Claims
- 1. In the process for well stimulation by fracture acidizing with an aqueous acidic solution wherein said acidic solution is injected into said well to contact a formation under pressure sufficient to fracture the formation, the improvement wherein said acidic solution contains as a friction reducer a copolymer soluble in water and aqueous acids and having a K-value of from 25 to 250 and which comprises in a statistical distribution in the macromolecule, at least 5% by weight of structural units of the formula ##STR65## wherein R.sup.1 is hydrogen, methyl or hydroxymethyl; and at least 10% by weight of structural units of the formula ##STR66## said acidic solution containing said copolymer in an amount of from 0.06 to 0.12% by weight.
- 2. The process according to claim 1 wherein the copolymer comprises in a statistical distribution, 5 to 50% by weight of moieties of the formula I ##STR67## 10to 95% by weight of moieties of the formula II ##STR68## and 0 to 85% by weight of moieties of the formula III ##STR69## wherein R.sup.1 is hydrogen, methyl or hydroxymethyl;
- R.sup.2 is hydrogen or methyl; and
- X is cyano, carboxyl or its alkali or ammonium salts, alkoxycarbonyl having 1 to 6 carbon atoms, hydroxyalkoxycarbonyl having 1 to 3 carbon atoms, N-methylolamidocarbonyl, methylol, methylol etherified with alkanols having 1 to 4 carbon atoms, alkanoylamino having 1 to 4 carbon atoms, N-substituted alkanoylamino of 1 to 4 carbon atoms substituted by methylol or alkyl having 1 to 4 carbon atoms, pyridinium, pyrrolidonyl-(1-), phenyl, sulfonic acid group, sulfoalkylamidocarbonyl having 1 to 4 carbon atoms, phosphonic acid group, alkali or ammonium salts of the sulfonic and phosphonic acid groups, a moiety of the formula IV ##STR70## wherein R.sup.3 and R.sup.4 are the same or different and each is alkyl having 1 to 4 carbon atoms, a moiety of the formula ##STR71## wherein p is a number from 1 to 4, a moiety of the formula VI ##STR72## wherein R.sup.5 and R.sup.6 are the same or different and each is alkyl having 1 to 4 carbon atoms, or the quaternary ammonium salt of formula (V) and (VI).
- 3. The process according to claim 2 wherein the copolymer comprises
- 5 to 30% by weight of moieties of formula I,
- 50 to 80% by weight of moieties of formula II, and 1 to 60 by weight of moieties of formula III.
- 4. The process according to claim 2 wherein X is carboxyl group, sulfonic acid group, 3-sulfo-2-methyl-propyl-(2)-amidocarbonyl of the formula ##STR73## alkanoylamino having 1 to 4 carbon atoms unsubstituted or N-substituted with methylol or alkyl having 1 to 4 carbon atoms, pyrrolidonyl-(1), a moiety of formula V or VI, or the Na-, K- or NH.sub.4 -salts of the carboxylic and sulfonic acids.
- 5. The process according to claim 1 or claim 2 wherein the copolymer has a K-value of about 50 to 200 corresponding to molecular weights of about 100,000 to 4.times.10.sup.6.
- 6. The process according to claim 2 wherein X is alkoxycarbonyl having 1 to 3 carbon atoms.
- 7. The process according to claim 2 wherein units of formula III are introduced into the copolymer by copolymerizing with a monomer selected from the group consisting of
- N-Vinyl-acetamide,
- N-Vinyl-N-methyl-acetamide,
- N-Vinylpyrrolidone,
- Acrylic acid, alkali or ammonium salts of acrylic acid, ##STR74## or the alkali or ammonium salt thereof, ##STR75##
- 8. The process according to claim 3 wherein units of formula III are introduced into the copolymer by copolymerizing with a monomer selected from the group consisting of
- N-Vinyl-acetamide,
- N-Vinyl-N-methyl-acetamide,
- N-Vinylpyrrolidone,
- Acrylic acid, alkali or ammonium salts of acrylic acid, ##STR76## or the alkali or ammonium salt thereof, ##STR77##
- 9. The process according to claim 2 or claim 3 wherein the units of formula I are introduced into the copolymer by copolymerizng with vinylformamide and the units of formula III are introduced into the copolymer by copolymerizing with vinylmethylacetamide, vinylpyrrolidone, 2-acrylamido-2-methylpropane sulfonic acid or mixtures thereof.
Parent Case Info
This application is a division of application Ser. No. 216,671, filed Dec. 15, 1980, now abandoned.
US Referenced Citations (25)
Foreign Referenced Citations (1)
Number |
Date |
Country |
482897 |
Apr 1938 |
GBX |
Divisions (1)
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Number |
Date |
Country |
Parent |
216671 |
Dec 1980 |
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