Title of Invention

AN OIL FIELD TREATMENT METHOD WITH RHEOLOGY MODIFIED VISCOELASTIC SURFACTANT SYSTEM

Abstract

A method for shortening the shear recovery time of zwitterionic viscoelastic surfactant fluids by adding a rheology enhancer having the structure: R<EO)x(PO)y-R'-OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 3 to about 18 carbon atoms, X is from 0 to about 14, y is from 0 to about 7, R' is an alkyl group that contains from 0 to about 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R' is from 3 to about 21, and the EO and PO groups, if present, may be in any order. The rheology enhancer also increases fluid viscosity and thermal stability. Preferred surfactants are betaines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Full Text

VISCOELASTIC SURFACTANT RHEOLOGY MODIFICATION concentration. For example, such materials may be beneficial at some concentration known, the concentration and ratios could not be, and were not, purposely optimized for rhecology enchancement. For example, small amounts of some suitable additives have in the past been added to commercial concentrates of surfactants, including VES conce concentrations of surfactant, rheology enhancer, and other fluid components to account for the effects of other components is wihtin the scope of the invetnion. enhancers of the invention were evaluated at several concentrations in 4.5% VES. As shown in Table 2, all of them reduces the shear reovery times to less than 15 seconds at all concentrations tested. We claim: An patient treatment method comprising a. providing a fluid viscosified with zwitterionic viscoelastic surfactant, b providing a rheology enhancer in a concentration of from 0.1 to 6% . said rheology enhancer comprising a compound or mixture of compounds selected from the group consisting of ethylene glycol monobutyl ether, n-butanof, dipropytene glycol methyl ether, and compounds having the structure: R-(CH,CH2O)x(CH2CH(CH3)O)y-R'-OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 4 to 18 carbon atoms, x is from 0 to 14, y is from 0 to 7, R' is an alkyl group that contains from 0 to 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R' is from 3 to 21, and the CH2CH2O and CH,CH(CH3)O groups, if present, may be in any order; and c. injecting said fluid down a well. 2 The method of claim 1 further wherein said rheology enhancer increases the viscosity of said fluid over the viscosity in the absence of the rheology enhancer. 3. The method of claim 1 or claim 2 wherein said zwitterionic surfactant comprises a surfactant or mixture of surfactants having the formula; wherein R is an alkyl group that contains from 17 to 23 carbon atoms which may be branched or straight chained and which may be saturated or unsaturated; a. b, a', and b are each from 0 to 10 and m and m' are each from 0 to 13, a and b are each 1 or 2 if m is not 0 and (a + b) is from 2 to 10 if m is 0: a' and b' are each 1 or 2 when m is not 0 and (a' + b") is from 1 to 5 if m' is 0; (m -^ m') is from 1 to 14; and CH2CH2O may also be OCH2CH2- 6 A method of shortening the shear recovery lime of a well treatment fluid comprising. 3. providing a fluid viscosified with a zwitterionic viscoeiastic surfactant, and b. providing a rheology enhancer in a concentration of from 0.1 to 6% . said rheology enhancer comprising a compound or mixture of compounds selected from the group consisting of ethylene giycoi monobutyl ether, n~butanol, dipropyiene glycol methyl ether, and compounds having the structure: R-(CH,CH2O)x(CH2CH(CH3)O)y-R-OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 4 to 18 carbon atoms, x is from 0 to 14. y is from 0 to 7, R' is an alkyl group that contains from 0 to 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R" is from 3 to 21, and the CH,CH,O and CH,CH(CH3)O groups, if present, may be in any order. 7 The method of ciaim 6 further wherein said rheology enhancer increases the viscosity of said fiuid over the viscosity in the absence of the rheology enhancer 8. The method of claim 6 or claim 7 wherein said zwittehonic surfactant comprises a surfactant or mixture of surfactants having the formula: RCONH-(CH:),(CH:CH,OuCH,)h-NVH3)r(CH2). 9. The method of claim 6 wherein said zwitterionic surfactant comprises a betaine. 10. The method of claim any of claims 6 through 9 wherein said rheoiogy enhancer is selected from the group consisting of ethylene glycol monobutyi ether, n-butanol, dipropylene glycol methyl ether, and mixtures thereof.

Documents:

2207-CHENP-2007 AMENDED PAGES OF SPECIFICATION 22-10-2013.pdf

2207-CHENP-2007 AMENDED PAGES OF SPECIFICATION 24-12-2013.pdf

2207-CHENP-2007 AMENDED CLAIMS 22-10-2013.pdf

2207-CHENP-2007 AMENDED CLAIMS 24-12-2013.pdf

2207-CHENP-2007 CORRESPONDENCE OTHERS 26-04-2013.pdf

2207-CHENP-2007 CORRESPONDENCE OTHERS 29-11-2013.pdf

2207-CHENP-2007 CORRESPONDENCE OTHERS 24-12-2013.pdf

2207-CHENP-2007 EXAMINATION REPORT REPLY RECEIVED 22-10-2013.pdf

2207-CHENP-2007 FORM-1 24-12-2013.pdf

2207-CHENP-2007 FORM-13 24-12-2013.pdf

2207-CHENP-2007 FORM-3 22-10-2013.pdf

2207-CHENP-2007 OTHER PATENT DOCUMENT 22-10-2013.pdf

2207-CHENP-2007 OTHERS 22-10-2013.pdf

2207-CHENP-2007 POWER OF ATTORNEY 22-10-2013.pdf

2207-chenp-2007-abstract.pdf

2207-chenp-2007-claims.pdf

2207-chenp-2007-correspondnece-others.pdf

2207-chenp-2007-description(complete).pdf

2207-chenp-2007-drawings.pdf

2207-chenp-2007-form 1.pdf

2207-chenp-2007-form 3.pdf

2207-chenp-2007-form 5.pdf

2207-chenp-2007-pct.pdf