Note: Descriptions are shown in the official language in which they were submitted.
CA 02520223 2005-09-19
METHOD FOR THE IN PLACE RECOVERY OF HEAVY OIL FROM A
SUBTERRANEAN DEPOSIT
TECHNICAL FIELD
This invention relates to the field of mining. More particularly, to
recovering heavy oil
from a subterranean oil sand deposit.
BACKGROUND
US patent 4,037,657 to Lekas describes a process for recovering carbonaceous
material
from a deposit by retorting. Lekas teaches that the deposit must be sealed and
that a deposit
should be blasted in a graded fashion so that smaller particles occur at one
area and larger
particles occur at another area. Other patents such as US 4,047,760 to Ridley
and CA
1,123,728 to Rom et al. also describe retorting techniques.
U.S. patent 4,333,684 to Ricketts, et al., U.S. 4,545,622 to Yang, U.S.
4,489,983 to
Ricketts describe methods of blasting subterranean deposits, including oil
shale deposits for
providing in situ retorting zones.
U.S. patent 4,101,172 to Rabbitts describes an in situ method of extracting
bitumen
from oil sand using a bitumen flotation method. Rabbitts describes a method
where the
overburden is not disturbed and a sealed or closed reservoir is provided.
U.S. patent 4,302,051 to Bass et al. describes an in situ method for the
separation of
crude oil from a reservoir whereby the deposit is drilled and flushed with hot
water and steam.
International patent application WO 03/060285 to Drake, et al. describes a
mechanical
device designed to excavate a hydrocarbon containing deposit with a cutter
head and separating
the hydrocarbon component in an enclosed vessel that is in communication with
the cutter
head. U.S. Patent 6,152,356 to Minden also describes a mechanical excavation
of a tar sand
deposit, termed hydraulic removal, and describes hot water/steam injection for
the recovery of
bitumen.
CA patent application 2,434,329 to Walsh describes a method of barge mining
tar sand.
The method describes flooding an oil sand deposit and dredge mining the
flooded deposit with
barges. A floating plant is provided for the dredged product to be processed
and the bitumen
extracted.
U.S. Patent 3,762,771 to Livingston provides a mine layout for the natural
resources
development of a broad region. The layout is particularly applicable to the
recovery of ore
from oil shale and tar sand.
CA 02520223 2005-09-19
U.S. patent 4,270,609 to Choules describes a tar sand extraction process. An
in situ or
ex situ method for separating and recovering bitumen from tar sand by heating
the tar sand in
an aqueous mixture of floating agent containing ammonia, a transfer agent
containing a
phosphate or silicon ion and a strong monovalent base.
U.S. patent 4,034,812 to Widmyer discloses a method whereby viscous petroleum
may
be recovered from a subterranean deposit, such as tar sand. Widmyer describes
injecting hot
fluid, such as hot water or steam, into the deposit and maintaining a pressure
on the deposit so
as to heat the deposit.
U.S. patent 4,406,499 to Yildirim describes that bitumen is recovered from an
underground tar sand formation by an in situ percolation process. The process
includes drilling
a bore hole and enlarging the hole by radially hydraulic jetting to form a
slurry. The resulting
slurry is then treated in situ with hot alkaline water to separate the bitumen
from the sand
matrix.
U.S. patent 4,475,592 to Pachovsky describes an in situ recovery process
whereby
bitumen is recovered from a subterranean formation of heavy oil sand traversed
by at least one
injection well and at least one associated production well in fluid
communication with the
injection well. Injection of hot fluids, such as low quality steam, are
injected into the injection
wells to release the bitumen from the heavy oil sand.
SUMMARY
In various aspects, there is provided a method comprising: a) removing
overburden
from a subterranean deposit; b) blasting the subterranean deposit; c) flooding
the blasted
deposit using a fluid under pressure; d) recovering a heavy oil from the
flooded deposit; and e)
removing the fluid from the flooded deposit. The flooding and the recovering
may be repeated
at least once. The heavy oil may be bitumen and the subterranean deposit may
be a
subterranean oil sand deposit.
In another aspect, there is provided a method comprising: a) removing an
overburden
from a subterranean deposit; b) blasting the subterranean deposit to maximize
the
fragmentation of the subterranean deposit thereby forming a blasted deposit,
the blasted deposit
being operable to permit a first flood volume of fluid to admix with the
blasted deposit, to
release a heavy oil from an inert material so that the heavy oil floats within
the flood volume of
fluid in the blasted deposit; c) flooding the blasted deposit with the first
flood volume of fluid
thereby forming a flooded deposit; d) recovering the heavy oil floating within
the first flood
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volume of fluid in the flooded deposit; and e) removing the fluid from the
flooded deposit,
thereby forming a treated deposit, the treated deposit being compacted by
removing a fluid
from the flooded deposit so that the treated deposit is less permeable than a
newly or freshly
blasted adjacent deposit. The flooding and the recovering may be repeated at
least once. The
heavy oil may be bitumen and the subterranean deposit may be a subterranean
oil sand deposit.
In another aspect, the blasting may comprise: i) drilling at least one
blasthole into the
subterranean deposit; ii) loading the at least one hole with at least one
explosive charge per
hole; iii) detonating the at least one explosive charge in such a manner that
the explosive
charge nearest the top surface of the subterranean deposit explodes before the
explosive charge
closer to the bottom surface of the subterranean deposit. This creates
progressive relief for the
lower and later detonating explosives charges by breaking and lifting, by
explosive gas
expansion from the upper and earlier detonating explosive charges.
In another aspect, methods described herein may further comprise defining a
limit to
the zone to be processed by creating a fractured or loosened plane on pre-
determined limit lines
through the use of a closely spaced line of blastholes which are lightly
charged with explosives.
In another aspect, the flooding may comprise: i) drilling at least one well
into the
blasted deposit; ii) inserting into the at least one well at least one
perforated casing per well; iii)
pumping the fluid under pressure into the at least one perforated casing. The
at least one well
may be a substantially horizontal well, a substantially vertical well,
comprise at least two wells
where a first well is substantially horizontal and a second well is
substantially vertical. The
substantially horizontal well may be closer to a bottom surface of the blasted
deposit when
compared with a top surface of the blasted deposit. The at least one vertical
well may be
drilled into a stable layer immediately below the blasted deposit.
In another aspect, the recovering may comprise collecting a reservoir of heavy
oil that
has formed on a top surface of the flooded deposit.
In another aspect, the fluid may be selected from at least one of the group
consisting of:
water, steam, air, carbon dioxide and light hydrocarbon solvents and may
further comprise an
additive that facilitates release of the heavy oil from the blasted deposit.
The additive may be
selected from at least one of the group consisting of: surfactants, ant-acids,
caustics and light
hydrocarbon solvent.
In another aspect, methods described herein may further comprise shaping the
blasted
deposit prior to the flooding. An explosive charge, a machine or a combination
of an explosive
charge and a machine may be used for shaping the blasted deposit. The
explosive charges used
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for shaping may be at least a portion of a set of explosive charges used for
blasting the
subterranean deposit. The sequence in which a group of explosive charges are
detonated, as
well as the relative depths of these charges from the top surface of the
subterranean deposit,
can be adjusted to control the expansion characteristics of the deposit after
blasting. The
shaping may provide an incline down which the heavy oil will flow or a
reservoir into which
the heavy oil may accumulate.
The term "subterranean deposit" as used herein is defined as a volume of
material that
is at least partly underground and contains a mixture of unwanted materials
and desired heavy
oil. Examples of subterranean deposits include oil sand, and tar sand. In some
cases the oil
sand has no overburden an d this should be considered a subterranean deposit
as described
herein.
The term "substantially vertical" as used herein is defined as within five
degrees of
completely vertical.
The term "substantially horizontal" as used herein is defined as within five
degrees of
completely horizontal.
The term "maximally fragmented", or like phrases as used herein means the
smallest
fragments possible formed from a single starting piece. The term "maximum
fragmentation"
as used herein means to produce the smallest fragments possible from a single
starting piece.
This typically provides or produces the largest amount of surface area and the
highest quantity
of new pieces or fragments from the single starting piece.
The term "heavy oil" as used herein is defined as a material containing carbon
that has
a gravity of not more than 25.7 on the American Petroleum Institute (API)
Scale. As used
herein "heavy oil" comprises both heavy and extra heavy oil. Examples of heavy
oil include,
but are not limited to, bitumen and crude oil. Crude oil is commonly
classified as light,
medium, heavy or extra heavy, referring to its gravity as measured on the API
scale. The API
gravity is measured in degrees and is calculated using the formula API
Gravity = (141.5/S .G.) - 131.5.
Light oil has an API gravity higher than 31.1 (lower than 870 kilograms/cubic
metre),
medium oil has an API gravity between 31.1 and 22.3 (870 kilograms/cubic
metre to 920
kilograms/cubic metre), heavy oil has an API gravity between 22.3 and 10
(920
kilograms/cubic metre to 1,000 kilograms/cubic metre), and extra heavy oil
(e.g. bitumen) has
an API gravity of less than 10 (higher than 1,000 kilograms/cubic metre). The
Canadian
government has only two classifications, light oil with a specific gravity of
less than 900
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kilograms/cubic metre (greater than 25.7 API) and heavy oil with a specific
gravity of greater
than 900 kilograms/cubic metre (less than 25.7 API).
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-section of a subterranean deposit.
Figure 2A is a cross-section of a subterranean deposit that has been prepared
for
blasting.
Figure 2B is a cross-section of a blasted deposit.
Figure 2C is a cross-section of a shaped and prepared blasted deposit.
Figure 2D is a cross-section of a deposit being flooded. The white lines
indicate fluid
being released into the deposit.
Figure 2E is a cross-section of a flooded deposit. The white arrows indicate
fluid being
released into the deposit and the thick black arrows indicate the direction of
a released heavy
oil and fluid mixture.
Figure 3A is a plan view of adjacent deposits at different stages of methods
described
herein.
Figure 3B is a cross-section of adjacent deposits at different stages of
methods
described herein.
Figure 3C is a cross-section of adjacent deposits during a flooding step of
methods
described herein.
DETAILED DESCRIPTION
In various aspects, there is provided a method for the recovery of a heavy oil
from a
subterranean deposit 12 comprising the steps of A) pre-production, site
drainage and topsoil
and/or muskeg 14 removal; B) removing an overburden 16; C) drilling and
blasting; D)
shaping and production preparation; E) in place flooding and recovery of the
heavy oil; F) lean
froth and froth treatment and tailings treatment; and G) reclamation.
A) Pre-Production, Site Drainage and Topsoil/Muskeg Removal
Referring to Figure 1, a topsoil and/or muskeg 14 are often found above a
subterranean
deposit 12. If required, trees and shrubs are removed from the muskeg and/or
topsoil 14.
Surface drainage of the topsoil and/or muskeg 14 is then established in order
to dry the material
overlying the subterranean deposit 12. Muskeg drainage may be achieved using
standard
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backhoe ditching techniques. For example, a series of finger ditches may be
dug into the
muskeg to a depth just slightly into the overburden, below the muskeg. These
drainage ditches
may be sloped so that they drain to a common settling pond where a runoff
water is held until
small sediment settles out. When the runoff water meets government regulations
it can be
released to the environment. Muskeg is known to be suitably dried when it
reaches a state that
it can be handled with backhoe/truck combinations or other suitable mining
equipment types.
When the muskeg and/or topsoil 14 is dry enough to allow access to heavy
mining equipment it
and an overburden 16 may be removed and stockpiled or placed on an area that
is ready for
reclamation materials.
The Overburden 16 and the subterranean deposit 12 may also need a ground water
control system. These systems are well know to the skilled practitioner in the
art and may
comprise a series of wells established around the perimeter of the site to
assist in the control of
the ground water.
Ground water is water that is naturally occurring and may be controlled by a
series of
perimeter wells established around the subterranean deposit 12. The ground
water may be
drawn down below the subterranean deposit 12, by a network of wells that are
located along
the perimeter of the subterranean deposit 12, prior to blasting. The water
level may be kept
below the subterranean deposit 12 so as to not interfere with a method
described herein.
Ground water may be released into the environment if acceptable or
incorporated into a method
described herein if acceptable. This reduces the demand for water from
surrounding major
water systems.
B) Removing Overburden
The material on top of the subterranean deposit 12 is called the overburden
16. The
overburden 16 is often composed of coarse sands, silts, shale and clays. The
overburden 16
may range in thickness from a few centimeters to many hundreds of meters.
Methods for removing the overburden 16 are well known to the skilled
practitioner in
the art. Typically, trucks and shovels are used to remove the overburden 16.
Other methods
may include draglines, and bucket wheel excavators. Drilling and blasting may
be used to
facilitate the overburden 16 removal. If the subterranean deposit 12 does not
have the
overburden 16 above it, then the step of removing the overburden 16 is
unnecessary and may
be skipped.
The removed overburden 16 and the topsoil/muskeg 14 may be stockpiled on top
of an
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area that does not have the subterranean deposit 12, or any other convenient
place. A lack of
the subterranean deposit 12 in an area may be attributed to the subterranean
deposit 12 never
having been there, or because the area has already been processed by a method
described
herein, a portion of a method described herein, or any other method known for
removing the
heavy oil from a subterranean deposit 12. The removed overburden may also be
placed on an
area that is un-economic for surface mining activities.
Removing the overburden 16 provides a space above the subterranean deposit 12.
The
space provided allows the subterranean deposit 12 room to expand. The room to
expand
facilitates the blasting of the subterranean deposit 12. In particular,
blasting the subterranean
deposit 12 into smaller fragments is improved by the removal of the overburden
16.
C) Drilling and Blasting
Referring to Figures 2A and 2B, the subterranean deposit 12 lying below the
overburden 16 may range in thickness from a few centimeters to hundreds of
meters.
Once the overburden 16 is removed, the subterranean deposit 12 is drilled to
produce at
least one bore hole 18. The number and the depth of the bore holes 18 will be
determined by
the depth of the subterranean deposit 12 to be blasted and the diameter of the
bore hole 18.
The bore hole 18 may extend as far down as the bottom of the subterranean
deposit 12, lower
than the bottom of the subterranean deposit 12 or to a desired distance above
the bottom of the
subterranean deposit 12. At least one explosive charge 20 is placed into the
bore hole 18. The
at least one explosive charge 20 is detonated and the subterranean deposit 12
is fragmented to
become a blasted deposit 22.
Blast design may be based on one or a combination of standard blasting
techniques,
including crater blasting and choke (or buffer) blasting.
Crater blasting may be used when only one free surface is provided for relief
and
displacement of the blasted material by the expanding detonation gasses. In
such a blast
geometry, short concentrated charges are used. It is desired to approximate an
ideal spherical
charge geometry to obtain a uniform distribution of stress on the surrounding
material in all
directions using this technique.
Choke (or buffer) blasting may be used when at least two free faces are
provided for
relief and displacement of the blasted material by the expanding detonation
gasses. In this
blast geometry, relatively long cylindrical charges may be used and
distributed in such a way
as to break the material into a previously blasted, and therefore loosened,
zone.
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Water resistant explosive charges, or explosive charges encapsulated in water
proof
containers may be used in methods described herein. The explosive charge may
also be
detonable under high hydrostatic pressures. Explosive charges that have a
relatively low shock
energy and a high gas generation property may be better suited to the
fragmentation and
displacement required by methods described herein. Propellants may also be
used in place of
common commercial explosives.
The blasting techniques described herein are merely examples to explain
possible
blasting methods. Any blasting technique known to the skilled practitioner in
the blasting art
may be used. In particular, the blasting techniques known to provide maximum
fragmentation
of a subterranean oil sand deposit are preferred.
The subterranean deposit 12 is blasted to maximize fragmentation of the
blasted deposit
22. To achieve maximum fragmentation the subterranean deposit 12 must have a
space into
which it may expand. Such a space is generally provided by the removed
overburden 16,
although any space, including naturally occurring spaces and spaces dug to the
side of the
subterranean deposit 12 may also assist with maximum fragmentation of the
subterranean
deposit 12.
Maximum fragmentation of the blasted deposit 22 provides greater permeability
of the
blasted deposit 22 for a flooding step. Maximum permeability allows a greater
yield of a
heavy oil to be released and recovered.
Maximum fragmentation of the blasted deposit 22 also provides maximum
compacting
of the blasted deposit 22 after a fluid from a flooding is removed from a
flooded deposit 24.
Maximum compacting of the blasted deposit 22 provides a zone which is less
permeable to the
fluid, thereby reducing leakage of the fluid from an adjacent flooded deposit.
Furthermore,
maximum compacting provides a more stable surface and a larger workable area
on which to
stockpile overburden and other materials.
A geometric distribution of the blast holes 18 and the elevations and masses
of the
explosive charges 20 in single or multiple blast holes 18 may be adjusted to
create an optimum
overlap of the radii of influence to maximize the fragmentation of the blasted
deposit 22 and
tailor the expansion of the subterranean deposit 12. Furthermore, a line of
closely spaced blast
holes 18 lightly charged with explosive charges 20 may be used to control the
size of the area
of fragmentation of the blasted deposit 22.
Blasting and blasting techniques known to those in the art may also be
practiced in
order to provide a desired shape and fragmentation of the blasted deposit 22.
For example, the
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distance from the bottom of the subterranean deposit 12 of the lower most
explosive charge 20
in each bore hole 18 may be staggered to maximize the fragmentation of the
blasted deposit 22.
Alternatively, special drilling techniques in which clusters of smaller
diameter bore
holes 18 may be used to concentrate explosives charges 20 in a deep location
to simulate single
large explosion may be used. This technique may be applied to a primary
drilling and blasting
step, after which a smaller diameter blast holes 18 may be distributed and
charged in the choke
(or buffer) blasting configuration as previously described.
Additional blasting may be done at any time after the blasted deposit 22 is
flooded to
assist in the agitation of the blasted deposit 22 and assist in the release of
the heavy oil.
D) Shaping and Production Preparation
Referring to Figure 2C, the blasted deposit 22 may then be shaped, or further
shaped if
already shaped using blasting techniques, to prepare the blasted deposit 22
for in place flooding
and heavy oil recovery. Large mining equipment, for example D10 CaterpillarTM
dozers or
large CaterpillarTM graders, may also be used to shape the blasted deposit 22.
Shaping the
blasted deposit 22 may be done to control the movement of the heavy oil and
fluid, the fluid or
a combination of the fluid and heavy oil called a froth 26. For example, a
collection reservoir
28 at the top of the blasted deposit 22 may be provided as a collection area
for the froth 26. A
collection reservoir 28 may comprise a perimeter of the blasted deposit 22
shaped to be higher
than a central area of the blasted deposit 22. An alternative collection
reservoir 28 may
comprise a portion of the blasted deposit 22 shaped to be lower than the rest
of the blasted
deposit 22. Furthermore, a slope may be provided in the blasted deposit 22 so
that the heavy
oil, the fluid or the froth 26, moves in a planned direction down the slope to
a desired location
from which it is collected and then transported to another facility like a
large tank farm prior to
being sent for further enhancement.
Removed overburden 16 may be used in the shaping of the blasted deposit 22.
For
example removed overburden 16 may be positioned around the blasted deposit 22
to act as a
wall 30 for the collection reservoir 28. Alternatively some overburden 16 may
be left in place
to act as a wall 30 for the collection reservoir.
One or a plurality of fluid wells 32 are drilled into the blasted deposit 22.
The drilled
angle of the fluid well 32 may vary. For example, the fluid well 32 may be
substantially
horizontal, substantially vertical, or at an angle in between horizontal and
vertical. A plurality
of fluid wells 32 may be provided so that some or all of the fluid wells 32
may be substantially
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horizontal, substantially vertical, or at an angle in between horizontal and
vertical.
Once the fluid well 32 is drilled, a perforated casing is inserted into the
fluid well 32.
The drilling and inserting may be done concurrently. In a particular
embodiment, a first
substantially horizontal fluid well 32 is drilled and the perforated casing is
inserted
concurrently. In this embodiment, substantially horizontal means parallel to
the bottom of the
blasted deposit 22. The first fluid well 32 and perforated casing may be
placed near the
bottom of the blasted deposit 22.
Vertical fluid wells 32 may be drilled and perforated casings may be inserted
into a
stable layer 34 that lies below the blasted deposit 22. In one embodiment, the
stable layer 34 is
a limestone layer. These may also act as support posts or pillars for a
shelter 36 on the top of
the blasted deposit 22, flooded deposit 24 or a treated deposit 38. If
required for a structure the
vertical wells will be anchored into the limestone using the appropriate civil
engineering
techniques known to the skilled practitioner.
After the fluid wells 32 and perforated casings have been provided in the
blasted
deposit 22, fluid injection equipment, pumping equipment and heating equipment
can be
installed. A froth sump may also be installed to collect the recovered heavy
oil in the form of
the froth 26.
E) In Place Flooding and Recovery of the Heavy Oil
Referring to Figure 2D, at least one fluid is pumped into the fluid wells 32
and the
perforated casings and the fluid is released into the blasted deposit 22 via
perforations in the
perforated casings (direction of flow of the fluid is illustrated by white
arrows 40) thereby
forming a flooded deposit. The fluid will cause the release of the heavy oil
from the blasted
deposit 22. The blasted deposit 22 may be fully or partially saturated with
the fluid. The fluid
may be under pressure and may be hot water, hot steam, hot compressed gas, or
(e.g., air or
CO2). The flooding of the blasted deposit 22 may accomplish: conditioning of,
agitation of,
and heavy oil extraction and flotation from the blasted deposit 22.
The blasted deposit 22 may be flooded or soaked using a fluid that may have a
temperature greater than 50 degrees Celsius. Flooding or soaking time may be
partially
dependent on the fluid temperature used. The longer the blasted deposit 22 is
flooded or
soaked the lower the fluid temperature that may be used.
The heavy oil is released from the flooded deposit 24 by the heat and
agitation effect of
the injected fluid as well as the chemical and mechanical properties of the
injected fluid. When
CA 02520223 2005-09-19
the fluid contacts the heavy oil in the blasted deposit 22. the hot fluid
raises the temperature of
the heavy oil and reduces the viscosity such that the heavy oil may detach
from the inert
material. This combined with the mechanical and chemical properties of the
fluid will
facilitate the release of the heavy oil and/or bitumen.
The blasted deposit 22 may be agitated using the high pressure agitation
effect of the
injected fluid which may also be injected using a pulsating process. A range
of pressures will
be used and may include pressures from ambient pressure to over 500 PSI in
order to
condition, agitate and release the heavy oil and/or bitumen from the blasted
deposit 22.
The fluid injected into the blasted deposit 22 may also provide a plethora of
fluid and/or
gas bubbles that facilitate and assist in the floatation of the heavy oil
and/or bitumen droplets to
the surface. Local fluidization may also be used to create passage for the
bitumen droplets to
rise. The froth 26 that floats to the surface may be continuously taken away
from the top
surface.
Additives like surfactants, ant-acids, acids, solvents and caustics may be
used to assist
in the releasing of the heavy oil from the inert materials or to improve the
floating of the heavy
oil on the surface of the fluid. Such additives are known to the skilled
practitioner in the art.
As the heavy oil is released from a flooded deposit 24 it moves towards the
top of the
flooded deposit 24 in the form of froth 26 (movement of the froth 26 is
indicated by thick black
arrows 42). The froth 26 is also moved by the fluid in a direction of flow of
the fluid. When
the froth 26 appears on a top surface of the flooded deposit 24, the heavy oil
is recovered and
collected as froth 26. The froth 26 may be collected by pumping or draining
the froth 26 into
holding structures. Collected froth 26 may be sent to a storage facility or
for further treatment
at a treatment facility. A flood volume of fluid is typically the amount of
fluid required to
maximize and optimize the flooding and/or soaking and agitation of the blasted
deposit 22 so
that the heavy oil and/or bitumen is released and combined with the fluid to
become a froth 26
which floats to the surface of the flooded deposit 24.
The specific volume of fluid in a flood volume for the blasted deposit 22 will
vary
depending on a number of factors including size dimensions of the blasted
deposit 22, degree
of fragmentation of the blasted deposit 22 and volume of heavy oil contained
in the blasted
deposit 22, as well as time required for proper soaking, ablation and
subsequent release of the
heavy oil and/or bitumen from the subterranean deposit.
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In place pressure flooding and heavy oil recovery steps may be repeated any
number of
times to maximize the recovery of the heavy oil. Additional blasting steps may
be carried out
before repeating the flooding step.
Instead of bringing the oil sand from a subterranean deposit to a separation
vessel,
where fluids are added, fluids are brought to the subterranean deposit and the
processing is
done in the ground. The ground in effect becomes the separation vessel. The
sand sinks to the
bottom and the water and heavy oil and/or bitumen float to the surface. The
released bitumen
is skimmed off the top and sent to storage and/or for further processing.
The main difference between using the ground as a separation vessel and
traditional
separation vessels is that materials to be treated in a traditional separation
vessels are often
supplied by a pipeline. Traditional separation vessels often need to process
the materials
provided to it in a short amount of time, in order to accommodate materials
arriving from the
pipeline. Using methods described herein, the duration of time for which the
flooded deposit is
flooded with fluid (that is the materials being treated) may range from
minutes to hours to days
to weeks. As the duration of time for which the flooded deposit is flooded
with fluid increases,
the amount of heavy oil recovered from the deposit will also increase.
Additional blasting may be done after the blasted deposit 22 is flooded to
assist in the
agitation of the blasted deposit 22 and assist in the release of the heavy
oil.
F) Lean Froth and Froth Treatment and Tailings Treatment
During the in place recovery of the heavy oil, the heavy oil will be released
from the
inert material and with the fluid it will form the froth 26. Depending on how
many times the
blasted deposit 22 has been flooded the percentage by weight of heavy oil in
the froth 26 will
vary. For example, the froth 26 released by a first flooding may have a higher
percentage of
heavy oil than the froth 26 that is released by a subsequent flooding from the
same blasted
deposit 22. This may be because more of the heavy oil is available to be
released in the first
flooding of a blasted deposit 22 than in the second flooding of the same
blasted deposit 22.
The froth 26 that is released in the subsequent flooding may be called lean
froth because it does
not have as much heavy oil as the froth 26 released by the first flooding.
The first flooding may be composed of two separate fluid injections that are
executed at
separate times. For example, the blasted deposit 22 may be flooded by
injecting a fluid that is
primarily hot water to a level that is near the top of the blasted deposit 22,
followed by an
injection with a fluid that is mostly comprised of compressed air or steam.
The compressed air
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or steam may release a plethora of tiny bubbles that assist in the release of
the heavy oil from
the inert material.
The froth 26 collected may need to be dewatered. Froth dewatering techniques
known
to the skilled practitioner, such as cyclones, de-aerators, inclined plate
separators and multi
stage settling vessels may be used to reduce the fluid content (i.e. the fluid
used to flood the
blasted deposit 22, for example water and air/gas) of the froth 26. This
provides a more pure
heavy oil. Secondary floatation techniques may also be used to produce more
pure heavy oil.
Once the fluid content of the froth 26 has been reduced to acceptable levels
further upgrading
may be achieved using techniques known to the skilled practitioner. The fluid
removed from
the froth 26 may be recycled and used again. Froth 26 may have a composition
of from 10% to
70% heavy oil, 10% to 70% water and 0% to 30% solids. Typical froth 26 has a
composition
of approximately: 60% heavy oil, 30% water and 10% solids. Lean froth may have
a
composition of approximately: 10% bitumen, 89% water and 1% solids.
The dewatering of the froth 26 produces a waste or tailings that are often
composed
of fine sands, silts and clays. The quantity of tailings produced by in place
methods are small
when compared to conventional ex situ methods. Typically, the sand and/or
fines and/or
mineral portion of an oil sand deposit accounts for over 80% by weight of the
oil sand deposit.
Some present surface mining techniques mine or dig up the entire oil sand
deposit. The oil
sand is then processed to release the heavy oil and then the rest of the
material, composed
mostly of the sand, is pumped as a fluid or slurry to massive tailings ponds.
In methods described herein, the oil sand does not need to be mined or dug up
and
consequently the large tailings structures or ponds do not have to be
constructed. The tailings
storage required for methods described herein may consist only of the finer
sand and fines
material that are released with the heavy oil and/or bitumen during flooding
or floatation.
Tailings may be treated using techniques that are known by a practitioner in
the art and
may include the use of a thickener, inground thickener or tailings
flocculants. Tailings may be
placed on top of a treated deposit 38 or in a conveniently located designated
tailings area.
G) Reclamation
After in place flooding and heavy oil recovery is complete, the fluid wells 32
may be
used to assist in the removal of fluid from the flooded deposit 24 by pumping
the fluid in the
reverse direction. Additional pumps and wells for providing artificial lift of
the fluid to the
surface may be used to maximize fluid recovery. When flooding has stopped and
fluid is
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removed the remaining materials from the deposit sink and compact providing a
treated deposit
38. The compacted materials in the treated deposit 38 provides a less
permeable surface which
may be used to reduce or prevent the fluid flowing into the treated deposit 38
from an adjacent
blasted deposit 22 that is being flooded or an adjacent flooded deposit 24.
Pipe and equipment are salvaged from the treated deposit 38 for future use.
After
equipment salvage, the treated deposit 38 may be further compacted by the use
of machinery.
When the treated deposit 38 is dry enough for placement of sand or overburden
on top
of the treated deposit to allow heavy equipment to move onto the treated
deposit, the tailings
and/or the removed overburden 16 and/or the topsoil/muskeg 14 may be placed on
top of the
treated deposit 38. The removed overburden 16 and topsoil/muskeg 14 may be
taken from
above the next subterranean deposit 12 to be blasted. Alternatively sand may
be placed
hydraulically over the treated deposit to act as a more stable foundation for
subsequent
overburden placement. Seeding and vegetation planting may be done to return
the surface of
the land to its original or better condition.
Deposit Treatment Planning
Referring to Figures 3A and 3B, a plurality of subterranean deposits 12 may be
adjacent
to one another and methods described herein may be repeated several times,
carried out
simultaneously, or carried out with staggered starting and finishing times to
optimize the
recovery process. Staggering the time at which a method described herein is
started and
combining this with selecting the next subterranean deposit 12 to treat may be
used to
maximize heavy oil production and facilitate an orderly development of the
resource.
Referring to Figure 3C, a substantially horizontal fluid well 32 may be
provided so that
the fluid well 32 may be used for a plurality of subterranean deposits 12.
This may require
blasting a plurality of subterranean deposits 12 prior to flooding.
Ex situ methods known to the skilled practitioner for the recovery of heavy
oil from
subterranean deposits 12 may be used to recover heavy oil from a top portion
of the
subterranean deposit 12 and the remaining, bottom portion of subterranean
deposit 12 may then
be treated by a method described herein. . For example, if a subterranean
deposit 12 is 100m
deep and conventional methods are used to remove 50m of the subterranean
deposit 12 for ex
situ processing, then the remaining 50m of the subterranean deposit 12 may be
treated using a
method described herein.
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Alternatively, moving the top portion of the subterranean deposit to an area
that can be
treated using methods described herein it is possible to eliminate any
problems that may be
encountered when the subterranean deposit is too thick or deep for the
blasting techniques
described herein.
EXAMPLES
Example 1 - Bench scale testing:
50 kilograms samples of oil sand from Fort McMurray were placed in a clear
reservoir
in such a manner as to simulate the density of a blasted oil sand deposit.
Water having a
temperature greater than 50 C and compressed air were injected into the
reservoir at various
locations over a period of 1 hour. Bitumen froth and hot water floated to the
surface and was
decanted into a secondary reservoir. The injection with hot water and
compressed air was
repeated four times. The remainder of the fluid was drained off the reservoir
and the balance
of the oil sand sample sank to the bottom of the reservoir and compacted to a
specific gravity
of 1.70.
Example 2 - Bench scale testing:
A bench scale test was conducted where 100 kilograms of oil sand from Fort
McMurray
was placed in a semi clear reservoir in such a manner as to simulate the
density of a blasted oil
sand deposit. Fluid having a temperature greater than 50 C and compressed air
were injected
into the reservoir at various locations over a period of 2 hours.
Bitumen froth and hot water floated to the surface and was decanted into a
secondary
reservoir. The injection with hot water and compressed air was repeated a
number of three
times.
The remainder of the fluid was drained off the reservoir and the balance of
the oil sand
sample sank to the bottom of the reservoir and compacted to a specific gravity
of
approximately 1.72.
