Subsea Sensors for Non-Intrusive Monitoring of Temperature, Pressure and Asset Integrity

Abstract

The growth in deep water field developments and the need for increased oil recovery with reduced capital expenditure are pushing the technical boundaries of subsea asset design. One of the challenges facing these new developments is monitoring the structural health of their subsea production asset in an inherently inaccessible location. This is usually done through structural modeling and either spot monitoring campaigns using MEMS accelerometers or through subsea conventional strain gauges. Both technics present weaknesses: MEMS sensors usually require a great deal of data processing to obtain functional strain information at a desired location and strain gauges are complicated to install in a marine environment, many failing during pressure testing or installation. Both are also suseptible to electromagnetic fields which can biais their measurement. This paper presents details of a new non-intrusive integrity monitoring sensor systems recently deployed in the Gulf of Mexico and West Africa on production lines. Inherently reliable, as presenting no moving parts, these sensors use optical fibers embedded within a composite frame for their measurements. Using field proven subsea fiber optic mapping technology these systems have delivered high frequency un-biaised, on the pipe, strain from which is derived pipe bending and axial loading in addition to temperature and pressure monitoring.By providing electromagneticly immune, low noise, un-biaised, strain measurements to structural engineers to verify and improve their fatigue behaviour models, the non-intursive integrity monitoring system has proven a reliable alternative to MEMS and strain gauges. Furthermore unlike alternative solutions, this system also monitors pressure, illustrating this technology's capability at providing production and flow assurance data in addition to integrity data making it an ideal tool within a subsea production surveillance strategy.