Melting and freezing of argon in a granular packing of linear mesopore arrays

Freezing and melting of Ar condensed in a granular packing of template-grown arrays of linear mesopores (SBA-15, mean pore diameter 8 nanometer) has been studied by specific heat measurements C as a function of fractional filling of the pores. While interfacial melting leads to a single melting peak in C, homogeneous and heterogeneous freezing along with a delayering transition for partial fillings of the pores result in a complex freezing mechanism explainable only by a consideration of regular adsorption sites (in the cylindrical mesopores) and irregular adsorption sites (in niches of the rough external surfaces of the grains, and at points of mutual contact of the powder grains). The tensile pressure release upon reaching bulk liquid/vapor coexistence quantitatively accounts for an upward shift of the melting/freeezing temperature observed while overfilling the mesopores.Comment: 4 pages, 4 figures, to appear as a Letter in Physical Review Letter

Modification of chemical and physical factors in steamflood in increase heavy oil recovery. Annual report, October 1, 1994--September 30, 1995

The objectives of this contract is to carry our fundamental research in heavy oil recovery in the following areas: displacement and flow properties of fluids involving phase change (condensation-evaporation) in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on oil recovery. The specific projects are motivated by and address the need to improve heavy oil recovery from typical reservoirs as well as less conventional fractured reservoirs. This report covers the work performed in these three areas in the past year. In the area of vapor-liquid flow we present a theoretical and numerical study of steam injection in a pore network. We characterize the displacement in terms of an effective mobility ratio and heat transfer parameters. Displacement patterns axe identified in the parameter space. In another study we discuss the problem of steam injection in fractured systems using visualization with micromodels. The interplay of drainage, imbibition and bubble growth is visualized. Conclusions are reached regarding the potential for steamflooding fractured systems. A third study focuses on the development of a pore-network model for foam formation and propagation in porous media. This model, for the first time, accounts for the fundamental mechanisms of foam propagation at the microscale and leads to the determination of various parameters that are currently treated empirically. The effect of viscous forces in displacements in heterogeneous media is described in two separate studies, one involving an extension of percolation theory to account for viscous effects, and another discussing the effect of geometry in general displacement processes

Capillary condensation in one-dimensional irregular confinement

Peer reviewedPublisher PD

On the Upscaling of Reaction-Transport Processes in Porous Media with Fast Kinetics

This report is organized as follows: Provide a brief review of the upscaling constraints of the type (2) for a typical diffusion-reaction system. In this an analogy with two-phase flow in porous media was drawn. Then, using the methodology of QW a problem at the unit cell for the computation of the effective mass transfer coefficient, in processes where local thermodynamic equilibrium applies was derived. This problem is found to be different than in QW, as it depends on the gradients of the macroscale variable, and can be cast in terms of an eigenvalue problem. Two simple, examples, one involving advection-dissolution and another involving drying in a pore network, was presented to illustrate the coupling between scales and to show the quantitative effect in case this coupling was neglected. Finally, similar ideas and an illustrative example was applied to reaction-diffusion systems with fast kinetics, where an equilibrium state is approached