Three-Dimensional Simulations of Scour around Pipelines of Finite Lengths

In the past few decades, there have been many numerical studies on the scour around offshore pipelines, most of which concern two-dimensional setups, with the pipeline infinitely long and the flow perpendicular to the pipeline. Based on the Ansys FLUENT flow solver, this study establishes a numerical tool to study the three-dimensional scour around pipelines of finite lengths. The user-defined functions are written to calculate the sediment transport rate, update the bed elevation, and adapt the computational mesh to the new boundary. The correctness of the model has been verified against the measurements of the conventional two-dimensional scour around a long pipe and the three-dimensional scour around a sphere. A series of computations are subsequently carried out to discover how the scour hole is dependent on the pipeline length. It is found that the equilibrium scour depth increases with the pipeline length until the pipeline length exceeds four times the pipe diameter.

Technical–Economic Feasibility Analysis of Subsea Shuttle Tanker

This paper presents the technical and economic feasibility analysis of the subsea shuttle tanker (SST). The SST is proposed as an alternative to subsea pipelines and surface tankers with the primary purpose of transporting CO2 autonomously underwater from onshore facilities to subsea wells for direct injection at marginal subsea fields. In contrast to highly weather-dependent surface tanker operations, the SST can operate in any condition underwater. The technical–economic analysis is performed in two steps. First, the SST’s technical feasibility is evaluated by investigating designs with lower and higher capacities. The purpose is to observe the appearance of technical limits (if present) when the SST is scaled down or up in size. Second, an economic analysis is performed using the well-reviewed cost models from the publicly available Zero Emissions Platform (ZEP) and Maritime Un-manned Navigation through Intelligence in Networks (MUNIN) D9.3 reports. The scenarios considered are CO2 transport volumes of 1 to 20 million tons per annum (mtpa) with transport distances of 180 km to 1500 km in which the cost per ton of CO2 is compared between offshore pipelines, crewed/autonomous tanker ships, and SST. The results show that SSTs with cargo capacities 10,569 m3, 23,239 m3, and 40,730 m3 are technically feasible. Furthermore, the SSTs are competitive for short and intermediate distances of 180–750 km and smaller CO2 volumes of 1–2.5 mtpa. Lastly, it is mentioned that the SST design used the DNVGL Rules for Classification for Naval Vessels, Part 4 Sub-surface ships, Chapter 1 Submarine, DNVGL-RU-NAVAL-Pt4Ch1, which is primarily catered towards military submarine design. It is expected that a dedicated structural design code that is optimized for the SST would reduce the structural weight and corresponding capital expenditure (CAPEX).

The New Technological Frontiers of CO2 and Hydrogen Transportation Via Pipelines

COVID-19 pandemic is accelerating the transition to decarbonized energy systems. In this context, major Operators and Contractors are bound to promote innovation and technological development. The paper describes how this is being applied to the design of offshore pipelines that are now required to transport not only Hydrocarbons but also anthropogenic CO2 and low-carbon Hydrogen. In order to evaluate all the new technical challenges presented in designing CO2 and H2 pipelines, a state of art has been carried out and is here presented focusing on all the new technical aspects associated to the main disciplines involved in the pipeline network design. Different technical aspects (such as performances evaluation of Equation of State in CCS, Design Standards application to both CO2 and hydrogen pipelines, energy capacity of hydrogen pipelines and others) have been also analytically or numerically addressed simulating credible pipeline operating scenarios. To achieve that, an intensive engineering effort is being dedicated to the development of knowledge, engineering tools, methods and procedures that will be the basis for the execution of future projects concerning H2 and CO2 transportation and storage. A particular focus has been dedicated to offshore pipeline design both for new installation and repurposing of existing ones. In parallel, the cooperation started between Operators, Contractors, Manufacturers, Institutions and Universities, as described in the present paper, acts as a "booster" for the consolidation of knowledge and for the advancing of technology to put in place to overcome those new challenges. Recommendations are made in relation to the gaps found in experimental evidence present in literature and gaps in Standards coverage for the proper pipeline design in those new scenarios.

Buckling Mechanism of Offshore Pipelines: A State of the Art

The buckling analysis of an offshore pipeline refers to the analysis of temperature-induced uplift and lateral buckling of pipelines by analytical, numerical, and experimental means. Thus, the current study discusses different research performed on thermal pipe-buckling and the different factors affecting the pipeline’s buckling behaviour. The current study consists of the dependency of the pipe-buckling direction on the seabed features and burial condition; the pre-buckling and post-buckling load-displacement behaviour of the pipeline; the effect of soil weight, burial depth, axial resistance, imperfection amplitude, temperature difference, interface tensile capacity, and diameter-to-thickness ratio on the uplift and lateral resistance; and the failure mechanism of the pipeline. Moreover, the effect of external hydrostatic pressure, bending moment, initial imperfection, sectional rigidity, and diameter-to-thickness ratio of the pipeline on collapse load of the pipeline during buckling were also included in the study. This work highlights the existing knowledge on the topic along with the main findings performed up to recent research. In addition, the reference literature on the topic is given and analysed to contribute to a broad perspective on buckling analysis of offshore pipelines. This work provides a starting point to identify further innovation and development guidelines for professionals and researchers dealing with offshore pipelines, which are key infrastructures for numerous maritime applications.

Assessment of the impact of ice gouging on the Arctic marine pipeline systems

Для исследования методик оценки влияния ледовой экзарации на подводные трубопроводы проанализирована отечественная и зарубежная нормативно-техническая база в области проектирования, строительства и эксплуатации морских трубопроводных систем, подробно рассмотрены общие подходы к решению данного вопроса. Систематизирован опыт строительства и эксплуатации трубопроводов в условиях замерзающих акваторий, представлены способы их защиты от повреждений в результате дрейфа ледовых образований. Дана оценка характера формирования и особенностей распределения ледово-экзарационных форм по глубине акваторий. Показано, что существующая методология оценки воздействия ледовой экзарации на морские трубопроводы не позволяет в полной мере учесть льдогрунтовое взаимодействие. Установлена целесообразность разработки критериев для определения минимальной безопасной глубины заложения подводных трубопроводов в районах с дрейфующими льдами. Обозначены направления дальнейших исследований механизмов ледового выпахивания, деформаций прилежащего к трубе грунтового массива и поведения заглубленного трубопровода. Полученные результаты позволят дополнить существующую методологию учета воздействия ледовой экзарации на морские трубопроводы, прокладываемые в замерзающих акваториях, с целью обеспечения их безопасности и надежности. To consider the methods of assessing the impact of ice gouging phenomenon on subsea oil and gas pipelines, the authors analyzed Russian and foreign codes and standards in the field of offshore pipeline systems design, construction and operation, and also considered in detail scientific approaches to investigate this issue. Within the framework of the analysis of peculiarities of offshore pipelines operation in areas with ice gouging, systematization of experience gained from pipeline systems operation in freezing waters was carried out, and methods of pipeline protection from damages caused by drifting ice formations were considered. The assessment of ice induced gouges formation and distribution features is performed. It is shown that the assessment methods presented in current codes and standards to determine the ice gouging impact on marine pipelines do not allow to directly take into account the ice-soil interaction. The feasibility of developing criteria for determining the minimum required burial depth for subsea pipelines in areas with ice gouging is determined. The directions of further research to ensure safe and failure-free operation of subsea pipeline systems in freezing water areas are presented.

Key Technology Qualification for Increasing Subsea Well Production via Drag Reducing Agents

Drag reducing agents (DRAs) are a cost-effective method to reduce pipeline pressure losses and maximize flowrates of onshore and offshore pipelines with over 40 years of proven results. With recent developments, production can also be significantly increased by injecting DRA into flow restricted subsea flowlines. This paper will provide a summary of the development and testing of a full-scale prototype subsea DRA storage and injection unit built to achieve the industry goal of alleviating flow restricted subsea pipelines. While DRA applications are proven in thousands of offshore and onshore applications, it has never been successfully injected subsea. System integration testing (SIT) is currently under way on the prototype unit, after which it will be qualified for offshore use. The technology is covered by numerous patents issued and pending in the US and other countries.

Hydrogen’s Peculiar Effect on Material Properties: Do We Need to Be Concerned About Hydrogen Transport in Pipelines?

Considering the vast number of articles that have been published during the last 150 years related to hydrogen embrittlement and the multiple attempts to explain the governing mechanisms, it is evident that hydrogen’s effect on mechanical properties in steel is still a controversial topic. This little atom has even by some authors been referred to as the “little devil”. We do not intend to explore this particular description of hydrogen any further. However, we would like to shed some light on the key technical aspects we believe need to be further scrutinized and understood to ensure that the decision-makers have sufficiently reliable data available to decide whether hydrogen gas can be safely transported in new or existing offshore pipelines at an acceptable cost.