OPTICAL PROCESSING AND INTERPRETATION

Although the use of optical techniques for enhancing seismic data has become well established, the applicability of these techniques to seismic interpretation is not so widely recognized. Optical processing is ideally suited for use as a direct aid to interpretation because of the precision with which filtering can be controlled and because of the flexibility made possible by the instantaneous visual presentation of the filtered data. Frequency relationships in seismic data have great value in interpretation, and optical techniques are particularly suitable for bringing out such relationships. The one‐dimensional optical transform displays a channel‐by‐channel spectrum of a seismic section from which useful geological information can be inferred. On such transforms significant effects can often be brought out which are not discernible on the corresponding record sections. Reefs, for example, often cause a thinning of overlying formations which gives rise to a high‐frequency anomaly on the transform, even at levels so shallow in the section that no evidence for reef effects is apparent to the eye on the original records. Characteristic frequency anomalies can also be observed over faults. One‐dimensional transforms from sections made over features of both kinds show diagnostic patterns that can be used as a basis for detection. The sharp cutoffs and flexibility available in optical filters make it possible to discriminate between conflicting events on record sections by frequency filtering alone. With proper monitoring, one can select those cutoff frequencies which bring out events that appear geologically most plausible. Multiple reflections, for example, can often be eliminated by frequency discrimination once the geophysicist identifies the primary reflections on the monitor. Often seismic records are discarded as useless, when in reality they are simply too complex to interpret because a large number of events, all potentially significant, overlap. Such events can be sorted out for possible use by optical filtering and concurrent monitoring. No other processing technique allows the geophysicist to do this so easily.