Apparatus, a production string comprising the apparatus, and a method for estimating a production flow rate at a certain position of a well

An apparatus for estimating a production flow rate at a certain position of a well, the apparatus comprises:

• a pipe for forming part of a production string in a wellbore, the pipe having a first end portion and a second end portion,
• a compartment arranged on an outside portion of the pipe, the compartment houses a source of releasable tracer, wherein the pipe is provided with at least one first passage through a wall of the pipe for communicating a portion of a wellbore fluid into the compartment, and-a least one second passage for communicating the portion of the wellbore fluid that has passed through the first passage, and tracer being released from the source of tracer material, back into the pipe, wherein the portion of wellbore fluid within the pipe is urged through the compartment by a non-movable flow diverter provided at least at one of the at least one first passage and the at least one second passage, and wherein the flow diverter and the passages are configured so that, in use in a producing well, a ratio between a flow (Fi, Fo) through the compartment and a flow (F) through the pipe is constant, wherein said constant ratio is known from tests and/or calculations.