Methods and apparatus for the downhole characterization of formation fluids

A method of investigating a hydrocarbon bearing geological formation traversed by a borehole, comprising:

• a) acquiring a sample of fluid in the formation with a formation fluid sampling tool located in the borehole;
• b) conducting a compositional analysis of the fluid sample located in the sampling tool while said sampling tool is in the borehole, wherein said compositional analysis includes an identification of methane, and an identification of at least one additional hydrocarbon or group of hydrocarbons;
• c) relating the compositional analysis to a model of the thermodynamic behavior of the fluid;
• and
• d) based on said relating, predicting a phase behavior of fluid remaining in the formation, wherein
• said sample of fluid is a contaminated sample which is contaminated with drilling mud,
• said conducting a compositional analysis includes correcting for said drilling mud contamination in order to obtain an indication of an uncontaminated composition of fluids in the geological formation, and
• said relating the compositional analysis relates an uncontaminated composition to said model of said fluid.