the pay) are heated such that the bitumen is caused to flow into one or more
wells drilled into
the pay while leaving formation rock in the reservoir in place. Both surface
mining and in situ
processes produce a bitumen product that is subsequently sent to an upgrading
and refining
facility, to be refined into one or more petroleum products, such as gasoline
and jet fuel.
Bitumen reserves that are too deep to feasibly permit bitumen recovery by
mining techniques
are typically accessed by drilling wellbores into the hydrocarbon bearing
formation (i.e. the pay)
and implementing an in situ technology. There are various in situ technologies
available, such
as steam driven based techniques, e.g., Steam Assisted Gravity Drainage
(SAGD), Cyclic
Steam Stimulation (CSS), etc. SAGD and CSS typically require horizontally
oriented wells that
are drilled directionally from surface and production equipment located at a
surface site.
[0003] For some bitumen reserves, steam driven techniques can be considered
less
desirable or less economical.
SUMMARY
[0004] In one aspect, there is provided a method for recovering bitumen
from a bitumen
reserve. The method comprises recovering a bitumen containing fluid from a pay
region in the
bitumen reserve via gravity drainage, by heating the bitumen in the pay region
using at least
one electromagnetic antenna that extends into the pay region from below from a
tunnel
excavated into a formation that at least in part underlies the pay region.
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. .
[0005] In another aspect, there is provided a system for recovering
bitumen from a bitumen
reserve. The system comprises a tunnel excavated into a formation from ground
level that at
least in part underlies a pay region in the bitumen reserve, at least one
electromagnetic (EM)
antenna extending into the pay region from the tunnel below the pay region, at
least one EM
transmitter for powering the at least one EM antenna, and at least one
production apparatus
configured to recover a bitumen containing fluid from the pay region via
gravity drainage.
[0006] In yet another aspect, the tunnel extends from the formation
to surface and is sized
to accommodate equipment configured to drill a well bore into which the at
least one
electromagnetic antenna is positioned.
[0007] In yet another aspect, the tunnel extends from the formation
to surface and is sized
to accommodate equipment configured to drill a well bore into which a producer
well extending
into the pay region near the at least one electromagnetic antenna is
positioned.
[0008] In yet another aspect, the tunnel extends from the formation
to surface and is sized
to accommodate equipment configured to drill a well bore into which a solvent
injector is
positioned.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments will now be described by way of example only with
reference to the
appended drawings wherein:
[0010] FIG. 1(a) is a cross-sectional elevation view of an
electromagnetic (EM) in situ
gravity drainage system deployed in a tunnel below a bitumen reservoir with a
producer well
drilled into the bitumen reservoir;
[0011] FIG. 1(b) is a cross-sectional elevation view of an EM in
situ gravity drainage
system deployed in a tunnel below a bitumen reservoir with a producer well
installed in the
tunnel;
[0012] FIG. 1(c) is a cross-sectional elevation view of an EM in
situ gravity drainage
system deployed in a tunnel below a bitumen reservoir with producer wells used
in both the
bitumen reserve and the tunnel;
[0013] FIG. 1(d) is a cross-sectional elevation view of an EM in
situ gravity drainage
system deployed in a tunnel below a bitumen reservoir and having additional
solvent injection
wells;
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,
[0014] FIG. 2(a) is a cross-sectional end view of a tunnel with a
substantially vertically
oriented EM antenna;
[0016] FIG. 2(b) is a cross-sectional end view of a tunnel with multiple
EM antennas drilled
from below at different angles with respect to vertical;
[0016] FIG. 3(a) is a cross-sectional elevation view of a horizontally
oriented tunnel;
[0017] FIG. 3(b) is a cross-sectional elevation view of a tunnel
configured to follow a
contour defined by the interface between a bitumen reservoir and an underlying
formation into
which the tunnel is excavated;
[0018] FIG. 3(c) is a cross-sectional elevation view of a sinkhole in the
pay targeted by EM
antennas extending from a tunnel below the sinkhole;
[0019] FIG. 4(a) is a schematic plan view of a network of tunnels for
deploying an EM in
situ gravity drainage system below a bitumen reservoir;
[0020] FIG. 4(b) is another schematic plan view of a network of tunnels
for deploying an
EM in situ gravity drainage system below a bitumen reservoir;
[0021] FIG. 4(c) is yet another schematic plan view of a network of
tunnels for deploying an
EM in situ gravity drainage system below a bitumen reservoir;
[0022] FIG. 4(d) is yet another schematic plan view of a network of
tunnels for deploying
an EM in situ gravity drainage system below a bitumen reservoir;
[0023] FIG. 5(a) is a cross-sectional elevation view of an access tunnel
for an EM in situ
gravity drainage system deployed in a tunnel below a bitumen reservoir;
[0024] FIG. 5(b) is a cross-sectional elevation view of an access shaft
for an EM in situ
gravity drainage system deployed in a tunnel below a bitumen reservoir;
[0025] FIG. 5(c) is a cross-sectional elevation view of an EM in situ
gravity drainage
system deployed in a tunnel below a bitumen reservoir, wherein the tunnel is
accessed from a
naturally occurring outcrop or a surface mine;
[0026] FIG. 6 is an enlarged cross-sectional elevation view of an EM
antenna and a
dedicated EM transmitter;
[0027] FIG. 7 is an enlarged cross-sectional elevation view of portion of
an array of EM
antennas powered by a shared EM transmitter;
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[0028] FIG. 8 is a schematic illustration of a phased array wavefront
generated using an
array of EM antennas;
[0029] FIG. 9 is a schematic diagram of an array of EM antennas deployed in
multiple
tunnels;
[0030] FIG. 10 is a flowchart illustrating operations performed in
controlling a distributed
array of EM antennas;
[0031] FIG. 11(a) is an enlarged cross-sectional view illustrating gravity
drainage through
an antenna well into a tunnel-deployed collector;
[0032] FIG. 11(b) is an enlarged cross-sectional view illustrating an
antenna well
configured to support both an EM antenna and solvent injection apparatus;
[0033] FIG. 12(a) is a cross-sectional elevation view illustrating an
implementation for a
producer well drilled from surface; and
[0034] FIG. 12(b) is a cross-sectional elevation view illustrating another
implementation for
a producer well drilled from surface.
DETAILED DESCRIPTION
[0035] In the following, there is provided a system and method of
recovering bitumen from a
bitumen reserve. The system and method operate to recover a bitumen containing
fluid from a
pay region in the bitumen reserve via gravity drainage, by heating the bitumen
in the pay region
using at least one electromagnetic antenna that extends into the pay region
from below, from a
tunnel excavated into a formation that at least in part underlies the pay
region.
[0036] In an implementation of the system and method, the electromagnetic
antennas can
be operated to produce radio frequency (RF) signals that penetrate the pay
region to heat the
bitumen. Solvent can also be injected subsequent to heating the pay region
using such RF
signals. In at least some implementations, the bitumen containing fluid is
recovered using a
producer well drilled into the pay region near the at least one
electromagnetic antenna, wherein
the producer well configured to produce the bitumen containing fluid to
surface. The bitumen
containing fluid can also (or alternatively) be recovered using other
production apparatus, such
as a collector located in the tunnel, the collector being fluidly connected to
the pay region.
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[0037] Each electromagnetic antenna can be powered by a dedicated
electromagnetic
transmitter, or an array having a plurality of electromagnetic antennas are
powered by a
common electromagnetic transmitter.
[0038] In at least some implementations the tunnel is part of a network of
tunnels. Such a
network of tunnels can be implemented in various configurations as will be
explained in greater
detail below.
[0039] The use of electromagnetic heating (such as RF heating) rather than
conductive
electrical heating avoids the creation of a temperature gradient away from the
heat source,
while reducing the temperature required at the source to generate enough heat
at further
distances from the heat source. The use of electromagnetic heating can be
advantageously
combined with solvent injection to reduce or eliminate the need to heat the
solvent prior to
injection in order to mobilize the bitumen at lower temperatures than
alternative in situ bitumen
recovery techniques such as steam-based SAGD and CSS. Moreover, by having
electromagnetic antennas extending into the pay from below via one or more
tunnels, the
footprint required at surface can be reduced, when compared to drilling into
the pay from above.
Also, abandonment of the tunnels post-production requires only backfilling of
the tunnels. The
equipment used for bitumen recovery, including the antennas, transmitters,
etc. are located
away from inclement weather thus reducing maintenance costs and disruptions
due to such
weather.
[0040] Turning now to the figures, FIG. 1(a) illustrates a bitumen reserve,
hereinafter
referred to as the "pay 10"; which is accessed for in situ bitumen recovery
using a tunnel 12
excavated into a formation that at least partially underlies the pay 10,
hereinafter referred to as
the "underlying formation 14". In the example shown in FIG. 1(a), the pay 10
itself underlies a
layer of overburden 16 between the pay 10 and the surface 18.
[0041] The tunnel 12 facilitates the installation of a series of EM
antennas 20 by drilling
antenna wells 21 into the pay 10, from the tunnel 12, which is below the pay
10. The EM
antennas 20 are powered in order to emit EM signals 22 into the pay 10 to
increase the
temperature of bitumen 24 in the pay 10 and thereby decrease the viscosity of
the bitumen
and/or to stimulate the bitumen for a solvent injection process. The bitumen
is therefore
mobilized at least in part by the EM signals 22, causing a bitumen containing
fluid 24 to flow
under the influence of gravity towards the tunnel 14.
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. .
[0042] In EM heating, one or more antennas 20 are inserted into the
bitumen reserve, and a
power transmitter 40, 50 (see also FIGS. 6 and 7) is used to power the
antennas 20, which
induces an EM field through the pay 10. The absorbed EM energy heats the water
and
oil/bitumen within the pay 10, thereby resulting in flow of the hydrocarbon
material. A producer
well 26 is then used to withdraw the mobilized as outlined above.
[0043] EM heating uses one or more of three energy forms: electric
currents, electric fields,
and magnetic fields at radio frequencies (i.e. RF energy). Depending on
operating parameters,
the heating mechanism can be resistive by Joule effect or dielectric by
molecular moment.
Resistive heating by Joule effect is often described as electric heating,
where electric current
flows through a resistive material, and dielectric heating occurs where polar
molecules, such as
water, change orientation when immersed in an electric field as is known in
the art. Magnetic
fields also heat electrically conductive materials through the formation of
eddy currents, which in
turn heat resistively. Thus magnetic fields can provide resistive heating
without conductive
electrode contact.
[0044] EM heating can use electrically conductive antennas 20 to
function as heating
applicators, e.g., dipole antennas. The antenna 20 is a passive device that
converts applied
electrical current into oscillating electromagnetic fields, and electrical
currents in the target
material, without having to heat the structure to a specific threshold level.
[0045] Antennas 20, including antennas 20 for EM heat application as
described herein, can
provide multiple field zones which are determined by the radius from the
antenna r and the
electrical wavelength A (lambda). Susceptors are materials that heat in the
presence of RF
energies. Salt water is a particularly good susceptor for EM heating; it can
respond to all three
RF energies: electric currents, electric fields, and magnetic fields. Oil
sands and heavy oil
formations commonly contain connate liquid water and salt in sufficient
quantities to serve as an
EM heating susceptor. "connate" refers to liquid trapped in the pores of the
oil sand formation.
[0046] As bitumen becomes mobile at or below the boiling point of
water at reservoir
conditions, liquid water may be a used as an EM heating susceptor during
bitumen extraction,
permitting well stimulation by the application of RF energy. In general, EM
heating has superior
penetration and heating rate compared to conductive heating in hydrocarbon
formations. EM
heating can also have properties of thermal regulation because steam is not an
EM heating
susceptor. In other words, once the water is heated sufficiently to vaporize,
it is no longer
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electrically conductive and is not further heated to any substantial degree by
continued
application of electrical energy.
[0047] In one implementation, a horizontally drilled producer well 26
recovers the bitumen
containing fluid 24, which can be pumped or otherwise transported to surface
for subsequent
processing, e.g., using a pump 27 as shown in FIG. 1(a). The horizontally
drilled producer well
26 can be inclined in order to have enough of a slope to allow bitumen to
drain towards the
pump 27.
[0048] As illustrated in FIG. 1(b), the mobilized bitumen containing fluid
24 can also be
collected within the tunnel 12 using a pipe or other collection mechanism,
hereinafter referred to
as a "collector 28". The collector 28 is installed in the tunnel 12 and
configured to permit the
bitumen containing fluid 24 to be recovered through the base portion of the
antenna wells 100
as discussed in greater detail below.
[0049] It can be appreciated that the bitumen containing fluid 24 can also
be recovered
using both an inclined horizontally drilled producer well 26 and a collector
28 located in the
tunnel 12, as illustrated in FIG. 1(c). As such, the bitumen containing fluid
24 can be recovered
and produced to surface 18 using one or more "production apparatuses", which
can include one
or more producer wells 26, one or more collectors 28, or both. It can also be
appreciated that
other types of production apparatus are possible, e.g., any well or passage
providing fluid
communication with the pay 10 to permit gravity drainage into the production
apparatus.
[0050] In addition to using EM signals 22 to mobilize the bitumen, solvent
can also be
injected into the pay 10, e.g., subsequent to applying EM heating, similar to
the Enhanced
Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH) advance oil
recovery
technique, described in U.S. Patent No. 8,616,273. Solvent can be used to
mobile the bitumen
at lower temperatures than, for example, steam-based heating techniques.
[0051] In the ESEIEH process, RF heating can be used to heat the pay 10
prior to solvent
injection. When the pay 10 reaches the desired temperature within a desired
region, an
appropriate solvent is then injected into the pay 10. The solvent partially
mixes with the bitumen
and further reduces its viscosity and partially displaces the hot-diluted
bitumen towards the
producer well 26. The choice of solvent can be similar to existing solvent
injection processes.
The RE-induced heating (or other EM heating) initially heats connate water and
bitumen near
the RE antennas 20. Water and the heated bitumen drain to the producer well 26
creating a flow
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pathway. The flow pathway thus created is then used as the primary conduit to
inject a solvent
from an appropriate well (e.g., the antenna well 21, a separate injector well
29 (see FIG. 1(d)),
or both).
[0052] The RF heating is applied so as to maintain the reservoir
temperature at a level that
is sufficient to allow efficient application of a solvent extraction process.
For example, the
reservoir can be maintained at a temperature of 40-70 C. The temperature can
be maintained
at least in the vicinity of the injected solvent, which dissolves the
partially heated bitumen. The
solvent/bitumen mixture then drains towards the producer well 26.
[0053] In the solvent injection phase, a solvent vapor comes into contact
with bitumen and
through diffusion it creates a mobile, dilute bitumen stream which in turn
drains towards a
producer well 26 via gravity drainage. However, directional RF-induced EM
heating (e.g., as
described herein and shown by way of example in FIG. 8) can be used to provide
the initial
energy to quickly and efficiently heat the bitumen, reducing viscosity by
several orders of
magnitude while simultaneously increasing the solvent diffusion within the
bitumen, while the
solvent mixing provides additional oil viscosity reduction to generate
threshold and higher
commercial rates. Alkanes such as ethane, propane, butane, pentane, etc., or
any mixture of
these alkanes can be used. Other suitable solvents include, without
limitation: naphtha,
toluene, xylene, benzene, diesel, natural gas, etc.
[0054] In any of the configurations shown in FIGS. 1(a) to 1(c), the
antenna wells 21 can be
configured to incorporate solvent injectors 29 (see also FIG. 11(b)). In other
implementations,
one or more solvent injectors 29 can also be drilled into separate wells
located anywhere in the
pay 10, as shown in FIG. 1(d).
[0055] The EM antennas 20 are drilled into the pay 10 from below, via
access provided by
the tunnel 12. The EM antennas 20 can be substantially vertically oriented as
shown in FIG.
2(a), or can be drilled at an angle to vertical as shown in FIG. 2(b). Such
angled EM antennas
20 can be used to target particular portions of the pay 10, to avoid
geological obstructions, etc.
[0056] The EM antennas 20 can be configured to transmit various types of EM
signals 22,
for example, electric currents, electric fields, and magnetic fields at radio
frequencies or
microwave frequencies. The type of EM signals 22 used can affect the number
of, and spacing
between the EM antennas 20. That is, the depth of penetration of the
particular EM signals 22
can require greater or fewer EM antennas 20 to target a bitumen reserve of a
particular size.
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,
The following examples illustrate the use of RF antennas 20 and RF signals 22,
however, it can
be appreciated that the principles described herein can be implemented using
other types of EM
antennas 20 and EM signals 22.
[0057] When a producer well 26 is used, after determining the access
location for the
producer well 26 (or producer wells 26 for multiple tunnels 12), and
determining where the one
or more producer wells 26 will be located relative to the RF antennas 20
(e.g., by conducting
typical computer simulations using geological and reservoir data), the
corresponding access
locations are prepared for drilling, including providing infrastructure for
water and electricity, as
is known in the art. A drilling rig is then installed at the location of the
producer well 26 (e.g.,
inside the tunnel 12 when the producer well 26 begins in the tunnel 12 as
shown in FIGS. 1(a),
1(c), 1(d), 5(a), 5(b), and 5(c)) and drilling commences subject to requisite
inspections. The
drilling phase includes steps of drilling, then running and cementing new
casing, which are
repeated until the drill bit reaches the desired well length by adding new
drill pipe as the well
lengthens. The access location is also prepared for pumping drilling fluid
through the interior of
the drill pipe, which circulates through the drill bit, and returns via the
annulus between the pipe
and the borehole to be cleaned (i.e. processed to remove drilled particles)
and cleaned fluid
pumped back down the drill pipe. It can be appreciated that measurement while
drilling (MWD)
technologies and bends can be utilized to steer the bit and the producer wells
26 in a particular
direction. When the drilling is completed and deemed to be ready for
production, casing is
installed, which extends from the entry of the borehole to the end of the
wells 26 and is
cemented in place. Alternatively, the pay section of the well can be lined
with a slotted liner or
other form of sand control that is not cemented into place. The liner can also
utilize packers and
inflow or injection control devices (ICDs) that divide the producer wells 26
into segments. The
drilling rig can then be moved and used to drill the next well 26 at the same
or a different access
location.
[0058] Drilling equipment is used to drill the producer wells 26. After
drilling the wells 26,
the pump 27 or production equipment 110 (see FIGS. 9(a) and 9(b)) is installed
in one or more
production facilities for recovering bitumen. Completing a particular well for
production can
involve several steps, as is known in the art. For example, a service rig is
moved into location
and used to perform a cleanout trip to the total length of the well to ensure
that there is no
cement or debris left inside the production casing. Alternatively, the well
can be completed by
the drilling rig after the production casing cement has hardened. To allow
mobilized bitumen
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containing fluid 24 to flow into the producer well 26, perforating is
performed to create holes
through the casing and cement, which can be performed before or after
production tubing is
installed in the wells 26. Alternatively, the pay section of the well can be
lined with a slotted
liner or other form of sand control that is not cemented in place. The liner
can utilize packers
and inflow or ICDs that divide the injector or production wells into segments.
The production
tubing is then installed using the service rig. In addition to production
tubing, the operator may
install downhole instrumentation that can include temperature sensors,
pressure sensors or
fiber optic cable. Once the tubing has been landed, a wellhead is installed
over the production
casing.
[0059] The antenna wells 21 can be drilled in a similar manner,
particularly when bitumen
containing fluid 24 is to be recovered using a collector 28. It can be
appreciated that other
drilling techniques can also be used, for example, rock bolt installation
methods employed in the
mining industry.
[0060] The tunnel 12 can be excavated using earth boring equipment,
drilling equipment, or
any other suitable excavation equipment. For example, conventional tunnel
boring equipment
used in the mining and construction industries is suitable for excavating the
tunnels 12. As
shown in FIG. 3(a), the tunnel 12 can be excavated to be substantially level
and horizontal with
relatively longer or shorter antennas 20 used depending on the distance
between the tunnel 12
and the pay 10. The tunnels 12 can also be excavated in order to, at least in
part, follow a
contour defined by the interface between the pay 10 and the underlying
formation 14, as shown
in FIG. 3(b). In this way, gaps between the tunnel 12 and the pay 10 can be
shortened in at
least some areas along the tunnel 12. The tunnel 12 is therefore, in general,
horizontally
oriented although portions of the tunnel 12 can include an incline or slope.
[0061] Referring to FIG. 3(c), it can be appreciated that since the RE
antennas 20 are drilled
into the pay 10 from below, sinkholes 29 or other dips in the formation 14
(e.g., Karst hole)
containing recoverable bitumen can be more easily accessed when compared to
other in situ
techniques such as SAGD where the producer wells are drilled from surface and
generally
extend horizontally above the interface between the pay 10 and the underlying
formation 14,
which may leave pay 10 stranded within the sinkhole or dip. In the present
example, RE
antennas 20 drilled into the sinkhole 29 can mobilize the bitumen and recover
bitumen
containing fluid 24 from that area of the pay 10, via gravity drainage.
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. .
[0062] The RF antennas 20 can be deployed in multiple tunnels 12,
creating a network 30
of RF antennas 20. There are numerous implementations for the network of
tunnels 30, several
of which are illustrated in FIGS. 4(a) through 4(d).
[0063] Referring to FIG. 4(a), a particularly convenient
configuration for the network of
tunnels 30 when using conventional boring equipment is shown. In the
implementation shown
in FIG. 4(a), a continuous tunnel 12 is excavated downwardly at an incline
into the underlying
formation 14 and extending into the underlying formation 14 in a serpentine
pattern. The tunnel
12 can then be excavated upwardly back to surface 12 to provide egress, e.g.,
to meet safety
requirements.
[0064] FIG. 4(a) illustrates an example of a tunnel network 30
configured in a serpentine
pattern using a continuous tunnel 12. The tunnel 12 includes a first tunnel
segment 12a, a
second tunnel segment 12b, a third tunnel segment 12c, a fourth tunnel segment
12d, and a
fifth tunnel segment 12e, which are connected to each other using a first bend
36a between the
first and second tunnel segments 12a, 12b; a second bend 36b between the
second and third
tunnel segments 12b, 12c; a third bend 36c between the third and fourth tunnel
segments 12c,
12d; and a fourth bend 36d between the fourth and fifth tunnel segments 12d,
12e.
[0065] In the implementation shown in FIG. 4(a), an ingress surface
access location 32a
connects the tunnel network 30 to surface 18 via an entry tunnel 34. Also, an
egress surface
access location 32b connects the tunnel network 30 to surface 18 via an exit
tunnel 35. The
entry and exit tunnels 34, 35 can be configured in various ways. For example,
one or more of
the entry and exit tunnels 34, 35 can be an inclined or sloped tunnel
extending from the surface
access location 32a, 32b down to particular segments of the tunnel network 30.
The surface
access locations 32 and entry and exit tunnels 34, 35 can be sized to permit
machinery to be
transported and/or driven down into and/or out of the tunnel network 30, e.g.,
to facilitate
installation, operation, and maintenance of the RF antennas 20 (only one
antenna 20 being
labeled in FIG. 4(a) for ease of illustration), and to permit personnel to
enter and exit the tunnel
network 30.
[0066] Various other tunnel network implementations are possible.
For example, as shown
in FIG. 4(b), a grid-like pattern can be employed for the tunnel network 30 in
which the tunnel
segments 12a-12e are connected at both ends by access tunnels 38a, 38b rather
than bends
36 between adjacent segments. As illustrated in FIG. 4(b), the ingress and
egress surface
access locations 32a, 32b can be located in any desired position relative to
the tunnel network
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,
,
30 such that the entry and exit tunnels 34a, 34b provide a connection between
the tunnel
network 30 and surface 18.
[0067] Another implementation is shown in FIG. 4(c), wherein a
single access tunnel 38 in
the underlying formation 14 is used to provide access to the tunnel segments
12a-12e, such
that the tunnel segments 12a-12e are effectively individual tunnels extending
from the access
tunnel 36. In yet another implementation shown in FIG. 4(d), a discontinuous
tunnel network 30
is created, in which multiple individual tunnels 12 are configured to have
dedicated ingress and
egress surface access locations 32a, 32b and corresponding entry and exit
tunnels 34, 35; and
a multi-segment continuous sub-network is provided using a first tunnel
segment 12a and a
second tunnel segment 12b connected by a bend 36. It can be appreciated that
the example
shown in FIG. 4(d) illustrates that any combination of tunnel patterns and
configurations are
possible within the principles discussed herein, and can therefore accommodate
various surface
access and underground constraints.
[0068] It can be appreciated that the number of tunnels (and/or
tunnel segments) 12 and
the particular implementations shown in FIGS. 4(a) to 4(d) are illustrative
only and various other
configurations are possible to accommodate different applications and/or
locations. For
example, a single ingress surface access location 32a and a single egress
surface access
location 32b can be used along with at least one access tunnel 38 or bend 36
(connecting the
tunnels 12 or tunnel segments 12a, 12b, etc.) to minimize the surface
footprint, whereas
multiple ingress surface access locations 32a and/or multiple egress surface
access locations
32b can also be used to accommodate other constraints such as geological or
surface space
constraints.
[0069] The ingress and egress surface access locations 32a, 32b and
entry and exit
tunnels 34, 35, can be configured in various ways in order to provide access
to the tunnel
network 30 from surface 18. For example, as shown in FIG. 5(a), an inclined or
sloped entry
tunnel 34 can be created by boring downwardly with a gradual slope towards the
underlying
formation 14 at which point the horizontally oriented tunnel 12 (or tunnel
segment) commences.
By providing a gradual sloped entry tunnel 34 as shown in FIG. 5(a),
machinery, equipment,
vehicles, and personnel can drive or be driven into and out of the tunnel
network 30. The
mobilized bitumen containing fluid 24 recovered by the producer well 26 can
also be pumped
out through the entry tunnel 34 to surface by installing a pump 27 and outlet
pipes 39 to
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transport the bitumen containing fluid 24 to surface 18. It can be appreciated
that a similar
configuration can be used with the egress surface access location 32b and exit
tunnel 35.
[0070] FIG. 5(b) illustrates another implementation for providing an entry
tunnel 34 and
ingress surface access location 32a, wherein the entry tunnel 34 is provided
using a vertically
drilled shaft, similar to a mine shaft. The vertically drilled shaft can be
equipped with a lift or
other elevation equipment to enable drilling equipment such as a drilling rig
to be transported
below surface. As illustrated in FIG. 5(b), the bitumen containing fluid 24
recovered by the
producer well 26 can be transported to surface 18 via the entry tunnel 34.
[0071] FIG. 5(c) illustrates yet another implementation for providing
access to a tunnel
network 30. In the example configuration shown in FIG. 5(c), a tunnel 12 is
excavated into the
underlying formation 14 from a naturally occurring outcrop or other exposure
of the underlying
formation 14 such as from a surface mine. In the implementation illustrated in
FIG. 5(c), the
outlet pipes 39 from the pump 27 can be configured to extend towards the
outcrop or other
exposure in order to be transported for subsequent processing. Likewise, the
surface access
location 32a in this example is located along a bank of the outcrop or other
exposure and
extends directly into the underlying formation 14.
[0072] The RF antennas 20 can be powered using various configurations. FIG.
6
illustrates one configuration in which an RF antenna 20 is powered by a
dedicated RF
transmitter 40 located in the tunnel 12 near the RF antenna 20 which it is
powering. The RF
transmitter 40 is configured to operate a single RF antenna 20 at a particular
frequency.
[0073] The particular frequency applied can vary depending on the
conductivity of the
media within a particular hydrocarbon formation, however, signals with
frequencies between
about 0 to 500 Hz and including direct current (DC) are contemplated to heat a
typical formation
through electric currents in at least one implementation.
[0074] A frequency signal is applied to the RF antennas 20, which is
sufficient to heat the
hydrocarbon formation through electric fields, magnetic fields, or both. It
can be appreciated
that once the water near the applicator is nearly or completely desiccated,
applying a different
frequency signal can provide more efficient penetration of heat the formation.
The frequencies
necessary to produce heating through electric fields varies depending on a
number of factors,
such as the dielectric permittivity of the hydrocarbon formation, however,
frequencies between
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. .
about 30 MHz and about 24 GHz are contemplated to heat a typical hydrocarbon
formation
through electric fields in another implementation.
[0075] The frequencies to produce heating through magnetic fields
can vary depending on
a number of factors, such as the conductivity of the hydrocarbon formation,
however,
frequencies between about 500 Hz and about 1 MHz are contemplated to heat a
typical
hydrocarbon formation through magnetic fields in another implementation.
Relatively lower
frequencies (e.g., lower than about 1 kHz) can provide greater heat
penetration while the
relatively higher frequencies (e.g., higher than about 1 kHz) can allow higher
power application
as the load resistance increases. The optimal frequency can relate to the
electrical conductivity
of the formation, thus the frequency ranges provided are listed as examples
and can be different
for different formations. The formation penetration is related to the radio
frequency skin depth at
radio frequencies. For example, signals greater than about 500 Hz are
contemplated to heat a
hydrocarbon formation through electric fields, magnetic fields, or both. Thus,
by changing the
frequency, the formation can be further heated without conductive electrical
contact with the
hydrocarbon formation.
[0076] At some frequencies, the hydrocarbon formation can be
simultaneously heated by a
combination of types of RF energy. For example, the hydrocarbon formation can
be
simultaneously heated using a combination of electric currents and electric
fields, electric fields
and magnetic fields, electric currents and magnetic fields, or electric
currents, electric fields, and
magnetic fields. A change in frequency can also provide additional benefits as
the heating
pattern can be varied to more efficiently heat a particular formation. For
example, the signal
applied can be configured to provide enhanced heating along the boundary
conditions between
the pay 10 and the overburden 16 and underlying formation 14, and this can
increase
convection in the pay 18. As the desiccated zone expands, the electromagnetic
heating
achieves deeper penetration within the reservoir. The frequency can be
adjusted to optimize RF
penetration depth and the power is selected to establish the desired size of
the desiccated zone
and thus establish the region of heating within the pay 10. Such
considerations can be factored
in when determining the number and spacing of the RF antennas 20 and the
tunnel pattern
within a tunnel network 30.
[0077] In another configuration shown in FIG. 7, a relatively higher
power RF transmitter 50
is used to power a distributed array of a plurality of RF antennas 20. In the
example shown in
FIG. 7, a first RF antenna 20a, a second RF antenna 20b and so forth are
powered by the
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single RF transmitter 50, which is configured to operate the multiple RF
antennas 20 in the
array. It can be appreciated that an array of antennas 20 powered by a single
RF transmitter 50
can be located in the same tunnel 12 or be distributed within multiple tunnels
12 of the tunnel
network 30.
[0078] An array of RF antennas 20 can be operated as a phased array as
shown in FIG. 8,
wherein each of the RF antennas 20a-20e is pulsed separately. As is known in
the art, a
phased array is an array of antennas in which the relative phases of the
respective signals
powering the antennas are varied in such a way that the effective radiation
pattern of the array
is compounded in a desired direction and suppressed in undesired directions.
As such, a
distributed array of RF antennas 20 used in the tunnel network 30 can be
controlled to direct the
EM signals 22 towards or away from particular portions of the pay 10.
Beamforming can be
implemented for directional signal transmission using either time domain
beamformers in which
time delays are used, or frequency domain beamformers in which multiple
frequency bins or
spatial frequencies are used.
[0079] As shown in FIG. 8, the rightmost RF antenna 20e is pulsed first,
and emits an
energy wave 22e that begins to spread first. Accordingly, the next RF antenna
20d to be pulsed
emits an energy wave 22d that is smaller than the first energy wave 22e due to
the delay
between pulses. The process continues for the other RF antennas 20c, 20b, and
20a until all
elements have been pulsed. The multiple EM energy waves 22a-22e add up to a
single wave
front 52 travelling at a particular angle. That is, the beam angle can be
controlled by controlling
the pulse timings of the RF transmitter 50 applied to the individual RF
antennas 20a-20e.
[0080] It can be appreciated that the RF antennas 20 can also be configured
to receive RF
signals. For example, EM signals 22 emitted from one RF antenna 20 can be
detected using
another RF antenna 20 to perform diagnostic checks and/or optimizations on the
control of an
array of RF antennas 20. In an implementation, array tuning can also be
performed, wherein
the performance of an RF signal in a particular portion of the pay 10 can be
detected in order to
perform modifications to the array control scheme being employed, e.g., to
perform
beamforming as shown in FIG. 8 in order to avoid geological obstacles, or to
adjust the power or
frequency to achieve better performance in that area of the pay 10.
[0081] FIG. 9 illustrates an example of an electrical schematic diagram for
powering an
array of RF antennas 20. The RF antennas 20 in this example are dipole RF
antennas 20 and
the array of RF antennas 20 are distributed in a first tunnel 12a and a second
tunnel 12b.
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[0082] The first tunnel 12a includes a first RF transmitter 50a that powers
a plurality of RF
antennas 20 over a first power line 60a, using a series of one or more
splitters 62. In this
example implementation, the first RF transmitter 50a and each RF antenna 20 in
the first tunnel
12a can be selectively controlled (i.e. turned "ON" or "OFF" or pulsed) using
a first controller
64a, via a series of switches 66 controlled using a first control line 68a. In
this way, while the
first RF transmitter 50a operates to generate RF signals to provide RF signals
22 into the pay
via the RF antennas 20, the first controller 64a can selectively target
different areas of the
pay 10 by turning ON or OFF selected ones of the RF antennas 20 using the
respective
switches 66 or by pulsing the RF antennas 20 as shown in FIG. 8 to direct the
wave front 52 in a
particular direction.
[0083] The second tunnel 12b similarly includes a second RF transmitter 50b
that powers a
plurality of RF antennas 20 in the second tunnel 12b over a second power line
60b, using a
series of one or more splitters 62. The second RF transmitter 50b and each RF
antenna 20 in
the second tunnel 12b is also selectively controlled using a second controller
64b, via a series of
switches 66 controlled using a second control line 68b. It can be appreciated
that, as illustrated
using dashed lines in FIG. 9, a single controller 64 and a single RF
transmitter 50 can also be
configured to control RF antennas 20 in both the first tunnel 12a and second
tunnel 12b by way
of inter-tunnel power and control lines, collectively identified using numeral
70. As such, the
provision of separate transmitters 50 and controllers 64 is illustrative only
and various
configurations are possible. For example, due to space and/or distance related
constraints,
some tunnels 12 can be operated using dedicated RF transmitters 40 with other
tunnels 12
being wholly or at least in part being operated using shared or common RF
transmitters 50
and/or controllers 64 located in outside of that tunnel 12. The control lines
68 and other
communication connections shown in FIG. 9 can be implemented using wired,
wireless or a
combination of wired and wireless technologies. Also, the control lines 68 can
also be used to
operate one or more of the RF antennas 20 as a receiver antenna, wherein the
controllers 64
can analyze and, if necessary, optimize further control of the array of RF
antennas 20.
[0084] FIG. 10 illustrates an example of a set of operations that are
performed in
controlling an array of RF antennas 20. At step 70 the controller 64 controls
operation of at
least one RF transmitter 50, e.g., by providing operating parameters such as
power level,
frequency, etc. At step 72 the controller 64 determines a control instruction,
e.g., by receiving
an input from a surface computer or operator in the tunnel 12 to selectively
control at least one
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RF antenna 20 (e.g., to turn OFF at least one RF antenna 20 in a particular
location, to pulse a
number of RF antennas 20 according to a beamforming scheme, etc.). At step 74
the controller
64 controls operation of at least one RF antenna 20 by operating the
corresponding switch(es)
66. The process shown in FIG. 10 can repeat during operation of the array of
RF antenna 20
until new instructions are determined. Also, as shown in dashed lines in FIG.
10, solvent can be
injected at step 76 after at least some RF heating occurs and the solvent
injection process at
step 76 can occur in parallel, e.g., when different segments of the pay 10 are
targeted
separately. Another optional step is shown in FIG. 10, namely step 78, which
uses an RF
antenna 20 as a receiver. As illustrated in FIG. 10, an RF antenna 20 which is
operated by an
RF transmitter 40, 50, can initiate steps of detecting and receiving signals
on another of the RF
antennas 20. For example, after powering an RF antenna 20, adjacent RF
antennas 20 can be
monitored for received signals in order to analyze the performance of the
sending RF antenna
20.
[0085] As illustrated in FIGS. 1(b) and 1(c), the tunnel 14 can be
configured to include a
collector 28 for recovering bitumen containing fluid 24 via antenna wells 21.
FIG. 11(a)
illustrates an antenna well 21 containing an RF antenna 20. The antenna well
21 is configured
to allow bitumen containing fluid 24 to penetrate the wall thereof (e.g., via
perforations) and
allow the bitumen containing fluid 24 to drain into a collection area 80 under
the influence of
gravity and then into the collector 28 by way of fluid communication between
the antenna well
21 and the collector 28. Similar to the producer well 26, the contents that
drain into the collector
28 can be pumped to surface 18 for subsequent processing. In this way,
mobilized bitumen
containing fluid 24 near the RF antennas 20 is more easily recovered when it
is mobilized such
that it flows towards and into the antenna well 20. The RF transmitter 40, 50
is not shown in
FIG. 11(a) for ease of illustration and can be located at or near the RF
antenna 20 or at some
distance depending on whether a dedicated transmitter 40 or an array-powering
RF transmitter
50 is configured for powering the particular RF antenna 20 which is shown.
[0086] FIG. 11(b) illustrates another implementation in which the antenna
well 21 is sized
and configured to include both an RF antenna 20 and a solvent injector 29,
that is, rather than
requiring a separate well to be drilled for the solvent injector 29.
Accordingly, in the
implementation shown, both an EM transmitter 40, 50 and solvent injection
equipment 90 are
configured to be connected to the RF antenna 20 and solvent injector 29
respectively. As
shown in FIG. 11(b), the solvent injector 29 is configured to inject solvent
92 through the
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. .
antenna well 21 and into the pay 10 to further mobilize the bitumen in the pay
10, e.g.,
subsequent to stimulation via RF heating.
[0087] The producer well 26 can be drilled up into the pay 10 from
the tunnel 12 with the
production equipment 110 located within the tunnel 12 as shown in the examples
described
above. It can be appreciated that in order to accommodate drilling equipment
such as a drilling
rig, the tunnels 12 are sized accordingly. For example, it has been found that
a tunnel with a
height (and/or diameter) of about 10 feet to about 14 feet is suitable,
although other sizes are
possible according to the size of the equipment being used in the tunnel 12.
In such a
configuration, the producer well 26 can be slightly inclined in order to
facilitate a gravity drainage
towards the pump 27. Also, the pump 27 can also be configured to direct
produced bitumen
containing fluid 24 into an outlet pipe 39 that is arranged to pump the
produced bitumen
containing fluid 24 to surface 18.
[0088] In other implementations, the producer well 26 can be
provided in various different
ways other than being drilled from within the tunnel 12. For example, as shown
in FIG. 12(a), a
SAGD-like producer well 26 can be drilled from surface down into the pay 10 to
extend along
the bottom of the pay 10 above the underlying formation 14 and tunnel 12. In
this example,
production equipment 100 is located at surface 18, similar to a SAGD or CSS
operation, and the
producer well 26 that extends generally in the same direction as the tunnel 12
such that the
production equipment 100 is located near the ingress surface access location
32a to minimize
the footprint at surface. It can be appreciated that, as shown in FIG. 12(b),
the producer well 26
can also be drilled in a direction which is generally opposite to the tunnel
12, e.g., due to space
or location constraints imposed at surface 18.
[0089] It will be appreciated that any module or component
exemplified herein that
executes instructions can include or otherwise have access to computer
readable media such
as storage media, computer storage media, or data storage devices (removable
and/or non-
removable) such as, for example, magnetic disks, optical disks, or tape.
Computer storage
media can include volatile and non-volatile, removable and non-removable media
implemented
in any method or technology for storage of information, such as computer
readable instructions,
data structures, program modules, or other data. Examples of computer storage
media include
RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital
versatile
disks (DVD) or other optical storage, magnetic cassettes, magnetic tape,
magnetic disk storage
or other magnetic storage devices, or any other medium which can be used to
store the desired
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information and which can be accessed by an application, module, or both. Any
such computer
storage media can be part of the controller 64, RE transmitters 40, 50, or any
component of or
related thereto, or accessible or connectable thereto. Any application or
module herein
described can be implemented using computer readable/executable instructions
that can be
stored or otherwise held by such computer readable media.
[0090] For simplicity and clarity of illustration, where considered
appropriate, reference
numerals may be repeated among the figures to indicate corresponding or
analogous elements.
In addition, numerous specific details are set forth in order to provide a
thorough understanding
of the examples described herein. However, it will be understood by those of
ordinary skill in the
art that the examples described herein may be practiced without these specific
details. In other
instances, well-known methods, procedures and components have not been
described in detail
so as not to obscure the examples described herein. Also, the description is
not to be
considered as limiting the scope of the examples described herein.
[0091] The examples and corresponding diagrams used herein are for
illustrative purposes
only. Different configurations and terminology can be used without departing
from the principles
expressed herein. For instance, components and modules can be added, deleted,
modified, or
arranged with differing connections without departing from these principles.
[0092] The steps or operations in the flow charts and diagrams described
herein are just for
example. There may be many variations to these steps or operations without
departing from the
principles discussed above. For instance, the steps may be performed in a
differing order, or
steps may be added, deleted, or modified.
[0093] Although the above principles have been described with reference to
certain specific
examples, various modifications thereof will be apparent to those skilled in
the art as outlined in
the appended claims.
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