Immiscible and Miscible Displacement in Heterogeneous Porous Media: from soil column experiments to a dynamic large-scale network simulator
Advancing the chemical engineering fundamentals
Transport Phenomena in Porous/Granular Media - III (T2-7c)
Keywords: hydrodynamic dispersion, two-phase flow, capillary pressure, numerical simulation, relative permeability
Immiscible and miscible displacement tests are performed on long undisturbed soil columns (length=30 cm, diameter=5 cm) characterized by heterogeneities at multiple scales. Multipoint measurements of the electrical resistance are employed to determine the axial distribution of the fluid saturation and the solute concentration breakthrough curves. The heterogeneous porous medium is regarded as a system of parallel flow pathways that are quantified by an absolute permeability distribution function. The miscible and immiscible displacement in such a multiregion model are described by analytical equations, the parameters of which are estimated by inverting successively (1) the transient response of the solute concentration (breakthrough curve) over three cross-sections, and (2) the transient responses of the total pressure drop across the soil column and fluid saturation averaged over five successive segments. The so-estimated parameters are employed to build a large-scale network, where each node represents a homogeneous region of constant permeability. The relative permeability and capillary pressure curves of the nodes (homogeneous blocks) are obtained by combining information from the soil pore structure analysis with percolation-type network simulations. To simulate rate-controlled drainage in such a network, the pressure field, at a given fluid distribution, is calculated by solving the system of coupled linear equations, resulting from mass balances in the nodes. Based on the calculated flow rates, a time interval is so selected that the displacement is completed in no more than one unit cells (each consisting of the 1/6th of two adjacent nodes). Then, the fluid saturation in each node is updated, and the entire procedure is repeated until no change of saturation and total pressure drop occur. The large-scale network simulator enables us to examine the sensitivity of the axial profile of the fluid saturation, and total pressure drop to independent parameters such as the absolute permeability distribution, capillary number, viscosity ratio, and Bond number. In this manner, we are allowed to interpret the results of flow tests in terms of pore space heterogeneities and dimensionless flow parameters, and calculate the up-scaled relative permeability and capillary pressure curves of the heterogeneous medium.
Presented Wednesday 19, 12:00 to 12:20, in session Transport Phenomena in Porous/Granular Media - III (T2-7c).
