Method and system for oil and water separation utilizing a hydrostatic pressure head for disposal of water

Abstract

A method and system for the downhole separation of a water and oil mixture and disposal of separated water utilizing a hydrostatic pressure head is disclosed. A separator apparatus is located in a wellbore at a depth substantially above a water disposal formation. A mixture of oil and water is received from an oil producing formation and delivered to the separator apparatus. The oil and water mixture is separated into separated water and separated oil by the separator apparatus. The separated oil is delivered to the well surface. The separated water is discharged from the separator apparatus into the wellbore creating a column of water above the water disposal formation. The hydrostatic pressure created by the column of water is ideally sufficient to cause the separated water to dissipate into the water disposal formation. Alternatively, an auxiliary disposal pump may also be used to augment the hydrostatic pressure in the wellbore to further cause dissipation of the separated water into the water disposal formation.

What is claimed is:  
     
         1 . A system for separating water and oil from a water and oil mixture received from an oil well, the system comprising: 
 a) a wellbore extending from a surface of a well to, and in fluid communication with, a water disposal formation and an oil producing formation, the oil producing formation supplying a mixture of water and oil to the wellbore;    b) a separator apparatus for separating water and oil from the water and oil mixture, the separator apparatus being disposed in the wellbore at a height above the water disposal formation and above the oil producing formation;    c) a first packer disposed within the wellbore which isolates the water disposal formation from the oil producing formation; and    d) a production string disposed within the wellbore and having a first segment which transports the mixture from the oil producing formation to the separator apparatus;    wherein the separator apparatus may separate water and oil from the mixture with the separated water being discharged from the separator apparatus and into the wellbore to create a hydrostatic column of water above the water disposal formation with the separated water being dissipated into the water disposal formation.    
     
     
         2 . The system of  claim 1  wherein the separator apparatus includes a separator membrane which substantially allows one of the oil and water to permeate through the membrane while substantially inhibiting the passage of the other of the oil and the water.  
     
     
         3 . The system of  claim 1  wherein the separator apparatus includes at least one of a hydrocyclone, a separator membrane, a centrifugal separator, and a vane separator.  
     
     
         4 . The system of  claim 1  further comprising a primary lift pump disposed within the wellbore that provides artificial lift to lift the water and oil mixture to the separator apparatus.  
     
     
         5 . The system of  claim 4  wherein the primary lift pump provides sufficient lift to the mixture to also lift the separated oil to the surface of the well without need for an additional oil lift pump.  
     
     
         6 . The system of  claim 4  wherein the primary lift pump is disposed in the wellbore adjacent to the oil producing formation.  
     
     
         7 . The system of  claim 1  further comprising a swirl inducing member to induce a swirling flow of the mixture within the separator apparatus such that heavier swirling water is placed in contact with the membrane so as to permeate out of the separator apparatus and into the column of water while the lighter oil continues to pass upwardly through the production string.  
     
     
         8 . The system of  claim 7  wherein the swirl inducing member is a generally spiral shaped vane.  
     
     
         9 . The system of  claim 1  wherein the separator apparatus includes a plurality of separation devices connected together in series within the wellbore.  
     
     
         10 . The system of  claim 1  wherein the depth to the top of the separator apparatus in the wellbore is less than 50% of the depth to the top of the water disposal formation.  
     
     
         11 . The system of  claim 1  wherein the depth to the top of the separator apparatus in the wellbore is less than 10% of the depth to the top of the water disposal formation.  
     
     
         12 . The system of  claim 1  wherein the depth to the top of the separator apparatus in the wellbore is less than 5% of the depth to the top of the water disposal formation.  
     
     
         13 . The system of  claim 1  wherein the separator apparatus is disposed beneath and generally adjacent to the surface of the well.  
     
     
         14 . The system of  claim 1  wherein the water disposal formation is located above the oil producing formation.  
     
     
         15 . The system of  claim 1  wherein the oil producing formation is located above the water disposal formation.  
     
     
         16 . The system of  claim 1  further comprising: 
 a) a second packer disposed within the wellbore which cooperates with the first packer to create an isolated water disposal chamber which is in fluid communication with the water disposal formation; and  
 b) an auxiliary disposal pump which pumps separated water into the water disposal chamber to increase the pressure within the water disposal chamber over and above the hydrostatic pressure head created by the column of water to enhance water disposal into the water disposal formation.  
 
     
     
         17 . A method of separating water and oil from a water and oil mixture received from an oil well having a wellbore extending between, and in fluid communication with, a water disposal formation and an oil producing formation, the method comprising the steps of: 
 receiving a water and oil mixture from an oil producing formation into a wellbore;    passing the water and oil mixture up the wellbore to a separator apparatus located within the wellbore;    separating the water and oil mixture into separated water and separated oil;    passing the separated water to the wellbore wherein a column of water is created above the water disposal formation; and    disposing of the separated water into the water disposal formation at least partially under the hydrostatic pressure created by the column of water.    
     
     
         18 . The method of  claim 17  further comprising providing additional pressure to the column of water to assist in the disposal of the separated water into the disposal formation.  
     
     
         19 . The method of  claim 18  wherein the additional pressure is provided by an auxiliary pump disposed in the wellbore.  
     
     
         20 . The method of  claim 17  wherein a primary lift pump is employed to lift the water and oil mixture to the separator apparatus.  
     
     
         21 . The method of  claim 20  wherein the primary lift pump provides sufficient lift to lift the mixture to the separator apparatus and to lift the separated oil to the surface of the well without need for an additional oil pump.  
     
     
         22 . The method of  claim 17  wherein the separator apparatus has no moving parts.  
     
     
         23 . The method of  claim 17  wherein the separator apparatus includes a membrane separator.  
     
     
         24 . The method of  claim 17  wherein the depth to the top of the separator apparatus is less than 50% of the depth to the top of the water disposal formation.  
     
     
         25 . The method of  claim 17  wherein the depth to the top of the separator apparatus is less than 10% of the depth to the top of the water disposal formation.  
     
     
         26 . The method of  claim 17  wherein the depth to the top of the separator apparatus is less than 5% of the depth of the top of the water disposal formation.  
     
     
         27 . The method of  claim 17  wherein the separator apparatus is disposed beneath and adjacent the surface of the wellbore to maximize hydrostatic head and ease of replacement of the separator apparatus from the wellbore.  
     
     
         28 . A system for separating water and oil from a water and oil mixture received from an oil well, the system comprising: 
 a) a wellbore extending from a surface of a well to, and in fluid communication with, a water disposal formation and an oil producing formation, the oil producing formation supplying a mixture of water and oil to the wellbore;    b) a first packer disposed within the wellbore which isolates the water disposal formation from the oil producing formation;    c) a separator apparatus for separating water and oil from the water and oil mixture, the separator apparatus being disposed in the wellbore at a height above the water disposal formation and above the oil producing formation and including a membrane separator;    d) a production string disposed within the wellbore and having a first segment which transports the mixture from the oil producing formation to the separator apparatus and a second segment which transports separated oil from the separator apparatus to the surface of the well;    e) a lift pump to lift the mixture of water and oil to the separator apparatus and the separated oil to the surface of the well; and    f)an auxiliary pump to provide additional pressure to the column of water to assist in the disposal of water into the water disposal formation.