WO2019183390A1 - Preformed particle gel for enhanced oil recovery - Google Patents

Abstract

Re-crosslinkable interpenetrating polymer network preformed particle gels (IPN PPGs) and compositions containing re-crosslinkable IPN PPGs, are provided, as well as methods of re-crosslinking the re-crosslinkable IPN PPGs with ionic crosslinkers, and the resultant re-crosslinked IPN PPG compositions. In addition, the use of the re-crosslinkable and re-crosslinked IPN PPGs are provided, e.g., in methods, processes, and techniques related to enhanced oil recovery, e.g., conformance control, wherein the use of said re-crosslinked IPN PPGs may improve hydrocarbon recovery, e.g., by improving sweep efficiency. These re-crosslinked IPN PPGs are also useful in water and gas shutoff, fluid loss control, zone abandonment, water and gas coning, squeeze and recompletion, chemical liner completions and lost circulation during drilling operations and plugging during drilling and drilling completion.

Description

PREFORMED PARTICLE GEL FOR ENHANCED OIL RECOVERY

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims the priority benefit of U.S. Provisional Application Ser. No. 62/646,531 (Atty. Docket No. 49704.2200), filed 03/22/2018, entitled“PREFORMED PARTICLE GEL FOR ENHANCED OIL RECOVERY”, which is incorporated by reference herein in its entirety.

FIELD OF THE ART

[002] The present disclosure generally relates to preformed particle gels and the use thereof in processes and techniques related to enhanced oil recovery, e.g., conformance control.

BACKGROUND

[003] Enhanced oil recovery (EOR) generally refers to techniques and processes that can be used to increase the amount of unrefined petroleum (for example, crude oil) that may be extracted from an oil reservoir (for example, an oil field). By way of example, using EOR, about 40-60% of the reservoir’s original oil can typically be extracted, compared with only 20-40% using traditional primary and secondary recovery techniques (for example, by water injection or natural gas injection). However, many reservoirs from which oil and gas may be produced may be heterogenous in their geologic properties (e.g. porosity and/or

permeability). For some reservoirs, permeability differences among the different geologic layers can vary as much as several orders of magnitude.

[004] Generally speaking, in the production of oil or gas from a reservoir, a fluid, such as water, may be injected into an injection well. The injected water may mobilize and push some of the oil in place to a nearby production well where the oil and injected fluid may be co-produced. A high degree of heterogeneity in the permeability among the geologic layers of rock that contain oil within its porous spaces in the subsurface reservoir may cause such water injections to lack uniformity, with the larger proportion of the water entering into higher permeability geologic layers, which may lead to non-uniform displacement of the oil within the reservoir. As a result, much of the oil may be quickly mobilized from high permeability layers and little mobilized from the lower permeability layers. Such conditions may result in fluid exiting production wells having a higher than desired percentage of water and a lower than desired percentage of oil. Based on the foregoing, it is desirable to develop compositions and methods for use with EOR processes that improve the recovery of the large volume of oil that may remain in the bypassed and not yet swept lower permeability regions of a reservoir, and that minimize the loss of water from production wells during EOR processes.

BRIEF SUMMARY

[005] The present disclosure generally relates to a composition comprising: a. a plurality of re-crosslinkable interpenetrating polymer network (“IPN”) preformed particle gel (“PPG”) particles that are swellable and dispersible in water or other aqueous composition, wherein each IPN PPG comprises an interpenetrating network of at least a first acrylamide

(co)polymer and a second polymer that is capable of ionic bonding; and b. at least one ionic crosslinker. Furthermore, the present disclosure generally encompasses a system for use in conformance control comprising: a. a plurality of re-crosslinkable IPN PPG particles that are swellable and dispersible in water or other aqueous composition, wherein each IPN PPG comprises an interpenetrating network of at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding; b. at least one ionic crosslinker; and c. a subterranean formation having the composition therein. Moreover, the present disclosure generally pertains to a method for producing a re-crosslinked IPN PPG comprising: i.

providing an aqueous composition comprising a plurality of re-crosslinkable IPN PPGs; ii. allowing the re-crosslinkable IPN PPGs to swell; and c. adding at least one ionic crosslinker in an amount sufficient to provide for re-crosslinking of the IPN PPGs; wherein the ionic crosslinker is added before, during and/or after swelling. Additionally, the present disclosure generally relates to a method of enhanced oil recovery, the method comprising: a. obtaining or providing a composition comprising a plurality of re-crosslinkable IPN PPGs; b. adding to the composition at least one ionic crosslinker; c. placing the composition in a subterranean formation downhole; d. swelling the plurality of re-crosslinkable IPN PPGs in an aqueous fluid; e. allowing the plurality of IPN PPGs to re-crosslink with the ionic crosslinker; and f. extracting oil from the subterranean formation downhole via a production wellbore.

Moreover, the present disclosure generally pertains to a method for remediation of a zone within a subterranean formation bearing heavy/viscous oil to inhibit breakthrough of water from a water injection well via the zone into a production well, the zone comprised of a void space, a halo region, or both, due to production of the heavy/viscous oil through the production well, thereby allowing for pressure communication between the injection well and the production well, which method comprises: a. injecting a composition into the zone via the injection well, the composition comprising a plurality of re-crosslinkable IPN PPGs and at least one ionic crosslinker; and allowing the IPN PPGs to re-crosslink for a sufficient time to form a plug that reduces fluid communication between the injection well and the production well.

DETAILED DESCRIPTION

[006] The present disclosure generally relates to re-crosslinkable interpenetrating polymer network (“IPN”) preformed particle gels (“PPGs”). The re-crosslinkable IPN PPGs comprise an interpenetrating network of a first polymer and a second polymer. When the re- crosslinkable IPN PPGs are contacted with at least one ionic crosslinker, e.g., a multivalent cation, it results in ionic crosslinking between polymers in adjacent IPN PPGs, forming“re- crosslinked” IPN PPGs that have enhanced conformance control properties. The present disclosure also describes methods for making the re-crosslinkable and re-crosslinked IPN PPGs, as well as methods and processes for using the IPN PPGs, such as EOR processes.

[007] The disclosed compositions and methods provide an improvement over similar methods and processes using conventional PPGs. It has been observed that under certain conditions, conventional PPGs may be removed from pores or voids under pressure, or may not be able to fill larger pores, wormholes, or voids. Also, conventional PPGs are generally not amenable to re-crosslinking (as described herein). In contrast, the exemplary re- crosslinkable IPN PPGs disclosed herein may more readily be re-crosslinked to each other, e.g., ionically crosslinked to one another, such as through formation of ionic crosslinks between PPG particles upon addition of a ionic crosslinker. The exemplary re-crosslinkable IPN PPGs also are capable of forming a strong and deformable gel when re-crosslinked which is better able to withstand pressure and remain for more prolonged time in the pores or voids of a subterranean formation.

DEFINITIONS [008] As used herein the singular forms "a", "and", and "the" include plural referents unless the context clearly dictates otherwise. All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

[009] As used herein, the term interpenetrating polymer network (“IPN”) generally refers to a mixture of two polymers that are interlaced and/or intertwined at the molecular level. For example, in exemplary embodiments a re-crosslinkable IPN PPG may comprise an alginate and polyacrylamide IPN wherein said (linear) alginate polymer is intertwined with covalently crosslinked polyacrylamide.

[0010] As used herein, the terms "polymer," "polymers," "polymeric," and similar terms are used in their ordinary sense as understood by one skilled in the art, and thus may be used herein to refer to or describe a large molecule (or group of such molecules) that may comprise recurring units, such as monomers. Polymers may be naturally occurring biopolymers. Polymers may be formed in various ways, including by polymerizing monomers and/or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer may comprise a "homopolymer" that may comprise substantially identical recurring units that may be formed by, e.g., polymerizing a particular monomer. Unless otherwise specified, a polymer may also comprise a "copolymer" that may comprise two or more different recurring units that may be formed by, e.g., copolymerizing, two or more different monomers, and/or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer or copolymer may also comprise a "terpolymer" that may comprise three or more different recurring units. The term“polymer” as used herein is intended to include both the acid form of the polymer as well as its various salts.

[0011] Polymers described herein may be natural or synthetic. As used herein,“natural polymers” generally refers to polymers that occur in nature and can be extracted. An example of natural polymer is a polysaccharide. As used herein“synthetic polymers” generally refers polymers that are synthesized, for example by covalently bonding a plurality of smaller organic or inorganic moieties (monomers) to form a (usually long) polymer chain or network.

[0012] Polymers may comprise nonionic, anionic, and/or cationic monomers. In some embodiments, the polymer may comprise a nonionic polymer that is later hydrolyzed to comprise carboxylate groups. In some embodiments hydrolyzation is effected by use of heat, adding metal or ammonium hydroxides or sodium carbonate. In some embodiments, nonionic polymers may include polyvinyl alcohol, polyethylene oxide and polyethylene glycol. Furthermore, polymers may be amphoteric in nature, i.e., comprising both anionic and cationic substituents, not necessarily in equal proportions.

[0013] As used herein, the term“monomer” generally refers to nonionic monomers, anionic monomers, cationic monomers, zwitterionic monomers, betaine monomers, and amphoteric ion pair monomers.

[0014] As used herein the term“nonionic monomer” generally refers to a monomer that possesses a neutral charge. Exemplary nonionic monomers may comprise but are not limited to comprising monomers selected from the group consisting of acrylamide (“AMD”), methacrylamido, vinyl, allyl, ethyl, and the like. Nonionic monomers may be unsubstituted, or may be substituted with a side chain selected from, for example, an alkyl, arylalkyl, dialkyl, ethoxyl, and/or hydrophobic group. In an exemplary embodiment, a nonionic monomer may comprise AMD. In some embodiments, nonionic monomers may comprise but are not limited to vinyl amide (e.g., acrylamide, methacrylamide, N-methylacrylamide, N,N- dimethylacrylamide), acryloylmorpholine, acrylate, maleic anhydride, N-vinylpyrrolidone, vinyl acetate, N-vinyl formamide and their derivatives, such as hydroxyethyl (methyl) acrylate CH2=CR— COO— CH2CH20H (I) and CH2=CR-C0-N(Z1)(Z2) (2) N-substituted

(methyl)acrylamide (II). R=H or Me; Zl=5-15C alkyl; 1-3C alkyl substituted by 1-3 phenyl, phenyl or 6-12C cycloalkyl (both optionally substituted) and Z2=H; or Zl and Z2 are each 3- 10C alkyl; (II) is N-tert. hexyl, tert. octyl, methylundecyl, cyclohexyl, benzyl,

diphenylmethyl or triphenyl acrylamide. Nonionic monomers may also include N- isopropylacrylamide and N-vinyl formamide. Nonionic monomers can be combined for example form a terpolymer of acrylamide, N-vinyl formamide with anionic acrylic acid.

[0015] As used herein, the term“anionic monomers” may refer to anionic monomers that are substantially anionic in whole or (in equilibrium) in part, at a pH in the range of about 4.0 to about 9.0. The“anionic monomers” may be neutral at low pH (from a pH of about 2 to about 6), or to anionic monomers that are anionic at low pH.

[0016] Examples of anionic monomers which may be used herein include but are not limited to those comprising acrylic, methacrylic, maleic monomers and the like, calcium diacrylate, and/or any monomer substituted with a carboxylic acid group or salt thereof. In some embodiments, these anionic monomers may be substituted with a carboxylic acid group and include, for example, acrylic acid, and methacrylic acid. In some embodiments, an anionic monomer which may be used herein may be a (meth)acrylamide monomer wherein the amide group has been hydrolyzed to a carboxyl group. Said monomer may be a derivative or salt of a monomer according to the embodiments. Additional examples of anionic monomers comprise but are not limited to those comprising sulfonic acids or a sulfonic acid group, or both. In some embodiments, the anionic monomers which may be used herein may comprise a sulfonic function that may comprise, for example, 2-acrylamido-2-methylpropane sulfonic acid (acrylamide tertiary butyl sulfonic acid or“ATBS”). In some embodiments, anionic monomers may comprise organic acids. In some embodiments, anionic monomers may comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamido methylpropane sulfonic acid, vinylphosphonic acid, styrene sulfonic acid and their salts such as sodium, ammonium and potassium. Anionic monomers can be combined for example to form a terpolymer of acrylamide, acrylic acid and 2 -acrylamido -2-methylpropane sulfonic acid.

[0017] As used herein, the term“cationic monomer” generally refers to a monomer that possesses a positive charge. Examples of cationic monomers may comprise but are not limited to those comprising acryloyloxy ethyl trimethyl ammonium chloride (“AETAC”), methacryloyloxyethyltrimethylammonium chloride,

methacrylamidopropyltrimethylammonium chloride (“MAPTAC”),

acrylamidopropyltrimethylammonium chloride, methacryloyloxyethyldimethylammonium sulfate, dimethylaminoethyl acrylate, dimethylaminopropylmethacrylamide, Q6, Q6o 4, and/or diallyldimethylammonium chloride (“D ADM AC”).

[0018] Said cationic monomers may also comprise but are not limited to those comprising dialkylamino alkyl acrylates and methacrylates and their quaternary or acid salts, including, but not limited to, dimethylaminoethyl acrylate methyl chloride quaternary salt

(“DMAEA.MCQ”), dimethylaminoethyl acrylate methyl sulfate quaternary salt

(“DMAEM.MCQ”), dimethyaminoethyl acrylate benzyl chloride quaternary salt

(“DMAEA.BCQ”), dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylamino ethyl acrylate, methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt,

dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt, dialkylaminoalkylacrylamides or methacrylamides and their quaternary or acid salts such as acrylamidopropyltrimethylammonium chloride,

dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammonium chloride, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, diethylaminoethylmethacrylate and dial lyldialkyl ammonium halides such as

diallyldiethylammonium chloride and diallyldimethyl ammonium chloride. Alkyl groups may generally but are not limited to those comprising C_l-8 alkyl groups. In some embodiments, cationic monomers may comprise quaternary ammonium or acid salts of vinyl amide, vinyl carboxylic acid, methacrylate and their derivatives. Exemplary cationic monomers may comprise but are not limited to comprising monomers selected from the group consisting of dimethylaminoethylacrylate methyl chloride quaternary salt,

dimethylaminoethylmethacrylate methyl chloride quaternary salt, and diallyldimethyl ammonium chloride.

[0019] As used herein, the terms“polyacrylamide” or“PAM” generally refer to polymers, including co-polymers and terpolymers that comprise one or more acrylamide moieties.

PAMs may be provided in one of various forms, including, for example, dry (powder) form (e.g., DP AM), water-in-oil emulsion (inverse emulsion), suspension, dispersion, solution, Polyacrylamides may be partly hydrolyzed, e.g., HP AM, in which some of the acrylamide units have been hydrolyzed to acrylic acid. PAMs may be used for polymer flooding.

Additionally, PAMs may be used in any EOR technique.

[0020] As used within, the term“covalent crosslinker” generally refers to an agent capable of creating covalent bonds or crosslinks between polymer chains (or within a polymer chain) during the polymerization of a polymer. Embodiments described herein contemplate the use of a“stable covalent crosslinker”, which is any covalent crosslinker that does not

disintegrate. Exemplary stable covalent crosslinkers for polyacrylamides include methylene bisacrylamide (“MBA”), hexamethylenetetramine, diallylamine, triallylamine, divinyl sulfone, diethyleneglycol diallyl ether and/or phenol aldehyde. In some embodiments, a covalent crosslinker may comprise MBA. In exemplary embodiments, a covalent crosslinker may comprise polyethylene glycol diacrylate.

[0021] As used herein, the term“alginate” generally refers to a linear polysaccharide biocopolymer comprised of guluronic and mannuronic acid. The alginate may be derived from brown seaweed or kelp. Sodium alginate, which is a linear anionic polymer, is a preferred soluble form. Alginate is generally available in low viscosity (“LV”), medium viscosity (“MV”), and high viscosity (“HV”) forms. Alginate polymers may be linked to one another by means of an ionic crosslinker, e.g., multivalent cations. The ionic crosslinker may exchange with the monovalent cation of the alginate polymer resulting in insoluble multivalent cation alginate. [0022] As used herein, the term“preformed particle gel” (“PPG”) generally refers to water swellable and dispersible polymer particles, typically covalently-crosslinked polymer particles, that may swell after their addition to an aqueous fluid such as fresh or salt water, brine, produced water, flowback water, and/or brackish water. PPG systems are used as fluid- diverting agents for conformance control of oil and gas reservoirs. Conventional PPGs may be prepared by first forming a bulk gel comprising a polymer, copolymer, and/or a terpolymer, and a covalent crosslinker, such as MBA, and subsequently mechanically processing the gel, e.g., by crushing and/or grinding, to produce particles of a desired size range. The PPG particles are then added to an injection fluid, allowed to swell, and the injected into a well. Inside the reservoir, the swollen PPG particles can selectively block and/or increase flow resistance of high permeability zones. The dried size of PPG particles following mechanical processing may range from about 0.10 micron to about 10 mm in diameter. PPGs may be prepared off-site, and then brought to a desired location for use. In use, PPGs are deformable, which property facilitates their flowing through porous media even when the PPGs are larger than the pore throats.

[0023] As used herein, the term“ionic crosslinking” or“ re-crosslinking” or the like generally refers to a process or method by which a polymer or polymer network is ionically crosslinked to itself or to another polymer or polymer network. Furthermore, in exemplary embodiments comprising a plurality of re-crosslinkable IPN PPGs, ionic crosslinking or re crosslinking may result in formation of intra-PPG and inter-PPG ionic crosslinks, as described in more detail herein.

[0024] As used herein, the term“ionic crosslinker” or“ ionic crosslinking agent” or the like generally refers to the use of an agent capable of creating ionic bonds or crosslinks between polymer chains (or within a polymer chain). In exemplary embodiments, an ionic crosslinker may comprise a multivalent cation. Non-limiting examples of said multivalent cations include both multivalent cations themselves as well as combinations, compounds and compositions comprising multivalent cations, such as salts thereof such as acetates, nitrates, phosphates, carbonates, propionates, benzoates, formates, citrates and the like. Non-limiting examples of multivalent cations further include alkaline earth metals such as Ca , Sr , Ba , Be and Mg⁺² and transition metals such as Al⁺³, Fe⁺², Fe⁺³, Mn⁺², Cr⁺³ and Zn⁺². In exemplary embodiments, Ca⁺² ion is used. In further exemplary embodiments, CaCl₂, CaS0₄ and CaC0₃ are preferred salt forms of said multivalent cations. In some embodiments, an ionic crosslinking agent may comprise one or more transition metals. In exemplary embodiments, exemplary ionic crosslinkers, such as ionic crosslinkers for use with alginate, include alkaline earth metals such as Ca⁺², Sr⁺², Ba⁺², Be⁺² and Mg⁺² and transition metals such as Al⁺³, Fe⁺², Fe⁺³, Mn⁺², Cr⁺³ and Zn⁺², combinations and salts thereof such as acetates, nitrates, phosphates, carbonates, propionates, benzoates, formates, citrates and the like. In some embodiments, ionic crosslinkers may comprise inorganic ionic crosslinkers, such as, for example, calcium and magnesium. In some embodiments, an ionic crosslinker may comprise a combination or blend of one or more ionic crosslinkers. In some embodiments, an ionic crosslinking agent may be any transitional multivalent ion. In some embodiments, said ionic crosslinker may comprise calcium chloride.

[0025] As used herein, the term“swell capacity” generally refers to the amount of liquid material that may be absorbed by a composition, such as PPGs and/or re-crosslinkable IPN PPGs and/or re-crosslinked PPGs. In some embodiments, the swell capacity may be determined by adding an amount of sample, for instance, 0.5 g of sample, to a graduated container containing 99.5 g of brine or other aqueous fluid. The polymer is permitted to swell for a specified period of time, and the volume of the swollen polymer is measured. The swell capacity may then be determined by dividing the measured swollen volume by the initial (unswollen) sample volume. Particles, such as, for example, re-crosslinkable IPN PPGs, that are“swellable”, generally comprise a swell capacity greater than 1.0.

[0026] As used herein, the term“elongation” generally refers to the ability of a material, such as re-crosslinked IPN PPGs that have bonded together, to be stretched. Elongation as discussed herein may be expressed as an alphabetic code, and/or in the terms that the letters of the code represent, as follows: A = viscoelastic; B = elastic, C = weak elastic; D = association; E = not a gel.

[0027] As used herein, the term“gel strength” generally refers to a measurement of the elastic modulus of a composition, such as re-crosslinked IPN PPGs. For example, a rheometer may be used to measure gel strength, such as of a composition comprising re- crosslinked IPN PPGs.

[0028] As used herein, the term“brittle” generally refers to the ability of a material, such as re-crosslinked IPN PPGs, to be weakly bonded, such that the bond breaks under stress.

[0029] As used herein, the term“enhanced oil recovery” or“EOR” (sometimes also known as improved oil recovery (“IOR”) or tertiary mineral oil production) generally refers to techniques for increasing the amount of unrefined petroleum (for example, crude oil) that may be extracted from an oil reservoir, such as an oil field. Examples of EOR techniques include, for example, miscible gas injection (e.g., carbon dioxide flooding), chemical injection (sometimes referred to as chemical enhanced oil recovery (“CEOR”)), and which includes, for example, polymer flooding, alkaline flooding, surfactant flooding, micellar polymer flooding, conformance control operations, as well as combinations thereof such as alkaline-polymer flooding or alkaline-surfactant-polymer flooding), microbial injection, and thermal recovery (e.g., cyclic steam, steam flooding, or fire flooding). In some embodiments, the EOR operation may include a polymer (“P”) flooding operation, an alkaline-polymer (“AP”) flooding operation, a surfactant-polymer (“SP”) flooding operation, an alkaline- surfactant-polymer (“ASP”) flooding operation, a conformance control operation, or any combination thereof.

[0030] As used herein, the terms“polymer flood” or“polymer flooding” generally refer to a chemical EOR technique that typically involves injecting an aqueous fluid that is viscosified with one or more water-soluble polymers through injection boreholes into an oil reservoir to mobilize oil left behind after primary and/or secondary recovery. As a general result of the injection of one or more polymers, the oil may be forced in the direction of the production borehole, and the oil may be produced through the production borehole. Details of exemplary polymer flooding and of polymers suitable for this purpose are disclosed, for example, in "Petroleum, Enhanced Oil Recovery, Kirk-Othmer, Encyclopedia of Chemical Technology, online edition, John Wiley & Sons, 2010", which is herein incorporated by reference in its entirety.

[0031] One or more surfactants may be injected (or formed in situ) as part of the EOR technique. Surfactants may function to reduce the interfacial tension between the oil and water, which may reduce capillary pressure and improve mobilization of oil. Surfactants may be injected with polymers, for example, in a surfactant-polymer flood or formed in-situ for example, in an alkaline-polymer (AP) flood, or a combination thereof, such as, for example, an alkaline-surfactant-polymer flood (ASP). As used herein, the terms“polymer flood” and “polymer flooding” encompass all of these EOR techniques.

[0032] As used herein, the term“thief zone” generally refers to zones within a reservoir into which injected water may preferentially enter over a comparably lower permeability zone, and said preferential entry may result in one or more unswept zones of the reservoir, A thief zone may be a pore, channel, and/or void into which water and/or other injected materials may enter in an undesirable manner.

[0033] As used herein, the term“conformance control” generally refers to any process by which the sweeping of a reservoir may be spread more evenly. For example, one method of conformance control is to strategically place gelling systems in a reservoir, e.g., at or near a thief zone, to block or control the volume of water entering the thief zone, and redirect water flow to a lower permeability unswept zone.

[0034] As used herein, the term“conformance control agent” generally refers to any material, technique, method, and/or process that may be used to effect conformance control.

[0035] As used herein, the term“sweep efficiency” generally refers to a measure of the effectiveness of an enhanced oil recovery process. Sweep efficiency of a reservoir may depend at least in part on a number of factors including, among others, the volume of the reservoir, injection patterns, off-pattern wells, fractures in the reservoir, position of gasoil and oil-water contacts, reservoir thickness, permeability and areal and vertical

heterogeneity, mobility ratio, density difference between the displacing and the displaced fluid, and flow rate.

PPGs, AND COMPOSITIONS AND METHODS COMPRISING THE USE THEREOF

[0036] The present invention provides re-crosslinkable IPN PPGs which when contacted with at least one ionic crosslinker, e.g., a multivalent cation, result in re-crosslinked IPN PPGs having enhanced conformance control properties.

[0037] Conventional PPGs are formed by polymerization of one or more monomers.

Typically, the PPG is covalently crosslinked with at least one covalent crosslinker, such as MBA. The resultant PPG is capable of swelling in water or aqueous fluids. Conventional PPGs generally comprise only a single type of polymer or copolymer, such as, for example, polyacrylamide or anionic polyacrylamide.

[0038] In contrast to conventional PPGs, exemplary re-crosslinkable IPN PPGs comprise an interpenetrating network of more than one polymer. According to some embodiments, the re- crosslinkable IPN PPG comprises an interpenetrating polymer network of at least a first polymer and a second polymer.

[0039] According to some embodiments, the re-crosslinkable IPN PPG comprises a first polymer that comprises a polyacrylamide (co)polymer. In some embodiments, the first polymer may further comprise nonionic, anionic, and/or cationic monomers. In some embodiments, the first polymer comprises an anionic copolymer of acrylamide and acrylic acid.

[0040] In some embodiments, the first polymer comprises less than about 50%, less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 15%, less than about 10%, or less than about 5% acrylamide. In some embodiments, the first polymer comprises greater than about 15%, greater than about 25%, greater than about 35%, or greater than about 40% acrylamide. In some embodiments, the first polymer comprises greater than about 35%, greater than about 40%, greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, greater than about 90%, or greater than about 99% acrylic acid. In some embodiments, the polymer may comprise a nonionic polymer that is later hydrolyzed to comprise carboxylate groups. In some embodiments, hydrolyzation can be produced by heat, adding metal or ammonium hydroxides or sodium carbonate. In some embodiments, the maximum amount of the first polymer, e.g., an AA/AMD polymer will comprise an amount which provides for PPG with a desired amount of intercrosslinking and the formation of interpenetrating network comprising the first acrylamide (co)polymer and a second polymer that is capable of ionic bonding. In some embodiments, the amount of AMD monomer in an acrylic acid/ AMD copolymer may comprise an amount that may allow for re-crosslinking (ionic crosslinking) of a re-crosslinkable IPN PPG upon addition of a re-crosslinker.

[0041] According to the various embodiments, the re-crosslinkable IPN PPG comprises a second polymer that is capable of ionic crosslinking. In some embodiments, the second polymer may be a polysaccharide. Exemplary polysaccharides that are capable of ionic crosslinking include alginates, pectin, carrageenan and gellan. In an exemplary embodiment, the second polymer is an alginate.

[0042] The amount of such second polymer may depend upon various parameters, e.g., its ability to promote ionic crosslinking with the first polymer, its solubility and/or its viscosity limit. According to the various embodiments, the re-crosslinkable and/or re-crosslinked IPN PPGs comprise less than about 35%, less than about 30%, less than about 20%, less than about 10%, less than about 5%, or less than about 1% of the second polymer. In some embodiments, the re-crosslinkable and/or re-crosslinked IPN PPGs comprises at least about 10%, or at least about 20% or at least about 30% of the second polymer. In some

embodiments, the re-crosslinkable and/or re-crosslinked IPN PPGs comprise a low molecular weight alginate which in some exemplary embodiments comprises at most 35% of the re- crosslinkable and/or re-crosslinked IPN PPGs.

[0043] Various embodiments described herein include a method for making a re- crosslinkable IPN PPG. As used herein,“re-crosslinkable IPN PPGs,”“interpenetrating network PPGs which may be re-crosslinked,” and the like, generally refer to swellable PPGs that comprise an interpenetrating polymer network of at least a first polymer and a second polymer. The re-crosslinkable IPN PPGs may comprise one or more individual PPG particles that each have an interpenetrating network of two or more polymers following polymerization, which particles are able to be bonded to one another, e.g., upon the addition of an ionic crosslinker. For example, the individual re-crosslinkable IPN PPG particles may comprise a network of crosslinked acrylamide (co)polymers intertwined with linear alginate polymers. In exemplary embodiments, re-crosslinkable IPN PPGs possess properties such as size, mechanical strength, and/or swell capacity that permits their use in processes wherein PPGs are commonly used, for example, in conformance control applications in EOR.

[0044] According to the embodiments, re-crosslinkable IPN PPGs may be produced by first dissolving a composition of monomers of a first polymer in a solution comprising a composition of a second polymer. Following dissolution of said monomers, polymerization of the first polymer may be effected by any means known in the art, preferably with a covalent crosslinker; to produce an IPN of cross-linked first polymer intermixed with the second polymer. Formation of the IPN may result in a gel-like structure that may be dried, ground, and sieved. Grinding and sieving may be used to provide re-crosslinkable IPN PPGs having a necessary desired particle size range.

[0045] According to certain embodiments, re-crosslinkable IPN PPGs may be produced by first polymerizing acrylic acid and acrylamide monomers in the presence of a covalent crosslinker (e.g., MBA) in a linear alginate polymer solution. This forms an IPN of covalently crosslinked anionic acrylamide co-polymer with linear alginate polymer. In some embodiments, the IPN may be dried to form a re-crosslinkable IPN PPG. The dried re- crosslinkable IPN PPG is swellable or dispersible in water or an aqueous brine solution. In some embodiments, a re-crosslinkable IPN PPG is formed by adding a water soluble alginate polymer solution to an acrylic acid and acrylamide monomer solution.

[0046] In some embodiments, the monomer composition of the first polymer may comprise at least one covalent crosslinker. In some embodiments, said covalent crosslinker may comprise MBA, In some embodiments, said covalent crosslinker may comprise an organic crosslinker. Exemplary organic crosslinkers may comprise MBA, hexamethylenetetramine, diallylamine, triallylamine, di vinyl sulfone, diethyleneglycol diallyl ether and/or phenol aldehyde. In preferred embodiments, a covalent crosslinker may comprise MBA.

[0047] In some embodiments, said re-crosslinkable IPN PPGs may have a wide range of initial PPG particle sizes. In some embodiments, the subject re-crosslinkable IPN PPGs may comprise any diameter that is suitable to obtain a desirable result in a method or process, such as their usage in EOR techniques, methods, and processes. In some embodiments, said re- crosslinkable IPN PPGs may comprise a diameter of 0.10 pm or less, 0.5 pm or less, 1.0 pm or less, 10.0 mih or less, 50.0 mih or less, 0.1 mm or less, 0.15 mm or less, 0.20 mm or less, 0.25 mm or less, 0.30 mm or less, 0.35 mm or less, 0.40 mm or less, 0.45 mm or less, 0.50 mm or less, 0.55 mm or less, 0.60 mm or less, 0.65 mm or less, 0.70 mm or less, 0.75 mm or less, 0.80 mm or less, 0.90 mm or less, 0.95 mm or less, 1.00 mm or less, 1.10 mm or less,

1.20 mm or less, 1.30 mm or less, 1.40 mm or less, 1.50 mm or less, 1.60 mm or less, 1.70 mm or less, 1.80 mm or less, 1.90 mm or less, 2.00 mm or less, 2.25 mm or less, 2.50 mm or less, 2.75 mm or less, 3.00 mm or less, 3.25 mm or less, 3.50 mm or less, 3.75 mm or less, 4.00 mm or less, 4,25 mm or less, 4.50 mm or less, 4.75 mm or less, 5.00 mm or less, 6.00 mm or less, 7.00 mm or less, 8.00 mm or less, 9.00 mm or less, 10.00 mm or less. In some embodiments, said re-crosslinkable IPN PPGs may comprise a diameter of 10.00 mm or more.

[0048] According to the various embodiments of the invention, the re-crosslinkable IPN PPG is then re-crosslinked to form a re-crosslinked IPN PPG. As used herein,“re-crosslinked PPGs” and“re-crosslinked IPN PPGs” and the like refer to a composition in which a plurality of re-crosslinkable IPN PPGs have been ionically crosslinked to bond the IPN PPGs to one another. After re-crosslinking, the resultant re-crosslinked IPN PPGs may exhibit increased strength during elongation. In exemplary embodiments, re-crosslinked IPN PPGs possess properties such as size, mechanical strength, and swell capacity that permit their use in processes wherein PPGs are commonly used, for example, in conformance control applications in EOR. In exemplary embodiments, re-crosslinked IPN PPGs may form a gel and/or have gel-like properties, such as elasticity.

[0049] In some embodiments, a method for re-crosslinking as described herein, may comprise (i) providing an aqueous composition comprising a plurality of swellable re- crosslinkable IPN PPG as discussed herein, (ii) allowing the re-crosslinkable IPN PPG to swell; and (iii) adding an amount of at least one ionic crosslinker sufficient to provide for recrosslinking of the IPN PPGs, wherein the at least one ionic crosslinker is added before, during and/or after swelling.

[0050] According to exemplary embodiments, the re-crosslinked IPN PPGs are formed by dispersing a plurality of the re-crosslinkable IPN PPGs in a solution, e.g., an aqueous solution or brine, and allowing the particles to swell. An ionic crosslinker, e.g., a multivalent cation, may be added to this solution, which results in formation of ionic bonds or crosslinks. The resulting ionic bonds may form between two available bonding sites within a PPG (intra-PPG bonds) which bond and reinforce a single PPG. The resulting ionic bonds may form between two available bonding sites on two PPG particles (inter-PPG bonds), which bond two or more PPG particles together. In some embodiments, the resulting ionic bonds result in crosslinking of the first polymer (within in the same chain and/or two different chains, and/or between two different PPG particles). In some embodiments, the resulting ionic bonds result in

crosslinking of the second polymer (within in the same chain and/or two different chains, and/or between two different PPG particles). In some embodiments, the resulting ionic bonds result in crosslinking of the first polymer, and crosslinking of the second polymer.

[0051] According to embodiments of the invention, the re-crosslinked IPN PPG may comprise an interpenetrating network of a first polymer that is covalently crosslinked and a second polymer that is ionically crosslinked. According to embodiments of the invention, the re-crosslinked IPN PPG may comprise an interpenetrating network of a first polymer that is covalently crosslinked and ionically re-crosslinked, and a second polymer that is ionically crosslinked.

[0052] In some embodiments, the re-crosslinked IPN PPG comprises a first polymer that is an anionic polyacrylamide (co)polymer and a second polymer that is an alginate polymer. In these embodiments, the re-crosslinked IPN PPG may comprise an interpenetrating network of covalently-crosslinked and also ionically-crosslinked acrylamide (co)polymers and ionically- crosslinked alginate polymers. In some embodiments, the re-crosslinked IPN PPG may comprise an interpenetrating network of an anionic polyacrylamide (co)polymer that is covalently crosslinked, and an alginate polymer that is ionically crosslinked. The re- crosslinked IPN PPG may comprise ionically crosslinked (re-crosslinked) PPGs, resulting from the ionic crosslinking of alginate polymer and/or polyacrylamide (co)polymer between two or more IPN PPG particles, creating a network of IPN PPGs. The re-crosslinked IPN PPG may also comprise intra-molecular ionic crosslinks of said alginate polymers and/or intra-molecular ionic crosslinks of said anionic polyacrylamide (co)polymers, which may thereby reinforce and strengthen said re-crosslinked PPGs.

[0053] In some embodiments, the re-crosslinkable IPN PPG may be swollen in water before adding to a brine comprising one or more multivalent ions. In some embodiments, a re- crosslinkable IPN PPG may be partially swollen in water before adding to brine comprising one or more multivalent ions.

[0054] According to various embodiments, an ionic crosslinking agent may be added to re- crosslinkable IPN PPGs before, during, and/or after swelling. According to the various embodiments, an ionic crosslinking agent may be added when the re-crosslinkable IPN PPG is in an unswollen, partially swollen, or substantially swollen state. In some exemplary embodiments, ionic crosslinking of re-crosslinkable PPGs may occur in situ in desired sites, for example by combining pre-formed re-crosslinkable IPN PPGs and at least one ionic crosslinker in situ at a desired site or structure, e.g., a subterranean structure comprising pores, voids, and/or channels.

[0055] In exemplary embodiments, re-crosslinking (ionic crosslinking) of said re- crosslinkable IPN PPGs may be effected over a desired time period, e.g., a few days. In some embodiments, re-crosslinking of said PPGs may occur in 1 day or less, 1 day or more, 2 days or more, 3 days or more, 4 days or more, 5 days or more, 6 days or more, 7 days or more, 8 days or more, 9 days or more, or 10 days or more.

[0056] In some embodiments, re-crosslinking (ionic crosslinking) of said re-crosslinkable IPN PPGs may occur at room temperature. In some embodiments, said re-crosslinkable IPN PPGs may be re-crosslinked at temperatures ranging from 4°C to 150°C.

[0057] In some embodiments, re-crosslinking of said re-crosslinkable IPN PPGs may be achieved over a wide range of pH values. In some exemplary embodiments, re-crosslinking of the re-crosslinkable IPN PPGs may occur at neutral pH. In some embodiments, pH stabilizers or pH modifiers may be used to control or change the pH.

[0058] In some embodiments, inhibitors may be added, such as, but not limited to, sodium citrate, calcium sulfate dihydrate, sodium sulfate, sodium lactate, trisodium phosphate, sodium phosphate, ethylenediaminetetraacetic acid (EDTA) and the like to deaccelerate the re-crosslinking and/or ionic crosslinking rate.

[0059] In some embodiments, the re- crosslinking may be accelerated using one or more chemical additives for re-crosslinking acceleration, for example, potassium titanium fluoride or chromic trichloride may be added. In some embodiments, buffering agents, such as sodium bicarbonate and the like, may be added to pH buffer the treatment fluid.

[0060] In some embodiments, a second covalent crosslinker, such as polyethylene glycol diacrylate, may be added to a composition comprising re-crosslinkable IPN PPGs and said second covalent crosslinker may further increase gel strength of a re-crosslinked PPG composition. In some embodiments, re-crosslinkable IPN PPGs may be covalently crosslinked using at least two covalent crosslinkers, e.g., MBA and polyethylene glycol diacrylate. In exemplary embodiments, re-crosslinkable IPN PPGs, which are obtained using at least two different covalent crosslinkers, e.g., MBA and polyethylene glycol diacrylate and subsequently re-crosslinked using at least one ionic crosslinker forms a re-crosslinked IPN PPG with increased gel strength, increased elongation and/or lower swell capacity compared to a similar composition having only one covalent crosslinker is used. In some embodiments, re-crosslinkable IPN PPGs and/or a composition comprising such re-crosslinkable IPN PPGs may comprise at least two ionic crosslinkers.

[0061] In exemplary embodiments, re-crosslinked IPN PPGs that are prepared in accordance with the methods described herein possess improved mechanical strength, and/or elasticity. In exemplary embodiments, re-crosslinked IPN PPGs form a gel-like structure as a result of said re-crosslinking and thereby provide a more effective sealing mechanism when used with EOR techniques and/or methods of conformance control.

[0062] In exemplary embodiments, a re-crosslinked IPN PPG may comprise ionically- crosslinked alginate polymer, ionically-crosslinked polyacrylamide (co)polymer and covalently-crosslinked polyacrylamide (co)polymer. Not wishing to be bound by theory, it is believed that when said re-crosslinked IPN PPG is stretched, the polyacrylamide network remains intact (due in part to the covalent crosslinks) and stabilizes the PPG, while the alginate network provides elasticity, as said alginate network“unzips” when the ionic bonds are stressed, first in in small areas, which then become wider as the stretch increases. Not wishing to be bound by theory, it is believed that if there is a sufficient level of acrylic acid in the anionic polyacrylamide (co)polymer, acrylic acid will crosslink with a multivalent cation providing additional strength and continuing the IPN network between the particles.

[0063] In exemplary embodiments, in a composition comprising re-crosslinked IPN PPG comprising polyacrylamide (co)polymer and sodium alginate, ionically-crosslinked alginate may provide stretching, and said polyacrylamide may provide swelling and strength to the composition. Said swollen gel may be sufficiently deformable to fill voids in a formation and to withstand pressure,

[0064] According to the various embodiments, the strength and elasticity of the resultant re- crosslinked IPN PPG may be configured to have any necessary or desired strength, by modifying the intra-particle and the inter-particle bonding of the PPG particles. For example, in some embodiments, the re-crosslinked IPN PPG may be a relatively strong, deformable viscoelastic gel. In further embodiments, the resultant re-crosslinked IPN PPG may have weaker or more brittle crosslinking bonds. In some embodiments, re-crosslinked IPN PPGs may be able to withstand pressure and remain in pores or voids when conventional PPGs may be displaced under similar conditions, e.g., similar pressure conditions.

[0065] In some embodiments, the subject re-crosslinkable IPN and/or re-crosslinked IPN PPGs may have a swell capacity of about 10.0 or less, 10.0 or more, 12.5 or more, 15.0 or more, 17.5 or more, 20.0 or more, 22.5 or more, 25.0 or more, 27.5 or more, 30.0 or more, 32.5 or more, 35.0 or more, 37.5 or more, 40.0 or more, 42.5 or more, 45.0 or more, 47.5 or more, 50.0 or more, 52.5 or more, 55.0 or more, 57.5 or more, 60.0 or more, 62.5 or more, 65.0 or more, 67.5 or more, 70.0 or more, 72.5 or more, 75.0 or more, 77.5 or more, 80.0 or more, 82.5 or more, 85.0 or more, 87.5 or more, 90.0 or more, 92.5 or more, 95.0 or more, 97.5 or more, 100.0 or more, 105.00 or more, 110.00 or more, 115,00 or more, 120.00 or more, 125.00 or more, 130.00 or more, 135.00 or more, 140.00 or more, 145.00 or more, 150.00 or more, 155.00 or more, 160.00 or more, 165.00 or more, 170.00 or more, 175.00 or more, 180.00 or more, 185.00 or more, 190.00 or more, 195.00 or more, or 200.00 or more.

[0066] In some embodiments, the exemplary re-crosslinked IPN PPGs may comprise a gel that is viscoelastic, elastic, or weakly elastic. In some embodiments, the exemplary re- crosslinked IPN PPGs may have a gel strength value of about 4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.2 or more, or 9.5 or more. In exemplary embodiments, re- crosslinked IPN PPGs may have a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.

[0067] Furthermore, embodiments of the present invention generally relate to a composition comprising: (i) a plurality of re-crosslinkable interpenetrating polymer network, preformed particle gel (“IPN PPG”) comprising an interpenetrating network of a first polymer and a second polymer, wherein said IPN PPG is swellable and dispersible in water or brine; and (ii) at least one ionic crosslinker. Upon combination of the re-crosslinkable IPN PPG and the ionic crosslinker in an aqueous system, the IPN PPGs may be converted to a re-crosslinked IPN PPG that is a viscoelastic gel.

[0068] In some embodiments, the composition may comprise a dry or solid ionic crosslinker and a dry re-crosslinkable IPN PPG that are mixed or blended in their respective dry form. In some embodiments, the ionic re-crosslinker may be provided as a liquid and dried on the re- crosslinkable IPN PPG particles. In some embodiments, the re-crosslinkable IPN PPG composition may be further ground. Addition of a re-crosslinker to the composition as a solid, liquid, or further grinding of the re-crosslinkable IPN PPG may allow for a single- package PPG system. The single-package re-crosslinkable IPN PPG with re-crosslinker already added, as described herein, may then be added to water or brine, which may result in swelling and formation of a viscoelastic gel by the ionic re-crosslinking of the IPN PPGs.

[0069] In some embodiments, said composition may further comprise one or more of a surfactant, an aqueous liquid, a fluid comprising at least one of water, an organic solvent, and an oil, a buffer, a mobility buffer, a drive fluid, or another viscosifier. In some embodiments the composition comprises an ethylene oxide/propylene oxide block copolymer surfactant, such as PLURONIC® F-127, which is commercially available from BASF. In some embodiments, an ionic re-crosslinker may be added before, during, and/or after swelling of said re-crosslinkable IPN PPG. In general, said composition generally relates to any composition comprising any of the re-crosslinkable IPN PPGs and/or re-crosslinked IPN PPGs as described herein.

[0070] Also, the present embodiments generally relate to any method and/or system that comprises the use of any composition comprising a swellable and re-crosslinkable IPN PPG and/or re-crosslinked IPN PPG as described herein, for applications such as enhanced oil recovery. For example, a system for use in conformance control may comprise (i) a re- crosslinkable swellable IPN PPG; (ii) at least one ionic crosslinker; and (iii) a subterranean formation having the composition therein. In some embodiments, the re-crosslinkable IPN PPG is converted into a gel during use as a conformance control agent. Said system may further comprise a fluid conduit disposed in an injection wellbore, and/or a pump configured to pump the composition through the conduit downhole.

[0071] In some embodiments, a composition comprising a re-crosslinkable IPN PPGs in association with at least one ionic crosslinker, and/or re-crosslinked IPN PPGs may be used in an enhanced oil recovery technique that may primarily target bypassed oil. In some embodiments, said compositions may be added to injection water for water flooding and/or polymer flooding. In some embodiments, said compositions may serve as water-shutoff, conformance control, and/or mobility control agents. In some embodiments, said compositions may divert injected fluid away from thief zones and into adjacent matrix rock or low-permeability zones, thereby increasing macroscopic sweep efficiency and improving hydrocarbon recovery. In some embodiments, use of compositions comprising re- crosslinkable IPN PPGs in association with at least one ionic crosslinker, and/or re- crosslinked IPN PPGs in EOR processes may result in a decrease in water production in water and gas shutoff, fluid loss control, zone abandonment, water and gas coning, squeeze and recompletion, chemical liner completions and lost circulation during drilling operations and plugging during drilling and drilling completion.

[0072] The exemplary embodiments described herein generally involve methods of using a composition comprising re-crosslinkable IPN PPGs in association with at least one ionic crosslinker, and/or re-crosslinked IPN PPGs in conjunction with enhanced oil recovery techniques and processes. Exemplary methods may improve the overall macroscopic sweep efficiency, may improve and/or increase hydrocarbon production, and may decrease associated water production. Exemplary compositions may generally be used for in processes and techniques related to conformance control as a conformance control agent. Also, exemplary compositions may generally comprise permeability reduction capabilities and may enable the strategic plugging of high-permeability channels. Said plugging may divert flooding fluid to relatively unswept adjacent low-permeability zones.

[0073] Additionally, the exemplary embodiments generally provide a method of

conformance control, wherein said method may comprise adding an amount of a composition comprising a plurality of swellable and re-crosslinkable IPN PPGs and at least one ionic crosslinker is effective to act as a conformance control agent.

[0074] Compositions comprising re-crosslinkable IPN PPGs in association with at least one ionic crosslinker and/or re-crosslinked IPN PPGs may be used as a part of any method and/or process related to enhanced oil recovery and/or conformance control, including water shutoff, drill fluids, and/or permeability control. Said IPN PPGs may be used as a part of any method and/or process where conventional PPGs may generally be used. The exemplary

compositions comprising re-crosslinkable and/or re-crosslinked IPN PPGs may be used in methods for improving production from an oil or gas well, wherein said methods may comprise: (i) providing a composition comprising a plurality of re-crosslinkable IPN PPGs and at least one ionic crosslinker, and (ii) delivering the composition into the oil or gas well, whereby the composition improves production from the well. The exemplary compositions may be used in methods for water blocking or water shutoff in an oil or gas well, wherein said methods comprise (i) providing a composition comprising a plurality of swellable re- crosslinkable IPN PPGs, and at least one ionic crosslinker, and (ii) delivering the composition into the oil or gas well, whereby the composition provides water blocking or water shutoff in the well,

[0075] Moreover, the re-crosslinkable IPN PPGs and/or re-crosslinked PPGs may be used in a method of enhancing oil recovery from an oil source, comprising (i) providing a

composition comprising a plurality of swellable and re-crosslinkable IPN PPGs, and at least one ionic crosslinker as discussed herein, and (ii) delivering the composition into the oil source, whereby the composition enhances oil recovery from the oil source. Additionally, the exemplary re-crosslinkable IPN PPGs and/or re-crosslinked PPGs may be used in a method of treating a petroleum-containing formation to reduce sand production, comprising: (i) providing a composition comprising re-crosslinkable IPN PPGs, and at least one ionic crosslinker , and (ii) delivering said composition into the petroleum-containing formation, whereby the composition reduces sand production in the formation. Furthermore, an exemplary method of displacing fluid from a wellbore by viscous plug flow, may comprise:

(i) providing a composition comprising a plurality of swellable re-crosslinkable IPN PPGs, and at least one ionic crosslinker as discussed herein, and (ii) delivering the composition into a wellbore, whereby the formulation forms a viscous plug in the wellbore, thereby displacing fluid therefrom.

[0076] Any of the methods provided herein may include one or more step of re-crosslinking such as, for example: (i) providing an aqueous composition comprising a plurality of swellable re-crosslinkable IPN PPG as discussed herein, (ii) allowing the re-crosslinkable IPN PPG to swell; and (iii) adding an amount of at least one ionic crosslinker sufficient to provide for re-crosslinking of the IPN PPGs, wherein the at least one ionic crosslinker is added before, during and/or after swelling.

[0077] In some embodiments, a method of enhanced oil recovery may comprise: (i) obtaining or providing a composition comprising a plurality of swellable re-crosslinkable IPN PPGs and at least one ionic crosslinker; (ii) placing the composition in a subterranean formation downhole; and (iii) extracting material comprising petroleum from the subterranean formation downhole via a production wellbore. In some embodiments, re-crosslinking of the IPN PPGs may occur in a subterranean formation. In some embodiments, during said method, the composition is placed downhole via an injection wellbore. In some embodiments of said method, extraction may be effected using a production wellbore. In some embodiments, the method comprises placing the composition in a producing zone downhole, and the extracting of the material comprising petroleum from the subterranean formation downhole comprises extracting of the material from the producing zone.

[0078] Additionally, in some embodiments, the compositions and methods may be useful for remediation of a zone within a subterranean formation bearing heavy/viscous oil to inhibit breakthrough of water from a water injection well via the zone into a production well, the zone comprised of a void space, a halo region, or both, within the zone due to production of the heavy/viscous oil through the production well, the zone thereby allowing for pressure communication between the injection well and the production well, may comprise: (i) injecting a composition into the zone via the injection well, the composition comprising swellable re-crosslinkable IPN PPGs, and at least one ionic crosslinker; and (ii) allowing the re-crosslinkable IPN PPGs re-crosslink sufficiently to form a plug which reduces flow communication of water between the injection well and the production well. In some embodiments of said method, the displacement fluid is selected from water, alcohols, fuel oil or crude oil. In some embodiments of said method, the displacement fluid is water. [0079] Due to the characteristics of the re-crosslinkable IPN PPGs, such as its hydrophilic nature, initial size, and that it may be re-crosslinked, re-crosslinkable IPN PPGs can propagate relatively far into a reservoir. In some embodiments, a composition comprising re- crosslinkable IPN PPGs and at least one ionic crosslinker may be added to injection water as part of a secondary or tertiary water recovery process, carbon dioxide injection, chemical, or air injection for recovery of hydrocarbon from subterranean sandstone or carbonate formation. This may allow for control of the near well-bore and in-depth formation conformance vertically and laterally by selectively blocking the high water channels.

[0080] In some embodiments, re-crosslinked IPN PPGs may be deformable so as to fill voids and withstand pressure during their use in techniques related to enhanced oil recovery and/or conformance control. In some embodiments, a second covalent crosslinker, such as polyethylene glycol diacrylate, may be added to a composition comprising re-crosslinkable IPN PPGs or re-crosslinked IPN PPGs, and said second covalent crosslinker may further increase gel strength of a re-crosslinked PPG composition. In some embodiments, re- crosslinkable IPN PPGs may be covalently crosslinked using at least two covalent crosslinkers, e.g., MBA and polyethylene glycol diacrylate. In exemplary embodiments, re- crosslinkable IPN PPGs may form a multivalent alginate polymer network with anionic polyacrylamides within the particles upon the addition of at least one ionic crosslinker, such as, for example calcium or a salt comprising calcium, for example. In exemplary

embodiments, re-crosslinkable IPN PPGs, which when obtained using at least 2 different covalent crosslinkers, e.g., MBA and polyethylene glycol diacrylate and subsequently re- crosslinked using at least one ionic crosslinker forms a re-crosslinked IPN PPG with increased gel strength, increased elongation and/or lower swell capacity compared to when one covalent crosslinker is used. In some embodiments, re-crosslinkable IPN PPGs and/or a composition comprising may comprise at least two ionic crosslinkers.

[0081] Having generally described various aspects of the invention, the invention will be described more in detail with reference to the following Examples; however the invention should not be limited to these examples. Indeed these examples are intended to be exemplary of methods for producing re-crosslinkable IPN PPGs and re-crosslinked IPN PPGS and processes of using same according to the invention.

EXAMPLES

Test Methods [0082] In the examples that follow, the following test methods are referenced:

Swell Capacity Test

[0083] The swell capacity of the PPG samples was measured before adding the PPG sample to a calcium chloride solution to re-crosslink. 0.5g of a PPG sample was added to 49.5 g of deionized water in a 50 mL centrifuge tube and allowed to swell for 24 hours. Next, each of the resultant gel dispersions was centrifuged at 2500 rpm for 15 minutes. The initial PPG volume was then determined from the density of the sample by weighing the sample in a centrifuge tube. The measured swell volume was divided by the initial PPG volume to obtain the swell capacity value.

Gel Strength Test

[0084] Each PPG sample was swelled in deionized water or a 1% calcium chloride solution for 24 hours. Then each PPG sample was pad dried to remove excess water, and the gel was cut to fit the Rheometer stage diameter (12.5 mm). As a measure of gel strength, the elastic modulus (G’) value was used, which was determined by using Anton-Paar MCR 300 Rheometer with 12.5 mm stage, a gap of 1 mm, and a temperature of 60°C. The gel strength was measured at 0.1 to 10 rad/sec, and the values were recorded at 0.926/s.

PPG Elongation Test

[0085] The elongation of re-crosslinked PPG samples was qualified as follows. A re- crosslinked PPG sample was stretched by hand and, if viscoelastic, was released and then stretched several more times, If a PPG sample broke when it was stretched, the elasticity before breakage was noted. The elongation of a re-crosslinked PPG sample was expressed as in alphabetic code A-E, as shown in Table 1. The elongation codes ranged from“A,” which was used for samples that demonstrated viscoelastic strength, to“E,” which was used for samples that remained distinct particles.

TABLE 1 : Elongation Codes

Example 1 : Re-crosslinkable IPN PPG Synthesis

[0086] Samples of re-crosslinkable PPG 1-4, and comparative samples 5-7 were prepared according to the following procedure.

[0087] For IPN PPG samples 1-4 and 6-7, an alginate solution was prepared by dissolving 2 or 4 parts of sodium alginate, as specified in Table 2, below, in about 48.8 parts of water. Each sodium alginate solution was stirred continuously while separately monomer solutions were prepared. For comparative PPG sample 5, no sodium alginate was added to the water.

[0088] For samples 1-7, the monomer solutions were prepared by combining acrylamide (AMD) solution (53.6%) and acrylic acid in the amounts specified in Table 2, below. The pH value of each solution was adjusted to 7.0 with 45% potassium hydroxide solution. Following pH adjustment, water was added if necessary to make up a total of 100 parts. After the pH adjustments, MBA was added to the solutions in the amounts specified in Table 2, below.

[0089] Next, each monomer solution was slowly added to each of the sodium alginate solutions (except sample 5) with continuous stirring before and during the addition of the monomer solutions. Each solution was then added to its own separate sealed flask, the temperature was adjusted to approximately 22°C, and the solution was subsequently purged with nitrogen for approximately 1 hour. Following the 1 hour purge, 0.003 parts of DTP A at 40%, 0.001 parts sodium thiosulphate, and 0.002 parts ammonium persulfate were added to each container. After a temperature increase was observed in the flask, stirring was stopped, and the monomers then polymerized to form a solid interpenetrating polymer network gel of anionic polyacrylamide and sodium alginate. Comparative PPG sample 5 was polymerized using a similar method, but no sodium alginate was added, resulting in a gel of anionic polyacrylamide.

Table 2: Samples 1-7 Monomer mixtures

[0090] After polymerization, the IPN PPG samples 1-4 and 6-7 and comparative PPG sample 5 were processed as follows. For each PPG, the polymer gel was dried overnight at 70°C and then was cut into approximately 2 c pieces. Next, each sample was added individually to a VITA-MIX® blender and ground. The dried gel particles were sieved to less than 75 mhi using U.S. standard sieve No. 200 to produce the each of the PPGs. Tests to measure the swell capacity of PPG samples 1-7 were performed using the procedure described above, with results shown in Table 3, below.

Example 2: Re-crosslinked PPG Synthesis and Evaluation

[0091] Each PPG sample (IPN PPG 1-4 and 6-7 and comparative PPG 5) was re-crosslinked using the following procedure. 0.5 parts of each PPG sample were added to 49.5 parts deionized water and then mixed by shaking for 90 seconds. Each of the mixtures was then allowed to swell for 3 hours at room temperature in order to produce swollen gel particles. After the 3-hour period, the swollen gel dispersion was added to 50 parts of a 1% calcium chloride solution and subsequently was mixed by stirring. The PPG particles were then allowed to settle in the container. Next, each of the mixtures was allowed to re-crosslink over a 7 day period at room temperature, thereby forming a gel, which was evaluated as described below.

[0092] Gel strength and elongation tests were performed on the samples as described above and results recorded in Table 3, below.

TABLE 3: Swell Capacity, Gel Strength and Elongation for Re-crosslinkable IPN PPG, Re- crosslinked IPN PPG, and Comparative PPG samples.

[0093] Referring to Table 3, for the exemplary re-crosslinkable IPN PPG samples 1-4, the swell capacity of the samples was higher for samples with lower MBA content (samples 1 and 2) which therefore had less covalent crosslinking. However, the swell capacity appeared unaffected by the level of sodium alginate present. The swell capacity of the exemplary re- crosslinkable IPN PPG samples was similar to the comparative PPG sample 5, which did not contain sodium alginate.

[0094] For the re-crosslinked IPN PPG samples, the gel strength values as measured in DI water and calcium chloride were higher for samples having the higher levels of MBA (1,000 ppm), indicating that higher levels of covalent crosslinking may provide higher gel strength. The gel strength values as measured in calcium chloride solutions, were higher than those performed in DI water. Additionally, the gel strength values were higher for the samples with increased amounts of sodium alginate as compared to those with less sodium alginate, indicating that the sodium alginate is contributing to the gel strength. Comparative PPG sample 5, which did not contain sodium alginate, displayed a similar gel strength in DI water as the exemplary IPN PPG samples 1-4. However, in calcium chloride solution, the gel strength of comparative PPG 5 was significantly lower than the exemplary IPN PPG samples 1-4.

[0095] The elongation test demonstrated that exemplary re-crosslinked IPN PPG samples 1-4 displayed viscoelastic and/or elastic properties. In comparison, the comparable PPG sample 5 did not display gel-like properties in the elongation test. [0096] Comparative samples PPG 6 and PPG 7, which contained similar levels of sodium alginate as compared to exemplary IPN PPG samples 1-4, did not display gel-like properties in the elongation test as did PPG 1-4. These samples had a much lower charge (less A A) than the exemplary IPN PPG samples 1-4. The results indicate that the charge of the acrylamide (co)polymer is one important factor to the re-crosslinking. Not wishing to be bound by any particular theory, a swollen IPN PPG that has a lower charge may have a larger volume than exemplary IPN PPG samples 1 -4 in the calcium chloride solution because of its lower charge, which would not allow the close contact between particles for desired re-crosslinking. In addition, an IPN PPG that has a lower charge has less acrylic acid available for re- crosslinking with calcium ions.

Example 3: Re-crosslinked IPN PPG having two covalent cross-linkers

[0097] In this example, exemplary re-crosslinkable IPN PPG samples 8-12 were prepared as described in Example 1, using the specified ratios in Table 4, except that each monomer mixture included an additional 0.002 or 0.004 parts of polyethylene glycol diacrylate

(“PEGDA”) covalent crosslinker, in addition to MBA. Further, for sample 12 only, the alginate solution comprised 3 parts of sodium alginate. The swell capacity of each sample was measured as described above, and the results were recorded in Table 4.

[0098] The samples were re-crosslinked using the method described in Example 2, above.

Gel strength and elongation tests were performed on the samples as described above and results recorded in Table 4, below.

TABLE 4: Swell Capacity, Gel Strength and Elongation for Re-crosslinkable IPN PPG and Re-crosslinked IPN PPG

[0099] Referring to Table 4, swell capacity was higher for exemplary re-crosslinkable IPN PPG samples that had lower MBA (compare sample 8 to sample 10, sample 9 to sample 11). The swell capacity seemed to increase with lower levels of sodium alginate (compare sample 8 to sample 9, sample 10 to sample 11). Comparing the results in Table 4 to Table 3, exemplary IPN PPG samples 8-12, all of which contained MBA and PEGDA, demonstrated lower swell capacity as compared to similar IPN PPG samples 1-4, which contained only MBA.

[00100] Referring to Table 4, the gel strengths of exemplary re-crosslinked IPN PPG samples 8-12 was lower for the samples that contained lower amounts of sodium alginate (compare sample 8 to sample 9, sample 10 to sample 11). Comparing the results in Table 4 to Table 3, the IPN PPG samples 8-12, all of which contained MBA and PEGDA, demonstrated higher gel strength in a calcium chloride solution, as compared to similar IPN PPG samples 1-4, which contained only MBA. The PEGDA crosslinker contained in the PPG’s apparently did not degrade under these conditions during this experiment.

[00101] Additionally, the elongation values for each of re-crosslinked IPN PPG samples 8-12 were the highest value possible.

Example 4: Elongation of re-crosslinked IPN PPG in other brines

[00102] In this example, exemplary re-crosslinkable IPN PPG samples 13-15 were prepared as described in Example 1, using the specified ratios in Table 5, below, except that sample 15 included 0.004 parts of PEGDA covalent crosslinker, in addition to MBA.

[00103] Re-crosslinkable IPN PPG sample 13 was swollen in DI water and

subsequently added to the 1% calcium chloride solution for re-crosslinking. After formation of the viscoelastic gel, the material was added to seawater (6.25% Instant Ocean® sea salt in tap water) at 1/2 solution/seawater ratio. Elongation tests were performed for the sample using the procedure described above, and the results recorded in Table 5. After 5 days, the gel demonstrated viscoelastic properties.

[00104] Re-crosslinkable IPN PPG sample 14 was swollen in tap water at 2% solids and was subsequently added to a 2% calcium chloride solution for re-crosslinking. After formation of the gel, the material was added to a 4% potassium chloride solution. Elongation tests were performed for the sample using the procedure described above, and the results recorded in Table 5. After 6 days, the gel demonstrated elastic properties. [00105] Re-crosslinkable IPN PPG sample 15 was swollen at 0.1% solids in a 0.1% potassium chloride solution and subsequently was added to a 1% calcium chloride solution for re-crosslinking. Elongation tests were performed for the sample using the procedure described above, and the results recorded in Table 5. After 13 days, the gel showed elastic properties. The PEGDA covalent crosslinker in the PPG apparently did not degrade under these conditions during this test.

TABLE 5: Elongation of re-crosslinked IPN PPG samples in Brines

[00106] Overall, re-crosslinked IPN PPG samples 13-15 demonstrated viscoelastic or elastic properties following the subsequent addition of monovalent cations under the conditions in this Example. It appears from the results that monovalent cations are capable of reverse ion exchange.

Example 5: Elongation Results at Different Particle Sizes

[00107] In this Example, exemplary re-crosslinkable IPN PPG samples 16-21 were prepared as follows. A monomer solution was prepared by combining 10.5 parts acrylamide (AMD) solution (38%) and 16.0 parts acrylic acid (AA). The pH value of the solution was adjusted to 7.0 with 24.7 parts 45% potassium hydroxide solution. Following pH adjustment, 0.07 parts of 2, 2’ azo bis (2-methylpropionamidine) dihydrogen chloride and 0.008 parts 2 mercaptobenzothiazole (50%) were added to the solution. Then 0.26 parts 0.75% methylene bisacrylamide (100 ppm on monomer) was added. Separately, an alginate solution was prepared by adding 2,4 parts sodium alginate to 45.7 parts DI water while stirring and dissolved. The monomer solution was added slowly to the sodium alginate solution.

Afterward, the resultant solution was added to a sealed Dewar container and purged with nitrogen for 1 hour. Following the one-hour purge with nitrogen, 0.2 parts 0.2% t-butyl hydroperoxide and 0.2 parts 0.4% sodium sulfite were added and the monomers then polymerized to form a solid polymer gel. [00108] For each sample, the polymer gel was cut into approximately 2 cm³ pieces. Cutting oil (2% Sorbitan monolaurate in paraffin oil) was then applied to completely coat the surfaces of each of the gel pieces for each of the PPG samples. Next, each PPG sample was individually added to a Weston commercial meat grinder and ground using said meat grinder. Each of the ground gels were then dried in a Sherwood fluid bed dryer. The dried gel particles were then pulverized in a Waring commercial blender for each of the PPG samples. The samples were sieved to < 75 pm particle size (sample 16), 75 to 177 pm particle size (sample 17), 177-300 pm particle size (sample 18), 300 pm to 1 mm particle size (sample 19), 1 to 3.35 mm particle size (sample 20) and 3.35 to 4 mm particle size (sample 21) using U.S. standard sieves No. 200, 80, 50, 18, 6 and 5, respectively.

[00109] Each sample was re-crosslinked according to a similar procedure as described in Example 2. Elongation was measured for each of the re-crosslinked IPN PPG samples 16- 21 using the procedure described above, and the results recorded in Table 6.

TABLE 6: Elongation of re-crosslinked IPN PPG samples having varied PPG particle sizes

[00110] Referring to Table 6, the re-crosslinked IPN PPG samples 16-21 displayed viscoelastic to weakly elastic results.

Example 6: Elongation of IPN PPG premixed with Calcium Chloride

[00111] In this Example, exemplary re-crosslinkable IPN PPG samples 22 and 23 were prepared and processed similar to sample 16 in Example 5, above, except 0.02 parts methylene bisacrylamide (1000 ppm on monomer), 1.2 parts sodium alginate, and 46.7 parts DI water were used during the preparation of PPG. [00112] For sample 22, 0.5 parts of dry re-crosslinkable IPN PPG sample 22 was mixed with 0.5 parts calcium chloride. The dry powder mixture was then added to 49 parts DI water and agitated for 90 seconds. A precipitate formed and settled. The sample was allowed to re-crosslink. The elongation of PPG sample 22 measured using the test method described above. After 10 days, the elongation was measured and rated A.

[00113] For sample 23, 0.5 parts of dry re-crosslinkable IPN PPG sample 23 was mixed with 1 part 50% calcium chloride solution. The wet powder mixture was then added to 48.5 parts DI water and agitated for 90 seconds. A precipitate formed and settled. The sample was allowed to re-crosslink. The elongation of PPG sample 22 measured using the test method described above. After 10 days, the elongation was measured and rated A.

[00114] In both cases, viscoelastic gel formed when calcium chloride was added to the re-crosslinkable IPN PPG before swelling of the PPG. A possible explanation for the resultant precipitation and not the instant crosslinking observed with sodium alginate and calcium chloride without polyacrylamide is that in both results the IPN PPG needs time to swell before crossl inking with the calcium ion.

Example 7: Elongation of Partially Swollen IPN PPG

[00115] In this Example, exemplary re-crosslinkable IPN PPG sample 24 was prepared and processed as described in Example 5.

[00116] Then 0.5 parts of re-crosslinkable IPN PPG sample 24 was added to 49.5 parts DI water. The dispersion was shaken for 90 seconds and allowed to swell for 1 hour.

The partially swollen IPN PPG dispersion was added to 50 parts 1% calcium chloride solution. The elongation of PPG sample 22 measured using the test method described above. After 7 days, the elongation was measured and rated A. The PPG demonstrated viscoelastic properties before full swelling.

[00117] In the preceding procedures, various steps have been described. It will, however, be evident that various modifications and changes may be made thereto, and additional procedures may be implemented, without departing from the broader scope of the exemplary procedures as set forth in the claims that follow.

Claims

1. A composition comprising:

a) a plurality of re-crosslinkable interpenetrating polymer network (“IPN”)

preformed particle gel (“PPG”) particles that are swellable and dispersible in water or other aqueous composition, wherein each IPN PPG comprises an interpenetrating network of at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding, and

b) at least one ionic crosslinker.

2. The composition of claim 1, wherein said second polymer comprises a

polysaccharide.

3. The composition of claim 2, wherein said polysaccharide comprises an alginate,

pectin, carrageenan and/or gellan.

4. The composition of claim 3, wherein said second polymer comprises alginate,

wherein said alginate is optionally a water soluble alginate, e.g., sodium alginate.

5. The composition of any of claims 1-4, wherein said composition comprises less than about 35%, or less than 30% or less than 20% or less than 10% or less than 5% or less than 1% of the second polymer.

6. The composition of any of claims 1-5, wherein said acrylamide (co)polymer

comprises acrylic acid monomers.

7. The composition of claim 6, wherein said acrylamide (co)polymer comprises greater than about 35%, greater than about 40%, greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, greater than about 90%, or greater than about 99% acrylic acid

8. The composition of any of claims 1-7, wherein said ionic crosslinker comprises a multivalent ion, e.g., a calcium salt or other source of calcium ions.

9. The composition of any of claims 1-8, wherein said acrylamide (co)polymer

comprises less than about 50%, less than about 45%, less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 15%, less than about 10%, or less than about 5% acrylamide.

10. The composition of any of claims 1-9, wherein said acrylamide (co)polymer

comprises a nonionic polymer that is later hydrolyzed to comprise carboxylate groups.

11. The composition of any of claims 1-10, wherein said acrylamide (co)polymer

comprises at least one covalent crosslinker.

12. The composition of claim 11, wherein said at least one covalent crosslinker comprises methylene bisacrylamide (“MBA”).

13. The composition of any of claims 1-12, wherein contacting part a. with part b. results in a re-crosslinked IPN PPG.

14. The composition of any of claims 1-13, wherein said composition comprises a dry or solid ionic crosslinker and a dry re-crosslinkable IPN PPG that are mixed or blended in their respective dry form.

15. The composition of any one of claims 1-14, wherein contacting part a. with part b. results in a re-crosslinked IPN PPG that has a gel strength value of about 4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8,5 or more, 9.0 or more, 9.2 or more, or 9.5 or more.

16. The composition of any one of claims 1-15, wherein contacting part a. with part b. results in a re-crosslinked IPN PPG that has a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.

17. A system for use in conformance control comprising:

a) a plurality of re-crosslinkable IPN PPG particles that are swellable and

dispersible in water or other aqueous composition, wherein each IPN PPG comprises an interpenetrating network of at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding; b) at least one ionic crosslinker; and

c) a subterranean formation having the composition therein.

18. The system of claim 17, wherein said re-crosslinkable IPN PPG is re-crosslinked in situ.

19. The system of claim 17 or 18, wherein said subterranean formation comprises pores, voids, and/or channels.

20. The system of any of claims 17-19, wherein re-crosslinking (ionic crosslinking) of said re-crosslinkable IPN PPGs is effected over a desired time period.

21. The system of claim 20, wherein said time period is 1 day or less, 1 day or more, 2 days or more, 3 days or more, 4 days or more, 5 days or more, 6 days or more, 7 days or more, 8 days or more, 9 days or more, or 10 days or more.

22. The system of any of claims 17-21, wherein said re-crosslinkable IPN PPGs are re- crosslinked and said re-crosslinked IPN PPGs withstand pressure and remain in pores or voids when conventional PPGs may be displaced under similar conditions, e.g., similar pressure conditions.

23. The system of any of claims 17-22, wherein said second polymer comprises a

polysaccharide.

24. The system of claim 23, wherein said polysaccharide comprises an alginate, pectin, carrageenan and/or gellan.

25. The system of any of claims 24, wherein said second polymer comprises alginate, wherein said alginate is optionally a water soluble alginate, e.g., sodium alginate.

26. The system of any of claims 17-25, wherein said at least one ionic crosslinker

comprises a multivalent ion, e.g., a calcium salt or other source of calcium ions.

27. The system of any of claims 17-26, wherein the re-crosslinkable IPN PPG is

converted into a gel during use as a conformance control agent.

28. The system of any of claims 17-27, wherein said system further comprises a fluid conduit disposed in an injection wellbore, and/or a pump configured to pump the composition comprising re-crosslinkable IPN PPGs through the conduit downhole.

29. The system of any one of claims 17-28, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a gel strength value of about 4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.2 or more, or 9.5 or more.

30. The system of any one of claims 17-29, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.

31. A method for producing a re-crosslinked IPN PPG comprising:

(i) providing an aqueous composition comprising a plurality of re- crosslinkable IPN PPGs;

(ii) allowing the re-crosslinkable IPN PPGs to swell; and

(iii) adding at least one ionic crosslinker in an amount sufficient to provide for re-crosslinking of the IPN PPGs, wherein the ionic crosslinker is added before, during and/or after swelling.

32. The method of claim 31, wherein said plurality of re-crosslinkable IPN PPGs comprises an interpenetrating network of at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding.

33. The method of claim 31 or 32, wherein said second polymer comprises a

polysaccharide,

34. The method of claim 33, wherein said polysaccharide comprises an alginate, pectin, carrageenan and/or gellan.

35. The method of claim 34, wherein said second polymer comprises alginate, wherein said alginate is optionally a water soluble alginate, e.g., sodium alginate.

36. The method of any of claims 31-35, wherein said first acrylamide (co)polymer

comprises acrylic acid monomers.

37. The method of any of claims 31-36, wherein said ionic crosslinker comprises a

multivalent ion, e.g., a calcium salt or other source of calcium ions.

38. The method of any of claims 31-37, wherein said method is effected in a subterranean formation.

39. The method of any of claims 31-38, wherein said re-crosslinkable IPN PPGs are suitable to form a plug which reduces flow communication of water between an injection well and a production well when re-crosslinked.

40. The method of any one of claims 31-39, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a gel strength value of about 4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.2 or more, or 9.5 or more.

41. The method of any one of claims 31-40, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.

42. A method of enhanced oil recovery, the method comprising:

a) obtaining or providing a composition comprising a plurality of re- crosslinkable IPN PPGs;

b) adding to the composition at least one ionic crosslinker;

c) placing the composition in a subterranean formation downhole;

d) swelling the plurality of re-crosslinkable IPN PPGs in an aqueous fluid; e) allowing the plurality of IPN PPGs to re-crosslink with the ionic crosslinker; and

f) extracting oil from the subterranean formation downhole via a production wellbore.

43. The method of claim 42, wherein the method is used for one or more of the following applications:^) water and gas shutoff, (ii) fluid loss control, (iii) zone abandonment, (iv) water and gas coning, squeeze and recompletion, (v) chemical liner completions and lost circulation during drilling operations and (vi) plugging during drilling and drilling completion.

44. The method of claim 42 or 43, wherein said method targets bypassed oil.

45. The method of any of claims 42-44, wherein said method improves the overall

macroscopic sweep efficiency.

46. The method of any of claims 42-45, wherein said method improves and/or increases hydrocarbon production.

47. The method of any of claims 42-46, wherein said method decreases associated water production.

48. The method of any of claims 42-47, wherein said plurality of re-crosslinkable IPN PPGs comprises an interpenetrating network of at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding.

49. The method of any of claims 42-48, wherein said second polymer comprises a

polysaccharide.

50. The method of claim 49, wherein said polysaccharide comprises an alginate, pectin, carrageenan and/or gellan.

51. The method of claim 50, wherein said second polymer comprises alginate, wherein said alginate is optionally a water soluble alginate, e.g., sodium alginate,

52. The method of any of claims 42-51, wherein said acrylamide (co)polymer comprises acrylic acid monomers.

53. The method of any of claims 42-52, wherein said ionic crosslinker comprises a

multivalent ion, e.g., a calcium salt or other source of calcium ions.

54. The method of any one of claims 42-53, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a gel strength value of about 4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.2 or more, or 9.5 or more,

55. The method of any one of claims 42-54, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.

56. A method for remediation of a zone within a subterranean formation bearing

heavy/viscous oil to inhibit breakthrough of water from a water injection well via the zone into a production well, the zone comprised of a void space, a halo region, or both, due to production of the heavy/viscous oil through the production well, thereby allowing for pressure communication between the injection well and the production well, which method comprises:

a) injecting a composition into the zone via the injection well, the composition comprising a plurality of re-crosslinkable IPN PPGs and at least one ionic crosslinker; and

b) allowing the IPN PPGs to re-crosslink for a sufficient time to form a plug that reduces fluid communication between the injection well and the production well.

57. The method of claim 56, wherein said method comprises use of a displacement fluid.

58. The method of claim 57, wherein said displacement fluid is selected from water, alcohols, fuel oil or crude oil.

59. The method of claim 58, wherein said displacement fluid is water.

60. The method of any of claims 56-59, wherein said plurality of re-crosslinkable IPN PPGs comprise at least a first acrylamide (co)polymer and a second polymer that is capable of ionic bonding.

61. The method of claim 60, wherein said acrylamide (co)polymer comprises acrylic acid monomers.

62. The method of claim 60, wherein said second polymer comprises a polysaccharide.

63. The method of claim 62, wherein said polysaccharide comprises an alginate, pectin, carrageenan and/or gellan.

64. The method of claim 63, wherein said second polymer comprises alginate, wherein said alginate is optionally a water soluble alginate, e.g., sodium alginate.

65. The method of any of claims 56-64, wherein said ionic crosslinker comprises a

multivalent ion, e.g., a calcium salt or other source of calcium ions.

66. The method of any one of claims 56-65, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a gel strength value of about

4.0 or less, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.2 or more, or 9.5 or more.

67. The method of any one of claims 56-66, wherein said re-crosslinkable IPN PPGs are re-crosslinked and said re-crosslinked IPN PPGs have a higher gel strength value as compared to re-crosslinkable IPN PPGs with no ionic crosslinking agent and/or a conventional PPG which lacks ionic crosslinking agent.