The spontaneous imbibition of liquid in nanopores of different roughness is investigated using coarse grain Molecular Dynamics (MD) simulation. The numerical model is presented and the simplifying assumptions are discussed in detail. The molecular-kinetic theory introduced by Blake is used to describe the effect of dynamic contact angle on fluid imbibition. The capillary roughness is modeled using a random distribution of coarse grained particles forming the wall. The Lucas-Washburn equation is used as a reference for analyzing the imbibition curves obtained by simulation. Due to the statistical nature of MD processing, a comprehensive approach was made to average and smooth the data to accurately define a contact angle. The results are discussed in terms of effective hydrodynamic and static capillary radii and their difference as a function of roughness and wettability.

We introduce a method for estimating the wettability of rock/oil/brine systems using noninvasive in situ nuclear magnetic relaxation dispersion. This technique scans over a large range of applied magnetic fields and yields unique information about the extent to which a fluid is dynamically correlated with a solid rock surface. Unlike conventional transverse relaxation studies, this approach is a direct probe of the dynamical surface affinity of fluids. To quantify these features we introduce a microscopic dynamical surface affinity index which measures the dynamical correlation (i.e., the microscopic wettability) between the diffusive fluid and the fixed paramagnetic relaxation sources at the pore surfaces. We apply this method to carbonate reservoir rocks which are known to hold about two thirds of the world's oil reserves. Although this nondestructive method concerns here an application to rocks, it could be generalized as an in situ liquid/surface affinity indicator for any multimodal porous medium including porous biological media.

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Heterogeneities of carbonate core plugs can be assessed by different measurements resulting in different interpretations. In this study, dielectric spectroscopy, NMR, and tracer displacement method performed on the same cores reflect different aspects of heterogeneity related to their own characteristic length scales and physics of the measurements, which complement each other in a multiphysical interpretation. The complex dielectric permittivity measured on carbonate core samples in the reflection mode in the range of 1 MHz to 1 GHz, exhibits a strong difference between the two extremities of the plugs when turning them upside down. The difference between the two extremities is a result of heterogeneity in the rock plug. It can be due to chemical composition, density, porosity, water saturation, presence of cavities, vugs and micro-fractures, crystalline structure and rock lithology, and, distribution of components inside the rock, which is a complex process need to be fully understand. The dielectric heterogeneity is compared with the NMR porosity profile which, in certain cases, indicates cross section averaged porosity heterogeneities along the core-plug axis and correlated with tracer displacement measurement, which characterizes the pore system hydraulic connection and its related heterogeneity. To complete this "multiphysics" approach, a numerical forward model of the electromagnetic propagation in the core-plugs was performed, focusing on the effect of artificial vugs at different locations inside the core-plug on the electromagnetic propagation patterns. From dielectrics and NMR profiles, quantitative heterogeneity indexes are proposed and compared, and correlated with tracer displacement measurement. This results in a better characterization of pore system (such as size, distribution, connectivity). A preliminary carbonate rock model taking into account the pore size effect is developed. The cementation factor is inverted from dielectrics dispersion curve measurements, a good match between inversion and laboratory measurements indicates the importance of pore partitioning in carbonates. These laboratory measurements on core plugs can be applied to well-bore measurements combining for instance Array Dielectric Scanner and NMR downhole tools.