This paper examines the factors influencing the modelling of soil-pipeline interaction for a pipeline which is used to transport chilled gas. The soil-pipeline interaction is induced by the generation of discontinuous frost heave at a boundary between soils with differing frost susceptibility. The three-dimensional modelling takes into consideration the time-dependent evolution of frost heave due to moisture migration, the creep and elastic behaviour of the frozen soil and flexural behaviour of the embedded pipeline. The results of the computational model are compared with experimental results obtained from the frost heave induced soil-pipeline interaction test performed at the full scale test facilities in Caen, France.

As more Alberta oil and gas fields become depleted, attention is being given to development of economically and environmentally sound abandonment procedures. The objective of this study was to identify and assess residual internal and external contaminants associated with abandoned pipelines, particularly those to be abandoned in place. Circumstances which might increase the risk of contaminant release, and other issues relating to residual pipeline contaminants, were also identified. It was found that there are thousands of different substances which could potentially be associated with abandoned pipelines. A wide range in the potential quantities of residual contaminants was also found. Of the issues identified, the effectiveness of pipeline pigging and cleaning procedures prior to abandonment was the most critical determinant of the potential quantities of residual contaminants. However, a number of trace contaminants, such as PCBs (Polychlorinated Biphenyls) and NORMs (Naturally Occurring Radioactive Materials) may remain after thorough cleaning. A brief review of the legislation and regulations from a number of jurisdictions shows that pipeline abandonment has only recently become an issue of concern. Regulations specific to abandonment are lacking, and more genera] regulations and guidelines are being applied on a contaminant-specific basis, or in terms of waste disposal requirements.

As the natural gas pipeline system in Western Canada expands northward, it traverses the discontinuous permafrost zone. As the ground temperature of the frozen soil in this zone is just below freezing, it can be expected that within the design life of a pipeline the permafrost adjacent to it will melt due to the disturbance of the insulating cover by construction activities. Differential settlement at the thawing frozen/unfrozen soil interfaces gives rise to pipeline strain. Based on the calculated settlement and resulting strain level, a cost effective mechanical or civil design solution can be selected to mitigate the differential settlement problem. Since these design solutions can be costly, it is desirable to combine them with a pipeline route that traverses the least amount of discontinuous permafrost terrain while minimizing the overall length of the pipeline. This paper will detail the framework utilized to select the routing for a package of pipeline projects in northwestern Alberta. The process began with a review of the state of the art in permafrost engineering in order to benefit from past experiences. Airphoto interpretation and terrain mapping were performed for potential pipeline corridors. Preliminary routing options through the corridors were chosen from this mapping information that minimized both pipeline length and amount of permafrost terrain traversed. The next step was to collect field data for each route that would determine the extent and characteristics of the permafrost. Essentially two sets of field data were collected: geophysical mapping of representative sections of each terrain type and physical sampling of the permafrost. Boreholes were located following field interpretation of the geophysical data to ensure they were optimally located to help in calibration of the geophysical data. Permafrost samples were tested in the laboratory for thaw settlement. Anticipated thaw settlements were used to estimate pipe strain levels. This information was then extrapolated for the entire proposed pipeline route and used to finalize both the pipeline route and the differential settlement design options. Monitoring sites will be instrumented to obtain data on the longer term performance of the pipeline, as well as for assessing permafrost degradation effects on the right-of-way such as settlement and impact on drainage patterns. It is believed that the increased front end effort will result in lower operating costs and an overall reduced life-cycle cost. This basic design methodology can be applied to any project that traverses discontinuous permafrost terrain.

Pipeline projects impact the environment through soil and habitat disturbance, noise during construction and compressor operation, river crossing disturbance and the risk of rupture. Assigning monetary value to these negative project consequences enables the environment to be represented in the project cost-benefit analysis. This paper presents the mechanics and implications of two environmental valuation techniques: (1) the contingent valuation method and (2) the stated preference method. The use of environmental value at the project economic-evaluation stage is explained. A summary of research done on relevant environmental attribute valuation is presented and discussed. Recommendations for further research in the field are made.

The susceptibility of oil and gas pipelines to seismic damage has been demonstrated in earthquakes everywhere around the world. The latest examples of the dangerous failures are the ruptures of gas pipelines caused by Los-Angeles earthquake 1994 and oil pipelines caused by Sakhalin earthquake 1995. A significant part of oil and gas pipelines were designed some decades ago. Earthquake design specifications acting today are more restrictive than before. That is why pipelines built more than ten years ago are of major concern to managers and engineers. Basic approaches to the aseismic design of new pipelines and retrofitting of buried pipes and above-ground transmission pipelines and piping systems located in high risk seismic regions represent the main topic of the paper. A realistic assessment of earthquake damage potentials is needed to develop construction and retrofitting procedures. Supporting this type of constructing and rehabilitation activity for pipelines requires a better definition of key input parameters like area seismicity, the identification and characterization of ground moving hazards. The nonlinear approach for predicting spatial bending, torsion, and upheaval buckling of curved pipeline is applied for stress and stability analysis of buried pipelines under operational and seismic loading. The example of calculations useful for retrofit design of pipelines is given. An experience of damping devices application to mitigate seismic movement of above-ground pipelines has demonstrated an excellent ability to prevent damages during earthquake and operational dynamic loading. These devices are useful for above-ground pipeline retrofitting. To reduce uncertainty regarding the ability of a pipe to continue to hold pressure after seismic damages and retrofitting measures, it is important to develop the test programs, which should include investigations of buried and above-ground pipeline samples.

The use of directional drilling techniques for pipeline river crossings has increased sharply over the past few years in Canada and the United States. Improvements in drilling technology and increased experience among a growing number of specialty contractors has helped to reduce the cost of directionally drilled installations and to reduce the risks. The advantages associated with reducing disturbance of the water course by the use of directional drilling are often considered to outweigh the additional costs typically associated with the method. While the advantages of using directional drilling methods are compelling, the technique is not universally suited to all river valleys due to considerations of valley topography and geological setting. Specifically, there are certain geological and geometrical conditions that make the method completely unsuitable. In other cases, the geology beneath the river channel and the valley geometry may present a challenge to a drilled installation that can be overcome with adjustments to the design and drilling technique if anticipated. The implications of encountering unfavourable geological conditions during construction can be significant. The implications can range from substantial construction cost overruns up to several times the original bid price, to installations that cannot be safely put into service and must be abandoned. Under certain geological and geometrical conditions, the risk of blowout or fluid leakage to the water course during installation may be significant. The role of geotechnical and subsurface investigations to identify geological conditions prior to commencing construction is more critical for a drilled installation than for conventional trench techniques, as the consequences of encountering unanticipated conditions can be much more severe with drilled crossings. In addition, a trenched crossing is inherently more flexible than a directional crossing in terms of the ability of the contractor to adapt to different conditions than those anticipated at the start of the work.

This paper reviews Trans Mountain’s progress in the development of vapour collection and control systems for petroleum storage tanks. These systems are specifically designed for removal of Hydrogen Sulphide (H 2 S) vapours. The basic principles for vapour emission control and the design basis for the vapour control systems are reviewed. Experience with a number of adsorption processes is documented and current development work on an alternative vapour collection systems is presented.

Pipeline crossings of streams, whether large or small, must consider the ability of the stream channel to scour its bed and erode its banks. Case studies are presented to illustrate the kinds of dynamic environments which must be considered in designing pipeline stream crossings. These characteristics may be determined through the use of comparative historical aerial photography and site photographs and surveys. The case studies presented as examples in this paper include gullies, bedrock-lined channels, entrenched meandering streams, multi-channel wandering streams, degrading channels, alluvial fans, and major channels affected by regulation and man-made structures. Natural hazards such as debris jams and beaver dams are also discussed. For each case study, the characteristics of the channels are described, the design approach discussed and site-specific constraints presented which affected the final design.

X-ray Computer Assisted Tomography (CAT or CT) Scanning has been used successfully for the determination of physical properties of porous rocks and for flow visualization in a variety of porous media including soils. CAT scanning has also been demonstrated as an effective tool for the visualization of different stress conditions in porous rocks with greater accuracy when dealing with unconsolidated media. This success was the motivation in trying to expand the diagnostic capabilities of CAT scanning in the phenomena associated with pipeline / soil interactions. For this purpose, a physical model was built. The model consisted of a x-ray transparent holder which had two pistons, one at each end. The pistons were mounted on a cylindrical rod of variable diameter. The holder was then filled with sand. The entire apparatus was placed in the CAT scanner gantry. A series of experiments were performed whereby the rod was forced through the sand pack. The holder was scanned from end to end and the images of various cross-sections were acquired and analyzed for bulk density and porosity. The experiments were coupled with calibration experiments where a uniformly packed sand was loaded under hydrostatic load in given increments. As the sand pack compacted, its bulk density increased. The normalized change in density (strain) was monitored as a function of the pressure load (stress). The results of the calibration tests were used to identify the levels of stress on the sand surrounding the moving rod. It was discovered that areas of compaction ahead of the moving rod and dilation behind the moving rod could be successfully identified and mapped. The stress / strain calibration data allowed the translation of the bulk density images into stress maps around the pipeline. Although the system and materials used in this work were utilized only for demonstration, it was evident that this type of experimental work could be successfully used to calibrate complicated field scale computer models that are very difficult to tune because of the lack of experimental data.

The technique is given which permit to determine stress and strain state (SSS) and to estimate actual strength of a section of a buried main gas pipeline (GP) in case of its deformation in landslide action zone. The technique is based on use of three-dimensional coordinates of axial points of the deformed GP section. These coordinates are received by full-scale survey. The deformed axis of the surveyed GP section is described by the polynomial. The unknown coefficients of the polinomial can be determined from the boundary conditions in points of connection with contiguous undeformed sections as well as by use one of minimization methods at mathematical processing of full-scale survey results. The received form of GP section’s axis allows to determine curvatures and, accordingly, bending moments along all the length of the considered section. The account for the influence of soil resistance to longitudinal displacements of a pipeline is used to determine longitudinal forces. Received by this technique values of bending moments and axial forces as well as known value of internal pressure are used to receive all necessary components of actual SSS of pipeline section and to estimate its strength by elastic analysis.

A common challenge for pipeline designers is the placement and safe operation of pipelines within unstable slopes. Consequently, special design and operation procedures must be created to maintain the integrity of the pipeline through its operating life. Nova Gas Transmission Limited (NGTL) has developed a methodology to monitor pipeline integrity in slow moving (creeping) unstable slopes. This methodology uses Pipeline-Soil Interaction models to produce parameters that are in turn placed in Pipeline Integrity Assessment Techniques such as finite element analysis. For slope movements, pipeline integrity is based on pipeline strain criteria that are established from regulated codes or NGTL’s risk-based criteria. The result is that pipe strain can be estimated over time given a particular soil type and predicted ground movement. The ability to predict when a pipeline is reaching a critical strain allows NGTL to effectively quantify the risk and associated cost for various remedial measures based on a given operating life (life-cycle cost). These remedial measures can take the form of strain relieving outages, re-routing of the pipeline, directional drilling, or conventional geotechnical remedial practices (dewatering, slope grading, buttressing, etc.). Two case studies are presented detailing this present state-of-practice methodology at NGTL.

Perhaps the greatest challenge to geotechnical engineers is to maintain the integrity of pipelines at river crossings where landslide terrain dominates the approach slopes. The current design process at NOVA Gas Transmission Ltd. (NGTL) has developed to the point where this impact can be reasonably estimated using in-house models of pipeline-soil interaction. To date, there has been no method to estimate ground movements within unexplored slopes at the outset of the design process. To address this problem, rainfall and slope instrumentation data have been processed to derive rainfall-ground movement relationships. Early results indicate that the ground movements exhibit two components: a steady, small rate of movement independent of the rainfall, and; increased rates over short periods of time following heavy amounts of rainfall. Evidence exists of a definite threshold value of rainfall which has to be exceeded before any incremental movement is induced. Additional evidence indicates a one-month lag between rainfall and ground movement. While these models are in the preliminary stage, results indicate a potential to estimate ground movements for both initial design and planned maintenance actions.

Increasingly stringent regulations by the EPA and state air quality agencies in the U.S., as well as new regulations by Environment Canada, are making the reduction of exhaust emissions from industrial engines and gas turbines ever more important far their operators. Not only are these regulations getting increasingly strict with time, but there will be both substantial fines and possible criminal penalties for non-compliance in the future. This presentation describes how harmful exhaust emissions are formed during the combustion process, what the current regulations are in various areas of North America and where they are probably headed in the foreseeable future. It then discusses possible emission reduction strategies in two broad categories, combustion modification and post-combustion treatment, using catalytic converters. The three types of catalyst substrates are discussed, with the advantages and disadvantages of each, as well as the relative advantages and disadvantages of the four possible catalyst locations.

A study was initiated in 1988 to evaluate the effects of pipeline construction on soil compaction in the province of Alberta. Cone penetration resistance (soil strength) of soils was monitored to a depth of 31.5 cm at 14 study areas. Soil strength measurements were taken from right-of-way locations as well as from an adjacent undisturbed control. Soil strength information from the 14 study areas suggests that pipeline construction procedures can cause changes in soil strength on pipeline rights-of-way. Decreases in soil strength on the RoW compared to adjacent controls are more common than increases. These differences in soil strength appear to be short lived. In the majority of cases most differences, both increases and decreases, had disappeared one year after construction.

In the past, industry and government independently conducted research and gathered information to address environmental issues. The results were not always mutually accepted. A number of emerging environmental issues arose in the mid 1980’s that demanded mutual resolution. As a result, the Alberta Pipeline Environmental Steering Committee was established in 1988. The Committee initially consisted of industry and government representatives. The membership has since been increased to include landowner representation, local government, federal interests and contractors. The Committee has four main purposes: 1. To assist government, industry and other interest groups in their pursuit of environmental protection and economical pipeline planning, construction, operation, abandonment and reclamation in Alberta; 2. To act as a vehicle for government to receive input from industry and other interest groups during policy formation; 3. To identify, prioritize and make recommendations for workable solutions on Alberta pipeline environmental issues and; 4. To help implement recommendations by organizations represented on the Committee. The benefits of this model are agreement on issue identification and mutual resolution. The success of the model has resulted in it being adopted for other sectors as well.