Note: Descriptions are shown in the official language in which they were submitted.
METHOD FOR TREATING PRODUCED WATER
FIELD OF THE ART
[001] The present disclosure generally relates to the treatment of produced
water which
comprises one or more water soluble polymers, such as from an enhanced oil
recovery process,
in order to reduce the viscosity thereof and/or degrade at least a portion of
the one or more water
soluble polymers contained therein.
BACKGROUND
[002] Enhanced oil recovery (EOR) is a technique that can be used to increase
the amount of
unrefined petroleum (e.g., crude oil) that may be extracted from an oil
reservoir (e.g., an oil
field). By way of example, using EOR, about 40-60% of the reservoir's original
oil can typically
be extracted, compared with only 20-40% using traditional primary and
secondary recovery
techniques (e.g., by water injection or natural gas injection). One type of
FOR technique is
polymer flooding, which typically involves the injection of large volumes of a
polymer solution
into a subterranean oil reservoir. The polymer solution can mobilize the oil
towards a production
well where it can be recovered. The produced water from a polymer flooding
process can include
various chemicals. These chemicals, including the polymer(s) used for the
polymer flooding,
may have a direct impact on viscosity and viscoelastic properties of the
produced water. The
properties and contents of the produced water can also influence discharge of
the produced water
into the sea, as polymers that may be used for polymer flooding, e.g.,
partially hydrolyzed
polyacrylamide (HPAM), typically may not be readily bio-degradable according
to current
regulations.
[003] Current technologies for the treatment of produced water (e.g., produced
water resulting
from FOR processes) can include mechanical treatments (e.g., membrane
filtration), chemical
treatments (e.g., oxidizing agents), and biological treatments (e.g.,
microbiological processes).
The development of other means for treating produced water which allow for the
treated water to
be stabilized or reused would be beneficial for both offshore and onshore
facilities.
BRIEF SUMMARY
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CA 3051369 2019-08-07
[004] The present embodiments generally pertain to a process for treating
produced water
comprising one or more water soluble polymers comprising treating the produced
water with an
amount of one or more reducing agents and one or more metals that is effective
to reduce the
viscosity of the produced water and/or to degrade at least a portion of the
one or more water
soluble polymers. In some embodiments, said water soluble polymers may include
high
molecular weight polymers used in industrial processes such as enhanced oil
recovery (EOR)
processes and other processes wherein produced water is produced and/or
treated. In some
embodiments, the treated produced water may be anoxic and/or the produced
water may be
treated in whole or in part under anoxic conditions. In some embodiments, said
one or more
water soluble polymers comprise oxygen. Moreover, in some embodiments, oxygen
may be
added to said produced water, and addition of said oxygen may occur before,
during, and/or after
treatment of said produced water with said one or more reducing agents and
said metal. Addition
of oxygen may occur through addition of water containing dissolved oxygen,
such as by the
addition of surface water; air bubbling; and/or pressurized air. In some
embodiments, addition of
oxygen may result in a corresponding increase in the degradation of said
polymer, optionally
wherein the amount of added oxygen correlates to the amount of degradation,
and/or a
corresponding decrease in the viscosity of the produced water.
[005] In some embodiments, said one or more metals comprise iron and/or a
compound
comprising iron, optionally in the Fe+2 form. In some embodiments, said one or
more reducing
agents comprise a compound comprising metabisulfite, bisulfite, (hydrated)
sulfur dioxide,
and/or sulfite. In some embodiments, said one or more reducing agents may
comprise hydrazine
and/or its hydroxylamine derivatives and/or a mixture of sodium borohydride
and bisulfite. In
some embodiments, said one or more reducing agents may comprise organic
sulfites such as
alkyl sulfites, alkyl hydrosulfites, sulfinates, sulfoxylates, phosphites, and
also oxalic or formic
acid or salts of erythorbate and carbohydrazides; an oxygen scavenger, such
as, but not limited
to, carbohydrazide, hydroquinone, diethylhydroxylamine (DEHA), methyl ethyl
ketoxime
(MEKO), erythorbate; iron; the salt form of any compound that may be
considered a reducing
agent, such as sodium metabisulfite; and/or sodium dithionite.
[006] Furtheimore, the present disclosure generally relates to a process of
treating produced
water that includes the addition of one or more reducing agents and one or
more metals during
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treatment of the produced water wherein at least one stabilizing agent is
added to slow, decrease,
prevent, inhibit and/or stop the degradation or further degradation of water
soluble polymers
and/or to increase or maintain the viscosity of the produced water. In some
embodiments, the at
least one stabilizing agent may be added while water soluble polymers are
present in the
produced water in order to slow, decrease, prevent, inhibit, and/or stop the
degradation or further
degradation of said at least one water soluble polymer and/or to increase or
maintain the
viscosity of the produced water. In some embodiments, the at least one
stabilizing agent may be
added contemporaneous or prior to the addition of at least one water soluble
polymer in order to
slow, decrease, prevent, inhibit, and/or stop the degradation of said added at
least one water
soluble polymer and/or to increase or maintain the viscosity of the produced
water.
[007] Additionally, the present disclosure generally relates to a process for
treating produced
water comprising one or more water soluble polymers, comprising: a. treating
the produced
water with an amount of one or more reducing agents and one or more metals
that is effective to
reduce the viscosity of the produced water and/or to degrade at least a
portion of the one or more
water soluble polymers; b. adding an amount of stabilizer effective to slow,
reduce, decrease,
inhibit, prevent, and/or stop degradation of said one or more water soluble
polymers; and
optionally c. adding new and/or fresh water soluble polymer. In some
embodiments, said
stabilizer reduces, decreases, stops, and/or prevents degradation of said new
and/or fresh water
soluble polymer. In some embodiments, said stabilizing agent comprises
thiourea,
diethylthiourea, sodium/ammonium thiocyanate, benzotriazole, MB I, and/or MBT.
[008] Moreover, the present disclosure generally pertains to a composition
suitable for use in
treating produced water, comprising the combination of (i) one or more
stabilizing agents and
either or both of the following: (ii) one or more reducing agents and one or
more metals, and (iii)
one or more water soluble polymers; wherein the one or more stabilizing agents
are capable of
preventing or inhibiting the degradation of (iii) one or more water soluble
polymer by the (ii) one
or more reducing agents and one or more metals if said (iii) one or more water
soluble present. In
some embodiments, said composition may comprise (i) one or more stabilizing
agents, (ii) one or
more reducing agents and one or more metals, and (iii) one or more water
soluble polymers.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
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[009] Figure 1 presents an image depicting the interconversion of various
reducing agents.
DETAILED DESCRIPTION
DEFINITIONS
[0010] As used herein the singular forms "a", "and", and "the" include plural
referents unless the
context clearly dictates otherwise. All technical and scientific terms used
herein have the same
meaning as commonly understood to one of ordinary skill in the art to which
this invention
belongs unless clearly indicated otherwise.
[0011] As used herein, the term "enhanced oil recovery" or "EOR" (sometimes
also known as
improved oil recovery ("IOR") or tertiary mineral oil production) generally
refers to techniques
for increasing the amount of unrefined petroleum (for example, crude oil) that
may be extracted
from an oil reservoir, such as an oil field. Examples of EOR techniques
include, for example,
miscible gas injection (e.g., carbon dioxide flooding), chemical injection
(sometimes referred to
as chemical enhanced oil recovery ("CEOR"), and which includes, for example,
polymer
flooding, alkaline flooding, surfactant flooding, micellar polymer flooding,
conformance control
operations, as well as combinations thereof such as alkaline-polymer flooding
or alkaline-
surfactant-polymer flooding), microbial injection, and thermal recovery (e.g.,
cyclic steam, steam
flooding, or fire flooding). In some embodiments, the EOR operation may
include a polymer
("P") flooding operation, an alkaline-polymer ("AP") flooding operation, a
surfactant-polymer
("SP") flooding operation, an alkaline-surfactant-polymer ("ASP") flooding
operation, a
conformance control operation, or any combination thereof.
[0012] As used herein, the terms "polymer flood" or "polymer flooding"
generally refer to a
chemical enhanced EOR technique that typically involves injecting an aqueous
fluid that is
viscosified with one or more water-soluble polymers through injection
boreholes into an oil
reservoir to mobilize oil left behind after primary and/or secondary recovery.
As a general result
of the injection of one or more polymers, the oil may be forced in the
direction of the production
borehole, and the oil may be produced through the production borehole. Details
of examples of
polymer flooding and of polymers suitable for this purpose are disclosed, for
example, in
"Petroleum, Enhanced Oil Recovery, Kirk-Othmer, Encyclopedia of Chemical
Technology,
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online edition, John Wiley & Sons, 2010, which is herein incorporated by
reference in its
entirety. One or more surfactants may be injected (or formed in situ) as part
of the EOR
technique. Surfactants may function to reduce the interfacial tension between
the oil and water,
which may reduce capillary pressure and improve mobilization of oil.
Surfactants may be
injected with polymers (e.g., a surfactant-polymer (SP) flood), or foimed in-
situ (e.g., an
alkaline-polymer (AP) flood), or a combination thereof (e.g., an alkaline-
surfactant-polymer
(ASP) flood). As used herein, the terms "polymer flood" and "polymer flooding"
encompass all
of these EOR techniques.
[0013] As used herein, the term "monomer" generally refers to nonionic
monomers, anionic
monomers, cationic monomers, zwitterionic monomers, betaine monomers, and
amphoteric ion
pair monomers.
[0014] 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 may
comprise 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.
Unless otherwise
specified, a polymer may comprise a "homopolymer" that may comprise
substantially identical
recurring units that may be formed by various methods e.g., by polymerizing a
particular
monomer. Unless otherwise specified, a polymer may also comprise a "copolymer"
that may
comprise two or more different recurring units that may be formed by, e.g.,
copolymerizing, two
or more different monomers, and/or by chemically modifying one or more
recurring units of a
precursor polymer. Unless otherwise specified, a polymer or copolymer may also
comprise a
"terpolymer" that may comprise polymers that may comprise three or more
different recurring
units. The term "polymer" as used herein is intended to include both the acid
foini of the
polymer as well as its various salts. Polymers may be amphoteric in nature,
i.e., containing both
anionic and cationic substituents, although not necessarily in the same
proportions.
[0015] As used herein the term "nonionic monomer" generally refers to a
monomer that
possesses a neutral charge. Nonionic monomers may comprise but are not limited
to comprising
monomers selected from the group consisting of acrylamide ("AMD"),
methacrylamido, vinyl,
allyl, ethyl, and the like, all of which may be substituted with a side chain
selected from, for
example, an alkyl, arylalkyl, dialkyl, ethoxyl, and/or hydrophobic group. In
some embodiments,
CA 3051369 2019-08-07
a nonionic monomer may comprise AMD. In some embodiments, nonionic monomers
may
comprise but are not limited to comprising vinyl amide (e.g., acrylamide,
methacrylamide, N-
methylacrylamide, N,N-dimethylacrylamide), acryloylmorpholine, acrylate,
maleic anhydride,
N-vinylpyrrolidone, vinyl acetate, N-vinyl formamide and their derivatives,
such as
hydroxyethyl (methyl)acrylate CH2=CR--000--CH2CH2OH (I) and CH2=CR--00--
N(Z1)(Z2)
(2) N-substituted (methyl)acrylamide (II). R=14 or Me; Z1=5-15C alkyl; 1-3C
alkyl substituted
by 1-3 phenyl, phenyl or 6-12C cycloalkyl (both optionally substituted) and
Z2=H; or Z1 and Z2
are each 3-10C alkyl; (II) is N-tert. hexyl, tert. octyl, methylundecyl,
cyclohexyl, benzyl,
diphenylmethyl or triphenyl acrylamide. Nonionic monomers further may include
dimethylaminoethylacrylate ("DMAEMA"), dimethylaminoethyl methacrylate
("DMAEM"), N-
isopropylacrylamide and N-vinyl formamide. Nonionic monomers can be combined,
for example
to form a terpolymer of acrylamide, N-vinyl formamide, and acrylic acid.
[0016] As used herein, the tem' "anionic monomers" may refer to either anionic
monomers that
are substantially anionic in whole or (in equilibrium) in part, at a pH in the
range of about 4.0 to
about 9Ø The "anionic monomers" may be neutral at low pH (from a pH of about
2 to about 6),
or to anionic monomers that are anionic at low pH.
[0017] Examples of anionic monomers which may be used herein include but are
not limited to
those comprising acrylic, methacrylic, maleic monomers and the like, calcium
diacrylate, and/or
any monomer substituted with a carboxylic acid group or salt thereof In some
embodiments,
these anionic monomers may be substituted with a carboxylic acid group, and
include, for
example, acrylic acid, and methacrylic acid. In some embodiments, an anionic
monomer which
may be used herein may be a (meth)acrylamide monomer wherein the amide group
has been
hydrolyzed to a carboxyl group. Said monomer may be a derivative or salt of a
monomer
according to the embodiments. Additional examples of anionic monomers comprise
but are not
limited to those comprising sulfonic acids or a sulfonic acid group, or both.
In some
embodiments, the anionic monomers which may be used herein may comprise a
sulfonic
function that may comprise, for example, 2-acrylamido-2-methylpropane sulfonic
acid
("AMPS"). In some embodiments, anionic monomers may comprise organic acids. In
some
embodiments, anionic monomers may comprise acrylic acid, methacrylic acid,
maleic acid,
itaconic acid, acrylamido methylpropane sulfonic acid, vinylphosphonic acid,
styrene sulfonic
acid and their salts such as sodium, ammonium and potassium. Anionic monomers
can be
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CA 3051369 2019-08-07
, ,
combined, for example, to form a terpolymer of acrylamide, acrylic acid and 2-
acrylamido-2-
methylpropane sulfonic acid.
[0018] As used herein, the term "cationic monomer" generally refers to a
monomer that
possesses a positive charge. Examples of cationic monomers may comprise but
are not limited to
those comprising acryloyloxy ethyl trimethyl ammonium chloride ("AETAC"),
methacryloyloxyethyltrimethylammonium chloride,
methacrylamidopropyltrimethylammonium
chloride ("MAPTAC"), acrylamidopropyltrimethylammonium chloride,
methacryloyloxyethyldimethylammonium sulfate, dimethylaminoethyl acrylate,
dimethylaminopropylmethacrylamide, Q6, Q6o 4, and/or diallyldimethylammonium
chloride
("DADMAC").
[0019] Said cationic monomers may also comprise but are not limited to
comprising
dialkylaminoalkyl acrylates and methacrylates and their quaternary or acid
salts, including, but
not limited to, dimethylaminoethyl acrylate methyl chloride quaternary salt
("DMAEA.MCQ"),
dimethylaminoethyl acrylate methyl sulfate quaternary salt ("DMAEM.MCQ"),
dimethyaminoethyl acrylate benzyl chloride quaternary salt ("DMAEA.BCQ"),
dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate
hydrochloric acid
salt, diethylaminoethyl acrylate, methyl chloride quaternary salt,
dimethylaminoethyl
methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate
methyl sulfate
quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary
salt,
dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl
methacrylate
hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid
salt,
dialkylaminoalkylacrylamides or methacrylamides and their quaternary or acid
salts such as
acrylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide
methyl sulfate
quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt,
dimethylaminopropyl
acrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammonium
chloride,
dimethylaminopropyl methacrylamide methyl sulfate quaternary salt,
dimethylaminopropyl
methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide
hydrochloric acid salt,
diethylaminoethyl acrylate, diethyl aminoethylmethacrylate and
diallyldialkylammonium halides
such as diallyldiethylammonium chloride and diallyldimethyl ammonium chloride.
Alkyl groups
may generally but are not limited to those comprising C18 alkyl groups. In
some embodiments,
cationic monomers may comprise quaternary ammonium or acid salts of vinyl
amide, vinyl
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carboxylic acid, methacrylate and their derivatives. Cationic monomers may
comprise but are not
limited to comprising monomers selected from the group consisting of
dimethylaminoethylacrylate methyl chloride quaternary salt,
dimethylaminoethylmethacrylate
methyl chloride quaternary salt, and diallyldimethyl ammonium chloride.
Cationic monomers
can be combined, for example, to form a terpolymer of
dimethylaminoethylmethacrylate methyl
chloride quaternary salt, and diallyldimethyl ammonium chloride and
acrylamide.
[0020] The term "water-soluble polymer" generally refers to any polymer that
may dissolve,
disperse, or swell in water. Said polymers may modify the physical properties
of aqueous
systems undergoing gellation, thickening, viscosification, or
emulsification/stabilization. Said
polymers may perform a variety of functions, including but not limited to use
as dispersing and
suspending agents, stabilizers, thickeners, viscosifiers, gellants,
flocculants and coagulants, film-
formers, humectants, binders, and lubricants.
[0021] In the context of polymer flooding, a water-soluble polymer may
include, but not be
limited to including, one or more high molecular weight polyacrylamide and/or
copolymers of
acrylamide and further monomers, for example, vinylsulfonic acid or acrylic
acid.
Polyacrylamide may be partly hydrolyzed polyacrylamide ("HPAM"), in which some
of the
acrylamide units have been hydrolyzed to acrylic acid. In some embodiments, a
water soluble
polymer may comprise a high molecular weight anionic polyacrylamide based
polymer.
Naturally occurring polymers may also be used, for example, xanthan or
polyglycosylglucan.
Naturally occurring polymers may be used in their natural form and/or in a
modified form.
[0022] In some embodiments, a water-soluble polymer may comprise one or more
acrylamide
(co)polymers. In some embodiments, one or more acrylamide (co)polymers may be
a polymer
useful for enhanced oil recovery (EOR) applications. In a particular
embodiment, a water-soluble
polymer is a high molecular weight polyacrylamide and/or partially hydrolyzed
products thereof.
[0023] According to some embodiments, one or more acrylamide (co)polymers may
be selected
from water-soluble acrylamide (co)polymers. In some embodiments, acrylamide
(co)polymers
may comprise at least 30% by weight, or at least 50% by weight acrylamide
units with respect to
the total amount of all monomeric units in the (co)polymer.
[0024] Optionally, one or more acrylamide (co)polymers may comprise acrylamide
and at least
one additional monomer. In some embodiments, an acrylamide (co)polymer may
comprise less
than about 50%, or less than about 40%, or less than about 30%, or less than
about 20% by
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weight of the at least one additional monomer. In some embodiments, the
additional monomer
may be a water-soluble, ethylenically unsaturated, in particular
monoethylenically unsaturated,
monomer. Additional water-soluble monomers may be miscible with water in any
ratio, but it is
typically sufficient that the monomers dissolve sufficiently in an aqueous
phase to copolymerize
with acrylamide. In general, the solubility of such additional monomers in
water at room
temperature may be at least 50 g/L, at least 150 g/L, and/or at least 250 g/L.
[0025] Other water soluble monomers may comprise one or more hydrophilic
groups. The
hydrophilic groups may be functional groups that may comprise atoms selected
from the group
of 0-, N-, S- or P-atoms. Nonlimiting examples of such functional groups
comprise carbonyl
groups >C=0, ether groups -0-, in particular polyethylene oxide groups -(CH2-
CH2-0-).-, where
n e.g., is a number from 1 to 200, hydroxy groups -OH, ester groups -C(0)0-,
primary,
secondary or tertiary amino groups, ammonium groups, amide groups -C(0)-NH- or
acid groups
such as carboxyl groups -COOH, sulfonic acid groups -S03H, phosphonic acid
groups -P03H2 or
phosphoric acid groups -0P(OH)3.
[0026] Some monoethylenically unsaturated monomers comprising acid groups may
comprise
monomers comprising -COOH groups, such as acrylic acid or methacrylic acid,
crotonic acid,
itaconic acid, maleic acid or fumaric acid, monomers comprising sulfonic acid
groups, such as
vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic
acid, 2-
methacrylamido-2-methylpropanesulfonic acid, 2-acrylamidobutanesulfonic acid,
3-acrylamido-
3-methylbutanesulfonic acid or 2-acrylamido-2,4,4-trimethylpentanesulfonic
acid, or monomers
comprising phosphonic acid groups, such as vinylphosphonic acid,
allylphosphonic acid, N-
(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkylphosphonic
acids. Said
monomers may be used as salts.
[0027] The -COOH groups in polyacrylamide (co)polymers may not only be
obtained by
copolymerizing acrylamide and monomers comprising -COOH groups but also by
hydrolyzing
derivatives of -COOH groups after polymerization. For example, amide groups -
CO-NH2 of
acrylamide may hydrolyze thus yielding -COOH groups.
[0028] Also to be mentioned are monomers which are derivatives of acrylamide,
such as, for
example, N-alkyl acrylamides and N-alkyl quaternary acrylamides, wherein the
alkyl group may
be C2-C28; N-methyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide, and N-
methylolacrylamide; N-vinyl derivatives such as N-vinylformamide, N-
vinylacetamide, N-
9
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vinylpyrrolidone or N-vinylcaprolactam; and vinyl esters, such as vinyl
formate or vinyl acetate.
N-vinyl derivatives may be hydrolyzed after polymerization to vinylamine
units, vinyl esters to
vinyl alcohol units.
[0029] Further monomers may comprise monomers comprising hydroxy and/or ether
groups,
such as, for example, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,
allyl alcohol,
hydroxyvinyl ethyl ether, hydroxyl vinyl propyl ether, hydroxyvinyl butyl
ether or
polyethyleneoxide(meth)acrylates.
[0030] Other monomers may be monomers comprising ammonium groups, i.e.,
monomers
having cationic groups. Examples of said monomers may comprise salts of 3-
trimethylammonium propylacrylamides or 2-trimethylammonium
ethyl(meth)acrylates, for
example the corresponding chlorides, such as 3-trimethylammonium
propylacrylamide chloride
(DIMAPAQUAT), and 2-trimethylammonium ethyl methacrylate chloride (MADAME-
QUAT).
[0031] Yet other monomers may comprise monomers which may cause hydrophobic
association
of the (co)polymers. Such monomers may comprise, in addition to an ethylenic
group and a
hydrophilic part, a hydrophobic part.
[0032] In some embodiments, one or more acrylamide (co)polymers may optionally
comprise
crosslinking monomers, i.e., monomers comprising more than one polymerizable
group. In
certain embodiments, one or more acrylamide (co)polymers may optionally
comprise
crosslinking monomers in an amount of less than about 0.5 %, or about 0.1%, by
weight, based
on the amount of all monomers.
[0033] In an embodiment, one or more acrylamide (co)polymers may comprise at
least one
monoethylenically unsaturated monomer comprising acid groups, for example
monomers that
comprise at least one group selected from -COOH, -S03H or -P03H2. Examples of
such
monomers may include, but are not limited to, acrylic acid, methacrylic acid,
vinylsulfonic acid,
allylsulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, preferably
acrylic acid and/or
2-acrylamido-2-methylpropanesulfonic acid, and more preferably acrylic acid or
salts thereof. In
some embodiments the one or more acrylamide (co)polymers, or each of the one
or more
acrylamide (co) polymers, may comprise 2-acrylamido-2-methylpropanesulfonic
acid or salts
thereof The amount of such monomers comprising acid groups may be from about
0.1% to
about 70%, about 1% to about 50%, or about 10% to about 50% by weight based on
the amount
of all monomers.
CA 3051369 2019-08-07
[0034] In an embodiment, one or more acrylamide (co)polymers may comprise from
about 50%
to about 90% by weight of acrylamide units and from about 10% to about 50% by
weight of
acrylic acid units and/or their respective salts. In an embodiment, one or
more acrylamide
(co)polymers may comprise from about 60% to 80% by weight of acrylamide units
and from
20% to 40% by weight of acrylic acid units.
[0035] In some embodiments, one or more acrylamide (co)polymers may have a
weight average
molecular weight (Mw) of greater than about 5,000,000 Dalton, or greater than
about 10,000,000
Dalton, or greater than about 15,000,000 Dalton, or greater than about
20,000,000 Dalton, or
greater than about 25,000,000 Dalton.
[0036] As used herein, the terms "polyacrylamide" or "PAM" generally refer to
polymers and
co-polymers comprising acrylamide moieties, and the terms encompass any
polymers or
copolymers comprising acrylamide moieties, e.g., one or more acrylamide
(co)polymers.
Furthermore, PAMs may comprise any of the polymers or copolymers discussed
herein.
Additionally, the PAMs described herein, e.g., one or more acrylamide
(co)polymers, may be
provided in one of various forms, including, for example, dry (powder) form
(e.g., DPAM),
water-in-oil emulsion (inverse emulsion), suspension, dispersion, or partly
hydrolyzed (e.g.,
HPAM, in which some of the acrylamide units have been hydrolyzed to acrylic
acid). In some
embodiments, PAMs, e.g., one or more acrylamide (co)polymers, may be used for
polymer
flooding. In some embodiments, PAMS, e.g., one or more acrylamide
(co)polymers, may be used
in any EOR technique.
[0037] As used herein, the term "produced water" generally refers to any
aqueous fluids
produced during any type of industrial process, e.g., an oil or gas extraction
or recovery process,
or any portion thereof, such as but not limited to any enhanced oil recovery
process or any
portion thereof wherein the produced water comprises one or more polymers,
e.g., one or more
water-soluble polymers. Typically the produced water may be obtained during an
industrial
process involving the use of water, generally copious amounts of water, and
the use of one or
more water soluble polymers, e.g., viscosifying or thickening polymers,
wherein the end product
of such industrial process may be an aqueous material or "produced water"
which may be of
undesirable viscosity and/or purity because of the presence of an undesirable
amount of said one
or more water soluble polymers.
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[0038] According to some embodiments, the produced water may be foiiiied
during any part of a
process related to polymer flooding and may comprise any components and/or
chemicals related
to any part of said polymer flooding. This may be referred to as "polymer
flooded produced
water" or "polymer flooding produced water", and the teiiii produced water is
to be understood
to encompass any type of polymer flooded produced water or polymer flooding
produced water.
Produced water may be anoxic produced water. Produced water may be anaerobic
produced
water or may be aerobic produced water.
[0039] As used herein, the term "metal" generally refers to both elements that
may be considered
metals, such as iron, and compounds comprising one or more metals, such as,
for example,
ferrous chloride.
[0040] As used herein, the term "iron" generally refers to any form of iron,
for example, iron of
any isotopic state, iron of any oxidation state, any form of an iron compound,
such as, for
example, iron (III) chloride, iron (II) chloride (also known as ferrous
chloride), iron (III) chloride
hexahydrate, and iron sulfate. In some embodiments, iron may comprise iron
(II).
[0041] As used herein, the temi "coagulant" generally may refer to an agent
that may typically
destabilize colloidal suspensions. Coagulants may comprise iron-based
coagulants, such as
ferrous chloride, e.g., PIX-411 sold by Kemira, and/or iron chloride. Other
examples of iron-
based coagulants may include, but are not limited to including iron sulfate
and polyferric
sulphate. Additional coagulants may comprise but are not limited to comprising
inorganic
coagulants such as aluminium sulfate ("ALS") and other metal sulfates and
gypsum, organic
coagulants such as polyamines and polyDADMACs, and other inorganic and organic
coagulants
known in the art.
[0042] Furthermore, a coagulant may comprise a poly(diallyldimethyl ammonium
chloride)
("polyDADMAC") compound; an epi-polyamine compound; a polymer that may
comprise one
or more quaternized ammonium groups, such as acryloyloxyethyltrimethylammonium
chloride,
methacryloyloxyethyltrimethylammonium chloride,
methacrylamidopropyltrimethylammonium
chloride, acrylamidopropyltrimethylammonium chloride; or a mixture thereof An
inorganic
coagulant may, for example, reduce, neutralize or invert electrical repulsions
between particles.
Inorganic coagulants may comprise but are not limited to inorganic salts such
as aluminum
chloride, aluminum sulfate, aluminum chlorohydrate, polyaluminum chloride,
polyaluminum
silica sulfate, ferric chloride, ferrous chloride, ferric sulfate, ferric
chloride sulfate, polyferric
12
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sulfate, ferrous sulfate, lime, calcium chloride, calcium sulfate, magnesium
chloride, sodium
aluminate, various commercially available iron or aluminum salts coagulants,
or combinations
thereof In some embodiments, a coagulant may comprise a combination or mixture
of one or
more organic coagulants with one or more inorganic coagulants. In some
embodiments, a
coagulant may comprise a combination or mixture of any of the above
coagulants.
[0043] As used herein, the term "reducing agent" generally refers to any
element or compound
that loses (or "donates") an electron to another chemical species in a
chemical reaction, e.g., a
redox reaction. In some embodiments, a reducing agent may comprise bisulfite,
metabisulfite,
sulfite, sulfur dioxide, and/or hydrated sulfur dioxide. In some embodiments,
a reducing agent
may comprise compounds such as sulfites, bisulfites, metabisulfites (and in
particular
metabisulfite, dithionites of alkali or alkaline-earth metals). In some
embodiments, a reducing
agent may comprise hydrazine and/or its hydroxylamine derivatives or a mixture
of sodium
borohydride and bisulfite. In some embodiments, a reducing agent may comprise
organic sulfites
such as alkyl sulfites, alkyl hydrosulfites, sulfinates, sulfoxylates,
phosphites, and also oxalic or
formic acid or salts of erythorbate and carbohydrazides. In some embodiments,
a reducing agent
may comprise an oxygen scavenger, such as, but not limited to, carbohydrazide,
hydroquinone,
diethylhydroxylamine (DEHA), methyl ethyl ketoxime (MEKO), and/or erythorbate.
In some
embodiments, a reducing agent may comprise a compound that comprises iron
and/or a metal. In
some embodiments, a reducing agent may comprise the salt form of any compound
that may be
considered a reducing agent, e.g., sodium metabisulfite. In some embodiments,
a reducing agent
may comprise sodium dithionite.
[0044] As used herein, the terms "stabilizer", "stabilizer additive", and
"stabilizing agent"
generally refer to generally refer to any material, technique, method,
process, composition,
and/or compound that may be used to decrease, slow down, prevent, inhibit
and/or stop
degradation of a polymer. In some embodiments, a stabilizer may comprise
thiourea,
diethylthiourea, sodium/ammonium thiocyanate, benzotriazole, MBI, and/or MBT.
In some
embodiments, a stabilizer may comprise a free radical scavenger. In some
embodiments, a
stabilizer may comprise thiourea, 2-mercaptobenzothiazole, dimedone, N,N'-
dimethylthiourea,
N,N'-diethylthiourea, N,N'-diphenylthio urea, ammonium thiocyanate,
tetramethylthiuram
disulphide, 2,2'-dithiobis(benzothiazole), sodium dimethyldithiocarbarnate,
paramethoxyphenol
propyl, 3,4,5-trihydroxybenzoate, 2,6-di-tert-butyl-4-methylphenol, 2,5-
di(tert-amyl)
13
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hydroquinone, 4,4'-thiobis(6-tert-butyl-m-cresol), ammonium N-
nitrosophenylhydroxylamine,
butylhydroxyanisole, hydroxy-8-quinoleine, 4-hydroxy-2,2,6,6-tetramethyl-
piperidinooxy, 5-
hydroxy-1,4-naphtoquinone, (N-(1,3-dimethylbutyl)N'phenyl-p-phenylenediamine,
2,6-di-tert-
buty1-4-methylphenol, 2,5-Di (tert-amyl) hydroquinone, 4,4'-thiobis(6-tert-
butyl-m-cresol),
dicyandiamide, guanidine, and/or cyanamide. In some embodiments, a stabilizer
may comprise
thioureas and alkyl thioureas, mercaptobenzoimidazole (MBI) or
mercaptobenzothiazole (MBT)
and combinations thereof, butyl hydroxyanisole, paramethoxy phenol,
quinolinol, 5,5-dimethyl-
1,3-cyclohexane dione, and/or sodium thiocyanate. In some embodiments, a
stabilizer may
comprise diethyl thiourea, dimethyl thiourea, mercaptobenzothiazole and
mercapto
benzoimidazole. In some embodiments, a stabilizer may comprise a precipitating
agent, such as,
but not limited hydroxides, carboxylates, carbonates, arsenates, cyanurates,
phosphorus
derivatives and/or sulfur derivatives; phosphorus salts, sodium phosphate,
sodium
hydrogenophosphate, phytic acid, or of sulfur salts, sodium sulfide, sodium
sulfydrate or, for the
family of carbonates, sodium carbonate; sodium carbonate and/or sodium
phosphate. In some
embodiments, a stabilizer may comprise a sacrificial agent such as those in
the family of
alcohols, such as, for example, monoalcohols, polyols, glycerol, propylene
glycol,
trimethyleneglycol, isopropanol, 1,2-butanediol, 1,3-butanediol, 1,4-
butanediol, 2,3-butanediol,
1,2,4-butanetriol, pentaerythritol (FETA), trirnethylolethane,
neopentylglycol, 1, -pentanedial,
2,4-pentanediol, 2,3-pentanediol, trimethylolpropane, and/or 1,5-pentanediol,
polyvinyl alcohol
partially or totally hydrolyzed. In some embodiments, a stabilizer may
comprise an antioxidant.
[0045] As used herein, the term "anoxic" generally refers to the absence of
free oxygen, but the
presence of bound oxygen, in an environment. In some embodiments, treatment of
produced
water may comprise treatment of anoxic produced water and/or treatment of
produced water in
an anoxic environment. In some embodiments, produced water may comprise one or
more water
soluble polymers, and said polymers may comprise oxygen. Said polymers may be
the only
source of oxygen in said produced water in some embodiments.
[0046] As used herein, the terms referring to the compounds found in Figure 1,
namely
"metabisulfite", "bisulfite", (hydrated) sulfur dioxide, and sulfite,
generally refer to the same
compound and may be used interchangeably as the compounds are subject to
interconversion
between the forms. One of skill in the art would know that there exists an
interconversion
between the forms presented in Figure 1, and the form that is present as the
major form may be
14
CA 3051369 2019-08-07
dependent on factors such as pH of a solution in which the forms are present.
A person of skill in
the art would know the desired form in order to produce a desired result,
and/or would know the
majority form that would be present given the conditions at which the compound
is used.
PROCESSES AND COMPOSITIONS
[0047] Disclosed herein are processes for the treatment of produced water,
such as produced
water resulting from any part of an EOR process, such as a polymer flood,
comprising one or
more water-soluble polymers, typically high molecular weight water soluble
polymers which are
conventionally used in oil or gas extraction or recovery processes, such as
enhanced oil recovery
processes. According to some embodiments, the process for treating produced
water comprises
adding to the produced water one or more reducing agents and one or more
metals in an amount
effective to reduce the viscosity of the produced water and/or to degrade at
least a portion of the
one or more water soluble polymers contained therein. The resultant treated
water may be
recycled and/or stabilized and reused in other industrial processes including
e.g., other oil
recovery processes or it may be released into the environment. Also disclosed
herein are
combinations comprising one or more reducing agents and one or more metals
suitable for use in
processes for treating produced water which comprises one or more water-
soluble polymers
resulting from at least a portion of the EOR process. Additionally, the
present disclosure
generally relates to treatment of produced water with one or more reducing
agents and one or
more metals as described herein, and further wherein a stabilizing agent is
added to said treated
produced water. Said stabilizing agent may decrease, slow down, prevent,
inhibit, and/or stop a
polymer degradation reaction that may otherwise occur as a result of treatment
of said produced
water with said one or more reducing agents and said one or more metals.
[0048] According to some embodiments, the produced water which is treated
results from a
polymer flood process. In some embodiments, the produced water comprises one
or more water-
soluble polymers, such as, for example, one or more water soluble, high
molecular weight
anionic polyacrylamide-based polymers. In some embodiments, the produced water
comprises
one or more acrylamide-containing (co)polymers and/or one or more polymers
comprising
monomers of acrylamide and acrylic acid.
CA 3051369 2019-08-07
[0049] According to some embodiments, the process for treatment of produced
water involves
adding to the produced water one or more reducing agents, such as MBS or its
related forms (see
Figure 1), and one or more metals, such as a iron and/or a compound comprising
iron, generally
in the Fe2+ form. Said related forms of MBS may comprise a compound comprising
metabisulfite, bisulfite, (hydrated) sulfur dioxide, and/or sulfite. In some
embodiments, the one
or more reducing agents for use with the processes and compositions described
herein may
comprise hydrazine and/or its hydroxylamine derivatives and/or a mixture of
sodium
borohydride and bisulfite. Furthermore, in some embodiments, one or more
reducing agents for
use with the processes and compositions described herein may comprise organic
sulfites such as
alkyl sulfites, alkyl hydrosulfites, sulfinates, sulfoxylates, phosphites, and
also oxalic or formic
acid or salts of erythorbate and carbohydrazides; an oxygen scavenger, such
as, but not limited
to, carbohydrazide, hydroquinone, diethylhydroxylamine (DEHA), methyl ethyl
ketoxime
(MEKO), erythorbate; iron; the salt form of any compound that may be
considered a reducing
agent, e.g., sodium metabisulfite; and/or sodium dithionite. In some
embodiments, one or more
metals for use with the processes and compositions described herein may
comprise iron and/or a
compound comprising iron.
[0050] According to the some embodiments, the one or more reducing agents and
one or more
metals may be pre-mixed or combined prior to being added to the produced
water. In some
embodiments, the one or more reducing agents and the one or more metals may be
added to the
produced water separately but simultaneously. In some embodiments, the one or
more reducing
agents and the one or more metals may be added to the produced water at
different times.
[0051] In some embodiments the amount of the one or more reducing agents and
one or more
metals used to treat the produced water comprises any amount that achieves a
desired effect,
generally reduction of viscosity of the treated produced water and/or
degradation of water
soluble polymers comprised therein. For example, the amount added may comprise
an amount
that achieves a desired reduction in viscosity of the produced water that is
to be or is treated or a
desired amount or degree of degradation of water soluble polymers comprised
therein.
Furthermore, in some embodiments, the dosage of either one or more reducing
agents or one or
more metals used in a treatment processes is that which produces a necessary
or desired effect.
The dosage of the one or more reducing agents or the dosage of the one or more
metals may
vary, for example, at least in part based upon the quality of the produced
water, the components
16
CA 3051369 2019-08-07
of the produced water, the concentration of the polymer in the produced water,
the type of
polymer in the produced water, oxygen content of the produced water, and/or
the treatment
process, the type of reducing agent and/or metal, as well as the desired
result.
[0052] In some embodiments, the process for the treatment of produced water
using one or more
reducing agents and one or more metals comprises mixing of the one or more
reducing agents
and/or one or more metals with the produced water. In general the type of
mixing used includes
any type conventionally used in industrial processes, such as EOR processes
that produce a
necessary or desired effect. In some embodiments, mixing may be conducted
using
a mixing apparatus, which may be a mixing tank with a mixer, a horizontal
mixer, or a screw
mixer. The mixing tank typically may be equipped with a blade mixer. In some
embodiments,
magnetic steering may be used for mixing. In some embodiments, an overhead
mixer may be
used for mixing.
[0053] In some embodiments, the process for the treatment of produced water
using one or more
reducing agents and one or more metals may be conducted, on-site, e.g., at any
onshore oil field,
at any offshore oil field, at a treatment facility, at a disposal well, or at
any other location where
produced water is present.
[0054] According to some embodiments, the process for treating produced water
which contains
one or more polymers may comprise treatment of anoxic produced water and/or
treatment of
produced water under anoxic conditions. In some embodiments, the only oxygen
present in the
produced water to be treated or undergoing treatment may originate or be
present in the one or
more polymers contained in said produced water. In some embodiments, oxygen
may be added
to the produced water before, during, and/or after treatment according to the
processes described
herein. In some embodiments, oxygen may added through the addition of water
containing
dissolved oxygen, e.g., by the addition of surface water, air bubbling, and/or
pressurized air. In
some embodiments, the addition of oxygen to the produced water may increase
the degradation
of the one or more polymers, optionally wherein the amount of added oxygen
correlates to the
amount of degradation. In some embodiments, the addition of oxygen to the
produced water may
decrease the viscosity of the produced water, optionally wherein the amount of
added oxygen
correlates to the reduction of viscosity.
[0055] In some embodiments, an increased dosage of one or more reducing agents
and/or one or
more metals used in treating the produced water may result in a corresponding
decrease in the
17
CA 3051369 2019-08-07
viscosity of said produced water. In some embodiments, an increased dosage of
one or more
reducing agents and/or one or more metals used in the processes for the
treatment of produced
water may result in a corresponding increase in the degradation of the one or
more polymers that
corresponds to the addition of oxygen to the produced water.
[0056] In some embodiments, the treatment of produced water comprising one or
more polymers
with one or more reducing agents and one or more metals may degrade said one
or polymers,
e.g., reduce the molecular weight of said one or more polymers in the produced
water.
Furthermore, in some embodiments, the treatment of produced water using one or
more reducing
agents and one or more metals may reduce the viscosity of the produced water.
Such treatment
processes may be used to reduce the viscosity of the produced water to any
necessary or desired
viscosity. For example, a treatment process may result in in a reduction in
viscosity of said
produced water by about 10% or less, 10% or more, 15% or more, 20% or more,
25% or more,
30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more,
60% or
more, 62% or more, or 65% or more.
[0057] According to some embodiments treatment of the produced water may
reduce the
viscosity to a level that is beneficial for reinjection, stabilization or
(environmentally acceptable)
disposal purposes. In some embodiments, treatment of the produced water
according to the
processes described herein may result in a treated produced water that may be
reused in the same
or other industrial processes such as EOR processes or it may be released into
the environment.
In some embodiments, produced water which has been treated in accordance with
the processes
described herein may be reused for polymer injection, backflow water
application, and/or water
injection. In some embodiments, treating produced water according to the
processes described
herein may result in treated produced water that may be used more efficiently
in skim tank
settling as compared to the untreated produced water and/or the produced water
treated by other
processes conventionally used in the industry. In some embodiments, the
treated water resulting
from the processes disclosed herein may be recycled to one or more oil
recovery processes, such
as an EOR process.
[0058] In some embodiments, the treatment process may occur at temperatures
ranging from
ambient temperature to about 100 C. In some embodiments, the treatment process
may occur at
about 50 C or less, 50 C or more, 55 C or more, 60 C or more, 65 C or more, 70
C or more,
75 C or more, 80 C or more, 85 C or more, 90 C or more, 95 C or more, or 100 C
or more.
18
CA 3051369 2019-08-07
[0059] In some embodiments, the process to treat produced water using one or
more reducing
agents and one or more metals may be used alone, e.g., consist of this
treatment method, or this
treatment method may be used in combination with one or more additional
processes, e.g., those
conventionally used in the industry to treat produced water. Other processes
for produced water
treatment include, for example, mechanical treatments (e.g., membrane
filtration), chemical
treatments (e.g., oxidizing agents), and biological treatments (e.g.,
microbiological processes).
[0060] Additionally, the present disclosure generally relates to treatment of
produced with one or
more reducing agents and one or more metals as described herein, wherein a
stabilizing agent is
further added to the produced water before, after or during treatment.
Specifically, the present
embodiments encompass a process of treating produced water that includes the
addition of one or
more reducing agents and one or more metals during treatment of the produced
water, wherein at
least one stabilizing agent is added to slow, decrease, prevent, inhibit,
and/or stop the
degradation or further degradation of water soluble polymers and/or to
increase or maintain the
viscosity of the produced water. In some embodiments, said at least one
stabilizing agent may be
added while water soluble polymers are present in the produced water in order
to slow, decrease,
prevent, inhibit and/or stop the degradation or further degradation of said at
least one water
soluble polymer and/or to increase or maintain the viscosity of the produced
water, and/or said at
least one stabilizing agent is added contemporaneous or prior to the addition
of at least one water
soluble polymer in order to slow, decrease, prevent, and/or stop the
degradation of said added at
least one water soluble polymer and/or to increase or maintain the viscosity
of the produced
water. In some embodiments, the process for treating produced water may
comprise (i) adding at
least one stabilizing agent while water soluble polymers are present in the
produced water in
order to slow, decrease, prevent, and/or stop the degradation or further
degradation of said at
least one water soluble polymer comprised in the produced water and/or to
increase or maintain
the viscosity of the produced water and/or (ii) adding an amount of at least
one additional water
soluble polymer contemporaneous or after the addition of the at least one
stabilizing agent in
order to slow, decrease, prevent, and/or stop the degradation of said further
added at least one
water soluble polymer and/or to increase or maintain the viscosity of the
produced water. In
other embodiments processes of treating produced water are provided which
include the addition
of at least one stabilizing agent at different times during treatment of the
produced water in order
to slow, decrease, prevent, inhibit and/or stop the degradation or further
degradation of water
19
CA 3051369 2019-08-07
soluble polymers or another material susceptible to degradation by the one or
more reducing
agents and one or more metals and/or to increase or maintain the viscosity of
the produced water.
[0061] In some embodiments, said stabilizing agent may decrease, slow down,
prevent, inhibit
and/or stop polymer degradation reaction that may otherwise occur as a result
of treatment of
said produced water with said one or more reducing agents and said one or more
metals. In some
embodiments, the produced water may be treated as described herein, a
stabilizing agent may be
added, and subsequently more polymer, e.g., water soluble polymer, may be
added to said
produced water, wherein addition of the stabilizing agent protects the newly
added polymer such
that said polymer is degraded to a lesser amount than said polymer would
otherwise degrade
without the addition of said stabilizing agent. In some embodiments, such
stabilizing agent may
comprise thiourea, diethylthiourea, sodium/ammonium thiocyanate,
benzotriazole, MBI, and/or
MBT. In some embodiments, a stabilizing agent may comprise a free radical
scavenger; thiourea,
2-mercaptobenzothiazole, dimedone, N,N'-dimethylthiourea, N,N'-
diethylthiourea, N,N'-
diphenylthio urea, ammonium thiocyanate, tetramethylthiuram disulphide, 2,2'-
dithiobis(benzothiazole), sodium dimethyldithiocarbarnate, paramethoxyphenol
propyl, 3,4,5-
trihydroxybenzoate, 2,6-di-tert-butyl-4-methylphenol, 2,5-di(tert-amyl)
hydroquinone, 4,4'-
thiobis(6-tert-butyl-m-cresol), ammonium N-nitrosophenylhydroxylamine,
butylhydroxyanisole,
hydroxy-8-quinoleine, 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy, 5-hydroxy-
1,4-
naphtoquinone, (N-(1,3-dimethylbutyl)N'phenyl-p-phenylenediamine, 2,6-di-tert-
buty1-4-
methylphenol, 2,5-Di (tert-amyl) hydroquinone, 4,4'-thiobis(6-tert-butyl-m-
cresol),
dicyandiamide, guanidine, and/or cyanamide; thioureas and alkyl thioureas,
mercaptobenzoimidazole (MBI) or mercaptobenzothiazole (MBT) and combinations
thereof,
butyl hydroxyanisole, paramethoxy phenol, quinolinol, 5,5-dimethy1-1,3-
cyclohexane dione,
and/or sodium thiocyanate; diethyl thiourea, dimethyl thiourea,
mercaptobenzothiazole and
mercapto benzoimidazole; a precipitating agent such as, but not limited
hydroxides,
carboxylates, carbonates, arsenates, cyanurates, phosphorus derivatives and/or
sulfur derivatives;
phosphorus salts, sodium phosphate, sodium hydrogenophosphate, phytic acid, or
of sulfur salts,
sodium sulfide, sodium sulfydrate or, for the family of carbonates, sodium
carbonate; sodium
carbonate and/or sodium phosphate; a sacrificial agent, such as those in the
family of alcohols,
such as, for example, monoalcohols, polyols, glycerol, propylene glycol,
trimethyleneglycol,
isopropanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol,
1,2,4-butanetriol,
CA 3051369 2019-08-07
pentaerythritol (FETA), trirnethylolethane, neopentylglycol, 1, -pentanedial,
2,4-pentanediol,
2,3-pentanediol, trimethylolpropane, and/or 1,5-pentanediol, polyvinyl alcohol
partially or totally
hydrolyzed; and/or an antioxidant.
[0062] In some embodiments, additional water soluble polymer may be added
after the addition
of said stabilizing agent. In further embodiments, addition of a stabilizing
agent to a treated
produced water sample may comprise the addition of fresh polymer to said
treated produced
water sample before, during or after the addition of said stabilizing agent.
[0063] In some embodiments, treatment of produced water as described herein in
conjunction
with addition of a stabilizing agent may slow down, decrease, prevent, inhibit
and/or stop
polymer degradation such that the treated produced water may be used to
dissolve new polymer
for injection without degradation of said new polymer. In some embodiments,
said produced
water may be anoxic produced water, and/or the treatment of said produced
water may be
conducted in an anoxic environment, and a stabilizing agent may additionally
be added to said
treated produced water prior to or contemporaneous to the addition of new
polymer, wherein said
new polymer may not be degraded or may not be degraded as much as said polymer
would
otherwise be without the addition of said stabilizing agent. In some
embodiments a stabilizing
agent may be added to produced water that has been treated as described
herein, i.e., treated with
one or more reducing agents and one or more metals, after the viscosity of
said produced water
has reached a desired value. In some embodiments, produced water may be
treated with one or
more reducing agents and one or more metals as described herein, and said
treated water may be
used as make-up water for injection with the addition of stabilizing agent,
such as, for example,
thiourea, diethylthiourea, sodium/ammonium thiocyanate, benzotriazole, MBI,
and/or MBT, as
said stabilizing agent may protect any polymer that may be newly added to said
treated produced
water from degradation.
[0064] In some embodiments, the treatment of produced water as described
herein in
conjunction with a stabilizing agent may result in a water which may be reused
and/or stabilized;
e.g., it may be reused the same or other industrial processes or released into
the environment. In
some embodiments, the treatment of produced water as described herein in
conjunction with a
stabilizing agent may be effected at different places, e.g., it may occur on-
site, at any onshore oil
field, at any offshore oil field, at a treatment facility, at a disposal well,
or at any other location
where produced water is present.
21
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[0065] Furthermore, the present disclosure generally encompasses a composition
suitable for use
in treating produced water, comprising the combination of (i) one or more
stabilizing agents and
either or both of the following (ii) one or more reducing agents and one or
more metals, and (iii)
one or more water soluble polymers; wherein the one or more stabilizing agents
are capable of
preventing or inhibiting the degradation of (iii) one or more water soluble
polymer by the (ii) one
or more reducing agents and one or more metals if said (iii) one or more water
soluble polymers
are present. In some embodiments, said composition may comprise (i) one or
more stabilizing
agents, (ii) one or more reducing agents and one or more metals, and (iii) one
or more water
soluble polymers. Moreover, in some embodiments, said produced water may
comprise anoxic
produced water and/or polymer flooded produced water and/or the treatment
process may occur
in an anoxic environment. In some embodiments, said produced water may
comprise one or
more PAMs, e.g., any polymers or co-polymers comprising acrylamide moieties,
e.g., one or
more acrylamide (co)polymers, e.g., one or more polymers comprising acrylamide
and acrylic
acid. Said one or more PAMs may comprise one or more HPAMs and/or one or more
DPAMs.
In some embodiments, said produced water may comprise one or more water
soluble, high
molecular weight anionic polyacrylamide-based polymers. In some embodiments, a
composition
suitable for use in treating produced water, comprising the combination of (i)
one or more
stabilizing agents and either or both of the following (ii) one or more
reducing agents and one or
more metals, and (iii) one or more water soluble polymers; wherein the one or
more stabilizing
agents are capable of preventing or inhibiting the degradation of (iii) one or
more water soluble
polymer by the (ii) one or more reducing agents and one or more metals if said
(iii) one or more
water soluble polymers are present. In some embodiments, said composition may
be used with
any of the processes described herein.
[0066] The following examples are presented for illustrative purposes only and
are not intended
to be limiting.
EXAMPLES
[0067] Example I
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[0068] In this example, a simulated produced water sample that included a
commercially
available water soluble, high molecular weight anionic polyacrylamide-based
polymer (Polymer
A) was prepared and treated. Sample solutions used in the present example were
made in an
anoxic chamber in order to minimize the oxygen concentration of the samples.
Mixing of the
solutions occurred in a reactor, and the viscosities were measured in an
anoxic chamber.
[0069] First, 300 mL of a first anoxic synthetic injection brine, SIB1, was
prepared (see Table 1
for composition) with the further addition of 15 ppm H503-, in the form of
NaHS03. Next, a
polymer mother solution containing 5,000 ppm of Polymer A was made in SIB1,
wherein
Polymer A was added and mixed for 2 hours with said brine. Separately, a
second synthetic
injection brine, SIB2, was prepared. 300 mL of SIB2 was prepared comprising
the composition
as presented as Table 1 with the further addition of 2 ppm of Fe2 . After
their respective
preparations, SIB1 and SIB2 were mixed together such that Polymer A was at a
concentration of
2500 ppm, and the total volume of the solution was 600 mL. The initial
viscosity value of this
solution was 49.9 cP. Next, the solution was mixed for 1 hour in an anoxic
chamber at 60 C.
After mixing for 1 hour the viscosity of the solution was measured (see Table
2). Following the
viscosity measurement, 11 mL of oxygen saturated SIB was added to the
solution. Next, this
solution was mixed for 1 hour at 60 C, and after the 1 hour time period, the
viscosity was once
again measured (see Table 2).
TABLE 1
CONCENTRATION
COMPONENT
(PPM)
NaC1 2936
KC1 114
CaC12=2 H20 858
MgC12. 6 H20 509
Na2SO4 473
NaHCO3 1067
TDS 5958
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CA 3051369 2019-08-07
[0070] As presented in Table 2, addition of the combination of a metal, iron,
and a reducing
agent was able to reduce the viscosity from 49.9 cP to 25.2 cP in 1 hour, and
to 19 cP after 2
hours with a low addition of oxygen between the 1 hour and 2 hour timepoint
measurements.
Additionally, the solution was noted to have turned to a light yellow color at
the 2 hour
timepoint, which thereby indicated that the iron in the system was being
oxidized.
TABLE 2
VISCOSITY
TIMEPOINT VISCOSITY
(cP)
REDUCTION
Oh 49.9 N/A
1 h 25.2 49.5%
2h 19.0 61.9%
ORP = Oxygen Reduction Potential
DO = Dissolved Oxygen
[0071] In the preceding procedures, various steps have been described. It
will, however, be
evident that various modifications and changes may be made thereto, and
additional procedures
may be implemented, without departing from the broader scope of the procedures
as set forth in
the claims that follow.
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CA 3051369 2019-08-07
