Final Comments and Future Expectations
As noted earlier in Fig. 1.B.5, the beginning of the second era of amplitude interpretation is keyed to Ostrander’s 1982 verification of AVO with prestack field data tied to drilling results. Since that time, the field of amplitude interpretation using AVO has been a fertile area of research, discoveries, and practical applications. The interpretation procedure in Fig. 8.A.1 outlines the AVO philosophy on validation that was followed in these notes. The sections in these notes on petrophysics, modeling, and amplitude attributes were key items that were discussed to reach the goal of validation through “Compute and Compare,” as defined in Fig. 1.A.3. However, this amplitude procedure is not new—it is almost identical to Pan’s amplitude procedure of the 1970s (Fig. 1.B.4). Little has changed in our validation philosophy. Only the available amplitude attributes have changed. Figure 8.A.2 summarizes some of the amplitude attributes that were developed or expanded in this second era of amplitude interpretation. Starting with the CDP gathers, there are two paths that can be followed in the figure. The path on the right of the figure provides the more robust attribute estimates. As one proceeds downward in either path more information to distinguish pore-fluid and/or lithology is derived from the amplitude attributes. At the same time, though, more interpretative bias is added to the amplitude interpretation in the downward path. This is not necessarily an unwanted result if petrophysical constraints are available. However, the interpreter must always be cognizant of the assumptions and interpretative bias that the amplitude attributes contain.