With millions of fuel storage tanks and oil pipelines installed around the
world, there is inevitably frequent leakage of potentially hazardous hydroc
arbons. As many of these installations are below ground, it can often be ma
ny years before the extent of the leak is discovered. We have previously re
ported the development of a sensor for the detection of such subterranean l
eaks, using infrared reflectometry to interrogate a hydrocarbon sensitive m
embrane. However, a single sensor cannot provide any information about the
flow rate or direction of the leak. This paper describes the extension of t
he technology to a multi-channel distributed sensing system, using optical
fibres capable of distributing the sensors over large subterranean areas. R
esults are reported from the evaluation of the device, which consisted of m
onitoring the movement of different hydrocarbons (gasoline, diesel and insu
lating oil) through a vertical sand-filled vessel.