Viscoelastic surfactant acid treatment
AssigneeSchlumberger Technology Corporation
InventorsYiyan Chen, Abbas Mahdi, Richard Marcinew, Matt Graham, Timothy L. Pope
Life of this patent
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Abstract
A method of treating a subterranean formation penetrated by a wellbore involves introducing an acid treatment fluid through the wellbore into the formation. The treatment fluid is formed from a zwitterionic viscoelastic surfactant, an acid in an amount to provide the treatment fluid with an initial pH of ≦0 and a rheology enhancer. The treatment fluid has a high viscosity at the initial pH and a lower viscosity when the pH of the treatment fluid is raised to an intermediate pH of from greater than 0 to about 5.
Claims21
A method of treating a wellbore, the method comprising introducing an acid treatment fluid through the wellbore, the treatment fluid comprising from 0.5 to 5.5% by weight of a zwitterionic viscoelastic surfactant, an acid in an amount more than 15% by weight to provide the treatment fluid with an initial pH of ≦0 and a rheology enhancer selected from at least one of a polyvinyl ester, a polyvinyl acetate, a polyacrylate and a sulfonate-containing polymer, and combinations thereof, the zwitterionic viscoelastic surfactant comprises a surfactant or mixture of surfactants having the formula:
- RCONH—(CH2)a(CH2CH2O)m(CH2)b—N+(CH3)2—(CH2)a′(CH2CH2O)m′(CH2)b′COO−
- wherein R is an alkyl group that contains from about 17 to about 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 0 to 14;
- and CH2CH2O may also be OCH2CH2, and, wherein the treatment fluid has a high viscosity at the initial pH and a lower viscosity when the pH of the treatment fluid is raised to an intermediate pH of from greater than 0 to about 5;
- and wherein:
- the treatment fluid has at least one property of (1) and (2), wherein (1) is a viscosity at the intermediate pH of less than about 20 mPas at a shear rate of 100 s−1, and (2) is the viscosity at the intermediate pH is decreased by as much as 70% or more compared to the high viscosity of the fluid at the initial pH.
A method of treating a subterranean formation penetrated by a wellbore, the method comprising introducing an acid treatment fluid through the wellbore into the formation, the treatment fluid comprising from 0.5 to 5.5% by weight of a viscoelastic surfactant, a mineral acid in an amount more than 15% by weight to provide the treatment fluid with an initial pH of ≦0 and a rheology enhancer selected from at least one of a polyvinyl ester, a polyvinyl acetate, a polyacrylate and a sulfonate-containing polymer, and combinations thereof, the viscoelastic surfactant comprising a surfactant or mixture of surfactants having the formula:
- RCONH—(CH2)a(CH2CH2)m(CH2)b—N+(CH3)2—(CH2)a′(CH2CH2O)m′(CH2)b′COO−
- wherein R is an alkyl group that contains from about 17 to about 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 0 to 14;
- and CH2CH2O may also be OCH2CH2;
- and, wherein the treatment fluid is has a high viscosity at the initial pH and a lower viscosity when the pH of the treatment fluid is increased to an intermediate pH of from greater than 0 to about 5;
- and wherein the treatment fluid has at least one property of (1) and (2), wherein (1) is a viscosity at the intermediate pH of less than about 20 mPas at a shear rate of 100 s−1, and (2) is the viscosity at the intermediate pH is decreased by as much as 70% or more compared to the high viscosity of the fluid at the initial pH.
A method comprising introducing an acid treatment fluid into a conduit, the treatment fluid comprising from 0.5 to 5.5% by weight of a zwitterionic viscoelastic surfactant, an acid in an amount more than 15% by weight to provide the treatment fluid with an initial pH of ≦0 and a rheology enhancer selected from at least one of a polyvinyl ester, a polyvinyl acetate, a polyacrylate and a sulfonate-containing polymer, and combinations thereof, the zwitterionic viscoelastic surfactant comprises a surfactant or mixture of surfactants having the formula:
- RCONH—(CH2)a(CH2CH2)m(CH2)b—N+(CH3)2—(CH2)a′(CH2CH2O)m′(CH2)b′COO−
- wherein R is an alkyl group that contains from about 17 to about 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 0 to 14;
- and CH2CH2O may also be OCH2CH2, and, wherein the treatment fluid has a high viscosity at the initial pH and a lower viscosity when the pH of the treatment fluid is raised to an intermediate pH of from greater than 0 to about 5;
- and wherein the treatment fluid has at least one property of (1) and (2), wherein (1) is a viscosity at the intermediate pH of less than about 20 mPas, at a shear rate of 100 s−1, and (2) is the viscosity at the intermediate pH is decreased by as much as 70% or more compared to the high viscosity of the fluid at the initial pH.
Dependencies are inferred from the claim text.