METHODS AND APPARATUS FOR MEASURING RETURN FLOW IN A WELL

The invention provides apparatus for use in a wellbore made of a casing and an annular with a fluid within, comprising: a reel of wound optic fiber line fixed to an object within the casing, and a light transmitter/receiver device able to generate a signal through the optic fiber line and to measure a change of said signal; wherein the optic fiber line is: (a) on a first position fixed to a reference point linked to the light transmitter/receiver device, and is (b) on a second position unwound from the reel; wherein the light transmitter/receiver device is able to measure the change of said signal when occurring at the second position; and the apparatus having a system able to measure the flow rate of the fluid exiting the annular at the surface level Q.