Gelation of acrylamide-containing polymers with furfuryl alcohol and water dispersible aldehydes

Abstract: A novel composition and process are disclosed for forming crosslinked gels at elevated temperatures utilize a novel cross linking agent comprising a furan derivative and a water dispersible aldehyde or aldehyde generating compound.

Description: The present invention relates to a novel process for crosslinking water-soluble polymers utilizing an organic crosslinking system composed of a furan derivative and a water dispersible aldehyde. It is well known to those skilled in the art that gelled or crosslinked water-soluble polymers are useful in enhanced oil recovery operations. They have been used to alter the permeability of underground formations in order to enhance the effectiveness of water flooding operations. Polymers along with an appropriate crosslinking system are injected in an aqueous solution into the formation. The polymers then permeate into and gel in the regions having the highest water permeability. Any fluids injected into the formation in subsequent water flooding operations, will then be diverted away from the regions in which the gel formed to areas of the formation now having a higher water permeability. EP-A-0 180 406 discloses a method of treating a subterranean formation for reducing its permeability by contacting it with an aqueous polymerizable composition comprising a polymerization monomer, a polymerization catalyst having a latent period, and an alcoholic compound which is a cyclic ether containing a hydroxymethylene substituent on a carbon atom bonded to the ether oxygen, or an aliphatic alcohol having a carbon-to-carbon double bond or a carbon-to-carbon triple bond. Although this technique is effective in enhancing hydrocarbon production, it does have problems. The primary one being that water-soluble polymers and conventional crosslinking agents gel fairly quickly after being injected into the formation at an elevated temperatures. Quite often only the regions near the well bore are treated, since the polymers and conventional crosslinking agent gel before they have an opportunity to percolate very far into the formation. It would therefore be a valuable contribution to the art to develop an organic crosslinking system which had a delayed gelation rate to permit greater penetration into the formation of the water-soluble polymer and crosslinking agent before gelation occurs. Thus, it is an object of the present invention to provide a novel crosslinking system with a delayed gelation rate in high temperature. It is a further object of the present invention to provide novel gels formed with said novel crosslinking system and water-soluble polymers. Other aspects and objects of this invention will become apparent here and after as the invention is more fully described in the following summary of the invention and detailed description of the invention, examples, and claims. In accordance with the present invention we have discovered that a method of altering the permeability of a porous subterranean formation having an ambient temperature of about 93°C (200°F) in fluid communication with a wellbore comprising transmitting into said porous subterranean formation via the fluid communication of said wellbore, either independently or in admixture, (a) a water-soluble polymer present in the range of from 0.1 to 5.0 weight percent wherein said water-soluble polymer contains in the range of 100 to 5 mole percent of at least one monomer of the formula: wherein R₁, R₂, and R₃ are independently selected from hydrogen and alkyl radicals containing from 1 to 3 carbon atoms and from 0 to 95 mole percent of at least one monomer selected from (i) a monomer which can be represented by the formula: wherein R₄ is selected from hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and arylene radical containing from 6 to 10 carbon atoms, and M is selected from hydrogen, ammonium, potassium, and sodium; (ii) a monomer represented by the following formula: where R₆, R₇, and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms; (iii) a monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, ammonium vinylbenzylsulfonate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, and (acryloyloxyethyl)diethylmethylammonium methyl sulfate; and mixtures of any two or more thereof; (b) a water dispersible aldehyde or aldehyde generating compound present in the range of 0.005 to 5.0 weight percent; (c) a furan derivative present in the range of from 0.005 to 5.0 weight percent of the formula: wherein R₉, R₁₀, R₁₁, and R₁₂, are independently selected from hydrogen, methyl, hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals, and at least one R₉, R₁₀, R₁₁, and R₁₂ radical must be selected from hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals; and (d) water present in the range of from 85 to 99.89 weight percent; and allowing the water-soluble polymer, water dispersible aldehyde or aldehyde generating compound, furan derivative and water to form a gel in said porous subterranean formation. In accordance with another embodiment of the present invention we have also discovered a gel composition produced from the gelation of the following components (a) a water-soluble polymer present in the range of from 0.1 to 5.0 weight percent wherein said water-soluble polymer contains in the range of 100 to 5 mole percent of at least one monomer of the formula: wherein R₁, R₂, and R₃ are independently selected from hydrogen and alkyl radicals containing from 1 to 3 carbon atoms and from 0 to 95 mole percent of at least one monomer selected from (i) a monomer which can be represented by the formula: wherein R₄ is selected from hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and an arylene radicals containing from 6 to 10 carbon atoms, and M is selected from hydrogen, ammonium, potassium, and sodium; (ii) a monomer represented by the formula: where R₆, R₇, and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms; (iii) a monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, ammonium vinylbenzylsulfonate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, and (acryloyloxyethyl)diethylmethylammonium methyl sulfate; and mixtures of any two or more thereof; (b) a water dispersible aldehyde or aldehyde-generating compound present in the range from of 0.005 to 5.0 weight percent; (c) a furan derivative present in the range of from 0.005 to 5.0 weight percent of the formula: wherein R₉, R₁₀, R₁₁, and R₁₂ are independently selected from hydrogen, methyl, hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals; and at least one R₉, R₁₀, R₁₁, and R₁₂ radical must be selected from hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals; and (d) water present in the range of from 85 to 99.89 weight percent. The organic crosslinking system of the present invention is formed from: (a) a furan derivative (b) a water dispersible aldehyde or aldehyde generating compound. Furan derivatives suitable for use in the present invention are of the formula: wherein R₉, R₁₀, R₁₁, and R₁₂, are independently selected from hydrogen, methyl, hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals, and at least one R₉, R₁₀, R₁₁ and R₁₂ radical must be selected from hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals. Suitable furan derivatives include but are not limited to those selected from furfuryl acetate, furanamine, furandiamine, furantriamine, furantetramine, furancarbinol, furandicarbinol (furandimethanol), furantricarbinol, furantetracarbinol, hydroxyfuran, dihydroxyfuran, trihydroxyfuran, tetrahydroxyfuran, furancarboxylic acid, furandicarboxylic acid, furantricarboxylic acid, furantetracarboxylic acid, furanmethylenecarboxylic acid, furanbis(methylenecarboxylic acid), furantris(methylenecarboxylic acid) and furantetrakis(methylenecarboxylic acid), mercaptofuran, and combinations of two or more thereof. The preferred furan derivative for the practice of the present invention is 2-furancarbinol, furfuryl alcohol mercaptofuran, furandicarbinol, furfuryl acetate and furanamine. Any water dispersible aldehyde or aldehyde generative compound can be utilized in the practice of the present invention. Thus, suitable aldehyde or aldehyde generating compounds can be selected from aliphatic aldehydes, aliphatic dialdehydes, and aromatic aldehydes, aromatic dialdehydes. Preferred aldehydes or aldehyde generating compounds can be selected from formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde, heptaldehyde, decanal, glyoxal, glutaraldehyde, terephthaldehyde, hexamethylenetetramine and mixtures thereof. As a general guide, the amount of furan derivative used in preparing the gelled compositions of the invention will be in the range of 0.005 to 5.0 wt.%, preferably from in the range of 0.01 to 2.0 wt.% and most preferably from in the range of 0.05 to 1.0 wt% based on the total weight of the gelable composition. The amount of aldehyde or aldehyde generating compound used will be in the range of 0.005 to 5.0 wt.%, preferably in the range of 0.01 to 2.0 wt.% and most preferably in the range of 0.05 to 1.0 wt% based on the total weight of the gelable composition. The molar ratio of furan derivative to aldehyde or aldehyde generating compound will be in the broad range of 30:1 to 1:30 with a more preferred range of 2:1 to 1:4. As used in this application, the term water-soluble polymer, copolymers, and terpolymers refers to those polymers which are truly water-soluble or those which are dispersible in water or other aqueous medium to form a stable colloidal suspension which can be pumped into a formation and gelled therein. The water-soluble polymers which are suitable for use in the present invention include those which contain from 5 to 100 mole percent of at least one monomer of the formula: wherein R₁, R₂, and R₃ are independently selected from hydrogen and alkyl radicals containing from 1 to 3 carbon atoms, of which acrylamide and methacrylamide are the preferred examples; and from 0 to 95 mole percent of at least one monomer selected from (a) monomers represented by the formula: wherein R₄ is selected from hydrogen or alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and arylene radicals containing from 6 to 10 carbon atoms, and M is selected from hydrogen, ammonium, potassium, and sodium, of which 2-acrylamido-2-methylpropane sulfonic acid or sodium 2-acrylamido-2-methylpropane sulfonate are the preferred examples; (b) monomers represented by the formula: where R₆, R₇ and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms of which N-vinyl-2-pyrrolidone is the preferred example; (c) at least one monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, ammonium vinylbenzylsulfonate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, and (acryloyloxyethyl)diethylmethylammonium methyl sulfate; and (d) mixtures of any two or more thereof. The polymerization of any of the above described monomers and the resulting polymers are well known to those skilled in the art. There are numerous references which disclose the methods of polymerizing these monomers, for example see U.S. Patent 4,244,826. The manner in which these monomers are polymerized into water-soluble polymers or the resulting polymers is not critical to the practice to the present invention. The molecular weight of the water-soluble polymers utilized in the present invention is not critical. It is presently preferred, however, that polymers have the molecular weight of at least 100,000 and more preferably 100,000 to 20,000,000. The upper limit is not critical as long as the polymer is still water dispersible and can be pumped into the formation. The presently preferred class of water-soluble polymers are those selected from homopolymers of acrylamide, homopolymers of methacrylamide, copolymers of acrylamide and acrylic acid, copolymers of acrylamide and sodium acrylate, copolymers of acylamide and N-vinyl-2-pyrrolidone, copolymers of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, copolymers of acrylamide and 2-acrylamido-2-ethylpropane sulfonic acid, terpolymers of acrylamide, N-vinyl-2-pyrrolidone, and sodium 2-acrylamido-2-methylpropane sulfonate and terpolymers of acrylamide, N-vinyl-2-pyrrolidone and 2-acrylamido-2-methylpropane sulfonic acid. The ratio of the monomers in the above-described polymers is not critical; provided however, that at least 5 mole percent of acrylamide is present in the above-described polymers. Particularly preferred are terpolymers of N-vinyl-2-pyrrolidone, acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate wherein said monomers are provided in a 30 to 15 to 55 weight percent terpolymer. Additionally within the scope of this invention is the use of combinations of copolymers and terpolymers utilizing the above listed monomers. The constituents of the present invention should be present in the following quantities: The order in which the constituents are mixed is not critical to the practice of the present invention. The use of gelled polymers to alter the water permeability of underground formations is well known to those skilled in the art. Generally, an aqueous solution containing the polymer and a crosslinking agent is transmitted into the formation from a well in fluid communication with the formation so that the aqueous solution can diffuse into the more water permeable portions of the formation and alter that water permeability by gelling therein. The present invention can be used in a similar manner. An aqueous solution containing the water-soluble polymer, aldehyde or aldehyde generating compound, and furan derivative is pumped into the formation so that it alters the water permeability of the formation in a similar manner when gelation takes place. The aqueous solution containing the water soluble polymer, aldehyde or aldehyde generating compound and furan derivative can be pumped into the formation in one slug, or alternatively the components may be sequentially injected in a manner to provide an appropriate concentration in the formation. The present invention's advantage lies in the fact that the onset of gelation is delayed allowing the aqueous solution to penetrate further into the formation. The nature of the underground formation treated is not critical to the practice of the present invention. The organic crosslinkers will gel the water-soluble polymers in fresh water, salt water, or brines, as well as at a temperature range of from 93 to 205°C (200 to 400°F). The following specific examples are intended to illustrate the advantages of this invention, but are not intended to unduly limit this invention. EXAMPLE I The purpose of this example is to demonstrate the delayed gelation of a water-soluble polymer by a furan derivate and an aldehyde. Additionally this example demonstrates the long term stability of a gel formed with a water-soluble polymer, a furan derivative and an aldehyde. A one percent solution of a terpolymer composed of 30 wt % of N-vinyl-2-pyrrolidone, 15 wt % of acrylamide, and 55 wt % of sodium 2-acrylamido-2-methylpropane sulfonate was prepared in the following manner. 16.3 ml of an inverse emulsion which contained 32.4 wt % of the above-described active terpolymer was mixed with 500 ml of synthetic sea water. The synthetic water used had the following formula: NaHCO₃ 3.69 grams Na₂SO₄ 77.19 grams NaCl 429.00 grams CaCl₂·2H₂O 29.58 grams MgCl₂·6H₂O 193.92 grams distilled H₂O q.s. to 18 liters 0.18 ml of furfuryl alcohol was added to 200 ml of the polymer and synthetic sea water mixture described above, to provide a 1000 ppm furfuryl alcohol concentration. Similarly 0.36 ml of furfuryl alcohol was added to 200 ml of the polymer and synthetic sea water mixture to generate a 2000 ppm furfuryl alcohol concentration. Five 20 ml samples of the solution, containing 1 percent of the terpolymer and 1,000 ppm furfuryl alcohol were placed in five 2.3 cm X 22.5 cm long ampules. Varying amounts of formaldehyde were added to the ampules to provide the formaldehyde concentration shown in Table I and Table IA. Five 20 ml ampules were prepared in an identical manner utilizing the 2000 ppm furfuryl alcohol solution containing the 1 percent terpolymer with varying quantities of formaldehyde added to the ampules to provide the concentration also shown in Table I and Table IA. The ten ampules were sealed under nitrogen and then placed upright in compartmented aluminum boxes with relief holes and placed in an oven and heated to 121°C (250°F). Periodically, the ampules were removed from the oven and the mechanical strength of the gel was determined behind a protective shield. The mechanical strength of the gel was determined by placing the ampules horizontally along a graduated scale and measuring the spread of the gel. If the gel is weak it will spread: The mechanical strength is then expressed mathematically as Percent Gel Strength = (AL-TL) x 100 / AL where AL equals asmpule length, and TL equals the tongue length of the gel measured in centimeters from the point at which the gel contacts the entire circumference of the tube to the farthest point to which the gel has spread. Thus the strongest gels would have a gel strength of 100% and the weakest gels would have a gel strength of 0. The following results were observed from day 5 to day 71 of aging at 121°C (250°F) in Synthetic Seawater. The following results were observed after from 146 days to 310 of aging at 121°C (250°F) in Synthetic Seawater. The results above demonstrate that the combination of a furan derivative and an aldehyde to crosslink a water-soluble polymer provide delayed gelation and long term stability. Example II The purpose of this example is to demonstrate the delayed gelation of a water-soluble polymer by a furan derivative and an aldehyde. Additionally this example demonstrates the long term stability of a gel formed with a water-soluble polymer, a furan derivative and an aldehyde at high temperatures. The ampules were prepared in a manner identical to those in Example I except that the aging was conducted at 149°C (300°F). The following results were observed from day 2 to day 19: The following results were observed from day 23 to day 310 Reasonable variations can be made in view of the following disclosure without departing from the spirit and scope of this invention.

Claims: A method of altering the permeability of a porous subterreanean formation with an ambient temperature above 93 °C, characterized by introducing into said formation, either independently or in admixture, (a) 0.1 to 5 percent of a water-soluble polymer being composed of (a1) 100 to 5 mole percent of at least one monomer of the formula I wherein R₁, R₂ and R₃ are independently selected from hydrogen and alkyl radicals containing from 1 to 3 carbon atoms, and (a2) 0 to 95 mole percent of at least one monomer selected from (i) a monomer of the formula II wherein R₄ is selected from hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and arylene radicals containing from 6 to 10 carbon atoms, and M is selected from hydrogen ammonium, potassium and sodium; (ii) a monomer of the formula III where R₆, R₇ and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms; and (iii) a monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, ammonium vinylbenzylsulfonate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, (acryloyloxyethyl)diethylmethylammonium methyl sulfate, and mixtures of any two or more thereof; (b) 0.005 to 5.0 percent of a water-dispersible aldehyde or aldehyde-generating compound (c) 0.005 to 5.0 percent of a furan derivative of the formula IV wherein R₉, R₁₀, R₁₁ and R₁₂ are independently selected from hydrogen, methyl, hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals; and at least one of R₉, R₁₀, R₁₁ and R₁₂ radical is selected from hydroxyl, carbinol, carboxyl, -CH₂COOH, acylamide, mercaptan and primary amine radicals; and (d) 85 to 99.89 percent water wherein all percentages are weight percent based on the total of all constituents (a) to (d); and allowing the constituents (a) to (d) to form a gel in said porous subterranean formation. The method of claim 1 wherein said water-soluble polymer (a) is selected from homopolymers of acrylamide, homopolymers of methacrylamide, copolymers of acrylamide and acrylic acid, copolymers of acrylamide and sodium acrylate, copolymers of acrylamide and N-vinyl-2-pyrrolidone, copolymers of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, copolymers of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid, terpolymers of N-vinyl-2-pyrrolidone, acrylamide, and sodium 2-acrylamido-2-methylpropane sulfonate and terpolymers of acrylamide, N-vinyl-2-pyrrolidone and 2-acrylamido-2-methylpropane sulfonic acid. The method of claims 1 or 2 wherein said furan derivative (c) is selected from furfuryl acetate, furanamine, furandiamine, furantriamine, furantetramine, furancarbinol, furandicarbinol, furantricarbinol. furantetracarbinol, hydroxyfuran, dihydroxyfuran, trihydroxyfuran, tetrahydroxyfuran, furancarboxylic acid, furandicarboxylic acid, furantricarboxylic acid, furantetracarboxylic acid, furanmethylenecarboxylic acid, furanbis(methylenecarboxylic acid), furantris(methylenecarboxylic acid), furantetrakis(methylenecarboxylic acid), mercaptofuran, and combinations of two or more therof. The method of any of the preceding claims wherein said aldehyde or aldehyde-generating compound (b) is selected from formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde, heptaldehyde, decanal, glyoxal, glutaraldehyde, terephthaldehyde, hexamethylenetetramine, and mixtures thereof. The method of any of the preceding claims wherein the consitutents (a) to (d) are used in the following amounts The method of any of the preceding claims wherein said water-soluble polymer (a) is a terpolymer of N-vinyl-2-pyrrolidone, acrylamide, and sodium 2-acrylamido-2-methylpropane sulfonate; said furan derivative (b) is furfuryl alcohol; and said aldehyde or aldehyde generating compound (c) is formaldehyde. A gel composition obtainable by gelation of the following constituents (a) 0.1 to 5 percent of a water-soluble polymer being composed of (a1) 100 to 5 mole percent of at least one monomer of the formula I wherein R₁, R₂ and R₃ are independently selected from hydrogen and alkyl radicals containing from 1 to 3 carbon atoms, and (a2) 0 to 95 mole percent of at least one monomer selected from (i) a monomer of the formula II wherein R₄ is selected from hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and arylene radicals containing from 6 to 10 carbon atoms, and M is selected from hydrogen ammonium, potassium and sodium; (ii) a monomer of the formula III where R₆, R₇ and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms; and (iii) a monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, ammonium vinylbenzylsulfonate, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, (acryloyloxyethyl)diethylmethylammonium methyl sulfate and mixtures of any two or more thereof; (b) 0.005 to 5.0 percent of a water-dispersible aldehyde or aldehyde-generating compound (c) 0.005 to 5.0 percent of a furan derivative of the formula IV wherein R₉, R₁₀, R₁₁ and R₁₂ are independently selected from hydrogen, methyl, hydroxyl, carbinol, carboxyl, -CH₂COOH, acyl amide, mercaptan and primary amine radicals; and at least one of R₉, R₁₀, R₁₁ and R₁₂ radical is selected from hydroxyl, carbinol, carboxyl, -CH₂COOH, acylamide, mercaptan and primary amine radicals; and (d) 85 to 99.89 percent water wherein all percentages are weight percent based on the total of all constituents (a) to (d). The gel composition of claim 7 wherein one or more of the constituents (a), (b), (c) and (d) are as defined in any of claims 2 to 6.

Inventors: MORADI-ARAGHI AHMAD, STAHL GLENN ALLAN, MORADI-ARAGHI, AHMAD, STAHL, GLENN ALLAN
Applicants: PHILLIPS PETROLEUM CO, PHILLIPS PETROLEUM COMPANY
Application year: 1991
Main classification: E21B43
IPC codes: C08F2, C09K8