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When a wetting liquid is displaced by air in a capillary tube, a wetting film develops between the tube wall and the air that is responsible for the snap-off mechanism of the gas phase. By dissolving a dye in the wetting phase it is possible to relate a measure of the absorbance in the capillary to the thickness of liquid films. These data could be used to compare with cutting edge numerical simulations of the dynamics of snap-off for which experimental and numerical data are lacking. Drainage experiments in constricted capillary tubes were performed where a dyed wetting liquid is displaced by air for varying flow rates. We developed an optical method to measure liquid film thicknesses that range from 3 to 1000μm. The optical measures are validated by comparison with both theory and direct numerical simulations. In a constricted capillary tube we observed, both experimentally and numerically, a phenomenon of snap-off coalescence events in the vicinity of the constriction that bring new insights into our understanding and modeling of two-phase flows. In addition, the good agreement between experiments and numerical simulations gives confidence to use the numerical method for more complex geometries in the future.

To cite this version:Moataz Abu-Al-Saud, Stéphane Popinet, Hamdi Tchelepi. A conservative and well-balanced surface tension model. AbstractThis article describes a new numerical scheme to model surface tension for an interface represented by a level-set function. In contrast with previous schemes, the method conserves fluid momentum and recovers Laplace's equilibrium exactly. It is formally consistent and does not require the introduction of an arbitrary interface thickness, as is classically done when approximating surface-to-volume operators using Dirac functions. Variable surface tension is naturally taken into account by the scheme and accurate solutions are obtained for thermocapillary flows. Application to the Marangoni breakup of an axisymmetric droplet shows that the method is robust also in the case of changes in the interface topology.

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The recent advancements in imaging techniques have allowed quantifying the transport and fluid flow inside the complex rock pores at the microscopic scale. Specifically, micro-computed tomography (micro-CT) can reconstruct the three-dimensional pore-space geometry with micron-scale resolution. In this work, a numerical investigation of single-phase fluid flow is conducted on micro-CT images of carbonate core-plug subsamples. The presented numerical model studies the fluid flow and transport inside the rock pores at the pore-scale. The flow dynamics is modeled using the Darcy-Brinkman formulation to consider the wide pore size distribution in carbonate rock samples. The simulation model takes into account pores at the micro-CT image resolution as well as the unresolved pores (microporosity) that are smaller than the micro-CT voxel sizes. These unresolved pores are usually categorized as microporosity, which is a parameter in the simulation model. The microporosity is quantified based on the micro-CT gray-scale intensity. Simulation results show that direct pore-scale simulation on micro-CT images can characterize the permeability, porosity, and microporosity. As a result, pore-scale simulation can supplement conventional core analysis as well as provide detailed information of the primary fluid flow paths inside the carbonate rock pores. It is also shown that the microporosity has a first order effect on the rock permeability. Neglecting the microporosity regions alters the pore connectivity, which is essential to compute the permeability and rock petrophysical properties accurately. The novelty of this study lies in solving the Darcy-Brinkman simulation model in a finite-volume framework to capture the effect of microporosity on carbonate rock samples in full three-dimensional space. The new findings shed light on the fluid flow and transport inside highly heterogeneous carbonate formations, which becomes an important first step to understand the fundamentals of oil recovery in advanced waterflooding process at the microscopic level.