Abstract: The complex tool for well monitoring comprises a cylindrical housing and at least two lever centralizers aligning the tool along a well axis. Each centralizer has at least three levers, as well as at least one fluid flow temperature sensor, at least one phase composition sensor and at least one thermal flow velocity sensor, all sensors are located on an axis of the tool. The tool also comprises at least three groups of sensors distributed around a perimeter of the wellbore when the levers of at least one centralizer are being opened. Each group of the sensors comprises at least a fluid flow temperature sensor, a fluid phase composition sensor and a thermal flow velocity sensor, disposed on the same line parallel to the axis of the tool.