Workflow for Upscaling Wettability from the Nanoscale to Core Scale

Wettability is a key factor influencing multiphase flow in porous media.In addition to the average contact angle, the spatial distribution of contact angles along the porous medium is important, as it directly controls the connectivity of wetting and non-wetting phases.The controlling factors may not only relate to the surface chemistry of minerals but also to their texture, which implies that a length-scale range from nanometres to centimetres has to be considered.So far, an integrated workflow addressing wettability consistently through the different scales does not exist.In this study, we demonstrate that such a workflow is possible by combining micro-computed tomography imaging with atomic force microscopy (AFM).We find that in a carbonate rock, consisting of 99.9% calcite with a dual-porosity structure, wettability is ultimately controlled by the surface texture of the mineral.Roughness and texture variation within the rock control the capillary pressure required for initializing proper crude-oil-rock contacts that allow ageing and subsequent wettability alteration.AFM enables us to characterize such surface-fluid interactions and to investigate the surface texture.In this study, we use AFM to image nano-scale fluid-configurations in 3D at connate water saturation and compare the fluid configuration with simulations on the rock surface, assuming different capillary pressures.