U.S. patent application number 14/337260 was filed with the patent office on 2014-11-06 for polymeric additives for enhancement of treatment fluids comprising viscoelastic surfactants and methods of use.
This patent application is currently assigned to Halliburton Energy Services, Inc.. The applicant listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Ryan G. Ezell, Ryan van Zanten.
Application Number | 20140329726 14/337260 |
Document ID | / |
Family ID | 42761996 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140329726 |
Kind Code |
A1 |
Ezell; Ryan G. ; et
al. |
November 6, 2014 |
Polymeric Additives for Enhancement of Treatment Fluids Comprising
Viscoelastic Surfactants and Methods of Use
Abstract
Polymeric additives used with viscoelastic surfactants, fluids
comprising such additives and viscoelastic surfactants, and
associated methods of use, are provided. In one embodiment, the
methods comprise: providing a treatment fluid that comprises an
aqueous base fluid, a viscoelastic surfactant, and an amphiphilic
polymer, the amphiphilic polymer comprising a hydrophobic
component, and a hydrophilic component comprising at least 15
monomer units; and introducing the treatment fluid into at least a
portion of a subterranean formation.
Inventors: |
Ezell; Ryan G.; (Spring,
TX) ; van Zanten; Ryan; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
42761996 |
Appl. No.: |
14/337260 |
Filed: |
July 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12608738 |
Oct 29, 2009 |
8813845 |
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14337260 |
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12551334 |
Aug 31, 2009 |
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12608738 |
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Current U.S.
Class: |
507/225 ;
507/221; 507/224; 507/229 |
Current CPC
Class: |
C09K 8/602 20130101;
C09K 8/035 20130101; C09K 8/882 20130101; C09K 8/68 20130101; C09K
2208/30 20130101; C09K 8/12 20130101 |
Class at
Publication: |
507/225 ;
507/221; 507/224; 507/229 |
International
Class: |
C09K 8/60 20060101
C09K008/60; C09K 8/88 20060101 C09K008/88 |
Claims
1-22. (canceled)
23. A treatment fluid comprising: an aqueous base fluid; a
viscoelastic surfactant; and an amphiphilic polymer that comprises
(1) a hydrophobic component selected from the group consisting of
polybutadiene, polyisoprene, polystyrene, and combinations thereof
and (2) a hydrophilic component comprising at least 15 monomer
units and being selected from the group consisting of an
ethoxylate, polyethylene oxide (PEO), polyacrylic acid (PAA),
polyethylacetate, dimethylacrylamide (DMA), n-isopropylacrylamide
(NIPAM), polyvinylpyrrolidone (PVP), polyethyleneimine (PEI),
derivatives thereof, and combinations thereof.
24. The treatment fluid of claim 23, wherein the aqueous base fluid
comprises at least one brine.
25. The treatment fluid of claim 23, wherein the viscoelastic
surfactant comprises at least one surfactant selected from the
group consisting of: a methyl ester sulfonate, a hydrolyzed
keratin, a sulfosuccinate, a taurate, an amine oxide, an
ethoxylated amide, an alkoxylated fatty acid, an alkoxylated
alcohol, an ethoxylated fatty amine, an ethoxylated alkyl amine, a
betaine, a modified betaine, an alkylamidobetaine, a quaternary
ammonium compound, any derivative thereof, and any combination
thereof.
26. The treatment fluid of claim 23, wherein the treatment fluid
does not comprise a zwitterionic surfactant.
27. The treatment fluid of claim 23, wherein the viscoelastic
surfactant comprises a catanionic surfactant system.
28. The treatment fluid of claim 23, wherein the viscoelastic
surfactant is present in the treatment fluid in an amount of from
about 0.1% to about 20% by weight of the treatment fluid.
29. The treatment fluid of claim 23, wherein the amphiphilic
polymer is present in the treatment fluid in an amount of from
about 1 mol % to about 5 mol % based on the amount of the
viscoelastic surfactant.
30. The treatment fluid of claim 23, wherein the treatment fluid
further comprises at least one salt.
31. A subterranean treatment additive comprising: a viscoelastic
surfactant; and an amphiphilic polymer that comprises (1) a
hydrophobic component selected from the group consisting of
polybutadiene, polyisoprene, polystyrene, and combinations thereof
and (2) a hydrophilic component comprising at least 15 monomer
units and being selected from the group consisting of an
ethoxylate, polyethylene oxide (PEO), polyacrylic acid (PAA),
polyethylacetate, dimethylacrylamide (DMA), n-isopropylacrylamide
(NIPAM), polyvinylpyrrolidone (PVP), polyethyleneimine (PEI),
derivatives thereof, and combinations thereof.
32. The subterranean treatment additive of claim 31, wherein the
viscoelastic surfactant comprises at least one surfactant selected
from the group consisting of: a methyl ester sulfonate, a
hydrolyzed keratin, a sulfosuccinate, a taurate, an amine oxide, an
ethoxylated amide, an alkoxylated fatty acid, an alkoxylated
alcohol, an ethoxylated fatty amine, an ethoxylated alkyl amine, a
betaine, a modified betaine, an alkylamidobetaine, a quaternary
ammonium compound, any derivative thereof, and any combination
thereof.
33. The subterranean treatment additive of claim 31, wherein the
treatment fluid does not comprise a zwitterionic surfactant.
34. The subterranean treatment additive of claim 31, wherein the
viscoelastic surfactant comprises a catanionic surfactant system.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
U.S. patent application Ser. No. 12/551,334, entitled "Treatment
Fluids Comprising Transient Polymer Networks," filed on Aug. 31,
2009, the entirety of which is herein incorporated by reference,
and from which priority is claimed pursuant to 35 U.S.C.
.sctn.120.
BACKGROUND
[0002] The present invention relates to methods and compositions
that may be useful in treating subterranean formations, and more
specifically, to polymeric additives used with viscoelastic
surfactants, fluids comprising such additives and viscoelastic
surfactants, and associated methods of use.
[0003] Viscosified treatment fluids may be used in a variety of
subterranean treatments. As used herein, 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. Examples of common subterranean
treatments include, but are not limited to, drilling operations,
pre-pad treatments, fracturing operations, perforation operations,
preflush treatments, afterflush treatments, sand control treatments
(e.g., gravel packing), acidizing treatments (e.g., matrix
acidizing or fracture acidizing), diverting treatments, cementing
treatments, and well bore clean-out treatments. For example, in
certain fracturing treatments generally a treatment fluid (e.g., a
fracturing fluid or a "pad fluid") is introduced into a well bore
that penetrates a subterranean formation at a sufficient hydraulic
pressure to create or enhance one or more pathways, or "fractures,"
in the subterranean formation. These cracks generally increase the
permeability of that portion of the formation. The fluid may
comprise particulates, often referred to as "proppant
particulates," that are deposited in the resultant fractures. The
proppant particulates are thought to help prevent the fractures
from fully closing upon the release of the hydraulic pressure,
forming conductive channels through which fluids may flow to a well
bore penetrating the formation.
[0004] Treatment fluids are also utilized in sand control
treatments, such as gravel packing. In "gravel-packing" treatments,
a treatment fluid suspends particulates (commonly referred to as
"gravel particulates"), and at least a portion of those
particulates are then deposited in a desired area in a well bore,
e.g., near unconsolidated or weakly consolidated formation zones,
to form a "gravel pack," which is a grouping of particulates that
are packed sufficiently close together so as to prevent the passage
of certain materials through the gravel pack. This "gravel pack"
may, inter alia, enhance sand control in the subterranean formation
and/or prevent the flow of particulates from an unconsolidated
portion of the subterranean formation (e.g., a propped fracture)
into a well bore. One common type of gravel-packing operation
involves placing a sand control screen in the well bore and packing
the annulus between the screen and the well bore with the gravel
particulates of a specific size designed to prevent the passage of
formation sand. The gravel particulates act, inter alia, to prevent
the formation sand from occluding the screen or migrating with the
produced hydrocarbons, and the screen acts, inter alia, to prevent
the particulates from entering the well bore. The gravel
particulates also may be coated with certain types of materials,
including resins, tackifying agents, and the like. Once the gravel
pack is substantially in place, the viscosity of the treatment
fluid may be reduced to allow it to be recovered. In some
situations, fracturing and gravel-packing treatments are combined
into a single treatment (commonly referred to as "FRAC PAC.TM."
operations). In such "FRAC PAC.TM." operations, the treatments are
generally completed with a gravel pack screen assembly in place
with the hydraulic fracturing treatment being pumped through the
annular space between the casing and screen. In this situation, the
hydraulic fracturing treatment ends in a screen-out condition,
creating an annular gravel pack between the screen and casing. In
other cases, the fracturing treatment may be performed prior to
installing the screen and placing a gravel pack.
[0005] Maintaining sufficient viscosity in treatment fluids may be
important for a number of reasons. Viscosity is desirable in
drilling operations since treatment fluids with higher viscosity
can, among other things, transport solids, such as drill cuttings,
more readily. Maintaining sufficient viscosity is important in
fracturing treatments for particulate transport, as well as to
create or enhance fracture width. Particulate transport is also
important in sand control treatments, such as gravel packing.
Maintaining sufficient viscosity may be important to control and/or
reduce leak-off into the formation, improve the ability to divert
another fluid in the formation, and/or reduce pumping requirements
by reducing friction in the well bore. At the same time, while
maintaining sufficient viscosity of a treatment fluid often is
desirable, it also may be desirable to maintain the viscosity of
the treatment fluid in such a way that the viscosity may be reduced
at a particular time, inter alia, for subsequent recovery of the
fluid from the formation.
[0006] To provide the desired viscosity, polymeric gelling agents
commonly are added to the treatment fluids. The term "gelling
agent" is defined herein to include any substance that is capable
of increasing the viscosity of a fluid, for example, by forming a
gel. Examples of commonly used polymeric gelling agents include,
but are not limited to guar gums and derivatives thereof, cellulose
derivatives, biopolymers, and the like. The use of polymeric
gelling agents, however, may be problematic. For instance, these
polymeric gelling agents may leave an undesirable gel residue in
the subterranean formation after use, which can impact
permeability. As a result, costly remedial operations may be
required to clean up the fracture face and proppant pack. Foamed
treatment fluids and emulsion-based treatment fluids have been
employed to minimize residual damage, but increased expense and
complexity often have resulted.
[0007] To combat perceived problems associated with polymeric
gelling agents, some surfactants have been used as gelling agents.
It is well understood that, when mixed with an aqueous fluid in a
concentration above the critical micelle concentration, the
molecules (or ions) of surfactants may associate to form micelles.
The term "micelle" is defined to include any structure that
minimizes the contact between the lyophobic ("solvent-repelling")
portion of a surfactant molecule and the solvent, for example, by
aggregating the surfactant molecules into structures such as
spheres, cylinders, or sheets, wherein the lyophobic portions are
on the interior of the aggregate structure and the lyophilic
("solvent-attracting") portions are on the exterior of the
structure. These micelles may function, among other purposes, to
stabilize emulsions, break emulsions, stabilize a foam, change the
wettability of a surface, solubilize certain materials, and/or
reduce surface tension. When used as a gelling agent, the molecules
(or ions) of the surfactants used associate to form micelles of a
certain micellar structure (e.g., rodlike, wormlike, vesicles,
etc., which are referred to herein as "viscosifying micelles")
that, under certain conditions (e.g., concentration, ionic strength
of the fluid, etc.) are capable of, inter alia, imparting increased
viscosity to a particular fluid and/or forming a gel. Certain
viscosifying micelles may impart increased viscosity to a fluid
such that the fluid exhibits viscoelastic behavior (e.g., shear
thinning properties) due, at least in part, to the association of
the surfactant molecules contained therein. As used herein, the
term "viscoelastic surfactant fluid" refers to fluids that exhibit
or are capable of exhibiting viscoelastic behavior due, at least in
part, to the association of surfactant molecules contained therein
to form viscosifying micelles.
[0008] However, the use of surfactants as gelling agents may be
problematic in several respects. In certain applications, large
quantities of viscoelastic surfactants may be required to impart
the desired rheological properties to a fluid. Certain viscoelastic
surfactants may be less soluble in certain fluids, which may impair
the ability of those surfactants to form viscosifying micelles.
Viscoelastic surfactant fluids also may be unstable at high
temperatures and/or in high salt concentrations due to, among other
things, the tendency of high salt concentrations to "screen out"
electrostatic interactions between viscosifying micelles.
SUMMARY
[0009] The present invention relates to methods and compositions
that may be useful in treating subterranean formations, and more
specifically, to polymeric additives used with viscoelastic
surfactants, fluids comprising such additives and viscoelastic
surfactants, and associated methods of use.
[0010] In one embodiment, the present invention provides a method
comprising: providing a treatment fluid that comprises an aqueous
base fluid, a viscoelastic surfactant, and an amphiphilic polymer,
the amphiphilic polymer comprising a hydrophobic component, and a
hydrophilic component comprising at least 15 monomer units; and
introducing the treatment fluid into at least a portion of a
subterranean formation.
[0011] In another embodiment, the present invention provides a
method comprising: providing a treatment fluid that comprises an
aqueous base fluid, a viscoelastic surfactant, and an amphiphilic
polymer, the amphiphilic polymer comprising an alkyl ethoxylate,
wherein the treatment fluid does not comprise a substantial amount
of a zwitterionic surfactant; and introducing the treatment fluid
into at least a portion of a subterranean formation.
[0012] In another embodiment, the present invention provides a
method comprising: providing a treatment fluid that comprises an
aqueous base fluid, a viscoelastic surfactant, and an amphiphilic
polymer, wherein the treatment fluid does not comprise a
substantial amount of a zwitterionic surfactant and the amphiphilic
polymer comprises: a hydrophobic component selected from the group
consisting of: an alkyl group, a polybutadiene group, a
polyisoprene group, a polystyrene group, a polyoxystyrene group,
any derivative thereof, and any combination thereof; and a
hydrophilic component selected from the group consisting of: a
polyethylene oxide group; a polyacrylic acid group, a
polyethylacetate group, a dimethylacrylamide group, an
n-isopropylacrylamide group, a polyvinylpyrrolidone group, a
polyethyleneimine group, any derivative thereof, and any
combination thereof; and introducing the treatment fluid into at
least a portion of a subterranean formation.
[0013] In another embodiment, the present invention provides a
method comprising: providing an aqueous base fluid, a viscoelastic
surfactant, and an amphiphilic polymer, the amphiphilic polymer
comprising a hydrophobic component, and a hydrophilic component
comprising at least 15 monomer units; and mixing the aqueous base
fluid, the viscoelastic surfactant, and the amphiphilic polymer
together to form a treatment fluid.
[0014] In another embodiment, the present invention provides a
treatment fluid comprising: an aqueous base fluid, a viscoelastic
surfactant; and an amphiphilic polymer that comprises a hydrophobic
component, and a hydrophilic component comprising at least 15
monomer units.
[0015] In another embodiment, the present invention provides a
subterranean treatment additive comprising: a viscoelastic
surfactant; and an amphiphilic polymer that comprises a hydrophobic
component, and a hydrophilic component comprising at least 15
monomer units.
[0016] The features and advantages of the present invention will be
readily apparent to those skilled in the art. While numerous
changes may be made by those skilled in the art, such changes are
within the spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These drawings illustrate certain aspects of some of the
embodiments of the present invention, and should not be used to
limit or define the invention.
[0018] FIGS. 1-8 illustrate data regarding the zero-shear viscosity
of certain viscoelastic surfactant fluids, including certain
embodiments of the treatment fluids of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] The present invention relates to methods and compositions
that may be useful in treating subterranean formations, and more
specifically, to polymeric additives used with viscoelastic
surfactants, fluids comprising such additives and viscoelastic
surfactants, and associated methods of use.
[0020] The fluids and additives of the present invention generally
comprise a viscoelastic surfactant and an amphiphilic polymer that
comprises a hydrophobic component and a hydrophilic component. The
term "viscoelastic surfactant" is defined herein to include any
surfactant that imparts or is capable of imparting viscoelastic
behavior to a fluid due, at least in part, to the association of
surfactant molecules to form viscosifying micelles.
[0021] Among the many potential advantages of the present
invention, the methods and compositions of the present invention
may, among other things, enhance the viscoelasticity, stability,
and/or other rheological properties of viscoelastic surfactant
fluids, particularly at high temperatures and/or in brines or other
high salinity conditions (greater than about 0.5 M). The methods of
the present invention also may enhance the solubility of certain
viscoelastic surfactants in a fluid, which may enhance the
viscoelasticity, stability, and/or other rheological properties of
the resulting viscoelastic surfactant fluid. Moreover, the methods
and compositions of the present invention may facilitate the
achievement of desired rheological properties in a fluid while
utilizing lower concentrations of viscoelastic surfactant. In
certain embodiments, the fluids of the present invention may
further comprise "transient polymer networks," which refers to
inter- and intramolecularly associative systems (i.e., networks) of
the amphiphilic polymer(s) that form associations via, e.g.,
physical crosslinks, Van der Waals forces and/or electrostatic
interactions, and impart elastic and suspension properties within a
fluid. It is believed that, in such embodiments, the hydrophobic
components of the amphiphilic polymer(s) may become incorporated
into viscosifying micelles, and thus may act as a type of
crosslinker. These transient polymer networks, the polymers that
may be used to form them, and the rheological properties they may
impart are further described in co-pending U.S. patent application
Ser. No. 12/551,334, filed on Aug. 31, 2009, entitled "Treatment
Fluids Comprising Transient Polymer Networks," the entire
disclosure of which is incorporated herein by reference for all
purposes.
[0022] The viscoelastic surfactants used in the present invention
may comprise any viscoelastic surfactant known in the art, any
derivative thereof, or any combination thereof. These viscoelastic
surfactants may be cationic, anionic, nonionic or amphoteric in
nature. The viscoelastic surfactants may comprise any number of
different compounds, including methyl ester sulfonates (e.g., as
described in U.S. patent application Ser. Nos. 11/058,660,
11/058,475, 11/058,612, and Ser. No. 11/058,611, filed Feb. 15,
2005, the relevant disclosures of which are incorporated herein by
reference), hydrolyzed keratin (e.g., as described in U.S. Pat. No.
6,547,871, the relevant disclosure of which is incorporated herein
by reference), sulfosuccinates, taurates, amine oxides, ethoxylated
amides, alkoxylated fatty acids, alkoxylated alcohols (e.g., lauryl
alcohol ethoxylate, ethoxylated nonyl phenol), ethoxylated fatty
amines, ethoxylated alkyl amines (e.g., cocoalkylamine ethoxylate),
betaines, modified betaines, alkylamidobetaines (e.g.,
cocoamidopropyl betaine), quaternary ammonium compounds (e.g.,
trimethyltallowammonium chloride, trimethylcocoammonium chloride),
derivatives thereof, and combinations thereof. The term
"derivative" is defined herein to include any compound that is made
from one of the listed compounds, for example, by replacing one
atom in the listed compound with another atom or group of atoms,
rearranging two or more atoms in the listed compound, ionizing the
listed compounds, or creating a salt of the listed compound.
[0023] Suitable viscoelastic surfactants may comprise mixtures of
several different compounds, including but not limited to: mixtures
of an ammonium salt of an alkyl ether sulfate, a cocoamidopropyl
betaine surfactant, a cocoamidopropyl dimethylamine oxide
surfactant, sodium chloride, and water; mixtures of an ammonium
salt of an alkyl ether sulfate surfactant, a cocoamidopropyl
hydroxysultaine surfactant, a cocoamidopropyl dimethylamine oxide
surfactant, sodium chloride, and water; mixtures of an ethoxylated
alcohol ether sulfate surfactant, an alkyl or alkene amidopropyl
betaine surfactant, and an alkyl or alkene dimethylamine oxide
surfactant; aqueous solutions of an alpha-olefinic sulfonate
surfactant and a betaine surfactant; and combinations thereof.
Examples of suitable mixtures of an ethoxylated alcohol ether
sulfate surfactant, an alkyl or alkene amidopropyl betaine
surfactant, and an alkyl or alkene dimethylamine oxide surfactant
are described in U.S. Pat. No. 6,063,738, the relevant disclosure
of which is incorporated herein by reference. Examples of suitable
aqueous solutions of an alpha-olefinic sulfonate surfactant and a
betaine surfactant are described in U.S. Pat. No. 5,879,699, the
relevant disclosure of which is incorporated herein by reference.
Suitable viscoelastic surfactants also may comprise "catanionic"
surfactant systems, which comprise paired oppositely-charged
surfactants that act as counterions to each other and may form
wormlike micelles. Examples of such catanionic surfactant systems
include, but are not limited to sodium oleate (NaO)/octyl
trimethylammonium chloride (C.sub.8TAC) systems, stearyl
trimethylammonium chloride (C.sub.18TAC)/caprylic acid sodium salt
(NaCap) systems, and cetyl trimethylammonium tosylate (CTAT)/sodium
dodecylbenzenesulfonate (SDBS) systems.
[0024] Examples of commercially-available viscoelastic surfactants
suitable for use in the present invention may include, but are not
limited to, Mirataine BET-O 30.TM. (an oleamidopropyl betaine
surfactant available from Rhodia Inc., Cranbury, N.J.), Aromox
APA-T (amine oxide surfactant available from Akzo Nobel Chemicals,
Chicago, Ill.), Ethoquad O/12 PG.TM. (a fatty amine ethoxylate quat
surfactant available from Akzo Nobel Chemicals, Chicago, Ill.),
Ethomeen T/12.TM. (a fatty amine ethoxylate surfactant available
from Akzo Nobel Chemicals, Chicago, Ill.), Ethomeen S/12.TM. (a
fatty amine ethoxylate surfactant available from Akzo Nobel
Chemicals, Chicago, Ill.), and Rewoteric AM TEG.TM. (a tallow
dihydroxyethyl betaine amphoteric surfactant available from Degussa
Corp., Parsippany, N.J.).
[0025] The viscoelastic surfactant should be present in a fluid of
the present invention in an amount sufficient to impart the desired
viscosity (e.g., sufficient viscosity to divert flow, reduce fluid
loss, suspend particulates, etc.) to the fluid. In certain
embodiments, the viscoelastic surfactant may be present in the
fluid in an amount in the range of from about 0.1% to about 20% by
weight of the fluid. In certain embodiments, the viscoelastic
surfactant may be present in an amount in the range of from about
0.5% to about 10% by weight of the fluid. In certain embodiments,
the viscoelastic surfactant may be present in an amount in the
range of from about 0.5% to about 3% by weight of the fluid.
[0026] The amphiphilic polymer(s) used in the present invention may
comprise a variety of polymers known in the art that comprise a
hydrophobic component and a hydrophilic component. For example, the
amphiphilic polymer(s) may comprise a hydrophobic component, and a
hydrophilic component comprising at least 15 monomer units. In
certain embodiments, the hydrophilic component may be larger and,
for example, have at least 20 monomer units. In certain
embodiments, the hydrophilic component may be larger and, for
example, have at least 50 monomer units. Examples of hydrophobic
components that may be suitable for use include, but are not
limited to alkyl groups, polybutadiene, polyisoprene, polystyrene,
polyoxystyrene, any derivatives thereof, and any combinations
thereof. Examples of hydrophilic components that may be suitable
for use include, but are not limited to polyethylene oxide (PEO),
polyacrylic acid (PAA), polyethylacetate, dimethylacrylamide (DMA),
n-isopropylacrylamide (NIPAM), polyvinylpyrrolidone (PVP),
polyethyleneimine (PEI), any derivatives thereof, and any
combinations thereof. Examples of amphiphilic polymers that may be
suitable for use include, but are not limited to polybutadiene-PEO,
polystyrene-PEO, polystyrene-polyacrylic acid, polyoxystyrene-PEO,
polystyrene-polyethylacetate, any derivatives thereof, and any
combinations thereof. Other examples of amphiphilic polymers that
may be suitable for use in the present invention include those that
comprise units based on one or more of the following: acrylamides,
vinyl alcohols, vinylpyrrolidones, vinylpyridines, acrylates,
polyacrylamides, polyvinyl alcohols, polyvinylpyrrolidones,
polyvinylpyridines, polyacrylates, polybutylene succinate,
polybutylene succinate-co-adipate, polyhydroxybutyrate-valerate,
polyhydroxybutyrate-covalerate, polycaprolactones, polyester
amides, polyethylene terephthalates, sulfonated polyethylene
terephthalate, polyethylene oxides, polyethylenes, polypropylenes,
aliphatic aromatic copolyester, polyacrylic acids, polysaccharides
(such as dextran or cellulose), chitins, chitosans, proteins,
aliphatic polyesters, polylactic acids, poly(glycolides),
poly(.epsilon.-caprolactones), poly(hydroxy ester ethers),
poly(hydroxybutyrates), poly(anhydrides), polycarbonates,
poly(orthoesters), poly(amino acids), poly(ethylene oxides),
poly(propylene oxides), poly(phosphazenes), polyester amides,
polyamides, polystyrenes, any derivative thereof, any copolymer,
homopolymer, or terpolymer, or any blend thereof. In certain
embodiments, the amphiphilic polymer may comprise a compound
selected from the group consisting of hydroxyethyl acrylate,
acrylamide and hydroxyethyl methacrylate.
[0027] In certain embodiments, the amphiphilic polymer(s) may
comprise one or more alkyl ethoxylates. In certain embodiments, the
alkyl ethoxylate may comprise an alkyl group, and an ethoxylate
group having at least 15 oxyethylene units. In certain embodiments,
the hydrophilic component may be larger and, for example, have at
least 20 oxyethylene units. In certain embodiments, the hydrophilic
component may be larger and, for example, have at least 50
oxyethylene units. Commercially available sources of such
amphiphilic polymers that may be suitable for use in the present
invention include, but are not limited to, certain detergents
available under the tradename BRIJ.RTM., such as BRIJ.RTM.-30
(comprises polyethylene glycol dodecyl ether), BRIJ.RTM.-35
(comprises polyoxyethyleneglycol dodecyl ether), BRIJ.RTM.-58
(comprises polyethylene glycol hexadecyl ether), BRIJ.RTM.-97
(comprises polyoxyethylene (10) oleyl ether), BRIJ.RTM.-98
(comprises polyoxyethylene (20) oleyl ether), and BRIJ.RTM.-700
(comprises polyoxyethylene (100) stearyl ether). Other commercially
available sources of such amphiphilic polymers that may be suitable
for use in the present invention include, certain detergents
available under the tradename IGEPAL.RTM..
[0028] The amphiphilic polymer should be present in a fluid of the
present invention in an amount sufficient to impart the desired
viscosity (e.g., sufficient viscosity to divert flow, reduce fluid
loss, suspend particulates, etc.) to the fluid. In certain
embodiments, the amphiphilic polymer may be present in the fluid in
an amount in the range of from about 1 mol % to about 5 mol % based
on the amount of the viscoelastic surfactant. In certain
embodiments, the amphiphilic polymer may be present in the fluid in
an amount in the range of from about 1 mol % to about 3 mol % based
on the amount of the viscoelastic surfactant. In some instances,
the presence of excessive amounts of amphiphilic polymer may reduce
the stability of the viscoelastic surfactant fluid (e.g., may
reduce the viscosity of the fluid). A person of skill in the art,
with the benefit of this disclosure, will recognize the amount of
amphiphilic polymer that may produce these effects in a particular
application of the present invention, and determine when they
should be avoided or employed. For example, certain embodiments of
the present invention may comprise adding sufficient amounts of the
amphiphilic polymer to reduce the viscosity of the fluid, among
other purposes, to permit the fluid to leak off into a subterranean
formation.
[0029] The fluids of the present invention generally comprise an
aqueous base fluid. Suitable aqueous base fluids may comprise,
among other things, fresh water, saltwater (e.g., water containing
one or more salts dissolved therein), brine, seawater, and/or any
combination thereof. Generally, the water may be from any source,
provided that it does not contain components that might adversely
affect the stability and/or performance of the fluids of the
present invention. In certain embodiments, the density of the
aqueous base fluid can be adjusted, among other purposes, to
provide additional particle transport and suspension in the fluids
of the present invention and/or to facilitate dissolving the
viscoelastic surfactant into the aqueous base fluid. In certain
embodiments, the pH of the aqueous base fluid may be adjusted
(e.g., by a buffer or other pH adjusting agent), among other
purposes, to reduce the viscosity of the fluid (e.g., activate a
breaker or other additive). In these embodiments, the pH may be
adjusted to a specific level, which may depend on, among other
factors, the type(s) of viscoelastic surfactant(s), amphiphilic
polymers, salts, and other additives included in the fluid. One of
ordinary skill in the art, with the benefit of this disclosure,
will recognize when such density and/or pH adjustments are
appropriate.
[0030] The fluids used in methods of the present invention
optionally may comprise any number of additional additives,
including, but not limited to, salts, co-surfactants, acids,
additional fluid loss control additives, gas, nitrogen, carbon
dioxide, surface modifying agents, tackifying agents, foamers,
corrosion inhibitors, scale inhibitors, catalysts, clay control
agents, biocides, friction reducers, antifoam agents, bridging
agents, dispersants, flocculants, H.sub.2S scavengers, CO.sub.2
scavengers, oxygen scavengers, lubricants, viscosifiers, breakers,
weighting agents, relative permeability modifiers, resins,
particulate materials (e.g., proppant particulates), wetting
agents, coating enhancement agents, and the like. In certain
embodiments, the fluids and additives of the present invention may
not comprise a substantial amount of a zwitterionic surfactant. A
person skilled in the art, with the benefit of this disclosure,
will recognize the types of additives that may be included in the
fluids of the present invention for a particular application.
[0031] For example, the fluids of the present invention optionally
may comprise one or more salts. The salts may be organic or
inorganic. Examples of suitable organic salts include but are not
limited to aromatic sulfonates and carboxylates (such as p-toluene
sulfonate, naphthalene sulfonate), hydroxynaphthalene carboxylates,
salicylate, phthalate, chlorobenzoic acid, salicylic acid, phthalic
acid, 5-hydroxy-1-naphthoic acid, 6-hydroxy-1-naphthoic acid,
7-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid,
3-hydroxy-2-naphthoic acid, 5-hydroxy-2-naphthoic acid,
7-hydroxy-2-naphthoic acid, 1,3-dihydroxy-2-naphthoic acid,
3,4-dichlorobenzoate, trimethylammonium hydrochloride and
tetramethylammonium chloride. Examples of suitable inorganic salts
include water-soluble potassium, sodium, and ammonium salts, (such
as sodium chloride, potassium chloride, and ammonium chloride),
calcium chloride, calcium bromide, magnesium chloride and zinc
halide salts. Examples of viscoelastic surfactant fluids comprising
salts suitable for use in the present invention are described in
U.S. patent application Ser. No. 10/800,478, the relevant
disclosure of which is incorporated herein by reference. Any
combination of the salts listed above also may be included in the
fluids of the present invention.
[0032] The optional salt may be present in any practicable amount.
In certain embodiments, the salt may be present in an amount in the
range of from about 0.1% to about 30% by weight of the fluid. In
certain embodiments, the salt may be present in an amount in the
range of from about 0.1% to about 10% by weight of the fluid. The
type(s) and amount of salts suitable in a particular application of
the present invention may depend upon a variety of factors, such as
the type(s) of viscoelastic surfactant(s) present in the fluid, the
composition of the aqueous-base fluid, the temperature of the fluid
and/or the region of desired use, and the like. In certain
embodiments of the present invention, the aqueous base fluid may
comprise a brine that already includes a certain amount of salt. In
these embodiments, additional salts may not be desired, or it may
be desirable to remove salt from or add further salt to the brine
in the preparation and/or use of a fluid of the present invention.
A person of ordinary skill, with the benefit of this disclosure,
will recognize when to include a salt in a particular application
of the present invention, as well as the appropriate type and
amount of salts to include.
[0033] In certain embodiments, the methods of the present invention
generally comprise: providing an aqueous base fluid, a viscoelastic
surfactant, and an amphiphilic polymer that comprises (a) a
hydrophobic component comprising an alkyl group, and (b) a
hydrophilic component comprising an ethoxylate having at least 20
oxyethylene units; and mixing the aqueous base fluid, the
viscoelastic surfactant, and the amphiphilic polymer together to
form a fluid of the present invention. The fluids of the present
invention and/or any component thereof (e.g., the amphiphilic
polymer) may be provided in any form that is suitable for the
particular application of the present invention. In certain
embodiments, the viscoelastic surfactant and/or amphiphilic polymer
may be provided as a liquid and/or solid additive that is admixed
or incorporated at any point prior to and/or during use of the
fluid. For example, in certain embodiments, the amphiphilic polymer
may be added to a fluid that is already present in a portion of a
subterranean formation. The different components of the fluids of
the present invention may be provided or incorporated together
(e.g., in the same additive or fluid), or they may be provided or
incorporated into a fluid as separate additives. Where they are
provided or incorporated into a fluid separately, the different
components may be provided or incorporated simultaneously, or
certain components may be provided or incorporated at some point in
time before or after the other components are provided or
incorporated. The fluids of the present invention and/or any
component thereof may be prepared at a job site, or they may be
prepared at a plant or facility prior to use, and may be stored for
some period of time prior to use. In certain embodiments, the
preparation of these fluids of the present invention may be done at
the job site in a method characterized as being performed "on the
fly." The term "on-the-fly" is used herein to include methods of
combining two or more components wherein a flowing stream of one
element is continuously introduced into flowing stream of another
component so that the streams are combined and mixed while
continuing to flow as a single stream as part of the on-going
treatment. Such mixing can also be described as "real-time"
mixing.
[0034] In certain embodiments, the methods of the present invention
comprise: providing a treatment fluid that comprises an aqueous
base fluid, a viscoelastic surfactant, and an amphiphilic polymer
that comprises (a) a hydrophobic component comprising an alkyl
group, and (b) a hydrophilic component comprising an ethoxylate
having at least 15 oxyethylene units; and introducing the treatment
fluid into at least a portion of a subterranean formation. In these
methods, the treatment fluid (and/or the separate components
thereof) may be introduced into a portion of a subterranean
formation by any means known in the art.
[0035] The methods and treatment fluids of the present invention
may be used during or in preparation for any subterranean operation
wherein a fluid may be used. Suitable subterranean operations may
include, but are not limited to, preflush treatments, afterflush
treatments, drilling operations, hydraulic fracturing treatments,
sand control treatments (e.g., gravel packing), acidizing
treatments (e.g., matrix acidizing or fracture acidizing),
"frac-pack" treatments, well bore clean-out treatments, and other
operations where a treatment fluid of the present invention may be
useful. For example, in certain embodiments, the present invention
provides fluids that comprise an aqueous base fluid, a viscoelastic
surfactant, an amphiphilic polymer that comprises (a) a hydrophobic
component comprising an alkyl group, and (b) a hydrophilic
component comprising an ethoxylate having at least 15 oxyethylene
units, and, in certain embodiments, a plurality of proppant
particulates. In certain embodiments, a treatment fluid of the
present invention may be used in a method of fracturing a
subterranean formation, wherein a treatment fluid of the present
invention is introduced into the subterranean formation at or above
a sufficient hydraulic pressure to create or enhance one or more
cracks, or "fractures," in the subterranean formation. "Enhancing"
one or more fractures in a subterranean formation, as that term is
used herein, is defined to include the extension or enlargement of
one or more natural or previously created fractures in the
subterranean formation. This may, among other things, form
conductive channels in the subterranean formation through which
fluids (e.g., oil, gas, etc.) may flow to a well bore penetrating
the subterranean formation.
[0036] To facilitate a better understanding of the present
invention, the following examples of certain aspects of some
embodiments are given. In no way should the following examples be
read to limit, or define, the entire scope of the invention.
EXAMPLES
Example 1A
[0037] A fluid was prepared comprising a 1.5% by weight aqueous
solution of a cetyl trimethylammonium tosylate (CTAT)/sodium
dodecylbenzenesulfonate (SDBS) (97:3 weight ratio) surfactant
system, and the zero-shear viscosity of the fluid was measured
using an Physica MCR501 rheometer (manufactured by Anton Paar GmbH)
at 70.degree. F. and ambient pressure. A certain amount of an
amphiphilic polymer (BRIJ-35 or BRIJ-700) was then added to 3
different samples of that fluid, and the zero-shear viscosity of
each fluid sample with the polymer added was measured at the same
conditions. The types and amounts (by weight of the surfactant
system) of amphiphilic polymer added to each fluid and the
resulting viscosities are listed in Table 1 and depicted in FIG.
1.
TABLE-US-00001 TABLE 1 Fluid Zero shear viscosity Sample No.
Composition (P a*s) A CTAT/SDBS surfactant 282 B CTAT/SDBS
surfactant + 231 1 mol % BRIJ-35 C CTAT/SDBS surfactant + 215 1 mol
% BRIJ-700 D CTAT/SDBS surfactant + 23 3 mol % BRIJ-700
Example 1B
[0038] A second fluid was prepared using the same surfactant system
and concentration described in Example 1A in an aqueous 0.7M
solution of sodium bromide (NaBr), and its zero-shear viscosity was
measured. An amphiphilic polymer (BRIJ-700) was added to 2
different samples of that fluid (1 mol % and 3 mol % by weight of
the surfactant system, respectively), and the zero-shear viscosity
of each fluid sample with the polymer added was measured. The
resulting viscosities are listed in Table 2 and are depicted in
FIG. 2, along with the zero-shear viscosity of the initial fluid
from Example 1A without polymer or sodium bromide for
comparison.
TABLE-US-00002 TABLE 2 Fluid Zero shear viscosity Sample No.
Composition (P a*s) E CTAT/SDBS surfactant 282 (from Example 1A) F
0.7M NaBr + CTAT/SDBS 1.7 surfactant G 0.7M NaBr + CTAT/SDBS 5.8
surfactant + 1 mol % BRIJ-700 H 0.7M NaBr + CTAT/SDBS 37 surfactant
+ 3 mol % BRIJ-700
Example 1C
[0039] A third fluid was prepared using the same surfactant system
and concentration described in Example 1A in an aqueous 1M solution
of sodium bromide (NaBr). An amphiphilic polymer (BRIJ-700) was
added to 2 different samples of that fluid (1 mol % and 3 mol % by
weight of the surfactant system, respectively), and the zero-shear
viscosity of each fluid sample with the polymer added was measured.
The resulting viscosities are listed in Table 3 and are depicted in
FIG. 3, along with the zero-shear viscosity of the initial fluid
from Example 1A without polymer or sodium bromide for
comparison.
TABLE-US-00003 TABLE 3 Fluid Zero shear viscosity Sample No.
Composition (P a*s) I CTAT/SDBS surfactant 282 (from Example 1A) J
1M NaBr + CTAT/SDBS 6.8 surfactant + 1 mol % BRIJ-700 K 1M NaBr +
CTAT/SDBS 35 surfactant + 3 mol % BRIJ-700
Example 1D
[0040] A fourth fluid was prepared using the same surfactant system
and concentration described in Example 1A in an aqueous 2M solution
of sodium bromide (NaBr). An amphiphilic polymer (BRIJ-700) was
added the fluid (3 mol % by weight of the surfactant system), and
the zero-shear viscosity of the fluid with the polymer added was
measured. The resulting viscosities are listed in Table 4 and are
depicted in FIG. 4, along with the zero-shear viscosity of the
initial fluid from Example 1A without any polymer or sodium bromide
for comparison.
TABLE-US-00004 TABLE 4 Fluid Zero shear viscosity Sample No.
Composition (P a*s) L CTAT/SDBS surfactant 282 (from Example 1A) M
2M NaBr + CTAT/SDBS 3.1 surfactant N 2M NaBr + CTAT/SDBS 33
surfactant + 3 mol % BRIJ-700
[0041] Thus, Examples 1A-1D illustrate that the methods and
additives of the present invention may enhance the rheology of
certain viscoelastic surfactant fluids.
Example 2A
[0042] A fluid was prepared comprising a 3% by weight aqueous
solution of a cetyl trimethylammonium tosylate (CTAT)/sodium
dodecylbenzenesulfonate (SDBS) (97:3 weight ratio) surfactant
system, and the zero-shear viscosity of the fluid was measured
using the same methods and parameters described in Example 1A. An
amphiphilic polymer (BRIJ-35 or BRIJ-700) was then added to 2
different samples of that fluid (1 mol % by weight of the
surfactant system in each), and the zero-shear viscosity of each
fluid sample with the polymer added was measured. The resulting
viscosities are listed in Table 5 and depicted in FIG. 5.
TABLE-US-00005 TABLE 5 Fluid Zero shear viscosity Sample No.
Composition (P a*s) O CTAT/SDBS surfactant 488 P CTAT/SDBS
surfactant + 436 1 mol % BRIJ-35 Q CTAT/SDBS surfactant + 573 1 mol
% BRIJ-700
Example 2B
[0043] A second fluid was prepared using the same surfactant system
and concentration described in Example 2A in an aqueous 0.7M
solution of sodium bromide (NaBr), and its zero-shear viscosity was
measured. An amphiphilic polymer (BRIJ-700) was added to the fluid
(1 mol % by weight of the surfactant system), and the zero-shear
viscosity of the fluid with the polymer added was measured. The
resulting viscosities are listed in Table 6 and are depicted in
FIG. 6, along with the zero-shear viscosity of the initial fluid
from Example 2A without polymer or sodium bromide for
comparison.
TABLE-US-00006 TABLE 6 Fluid Zero shear viscosity Sample No.
Composition (P a*s) R CTAT/SDBS surfactant 488 S 0.7M NaBr +
CTAT/SDBS 4.3 surfactant T 0.7M NaBr + CTAT/SDBS 16.7 surfactant +
1 mol % BRIJ-700
[0044] Thus, Examples 2A and 2B illustrate that the methods and
additives of the present invention may enhance the rheology of
certain viscoelastic surfactant fluids.
Example 3A
[0045] A fluid was prepared comprising a 3% by weight aqueous
solution of a sodium oleate (NaO)/octyl trimethylammonium chloride
(C.sub.8TAC) (7:3 weight ratio) surfactant system, and the
zero-shear viscosity of the fluid was measured using the same
methods and parameters described in Example 1A. An amphiphilic
polymer (BRIJ-30, BRIJ-35, or BRIJ-700) was then added to 3
different samples of that fluid (1 mol % by weight of the
surfactant system in each), and the zero-shear viscosity of each
fluid sample with the polymer added was measured. The resulting
viscosities are listed in Table 7 and depicted in FIG. 7.
TABLE-US-00007 TABLE 7 Fluid Zero shear viscosity Sample No.
Composition (P a*s) U NaO/C.sub.8TAC surfactant 1180 V
NaO/C.sub.8TAC surfactant + 41 1 mol % BRIJ-30 W NaO/C.sub.8TAC
surfactant + 154 1 mol % BRIJ-35 X NaO/C.sub.8TAC surfactant + 629
1 mol % BRIJ-700
Example 3B
[0046] A second fluid was prepared using the same surfactant system
and concentration described in Example 3A in an aqueous 0.15M
solution of sodium bromide (NaBr), and its zero-shear viscosity was
measured. An amphiphilic polymer (BRIJ-700) was added to the fluid
(1 mol % by weight of the surfactant system), and further sodium
bromide was added to bring the solution to a 0.2M NaBr
concentration. The zero-shear viscosity of the fluid with the
polymer and additional NaBr was measured. The resulting viscosities
are listed in Table 8 and are depicted in FIG. 8, along with the
zero-shear viscosity of the initial fluid from Example 3A without
polymer or sodium bromide for comparison.
TABLE-US-00008 TABLE 8 Fluid Zero shear viscosity Sample No.
Composition (P a*s) Y NaO/C.sub.8TAC surfactant 1180 Z 0.15M NaBr +
NaO/C.sub.8TAC 2.4 surfactant AA 0.2M NaBr + NaO/C.sub.8TAC 24
surfactant + 1 mol % BRIJ-700
[0047] Thus, Examples 3A and 3B illustrate that the methods and
additives of the present invention may enhance the rheology of
certain viscoelastic surfactant fluids.
[0048] Therefore, the present invention is well adapted to attain
the ends and advantages mentioned as well as those that are
inherent therein. The particular embodiments disclosed above are
illustrative only, as the present invention may be modified and
practiced in different but equivalent manners apparent to those
skilled in the art having the benefit of the teachings herein.
Furthermore, no limitations are intended to the details of
construction or design herein shown, other than as described in the
claims below. It is therefore evident that the particular
illustrative embodiments disclosed above may be altered or modified
and all such variations are considered within the scope and spirit
of the present invention. While compositions and methods are
described in terms of "comprising," "containing," or "including"
various components or steps, the compositions and methods can also
"consist essentially of" or "consist of" the various components and
steps. All numbers and ranges disclosed above may vary by some
amount. Whenever a numerical range with a lower limit and an upper
limit is disclosed, any number and any included range falling
within the range is specifically disclosed. In particular, every
range of values (of the form, "from about a to about b," or,
equivalently, "from approximately a to b," or, equivalently, "from
approximately a-b") disclosed herein is to be understood to set
forth every number and range encompassed within the broader range
of values. Also, the terms in the claims have their plain, ordinary
meaning unless otherwise explicitly and clearly defined by the
patentee. Moreover, the indefinite articles "a" or "an", as used in
the claims, are defined herein to mean one or more than one of the
element that it introduces. If there is any conflict in the usages
of a word or term in this specification and one or more patent or
other documents that may be incorporated herein by reference, the
definitions that are consistent with this specification should be
adopted.
* * * * *