Laboratory pressure pulse decay permeability measurement of Boda Claystone, Mecsek Mts., SW Hungary

Abstract The Boda Claystone Formation (BCF), explored as a possible geological disposal of HLW in Hungary, has peculiar physical and chemical characteristics. Due to the petrophysical behaviour many new methods and experimental development were applied, while the traditional methods, e.g. steady state flow test on the basis of Darcy’s law, are too time-consuming. The pressure pulse decay (PPD) technique destinated to estimating gas and water permeability is one of these new methods developed for the BCF study. The main advantage of the PPD permeability compared with traditional permeability measurements is that very fast (in case of k g  ∼ 10 −19  m 2 15–25 min, k w  ∼ 10 −21  m 2 6–7 h), only 0.1–0.5 MPa pressure difference applied in the two sides of the examined core, quasi in situ circumstances can be provided and their uncertainty estimated. For the correct interpretation of results of the three cores originated from different underground boreholes of the formerly URL’s Alpha-1 drift, geochemical, minerological and petrophysical analysis were carried out. The time-consumption of drying, the fact that the dry core absorbed humidity of the atmosphere very fast, as well as the unsuccess of saturation under vacuum drew attention to the importance of the necessity of careful preparation and handling as well as the necessity of geochemical and mineralogical analysis.