Critical point network for drainage between rough surfaces

In this paper, we present a network method for computing two-phase flows between two rough surfaces with significant contact areas. Low-capillary number drainage is investigated here since one-phase flows have been previously investigated in other contributions. An invasion percolation algorithm is presented for modeling slow displacement of a wetting fluid by a non wetting one between two rough surfaces. Short-correlated Gaussian process is used to model random rough surfaces.The algorithm is based on a network description of the fracture aperture field. The network is constructed from the identification of critical points (saddles and maxima) of the aperture field. The invasion potential is determined from examining drainage process in a flat mini-channel. A direct comparison between numerical prediction and experimental visualizations on an identical geometry has been performed for one realization of an artificial fracture with a moderate fractional contact area of about 0.3. A good agreement is found between predictions and observations

X-ray micro-tomography and pore network modeling of single-phase fixed-bed reactors.

A three-dimensional (3D) irregular and unstructured pore network was built using local topological and geometrical properties of an isometric bead pack imaged by means of a high-resolution X-ray computed micro-tomography technique. A pore network model was developed to analyze the 3D laminar/inertial(non-Darcy) flows at the mesoscopic (pore level) and macroscopic (after ensemble-averaging) levels. The non-linear laminar flow signatures were captured at the mesoscale on the basis of analogies with contraction and expansion friction losses. The model provided remarkably good predictions of macroscopic frictional loss gradient in Darcy and non-Darcy regimes with clear-cut demarcation using channel-based Reynolds number statistics. It was also able to differentiate contributions due to pore and channel linear losses, and contraction/expansion quadratic losses. Macroscopic mechanical dispersion was analyzed in terms of retroflow channels, and transverse and longitudinal Péclet numbers. The model qualitatively retrieved the Péclet-Reynolds scaling law expected for heterogeneous networks with predominance of mechanical dispersion. Advocated in watermark is the potential of pore network modeling to build a posteriori constitutive relations for the closures of the more conventional macroscopic Euler approaches to capture more realistically single-phase flow phenomena in fixed-bed reactor applications in chemical engineering

Quantification of three macrolide antibiotics in pharmaceutical lots by HPLC: Development, validation and application to a simultaneous separation

A new validated high performance liquid chromatographic (HPLC) method with rapid analysis time and high efficiency, for the analysis of erythromycin, azithromycin and spiramycin, under isocratic conditions with ODB RP18 as a stationary phase is described. Using an eluent composed of acetonitrile –2-methyl-2-propanol –hydrogenphosphate buffer, pH 6.5, with 1.5% triethylamine (33:7: up to 100, v/v/v), delivered at a flow-rate of 1.0 mL min-1. Ultra Violet (UV) detection is performed at 210 nm. The selectivity is satisfactory enough and no problematic interfering peaks are observed. The procedure is quantitatively characterized and repeatability, linearity, detection and quantification limits are very satisfactory. The method is applied successfully for the assay of the studied drugs in pharmaceutical dosage forms as tablets and powder for oral suspension. Recovery experiments revealed recovery of 97.13–100.28%

Inertial Effects in Two-Phase Flow Through Fractures

Different approaches for modeling inertial effects during single-phase and two-phase flows through a fracture are presented: inertial factor, passability and Lockhart-Martinelli models. These different approaches are then used to interpret experiments for air/water flow through a rough fracture. For these two-phase flow experiments, the standard relative permeabilities (no inertial terms) are not only functions of the saturation but also of the flow rate ratio. This family of curves at high velocity can be seen as a criterion for the presence of inertial effects. By taking account of inertial effects, the inertial factor and passability models are similar and provide a good representation of the experimental data. However, four unknown parameters must be determined and the models cannot be used for prediction without further research. The Lockhart-Martinelli approach has only two parameters to fit and can be used for prediction. An empirical law used for porous media in chemical engineering agrees within 20% with air/water experiments without any additional adjustment of parameters. For the three approaches, the use of the ratio of the flow rates as variable instead of the saturation gives better results

Proceedings of the Workshop on Geothermal Reservoir Engineering

Two-phase (air-water) flow experiments were conducted in horizontal artificial fractures. The fractures were between glass plates (1 x 0.5 m) artificially roughened by gluing a layer of glass beads of Imm diameter. Three rough fractures were studied: one with the two surfaces in contact, and two without contact. Videotape observations revealed flow structures similar to those observed in two-phase flow in pipes, with structures depending upon the gas and liquid flow rates. The data of flow rates, pressure gradients and saturations were interpreted using the generalized Darcy's law. Relative permeabilities curves were found to be similar to classical curves in porous medium, but not unique functions of saturations. The sum of gas and liquid relative permeabilities were found to be less than one at all saturations

Transport Properties of Lavoux Limestone at Various Stages of CO

Since 2005, the French National Research Agency supports several scientific projects intended to select, validate and implement a geological site for CO2 storage in France. The work presented in this paper was carried out within the Geocarbone-Injectivity project, aimed to study the suitability of a carbonate deep saline aquifer located in the Paris basin for a geological CO2 storage. A geological analog to the aquifer rock was chosen in order to perform several petrophysical and transport characterizations. Measured parameters were intrinsic permeability, inertia coefficient, Klinkenberg coefficient, relative permeabilities and transport properties such as the dispersion coefficient and the stratification factor. Samples of Lavoux limestone were characterized in their original state and also after a phase of CO2-like acid-rock alteration. Results show sensible changes in porosity, permeability and inertia coefficient and almost no change in relative permeabilities, dispersion coefficient and stratification coefficient. These results mean that the CO2 injectivity would be maintained and even enhanced during its injection in the considered Dogger formation. Nevertheless, to confirm this observation, additional experimental and modeling work should be performed, taking into account the potential fine migration. A permeability alteration could be expected due to these fine displacements