Permeability variation in a tidal Jurassic deposit, Höganäs basin, Fennoscandian Border Zone

Sammanfattning: An examination of permeability differences was made on plugs obtained from six drill cores in both horizontal and vertical directions, representing different facies of the Hettangian strata from the Höganäs Formation. The permeability analyses distinguish permeability differences from anisotropy and an index was created to evaluate the anisotropy. The cause of the measured anisotropy in this study is a direct function of the depositional effects, related to tide-dominated deltaic environment. All thirty-eight permeability and porosity data were obtained from plugs taken from a drill core succession with a total length of thirty metres. BSE point-counting was used to obtain correct mineralogical results. The technique was particular convenient for the fine-grained sandstones. The relationship between anisotropy and depositional and diagenetic history is interpreted and a diagenetic model is proposed. Quartz cement occurs abundantly in some sandstone beds and scarcely in other similar strata, which suggests that the fluid flow in the strata was the controlling factor of the diagenetic processes. Jurassic heterolithic sandstone reservoirs are economically important for the oil industry and the anisotropy provide sealing conditions for the reservoirs and prevents oil migration, which have an inhibiting effect on exploitation. It is suggested that prediction (modelling) of reservoir qualities needs to evaluate the importance of petrographic and petrophysical properties.