Flow behaviors of shale oil in kerogen slit by molecular dynamics simulation

Abstract

In the last decades, shale oil, mainly distributed in the nanopores of shale, has been considered as the representative of unconventional energy to alleviate the energy crisis. But the ideal pore models greatly overestimate the flowing capability of shale oil. To get more accurate and reasonable flow behavior, the multicomponent shale oil in the realistic kerogen channel is studied by using molecular dynamic simulation. Both density and velocity distributions that along and perpendicular to the flow direction are studied in kerogen channel, where the influence of branch chain of kerogen is also took into consideration. The heavy component tends to form the adsorbed layers on the kerogen wall, as a result of the extremely strong affinity between kerogen and hydrocarbons, and some asphaltene molecules in bulk phase form the cluster in middle of slit. On the flow direction, the velocity profile preforms the peristaltic behavior due to the effect of branch chain of kerogen, and the toluene and asphaltene components contribute it mostly. According to the heterogeneous characteristics of shale oil flow, we define the fictitious slip boundary, which corresponds to the boundary between bulk phase and adsorbed phase, to describe shale oil flow precisely. We also examine the effects of driving pressure gradient, temperature and pore size on the flow behaviors. The enhancements of driving force and temperature both facilitate shale oil flow, and the maximum velocity reaches the stable value within larger kerogen pores. The potential energy distribution and the interaction force contour verified the peristaltic flow behavior and the validity of fictitious slip boundary.