Enhanced oil recovery using seawater and edta

Abstract

The enhanced oil recovery using seawater and EDTA (ethylenediaminetetraacetic acid) is a method that uses injection of EDTA in seawater to enhance the recovery of oil from sandstone reservoirs. The EDTA may be introduced into seawater during the initial extraction of oil from the reservoir by seawater injection, or a solution of EDTA in seawater may be used to flush residual oil from the reservoir after the initial extraction by seawater injection. In either case, the EDTA is present in about 1.0 wt % to about 5.0 wt % of the seawater solution, and the solution has a pH of between 10.5 and 11.0.

1 . A method for enhanced oil recovery from a sandstone oil reservoir, comprising the step of injecting a solution consisting of an effective amount of ethylenediaminetetraacetic acid (EDTA) in seawater into the reservoir for chelating cations in the formation brine to prevent scaling caused by mixing the seawater with the formation brine. 
     
     
         2 . The method for enhanced oil recovery according to  claim 1 , wherein the effective amount of EDTA comprises about 1 wt % EDTA. 
     
     
         3 . The method for enhanced oil recovery according to  claim 1 , wherein the effective amount of EDTA comprises about 5 wt % EDTA. 
     
     
         4 . The method for enhanced oil recovery according to  claim 1 , wherein the solution has a pH of about 11. 
     
     
         5 . The method for enhanced oil recovery according to  claim 1 , wherein the step of injecting the solution comprises injecting the solution for the initial recovery of oil from the reservoir. 
     
     
         6 . The method for enhanced oil recovery according to  claim 1 , wherein the step of injecting the solution comprises injecting the solution containing the EDTA after the initial recovery of oil from the reservoir by seawater flooding in order to recover residual oil from the reservoir. 
     
     
         7 . A method for enhanced oil recovery from a sandstone oil reservoir, comprising the step of injecting a solution consisting of between 1 wt % and 5 wt % ethylenediaminetetraacetic acid (EDTA) in seawater into the reservoir, the solution having a pH of about 11. 
     
     
         8 . The method for enhanced oil recovery according to  claim 7 , wherein the solution comprises 1 wt % EDTA. 
     
     
         9 . The method for enhanced oil recovery according to  claim 7 , wherein the solution comprises 5 wt % EDTA. 
     
     
         10 . The method for enhanced oil recovery according to  claim 7 , wherein the step of injecting the solution comprises injecting the solution for the initial recovery of oil from the reservoir. 
     
     
         11 . The method for enhanced oil recovery according to  claim 7 , wherein the step of injecting the solution comprises injecting the solution containing the EDTA after the initial recovery of oil from the reservoir by seawater flooding in order to recover residual oil from the reservoir.