Pressure-corrected density of a fluid

Abstract

This disclosure is drawn to methods, systems, devices and/or apparatus related to determining the density of a fluid. Specifically, the disclosed methods, systems, devices and/or apparatus relate to determining the density of a fluid in situ (e.g., in a downhole tool) under the Earth's surface using extrapolation and/or interpolation technique(s). Some example methods may include obtaining a fluid sample from a formation, measuring, in a downhole tool, a plurality of density values of the fluid sample, each density value being measured at a distinct pressure level within a pressure range, and extrapolating and/or interpolating the plurality of density values of the fluid sample to a pressure level different that the distinct pressure in which the density value is measured. Some example methods may include tuning one or more Equation-of-State model based, at least in part, on the density values.

What is claimed is: 
     
         1 . A method of determining a density of a fluid in a formation, the method comprising:
 obtaining a fluid sample from a formation;   measuring, in a downhole tool, a plurality of density values of the fluid sample, each density value being measured at a distinct pressure level within a pressure range; and   at least one of extrapolating and interpolating the plurality of density values of the fluid sample to a pressure level different that the distinct pressure in which the density value is measured.   
     
     
         2 . The method of  claim 1 , wherein extrapolating the plurality of density values of the fluid sample to the pressure level different than the distinct pressure level in which the density value is measured comprises extrapolating the plurality of density values to the pressure level outside of the pressure range. 
     
     
         3 . The method of  claim 1 , wherein interpolating the plurality of density values of the fluid sample to the pressure level different than the distinct pressure level in which the density value is measured comprises interpolating the plurality of density values to the pressure level inside of the pressure range. 
     
     
         4 . The method of  claim 1 , wherein measuring the plurality of density values of the fluid sample comprises:
 measuring a first density value at a first pressure level within the pressure range;   altering the first pressure level to a second pressure level within the pressure range; and   measuring a second density value at the second pressure level.   
     
     
         5 . The method of  claim 4 , wherein the at least one of extrapolating and interpolating the plurality of density values of the fluid sample to a pressure level different that the distinct pressure in which the density value is measured comprises at least one of extrapolating and interpolating the first density value and the second density value. 
     
     
         6 . The method of  claim 5 , further comprising:
 determining a third density value at a third pressure level outside of the pressure range based, at least in part, on extrapolating the first density value and the second density value.   
     
     
         7 . The method of  claim 5 , further comprising:
 determining a third density value at a third pressure level inside of the pressure range based, at least in part, on interpolating the first density value and the second density value.   
     
     
         8 . The method of  claim 1 , wherein extrapolating the plurality of density values of the fluid sample to the pressure level different than the distinct pressure level in which the density value is measured comprises at least one of:
 linearly extrapolating the plurality of density values to the pressure level outside the pressure range, and   logarithmically extrapolating the plurality of density values to the pressure level outside the pressure range.   
     
     
         9 . The method of  claim 1 , wherein interpolating the plurality of density values of the fluid sample to the pressure level different than the distinct pressure level in which the density value is measured comprises at least one of:
 linearly interpolating the plurality of density values to the pressure level inside the pressure range, and   logarithmically interpolating the plurality of density values to the pressure level inside the pressure range.   
     
     
         10 . The method of  claim 1 , wherein the pressure level different that the distinct pressure comprises at least one of a formation pore pressure level, a predetermined pressure level, and an arbitrary pressure level. 
     
     
         11 . The method of  claim 1 , wherein measuring the plurality of density values of the fluid sample comprises measuring, by at least one of a vibrating rod, a tuning fork and a vibrating tube, the plurality of density values of the fluid sample. 
     
     
         12 . The method of  claim 1 , wherein each respective pressure level within the pressure range is determined by at least one of a crystal quartz gauge, a silicon-on-isolator gauge and a strain gauge. 
     
     
         13 . A method of determining a density of a fluid in a formation, the method comprising:
 measuring a first fluid density value of a fluid sample at a first pressure;   altering the first pressure to a second pressure different than the first pressure;   measuring a second fluid density value of the fluid sample at the second pressure; and   at least one of extrapolating and interpolating a third fluid density value at a third pressure based, at least in part, on the first fluid density value at the first pressure and the second fluid density value at the second pressure;   wherein the third pressure is different than the first pressure and the second pressure.   
     
     
         14 . The method of  claim 13 , further comprising:
 tuning one or more Equation-of-State model based, at least in part, on the third fluid density value.   
     
     
         15 . The method of  claim 14 , further comprising:
 verifying the third density value with the one or more Equation-of-State model; and   correcting the third density value based, at least in part, on a temperature of the fluid sample and a contamination of the fluid sample.   
     
     
         16 . The method of  claim 13 , wherein altering the first pressure to a second pressure different than the first pressure comprises at least one of increasing the first pressure and decreasing the first pressure. 
     
     
         17 . An apparatus for determining a density of a fluid in a formation, the apparatus comprising:
 a fluid chamber adapted to at least temporarily hold a fluid sample;   one or more pressure regulator to regulate a pressure applied to the fluid sample between a first pressure and a second pressure, the first pressure being different than the second pressure;   one or more pressure gauge to measure the pressure applied to the fluid sample;   one or more density sensor to measure the density of the fluid sample at the first pressure and the second pressure; and   one or more signal processor to determine a density of the fluid sample at a third pressure via at least one of an extrapolation technique and an interpolation technique, the third pressure being different than the first pressure and the second pressure.   
     
     
         18 . The apparatus of  claim 17 , wherein the fluid chamber, the one or more pressure regulator, the one or more pressure gauge and the one or more density sensor are housed in a downhole tool. 
     
     
         19 . The apparatus of  claim 17 ,
 wherein the one or more density sensor generates density data representative of the density of the fluid sample at the first pressure and the second pressure, and stores the density data in the memory in a downhole tool; and   wherein the one or more signal processor is housed in a surface logging unit.   
     
     
         20 . The apparatus of  claim 17 , wherein the one or more signal processor linearly extrapolates the density of the fluid sample at the pressure level outside of the pressure range when the fluid sample is at least one of water and oil, and logarithmically extrapolates the density of the fluid sample at the pressure level outside of the pressure range when the fluid sample is a gas.