The use of production logs (P.L.) to evaluate perform- ance of oil wells and water-injection wells is reasonably well established and accepted. Evaluation of gas-well performance by production logging, however, is not so well accepted. A Logging project to study productivity of gas wells in the Quirk Field near Calgary, Alberta, using Schlumberger’s High Resolu- tion Thermometers (H.R.T.), was initiated in 1968. The Ther- mometers by themselves failed to give satisfactory results and two more P.L. devices – the Continuous Flowmeter (C.F.M.) and the Gradiomanometer (GM) – were added to the program to give thorough analysis of flow direction, type and rate.