Phase behavior of single and multi-component liquid hydrocarbons in real reservoir rocks.

Phase-alteration phenomenon has a considerable influence on the dynamics and distribution of fluids in porous media. One of the major factors affecting the phase behaviour of fluids in reservoirs is the capillarity effect, which becomes unavoidably significant as the media becomes tighter (confinement effect) and contains more pores at nano sizes. Comprehending the nature of vaporization and condensation of hydrocarbon in such confined media is important for accurate modelling of two-phase envelopes and thereby the performance of energy production from hydrocarbon reservoirs. This paper studies the vaporization of single- and multicomponent hydrocarbons in different types of rocks (namely sandstones, limestones, tight sandstones, and shales). The vaporization temperatures were measured experimentally in each rock type and compared with boiling points measured at bulk conditions to investigate the deviation between the phase-change temperatures in capillary media and bulk values. The deviation between the measured vaporization temperatures and the bulk measurements ranged from 4.4% (1.6% in Kelvin unit) to 19.7% (5.2% in Kelvin unit) with single-component solvents and 1.4% (0.4% in Kelvin unit) to 27.6% (5.3% in Kelvin unit) with the hydrocarbon mixtures. The vaporization temperatures, obtained from the experiments, were also compared with the computed two-phase envelopes, calculated by the classical Peng-Robinson Equation of State. The deviation percentages of measured vaporization temperatures from the computed values were at least 4.4% (1.6% in Kelvin unit) with single-component solvents and 2.1% (0.7% in Kelvin unit) with the hydrocarbon mixtures.