A mud logger in a modern oil field drilling operation is an employee who determines positions of hydrocarbons with respect to depth, identifies downhole lithology, monitors natural gas entering the drilling mud stream, and draws well logs for use by oil company geologists. Rock cuttings circulated to the surface in drilling mud are sampled and analyzed. (Under some circumstances compressed air is employed as a circulating fluid. And although most commonly used in petroleum exploration, mud logg… (More on Mudlogger)