Impact of pore confinement and adsorption on gas condensate critical properties confined in Marcellus Shale

Abstract

Gas condensate reservoirs present significant challenges in reservoir engineering due to their complex phase behavior, which is influenced by continuous compositional changes. In particular, nanopore confinement and adsorption significantly alter the thermodynamic properties of hydrocarbons, affecting phase transitions such as dew point pressure and condensate accumulation. This study investigates these effects within the Marcellus Shale formation by developing a compositional fluid model that integrates critical property shifts induced by pore confinement and adsorption. The model is compared with experimental measurements to ensure accuracy. To evaluate the impact of confinement, six fluid models were constructed using the Peng–Robinson equation of state, representing different pore sizes (1 nm, 2 nm, 5 nm, 10 nm, and 50 nm) alongside an unconfined reference case. The results demonstrate that smaller nanopores lead to significant shifts in critical pressure and temperature, ultimately delaying the onset of liquid condensation. Additionally, adsorption effects enhance reservoir pressure maintenance by storing hydrocarbons in the adsorbed phase, which desorbs as pressure declines, supplementing gas production. By incorporating confinement-induced phase behavior modifications, this research provides key insights into optimizing gas condensate production. The findings highlight the necessity of considering nanoscale confinement and adsorption effects in reservoir simulations to improve forecasting accuracy and develop more effective reservoir management strategies.