1 :
I FIELD OF INVENTION
This invention relates to boronated biopolymer crosslinking agents and C
methods relating thereto wherein said boronated biopolymer crosslinking agents
are for use in viscosifying treatment fluids.
BACKGROUND TECHNICAL INFORMATION
Viscosified treatment fluids are used in many subterranean operations. For
example, in fracturing and gravel packing operations, viscosified treatment fluids
may be used to suspend and transport particulates to a desired location in a
wellbore penetrating the subterranean formation and/or the subterranean
formation, so as to form a particulate pack therein (e.g., a proppant pack or a
gravel pack).In other instances, viscosified treatment fluids may act to transfer
hydraulic pressure in a fracturing operation or to prevent undesired leak-off of
fluids into the subterranean formation in a variety of subterranean operations. In
many instances, during or after the operation the viscosified treatment fluid is
broken (Le., treated to reduce the viscosity of the treatment fluid) so that the
fluid may be more effectively and efficiently removed from the wellbore or
formation.
In many instances, viscosified treatment fluids include a base polymer
compound that is crosslinked with a crosslinking agent. Common crosslinking
agents include metals like boron, aluminum, zirconium, and titanium. However,
zirconium and titanium-containing crosslinking agents are used to a lesser
degree because of their cost and their crosslinking strength makes the
crosslinked fluids difficult to break. Boron-containing crosslinking agents, on the
other hand, are more widely available. However, viscosified fluids using boroncontaining
crosslinking agents are more susceptible to shear thinning wherein
the viscosity of the treatment fluid reduces when the fluid is placed under shear.
Reduced viscosity can lead to particulate settling in undesired locations, a
depressed maximum hydraulic pressure transfer capability, fluids leaking-off into
the formation, and the like. To overcome this propensity, boron crosslinking
agents typically are added in excess of the stoichiometric amount required to
crosslink the treatment fluids, which may increase the environmental footprint s
and the costs associated with the treatment fluid.
SUMMARY OF THE INVENTION
The present invention relates to boronated biopolymer crosslinking agents
for use in viscosiving treatment fluids and methods relating thereto.
One embodiment of the present invention provides for a method that
includes introducing a viscosified treatment fluid into a wellbore penetrating a
subterranean formation, the viscosified treatment fluid comprising an aqueous
fluid, a base polymer, and a boronated biopolymer crosslinking agent, wherein
the boronated biopolymer crosslinking agent comprises a biopolymer derivatized
with a boronic acid, a boronate ester, or both.
Another embodiment of the present invention provides for a method that
includes introducing a first treatment fluid into a wellbore penetrating a
subterranean formation at a pressure sufficient to create or extend at least one
fracture in the subterranean formation; and forming a particulate pack in the
fracture with a second treatment fluid that comprises an aqueous fluid, a base
polymer, a boronated biopolymer crosslinking agent, and a plurality of
particulates, wherein the boronated biopolymer crosslinking agent comprises a
biopolymer derivatized with a boronic acid, a boronate ester, or both.
Yet another embodiment of the present invention provides for a
viscosified treatment fluid that includes an aqueous fluid, a base polymer, and a
boronated biopolymer crosslinking agent, wherein the boronated biopolymer
crosslinking agent comprises a biopolymer derivatized with a boronic acid, a
boronate ester, or both.
BRIEF DESCRIPTION OF THE DRAWINGS
The following figures are included to illustrate certain aspects of the
present invention, and should not be viewed as exclusive embodiments. The
subject matter disclosed is capable of considerable modifications, alterations,
combinations, and equivalents in form and function, as will occur to those skilled
in the art and having the benefit of this disclosure.
Figure 1: shows a viscosity profile of viscosified treatment fluids
described herein and a control treatment fluid.
Figure 2: shows a viscosity profile of control treatment fluids utilizing
traditional boron-containing crosslinking agents.
Figure 3: shows an illustrative schematic of a system that can deliver
treatment fluids of the present invention to a downhole location.
The features and advantages of the present invention will be readily
apparent to those skilled in the art upon a reading of the description of the
preferred embodiments that follows.
DESCRIPTION OF INVENTION w.r.t. DRAWINGS
The present invention relates to boronated biopolymer crosslinking agents
for use in viscosifying treatment fluids and methods relating thereto.
As used herein, the terms "boronated biopolymer crosslinking agents"
(referred to herein as "BB crosslinking agents")refer to crosslinking agents that
comprise a biopolymer derivatized with (1) a boronic acid,(2) a boronate ester,
or (3) both, examples of which are provided herein. As used herein, the term
"biopolymer" refers to a polymer produced in a living organism (e.g., a plant or a
microorganism such as bacteria) or a derivative thereof (including a biopolymer
having been synthetically derivatized).
The BB crosslinking agents described herein advantageously have
polymeric molecules containing multiple boron-containing groups available for
crosslinking a base polymer, which may reduce shear thinning of the viscosified
treatment fluid, thereby yield a more effective treatment fluid. Further, because
the BB crosslinking agents described herein are based on biopolymers, the BB
cross1 inking agents may be readily degraded (e.g., with acids), thereby allowing
for a straight-forward avenue for breaking the viscosified treatment fluid.
Therefore, the viscosified treatment fluids described herein may have
enhanced stability under shear and still be readily broken.
Additionally, the use of a polymeric crosslinking agent provides for more
sites of crosslinking in a single crosslinking agent molecule, which, in turn, may
allow for achieving the same level of viscosification with less of the base polymer
and the BB crosslinking agents, which reduces costs. This may be especially
advantageous in systems where the base polymer has become less available
and/or more costly (e.g., guar) and the BB crosslinking agent is derived from a
readily available biopolymer (e.g., cellulose or a cellulose derivative).Such a
system may synergistically reduce costs while enhancing performance of the
viscosified treatment fluid.
It should be noted that when "about" is provided herein at the beginning
of a numerical list, "about" modifies each number of the numerical list. It should
be noted that in some numerical listings of ranges, some lower limits listed may
be greater than some upper limits listed. One skilled in the art will recognize that
the selected subset will require the selection of an upper limit in excess of the
selected lower limit.
In some embodiments, a viscosified treatment fluid described herein may
comprise an aqueous fluid, a base polymer, and a BB crosslinking agent that
itself comprises a biopolymer derivatized with a boronic acid, a boronate ester, or
both. As used herein, the term "derivatized" or grammatical equivalents thereof
encompasses both covalent bonding, ionic interactions, and other suitable atomic
interactions as would be apparent to one of ordinary skill in the art.
Suitable aqueous fluids may comprise fresh water, saltwater (e.g., water
containing one or more salts dissolved therein), brine (e.g., saturated salt
water), seawater, and 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 BB crosslinking agent or
viscosified treatment fluid. In certain embodiments; the density of the aqueous
fluid can be adjusted, among other purposes, to provide additional particulate
transport and suspension in the viscosified treatment fluids used in the methods
of the present invention. In some embodiments, the pH range of the aqueous
fluid may preferably be from about 4 to about 1l.One of ordinary skill in the art,
with the benefit of this disclosure, will recognize when density and/or pH
adjustments are appropriate.
In some instances, the aqueous fluid may further comprise an aqueousmiscible
fluid. Suitable aqueous-miscible fluids may, in some embodiments,
include, but not be limited to, alcohols (e.g., methanol, ethanol, n-propanol,
isopropanol, n-butanol, sec-butanol, isobutanol, and t-butanol), glycerins, glycols
(e.g., polyglycols, propylene glycol, and ethylene glycol), polyglycol amines,
polyols, any derivative thereof, any in combination with salts (e.g., sodium
chloride, calcium chloride, calcium bromide, zinc bromide, potassium carbonate,
sodium formate, potassium formate, cesium formate, sodium acetate, potassium
acetate, calcium acetate, ammonium acetate, ammonium chloride, ammonium
bromide, sodium nitrate, potassium nitrate, ammonium nitrate, ammonium
sulfate, calcium nitrate, sodium carbonate, and potassium carbonate), and any
combination thereof.
In some instances, the aqueous fluid (optionally comprising an aqueousmiscible
fluid) may be a portion of an emulsion having an aqueous continuous
phase and an oleaginous discontinuous phase or invert emulsion having an
oleaginous continuous phase and an aqueous discontinuous phase, wherein the
base polymer and BB crosslinking agent are within the aqueous phase. A suitable
oleaginous phase may include any oleaginous continuous phase fluid suitable for
use in subterranean operations. By way of non-limiting example, an oleaginous
phase may include an alkane, an olefin, an aromatic organic compound, a cyclic
alkane, a paraffin, a diesel fluid, a mineral oil, a desulfurized hydrogenated
kerosene, and any combination thereof. Suitable invert emulsions may have an
oil-to-water ratio from a lower limit of greater than about 50:50, 55:45, 60:40,
65:35, 70:30, 75:25, or 80:20 to an upper limit of less than about 100:0, 95:5,
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90:10, 85:15, 80:20, 75:25, 70:30, or 65:35 by volume in the treatment fluid,
where the amount may range from any lower limit to any upper limit and
encompass any subset there between. Examples of suitable invert emulsions
include those disclosed in U.S. Patent Numbers 5,905,061 entitled "Invert
Emulsion Fluids Suitable for Drilling" filed on May 23, 1997, 5,977,031 entitled
"Ester Based Invert Emulsion Drilling Fluids and Muds Having Negative Alkalinity"
filed on August 8, 1998, 6,828,279 entitled 'Biodegradable Surfactant for Invert
Emulsion Drilling Fluid" filed on August 10, 2001, 7,534,745 entitled 'Gelled
Invert Emulsion Compositions Comprising Polyvalent Metal Salts of an
Organophosphonic Acid Ester or an Organophosphinic Acid and Methods of Use
and Manufacture" filed on May 5, 2004, 7,645,723 entitled "Method of Drilling
Using Invert Emulsion Drilling Fluids" filed on August 15, 2007, and 7,696,131
entitled "Diesel Oil-Based Invert Emulsion Drilling Fluids and Methods of Drilling
Boreholes" filed on July 5, 2007, each of which are incorporated herein by
reference in their entirety.
Base polymers may be natural polymers or synthetic polymers capable of
being crosslinked by boric acid. Examples of natural base polymers may include,
but are not limited to, guar, a guar derivative, hydroxypropylguar, oxidized guar,
carboxymethyl hydroxypropylg uar, carboxy methyl guar, hydrophobically modified
guar derivative, locust bean gum, a locust bean gum derivative, fenugreek gum,
a fenugreek gum derivative, Tara gum, a tara gum derivative, and the like, and
any combination thereof. Examples of synthetic base polymers may include, but
are not limited to, polyols, polyvinyl alcohols, polymers comprising a monomer
having a 1,4 diol substitution, polymers comprising a monomer having a 1,3 diol
substitution, polymers comprising a monomer having a 1,2 diol substitution, and
the like, and any combination thereof.
Suitable base polymers may have a molecular weight ranging from a
lower limit of about 100,000 gfmol, 250,000 gfmol, 500,000 gfmol, or 1,000,000
gfmol to an upper limit of about 5,000,000 gfmol, 2,500,000 gfmol, 1,000,000
g/mol, or 750,000 g/mol, and wherein the molecular weight may range from any
lower limit to any upper limit and encompasses any subset therebetween.
In some embodiments, the viscosified treatment fluids described herein
may comprise the base polymers at a concentration ranging from a lower limit of
about 0.1%, 0.5%, or 1% by weight of the treatment fluid to an upper limit of
about 10%, 5%, or 1% by weight of the treatment fluid, and wherein the
amount may range from any lower limit to any upper limit and encompasses any
subset therebetween. In some embodiments, the viscosified treatment fluids
described herein that comprises a BB crosslinking agent may have a base
polymer concentration about 25% to about 50% lower than a commensurate
viscosified treatment fluid having the same viscosity and comprising the base
polymer and a traditional boron-containing crosslinking agent (e.g., a molecular
boron-containing crosslinking agent like versus the sodium pentaborate as
compared to a polymeric boron-containing crosslinking agent like the BB
crosslinking agents described herein).
Suitable BB crosslinking agents may comprise a biopolymer derivatized
with a boronic acid or a boronate ester. Examples of biopolymers suitable for
derivatization may include, but are not limited to, a guar gum, oxidized guar,
hydroxyethyl g uar, hydroxypropyl g uar, carboxymethyl g uar,
carboxymethyl hydroxyethyl g uar, carboxymethyl hydroxypropyl g uar, a cellulose,
a cellulose derivative selected from h ydroxyethyl cellulose, carboxyethylcellulose,
carboxymethylcellulose, carboxymethyl hydroxyethylcelluiose, methyl cellulose,
ethylcellulose, methyl hydroxyethyl cellulose, xanthan, sclerog lucan,
succinoglycan, diutan, an alginate, a pectinate, chitosan, a hyaluronic acid, a
polysaccharide, a polypeptide, and the like, and any combination thereof.
In some cases, the biopolymer that is derivatized with a boronic acid or a
boronate ester selected base polymer may be identical to the selected base
polymer. In other cases it may be desirable to have the selected base polymer
be different from the biopolymer. In some embodiments, the base polymer is
preferably a biopolymer, but may be different form the selected derivatized
biopolymer of the BB crosslinking agent.
Suitable BB crosslinking agents may have a molecular weight ranging from
a lower limit of about 1,000 g/mol, 10,000 g/mol, 100,000 g/mol 250,000 g/mol,
500,000 g/mol, or 1,000,000 g/mol to an upper limit of about 5,000,000 g/mol,
2,500,000 g/mol, 1,000,000 g/mol, 750,000 g/mol, or 500,000 g/mol, and
wherein the molecular weight may range from any lower limit to any upper limit
and encompasses any subset therebetween.
Suitable boronic acids or boronate esters for derivatizing a biopolymer
may include, but are not limited to, boronic acid comprising an alkylene, alkenyl,
aryl, aralkyl, alkylaryl, alicyclic, or heteroaryl group, that comprises a functional
group capable of reacting with a functional group of the biopolymer. Formula I
provides a general structure of a boronic acid or boronate ester suitable for
derivatizing a biopolymer, wherein R may be an alkylene, alkenyl, aryl, aralkyl,
alkylaryl, alicyclic, or heteroaryl group containing 1 to 12 carbons, X may be a
functional group capable of reacting with a functional group of the biopolymer
(e.g., amine, alcohol, carboxylic acid, toluene sulfonate, methane sulfonate,
halide, cyano, and the like), and Rl and R2may independently be H or alkylene,
alkenyl, aryl, aralkyl, alkylaryl, alicyclic, or heteroaryl groups containing 1 to 12
carbons.
Formula I
Examples of boronic acids or boronate esters suitable for functionalizing a
biopolymer to yield a BB crosslinking agent described herein may include, but are
not limited to, bromopentyl boronic acid, chloromethylvinyl boronic acid, 4-
cyanopheylboronic acid, aminophenyl boronic acid and its salts with mineral or
organic acid, esters with pinacol, formylphenyl bomic acids, carboxyphenyl
borornic acids, bromomethyl boronic acid, alkoxycarbonyl bomic acids, boronate
esters such as bromopropyl ester, formylphenyl boronic acid pinacol ester, and
the like, and any combination thereof.
In some embodiments, the BB crosslinking agents described herein may
have a boron weight percent ranging from a lower limit of about 0.005%,
O.OlO/~, or 0.05% to an upper limit of about 0.05%, O.lO/~, or 0.5%, and wherein
the boron weight percent may range from any lower limit to any upper limit and
encompasses any subset therebetween.
In some embodiments, the BB crosslinking agents described herein may
have molar ratio of boron to monomeric units in the biopolymer ranging from a
lower limit of about 1:20, 1:10, or 1:5 to an upper limit of about l:l1,:2 , or 1:5,
and wherein the molar ratio may range from any lower limit to any upper limit
and encompasses any subset therebetween.
In some embodiments, the viscosified treatment fluids described herein
may comprise the BB crosslinking agents at a concentration ranging from a lower
limit of about 0.005%, 0.01%, or 0.05% by weight of the treatment fluid to an
upper limit of about 5%, 2%, I%, or 0.5% by weight of the treatment fluid, and
wherein the amount may range from any lower limit to any upper limit and
encompasses any subset therebetween.
By way of non-limiting example, in some embodiments, a viscosified
treatment fluid described herein may comprise an aqueous base fluid, a base
polymer that comprises guar, and a BB crosslinking agent that comprises
carboxymethylcellulose derivatized with aminophenyl boronic acid.
In some embodiments, the viscosified treatment fluids described herein
may optionally further comprise a plurality of particulates. It should be
understood that the term "particulate," as used in this disclosure, includes all
known shapes of materials, including substantially spherical materials, fibrous
materials, polygonal materials (such as cubic materials), and any combination
thereof.
Suitable particulates for use in conjunction with the fluids and methods
described herein may comprise any material suitable for use in subterranean
operations. Suitable materials for these particulates include, but are not limited
to, sand, bauxite, ceramic materials, glass materials, polymer materials,
polytetrafluoroethylene materials, nut shell pieces, cured resinous particulates
comprising nut shell pieces, seed shell pieces, cured resinous particulates
comprising seed shell pieces, fruit pit pieces, cured resinous particulates
comprising fruit pit pieces, wood, composite particulates, glass and mineral
fibers, and combinations thereof. Suitable composite particulates may comprise a
binder and a filler material wherein suitable filler materials include silica, alumina,
fumed carbon, carbon black, graphite, mica, titanium dioxide, meta-silicate,
calcium silicate, kaolin, talc, zirconia, boron, fly ash, hollow glass microspheres,
solid glass, organophilic clay, and combinations thereof. The mean particulate
size generally may range from about 2 mesh to about 400 mesh on the U.S.
Sieve Series; however, in certain circumstances, other mean particulate sizes
may be desired and will be entirely suitable for practice of the present invention.
In particular embodiments, preferred mean particulates size distribution ranges
are one or more of 6/12, 8/16, 12/20, 16/30, 20/40, 30/50, 40/60, 40/70, or
50170 mesh.
In some embodiments, the particulates may be present in the viscosified
treatment fluids in an amount in the ranging from a lower limit of about 0.5
pounds per gallon ("ppg"), 1 ppg, or 5 ppg by volume of the treatment fluid to
an upper limit of about 30 ppg, 20 ppg, or 10 ppg by volume of the treatment
fluid, and wherein the amount may range from any lower limit to any upper limit
and encompasses any subset therebetween.
In some embodiments, the viscosified treatment fluids described herein
may optionally further comprise additives. Suitable additives may include, but are
not limited to, weighting agents, inert solids, fluid loss control agents,
emulsifiers, demulsifiers, oxygen scavengers, dispersion aids, corrosion
inhibitors, emulsion thinners, emulsion thickeners, surfactants, lost circulation
materials, foaming agents, gases, pH control additives, breakers, biocides,
stabilizers, chelating agents, scale inhibitors, gas hydrate inhibitors, mutual
solvents, oxidizers, reducers, friction reducers, clay stabilizing agents, and the
like, and any combination thereof. One of ordinary skill in the art should
understand which additives and an what concentration should be included in the
treatment fluid for use in a desired method.
In some embodiments, the viscosified treatment fluids described herein
(i.e., comprising an aqueous fluid, a based polymer, a BB crosslinking agent,
optionally a plurality of particulates, and optionally additives) may be used in
subterranean operations like drilling operations, stimulation treatments (e.g.,
fracturing treatments, acidizing treatments, or fracture acidizing treatments), and
completion operations.
Some embodiments may involve drilling at least a portion of a wellbore
penetrating a subterranean formation with a viscosified treatment fluid described
herein.
Some embodiments may involve introducing a viscosified treatment fluid
described herein into a wellbore penetrating a subterranean formation. In some
embodiments, the viscosified treatment fluid may comprise a plurality of
particulates and the method may involve forming a particulate pack in the
wellbore, in the subterranean formation, or both (e.g., forming a gravel pack or
forming a proppant pack).
In some embodiments, the viscosified treatment fluids described herein
may be used in a fracturing operation. Some embodiments may involve
introducing a first treatment fluid into a wellbore penetrating a subterranean
formation at a pressure sufficient to create or extend at least one fracture in the
subterranean formation; and forming a particulate pack in the fracture with a
second treatment fluid that comprises a plurality of particulates. In some
embodiments, the first treatment fluid, the second treatment fluid, or both may
be viscosified as described herein (Le., comprising a base polymer and a BB
crosslinking agent).It should be noted that when both treatment fluids are
viscosified as described herein, the composition of the first treatment fluid and
the second treatment fluid may have the same or different components (e.g., the
aqueous fluid, the base polymer, the BB crosslinking agent, and the like) and
each component may independently be at the same or different concentrations
in the two treatment fluids.
Some embodiments may further involve breaking the first and/or second
treatment fluids. Breaking may be achieved by including a breaker in the
treatment fluid or contacting the treatment fluid with a breaking treatment fluid.
Some embodiments may further involve contacting the first and/or second
treatment fluids with a breaking treatment fluid so as to reduce the viscosity of
the treatment fluid. Breaking treatment fluids may comprise breakers suitable for
degrading the BB crosslinking agents described herein. Examples of breakers
may include, but are not limited to, acids.
In some embodiments, the viscosified treatment fluids described herein
may be used in a gravel packing operation. Some embodiments may involve
introducing a viscosified treatment fluid comprising an aqueous fluid, a base
polymer, a BB crosslinking agent, and a plurality of particulates into a wellbore
penetrating a subterranean formation; and forming a gravel pack comprising the
particulates in an annulus within the wellbore (e.g., an annulus between the
wellbore and a screen). Some embodiments may further involve breaking the
viscosified treatment fluid so as to reduce the viscosity of the viscosified
treatment fluid.
In various embodiments, systems configured for delivering the treatment
fluids described herein to a downhole location are described. In various
embodiments, the systems can comprise a pump fluidly coupled to a tubular, the
tubular containing a viscosified treatment fluid that includes an aqueous fluid, a
base polymer, and a boronated biopolymer crosslinking agent, wherein the
boronated biopolymer crosslinking agent comprises a biopolymer derivatized with
a boronic acid, a boronate ester, or both.
The pump may be a high pressure pump in some embodiments. As used
herein, the term "high pressure pump" will refer to a pump that is capable of
delivering a fluid downhole at a pressure of about 1000 psi or greater. A high
pressure pump may be used when it is desired to introduce the viscosified
treatment fluid to a subterranean formation at or above a fracture gradient of
the subterranean formation, but it may also be used in cases where fracturing is
not desired. In some embodiments, the high pressure pump may be capable of
fluidly conveying particulate matter, such as proppant particulates, into the
subterranean formation. Suitable high pressure pumps will be known to one
having ordinary skill in the art and may include, but are not limited to, floating
piston pumps and positive displacement pumps.
In other embodiments, the pump may be a low pressure pump. As used
herein, the term "low pressure pump" will refer to a pump that operates at a
pressure of about 1000 psi or less. In some embodiments, a low pressure pump
may be fluidly coupled to a high pressure pump that is fluidly coupled to the
tubular. That is, in such embodiments, the low pressure pump may be
configured to convey the viscosified treatment fluid to the high pressure pump.
In such embodiments, the low pressure pump may "step up" the pressure of the
viscosified treatment fluid before it reaches the high pressure pump.
In some embodiments, the systems described herein can further comprise
a mixing tank that is upstream of the pump and in which the viscosified
treatment fluid is formulated. In various embodiments, the pump (e.g., a low
pressure pump, a high pressure pump, or a combination thereof) may convey
the viscosified treatment fluid from the mixing tank or other source of the
viscosified treatment fluid to the tubular. In other embodiments, however, the
viscosified treatment fluid can be formulated offsite and transported to a
worksite, in which case the viscosified treatment fluid may be introduced to the
tubular via the pump directly from its shipping container (e.g., a truck, a railcar,
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a barge, or the like) or from a transport pipeline. In either case, the viscosified
treatment fluid may be drawn into the pump, elevated to an appropriate
pressure, and then introduced into the tubular for delivery downhole.
Figure 3 shows an illustrative schematic of a system that can deliver
viscosified treatment fluids of the present invention to a downhole location,
according to one or more embodiments. It should be noted that while Figure 3
generally depicts a land-based system, it is to be recognized that like systems
may be operated in subsea locations as well. As depicted in Figure 3, system 1
may include mixing tank 10, in which a viscosified treatment fluid of the present
invention may be formulated. The viscosified treatment fluid may be conveyed
via line 12 to wellhead 14, where the viscosified treatment fluid enters tubular
16, tubular 16 extending from wellhead 14 into subterranean formation 18.
Upon being ejected from tubular 16, the viscosified treatment fluid may
subsequently penetrate into subterranean formation 18. Pump 20 may be
configured to raise the pressure of the viscosified treatment fluid to a desired
degree before its introduction into tubular 16. It is to be recognized that system
1 is merely exemplary in nature and various additional components may be
present that have not necessarily been depicted in Figure 3 in the interest of
clarity. Non-limiting additional components that may be present include, but are
not limited to, supply hoppers, valves, condensers, adapters, joints, gauges,
sensors, compressors, pressure controllers, pressure sensors, flow rate
controllers, flow rate sensors, temperature sensors, and the like.
Although not depicted in Figure 3, the viscosified treatment fluid may, in
some embodiments, flow back to wellhead 14 and exit subterranean formation
18. In some embodiments, the viscosified treatment fluid that has flowed back
to wellhead 14 may subsequently be recovered and recalculated to subterranean
formation 18.
It is also to be recognized that the disclosed viscosified treatment fluids
may also directly or indirectly affect the various downhole equipment and tools
that may come into contact with the viscosified treatment fluids during
operation. Such equipment and tools may include, but are not limited to,
wellbore casing, wellbore liner, completion string, insert strings, drill string,
coiled tubing, slickline, wireline, drill pipe, drill collars, mud motors, downhole
motors and/or pumps, surface-mounted motors and/or pumps, centralizers,
turbolizers, scratchers, floats (e.g., shoes, collars, valves, etc.), logging tools and
related telemetry equipment, actuators (e.g., electromechanical devices, hydromechanical
devices, etc.), sliding sleeves, production sleeves, plugs, screens,
filters, flow control devices (e.g., inflow control devices, autonomous inflow
control devices, outflow control devices, etc.), couplings (e.g., electro-hydraulic
wet connect, dry connect, inductive coupler, etc.), control lines (e.g., electrical,
fiber optic, hydraulic, etc.), surveillance lines, drill bits and reamers, sensors or
distributed sensors, downhole heat exchangers, valves and corresponding
actuation devices, tool seals, packers, cement plugs, bridge plugs, and other
wellbore isolation devices, or components, and the like. Any of these
components may be included in the systems generally described above and
depicted in Figure 3.
Embodiments disclosed herein include (A) a viscosified treatment fluids
that includes an aqueous fluid, a base polymer, and a boronated biopolymer
crosslinking agent, wherein the boronated biopolymer crosslinking agent
comprises a biopolymer derivatized with a boronic acid, a boronate ester, or
both.
Additional embodiments may include embodiment A with one or more of
the following additional elements in any combination: Element 1: the base
polymer comprising a natural polymer selected from the group consisting of
g uar, a g uar derivative, hydroxypropylg uar, oxidized g ua r,
carboxymethylhydroxypropylguar, carboxymethyl guar, hydrophobically modified
guar derivative, locust bean gum, a locust bean gum derivative, fenugreek gum,
a fenugreek gum derivative, tara gum, a tara gum derivative, and any
combination thereof; Element 2: the base polymer comprising a synthetic
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I -- polymer selected from the group consisting of a polyol, a polyvinyl alcohol, a
polymer comprising a monomer having a 1,4 diol substitution, a polymer
comprising a monomer having a 1,3 diol substitution, a polymer comprising a
monomer having a 1,2 diol substitution, and any combination thereof; Element
3: the base polymer having a molecular weight of about 100,000 g/mol to about
5,000,000 g/mol; Element 4: the base polymer being present at about O.l0/0 to
about 1O0/o by weight of the viscosified treatment fluid; Element 5: the
biopolymer comprising at least one selected from the group consisting of a guar
gum, oxidized guar, hydroxyethyl guar, hydroxypropyl guar, carboxymethyl guar,
carboxymethyl hydroxyethyl guar, carboxymethyl hydroxypropyl guar, a cellulose,
a cellulose derivative selected from hydroxyethyl cellulose, carboxyethylcellulose,
carboxymethylcellulose, carboxymethyl hydroxyethylcellulose, methyl cellulose,
ethylcellulose, methyl hydroxyethyl cellulose, xanthan, sclerog lucan,
succinoglycan, diutan, an alginate, a pectinate, chitosan, a hyaluronic acid, a
polysaccharide, a polypeptide, and any combination thereof; Element 6: the
boronated biopolymer crosslinking agent having a molecular weight of about
1,000 g/mol to about 5,000,000 g/mol; Element 7: the boronic acid or boronate
ester having a general structure according to Formula I above, wherein R may be
an alkylene, alkenyl, aryl, aralkyl, alkylaryl, alicyclic, or heteroaryl group
containing 1 to 12 carbons, X may be a functional group capable of reacting with
a functional group of the biopolymer, and R1 and R2 may independently be H or
alkylene, alkenyl, aryl, aralkyl, alkylaryl, alicyclic, or heteroaryl groups containing
1 to 12 carbons; Element 8: the boronic acid or boronate ester comprising at
least one selected from the group consisting of bromopentyl boronic acid,
chloromethylvinyl boronic acid, 4-cyanopheylboronic acid, aminophenyl boronic
acid and its salts with mineral or organic acid, esters with pinacol, formylphenyl
bornic acids, carboxyphenyl boromic acids, bromomethyl boronic acid,
alkoxycarbonyl bornic acids, boronate esters such as bromopropyl ester,
formylphenyl boronic acid pinacol ester, and the like, and any combination
thereof; Element 9: the boronated biopolymer crosslinking agent having a boron
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weight percent of about 0.005% to about 0.05% by weight of the boronated
biopolymer crosslinking agent; Element 10: the boronated biopolymer
crosslinking agent having a molar ratio of boron to monomeric units in the
biopolymer of about 1:20 to about 1:l; Element 11: the boronated biopolymer
crosslinking agent being present at about 0.005% to about 5% by weight of the
viscosified treatment fluid; Element 12: the base polymer being guar, the
biopolymer being carboxymethylcelIulose, and the boronic acid being
aminophenyl boronic acid; and Element 13: the treatment fluid being an invert
emulsion.
By way of non-limiting example, exemplary combinations applicable to
Embodiment A include: Element 1 in combination with Element 5; Element 2 in
combination with Element 5; at least two of Elements 7-10 in combination;
Element 1 in combination with Element 5 and at least one of Elements 7-10;
Element 2 in combination with Element 5 and at least one of Elements 7-10; at
least one of Elements 3, 4, and 11 in combination with any of the foregoing;
Element 12 in combination with at least one of Elements 3, 4, 9, 10, and 11;
Element 13 in combination with any of the foregoing; and so on.
Embodiments disclosed herein also include:
B. a method that includes introducing a viscosified treatment
fluid according to Embodiment A (or variations thereof with the Elements
described herein) into a wellbore penetrating a subterranean formation; and
C. introducing a first treatment fluid into a wellbore penetrating
a subterranean formation at a pressure sufficient to create or extend at least one
fracture in the subterranean formation; and forming a particulate pack in the
fracture with a second treatment fluid according to Embodiment A (or variations
thereof with the Elements described herein) and further comprising a plurality of
particulates.
Additional embodiments may include Embodiment B with one or more of
the following additional elements in any suitable combination: Element 14:
wherein introducing is at a pressure sufficient to create or extend at least one
fracture in the subterranean formation; Element 15: drilling at least a portion of
the wellbore with the viscosified treatment fluid; Element 16: wherein the
viscosified treatment fluid further comprises a plurality of particulates; and the
method further comprises forming a gravel pack comprising the particulates in
an annulus within the wellbore; and Element 17: breaking the viscosified
treatment fluid so as to reduce the viscosity of the viscosified treatment fluid. By
way of non-limiting example, exemplary combinations applicable to Embodiment
B include: Element 17 in combination with any of Elements 14-16.
Additional embodiments may include Embodiment C with one or more of
the following additional elements in any suitable combination: Element 18:
breaking the second treatment fluid so as to reduce the viscosity of the second
treatment fluid.
To facilitate a better understanding of the present invention, the following
examples of preferred or representative embodiments are given. In no way
should the following examples be read to limit, or to define, the scope of the
invention.
EXAMPLES
Two BB crosslinking agents were prepared by reacting
carboxymethylcellulose (CMC) of two different molecular weights (700,000 g/mol
and 250,000 g/mol) with aminophenyl boronic acid in the presence of a coupling
agent. The coupling agent used was N-(3-dimethylaminopropyl)-Nfethylcarbodiimide
hydrochloride (EDC) or N, N'dicyclohexylcarbodiimide (DCC).
Underivatized CMC with a molecular weight of 700,000 mixed with (not coupled
to) aminophenyl boronic acid was used as a control.
A viscosified fluid was produced by mixing hydrated BB crosslinking agent
and hydrated guar, each at 10 pounds per gallon (ppg) in the final mixture, and
then raising the pH to about 8.The viscosified fluid was tested at 90°F using
Chandler 5550 rheometer at a shear rate of 40 sec-', results shown in Figure 1.
The two derivatized CMC provided viscosities over 300 cP for two hours as 90°F.
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Further, of the two derivatized CMC, the higher molecular weight CMC provided a
higher viscosity (above about 450 cP) versus the lower molecular weight CMC,
which dropped from about 400 cP to sustaining about 300 cP. Visually, the
viscosified fluids with the BB crosslinking agents were well viscosified with a
lipping character of about 1.5" to about 2".
This example demonstrates that boronated CMC is an effective
crosslinking agent for guar and may be suitable for use in wellbore operations
(e.g., fracturing operations that utilize viscosified fluids for suspending and
transporting particulates such as proppants). The results also indicate that a CMC
with higher molecular weight will provide higher viscosities.
A control experiment was performed with two samples of 15 ppg and 20
ppg guar solutions crosslinked with sodium pentaborate (Le., not a BB
crosslinking agent described herein but rather a conventional borate crosslinker).
The viscosity of the two control samples was measured at 90°Fover 1
hour at a shear rate of 40 sec-'. The results are presented in Figure 2 where the
15 ppg sample has a viscosity of about 400 cP and the 20 ppg guar a viscosity
that decreases to about 800 cP.
The viscosities demonstrated with the BB crosslinking agent above are
commensurate with the viscosities achieved with conventional borate crosslinking
systems at a 33% reduced base polymer concentration. Therefore, it is apparent
that by using a BB crosslinking agent described herein with a derivatized
biopolymer of suitable molecular weight and optimum level of boronate
substitution, a reduction in the range of 25-50% the amount of base polymer
can be achieved.
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. 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.

0
We claim:
1. Boronated biopolymer crosslinking agents and methods relating
thereto wherein a method comprising:
introducing a viscosified treatment fluid into a wellbore penetrating
a subterranean formation, the viscosified treatment fluid comprising an aqueous
fluid, a base polymer, and a boronated biopolymer crosslinking agent, wherein
the boronated biopolymer crosslinking agent comprises a biopolymer derivatized
with a boronic acid, a boronate ester, or both.
2. A method as claimed in claim 1, wherein the base polymer a
natural polymer selected from the group consisting of guar, a guar derivative,
hydroxypropylg uar, oxidized g uar, carboxymethyl hydroxypropylg uar,
carboxymethyl guar, hydrophobically modified guar derivative, locust bean gum,
a locust bean gum derivative, fenugreek gum, a fenugreek gum derivative, tara
gum, a tara gum derivative, and any combination thereof.
3. A method as claimed in claim 1, wherein the base polymer
comprises a synthetic polymer selected from the group consisting of a polyol, a
polyvinyl alcohol, a polymer comprising a monomer having a 1,4 diol
substitution, a polymer comprising a monomer having a 1,3 diol substitution, a
polymer comprising a monomer having a 1,2 diol substitution, and any
combination thereof.
4. A method as claimed in claim 1, wherein the base polymer has a
molecular weight of about 100,000 g/mol to about 5,000,000 g/mol.
5. A method as claimed in claim 1, wherein the base polymer is at
about 0.1% to about 10% by weight of the viscosified treatment fluid.
I 6. A method as claimed in claim 1, wherein the biopolymer comprises
at least one selected from the group consisting of a guar gum, oxidized guar,
hydroxyethyl g uar, hydroxypropyl g uar, carboxymethyl g uar,
carboxymethyl hydroxyethyl g uar, carboxymethyl hydroxypropyl guar, a cellulose,
a cellulose derivative selected from hydroxyethyl cellulose, carboxyethylcell ulose,
carboxymethylcell ulose, carboxymethyl hydroxyethylcellulose, methyl cellulose,
ethylcellulose, methyl hydroxyethyl cellulose, xanthan, sclerog lucan,
succinoglycan, diutan, an alginate, a pechnate, chitosan, a hyaluronic acid, a
polysaccharide, a polypeptide, and any combination thereof.
7. A method as claimed in claim 1, wherein the boronated biopolymer
crosslinking agent has a molecular weight of about 1,000 g/mol to about
5,000,000 g/mol.
8. A method as claimed in claim 1, wherein the boronic acid or
boronate ester has a general structure according to Formula I
OR2 Formula I
wherein R may be an alkylene, alkenyl, aryl, aralkyl, alkylaryl,
alicyclic, or heteroaryl group containing 1 to 12 carbons, X may be a functional
group capable of reacting with a functional group of the biopolymer (e.g., amine,
alcohol, carboxylic acid, toluene sulfonate, methane sulfonate, halide, cyano, and
the like), and R1 and R2 may independently be H or alkylene, alkenyl, aryl,
aralkyl, alkylaryl, alicyclic, or heteroaryl groups containing 1 to 12 carbons.
9. A method as claimed in claim 1, wherein the boronic acid or
boronate ester comprises at least one selected from the group consisting of
bromopentyl boronic acid, chloromethylvinyl boronic acid, 4-cyanopheylboronic
acid, aminophenyl boronic acid and its salts with mineral or organic acid, esters
with pinacol, formylphenyl bomic acids, carboxyphenyl boromic acids,
bromomethyl boronic acid, alkoxycarbonyl bomic acids, boronate esters such as
bromopropyl ester, formylphenyl boronic acid pinacol ester, and the like, and any
com bination thereof.
10. A method as claimed in claim 1, wherein the boronated biopolymer
crosslinking agent has a boron weight percent of about 0.005% to about 0.05%
by weight of the boronated biopolymer crosslinking agent.
11 A method as claimed in claim 1, wherein the boronated biopolymer
crosslinking agent is at about 0.005% to about 5% by weight of the viscosified
treatment fluid.
12. A method as claimed in claim 1, wherein the base polymer is guar,
the biopolymer is carboxymethylcellulose, and the boronic acid is aminophenyl
boronic acid.
13. A method as claimed in claim 1, wherein the treatment fluids is an
invert emulsion.
14. A method as claimed in claim 1, wherein introducing is at a
pressure sufficient to create or extend at least one fracture in the subterranean
formation.
15. A method as claimed in claim 1 further comprising:
drilling at least a portion of the wellbore with the viscosified
treatment fluid.
16. A method as claimed in claim 1, wherein the viscosified treatment
fluid further comprises a plurality of particulates; and the method further
comprises forming a gravel pack comprising the particulates in an annulus within
the wellbore.
17. A method as claimed in claim 1 further comprising:
breaking the viscosified treatment fluid so as to reduce the viscosity
of the viscosified treatment fluid.
18. A method comprising:
introducing a first treatment fluid into a wellbore penetrating a
subterranean formation at a pressure sufficient to create or extend at least one
fracture in the subterranean formation; and
forming a particulate pack in the fracture with a second treatment
fluid, the second treatment fluid comprising an aqueous fluid, a base polymer, a
- 24 -
boronated biopolymer crosslinking agent, and a plurality of particulates, wherein
the boronated biopolymer crosslinking agent comprises a biopolymer derivatized
with a boronic acid, a boronate ester, or both.
19. A method as claimed in claim 18 further comprising:
breaking the second treatment fluid so as to reduce the viscosity of
the second treatment fluid.
20. A treatment fluid comprising:
an aqueous fluid;
a base polymer; and
a boronated biopolymer crosslinking agent, wherein the boronated
biopolymer crosslinking agent comprises a biopolyrner derivatized with a boronic
acid, a boronate ester, or both.
Dated: this I* day of July, 2013
(V.D. GULWANI)
Applicant's Patent Attorney
DUA ASSOCIATES