Abstract: Composition and method for shortening the shear recovery time of cationic, zwitterionic, and amphoteric viscoelastic surfactant fluid systems by adding an effective amount of a co-gelling agent selected from triblock oligomeric compounds having hydrophilic (for example polyether) and hydrophobic (for example alkyl) portions. The co-gelling agent also increases fluid viscosity and very low co-gelling agent concentration is needed. Preferred surfactants are betaines and quaternary amines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Abstract: An aqueous viscoelastic surfactant (VES) fluid foamed or energized with carbon dioxide, in which the VES is more compatible with the carbon dioxide, is made by the addition of one or more than one synergistic co-surfactant. The synergist co-surfactant includes quaternary amines and ethoxylated carboxylates having a hydrophobic chain shorter than the hydrophobic chain of the VES. Improved compatibility is evidenced for a given surfactant concentration either by formation and maintenance of a foam under conditions at which the foam could not otherwise have been formed or maintained, or by either higher viscosity of the foamed fluid at a given temperature or longer foam life at a given temperature or a higher temperature at which useful fluid viscosity can be generated or maintained for a useful time. The aqueous carbon dioxide foamed fluids may be used in acidizing, acid fracturing, gravel packing, diversion, and well cleanout.

Abstract: A method is disclosed for using aqueous VES-based gravel carrier fluids in gravel packing operations using screens and shunt tubes that have been run into a well completed with an oil-based mud. With this method, the previously necessary but undesirable steps of first running in a perforated liner and then displacing the oil-based mud with an aqueous-based fluid in the region to be gravel packed are both avoided while the advantages of gravel packing with an aqueous-based fluid are retained.

Abstract: A method is disclosed for using aqueous VES-based gravel carrier fluids in gravel packing operations using screens and shunt tubes that have been run into a well completed with an oil-based mud. With this method, the previously necessary but undesirable steps of first running in a perforated liner and then displacing the oil-based mud with an aqueous-based fluid in the region to be gravel packed are both avoided while the advantages of gravel packing with an aqueous-based fluid are retained.

Abstract: A viscous aqueous high density well treatment fluid composition stable at high temperature containing a surfactant and inorganic salts is described. Methods of preparing the fluid and increasing the stability and viscosity of the fluid are given. The fluid is useful for wellbore cleanout, hydraulic fracturing, gravel packing, completion, acid diversion, lost circulation reduction, well killing, cementing, selective water shutoff, and fracture fluid diversion.