Poroelastic analysis of amplitude-versus-frequency variations

摘要

Although significant advancement has occurred in theinterpretation of seismic amplitude-variation-with-offsetAVO anomalies, a theory is lacking to guide the interpretationof frequency-dependent seismic anomalies. Using analyticequations and numerical modeling, we have investigatedcharacteristics of the normal-incident reflection coefficientNI as a function of frequency at an interface between anondispersive medium and a patchy-saturated dispersive medium.Because of velocity dispersion, the variation of NImagnitude is divided into three general classes. These classesare 1 low-frequency dim-out reservoirs, in which NI magnitudedecreases toward lower frequencies; 2 phase-shiftreservoirs, in which NI is a small negative value at low frequenciesbut becomes positive at higher frequencies; and 3low-frequency bright-spot reservoirs, in which NI magnitudeincreases toward lower frequencies. This classification couldprovide insight for frequency-dependent seismic interpretation.