Methods of generating gas in well treating fluids

Abstract

The present invention relates to methods of generating gas in and foaming well treating fluids during pumping of the treating fluids or after the treating fluids are placed in a subterranean zone, or both. A method of the present invention provides a method of treating a subterranean zone comprising the steps of providing a well treating fluid that comprises a water component, a gas generating chemical, and an encapsulated activator, placing the well treating fluid in a subterranean zone, and allowing the gas generating chemical to react so that a gas is generated in the cement composition. Methods of cementing, fracturing, cementing compositions, fracturing fluid compositions, and foamed well fluid compositions also are provided.

1 . A method of treating a subterranean zone comprising the steps of: 
 providing a well treating fluid that comprises a water component, a gas generating chemical, and an encapsulated activator;    placing the well treating fluid in a subterranean zone; and    allowing the gas generating chemical to react so that a gas is generated in the cement composition.    
     
     
         2 . The method of  claim 1  wherein the gas generating chemical comprises a hydrazine or an azo group.  
     
     
         3 . The method of  claim 1  wherein the gas generating chemical is present in the well treating fluid in an amount in the range of from about 0.1% to about 10% by weight of the well treating fluid.  
     
     
         4 . The method of  claim 1  wherein the encapsulated activator comprises an alkaline material or an oxidizing agent.  
     
     
         5 . The method of  claim 1  wherein the encapsulated activator comprises at least one of the following: a coating material, an undercoating, or a membrane that has at least one imperfection through which an aqueous fluid may diffuse.  
     
     
         6 . The method of  claim 5  wherein the coating material comprises a wax, a drying oil, a polyurethane, a polyacrylic, or styrene butadiene.  
     
     
         7 . The method of  claim 5  wherein the undercoating comprises styrene butadiene.  
     
     
         8 . The method of  claim 5  wherein the membrane comprises a partially hydrolyzed acrylic cross-linked with an aziridine prepolymer or a carbodiimide.  
     
     
         9 . The method of  claim 1  wherein at least a portion of the encapsulated activator is in the form of an aqueous solution on porous solid particulates.  
     
     
         10 . The method of  claim 9  wherein the portion of the encapsulated activator that is in the form of an aqueous solution on porous solid particulates further comprises a polymeric external coating.  
     
     
         11 . The method of  claim 1  wherein the well treating fluid further comprises a gas production rate enhancing chemical.  
     
     
         12 . The method of  claim 11  wherein the gas production rate enhancing chemical comprises a copper salt, a complex of a copper salt, an iron salt, or ethylene diamine tetraacetic acid.  
     
     
         13 . A method of fracturing a subterranean zone comprising the steps of: 
 providing a fracturing fluid that comprises a water component, a gelling agent, a gas generating chemical, and an encapsulated activator;    contacting the subterranean zone with the fracturing fluid at a pressure sufficient to create or enhance at least one fracture therein; and    allowing the gas generating chemical to react so that generated gas is incorporated in the fracturing fluid; and    reducing the viscosity of the fracturing fluid so as to produce a reduced viscosity fracturing fluid.    
     
     
         14 . The method of  claim 13  wherein the gelling agent comprises a cross-linked gelling agent.  
     
     
         15 . The method of  claim 13  wherein the fracturing fluid further comprises a crosslinking agent.  
     
     
         16 . The method of  claim 13  wherein the fracturing fluid further comprises a delayed gel breaker.  
     
     
         17 . The method of  claim 13  wherein the encapsulated activator comprises at least one of the following: a coating material, an undercoating, or a membrane that has at least one imperfection through which an aqueous fluid may diffuse.  
     
     
         18 . A method of cementing in a subterranean zone comprising the steps of: 
 providing a cement composition that comprises a hydraulic cement, a water component, a gas generating chemical, and an encapsulated activator;    placing the cement composition in a subterranean zone;    allowing the gas generating chemical to react so that a gas is generated in the cement composition; and    allowing the cement composition to set in the subterranean zone.    
     
     
         19 . The method of  claim 18  wherein the hydraulic cement comprises a Portland cement, a pozzolana cement, a gypsum cement, an aluminous cement, or a silica cement.  
     
     
         20 . The method of  claim 18  wherein the encapsulated activator comprises at least one of the following: a coating material, an undercoating, or a membrane that has at least one imperfection through which an aqueous fluid may diffuse.