Petrophysics is the first step towards a better understanding of the subsurface. It is an important step for reservoir characterization and modeling. Petrophysical calculations can be based on logs, core or cutting analyses, chemical analyses of reservoir fluids, or a combination of these. The primary objective of petrophysical calculations is to characterize the lithology of the various subsurface strata, evaluate reservoir parameters, primarily porosity and permeability, and estimate reservoir quality as a function of project requirements. These evaluations begin at the borehole and can be extended through either log correlations or extrapolation.

This process provides the initial building blocks for reservoir characterization. In conjunction with seismic data, it allows differentiation of various lithologic formations and provides the basic reservoir parameters, which are then modeled in 3D.