The WellTracer® (CO2 Tracer) Survey method provides a simple, inexpensive method for troubleshooting a gas-lift well. The method is performed while the well is in operation, and without the use of wireline tools. It may be used to determine the well’s lift-depth, whether gas-lift valves on a production tubing string are open or closed and certain producing characteristics of the well (i.e. multi-pointing).