Visualization of imbibition in porous media by environmental scanning electron microscopy: application to reservoir rocks

The study of wettability and fluid distribution in porous media has been approached by means of environmental scanning electron microscope (ESEM). This method allows visualization of rock samples in the presence of fluids (both oil and brine). Fluids consisted of water and dodecane, which remain liquid under the observation conditions. Porous media consisted of homogeneous wettability sintered glass, and mixed wettability reservoir rock samples: a sandstone from the North Sea and a carbonate from the Middle East (preserved state). For sintered glass, (treated with octadecyltrichlorosilane to obtain an oil-wet surface), after the sample was saturated with water (nonwetting fluid), it was clearly possible to follow its appearance at the upper face of the core sample. For the sandstone samples, it was possible to observe the rise of oil through the water phase at the junction between quartz and kaolinite. For carbonate samples, tentative correlations were made between the appearance of oil at the upper face and the pore structure of the sample.