Process for recovery of oil from an oil-bearing formation

Abstract

The present invention is directed to a process for producing oil. The mass action ratio (MAR) of divalent cations to monovalent cations of water from an oil-bearing formation is determined, and an aqueous displacement fluid having a total dissolved solids content of from 200 ppm to 5,000 ppm and a MAR of divalent cations to monovalent cations of from 70% to 130% of the MAR of divalent cations to monovalent cations of the formation water is introduced into the formation. Oil is produced from the formation after introducing the aqueous displacement fluid into the formation.

What is claimed: 
     
         1 . A process for producing oil from an oil-bearing formation, comprising:
 determining the mass action ratio of divalent cations to monovalent cations of water from the oil-bearing formation;   providing an aqueous displacement fluid comprising water and an ionically charged polymer, wherein the water of the aqueous displacement fluid has a total dissolved solids content of from 200 parts per million by weight (ppmw) to 5,000 ppmw and a mass action ratio of divalent cations to monovalent cations from 70% to 130% of the mass action ratio of divalent cations to monovalent cations of the water from the oil-bearing formation;   introducing the aqueous displacement fluid into the oil-bearing formation to displace oil within the formation;   producing oil from the oil-bearing formation subsequent to introducing the aqueous displacement fluid into the formation.   
     
     
         2 . The process of  claim 1  further comprising the steps of:
 determining the viscosity of oil of the oil-bearing formation at a temperature within the range of temperatures in the formation; 
 providing the aqueous displacement fluid having a viscosity of from 10% to 500% of the viscosity of the oil of the oil-bearing formation, where the viscosity of the aqueous displacement fluid is determined at the temperature at which the viscosity of the oil of the oil-bearing formation is determined. 
 
     
     
         3 . The process of  claim 2  wherein the ionic polymer of the aqueous displacement fluid is mixed with the water of the aqueous displacement fluid in an amount effective to increase the viscosity of the water of the aqueous displacement fluid to a viscosity of from 10% to 500% of the viscosity of the oil of the oil-bearing formation. 
     
     
         4 . The process of  claim 1  wherein the ionically-charged polymer is a water-dispersible polymer. 
     
     
         5 . The process of  claim 1  wherein the ionically-charged polymer is a water soluble polymer. 
     
     
         6 . The process of  claim 1  wherein the ionically-charged polymer is a selected from the group consisting of a water-soluble polyacrylamide, a water-soluble polyacrylate, a partially hydrolyzed water-soluble polyacrylamide, and mixtures thereof. 
     
     
         7 . The process of  claim 1  wherein the MAR of divalent cations to monovalent cations of water of the oil-bearing formation is determined by obtaining a sample of water from the oil-bearing formation, measuring the concentrations of each divalent cation species and each monovalent cation species in the water obtained from the oil-bearing formation, and calculating the MAR of the water obtained from the oil-bearing formation according to formula (I)
   MAR fw =( C   +   (fw) ) 2   /C   2+   (fw) )  (I)
 
 
       where MAR fw  is the mass action ratio of divalent cations to monovalent cations of the water from the formation, C +   (fw)  is the sum of the concentrations of the monovalent cation species in the water from the formation, and C 2+   (fw)  is the sum of the concentrations of the divalent cation species in the water from the formation. 
     
     
         8 . The process of  claim 1  wherein the water of the aqueous displacement fluid is provided from a natural source water having a TDS content of from 200 ppm to 5,000 ppm. 
     
     
         9 . The process of  claim 1  wherein the water of the aqueous displacement fluid is provided from a saline source water having a TDS content greater than 10,000 ppm wherein the saline source water is treated to adjust the TDS content of the saline source water to within a range of from 200 ppm to 5,000 ppm. 
     
     
         10 . The process of  claim 1  wherein the water of the aqueous displacement fluid is provided from a source water having a TDS content less than 500 ppm wherein the source water is treated to adjust the TDS content of the source water to within a range of from 500 ppm to 5,000 ppm. 
     
     
         11 . The process of  claim 1  wherein the water of the aqueous displacement fluid is provided from a source water having a MAR of divalent cations to monovalent cations that is from 70% to 130% of the MAR of divalent cations to monovalent cations of the water of the formation, where the MAR of the water of the aqueous displacement fluid is calculated according to formula (II)
   MAR adf =( C   +   (adf) ) 2   /C   2+   (adf) )  (II)
 
 
       where MAR adf  is the mass action ratio of divalent cations to monovalent cations of the water of the aqueous displacement fluid, C +   (adf)  is the sum of concentrations of monovalent cation species in the water of the aqueous displacement fluid, and C 2+   (adf)  is the sum of concentrations of divalent cation species in the water of the aqueous displacement fluid. 
     
     
         12 . The process of  claim 1  wherein the water of the aqueous displacement fluid is provided from a source water having a MAR of divalent cations to monovalent cations that is less than 70% or greater than 130% of the MAR of divalent cations to monovalent cations of the water of the formation and the MAR of divalent cations to monovalent cations of the source water is adjusted to a range of from 70% to 130% of the MAR of divalent cations to monovalent cations of the water of the formation, where the MAR of the water of the aqueous displacement fluid is calculated according to formula (II)
   MAR adf =( C   +   (adf) ) 2   /C   2+   (adf) )  (II)
 
 
       where MAR adf  is the mass action ratio of divalent cations to monovalent cations of the water of the aqueous displacement fluid, C +   (adf)  is the sum of concentrations of monovalent cation species in the water of the aqueous displacement fluid, and C 2+   (adf)  is the sum of concentrations of divalent cation species in the water of the aqueous displacement fluid. 
     
     
         13 . The process of  claim 1  further comprising producing water from the oil-bearing formation along with oil from the oil-bearing formation and separating the produced oil from the produced water.