IN-SITU BITUMEN RECOVERY FROM OIL SANDS

PROCEDE D'EXTRACTION IN SITU DU BITUME DES SABLES BITUMINEUX

English Abstract

ABSTRACT OF THE DISCLOSURE
Bitumen is recovered from subterranean oil sand
formations by forming a generally horizontal production
well or gallery in the formation and causing bitumen to
flow by gravity from the formation into the production
well, generally by heating bitumen in the formation using
steam. Bitumen in the production well is emulsified using
a dilute aqueous solution of sodium hydroxide and the
emulsion is transported to the surface or to another
remote location for recovery of bitumen from the emulsion
at the remote location.

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A method for the recovery of hydrocarbons
from a hydrocarbon deposit having an aquifer at the
base of the hydrocarbon deposit, the method comprising
the steps of:
injecting a hydrocarbon solvent in the
vapour phase along a predominantly horizontal
injection well into the aquifer to mobilize
hydrocarbons in the hydrocarbon deposit; and
producing mobilized hydrocarbons from the
hydrocarbon deposit.
2. The method of claim 1 in which the mobilized
hydrocarbons are produced from the aquifer.
3. The method of claim 1 in which the
hydrocarbon solvent is injected into a pre-existing
aquifer.
4. The method of claim 1 in which the mobilized
hydrocarbons are produced along a predominantly
horizontal production well in the aquifer.
5. The method of claim 4 in which the
hydrocarbon solvent is injected along an array of
predominantly horizontal injection wells spaced from
each other in the aquifer and the mobilized
hydrocarbons are produced along an array of horizontal
production wells in the aquifer, and the production
and injection wells alternate.

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6. The method of claim 1 further including
initially creating an aquifer at the base of the
hydrocarbon deposit by:
hydraulic fracturing of the hydrocarbon
deposit to create a horizontal fracture in the
hydrocarbon deposit; and
injecting water into the horizontal
fracture.
7. The method of claim 1 in which the
hydrocarbon solvent in the vapour phase is injected
into the hydrocarbon deposit at about the hydrocarbon
deposit temperature.
8. The method of claim 3 in which the
hydrocarbon solvent is injected along an array of
predominantly horizontal injection wells spaced from
each other in the aquifer and the mobilized
hydrocarbons are produced along an array of horizontal
production wells in the aquifer, and the production
and injection wells alternate..
9. The method of claim 1 in which the
hydrocarbon solvent is selected from the group
consisting of ethane, propane and butane.
10. The method of claim 1 further including
injecting the hydrocarbon solvent into the aquifer
along with a diluent gas that is less soluble in the
hydrocarbon deposit than the hydrocarbon solvent.
11. The method of claim 1 in which the solvent
vapour is dry.

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12. The method of claim 1 further including
producing free gas along with the mobilized
hydrocarbons.
13. Apparatus for the recovery of hydrocarbons
from a hydrocarbon deposit having an aquifer at the
base of the hydrocarbon deposit, the apparatus
comprising:
a source of hydrocarbon solvent vapour;
a first injection well drilled horizontally
into the aquifer, the injection well having a portion
open to fluid communication with the aquifer and being
connected to the source of hydrocarbon solvent vapour;
and
a first production well drilled horizontally
into one of the aquifer and the deposit, and spaced
horizontally from the injection well, the first
production well including a pump for pumping oil from
the well.
14. The apparatus of claim 13 further including
a solvent stripper connected between the first
injection well and the first production well.
15. The apparatus of claim 13 further including
a second injection well drilled into and lying
horizontally in the aquifer spaced from the first
production well, with the first production well
located between the first and second injection wells.
16. The apparatus of claim 13 further including
a gas recovery system attached to the production well.

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17. A method for the production of hydrocarbons
from a hydrocarbon deposit having a base, the method
comprising:
drilling a first horizontal well into the
base of the hydrocarbon deposit;
drilling a second horizontal well into the
base of the hydrocarbon deposit spaced from the first
horizontal well;
fracturing the base of the hydrocarbon
deposit to form horizontal fractures extending between
the first horizontal well and the second horizontal
well;
injecting a saturated hydrocarbon solvent
vapour into the base of the hydrocarbon deposit
through the first horizontal well; and
producing hydrocarbons from the second
horizontal well.
18. The method of claim 17 in which the
hydrocarbon solvent vapour is selected from the group
consisting of ethane, propane and butane.
19. The method of claim 18 in which the
hydrocarbon deposit is a bitumen deposit.
20. The method of claim 17 in which fracturing
the base of the hydrocarbon deposit includes:
injecting a fracturing fluid into the base
of the hydrocarbon deposit from the first horizontal
well.
21. The method of claim 17 in which injecting a
saturated hydrocarbon solvent vapour into the base of
the hydrocarbon deposit through the first horizontal

well includes initially injecting a mixture of the
hydrocarbon solvent vapour and a diluent gas into the
base of the hydrocarbon deposit.
22. A method for the recovery of hydrocarbons
from a hydrocarbon deposit having a aquifer at the
base of the hydrocarbon deposit, the method comprising
the steps of:
injecting a hydrocarbon solvent in the
vapour phase into the aquifer at about the hydrocarbon
deposit temperature to mobilize hydrocarbons in the
hydrocarbon deposit; and
producing mobilized hydrocarbons from the
hydrocarbon deposit.
23. The method of claim 22 in which the aquifer
is pre-existing.

Description

` 2~8723
IN-SITU BITUMEN RECOVERY FROM OIL SANDS
The present invention relates to the recovery of
bitumen from oil sands by an in-sltu procedure.
One procedure which has been proposed for the
recovery of bitumen from subterranean oil sands deposits
is by employing dilute alkali, such as a 0.1 wt% sodium
hydroxide solution, to emulsify and remove bitumen from
the formation, with the resulting emulslon being broken
at the surface for recovery of the bitumen.
One problem that can be encountered with such
procedure is channelling between the injector and
producer wells. After an initial production of bitumen,
a pathway of clean sand is produced between the wells.
As more alkali is pumped into the formation, it takes the
path of least resistance and continues to flow through
the bitumen-depleted pathway and out of the producer
well. Accordingly, there is an initial production of
rich bitumen-in-oil emulsion that becomes progressively
thinner as pumping proceeds.
In accordance with the present invention, we provide
an improved procedure for the in-situ recovery of bitumen
from oil sands deposits by a horizontal gallery provided
in an oil sands formation arrangement in which dilute
aqueous alkali is pumped through the gallery to emulsify
bitumen therefrom and in which some means is provided to
cause bitumen to flow and drain from the formation into
the gallery, such as heat from steam pumped into an upper
gallery or otherwise into the formation above the
gallery. As bitumen flows by gravity into the gallery,
it is emulsified by the alkali and then is pumped to the
surface for recovery of the bitumen.
The horizontal gallery or well from which the
bitumen is recovered may be provided in any convenient
manner in the formation, such as by suitable drilling
procedures using conventional techniques or hydraulic
jetting techniques. Such horizontal gallery may have any
desired length and may be substantially vertically

2~723
aligned with an upper gallery or well for introduction of
steam. Steam may be pumped into the upper well through
the drill line used to form the gallery. Alternatively,
steam may be introduced by a plurality of steam injection
wells drilled vertically down from the top of the
formation.
The bitumen flows through the formation under the
influence of the heat introduced to the formation by the
steam to the lower gallery wherein it is emulsified with
the dilute alkali. Such lower gallery may be a Elow
through one, whereby dilute alkali flows through the
gallery and the upwardly to the surface, or may be blind
ended, in which case dilute alkali can be introduced
through an insert pipe extending along the gallery and
emulsion is recovered through the annular gap.
perforated outer pipe may be employed or omitted, as
desired. A "mud motor" used in the drilling operation
may be left at the end of the drill steam during
production from the formation.
The emulsion so formed in the lower gallery has a
low viscosity and can be readily pumped to the surface,
thereby reducing pumping costs. The concentration of
bitumen in the emulsion may be controlled by the pumping
rate of dilute alkali through the lower gallery emulsion
formation may be effected at temperature up to 100C or
higher. Heat 109s from the emulsion would not
significantly increase the viscosity of the emulsion
during pumping since the emulsion has the characteristics
of water. The use of dilute alkali minimizes well
corrosion.
Further processing of the emulsion is required at
the surface to break the emulsion, for example by
dilution and/or addition of calcium hydroxide. Bitumen
recovery then may be made by flotation or gravity
separation, depending on the density of the bitumen.

7 2 ~
Clean up of bitumen, for example, by dilution and
centrifugation, may be facilitated by high pH, as
descrlbed in our CP 1,243,468. Further incremental
addition of calcium hydroxide flocculates any residual
mineral materlal and, after removal of the flocculated
materials by setting or any suitable mechanical means,
provides a clean sodium hydroxide solution for recycle to
the well.
Quantities of sodium carbonate, generally 0 to 500
ppm, may be added to the recycle stream to remove any
excess free calcium ion remaining in the recovered
alkaline solution and to remove any free calcium ion that
might be present in the connate water.
The procedure of formation of emulsion from bitumen,
transportation to another location, in this case the
surface, and processing of the bitumen is somewhat
analogous to the procedure described in our Canadian
Patent No. 1,137,005. The process conditions described
therein for emulsion formation and subsequent bitumen
recovery may be employed in the present invention.
The procedure is characterized by a low chemical
cost for the calcium hydroxide used in emulsion breaking
and clean up and for make up quantities of sodium
hydroxide.
The invention is described further, by way of
illustration, with reference to the accompanying
drawings, in which:
Figure 1 illustrates the method of the present
invention with two alternative manners of introduction of
steam being illustrated; and
Figure 2 illustrates a alternative configuration for
the producing well gallery.
Referring to the drawings, a horizontal producing
well or gallery 10 is drilled into a lower region of an
oil sands formation 12. Such producing well or gallery
10 may comprise an outer perforated casing 14 and an

21 ~8 72~3
inner feed plpe 16. Alternatively, the outer perforated
casing 14 may be omitted.
Dilute alkali flows from the surface 18 through the
drlll line 20, whlch may extend through overburden 21
from the surface 18 or from galleries formed in limestone
22 underlying the oil sands formation 12. Such dilute
alkali flows through the inner pipe 16 in the horizontal
gallery or well 14 and exits adjacent the blind end of
the gallery and then flows countercurrently in the outer
annulus 24, emulsifying bitumen draining into the gallery
10 .
Bitumen may be caused to flow from the formation 12
by gravity into the lower gallery by any suitable means.
Most conveniently, steam is used in this regard, which
may be introduced to the upper region cf the oil sands
formation 12 above the lower gallery or well 10. In one
alternative, a second gallery or well 26 is provided in
the formation 12 aligned vertically with the lower
gallery and steam may be introduced thereto via the drill
line 28, which may extend from the surface 18 or from
galleries formed in the limestone 22.
In another alternative, a series of vertical steam
injection wells 30 may be formed extending from the
surface 18 to the oil sands formation 12 through which
steam is introduced to the formation. The steam
introduced by either alternative, or both, if desired,
causes bitumen to flow in the formation 12 and drain by
gravity into the producing well 10 where, as described
above, the bitumen is emulsified by dilute alkali for
transportation to the surface 18 or to galleries in the
limestone 22, to permit recovery of the bitumen therefrom
and recycle of the alkali.
In summary of this disclosure, the present invention
provides a novel manner of 1n situ recovery of bitumen
from oil sands using dilute alkali. Modifications are
possible within the scope of this invention.