Experimental and Molecular Modeling Study of Bubble Points of Hydrocarbon Mixtures in Nanoporous Media

The shale play resources have played a key role in increasing oil production in the past decade in the United States. The sizes of pores in shales storing the oil are believed to be on the order of nanometers. It is believed that the fluids present in such small nanometer-scale pores have different properties compared to properties measured in the bulk. Fluid saturation pressures at given temperatures, bubble points for oils and dew points for condensates, in the nanopores are affected by the influence of pore walls in the vicinity of the fluid molecules. An approach to bubble point or dew point influences the proportion of liquid or gas produced from a given well and, thus, impacts the economic viability. Hence, an accurate measure of saturation pressures is important. In this paper, we describe experiments in well-characterized synthesized mesoporous materials and present Gibbs ensemble Monte Carlo (GEMC) simulations for understanding the possible reason(s) for observations made in the experiments. The experimentally measured saturation pressure of a mixture of decane–methane in confined spaces of the mesoporous material is observed to be less than the saturation pressure of the mixture in the bulk state. The GEMC simulations were performed to investigate fluid-phase equilibrium in confined pores and find possible reason(s) behind the suppression of bubble points in the confined spaces. The simulations show that reduction in critical properties of the nano-confined fluids lead to the suppression of bubble point pressures of the fluid mixtures in confined pores.