Note: Descriptions are shown in the official language in which they were submitted.
CA 02828710 2013-10-01
OPENING ISOLATION FOR FLUID INJECTION INTO A FORMATION FROM AN
EXPANDED CASING
TECHNICAL FIELD
The present invention generally relates to enhanced recovery of petroleum
fluids from the
subsurface by initiating and propagating vertical permeable inclusions in a
plane substantially
orthogonal to the borehole axis. These inclusions containing proppant are thus
highly permeable
and enhance drainage of heavy oil from the formation, and also by steam
injection into these
planes, enhance oil recovery by heating the oil sand formation, the heavy oil
and bitumen, which
will drain under gravity and be produced. The present invention generally
relates to a method of
isolating openings in an expanded casing to provide for fluid injection in a
single longitudinal
plane with the wellbore axis.
BACKGROUND OF THE INVENTION
Heavy oil and bitumen oil sands are abundant in reservoirs in many parts of
the world
such as those in Alberta, Canada, Utah and California in the United States,
the Orinoco Belt of
Venezuela, Indonesia, China and Russia. The hydrocarbon reserves of the oil
sand deposit is
extremely large in the trillions of barrels, with recoverable reserves
estimated by current
technology in the 300 billion barrels for Alberta, Canada and a similar
recoverable reserve for
Venezuela. These vast heavy oil (defined as the liquid petroleum resource of
less than 20 API
gravity) deposits are found largely in unconsolidated sandstones, being high
porosity permeable
SGR/10173716.1
CA 02828710 2013-10-01
.5 cohensionless sands with minimal grain to grain cementation. The
hydrocarbons are extracted
from the oils sands either by mining or in situ methods.
The heavy oil and bitumen in the oil sand deposits have high viscosity at
reservoir
temperatures and pressures. While some distinctions have arisen between tar or
oil sands,
bitumen and heavy oil, these terms will be used interchangeably herein. The
oil sand deposits in
Alberta, Canada extend over many square miles and vary in thickness up to
hundreds of feet
thick. Although some of these deposits lie close to the surface and are
suitable for surface
mining, the majority of the deposits are at depth ranging from a shallow depth
of 150 feet down
to several thousands of feet below ground surface. The oil sands located at
these depths
constitute some of the world's largest presently known petroleum deposits. The
oil sands contain
a viscous hydrocarbon material, commonly referred to as bitumen, in an amount
that ranges up to
15% by weight. Bitumen is effectively immobile at typical reservoir
temperatures. For example
at 15 C, bitumen has a viscosity of ¨1,000,000 centipoise. However at
elevated temperatures the
bitumen viscosity changes considerably to be ¨350 centipoise at 100 C down to
¨10 centipoise
at 180 C. The oil sand deposits have an inherently high permeability ranging
from ¨1 to 10
Darcy, thus upon heating, the heavy oil becomes mobile and can easily drain
from the deposit.
Solvents applied to the bitumen soften the bitumen and reduce its viscosity
and provide a
non-thermal mechanism to improve the bitumen mobility. Hydrocarbon solvents
consist of
vaporized light hydrocarbons such as ethane, propane or butane or liquid
solvents such as
pipeline diluents, natural condensate streams or fractions of synthetic
crudes. The diluent can be
added to stem and flashed to a vapor state or be maintained as a liquid at
elevated temperature
and pressure, depending on the particular diluent composition. While in
contact with the
bitumen, the saturated solvent vapor dissolves into the bitumen. This
diffusion process is due to
2
SGR/101737161
CA 02828710 2013-10-01
the partial pressure difference between the saturated solvent vapor and the
bitumen. As a result
of the diffusion of the solvent into the bitumen, the oil in the bitumen
becomes diluted and
mobile and will flow under gravity. The resultant mobile oil may be
deasphalted by the
condensed solvent, leaving the heavy asphaltenes behind within the oil sand
pore space with
little loss of inherent fluid mobility in the oil sands due to the small
weight percent (5-15%) of
the asphaltene fraction to the original oil in place. Deasphalting the oil
from the oil sands
produces a high grade quality product by 3 -5 API gravity. If the reservoir
temperature is
elevated the diffusion rate of the solvent into the bitumen is raised
considerably being two orders
of magnitude greater at 100 C compared to ambient reservoir temperatures of
¨15 C.
In situ methods of hydrocarbon extraction from the oil sands consist of cold
production,
in which the less viscous petroleum fluids are extracted from vertical and
horizontal wells with
sand exclusion screens, CHOPS (cold heavy oil production system) cold
production with sand
extraction from vertical and horizontal wells with large diameter perforations
thus encouraging
sand to flow into the well bore, CSS (cyclic steam stimulation) a huff and
puff cyclic steam
injection system with gravity drainage of heated petroleum fluids using
vertical and horizontal
wells, steam flood using injector wells for steam injection and producer wells
on 5 and 9 point
layout for vertical wells and combinations of vertical and horizontal wells,
SAGD (steam
assisted gravity drainage) steam injection and gravity production of heated
hydrocarbons using
two horizontal wells, VAPEX (vapor assisted petroleum extraction) solvent
vapor injection and
gravity production of diluted hydrocarbons using horizontal wells, and
combinations of these
methods.
Cyclic steam stimulation and steam flood hydrocarbon enhanced recovery methods
have
been utilized worldwide, beginning in 1956 with the discovery of CSS, huff and
puff or steam-
3
SGR/101737161
CA 02828710 2013-10-01
soak in Mene Grande field in Venezuela and for steam flood in the early 1960s
in the Kern River
field in California. These steam assisted hydrocarbon recovery methods
including a combination
of steam and solvent are described in U.S. Patent No. 3,739,852 to Woods et
al, U.S. Patent No.
4,280,559 to Best, U.S. Patent No. 4,519,454 to McMillen, U.S. Patent No.
4,697,642 to Vogel,
and U.S. Patent No. 6,708,759 to Leaute et al. The CSS process raises the
steam injection
pressure above the formation fracturing pressure to create fractures within
the formation and
enhance the surface area access of the steam to the bitumen. Successive steam
injection cycles
reenter earlier created fractures and thus the process becomes less efficient
over time. CSS is
generally practiced in vertical wells, but systems are operational in
horizontal wells, but have
complications due to localized fracturing and steam entry and the lack of
steam flow control
along the long length of the horizontal well bore.
Descriptions of the SAGD process and modifications are described in U.S.
Patent No.
4,344,485 to Butler, and U.S. Patent No. 5,215,146 to Sanchez and thermal
extraction methods in
U.S. Patent No. 4,085,803 to Butler, U.S. Patent No. 4,099,570 to Vandergrift,
and U.S. Patent
No. 4,116,275 to Butler et al. The SAGD process consists of two horizontal
wells at the bottom
of the hydrocarbon formation, with the injector well located approximately 10-
15 feet vertically
above the producer well. The steam injection pressures exceed the formation
fracturing pressure
in order to establish connection between the two wells and develop a steam
chamber in the oil
sand formation. Similar to CSS, the SAGD method has complications, albeit less
severe than
CSS, due to the lack of steam flow control along the long section of the
horizontal well and the
difficulty of controlling the growth of the steam chamber.
A thermal steam extraction process referred to a HASDrive (heated annulus
steam drive)
and modifications thereof heat and hydrogenate the heavy oils insitu in the
presence of a metal
4
SGR/101737161
CA 02828710 2013-10-01
catalyst. See U.S. Patent No. 3,994,340 to Anderson et al., U.S. Patent No.
4,696,345 to Hsueh,
U.S. Patent No. 4,706,751 to Gondouin,U.S. Patent No. 5,054,551 to Duerksen,
and U.S. Patent
No. 5,145,003 to Duerksen. It is disclosed that at elevated temperature and
pressure the injection
of hydrogen or a combination of hydrogen and carbon monoxide to the heavy oil
in situ in the
presence of a metal catalyst will hydrogenate and thermal crack at least a
portion of the
petroleum in the formation.
Thermal recovery processes using steam require large amounts of energy to
produce the
steam, using either natural gas or heavy fractions of produced synthetic
crude. Burning these
fuels generates significant quantities of greenhouse gases, such as carbon
dioxide. Also, the
steam process uses considerable quantities of water, which even though may be
reprocessed,
involves recycling costs and energy use. Therefore a less energy intensive oil
recovery process is
desirable.
Solvents applied to the bitumen soften the bitumen and reduce its viscosity
and provide a
non-thermal mechanism to improve the bitumen mobility. Hydrocarbon solvents
consist of
vaporized light hydrocarbons such as ethane, propane or butane or liquid
solvents such as
pipeline diluents, natural condensate streams or fractions of synthetic
crudes. The diluent can be
added to steam and flashed to a vapor state or be maintained as a liquid at
elevated temperature
and pressure, depending on the particular diluent composition. While in
contact with the
bitumen, the saturated solvent vapor dissolves into the bitumen. This
diffusion process is due to
the partial pressure difference in the saturated solvent vapor and the
bitumen. As a result of the
diffusion of the solvent into the bitumen, the oil in the bitumen becomes
diluted and mobile and
will flow under gravity. The resultant mobile oil may be deasphalted by the
condensed solvent,
leaving the heavy asphaltenes behind within the oil sand pore space with
little loss of inherent
5
SGR/10173716.1
CA 02828710 2013-10-01
fluid mobility in the oil sands due to the small weight percent (5-15%) of the
asphaltene fraction
to the original oil in place. Deasphalting the oil from the oil sands produces
a high grade quality
product by 3 -5 API gravity. If the reservoir temperature is elevated the
diffusion rate of the
solvent into the bitumen is raised considerably being two orders of magnitude
greater at 100 C
compared to ambient reservoir temperatures of ¨15 C.
Solvent assisted recovery of hydrocarbons in continuous and cyclic modes are
described
including the VAPEX process and combinations of steam and solvent plus heat.
See U.S. Patent
No. 4,450,913 to Allen et al, U.S. Patent No. 4,513,819 to Islip et al, U.S.
Patent No. 5,407,009
to Butler et al, U.S. Patent No. 5,07,016 to Butler, U.S. Patent No. 5,899,274
to Frauenfeld et
al, U.S. Patent No. 6,318,464 to Mokrys, U.S. Patent No. 6,769,486 to Lim et
al, and U.S. Patent
No. 6,883,607 to Nenniger et al. The VAPEX process generally consists of two
horizontal wells
in a similar configuration to SAGD; however, there are variations to this
including spaced
horizontal wells and a combination of horizontal and vertical wells. The
startup phase for the
VAPEX process can be lengthy and take many months to develop a controlled
connection
between the two wells and avoid premature short circuiting between the
injector and producer.
The VAPEX process with horizontal wells has similar issues to CSS and SAGD in
horizontal
wells, due to the lack of solvent flow control along the long horizontal well
bore, which can lead
to non-uniformity of the vapor chamber development and growth along the
horizontal well bore.
Direct heating and electrical heating methods for enhanced recovery of
hydrocarbons
from oil sands and oil shales have been disclosed in combination with steam,
hydrogen, catalysts
and/or solvent injection at temperatures to ensure the petroleum fluids
gravity drain from the
formation and at significantly higher temperatures (300 to 400 range and
above) to pyrolysis
the oil shales. See U.S. Patent No. 2,780,450 to Lfungstrom, U.S. Patent No.
4,597,441 to Ware
6
SGR/10173716.1
CA 02828710 2013-10-01
.5 et al, U.S. Patent No. 4,926,941 to Glandt et al, U.S. Patent No.
5,046,559 to Glandt, U.S. Patent
No. 5,060,726 to Glandt et al, U.S. Patent No. 5,297,626 to Vinegar et al,
U.S. Patent No.
5,392,854 to Vinegar et al, U.S. Patent No. 6,722,431 to Karanikas et al. In
situ combustion
processes have also been disclosed see U.S. Patent No. 5,211,230 to Ostapovich
et al, U.S.
Patent No. 5,339,897 to Leaute, U.S. Patent No. 5,413,224 to Laali, and U.S.
Patent No.
5,954,946 to Klazinga et al.
In situ processes involving down hole heaters are described in U.S. Patent No.
2,634,961
to Ljungstriim, U.S. Patent No. 2,732,195 to LjungstrOm, U.S. Patent No.
2,780,450 to
Ljungstrom. Electrical heaters are described for heating viscous oils in the
forms of downhole
heaters and electrical heating of tubing and/or casing, see U.S. Patent No.
2,548,360 to Germain,
U.S. Patent No. 4,716,960 to Eastlund et al, U.S. Patent No. 5,060,287 to Van
Egmond, U.S.
Patent No. 5,065,818 to Van Egmond, U.S. Patent No. 6,023,554 to Vinegar and
U.S. Patent No.
6,360,819 to Vinegar. Flameless down hole combustor heaters are described, see
U.S. Patent No.
5,255,742 to Mikus, U.S. Patent No. 5,404,952 to Vinegar et al, U.S. Patent
No. 5,862,858 to
Wellington et al, and U.S. Patent No. 5,899,269 to . Wellington et al. Surface
fired heaters or
surface burners may be used to heat a heat transferring fluid pumped down hole
to heat the
formation as described in U.S. Patent No. 6,056,057 to Vinegar et al and U.S.
Patent No.
6,079,499 to Mikus et al.
The thermal and solvent methods of enhanced oil recovery from oil sands, all
suffer from
a lack of surface area access to the in place bitumen. Thus the reasons for
raising steam pressures
above the fracturing pressure in CSS and during steam chamber development in
SAGD, are to
increase surface area of the steam with the in place bitumen. Similarly the
VAPEX process is
limited by the available surface area to the in place bitumen, because the
diffusion process at this
7
SCR/10173716.1
CA 02828710 2013-10-01
.5 contact controls the rate of softening of the bitumen. Likewise during
steam chamber growth in
the SAGD process the contact surface area with the in place bitumen is
virtually a constant, thus
limiting the rate of heating of the bitumen. Therefore both methods (heat and
solvent) or a
combination thereof would greatly benefit from a substantial increase in
contact surface area
with the in place bitumen. Hydraulic fracturing of low permeable reservoirs
has been used to
increase the efficiency of such processes and CSS methods involving fracturing
are described in
U.S. Patent No. 3,739,852 to Woods et al, U.S. Patent No. 5,297,626 to Vinegar
et al, and U.S.
Patent No. 5,392,854 to Vinegar et al. Also during initiation of the SAGD
process over
pressurized conditions are usually imposed to accelerate the steam chamber
development,
followed by a prolonged period of under pressurized condition to reduce the
steam to oil ratio.
Maintaining reservoir pressure during heating of the oil sands has the
significant benefit of
minimizing water inflow to the heated zone and to the well bore.
Electrical resistive heating of oil shale and oil sand formations utilizing a
hydraulic
fracture filled with an electrically conductive material are described in U.S.
Patent No. 3,137,347
to Parker, involving a horizontal hydraulic fracture filled with conductive
proppant and with the
use of two (2) wells to electrically energizing the fracture and raise the
temperature of the oil
shale to pyrolyze the organic matter and produce hydrocarbon from a third
well, in U.S. Patent
No. 5,620,049 to Gipson et al. with a single well configuration in a
hydrocarbon formation
predominantly a vertical fracture filled with conductive temperature setting
resin coated proppant
and the electric current passes through the conductive proppant to a surface
ground and the
single well is completed to raise the temperature of the oil in-situ to reduce
its viscosity and
produce hydrocarbons from the same well, in U.S. Patent No. 6,148,911 to
Gipson et al. with a
single well configuration in a gas hydrate formation with predominantly a
horizontal fracture
8
SGR/10173716.1
CA 02828710 2013-10-01
filled with conductive proppant and the electric current passes through the
conductive proppant
to a surface ground, raising the temperature of the formation to release the
methane from the gas
hydrates and the single well is completed for methane production, in U.S.
Patent No. 7,331,385
to Symington et al. in U.S. Patent No. 7,631,691 to Symington et al. and in
Canadian Patent No.
2,738,873 to Symington et al. all with a predominantly vertical fracture
filled with conductive
proppant and the conductive fracture is electrically energized by contact with
at least two (2)
wells or in the case of a single well presumably through the well and surface
ground with the oil
shale raised to a temperature to pyrolyze the organic matter into producible
hydrocarbons, with
the electrically conductive fracture composed of electrically conductive
proppant and non-
electrically conductive non-permeable cement. The single well systems
described above all
suffer from low efficiency and high energy loss due to the current passes
through a significant
distance of the formation from the conductive fracture to the surface ground.
Also the systems
with two or more wellbores do not disclosed how the electrode to conductive
fracture contact
will be other than a point contact resulting in significant energy loss and
overheating at such a
contact.
It is well known that extensive heavy oil reservoirs are found in formations
comprising
unconsolidated, weakly cemented sediments. Unfortunately, the methods
currently used for
extracting the heavy oil from these formations have not produced entirely
satisfactory results.
Heavy oil is not very mobile in these formations, and so it would be desirable
to be able to form
increased permeability planes in the formations and by injecting steam or
solvents into these
planes and/or by direct electrical resistive heating of the plane, heating the
formation and thus
increase the mobility of the heavy oil in the formation and by drainage
through the permeable
planes to the wellbore for production up the well. Steam injection into
multiple azimuth vertical
9
SGR/10173716.1
CA 02828710 2013-10-01
permeables planes has been disclosed earlier in U.S. Patent No. 7,591,306 to
Hocking; however
the method cited is for a single well being both a steam injector and liquids
producer, whereas
the current invention contains multiple wells with the significant advantage
of much faster
production and lower steam to oil ratio (SOR).
However, techniques used in hard, brittle rock to form fractures therein are
typically not
applicable to ductile formations comprising unconsolidated, weakly cemented
sediments. The
method of controlling the azimuth of a vertical hydraulic planar inclusion in
formations of
unconsolidated or weakly cemented soils and sediments by slotting the well
bore or installing a
pre-slotted or weakened casing at a predetermined azimuth has been disclosed.
The method
disclosed that a vertical hydraulic planar inclusion can be propagated at a
pre-determined
azimuth in unconsolidated or weakly cemented sediments and that multiple
orientated vertical
hydraulic planar inclusions at differing azimuths from a single well bore can
be initiated and
propagated for the enhancement of petroleum fluid production from the
formation. See U.S.
Patent No. 6,216,783 to Hocking et al, U.S. Patent No. 6,443,227 to Hocking et
al, U.S. Patent
No. 6,991,037 to Hocking, U.S. Patent No. 7,404,441 to Hocking, U.S. Patent
No. 7,640,975 to
Cavender et al., U.S. Patent No. 7,640,982 to Schultz et al., U.S. Patent No.
7,748,458 to
Hocking, U.S. Patent No. 7,814,978 to Steele et al., U.S. Patent No. 7,832,477
to Cavender etal.,
U.S. Patent No. 7,866,395 to Hocking, U.S. Patent No. 7,950,456 to Cavender et
al., U.S. Patent
No. 8,151,874 to Schultz et al. The method disclosed that a vertical hydraulic
planar inclusion
can be propagated at a pre-determined azimuth in unconsolidated or weakly
cemented sediments
and that multiple orientated vertical hydraulic planar inclusions at differing
azimuths from a
single well bore can be initiated and propagated for the enhancement of
petroleum fluid
production from the formation. It is now known that unconsolidated or weakly
cemented
10
SGR/10173716.1
CA 02828710 2013-10-01
sediments behave substantially different from brittle rocks from which most of
the hydraulic
fracturing experience is founded. The above cited, U.S. Patent No. 6,991,037
to Hocking, and
U.S. Patent No. 7,748,458 to Hocking, disclose a method to create a planar
inclusion by
selectively injecting the fluid into a single plane on a particular azimuth,
via ports and channels
that connect to each discrete plane. It is preferable to remove such ports and
channels from the
casing construction and thus provide for a smaller diameter casing; whilst
still maintaining
selective injection of the fluid into a single plane on a particular plane.
The methods disclosed above find especially beneficial application in ductile
rock
formations made up of unconsolidated or weakly cemented sediments, in which it
is typically
very difficult to obtain directional or geometric control over inclusions as
they are being formed.
Weakly cemented sediments are primarily frictional materials since they have
minimal cohesive
strength. An uncemented sand having no inherent cohesive strength (i.e., no
cement bonding
holding the sand grains together) cannot contain a stable crack within its
structure and cannot
undergo brittle fracture. Such materials are categorized as frictional
materials which fail under
shear stress, whereas brittle cohesive materials, such as strong rocks, fail
under normal stress.
The term "cohesion" is used in the art to describe the strength of a material
at zero
effective mean stress. Weakly cemented materials may appear to have some
apparent cohesion
due to suction or negative pore pressures created by capillary attraction in
fine grained sediment,
with the sediment being only partially saturated. These suction pressures hold
the grains together
at low effective stresses and, thus, are often called apparent cohesion.
The suction pressures are not true bonding of the sediment's grains, since the
suction
pressures would dissipate due to complete saturation of the sediment. Apparent
cohesion is
11
SGR/10173716.1
CA 02828710 2013-10-01
generally such a small component of strength that it cannot be effectively
measured for strong
rocks, and only becomes apparent when testing very weakly cemented sediments.
Geological strong materials, such as relatively strong rock, behave as brittle
materials at
normal petroleum reservoir depths, but at great depth (i.e. at very high
confining stress) or at
highly elevated temperatures, these rocks can behave like ductile frictional
materials.
Unconsolidated sands and weakly cemented formations behave as ductile
frictional materials
from shallow to deep depths, and the behavior of such materials are
fundamentally different from
rocks that exhibit brittle fracture behavior. Ductile frictional materials
fail under shear stress and
consume energy due to frictional sliding, rotation and displacement.
Conventional hydraulic dilation of weakly cemented sediments is conducted
extensively
on petroleum reservoirs as a means of sand control. The procedure is commonly
referred to as
"Frac-and-Pack." In a typical operation, the casing is perforated over the
formation interval
intended to be fractured and the formation is injected with a treatment fluid
of low gel loading
without proppant, in order to form the desired two winged structure of a
fracture. Then, the
proppant loading in the treatment fluid is increased substantially to yield
tip screen-out of the
fracture. In this manner, the fracture tip does not extend further, and the
fracture and perforations
are backfilled with proppant.
The process assumes a two winged fracture is formed as in conventional brittle
hydraulic
fracturing. However, such a process has not been duplicated in the laboratory
or in shallow field
trials. In laboratory experiments and shallow field trials what has been
observed is chaotic
geometries of the injected fluid, with many cases evidencing cavity expansion
growth of the
treatment fluid around the well and with deformation or compaction of the host
formation.
12
SGR/10173716.1
CA 02828710 2013-10-01
Weakly cemented sediments behave like a ductile frictional material in yield
due to the
predominantly frictional behavior and the low cohesion between the grains of
the sediment. Such
materials do not "fracture" and, therefore, there is no inherent fracturing
process in these
materials as compared to conventional hydraulic fracturing of strong brittle
rocks.
Linear elastic fracture mechanics is not generally applicable to the behavior
of weakly
cemented sediments. The knowledge base of propagating viscous planar
inclusions in weakly
cemented sediments is primarily from recent experience over the past ten years
and much is still
not known regarding the process of viscous fluid propagation in these
sediments.
Accordingly, there is a need for a method and apparatus for enhancing the
extraction of
hydrocarbons from oil sands via permeable vertical inclusions installed in the
formation, and
selectively injecting a fluid into each discrete plane on a particular azimuth
without the necessity
for ports and channels to be in the casing section.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for enhanced recovery of
petroleum
fluids from the subsurface by initiating and propagating vertical permeable
inclusions in a plane
substantially orthogonal to the borehole axis. These inclusions containing
proppant are thus
highly permeable and enhance drainage of heavy oil from the formation, and
also by steam
injection into these planes, enhance oil recovery by heating the oil sand
formation, the heavy oil
and bitumen, which will drain under gravity and be produced. In one embodiment
of this
invention, multiple propped vertical inclusions are constructed at various
azimuths from a well
by expansion of a casing section and propagating the proppant filled
inclusions into the oil sand
formation. The vertical inclusions are propagated discretely by selectively
injecting fluid into
13
SGR/101737161
CA 02828710 2013-10-01
each plane independent of the other planes, without the need for ports and
channels to be
constructed in the casing.
Although the present invention contemplates the formation of vertical propped
inclusions
which generally extend laterally away from a vertical or near vertical well
penetrating an earth
formation and in a generally vertical plane, those skilled in the art will
recognize that the
invention may be carried out in earth formations wherein the fractures and the
well bores can
extend in directions other than vertical.
Other objects, features and advantages of the present invention will become
apparent
upon reviewing the following description of the preferred embodiments of the
invention, when
taken in conjunction with the drawings and the claims.
14
SGR/10173716.1
CA 02828710 2013-10-01
,5 BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic isometric view of a well system and associated method
embodying
principles of the present invention;
FIG. 2 is a schematic isometric view of a well system and associated method of
the
treatment tool in a section of the well casing;
FIG. 3 is a horizontal cross-sectional view of the wing isolation device in an
expanded
section of the casing;
FIG. 4 is a horizontal cross-sectional view of the wing isolation device in an
expanded
section of the casing and with fluid injection into a single plane.
SGR/10173716.1
CA 02828710 2013-10-01
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT
Several embodiments of the present invention are described below and
illustrated in the
accompanying drawings. The present invention involves a method and apparatus
for enhanced
recovery of petroleum fluids from the subsurface by construction of propped
vertical inclusions
in the oil sand formation from a substantially vertical wellbore for enhancing
drainage of heavy
oil from the formation and/or to provide a means of injecting fluid into each
discrete plane
independent of other planes on differing azimuths, by injection isolation of
the discrete plane by
a wing isolation device contained within a treatment tool lowered into the
well.
It is well known that extensive heavy oil reservoirs are found in formations
comprising
unconsolidated, weakly cemented sediments. Unfortunately, the methods
currently used for
extracting the heavy oil from these formations have not produced entirely
satisfactory results.
Heavy oil is not very mobile in these formations, and so it would be desirable
to be able to form
increased permeability planes in the formations and by injecting steam into
the permeable planes,
heating the formation and in-situ hydrocarbons and thus increase the mobility
of the heavy oil in
the formation and by gravity drainage through the permeable planes to the
wellbore for
production up the wells.
Representatively illustrated in FIG. 1 is a well system 10 and associated
method which
embody principles of the present invention. The system 10 is particularly
useful for producing
heavy oil 42 from a formation 14. The formation 14 may comprise unconsolidated
and/or weakly
cemented sediments for which conventional fracturing operations are not well
suited. The term
"heavy oil" is used herein to indicate relatively high viscosity and high
density hydrocarbons,
such as bitumen. Heavy oil is typically not recoverable in its natural state
(e.g., without heating
or diluting) via wells, and may be either mined or recovered via wells through
use of steam and
16
SGR/101737161
CA 02828710 2013-10-01
.5
solvent injection, in situ combustion, etc. Gas-free heavy oil generally has
a viscosity of greater
than 100 centipoise and a density of less than 20 degrees API gravity (greater
than about 900
kilograms/cubic meter).
As depicted in FIG. 1, a substantially vertical well has been drilled into the
formation 14
and the well casing 11 has been cemented in the formation 14 or is in contact
with the formation
by a swellable elastomer. The term "casing" is used herein to indicate a
protective lining for a
wellbore. Any type of protective lining may be used, including those known to
persons skilled in
the art as liner, easing, tubing, etc. Casing may be segmented or continuous,
jointed or unjointed,
conductive or non-conductive made of any material (such as steel, aluminum,
polymers,
composite materials, etc.), and may be expanded or unexpanded, etc.
The well casing string 11 has expansion devices 12 and a sump section 40
interconnected
therein. The expansion device 12 operates to expand the casing string 11
radially outward and
thereby dilate the formation 14 proximate the device, in order to initiate
forming of generally
vertical and planar inclusions 18 extending outwardly from the wellbore at
various azimuths.
Suitable expansion devices 12 for use in the well system 10 are described in
U.S. Patent Nos.
6,216,783, 6,330,914, 6,443,227, 6,991,037, 7,404,441, 7,640,975, 7,640,982,
7,748,458,
7,814,978, 7,832,477, 7,866,395, 7,950,456 and 8,151,874. The entire
disclosures of these prior
patents are incorporated herein by this reference. Other expansion devices may
be used in the
well system 10 in keeping with the principles of the invention.
Once the device 12 is operated to expand the casing string 11 radially
outward, fluid 22 is
forced into the dilated formation 14 to propagate the inclusions 18 into the
formation. It is not
necessary for the inclusions 18 to be formed simultaneously. Shown in FIG. 1
is an eight (8)
wing inclusion well system 10, with eight (8) inclusions 18 formed. The well
system 10 does not
17
SGR/10173716,1
CA 02828710 2013-10-01
'5 necessarily need to consist of eight (8) inclusions at the same depth
orientated at various
azimuths, but could consist of one, two, three, four, five, six or even seven
vertical planar
inclusions at various azimuths at the same depth, with such choice of the
number of inclusions
constructed depending on the application, formation type and/or economic
benefit. Also there are
upper inclusions on the same azimuth, and in fact there could be numerous of
these upper
inclusions at progressively shallower depths, or there could only be a single
inclusion at a
particular depth.
Typically, the lower inclusions 18 are constructed first, with each wing of
the eight (8)
inclusions 18 injected independently of the others. The formation 14, pore
space may contain a
significant portion of immobile heavy oil or bitumen generally up to a maximum
oil saturation of
90%; however, even at these very high oil saturations of 90%, i.e. very low
water saturation of
10%, the mobility of the formation pore water is quite high, due to its
viscosity and the formation
permeability. The injected fluid 22 carries the proppant to the extremes of
the inclusions 18.
Upon propagation of the inclusions 18 to their required lateral and vertical
extent, the thickness
of the inclusions 18 may need to be increased by utilizing the process of tip
screen out. The tip
screen out process involves modifying the proppant loading and/or inject fluid
22 properties to
achieve a proppant bridge at the inclusion tips. The injected fluid 22 is
further injected after tip
screen out, but rather then extending the inclusion laterally or vertically,
the injected fluid 22
widens, i.e. thickens, and fills the inclusion from the inclusion tips back to
the well bore.
The behavioral characteristics of the injected viscous fluid 22 are preferably
controlled to
ensure the propagating viscous inclusions maintain their azimuth
directionality, such that the
viscosity of the injected fluid 22 and its volumetric rate are controlled
within certain limits
depending on the formation 14, proppant 20 specific gravity and size
distribution. For example,
18
SGR/10173716.1
CA 02828710 2013-10-01
the viscosity of the injected fluid 22 is preferably greater than
approximately 100 centipoise.
However, if foamed fluid is used, a greater range of viscosity and injection
rate may be permitted
while still maintaining directional and geometric control over the inclusions.
The viscosity and
volumetric rate of the injected fluid 22 needs to be sufficient to transport
the proppant 20 to the
extremities of the inclusions. The size distribution of the proppant 20 needs
to be matched with
that of the formation 14, to ensure formation fines do not migrate into the
propped pack inclusion
during hydrocarbon production. Typical size distribution of the proppant would
range from #12
to #20 U.S. Mesh for oil sand formations, with an ideal proppant being sand or
ceramic beads.
Ceramic beads coated with a resin such as phenol formaldehyde, being heat
hardenable, is
capable of mechanically binding the proppant together 21 in the presence of
steam without loss
of permeability of the propped inclusion.
In the well system 10, heavy oil 42 will flow under gravity through the
inclusions and the
formation towards the well and enter the sump 40 and is pumped to surface via
a PCP
(progressive cavity pump), ESP (electrical submersible pump), gas lift or
natural lift 41,
depending on operating temperatures, pressures and depth, via a production
tubing 40.
As depicted in FIG. 2, is a configuration of the well system 10, after radial
expansion of
the casing 11 by expansion device 12 in a section of the well with the
expanded casing section
shown 11'. The well system 10 is conveyed on tubing or drill pipe 13 and
upward and downward
facing cups 19 are position to straddle the expanded section 11'. A slot
isolation device
comprises the straddle cups 19 and slot isolation elements 15. The slot
isolation elements
15 are orientated to the azimuth of the inclusion 18 to be propagated by fluid
injection
22, containing proppant 20. The straddle cups 19 and the slot isolation
elements 15 consists
of an elastomer, such as rubber, reinforced and molded onto steel base to form
a flexible but
strong
19
CA 02828710 2013-10-01
system for fluid isolation. Such straddle cups 19 are currently in common use
in the stimulation
of wells for hydrocarbon production.
As depicted in FIG. 3, is a horizontal cross-section of the well system 10,
after radial
expansion of the casing 11 by expansion device 12 in a section of the well
results in an expanded
casing section shown 11', with slots 24 opening in the sidewall of the casing
11 during
expansion. The slot isolation elements 15 are orientated to the azimuth 23 of
the inclusion to be
propagated. In FIG. 3 there are six (6) sets of slots 24 at various azimuths,
whereas there could
be any number of sets of slots 24 depending on the application and could be
two (2) sets or more.
Each set of slots 24 as shown consist of three (3) individual slots 24, where
there could be any
number of individual slots 24 in a set of slots. The slot isolation elements
15 are shown as three
(3) sets for isolation over three (3) sets of slots 24 at three (3) differing
azimuths 23. There could
be only a single set of slot isolation elements 15 for isolation across a
single set of slots 24 on a
particular azimuth 23. The number of slot isolation element 15 contained in
the well system 10
will depend on the number of inclusions that are to be formed at differing
azimuths at a
particular depth. Each set of slot isolation elements 15 are connected to a
fluid injection tubing
17 via an opening 16.
As depicted in FIG. 4, is a horizontal cross-section of the well system 10,
after radial
expansion of the casing 11 by expansion device 12 in a section of the well
resulting in the
expanded casing section shown 11', with slots 24 opening in the sidewall of
the casing 11 during
expansion. The slot isolation elements 15 are orientated to the azimuth 23 of
the inclusion to be
propagated. Fluid 22 is injected through tubing 17 contained within the well
tubing 13 through
opening 16 into the formation 14 through slots 24 on a particular azimuthal
plane 23. The slot
isolation elements 15' deform to seal against the casing 11, 11' and isolate
the slots 24 along the
20
SGR/10173716.1
CA 02828710 2013-10-01
-5
azimuth 23 from the remaining sets of slots 24. Upon completion of fluid 22
injection for planar
inclusion on a particular azimuth 23, sequentially another set of slots 24 can
be injected with
fluid via other tubing and opening shown for three (3) sets of slot isolation
elements 15.
Subsequently, the isolation elements 15 could be rotated 600 and thus inject
in the other three (3)
sets of slots 12 shown.
The formation 14 could be comprised of relatively hard and brittle rock, but
the system
10 and method find especially beneficial application in ductile rock
formations made up of
unconsolidated or weakly cemented sediments, in which it is typically very
difficult to obtain
directional or geometric control over inclusions as they are being formed.
However, the present
disclosure provides information to enable those skilled in the art of
hydraulic fracturing, soil and
rock mechanics to practice a method and system 10 to initiate and control the
propagation of a
viscous fluid in weakly cemented sediments, and importantly for the fluid to
be injected in a
specific discrete plane in the formation without the necessity of having ports
and channels in the
casing string.
Finally, it will be understood that the preferred embodiment has been
disclosed by way of
example, and that other modifications may occur to those skilled in the art
without departing
from the scope and spirit of the appended claims.
21
SGR/10173716.1
