Convection and dispersion in a naturally fractured reservoir

In this work, theoretical and experimental studies are presented on the natural convection flow in a naturally fractured reservoir, produced by a vertical geothermal gradient. The present approach considers finite oil-filled, tilted fractures with small aspect ratios, with a fluid thermal conductivity assumed to be very small compared with the thermal conductivity of the rock matrix. These assumptions are fully justified for actual Mexican naturally fractured reservoirs. Finite tilted porous layers saturated with oil have also been considered. In all the cases studied, convection occurs under any vertical temperature gradient. In addition, the diffusion and dispersion of nitrogen (N₂) is studied, with this substance located initially at the top of the fracture. In these types of flows, the influence of convection over diffusion and dispersion of passive substances is extremely small.