Porous Media

Fluids in porous media are commonly studied with analytical or simulation methods, usually assuming that the host medium is rigid. By evaluating the substrate’s response (relaxation) to the presence of the fluid we assess the error inherent in that assumption. One application is a determination of the ground state of 3He in slit and cylindrical pores. With the relaxation, there results a much stronger cohesion than would be found for a rigid host. Similar increased binding effects of relaxation are found for classical fluids confined within slit pores or nanotube bundles.

Transport of emulsions in porous media is relevant to several subsurface applications. Many enhanced oil recovery (EOR) processes lead to emulsion formation and as a result conformance originating in the flow of a dispersed phase may arise. In some EOR processes, emulsion is injected directly as a mobility control agent. Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and numerous interfaces. The descriptions based on effective viscosity are not valid when the drop size is of the same order of magnitude as the pore-throat characteristic length scale. An accurate model of emulsion flow through porous media should describe this local change in mobility. The available filtration models do not take into account the variation of the straining and capturing rates with the local capillary number. In this work, we present experiments of emulsion flow through sandstone cores of different permeability and a first step on a capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of the permeability and dispersed phase droplet size on the flow response to emulsion flooding in porous media. The network model predictions qualitatively describe the oil-water emulsion flow behavior observed in the experiments.

In this study we extend the results given in a previous report regarding the propagation features of high-frequency energy in slender structures to the case of three-dimensional porous media. The mathematical theory of microlocal analysis of hyperbolic partial differential equations shows that the energy associated to their high-frequency solutions (in a sense to be precised) satisfies Liouville-type transport equations, or radiative transfer equations for randomly heterogeneous materials. For long propagation times these equations can be asymptotically approached by diffusion equations. Some classical results of the engineering mechanics literature about the heat conduction analogy and the statistical energy analysis of structural vibrations at high frequencies are recovered in this process. The purpose of this report is to focus on such a diffusive regime for isotropic porous media.

We describe here a new experimental device developed for the study of a combustion front propagation in a reactive medium: crushed oil shale (500 to 1000 µm). We are interested in the propagation of a front supplied by air in co-current. The cell is a vertical cylinder of 90mm internal diameter and 300mm height, made up of an insulating material. To start the combustion and to obtain a plane flame front, it was set up a sophisticated device of ignition, namely the cone calorimeter. The reactor is finely instrumented. A whole of thermocouples makes it possible to measure the temperature along the axis for the cell and over a horizontal cross section (at middle height) of the packed bed. The pressure drop and the total mass of the particle bed are continuously recording. A new device was developed and set up to improve the physicochemical investigation of the structure of the flame front: micro-sampling. Its originality lies in the possibility of micro sampling gas at a fined point in...

Correlations are presented to compute the mutual solubilities of CO2 and chloride brines at temperatures 12–300°C, pressures 1–600 bar (0.1–60 MPa), and salinities 0–6 m NaCl. The formulation is computationally efficient and primarily intended for numerical simulations of CO2-water flow in carbon sequestration and geothermal studies. The phase-partitioning model relies on experimental data from literature for phase partitioning between CO2 and NaCl brines, and extends the previously published correlations to higher temperatures. The model relies on activity coefficients for the H2O-rich (aqueous) phase and fugacity coefficients for the CO2-rich phase. Activity coefficients are treated using a Margules expression for CO2 in pure water, and a Pitzer expression for salting-out effects. Fugacity coefficients are computed using a modified Redlich–Kwong equation of state and mixing rules that incorporate asymmetric binary interaction parameters. Parameters for the calculation of activity and fugacity coefficients were fitted to published solubility data over the P–T range of interest. In doing so, mutual solubilities and gas-phase volumetric data are typically reproduced within the scatter of the available data. An example of multiphase flow simulation implementing the mutual solubility model is presented for the case of a hypothetical, enhanced geothermal system where CO2 is used as the heat extraction fluid. In this simulation, dry supercritical CO2 at 20°C is injected into a 200°C hot-water reservoir. Results show that the injected CO2 displaces the formation water relatively quickly, but that the produced CO2 contains significant water for long periods of time. The amount of water in the CO2 could have implications for reactivity with reservoir rocks and engineered materials.