Encapsulated breakers, compositions and methods of use

Abstract

An encapsulated breaker is enclosed within a hydrolytically degradable polymer coating. Compositions containing this encapsulated breaker, methods of making and methods of use are also described.

1 . An encapsulated breaker comprising a breaker capable of reducing the viscosity of a fracturing fluid enclosed within a hydrolytically degradable coating.  
     
     
         2 . The encapsulated breaker of    claim 1   , wherein said coating is formed from a composition comprising poly(alkyl-2-cyanoacrylate).  
     
     
         3 . The encapsulated breaker of    claim 2   , wherein said coating is formed from a composition additionally comprising one or more comonomers that are copolymerizable with alkyl-2-cyanoacrylate.  
     
     
         4 . The encapsulated breaker of    claim 3   , wherein said comonomers are selected from the esters of acrylic acid and methacrylic acid.  
     
     
         5 . The encapsulated breaker of    claim 3   , wherein said comonomers are selected from the group consisting of acrylic or methacrylic esters of non-tertiary alcohols, which alcohols are selected from the group consisting of ethanol, 1propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2methyl-1-butanol, 1-hexanol, 2-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 3,5,5-trimethyl-1-hexanol, 3-heptanol, 1-octanol, 2-octanol, isooctanol, 2-ethyl-1-hexanol, 1-decanol, 1-dodecanol, 1-tridecanol and 1-tetradecanol or mixtures thereof.  
     
     
         6 . The encapsulated breaker of    claim 3   , wherein said comonomers are selected from the group consisting of acrylamides and styrenes.  
     
     
         7 . The encapsulated breaker of    claim 2   , wherein said coating is formed from a composition comprising at least about 50% by weight of poly(alkyl-2cyanoacrylate) based on the total weight of the coating.  
     
     
         8 . The encapsulated breaker of    claim 2   , wherein said coating is formed from a composition comprising at least about 70% by weight of poly(alkyl-2-cyanoacrylate) based on the total weight of the coating.  
     
     
         9 . The encapsulated breaker of    claim 2   , wherein said coating is formed from a composition comprising at least about 90% by weight of poly(alkyl-2cyanoacrylate) based on the total weight of the coating.  
     
     
         10 . The encapsulated breaker of    claim 2   , wherein the alkyl group of poly(alkyl-2-cyanoacrylate) is C1-20 alkyl.  
     
     
         11 . The encapsulated breaker of    claim 2   , wherein the alkyl group of poly(alkyl-2-cyanoacrylate) is C1-6 alkyl.  
     
     
         12 . The encapsulated breaker of    claim 1   , wherein said breaker comprises a persulfate salt.  
     
     
         13 . The encapsulated breaker of    claim 12   , wherein said persulfate salt is potassium persulfate.  
     
     
         14 . A breaker slurry composition comprising a slurry of encapsulated breaker of    claim 1    in an organic solvent.  
     
     
         15 . The slurry composition of    claim 14   , wherein said organic solvent is predominantly aliphatic.  
     
     
         16 . The slurry composition of    claim 14   , wherein said organic solvent comprises kerosene.  
     
     
         17 . The slurry composition of    claim 14   , wherein said organic solvent comprises mineral oil.  
     
     
         18 . The slurry composition of    claim 14   , wherein said organic solvent comprises a blend of one or more hydrocarbons.  
     
     
         19 . The slurry composition of    claim 14   , comprising one or more surfactants.  
     
     
         20 . The slurry composition of    claim 19   , wherein said surfactant is selected from the group consisting of oxyalkylated phenolic resin surfactants, resin ester surfactants, polyol surfactants, alkylaryl sulfonate surfactants, polymeric amine surfactants, alcohol ether sulfonates, imidazoline cationic surfactants, complex phosphate esters, amine alkylaryl sulfonates, alkyl amidoamine surfactants, polyamido imidazoline surfactants, fatty imidazoline surfactants, dimer trimer acid surfactants, polyoxyethylated rosin amines, polyoxyethylated rosin amines, polyoxyethylene glycol surfactants, alcohol ether sulfonate surfactants, alcohol ether sulfate surfactants, sulfonate surfactants, sodium alpha olefin sulfonates, sodium alcohol ether sulfates, calcium alkylaryl sulfonates, amine dodecylbenzene sulfonates, fatty acid amides, alkanolamides, fluorinated surfactants, and mixtures thereof.  
     
     
         21 . An encapsulated breaker comprising a breaker capable of reducing the viscosity of a fracturing fluid, said breaker enclosed within a hydrolytically degradable polymer coating wherein said encapsulated breaker does not reduce viscosity lower than 50% at 5 hours at 25° C. in a Standard Breaking Test, but said encapsulated breaker does not reduce viscosity lower than 50% at 70° C. at a first predetermined time selected between fifteen minutes and 12 hours, but does reduce viscosity lower than 50% at a second predetermined time period selected between fifteen minutes and 12 hours after said first predetermined time at 70° C. in a Standard Breaking Test and wherein said encapsulated breaker reduces viscosity lower than 50% in a Standard Breaking Test at least 20 minutes after a like composition where the breaker is not encapsulated.  
     
     
         22 . The encapsulated breaker of    claim 21   , wherein said first predetermined time is between about 1 and 3 hours and said second predetermined time period is between about 3 and 5 hours.  
     
     
         23 . A method of breaking a fracturing fluid comprising introducing an encapsulated breaker of    claim 1    into a subterranean formation being treated with the fracturing fluid and exposing said breaker to temperatures in excess of about 40° C., thereby hydrolytically releasing said breaker.  
     
     
         24 . The method of    claim 23   , wherein said encapsulated breaker is provided as a slurry.  
     
     
         25 . Method of manufacturing encapsulated breaker comprising: 
 a) suspending a solid breaker particle in a reaction solution comprising non-aqueous solvent and an effective amount of (alkyl-2-cyanoacrylate),    b) adding weak base in an amount effective to initiate polymerization of the (alkyl-2-cyanoacrylate).    
     
     
         26 . The method of    claim 25   , further comprising the step of filtering said encapsulated breaker from the non-aqueous solvent.  
     
     
         27 . The method of    claim 25   , wherein said alkyl-2-cyanoacrylate comprises about 1-20% by weight of the reaction solution.