Low salinity water injection alternating with immiscible gas injection to increase oil recovery

Abstract

A method for recovering oil from an earth reservoir includes injecting low salinity water into the reservoir using a low salinity water injection system, the low salinity water having a salinity that is less than connate water of the reservoir or normal water that was injected in a previous water-flooding process, the normal water having a salinity that is within plus or minus ten percent of the reservoir connate water. The method further includes injecting an immiscible gas into the reservoir using an immiscible gas injection system following the injection of the low salinity water, the immiscible gas being immiscible to the low salinity water and the oil in order to recover the oil.

What is claimed is: 
     
         1 . A method for recovering oil from an earth reservoir, the method comprising:
 injecting low salinity water into the reservoir using a low salinity water injection system, the low salinity water having a salinity that is less than connate water of the reservoir or normal water that was injected in a previous water-flooding process, the normal water having a salinity that is within plus or minus ten percent of the reservoir connate water; and   injecting an immiscible gas into the reservoir using an immiscible gas injection system following the injection of the low salinity water, the immiscible gas being immiscible to the low salinity water and the oil in order to recover the oil.   
     
     
         2 . The method according to  claim 1 , further comprising recovering the oil using an oil recovery system after the injecting the immiscible gas. 
     
     
         3 . The method according to  claim 1 , further comprising measuring an indication of an amount of oil recovered due to the low salinity water injection and the immiscible gas injection using a sensor. 
     
     
         4 . The method according to  claim 2 , further comprising determining if the amount exceeds a threshold level using a controller. 
     
     
         5 . The method according to  claim 4 , further comprising repeating the injecting low salinity water, injecting immiscible water, measuring and determining in response to the amount exceeding the threshold level. 
     
     
         6 . The method according to  claim 4 , further comprising not repeating the injecting low salinity water, injecting immiscible water, measuring and determining in response to the amount not exceeding the threshold level. 
     
     
         7 . The method according to  claim 1 , wherein the immiscible gas comprises at least one of nitrogen gas, carbon dioxide gas, and methane gas. 
     
     
         8 . The method according to  claim 1 , wherein the immiscible gas comprises flue gas from hydrocarbon combustion. 
     
     
         9 . The method according to  claim 1 , wherein the injecting low salinity water and the immiscible gas is performed using a fluid injection borehole and the oil is recovered using an oil recovery borehole that is different from the fluid injection borehole. 
     
     
         10 . An apparatus for recovering oil from an earth reservoir, the apparatus comprising:
 a low salinity water injection system configured to inject low salinity water into the reservoir through a borehole penetrating the reservoir, the low salinity water having a salinity that is less than connate water of the reservoir or normal water that was injected in a previous water-flooding process, the normal water having a salinity that is within plus or minus ten percent of the reservoir connate water;   an immiscible gas injection system configured to inject an immiscible gas into the reservoir through a borehole penetrating the reservoir, the immiscible gas being immiscible to the low salinity water and the oil; and   a controller configured to operate the low salinity water injection system and the immiscible gas injection system such that the immiscible gas is injected after the low salinity water is injected.   
     
     
         11 . The apparatus according to  claim 10 , further comprising an oil recovery system configured to recover the oil after the injecting the immiscible gas. 
     
     
         12 . The apparatus according to  claim 10 , further comprising a sensor configured to measure an indication of an amount of oil recovered due to the low salinity water injection and the immiscible gas injection. 
     
     
         13 . The apparatus according to  claim 12 , wherein the controller is further configured to (a) receive the indication or an amount of oil recovered by an oil recovery system due to the injecting of the low salinity water and the immiscible gas and (b) determine if the amount exceeds a threshold level. 
     
     
         14 . The apparatus according to  claim 13 , wherein the controller is further configured to repeat the injecting low salinity water, injecting immiscible water, measuring and determining in response to the amount exceeding the threshold level. 
     
     
         15 . The apparatus according to  claim 13 , wherein the controller is further configured to not repeat the injecting low salinity water, injecting immiscible water, measuring and determining in response to the amount not exceeding the threshold level. 
     
     
         16 . The apparatus according to  claim 10 , wherein the immiscible gas comprises at least one of nitrogen gas, carbon dioxide gas, and methane gas. 
     
     
         17 . The apparatus according to  claim 10 , wherein the immiscible gas comprises flue gas from hydrocarbon combustion.