A professional who measures sonar, electrical, or radioactive characteristics of earth formations in oil- or gas-well boreholes to evaluate productivity of oil- or gas-bearing reservoirs, using sonic, electronic, or nuclear measuring instruments. Responsibilities include:

• Signals hoisting engineer (any industry) to lower instruments into well, observing oscillograph and meters on control panel to verify operating condition of instruments.
• Turns dials on control panel to adjust instrument for specified recording and starts recording device when instruments reach bottom of borehole.
• Prints copies of recorded graphs in truck darkroom (developer (photofinishing)).
• Interprets graphs for customer to indicate identity, porosity, oil- or gas-bearing content, and productivity of geological formations.
• Measures borehole diameters, direction of borehole, and inclination of geological strata, using microcalipers, directional indicators (clinometers), and dipmeters.
• May be designated according to measuring instruments used as Acoustical Logging Engineer; Nuclear Logging Engineer.