Engineering properties of chalk related to diagenetic variations of Upper Cretaceous onshore and offshore chalk in the North Sea area

Matrix permeability is related not only to porosity but also to specific surface area of chalk which is controlled partly by calcite recrystallization partly by type and amount of non-carbonate minerals. In onshore chalk significant mineralogical differences are reflected in varying specific surface area. In contrast, specific surface area of Upper Cretaceous reservoir chalk show little variation indicating that care must be taken when choosing an outcrop chalk as substitute for reservoir chalk during flooding experiments.