Stratigraphic Correlation of Well Logs by Computer Techniques

Stratigraphic correlation by computer of two geophysical logs involved the vertical shifting of one log relative to another until their characteristics were aligned as indicated by the maximum value of the cross correlation function. Correlation of logs with different thicknesses of strata was more complicated and involved a two-step process: (1) resampling the log at an expanded or stretched interval, and (2) using the stretched log to determine the vertical shifting necessary to align the common characteristics of two logs. Models simulating geophysical logs and geophysical logs of actual sites in Indiana were correlated in the form of computer plots of the logs. Correlation lines were drawn in the plots to connect equivalent units of strata in each log.