The Contribution of Logging Data to Sedimentology and Stratigraphy

Until recently, the lithology and sedimentology of formations penetrated by a well could be studied only through the analysis of cores. Now a technique has been developed using multivariate analysis of logging data to give a high-resolution sedimentological description of any sequence of formations. The number of different logs and their range allow determination of many of the physical characteristics of the rock. The definition of a lithofacies has been extended by introducing the concept of an electrofacies, constructed on the basis of all the logging data at any depth interval. Thus, each logging datum is considered a descriptor for purposes of establishing electrofacies in a logged interval. Once established, electrofacies then can be correlated with actual geologic facies, if the logged interval has been cored.