Preliminary results for the diffusion of water into fibre optic oil well sensors

Description/Abstract

Preliminary results are presented on a measurement technique for determination of water penetration into fibre optic sensors under high pressure, high temperature conditions. Both fibre optic sensors and communication fibres were subjected to prolonged treatment in heavy water at temperatures up to 250°C and pressures of 40 bar. Deuterium penetration is measured by a nuclear reaction technique based on a 3He micro-focussed ion beam, which permits two-dimensional mapping of the deuterium penetration into cleaved fibres. Water penetration can be detected whilst still confined to the cladding, well before any optical effects become apparent, permitting prediction of likely fibre lifetime under down-hole conditions after realistic experimental times.