A recent development in digital process technology yields synthetic sonic logs from seismic reflection data recorded at the ground surface. Synthetic sonic logs are similar to, and have most of the properties of, long source-receiver borehole sonic logs. The synthetics have been found to be particularly useful for the delineation of petroleum reservoirs, including the extent, thickness, and porosity of the reservoir rocks.

In a typical survey, field data, obtained from seismic line profiles across reservoirs, yield a sequence of synthetic sonic logs. Continuous vertical cross sections which display color-coded transit time units can be interpreted in terms of lithology, porosity, and related subsurface information, within the limits of interpretation of the single sonic curve and the resolution of the method.

Applications include the optimization of development drilling patterns to obtain maximum production, the design of secondary recovery programs and the positioning of injection wells, and the location of offshore drilling platforms to ensure maximum recovery.

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