a: original oolitic grainstone of the upper reservoir (plane-polarized light); b: dolomitized grainstone showing oolithe ghosts; it is affected by cataclase observed on the right (cross-polarised light). The upper reservoir provides evidence of dissolution of calcite and successive dolomitization and dedolomitization, as shown by SEM image (c). SEM chemical mapping of Ca (blue, d) and Mg (green, e) displays successive zones of calcite and dolomite, respectively; f: dolomitization front of the mudstone in the lower reservoir (natural light; cal.: calcite; dol.: dolomite); g: dolomite in the lower reservoir showing a significant amount of porosity (plane-polarized polarised light).