Nano-Sized Particles for Stabilizing Viscoelastic Surfactant Fluids

Abstract

An aqueous, viscoelastic fluid gelled with a viscoelastic surfactant (VES) is stabilized and improved with an effective amount of an alkaline earth metal oxide alkaline earth metal hydroxide, alkali metal oxides, alkali metal hydroxides transition metal oxides, transition metal hydroxides, post-transition metal oxides, and post-transition metal hydroxides. These fluids are more stable and have a reduced or no tendency to precipitate, particularly at elevated temperatures. The additives may reduce the amount of VES required to maintain a given viscosity. These stabilized, enhanced, aqueous viscoelastic fluids may be used as treatment fluids for subterranean hydrocarbon formations, such as in hydraulic fracturing. The particle size of the magnesium oxide or other agent may be nanometer scale, which scale may provide unique particle charges that use chemisorption, crosslinking and/or other chemistries to associate and stabilize the VES fluids.

1 . An aqueous viscoelastic surfactant treating fluid comprising:
 an aqueous base fluid;   a viscoelastic surfactant (VES) gelling agent; and   a particulate additive having a mean particle size of 100 nm or less, selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, alkali metal oxides, alkali metal hydroxides, transition metal oxides, transition metal hydroxides, post-transition metal oxides, and post-transition metal hydroxides, and mixtures thereof, where the transition metal in the transition metal oxide is selected from the group consisting of titanium and zinc and the post-transition metal in the post-transition metal oxide is selected from the group consisting of gallium, indium, thallium, lead and bismuth.   
     
     
         2 . The aqueous viscoelastic surfactant treating fluid of  claim 1  where the aqueous base fluid is brine. 
     
     
         3 . The aqueous viscoelastic surfactant treating fluid of  claim 1  where the alkaline earth metal is selected from the group consisting of magnesium, calcium, strontium, barium and mixtures thereof, where the alkali metal is selected from the group consisting of lithium, sodium, potassium, and mixtures thereof. 
     
     
         4 . The aqueous viscoelastic surfactant treating fluid of  claim 1  where the effective amount of the additive ranges from about 0.5 to about 20.0 pptg (about 0.06 to about 2.4 kg/1000 liters) based on the aqueous viscoelastic treating fluid. 
     
     
         5 . The aqueous viscoelastic surfactant treating fluid of  claim 1  further comprising a property selected from the group consisting of
 improved stability as compared with an otherwise identical fluid absent the additive, 
 reduced precipitates as compared with an otherwise identical fluid absent the additive, 
 or both. 
 
     
     
         6 . The aqueous viscoelastic surfactant treating fluid of  claim 1  where the mean particle size of the additive is 50 nm or less. 
     
     
         7 . An aqueous viscoelastic surfactant treating fluid comprising:
 an aqueous brine base fluid;   a viscoelastic surfactant (VES) gelling agent; and   about 0.5 to about 20.0 pptg (about 0.06 to about 2.4 kg/1000 liters) based on the aqueous viscoelastic treating fluid of an additive having a mean particle size of 100 nm or less, selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, alkali metal oxides, alkali metal hydroxides, transition metal oxides, transition metal hydroxides, post-transition metal oxides, and post-transition metal hydroxides, and mixtures thereof, where the transition metal in the transition metal oxide is selected from the group consisting of titanium and zinc and the post-transition metal in the post-transition metal oxide is selected from the group consisting of gallium, indium, thallium, lead and bismuth.   
     
     
         8 . The aqueous viscoelastic surfactant treating fluid of  claim 7  where the alkaline earth metal is selected from the group consisting of magnesium, calcium, strontium, barium and mixtures thereof, where the alkali metal is selected from the group consisting of lithium, sodium, potassium, and mixtures thereof. 
     
     
         9 . The aqueous viscoelastic surfactant treating fluid of  claim 7  further comprising a property selected from the group consisting of
 improved stability as compared with an otherwise identical fluid absent the additive, 
 reduced precipitates as compared with an otherwise identical fluid absent the additive, 
 or both. 
 
     
     
         10 . The aqueous viscoelastic surfactant treating fluid of  claim 7  where the mean particle size of the additive is 50 nm or less. 
     
     
         11 . An aqueous viscoelastic surfactant treating fluid comprising:
 an aqueous brine base fluid;   a viscoelastic surfactant (VES) gelling agent; and   about 0.5 to about 20.0 pptg (about 0.06 to about 2.4 kg/1000 liters) based on the aqueous viscoelastic treating fluid of an additive having a mean particle size of 50 nm or less, selected from the group consisting of alkaline earth metal oxides, alkaline earth metal hydroxides, alkali metal oxides, alkali metal hydroxides, transition metal oxides, transition metal hydroxides, post-transition metal oxides, and post-transition metal hydroxides, and mixtures thereof, where the alkaline earth metal is selected from the group consisting of magnesium, calcium, strontium, barium and mixtures thereof, where the alkali metal is selected from the group consisting of lithium, sodium, potassium, where the transition metal in the transition metal oxide is selected from the group consisting of titanium and zinc and the post-transition metal in the post-transition metal oxide is selected from the group consisting of gallium, indium, thallium, lead and bismuth.   
     
     
         12 . The aqueous viscoelastic surfactant treating fluid of  claim 11  further comprising a property selected from the group consisting of
 improved stability as compared with an otherwise identical fluid absent the additive, 
 reduced precipitates as compared with an otherwise identical fluid absent the additive, 
 or both.