Triphasic Production Log using PLT with Electrosumergible Pumps (ESP).Application and Results of Campaign in YPF 2012-2014 Mature fields have a great economical potential if his operation are optimized properly. In recent years the water balance and management to improve the Oil Recovery are worldwide growing concern in nowadays production strategies. In field maturation process, the growing production of water is a key element in term of management involving critical early upstream decision. The companies need to face the dilemma of justifying more drilling means more water to accommodate. Do not properly manage the water balance can turn an economic field in marginal. YPF is the biggest oil field company in Argentina and have to face this dilemma, since 2012 has been started to search a realistic solution for production optimization. The solution is technologies that allow obtain a detailed production logging on none naturally flowing wells with artificial lift systems where the access with Y-Tool was not possible. The collaborative effort gave birth of a solution technology, a multi disciplinary technique that allows for real time diagnosis of three phase production logging below electro Submergible Pump in no naturally flowing wells for insitu determination of water/oil and gas producing zones. YPF has been testing since 2012 this technology in different mature fields in Mendoza, Neuquén and Chubut. This paper describes the design-execution, evaluation and results of the application of this technology in YPF.