Experimental evaluation of pore proximity effects on gas and condensate phase behaviour in real reservoirs: Implications of fluid composition

Unconventional reservoirs can play a pivotal role in meeting the growing energy demand and compensating for the decline in production from conventional hydrocarbon resources. However, the flow and phase behaviours of fluids within these porous media are not yet fully comprehended. This study investigates the impact of fluid confinement, small pore spaces, and pore walls on gas-condensate systems within real unconventional rocks. A novel experimental workflow was developed to measure the effective dew point pressure (Pdew) of various gascondensate mixtures in different real rock samples. The proposed workflow, for the first time allows to compare the Pdew of gas condensate mixtures in bulk and inside porous media. The research reveals that pore confinement increases Pdew of gas condensate mixtures while reducing it in single-component fluids. The concentration of heavier components significantly influenced Pdew under the influence of confinement. For the fluid mixtures used in this study, pore confinement effects increased the Pdew by around 25 psi for the mixture with the lightest components and by more than 250 psi for the mixture with the highest concentration of heavier components. These experimental findings enhance our understanding of fluid phase behaviour under pore confinement conditions and emphasize the significant role of heavier component concentration and type. The results provide valuable data for validating theoretical methods and practical applications in estimating confinement effects in unconventional gas-condensate reservoirs. This research supports the development of modified equations of state (EOS) to describe the behaviour of gas condensate mixtures under confinement, contributing significantly to energy resource management and the effective exploitation of unconventional reservoirs.