Self-diverting acidizing system
A method of acidizing a formation penetrated by a wellbore that includes the steps of injecting into the wellbore at a pressure below formation fracturing pressure a treatment fluid that includes a gelling fluid including a gelling agent and a hydrophobically-modified associative polymer, and an aqueous acid; and allowing the treatment fluid to acidize the formation.
1. A method of acidizing a formation penetrated by a wellbore comprising the steps of:
a. injecting into the wellbore at a pressure below formation fracturing pressure a treatment fluid comprising a gelling fluid comprising a gelling agent and a hydrophobically-modified associative polymer, and an aqueous acid, wherein the hydrophobically-modified associative polymer comprises a polymer backbone, at least one water-soluble part, at least one water-insoluble part comprising ethylhexyl acrylate, and an ester bond between the polymer backbone and the water-insoluble part;
b. allowing the treatment fluid to acidize the formation; and
c. allowing the ester bond to hydrolyze over time and act as a breaker for the treatment fluid.
2. The method of claim 1 further comprising the step of allowing the treatment fluid to self-divert into the formation.
3. The method of claim 1 , wherein the gelling agent comprises a surfactant according to Formula I:
wherein R 1 is selected from the group consisting of alkyl, alkenyl, alkylarylalkylene, alkenylarylalkylene, alkylaminoalkylene, alkenylamino-alkylene, alkylamidoalkylene, and alkenylamidoalkylene, wherein each of said alkyl groups contain from about 14 to about 24 carbon atoms and wherein said alkylene groups contain from about 1 to about 6 carbon atoms; and R 2 , R 3 and R 4 are the same or different and are alkyl or hydroxyalkyl of from 1 to about 5 carbon atoms, or R 3 and R 4 or R 2 together with the nitrogen atom to which they are bonded form a heterocyclic ring of up to 6 members.
4. The method of claim 1 , wherein the gelling agent comprises a surfactant according to Formula II:
wherein R 1 is a hydrocarbyl group and contains from about 8 to about 30 carbon atoms; R 2 and R 3 are individually hydrogen or a methyl group; R 4 and R 5 or R 6 are individually hydrogen or a hydroxyl group with the provision that at least one of the R 4 and R 5 or R 6 is a hydroxyl groups.
5. The method of claim 1 , wherein the gelling agent comprises a surfactant according to Formula III:
wherein R 1 is a hydrocarbyl group and contains from about 8 to about 30 carbon atoms; and R 2 , R 3 and R 4 are the same or different and are alkyl or hydroxyalkyl of from 1 to about 5 carbon atoms, or R 3 and R 4 or R 2 together with the nitrogen atom to which they are bonded form a heterocyclic ring of up to 6 members.
6. The method of claim 1 , wherein the gelling agent comprises a surfactant according to Formula IV:
wherein R 7 is an aliphatic group of from about 7 to about 30 carbon atoms; R 9 is a divalent alkylene group of from 2 to about 6 carbon atoms; R 10 and R 11 are the same or different and are alkyl or hydroxyalkyl of from 1 to about 4 carbon atoms, or R 10 and R 11 together with the nitrogen atom to which they are bonded form a heterocyclic ring of up to 6 members; and R 8 is hydrogen or a alkyl or hydroxyalkyl group of from 1 to about 4 carbon atoms.
7. The method of claim 1 , wherein the at least one water-soluble part selected from the group consisting of acrylamide, methacrylamide, acrylic acid, methacrylic acid, 2-acrylamidomethylpropanesulfonic acid, N-vinyl pyrrolidone, N-vinyl formamide, and mixtures thereof.
8. The method of claim 1 , wherein the hydrophobically-modified associative polymer is present in an amount from about 0.001C* to 0.95C* by total weight of the gelling fluid.
9. The method of claim 1 , wherein the gelling fluid further comprises at least one solvent selected from the group consisting of water, alcohols, and combinations thereof.
10. A method of treating an oilfield well comprising the steps of injecting into the well a fluid comprising: (i) a gelling agent and (ii) a hydrophobically-modified associative polymer in an amount below its C* concentration, wherein the hydrophobically-modified associative polymer comprises a polymer backbone, at least one water-soluble part, at least one water-insoluble part comprising ethylhexyl acrylate, and an ester bond between the polymer backbone and the water-insoluble part; and allowing the ester bond to hydrolyze over time and act as a breaker for the treatment fluid.
11. The method of claim 10 , wherein the gelling agent comprises a surfactant according to Formula I:
wherein R 1 is selected from the group consisting of alkyl, alkenyl, alkylarylalkylene, alkenylarylalkylene, alkylaminoalkylene, alkenylamino-alkylene, alkylamidoalkylene, and alkenylamidoalkylene, wherein each of said alkyl groups contain from about 14 to about 24 carbon atoms and wherein said alkylene groups contain from about 1 to about 6 carbon atoms; and R 2 , R 3 and R 4 are the same or different and are alkyl or hydroxyalkyl of from 1 to about 5 carbon atoms, or R 3 and R 4 or R 2 together with the nitrogen atom to which they are bonded form a heterocyclic ring of up to 6 members.