Abstract: The present invention addresses to a method for the identification of operational problems based on the hydrodynamic characterization of the gas-lift and production well/lines set, by means of the injection of an alcohol, preferably ethanol, in the gas-lift line. The detection of the passage and the return of the alcohol is carried out by the direct analysis of information about the process variables (pressure and temperature at the bottom of the well, at the Christmas tree and at the surface, gas or liquid flowmeters, etc.). Preferably, this detection should also be confirmed by measuring the alcohol concentration at the return, either by sequential collection of samples of the liquid produced by the well and subsequent physicochemical analysis in the laboratory, or by an online meter specially installed for this purpose. A practical sample collection procedure has been developed for application together with this invention.