Methods of calculating a fluid composition n a wellbore

Abstract

The subject disclosure relates to methods for passively measuring a composition of a wellbore.

1 . A method for obtaining a composition estimate of a fluid in a wellbore traversing a subterranean formation, comprising:
 measuring a temperature and a pressure of a fluid in the wellbore;   obtaining a density by differentiating the pressure with respect to vertical height; and   calculating the composition of the fluid using an equation of state.   
     
     
         2 . The method of  claim 1 , further comprising introducing carbon dioxide to the formation. 
     
     
         3 . The method of  claim 1 , further comprising measuring brine displacement. 
     
     
         4 . The method of  claim 1 , further comprising using an observation wellbore and an injection wellbore. 
     
     
         5 . The method of  claim 1 , further comprising identifying interventions. 
     
     
         6 . The method of  claim 1 , further comprising determining the injected carbon dioxide composition. 
     
     
         7 . The method of  claim 1 , wherein the equation of state is European Gas Research Group—2004. 
     
     
         8 . The method of  claim 1 , wherein the equation of state is European Gas Research Group—2008. 
     
     
         9 . The method of  claim 1 , wherein the equation of state is virial. 
     
     
         10 . The method of  claim 1 , wherein the equation of state is cubic. 
     
     
         11 . The method of  claim 1 , wherein the measuring comprises using a device selected from the group consisting of a gradiomanometer, vibrating tube, and vibrating wire. 
     
     
         12 . The method of  claim 1 , further comprising comparing the obtained and observed density measurements. 
     
     
         13 . The method of  claim 12 , further comprising repeating the obtaining the density measurement. 
     
     
         14 . A method for obtaining a composition estimate of a fluid in a wellbore traversing a subterranean formation, comprising:
 measuring density, temperature, and a pressure of a fluid in the wellbore; and   calculating the composition of the fluid using an equation of state.   
     
     
         15 . The method of  claim 14 , further comprising introducing carbon dioxide to the formation. 
     
     
         16 . The method of  claim 14 , further comprising measuring brine displacement. 
     
     
         17 . The method of  claim 14 , further comprising using an observation wellbore and an injection wellbore. 
     
     
         18 . The method of  claim 14 , further comprising identifying interventions. 
     
     
         19 . The method of  claim 14 , further comprising determining the injected carbon dioxide composition. 
     
     
         20 . The method of  claim 14 , wherein the equation of state is European Gas Research Group—2004. 
     
     
         21 . The method of  claim 14 , wherein the equation of state is European Gas Research Group—2008. 
     
     
         22 . The method of  claim 14 , wherein the equation of state is virial. 
     
     
         23 . The method of  claim 14 , wherein the equation of state is cubic. 
     
     
         24 . The method of  claim 14 , further comprising comparing the obtained and observed density measurements and repeating the obtaining the density measurement.