The correlation of sedimentary facies and palaeogeography and ground water from the Cretaceous strata in the Ordos Basin

The rocks in the crust always serve as the important media for the storage and migration of ground water. The accommodation spaces have changed with varying rock types. The sedimentary facies and palaeogeography tend to be the significant controls on the physical properties of the reservoir rocks. The differences of sandstone types generated under different hydrodynamic regimes are responsible for the differences of lithology, grain size, sorting, infilling, lithofacies association and spatio-temporal distribution. The study of the sedimentary facies and palaeogeography may help assist in the exploration of the environmental conditions, distribution and physical properties of the resultant rocks, and the prediction and evaluation of water quality and distribution of the regional ground water. The results of research in this paper show that the dune sandstones in the desert facies, braided channel sandstones, deltaic distributary channel sandstones, meandering channel point bar sandstones and (littoral) sandstones are good water-filled rock bodies. The Luohe Formation in the desert facies and the Huanhe Formation in the alluvial and braided stream facies may be delineated as major aquifers.