Viscoelastic surfactant rheology modification
AssigneeSchlumberger Technology Corporation
InventorsYiyan Chen, Jesse C. Lee, Philip F. Sullivan, Timothy L. Pope
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Abstract
A method for shortening the shear recovery time of cationic, zwitterionic, and amphoteric viscoelastic surfactant fluid systems by adding an effective amount of a rheology enhancer selected from partially hydrolyzed polyvinyl ester and partially hydrolyzed polyacrylates. The rheology enhancer also increases fluid viscosity and very low rheology enhancer concentration is needed. Preferred surfactants are betaines and quaternary amines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.
Claims28
An oilfield treatment method comprising:
- a. viscosifying a fluid with a viscoelastic surfactant system comprising a viscoelastic surfactant selected from at least one of zwitterionic, amphoteric, and cationic surfactants and mixtures thereof, wherein the viscosified fluid has a rheology comprising a viscosity and a viscosity recovery time at low shear conditions following a reduced viscosity from high shear conditions,
- b. providing a rheology enhancer in the fluid at a concentration sufficient to shorten the viscosity recovery time of the viscoelastic surfactant system, said rheology enhancer selected from at least one partially hydrolyzed polyvinyl ester;
- and
- c. injecting said fluid down a well through tubulars into a subterranean formation, wherein the high shear conditions are the conditions in the tubulars and the low shear conditions are the conditions in the formation, and wherein the viscosified fluid is subjected to high shear conditions for at least about 30 seconds to reduce the viscosity and then the viscosified fluid is subjected to reduced shear to recover the viscosity.
A method of shortening the shear recovery time of a fluid viscosified with a viscoelastic surfactant system comprising:
- a. providing a viscosified fluid comprising a viscoelastic surfactant selected from at least one of zwitterionic, amphoteric, and cationic surfactants and mixtures thereof;
- b. subjecting the fluid to high shear for at least about 30 seconds to reduce the viscosity of the fluid;
- and
- c. then reducing the shear for a period of time to recover the viscosity in the presence of a rheology enhancer in a concentration sufficient to shorten the shear recovery time of said fluid, said rheology enhancer selected from at least one partially hydrolyzed polyvinyl ester, wherein the period of time at reduced shear is shortened to about six seconds or less.
A composition comprising a fluid comprising a viscoelastic surfactant selected from at least one of zwitterionic, amphoteric, and cationic surfactants and mixtures thereof;
- a fluid rheology comprising a reduced viscosity following high shear for at least about 30 seconds and a viscosity recovery time at reduced shear;
- and a rheology enhancer in a concentration sufficient to shorten the viscosity recovery time of said fluid to less than about 15 seconds, said rheology enhancer selected from the group consisting of partially hydrolyzed polyvinyl esters.
A method of hydraulic fracturing comprising:
- a. viscosifying a fluid with a viscoelastic surfactant system comprising a viscoelastic surfactant selected from at least one of zwitterionic, amphoteric, and cationic surfactants and mixtures thereof, wherein the viscosified fluid has a rheology comprising a viscosity recovery time;
- b. providing a rheology enhancer in the fluid at a concentration sufficient to shorten the viscosity recovery time of the viscoelastic surfactant system, said rheology enhancer selected from at least one partially hydrolyzed polyvinyl ester;
- and
- c. injecting said fluid down a well into a fracture by means of a tubular conveyance, said viscosified fluid having a recovery time of less than 15 seconds after exiting the tubular and entering the low-shear environment in the fracture.
Dependencies are inferred from the claim text.