Numerical Simulation of the “Floating Spiral” Pipeline Installation Procedure: Second Stage, Spiral Transportation, Behavior Under Waves

The Floating Spiral pipeline installation method consists basically in winding the pipeline into a huge floating spiral, and towing this assembly to the installation site, where the spiral is then unwound and lowered to the seabed. In this method the pipeline is fabricated onshore, as the spiral is created, under well controlled conditions and relatively relaxed time constraints. Therefore the welds can be better inspected, which allows for optimal control of quality in pipeline manufacturing. The first stage of the installation process by this method consists in setting the pipeline afloat and winding it elastically to form a large flat spiral. This stage is studied in a companion paper [1], to be also presented at IPC2008. The second stage consists in towing the floating spiral pipeline employing standard tugboats before laying it at the installation site. The objective of this work is, therefore, to present results of parametric studies for a large length pipeline at this second stage of the Floating Spiral method. The focus now is in the pipeline behavior under wave environmental conditions during transportation. Several numerical simulations are performed and the results are discussed and compared.

A Methodology for the Prediction of Pipeline Failure Frequency Due to External Interference

The United Kingdom Onshore Pipeline Operators Association (UKOPA) is developing supplements to the UK pipeline codes BSI PD 8010 and IGE/TD/1. These supplements will provide a standardized approach for the application of quantified risk assessment to pipelines. UKOPA has evaluated and recommended a methodology: this paper covers the background to, and justification of, this methodology. The most relevant damage mechanism which results in pipeline failure is external interference. Interference produces a gouge, dent or a dent-gouge. This paper describes the fracture mechanics model used to predict the probability failure of pipelines containing dent and gouge damage and contains predictions of failure frequency obtained using the gas industry failure frequency prediction methodologies FFREQ and operational failure data from the UKOPA fault database. The failure model and prediction methodology are explained and typical results are presented and discussed.

Cut Point Optimization of Diesel Oil: Gasoline Interfaces

This paper presents the technical solution developed by Repsol YPF in one of its pipeline systems to reduce contaminated product generation as a result of the interfaces that are generated between diesel oil and gasolines during transport.

Study on Natural Gas Drag Reduction Agent and Mechanism of Gas Pipelines Drag Reduction

On the basis of the study on the principle of oil flow and that on mechanism of drag reduction and transportation promotion of oil pipelines, the article makes a further research on the Mechanism of Drag Reduction in the gas pipelines. It points out that the basic cause for gas pipelines drag reduction is to control effectively the radial pulsation of gas adjacent to pipeline wall. It is considered that the most effective drag reduction method is to reduce the pipeline wall’s roughness degree and pipeline wall’s undercoat and to make gas drag reduction agent adjacent to pipeline wall. The research shows that gas drag reduction agent should be a polymer and compound with polarity and nonpolarity long chain.

Educational Program “To Practice Safety Is to Value Life”

Accidents which resulted in lost work time: using a different concept to deal with safety, focusing directly on the behavior of the worker, leading the worker to a sharper perception of the risks and thus enabling a change of behavior towards a safer attitude. “Sounds and Links” Project: the programmatic content was made through musical dynamics because music has the power to evoke feelings, stimulating the participants to live intrapersonal and interpersonal relationships in order to promote safe behaviors. The methodology used was: • “Andragogic (adult education) Model”; • multidiscipline language; • Methodology of “experiencing and living”; and • Focus on the day-by-day situations of work and life. The project was applied to four groups with 60 people, consisting of employees from TRANSPETRO and its contractors, other group with 60 people, composed by leaders, and one group with all participants of the five groups for the general closing session. Expected Results and consequences of the Project: • to turn the concept of safety as a real value to the worker; • to preserve the integrity and to value the life; pursuit a lasting and stable changing of behavior, based on a safety culture; and • to support the management safety system and reduction of the accidents.

Designing Offshore Pipeline Safety Systems Utilising Flow and Pressure in Multi Design Pressure Pipeline Systems

The Norwegian Continental Shelf (NCS) has been a main arena for development of subsea pipeline technology over the last 25 years. The pipeline infrastructure in the North Sea is well developed and new field developments are often tied in to existing pipeline systems, /3/. Codes traditionally require a pipeline system to be designed with a uniform design pressure. However, due to the pressure drop when transporting gas in a very long pipeline, it is possible to operate multi design pressure systems. The pipeline integrity is ensured by limiting the inventory and local maximum allowable pressure in the pipeline using inlet and outlet pressure measurements in a Safety Instrumented System (SIS). Any blockage in the pipeline could represent a demand on the safety system. This concept was planned to be used in the new Gjo̸a development when connecting the 130 km long rich gas pipeline to the existing 450 km long FLAGS pipeline system. However, a risk assessment detected a new risk parameter; the formation of a hydrate and subsequent blockage of the pipeline. In theory, the hydrate could form in any part of the pipeline. Therefore, the pipeline outlet pressure could not be used in a Safety Instrumented System to control pipeline inventory. The export pressure at Gjo̸a would therefore be limited to FLAGS pipeline code. Available pressure drop over the Gjo̸a pipeline was hence limited and a large diameter was necessary. Various alternatives were investigated; using signals from neighbour installations, subsea remote operated valves, subsea pressure sensors and even a riser platform. These solutions gave high risk, reduced availability, high operating and/or capital expenses. A new idea of introducing flow measurement in the SIS was proposed. Hydraulic simulations showed that when the parameters of flow, temperature and pressure, all located at the offshore installation, were used; a downstream blockage could be detected early. This enabled the topside export pressure to be increased, and thereby reduced the pipeline diameter required. Flow measurement in Safety Instrumented Systems has not been used previously on the NCS. This paper describes the principles of designing a pipeline safety system including flow measurement with focus on the hydraulic simulations and designing the safety system. Emphasis will be put on improvements in transportation efficiency, cost reductions and operational issues.

Comparison of US and Canadian Transmission Pipeline Consensus Standards

A coordinated effort between the pipeline regulatory entities in the United States and Canada is paramount for reducing energy congestion across the border. The interconnected nature of the pipeline infrastructure in North America and the growing demand for energy in the US are clear drivers for cross border coordination and collaboration. Regulatory agency cooperation by the Canadian National Energy Board (NEB) and the US Pipeline and Hazardous Materials Safety Administration (PHMSA) recognizes this dependency and the continued safe operation and expansion of the pipeline infrastructure. To achieve these goals, much is dependent on the adequacy and effectiveness of safety and specification consensus standards covering a wide range of pipeline transportation activities. Pipeline regulations in the US and Canada rely largely on the partial or complete incorporation of industry standards by reference. The US and Canadian national pipeline regulations are compared in this paper in design and construction areas, noting the important differences.

Reduction Factors for Estimating the Probability of Failure of Mechanical Damage Due to External Interference

Quantified risk assessments (QRAs) are widely used in the UK to assess the significance of the risk posed by major accident hazard pipelines on the population and infrastructure in the vicinity of the pipeline. A QRA requires the calculation of the frequency of failures and the consequences of failures. One of the main causes of failures in onshore pipelines is mechanical damage due to external interference, such as a dent, a gouge, or a dent and gouge. In the published literature, two methods have been used to calculate the probability of failure due to external interference: • historical failure data and • limit state functions combined with historical data (i.e. structural reliability-based methods). Structural reliability-based methods are mathematically complicated, compared to using historical failure data, but have several advantages, e.g. extrapolation beyond the limited historical data, and the identification of trends that may not be apparent in the historical data. In view of this complexity, proposed supplements to the UK pipeline design codes IGE/TD/1 (natural gas) and PD 8010 (all substances) — on the application of QRAs to proposed developments in the vicinity of major accident hazard pipelines — include simple ‘reduction factors’ for use in ‘screening’ risk assessments. These ‘reduction factors’ are based on a comprehensive parametric study using a structural reliability-based model to calculate the probability of failure due to mechanical damage, defined as: gouges, and dents and gouges. The two ‘reduction factors’ are expressed in terms of the design factor and wall thickness of the pipeline. It is shown that, through appropriate normalisation, the effects of diameter, grade and toughness are secondary. Reasonably accurate, but conservative, estimates of the probability of failure can be obtained using these ‘reduction factors’. The proposed methodology is considerably simpler than a structural reliability-based analysis. The development and verification of these ‘reduction factors’ is described in this paper.

Enhanced Valve Placement Decision Making Approach for Liquid Transmission Pipelines That Utilizes Risk Reduction Techniques

The Intelligent Valve Placement (IVP) approach that considers risk (defined as likelihood × consequence) reduction techniques to identify optimum locations for sectionalizing (block valves) for new liquid transmission pipelines has been enhanced to straightforwardly optimize valve placements based on the effectiveness and potential volume out reduction of valves. Valve effectiveness is a measure that quantifies the effectiveness of a valve in reducing volume out for pipe sections that can affect one or more identified sensitive areas. The valve effectiveness calculation does not adequately consider those situations where there is significant volume out reduction potential with few or no sensitive areas present, thus the potential volume out reduction for a given valve must also be considered. The enhanced IVP approach incorporates risk reduction by reducing consequence. This is achieved through potential reduction of impacts to sensitive areas and potential volume out reduction for pipeline ruptures. A method of establishing a decision making threshold for both the valve effectiveness and potential volume out calculations has been incorporated into the approach. The valve placement effectiveness and volume out calculations are applied in an iterative manner that facilitates quick and simplified interpretation and identification of optimum valve placement. The IVP approach meets and exceeds the requirements set forth in both the National Energy Board’s On-shore Pipeline Regulations and the U.S. Department of Transport’s Emergency Flow Restricting Device expectations set out in its HCA Rulemaking. This paper outlines the approach used to augment decision making within the enhanced IVP process and presents its application to new pipeline development. Limitations to the approach are also addressed.

Subsea Pipelaying Simulation by the “Situa-Petropipe” Software: A User Friendly Alternative

Currently, Petrobras (the Brazilian state oil company) performs numerical simulations of pipelaying operations employing commercial software, such as OffPipe [1]. However, such tools presents restrictions/limitations related to the user interface, model generation and analysis formulations. These limitations hinder its efficient use for analyses of installation procedures for the scenarios considered by Petrobras, using the BGL-1 barge (owned by Petrobras) or other vessels, considering for instance particular types of stingers depending on depth and pipeline, with different lengths and geometries adapted to certain laying conditions in S-Lay procedures. Therefore, the objective of this work is to present the development and application of a tailored, in-house non-commercial computational tool in which the modules follow Petrobras users’ specifications, in order to overcome the limitations for specific needs and particular scenarios in the simulation of several types of pipeline procedures. Such tool, called SITUA-PetroPipe, presents a friendly interface with the user, for instance allowing the complete customization of the configuration of laybarge and stinger rollers. It also includes novel analysis methods and formulations, including the ability of coupling the structural behavior of the pipe with the hydrodynamic behavior of the vessel motions under environmental conditions.