Pipelines are naturally vulnerable to operational, environmental and man-made effects such as internal erosion and corrosion; mechanical deformation due to geophysical risks and ground movements. This paper describes the on-line monitoring ofmultiple critical sections ofburied oil pipelines, part of Ecopetrol’s transportation network across the country, which were experiencing mechanical deformations due to local soil and geohazard effects using fiber optic strain sensors. Over 1,000 individual fiber optic Bragg grating (FBG) strain sensors were installed across 72 different sectors dispersed across the Colombian pipeline network. The system has been in service since 2013 and has helped provide early warning on several severe pipeline accumulated strain deformations and imminent ruptures, as well as to understand the mechanical behavior on buried pipelines under diverse soil geohazard conditions.

Many pipelines are built in regions affected by harsh environmental conditions where changes in soil texture between winter and summer increase the likelihood of risks. Pipeline routes also cross the mountains that are characterized by steep slopes and unstable soils as in the Andes and along the coastal range of Brazil. In other cases, these pipelines are laid in remote areas with significant seismic activity or exposure to permafrost. Depending on weather conditions and location, visual inspection is difficult or even impossible and therefore remote sensing solutions for pipes offer significant advantages over conventional inspection techniques. Optical fibers can help solve these challenges. Optical fiber based geotechnical and structural monitoring use distributed measurement of strain and temperature thanks to the sensitivity of Brillouin scattering to mechanical and thermal stresses. The analysis of scattering combined with a time domain technique allows the measurement of strain and temperature profiles. Temperature measurement is carried out to control soil erosion or dune migration through event quantification and spatial location. Direct measurement of strain in the soil also improves the detection of environmental hazards. As an example the technology can pinpoint the early signs of landslide. In some cases, pipe actual deformation must be monitored such as in case of active tectonic fault crossing. Pipe deformation monitoring operation is achieved by the measurement of distributed strain along fiber sensors attached to the structure. This paper comprehensively reviews over 10 years of continuous development from technology qualification and validation to its implementation in real cases as well as its successful continuous operation. Case studies present pipeline monitoring in Arctic and Siberian environment as well as in the Andes. They illustrate how the technology is used and demonstrate proof of early detection and location of events such as erosion, landslide, subsidence and pipe deformation.

The 408 km × 34" PERULNG pipeline (operated by Hunt LNG Operating Company) is monitored in its first 62 km by a geotechnical fiber optic cable, since these first 62 km are exposed to major geohazard threats such as landslides, large river crossings, high slopes, bofedales, etc. The fiber optic cable geotechnical monitoring relies on the measurement of strain and temperature in the pipeline right-of-way. Due to the continuous and real-time monitoring of the duct, it was possible to detect a tension cracking near KP 25 + 600 as an abnormal temperature change was captured by the temperature sensing cable; also near KP 27 + 900 and KP 34 + 750 unusual cable stresses were detected which announced landslides of the rotational type in both locations. In these three cases, protection decisions could be taken to secure pipeline’s integrity.

The Camisea Pipeline Transmission System (PTS), owned by Transportadora de Gas del Perú (TgP) in Peru, consists of two parallel pipelines, a Natural Gas (NG) pipeline and a Liquefied Natural Gas (LNG) pipeline. The NG pipeline is 834 km in length, including a 105 km loop. The LNG pipeline is 557 km in length. The first 210 km, are defined as having Amazonian geotechnical characteristics, with the presence of sedimentary and metamorphic rocks and a deposit of materials that are easily altered, which are associated with the transition between the Amazon plain and the Andes mountains. The area between km 210 and km 420 is defined as a mountainous sector with materials having better mechanical properties while the section between km 420 and km 730 located in the coastal sector and has erosive processes such as those associated with wind erosion, seismic activity, alluvial deposits, etc. Due to the variety of geological and geotechnical circumstances of the TgP’s RoW, its PTS incorporates many types of geotechnical monitoring in order to maintain and increase the reliability and integrity of the system. In several sectors not all of the types of monitoring are applicable. Some types of monitoring are: inclinometers and piezometers, aerial surveillance, patrolling, strain gauges (SG), topographic, GIS images (satellite, laser, radar, etc.), culverts, geotechnical optical fiber, accelerometer stations, etc. This article describes some unprovoked errors that can occur in a complex operation (in terms of logistics, geological, geotechnical and socially), in the development of geotechnical monitoring activities of an RoW. Some of the errors that can occur are: • Unacceptable photographic record through aerial surveillance; • Damage to the coating during topographic verification; • Field reports with incorrect data; • Incorrect SG records; • Improper placement of equipment over the pipeline; • Incorrect records in the GIS database; • Errors in the topographical record; and • Inexperience of monitoring staff, etc. However, occurrence of the above-mentioned errors has been lessened through improved operating procedures. These procedures are based on discussions from the various “lessons learned” sessions, which improved: • the appropriate recording of conditions identified in the field; • the labor climate; • crosswise communication between the different areas; and • the preventive approach within the operation of the PTS.

The present work introduces the technology background at the origin of FOPIMS (Fiber Optic Pipeline Integrity Monitoring Systems) with an emphasis on geotechnical monitoring. It shows how temperature sensing can be implemented to control soil erosion or dune migration through event localization and spatial quantification. Arctic pipeline monitoring project illustrates the application of soil erosion detection. Direct measurement of strain in soil also enhances environmental threat detection. Combined with temperature sensing, strain sensing composes the geotechnical monitoring system. Transandean pipeline monitoring examples are presented where the DITEST AIM was implemented for geohazard prevention. These study cases concern new pipeline installation as well as retrofit of existing lines. The technique successfully evidenced early events and allowed preventive measures to be taken. In some applications actual pipeline deformation need to be monitored. Such operation is achieved by measuring distributed strain along sensing cables attached to the structure. We show how such measurements complement the geotechnical measurements. We also describe a real implementation in seismic active area. As a whole, the work focuses on the technique principles, the installation and how the system is being implemented for pipeline preventive maintenance. We intend to present a comprehensive set of design guidelines based on real results and lessons learned from the various projects in what concerns geohazard detection and pipeline deformation monitoring.