Experimental and numerical study of compositional two-phase displacements in layered porous media

This paper presents an experimental and numerical study to investigate the effects of viscous, capillary, and gravity forces on compositional two-phase displacements in layered porous media. We use glass bead packs of different sizes to construct a quasi 2-D porous medium of three layers with different uniform permeabilities. We adapt an analog ternary fluid system (isooctane, brine, and isopropanol) which allows us to control interfacial tension between the phases at ambient laboratory conditions. Flooding experiments mimic condensing drives and use immiscible and near miscible fluids from the analog ternary system. We report recovery of phases, compositional analysis, and snapshots of saturation distributions during each experiment.We show that the high flow capacity domain as defined by the high permeability layer and its thickness always dominate displacements. However, its degree depends on the location of the high-permeability layer and the balance between the driving forces. Compositional analysis of effluent indicates that the compositional path is slightly different for the low and high injection rates in the high interfacial tension (IFT) immiscible displacements whereas it is sensitive to the location of high-permeability layer in the low-IFT near-miscible floods. The Peclet numbers indicate the presence of dispersion in the experiments and crossflow affects the recoveries.We also perform black oil simulations to interpret the experimental observations. In general, we obtain consistent results between the experimentally measured and numerically obtained data. However, in order to account for the displacement physics and accurately predict the recovery performance, one may need to employ a fully compositional simulation model that captures the tie-line slopes correctly along with the transport properties and gravity. The compositional simulations can provide additional details in terms of component recoveries.

► Effect of high-permeability layer location on recovery is moderate in immiscible floods.
► In near-miscible floods, gravity clearly dominates flow.
► High-permeability layer location affects swept area significantly in near miscible floods.
► Black oil simulations predict recovery behavior of immiscible displacements.
► Fully compositional simulation model is recommended for near miscible cases.