FIELD OF INVENTION
This invention relates to a sealant composition for use in
subterranean formations and, in specific examples, sealant compositions that
may be used for creating fluid flow preventing barriers in a subterranean
formation.
BACKGROUND TECHNICAL INFORMATION
When hydrocarbons xire produced fiom wells that penetrate
hydrocarbon producing formations, water often accompanies the
hydrocarbons, particularly as the wells mature in time. The water can be the
result of a water producing zone communicated with the hydrocarbon
producing formations or zones by fractures, hgh permeability streaks and
the like, or the water can be caused by a variety of other occurrences which
are well known to those slulled in the art, such as water coning, water
cresting, bottom water, channeling at the wellbore, etc. As used herein, the
term "zone" simply refers to a portion of the formation and does not imply a
particular geological strata or composition. Over the life of such wells, the
ratio of water to hydrocarbons recovered may be undesirable in view of the
cost of producing the water, separating it from the hydrocarbons, and
disposing it, which can represent a significant economic loss.
A variety of techniques have been used to reduce the production
of undesired water. Generally, these techniques involve the placement of a
material in a wellbore penetrating a water-bearing portion of a subterranean
formation that may prevent or control the flow of water into the wellbore.
The techniques used to place these materials are referred to herein as
'b~~nformatne~chen iques" or "conformance treatments." Some techniques
involve the injection of particulates, foams, gels, sealants, or blocking
polymers into the subterranean formation so as to plug off the water-bearing
I portions. For example, squeeze cementing techniques may be used wherein
a cement slurry is forced with pressure into a void or channel through which
water would otherwise flow into the wellbore, and the cement is allowed to
set and seal off that channel. In other techniques, polymers referred to as
"relative permeability modifiers" recently have been used, in some
instances, to decrease the proportion of water with produced hydrocarbons.
I ~ K ~ ~ Z E Z L ~ , ~ L- -C - L3 L ~- 2 .
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BRIEF DESCRIPTION OF THE DRAWINGS
I These drawings illustrate certain aspects of some of the I
embodiments of the present invention, and should not be used to limit or I
define the invention.
FIG. 1 is a schematic illustration of in example fluid handling 1
system for the preparation and delivery of a sealant composition into a
wellbore.
FIG. 2 is a schematic illustration of example well system showing
placement of a sealant composition into a wellbore.
DESCRIPTION OF INVENTION w.r.t. DRAWINGS
The present disclosure relates to treatment of subterranean
formations and, in specific examples, sealant compositions that may be used
for creating fluid flow preventing barriers in a subterranean formation.
Disclosed herein are sealant compositions that comprise an
aqueous-base fluid, an oxazoline functionalized polymer, and a crosslinking
agent. The sealant composition may be formed on the surface and
introduced into the formation or, alternatively, the oxazoline functionalized
polymer and the crosslinking agent may be introduced into the formation to
form the sealant composition downhole. The oxazoline functionalized
polymer contains oxazoline groups that crosslinks to form a gel network.
The crosslinking agent contains groups that are reactive towards the
oxazoline groups on the oxazoline hnctionalized polymer to form
crosslinks. The crosslinking agent may thereby crosslink the oxazoline
functionalized polymer to form the gel network. To delay the crosslinking
reaction, the release of the groups reactive towards the oxazoline groups or
functionality on the oxazoline functionalized polymer may be delayed, for
example, through use of appropriate encapsulation techniques or by
generation of the reactive groups downhole. The gel network may be formed
in the subterranean formation to block certain flow paths in the subterranean
formation, reducing the flow of fluids through the subterranean formation,
especially the flow of aqueous fluids. Examples of the types of flow paths
that may be blocked by the gel network include, but are not limited to,
perforations, such as those formed by a perforation gun, fissures, cracks,
fractures, streaks, flow channels, voids, high permeable streaks, annular
voids, or combinations thereof, as well as any other zone in the formation
through which fluids may undesirably flow.
Of the many advantages of the various methods and compositions
disclosed herein, one advantage may be that the sealant composition may be
environmentally friendly allowing for use in locations that are subject to
strict environmental regulations, such as the North Sea, Gulf of Mexico, etc.
In contrast, many sealant compositions used heretofore are subject to strict
environmental regulation and cannot be used in many areas of the world.
Yet another advantage may be that only one sealant composition may need
to be pumped downhole to create a fluid flow preventing barrier, as the
crosslinking reaction may be controlled by delaying the release of the
groups on the crosslinking agent that are reactive towards oxazoline
functionality. Still another potential advantage may be that the crosslinking
reaction should not generate any undesirable by product. Yet another
potential advantage may be that the gel network formed downhole should be
inert and stable for other chemical and geological stresses that may be
presented after placement.
The oxazoline functionalized polymer may be a polymer that
comprises an oxazoline group. Oxazolines are five-membered heterocyclic
compounds that contain oxygen and nitrogen atoms and any derivative
thereof. Various structural isomers of oxazoline are available, but typically
the oxygen and nitrogen atoms are provided in the 1, 3 positions of the
heterocycle, spaced apart by a single carbon atom.
A typical oxazoline group may have the following structure:
Wherein R', R2, R3, and R4 independently denote a hydrogen atom, halogen
atom, an alkyl group, an aralkyl group, a phenyl group, or a substitute
phenyl group.
The oxazoline functionalized polymer may be a homopolymer or
copolymer, which can be soluble in water or capable of forming a stable
emulsion in water. The term copolymer polymer is intended to include
polymers formed by linking two or more different monomers. Suitable
oxazoline functionalized polymers may be prepared by polymerizing the
corresponding oxazoline monomers. Suitable oxazoline functionalized
polymer may also be prepared by functionalizing polymers that do not
contain oxazoline groups, thereby attaching or forming oxazoline functional
groups directly onto suitable polymer backbones. In addition, suitable
oxazoline hctionalized polymer may be extended by reacting them with , '
polyacids, e.g. citric acid, or carboxylic acid functional polymers or
1 oligomers. One example of a suitable oxazoline functionalized polymer is
~ ~ ~ ~ R ~ ~ @ o x afuzncotiolnianlizeed polymer, available from Nippon
Shokubai.
Suitable oxazoline functionalized polymers may be formed by
copolymerizing oxazoline-functional monomers such as isopropenyl
oxazoline with another addition monomer to form an addition polymer.
Suitable emulsion polymers may be made from ethylenically unsaturated
oxazoline-functional monomers in the amount of fiom 10 to 100 weight
percent, based on emulsion copolymer solids. Examples of oxazolinefunctional
monomers may include 2-isopropenyl2-oxazoline and 2-vinyl 2-
oxazoline. The addition monomer may be any polymerizable monomer that
does not contain an oxazoline monomer. Suitable non-oxazoline containing
addition monomers may include, for example, acrylates and vinyl
monomers, such as styrene. The term "acrylate" is intended to acrylate or
methacrylate monomers, including acids, esters, amides, and substituted
derivatives thereof
Examples of suitable oxazoline functionalized polymers may
include, but are not limited to, homopolymers and copolymers, that have
been functionalized with oxazoline groups. For example, oxazoline
functionalized polymers may include, but are not limited to; homopolymers
and copolymers, of one or more of acrylate, methacrylate, or vinyl
monomers, such as styrene. Styrene monomers that may be used in the
formation of the oxazoline hctionalized polymer may include at least one
of styrene, a substituted styrene, or any derivative thereof. A suitable
oxazoline hctionalized polymer may comprise polystyrene that has been
functionalized with oxazoline groups. Acjlate monomers that may be used -
in the formation of the oxazoline functionalized polymer may include at
least one of acrylate, methacrylate, ethylacrylate, prop ylacrylate,
butylacrylate, tert-butyl-acrylate, n-hydroxyethyl methacrylate, potassium
acrylate, pentabromobenzyl acrylate, methyl methacrylate, ethyl
methacrylate, n-nitrophenyl acrylate, methyl 2-(acyloxymethyl)acrylate,
cyclohexyl acrylate, n-ethylhexyl acrylate, or any derivative thereof.
An example of a suitable oxazoline functionalized polymer may
have the following structure:
Wherein m is an integer fiom 2 to 1,000,000, n is an integer fiom 0 to
1,000,000, M is an organic pendant group, and R', R2, R ~ , and R4
independently denote a hydrogen atom, halogen atom, an alkyl group, an
aralkyl group, a phenyl group, or a substitute phenyl group.
The oxazoline functionalized polymer should be present to impart
the desired gelation upon crosslinking. For example, the oxazoline
functional polymer'may be present in an amount in the range of from about
0.1% to about 80% by weight of the sealant composition, from about 10% to
about 60% by weight of the sealant composition, or from about 30% to
about 40% by weight of the sealant composition. For example, the oxazoline
functional polymer may be present in an amount ranging between or
including about 0.1%, 5%, lo%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%
by weight of the sealant composition. One of ordinary skill in the art, with
the benefit of this disclosure, should be able to select an appropriate amount
of the oxazoline functionalized polymer for a particular application.
The crosslinking agent may contain two or more groups that react
with the oxazoline groups on the oxazoline functionalized to form
crosslinks. The reactive groups may be any of a number of different reactive
groups known to be reactive with oxazolines, including carboxylic groups,
phenol groups, thiol groups, combinations thereof, or derivatives thereof.
Aromatic phenolic groups may be present on the crosslinking agent in one
example. Aromatic thiophenol groups may present on the crosslinking agent
in another example. However, there is no limit on the type or amount of
reactive groups that may be present on the crosslinking agents. Whenever
bottomhole static temperatures are relatively lower, e.g., less than 100°F,
aromatic compounds comprising two or more phenolic groups or
thiophenolic groups may be used for crosslinking of the oxazoline
functionalized polymer.
It may be desired to delay the release of the reactive groups in the
crosslinking agent, for example, to delay the crosslinking reaction until
placement of the sealant composition into the subterranean formation. The
delayed release may be achieved by any suitable mechanism, including
encapsulation of the crosslinking agent (e.g., by a wax or other material) or
by using materials that release the reactive groups downhole. For example,
materials may be used that should release carboxylic groups, such as esters
or amides of carboxylic acids; release phenol groups, such as esters of
phenolic acids; or releasethiol groups. For release of carboxylic groups,
esters may be used. Examples of suitable esters may include, but are not
limited to, alkyl esters of dicarboxylic acids. Dicarboxylic acids can be
saturated or unsaturated or aromatic dicarboxylic acids. Specific examples
1
I of suitable esters may include, but are not limited to, methyl or ethyl esters
I
I of saturated dicarboxylic acids such as oxalic, malonic, succinic, glutaric,
adipic or pimelic acid etc., methyl or ethyl esters of unsaturated dicarboxylic
acids such as maleic, fumaric or glutaconic acid etc., methyl or ethyl esters
of aromatic dicarboxylic acids such as phthalic, isophthalic, terephthalic or
diphenic acid etc. Aromatic thio esters that would release upon hydrolysis a
thio group and a carboxylic acid group may also be suitable. Delaying the
I crosslinking reaction may be particularly desired where elevated bottom
I hole static temperatures may be present. For example, at bottom hole static
temperature of 135°F or greater, delayed release of the groups reactive to
oxazoline functionality may be desired due to the increased reaction rates.
The crosslinking agent should be present to provide the desired
I crosslinking of the oxazoline functional polymer. For example, the
crosslinking agent may be present in an amount in the range of fiom about
0.1% to about 50% by weight of the sealant composition, fiom about 1% to
about 10% by weight of the sealant composition, or fiom about 1.5% to
about 5% by weight of the sealant composition. In some examples, the
crosslinking agent may be present in an amount ranging between or
including about 0.1%, about 5%, about lo%, about 20%, about 30%, about
40%, or about 50% by weight of the sealant composition. One of ordinary
skill in the art, with the benefit of this disclosure, should be able to select an
appropriate amount of the crosslinking agent for a particular application.
The ratios of the oxazoline crosslinking agent and the oxazoline
functional polymer may vary, depending on a number of factors including
the structure of the oxazoline crosslinking agent and oxazoline function
polymer, downhole conditions, and desired properties of the gel network,
among others. For example, the molar ratio of oxazoline functional groups
in the oxazoline functional polymer to reactive groups in the crosslinking
agent may vary fiom a range of about 1000:l to about 1 :2 or fiom about
1000: 1 to about 1 : 1, or from about 50: 1 to about 1 : 1 or fiom about 25:l to
about 1 : 1 or from about 1.5: 1 to about 1 : 1.
As previously mentioned, the groups on the crosslinking agent
should react with the oxazoline groups on the oxazoline functionalized
polymer to form crosslinks. The extent of the reaction may be adjusted by
controlling a number of factors, including, without limitation, the number of
oxazoline functional groups, crosslinker concentration, polymer
concentration, and crosslinker type, among others. The reaction mechanism
for crosslinking an oxazoline functionalized polymer by a dicarboxylic acid
is provided by equations (3) to (4) below. Equation (3) shows the hydrolysis ~ of a diester to release a dicarboxylic acid in situ. Equation (4) shows the ring ~ opening polymerization of two oxazoline rings with a dicarboxlic acid.
(Hydrolysis of a diester releases in-situ a dicarboxylic acid)
(4)
(Ring opening polymerization of two oxazoline rings with a
dicarboxylic acid)
Equations (5) and (6) below show reactions of phenols and
thiophenols with oxazoline groups, respectively:
(6)
Aqueous base fluids that may be suitable for use in the disclosed
methods may comprise fresh water, saltwater (e.g., water containing one or
more salts dissolved therein), brine, seawater, or combinations thereof.
Generally, the water may be from any source, provided that it does not
contain components that might undesirably affect the stability and/or
performance of the treatment fluids of the present invention. If desired, the
density of the aqueous base fluid can be adjusted, among other purposes, to
provide additional particle transport and suspension in the sealant
compositions. If desired, the pH of the aqueous base fluid may be adjusted
(e.g., by a buffer or other pH adjusting agent), among other purposes, to
facilitate crosslinking and/or reduce the viscosity of the sealant composition
(e.g., activate a breaker or other additive). The pH may be adjusted to a
specific level, which may depend on, among other factors, the type(s) of
particular components included in the treatment fluid.. One of ordinary skill
in the art, with the benefit of this disclosure, will recognize when such
density and/or pH adjustments are appropriate.
,The sealant compositions optionally may comprise any number of
additional additives, including, but not limited to, salts, surfactants, acids,
fluid loss control additives, gas, nitrogen, carbon dioxide, surface modifying
agents, tackifylng agents, foamers, corrosion inhibitors, scale inhibitors,
catalysts, clay control agents, biocides, fiction reducers, antifoam agents,
bridging agents, dispersants, flocculants, H2S scavengers, C02 scavengers,
oxygen scavengers, lubricants, viscosifiers, breakers, weighting agents,
relative permeability modifiers, resins, particulate materials (e.g., proppant
particulates), wetting agents, coating enhancement agents, and the like.. A
person skilled in the art, with the benefit of this disclosure, should recognize
the types of additives that. may be included in the sealant compositions for a
particular application.
As will be appreciated by those of ordinary skill in the art, the
sealant composition may be used in a variety of subterranean operations,
where formation of a fluid diverting (or flow preventing) barrier may be
desired, such as conformation treatments and lost circulation control, among
others. The sealant composition may be used prior to, during, or subsequent
to a variety of subterranean operations. Methods of using the sealant
compositions may first include preparing the sealant compositions. The
sealant compositions may be prepared in any suitable manner, for example,
by combining the oxazoline crosslinking agent, the oxazoline functional
polymer, and the aqueous base fluid in any suitable order. The sealant
composition may be used as a single step treatment in which the oxazoline
crosslinking agent and the oxazoline functional polymer, are premixed with
the aqueous base fluid and then introduced into the subterranean formation
for crosslinlung. It may be desired to form the sealant composition
immediately prior to use to prevent premature gelation before reaching the
desired location in the subtckanean formation. Alternatively, the sealant
composition may be used as a multi-step treatment in which the oxazoline
crosslinking agent and the oxazoline functional polymer may be separately
introduced into the subterranean formation for crosslinking. For example,
the oxazoline functional polymer may be mixed with an aqueous base fluid
and placed into the subterranean formation where it may be contacted with
I an oxazoline crosslinking agent, which may already be present in the
formation or subsequently introduced.
Methods may include introduction of the sealant composition into
1 a subterranean formation. In the subterranean formation, the sealant
composition may undergo a crosslinking reaction to form a gel network that
blocks certain flow paths therein, reducing the flow of fluids through the
subterranean formation, especially the flow of aqueous fluids. Examples of
the types of flow paths that may be blocked by the gel network include, but
are not limited to, perforations, such as those formed by a perforation gun,
fissures, cracks, fractures, streaks, flow channels, voids, high permeable
streaks, annular voids, or combinations thereof, as well as any other zone in
the formation through which fluids may undesirably flow. Methods may
further include selecting one or more zones of the subterranean formation
for conformance control in which the sealant composition may be
introduced.
I , A method may comprise reacting components comprising an
I oxazoline functionalized polymer and a crosslinking agent in a subterranean
formation to create a barrier in the subterranean formation. The oxazoline
functionalized polymer may be a polymer with one or more oxazoline
I functional groups attached to the polymer backbone. The oxazoline
I functionalized polymer may be a copolymer of an oxazoline monomer and
an addition monomer that does not contain an oxazoline functional group.
The oxazoline functionalized polymer comprises a copolymer of one or
more . monomers selected fiom the group consisting of acrylate,
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I methacrylate, and a styrene monomer. The crosslinking agent may comprise
reactive groups selected from the group consisting of a carboxylic group,
phenol group, thiol group, a combination thereof, and a derivative thereof
The crosslinking agent may comprise reactive groups that are delayed
i I release such that step of reacting is delayed until release of the reactive
groups. The method may further comprise introducing a sealant composition
comprising an aqueous-base fluid, the oxazoline functionalized polymer and
I the crosslinking agent into the subterranean formation. The crosslinking
~ agent may comprise an ester or amide of a carboxylic acid that hydrolyzes
I to release groups reactive to oxazoline functionality. The crosslinking agent
I may comprise an ester of at least one carboxylic acid selected fiom the
group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid,
adipic acid, pimelic acid, maleic acid, fumaric acid, glutaconic acid, phthalic
.
acid, isophthalic acid, terephthalic acid, and diphenic acid. The oxazoline
functionalized polymer may present in the sealant composition in an amount
of about 0.1% to about 80% by weight of the sealant composition. Themolar
ratio of oxazoline functional groups in the oxazoline functional polymer to
reactive groups in the crosslinking agent may be in a range of from about
1000: 1 to about 1 :2.
A sealant composition may comprise an aqueous-base fluid; an
oxazoline fimctionalized polymer; and a crosslinking agent. The oxazoline
functionalized polymer may be a polymer with one or more oxazoline
functional groups attached to the polymer backbone. The oxazoline
fimctionalized polymer may be a copolymer of an oxazoline monomer and
an addition monomer that does not contain an oxazoline functional group.
The oxazoline hctionalized polymer comprises a copolymer of one or
more monomers selected from the group consisting of acrylate,
methacrylate, and a styrene monomer. The crosslinking agent may comprise
reactive groups selected fiom the group consisting of a carboxylic group,
phenol group, thiol group, a combination thereof, and a derivative thereof.
The crosslinking agent may comprise reactive groups that are delayed
release such that step of reacting is delayed until release of the reactive
groups. The crosslinking agent may comprise an ester or amide of a
carboxylic acid that hydrolyzes to release groups reactive to oxazoline
functionality. The crosslinking agent may comprise an ester of at least one
carboxylic acid selected from the group consisting of oxalic acid, malonic
acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid,
h a r i c acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic
acid, and diphenic acid. The oxazoline functionalized polymer may present
in the sealant composition in an amount of about 0.1% to about 80% by
weight of the sealant composition. Themolar ratio of oxazoline functional
groups in the oxazoline functional polymer to reactive groups in the
crosslinking agent may be in a range of fiom about 1000: 1 to about 1:2.
A well system may comprise a sealant composition comprising an
aqueous-base fluid, an oxazoline hnctionalized polymer, and a crosslinking
agent; a fluid handling system comprising the sealant composition; and a
conduit in fluidically coupled to the fluid handling system and a wellbore. The
'fluid handling system may comprise a fluid supply and pumping equipment.
The oxazoline functionalized polymer may be a polymer with one or more
oxazoline functional groups attached to the polymer backbone. The
,oxazoline functionalized polymer may be a copolymer of an oxazoline
monomer and an addition monomer that does not contain an' oxazoline
functional group. The oxazoline 'hctionalized polymer comprises a
copolymer of one or more monomers selected from the group consisting of
acrylate, methacrylate, and a styrene monomer. The crosslinking agent may.
comprise reactive groups selected from the group consisting of a carboxylic
group, phenol group, thiol group, a combination thereof, and a derivative
thereof. The crosslinking agent may comprise reactive groups that are
delayed release such that step of reacting is delayed until release of the
reactive groups. The crosslinking agent may comprise an ester or amide of a
carboxylic acid that hydrolyzes to release groups reactive to oxazoline
functionality. The crosslinlung agent may comprise an ester of at least one
carboxylic acid selected fiom the group consisting of oxalic acid, malonic
acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid,
fumaric acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic
acid, and diphenic acid. The oxazoline functionalized polymer may present
in the sealant composition in an amount of about 0.1% to about 80% by
weight of the sealant composition. Themolar ratio of oxazoline functional
groups in the oxazoline functional polymer to reactive groups in the
crosslinking agent may be in a range of fiom about 1000: 1 to about 1.2.
Example methods of using the sealant compositions will now be
described in more detail with reference to FIGs. 1 and 2. Any of the
previous embodiments of the sealant composition may apply in the context
of FIGs. 1 and 2. Refening now to FIG. 1, a fluid handling system 2 is
illustrated. The fluid handling system 2 may be used for preparing the
sealant composition and introduction of the sealant composition into a
wellbore. The fluid handling system 2 may include mobile vehicles,
immobile installations, skids, hoses, tubes, fluid tanks or reservoirs, pumps,
valves, andlor other suitable structures and equipment. For example, the
fluid handling system 2 may include a fluid supply 4 and pumping
equipment 6, which both may be fluidically coupled with a wellbore supply
conduit 8. The fluid supply 4 may contain the sealant composition. The
pumping equipment 6 may be used to supply the sealant composition from
the fluid supply 4, which may include tank, reservoir, connections to
external fluid supplies, and/or other suitable structures and equipment.
While not illustrated, the fluid supply 4 may contain one or more
components of the sealant composition in separate tanks or other containers
that may be mixed at any desired time. Pumping equipment 6 may be
fluidically coupled with the wellbore supply conduit 8 to communicate the
sealant composition into wellbore. Fluid handling system 2 may also
include surface and down-hole sensors (not shown) to measure pressure,
rate, temperature and/or other parameters of treatment. Fluid handling
system 2 may include pump controls andlor other types of controls for
starting, stopping and/or otherwise controlling pumping as well as controls
for selecting and/or otherwise controlling fluids pumped during the injection
treatment. An injection control system may communicate with such
equipment to monitor and control the injection treatment. Fluid handling
system 2 can be configured as shown in FIG. 1 or in a different manner, and
may include additional or different features as appropriate. Fluid handling
system 2 may be deployed via skid equipment, marine vessel deployed or
may be comprised of sub-sea deployed equipment.
Turning now to FIG. 2, an example well system 10 is shown. As
illustrated, the well system 10 may include a fluid handling system 2, which
may include fluid supply 4, pumping equipment 6, and wellbore supply
conduit 8. As previously described in connection with FIG. 1, pumping
equipment 6 may be fluidically coupled with the wellbore supply conduit 8
to communicate the sealant composition into wellbore. As depicted in FIG.
2, the fluid supply 4 and pumping equipment 6 may be above the surface 12
while the wellbore 14 is below the surface. Well system 10 can be
configured as shown in FIG. 2 or in a different manner, and may include
additional or different features as appropriate.
As illustrated FIG: 2, the well system 10 may be used for
introduction of a sealant composition 16 into subterranean formation
18surrounding the wellbore 14. Generally, a wellbore 14 may include
horizontal, vertical, slanted, curved, and other types of wellbore geometries
and orientations, and the sealant composition1 6 may generally be applied to
subterranean formation 18 surrounding any portion of wellbore 14. As
illustrated, the wellbore 14 may include a casing 20 that may be cemented
(or otherwise secured) to wellbore wall by cement sheath 22. Perforations
24 can be formed in the casing 20and cement sheath 22 to allow treatment
fluids (e.g., sealant composition 16) and/or other materials to flow into and
out of the subterranean formation 18. Perforations 24 can be formed using
shape charges, a perforating gun, and/or other tools. A plug 26, which may
be any type of plug (e-g., bridge plug, etc.) may be disposed in wellbore 14
below the perforations 24.
The sealant composition 16 comprising an aqueous-base fluid, an
oxazoline functionalized polymer, and a crosslinking agent may be pumped
fi-om fluid supply 4 down the interior of casing 20 in wellbore 14. As
illustrated, well conduit 28 (e.g., coiled tubing, drill pipe, etc.) may be
disposed in casing 20 through which the sealant composition 16 may be
pumped. The well conduit 28 may be the same or different than the wellbore
supply conduit 8. For example, the well conduit 28 may be an extension of
the wellbore supply conduit 8 into the wellbore 14 or may be tubing or other
conduit that is coupled to the wellbore supply conduit 8. The sealant
composition 16 may be allowed to flow down the interior of well conduit
28, exit the wellbore conduit, and finally enter subterranean formation 18
surrounding wellbore 14 by way of perforations 24 through the casing 20
and cement sheath 24. The sealant composition 16 may undergo a
crosslinking reaction in the subterranean formation 18 to form a gel network
that blocks certain flow paths therein, reducing the flow of fluids through
the subterranean formation 18, especially the flow of aqueous fluids.
The exemplary sealant composition disclosed herein may directly
or indirectly affect one or more components or pieces of equipment
associated with the preparation, delivery, recapture, recycling, reuse, andlor
disposal of the sealant composition. For example, the sealant composition
may directly or indirectly affect one or more mixers, related mixing
equipment, mud pits, storage facilities or units, composition separators, heat
exchangers, sensors, gauges, pumps, compressors, and the like used
generate, store, monitor, regulate, and/or recondition. the sealant
composition. The sealant composition may also directly or indirectly affect
any transport or delivery equipment used to convey the sealant composition
to a well site or downhole such as, for example, any transport vessels,
conduits, pipelines, trucks, tubulars, and/or pipes used to compositionally
move the sealant composition from one location to another, any pumps,
compressors, or motors (e.g., topside or downhole) used to drive the sealant
composition into motion, any valves or related joints used to regulate the
pressure or flow rate of the resin composition and spacer fluids (or fluids
containing the same sealant composition, and any sensors (i.e., pressure and
temperature), gauges, and/or combinations thereof, and the like. The
disclosed sealant composition may also directly or indirectly affect the
various downhole equipment and tools that'may come into contact with the
sealant composition such as, but 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, cement 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, 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.
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EXAMPLES
To facilitate a better understanding of the present embodiments,
the following examples of some of the preferred embodiments are given. In
no way should such examples be read to limit, or to define, the scope of the
disclosure.
Example 1
A sealant composition was prepared by mixing 100 milliliters of
an aqueous dispersion of an oxazoline functionalized polymer (40 wt%
active) with three milliliters of diethyl malonate. The mixture was placed in
a glass vial and exposed to 167°F (75°C) for sixteen hours in an autoclave at
7nn nci nreccllre tn triuuer nlrinu The rl~r~ral mnle fnrmprl a Am'A hlnrt
that took the shape of the glass vial. In comparison, the uncured sample was
very fluid and easy to flow.
Example 2
Water shutoff testing was next performed using the sealant
composition of Example 1. A sand pack test cell was prepared that
comprised 100 mesh sand (75 grams), U.S. sieve series, with a layer of
20140 mesh sand (35 grams) on top to allow flow to be uniformly distributed
within the 100 mesh sand. The sand pack had a length of 12. 5 centimeters
and a diameter of 2.56 centimeters.
The initial permeability of the sand pack was first determined by
n- ~im-nin-un ?O/n KPl hrine intn thp tect re11 at a f l n x x r rate nf 3 m;ll;l;t~rcn er
minute until a constant differential pressure was obtained. The initial
Next, the sand pack was flooded with the sealant composition by pumping
the sealant composition into the sand pack at a rate of 2 milliliters per I
minute while monitoring the differential pressure. After two pore volumes I
of the sealant composition were run through the sand pack, the sand pack 1
test cell was shut in for curing at 167°F (75°C) for 16 hours. A jacket heater I
was used for heating the test cell.
Since the sealant composition is proposed for conformance
applications, it was desired to tests the cured sand pack to the flow of fluids
under increasing differential pressures (AP). After the shut-in, the sand pack
test cell was configured, for pressure testing. During the pressure testing, a
particular AP was maintained across the sand pack, and the sand pack was
observed for any leakage while applying 3% KC1, which would be indicated
by a drop of the applied AP for about 5 minutes. Once the appli.cability of
the sand pack to resist a particular AP was established, the AP across the
sand pack was increased to the next level. This was continued until leakage
was observed. The percent permeability reduction (PPR) was evaluated as
well.
The table below shows the data generated £?om the water shutoff
testing.
Table 1
The above results indicate the oxazoline functionalized polymers
can be used for formation of barriers that can reduce or stop fluid flow. To
Sealant Composition: Aqueous Solution of Oxazoline Functionalized Polymer
+ Diethyl Malonate 3% (vlv) wrt the Polymer
Curing: 16 hours at 167OF (7S°C)
Sand Pack: Length = 12.5 cm; Diameter = 2.56 cm
Leak Rate,
Q (mumin)
0
0
0
0
0
0
0 . ,
0
0
0.7
Differential
Pressure,AP (psi)
5 0
100
200
3 00
400
600
700
800
900
1000
Comment
No Leak
No Leak
No Leak
No Leak
No Leak
No Leak
No Leak
No Leak
No Leak
Small Leakage
Final
Permeability,
Kf (mD)
0
0
0
0
0
0
0
0
0
0.27
'PPR
= 100 (1-
Kf/Ki)
100%
100%
100%
100%
100%
100%
100%
100%
100%
99.99%
evaluate the extent of curing the unconfined compressive strength of the
cured sand pack was determined. The cured sand pack was cut in half and
the top and bottom portions were separately evaluated. The compressive
strength was determined by separately crushng the top and bottom portions
in a compression-testing machine. The compressive strength is calculated
from the failure load divided by the cross-sectional area resisting the load
and is reported in units of pound-force per square inch (psi). Compressive
strengths may be determined in accordance with API RP 10B-2,
Recommended Practice for Testing Well Cements, First Edition, July 2005.
The top portion of the cured sand pack had a compressive strength of 365
psi, and the bottom portion of the cured sand pack had a compressive
strength of 1 90 psi.
It should be understood that the compositions and methods are
described in terms of "comprising,"c'containing,77 or "including" various
components or steps, the compositions and methods can also "consist
essentially of' or "consist of' the various components and steps. 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.
For the sake of brevity, only certain ranges are explicitly disclosed
herein. However, ranges from any lower limit may be combined with any upper
limit to recite a range not explicitly recited, as well as, ranges fiom any lower
limit may be combined with any other lower limit to recite a range not
explicitly recited, in the same way, ranges from any upper limit may be
combined with any other upper limit to recite a range not explicitly recited.
I Additionally, whenever a numerical range with a lower limit and an upper limit
' is disclosed, any number and any included range falling within the range are
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
I I set forth every number and range encompassed within the broader range of
I
values even if not explicitly recited. Thus, every point or individual value may
serve as its .own lower or upper limit combined with any other point or
individual value or any other lower or upper limit, to recite a range not
explicitly recited.
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.
Although individual embodiments are discussed, the invention covers all
combinations of all those embodiments. Furthermore, no limitations are
intended to the details of construction or design herein shown, other than as
described in the claims below. Also, the terms in the claims have their plain,
ordinary meaning unless otherwise explicitly and clearly defined by the
patentee. It is therefore evident that the particular illustrative embodiments
disclosed above may be altered or modified and all such variations are
considered within the scope and spirit of the present invention. If there is any
conflict in the usages of a word or term in this specification and one or more
patent(s) or other documents that may be incorporated herein by reference, the
definitions that are consistent with this specification should be adopted.

We claim:
1. A method comprising:
reacting components comprising an oxazoline hnctionalized
polymer and a crosslinking agent in a subterranean formation to create a bamer
in the subterranean formation.
2. A niethod as claimed in claim 1 wherein the oxazoline
functionalized polymer is a polymer with one or more oxazoline functional
groups attached to the polymer backbone.
3. A method as claimed in claim 1 wherein the oxazoline
functionalized polymer is a copolymer of an oxazoline monomer and an
addition monomer that does not contain an oxazoline functional group.
4. A method as claimed in claim 1 wherein the oxazoline
functionalized polymer comprises a copolymer of one or more monomers
selected from the group consisting of acrylate, methacrylate, and a styrene
monomer.
5. A method as claimed in any preceding claim wherein the
crosslinking agent comprises reactive groups selected from the group consisting ,
I of a carboxylic group, phenol group, thiol group, a combination thereof, and a
derivative thereof.
6. A method as claimed in any preceding claim wherein the
crosslinking agent comprises reactive groups that are delayed release such that
step of reacting is delayed until release of the reactive groups.
7. A method as claimed in any preceding claim, mher
comprising introducing a sealant composition comprising an aqueous-base
fluid, the oxazoline functionalized polymer and the crosslinking agent into the
subterranean formation.
8. A method as claimed in claim 7, wherein crosslinking agent
comprises an ester or amide of a carboxylic acid that hydrolyzes to release
groups reactive to oxazoline functionality.
- - - -
9. A method as claimed in claim 7, wherein the crosslinking agent
comprises an ester of at least one carboxylic acid selected fi-om the group
consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, pimelic acid, maleic acid, fumaric acid, glutaconic acid, phthalic acid,
isophthalic acid, terephthalic acid, and diphenic acid.
10. A method as claimed in any one of claims 7 to 9, wherein the
oxazoline hctionalized polymer is present in the sealant composition in an
amount of about 0.1% to about 80% by weight of the sealant composition, and
wherein the molar ratio of oxazoline functional groups in the oxazoline
functional polymer to reactive groups in the crosslinking agent is in a range
of from about 1000: 1 to about 1 :2.
11. A sealant composition for use in. subterranean formations
comprising:
an aqueous-base fluid;
an oxazoline functionalized polymer; and
a crosslinking agent.
12. A sealant composition as claimed in claim 11 wherein the
crosslinking agent comprises reactive groups selected fiom the group consisting
of a carboxylic group, phenol group, thiol group, a combination thereof, and a
derivative thereof.
13. A sealant composition as claimed in claim 11 or claim
12,wherein the crosslinking agent contains reactive groups that are delayed
release.
14. A sealant composition as claimed in any one of claims 11 to 13,
wherein the crosslinking agent is encapsulated.
15. A sealant composition as claimed in any one of claims 1 1 to 14,
wherein crosslinking agent comprises an ester or amide of a carboxylic acid
that hydrolyzes to release groups reactive to oxazoline functionality..
16. A sealant composition as claimed in any one of claims 11 to 15,
wherein the crosslinking agent comprises an ester of at least one carboxylic
acid selected fiom the group consisting of oxalic acid, malonic acid, succinic
acid, glutaric acid, adipic acid, pimelic acid, maleic acid, fumaric acid,
glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and
diphenic acid.
17. A sealant composition as claimed in any one of claims 1 1 to 16,
wherein the oxazoline functionalized polymer is present in the sealant
composition in an amount of about 0.1 % to about 80% by weight of the sealant
composition, and wherein the molar ratio of oxazoline functional groups in
the oxazoline functional polymer to reactive groups in the crosslinking
agent is in a range of fiom about 1000: 1 to about 1.2.
18. A well system comprising:
a sealant composition comprising an aqueous-base fluid, an
oxazoline functionalized polymer, and a crosslinking agent;
a fluid handling system comprising the sealant composition; and
a conduit in fluidically coupled to the fluid handling system and
a wellbore.
19.A well system as claimed in claim 18 wherein the fluid handling
system comprises a fluid supply and pumping equipment.
20.A well system as claimed in claim 18 or claim 19 wherein
crosslinking agent comprises an ester or arnide of a carboxylic acid that
hydrolyzes to release groups reactive to oxazoline functionality.