A method for generating a phase envelope log to characterize a subsurface formation includes drilling the borehole with a drill string, circulating a drilling fluid in the borehole, drawing a fluid sample representing a fluid contained in the subsurface formation, estimating a PVT parameter indicative of an in-situ condition of the subsurface formation from the drawn fluid sample, determining at least two phase envelopes at different depths using the estimated PVT parameter, and creating a phase envelope log formed of a continuous series of phase envelopes using the phase envelopes. A related system includes a drill string, a fluid sampling system, and a processor that estimates a PVT parameter indicative of an in-situ condition of the subsurface formation, determines at least two phase envelopes at different depths using the PVT parameter, and creates the phase envelope log.