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Analysing and learning lessons from events are key elements in risk management. The objective of studying detailed information and data regarding pipeline events was to:
A new approach linking integrity management, QRA and barriers has been developed. A key concept is “Loss of integrity (unwanted event)” defined as any condition outside the design limit that might lead to loss of containment. The new analysis approach and results from analysing 21 events in detail will be presented. A digital portal solution for data drilldown and presentation of statistics will be demonstrated.
Authors: Karsten Harneshaug, Gassco - Finn Roar Berg, Gassco - Dian Adisty, DNV GL – Øyvin Eriksen, DNV GL
This paper presents the application of an optimised design methodology for interference between trawl gear and pipelines, and the associated savings in seabed intervention. Implementation of the optimised methodology within the time frame of the project was made possible by open and constructive collaboration between Wintershall (Client), Subsea 7 (SURF Contractor) and DNV GL (Independent Verification Body). As part of Wintershall Norge’s Maria development project, a 26 km long 14” production flowline and a 46 km long 12” water injection pipeline has been installed and left exposed on the seabed. Preliminary analysis indicated that by using the traditional approach as per DNV-RP-F111, a large number of free spans would require rock infill to limit the trawl pull-over load. In order to optimise the design and potentially reduce the requirement for free span infill, an optimized methodology based on SRA (Structural Reliability Assessment) was proposed. The optimised methodology involves FE analyses of sensitivity to various parameters and Monte Carlo simulations, in order to quantitatively assess the probability of failure. It was demonstrated that the target safety levels in DNV-OS-F101 were reached without free span infill, and hence significant savings in rock dumping could be achieved without any deviation from the DNV-OS-F101 code. The collaborative attitude exhibited by all three parties involved was a key success factor. Cost saving due to reduced rock dumping scope is estimated to ~10 mill Euro.
Authors: Kristian Norland, Subsea 7 and Sigbjørn Røneid, DNV GL; Zhengmao Yang, Subsea 7; Baard Owe Bakken, Wintershall; Gaute Kolstad, DNV GL
Subsea pipeline design activities, in particular in-place thermo-mechanical analyses, require significant engineering hours, most of them related to data pre and post processing. Surveys show that a great share of engineers’ time is spent collecting, handling, converting & plotting data, and writing reports. This low added-value timeshare impacts project cost and schedule. Stepping into more systematic, scripted & standardized protocols allows efforts to be spent on higher value activities. This paper presents the development of a framework that automates pipeline design activities down to production of design reports. Design data is centralized and segregated to a database. Tasks are coded in unitary applications, collecting inputs from and relaying final results to the database. Applications include analytical computations as well as advanced FEA models, using software open API. Commercially available or in-house software are integrated, running on and sharing common datasets. Design reports are automatically created or updated in various file formats or templates. The development of this framework ensure consistent design on multiple pipeline instances. Thus, engineering productivity is improved drastically and impact of rework is reduced. The framework enables more advanced data analytics, modern optimization algorithms as well as machine learning techniques to be used, thus shrinking the time and effort previously required to compile a robust detailed design.
Authors: Amandine Laye, Kevin Victoire, Baptiste Fournier and Vincent Cocault-Duverger, Saipem
The residual curvature method (Statoil (2002), “Method for pipelaying from a coil to the seabed, controlling thermal expansion”, patents US 6,910,830, WO 02/057674 A1 (EP1358420) and NO 314056) for controlling global expansion forces is gaining popularity and has now been successfully applied to three subsea pipeline projects. Short sections of residual curvature introduced to the pipeline in the vertical direction at the reel-lay vessel can introduce an instability to the system, though it depends on the lay parameters. Different outcomes are possible: the residual curvature section may rotate over into the horizontal plane on the seabed; or it may remain vertical. If it remains vertical, it is further possible that self-weight straightens the pipe out. It is preferable for the pipeline to rotate approximately 90degrees during installation, for the purposes of reducing the critical buckling force and preventing the creation of artificial free-spans at the residual curvature sections. Therefore, it is important to predict the rotation behaviour at the design stage. Experience from, for example Statoil’s Skuld Pipeline Project, indicates that the residual curvature sections tend to rotate but rotational fixedness at the lay-vessel and resistance from soil friction restrain the pipe. Recent analysis work on rotation during installation of the Johan Sverdrup in-field pipelines is presented. The shallower depth reduced the tendency to rotation compared to reference projects, and the analysis results were used to guide installation settings to assure a robust rotation response during lay.
Authors: Pål Foss, IKM Ocean Design; Anders Rødstøl, Statoil; Nicholas Vaughan and Per Nystrøm, IKM Ocean Design; Andreas Tennoe, TechnipFMC
In February 2017 Baker Hughes had an incident during the precommissioning of a deepwater subsea pipeline, which was being conducted using monoethylene glycol (MEG) swabbing to dewater the pipeline. The incident resulted in a catastrophic failure of part of the equipment spread. A detailed investigation was conducted to determine the root cause of the incident. This paper will present details of the incident, the investigation and the findings, the conclusions of which will potentially impact pipeline precommissioning philosophies globally in the offshore pipeline industry.
The current oil price environment challenges the Offshore Industry to develop fields at lower costs, translating to a need of lower risk and more cost effective solutions.
Shawcor addressed this challenge by combining Shawcor’s ULTRA best-in-class wet insulation with rapid cast-in-place NEMO 1.1 field joints, which proved to be the most efficient end-to-end solution for an Offshore Project in Australia.
This paper addresses the use of styrenic alloys as multi-layered solids and foams offering the lowest thermal conductivity wet insulation system available on the market. Together, with a thermally efficient epoxy-urethane hybrid solid field jointing material, offers many advantages over historically used solutions. Some of the key features to be discussed are: improved thermal efficiency of the end-to-end solution, thinner insulation systems, rapidly cast field joints, increased resistance to hot/wet environments, compliance with ISO 12736 wet ageing requirements, etc.
The industry will benefit from this paper by developing a further understanding of new technologies available in the market that could bring to relevant savings when compared to traditional wet insulation solutions.
Pipeline flow assurance can be challenging; restrictions, from minor deposit buildup to full blockages, can limit or prevent production. To help ensure a pipeline remains in an optimum operational state, it is necessary to understand its contents so that any debris buildup can be managed and maintained in an efficient and cost effective way, using methods, such as routine pigging, chemical injection, or cleaning campaigns. Current methods for deposit assessment are limited to measuring small sections of the pipeline, intrusive methods, or theoretical modeling. The methodology presented is a proven, nonintrusive technology that enables operators to review deposit buildup in a safe and cost effective way without having to stop production, risking inserting tools, or investing in costly onshore excavations or offshore vessel-based intervention campaigns, thereby maximizing production uptime and throughput quickly and safely with a repeatable and verifiable high level of accuracy.
Authors: Neil Stewart, Graham Jack and Thomas Redares, Halliburton
There are a number of theories related to FBE disbondment which include but are not limited to cathodic disbondment, inadequate surface preparation of the steel pipe surface during pipeline coating application, and the build-up of residual stresses within a coating system. Insulation coating systems with a high thickness, such as multi-layer polypropylene (MLPP), carry residual stresses along the longitudinal axis. The higher the coating thickness, the higher the residual stress. The stress concentration within the coating is highest at the cutback locations which are heated during the field joint coating (FJC) process.
FBE has been observed, by the author, to disbond from the steel substrate during heating of the field joint, prior to field joint coating application. Significant disbondment of pipeline coatings is not acceptable and will damage the integrity of any pipeline system. Minimising the risk of disbondment is critical to ensure the integrity of a pipeline system.
This paper will describe the authors’ experience where FBE disbondment issues were present during the FJC pre-qualification phase. The main focus of this paper is to give an insight into the causes of FBE disbondment for pipeline coatings, how it can be mitigated, and practical solutions to resolve the FBE disbondment at the FJC stage.
Stress concentrations at cutback locations are high so it is important that the effects of residual stresses are taken into consideration for high build coating systems. Also, protection of the pipe ends is critical, even more so for high build coatings where the stresses are higher. Surface preparation of the steel substrate prior to coating application is one of the most important stages in coating application to determine the integrity of a pipeline system. It is key for all parties to work together in a collaborative manner in order to minimise the risk of FBE disbondement.
A novel method of pre-deforming a pipeline continuously into specific local wavelengths and deformation amplitudes prior to installation on the seabed has been studied as a method of controlling and possible eliminating lateral buckling. This paper first introduces the concept of pre-deformed pipelines and then presents the results of numerical analysis of different initial pre-deformation shapes that can influence the potential buckling behaviour of this pipeline system due to high temperatures and pressures. Several random distributions of out-of-straightness (OOS) are also considered along the pre-deformed pipeline to investigate the sensitivity of the system to post-installation out-of-straightness which is the largest uncertainty in pipeline design. Results found shows that with suitable selection of initial pre-deformed shape and dimension, the pipeline will only buckle at very high temperature and pressure that are far in excess of unrealistic realistic practical values. It is found that both the buckle initiation load, i.e. effective force due to applied pressure and temperature, and the longitudinal strains along the -pipe are not sensitive to the inherent distribution of OOS. This makes such a continuously pre-deformed pipeline a reliable, robust and safe lateral buckling management system.
Authors: Jayden Chee, Alastair Walker and David White (University of Western Australia)
Owing to challenging installation requirements, architectural constraints and corrosive fluid compositions, the use of flexible flowlines for offshore developments has been developing substantially over the last number of years. In-place design methodologies and analysis tools for flexible flowlines, particularly for HPHT applications, are constantly improving in line with this trend. Whilst the majority of the local mechanical design is undertaken by the flexible manufacturers, it is essential to assess the global buckling behaviour of the flexible under different loading conditions. A number of design and installation advances have been made in order to reduce the buckling propensity and overburden requirements. This paper, co-authored by Xodus and Shell, presents a case study for the recent Gannet G project where pre-trenching pressurization technique was utilized to eliminate rockdumping for buckling mitigation for an oil flowline. The effects on flowline lateral and upheaval response and the associated integrity implications were modelled during installation, pressurization, trenching, and backfilling. This included non-linear FE modelling of the flexible in order to calibrate the initial pipe shape and mimic the variation in bending stiffness, temperature and pressure expansion coefficients, and driving force under pressurization. This yielded safe, on target installation and start-up, and negated the requirement for rockdumping. The paper also shares a number of lessons learned around modelling flexible pipe behaviour, analysis techniques, and the importance of engaging with manufacturers and installation contractors early in the design in order to ensure the flexible pipeline integrity throughout its design life.
Authors: Cliff Ho, Shell UK Ltd – John Melville, Shell UK Ltd – Mostafa Tantawi, Xodus Group Ltd – Mohamad Farid, Xodus Group Ltd
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