1. A computer-implemented method for generating a facies definition, the method comprising: receiving well logging data indicative of one or more properties of geologic formations penetrated by one or more wellbores, wherein no assumptions are being introduced to the well logging data; determining a type well; developing an appropriate scaling of the well logging data based on the type well; creating a training set by drawing samples from the well logging data at random depths; modifying the training set to remove interfering data; performing an unsupervised classification procedure on the training set to group samples in the training set; comparing a suite of values of the well logging data in the groups to classify lithofacies of the type well; developing classification functions; classifying unknown wells using the classification functions to generate the facies definition; populating an earth model of the geological formations using the facies definition; determining a distribution of rock types within the geologic formations, based on the populated earth model; selecting a location for a new wellbore to be drilled within the geologic formations, based on the distribution of rock types; and drilling the new wellbore at the selected location within the geological formations.