Two-stage downhole oil-water separation

Abstract

A method for downhole oil-water separation, according to one or more aspects of the present disclosure, comprises disposing a oil-water separation system in a wellbore, the system comprising a first separator connected in hydraulic series with a second separator; separating a well fluid in the first separator into a first injection stream and a first production stream; discharging the first injection stream to an inlet of the second separator; separating the first injection stream in the second separator into an output injection stream and a second production stream; and injecting the output injection stream from the wellbore into an injection formation.

1 . A downhole fluid separation system comprising:
 a first oil-water separator comprising an inlet, a first water outlet and a first oil outlet; and   a second oil-water separator comprising an inlet, a second water outlet and a second oil outlet, wherein the inlet of the second oil-water separator is connected in hydraulic series to the first water outlet.   
     
     
         2 . The system of  claim 1 , wherein the first oil-water separator comprises a static separator. 
     
     
         3 . The system of  claim 1 , wherein the second oil-water separator comprises a static separator. 
     
     
         4 . The system of  claim 1 , wherein:
 the first oil-water separator comprises one selected from the group of a static separator and a dynamic separator; and   the second oil-water separator comprises one selected from the group of a static separator and a dynamic separator.   
     
     
         5 . The system of  claim 4 , wherein the first oil-water separator and the second oil-water separator are of the same type of separator. 
     
     
         6 . The system of  claim 1 , further comprising a downhole pump having a discharge in fluid communication with the inlet of the first oil-water separator. 
     
     
         7 . The system of  claim 6 , wherein:
 the first oil-water separator comprises one selected from the group of a static separator and a dynamic separator; and   the second oil-water separator comprises one selected from the group of a static separator and a dynamic separator.   
     
     
         8 . The system of  claim 7 , wherein the first oil-water separator and the second oil-water separator are of the same type of separator. 
     
     
         9 . A system comprising:
 a wellbore in communication with a production zone and an injection zone;   a pump positioned in the wellbore having an inlet in fluid communication with a well fluid;   a first separator having an inlet, a first water outlet and a first oil outlet, the inlet in fluid connection with a pump discharge; and   a second separator having an inlet, a second water outlet and a second oil outlet, the inlet of the second separator connected in hydraulic series to the first water outlet and the second water outlet in fluid communication with the injection zone.   
     
     
         10 . The system of  claim 9 , wherein:
 the first oil-water separator comprises one selected from the group of a static separator and a dynamic separator; and   the second oil-water separator comprises one selected from the group of a static separator and a dynamic separator.   
     
     
         11 . The system of  claim 10 , wherein the first oil-water separator and the second oil-water separator are of the same type of separator. 
     
     
         12 . The system of  claim 9 , wherein:
 the production zone is located above the injection zone; and.   the first separator is positioned above the second separator.   
     
     
         13 . The system of  claim 9 , wherein:
 the production zone is located above the injection zone; and.   the second separator is positioned above the first separator.   
     
     
         14 . A method for downhole oil-water separation, comprising:
 disposing a oil-water separation system in a wellbore, the system comprising a first separator connected in hydraulic series with a second separator;   separating a well fluid in the first separator into a first injection stream and a first production stream;   discharging the first injection stream to an inlet of the second separator;   separating the first injection stream in the second separator into an output injection stream and a second production stream; and   injecting the output injection stream from the wellbore into an injection formation.   
     
     
         15 . The method of  claim 14 , wherein the well fluid comprises a water cut in the range of about 80 percent water or greater. 
     
     
         16 . The method of  claim 15 , wherein the output injection stream comprises an oil content in the range of 100 parts per million or less. 
     
     
         17 . The method of  claim 14 , further comprising:
 directing the first production stream to the surface; and   directing the second production stream into the wellbore.   
     
     
         18 . The method of  claim 14 , comprising:
 directing the first production stream to the surface; and   directing the second production stream to the surface.   
     
     
         19 . The method of  claim 14 , wherein the well fluid comprises a water cut in the range of about 50 percent to 80 percent water. 
     
     
         20 . The method of  claim 19 , wherein the output injection stream comprises an oil content of about 500 parts per million or less.