Permeability Estimations Based on Internal Surface and NMR T2 for Chesapeake Bay Impact Structure (Eyreville Cores)

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Hydraulic permeability is not only necessary for hydraulic purposes, but also for heat flow determinations. Often no measurements of hydraulic permeability are available, therefore it is necessary to go back on estimations. The choice of the estimation method depends on the available measured physical properties, a comparison of more than one estimation is advisable. Estimations by means of internal surface and porosity (PaRiS-model) as well as NMR-relaxation time and porosity are frequently used petrophysical models. We compare estimations of permeability by means of these models for the post impact (clay) and Exmore section (diamicton, clay and sandstone) from the corehole Eyreville (Impact structure Chesapeake, USA), and compare them with some literature data. We indicate that both methods don’t account for closed porosity and anisotropy. For the rocks of the Exmore section the PaRiS-model leads to considerable overestimation for the sandstones and underestimation for the clay samples. Besides these limitations both methods give results which lie in the same order of magnitude. We estimate mean bulk permeability values on sample scale between 0.1 mD and 1000 mD. On field scale the permeability will be higher. Therefore, advective mass transport and a convective contribution to heat transport is to be expected.