The following pages will familiarize you with the basics of the geological interpretation of common logs as they appear on hard-copy blue-line logs (or their electronic raster copies). The lithologies considered are those common in sedimentary successions, with particular emphasis on sandstones, limestones, and dolomites, which have potential for oil, gas, or water production. However, other log keys are given of evaporite sequences and coal-bearing clastic successions. The logs used in interpretation are all measurements of nuclear properties, which are sensitive to both fluids and gases within the pore space and the mineral composition of the rock framework. They are the gamma-ray, neutron porosity, bulk density, and photoelectric index logs. These logs are available for thousands of wells across Kansas, either as paper copy, raster or digital logs. Mastery of the principles described in this tutorial and practice with the Oz Machine will give you a start with the skills to "read the rocks" from these wireline logs.