A professional who analyzes mud and drill cuttings that are circulated through oil- or gas-well boreholes during drilling operations, using special testing equipment, to detect presence of oil or gas, and interprets findings to locate productive stratum. Responsibilities include:

• Attaches pump-stroke counter, mud-tank level indicator, and other measurement devices to drilling rig equipment, and connects electrical conductor cables to measurement devices and drilling rig monitoring instruments to prepare field laboratory for testing of mud and well cuttings.
• Detects presence of gas in mud by reading dial of gas-detection meter hooked up to detection devices in mud.
• Collects mud and drill cutting samples during drilling operations, and inspects samples to determine nature of earth formations encountered and presence of oil or gas in formation, using ultraviolet light, microscope, and other laboratory equipment.
• Keeps records of dial readings and tests made, and calculates depth of formations found to contain gas or oil.
• Performs minor repairs to electrical and mechanical equipment.