Fluid properties including equation of state modeling with optical constraints

Abstract

The invention relates to a method of determining an unknown property or information of a reservoir fluid. The method includes measuring a set of responses of a measuring instrument to the fluid and measuring one or more physical or chemical properties of the fluid. The method further includes determining the unknown property or information of the fluid based on the relationship between the instrument responses and the measured properties of the fluid using equation-of-state (EOS) model.

1 - 18 . (canceled) 
     
     
         19 . A method of calibrating a measuring instrument, the method comprising the steps of:
 measuring one or more responses of a measuring instrument to a fluid;   obtaining one or more properties of the fluid; and   determining calibration information of the measuring instrument by correlating the instrument responses and the obtained properties of the fluid using equation of state (EOS) model.   
     
     
         20 . The method of  claim 19 , wherein the measuring instrument contains at least one detector and/or sensor selected from the group consisting of a density sensor, capacity sensor, resistivity sensor, viscosity sensor, radioactivity sensor, acoustic sensor, and optical sensor. 
     
     
         21 . The method of  claim 19 , wherein the fluid is a clean sample. 
     
     
         22 . The method of  claim 19 , wherein the fluid is a drilling fluid having a known composition. 
     
     
         23 . The method of  claim 19 , wherein the calibration is absolute calibration. 
     
     
         24 . The method of  claim 19 , wherein one or more constraints are used in the EOS model for calibrating the measuring instrument. 
     
     
         25 . The method of  claim 19 , wherein the calibration is made at or about the same time that the measurements are made. 
     
     
         26 . The method of claim  1 , further comprising the steps of:
 obtaining one or more constraints through equation of state modeling; and   adjusting the accuracy of the measuring instrument using the constraints.   
     
     
         27 . The method of  claim 26 , wherein the act of obtaining the constraint through equation-of-state modeling includes measuring the optical response of at least one physical property under at least two different conditions. 
     
     
         28 . The method of  claim 27 , wherein the constraint corrects for offsets in the measurements of the one or more properties. 
     
     
         29 . The method of  claim 19 , wherein the one or more properties of the fluid is selected from the group consisting of dew point, phase envelope, viscosity, density, compressibility, bubble point, saturation pressure, mobility, heat capacity, and thermal conductivity. 
     
     
         30 . The method of  claim 19 , wherein the one or more properties of the fluid is one or more physical properties derived from physical measurements taken downhole in a well. 
     
     
         31 . The method of  claim 19 , wherein the one or more properties of the fluid is one or more chemical properties selected from the group consisting of component concentrations, molecular weight, molecular weight distribution, and gas-to-oil ratio (GOR).