U.S. patent application number 11/360140 was filed with the patent office on 2007-08-23 for method of treating a formation using deformable proppants.
Invention is credited to Robert Gordon Fulton, Garnet Ross Olson, Adolph Joseph John Peskunowicz.
Application Number | 20070193745 11/360140 |
Document ID | / |
Family ID | 37806538 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070193745 |
Kind Code |
A1 |
Fulton; Robert Gordon ; et
al. |
August 23, 2007 |
Method of treating a formation using deformable proppants
Abstract
A substance and method for treating a subterranean formation
using hydraulic fracturing. A non-metallic, substantially
deformable, proppant particle is "elastically flexible" or
"plastically compressible" and adapted for use at concentrations
which will substantially create a partial monolayer. The method for
treating a formation with a non-metallic deformable proppant,
includes the steps of injecting a carrier fluid into the formation,
the carrier fluid carrying an amount of the deformable proppant,
wherein the carrier fluid is injected at a pressure and a flow rate
sufficient to create or open an existing fracture or fracture
network in the formation, and placing at least a portion of the
deformable proppant in the fracture, the deformable proppant
forming substantially a partial monolayer in the fracture, and
reducing the pressure and/or the flow rate sufficient to allow the
fracture in the formation to at least partially close, wherein at
least a portion of the deformable proppant remains in the fracture
to prop open at least a portion of the fracture.
Inventors: |
Fulton; Robert Gordon;
(Calgary, CA) ; Peskunowicz; Adolph Joseph John;
(Redwood Meadows, CA) ; Olson; Garnet Ross;
(Calgary, CA) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
1279 OAKMEAD PARKWAY
SUNNYVALE
CA
94085-4040
US
|
Family ID: |
37806538 |
Appl. No.: |
11/360140 |
Filed: |
February 22, 2006 |
Current U.S.
Class: |
166/280.2 ;
166/280.1; 507/924 |
Current CPC
Class: |
Y10T 428/2982 20150115;
C09K 8/80 20130101; E21B 43/267 20130101 |
Class at
Publication: |
166/280.2 ;
166/280.1; 507/924 |
International
Class: |
E21B 43/267 20060101
E21B043/267 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2006 |
CA |
2536957 |
Claims
1. A non-metallic, substantially deformable, proppant particle that
is "elastically flexible" or "plastically compressible" adapted for
use as a propping agent in subsurface formation fracturing
operations at concentrations which will substantially create a
partial monolayer.
2. The deformable proppant of claim 1, comprising an organic,
inorganic, or combination polymer.
3. The deformable proppant of claim 2, where the polymer is manmade
or naturally occurring.
4. The deformable proppant of claim 1, comprising a single polymer
or a mixture of polymers to create the particle.
5. The deformable proppant of claim 1, comprising a single polymer
or a combination of polymers that are layered or coated to create a
particle.
6. The deformable proppant of claim 1, comprising a solid outer
shell or layers of polymer that encase an inner fluid.
7. The deformable proppant of claim 1, having a sphericity of 0.9
to 0.3, tested in accordance with API RP 56.
8. The deformable proppant of claim 1, having a roundness of 0.1 to
0.90, tested in accordance with API RP 56.
9. The deformable proppant of claim 1, being crush resistant under
a closure stress.
10. The deformable proppant of claim 9, wherein the closure stress
is between about 10 MPa and about 80 MPa.
11. The deformable proppant of claim 10, wherein the closure stress
is between about 20 MPa and about 50 MPa.
12. The deformable proppant of claim 1, wherein the deformable
proppant is substantially chemically inert.
13. The deformable proppant of claim 1, wherein the deformable
proppant is adapted to be substantially non-soluble in a formation
fluid.
14. The deformable proppant of claim 1, wherein the proppant
comprises a material selected from the group of high density
polyethylene (HDPE), polyethylene terephthalate (PET),
polypropylene (PP), or styrene-divinyl-benzene copolymer.
15. The deformable proppant of claim 1, wherein the particle has a
specific gravity of between about 0.1 and about 2.5.
16. The deformable proppant of claim 15, wherein the particle has a
specific gravity of between about 0.5 and about 2.2.
17. The deformable proppant of claim 16, wherein the particle has a
specific gravity of between about 0.9 and about 2.0.
18. The deformable proppant of claim 1, wherein the proppant has a
crush resistance of more than substantially 50 MPa.
19. The deformable proppant of claim 18, wherein the proppant has a
crush resistance of more than substantially 80 MPa.
20. The deformable proppant of claim 1, wherein the proppant is
substantially non-permeable.
21. The deformable proppant of claim 1, wherein the proppant is
substantially non-absorbent of fracturing fluid.
22. The deformable proppant of claim 1, wherein the proppant has a
predeformed maximum cross sectional measurement of about 5.0
mm.
23. The deformable proppant of claim 1; wherein the proppant is
formed to have a pre-deformed initial shape, the initial shape
comprising a disk, rice-shape, cubeoid, spheroid, or toroid
(donut).
24. A method of treating a subterranean formation with a
non-metallic deformable proppant, comprising the steps of: a.
injecting a carrier fluid into the formation, the carrier fluid
carrying an amount of the deformable proppant, wherein the carrier
fluid is injected at a pressure and a flow rate sufficient to open
a fracture (creating a new fracture or opening an existing
fracture) in the formation; b. placing at least a portion of the
deformable proppant in the fracture, the deformable proppant
forming substantially a partial monolayer in the fracture; and c.
reducing the pressure and/or the flow rate sufficient to allow the
fracture in the formation to at least partially close, wherein at
least a portion of the deformable proppant remains in the fracture
to prop open at least a portion of the fracture.
25. The method of claim 24, wherein the amount selected such that
the proppant is placed in the fracture in a monolayer or 1.0 layer
thick.
26. The method of claim 24, wherein the amount is between about 10
and 40 kg/m3 of carrier fluid.
27. The method of claim 24, wherein the amount is between about 25
and 100 kg/m3 of carrier fluid.
28. The method of claim 24, wherein the amount is less than about
200 kg/m3 of carrier fluid.
29. The method of claim 24, wherein the portion of the deformable
proppant that remains in the fracture to prop open at least a
portion of the fracture is distributed at a proppant concentration,
the proppant concentration in kg/m2 being less than 1.088(r)(SG),
wherein r is the equivalent radius of the proppant in millimeters
and SG is the specific gravity of the proppant.
30. The method of claim 24, wherein the fracture is a generally
horizontal fracture.
31. The method of claim 24, wherein the fracture has both a
generally vertical and a generally horizontal component.
32. The method of claim 24, wherein the carrier fluid is a gas, a
liquid, a foam or a combination thereof.
33. The method of claim 24, wherein the proppant is elastically,
plastically, or elastically and plastically deformed under a
closure stress.
34. The method of claim 33 wherein the closure stress is between
about 20 MPa and about 80 MPa.
35. The method of claim 24, wherein the proppant has an elastic
deformation resistance and a plastic deformation resistance, and
the closure stress is greater than the elastic deformation
resistance and the closure stress is less than the plastic
deformation resistance.
36. The method of claim 24, wherein the proppant is deformed when a
closure stress is applied.
37. A method of treating a formation with a non-metallic deformable
proppant, comprising the steps of: a. applying a treatment cycle
comprising the steps of: i. injecting a carrier fluid into the
formation, the carrier fluid carrying an amount of the deformable
proppant, wherein the carrier fluid is injected at a pressure and a
flow rate sufficient to open a fracture in the formation; ii.
placing at least a portion of the deformable proppant in the
fracture, the deformable proppant forming substantially a partial
monolayer in the fracture; and iii. reducing the pressure and/or
the flow rate sufficient to allow the fracture in the formation to
at least partially close, wherein at least a portion of the
deformable proppant remains in the fracture to prop open at least a
portion of the fracture; and b. repeating the treatment cycle at
least one time.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Canadian Application
filed Feb. 17, 2006, which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to proppants for
fracturing operations for subterranean formations. More
particularly, the present invention relates to deformable
proppants.
BACKGROUND OF THE INVENTION
[0003] In oil and gas operations, stimulation or treatment of the
subterranean formations using a fluid containing suspended
particles, referred to as hydraulic fracturing, may be used to
improve production. That is, a fluid, referred to in the art as a
fracturing fluid, is pumped or injected through a well bore into a
subterranean formation to be stimulated at a rate and pressure such
that existing fractures are opened and/or new fractures are formed
and extended into the subterranean formation. The fracturing fluid
carries particles, referred to in the art as proppant particles,
into the fractures. The particles are deposited in the fractures
and the fracturing fluid dissipates into the subterranean formation
and/or is returned to the surface. The particles function to "prop"
open or prevent the fractures from closing whereby conductive
channels remain through which produced fluids can flow to the well
bore.
[0004] The paper "Propping Fractures with Aluminum Particles", Kern
L. R. in (Petroleum Technology, June 1961 p. 583) teaches the use
of malleable aluminum particles for producing high-conductivity
fractures. Kern also teaches that flow capacity may be increased
several fold with a sparse distribution of particles, but such flow
capacity is limited by both crushing of the propping particles and
by embedment of the propping particles in the walls of the
formation. Kern teaches that as high loads are applied to the
malleable aluminum particles, they deform slightly but do not
shatter resulting in an increased bearing area against the
formation wall, reducing stress on the malleable aluminum particle
and reducing penetration of the malleable aluminum particle into
the formation. Kern assesses the performance of nearly spherical
aluminum particles which are deformed to produce nearly uniform
disks (deformed thickness less than or equal to 0.5 times the
original nearly spherical diameter). Kern suggests that malleable
aluminum could be used in combination with sand to lower costs
(compared to aluminum alone) and to provide a safety net in the
event the aluminum does not perform as expected.
[0005] Disadvantages of propping with aluminum include limitations
associated with the specific gravity of aluminum which restricts
the fluids which may be used to place aluminum proppant particles,
and the fluid may require special treatment such as viscosification
or emulsification, etc., and in addition, as suggested by Kern, the
high cost of aluminum is a factor. In addition, formations
typically fractured today are very susceptible to damage produced
by the fracturing fluid itself. This requires the use of less
viscous fluids and physically less liquid (or foam) or gas
(nitrogen, carbon dioxide etc.). Less viscous fluids and less
volume of liquid or foam or gas means less carrying capacity for
proppants, which may mean that proppants may not always enter the
fracture or many not be distributed along the full length of the
fracture.
[0006] U.S. Pat. No. 3,933,205 (Kiel) teaches a method for
increasing well productivity by multiple hydraulic fracturing
cycles using no proppant (self propping) or using sand as a
proppant. The initial cycles are designed to form spalls of the
formation material in the fracture and subsequent cycles displace
the spalls into the fracture, thus propping the fracture open or
creating extensions or branches and propping open the extensions or
branches.
[0007] However, this method relies on causing formation damage to
create the desired spalls and teaches only the use of no proppant
or sand as a proppant.
[0008] U.S. Pat. No. 5,531,274 (Bienvenu) teaches a high strength,
lightweight proppant for use in hydraulic fracturing, having a
specific gravity approximately equal to the specific gravity of
water. Bienvenu teaches that such a proppant, such as a
styrene-divinyl-benzene copolymer bead, set in a formation as a
packed mass of particles adjacent to a fracture, will prop open the
fracture.
[0009] However, when closure stress exceeds the deformation limits
of the proppant in the packed mass, the effective permeability of
the packed mass (and the related conductivity of the formation)
decreases as the proppant is deformed, thus reducing or eliminating
the flow channels that normally exist between the particles forming
the packed mass.
[0010] U.S. Pat. No. 6,059,034 (Rickards et al.) teaches a
formation treatment method using deformable particles, the
deformable particles formed of a blend of fracture proppant
material and deformable particulate. As examples, the fracture
proppant material may be a material such as sand, and the
deformable particulate may be a material such as polystyrene, as
divinylbenzene beads.
[0011] However, this blend requires that both materials be blended
and sufficiently mixed, and may result in the usual problems with
sand type fracturing, such as fines.
[0012] It is, therefore, desirable to provide a deformable proppant
that avoids the problems of metallic proppants, that is not formed
into a deformed packed mass, and can be used on its own without
additional proppants to improve stimulation and increase
productivity in the fracturing operations of subterranean
formations.
SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to obviate or
mitigate at least one disadvantage of previous proppants.
[0014] In a first aspect, the present invention provides a
non-metallic, substantially deformable, proppant particle that is
"elastically flexible" or "plastically compressible" adapted for
use alone as a propping agent in subsurface formation fracturing
operations at concentrations which will substantially create a
partial monolayer. The proppant may be an organic, inorganic, or
combination polymer. The proppant may be manmade or naturally
occurring. The proppant may be a single polymer or a mixture of
polymers to form the particles. The proppant may include a single
polymer or a combination of polymers that are layered or coated to
create a particle. The proppant may include a solid outer shell or
layers of polymer that encase an inner fluid.
[0015] Preferably, the proppant has a sphericity of 0.9 to 0.3,
tested in accordance with API RP 56. Preferably, the proppant has a
roundness of 0.1 to 0.90, tested in accordance with API RP 56.
[0016] Preferably, the proppant is shatter resistant under a
closure stress. Preferably, the expected closure stress to be
resisted is between about 10 MPa and about 80 MPa. More preferably,
that closure stress is between about 20 MPa and about 50 MPa.
[0017] Preferably, the proppant is resistant to chemical reaction.
Preferably, the proppant is adapted to be substantially non-soluble
in a formation fluid, and vice versa. Preferably, the proppant is
substantially non-permeable. Preferably, the proppant is a material
selected from the group of high density polyethylene (HDPE),
polyethylene terephthalate (PET), polypropylene (PP), or
styrene-divinyl-benzene copolymer.
[0018] Preferably, the proppant includes particles having a
specific gravity of between about 0.1 and about 2.5. More
preferably, the particles have a specific gravity of between about
0.5 and about 2.2. Most preferably, the particles have a specific
gravity of between about 0.9 and about 2.0.
[0019] Preferably, the proppant has a crush resistance of more than
substantially 50 MPa. More preferably, the proppant has a crush
resistance of more than substantially 80 MPa.
[0020] Preferably, the proppant has an undeformed maximum cross
sectional measurement of about 5.0 mm. Preferably, the proppant is
formed to have a pre-deformed initial shape, the initial shape
comprising a disk, rice-shape, cubeoid, spheroid, or toroid
(donut).
[0021] In further aspect, the present invention provides a method
of treating a subterranean formation with a non-metallic deformable
proppant, including the steps of injecting a carrier fluid into the
formation, the carrier fluid carrying an amount of the deformable
proppant, wherein the carrier fluid is injected at a pressure and a
flow rate sufficient to open a fracture (creating a new fracture or
opening an existing fracture) in the formation, placing at least a
portion of the deformable proppant in the fracture, the deformable
proppant forming substantially a partial monolayer in the fracture,
and reducing the pressure and/or the flow rate sufficient to allow
the fracture in the formation to at least partially close, wherein
at least a portion of the deformable proppant remains in the
fracture to prop open at least a portion of the fracture.
[0022] Preferably, the amount is selected such that the proppant is
placed in the fracture in a monolayer about 1.0 layer thick.
Preferably, the amount is between about 10 and 40 kg/m3 of carrier
fluid. More preferably, the amount is between about 25 and 100
kg/m3 of carrier fluid. Most preferably, the amount is less than
about 200 kg/m3 of carrier fluid.
[0023] Preferably, the portion of the proppant that remains in the
fracture to prop open at least a portion of the fracture is
distributed at a proppant concentration, the proppant concentration
in kg/m2 being less than 1.088(r)(SG), wherein r is the equivalent
radius of the proppant in millimeters and SG is the specific
gravity of the proppant.
[0024] Preferably, the fracture is a single or multiple fracture
with both generally vertical components and generally horizontal
components. The fracture may include a portion that is a generally
horizontal fracture.
[0025] Preferably, the carrier fluid is a gas (for example CO2,
N2), a liquid (for example Water, HC), a foam (for example liquid,
gas, and surfactant) or a combination thereof (for example
N2+CO2+Water).
[0026] Preferably, the proppant is elastically deformed under a
closure stress. Preferably, the proppant is plastically deformed
under a closure stress. Preferably, the proppant is elastically and
plastically deformed under a closure stress. Preferably, the
closure stress is between about 20 MPa and about 80 MPa.
[0027] Preferably, the proppant has an elastic deformation
resistance and a plastic deformation resistance, and the closure
stress is greater than the elastic deformation resistance and the
closure stress is less than the plastic deformation resistance.
[0028] Preferably, the proppant is deformed when a closure stress
is applied.
[0029] In a further aspect, the present invention provides a method
of treating a formation with a non-metallic deformable proppant,
comprising the steps of applying a treatment cycle comprising the
steps of i) injecting a carrier fluid into the formation, the
carrier fluid carrying an amount of the deformable proppant,
wherein the carrier fluid is injected at a pressure and a flow rate
sufficient to open a fracture in the formation, ii) placing at
least a portion of the deformable proppant in the fracture, the
deformable proppant forming substantially a partial monolayer in
the fracture, and iii) reducing the pressure and/or the flow rate
sufficient to allow the fracture in the formation to at least
partially close, wherein at least a portion of the deformable
proppant remains in the fracture to prop open at least a portion of
the fracture, and then repeating the treatment cycle at least one
time.
[0030] Other aspects and features of the present invention will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments of the
invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Embodiments of the present invention will now be described,
by way of example only, with reference to the attached Figures,
wherein:
[0032] FIG. 1 is a simplified cross-sectional view of a
subterranean formation showing hydraulic fracture treatment of the
formation and typical examples of resulting fractures using the
method and substance of the present invention;
[0033] FIGS. 2a-e are representative simplified drawings of a
portion of a fracture propped with a partial monolayer placement of
proppant using the substance and method of the present
invention;
[0034] FIGS. 3a-e are representative simplified drawings the
fractures of FIGS. 2a-e taken along the lines a-a through e-e.;
and
[0035] FIG. 4 is a magnified view of a proppant of the present
invention.
DETAILED DESCRIPTION
[0036] Generally, the present invention provides a method and
substance for propping a fracture in a subterranean formation, such
as in hydraulic fracturing operations in the oil and gas production
industry used to fracture underground reservoirs bearing oil and
gas, to provide or enhance flow channels to improve the fluid
conductivity of the formation to provide increased oil and gas
production rates.
[0037] Referring generally to FIG. 1, the method and substance of
the present invention are applicable to a wide variety of
fractures, including (but not limited to) substantially vertical,
substantially horizontal, and dendritic (or branched) fractures.
The method and substance of the present invention may be used for
hydraulic fracturing operations using equipment commonly used for
conventional (sand) fracturing operations, known to one skilled in
the art.
[0038] Referring generally to FIGS. 2 and 3, the method and
substance of the present invention includes a monolayer of varying
concentrations.
[0039] Referring generally to FIG. 4, one example of a proppant of
the present invention is shown, in a pre-deformed state.
[0040] The deformable proppant of the present invention may be of a
unitary material or may include a core surrounded by a shell. The
core may be a fluid (liquid), such as water, hydrocarbon, or other
fluid known in the industry. This composite (liquid with shell)
design provides a less compressible base and increases the elastic
limit while allowing the shell to deform, reducing embedment into
the formation. The core may be a gas. This composite (gas with
shell) design provides reduced specific gravity.
[0041] The proppant and method of the present invention can be used
with equipment typically used for fracturing operations known to
one skilled in the art, using conventional carrier fluids.
[0042] The art has been developing with very high concentrations of
proppants and very viscous carriers to substantially create a
multilayer proppant pack. The state of the art requires a large
amount of proppant to maximize the propping open of the cracks
formed in the formation, such as 1,000 kg/m3 of proppant (or
more).
[0043] Placing that much proppant that is a deformable proppant
leads to a "pack" that is deformed into a low conductivity mass by
closure stresses in the formation. This leads to the practical
necessity that the proppant be spherical and very rigid to allow
the spaces in-between individual proppant particle when closely
packed act as flow channels (i.e. remaining open even under the
closure stress of the formation). However, the rigid particles may
then become embedded into the formation when closure stress is
applied, leading to lower conductivity or formation damage.
[0044] In the present invention, a partial monolayer is formed to
prop open fractures. The partial monolayer arrangement allows
improved conductivity and the deformable proppant reduces embedment
of proppant particles into the formation. In order to obtain the
partial monolayer placement of the proppant, the proppant is
introduced into the carrier fluid at a relatively low concentration
to substantially create a partial proppant monolayer rather than a
closely packed multilayer.
[0045] The deformable proppant may be any shape, including but not
limited to: spherical, disk shaped, rice-shaped, or cubical.
[0046] "Proppant concentration" refers to the amount of proppant
per unit area of fracture wall (measured on one side only). In US
customary units, it is expressed in pounds of proppant per square
foot of one wall of fracture. In SI units it is expressed in
kilograms per square meter of one wall of fracture face. In SI
units, the Deformable Proppant Concentration in
kg/m2<1.088(r)(SG) where r is the equivalent radius of the
proppant in millimeters and SG is the specific gravity of the
proppant. In US customary units, the Deformable Proppant
Concentration in lbm/ft2<5.647(r)(SG) where r is the radius of
the proppant in millimeters and SG is the specific gravity of the
proppant.
[0047] Two example applications are outlined below:
[0048] Case#1
[0049] A sandstone formation in Alberta, Canada was treated with
conventional fracturing techniques with initial flow rates being
too small to measure (TSTM). A similar treatment on the same
formation utilizing 2270 kg of light weight polystyrene divinyl
benzene deformable proppant (CBM-LWP) with a specific gravity of
1.05 was placed in stages. Each stage was engineered to place
proppant within the fracture at a concentration of 0.0825 kg/m2.
Proppant was pumped at a concentration between 25 and 150 kg/m3 of
carrier fluid. After initial flow back, the well produced
measurable gas and the subsequent pressure build up and analysis
showed a stimulated well.
[0050] Case#2
[0051] A dry coal (Horse Shoe Canyon Formation) in Alberta, Canada
is normally treated with high rate nitrogen fracturing. A well from
the field was fractured using 330 kg of light weight polystyrene
divinyl benzene deformable proppant (CBM-LWP) in each of two coal
seams. Each stage was engineered to place proppant within the
fracture at a concentration of 0.0825 kg/m2. Proppant was pumped at
a concentration of approximately 13 kg/m3 of carrier fluid. After
initial 300 hour flowback, gas rates were higher than surrounding
wells.
[0052] As used herein, "crush" means catastrophic failure of the
proppant and "deformation" means any change in shape of the
proppant.
[0053] The above-described embodiments of the present invention are
intended to be examples only. Alterations, modifications and
variations may be effected to the particular embodiments by those
of skill in the art without departing from the scope of the
invention, which is defined solely by the claims appended
hereto.
* * * * *