Downhole Fluid Analysis Method And Apparatus For Determining Hydrogen Indexes

Abstract

The present disclosure relates to determining hydrogen indexes of downhole fluids using fluid composition data. In certain embodiments, the type of the fluid, such as gas, water, or oil, may be determined downhole and used to select a method for determining the hydrogen index of the fluid. The selected method may then be employed while the tool is downhole to calculate the hydrogen index of the fluid.

What is claimed is: 
     
         1 . A downhole fluid analysis method comprising:
 analyzing formation fluid within a fluid analyzer of a downhole tool to determine properties of the formation fluid;   determining a type of the formation fluid based on the determined properties of the formation fluid;   selecting a method for calculating a hydrogen index of the formation fluid based on the determined type of the formation fluid; and   calculating the hydrogen index of the formation fluid using the selected method while the downhole tool is disposed within a wellbore.   
     
     
         2 . The downhole fluid analysis method of  claim 1 , wherein analyzing comprises measuring an absorption spectra of the formation fluid. 
     
     
         3 . The downhole fluid analysis method of  claim 1 , wherein analyzing comprises measuring a resistivity of the formation fluid or a density of the formation fluid, or both. 
     
     
         4 . The downhole fluid analysis method of  claim 1 , wherein analyzing comprises determine concentrations of components within the formation fluid. 
     
     
         5 . The downhole fluid analysis method of  claim 1 , wherein determining comprises determining whether the formation fluid is a water-based fluid, a gas, or a live oil. 
     
     
         6 . The downhole fluid analysis method of  claim 1 , wherein selecting comprises selecting the method from a first method for a water-based fluid, a second method for a gas, and a third method for a live oil. 
     
     
         7 . The downhole fluid analysis method of  claim 6 , wherein the first method computes the hydrogen index based on a measured resistivity of the formation fluid. 
     
     
         8 . The downhole fluid analysis method of  claim 6 , wherein the second method computes the hydrogen index based on a density of the formation fluid and concentrations of components of the formation fluid. 
     
     
         9 . The downhole fluid analysis method of  claim 6 , wherein the third method computes the hydrogen index based on delumped C 3 -C 5  and C 6+  concentrations. 
     
     
         10 . The downhole fluid analysis method of  claim 1 , further comprising using the calculated hydrogen index to calibrate a porosity measurement. 
     
     
         11 . A downhole tool comprising:
 a fluid analyzer to determine properties of formation fluid; and   a controller configured to execute instructions stored within the downhole tool to:
 determine a type of the formation fluid based on the determined properties; and 
 calculate a hydrogen index of the formation fluid using a method selected based on the determined type of the formation fluid. 
   
     
     
         12 . The downhole tool of  claim 11 , wherein the fluid analyzer comprises an optical spectrometer, or a gas chromatograph, or both. 
     
     
         13 . The downhole tool of  claim 11 , wherein the controller is configured to execute the instructions to determine a gas oil ratio of the formation fluid. 
     
     
         14 . The downhole tool of  claim 11 , wherein the fluid analyzer comprises a resistivity sensor for measuring a resistivity of the formation fluid, and wherein the controller is configured to execute the instructions to calculate the hydrogen index, based on the measured resistivity, in response to determining that the type of the formation fluid is a water-based fluid. 
     
     
         15 . The downhole tool of  claim 11 , wherein the fluid analyzer comprises a density sensor for measuring a density of the formation fluid, and wherein the controller is configured to execute the instructions to calculate the hydrogen index, based on the measured density, in response to determining that the type of the formation fluid is a gas. 
     
     
         16 . The downhole tool of  claim 11 , wherein the fluid analyzer comprises an optical spectrometer for measuring an absorption spectra of the formation fluid, and wherein the controller is configured to execute the instructions to calculate the hydrogen index based on the measured absorption spectra in response to determining that the type of the formation fluid is a gas or a live oil. 
     
     
         17 . The downhole tool of  claim 11 , wherein the controller is configured to execute the instructions to delump concentrations of carbon components in response to determining the type of formation fluid is a live oil. 
     
     
         18 . The downhole tool of  claim 11 , further comprising a probe module configured to direct the formation fluid into the downhole tool. 
     
     
         19 . The downhole tool of  claim 18 , wherein the probe module comprises a resistivity sensor for measuring a resistivity of the formation fluid, and wherein the controller is configured to execute the instructions to calculate the hydrogen index, based on the measured resistivity, in response to determining that the type of the formation fluid is a water-based fluid. 
     
     
         20 . The downhole tool of  claim 11 , further comprising a sample module configured to store the formation fluid.