permeability measurements on core samples have evolved to include accurate
measurements in nanodarcy or lower permeability samples. In conventional
quality reservoirs, measurement techniques transitioned from steady-state to unsteady state methods, however in unconventional reservoirs the majority of permeability measurements
are conducted using disaggregated samples, unsteady-state techniques, closely following SPE 26633 Luffel et al, 1993 recommended methods. The methods have now expanded to include measurements on full plug samples at an appropriate reservoir net confining stress.
Permian Basin core calibrated petrophysical models have long incorporated permeability data from core measurements. These core measurements
are used to upscale correlations to the wireline data by various techniques. Originally, the measured core data were used to adjust inputs into conventional log- based permeability calculations (Wyllie-Rose, Timur et al, 1986). Simple functions have been developed to relate permeability measurements to various core attributes
(porosity, clay content, etc.) or log measurements. Core level data are then
upscaled to construct log models. The evolution of the core- derived model for
the Permian Basin has taken the correlation from a single variable, or
piecewise function, to multiple variables. Using a multi-variate analysis approach allows interpolation of data to fill
the gaps in measured data, especially in heterogeneous formations. Modeling based on this approach aid in development of more robust models leading to more accurate engineering calculations.