Enhanced oil recovery methods for producing oil from heavy oil fields

Abstract

The present disclosure relates to enhanced oil recovery methods for highly viscous oil reservoirs containing large amounts of mobile water. One method includes injecting a carbon disulfide formulation or fluid into the formation via a first well and displacing the mobile water from the formation with the carbon disulfide fluid. The highly viscous oil is then solubilized using the carbon disulfide fluid, thereby generating a mixture of mobilized oil. The mixture of mobilized oil is then forced towards a second well and subsequently produced from the second well.

What is claimed is: 
     
         1 . A method for producing oil, comprising:
 placing a carbon disulfide fluid into a formation comprising oil and mobile water wherein the formation oil has a viscosity of at least 1,000 centipoise at 20° C.;   displacing the mobile water in the formation with the carbon disulfide fluid;   contacting the carbon disulfide fluid with the oil in the formation to generate mobilized oil comprised of a mixture of the solvent and the formation oil;   displacing the mobilized oil through the formation; and   producing the displaced mobilized oil from the formation.   
     
     
         2 . The method of  claim 1 , wherein displacing the mobile water comprises producing the mobile water from the formation. 
     
     
         3 . The method of  claim 1 , wherein displacing the mobile water comprises contacting the mobile water with the carbon disulfide fluid placed into the formation. 
     
     
         4 . The method of  claim 1 , wherein the formation oil has a viscosity of 1,000,000 centipoise or more at 20° C. 
     
     
         5 . The method of  claim 4 , wherein contacting the carbon disulfide fluid with the formation oil further comprises reducing the viscosity of the oil to 1,000 centipoise or less at 20° C. 
     
     
         6 . The method of  claim 4 , wherein the carbon disulfide fluid is mixed with the oil until the mixture of the solvent and the oil contains at least 20 vol. % of the carbon disulfide fluid. 
     
     
         7 . The method of  claim 1 , wherein contacting the carbon disulfide fluid with the formation oil further comprises reducing the viscosity of the oil to less than 1,000 centipoise at 20° C. 
     
     
         8 . The method of  claim 1 , wherein the formation oil has a viscosity of about 5,000,000 centipoise or more at 20° C. 
     
     
         9 . The method of  claim 8 , wherein contacting the carbon disulfide fluid with the formation oil further comprises reducing the viscosity of the oil to 1,000 centipoise or less at 20° C. 
     
     
         10 . The method of  claim 1 , wherein the carbon disulfide fluid is mixed with the formation oil until the mixture of the oil and solvent contains at least 10 vol. % of the carbon disulfide fluid. 
     
     
         11 . The method of  claim 1 , wherein displacing the mobilized oil through the formation further comprises placing one or more chase fluids into the formation. 
     
     
         12 . The method of  claim 11 , wherein the one or more chase fluids comprises an aqueous polymer fluid. 
     
     
         13 . The method of  claim 11 , wherein the one or more chase fluids comprises carbon dioxide. 
     
     
         14 . The method of  claim 11 , further comprising repeating the placement of the carbon disulfide fluid and the one or more chase fluids into the formation in an alternating sequence. 
     
     
         15 . The method of  claim 1 , further comprising identifying the formation that comprises the oil and the mobile water. 
     
     
         16 . The method of  claim 1 , wherein the formation is a subterranean formation, the carbon disulfide fluid is placed into the subterranean formation by injecting the carbon disulfide fluid into the formation via a first well, the mobilized oil is displaced through the formation towards a second well, and oil is produced from the formation via the second well. 
     
     
         17 . A method for producing oil from a formation containing oil and mobile water, comprising:
 placing a solvent into the formation, the formation having an initial total water saturation at least 10% greater than the connate water saturation in the formation;   displacing the mobile water in the formation with the solvent so as to expose the oil in the formation to the solvent; and   contacting the exposed oil with the solvent to generate a mobilized oil comprised of a mixture of the formation oil and the solvent.   
     
     
         18 . The method of  claim 17 , further comprising producing the mobilized oil from the formation. 
     
     
         19 . The method of  claim 17 , further comprising:
 displacing the mobilized oil through the formation; and   producing the displaced mobilized oil from the formation.   
     
     
         20 . The method of  claim 19 , wherein displacing the mobilized oil through the formation further comprises placing one or more chase fluids in the formation. 
     
     
         21 . The method of  claim 20 , wherein the one or more chase fluids comprises a aqueous polymer fluid. 
     
     
         22 . The method of  claim 17 , wherein the solvent comprises a carbon disulfide fluid. 
     
     
         23 . The method of  claim 17 , wherein the oil in the formation has a viscosity of at least 1,000 centipoise at 20° C. 
     
     
         24 . The method of  claim 17 , wherein the oil in the formation has a viscosity of at least 5,000,000 centipoise at 20° C. 
     
     
         25 . The method of  claim 24 , wherein the oil in the formation is mixed with the solvent to reduce the viscosity of the oil to about 1,000 centipoise or less at 20° C. 
     
     
         26 . The method of  claim 17 , wherein the solvent in contacted with the exposed oil until the mobilized oil contains at least 10 vol. % of the solvent. 
     
     
         27 . The method of  claim 17 , further comprising soaking the formation oil with the solvent to generate the mobilized oil. 
     
     
         28 . The method of  claim 17 , wherein the formation is a subterranean oil-bearing formation, the carbon disulfide fluid is placed into the subterranean formation via a first well, and oil is produced from the formation via a second well.