Nano-encapsulated triggered-release viscosity breakers

Abstract

A method for the encapsulation and triggered-release of water-soluble or water-dispersible materials. The method comprises a) providing an amount of electrolyte having a charge, b) providing an amount of counterion having a valence of at least 2, c) combining the polyelectrolyte and the counterion in a solution such that the polyelectrolyte self-assembles to form aggregates, d) adding a compound to be encapsulated, and e) adding nanoparticles to the solution such that nanoparticles arrange themselves around the aggregates. Release of the encapsulated species is triggered by disassembly or deformation of the microcapsules though disruption of the charge interactions. This method is specifically useful for the controlled viscosity reduction of the fracturing fluids commonly utilized in the oil field.

1 . A method for making a nanoencapsulate, comprising:
 a) providing an amount of a polyelectrolyte having a charge;   b) providing an amount of a counterion having a valence of at least 2;   c) combining the polyelectrolyte and the counterion in a solution such that the polyelectrolyte self-assembles to form aggregates;   d) adding to the aggregates a compound to be encapsulated; and   e) adding nanoparticles to the solution such that nanoparticles arrange themselves around the aggregates.   
     
     
         2 . The method according to  claim 1  wherein step d) includes aging a mixture containing the aggregates and the compound to be encapsulated. 
     
     
         3 . The method according to  claim 1  wherein step c) is carried out such that the polyelectrolyte self-assembles to form spherical aggregates. 
     
     
         4 . The method according to  claim 1  wherein the compound to be encapsulated comprises an enzyme. 
     
     
         5 . The method according to  claim 1  wherein the compound to be encapsulated comprises an organic dye. 
     
     
         6 . The method according to  claim 1  wherein the compound to be encapsulated comprises a sol. 
     
     
         7 . The method according to  claim 1  wherein the compound to be encapsulated comprises a ferro-fluid. 
     
     
         8 . The method according to  claim 1  wherein the compound to be encapsulated comprises a magnetic contrast agent. 
     
     
         9 . The method according to  claim 1  wherein the compound to be encapsulated comprises a cosmetic. 
     
     
         10 . The method of  claim 1  wherein step d) is carried out so as to produce sub-micron or micron-sized organic-inorganic spheres in which the shell consists of nanoparticles and polyelectrolyte molecules that hold the nanoparticles together. 
     
     
         11 . The method according to  claim 1  wherein the polyelectrolyte is functionalized with at least one moiety selected from the group consisting of organic molecules, organic fluorophores, and biomolecules. 
     
     
         12 . The method according to  claim 1  wherein the nanoparticles are functionalized. 
     
     
         13 . The method according to  claim 1  wherein the nanoparticles comprise metals, metal oxides, metal-nonoxides, organic particles, linear polymer, biomolecules, fullerenols or single/multi-walled carbon nanotubes. 
     
     
         14 . The method according to  claim 1  wherein the nanoparticles comprise silica nanoparticles. 
     
     
         15 . The method according to  claim 1  wherein at least one of steps c) and d) is carried out at ambient temperature. 
     
     
         16 . The method according to  claim 1  wherein steps c) and d) are carried out simultaneously. 
     
     
         17 . The method according to  claim 1  wherein steps d) and e) are carried out simultaneously. 
     
     
         18 . The method according to  claim 1  wherein steps c)-e) are carried out sequentially. 
     
     
         19 . The nanoencapsulate produced according to the method of  claim 1 . 
     
     
         20 . A method for making treating a hydrocarbon-producing formation, comprising:
 a) providing an amount of a polyelectrolyte having a charge;   b) providing an amount of a counterion having a valence of at least 2;   c) combining the polyelectrolyte and the counterion in a solution such that the polyelectrolyte self-assembles to form aggregates;   d) adding to the aggregates a compound to be encapsulated; and   e) adding nanoparticles to the solution such that nanoparticles arrange themselves around the aggregates to form nanoencapsulates;   f) including the nanoencapsulates in a well-servicing fluid; and   g) using the well-servicing fluid to treat a hydrocarbon-producing formation.   
     
     
         21 . The method of  claim 20 , further including the step h) of releasing the compound from the nanocapsules.