New Interpretation Techniques for Predicting Pore Fluid, Lithology and Sw from Seismic AVO

            The prediction of lithology and pore-fluid properties using only seismic reflection amplitudes over a prospect is highly questionable, even if the seismic amplitudes are calibrated at a well location.   However, by comparing amplitude properties on the prospect to the same amplitude properties off the prospect at a down-dip brine-saturated location, predictions of lithology and pore-content are highly enhanced.

            In order to reduce interpretation ambiguity, Lithology and Pore-Fluid transforms are derived from well-log data.  It is shown that the AVO response (comparing the near-angle amplitude to the far-angle amplitude) is dominated by lithologic properties, thus the name, Lithology Transform.  Basically, the far-angle amplitude is linearly related to the near-angle normal-incident response (NI).  This linear relationship holds for high- to low-porosity sands.  Meanwhile, the pore-fluid interpretation is contained in a linear relationship of the NI for a hydrocarbon-charged sand to the NI for its equivalent brine-saturated state.  This linear relationship is called the Pore-Fluid Transform.  As an example, gas sands with a S_W=0.3 have a linear NI relationship to their brine-saturated NI regardless of the sand porosity.

Both the lithology and pore-fluid interpretations depend on NI values. What was lacking for many years was a method to determine the normal-incident values from the seismic amplitudes observed on the workstation.  To solve for NI values, a seismic interpretation technique is introduced that combines near- and far-angle horizon maps to yield a map whose values are estimates of normal incidence.  By comparing NI values at the prospect to NI values at down-dip brine-saturated locations, estimates of S_W are possible. 

Fred J. Hilterman received a geophysical engineering degree and PhD in geophysics from Colorado School of Mines (CSM). He worked with Mobil from 1963-1973.  In 1973, he joined the University of Houston where he was a Professor of Geophysics. At UH, Fred co-founded the Seismic Acoustics Laboratory (SAL).  In 1981, he co-founded GDC, now a subsidiary of Geokinetics where he is Chief Scientist.  Fred also lectures at UH where he is a Distinguished Research Professor.

Fred is a longstanding member of GSH, SEG, EAGE and AAPG and was the 1996-97 SEG President.  He received numerous awards from CSM and SEG including the SEG Maurice Ewing Award.