bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Least-Cost Pipeline Route Development in Niger Using Remotely-Sensed Imagery and GIS
Authors: Slayter David L. , Hitchcock Christopher S. , Oehlers Mike , Chiles Richard
Published: April 2011

An important part of successful pipeline route selection includes the identification of geologic hazards and man-made (anthropogenic) features along any proposed route. Fugro William Lettis & Associates, Inc. (Fugro WLA) was contracted to provide a preferred crude oil transmission pipeline route between the Agadem oil field and the Zinder refinery in south-central Niger. The development of the 460-km long, 500-meter wide corridor involved the use of new geologic mapping and a digital elevation model (DEM) derived from Satellite Pour l’Observation de la Terre (SPOT) remotely-sensed imagery and SPOT High Resolution Stereo (HRS), respectively. The base geologic, anthropogenic and DEM data were provided by Fugro NPA Ltd. (Fugro NPA) and augmented with additional mapping by Fugro WLA. The area of the proposed pipeline route covers varying geologic conditions such as active and relict sand dunes, bedrock outcrops and escarpments, wadis and areas of recent erosion. Anthropogenic features included reservoirs, roads, towns and settlements, agricultural areas and oases. Our study found significant height differences between the dunes and evidence for varying dune activity. Selection of the optimal pipeline route required minimization of total elevation change and exposure to geologic hazards and existing anthropogenic development while obtaining the safest, most direct and economic route between the oil field and refinery. Using a geographic information system (GIS) the digitally-mapped geologic and anthropogenic features and elevation-derived parameters were assigned a relative risk ranking surface. Next, a cumulative cost distance surface and a cost path surface were created between the oil field and the refinery. Lastly, using GIS we developed a least-cost pipeline route option from the cost path surface.
A Practical Application to Calculating Corrosion Growth Rates by Comparing Successive ILI Runs From Different ILI Vendors
Authors: Spencer Kevin , Kariyawasam Shahani , Tetreault Cathy , Wharf Jon
Published: April 2011

Corrosion growth rates are an essential input into an Integrity Management Program but they can often be the largest source of uncertainty and error. A relatively simple method to estimate a corrosion growth rate is to compare the size of a corrosion anomaly over time and the most practical way to do this for a whole pipeline system is via the use of In-Line Inspection (ILI). However, the reported depth of the anomaly following an ILI run contains measurement uncertainties, i.e., sizing tolerances that must be accounted for in defining the uncertainty, or error associated with the measured corrosion growth rate. When the same inspection vendor performs the inspections then proven methods exist that enable this growth error to be significantly reduced but these methods include the use of raw inspection data and, specialist software and analysis. Guidelines presently exist to estimate corrosion growth rates using inspection data from different ILI vendors. Although well documented, they are often only applicable to “simple” cases, pipelines containing isolated corrosion features with low feature density counts. As the feature density or the corrosion complexity increases then different reporting specifications, interaction rules, analysis procedures, sizing models, etc can become difficult to account for, ultimately leading to incorrect estimations or larger uncertainties regarding the growth error. This paper will address these issues through the experiences of a North American pipeline operator. Accurately quantifying the reliability of pipeline assets over time requires accurate corrosion growth rates and the case study will demonstrate how the growth error was significantly reduced over existing methodologies. Historical excavation and recoat information was utilized to identify static defects and quantify systemic bias between inspections. To reduce differences in reporting and the analyst interpretation of the recorded magnetic signals, novel analysis techniques were employed to normalize the data sets against each other. The resulting uncertainty of the corrosion growth rates was then further reduced by deriving, and applying a regression model to reduce the effect of the different sizing models and the identified systemic bias. The reduced uncertainty ultimately led to a better understanding of the corrosion activity on the pipeline and facilitated a better integrity management decision process.
Petrobras Amazonia Gas Pipeline: Repair Logistics Evaluation Study
Authors: Faertes Denise , Domingues Joaquim
Published: April 2011

The purpose of this paper is to present the study concerning the evaluation of the repair logistics of gas pipeline Urucu-Coari-Manaus (extension of 600 km), that was constructed to operate in the Amazon Brazilian region. Repair logistics is a challenge, regarding specific operation conditions in the jungle, environment and flood variations, difficulty on accessing pipeline right-of-way, difficulty on transportation, etc. Workshops were held, gathering most experienced company personnel from different PETROBRAS sectors (engineering, operation, repair centre, integrity area, Brazilian Army, offshore sector, etc.), in order to evaluate and establish strategies for each identified failure scenario, considering type of repair, logistics, resources and costs. The first step of the study was to incorporate the experience obtained from the engineering team, responsible for the construction of Urucu-Coari-Manaus gas pipeline as they had to face unexpected and adverse conditions. Based on their experience, different pipeline sections were defined, considering specific features, like isolation, flooded areas, river crossings, access limitations, etc. The second step was brain-storming workshops with the purpose of providing the best PETROBRAS evaluation of pipeline sections repair strategies, logistics and resources. Failure frequencies were raised and addressed, as well as variables like: - time for failure detection, for digging, for repair, for resources arrival, considering different logistics and transportation modes (using specific boats, helicopters with special characteristics, such as suitable for long line operations (load line greater than one rotor diameter in length), capable of transporting heavy equipment, etc.). Innovative ways of repair were conceived and proposed to be used. Supply contract conditions for thermo plants, industrial and residential consumers were considered. Finally, a cost/benefit analysis was performed, considering expenses on logistics and resources and benefits associated with avoided losses for each specific failure scenario, in order to provide support for decision making process.
Reliability Modelling: Petrobras 2010 Integrated Gas Supply Chain
Authors: Faertes Denise , Saker Leonardo , Heil Luciana , Vieira Flavia , Risi Francisco , Domingues Joaquim , Alvarenga Tobias , Mussel Patricia , Carvalho Eduardo
Published: April 2011

The purpose of this paper is to present the innovative reliability modeling of Petrobras 2010 integrated gas supply chain. The model represents a challenge in terms of complexity and software robustness. It was jointly developed by PETROBRAS Gas & Power Department and Det Norske Veritas. It was carried out with the objective of evaluating security of supply of 2010 gas network design that was conceived to connect Brazilian Northeast and Southeast regions. To provide best in class analysis, state of the art software was used to quantify the availability and the efficiency of the overall network and its individual components (such as gas processing units, city-gates, compressor stations, pipelines). The study requests, as input, a lot of information, that should be provided from different sectors of Petrobras, since it is supposed to depict reliability performance of all gas supply chain players. Information such as 2010 design configurations, gas offer and demand profiles, shedding priority, pressure delivery conditions, supply contract and associated penalties, commodity prices, etc., should be raised and addressed. More than twelve processing plants were modeled, in a detailed manner, and have their performance indicators compared. Different gas sources were considered in the study, such as offshore platforms, onshore fields, Bolivia pipeline and LNG ships. Detailed failure probability and repair data were addressed. Contingency plans, for each identified scenario, were made, in order to evaluate probable losses that constitute an input for the reliability modeling. Therefore, two additional software’s were used for their validation: - Pipeline studio – TGNET (from Energy Solutions), to check pressure conditions; and an in-house Petrobras software (PLANAGE), used for best gas allocation purposes. Experienced operational team opinion was incorporated on that contingency plans elaboration. This work constitutes a powerful tool for Petrobras planning and optimization of gas supply chain future configurations. The simulation provides propositions for investments prioritization, based on cost benefit analysis, and as a by-product, contingency plans, that were developed, considering different failure scenarios.
On the Applicability of Extreme Value Statistics in the Prediction of Maximum Pit Depth in Heavily Corroded Non-Piggable Buried Pipelines
Authors: Alfonso L. , Caleyo F. , Hallen J. M. , Araujo J.
Published: April 2011

There exists a large number of works aimed at the application of Extreme Value Statistics to corrosion. However, there is a lack of studies devoted to the applicability of the Gumbel method to the prediction of maximum pitting-corrosion depth. This is especially true for works considering the typical pit densities and spatial patterns in long, underground pipelines. In the presence of spatial pit clustering, estimations could deteriorate, raising the need to increase the total inspection area in order to obtain the desired accuracy for the estimated maximum pit depth. In most practical situations, pit-depth samples collected along a pipeline belong to distinguishable groups, due to differences in corrosion environments. For example, it is quite probable that samples collected from the pipeline’s upper and lower external surfaces will differ and represent different pit populations. In that case, maximum pit-depth estimations should be made separately for these two quite different populations. Therefore, a good strategy to improve maximum pit-depth estimations is critically dependent upon a careful selection of the inspection area used for the extreme value analysis. The goal should be to obtain sampling sections that contain a pit population as homogenous as possible with regard to corrosion conditions. In this study, the aforementioned strategy is carefully tested by comparing extreme-value-oriented Monte Carlo simulations of maximum pit depth with the results of inline inspections. It was found that the variance to mean ratio, a measure of randomness, and the mean squared error of the maximum pit-depth estimations were considerably reduced, compared with the errors obtained for the entire pipeline area, when the inspection areas were selected based on corrosion-condition homogeneity.
On the Use of the Generalized Lambda Distribution and Parametric Bootstrap Method in the Prediction of Maximum Pit Depths: Comparison With Experimental Pipeline Data
Authors: Alfonso L. , Caleyo F. , Hallen J. M. , Araujo J.
Published: April 2011

The approach proposed by Najjar and coworkers for the prediction of maximum pit depth is applied and validated through direct comparison with real pipeline steel pitting corrosion data. This methodology combines the Generalized Lambda Distribution (GLD) and the Bootstrap Method (BM) in order to estimate both the maximum pit depth and confidence intervals associated with the estimation. Samples are drawn from real-life pitting corrosion data and the GLD is used to obtain modeled pit depth distributions emulating the experimental ones. In order to estimate the maximum pit depth over an N-times larger area, simulated distributions, N-times larger than the experimental ones, are generated 104 times. The deepest pit depth is extracted from each simulated bootstrap sample to obtain a dataset of 104 extreme pit-depth values. An estimate of the maximum pit depth for the N-times larger surface can be obtained from this dataset by calculating the average of the 104 extreme values. The uncertainty in the estimation is derived from the 95% confidence interval of the bootstrap estimate. In this report, the results of the application of the GLD-BM framework are compared with extreme pit depth values observed in real pitting corrosion data. The agreement between the estimated and actual maximum pit depths points to the applicability of the GLD-BM as an alternative in estimating the maximum pit depth when only a small number of samples are available. The main advantage of the combined methodology over the Gumbel method is its great simplicity, since fast and reliable estimations can be made with at least only two experimental samples.
Integration of Pipeline Specifications, Material, and Construction Data: A Case Study
Authors: Hambrook Jeffery E. , Buchanan Douglas A.
Published: April 2011

This paper introduces the concept of a Pipe Data Log (Pipe Log). The idea is not new but a Pipe Log is rarely created for new pipeline projects. A Pipe Log is frequently created as part of the post-construction process and is intended for Integrity purposes. However, creating and populating the Pipe Log as construction proceeds can provide multiple benefits: • Progress of all aspects of construction can be tracked. • Anomalies in data received can be identified immediately and rectified before the project proceeds. • Missing information can be captured before the project is completed and crews are demobilized. • The field engineer can compare with design to verify that the project is being constructed as it was designed. • When construction is complete the Pipe Log will be as well. WorleyParsons Canada Services Ltd., acting as Colt Engineering, worked on behalf of Enbridge Pipelines Inc. and created a detailed Pipe Data Log for the Canadian portion of the Southern Lights LSr Project. The Pipe Log was created using Microsoft® Excel with a line item for each individual piece of pipe that was welded in the pipeline. Information corresponding to the location of each pipe segment, welds performed, material, terrain, coating, protection, and testing was recorded. The Pipe Data Log is excellent for auditing data as the information is being entered. Information collected by the surveyor can be matched to that provided by the pipe mill and by weld and NDE inspectors. Missing or questionable information can be corrected during construction much easier than post-construction. At post-construction, the Pipe Log allows the Integrity team to quickly determine if there are other areas of concern that have similar properties to another problem area.
Risk Based Guidelines for Natural Gas Pipeline in Operation
Authors: Cardoso Ca´ssia , Oliveira Luiz Fernando de , Faertes Denise
Published: April 2011

During the life of a gas pipeline, some significant changes in the population may happen along its route. Such changes are indirectly evaluated by the increase in the amount of buildings constructed along the route, which determines the so called Location Class. Such changes, when pipeline is operating, provoke differences between what is required by the standards and what is actually done. The main goal of this paper is to present a risk-based methodology for the guideline development which can be used in decision-making concerning what to do in case of any location class change. Particularly, it has given special attention to the requirements which are imposed for the pipeline operational license continuation in Brazil. Moreover, a summary of the main solutions found in other countries together with a guideline, customized for the Brazilian reality, is presented.
Parametric Study of Sleeve Repair on Wrinkled Energy Pipelines
Authors: Song Peter , Cheng J. J. Roger , Ironside Scott , Skibinsky Darren
Published: April 2011

Field experience showed that repairing wrinkles developed on energy pipelines using steel sleeves is an efficient and cost effective method. Based on the previous successful numerical simulations of a field wrinkle sleeve repair work, a parametric study was conducted by using Finite Element (FE) method to further investigate the effectiveness of the sleeve repair technique. The FE package ABAQUS 6.4 was utilized in conducting the parametric study. The parameters studied include the length, the thickness, and the material properties of the sleeve, and the thickness of the collar, which is used to fit between the wrinkled pipe and the repairing sleeve. The range of the parameters studied covers the most commonly used typical values in the pipeline industry. Two phases were used in carrying out the parametric study. In Phase I, the parameter that plays the most important role in determining the behavior of the wrinkle sleeve repair system (WSRS) was studied. It is found this parameter is the length of the repairing sleeve. Brief discussion was given regarding the way this parameter affects the behavior of the pipe using the WSRS. In Phase II, based on the results from the Phase I study, the effects of other parameters were investigated through a series of FE analyses. Conclusions were drawn and recommendations for future wrinkle sleeve repair work were given based on the results of the parametric study.
In-Line Inspection Techniques for “Non-Piggable” Liquid Pipelines
Authors: Grmek Damir
Published: April 2011

While in-line inspection tools have been around for many years, the primary focus for this technology has always been on long sections of mainline pipe. The recent increased attention on facility integrity, as well as US Department of Transportation (DOT) baseline assessment requirements, have made it necessary to develop inspection tools and techniques for pipelines that have previously been considered non-piggable. Within industry, the term non-piggable has been used to describe pipelines that cannot be inspected with traditional free swimming mainline inspection tools using standard launch and receive traps. Typical reasons for classifying a pipeline as non-piggable include: • No launch or receive facilities; • Mechanical design (number/type of bends, diameter changes, offtakes etc.); • Operating conditions (zero/low/high pressure, zero/low/high flow, type of product, pipeline cleanliness etc.). Within the Enbridge system, a lack of launch and receive facilities has been the main obstacle on laterals and delivery/receipt pipelines. However, mechanical design and operating conditions have been factors on certain pipelines. The preferred method to inspect these pipelines, whenever possible, is to use in-line inspection tools, as opposed to other options such as External Corrosion Direct Assessment (ECDA) or hydrostatic test. While inspecting these short sections of pipe has proven challenging, various in-line inspection tools and techniques have been developed to meet this requirement. This paper will discuss some of the challenges faced and different solutions that have been developed to successfully inspect these types of pipelines.
Effect of Strain Ageing on Yield Strength and Post Yield Behavior of FCAW-G Ferritic Weld Metal
Authors: Narayanan Badri K. , Brady Noel , Wang Yong-Yi , Ogborn Jon
Published: April 2011

Ferritic weld metal was deposited with gas shielded flux cored arc welding (FCAW-G) process. The nitrogen level in the deposited weld metal varies typically between 20 to 100 ppm. Nitrogen is a fast diffusing solute element that is known to cause strain ageing affecting both strength and toughness. Weld metal was produced with intentional additions of two strong nitride formers, titanium and vanadium. All-weld metal tensile samples were subjected to varying levels of strain, aged at 170°C for 20 minutes and reloaded to failure. Both the yield and tensile strength increased with increase in pre-strain confirming the presence of strain ageing. The strain hardening rate is also seen to change with strain ageing. There is also a corresponding decrease in the uniform elongation with increase in nitrogen and prestrain. The effect of strain ageing treatment on weld metal toughness was also evaluated. A nominal 2%–3% strain was imposed on the weld metal by straining it in the direction of welding and Charpy V-Notch toughness of the weld was measured. The ductile to brittle transition temperature (DBTT) of the weld metal was estimated by measuring the percent shear and the weld metal toughness at different temperatures. The DBTT of the weld metal is seen to shift slightly to higher temperatures with increase in pre-strain. However there was a dramatic drop in the upper shelf energy and a consistent decrease in the average toughness of the weld metal at all temperatures. The as-welded and reheat microstructure of the weld metal was characterized using optical and electron microscopy techniques. The possible implications of strain ageing on pipeline girth weld procedure qualification and inservice integrity are discussed.
Considerations of Linepipe and Girth Weld Tensile Properties for Strain-Based Design of Pipelines
Authors: Wang Yong-Yi , Liu Ming , Gianetto James , Tyson Bill
Published: April 2011

Pipelines in certain regions are expected to survive high longitudinal strains induced by seismic activities, slope instability, frost heave, and mine subsidence. Material properties, of both pipes and girth welds, are critical contributing factors to a pipeline’s strain capacity. These factors are examined in this paper with particular focus on the modern high strength pipes (grade X70 and above) usually made from microalloyed control-rolled TMCP steels. The examination of the tensile properties of pipes includes some of the most basic parameters such as yield strength, strength variation within a pipe, and newly emerging issues of strength and strain hardening dependence on temperature. The girth weld tensile properties, particularly yield strength, are shown to be dependent on the location of the test specimen. There are strong indications from the tested welds that strain hardening of the welds is dependent on test temperature. The effects of strain aging on pipe and girth weld properties are reviewed. This line of reasoning is extended to possible strain aging effects during field construction, although experimental evidence is lacking at this moment. The paper concludes with considerations of practical implementation of the findings presented in the early part of the paper. Recommendations are made to effectively deal with some of the challenging issues related to the specification and measurement of tensile properties for strain-based design.
Method to Reduce Arc Blow During DC Arc Welding of Pipelines
Authors: Espina-Herna´ndez J. H. , Caleyo F. , Hallen J. M. , Rueda-Morales G. L. , Pe´rez-Baruch E. , Lo´pez-Montenegro A.
Published: April 2011

Arc blow is a phenomenon associated with the deviation of the arc that usually occurs during arc welding of pipelines under repair. This phenomenon is most commonly observed after the pipeline has been inspected using an in-line magnetic flux leakage (MFL) inspection tool, which magnetized the pipe wall during the inspection run. Among the different welding techniques, DC arc welding is one of the most popular in the oil and gas industry due to its versatility and relative low cost. The interaction between the magnetic field associated with the current flowing through the electrode, and the residual magnetic field in the pipeline under repair can produce arc blow. In this work, a simple method to reduce arc blow during DC arc welding of pipelines has been developed. In contrast to the methods so far available in the literature [1,2], the method proposed here gives simple rules to be followed by welders with little background on magnetism. Residual magnetic field levels from different pipelines in southern Mexico were measured in the gap after damaged pipeline sections had been cut, and in the V groove once the new pipeline sections had been inserted. Magnetic finite element simulations were performed with freeware (FEMM) for the residual magnetic field compensation using real-life pipeline dimensions and field parameters. A large number of simulations were performed, using as variables the residual magnetic field in the groove, the number of coil turns required for the residual magnetic field compensation, the DC current flowing through the coil and the electrode, the position of the coil with respect to the groove, and the pipeline wall thickness and diameter. An empirical predictive equation was developed for the compensation of the residual magnetic field from the results obtained during the simulations. Most of the procedures developed in the past propose to adjust the current in order to compensate for the magnetic field in the groove, which is a disadvantage during DC arc welding since the electrodes specifications do not cover a wide range of current values. In contrast, the method proposed herein supersedes this disadvantage by granting the possibility of properly selecting the number of coil turns and the position of the coil with respect to the groove, in order to compensate for the residual magnetic field in the groove.
Detection of Active Corrosion From a Comparison of ILI Runs
Authors: Desjardins Guy
Published: April 2011

Repeated in-line inspections (ILI) of transmission pipelines have been used for many years to estimate corrosion rates. However, the calculation of a corrosion rate from a direct comparison of ILI anomalies is often dominated by the ILI measurement error. As an alternative to assessing a corrosion rate, it may be possible to use repeated in-line inspections to simply detect the presence of active corrosion. This paper presents the application of various statistical measures to detect active corrosion with a high-level of confidence. From a pipeline integrity management perspective, this method will enable the operator to address each location where there is a high probability of active corrosion. Furthermore, despite there being no explicit calculation of corrosion rates, the advantage of the method is that it can yield an upper bound on the corrosion rate of anomalies left unexcavated on the pipeline.
Mechanical Damage of Pipelines at Low Operating Pressure
Authors: Farrag Khalid A. , Francini Robert B.
Published: April 2011

The paper presents the results of a testing program to characterize mechanical damage (dents and gouges) to pipelines at low operating pressures (i.e., at stress levels below 40% of the Specified Minimum Yield Strength, SMYS of the pipe material). The testing program was performed on pipelines of different sizes and grades; and the pipes were subjected to various gouges and dents when pressurized at 40% SMYS. The results of rupture tests on the pipes were compared with the ‘European Pipeline Research Group (EPRG) Simplified Model’ criterion. The results show that the model is sufficiently conservative to be used for evaluating mechanical damage of low-stress gas pipelines. The results provide guidelines for gas utilities to assess the damage at these stress levels. These guidelines allow a pipeline operator to assess the repair needs of a pipeline based on its operating pressure and damage level.
Balancing Pipeline Safety and Cost Integrity Management Through Performance Validation of In-Line Inspection Data
Authors: McNealy Rick , Limon-Tapia Sergio , Kania Richard , Fingerhut Martin , Haines Harvey
Published: April 2011

In-Line Inspection (ILI) surveys are widely employed to identify potential threats by capturing changes in pipe condition such as metal loss, caused by corrosion. The better the performance and interpretation of these survey data, the higher the reliability of being able to predict the actual condition of the pipe and required remediation. Each ILI survey has a certain level of conservatism from the assessment equations such as B31G and sensitivity to ILI performance for measurement uncertainty. Multiple levels of conservatism intended to limit the possibility of a non-conservative assessment can result in a significant economic penalty and excessive digs without improving safety. A study was undertaken to evaluate the reliability of responses to ILI corrosion features through multiple case studies examining the effects of failure criteria and data analysis parameters. This paper discusses the effect of validated ILI performance on safety, and addresses the risk of false acceptance of corrosion indications at a prescribed safety factor. The cost of unnecessary excavations due to falsely rejecting ILI predictions is also discussed.
X100 Welding Technology: Past, Present and Future
Authors: Quintana Marie A. , Hammond John
Published: April 2011

A significant amount of research has been conducted within the last decade on the development of X100 line pipe and associated welding technology; including, several field demonstration projects of limited size and scope. Although considerable advances in steelmaking and pipeline construction have occurred, innovations in welding process technology generally lag pipeline industry needs. Clearly, the number of historically viable welding options declines as pipe strength increases. Weld strength becomes more sensitive to cooling rate variation, cold cracking sensitivity increases, and overall weldability tends to decline. Also, achieving the balance between weld strength, toughness, and ductility necessary for pipeline performance requires more highly controlled welding practice, procedures, precision in weld bevel design, and pass sequence. Successful fabrication and field pipelay welding requires greater control of essential welding variables in order to satisfy increasingly stringent weld property requirements. Accordingly, there are few proven welding process options for X100 and detailed knowledge resides within a small number of oil/gas and contractor companies. Recognizing that industry wide implementation of X100 requires the range of manual, semi-automatic and automatic (mechanized) welding processes needed for double jointing, mainline, tie-in and repair, US Department of Transportation Pipeline and Hazardous Materials Safety Administration (DOT-PHMSA) and Pipeline Research Council International (PRCI) have co-funded a consolidated program to begin addressing the issues (Project PR-354-074506). This paper summarizes the program findings that address the current state of the art regarding welding technology applied to X100 pipeline construction. The main issues addressed are: • synopsis of experience, • current status and pending developments in welding processes and consumables, • assessment of first and second level contractor capability, and • key knowledge and experience gaps.
Effective Improvements to Reliability Based Corrosion Management
Authors: Kariyawasam Shahani , Peterson Warren
Published: April 2011

Reliability methods have being adopted by oil and gas operators for integrity management decisions. These methods explicitly account for all relevant uncertainties and are designed to provide consistent safety. Consequently, a risk or reliability based approach is a very appropriate basis for decision making in the face of uncertainties. However, as in the effective use of any powerful methodology the sensitivities of the method to assumptions and limitations of applicability need to be well understood. This paper presents how improvements were made to reliability based integrity program by understanding its limitations and sensitivities. First the inputs that have the highest impact on the results were identified. These inputs are the most appropriate areas for improvement and data gathering. It is also very important to understand how the results are to be used and for what purpose. The results of this particular inline inspection based reliability assessment are used to make better excavation and repair decisions. A defect-based and joint-based decision making process is essential for determining with sufficient confidence if each defect and joint is in a safe condition. Consequently, the improvements are focused on discriminating between the myriad of defects found during an inline inspection run. Distinct field characteristics of corrosion growth are also taken into account in these improvements. The paper presents the implementation of effective area methods for future integrity probabilistic evaluations. It also describes the benefit of applying defect-specific growth rates. Finally, case studies are presented to demonstrate the effectiveness of the changes.
Effectiveness of Hydrostatic Testing for High Strength Pipe Material
Authors: Cameron Kimberly , Pettinger Alfred M.
Published: April 2011

Pipeline systems are typically subjected to hydrostatic testing to help ensure pipeline integrity. It can be desirable to use the highest feasible test pressure to eliminate as many defects as possible. It is widely accepted that safe control of yielding can be achieved during hydrostatic testing and that the hydrostatic testing does not create a stress state that is less safe from the standpoint of pre-existing flaws. For a small percentage of cases, however, hydrostatic testing can produce flaws that were longer than the ones removed. In these few cases, the flaws can then fail at a lower test pressure than the original hydrostatic test. The low probability of these events, however, means that the effectiveness of the hydrostatic test is not significantly diminished in this case. Because crack growth from a pre-existing flaw is retarded in a plastically deformed material, it is also typically assumed that hydrostatic testing should not lead to accelerated crack growth. However, this does not take into account that the hydrostatic testing itself can cause some increment in crack growth and that for many higher strength pipe materials significantly large defects can survive hydrostatic testing. These longer defects can potentially grow after surviving a hydrostatic test. This paper discusses this difference in crack growth rates for cracks that have survived hydrostatic testing in different grade pipeline steels and the implications for hydrostatic testing.
Growth of Surface-Type Stress Corrosion Cracks in Near-Neutral pH Environments Under Disbonded Coatings
Authors: Egbewande Afolabi T. , Eslami AbdoulMajid , Chen Weixing , Worthingham Robert , Kania Richard , VanBoven Greg
Published: April 2011

Near-neutral pH stress corrosion cracking (NNPHSCC), which occurs when ground water penetrates under the pipe coating, causes longitudinal cracks to develop on the surface of pipelines. Such cracks grow over time and can ultimately lead to pipeline failure. NNPHSCC is currently managed by in-line inspection or hydrostatic testing for oil and gas pipelines respectively. These procedures are enormously expensive and have to be repeated at predetermined intervals. Re-inspection intervals are currently determined by empirical models, which have been found rather imprecise. A major flaw in currently applied models is that they assume that once a NNPHSCC crack is formed, it grows at a constant rate that is independent of pipeline operating variables and both pre- and in-service history of the pipeline material. This is not necessarily true as pipeline history, the nature of the service environment and operating factors, among several other factors, have a strong influence on the rate of NNPHSCC crack propagation. Most existing models also treat NNPHSCC cracks as long through thickness cracks rather than surface type cracks typically observed in the field. This research proposes to provide an empirical model that more accurately predicts the growth rate of near-neutral pH SCC cracks in near-neutral pH environments by studying the growth rate of surface type flaws while also accounting for the influence of operating factors, environmental factors, coating disbondment and cathodic protection on the rate of crack propagation. This paper reports some preliminary test results obtained using a long specimen with three semi elliptical surface flaws located in three reduced sections to simulate field observed NNPHSCC cracks. Preliminary results suggest that: 1) crack grows much faster at the open mouth, which was attributed to hydrogen effects; 2) crack dormancy can occur under certain combined mechanical factors; 3) although the benign mechanical loading cannot lead to a direct crack growth (crack dormancy), it causes damage to the crack tip, which makes the crack more susceptible to crack growth upon a more aggressive condition is encountered.
Burst Tests on Pipeline Containing Circumferential Corrosion Defects
Authors: Benjamin Adilson C. , Freire Jose´ Luiz F. , Vieira Ronaldo D. , Diniz Jorge L. C.
Published: April 2011

Circumferential defects are the ones in which the width w is greater than the length L (w > L). In this paper the burst tests of three tubular specimens are presented. In these tests the tubular specimens were loaded with internal pressure only. The specimens were cut from longitudinal welded tubes made of API 5L X80 steel with a nominal outside diameter of 457.2 mm (18 in) and a nominal wall thickness of 7.93 mm (0.312 in). Each of the three specimens had one external circumferential corrosion defect, machined using spark erosion. Measurements were carried out in order to determine the actual dimensions of each tubular specimen and its respective defect. Tensile specimens and impact test specimens were tested to determine material properties. The failure pressures measured in the burst tests are compared with those predicted by five assessments methods, namely: the ASME B31G method, the RSTRENG 085dL method, the DNV RP-F101 method for single defects (Part B), the RPA method and the Kastner equation.
Waveform Controlled Welding in ASME Section IX
Authors: Melfi Teresa , Rajan Vaidyanath
Published: April 2011

Metallic pipe is produced to meet API, ISO or other industry specifications. When the manufacturing process involves welding of a longitudinal or spiral seam, the welding is typically done to the standards of ASME Section IX. Girth welding of pipe is often performed using ASME Section IX standards and pulsing waveforms. In 2006, a task group was set up in ASME Section IX to explore waveform controlled welding and recommend code changes. The recommendations were submitted for approval, and the resulting code changes were published in the 2010 edition of ASME Section IX. The changes deal with the way energy or power is measured and the resulting calculation of heat input. This paper will explore differences in the measurement and calculation methods when using waveform controlled welding and discuss why these occur. The code changes will be presented. Detailed explanations will be given of how to comply with the new standards using either new or existing procedure qualifications.
Rheological Property of Waxy Crude Oil in Restart Process of Pipeline
Authors: Xu Yanbo , Huang Qiyu
Published: April 2011

In the restart process of pipeline containing waxy crude oil after shutdown, the rheological properties of oil, including viscosity, yield stress and thixotropy is studied. The entire restart process is decided by various factors; in this paper the effects of outlet temperature, shutdown and restart temperature as well as shutdown time duration to the rheological property are taken into the consideration. The measurements are employed using a controlled shearing rheometer to investigate rheological property based on different restart conditions. In addition, this paper has also researched affection of emulsion and blended samples mixing with two types of crude oil in various ratios. Finally comprehensive rheological evaluation to restartability is obtained.
Autonomous Underwater Riser Inspection Tool
Authors: Camerini Claudio , Freitas Miguel , Langer Ricardo Artigas , von der Weid Jean Pierre , Marnet Robson
Published: April 2011

The inspection of the vertical section of an offshore pipeline, known as the riser, plays a critical part of any integrity management program. This section connects the pipe that runs on the seabed to the production facility, be it a floating platform or a FPSO. Hanging from the platform over deep waters, risers are subject to very extreme operating conditions such as high loads and underwater currents. Corrosion, fatigue, abrasion and damages caused by stray object collisions are factors that must be taken into account, so that oil and gas production are not compromised. A flexible pipeline, a well engineered solution used in most riser installations, provides high reliability while requiring little maintenance but, in spite of advances in project and installation, the inspection of riser pipelines is an immature field where technology has not yet met the user’s demands. In the search for better riser inspection techniques, a project was started to design a new inspection tool. The basic concept consists of an autonomous vehicle, the Autonomous Underwater Riser Inspection tool (AURI), that uses the riser itself for guidance. The AURI tool can control its own velocity and is suited to carry different types of inspection devices. The first AURI prototype is designed to perform visual inspection with an built-in camera system, covering 100% of the external riser surface. The AURI can reach water depths up to a thousand meters. It was built with several embedded security mechanisms to ensure tool recovery in case of failure and also to minimize chances of damage to the pipeline or other equipment. It uses two electrical thrusters to push it along the riser. The mission is set to a maximum depth to be inspected and is considered complete when one of the following conditions is met: (1) maximum pressure on depth sensor is reached or (2) the length of the run is achieved or (3) maximum mission duration is exceeded or (4) maximum allowed tilt is detected by the inclinometer. Thanks to its positive buoyancy, the AURI will always return to the surface even if the electronics fail or the batteries get exhausted. This paper presents the first AURI prototype as well as the preliminary test results.
Flow Control at City Gates: A Low Budget Approach
Authors: Teixeira Paulo L. B. , Hasselmann Stella A. , Pezzini Ca´ssio
Published: April 2011

The Bolivia Brasil Gas Pipeline (GASBOL) is a pipeline extending from the gas producing fields of Rio Grande, Bolivia, to Canoas, Brazil. It distributes gas to five states in Brazil, with a total extension of 3 160 km (1,970 mi) and a rated operating pressure of 100 kgf/cm2g (1,420 psig). GASBOL is owned and operated by Transportadora Brasileira Gasoduto Bolivia-Brasil S.A., TBG, a company whose shareholders are Petrobras, AEI Ame´rica do Sul, Transredes, BBPP Holdings and Bear Ga´s. After several occurrences of flow turbine failures caused by large flow variations at some city gates, the design of new stations was modified to include a control valve upstream of the interconnection point with consumers. For operational city gates such functionality would imply delivery interruption to perform costly hot tapping procedures in order to install a flow control valve. Therefore, TBG’s engineering team was challenged to develop a cheaper and quicker solution. This paper describes TBG’s answer to that challenge, developing a low cost flow control solution at ten selected city gates along the pipeline. The stations were chosen based on several aspects such as volume capacity, line packing to the consumer, etc. The main objective is to ensure that the daily volume effectively delivered does not exceed the contracted volume, avoiding delivery failures due to imbalances caused by unplanned withdrawals, as a means to improve planning of the pipeline operational profile.
The Remaining Strength of Corroded Casing With Combined Hoop and Longitudinal Stress
Authors: Francini Robert B. , Wahl Jacob D. , Quade Nolan T.
Published: April 2011

The casings in a gas storage or production well can have large longitudinal loads in addition to the hoop stress resulting from internal pressure. Under certain circumstances these loads need to be taken into account when evaluating the remaining strength of corroded areas. The most commonly used method for corrosion evaluation is based on B31G which does not include longitudinal loads. This paper outlines the range of longitudinal loading where the B31G approach is valid. In addition, it presents a method to evaluate the remaining strength of the corroded area where the B31G approach is not valid. The procedure has been validated by burst tests of casing with real and machined metal loss under axial loading.
Assisting Project Managers to Manage Risk by Planned Verification
Authors: Stirling Gunn , Ho̸gmoen Ka˚re
Published: April 2011

Operators of large and complex pipeline systems face numerous risks and verification is a means to manage risk. Important factors to be considered when selecting a verification strategy are; legislative requirements and expectations, contracting philosophy, interface management, communication strategy, project technical challenges and quality assurance philosophy. To assist project managers in planning and communicating the verification strategy, a standardized three tiered verification scope is described.
Corrosion Behavior of HAZ Between C4 Nickel-Base Alloy/X60 Steel Dissimilar Metal Weldments
Authors: Liu Wei , Yang Liying , Lu Minxu
Published: April 2011

C4 nickel-base alloy and X60 steel were fabricated by Tungsten Inert Gas Welding (TIG) process using a CrNiMo-3 nickel base alloy welding wire filler metal under 100A welding current. The microstructure of welding joint was analyzed by SEM. Corrosion behaviors of heat effect zone (HAZ) and X60 steel matrix were investigated by electrochemical measurement. The obtained results show that weld metal zone consists of fully dendrite structure and the austenite grain of C4 nickel-base alloy coarsening in over-heat HAZ. The HAZ of X60 steel includes coarse (GHAZ) and fine grained zones (FGHAZ). Phase change from bulk ferrite with a small amount of pearlite to granular bainite at CGHAZ. Corrosion current density of matrix of X60 steel is between FGHAZ and CGHAZ.
Strain Demand Estimation for Pipelines in Challenging Arctic and Seismically Active Regions
Authors: Arslan Haydar , Hamilton Jed , Lele Suvrat , Minnaar Karel , Albrecht Bob , Cook Mike F. , Wong Patrick
Published: April 2011

The need to use strain-based design is growing due to potential pipeline projects in environments that include permafrost, offshore ice hazards, active seismic areas and high temperature/high pressure operations. Proper design and construction of such pipelines poses numerous special challenges and requires consideration of some important processes that govern the behavior of soils. ExxonMobil has been conducting research to improve understanding of geotechnical mechanisms that result in large plastic strains in the pipelines, and to develop pipeline strain demand prediction methodologies in harsh arctic and seismically active regions. This paper discusses key challenges in strain demand estimates for Arctic onshore and offshore pipelines and is aimed at promoting industry discussion of strain demand prediction methodologies. The paper highlights ExxonMobil’s efforts in developing predictive technologies for strain demand estimation that forms the basis for the design, testing, and model development in strain-based pipeline applications.