In-situ combustion restimulation process for a hydrocarbon well

Abstract

A process of enhancing hydrocarbon production from wells previously hydraulically fractured with a polymer based fluid(s). An in-situ combustion process is initiated in the reservoir for a short duration wherein thermal and chemical processes act to reduce the viscosity of unbroken gels and other fluids retained in the propped hydraulic fracture and immediate reservoir matrix vicinity.

What is claimed is:  
     
         1 . A method for restimulating a previously fractured hydrocarbon reservoir comprising the steps of: 
 a) shutting in a producing well bore in communication with said previously fractured hydrocarbon reservoir to prevent flow;    b) displacing at least a portion of a hydrocarbon product existing in said producing well bore with a fluid;    c) injecting air down said hydrocarbon well bore and into the hydrocarbon reservoir to create an in-situ combustion reaction in said previously fractured hydrocarbon reservoir;    d) shutting in the hydrocarbon well bore for a period of at least about 12 hours; and    e) producing the hydrocarbon products from said well bore.    
     
     
         2 . The method of  claim 1 , wherein said previously fractured hydrocarbon reservoir includes a residual polymer.  
     
     
         3 . The method of  claim 1 , further comprising the step of monitoring a bottom-hole temperature of said producing well bore.  
     
     
         4 . The method of  claim 1 , further comprising the step of injecting a combustion catalyst into said hydrocarbon reservoir.  
     
     
         5 . The method of  claim 4 , wherein said combustion catalyst comprises at least one transitional metal in the form of a metallic salt.  
     
     
         6 . The method of  claim 1 , wherein said hydrocarbon reservoir fluids have an API gravity of no less than about 35 degrees.  
     
     
         7 . The method of  claim 1 , wherein a combustion temperature in said hydrocarbon reservoir does not exceed about 700° F.  
     
     
         8 . The method of  claim 1 , wherein the volume of air injected into said hydrocarbon reservoir is at least about ten times the volume of an existing permeable fracture found in said previously fractured reservoir.  
     
     
         9 . The method of  claim 1 , further comprising the step of increasing the percentage of oxygen present in said injected air to enhance said in-situ combustion reaction.  
     
     
         10 . The method of  claim 1 , wherein said step of displacing at least a portion of a hydrocarbon product in said producing well bore comprises injecting water down said well bore.  
     
     
         11 . The method of  claim 1 , wherein said step of displacing at least a portion of a hydrocarbon product in said producing well bore comprises injecting a nitrogen gas down said well bore.  
     
     
         12 . The method of  claim 1 , further comprising an ignition step to initiate said in-situ combustion process.  
     
     
         13 . The method of  claim 12 , wherein said ignition step comprises the steps of: 
 a) injecting an air mixture at a surface rate of between about 50,000 to 100,000 standard cubic feet per day per foot of perforations;    b) restricting injection pressure below a reservoir fracture pressure; and    c) maintaining a continuous injection of said air mixture for a time period not less than about 5 hours.    
     
     
         14 . A method of improving the productivity of a previously fractured hydrocarbon reservoir, comprising the steps of: 
 a) providing a well bore in communication with the previously fractured hydrocarbon reservoir having an API fluid gravity of at least about 35 degrees;    b) shutting in said producing well bore;    c) injecting a non-combustible fluid down said well bore to evacuate said well bore of substantially any combustible hydrocarbons;    d) injecting a predetermined volume of air down said well bore and into said previously fractured hydrocarbon reservoir to initiate an in-situ combustion reaction and generate heat;    e) shutting in said well bore for a predetermined period of time; and    f) producing a hydrocarbon product from said previously fractured hydrocarbon reservoir and said well bore.    
     
     
         15 . The method of  claim 14 , wherein said heat generated in said previously fractured hydrocarbon reservoir improves the fracture conductivity and adjacent reservoir permeability by reducing a viscosity of a residual polymer gel present in at least a portion of a fracture system in said previously fractured hydrocarbon reservoir.  
     
     
         16 . The method of  claim 14 , further comprising the step of monitoring a bottom-hold temperature of said well bore to assure said bottom hole temperature does not exceed about 1000° F.  
     
     
         17 . The method of  claim 14 , further comprising the step of injecting combustion catalyst into said hydrocarbon reservoir.  
     
     
         18 . The method of  claim 17 , wherein said combustion catalyst comprises a transitional metal in the form of metallic salt.  
     
     
         19 . The method of  claim 14 , further comprising the step of injecting a noncombustible fluid down said well bore prior to producing a hydrocarbon product from said well bore.  
     
     
         20 . A method for restimulating a previously fractured hydrocarbon reservoir comprising the steps of: 
 a) shutting in a producing well bore in communication with said previously fractured hydrocarbon reservoir to prevent flow;    b) displacing at least a portion of a hydrocarbon product existing in said producing well bore with a fluid;    c) injecting air down said hydrocarbon well bore and into the hydrocarbon reservoir to create an in-situ combustion reaction;    d) shutting in the hydrocarbon well bore for a period of at least 12 hours; and    e) producing the hydrocarbon products from said well bore.