Determinação das propriedades de transporte de misturas n-alcanos não confinadas e confinadas em poros de calcita utilizando dinâmica molecular

Abstract

To meet current and future hydrocarbon demands and overcome the shortage of newly discovered in conventional reservoirs, the oil industry has concentrated its efforts in more complex (unconventional) reservoirs. Among the complexities can be highlighted systems that are subjected to vertical and horizontal temperature gradients . In this context, the recovery of fluids present in unconventional reservoirs has been promising. The presence of temperature gradients in mixtures induces the emergence of diffusive mass flow, giving rise to a gradient of concentration. This phenomenon is called the Soret effect or thermodiffusion. The gradient of concentration formed by thermodiffusion is the driving force for the emergence of a diffusive mass. At steady state, the net mass flow is zero, resulting in a fully developed temperature and concentration gradients. This work aims to use equilibrium and non-equilibrium molecular dynamics to evaluate transport and structural properties of hydrocarbon mixtures in bulk and confined systems structured pores of calcite. The transport properties were obtained via equilibrium molecular simulation through the Green-Kubo formalism and the Soret coefficient was determined using the BD-NEMD algorithm. The effect of finite size on transport properties determination was also evaluated. Two hydrocarbon mixtures were studied, one to validate the methods (n-pentane/n-decane), and one for light hydrocarbons (methane/n-butane) simulating fluid in shale gas reservoirs. The effect of confinement on these properties were evaluated for the degrees of confinement studied. The distribution of vertical and horizontal densities in the pores studied varied according to the degree of confinement, temperature, and composition, emphasizing the high interaction between mixture and pore wall