ABSTRACT

Sonic log span adjustment is achieved by using modern filter theory in which a filter, called a converter, is obtained via least mean squares deconvolution. This converter when convolved with one sonic tool vertical response produces another desired sonic tool vertical response of different span. The convolution is performed on digitized sonic logs using a high speed computer. The quality of the span adjusted sonic log, computed via such a procedure, depends on the ratio of the length of the sampling interval to the length of the desired final span. A low ratio tends to produce better quality results than a high ratio. A number of field cases are shown to illustrate the general quality of these computed logs. The types of error and distortion which can result and in particular the sensitivity of these results to the size of the sampling interval are discussed.

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