Process for oil recovery using surfactant gels

Abstract

A composition and process for recovering oil by injecting an aqueous solution into a subterranean oil-bearing formation through one or more injection wells, displacing the solution into the formation, and recovering the oil from one or more production wells. This aqueous solution contains one or more amphoteric alkyl amido betaine surfactants that form a viscoelastic surfactant gels that can reduce the interfacial tension (IFT) and increase the viscosity of the injection fluid simultaneously in certain oils and brines. These viscoelastic gels are tolerant to electrolytes and multivalent cations. They are shear reversible and adsorbed little on the reservoir rock. The viscosity of the gels is reduced when they encountered certain hydrocarbons but remains high when contacting water or brine. This allows the fluid to preferentially penetrate the oil-bearing portions of the formation and resulting additional oil recovery. These amphoteric viscoelastic surfactant gels are particular suitable for use with reservoirs and brines characterized by medium to high temperatures, higher salinity, higher concentrations of divalent cations, and low formation porosities.

1 . A composition for the recovery of oil comprising: 
 a) one or more amphoteric surfactants chosen for their ability to both lower interfacial tension and increase viscosity,    b) an aqueous medium, and;    c) optionally one or more polymers to provide residual viscosity.    
   
   
       2 . The composition for the recovery of oil described in  claim 1  where the one or more amphoteric surfactants are present in amounts from about 0.1% to about 10% by weight.  
   
   
       3 . The composition for the recovery of oil described in  claim 1  where the one or more amphoteric surfactants have the following structure:  
     
       
         
         
             
             
         
       
     
     Where, 
 R 1  and R 2  are the same or different and preferably represent a low molecular weight alkyl residue, especially straight-chain alkyl residue with 1 to 4 carbon atoms, or hydroxy alkane; and R is C12 to C30, preferably C16 to C24 alkane or alkylene, and n is 2 to 6.  
 
   
   
       4 . The composition for the recovery of oil described in  claim 1  where the aqueous medium is water.  
   
   
       5 . The composition for the recovery of oil described in  claim 1  where the aqueous medium is water containing salts of mono and multivalent cations.  
   
   
       6 . The composition for the recovery of oil described in  claim 1  where the aqueous medium is an oilfield brine.  
   
   
       7 . The composition for the recovery of oil described in  claim 1  where the polymer used to provide residual viscosity is a polymer chosen from the group: polyacrylamide, partially hydrolyzed polyacrylamide, xanthan gum, guar gum, hydroxyethyl cellulose.  
   
   
       8 . The composition for the recovery of oil described in  claim 1  where the optional polymer used to provide residual viscosity is used at concentrations from about 0.01% to about 0.5% by weight.  
   
   
       9 . A composition for the recovery of oil comprising: 
 a. one or more amphoteric surfactants chosen for their ability to both lower interfacial tension and increase viscosity,    b. an aqueous medium,    c. a secondary surfactant and;    d. optionally one or more polymers to provide residual viscosity.    
   
   
       10 . The composition for the recovery of oil described in  claim 9  where the one or more amphoteric surfactants are present in amounts from about 0.1% to about 10% by weight.  
   
   
       11 . The composition for the recovery of oil described in  claim 9  where the one or more amphoteric surfactants have the following structure:  
     
       
         
         
             
             
         
       
     
     Where, 
 R 1  and R 2  are the same or different and preferably represent a low molecular weight alkyl residue, especially straight-chain alkyl residue with 1 to 4 carbon atoms, or hydroxy alkane; and R is C12 to C30, preferably C16 to C24 alkane or alkylene, and n is 2 to 6.  
 
   
   
       12 . The composition for the recovery of oil described in  claim 9  where the aqueous medium is water.  
   
   
       13 . The composition for the recovery of oil described in  claim 9  where the aqueous medium is water containing salts of mono and multivalent cations.  
   
   
       14 . The composition for the recovery of oil described in  claim 9  where the aqueous medium is an oilfield brine.  
   
   
       15 . The composition for the recovery of oil described in  claim 9  where the secondary surfactant is chosen from the group: anionic, nonionic, cationic surfactant.  
   
   
       16 . The composition for the recovery of oil described in  claim 9  where the polymer used to provide residual viscosity is a polymer chosen from the group: polyacrylamide, partially hydrolyzed polyacrylamide, xanthan gum, guar gum, hydroxyethyl cellulose.  
   
   
       17 . The composition for the recovery of oil described in  claim 9  where the polymer used to provide residual viscosity is used at concentrations from about 0.01% to about 0.5% by weight.