Note: Descriptions are shown in the official language in which they were submitted.
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Apparatus and Method for Oil Sand Exploitation
Field of the invention
The invention relates to a method and an apparatus for in situ mobilizing of
heavy oil or crude oil by steam injection.
Description of the related art
Oil sand, as well referred to as tar sand, comprises sand grains coated with
tar
like petroleum crude oil, briefly referred to as crude oil. The crude oil in
the oil
sand has a high viscosity and must be heated or diluted to flow. In-situ
exploita-
tion of oil sands can be accomplished by "steam assisted gravity drainage", ab-
breviated as SAGD. SAGD uses a horizontally extending steam injection well
forming a steam generation chamber for mobilizing the crude oil in the oil
sand.
The mobilized crude oil pours downward and is recovered by a second horizon-
tally extending well, as so called production well, as disclosed in
US2001/0278001A1.
The steam can be either produced by above ground facilities or downhole by an
electrical heater as suggested by US-Patent 4,805,698. The water is supplied
from above ground by a water supply line. The electrical steam generator heats
the water to generate steam. The steam is injected into the sand and mobilizes
the crude oil, which is collected by adjacent production wells.
Summary of the invention
The problem to be solved by the invention is to improve in-situ oil sand
exploita-
tion.
Solutions of the problem are provided by a downhole apparatus and a method
for exploitation of an oil sand reservoir as described by the respective
independ-
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ent claims. The dependent claims relate to further improvements of the inven-
tion.
The downhole apparatus for oil sand exploitation, comprises a least a casing
which houses a water conduit for receiving water via a water pipe and at least
one steam generation chamber being in fluid communication with said water
conduit and having at least one steam outlet. The steam generation chamber is
thermally connected to an electrical heater. The downhole apparatus further
comprises at least one crude oil conduit for recovering crude oil, which has
been
mobilized by said steam. Such downhole apparatus permits to inject steam for
mobilization of the crude oil into the oil sand and to recover the crude oil
by a
single apparatus, and thus requires only a single bore.
The casing may preferably house the at least one crude oil conduit. The casing
may for example be or include a multiple conduit tube, wherein the at least
one
water conduit and the at least one crude oil conduit are each at least one of
the
multiple conduits. This permits a stable design of the housing.
The at least one steam generation chamber is preferably supported by the pe-
ripheral surface of the casing. This position of the steam generation chamber
permits a simple injection of the steam generated in said steam generation
chamber into the oil sand.
Preferably there are multiple, e.g. five or nine, at least two steam
generation
chambers arranged around the peripheral surface of the casing defining a
bundle
of steam generation chambers. The downhole apparatus may have one or more
bundles. In one embodiment, there is one bundle of steam generation chambers.
In another embodiment, there are two or more bundles arranged at different
positions along a distal length of the casing. The one or more bundles of
steam
generation chambers permit homogeneous injection of steam and thus an effi-
cient exploitation of the oils sand. Because the one or more bundles of steam
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generation chambers are arranged around the casing, the one or more bundles
also act to maintain or raise a temperature of the casing which aids in
removal of
crude oil from a reservoir (via the crude oil conduit in the casing).
Each steam generation chamber preferably has a cladding compartment sur-
rounding a heater tube. The heater tube may house at least one electrical
heater
cartridge. This permits on the one hand to efficiently heat the water and on
the
other hand a simple replacement of the electrical heater cartridge in case of
fail-
ure. The heater tube preferably houses at least one spare electrical heater
car-
tridge. This permits longer operating intervals between retracting the
downhole
apparatus.
The heater tube may be hollow and may have an interior containing a composi-
tion of inorganic compounds and possibly pure elemental species. Examples for
such a composition are described in the patents US 6,132,823, US 6,911,231, US
6916,430, US 6811720 and the application US2005/0056807, which are incorpo-
rated by reference as if fully disclosed herein. Such composition acts as a
ther-
mally conductive material or medium to provide at least an almost perfect ho-
mogenous distribution by the heater tube of the heat provided by the heater
cartridge. The heater tube may as well be evacuated as suggested in the above
references. In a preferred embodiment the heater tube is evacuated and an
amount of a liquid inorganic compound, e.g., a solution of at least one
inorganic
salt is inserted into the tube. Subsequently the electrical heater is powered.
Thereby the liquid inorganic compound in the above example the solution evap-
orates and the at least one inorganic salt remains coats the inner surface of
the
heater tube and the electrical heater, thermally connecting the electrical
heater
with the heater tube. Preferably the heater tube is rotated or pivoted while
powering the heating element to obtain a better distribution of the solution
in
the heater tube and thereby to obtain a more homogeneous coating. The
amount of the solution inserted into the heater tube is preferably
significantly
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smaller than the volume of the tube, e.g. smaller as 1/10 or better smaller as
1/50 of the heater tube's volume. Preferred coating solutions are disclosed in
the
above cited documents. Coating of the heater tube is preferably accomplished
before attaching the heater tube to the downhole apparatus.
The heater tube may extend over the steam generation chamber, e.g. extend
axially. Thus, at least one section of the heater tube extends out of the
steam
generation chamber into the bore. The heater tube thus not only heats water
inside the steam generation chamber to steam, but as well reheats steam or wa-
ter that cooled in a reservoir after its injection. Therby the efficiency of
the ex-
ploitation is enhanced.
The method for exploitation of an oil sand reservoir comprises at least the
steps
of producing steam in a steam generation chamber of a downhole apparatus,
injecting said steam via steam outlets into the oil sand reservoir for
mobilizing
crude oil of the oil sand reservoir. At least part of the mobilized crude oils
is re-
covered by said downhole apparatus. This method reduces the minimum num-
ber of bores for in situ oil sand exploitation compared to SAGD, and thus the
costs.
Description of Drawings
In the following the invention will be described by way of example, without
limi-
tation of the general inventive concept, on examples of embodiment with refer-
ence to the drawings.
Figure 1 shows a schematic depiction of an oil sand exploitation system,
Figure 2 shows a perspective view of a section of downhole apparatus,
Figure 3 shows section of steam generation chamber.
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Figure 4 shows a schematic depiction of a second embodiment of an oil sand
exploitation system.
Detailed Description
The oil sand exploitation system 100 in Figure 1 has a ground station 110 for
5 housing the above ground facilities, like for example a controlling
station 115 for
monitoring and controlling the oil sand exploitation. Ground station 110 may
also include a power source to, for example, provide power to an extraction
well.
Ground station 110 may include a water source, such as a reservoir, to provide
water (e.g., fresh water) to an extraction well. The ground station 110 is
depicted
as an onshore station, but can as well be a swimming station for exploitation
of
water covered oil sands.
The oil sand exploitation system 100 includes an extraction well 120 with a
downhole apparatus inserted into bore 105. The downhole apparatus includes a
multi conduit tube like casing 130, e.g. for a power cable 230 (see Figure 2)
for
supplying power to downhole equipment, for example a protector 165, and/or a
motor 153 for driving a well head and a well monitor device 140, as
schematical-
ly depicted in Figure 1. The extraction well 120 includes a steam generator
200
which may be mounted to the peripheral surface of the casing 130. The steam
generator 200 is explained below in more detail with respect to Figures 2 and
3.
The steam generator 200 is positioned in this embodiment around casing 130 at
a bottom or distal portion of casing 130, being positioned in a first
preferably
vertical section of the extraction bore 105. The steam generator 200 injects
steam preferably laterally into oil sand as shown in Figure 1. The steam
mobilizes
crude oil in the oil sand.
Extraction well 120 is configured to collect oil, in particular may the
extraction
well be configured to collect the mobilized crude oil in the oil sand. To this
end
casing 130 of the extraction well 120 includes one or more oil inlets 135
along its
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length that allow oil to infiltrate the casing. Disposed within casing 130 is
at least
one oil conduit 125. The oil conduit 125 extends from the bottom or distal por-
tion of casing 130 to the above ground station 110. Oil that infiltrates
casing 130
may enter oil conduit 125 at the conduit's distal end, e.g. via one of the oil
inlets
135 and may be pumped to the surface and fed to a production line 109 for ex-
ample by a centrifugal pump 180 being preferybly arranged in the bottom or
distal portion of casing 130. Before pumping the crude oil to the above ground
station 110, water may be separated from the crude oil by separator 176. Also,
in
the bottom or distal portion of casing 130 are an Electric Cable Clip 195, a
Vent-
ing Valve 172, Single Flow Valve 185, a Power Cable 175, the Rotary Separator
176, a Protector 165, a Cable Head 162, a Motor 152 and Well Monitor Device
140. In between are a couple of water spray holes 145 and further oil inlets
135.
The water spray holes 145 are preferably in fluid communication with steam
generation means, for example with at least one of the steam generation cham-
bers 375 (cf. Figure 3) and thus permit to inject steam into the oil sand for
mobi-
lizing crude oil.
Figure 2 shows a section of an isometric view of casing 130 including a steam
generator 200 of extraction well 120. The steam generator 200 comprises a bun-
dle of heating members 300 (cf. Fig. 3.) The heating members 300 are arranged
around the peripheral surface of the casing 130. The casing 130 is tube like.
Cas-
ing 130 and has multiple compartments or conduits around an inner periphery
which may serve as water conduit 250 (for water from ground station 110 to
steam generator 200), oil conduit 125 (for oil infiltrating oil inlets 135 in
casing
130) or as cable conduit (for providing power to components in the casing
(e.g.,
centrifugal pump 180, motor 152) and to heat cartridges associated with the
steam generator 200).
The steam generator 200 comprises a bundle of heating members 300 (cf. Fig-
ure 3). The heating members 300 are arranged around the peripheral surface of
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the casing 130 and are each connected to the casing 130 by, for example, one
or
more weld connections. Where it is desired to have more than one bundle asso-
ciated with a well like extraction well 120, the bundles may be stacked one
above
the other along the casing 130. Referring to Figure 3, each heating member 300
includes a heater tube 310 and a steam generation chamber 375 respectively.
The front facing (upper) side of the heater tube 310 is closed by conical cap
330,
which may be weld connected to the heater tube 310. The rear facing side of
the
heater tube 310 may be closed by an end cap 340, which may preferably be a
water tight but releasable connection, e.g. a threaded connection. Heater tube
310, conical cap 330 and end cap 340 define a volume or chamber 335.
As shown in Figure 3, chamber 335 of heating member 300 is divided into a
first
portion and a second portion by cap 360 of a thermally conductive material
such
as a metal material (e.g., steel). In one embodiment, electrical heater car-
tridge 350 with positive and negative terminals located at a single end (a
proxi-
mal end as viewed) is positioned in a first portion of chamber 335 (proximal
to
cap 340). Cap 360 may divide chamber 335 at a distance from a first end to be
sufficient to allow heater cartridge 350 to be disposed in a first portion of
cham-
ber 335 but minimizes any additional volume for the first portion. As shown in
Figure 3, when heater cartridge 350 is disposed in a first portion of chamber
335
terminals 355 may extend into a volume of end cap 340. End cap 340 preferably
includes lateral opening 365 that is, for example, a threaded opening for
power
connection to terminals 355. A conductor is fed through a peripheral conduit
of
casing 130 into lateral opening 365. Current can be supplied to the conductor
from an above ground power source in ground station 110.
Each steam generation chamber 375 is defined by, for example, cylindrical
shell 320 a front wall 380 and a rear wall 370 connected by, for example, weld
connections. The front wall 380 and the rear wall 370 each have an opening
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through which a heater tube 310 is disposed. The heater tube 310 extends
axially
through the steam generation chamber 375. The connection of the heater
tube 310 and the front wall 380 and/or the rear wall 370 may be a weld connec-
tion.
The electrical heater cartridge 350 is thermally connected to the heater tube
310
and electrically connected with a power line e.g. by power cable 230. The
power
(e.g., electrical current) is preferably controlled by the controlling station
115
and may be ducted via a lateral opening like lateral opening 365. A gasket may
be used for sealing the cable feedthrough. Inside heater tube 310 is a
thermally
conductive material like it is described in the US-Patents 6,132,823;
6,911,231;
6,916,430; 7,220,365 and United States Patent Publication No. 2005/0056807.
Rear wall 370 of shell 320 includes inlet 395 for a water source to be
connected
thereto to provide water to steam generation chamber 375. Water is provided
from a water source at, for example, ground station 110 to steam generation
chamber 375 by a peripheral conduit of casing 130 that is in fluid
communication
with inlet 395. For heating the water to steam, power may be supplied to the
electrical heater cartridge 350. The heater cartridge 350 thus produces heat,
be-
ing transferred to the steam generation chamber 375 via the heater tube 310.
Steam develops inside the steam generation chamber 375 and escapes through
steam outlet 390 into the oil sand. A single flow pressure valve may be
provided
in the steam outlet 390. Thereby it can be avoided that foreign matter, like
sand
grains and the like enter the steam generation chamber 375. Further, the steam
can be pressurized. As the heater tube 310 extends over the steam generation
chamber a part of the heat provided by the electrical heater cartridge 350 is
as
well transferred directly to the oil sand. This heat reduces the condensation
of
the steam close to the extraction well 120 and thus permits the steam to heat
a
bigger area around the extraction well and thereby to better mobilize the
crude
oil. The mobilized crude oil can be collected via oil inlets 135 (see Figures
1 and
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2), separated from water by rotary separator 176 and pumped by centrifugal
pump 180 into the production line 109 a schematically represented in Figure 1.
Representatively, as described above with reference to Figure 1, one or more
tube bundles 200 of extraction well 120 may be used to generate and discharge
steam into a petroleum reserve to, in the case of oil sands, provide
sufficient
liquidity to the crude oil in oil sands to allow its extraction through casing
130
and pumping conduit 125, and secondarily to heat as well the casing 130.
Prefer-
ably the temperature of the steam produced in the steam generation cham-
ber 375 is monitored and/or controlled by controller 115. For example, a pro-
cessing protocol delivered to control computer 115 may include instructions
for
receiving temperature measurements from at least one temperature sensor.
Based on these measurements, instructions are provided in a machine-readable
form to be executed by controller 115. Accordingly, controller 115 executes
the
instructions to increase or decrease the power output to one or more heating
rods 350 to achieve a target temperature in a range f (e.g., 250 C to 280 C).
It is
appreciated that controller 115 may be increasing power to some heating car-
tridges 350 while at the same time decreasing power to other heating
cartridges
350. The controller 115 may alternatively or additionally control, i.e.
enhance or
reduce the water flow provided to the steam generation chamber(s) 375 to
thereby control the steam temperature. Still further, controller 115 may be
con-
nected to pump 180 and other components in pumping conduit 125 and control
the pump and/or other components based on program instructions to achieve a
desired throughput from the well.
Figure 4 shows an another embodiment of an oil sand exploitation system. In
this
embodiment, oil sand exploitation system 400 includes ground station 410 for
housing the above ground facilities, like for example, a controller 415, a
power
source and a water source. Similar to Figure 1, the above ground station 410
is
depicted as onshore station, but can as well be a swimming station for
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exploitation of water covered oil sands. The system 400 includes a bore 405
into
which an extraction well 420 with a downhole apparatus is inserted. In Figure
1,
the extraction well was inserted vertically or approximately vertically the
entire
length of the well. In Figure 4, the extraction well 420 extends vertically
through
5 bore 405 at a ground surface of the well, but then extends laterally into
the well.
Otherwise, the construction and operation of extraction well 420 and system
400
is similar to the construction and operation of extraction well 120 and system
100 described with reference to Figures 1-3. The downhole apparatus includes
casing 430 which is, for example a multi-conduit casing configured similar to
10 casing 130 in Figure 1, and one or more bundles of steam generators 500
configured similar to steam generators 200. Figure 4 shows a single bundle
disposed about and connected to a distal portion of casing 430. Water provided
to each steam generation chamber of steam generator 500 is converted to steam
by heat provided to the chamber by a heater tube containing a heater cartridge
and a thermally conductive material as described above with reference to
Figures 1-3. The steam is dispensed from steam outlets 490 of a steam
generation chamber into the oil sands reservoir to mobilize oil in the oil
sand.
Mobilized oil infiltrates casing 430 through oil inlets 435 and is pumped to
the
surface of the well.
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List of reference numerals
100 system
105 bore
108 well head
109 production line
111 valve
110 ground level station
115 controlling station
120 extraction well
125 oil conduit
130 extraction tube
135 oil inlet
140 well monitor device
150 motor
162 cable head
165 protector
170 rotary separator
172 venting valve
175 power cable
176 rotary separator
180 centrifugal pump
185 single flow valve
190 venting valve
195 electric cable clip
200 tube bundle/steam generator
230 electric cable
250 water conduit
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300 heating member
310 heater tube
320 shell
330 conical cap
335 chamber
340 end cap
350 electrical heater cartridge
360 end cap of heater cartridge
365 lateral opening
370 rear wall (down facing)
375 steam generation chamber
380 front wall (up facing)
390 steam outlet
395 water inlet
400 system
405 bore
410 above ground station
415 controller
420 extraction well
430 casing
435 oil inlets
490 steam outlets
500 steam generator
