Optimizing enhanced oil recovery by the use of oil tracers

Abstract

A method of optimizing recovery of oil from a formation that includes injecting an oil tracer into an injection well in the formation and applying a tertiary oil recovery process for recovering the oil from the formation. A production well is monitored to detect the oil tracer in oil from the production wells within particular times. The method also includes modifying the tertiary oil recovery process based on the detection of the oil tracer in oil from the production well.

What is claimed is: 
     
         1 . A method of optimizing recovery of oil from a formation comprising a production well and an injection well; said method comprising:
 water flooding said formation to a residual oil saturation between said injection well and said production well;   after said residual oil saturation, injecting an oil tracer into said injection well in said formation;   applying a tertiary oil recovery process for recovering said oil from said formation;   monitoring said production well to detect said oil tracer, said monitoring being conducted within a period that starts at the time the oil tracer is injected and ends 30 days after the oil tracer is injected or the period starts when the tertiary oil recovery process is started and ends 30 days after the oil recovery process is started; and   modifying said tertiary oil recovery process based on a detection of said oil tracer in oil recovered from said production well during said period.   
     
     
         2 . The method of  claim 1  wherein said applying of said tertiary oil recovery process is started before said injection of said oil tracer. 
     
     
         3 . The method of  claim 1  wherein said tertiary oil recovery process includes a selection from the list consisting of: microbial enhanced oil recovery, surfactant injection, polymer injection, water injection, natural gas reinjection, air injection, air injection, carbon dioxide injection, other gas injection, pressure pulses and combinations thereof. 
     
     
         4 . The method of  claim 1  wherein said monitoring comprises determining the quantity of tracer detected as a function of time. 
     
     
         5 . The method of  claim 1  wherein said modification comprises a selection from the list consisting of: changing a type or amount of surfactant used in a surfactant flooding process, changing amount of gas used in a gas injection process, changing a type or amount of nutrients used in a microbial enhanced oil recovery process. 
     
     
         6 . The method of  claim 1  wherein said period is further limited to start at the time the oil tracer is injected and end 7 days after the oil tracer is injected or to start when the tertiary oil recovery process is started and end 7 days after the oil recovery process is started. 
     
     
         7 . The method of  claim 1  wherein said residual oil saturation is determined by detecting water breakthrough in said production well. 
     
     
         8 . The method of  claim 1  wherein the oil tracer is an oil soluble tracer. 
     
     
         9 . The method of  claim 1  wherein the oil tracer is a partitioning tracer. 
     
     
         10 . A method of optimizing recovery of oil from a formation comprising a production well and an injection well; said method comprising:
 water flooding said formation until water breakthrough occurs at said production well;   after said water breakthrough, injecting an oil tracer into said injection well in said formation;   applying a tertiary oil recovery process for recovering said oil from said formation;   monitoring said production well to detect said oil tracer, said monitoring being conducted within a period that starts at the time the oil tracer is injected and ends 30 days after the oil tracer is injected or the period starts when the tertiary oil recovery process is started and ends 30 days after the oil recovery process is started; and   modifying said tertiary oil recovery process based on a detection of said oil tracer in oil recovered from said production well during said period.   
     
     
         11 . The method of  claim 10  wherein said applying of said tertiary oil recovery process is started before said injection of said oil tracer. 
     
     
         12 . The method of  claim 10  wherein said tertiary oil recovery process includes a selection from the list consisting of: microbial enhanced oil recovery, surfactant injection, polymer injection, water injection, natural gas reinjection, air injection, air injection, carbon dioxide injection, other gas injection, pressure pulses and combinations thereof. 
     
     
         13 . The method of  claim 10  wherein said monitoring comprises determining the quantity of tracer detected as a function of time. 
     
     
         14 . The method of  claim 10  wherein said modification comprises a selection from the list consisting of: changing a type or amount of surfactant used in a surfactant flooding process, changing amount of gas used in a gas injection process, changing a type or amount of nutrients used in a microbial enhanced oil recovery process. 
     
     
         15 . The method of  claim 10  wherein said period is further limited to start at the time the oil tracer is injected and end 7 days after the oil tracer is injected or to start when the tertiary oil recovery process is started and end 7 days after the oil recovery process is started. 
     
     
         16 . The method of  claim 10  wherein the oil tracer is an oil soluble tracer. 
     
     
         17 . The method of  claim 10  wherein the oil tracer is a partitioning tracer. 
     
     
         18 . A method of optimizing recovery of oil from a formation comprising a production well and an injection well; said method comprising:
 water flooding said formation to a residual oil saturation between said injection well and said production well;   after said residual oil saturation, injecting an oil tracer into said injection well in said formation;   applying a tertiary oil recovery process for recovering said oil from said formation;   monitoring said production well to detect said oil tracer, said monitoring being conducted within a period that starts at the time the oil tracer is injected and ends 30 days after the oil tracer is injected; and   modifying said tertiary oil recovery process based on a detection of said oil tracer in oil recovered from said production well during said period.   
     
     
         19 . The method of  claim 18  wherein said applying of said tertiary oil recovery process is started before said injection of said oil tracer. 
     
     
         20 . The method of  claim 18  wherein said tertiary oil recovery process includes a selection from the list consisting of: microbial enhanced oil recovery, surfactant injection, polymer injection, water injection, natural gas reinjection, air injection, air injection, carbon dioxide injection, other gas injection, pressure pulses and combinations thereof.