Fig. 6

Initial and general permeability model. Averaged log-derived porosity is plotted versus averaged log-derived permeability for a number of Danish onshore wells penetrating the Gassum formation, with the scope of setting up of a general permeability model (bold line). Each symbol (diamond) represents an average porosity and permeability value assigned to a particular well. The calculation of the averages is also based on two cut-off criteria: 15 % porosity cut-off and 30 % shale cut-off. Log-derived total porosity (PHIT) originates from interpretation of well-log data. Log-derived permeability is based on the log-porosity combined with the use of an empirical porosity–permeability relationship. The latter relationship corresponds to the initial model that is based on core analysis data only. Note that the averaging leads to an upward shift of the curve established prior to averaging. Permeability estimates based on the general model (bold line) are therefore somewhat higher than permeability estimates obtained from the initial model (thin line)