Porosity Prediction From Seismic Data*

A bstract The inversion of seismic traces allows the estimation of reservoir porosity from an analysis of transit times derived from the pseudo‐velocity logs. A four‐step computational procedure is illustrated consisting of (i) inversion of seismic traces and calculation of interval velocities; (ii) accurate stratigraphic interpretation; (iii) determination of the petrophysical parameters for the porosity evaluation; (iv) analysis of the reliability of the results and final corrections. Both the possibilities and the limits of the method are discussed. One of the causes of error is the fact that impedances—and not velocities—are readily obtainable from seismic data. Moreover, the porosity due to fracturation contributes only slightly to velocity, while it often contributes most importantly to the permeability. Results are shown for two of the most significant reservoir types, i.e. carbonatic and clastic. Two cases belonging to the latter type will be examined. In the first case the primary porosity is dominant. The second case is very complex and both primary and secondary porosity are present.