A new classification for AVO (amplitude versus offset) is proposed that considers all clastic reservoirs regardless of the polarity of impedance contrast with the overlying shale or its change with increasing offset. The new classification includes ten classes of AVO types.

Examples from the Gulf Coast illustrate the application of this approach in exploration for pressured Wilcox objectives: typical, type II and less-common, type III AVO responses can be productive. Other examples include a classic “AVO-flip” where pressured, brine-filled sand has a negative AVO response and the gas-filled case has a positive AVO response.

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