CA2491934A1

CA2491934A1 - Self-diverting pre-flush acid for sandstone

Info

Publication number: CA2491934A1
Application number: CA002491934A
Authority: CA
Inventors: Diankui Fu
Original assignee: Schlumberger Canada Limited; Diankui Fu; Schlumberger Technology Corporation
Current assignee: Schlumberger Canada Ltd
Priority date: 2002-07-09
Filing date: 2003-07-09
Publication date: 2004-01-15
Anticipated expiration: 2023-07-09
Also published as: CA2491934C; BR0312349B1; WO2004005672A1; NO20050025L; BR0312349A; EP1520086A1; AU2003250012A1; MXPA05000043A

Abstract

Embodiments of the Present Invention relate to a reversibly thickenable non-polymeric fluid that has low viscosity in strong acid, gels when the acid concentration is reduced by only a small amount, and is subsequently decomposed by the acid. In particular it relates to an aqueous mixture of zwitterionic surfactants, inorganic acids, and organic acids Most particularly it relates to the use of this fluid as a diverting agent for easily-damaged sandstones, for example prior to matrix acidizing.

Claims

1. A self-diverting pre-flush sandstone acid comprising water, an acid-hydrolyzable surfactant capable of forming a viscoelastic gel, an inorganic acid, and an organic acid selected from formic acid, citric acid, acetic acid, boric acid, lactic acid, methyl sulfonic acid and ethyl sulfonic acid.

2. The composition of claim 1 wherein the surfactant has the following amide structure:

wherein R1 is a hydrocarbyl group that may be branched or straight chained, aromatic, aliphatic or olefinic and has from about 14 to about 26 carbon atoms and may contain an amine; R2 is hydrogen or an alkyl group having from 1 to about 4 carbon atoms; R3 is a hydrocarbyl group having from 1 to about 10 carbon atoms; and Y is an electron withdrawing group, preferably a functional group selected from the group consisting of a quaternary amine, an amine oxide, a sulfonate and a carboxylic acid, rendering the amide group difficult to hydrolyze.

3. The composition of claim 2 wherein the surfactant is a betaine having the structure:

wherein R is a hydrocarbyl group that may be branched or straight chained, aromatic, aliphatic or olefinic and has from about 14 to about 26 carbon atoms, preferably from about 17 to about 22 carbon atoms, and may contain an amine; n = about 2 to about 10, preferably about 3 to about 5;
and p = 1 to about 5, preferably 1 to about 3, and mixtures of these compounds.

4. The composition of claim 3 wherein the surfactant is a betaine having the structure:

or the structure:

wherein n = 3 and p = 1.

5. The composition of any of the preceding claims wherein the inorganic acid is selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid.

6. The composition of any of the preceding claims further comprising an alcohol selected from the group consisting of methanol, ethanol, propanol, isopropanol, ethylene glycol and propylene glycol.

7. A method of treating a sandstone formation having a non-target zone or zones and a target zone or zones penetrated by a wellbore comprising injecting the self-diverting pre-flush sandstone acid of any of the preceding claims into the wellbore to selectively block the pore structure in the non-target zone or zones.

8. The method of claim 7 comprising injecting the self-diverting pre-flush sandstone acid of any of claims 1 through 6 into the wellbore to selectively block the pore structure in the non-target zone or zones in order to selectively retard entry of fluid into the non-target zone or zones and to allow entry of fluid info the target zone or zones; and then injecting a matrix stimulation fluid into the formation, wherein the matrix stimulation fluid is diverted from the non-target zone or zones into the target zone or zones.