A method is given in which there is delayed release from the treatment fluid of solid chemicals that are obtained in bulk powder form. The method is used in situations in which it is difficult to encapsulate the chemical to achieve delayed release because the chemical is obtained in powdered form. The method involves delivering the powdered chemical in capsules consisting of encapsulated granulates obtained by aggregating the bulk powder under pressure to form a densified material and, optionally, then dry comminuting the densified material to produce granulates of the desired size. The treatment is hydraulic fracturing and the chemical is a breaker, or the treatment is well cementing and the chemical is a dispersing agent, fluid loss control additive, set accelerator, or extender.
A method of treating a subterranean formation by injecting down a well an aqueous fluid containing a viscoelastic surfactant fluid comprising an enhanced shear recovery agent wherein shear recovery time of the viscoelastic surfactant fluid is reduced by the addition of the enhanced shear recovery agent, and a viscoelastic surfactant fluid composition thereof.
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.
The present invention involves methods and compositions for treating subterranean formations, and more specifically, relates to improved methods and compositions for degrading filter cake deposited in a subterranean formation by effecting a uniform distribution of a filter cake breaker. One embodiment of the present invention provides a weighted encapsulated breaker comprising a breaker material; and, a coating material comprising a polymer material and a filler material having a specific gravity of at least about 6.5.
It was found that the addition of polymers to viscoelastic surfactant base system allows to adjust the rheological properties of the base fluid. Depending in particular on one side of the ratio of the concentration of added polymer and the concentration of viscoelastic surfactant and on the other side of the molecular weight of the added polymer, the same polymer--or the same type of polymer--may perform different functions such as viscosity enhancer, viscosity breaker or viscosity-recovery enhancer.
The invention provides a method of treating of a well, a formation, or both, with the solids, liquids, or apparatuses, by 1) encasing said solids, liquids, or apparatuses in a water-soluble shell, 2) conveying said encased solids, liquids, or apparatuses to a predetermined location in the well, and then 3) allowing the water-soluble shell to dissolve in the aqueous phase in the wellbore. The shell is preferably made of water-soluble polyvinyl alcohol copolymers and a waterproofing agent. The shell encases a variety of solids, liquids, or combinations thereof, where said solids or liquids are useful in the treatment of the well or of the producing formation. Illustrative encased material includes soap, acid, corrosion inhibitors, chelating agents, scale inhibitors, mutual solvents, paraffin inhibitors, paraffin dissolvers, clay stabilizers, and tracer materials. The encased materials may also be apparatuses, such as a prefabricated screen completion or a prefabricated sand-pack. The tool used to deliver the apparatuses may also be made from a water-soluble polyvinyl alcohol copolymer.
