Porosity development and distribution in the Rüdersdorfer Schaumkalk (Middle Triassic) of the Gas Store Berlin, Germany

Abstract

Gas is stored in the Triassic Buntsandstein units above the salt-pillow structure of Spandau. Brines obtained collaterally when bringing the gas back to the surface are reinjected into the oomoldic limestone of the Lower Muschelkalk. Cores of the limestone were investigated with respect to microfacies, diagnetic development, porosity, and permeability to provide the input for modeling reservoir configuration and capacity of this unit. In the porous portions of this unit, six microfacies types were distinguished by varying proportions of ooids, peloids and biogenic (skeletal) particles. Microfacies types do not correlate with porosity and permeability. The rocks were altered by varying successions of dissolution and cementation stages; four diagenetic grades were defined on the basis of development of moldic pores and their fillings. The diagenetic grades correlate with porosity and permeability showing that kind and intensity of diagenetic alterations largely overprinted initial control of microfacies on fluid flow.