An apparatus and method of sensing fluid flow are provided to measure fluid flow
rates in production tubing, pipelines, open wells and tunnels. The proposed invention
takes advantage of a sensor with processing means to interpret the fluid flow rate,
the sensor being responsive to the mechanical perturbations of the sensor itself
arising from the impingement of turbulent fluid flow on the sensor. In operation,
the sensor is mounted in the fluid flow such that the fluid flows through an aperture
in the sensor and/or around the outside surface of the sensor. The sensor of the
invention bears definite advantage over known sensors and it is particularly suited
to downhole oil and gas applications. Preferably, the invention employs fiber optic
sensing techniques which are amenable to multiplexing a plurality of the sensors
with long down leads. Such an arrangement is robust to withstand the high temperature
and pressure environment. Advantageously, the invention allows non-intrusive measurement
of fluid flow in production pipes and measurement of differential fluid flows along
perforated casing or open well sections in the pay zone.