Oil recovery using non-cryogenically produced nitrogen and off-gas recycling

Abstract

An enhanced oil recovery process includes non-cryogenically generating a relatively inert gas, such as nitrogen, or nitrogen-enriched air, near the site of an oil-bearing formation. The relatively inert gas is injected into the formation, so as to displace oil from the formation. One or more off-gases, also obtained from the formation with the oil, are separated from the oil, compressed, and recycled into the formation. The use of the compressed off-gas therefore reduces the amount of relatively inert gas required, and reduces the required size and energy consumption of the equipment used to produce the inert gas. The invention therefore substantially reduces the cost of an enhanced oil recovery process.

1 . In an enhanced oil recovery process, the recovery process including non-cryogenically generating a relatively inert gas at a site of an oil-bearing formation, and directing the relatively inert gas into the formation so as to displace oil from the formation, 
 the improvement comprising recovering an off-gas from the formation and directing said off-gas into the formation so as to aid in displacement of oil from the formation.    
   
   
       2 . The improvement of  claim 1 , further comprising compressing the off-gas before directing the off-gas into the formation.  
   
   
       3 . The improvement of  claim 2 , wherein the directing step includes conveying the off-gas into a conduit which carries the relatively inert gas.  
   
   
       4 . The improvement of  claim 1 , wherein the process is operated continuously.  
   
   
       5 . In an enhanced oil recovery process, the recovery process including non-cryogenically generating a relatively inert gas at a site of an oil-bearing formation, directing the relatively inert gas into the formation so as to displace oil from the formation, the improvement comprising: 
 recovering an off-gas from the formation;    compressing said recovered off-gas;    conveying said compressed off-gas into a conduit which carries said relatively inert gas.    
   
   
       6 . The improvement of  claim 5 , wherein the process is operated continuously.  
   
   
       7 . A process for enhanced oil recovery, comprising: 
 a) generating a relatively inert gas, in a vicinity of an oil-bearing formation,    b) directing said relatively inert gas into the formation so as to displace oil from the formation,    c) recovering an off-gas from the formation, and    d) recycling the off-gas into the formation.    
   
   
       8 . The process of  claim 7 , wherein step (d) is preceded by the step of compressing the off-gas.  
   
   
       9 . The process of  claim 7 , wherein step (d) is preceded by the step of mixing the off-gas with said relatively inert gas.  
   
   
       10 . The process of  claim 8 , wherein step (d) is preceded by the step of mixing the off-gas with said relatively inert gas.  
   
   
       11 . The process of  claim 7 , wherein the generating step comprises passing air through a pressure swing adsorption (PSA) system.  
   
   
       12 . The process of  claim 7 , wherein the generating step comprises passing air through a membrane system.  
   
   
       13 . The process of  claim 7 , wherein the process is operated continuously.  
   
   
       14 . A process for enhanced oil recovery, comprising: 
 a) generating a relatively inert gas, in a vicinity of an oil-bearing formation, and compressing said relatively inert gas,    b) directing said relatively inert gas, through a conduit, into the formation, so as to a displace liquid oil from the formation, the liquid oil being mixed with at least one off-gas,    c) separating the off-gas from the liquid oil, and conveying the liquid oil through an output conduit,    d) compressing the off-gas, and    e) directing the compressed off-gas into said conduit, wherein the compressed off-gas is injected into the formation with said relatively inert gas.    
   
   
       15 . The process of  claim 14 , wherein the process is operated continuously, wherein at least some off-gas is recycled more than once through the formation.  
   
   
       16 . The process of  claim 14 , wherein the compressed off-gas is mixed with the relatively inert gas before being injected into the formation.