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This paper describes a development initiative intended to reduce significantly design cost and duration using digitalization. Subsea pipeline design, and in-place studies in particular, is a complex process that is broken down into a systematic sequence of calculations, all connected to a normalized and serialized meta model. The pipeline digital data model is interpreted by a framework that distributes and collects design data to various algorithms and software, thus automating the entire pipeline design workflow down to production of standardized design reports. The implementation of such an objective requires: Developing a systematic design methodology, covering industry standards as well as the client's special requirements, under a "one-size-fits-most" process; Standardizing a data model serving as a meta-model to necessary models and solvers; Standardizing data format and exchange protocol so that all models are served with required inputs and instructions; Coding design procedures as unitary applications collecting inputs from and relaying relevant results to the data model; Integrating applications into a framework that serves inputs and collects outputs from models and calculations to produce final standardized reports. Design reports with input data, results and methodology are automatically created or updated under various file formats or templates. Engineering productivity is improved drastically and the impact of rework is minimized. The productivity gain is multiplied when the design is still in the early stage and when multiple multi-disciplinary design cycles, including the stakeholder's review, are necessary.
This paper describes a development initiative intended to reduce significantly design cost and duration using digitalization. Subsea pipeline design, and in-place studies in particular, is a complex process that is broken down into a systematic sequence of calculations, all connected to a normalized and serialized meta model. The pipeline digital data model is interpreted by a framework that distributes and collects design data to various algorithms and software, thus automating the entire pipeline design workflow down to production of standardized design reports. The implementation of such an objective requires: Developing a systematic design methodology, covering industry standards as well as the client's special requirements, under a "one-size-fits-most" process; Standardizing a data model serving as a meta-model to necessary models and solvers; Standardizing data format and exchange protocol so that all models are served with required inputs and instructions; Coding design procedures as unitary applications collecting inputs from and relaying relevant results to the data model; Integrating applications into a framework that serves inputs and collects outputs from models and calculations to produce final standardized reports. Design reports with input data, results and methodology are automatically created or updated under various file formats or templates. Engineering productivity is improved drastically and the impact of rework is minimized. The productivity gain is multiplied when the design is still in the early stage and when multiple multi-disciplinary design cycles, including the stakeholder's review, are necessary.
Mobile mudmats are increasingly adopted as foundation solution for subsea structures in offshore field developments, to allow their horizontal movement under the cyclically imposed expansion/contraction operating loads from the connected lines. The foundation compliance grants the dissipation of the applied loads while the structure slides on the seabed and the required base dimensions are reduced. Foldable solutions can even be installed integrated with the related lines, passing through the pipelay vessel tower. The described experience is based upon design and installation of mobile mudmats for subsea structures in the last twenty years of activity in several deepwater areas all over the world. The design has been improved with time and its robustness has been demonstrated using alternative analytical approaches and Finite Element Model of the system with proper definition of soil-foundation behavior through equivalent springs. The geotechnical engineering effort focused to ensure the foundation adequate bearing capacity and its ability to slide under repeated thermal/pressure expansion loads during design lifetime, without developing excessive settlements and pitch/roll unacceptable rotations that could compromise the system performance. The purpose of the present work is to raise awareness of the need for reference international criteria for the design of mobile foundations, which represent an important solution for a subsea field development. Available Codes and Standards do not cover the relevant aspects of the mobile foundation engineering: they are based upon fixed foundation concept, which is expected to be stable under all the applied load combinations without developing any significant displacement. The mobile foundation engineering challenge is to accept that a failure mechanism develops in sliding condition while proper design criteria of system stability and reliability are fulfilled. Valuable and impressive research works have been carried out and published on the subject in the recent years. However, for practical application, specific criteria are required to provide a unique basic reference for design (minimum safety requirements/methodology/guidelines), which might be supported or not by more detailed and complex approaches, as occurs for traditional "fixed" foundations. Subsea structures could be regarded in the future as special components of the pipeline with a proper methodology to investigate their interaction with the seabed for the subsequent structural analyses.
This paper is based on experience obtained during design of Payara Project, offshore Guyana, where 10" production and 16" water injection pipelines were found to be potentially susceptible to walking. Offshore pipelines that are subject to HT/HP conditions, riser tensions and seabed slopes can be susceptible to walking, which may jeopardize the integrity of connected subsea structures. Should the cumulated walking during the operating life of the pipeline exceed the maximum allowed displacement, an anchoring system could be required to mitigate the movement. However, predicting pipeline walking is a complex matter, depending on parameters often affected by significant uncertainty, such as pressure and temperature conditions, heating and cooldown cycles, soil pipe interaction, planned buckle evolution and route modifications. For this reason, a walking assessment performed during detail design can lead to uncertain results, and question arises as to the best timing to install walking mitigation structures (WMS). A Wait-and-See approach represents a good compromise, mediating between CAPEX and OPEX needs, and allowing a risk-based decision process based on pipeline behavior as monitored during planned surveys. However, the installation of WMS during operation may require ancillary structures to be installed on ‘day one’ that could nullify the strategic advantage given by the Wait-and-See, not to mention the mob/demob cost of the vessel used for installation. The Pipe Clamping Mattress (PCM), patented by Shell and commercialized by MMA Offshore, has been proposed as a convenient and effective way to anchor the pipeline, either at day one or during operation. The PCM comprises a two-winged mattress fabricated by pivoting two concrete blocks around a central hinge, and which is shaped to engage and clamp the pipe. A log mattress is then positioned to provide additional clamping force. The overall weight of PCM provides the clamping grip required to prevent pipeline slippage as well as the additional axial resistance needed to mitigate or arrest walking. An advanced FE Model for PCM performance study has been developed in ABAQUS based on the CEL methodology (Coupled Eulerian-Lagrangian). In comparison to more conventional models, this technique models the seabed as a deformable Eulerian domain, in which PCM and pipeline can penetrate. Seabed settlement and soil displacement due to system motion can be fully calculated, estimating the evolution of axial resistance and the growth of berms at the PCM sides. The objective of this paper is to improve the understanding of pipeline/PCM interaction, in particular with respect to: Verifying the overall embedment of the pipeline/PCM system.Verifying and assessing the PCM restraining capacity against axial displacement.Assessing the minimum number of PCMs required to ensure walking prevention/arrest.
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