File:Hydrocarbon-recovery-from-unconventional-reservoirs.jpg

English: Hydrocarbon recovery from unconventional reservoirs. Schematic illustration of a fracture network (blue), created by hydrofracking, penetrating previously isolated hydrocarbon-rich kerogen pockets (yellow) within a mineral matrix (brown). Here we consider the post-fracking situation in which water within the hydrofracking network is in contact with the kerogen surface. Extraction of the hydrocarbon requires formation of a nucleus with a high interfacial energy. The zoomed image illustrates such a scenario, in which a methane nucleus (dark grey) forms at a kerogen surface (yellow) adjacent to hydrophilic mineral surfaces present in shales (here quartz, with Si and O atoms as red and golden spheres). Considering other inorganic phases such as clays will lead to the same consistent picture of interfacial activated transport as they have similar wetting properties towards methane and water. However, local variations in surface chemistry and geometry will determine the magnitudes of the energy barriers preventing extraction, which will have a broad range of values due to the heterogeneous, multiscale texture of the shale.