Enhanced oil recovery process to inject low salinity water and gas in carbonate reservoirs

Abstract

The present invention relates to a method to enhance oil recovery from a hydrocarbon reservoir. One aspect of the invention includes injecting high salinity water into the reservoir followed by alternating the injection of low salinity water and gas.

1 . A method to enhance recovery of oil in a hydrocarbon reservoir, comprising:
 injecting a low salinity water into the reservoir; and   injecting a gas into the reservoir after the injection of the low salinity water into the reservoir.   
     
     
         2 . The method of  claim 1 , further comprising alternating injecting the low salinity water into the reservoir, and injecting the gas into the reservoir. 
     
     
         3 . The method of  claim 1 , wherein the gas is at least one of a carbon dioxide, a natural gas liquid, a nitrogen, a liquid petroleum gas and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the gas is produced from the reservoir. 
     
     
         5 . The method of  claim 1 , further comprising injecting a high salinity water into the reservoir prior to injecting the low salinity water into the reservoir. 
     
     
         6 . The method of  claim 5 , wherein the high salinity water is at least one of seawater, produced hydrocarbon reservoir water, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the low salinity water is at least one of a desalinated seawater, a diluted seawater, a desalinated hydrocarbon reservoir formation water, a diluted hydrocarbon reservoir water, a river water, a lake water, or a produced hydrocarbon reservoir water. 
     
     
         8 . The method of  claim 1 , wherein the reservoir is an oil-wet carbonate reservoir, a shale reservoir or a sandstone reservoir. 
     
     
         9 . A method to enhance oil recovery from a hydrocarbon reservoir, comprising:
 injecting high salinity water into the reservoir;   injecting a low salinity water into the reservoir following the injection of the high salinity water, wherein a salinity level of the low salinity water is less than a salinity level of the high salinity water;   injecting a gas into the reservoir following the injection of the low salinity water; and   alternating the injection of the low salinity water and the gas into the reservoir.   
     
     
         10 . The method of  claim 9 , wherein the gas is at least one of a carbon dioxide, a natural gas liquid, a nitrogen, a liquefied petroleum gas and combinations thereof. 
     
     
         11 . The method of  claim 10 , wherein the high salinity water is at least one of a seawater, a reservoir formation water and combinations thereof. 
     
     
         12 . The method of  claim 9 , wherein the low salinity water is at least one of a desalinated seawater, a diluted seawater, a desalinated hydrocarbon reservoir formation water, a diluted hydrocarbon reservoir water, a river water, a lake water, or a produced hydrocarbon reservoir water. 
     
     
         13 . The method of  claim 9 , wherein the reservoir is an oil-wet carbonate reservoir, a shale reservoir or a sandstone reservoir. 
     
     
         14 . The method of  claim 9 , wherein the alternating injection of the low salinity water and the gas is repeated until a water cut is greater than about 80%. 
     
     
         15 . The method of  claim 10 , wherein the gas is the carbon dioxide. 
     
     
         16 . The method of  claim 10 , wherein the gas is the natural gas liquid. 
     
     
         17 . A method to enhance recovery of a hydrocarbon in a reservoir, comprising:
 waterflooding the reservoir with a high salinity water;   injecting a first injection of a low salinity water into the reservoir, wherein at least about 0.2 of a pore volume of the reservoir is occupied by the low salinity water;   injecting a first injection of a gas into the reservoir, wherein at least about 0.2 of the pore volume of the reservoir is occupied by the gas;   alternating at least one additional injection of the low salinity water into the reservoir and at least one additional injection of the gas into the reservoir.   
     
     
         18 . The method of  claim 17 , further comprising injecting an initial injection of the gas into the reservoir prior to the first injection of the low salinity water into the reservoir. 
     
     
         19 . The method of  claim 17 , wherein the hydrocarbon is at least one of crude oil or natural gas. 
     
     
         20 . The method of  claim 17 , wherein the gas is at least one of a carbon dioxide, a natural gas liquid, a nitrogen, or a liquid petroleum gas.