Methods of use of expandable grout for improved zonal isolation

Abstract

Systems and methods for employing hardened mixtures into perforations during hydraulic fracturing.

What is claimed is: 
     
         1 . A method for zonal isolation and protection of sensitive lithologies in a wellbore, comprising:
 injecting a polyurethane-precursor mixture into a target interval;   introducing a displacement fluid to displace the blend to the target depth;   allowing the mixture to expand and bond within the target interval to form an expanded volume;   shutting in the wellbore to enable the mixture to harden, thereby creating a rigid, low-permeability porous plug that isolates the target interval; and   
     
     
         2 . The method of  claim 1 , wherein the precursors are injected into the wellbore at a rate sufficiently low to avoid exceeding the fracturing pressure of the formation. 
     
     
         3 . The method of  claim 1 , wherein the mixture comprises an isocyanate precursor and a polyol precursor. 
     
     
         4 . The method of  claim 1 , wherein volume comprises polyurethane. 
     
     
         5 . The method of  claim 1 , where drilling operations through the hardened mixture occur subsequent to curing of the expandable grout. 
     
     
         6 . The method of  claim 5 , wherein the protective barrier is maintained across one or more sensitive lithologies following drilling. 
     
     
         5 . The method of  claim 4 , wherein the volume preferentially seals across only one or more predetermined lithologies. 
     
     
         6 . A method for zonal isolation and reinforcement of hydraulic fractures and perforations in a wellbore, comprising:
 introducing a mixture of an isocyanate precursor and a polyol precursor into one or more hydraulic fractures within the wellbore;   allowing the mixture to chemically bond to the walls of the fractures, followed by expansion within the fractures to form an expanded material configured to provide zonal isolation and reinforcement;   utilizing the chemically bonded and expanded mixture to create a barrier with significant resistance to injection into and production from the treated fractures or perforations.   
     
     
         7 . The method of  claim 6 , wherein the method is employed in wellbores of any inclination.