System for producing and separating oil

Abstract

The present invention is directed to a system for producing and separating oil. The system comprises an oil-bearing formation, a low salinity aqueous fluid having an ionic strength of less than 0.15M and having a total dissolved solids content of from 200 ppm to 10000 ppm, a brine solution having a total dissolved solids content of greater than 10000 ppm, and a demulsifier. The system further comprises a mechanism for introducing the low salinity aqueous fluid into and oil-bearing formation, a mechanism for producing oil and water from the formation subsequent to introducing the low salinity aqueous fluid into the formation, and a mechanism for contacting the brine solution and the demulsifier with the oil and water produced from the formation and for separating the produced oil from the produced water.

What is claimed is: 
     
         1 . A system, comprising:
 an oil-bearing formation;   a low salinity aqueous fluid having an ionic strength of less than 0.15M and having a total dissolved solids content of from 200 ppm to 10000 ppm;   a brine solution having a total dissolved solids content of greater than 10000 ppm;   a demulsifier;   a mechanism for introducing the low salinity aqueous fluid into the oil-bearing formation;   a mechanism for producing oil and water from the oil-bearing formation subsequent to introducing the low salinity aqueous fluid into the formation; and   a mechanism for contacting the brine solution and the demulsifier with the oil and water produced from the oil-bearing formation and for separating the produced oil from the produced water.   
     
     
         2 . The system of  claim 1 , further comprising:
 a saline water source having a total dissolved solids content of at least 10000 ppm;   a mechanism for processing the saline water source to produce at least a portion of the low salinity aqueous fluid.   
     
     
         3 . The system of  claim 2  wherein the saline water source is selected from the group consisting of seawater, brackish water, water produced from the oil-bearing formation, and a brine formed in separating the produced oil from the produced water and processing the separated produced water to produce at least a portion of the low salinity aqueous fluid. 
     
     
         4 . The system of  claim 2  wherein the mechanism for processing the saline water source to produce at least a portion of the low salinity aqueous fluid is an ionic filter. 
     
     
         5 . The system of  claim 4  wherein the ionic filter comprises a mechanism for producing at least a portion of the brine solution. 
     
     
         6 . The system of  claim 4  wherein the ionic filter is comprised of one or more nanofiltration membrane units. 
     
     
         7 . The system of  claim 4  wherein the ionic filter is comprised of one or more reverse osmosis units. 
     
     
         8 . The system of  claim 4  wherein the ionic filter is comprised of two or more ionic membranes selected from the group consisting of one or more nanofiltration membrane units, one or more reverse osmosis membrane units, and combinations thereof, wherein at least two of the two or more ionic membranes are arranged in series. 
     
     
         9 . The system of  claim 4  wherein the ionic filter is comprised of two or more ionic membranes selected from the group consisting of one or more nanofiltration membrane units, one or more reverse osmosis membrane units, and combinations thereof, wherein at least two of the two or more ionic membranes are arranged in parallel. 
     
     
         10 . The system of  claim 9  wherein the ionic filter is comprised of one or more nanofiltration membrane units arranged in parallel with one or more reverse osmosis membrane units. 
     
     
         11 . The system of  claim 1  wherein the mechanism for introducing the low salinity aqueous fluid into the oil-bearing formation is comprised of a first well and a pump. 
     
     
         12 . The system of  claim 1  wherein the mechanism for producing oil and water from the oil-bearing formation is comprised of a second well and a pump or a compressor. 
     
     
         13 . The system of  claim 1  wherein the oil-bearing formation comprises one or more minerals having a negative-zeta potential. 
     
     
         14 . The system of  claim 1  wherein the oil-bearing formation has an Amott-Harvey wettability index of from −0.3 to 1.0 and an initial water saturation of less than 0.3. 
     
     
         15 . The system of  claim 1  wherein the oil-bearing formation comprises connate water. 
     
     
         16 . The system of  claim 1  wherein the connate water has an ionic strength greater than the ionic strength of the low salinity aqueous fluid. 
     
     
         17 . The system of  claim 1  wherein the oil-bearing formation comprises sandstone or a carbonate selected from limestone, dolomite, and combinations thereof. 
     
     
         18 . The system of  claim 1  wherein the oil-bearing formation is a subsea formation. 
     
     
         19 . The system of  claim 1  further comprising:
 an oil-immiscible formulation; 
 a mechanism for introducing the oil-immiscible formulation into the oil-bearing formation subsequent to introduction of the low salinity aqueous fluid into the formation. 
 
     
     
         20 . The system of  claim 19  wherein the oil-immiscible formulation comprises an aqueous polymer fluid. 
     
     
         21 . The system of  claim 1  wherein the mechanism for contacting the brine solution, the demulsifier, the produced oil, and the produced water and for separating the produced oil from the produced water comprises a water-knockout vessel. 
     
     
         22 . The system of  claim 1  further comprising a mechanism for separating gas from the oil and water produced from the oil-bearing formation. 
     
     
         23 . The system of  claim 22  wherein the mechanism for separating gas from the oil and water produced from the oil-bearing formation is a 2-phase separator. 
     
     
         24 . A system, comprising:
 an oil-bearing formation;   a low salinity aqueous fluid having an ionic concentration of less than 0.15M and having a total dissolved solids content of from 200 ppm to 10000 ppm;   a brine solution having a total dissolved solids content of greater than 10000 ppm;   a demulsifier; a mechanism for introducing the low salinity aqueous fluid into the oil-bearing formation;   a mechanism for producing oil and water from the oil-bearing formation subsequent to introducing the low salinity aqueous fluid into the formation;   a mechanism for contacting the brine solution and the demulsifier with the oil and water produced from the oil-bearing formation; and   a mechanism for separating the produced oil from the produced water after contacting the produced oil and the produced water with the brine solution and the demulsifier.   
     
     
         25 . The system of  claim 24 , wherein the mechanism for contacting the brine solution and the demulsifier with the oil and water produced from the oil-bearing formation is comprised of a mixing tank. 
     
     
         26 . The system of  claim 24  wherein the mechanism for separating the produced oil from the produced water after contacting the produced oil and the produced water with the brine solution and the demulsifier is comprised of a water-knockout vessel. 
     
     
         27 . A system, comprising:
 an oil-bearing formation;   a low salinity aqueous fluid having an ionic strength of less than 0.15M and having a total dissolved solids content of from 200 ppm to 10000 ppm;   a brine solution having a total dissolved solids content of greater than 10000 ppm;   a demulsifier;   a mechanism for introducing the low salinity aqueous fluid into the oil-bearing formation;   a mechanism comprising a producing well for producing oil and water from the oil-bearing formation subsequent to introducing the low salinity aqueous fluid into the formation;   a mechanism for introducing the demulsifier into the producing well and mixing the demulsifier with the produced oil and produced water in the produced well;   a mechanism for contacting the brine solution with the mixture of produced oil, produced water, and demulsifier; and   a mechanism for separating the produced oil from the mixture of produced oil, produced water, brine solution, and demulsifier.   
     
     
         28 . The system of  claim 27 , further comprising:
 a saline water source having a total dissolved solids content of at least 10000 ppm;   a mechanism for processing the saline water source to produce at least a portion of the low salinity aqueous fluid.   
     
     
         29 . The system of  claim 28  wherein the saline water source is selected from the group consisting of seawater, brackish water, water produced from the oil-bearing formation, and a brine formed in separating the produced oil from the produced water and processing the separated produced water to produce at least a portion of the low salinity aqueous fluid. 
     
     
         30 . The system of  claim 28  wherein the mechanism for processing the saline water source to produce at least a portion of the low salinity aqueous fluid is an ionic filter. 
     
     
         31 . The system of  claim 30  wherein the ionic filter comprises a mechanism for producing at least a portion of the brine solution. 
     
     
         32 . The system of  claim 27  wherein the oil-bearing formation comprises one or more minerals having a negative-zeta potential. 
     
     
         33 . The system of  claim 27  wherein the oil-bearing formation has an Amott-Harvey wettability index of from −0.3 to 1.0 and an initial water saturation of less than 0.3. 
     
     
         34 . The system of  claim 27  wherein the oil-bearing formation comprises connate water. 
     
     
         35 . The system of  claim 34  wherein the connate water has an ionic strength greater than the ionic strength of the low salinity aqueous fluid. 
     
     
         36 . The system of  claim 27  wherein the oil-bearing formation is a subsea formation. 
     
     
         37 . The system of  claim 27  further comprising:
 an oil-immiscible formulation; 
 a mechanism for introducing the oil-immiscible formulation into the oil-bearing formation subsequent to introduction of the low salinity aqueous fluid into the formation.