Distributed Temperature Sensing for Erosion Detection and DoC Estimation: The Peru LNG Experience in Ayacucho and Ica Departments

Pipelines often cross challenging terrains where natural hazards are the main risk for their integrity. Environmental conditions can also worsen over the infrastructure lifetime. To reduce the risk of disasters, integrity programs are developed and require tools for early detection of threats that can lead to a failure with dramatic social, environmental and economic consequences. Fiber optic based Geotechnical Monitoring System (GMS) have been used and implemented as an efficient prevention tools of these programs. As a good example, GMS is successfully in operation to detect landslides using Distributed Strain Sensing along the Sierra section of the Peru LNG pipeline since 2010. The continuous operation of the GMS also revealed that infiltration, erosion and sand dune migration can be detected using Distributed Temperature Sensing (DTS). First, hydraulic erosion was evidenced in the Sierra region. More recently, events whose origin is eolian erosion and sand dune migration have been identified. A thermal analysis was then conducted to analyze the measured thermal signatures of the detected event. It revealed that the DoC (Depth-of-Cover) can be computed from the temporal response of the fiber optic cable. The time lag between ambient temperature and temperature of the cable directly relates to its burial depth. The obtained data are compared with site inspection observation which confirm the validity of the DTS approach. The method, combining DTS measurements on existing communication cable with thermal analysis, offers the ability to monitor erosion related geohazards in both Sierra and desert sections of the pipeline. The results of the presented work illustrate the potential value of fiber optic sensing 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.