THERMALLY-ACTIVATED, HIGH-TEMPERATURE PARTICULATE
SUSPENDING AGENTS AND METHODS RELATING THERETO
BACKGROUND
[0001] The present invention relates to particulate suspending agents
for use in high-temperature and/or at near-neutral or higher pH (e.g., greater
than about 5) wellbore applications, and methods relating thereto.
[0002] Subterranean operations often involve fluids that include
particulates. For example, cement slurries include hydraulic cement
particulates, and drilling fluids often include particulate weighting agents. To
maintain particulates in suspension, the fluids are often viscosified. As the
bottom hole circulating temperature of a wellbore increases, the viscosity of a
fluid decreases, which is known as thermal thinning, which can cause
undesirable settling of the particulates from the fluid.
[0003] Particulate settling can cause the density of the fluid to change,
which can lead to, inter alia, an influx of formation fluids. To inhibit settling,
suspending agents, e.g., crosslinked polymers, can be added to fluids. As the
fluid temperature increases, the suspending agent is thought to increase the
viscosity of the fluid, for example, by breaking crosslinks to release a polymer
into the fluid. One important feature of a suspending agent is that it not
adversely affect low-temperature rheology.
[0004] Existing suspending agents, e.g., guar or guar derivatives
crosslinked with borate, delay crosslink breakage sufficiently to allow mixing and
pumping of a fluid without imparting an excessively-high viscosity. However,
existing suspending agents are known to degrade above 300°F. This
temperature limitation makes these suspending agents more impractical for use
in higher temperature applications. Synthetic polymers crosslinked with esters or
amides are effective at temperatures in excess of 400°F, but the crosslinks may
not be degraded rapidly enough at near-neutral pH values (e.g., about pH 5 to
about pH 8) to offset thermal thinning as the fluid heats up in the wellbore.
SUMMARY OF THE INVENTION
[0005] The present invention relates to particulate suspending agents
for use in high-temperature and/or at near-neutral or higher pH (e.g., greater
than about 5) wellbore applications, and methods relating thereto.
[0006] One embodiment of the present invention provides for a method
that comprises providing a treatment fluid comprising an aqueous liquid, a
plurality of particulates, and a particulate suspending agent, wherein the
particulate suspending agent comprises a crosslinked polymer particulate formed
by a reaction comprising a first monofunctional monomer and an orthoester
crosslinker, the orthoester crosslinker comprising an orthoester linkage and at
least two crosslinking moieties; and placing the treatment fluid in a wellbore
penetrating a subterranean formation.
[0007] Another embodiment of the present invention provides for a
method that comprises providing a treatment fluid comprising an aqueous liquid,
a plurality of particulates, and a particulate suspending agent, wherein the
particulate suspending agent comprises a crosslinked polymer particulate that
comprises a polymer crosslinked with an orthoester crosslinker that comprises
an orthoester linkage and at least two crosslinking moieties; placing the
treatment fluid in a wellbore penetrating a subterranean formation with a bottom
hole static temperature of about 150°F or greater; and allowing the orthoester
linkage to degrade thereby allowing at least some of the polymer to dissolve and
suspend the particulates.
[0008] Yet another embodiment of the present invention provides for
treatment fluid that comprises an aqueous fluid, a plurality of particulates, and a
particulate suspending agent comprising a crosslinked polymer particulate,
wherein the crosslinked polymer particulate is produced from a reaction
comprising: a first monofunctional monomer, and an orthoester crosslinker that
comprises an orthoester linkage and at least two crosslinking moieties.
[0009] Another embodiment of the present invention provides for a
method of producing a particulate suspending agent, such that the method
comprises providing an oil solution comprising an oil-based solvent and a
surfactant; providing a monomer mixture comprising an aqueous liquid and a
first monofunctional monomer; forming an inverse suspension with the monomer
mixture and the oil solution; reacting the monomer mixture in the inverse
suspension with a free-radical initiator to form a polymer particulate; isolating
the polymer particulate; and diffusing an orthoester crosslinker into the polymer
particulate so as to form a crosslinked polymer particulate.
[00 10] The featu res and advantages of the present invention will be
read ily appa rent to those ski lled in the art upon a read ing of the descri ption of
the preferred embod iments that fol lows.
DETAILED DESCRIPTION
[00 11] The present invention relates to particu late suspendi ng agents
for use in high-temperatu re and/or at nea r- neutra l or hig her pH (e.g., greater
tha n about 5) wel lbore appl ications, and methods relati ng thereto .
[00 12] Of the many advantages of the present invention, the present
invention provides compositions that protect agai nst therma l thi nni ng at
elevated tem peratu res of f luids comprisi ng particu lates (e.g., hydrau lic cements,
weig hti ng agents, proppa nts, and the like), and methods relati ng thereto. The
present invention provides particu late suspendi ng agents that are usefu l in
subterranean formations that have bottom hole static tem peratu res (BHST) of
150°F or greater, incl udi ng those formations that have a bottom hole static
tem peratu re in excess of about 400°F. Fu rther, the particu late suspend ing
agents may be usefu l in f luids havi ng a pH of about 5 or greater. Thus, the
appl ica bility of the particu late suspend ing agents of the present invention is able
to provide needed particle suspension at a sig nifica ntly hig her tem peratu re
range and a higher pH range than other known particu late suspend ing agents.
[00 13] The particu late suspend ing agents of the present invention are
desig ned to minima lly affect the low-tem peratu re (e.g., ambient tem peratu re)
viscosity of a treatment f luid . Add itiona lly, the particu late suspendi ng agents of
the present invention may be appl ica ble to a wide variety of subterranea n
formations and/or wel lbore treatments where a particu late suspend ing aid is
needed in hig h tem peratu re appl ications, incl uding in cementi ng f luids, spacer
f luids, f lush f luids, and fractu r ing f luids. When used in cementi ng f luids, the
particu late suspendi ng agents may not adversely affect the setti ng t ime of a
hydraulic cement or the f inal strength of the set cement.
[00 14] It shou ld be noted that when "about" is used herei n at the
beg inni ng of a numerica l list, "about" modifies each number of the numerica l list.
It shou ld be noted that in some numerical listi ngs of ranges, some lower limits
listed may be greater than some upper limits listed . One ski lled in the art will
recog nize that the selected subset wil l req uire the selection of an upper limit in
excess of the selected lower limit.
[0015] I n some embodiments, a treatment fluid described herein may
comprise an aqueous liquid, a plurality of particulates, and a particulate
suspending agent that comprises a plurality of crosslinked polymer particulates
that include a polymer that comprises a first monofunctional monomer and
optionally a second monofunctional monomer, the polymer being crosslinked
with an orthoester crosslinker that comprises an orthoester linkage and at least
two crosslinking moieties (e.g., amine and/or vinyl groups). In some
embodiments, the crosslinked polymer particulate may be formed by a reaction
comprising a first monofunctional monomer, an orthoester crosslinker that
comprises an orthoester linkage and crosslinking moieties, and optionally a
second monofunctional monomer. It should be understood that the term
"particulate" as used in this disclosure, includes all known shapes of materials,
including, but not limited to, spherical materials, substantially spherical
materials, low to high aspect ratio materials, fibrous materials, polygonal
materials (such as cubic materials), and mixtures thereof.
[0016] I n some embodiments, when the temperature in the wellbore
exceeds the temperature at which the orthoester crosslinker hydrolyzes, the
crosslinker may hydrolyze thereby enabling the polymer to dissolve in the
treatment fluid, the polymer comprising the first monofunctional monomer and
optionally the second monofunctional monomer. In some embodiments, the
polymer dissolved in the treatment fluid may inhibit settling of a particulate
suspended in the treatment fluid.
[0017] Monofunctional monomers suitable for use in conjunction with
forming crosslinked polymer particulates described herein may, in some
embodiments, be a monomer containing a vinyl or vinylidene group that is
stable in a polymerized and/or crosslinked form at a high temperature, i.e.,
above 150°F. As used herein, "stable" refers to substantially nondegradable on
the timescale of the performance requirement. Suitable monofunctional
monomers may include, but are not limited to, acrylamide, /V-substituted
acrylamides, L/,/V-disubstituted acrylamides, /V-vinylamides, A/-alkyl-/Vvinylamides,
L/,/V-dimethylacrylamide, sodium 2-acrylamido-2-
methylpropanesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, N-
(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide, acrylamide,
methacrylamide, /V-vinylformamide, l-vinyl-2-pyrrolidinone, /V-vinylcaprolactam,
/V-acryloyl morpholine, A/-methyl-/V-vinylacetamide, /V-isopropylacrylamide, N,Ndiethylacrylamide,
/V-vinylacetamide, acrylic acid, sodium 4-styrenesulfonate,
vinylsulfonic acid, and any derivative thereof. It should be noted that, in some
embodiments, a mixture of monofunctional monomers may also be useful in
conjunction with forming crosslinked polymer particulates described herein.
[0018] In some embodiments, a crosslinked polymer particulate
described herein may be formed from a reaction that comprises a first
monofunctional monomer and a second monofunctional monomer. A ratio of first
monofunctional monomer to second monofunctional monomer may, in some
embodiments, be present in the reaction in an amount ranging from a lower limit
of about 0. 1:99.9, 1:99, 5:95, 10:90, 25:75, or 50: 50 to an upper limit of about
99.9:0. 1, 99: 1, 90: 10, 75:25, or 50: 50, and wherein the amount may range
from any lower limit to any upper limit and encompass any subset
therebetween.
[0019] Orthoester crosslinkers suitable for use in conjunction with
forming crosslinked polymer particulates described herein may, in some
embodiments, comprise an orthoester linkage and at least two crosslinking
moieties (e.g., amine or vinyl groups). Examples of orthoester crosslinkers
include, but are not limited to, 2-(5-amino-l,3-dioxan-2-yloxy)triethoxy-l,3-
dioxan-5-ylamine, divinyl ethyl orthoacetate, and any derivative thereof.
[0020] In some embodiments, orthoester crosslinkers suitable for use in
conjunction with forming crosslinked polymer particulates described herein may
be hydrolytically stable at ambient temperatures and hydrolytically unstable at
high temperatures, i.e., above 150°F, on the timescale of the well treatment. As
used herein, "hydrolytically stable," and any derivative thereof, indicates stable
against hydrolysis. In some embodiments, orthoester crosslinkers suitable for
use in conjunction with forming crosslinked polymer particulates described
herein may hydrolyze at temperatures ranging from a lower limit of about
100°F, 150°F, 175°F, or 200°F to an upper limit of about 250°F or 225°F, and
wherein the temperature may range from any lower limit to any upper limit and
encompass any subset therebetween.
[0021] In some embodiments, orthoester crosslinkers suitable for use in
conjunction with forming crosslinked polymer particulates described herein may
be hydrolytically unstable on the timescale of the well treatment at elevated
temperatures in conjunction with a pH greater than about 5. In some
embodiments, orthoester crosslinkers suitable for use in conjunction with
forming crosslinked polymer particulates described herein may be chosen to
hydrolyze rapidly, e.g., at temperatures greater than about 150°F in conjunction
with a pH value ranging from a lower limit of about 5 to an upper limit of about
8, including any subset therebetween. For example, in some embodiments, rapid
hydrolysis may be advantageous in treatment fluids like spacers.
[0022] In some embodiments, orthoester crosslinkers suitable for use in
conjunction with forming crosslinked polymer particulates described herein may
be chosen to hydrolyze slowly, e.g., at temperatures greater than about 150°F
in conjunction with a pH value greater than about 8. For example, in some
embodiments, slow hydrolysis may be advantageous in treatment fluids like
drilling fluids and fracturing fluids.
[0023] I n some embodiments, the pH value of the treatment fluid may
be intentional or as a consequence of the additives therein (e.g., weighting
agents described herein).
[0024] In some embodiments, orthoester crosslinkers described herein
may be present in the reaction to form a crosslinked polymer particulate in an
amount ranging from a lower limit of about 0.1%, 0.5%, 1%, 5%, or 10% by
weight of total monomer to an upper limit of about 20%, 15%, 10%, 5%, or 1%
by weight of total monomer, and wherein the amount may range from any lower
limit to any upper limit and encompass any subset therebetween.
[0025] I n some embodiments, the particulate suspending agents may
be used in a treatment fluid comprising a particulate, wherein the particulate
needs to be maintained in suspension at temperatures greater than about
150°F, 175°F, 200°F, 225°F, 275°F, 300°F, 325°F, 350°F, 400°F, or 450°F.
[0026] Particulates suitable for use in conjunction with the particulate
suspending agents of the present invention may, in some embodiments, be any
particulate suitable for use in a subterranean formation including, but not limited
to, hydraulic cement, weighting agents, proppants, fine aggregate particulates,
hollow glass spheres, and the like, and any combination thereof.
[0027] Particulates suitable for use in conjunction with the particulate
suspending agents of the present invention may, in some embodiments, have a
diameter ranging from a lower limit of about 0.5 miti , 1 miti , 10 miti , 50 miti , 0.1
mm, or 1 mm to an upper limit of about 10 mm, 1 mm, 0.5 mm, 0.1 mm, or 50
miti , and wherein the diameter may range from any lower limit to any upper limit
and encompass any subset therebetween.
[0028] Pa rticu lates suita ble for use in conj unction with the particu late
suspend ing agents of the present invention may, in some embodi ments, be
present in a treatment f luid in an amount rangi ng from a lower limit of about
10%, 20%, 30%, 40%, or 50% by weig ht of treatment f luid to an upper limit of
about 90%, 80%, 70%, 60%, 50%, or 40% by weig ht of treatment f luid, and
wherei n the amou nt may range from any lower limit to any upper limit and
encom pass any subset therebetween .
[0029] The terms "cement" and " hydrau lic cement" may be used
intercha ngea bly in t his appl ication . As used herei n, the terms refer to
compou nds and/or particu lates of a cementitious natu re that set and/or harden
in the presence of water. Hyd raulic cements suita ble for use in conj unction with
the particu late suspend ing agents of the present invention may, in some
embod iments, be any known hydraulic cement incl uding, but not limited to,
Portla nd cements (e.g., API classes A, B, C, G, and H), slag cements, pozzolana
cements, gypsum cements, aluminous cements, silica cements, hig h alkal inity
cements, and the like, and any combination thereof. I n some embod iments, a
cementi ng f luid may comprise an aqueous liq uid, a hydraulic cement, and a
particu late suspend ing agent.
[0030] Weighti ng agents suita ble for use in conj unction with the
particu late suspend ing agents of the present invention may, in some
embod iments, be any known weig hti ng agent that is a particu late includi ng, but
not limited to, barite, hematite, manganese tetraoxide, galena, silica, siderite,
celestite, ilmenite, dolom ite, calci um carbonate, and the like, and any
combination thereof.
[003 1] Proppants suitable for use in conju nction with the particu late
suspendi ng agents of the present invention may, in some embodi ments, be any
known proppa nt incl uding, but not limited to, sand, bauxite, ceramic materia ls,
glass materia ls, polymer materia ls, polytetrafl uoroethylene materia ls, nut shel l
pieces, cured resinous particu lates comprisi ng nut shel l pieces, seed shel l pieces,
cured resi nous particu lates comprisi ng seed shel l pieces, fru it pit pieces, cured
resi nous particu lates comprisi ng fru it pit pieces, wood, composite particu lates,
and the like, and any combination thereof. Suita ble composite particu lates may
comprise a binder and a fil ler material wherein suita ble f iller materia ls incl ude
silica, alumina, fumed carbon, carbon black, graphite, mica, tita nium dioxide,
meta-si licate, calci um silicate, kaoli n, talc, zircon ia, boron, fly ash, hol low glass
microspheres, sol id glass, and the like, and any combination thereof.
[0032] Fine agg regate particu lates suita ble for use in conju nction with
the particu late suspend ing agents of the present invention may, in some
embod iments, incl ude, but are not limited to, fly ash, silica flou r, f ine sand,
diatomaceous earth, lig htweig ht agg regates, hol low spheres, and the like, and
any combination thereof.
[0033] Aqueous f luids suita ble for use in conj unction with the
particu late suspend ing agents of the present invention may, in some
embod iments, comprise fresh water, saltwater (e.g., water contai ning one or
more salts dissolved therei n), brine (e.g., satu rated salt water), seawater, and
any combination thereof. Genera lly, the water may be from any sou rce, provided
that it does not conta in components that might adversely affect the stabi lity
and/or performance of the compositions or methods of the present invention .
[0034] In some embodi ments, treatment flu ids comprisi ng particu late
suspendi ng agents of the present invention may have a pH of about 5 or
greater. In some embod iments, treatment f luids comprisi ng particu late
suspend ing agents of the present invention may have a pH ranging from a lower
limit of about 5, 6, 7, or 8 to an upper limit of about 12, 10, or 8, and wherei n
the pH value may range from any lower limit to any upper limit and encom pass
any subset therebetween .
[0035] Treatment f luids descri bed herei n may, in some embod iments,
incl ude, but are not limited to, cementi ng f luids, spacer f luids, dr illing f luids,
fractu r ing f luids, lost circu lation f luids, and kill pills. As referred to herei n, the
term "spacer f luid" shou ld be understood to mean a flu id placed withi n a
wel lbore to sepa rate f luids, e.g., to separate a dri lling f luid with in the wel lbore
from a cementing f luid that will subseq uently be placed withi n the wel lbore. As
used herei n, the term " kill pill" refers to a pill that when implemented prevents
the infl ux of formation f luids into the wel lbore and the loss of well bore f luids to
the formation whi le the wel l is open . As used herei n, a " pill" is a type of
relatively small vol ume of specia lly prepa red treatment f luid placed or circu lated
in the wel lbore.
[0036] I n some embod iments, a particu late suspend ing agent may be
incl uded in a f irst f luid that is placed in a wel lbore and/or subterra nea n
formation before and/or after a second f luid, wherei n the second f luid comprises
a plural ity of particu lates and the particu late suspend ing agent. In some
embod iments, the concentration of particu late suspend ing agent may be
different in a f irst f luid tha n in a second f luid . In some embodi ments, the f irst
f luid may be a spacer f luid and the second f luid may be a treatment f luid .
[0037] The teachi ngs of the present invention and the methods and
compositions of the present invention may be used in many different types of
subterranea n treatment operations. Such operations incl ude, but are not limited
to, casi ng operations, plugg ing operations, dr illing operations, lost circu lation
operations, completion operations, and water- blocki ng operations. I n some
embod iments, the suspend ing aid of the present invention may be used as a
secondary gel ling agent in a high-tem peratu re fractu r ing treatment. The
methods and compositions of the present invention may be used in la rge-sca le
operations or pills.
[0038] By way of nonl imiti ng example, a spacer f luid may, in some
embod iments, comprise a base f luid, a plurality of particu lates (e.g., weig hti ng
agents), and a particu late suspend ing agent descri bed herei n. Some
embod iments may involve introd uci ng the spacer f luid into a wel lbore between
two other f luids (e.g., between a cement slurry and a dr ill ing f luid) . Some
embod iments may further involve allowi ng the cement slurry to set withi n at
least a portion of the wel lbore. Usi ng the particu late suspend ing agent may, in
some embod iments, advantageously mitigate particu late settl ing from the spacer
flu id, which in turn may mitigate density cha nges in the spacer f luid that cou ld
lead to mixing of the spacer f luid with two other flu ids.
[0039] By way of another non limiti ng exam ple, a dr illing f luid may, in
some embod iments, comprise a base f luid, a plurality of particu lates (e.g.,
weig hti ng agents), and a particu late suspend ing agent described herei n. Some
embod iments may involve dr illing at least a portion of a wel lbore penetrati ng a
subterranea n formation with the dr illing f luid . Usi ng the particu late suspend ing
agent may, in some embod iments, advantageously mitigate particu late settl ing
from the dr illing f luid .
[0040] By way of yet another non limiti ng example, a fractu r ing f luid
may, in some embodi ments, comprise a base f luid, a plural ity of particu lates
(e.g., weig hti ng agents and/or proppant particles), and a particu late suspend ing
agent descri bed herei n. Some embodi ments may involve introd uci ng the
fractu r ing f luid into a wel lbore penetrati ng a subterra nea n formation at a
pressure sufficient to create or extend at least one fracture in the subterranean
formation. Using the particulate suspending agent may, in some embodiments,
advantageously mitigate particulate settling from the fracturing fluid, which may
enable a more uniform proppant placement operation.
[0041] I n some embodiments, a particulate suspending agent may be
used in a wellbore and/or subterranean formation with a bottom hole static
temperature (BHST) ranging from a lower limit of about 150°F, 175°F, 200°F,
225°F, 275°F, 300°F, 325°F, 350°F, or 400°F to an upper limit of about 500°F,
450°F, or 400°F, and wherein the temperature may range from any lower limit
to any upper limit and encompass any subset between the upper and lower
limits.
[0042] It should be understood that the compositions and methods
provided herein are applicable to wellbores at any angle including, but not
limited to, vertical wells, deviated wells, highly deviated wells, horizontal wells,
and hybrid wells comprising sections of any combination of the aforementioned
wells. As used herein, the term "deviated wellbore" refers to a wellbore or
portion thereof that is oriented between about 55-degrees and about 125-
degrees from a vertical inclination. As used herein, the term "highly deviated
wellbore" refers to a wellbore or portion thereof that is oriented between about
75-degrees and about 105-degrees off-vertical. In some embodiments, a
particulate suspending agent may be advantageously used in a wellbore that is
deviated or highly deviated so as to minimize particulate settling along the
cross-section of the wellbore.
[0043] In some embodiments, a particulate suspending agent of the
present invention may be provided in wet or dry form. In some embodiments, a
particulate suspending agent of the present invention may be added to a
treatment fluid on-site or off-site of the wellbore location.
[0044] I n some embodiments, crosslinked polymer particulates of a
particulate suspending agent of the present invention may be produced by
providing an oil solution comprising an oil-based solvent and a surfactant;
providing a monomer mixture comprising an aqueous liquid and the monomers
and the crosslinkers needed for a desired crosslinked polymer particulate;
forming an inverse suspension with the monomer mixture and the oil solution;
and reacting a free-radical initiator with the monomer mixture in the inverse
suspension to form a crosslinked polymer particulate. Without being limited by
theory or mechan ism, it is bel ieved that as a crossl inked polymer forms in the
inverse suspension, it generates crossl inked polymer particu lates. In some
embod iments, a crossl inked polymer particu late may be isolated by a method
incl uding, but not limited to, dryi ng either by water-m isci ble solvent extraction
or azeotropic disti llation ; fol lowed by f iltration or centrifugation to remove the
oil- based solvent. Alternatively, the crossl inked polymer particu late may be
isolated from the oil-based solvent before dryi ng with air. One ski lled in the art,
with the benefit of t his disclosu re, will recog nize suitable proced ural variations,
incl udi ng order of add ition, to achieve the desi red crossl inked polymer
particu late. For exam ple, when reacti ng the free rad ica l initiator with the
monomer mixtu re, the free rad ica l initiator may be added to the monomer
mixtu re shortly before form ing the inverse emulsion, to the oil sol ution before
form ing the inverse suspension, to the inverse suspension, or any combination
thereof.
[0045] I n some embod iments, crossl inked polymer particu lates of a
particu late suspend ing agent of the present invention may be prod uced by
provid ing an oil sol ution comprisi ng an oil- based solvent and a surfacta nt;
provid ing a monomer mixtu re comprisi ng an aqueous liqu id and the monomers
for a desi red polymer of the crossl inked polymer particu late; form ing an inverse
suspension with the monomer mixtu re and the oil sol ution ; and reacti ng a freerad
ica l initiator with the monomer mixtu re in the inverse suspension to form
polymer particu lates. The polymer particu lates may extracted (or isolated) by a
method incl udi ng, but not limited to, dryi ng either by water-m isci ble solvent
extraction or azeotropic disti llation ; fol lowed by f iltration or centrifugation to
remove the oil-based solvent. Alternatively, the polymer particu lates may be
isolated from the oil- based solvent before dryi ng with air. The isolated polymer
particu lates may then be contacted with a sol ution that comprises an orthoester
crossl inker descri bed herei n and is substa ntia lly free of water. The orthoester
crossl inker may diffuse into the polymer and crossl ink the polymer so as to yield
crossli nked polymer particu lates that are, in some embod iments, suita ble for use
in particu late suspend ing agents of the present invention . For example, an
acryl ic acid copolymer particu late may be prod uced and then treated with an
orthoester crossli nker (e.g., 2- (5-a mino- l,3-d ioxan-2-yloxy)triethoxy- l,3-
dioxan- 5-yla mine) that absorbs into the particu late and crossli nks the acryl ic
acid copolymer.
[0046] Suitable oil-based solvents may include, but are not limited to,
paraffinic hydrocarbons, aromatic hydrocarbons, olefinic hydrocarbons,
petroleum distillates, synthetic hydrocarbons, and any combination thereof.
Examples of a suitable oil-based solvent include ESCAID® (a low viscosity
organic solvent, available from ExxonMobil, Houston, TX). Suitable surfactants
may include, but are not limited to, a HYPERMER® (a nonionic, polymeric
surfactant, available from Croda, Edison, NJ), block copolymers of ethylene
oxide and propylene oxide, block copolymers of butylene oxide and ethylene
oxide, sorbitan esters, copolymers of methacrylic acid and C12-C18 alkyl
methacrylates, alkylarylsulfonate salts, and any combination thereof. Suitable
free radical initiators may be any water-soluble free radical initiator including,
but not limited to, persulfate salts, organic peroxides, organic hydroperoxides,
azo compounds (e.g., 2,2'-azobis(2-amidinopropane) dihydrochloride), and any
combination thereof. One skilled in the art with the benefit of this disclosure will
recognize the plurality of applicable oil-based solvents, surfactants, and free
radical initiators and the appropriate concentrations of each needed for
producing a crosslinked polymer particulate.
[0047] The exemplary particulate suspending agents disclosed herein
may directly or indirectly affect one or more components or pieces of equipment
associated with the preparation, delivery, recapture, recycling, reuse, and/or
disposal of the disclosed particulate suspending agents. For example, the
disclosed particulate suspending agents may directly or indirectly affect one or
more mixers, related mixing equipment, mud pits, storage facilities or units,
fluid separators, heat exchangers, sensors, gauges, pumps, compressors, and
the like used generate, store, monitor, regulate, and/or recondition the
exemplary particulate suspending agents. The disclosed particulate suspending
agents may also directly or indirectly affect any transport or delivery equipment
used to convey the particulate suspending agents to a well site or downhole such
as, for example, any transport vessels, conduits, pipelines, trucks, tubulars,
and/or pipes used to fluidically move the particulate suspending agents from one
location to another, any pumps, compressors, or motors (e.g., topside or
downhole) used to drive the particulate suspending agents into motion, any
valves or related joints used to regulate the pressure or flow rate of the
particulate suspending agents, and any sensors (i.e., pressure and
temperature), gauges, and/or combinations thereof, and the like. The disclosed
particulate suspending agents may also directly or indirectly affect the various
downhole equipment and tools that may come into contact with the
chemicals/fluids such as, but not limited to, drill string, coiled tubing, drill pipe,
drill collars, mud motors, downhole motors and/or pumps, floats, MWD/LWD
tools and related telemetry equipment, drill bits (including roller cone, PDC,
natural diamond, hole openers, reamers, and coring bits), sensors or distributed
sensors, downhole heat exchangers, valves and corresponding actuation devices,
tool seals, packers and other wellbore isolation devices or components, and the
like.
[0048] Some embodiments disclosed herein include
[0049] A. A method comprising: providing a treatment fluid comprising
an aqueous liquid, a plurality of particulates, and a particulate suspending agent,
wherein the particulate suspending agent comprises a crosslinked polymer
particulate formed by a reaction comprising a first monofunctional monomer and
an orthoester crosslinker, the orthoester crosslinker comprising an orthoester
linkage and at least two crosslinking moieties; and placing the treatment fluid in
a wellbore penetrating a subterranean formation.
[0050] Embodiment A may have one or more of the following additional
elements in any combination:
[0051] Element 1: The embodiment A wherein the treatment fluid is a
spacer fluid.
[0052] Element 2 : The embodiment A wherein the treatment fluid has
a pH between about 5 and about 8.
[0053] Element 3 : The embodiment A wherein the treatment fluid has
a pH of about 8 or greater.
[0054] Element 4 : The embodiment A wherein the plurality of
particulates comprise at least one selected from the group consisting of a
hydraulic cement, a weighting agent, a proppant, a fine aggregate particulate,
and any combination thereof.
[0055] Element 5 : The embodiment A wherein the subterranean
formation is about 150°F to about 500°F.
[0056] Element 6 : The embodiment A wherein the crosslinked polymer
particulate begins to degrade and dissolve above about 150°F.
[0057] Element 7 : The embodiment A wherein the first monofunctional
monomer comprises a monomer selected from the group consisting of
acrylamide, an N-substituted acrylamide, an N,N-disubstituted acrylamide, an Nvinylamide,
an N-alkyl-N-vinylamide, N,N-dimethylacrylamide, sodium 2-
acrylamido-2-methylpropanesulfonate, 2-acrylamido-2-methylpropanesulfonic
acid, N-(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide,
methacrylamide, N-vinylformamide, l-vinyl-2-pyrrolidinone, N-vinylcaprolactam,
N-acryloyl morpholine, N-methyl-N-vinylacetamide, N-isopropylacrylamide, N,Ndiethylacrylamide,
N-vinylacetamide, acrylic acid, sodium 4-styrenesulfonate,
vinylsulfonic acid, and any derivative thereof.
[0058] Element 8 : The embodiment A wherein the orthoester
crosslinker is present in the reaction at about 0.1% to about 20% by weight of
total monomer.
[0059] Element 9 : The embodiment A wherein the reaction further
comprises a second monofunctional monomer, wherein the second
monofunctional monomer and the first monofunctional monomer are different.
[0060] Element 10: The embodiment A wherein the weight ratio of the
first monofunctional monomer to the second monofunctional monomer in the
reaction ranges from about 0.1:99.9 to about 99.9:0. 1
[0061] Other embodiments disclosed herein include
[0062] B. treatment fluid comprising: an aqueous fluid, a plurality of
particulates, and a particulate suspending agent comprising a crosslinked
polymer particulate, wherein the crosslinked polymer particulate is produced
from a reaction comprising: a first monofunctional monomer, and an orthoester
crosslinker that comprises an orthoester linkage and at least two crosslinking
moieties.
[0063] Embodiment B may have one or more of the following additional
elements in any combination:
[0064] Element 1: The embodiment B wherein the plurality of
particulates comprise at least one selected from the group consisting of a
hydraulic cement, a weighting agent, a proppant, a fine aggregate particulate,
and any combination thereof.
[0065] The treatment fluid of claim 12, wherein the reaction further
comprises a second monofunctional monomer, wherein the first monofunctional
monomer and the second monofunctional monomer are different.
[0066] The treatment fluid of claim 12, wherein the treatment fluid has
a pH between about 5 and about 8.
[0067] Still other embodiments disclosed herein include
[0068] C. A method comprising: providing a treatment fluid comprising
an aqueous liquid, a plurality of particulates, and a particulate suspending agent,
wherein the particulate suspending agent comprises a crosslinked polymer
particulate that comprises a polymer crosslinked with an orthoester crosslinker
that comprises an orthoester linkage and at least two crosslinking moieties;
placing the treatment fluid in a wellbore penetrating a subterranean formation
with a bottom hole static temperature of about 150°F or greater; and allowing
the orthoester linkage to degrade thereby allowing at least some of the polymer
to dissolve and suspend the particulates.
[0069] Embodiment C may have one or more of the following additional
elements in any combination:
[0070] Element 1: The embodiment C wherein the treatment fluid is
selected from the group consisting of a cement slurry, a flush fluid, a spacer
fluid, and a fracturing fluid.
[0071] Element 2 : The embodiment C wherein the polymer comprises
a first monofunctional monomer that comprises a monomer selected from the
group consisting of acrylamide, an N-substituted acrylamide, an N,Ndisubstituted
acrylamide, an N-vinylamide, an N-alkyl-N-vinylamide, N,Ndimethylacrylamide,
sodium 2-acrylamido-2-methylpropanesulfonate, 2-
acrylamido-2-methylpropanesulfonic acid, N-(hydroxymethyl)acrylamide, N-
(hydroxyethyl)acrylamide, methacrylamide, N-vinylformamide, l-vinyl-2-
pyrrolidinone, N-vinylcaprolactam, N-acryloyl morpholine, N-methyl-Nvinylacetamide,
N-isopropylacrylamide, N,N-diethylacrylamide, Nvinylacetamide,
acrylic acid, sodium 4-styrenesulfonate, vinylsulfonic acid, and
any derivative thereof.
[0072] Element 3 : The embodiment C wherein the treatment fluid has
a pH between about 5 and about 8.
[0073] Element 4 : The embodiment C wherein the treatment fluid has
a pH of about 8 or greater.
[0074] Element 5 : The embodiment C wherein the subterranean
formation is about 150°F to about 500°F.
[0075] Element 6 : The embodiment C wherein the orthoester
crosslinker is present in the reaction at about 0.1% to about 20% by weight of
total monomer.
[0076] 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, combined, or modified and all such variations are considered within the
scope and spirit of the present invention. The invention illustratively disclosed
herein suitably may be practiced in the absence of any element that is not
specifically disclosed herein and/or any optional element disclosed herein. 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. I n
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.
CLAIMS
The invention claimed is:
1. A method comprising:
providing a treatment fluid comprising an aqueous liquid, a plurality
of particulates, and a particulate suspending agent, wherein the particulate
suspending agent comprises a crosslinked polymer particulate formed by a
reaction comprising a first monofunctional monomer and an orthoester
crosslinker, the orthoester crosslinker comprising an orthoester linkage and at
least two crosslinking moieties; and
placing the treatment fluid in a wellbore penetrating a subterranean
formation.
2. The method of claim 1, wherein the treatment fluid is a spacer fluid.
3. The method of claim 1, wherein the treatment fluid has a pH
between about 5 and about 8.
4. The method of claim 1, wherein the treatment fluid has a pH of
about 8 or greater.
5. The method of claim 1, wherein the plurality of particulates
comprise at least one selected from the group consisting of a hydraulic cement,
a weighting agent, a proppant, a fine aggregate particulate, and any
combination thereof.
6. The method of claim 1, wherein the subterranean formation is
about 150°F to about 500°F.
7. The method of claim 1, wherein the crosslinked polymer particulate
begins to degrade and dissolve above about 150°F.
8. The method of claim 1, wherein the first monofunctional monomer
comprises a monomer selected from the group consisting of acrylamide, an Nsubstituted
acrylamide, an L/,/V-disubstituted acrylamide, an /V-vinylamide, an Nalkyl-/
V-vinylamide, L/,/V-dimethylacrylamide, sodium 2-acrylamido-2-
methylpropanesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, N-
(hydroxymethyl)acrylamide, N-(hydroxyethyl)acrylamide, methacrylamide, Nvinylformamide,
l-vinyl-2-pyrrolidinone, /V-vinylcaprolactam, /V-acryloyl
morpholine, A/-methyl-/V-vinylacetamide, /V-isopropylacrylamide, N,Ndiethylacrylamide,
/V-vinylacetamide, acrylic acid, sodium 4-styrenesulfonate,
vinylsulfonic acid, and any derivative thereof.
9. The method of claim 1, wherein the orthoester crosslinker is
present in the reaction at about 0.1% to about 20% by weight of total monomer.
10. The method of claim 1, wherein the reaction further comprises a
second monofunctional monomer, wherein the second monofunctional monomer
and the first monofunctional monomer are different.
11. The method of claim 10, wherein the weight ratio of the first
monofunctional monomer to the second monofunctional monomer in the reaction
ranges from about 0.1:99.9 to about 99.9:0.1.
12. A treatment fluid comprising:
an aqueous fluid,
a plurality of particulates, and
a particulate suspending agent comprising a crosslinked polymer
particulate, wherein the crosslinked polymer particulate is produced from a
reaction comprising:
a first monofunctional monomer, and
an orthoester crosslinker that comprises an orthoester
linkage and at least two crosslinking moieties.
13. The treatment fluid of claim 12, wherein the plurality of particulates
comprise at least one selected from the group consisting of a hydraulic cement,
a weighting agent, a proppant, a fine aggregate particulate, and any
combination thereof.
14. The treatment fluid of claim 12, wherein the reaction further
comprises a second monofunctional monomer, wherein the first monofunctional
monomer and the second monofunctional monomer are different.
15. The treatment fluid of claim 12, wherein the treatment fluid has a
pH between about 5 and about 8.
16. A method comprising:
providing a treatment fluid comprising an aqueous liquid, a plurality
of particulates, and a particulate suspending agent, wherein the particulate
suspending agent comprises a crosslinked polymer particulate that comprises a
polymer crosslinked with an orthoester crosslinker that comprises an orthoester
linkage and at least two crosslinking moieties;
placing the treatment fluid in a wellbore penetrating a subterranean
formation with a bottom hole static temperature of about 150°F or greater; and
allowing the orthoester linkage to degrade thereby allowing at least
some of the polymer to dissolve and suspend the particulates.
17. The method of claim 16, wherein the treatment fluid is selected
from the group consisting of a cement slurry, a flush fluid, a spacer fluid, and a
fracturing fluid.
18. The method of claim 16, wherein the polymer comprises a first
monofunctional monomer that comprises a monomer selected from the group
consisting of acrylamide, an /V-substituted acrylamide, an L/,/V-disubstituted
acrylamide, an /V-vinylamide, an /V-alkyl-/V-vinylamide, L/,/V-dimethylacrylamide,
sodium 2-acrylamido-2-methylpropanesulfonate, 2-acrylamido-2-
methylpropanesulfonic acid, /V-(hydroxymethyl)acrylamide, N-
(hydroxyethyl)acrylamide, methacrylamide, /V-vinylformamide, l-vinyl-2-
pyrrolidinone, /V-vinylcaprolactam, /V-acryloyl morpholine, /V-methyl-/Vvinylacetamide,
/V-isopropylacrylamide, L/,/V-diethylacrylamide, Nvinylacetamide,
acrylic acid, sodium 4-styrenesulfonate, vinylsulfonic acid, and
any derivative thereof.
19. The method of claim 16, wherein the treatment fluid has a pH
between about 5 and about 8.
20. A method of producing a particulate suspending agent, the method
comprising:
providing an oil solution comprising an oil-based solvent and a
surfactant;
providing a monomer mixture comprising an aqueous liquid and a
first monofunctional monomer;
forming an inverse suspension with the monomer mixture and the
oil solution;
reacting the monomer mixture in the inverse suspension with a
free-radical initiator to form a polymer particulate;
isolating the polymer particulate; and
diffusing an orthoester crosslinker into the polymer particulate so as
to form a crosslinked polymer particulate.