# US 5,701,955 A · Downhole fluid control processes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,701,955 A - Document ID: US5701955A - Status: Granted - Kind: A - Application number: 08/566,092 - Filed: 1995-12-01 - Granted: 1997-12-30 - Earliest claimed: 1994-12-02 - Assignees: Allied Colloids Limited - Inventors: Harry Frampton - Web page: https://patentgrep.com/patent/US5701955A ## CPC - C09K 8/502: Oil-based compositions - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE ## Abstract The invention provides a downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water swellable, reverse-phase polymerized, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ## Claims ### Claim 1 A downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water swellable, reverse-phase polymerised, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ### Claim 2 (depends on 1) A process according to claim 1, in which the dispersion has a water content of not more than 70% by weight of polymer. ### Claim 3 (depends on 1) A process according to claim 1 in which the dispersion has a water content of not more than 20% by weight of polymer. ### Claim 4 (depends on 1) A process according to claim 1 in which the concentration of absorbent polymer in the dispersion is from 0.01 to 5% by weight of the dispersion. ### Claim 5 (depends on 1) A process according to claim 1 in which the concentration of absorbent polymer in the dispersion is from 0.05 to 1% by weight of the dispersion. ### Claim 6 (depends on 1) A process according to claim 1 in which the non-aqueous liquid consists substantially only of filtered base diesel. ### Claim 7 (depends on 1) A process according to claim 1, in which the dispersion has been produced by a process comprising reverse phase polymerisation of water soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid and optional dehydration and mixing the product of the reverse phase polymerisation and optionally dehydration with a second non-aqueous liquid, wherein the first and second non-aqueous liquids may be the same or different and the second does not cause coagulation to a size of above 10 .mu.m of the absorbent polymer particles. ### Claim 8 (depends on 1) A process according to claim 1 in which the absorbent polymer is a polymer produced from water soluble ethylenically unsaturated monomer or monomer blend the monomers being selected from cationic monomers and blends of cationic monomer with non-ionic monomer. ### Claim 9 (depends on 1) A process according to claim 1 in which the absorbent polymer is a cationic, water swellable, water insoluble polymer. ### Claim 10 (depends on 1) A process according to claim 1 in which the absorbent polymer is a cationic polymer having ionic regain of 20 to 60%. ### Claim 11 (depends on 10) A process according to claim 10 in which the absorbent polymer has an intrinsic viscosity of above 4, preferably above 6, dl/g. ### Claim 12 (depends on 1) A process according to claim 1 in which the absorbent polymer has a gel capacity of at least 20 g deionised water per gramme polymer. ### Claim 13 (depends on 1) A process according to claim 1 in which at least 90% of the particles have a diameter from 0.5 to 5.5 .mu.m. ### Claim 14 (depends on 1) A process according to claim 1 in which the subterranean formation has an average permeability of not greater than 5 Darcy. ### Claim 15 A stable dispersion in a non-aqueous liquid of reverse phase polymerised, substantially spherical, absorbent polymer particles of which at least 90% by weight have a size below 10 .mu.m and in which the concentration of polymer is not greater than 5% by weight of the dispersion. ### Claim 16 (depends on 15) A dispersion according to claim 15 in which the concentration of polymer is not greater than 1% by weight of the dispersion. ### Claim 17 (depends on 15) A dispersion according to claim 15 in which the concentration of polymer is from 0.05 to 1% by weight of the dispersion. ### Claim 18 (depends on 15) A dispersion according to claim 15 which has a water content of not more than 70% by weight of polymer. ### Claim 19 (depends on 15) A dispersion according to claim 15 which has a water content of not more than 20% by weight of polymer. ### Claim 20 (depends on 15) A dispersion according to claim 15 in which the non-aqueous liquid consists substantially only of filtered base diesel. ### Claim 21 A downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water swellable, reverse-phase polymerized, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m, wherein the dispersion has a water content of not more than 20% by weight of polymer whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ### Claim 22 (depends on 21) A process according to claim 21, in which the dispersion has a water content of not more than 10% by weight of polymer. ### Claim 23 (depends on 21) A process according to claim 21, in which at least 90% of the polymer particles have a diameter of not more than 3 .mu.m. ### Claim 24 A downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water swellable, reverse-phase polymerized, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m, wherein the dispersion has been produced by a process comprising reverse phase polymerization of water-soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid and dehydration of the emulsion whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ### Claim 25 (depends on 24) A process according to claim 24, in which the dispersion has been produced by a process comprising reverse phase polymerization of water-soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid to produce a reverse phase emulsion and dehydrating the reverse phase emulsion by distillation and adding to the emulsion, before, during or after the dehydration a second non-aqueous liquid which is less volatible than the first non-aqueous liquid and distilling the non-aqueous liquid from the emulsion until the amount of the first non-aqueous liquid remaining in the dispersion is from about 0 to about 20% by weight of the liquid phase. ### Claim 26 A downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water swellable, reverse-phase polymerized, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m, in which the polymer particles comprise a substantial fraction of soluble polymer such that the polymer gives an intrinsic viscosity value greater than 3, whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ### Claim 27 (depends on 26) A process according to claim 26 in which the polymer gives an intrinsic viscosity value greater than 6 dl/g. ### Claim 28 (depends on 26) A process according to claim 26 in which the absorbent polymer is a polymer produced from water-soluble ethylenically unsaturated monomer blend, the monomers being selected from cationic monomers and blends of cationic monomer with non-ionic monomer. ### Claim 29 (depends on 28) A process according to claim 28 in which the polymer has ionic regain of from 20 to 60%. ### Claim 30 A downhole process for the reduction of the permeability to water of a microporous subterranean formation which has average permeability of not greater than 10 Darcy, the process comprising applying to the formation a dispersion in non-aqueous liquid of water-swellable, reverse-phase polymerized, substantially spherical particles of absorbent polymer of which at least 90% by weight have a diameter less than 10 .mu.m, in which the non-aqueous liquid consists substantially only of filtered base diesel, whereby the dispersion of the substantially spherical particles of which at least 90% by weight have a size below 10 .mu.m is injected into the micropores of the subterranean formation and the particles are allowed to swell on contact with water and cause the reduction in permeability. ### Claim 31 (depends on 30) A process according to claim 30 in which the dispersion has been produced by a process comprising reverse-phase polymerization of water-soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid which is not filtered base diesel and optional dehydration and mixing the product of the reverse-phase polymerization and optional dehydration with a second non-aqueous liquid which consists substantially only of filtered base diesel. ### Claim 32 (depends on 31) A process according to claim 31 in which the dispersion has been produced by a process comprising reverse-phase polymerization of water-soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid which is not filtered base diesel to form a reverse-phase emulsion and dehydrating the reverse-phase emulsion by distillation and adding to the emulsion before, during or after dehydration a second non-aqueous liquid which consists substantially only of filtered base diesel and distilling the non-aqueous liquid from the emulsion until the amount of the first non-aqueous liquid remaining in the dispersion is from about 0 to above 20% by weight of the liquid phase. ### Claim 33 (depends on 32) A process according to claim 32 in which the amount of the first non-aqueous liquid remaining in the dispersion is from about 0 to about 10% by weight of the liquid phase. ### Claim 34 (depends on 30) A process according to claim 30 in which the dispersion has been produced by a process comprising reverse-phase polymerization of water-soluble monomer or monomer blend in aqueous solution emulsified into a first non-aqueous liquid to form a reverse-phase emulsion and dehydrating the emulsion. ### Claim 35 A stable dispersion in non-aqueous liquid of reverse-phase polymerized, substantially spherical, absorbent polymer particles of which at least 90% by weight have a size below 10 .mu.m in which the concentration of polymer is not greater than 5% by weight of the dispersion and the dispersion has a water content of not more than 20% by weight of polymer. ### Claim 36 (depends on 35) A dispersion according to claim 35 which has a water content of not more than 10% by weight of polymer. ### Claim 37 (depends on 35) A dispersion according to claim 35 in which at least 90% by weight of the polymer particles have a size below 3 .mu.m.