U.S. patent application number 17/660857 was filed with the patent office on 2022-08-11 for cross-linked acrylamide polymer or copolymer gel and breaker compositions and methods of use.
The applicant listed for this patent is Kemira OYJ. Invention is credited to Jiang Li, Scott Rosencrance, Roopa Tellakula.
Application Number | 20220251440 17/660857 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220251440 |
Kind Code |
A1 |
Li; Jiang ; et al. |
August 11, 2022 |
CROSS-LINKED ACRYLAMIDE POLYMER OR COPOLYMER GEL AND BREAKER
COMPOSITIONS AND METHODS OF USE
Abstract
Well treatment fluids, and methods for treating wellbores or
fracturing subterranean formations, which include acrylamide
polymer or copolymer crosslinked with one or more crosslinkers and
one or more iron-containing compounds are provided. The fluids and
methods may be used to carry proppants into fractures and to
increase fluid recovery in hydraulic fracturing applications
Inventors: |
Li; Jiang; (Johns Creek,
GA) ; Tellakula; Roopa; (Suwanee, GA) ;
Rosencrance; Scott; (Douglasville, GA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Kemira OYJ |
Helsinki |
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FI |
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Appl. No.: |
17/660857 |
Filed: |
April 27, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15102434 |
Jun 7, 2016 |
11339322 |
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PCT/US2014/072668 |
Dec 30, 2014 |
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17660857 |
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61922517 |
Dec 31, 2013 |
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International
Class: |
C09K 8/68 20060101
C09K008/68; C09K 8/88 20060101 C09K008/88; E21B 43/26 20060101
E21B043/26; E21B 43/267 20060101 E21B043/267 |
Claims
1-2. (canceled)
3. A well treatment fluid comprising: (i) a gel composition
comprising an acrylamide polymer or copolymer; (ii) one or more
crosslinkers; and (iii) a breaker composition comprising one or
more iron-containing compounds and one or more booster compounds
selected from the group consisting of ethylenediaminetetraacetic
acid (EDTA); salts of EDTA; citric acid; aminotricarboxylic acid
and its salts; ethylenediaminetetra(methylenephosphonic acid),
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts; boric acid and its salts; alkali
metal salts of carbonates; diethylenetriaminepentaacetic acid
(DTPA); and lignosulfates.
4. The well treatment fluid of claim 3, wherein the gel composition
is formed by combining the monomers of the acrylamide polymer or
copolymer and the one or more crosslinkers in an aqueous solution
at a pH in the range of about 5 to about 12, and wherein the molar
ratio of the one or more crosslinkers to monomers of the acrylamide
polymer or copolymer is in the range of about greater than about
0.1 to about 2.0.
5-8. (canceled)
9. A method of treating a wellbore comprising: injecting into the
wellbore: (i) a first composition comprising monomers of an
acrylamide polymer or copolymer, or an aqueous dispersion or
emulsion of an acrylamide polymer or copolymer; (ii) a second
composition comprising one or more crosslinkers; and (iii) a
breaker composition comprising one or more iron-containing
compounds and one or more booster compounds selected from the group
consisting of ethylenediaminetetraacetic acid (EDTA); salts of
EDTA; citric acid; aminotricarboxylic acid and its salts;
ethylenediaminetetra(methylenephosphonic acid),
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts; boric acid and its salts; alkali
metal salts of carbonates; diethylenetriaminepentaacetic acid
(DTPA); and lignosulfates.
10. (canceled)
11. The method of claim 9, wherein the breaker composition is
injected into the wellbore substantially at the same time as the
first and second compositions.
12. The method of claim 9, wherein the breaker composition is
injected into the wellbore after the first and second
compositions.
13. A method of treating a wellbore comprising: injecting into a
wellbore a gel composition comprising an acrylamide polymer or
copolymer, one or more crosslinkers, and a breaker composition
comprising one or more iron-containing compounds and one or more
booster compounds selected from the group consisting of
ethylenediaminetetraacetic acid (EDTA); salts of EDTA; citric acid;
aminotricarboxylic acid and its salts;
ethylenediaminetetra(methylenephosphonic acid),
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts; boric acid and its salts; alkali
metal salts of carbonates; diethylenetriaminepentaacetic acid
(DTPA); and lignosulfates.
14. The method of claim 13, wherein the gel composition is formed
by combining the monomers of the acrylamide polymer or copolymer
and the one or more crosslinkers in an aqueous solution at a pH in
the range of about 5 to about 12, and wherein the molar ratio of
the one or more crosslinkers to monomers of the acrylamide polymer
or copolymer is in the range of about greater than about 0.1 to
about 2.0.
15. The method of claim 13, wherein the breaker composition is
injected into the wellbore substantially at the same time as the
gel composition.
16. The method of claim 13, wherein the breaker composition is
injected into the wellbore after the gel composition.
17. A method of fracturing a subterranean formation comprising:
providing: (i) a first composition comprising monomers of an
acrylamide polymer or copolymer, or an aqueous dispersion or
emulsion of an acrylamide polymer or copolymer; (ii) a second
composition comprising one or more crosslinkers; and (iii) a
breaker composition comprising one or more iron-containing
compounds and one or more booster compounds selected from the group
consisting of ethylenediaminetetraacetic acid (EDTA); salts of
EDTA; citric acid; aminotricarboxylic acid and its salts;
ethylenediaminetetra(methylenephosphonic acid),
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts; boric acid and its salts; alkali
metal salts of carbonates; diethylenetriaminepentaacetic acid
(DTPA); and lignosulfates; and placing the compositions into a
subterranean formation so as to create or enhance a fracture in the
subterranean formation.
18. (canceled)
19. A method of fracturing a subterranean formation comprising:
providing: (i) a gel composition comprising an acrylamide polymer
or copolymer; (ii) one or more crosslinkers; and (iii) a breaker
composition comprising one or more iron-containing compounds and
one or more booster compounds selected from the group consisting of
ethylenediaminetetraacetic acid (EDTA); salts of EDTA; citric acid;
aminotricarboxylic acid and its salts;
ethylenediaminetetra(methylenephosphonic acid),
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts; boric acid and its salts; alkali
metal salts of carbonates; diethylenetriaminepentaacetic acid
(DTPA); and lignosulfates; and placing the compositions into a
subterranean formation so as to create or enhance a fracture in the
subterranean formation.
20. The method of claim 19, wherein the gel composition is formed
by combining the monomers of the acrylamide polymer or copolymer
and the one or more crosslinkers in an aqueous solution at a pH in
the range of about 5 to about 12, and wherein the molar ratio of
the one or more crosslinkers to monomers of the acrylamide polymer
or copolymer is in the range of about greater than about 0.1 to
about 2.0.
21. (canceled)
22. The well treatment fluid of claim 3, wherein the gel
composition is in the form of monomers of an acrylamide polymer or
copolymer, and wherein the one or more crosslinkers crosslink the
monomers of the acrylamide polymer or copolymer.
23. The well treatment fluid of claim 22, wherein the one or more
iron-containing compounds is selected from the group consisting of
a ferrous compound, a ferrous salt, a ferric compound and a ferric
salt.
24. The well treatment fluid of claim 22, wherein the one or more
iron-containing compounds is selected from the group consisting of
ferrous chloride, ferrous bromide, ferrous fluoride, ferrous
sulfate, ammonium iron sulfate, and combinations thereof.
25. The well treatment fluid of claim 22, wherein the one or more
crosslinkers are selected from the group consisting of compounds
comprising zirconium, titanium, chromium, barium, calcium
manganese, zinc, nickel, strontium, boron, and mixtures
thereof.
26. The well treatment fluid of claim 22, wherein the one or more
crosslinkers are selected from the group consisting of glyoxal,
malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde,
o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, polyethylene imine,
phenol/formaldehyde, glyoxlic acid, and mixtures thereof.
27. The well treatment fluid of claim 3, wherein the gel
composition is in the form of an aqueous dispersion or emulsion of
an acrylamide polymer or copolymer.
28. The well treatment fluid of claim 27, wherein the one or more
water-soluble iron-containing compounds is selected from the group
consisting of a ferrous compound, a ferrous salt, a ferric
compound, and a ferric salt.
29. The well treatment fluid of claim 27, wherein the one or more
water-soluble iron-containing compounds is selected from the group
consisting of ferrous chloride, ferrous bromide, ferrous fluoride,
ferrous sulfate, ferrous citrate, ammonium iron sulfate, and
combinations thereof.
30. The well treatment fluid of claim 27, wherein the one or more
crosslinkers are selected from the group consisting of compounds
comprising zirconium, titanium, chromium, barium, calcium,
manganese, zinc, nickel, strontium, boron, and mixtures
thereof.
31. The well treatment fluid of claim 27, wherein the one or more
crosslinkers are selected from the group consisting of glyoxal,
malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde,
o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, polyethylene imine,
phenol/formaldehyde, glyoxlic acid, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present disclosure claims priority to U.S. Provisional
Application No. 61/922,517, filed Dec. 31, 2013.
FIELD OF THE ART
[0002] The present disclosure generally relates to compositions and
well treatment fluids for use in hydraulic fracturing
applications.
BACKGROUND
[0003] In the drilling, completion, and stimulation of oil and gas
wells, well treatment fluids are often pumped into well bore holes
under high pressure and at high flow rates causing the rock
formation surrounding the well bore to fracture. A type of well
treatment commonly utilized for stimulating hydrocarbon production
from a subterranean zone penetrated by a well bore is hydraulic
fracturing. Hydraulic fracturing, also referred to as fracing (or
fracking), is used to initiate production in low-permeability
reservoirs and re-stimulate production in older producing wells. In
hydraulic fracing, a fluid composition is injected into the well at
pressures effective to cause fractures in the surrounding rock
formation. Fracing is used both to open up fractures already
present in the formation and create new fractures.
[0004] Proppants, such as sand and ceramics, are used to keep
induced fractures open both during and after a fracturing
treatment. To place the proppants inside the fracture, the proppant
particles are suspended in a fluid that is pumped into the
subterranean formation. Generally, this fluid has a viscosity
sufficient to maintain suspension of the particles.
[0005] For ideal performance, a hydraulic fracturing fluid should
be sufficiently viscous to create a fracture of adequate width and
be able to transport large quantities of proppants into the
fracture. Rheology modifiers (thickeners or viscosifiers), may be
used in these fluids to increase the viscosity. The viscosity of
the fluid can be enhanced or modified by addition of synthetic
and/or natural polymers. Examples of polymer-enhanced fluids
include slickwater systems, linear gel systems, and crosslinked gel
systems.
[0006] A crosslinked gel system is a more viscous type of hydraulic
fracturing fluid used for transporting of proppant. In crosslinked
gel systems, a linear polymer or gel, for example, a fluid based on
guar or modified guar, is crosslinked with added reagents such as
borate, zirconate, and titanate in the presence of alkali. The most
common version of crosslinked gel is known in the art as
guar-borate gel. Upon crosslinking of the linear polymer into a
crosslinked gel fluid, the viscosity of the fluid increases and
proppants can be effectively suspended.
[0007] Once the hydraulic fracturing fracturing fluid has delivered
proppant to the fracture or delivered sand in gravel packing or
frac packing operations, it is often desirable to lower the
viscosity of the fracturing fluid such that the fluid can be
recovered from the formation using minimal energy. The removal of
the spent fracturing fluids from the subterranean formation is
typically required to allow hydrocarbon production. This reduction
in viscosity of the fracturing fluid is often achieved using a
breaker that breaks the cross-linking bonds of the crosslinked
gels.
[0008] Synthetic polymers, for example polyacrylamide (PAM)
polymers, can form permanent gel under acidic conditions with metal
crosslinking agents, such as aluminum-, chromium-, zirconium- and
titanium-based complexes. Such gels can be used, for example, to
control conformance in enhanced oil recovery (EOR) applications,
where subsequent breaking to significantly reduce viscosity is not
necessary. However, for fracing fluid applications, the acidity of
the formation in hydraulic fracturing is usually not high, and
breaking of the crosslinked gel improves fluid recovery.
SUMMARY
[0009] Disclosed herein are well treatment fluids comprising: a
first composition comprising monomers of an acrylamide polymer or
copolymer or an aqueous dispersion or emulsion of an acrylamide
polymer or copolymer; a second composition comprising one or more
crosslinkers; and a breaker composition comprising one or more
iron-containing compounds. Also disclosed herein are well treatment
fluids comprising a gel composition and a breaker composition
comprising one or more iron-containing compounds; wherein the gel
composition comprises an acrylamide polymer or copolymer
crosslinked with one or more crosslinkers. Methods of treating a
wellbore, or of fracturing a subterranean formation, with the well
treatment fluid, are also provided. Methods of treating a wellbore,
or of fracturing a subterranean formation, comprise injecting into
a wellbore: a first composition comprising monomers of an
acrylamide polymer or copolymer or an aqueous dispersion or
emulsion of an acrylamide polymer or copolymer; a second
composition comprising one or more crosslinkers; and a breaker
composition comprising one or more iron-containing compounds. A
method of treating a wellbore, or of fracturing a subterranean
formation, comprises injecting into a wellbore a gel composition
and a breaker composition comprising one or more iron-containing
compounds; wherein the gel composition comprises an acrylamide
polymer or copolymer crosslinked with one or more crosslinkers.
[0010] The disclosure may be understood more readily by reference
to the following detailed description of the various features of
the disclosure and the examples included therein.
BRIEF DESCRIPTION OF FIGURES
[0011] FIG. 1 shows the results of the viscosity analyses for
exemplary gels according to the embodiments and a guar gel.
[0012] FIGS. 2 and 3 show the change in viscosity for compositions
comprising exemplary gels and exemplary gels in combination with
exemplary breakers.
DETAILED DESCRIPTION
[0013] The present disclosure provides certain well treatment
fluids and methods of treating a wellbore, or fracturing a
subterranean formation. The fluids and methods, which involve
acrylamide polymers or copolymers crosslinked with certain
crosslinkers, and breaker compositions comprising one or more
iron-containing compounds, are for use in hydraulic fracturing
applications. In particular, the fluids and methods may be used to
carry proppants into fractures and to increase fluid recovery in
hydraulic fracturing applications. The exemplary fluids and methods
may be used to facilitate the replacement of crosslinked guar in
hydraulic fracturing applications with comparable or improved
performance.
[0014] Polymer and Gel Compositions
[0015] In exemplary embodiments, a composition comprises an
acrylamide polymer or copolymer crosslinked with one or more
crosslinkers. In exemplary embodiments, the composition is a gel
composition. In exemplary embodiments, the gel composition is
formed by combining the monomers of the acrylamide polymer or
copolymer and the one or more crosslinkers. In exemplary
embodiments, the gel composition is formed by combining an aqueous
dispersion or emulsion of the acrylamide polymer or copolymer and
the one or more crosslinkers. In exemplary embodiments, the
monomers of the acrylamide polymer or copolymer may be provided as
a composition comprising monomers of the acrylamide polymer or
copolymer. In exemplary embodiments, the aqueous dispersion or
emulsion of the acrylamide polymer or copolymer may be provided as
a composition comprising an aqueous dispersion or emulsion of the
acrylamide polymer or copolymer. In exemplary embodiments, the
aqueous dispersion or emulsion of the acrylamide polymer or
copolymer is a fine aqueous dispersion or emulsion of the
acrylamide polymer or copolymer. In exemplary embodiments, the one
or more crosslinkers may be provided as a composition comprising
the one or more crosslinkers. In exemplary embodiments, the
monomers of the acrylamide polymer or copolymer and the one or more
crosslinkers are each in the form of aqueous solutions, dispersions
or emulsions.
[0016] As used herein, the term "acrylamide polymer" refers to a
homopolymer of acrylamide and encompasses acrylamide polymers
chemically modified (e.g., hydrolyzed) following
polymerization.
[0017] As used herein the term "acrylamide copolymer" refers to a
polymer comprising an acrylamide monomer and one or more
comonomers. The comonomer may be anionic, cationic or non-ionic. In
certain embodiments, the comonomer is hydrophobic. The acrylamide
copolymer may be unmodified or chemically modified. Representative,
non-limiting co-monomers include acrylic acid, vinyl acetate, vinyl
alcohol and/or other unsaturated vinyl monomers.
[0018] In one embodiment, the acrylamide copolymer comprises an
anionic comonomer. In some embodiments, the anionic monomer is
selected from the group consisting of (meth)acrylic acid,
alkali/alkaline/ammonium salts of (meth)acrylic acid,
2-acrylamido-2-methylpropanesulfonic acid, alkali/alkaline/ammonium
salts of 2-acrylamido-2-methylpropanesulfonic acid, maleic acid,
alkali/alkaline/ammonium salts of maleic acid and the like.
[0019] In another embodiment, the acrylamide copolymer comprises a
cationic comonomer. In some embodiments, the cationic monomer is
selected from the group consisting of
(meth)acrylamidoethyltrimethylammonium chloride, (meth) acrylamido
propyltrimethylammonium chloride and the like.
[0020] In another embodiment, the acrylamide copolymer comprises a
non-ionic comonomer. In some embodiments, the non-ionic monomer is
selected from the group consisting (meth)acrylamide, maleic
anhydride.
[0021] In an exemplary embodiment, the acrylamide copolymer
comprises an acrylamide monomer and an anionic comonomer, but does
not include a cationic comonomer.
[0022] In one embodiment, the acrylamide polymer or copolymer is
characterized by a charge of about 0% to about 40%, about 5% to
about 35%, about 15% to about 30%, about 15% to about 20% or about
20% to about 30%. In one embodiment, the charge is in the range of
about 5% to about 35% and provides a particularly high viscosity
that provides substantial suspending power. In another embodiment,
the charge is in the range of about 15% to about 20% and provides a
particularly high viscosity that provides substantial suspending
power.
[0023] In another embodiment, the acrylamide polymer or copolymer
is characterized by a charge of about 10%, about 15%, about 20%,
about 25%, about 30%, about 35% or about 40%. In an exemplary
embodiment, the charge is an anionic charge.
[0024] The range of charge for the gel composition disclosed herein
is a function of the charge of the polyacrylamide copolymer
comprising charged monomers or the chemically modified
polyacrylamide polymer or copolymer.
[0025] In a particular embodiment, the acrylamide copolymer
comprises from about 30 to about 90, about 40 to about 80, about 50
to about 70 or about 60 mole % acrylamide.
[0026] In a particular embodiment, the weight ratio of the
acrylamide monomer to the one or more comonomers is about 10:90 to
90:10.
[0027] In a particular embodiment, the acrylamide polymer or
copolymer is characterized by a degree of hydrolysis of about 5 to
about 10%, about 10 to about 15%, about 15 to about 20%, about 20
to about 25%, about 25 to about 30% or greater than about 30%. In a
more particular embodiment, the acrylamide--polymer or copolymer is
characterized by a degree of hydrolysis of about 15, about 16,
about 17, about 18, about 19 or about 20%.
[0028] In one embodiment, acrylamide polymers or copolymers are
water dispersible.
[0029] In exemplary embodiments, a gel composition comprising an
acrylamide polymer or copolymer crosslinked with one or more
crosslinkers is formed by combining the monomers of the acrylamide
polymer or copolymer and the one or more crosslinkers in an aqueous
solution at a pH in the range of about 5 to about 12, or about 7.5
to about 11, and wherein the molar ratio of the one or more
crosslinkers to monomers of the acrylamide polymer or copolymer is
in the range of about greater than about 0.1 to about 2.0, or about
0.2 to about 2.0.
[0030] In exemplary embodiments, a gel composition comprising an
acrylamide polymer or copolymer crosslinked with one or more
crosslinkers is formed by combining an aqueous dispersion or
emulsion of the acrylamide polymer or copolymer and the one or more
crosslinkers in an aqueous solution at a pH in the range of about 5
to about 12, or about 7.5 to about 11, and wherein the molar ratio
of the one or more crosslinkers to monomers of the acrylamide
polymer or copolymer is in the range of about greater than about
0.1 to about 2.0, or about 0.2 to about 2.0.
[0031] In exemplary embodiments, a composition comprising an
acrylamide polymer or copolymer crosslinked with one or more
crosslinkers is formed by combining the monomers of the acrylamide
polymer or copolymer and the one or more crosslinkers in an aqueous
solution at a pH in the range of about 5 to about 12, or about 7.5
to about 11, and wherein the molar ratio of the one or more
crosslinkers to monomers of the acrylamide polymer or copolymer is
in the range of about greater than about 0.1 to about 2.0, or about
0.2 to about 2.0.
[0032] In exemplary embodiments, a composition comprising an
acrylamide polymer or copolymer crosslinked with one or more
crosslinkers is formed by combining a fine aqueous dispersion or
emulsion of the acrylamide polymer or copolymer and the one or more
crosslinkers in an aqueous solution at a pH in the range of about 5
to about 12, or about 7.5 to about 11, and wherein the molar ratio
of the one or more crosslinkers to monomers of the acrylamide
polymer or copolymer is in the range of about greater than about
0.1 to about 2.0, or about 0.2 to about 2.0.
[0033] In exemplary embodiments, the acrylamide polymer or
copolymer has a weight average molecular weight of greater than or
equal to about 0.5 million g/mol. In exemplary embodiments, the
acrylamide polymer or copolymer has a weight average molecular
weight of in the range of about 0.5 million g/mol to about 30
million g/mol.
[0034] In exemplary embodiments, the amount of the acrylamide
polymer or copolymer used in the gel compositions can vary widely
depending on the particular polymer used, the purity of the
polymer, and properties desired in the final composition. In
exemplary embodiments, the amount of the polymer used in the
compositions is in the range of about 0.05 to about 5, about 0.1 to
about 3, about 0.2 to about 2, or about 0.3 to about 1, weight
percent based on the total weight of the composition.
[0035] As used herein, the terms "polymer," "polymers,"
"polymeric," and similar terms are used in their ordinary sense as
understood by one skilled in the art, and thus may be used herein
to refer to or describe a large molecule (or group of such
molecules) that contains recurring units. Polymers may be formed in
various ways, including by polymerizing monomers and/or by
chemically modifying one or more recurring units of a precursor
polymer. A polymer may be a "homopolymer" comprising substantially
identical recurring units formed by, e.g., polymerizing a
particular monomer. A polymer may also be a "copolymer" comprising
two or more different recurring units formed by, e.g.,
copolymerizing two or more different monomers, and/or by chemically
modifying one or more recurring units of a precursor polymer. A
copolymer may be a "terpolymer" comprising three or more different
recurring units formed by, e.g., copolymerizing three or more
different monomers, and/or by chemically modifying one or more
recurring units of a precursor polymer. A copolymer may be a
"tetrapolymer" comprising four or more different recurring units
formed by, e.g., copolymerizing four or more different monomers,
and/or by chemically modifying one or more recurring units of a
precursor polymer.
[0036] In exemplary embodiments, the one or more crosslinkers
comprises an inorganic compound, for example a compound comprising
zirconium, titanium, chromium, barium, calcium, manganese, zinc,
nickel, strontium, boron or mixtures thereof. In exemplary
embodiments, the compound is boric acid or a borate. In exemplary
embodiments, the inorganic compound is a compound that releases
multivalent metal ions.
[0037] In exemplary embodiments, the one or more crosslinkers
comprises an organic compound, for example glyoxal,
malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde,
o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, any suitable
dialdehyde compound, polyethylene imine, phenol/formaldehyde,
glyoxlic acid, or mixtures thereof. In exemplary embodiments, the
one or more crosslinkers comprises a dialdehyde, for example
glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde,
adipaldehyde, o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, any
suitable dialdehyde compound, and mixtures thereof. In certain
embodiments, the dialdehyde is glyoxal.
[0038] In exemplary embodiments, the one or more crosslinkers are
used to crosslink the acrylamide moieties of the polymer. In
exemplary embodiments, dialdehyde is used to crosslink the
acrylamide moieties of the polymer.
[0039] In one embodiment, the gel composition comprises an
acrylamide polymer or copolymer, crosslinked with glyoxal. In a
particular embodiment, the gel composition comprises an acrylamide
polymer or copolymer crosslinked with glyoxal, wherein the
acrylamide polymer or copolymer is characterized by a charge in the
range of about 5% to about 40% and provides a particularly high
viscosity that provides substantial suspending power. In one
embodiment, the charge is in the range of about 15% to about 20%
and provides a particularly high viscosity that provides
substantial suspending power. In a particular embodiment, the
charge is about 10%, about 15%, about 20%, about 25%, about 30%,
about 35% or about 40%.
[0040] In another embodiment, the gel composition comprises an
acrylamide copolymer crosslinked with glyoxal. In a particular
embodiment, the gel composition comprises an acrylamide copolymer
crosslinked with glyoxal, wherein the acrylamide copolymer is
characterized by a charge in the range of about 5% to about 40% and
provides a particularly high viscosity that provides substantial
suspending power. In one embodiment, the charge is in the range of
about 15% to about 20% and provides a particularly high viscosity
that provides substantial suspending power. In a particular
embodiment, the charge is about 10%, about 15%, about 20%, about
25%, about 30%, about 35% or about 40%.
[0041] In exemplary embodiments, the molar ratio of the one or more
crosslinkers to monomers of the acrylamide polymer or copolymer is
greater than about 0.2, about 0.3, about 0.4, about 0.5, about 0.6,
about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2,
about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8,
about 1.9, about 2.0. In exemplary embodiments, the molar ratio of
dialdehyde to monomers of the acrylamide polymer or copolymer is in
the range of about greater than about 0.2 to about 2.0, about 0.5
to about 2.0, about 0.7 to about 2.0, about 0.8 to about 2.0, about
1.0 to about 2.0, about 1.1 to about 2.0, or about 1.0 to about
1.5. In a particular embodiment, the molar ratio of the one or more
crosslinkers to monomers of the acrylamide polymer or copolymer is
greater than about 1.0.
[0042] In exemplary embodiments, the gel composition is formed by
combining the monomers of the acrylamide polymer or copolymer and
the one or more crosslinkers in an aqueous solution at a pH greater
than about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about
7.5, about 8.0, about 8.5, about 9.0, about 10.0, about 10.2, about
10.5, about 10.7, about 11, or about 11.5. In exemplary
embodiments, the pH is in the range of about 5 to about 12, about
7.5 to about 11, about 8.5 to about 11, about 9.0 to about 11,
about 10 to about 11, or about 10.2 to about 10.7. In a particular
embodiment, the pH is greater than about 9.0. The pH modifying
agents which may be used to modify the pH of the gel or the
composition in which the gel is formed are any pH modifying agents
suitable, for example basic compounds, which are inert relatively
to the polymer and the one or more crosslinkers, for example
inorganic compounds, such as alkaline and alkaline-earth hydroxides
or salts, including but not limited to alkaline carbonate or
phosphate.
[0043] In exemplary embodiments, the formation of the gel
composition or the crosslinking of the acrylamide polymer or
copolymer and the one or more crosslinkers occurs in less than
about 1 hour, about 40 minutes, about 30 minutes, about 20 minutes,
about 10 minutes, about 5 minutes, about 2 minutes, or about 1
minute.
[0044] In exemplary embodiments, the compositions or gel
compositions according to the embodiments have a complex viscosity
of greater than or equal to about 100 cP at about 100
sec.sup.-1.
[0045] In exemplary embodiments, a method to produce a gel
composition comprises combining or contacting an acrylamide polymer
or copolymer component with a crosslinker component in an aqueous
medium at a pH in the range of about 5 to about 12, or about 7.5 to
about 11, wherein the molar ratio of the one or more crosslinkers
in the crosslinker component to monomers of the acrylamide polymer
or copolymer in the acrylamide polymer or copolymer component is in
the range of about greater than about 0.1 to about 2.0, or about
0.2 to about 2.0, at a temperature and for a period of time
sufficient to produce the gel composition.
[0046] In exemplary embodiments, acrylamide polymer or copolymer
component comprises, or is in the form of, a fine aqueous
dispersion or emulsion of the acrylamide polymer or copolymer. In
exemplary embodiments, acrylamide polymer or copolymer component
comprises, or is in the form of, monomers of the acrylamide polymer
or copolymer in a solution, dispersion or emulsion. In exemplary
embodiments, the acrylamide polymer or copolymer component
comprises about 0.4 wt % of the acrylamide polymer or copolymer in
the solution, dispersion or emulsion.
[0047] In exemplary embodiments, the crosslinker component
comprises, or is in the form of, one or more crosslinkers in an
aqueous solution. In exemplary embodiments, the crosslinker
component comprises about 0.06 to about 0.7 wt. % of the one or
more crosslinkers in an aqueous solution. In exemplary embodiments,
the acrylamide polymer or copolymer component and the crosslinker
component are each independently adjusted to a pH in the range of
about 5 to about 12, or about 7.5 to about 11, prior the step of
combining or contacting the components.
[0048] In exemplary embodiments, the aqueous medium comprises, or
is in the form of, an aqueous solution, an aqueous emulsion, an
aqueous dispersion or an aqueous slurry.
[0049] In exemplary embodiments, a method to produce a gel
composition comprises combining or contacting monomers of an
acrylamide polymer or copolymer, or a fine aqueous dispersion or
emulsion of the acrylamide polymer or copolymer, with one or more
crosslinkers in an aqueous solution at a pH in the range of about 5
to about 12, about 7.5 to about 11, wherein the molar ratio of one
or more crosslinkers to monomers of the acrylamide polymer or
copolymer is in the range of about greater than about 0.1 to about
2.0, or 0.2 to about 2.0, at a temperature and for a period of time
sufficient to produce the gel composition.
[0050] In exemplary embodiments, the acrylamide polymer or
copolymer component is prepared by shearing, agitating or stirring
the acrylamide polymer or copolymer in an aqueous medium until a
fine dispersion or emulsion is obtained. In exemplary embodiments,
the pH of the fine aqueous dispersion or emulsion of the acrylamide
polymer or copolymer is adjusted as desired, for example, adjusted
to a pH in the range of about 5 to about 12, about 7.5 to about
11.
[0051] In exemplary embodiments, the step of combining or
contacting the acrylamide polymer or copolymer component with
crosslinker component in an aqueous solution, includes shearing,
agitating or stirring the components to form a thoroughly blended
mixture or a gel composition.
[0052] In exemplary embodiments, the final pH of the mixture or gel
composition is recorded and tested for viscosity in a viscometer
(e.g. a Grace Instrument M5600 HPHT Viscometer, or a Grace M3600
Viscometer).
[0053] In exemplary embodiments, the gel composition is produced at
a temperature of greater than or equal to about 20.degree. C.,
about 30.degree. C., about 40.degree. C., about 50.degree. C.,
about 60.degree. C., about 70.degree. C., about 80.degree. C., or
about 90.degree. C. In exemplary embodiments, the gel composition
is produced in a period of time of about 1 minute to about 24
hours, about 5 minutes to about 2 hours, or about 10 minutes to
about 1 hour.
[0054] In exemplary embodiments, emulsion polymerization may be
used to prepare the polymers described herein.
[0055] Breakers
[0056] As used herein, the term "breaker" refers to any compound or
mixture of compounds which reduces the viscosity of the well
treatment fluid. In exemplary embodiments, the breaker is an
iron-containing compound, for example a ferrous compound, ferrous
salt, ferric compound or ferric salt. In exemplary embodiments, the
ferrous salt is, for example, a ferrous salt having an organic
anion, a ferrous salt having an inorganic anions, or a mixture
thereof. In exemplary embodiments, the breaker or ferrous salt is
ferrous chloride, ferrous bromide, ferrous fluoride, ferrous
sulfate, ammonium iron sulfate and combinations thereof. In
exemplary embodiments, the ferrous salt breaker comprises ferrous
sulfate.
[0057] In exemplary embodiments, the ferric salt is, for example, a
ferric salt having an organic anion, a ferric salt having an
inorganic anion, or a mixture thereof. In exemplary embodiments,
the ferric salt is, for example, a ferric salt having an organic
anion, a ferric salt having an inorganic anion, or a mixture
thereof. In exemplary embodiments, the breaker or ferric salt is
ferric citrate, ferric chloride, ferric bromide, ferric fluoride,
ferric sulfate, and combinations thereof. In exemplary embodiments,
the ferric salt breaker comprises ferric citrate.
[0058] In exemplary embodiments, the breaker may be used or
combined with other breakers, for example ammonium sulfate,
ammonium persulfate, enzymes, copper compounds, ethylene glycol,
glycol ethers and combinations thereof. In exemplary embodiments,
the breaker comprises ferrous citrate in combination with ammonium
persulfate. In exemplary embodiments, the breaker comprises ferrous
sulfate in combination with ammonium persulfate.
[0059] In exemplary embodiments, the breaker may be used to
facilitate decomposition of an exemplary gel composition or
acrylamide polymer or copolymer as described herein. In exemplary
embodiments, the breaker may be used to reduce the viscosity of an
exemplary gel composition. In exemplary embodiments, the breaker
may be used to facilitate decomposition of a gel composition or
acrylamide polymer or copolymer into oligomeric fragments.
[0060] In exemplary embodiments, a breaker composition may consist
essentially of one or more iron-containing compounds or, may
further comprise the one or more iron-containing compounds,
solvents, diluents, other breakers, and/or other suitable
additives.
[0061] In exemplary embodiments, the breaker composition may
comprise, or be used in combination with, one or more compounds or
agents which may enhance or boost the performance of the breaker
composition, e.g. booster compounds. Exemplary booster compounds
may be used to enhance the rate of breaking compared to the rate of
the breaker compound or composition in the absence of booster
compounds. For example, booster compounds include, but are not
limited to, urea; ethylenediaminetetraacetic acid (EDTA); salts of
EDTA, e.g. sodium salts of EDTA; or other chelating agents such as
citric acid, aminotricarboxylic acid and its salts,
polyphosphonated and poly phosphate compounds, boric acid and its
salts, alkali metal salts of carbonates,
diethylenetriaminepentaacetic acid (DTPA), humic acids, and
lignosulfates. Polyphosphonates include, for example,
ethylenediaminetetra(methylenephosphonic acid);
1-hydroxyethylidene-1, 1-diphosphonic acid and aminotri(methylene
phosphonic acid) and their salts. Examples of polyphosphates
include adducts made from the reaction of polyhedric solvents such
as glycerin and ethylene glycol with P.sub.2O.sub.5 to form
polyphosphated mixtures. In a particular embodiment, the booster
compound is urea, EDTA or a salt of EDTA. In another particular
embodiment, the booster compound is a sodium salt of EDTA.
[0062] Well Treatment Fluids
[0063] In exemplary embodiments, a well treatment fluid comprises:
a first composition comprising monomers of an acrylamide polymer or
copolymer; a second composition comprising one or more
crosslinkers; and a breaker composition comprising one or more
iron-containing compounds. In exemplary embodiments, a well
treatment fluid comprises: a first composition comprising an
aqueous dispersion or emulsion of an acrylamide polymer or
copolymer; a second composition comprising one or more
crosslinkers; and a breaker composition comprising one or more
iron-containing compounds. In exemplary embodiments, a well
treatment fluid comprises a gel composition according to the
embodiments and a breaker composition comprising one or more
iron-containing compounds. In exemplary embodiments, the well
treatment fluid further comprises water, wherein water is selected
from fresh water, brine, aqueous-based foams, water-alcohol
mixtures, and combinations thereof.
[0064] In exemplary embodiments, the well treatment fluid may
further comprise, or maybe added to a wellbore in combination with,
a pH modifying agent. In exemplary embodiments, the pH modifying
agent is any suitable pH modifying agent and may be in the form of
an aqueous solution, for example an aqueous solution comprising a
base, an acid, a pH buffer, or any combination thereof. In
exemplary embodiments, the pH modifying agent is a potassium
carbonate and potassium hydroxide mixture or a sodium bicarbonate
and sodium carbonate mixture. In exemplary embodiments, the pH
modifying agent is in an amount sufficient (or calculated to be
sufficient) to produce a downhole solution pH in the range of about
5 to about 12, about 7.5 to about 11. In exemplary embodiments, the
pH modifying agent is in an amount sufficient (or calculated to be
sufficient) to produce an in-situ gel composition comprising an
acrylamide polymer or copolymer.
[0065] In exemplary embodiments, the well treatment fluid further
comprises, or may be used in combination with, compounds or agents
which may enhance or boost the performance of the breaker
composition, i.e. booster compounds.
[0066] In exemplary embodiments, the well treatment fluid may
further comprise other viscosifiers, other friction reducers,
borate salts, proppants, acids, sodium chloride, emulsifiers,
sodium and potassium carbonates, biocides, anti-scaling compounds,
corrosion preventing compounds, or other suitable additives.
[0067] In exemplary embodiments, the wellbore treatment fluid
optionally comprises a proppant, for example natural or synthetic
proppants, including but not limited to glass beads, ceramic beads,
sand, gravel, and bauxite. Exemplary proppants may be coated or
contain chemicals; more than one can be used sequentially or in
mixtures of different sizes or different materials. The proppant
may be resin coated (curable), or pre-cured resin coated. The
proppant may be any suitable shape, including substantially
spherical materials, fibrous materials, polygonal materials (such
as cubic materials), and combinations thereof. In one embodiment,
the proppant is a reduced density proppant.
[0068] In exemplary embodiments, the monomers of the acrylamide
polymer or copolymer are in an amount of about 0.005% to about 5%,
0.01% to about 1%, or 0.05% to about 0.5% of the well treatment
fluid volume. In exemplary embodiments, the one or more
crosslinkers are in an amount of about 0.01% to about 1% of the
well treatment fluid volume. In exemplary embodiments, the one or
more iron-containing compounds are in an amount of 0.005% to about
0.05%, or about 0.075% to about 0.02% of the well treatment fluid
volume.
[0069] In exemplary embodiments, friction reducers, viscosifiers,
other breakers, proppants, and/or other additives used in the oil
industry and known in the art may be added to a well treatment
fluid. In exemplary embodiments, the well treatment fluid may
further comprise acids, hydrochloric acid, acetic acid, sodium
chloride, ethylene glycol, scale reducers, sodium carbonate,
potassium carbonate, biocides, borate salts, corrosion inhibitors,
citric acid, non-emulsifiers, emulsifiers, mineral control agents,
delay additives, silt suspenders, flowback additives, isopropanol,
methanol, and combinations thereof.
[0070] In exemplary embodiments, the well treatment fluid comprises
one or more viscosifiers. In exemplary embodiments, the well
treatment fluid comprises one or more viscosifiers that is a
hydratable polymer, for example galactomannan gums, guars,
derivatized guars, cellulose and cellulose derivatives, starch,
starch derivatives, xanthan, derivatized xanthan and mixtures
thereof. In exemplary embodiments, the viscosifier comprises a
hydratable polymer selected form the group consisting of guar gum,
guar gum derivative, locust bean gum, welan gum, karaya gum,
xanthan gum, scleroglucan, diutan, cellulose, cellulose derivatives
and combinations thereof. In exemplary embodiments, the viscosifier
comprises a hydratable polymer selected form the group consisting
of hydroxypropyl guar (HPG), carboxymethyl hydroxypropyl guar
(CMHPG), hydroxyethyl cellulose (HEC), carboxymethyl hydroxyethyl
cellulose (CMHEC), carboxymethyl cellulose (CMC), dialkyl
carboxymethyl cellulose, and combinations thereof. In exemplary
embodiments, the viscosifier is selected form the group consisting
of phosphomannans, scleroglucans, dextrans and combinations
thereof. In exemplary embodiments, the well treatment fluid does
not comprise one or more of the group consisting of: galactomannan
gums, guars, derivatized guars, cellulose and cellulose
derivatives, starch, starch derivatives, xanthan, and derivatized
xanthan.
[0071] In exemplary embodiments, the viscosifier can be in the form
of dry powder, carried (suspended) in liquid or dissolved in a
liquid.
[0072] As used herein, the terms "well treatment fluid",
"pressurized fluid" or "fracturing fluid" refer to a fluid
composition that useful in oil field applications including, for
example, low-volume hydraulic fracturing, high-volume hydraulic
fracturing, slick water fracturing and well stimulation; for oil,
gas or geothermal energy wells, as well as cleanup related thereto.
In exemplary embodiments, the well treatment fluid can be an
aqueous fluid, gel, foam or slickwater-based. In exemplary
embodiments, the well treatment fluid is of sufficient viscosity to
facilitate fracturing of a formation.
[0073] In exemplary embodiments, the well treatment fluid is used
in a hydraulic fracturing application before, with or after other
well treatment fluids. In exemplary embodiments, the wellbore
treatment fluid can be used in any well treatment where
viscosification is desired including but not limited to stimulation
and completion operations. For example, the wellbore treatment
fluid can be used for hydraulic fracturing applications. In these
applications, the fracturing fluid, i.e. well treatment fluid, can
be configured as a gelled fluid, a foamed gel fluid, acidic fluids,
water and potassium chloride treatments, and the like. The fluid is
injected at a pressure effective to create one or more fractures in
the subterranean formation. Depending on the type of well treatment
fluid utilized, various additives may also be added to the
fracturing fluid to change the physical properties of the fluid or
to serve a certain beneficial function. In one embodiment, a
propping agent such as sand or other hard material is added which
serves to keep the fractures open after the fracturing operation.
Also, fluid loss agents may be added to partially seal off the more
porous sections of the formation so that the fracturing occurs in
the less porous strata. Other oilfield additives that may also be
added to the fracturing fluid include antifoams, scale inhibitors,
H.sub.2S and or O.sub.2 scavengers, biocides, crosslinking agents,
surface tension reducers, breakers, buffers, surfactants and
non-emulsifiers, fluorocarbon surfactants, clay stabilizers, fluid
loss additives, foamers, friction reducers, temperature
stabilizers, diverting agents, shale and clay stabilizers,
paraffin/asphaltene inhibitors, corrosion inhibitors.
[0074] In exemplary embodiments, the wellbore treatment fluid may
optionally further comprise additional additives, including, but
not limited to, acids, fluid loss control additives, gas, corrosion
inhibitors, scale inhibitors, catalysts, clay control agents,
biocides, friction reducers, combinations thereof and the like. For
example, in some embodiments, it may be desired to foam the
storable composition using a gas, such as air, nitrogen, or carbon
dioxide.
[0075] In exemplary embodiments, the well treatment fluid may be
added to the wellbore in a proppant-free stage or a proppant-laden
stage. In exemplary embodiments, they may be added to the wellbore
may be added in a friction reducer-free stage or a friction
reducer-laden stage.
[0076] Methods
[0077] In exemplary embodiments, a method of treating a wellbore
comprises injecting into the wellbore: a first composition
comprising monomers of an acrylamide polymer or copolymer; a second
composition comprising one or more crosslinkers; and a breaker
composition comprising one or more iron-containing compounds. In
exemplary embodiments, a method of treating a wellbore comprises
injecting into the wellbore: a first composition comprising an
aqueous dispersion or emulsion of an acrylamide polymer or
copolymer; a second composition comprising one or more
crosslinkers; and a breaker composition comprising one or more
iron-containing compounds. In exemplary embodiments, the breaker
composition is injected into the wellbore substantially at the same
time as the first composition. In exemplary embodiments, the first
composition and the breaker composition are blended and injected
into the wellbore. In exemplary embodiments, the breaker
composition is injected into the wellbore substantially at the same
time as the first and second compositions. In exemplary
embodiments, the breaker composition is injected into the wellborc
after the first and second compositions, for example after a delay.
In exemplary embodiments, the breaker composition is injected into
the wellbore after the first and second compositions, for example
immediately after injection of the first and second compositions or
without delay. In exemplary embodiments, the breaker composition is
injected into the wellbore before the first and second
compositions. In exemplary embodiments, the breaker composition is
injected into the wellbore first, the first composition is injected
into the wellbore after the breaker composition, and the second
composition is injected into the wellbore after the first
composition. In exemplary embodiments, the injection of a
composition as described herein immediately follows the injection
of another composition, e.g. without delay. In exemplary
embodiments, the injection of a composition as described herein
follows the injection of another composition within about 5
minutes, about 4, minutes, about 3 minutes, about 2 minutes or
about 1 minute.
[0078] In exemplary embodiments, a method of treating a wellbore
comprises injecting into the wellbore a gel composition according
to the embodiments and a breaker composition comprising one or more
iron-containing compounds. In exemplary embodiments, the gel
composition is pre-formed and subsequently injected into the
wellbore. In exemplary embodiments, the breaker composition is
injected into the wellbore substantially at the same time as the
gel composition. In exemplary embodiments, the breaker composition
is injected into the wellbore after the gel composition, for
example after a delay. In exemplary embodiments, the breaker
composition is injected into the wellbore before the gel
composition.
[0079] In exemplary embodiments, a method of treating a wellbore
comprises injecting into the wellbore a wellbore treatment fluid
according to the embodiments.
[0080] In exemplary embodiments, a method of treating a wellbore
comprises: injecting into the wellbore a composition comprising
monomers of an acrylamide polymer or copolymer; injecting into the
wellbore a composition comprising one or more crosslinkers; and
injecting into the wellbore a pH modifying agent in an amount
sufficient (or calculated to be sufficient) to produce a downhole
solution pH in the range of about 5 to about 12, about 7.5 to about
11, to produce an in-situ gel composition comprising an acrylamide
polymer or copolymer crosslinked with one or more crosslinkers; and
injecting into the wellbore a breaker composition comprising one or
more iron-containing compounds.
[0081] In exemplary embodiments, a method of treating a wellbore
comprises: injecting into the wellbore a composition comprising an
aqueous dispersion or emulsion of an acrylamide polymer or
copolymer into a wellbore; injecting into the wellbore a
composition comprising one or more crosslinkers; and injecting into
the wellbore a pH modifying agent in an amount sufficient (or
calculated to be sufficient) to produce a downhole solution pH in
the range of about 5 to about 12, about 7.5 to about 11, to produce
an in-situ gel composition comprising an acrylamide polymer or
copolymer crosslinked with one or more crosslinkers; and injecting
into the wellbore a breaker composition comprising one or more
iron-containing compounds.
[0082] In exemplary embodiments, the composition comprising
monomers of an acrylamide polymer or copolymer, the composition
comprising one or more crosslinkers, the breaker composition
comprising one or more iron-containing compounds, and the pH
modifying agents or agents are injected into the wellbore
separately, simultaneously, or any combination thereof. In
exemplary embodiments, the composition comprising an aqueous
dispersion or emulsion of an acrylamide polymer or copolymer, the
composition comprising one or more crosslinkers, the breaker
composition comprising one or more iron-containing compounds, and
the pH modifying agents or agents are injected into the wellbore
separately, simultaneously, or any combination thereof.
[0083] In exemplary embodiments, the gel, the breaker composition
comprising one or more iron-containing compounds, and the pH
modifying agents or agents are injected into the wellbore
separately, simultaneously, or any combination thereof.
[0084] In exemplary embodiments, the composition comprising
monomers of an acrylamide polymer or copolymer comprises pH
modifying agents. In exemplary embodiments, the composition
comprising an aqueous dispersion or emulsion of an acrylamide
polymer or copolymer comprises pH modifying agents. In exemplary
embodiments, the composition comprising the one or more
crosslinkers, or crosslinker component, comprises pH modifying
agents. In exemplary embodiments, the gel composition comprises pH
modifying agents. In exemplary embodiments, the composition
comprising monomers of an acrylamide polymer or copolymer and the
composition comprising one or more crosslinkers may be combined and
then injected into the well bore either prior to or after the
injection of the pH modifying agents. In exemplary embodiments, the
composition comprising an aqueous dispersion or emulsion of an
acrylamide polymer or copolymer and the composition comprising one
or more crosslinkers may be combined and then injected into the
well bore either prior to or after the injection of the pH
modifying agents.
[0085] In exemplary embodiments, the pH modifying agents include
one or more types of pH modifying agents and may be in the form of
an aqueous solution, for example an aqueous solution comprising a
base, an acid, a pH buffer, or any combination thereof. In
exemplary embodiments, the pH modifying agent is a potassium
carbonate and potassium hydroxide mixture or a sodium bicarbonate
and sodium carbonate mixture.
[0086] In exemplary embodiments, a composition comprising monomers,
or an aqueous dispersion or emulsion, of an acrylamide polymer or
copolymer may contain from about 0.05 to about 5%, or from about
0.2 to about 5% by weight monomers or polymer, based on the total
weight of the composition. In exemplary embodiments, a composition
comprising one or more crosslinkers may contain a sufficient amount
of the one or more crosslinkers to provide a crosslinker to monomer
ratio of from about 0.1 to about 2.0, or about 0.2 to about 2.0.
Accordingly, the amounts sufficient may be determined based on
calculations which include assumptions about the downhole
conditions. The presence of a gel down hole may be determined by
indicators other than rheological measurements.
[0087] In exemplary embodiments, the methods, compositions and
wellbore treatment fluids described herein may be used for carrying
out a variety of subterranean treatments, including, but not
limited to, drilling operations, fracturing treatments, and
completion operations (e.g., gravel packing). In exemplary
embodiments, the methods, compositions and wellbore treatment
fluids may be used in treating a portion of a subterranean
formation. In exemplary embodiments, the methods, compositions and
wellbore treatment fluids may be introduced into a well bore that
penetrates the subterranean formation. In exemplary embodiments,
the methods, compositions and wellbore treatment fluids may be used
in fracturing treatments.
[0088] The methods, compositions and wellbore treatment fluids of
the present embodiments may be used in any subterranean treatment
as desired. Such subterranean treatments include, but are not
limited to, drilling operations, stimulation treatments, and
completion operations. Those of ordinary skill in the art, with the
benefit of this disclosure, will be able to recognize a suitable
subterranean treatment where friction reduction may be desired.
[0089] In exemplary embodiments, the wellbore treatment fluid,
compositions and methods can be used in or injected into fresh
water, salt water or brines.
[0090] In exemplary embodiments, wellbore treatment fluid, gel
compositions and methods can be used within a temperature range of
about 20.degree. C. to about 205.degree. C., about 50.degree. C. to
about 200.degree. C., or about 70.degree. C. to about 200.degree.
C.
[0091] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a wellbore treatment
fluid according to the present embodiments, and placing the
wellbore treatment fluid into a subterranean formation so as to
create or enhance a fracture in the subterranean formation.
[0092] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a first composition
comprising monomers of an acrylamide polymer or copolymer; a second
composition comprising one or more crosslinkers, and a breaker
composition comprising one or more iron-containing compounds; and
placing the compositions into a subterranean formation so as to
create or enhance a fracture in the subterranean formation.
[0093] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a first composition
comprising an aqueous dispersion or emulsion of an acrylamide
polymer or copolymer; a second composition comprising one or more
crosslinkers, and a breaker composition comprising one or more
iron-containing compounds; and placing the compositions into a
subterranean formation so as to create or enhance a fracture in the
subterranean formation.
[0094] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a gel composition as
described herein and a breaker composition comprising one or more
iron-containing compounds; and placing the compositions into a
subterranean formation so as to create or enhance a fracture in the
subterranean formation.
[0095] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a wellbore treatment
fluid according to the present embodiments, pumping the wellbore
treatment fluid or gel composition so as to form or extend a
fracture in the subterranean formation and deposit the wellbore
treatment fluid or gel composition in the fracture.
[0096] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a first composition
comprising monomers of an acrylamide polymer or copolymer; a second
composition comprising one or more crosslinkers, and a breaker
composition comprising one or more iron-containing compounds;
pumping the compositions so as to form or extend a fracture in the
subterranean formation and deposit the compositions in the
fracture.
[0097] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a first composition
comprising an aqueous dispersion or emulsion of an acrylamide
polymer or copolymer; a second composition comprising one or more
crosslinkers, And a breaker composition comprising one or more
iron-containing compounds; pumping the compositions so as to form
or extend a fracture in the subterranean formation and deposit the
compositions in the fracture.
[0098] In exemplary embodiments, a method of fracturing a
subterranean formation comprises: providing a gel composition as
described herein and a breaker composition comprising one or more
iron-containing compounds; pumping the compositions so as to form
or extend a fracture in the subterranean formation and deposit the
compositions in the fracture.
[0099] In exemplary embodiments, the method further comprises
allowing the well treatment fluid, gel composition, or the gel
formed from the compositions, in the fracture to break. In
exemplary embodiments, the method further comprises the addition of
one or more other breaking agents or breakers, for example
persulfates of ammonium, sodium and potassium, sodium perborate,
hydrogen peroxide, organic peroxides, percarbonates, perphosphates,
organic acids, perphosphate esters, amides, ammonium sulfate,
enzymes, copper compounds, ethylene glycol, glycol ethers, and
combinations thereof. In exemplary embodiments, the one or more
breakers can be applied to the fluids or compositions in the form
of solid, liquid, solution, dry powder, or suspension.
[0100] In exemplary embodiments, the one or more breakers can be
applied to the compositions or fluids in an encapsulated form, for
example is a form which delays the release of the one or more
breakers to the composition or gel composition. In exemplary
embodiments, the one or more breakers may be used to facilitate
decomposition of an exemplary composition or fluid described
herein, for example to facilitate decomposition of the crosslinked
acrylamide polymer or copolymer into fragments.
[0101] In exemplary embodiments, the one or more breakers reduces
the viscosity of the exemplary well treatment fluid or compositions
over a period of time. In exemplary embodiments, the one or more
breakers reduces the molecular weight, or generates fragments, of
the crosslinked acrylamide polymer or copolymer. In exemplary
embodiments, the addition of the one or more breakers results in
decreasing the viscosity of the exemplary well treatment fluid or
compositions.
[0102] In exemplary embodiments, the method of fracturing a
subterranean formation comprises placing the breaker composition
into the subterranean formation simultaneously or sequentially with
the wellbore treatment fluid or other compositions. In exemplary
embodiments, the breaker composition is placed into the
subterranean formation simultaneously with the wellbore treatment
fluid or other compositions. In exemplary embodiments, the breaker
composition is placed into the subterranean formation before with
the wellbore treatment fluid or other compositions. In exemplary
embodiments, the breaker composition is placed into the
subterranean formation simultaneously after the wellbore treatment
fluid or other compositions.
[0103] In exemplary embodiments, the method of fracturing a
subterranean formation comprises pumping the breaker composition
into the subterranean formation simultaneously or sequentially with
the wellbore treatment fluid or other compositions. In exemplary
embodiments, the breaker composition is pumped into the
subterranean formation simultaneously with the wellbore treatment
fluid or other compositions. In exemplary embodiments, the breaker
composition is pumped into the subterranean formation before with
the wellbore treatment fluid or other compositions. In exemplary
embodiments, the breaker composition is pumped into the
subterranean formation simultaneously after the wellbore treatment
fluid or other compositions.
[0104] In exemplary embodiments, the methods comprise injecting the
well treatment fluids or compositions into the well bore at a
pressure and flow rate sufficient to fracture the subterranean
formation. In exemplary embodiments, the well treatment fluid
further comprises a proppant. In exemplary embodiments, the gel
composition further comprises a proppant. In exemplary embodiments,
the breaker composition further comprises a proppant. In exemplary
embodiments, the first composition comprising monomers of an
acrylamide polymer or copolymer or an aqueous dispersion or
emulsion of an acrylamide polymer or copolymer further comprises a
proppant. In exemplary embodiments, the second composition
comprising one or more crosslinkers further comprises a
proppant.
[0105] In exemplary embodiments, the breaker composition reduces
the viscosity of the well treatment fluid or other compositions to
less than about 10 cP at a shear late of 100 about 5 cP at a shear
rate of 100 s.sup.-1, about 2 cP at a shear rate of 100 s.sup.-1,
about 20 cP at a shear rate of 100 about 10 cP at a shear rate of
100 s.sup.-1, or about 3 cP at a shear rate of 100 s.sup.-1.
[0106] In exemplary embodiments, the breaker composition initiates
breaking at ambient temperatures. In exemplary embodiments, the
breaker composition initiates breaking under heating.
[0107] In exemplary embodiments, the methods may be used to enhance
the biodegradation of the well treatment fluid or other
compositions according to the embodiments.
[0108] In exemplary embodiments, the breaker composition generates
oligomeric fragments of an acrylamide-containing polymer in the
well treatment fluid or other compositions. In exemplary
embodiments, the oligomeric fragments of the acrylamide-containing
polymer generated by the breaker composition are biodegradable. In
exemplary embodiments, the breaker composition generates oligomeric
fragments of the acrylamide-containing polymer having a molecular
weight of less than about 400,000, about 300,000, or about 200,000
g/mol.
[0109] In exemplary embodiments, the decrease in the viscosity of
the well treatment fluid or other compositions allows for easier
recovery of the well treatment fluid or other compositions. In
exemplary embodiments, the viscosity of the well treatment fluid or
other compositions with the breaker composition is less than the
viscosity of well treatment fluid or other compositions without the
breaker composition. In exemplary embodiments, the exemplary
breaker composition reduces the viscosity of the well treatment
fluid or other compositions faster than conventional breakers. In
exemplary embodiments, the exemplary breaker composition reduces
the viscosity of the well treatment fluid or other compositions
faster than ammonium persulfate. In exemplary embodiments, the
breaker composition acting on the well treatment fluid or other
compositions increases the fracture conductivity within the
formation.
[0110] In any of the foregoing methods, the breaker composition may
comprise, or be used in combination with, compounds or agents which
may enhance or boost the performance of the breaker composition,
i.e. booster compounds.
[0111] Suitable adjustments to the ratios of the components that
will affect the conditions in which the viscosity of the well
treatment fluid or other compositions is reduced, or in which the
acrylamide-containing polymer breaks down, will be apparent to
those of skill in the art.
[0112] In the exemplary embodiments, the well treatment fluid or
other compositions may be handled or processed in any manner as
necessary or desired. In exemplary embodiments, the well treatment
fluid or other compositions should be handled in compliance with
governmental regulations. In exemplary embodiments, the well
treatment fluid or other compositions may be disposed of, processed
for environmental remediation, or recycled. In the exemplary
embodiments, the breaker composition may be used in the disposal,
environmental remediation or recycling of the well treatment fluid
or other compositions. In the exemplary embodiments, recycled well
treatment fluid or other compositions may be used at any point
where the well treatment fluid or other compositions is used.
[0113] The term "treatment", or "treating", refers to any
subterranean operation that uses a fluid in conjunction with a
desired function and/or for a desired purpose. The term
"treatment", or "treating", does not imply any particular action by
the fluid.
[0114] The term "fracturing" refers to the process and methods of
breaking down a geological formation and creating a fracture, i.e.
the rock formation around a well bore, by pumping fluid at very
high pressures (pressure above the determined closure pressure of
the formation), in order to increase production rates from or
injection rates into a hydrocarbon reservoir. The fracturing
methods otherwise use conventional techniques known in the art.
[0115] The following examples are presented for illustrative
purposes only, and are not intended to be limiting.
EXAMPLES
Example 1. Preparation and Viscosity Analysis of Exemplary
Glyoxal-Crosslinked-Polymer Gels
[0116] Exemplary gels were prepared by the following protocol.
About 0.4 wt % of active acrylamide polymer in water was stirred
for about 10 minutes to about 20 minutes at room temperature. Once
the solution was thoroughly blended, the pH of the solution was
measured and adjusted using a pH buffer solution to about 9.8 to
about 10.3. The solution was divided, and three levels of glyoxal
were added to the solutions: 0.33, 0.49 or 0.65 wt. % of glyoxal.
The mixture was stirred until the glyoxal was well incorporated.
The viscosity of each of the resulting gels was measured on a Grace
Instrument M5600 HPHT Viscometer at 180.degree. F.
[0117] The Grace Instrument M5600 HPHT Viscometer is a true
Couette, coaxial cylinder, rotational, high pressure and
temperature viscometer. The instrument is fully automated and all
data acquisition was under computer control. The temperature of the
sample was maintained with an oil bath. The gel was also subjected
to pressure with nitrogen gas to prevent boiling off the solvent.
After 20 minutes of shear conditioning, the gel was subjected to a
shear sweep which could be programmed in the software that
accompanies the Viscometer. The data acquired from the computer was
processed and plotted as desired.
[0118] FIG. 1 shows the viscosity analyses of three exemplary gels
and, for comparison, a guar gel.
Example 2. Charge-Viscosity Analysis of Exemplary Dry and Emulsion
Glyoxal-Crosslinked-Polymer Gels
[0119] In the example, compositions were prepared by adding 200 mL
of 2% KCl to a Waring blender jar. Approximately 0.3% of active
acrylamide/acrylic acid copolymer was added along with the pH
buffer and mixed for a few minutes. Approximately 0.33% glyoxal was
added (to provide a molar ratio of glyoxal to monomer of about
1.35) and blended for a few seconds. The obtained crosslinked gel
was evaluated on an Anton Paar Physica Rheometer setup with
concentric cylinder geometry. The gel was sheared at a constant
shear rate of 100 s.sup.-1 and at a temperature of 180.degree. F.
The viscosity reported in the table is an average reading measured
over 30 minutes.
[0120] Analysis of Charge-Viscosity was evaluated for a range of
dry PAM (DPAM), partially hydrolyzed PAM (HYPAM) and emulsion PAM
(EPAM) polymers. Series were arranged in three groups with
increasing charges for each group.
TABLE-US-00001 TABLE 1 Viscosity of Exemplary Dry and Emulsion
Glyoxal-Crosslinked-Polymer Gels Charge Viscosity Sample# Product
Form (mole %) (cP) 1 DPAM 2 5 2 DPAM 13 463 3 DPAM 23 343 4 DPAM 33
33 5 DPAM 53 14 6 HYPAM 3 18 7 HYPAM 10 677 8 HYPAM 15 1326 9 HYPAM
20 463 10 HYPAM 30 118 11 HYPAM 40 57 12 EPAM 5 44 13 EPAM 10 412
14 EPAM 15 818 15 EPAM 20 475 16 EPAM 30 306 17 EPAM 40 32
[0121] Conditions: 0.3% active polymer, crosslinked with 0.33%
glyoxal, in 2% KCl solution.
[0122] As shown in the Table 1, there is an influence of charge on
gel viscosity and performance.
Example 3. Viscosity Analysis of Breakers on Exemplary
Glyoxal-Crosslinked-Polymer Gels
[0123] In this example, reduction in the viscosity of a fluid was
examined by treatment with exemplary and commercially available
(comparative) breaker compositions. The compositions were prepared
by adding 200 g of 2% KCl to a Waring blender jar. Approximately
0.3% of hydrolyzed polyacrylamide (HYPAM) was added to the
compositions along with the pH buffer and mixed for a few minutes.
Approximately 0.33% glyoxal was added to the samples and blended
for a few seconds to form crosslinked gel samples.
[0124] Breaker compositions were added to the samples, in the
amounts indicated. Breaker composition #1 included
FeSO.sub.4.7H.sub.2O. Breaker composition #2 included
FeSO.sub.4.7H.sub.2O and Na.sub.2(EDTA)2H.sub.2O (43:57, by
weight). The breaker compositions were prepared by dissolving the
breaker composition in water to form 10% solution. Then the breaker
compositions were mixed with the exemplary gel samples.
[0125] The pH of each sample formulation was measured and recorded,
as shown in FIG. 2. Each sample formulation was heated at
180.degree. F. for about 3 hours and the viscosity was measured
during the heating period by a Grace 3600 Viscometer (see FIGS. 2
and 3). Grace 3600 Viscometer is a true Couette, coaxial cylinder,
rotational viscometer. The instrument was controlled by a computer
program. The temperature of the sample was maintained by a heater
cup provided with the instrument. The data acquired over time was
processed and plotted as desired.
[0126] Additional buffer was added so some samples to increase the
pH. The volume of the buffer added dictated the change in pH in the
samples shown in FIG. 3. FIG. 3 shows the results obtained when
Grace 3600 Viscometer was used to measure the viscosity of the
samples at a shear rate of 100 s.sup.-1 and temperature of
180.degree. F.
[0127] In the preceding specification, various exemplary
embodiments have been described. It will, however, be evident that
various modifications and changes may be made thereto, and
additional embodiments may be implemented, without departing from
the broader scope of the exemplary embodiments as set forth in the
claims that follow. The specification and drawings are accordingly
to be regarded in an illustrative rather than restrictive
sense.
* * * * *