U.S. patent application number 13/663762 was filed with the patent office on 2014-05-01 for opening isolation for fluid injection into a formation from an expanded casing.
This patent application is currently assigned to GeoSierra LLC. The applicant listed for this patent is GEOSIERRA LLC. Invention is credited to Grant Hocking.
Application Number | 20140116697 13/663762 |
Document ID | / |
Family ID | 50545921 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140116697 |
Kind Code |
A1 |
Hocking; Grant |
May 1, 2014 |
OPENING ISOLATION FOR FLUID INJECTION INTO A FORMATION FROM AN
EXPANDED CASING
Abstract
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 into
the formation in a single longitudinal plane with the wellbore
axis.
Inventors: |
Hocking; Grant; (Alpharetta,
GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GEOSIERRA LLC |
Alpharetta |
GA |
US |
|
|
Assignee: |
GeoSierra LLC
Alpharetta
GA
|
Family ID: |
50545921 |
Appl. No.: |
13/663762 |
Filed: |
October 30, 2012 |
Current U.S.
Class: |
166/280.1 ;
166/305.1 |
Current CPC
Class: |
E21B 43/267
20130101 |
Class at
Publication: |
166/280.1 ;
166/305.1 |
International
Class: |
E21B 43/16 20060101
E21B043/16; E21B 43/267 20060101 E21B043/267 |
Claims
1. A method of injecting fluid into a formation through openings in
a sidewall of a casing of a wellbore having an axis, the method
comprising the steps of: installing an opening isolation device in
proximity of the openings and orientated in a plane intersecting
the openings and the wellbore axis, and injecting fluid into the
formation through the openings.
2. The method of claim 1, wherein the opening isolation device-is
comprises straddle cups and opening isolation elements.
3. The method of claim 2, wherein the opening isolation device is
constructed of flexible rubber.
4. The method of claim 1, wherein two or more sets of openings
contained in the wellbore casing are located on differing
longitudinal planes along the wellbore axis.
5. The method of claim 1, wherein the openings are widened and
connected to the formation by expansion of the casing.
6. The method of claim 5, wherein the casing is in contact with the
formation by a cement based grout.
7. The method of claim 5, wherein the casing is in contact with the
formation by swellable rubber.
8. The method of claim 1, wherein the injected fluid contains a
proppant.
9. The method of claim 8, wherein the proppant particles are of a
size ranging from #4 to #100 U.S. mesh, and the proppant particles
include sand, ceramic beads, resin coated sand, resin coated
ceramic beads or mixtures thereof.
10. The method of claim 1, wherein the openings comprise a first
set of openings and a second set of openings and wherein the second
set of openings is in a different plane from the first set of
openings and the openings of the second set of openings are
isolated by the opening isolation device without moving or rotating
the opening isolation device within the casing.
11. The method of claim 10, wherein a third set of openings in a
different plane from the first and second sets of openings and
wherein the openings of the third set of openings are isolated by
the opening isolation device without moving or rotating the opening
isolation device within the casing.
12. A well system for injecting fluid into a formation to form
inclusions in the formation, the well system comprising: a. a
wellbore having an axis; b. a casing installed in the wellbore, the
casing having a sidewall with openings through the sidewall; c. an
opening isolation device installed in the casing in proximity to
the openings and orientated in a plane intersecting the openings
and the wellbore axis; and d. means for injecting fluid into the
formation through the openings.
13. The well system of claim 12, wherein the opening isolation
device comprises straddle cups and opening isolation elements.
14. The well system of claim 13, wherein the opening isolation
device is constructed of flexible rubber.
15. The well system of claim 12, wherein two or more sets of
openings contained in the wellbore casing are located on differing
longitudinal planes along the wellbore axis.
16. The well system of claim 12, wherein the openings are widened
and connected to the formation by expansion of the casing.
17. The well system of claim 16, wherein the casing is in contact
with the formation by a cement based grout.
18. The well system of claim 16, wherein the casing is in contact
with the formation by swellable rubber.
19. The well system of claim 12, wherein the injected fluid
contains a proppant.
20. The well system of claim 19, wherein the proppant particles are
of a size ranging from #4 to #100 U.S. mesh, and the proppant
particles include sand, ceramic beads, resin coated sand, resin
coated ceramic beads or mixtures thereof.
21. The well system of claim 12, wherein the openings comprise a
first set of openings and a second set of openings and wherein the
second set of openings is in a different plane from the first set
of openings, and the openings of the second set of openings are
isolated by the opening isolation device without moving or rotating
the opening isolation device with in the casing.
22. The well system of claim 21, wherein a third set of openings in
a different plane from the first and second sets of openings and
wherein the openings of the third set of openings are isolated by
the opening isolation device without moving or rotating the opening
isolation device within the casing.
Description
TECHNICAL FIELD
[0001] 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
[0002] 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.degree. API gravity) deposits
are found largely in unconsolidated sandstones, being high porosity
permeable cohensionless sands with minimal grain to grain
cementation. The hydrocarbons are extracted from the oils sands
either by mining or in situ methods.
[0003] 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.degree. C., bitumen has a viscosity
of .about.1,000,000 centipoise. However at elevated temperatures
the bitumen viscosity changes considerably to be .about.350
centipoise at 100.degree. C. down to .about.10 centipoise at
180.degree. C. The oil sand deposits have an inherently high
permeability ranging from .about.1 to 10 Darcy, thus upon heating,
the heavy oil becomes mobile and can easily drain from the
deposit.
[0004] 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 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.degree.-5.degree. 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.degree. C. compared to
ambient reservoir temperatures of .about.15.degree. C.
[0005] 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.
[0006] 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-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. Pat. No. 3,739,852 to Woods et al,
U.S. Pat. No. 4,280,559 to Best, U.S. Pat. No. 4,519,454 to
McMillen, U.S. Pat. No. 4,697,642 to Vogel, and U.S. Pat. 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.
[0007] Descriptions of the SAGD process and modifications are
described in U.S. Pat. No. 4,344,485 to Butler, and U.S. Pat. No.
5,215,146 to Sanchez and thermal extraction methods in U.S. Pat.
No. 4,085,803 to Butler, U.S. Pat. No. 4,099,570 to Vandergriji,
and U.S. Pat. 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.
[0008] 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
catalyst. See U.S. Pat. No. 3,994,340 to Anderson el al., U.S. Pat.
No. 4,696,345 to Hsueh, U.S. Pat. No. 4,706.751 to Gondouin. U.S.
Patent No. 5,054,551 to Duerksen, and U.S. Pat. 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.
[0009] 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.
[0010] 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 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.degree.-5.degree. 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.degree. C. compared to ambient reservoir
temperatures of .about.15.degree. C.
[0011] 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. Pat. No.
4,450,913 to Allen et al, U.S. Pat. No. 4,513,819 to Islip el al,
U.S. Pat. No. 5,407,009 to Butler et al, U.S. Pat. No. 5,607,016 to
Butler, U.S. Pat. No. 5,899,274 to Frauenfeld et al, U.S. Pat. No.
6,318,464 to Mokrys, U.S. Pat. No. 6,769,486 to Lirn et al, and
U.S. Pat. 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.
[0012] 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.degree. to 400.degree. range and above) to
pyrolysis the oil shales. See U.S. Pat. No. 2,780,450 to
Ljungstrom, U.S. Pat. No. 4,597,441 to Ware et al, U.S. Pat. No.
4,926,941 to Glandt et al, U.S. Pat. No. 5,046,559 to Glandt, U.S.
Pat, No. 5,060,726 to Glandt et al, U.S. Pat, No. 5,297,626 to
Vinegar el al, U.S. Pat, No. 5,392,854 to Vinegar et al, U.S. Pat.
No. 6,722,431 to Karanikas et al. In situ combustion processes have
also been disclosed see U.S. Pat. No. 5,211,230 to Ostapovich et
al, U.S. Pat. No. 5,339,897 to Leaute, U.S. Pat. No. 5,413,224 to
Laali, and U.S. Pat. No. 5,954,946 to Klazinga et al.
[0013] In situ processes involving down hole heaters are described
in U.S. Pat. No. 2,634,961 to Ljungstrom, U.S. Pat. No. 2,732,195
to Ljungstrom, U.S. Pat. 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. Pat. No. 2,548,360 to Germain, U.S. Pat. No. 4,716,960 to
Eastlund et al, U.S. Pat. No. 5,060,287 to Van Egmond, U.S. Pat.
No. 5,065,818 to Van Egmond, U.S. Pat. No. 6,023,554 to Vinegar and
U.S. Pat. No. 6,360,819 to Vinegar. Flameless down hole combustor
heaters are described, see U.S. Pat. No. 5,255,742 to Mikus, U.S.
Pat. No. 5,404,952 to Vinegar et al, U.S. Pat. No. 5,862,858 to
Wellington et al, and U.S. Pat. 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. Pat. No. 6,056,057 to Vinegar et al and U.S. Pat.
No. 6,079,499 to Mikus et al.
[0014] 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 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. Pat. No. 3,739,852 to Woods et al,
U.S. Pat. No. 5,297,626 to Vinegar et al, and U.S. Pat. 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.
[0015] 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. Pat. 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. Pat. 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. Pat. No. 6,148,911 to Gipson et al. with a
single well configuration in a gas hydrate formation with
predominantly a horizontal fracture 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. Pat. No. 7,331,385 to
Symington et al. in U.S. Pat. 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.
[0016] 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 permeables planes has been disclosed earlier in U.S. Pat.
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).
[0017] 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. Pat. No. 6,216,783 to Hocking et al, U.S. Pat.
No. 6,443,227 to Hocking et al, U.S. Pat. No. 6,991,037 to Hocking,
U.S. Pat. No. 7,404,441 to Hocking, U.S. Pat. No. 7,640,975 to
Cavender et al., U.S. Pat. No. 7,640,982 to Schultz et al., U.S.
Pat. No. 7,748,458 to Hocking, U.S. Pat. No. 7,814,978 to Steele et
al., U.S. Pat. No. 7,832,477 to Cavender et al., U.S. Pat. No.
7,866,395 to Hocking, U.S. Pat. No. 7,950,456 to Cavender et al.,
U.S. Pat. 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 sediments behave substantially different from
brittle rocks from which most of the hydraulic fracturing
experience is founded. The above cited, U.S. Pat. No. 6,991,037 to
Hocking, and U.S. Pat. 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.
[0018] 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.
[0019] 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.
[0020] 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 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.
[0021] 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.
[0022] 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
[0023] "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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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
[0028] 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 each plane independent of the other planes, without the need
for ports and channels to be constructed in the casing.
[0029] 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.
[0030] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic isometric view of a well system and
associated method embodying principles of the present
invention;
[0032] 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;
[0033] FIG. 3 is a horizontal cross-sectional view of the wing
isolation device in an expanded section of the casing;
[0034] 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.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT
[0035] 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.
[0036] 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.
[0037] 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 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).
[0038] 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, casing, 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.
[0039] 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. Pat. 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.
[0040] 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 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.
[0041] 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.
[0042] 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,
the viscosity of the injected fluid 22 is preferably greater than
approximately 100 centipoise.
[0043] 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.
[0044] 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'. 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 system for fluid isolation. Such
straddle cups 19 are currently in common use in the stimulation of
wells for hydrocarbon production.
[0045] 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.
[0046] 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 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 60.degree. and thus inject in the
other three (3) sets of slots 12 shown.
[0047] 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.
[0048] 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.
* * * * *