Drilling Fluid Contamination Determination for Downhole fluid Sampling Tool

A fluid sampling method, comprising:

• running a downhole fluid sampling tool in a wellbore;
• obtaining a fluid sample of a reservoir fluid using the downhole fluid sampling tool;
• determining a fluid contamination of the fluid sample, wherein the determining the fluid contamination includes uses of a mole fraction distribution function in conjunction with an equation of state;
• and
• storing the fluid sample in the downhole fluid sampling tool based on the fluid contamination.

A system for determining fluid contamination, comprising:

• a downhole fluid sampling tool operable to obtain fluid samples of a reservoir fluid contaminated with a well fluid while the downhole fluid sampling tool is disposed in a wellbore;
• and
• a processing unit operable to (i) obtain input parameters, wherein the input parameters comprise fluid properties obtained from measurement of the fluid sample and a mud filtrate composition;
• (ii) obtain initial values of iterative parameters, wherein the iterative parameters comprise fluid contamination of fluid sample;
• (iii) determine component mole fractions of the reservoir fluid using the initial values of the iterative parameters in a mole fraction distribution function;
• (iv) determine calculated fluid properties of the reservoir fluid using equation of state flash calculating;
• and (v) repeatedly determine component mole fractions and determining calculated fluid properties and further obtain updated values of the iterative parameters for use in the mole fraction distribution function until a comparison of one or more of the calculated fluid properties with one or more of the input parameters is within a tolerance error.