Gellable aqueous composition and its use in enhanced petroleum

{
  "publication_number": "US5143958A",
  "country": "US",
  "kind": "A",
  "title": "Gellable aqueous composition and its use in enhanced petroleum",
  "abstract": "The permeability of high-permeability zones in a oil reservoir can be reduced by using a gellable aqueous composition with delayed gelation. The composition comprises: a) water; b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr 3+ ions; c) a water-soluble inorganic Cr 3+ salt; d) a gelation-retardant organic ligand definable by the formula: ##STR1## where: R is a direct single bond, or a saturated or unsaturated linear or branched aliphatic hydrocarbon radical with from 1 to 6 carbon atoms, or a cycloalkyl radical with from 3 to 7 carbon atoms, or an aryl radical; X is OH or OR' (where R' is an alkyl radical with from 1 to 5 carbon atoms), or NR\"R\"' (where R\" and R\"', which may be equal or different, are H or an alkyl radical with from 1 to 5 carbon atoms); and relative water-soluble salts; the polymer b) being present in a concentration of between 1000 and 50,000 ppm; the salt c) being present in a concentration of between 10 and 5000 ppm evaluated as metal; the polymer/Cr 3+ weight ratio varying from 1:1 to 1000:1; the molar organic ligand/Cr 3+ ratio varying from 0.5 to 500:1; the composition having a pH equal to or less than about 7.0.",
  "claims": [
    "1. A gellable aqueous composition for reducing the permeability of high-permeability zones in an oil reservoir, comprising: a) water; b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr 3+ ions; c) a water-soluble inorganic Cr 3+ salt; d) a gelation-retardant organic ligand definable by the formula: ##STR4## where: R is a direct single bond, or a saturated or unsaturated linear or branched aliphatic hydrocarbon radical with from 1 to 6 carbon atoms, or a cycloalkyl radical with from 3 to 7 carbon atoms, or an aryl radical; X is NR\"R'\" (where R\" and R'\", which may be equal or different, are H or an alkyl radical with from 1 to 5 carbon atoms); and relative water-soluble salts; the polymer b) being present in a concentration of between 1000 and 50,000 ppm (ppm=parts per million by weight); the salt c) being present in a concentration of between 10 and 5000 ppm evaluated as metal; the polymer/Cr 3+ weight ratio varying from 1:1 to 1000:1; the organic ligand/Cr 3+ molar ratio varying from 0.5 to 500:1; the composition having a pH equal to or less than about 7.0.",
    "2. A composition as claimed in claim 1, wherein b) is an acrylamide polymer or a polysaccharide.",
    "3. A composition as claimed in claim 2, wherein the acrylamide polymer is chosen from polyacrylamide, partially hydrolyzed polyacrylamide, and copolymers of acrylamide with copolymerizable monomers.",
    "4. A composition as claimed in claim 2, wherein the polysaccharide is chosen from guar gum, xanthan gum, scleroglucan, carboxymethyl cellulose, hydroxyethyl cellulose and modified starches.",
    "5. A composition as claimed in claim 1, wherein the polymer b) has a weight average molecular weight of between 100,000 and 20,000,000.",
    "6. A composition as claimed in claim 5, wherein said polymer b) has a weight average molecular weight of between 200,000 and 12,000,000.",
    "7. A composition as claimed in claim 1, wherein c) is a Cr 3+ salt chosen from chlorides, nitrates and sulphates.",
    "8. A composition as claimed in claim 1, wherein d) is defined by formula I where R is a direct single bond or a saturated or unsaturated linear aliphatic hydrocarbon radical with from 1 to 6 carbon atoms, and X is NR\"R'\".",
    "9. A composition as claimed in claim 1, wherein the polymer b) is present in a concentration of between 4000 and 30,000 ppm, the salt c) is present in a concentration of between 5 and 500 ppm evaluated as metal, and the polymer/Cr 3+ weight ratio varies from 5:1 to 500:1.",
    "10. A composition as claimed in claim 1, wherein the organic ligand/Cr 3+ molar ratio varies from 1:1 to 100:1.",
    "11. A composition as claimed in claim 1, wherein the composition pH varies from about 2.0 to about 7.0.",
    "12. A composition as claimed in claim 1, wherein the components c) and d) are furnished, totally or partially, as a preformed complex comprising trivalent chromium, a ligand of formula I, and ion selected from Na + or K +, and optionally a molecule selected from water or pyridine.",
    "13. A composition as claimed in claim 5, wherein component D is the monoamide of glutaric acid."
  ],
  "cpc": [
    "C09K 8/887",
    "C09K 8/512"
  ],
  "assignees": [
    "ENIRICERCHE SPA",
    "AGIP SPA"
  ],
  "filing_date": "1990-03-27",
  "publication_date": "1992-09-01",
  "grant_date": "1992-09-01",
  "priority_date": "1989-03-31",
  "application_number": "US-49968290-A",
  "family_id": "11162731",
  "citations": [
    "EP0170893A1",
    "EP0251638A2",
    "US3615794A",
    "US3978925A",
    "US4657081A",
    "US4706754A",
    "US4722397A",
    "US4917186A"
  ]
}