Ultra low concentration surfactant flooding

Abstract

A method of recovering oil from a formation that includes the use of surfactants at low concentrations. The surfactant may be an oleophilic surfactant. The method may include conditioning an oil recovery system to inhibit microbes that could consume the oleophilic surfactant. A method that determines the concentration of a surfactant that is sufficient to change the interfacial tension between oil and water in a near well bore area of an injection well in a formation but does not require changing the interfacial tension between oil and water outside the near well bore area.

What is claimed is: 
     
         1 . A method of recovering oil from a formation, said method comprising:
 injecting a drive fluid into said formation;   injecting an oleophilic surfactant into said formation at a concentration of 0.1 to 100 mg/l of said injected fluid; and   recovering said oil from said formation.   
     
     
         2 . The method of  claim 1  further comprising:
 reducing a microbe population in said formation. 
 
     
     
         3 . The method of  claim 2  wherein said reduction of microbe population comprises injecting, into said formation, a selection from the list consisting of: a biocide, a biostat and combinations thereof. 
     
     
         4 . The method of  claim 2  wherein said reduction of microbe population comprises adjusting the pH of the injection fluid to inhibit microbial growth. 
     
     
         5 . The method of  claim 2  wherein said reduction of microbe population comprises exposing said microbe population to a predetermined temperature to inhibit microbial growth. 
     
     
         6 . The method of  claim 1  wherein said injection of drive fluid and said injection of oleophilic surfactant includes preparing a mixture of said drive fluid and said oleophilic surfactant and injecting said mixture via an injection well in said formation. 
     
     
         7 . The method of  claim 1  wherein said injection of fluid is done via an injection well in said formation and said injection of said oleophilic surfactant is done via a capillary tube leading from a surfactant source to the near well bore area of said injection well. 
     
     
         8 . The method of  claim 1  wherein said oleophilic surfactant is injected in batches to achieve said concentration of 0.1 to 100 mg/l over a predetermined period. 
     
     
         9 . The method of  claim 1  wherein said oleophilic surfactant is injected continuously to achieve said concentration of 0.1 to 100 mg/l. 
     
     
         10 . The method of  claim 1  wherein said oleophilic surfactant is selected from the list consisting of: sorbitan trioleate, sorbitan tristearate, sorbitan monooleate, sorbitan monolaurate, compounds comprising: amyl alcohols, hexyl alcohols, decyl alcohols, cresols and p-nonyl phenol and combinations thereof. 
     
     
         11 . The method of  claim 1  wherein said fluid comprises material selected from the list consisting of: water, brine, produced water and combinations thereof. 
     
     
         12 . The method of  claim 1  wherein said recovering does not include the use of a mobility control slug. 
     
     
         13 . The method of  claim 1  wherein said recovering does not include the use of a preflush slug. 
     
     
         14 . The method of  claim 1  wherein said formation has been water flooded to a residual oil saturation. 
     
     
         15 . A method of recovering oil from a formation, said method comprising:
 injecting a drive fluid into said formation;   injecting an oleophilic surfactant into said formation at a concentration that allows said surfactant to change interfacial tension between oil and water in a near well bore area of an injection well in a formation, but does not change interfacial tension between oil and water outside said near well bore area; and   recovering said oil from said formation.   
     
     
         16 . The method of  claim 15  wherein said oleophilic surfactant is selected from the list consisting of: sorbitan trioleate, sorbitan tristearate, sorbitan monooleate, sorbitan monolaurate, compounds comprising: amyl alcohols, hexyl alcohols, decyl alcohols, cresols and p-nonyl phenol and combinations thereof. 
     
     
         17 . The method of  claim 15  wherein said near well bore area is 50 meters or less from said well. 
     
     
         18 . A method of recovering oil from a formation, said method comprising:
 injecting an oleophilic surfactant into said formation,   injecting flood water into said formation, wherein said oleophilic surfactant is injected at a concentration of 0.1 to 100 mg/l of said injected flood water and wherein said injection of fluid is done via an injection well in said formation and said injection of surfactant is done via a capillary tube leading from a surfactant source to the near well bore area of said injection well;   injecting, into said formation, a selection from the list consisting of: a biocide, a biostat and combinations thereof;   recovering said oil from said formation.   
     
     
         19 . The method of  claim 18  wherein said injection of said flood water and said injection of oleophilic surfactant is done via an injection well in said formation and said recovery is via a production well in said formation. 
     
     
         20 . The method of  claim 18  wherein said oleophilic surfactant is selected from the list consisting of: sorbitan trioleate, sorbitan tristearate, sorbitan monooleate, sorbitan monolaurate, compounds comprising: amyl alcohols, hexyl alcohols, decyl alcohols, cresols and p-nonyl phenol and combinations thereof.