The Wapiti River South Slope (the Slope) near Grand Prairie, Alberta, Canada, is 500 m long and consists of a steep lower slope and a shallower upper slope. Both the upper and the lower slopes are located within a landslide complex with ground movements of varying magnitudes and depths. The Alliance Pipeline (Alliance) NPS 42 Mainline (the pipeline) was installed in the winter of 2000 using conventional trenching techniques at an angle of approximately 8° to the slope fall line. Evidence of slope instability was observed in the slope since 2007. The surficial geology of the slope comprises a colluvium layer draped over bedrock formation in the lower slope, and glacial deposits in the upper slope. Available data indicated two different slide mechanisms. In the lower slope, there is a shallow translational slide within a colluvium layer, and in the upper slope there is a deep-seated translational slide within the glacial deposits. Both the upper and lower slope landslides have been confirmed to be active in the past decade. Gradual ground displacements in the order of several centimeters per year were observed in both the upper and lower slopes between 2007 and 2012. Large ground displacements in the order of several meters were observed between 2012 and 2014 in the lower slope that led to the first stress relief and subsequent slope mitigation measures in the spring and summer of 2014. Monitoring of the slope after mitigations indicated significant reduction in the rate of ground movement in the lower slope. Surveying of the pipeline before and after stress relief indicated an increase in lateral pipeline deformation in the direction of ground movement, following the stress relief. This observation raised questions regarding the effectiveness of partial stress relief to reduce stresses and strains associated with ground movements. Finite element analysis (FEA) was conducted in 2016 to aid in assessing the condition of the pipeline after being subject to ground displacements prior to 2014, stress relief in 2014, and subsequent ground displacement from July 2014 to December 2016. The results and findings of the FEA reasonably matched the observed pipeline behaviour before and after stress relief in the lower slope. The FEA results demonstrated that while the lateral displacement of the pipeline, originally caused by ground movement, increased following the removal of the soil loading during the stress relief, the maximum pipeline strain was reduced within the excavated portion. The FEA was also employed to assess the pipeline response to potential ground displacement scenarios following December 2016. For this assessment, three ground displacement scenarios that comprise different lengths of the pipeline were analyzed. An increased rate of ground displacement, with a pattern that matched one of the analyzed scenarios, was observed in the upper slope in the spring of 2017. The results of FEA were used to assess the pipeline response to the increased rate of displacement in the upper slope. Subsequently a decision was made to stress-relieve the pipeline. The second stress-relief was conducted in the summer of 2017. This stress relief was conducted locally at the toe and head of the active slide in the upper slope, where the FEA showed the greatest stress concentrations in the pipeline.

Geotechnical monitoring based on optical fiber sensor technology has been used over more than a decade to detect hazards than can affect the integrity of pipelines. In particular when these sensors are implemented in the form of distributed temperature and strain sensors, respectively known as DTS and DSS, they provide information about hazard location and spatial extension. In addition, these sensors can capture the speed at which the event developing in particular when implemented as a permanent monitoring solution. So far these sensors were implemented as part of an alarming system detecting events such as landslides, erosion and subsidence. The current work aims at presenting simple method to extract additional information about the hazard such as the amplitude of the soil displacement in the case of landslides and subsidence or dirt cover for erosion. Estimation of stress in soil is also discussed based on the cable strain-stress relation obtained from the sensing cable qualification. The approach is validated by academic works conducted in parallel of the technology development. The method use is then illustrated by its application to field data collected from several events occurred over the past 10 years.

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 Weather and External Forces hazard (WEF) is considered in ASME B31.8 as a non-time-dependent hazard due to its random nature and the high uncertainty of the effects on pipelines given the occurrence of natural events, especially associated with hydro and geotechnical processes. Although there is a wide range of events associated with geological, hydrological and hydraulic conditions (among other things) that can affect a certain infrastructure, only a limited number of these geohazards can cause direct damage to hydrocarbon transportation infrastructure. The identification and understanding of a ground failure process and its association with the susceptibility or physical fragility of the pipeline facing the potential adverse effects of a hazard event, allow to estimate the conditional probability of pipeline failure under loading stresses induced by the event and to estimate the actions needed to mitigate this hazard with methodologies ranging from approaches of structured expert knowledge to methods of structured analysis that incorporate incorporating subsurface investigation, detailed study of the results from terrain monitoring, pipeline and triggering agents through mechanical modeling. This document presents a technical proposal for the management of geohazards which, due to the nature and characteristics of the instability processes and its relation with the activity of triggering agents, and the vulnerability of the pipeline, allow them to be analyzed as time dependent.

Hydrocarbon pipelines are exposed to hazards from natural processes, which may affect their integrity and trigger processes that have consequences on the environment. Among the natural hazards are the effects of the earthquakes, the neotectonic activity, the volcanism, the weathering of soils and rocks, the landslides, the flows or avalanches of mud or debris, the processes related to sediment transport such as the erosion, the scour by streams, the floods and the sloughing due to rains. Those processes are sometimes related to each other, e.g. the earthquakes can produce slides, or movement of geological faults, or soil liquefaction; the rain can trigger landslides and can cause avalanches and mudslides or debris flow; the volcanic eruptions can originate landslides and avalanches, or pyroclastic flows. Human activities can also induce or accelerate “natural” processes that affect the integrity of the pipelines. The strength and stiffness of the pipelines allow them to tolerate the effects of natural hazards for some period of time. The amount of time depends on the strength and deformability, the stress state, the age, the conditions of installation and operation of the pipelines and their geometric arrangement with regard to the hazardous processes. In the programs for pipeline integrity management, the risk is defined as a function that relates the probability of the pipeline rupture and the consequences of the failure. However, some people define risk as the summation of the indicators of probability and consequences, such as a RAM matrix. Others define the risk as the product of the probability of failure times the cost of the consequences, while the overall function used to evaluate the rupture probability of a pipeline facing hazards considered in the ASME b31.8 S standard includes all the elements involved in the failure process. In that standard, for the specific analysis of natural hazards, it is proposed that the function is separated in the two following principal elements: the probability of occurrence of the threatening process (hazard) and the pipeline’s capacity to tolerate it. In this paper a general function is proposed, which is the product of the probability of occurrence of the threatening process, the vulnerability of the pipeline (expressed as the fraction of the potential damage the pipe can undergo), and the consequences of the pipeline failure (represented in the summation of the costs of the spilled product, its collection, the pipeline repair and the damages made by the rupture).

The present paper presents the analysis, carried out by the Ocensa pipeline, against a case of longitudinal or axial landslide to the pipeline in the KM 35 + 690, starting from the identification by inertial tool, the geotechnical characterization and the analysis of Soil-pipe interaction, excavation and stress relief and the techniques used to mitigate the effects of sliding on the pipe.

Pipelines crossing mountainous areas are susceptible to ground movement loading from landslides. Structural analysis of pipeline performance from landslide loads is critical for making decisions on the requirement and timing of intervention activities. Current analytical assessment methodologies for pipelines affected by ground movement tend to assume the landslide as an abrupt boundary from the stable region to moving ground, causing an over conservative estimation of the condition of the pipeline. In-line inspection using inertial mapping tools provides invaluable information to assist in the determination of the current pipeline integrity but does not provide a complete picture because axial loads are not defined. Interpretation of in-line inspection data allows the estimation of a transition zone width between stable and unstable ground, where there is a progressive increase in ground movement. Due allowance for the transition zone can remove conservatisms in the assessment methodology and allow a pipeline integrity plan to be created. This paper investigates the influence of landslide transition zone dimensions on the pipeline response and a methodology is developed for the prediction of the transition zone width. The interaction between the ground and the pipe movement is modelled using finite element analysis techniques. The definition of the transition zone properties provides a more reliable prediction of the pipeline performance and enables the current and future pipe integrity to be established with greater confidence.

The transportation system for hydrocarbons consists of an important and complex network of pipelines used by oil and gas logistics companies, designed to quickly and efficiently transport oil and gas from its origin, to areas of some demand along territory where operates. Currently Brazil has 15,000 km of transportation pipelines within about 7,500 km of right-of-way pipelines. Along its territorial extension it faces several influences along its route, being the main ones influenced by the external hazards from nature and by third party actions. TRANSPETRO has about 450 water crossings in cataloged water bodies currently. These crossings are currently characterized only according to their geometric characteristics, not considering several aspects inherent to them. The inspections at these crossings are laborious and have a high cost due to necessity of divers and bathymetry in some cases. To monitor the condition of all pipeline water crossings it is important to ensure the pipeline integrity. Depending on hydraulic phenomena, it is possible result in an exposure of the pipelines, free spans, changes in the original pipeline or excessive vibration. These changes can generate high mechanical stresses with both static and dynamic loads. The present study was characterized by the development of a methodology for assessing the susceptibility to the exposure of pipelines as a result of the hydrological hazards present at the crossings in which they are found. Moreover, this evaluation methodology offers a tool to define inspection extent and frequency, as well as the corresponding risk control actions. For this purpose, a pipeline management program has been set up, which consists in the definition of water crossings that constitute a potential hydrological hazard and where they can interact with the pipeline considering the probability of a specific hydrotechnical hazard leading the pipeline the exposure. As a result of this research it was defined a methodology to characterize pipeline crossing areas as well as field survey, evaluation of the susceptibility of pipeline exposure at crossings and the programming of control actions were defined according to the susceptibility found. Finally, the study has also presented a cost analysis of crossings inspections comparing the traditional method to the new premises adopted in this project.

The OCENSA pipeline crosses the Valley of the Magdalena river flood on its way to the Caribbean Sea, the area of the valley is commonly inundated during the rainy season on shallow waters that remain flooded swamps. These swamps soils are composed by extremely soft peat with thicknesses greater than 15 meters. In June 2016 started the construction of a highway with an embankment of 6 meters in height which was more than 30 meters away from the OCENSA 30” pipeline, Due to the high compressibility of peat, to construct the road the soil is subjected to a process of consolidation and the height of the embankment was corrected adding more material. In July 29 2016 occurs a failure by load capacity on the ground under the embankment and as a result of this fault a lateral displacement of the adjacent soil producing a horizontal displacement in the pipeline of more than 50 cm. This document shows results from the affectation to the pipe and the measures taken to correct the situation.

The OPASC and the OSPAR are 10″ and 30″ pipelines, respectively, which interconnect the State of Santa Catarina and Paraná, crossing the Serra do Mar, in southern Brazil. In 2003, after conducting slope stabilization works on a point of geotechnical activity, vibrating string gauges were installed to monitor the stress in these pipelines, in addition to geotechnical instruments installed to monitor the slope. These gauges were installed in seven sections, with 3 instruments per section, along a span of 180 meters. Although the geotechnical instrumentation has shown no evidence of movement in the slope, the gauges recorded an increase in stress values in some of the sections within three months from the time of installation, however, they remained stable in their values for the next ten years. In 2013, blind hole tests were performed to determine the stresses in these sections and to verify the proper function of the gauges. The combination of these two measurement techniques, vibrating string gauges and blind hole tests, allowed for the determination of the stress state in sections, over time. From there, equivalent stress could be determined and compared with allowable stresses defined in standards. After the completion of the blind hole test and subsequent backfill, stress rose again at the same rate, returning to the level reached after the initial installation of the strain gauges. To reduce the stress level additional excavations have been made to relieve the stress on the pipeline, followed by backfilling performed in a controlled manner in order for the soil to properly compact, which reduced the stress value over the pipes. The graphs depicting variation over time of stress showed a significant reduction in the level of stress after the backfill. The main conclusions are listed as follows: a) the evolution of stress observed by the extensometers was primarily caused by pipeline settling; b) the vibrating string gauges are functioning properly and provide reliable readings even after ten years of service; c) the blind hole testing performed in conjunction with monitoring by vibrating string gauges can provide approximate values of the full stress state; d) after stress relief, backfilling of the trench must be carried out by compacting the soil beneath the pipe in order to reduce bending stresses due to the weight of the soil; e) backfilling of the trench, when not properly performed, can cause compressive stress in bending, reaching 390 mPa over the next few months.

Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.

ECOPETROL S.A. has been working since 2006 in Pipeline Integrity Management Process. In that process, the threat related to climate and external forces play an important role, because of the vulnerability of ECOPETROL pipelines to this threat, not only by the geomorphology of Colombia, but also because of the strong impact of climate phenomenon such as “La Niña”, that consists in an unusual quantity of rain precipitation, represented in the increasing of slopes instability that affects the rights of way. Due to these events and the evolution of optical strain sensors monitoring technology, ECOPETROL has introduced an instrumentation pipeline program for monitoring the strain and advanced in the understanding of the behavior of pipelines. This paper describes the technology selected, the criteria used to select the monitoring sites and the thresholds stress/strain. The results of monitoring are discussed for a particular case.

The principle of redundancy in the analysis of pipeline integrity has taken on particular significance in recent years, thanks to the integration and relating of information obtained from various sources, which include, smart pig runs, visual right-of-way inspections and monitoring of the land and the pipeline. This document contains information related to the monitoring and analysis prior to emergency actions taken in the case study presented, located in northeast Colombia, where the effects of mining activity and excess rain during the winter period of 2010–2011 combined. The integrity information available with regard to background, visual right-of-way inspection, threat and risk assessments, direct monitoring of the pipeline and the analysis of deformation by bending, which Ecopetrol’s Office of Vice-president for Transportation and Logistics (VIT) made at the site, was taken into account. In addition, it includes a description of the interrelationship of such information, the findings in the activities conducted during the attention to the site, for the purpose of identifying the evidence related to external loads exerted by the land in the soil-pipeline interaction, which made it possible to better determine the proposed plan of action. The redundancy in the analysis of this information makes it possible to more accurately determine the root cause of the problem, the interaction between the phenomenon (external load - geotechnical event) and the pipeline, by which attention was directed in the field and action plans were obtained that better mitigate the threat and guarantee more safe and reliable operation.

By their nature, Pipeline Transmission Systems are exposed to threats from various sources. These include the threat of Weather and Outside Forces (WOF), this threat has a destructive potential associated with landslides, creeping, soil erosion and scouring in rivers, etc. Their hazards increase when pipelines are installed in areas with a tropical climate, having rains of a magnitude that often tend to destabilize the soil surrounding the pipelines, affecting its integrity and therefore the safety of people and the environment. The identification and monitoring of geotechnical risk areas, using inertial data, is based on the reprocessing and analysis of the raw data provided by in line inspection tools. The result of this analysis, after the noise reduction process using a variety of filters at different intervals, reveals areas where there is possible deformation. These zones are transformed into indications that are studied by an analyst, correlating other data sources such as terrain topography, soil characteristics, hydrology, ground motion records, ILI records (caliper records, MFL records, etc.), as-built data, stress concentrators, etc. The analyst determines if they are pipeline deformations due to soil movement or if the indication is caused by another source such as the noise caused by the electronic components of the tool, the operating conditions during the inspection, the filtering process, etc. Areas with signs of strain are evaluated to determine the tensional state in critical conditions for each specific case. If the stresses are close to the limits, a field inspection and an action plan are needed for each case. In certain cases, according to the experts, field indications are evaluated to verify the data obtained by the ILI Tool and to simultaneously give feedback to the noise reduction process. The execution of the calculation process allows the monitoring and identification of geotechnical risk areas, providing better control over parameters such as limits for reporting indications, control of discrimination and selection criteria, detailed assessment of each indication, etc. Finally, this process provides the opportunity to obtain additional information from the ILI inspection such as unregistered bending, misaligned welds, areas with excess root welding, etc.

The strength and stiffness of the pipelines allow them to tolerate the effects of natural hazards for some period of time. The amount of time depends on the strength and deformability, the stress state, the age, the conditions of installation and operation of the pipeline and their geometric arrangement with regard to the hazardous process. Accordingly, some of the hazards due to weather conditions and external forces would not be time independent. In consequence the designing of monitoring systems to predict the behavior of the pipelines against natural hazards is required in order to carry out the preventive actions which are necessary to avoid failure of the pipes due to the exposition to those hazards. In this paper a method for assessing the transport system vulnerability is developed, a function for risk analysis is proposed (which is determined by the probability of the natural hazard, the pipeline’s vulnerability to the hazard and the consequences of the pipe rupture). The elements that are part of that evaluation are presented and illustrated by means of examples.

In-line inspection by inertial mapping techniques is an essential tool for pipeline operators in areas susceptible to geohazards. The detection of previously unknown movements can provide early warning of the presence of a hazard. Positional change and the nature of the loading process can be monitored using the results of multiple inspections over time. Structural modelling is required to fully evaluate the integrity of the pipeline and whether a failure condition is being approached. Finite element techniques can be used, including the effects of soil-pipe interaction, axial forces and operational loads. This enables the prediction of future performance, based on trends from multiple inspections, so that mitigation or intervention methods are efficiently designed and scheduled. This paper considers some key aspects of the analysis process. The use of ILI mapping data to detect small movements below the tool measurement tolerance is examined. The importance of structural analysis is demonstrated by consideration of the axial force component. The inherent variability of the soil surrounding the pipe and its influence on the load transfer effects is illustrated, together with the issues of significant interaction within the transition zones of landslides or faults.

Gasoducto del Pacífico is a pipeline that carries natural gas from southern Argentina to Chile, through the Patagonian Andes. During previous years of operation only minor sign of soil movement were registered by the monitoring program, taking the form of ditch settlements. However, on September, 2005 a landslide took place producing a gas leak, at a segment that was previously characterized as a non-critical one. An initial office review of available information and site pictures would not yield a clear reason of land movement initiation given the terrain mild slope. Actions were taken aiming at three different time frames. Immediate remedial actions were taken such as ditch opening to free stresses and replacement of buckled pipeline. Integrity specialist flew to the site to conduct geological survey and a stress analysis was conducted at a lab, allowing to asses and manage present risk before transportation began. Mid-term solutions were implemented as the ditch remained open until the next summer season, when access to the site was guaranteed. Finally, two new river crossings were constructed to mitigate this natural hazard permanently. Lessons from this incident revealed design aspects that need to be reconsidered to assure mountain pipelines integrity.

The experience gained during the operation and maintenance activities on the Camisea Pipeline Gas Transport System (SDT) owned by TGP in Peru — which goes from the Amazon rainforest in the region of Cusco to the Pacific coast near Lima, along 729 Km — has led to the evolution and the optimization of the design, construction and maintenance processes regarding works focused on the stabilization of the slopes along the right of way of the pipeline carrying natural gas and natural gas liquid. This section of the right of way is 95 km long and crosses tropical mountains in the Amazon rainforest, in a transitional area between the Manugaly valley and the basin top boundary. It was noticed since 2005 that the right of way had being affected by a land slide consisting of a horizontal crack in the ground, between both pipelines and along them. So, after number of in-site inspections, the team concluded that the area was being affected by a large ground removal event. As a consequence, traces of geotechnical instability were found on the right side of the right of way, consisting of stress cracks, transverse settlements and leaks. All of those were affecting the stability conditions of the ground. From the annual in-site follow-up, monitoring and geotechnical testing, the team established that this process affecting the right of way was caused by a large mass removal process directly related to the increase of the imbalance rate of an old colluvial deposit below the entire area, triggered by the heavy rainfall in the area — ca. 3 500 mm a year, mainly between October and April. It is to be mentioned that the axis of the NG and NGL pipelines is located on the top of this colluvial deposit, which is susceptible to landslides. This is noticeable because of cracks present in the place. Local geomorphology and heavy deforestation — caused by locals — triggers an increase of the rainfall water filtration rate into the ground, thus speeding up the slide processes. Piezometers installed in the area showed high levels of the local water table. Movement readings are: top length: 70 m; length: 250 m; width: 150 m. Criteria for the construction of landslide mitigation structures in the pipeline área are being established based on a permanent land survey monitoring system — including inclinometers, piezometers and strain-gages — as this is a large regional movement. This control action allowed the operation to continue free of damages to the pipelines and under controlled costs.

The Andes Mountains, rich in geographical features and diversity, poses a significant threat to the integrity of oil and gas pipelines due to geohazards. Land movement and unstable soil conditions can trigger changes in the original trajectory of the pipeline resulting in undesired bending strain which can result on failure of the facility. OCENSA – Oleoducto Central S.A. from Colombia assesses the pipeline condition in geotechnical unstable places by comparison of In Line inspection results taking into account pipeline movements and bending strains changes along the zone of study. Bending strains in the pipe are compared against allowable values and emergency values which constitute the criteria to execute mitigation and/or remediation activities that must be done in order to maintain the pipe integrity. To project the pipeline behavior in time, 3D finite element models are developed, allowing the programming of future activities. This paper presents results obtained in a study case to show how pipeline is assessed and how different mitigation activities are developed. Mitigation Techniques such as stress relief procedures and EPS (Expanded Poly-Styrene) blocks incorporations are explained. These techniques are executed in order to reduce the pipe response due to soil displacements during landslide events and creeping slopes, with the final scope of assuring a safe operation.

Due to their length, oil and gas pipelines usually face different geotechnical problems along their routes (fast or slow, shallow or deep landslides) that impact the pipe integrity. In the current state of practice, this problems are analyzed considering the system as a beam on elastic foundation ( Winkler type models), in which the loads on the pipe (e.g. internal pipe pressure and geostatic loads) are studied independently. A more realistic description of the soil-pipe interaction phenomenon that allows the prediction and explanation of the pipe failures found in the practice requires more advanced methodologies, involving the constitutive behavior of soil and pipe and the combined effect of different types of loads. In order to assess in a better way the soil-pipe interaction problem in landslides, this paper presents a 3D numerical model of the system, including the combined effect of different loads (such as landslide loads, geostatic loads and pipe internal pressure). The results obtained with the model were validated against real field measures in the OCENSA pipeline system and are expressed as soil displacement versus pipe strain relations. These relations are being used successfully in the evaluation of the behavior of the pipeline in unstable slopes, resulting in an important tool in the OCENSA pipeline integrity program.