Abstract
The article aims at demonstrating that distributed temperature sensing (DTS) using telecommunication cable laid along a pipeline can detect the early signs of erosion. It shows that the technique not only applies to both hydraulic and aeolian erosion, it also allows the localization of the event and the estimation of its severity.
The article introduces the physical principle behind the proposed detection solution. It reviews the heat propagation theory that sustains the approach for any water saturation conditions and soil type. It describes distributed temperature sensing capability and its uniqueness to measure and locate temperature events with meter accuracy. The technique is then validated by analyzing temperature data collected along a Natural Gas Transport System instrumented with DTS. These observations are compared with periodic surveys conducted by the operator integrity team.
FO based geotechnical monitoring is successfully used in operation to detect landslides along the Sierra section of the Peru LNG pipeline since 2010. These natural hazards are not the only ones threatening the pipeline. First, in the Sierra region, it is common to observe severe hydraulic erosion during the rainy season. Second, the coastal section, which is a desert, experiences other phenomenon such as sand dune migration and eolian erosion that put the pipeline at risk. DTS instrumentation measures continuously and automatically the fiber optic communication cable. The analysis of the monitoring data in both regions shows the detection of very localized events. Their spatial and temporal signatures are analyzed. The comparison of these data with thermal models identified sections that are near to be exposed or whose soil cover is less than 50cm over a spatial extension that does not exceed a couple of meters. Depth of cover of 10 to 30cm are estimated from such analysis. These results are confirmed by past and ongoing site inspections.
The successful detection and localization of hydraulic and aeolian erosions and confirm the value of DTS to mitigate geohazard risks. It not only enhances the efficiency of the integrity program detecting and localizing threats, it also improves and rationalizes the maintenance activities as focused surveys can be conducted.
