Within the framework of the FPSO Integrity JIP, a comparative study of fatigue analysis methods used by the participant Classification Societies (ABS, Bureau Veritas, DNV, Germanischer Lloyd, and Lloyd's Register) is being performed. The objectives of this study are to compare the results produced by the application of various existing fatigue analysis procedures, both with each other and with field data from the full-scale monitoring of the Glas Dowr FPSO. In the completed first phase of work, a base case for comparison was defined and each participating Classification Society made predictions of the fatigue loading and damage using its own procedures and software. In this paper, the analytical procedures applied in the first phase are described and their results compared in terms of both the predicted fatigue damage and the intermediate fatigue loading steps. This comparative process is valuable in that it provides insight into the source of any observed differences. In the ongoing second phase of work, the results of fatigue analysis procedures are being compared to site measurements from the Glas Dowr. This paper presents results from the initial study of the second phase, in which one participating Society (GL) compared analytical results against site measurements for one typical storm. Given the broad spectrum of methods that were investigated in the base case comparison, reasonably good convergence of the results for certain response quantities is observed. Other response quantities, such as the fatigue damage calculated at individual locations, can vary substantially. Introduction The JIP FPSO Integrity, led by MARIN, was initiated in 1996. Its primary focus is a full-scale monitoring and measurement campaign of the FPSO Glas Dowr, operated by Bluewater for Amerada Hess on the Dauntless and Durward field in the North Sea. Further descriptions of the JIP activities and monitoring system may be found in companion papers [1,2]. Within the framework of this JIP, a comparative study of fatigue analysis methods used by the five participating Classification Societies (ABS, Bureau Veritas, DNV, Germanischer Lloyd, and Lloyd's Register) is being performed. The objectives of the comparative study are toCompare the results produced by the various analytical procedures and software proposed by the participants.Identify the differences and gain insight into the source of these differences.Compare existing analytical procedures for FPSOs with field data from the full-scale monitoring of the FPSO Glas Dowr. To accomplish the above objectives, the comparative study has concentrated on the fatigue loading experienced by the FPSO Glas Dowr hull. In the completed first phase of work, a base case for comparison was defined and each participating Classification Society made predictions of the fatigue loading and damage using its own procedures and software. The task leader (Bureau Veritas) compiled and evaluated the results in order to identify and interpret any observed convergence or divergence between the methods. In this paper, the analytical procedures applied in the first phase are described and their results compared in terms of both the predicted fatigue damage and the intermediate fatigue loading steps.
The introduction of Integrated Operations causes a demand for integrating process control systems with office systems. A secure and reliable connection between these systems enables considerable cost savings related to:Process OptimizationMaintenanceCollaborationRemote support Shell operates two oil fields on the Norwegian Continental Shelf; Draugen and Ormen Lange. Draugen is an established oil-field having been in operation since 1993. Ormen Lange is a new gas-field based on subsea installations remotely operated from an onshore process plant. In implementation of a technological basis for IT Architecture and Security supporting Integrated Operations, certain products and services are essential for achieving the ambitious expectations. The technological basis may be separated in three fundamental areas:Establishment of plant Security Policies, a management tool for establishing plant security.Design of a Plant Network, which will facilitate communication between the office and process control networks, and communication with other subsystem networks.Implementation of Remote Services, a solution for a secure connection between the Plant Network and the office network. IT security is a major issue when integrating office systems with process control systems. Corporate, national and international standards must be adhered to, and good technical and procedural solutions must be developed. The technological nature of the underlying process control systems must be addressed when an architecture for integration is created. Both Draugen and Ormen Lange have recently been designed to facilitate Integrated Operations according to Shell requirements, integrating information from various subsystems and making real-time data available in Shell's newly developed collaboration centre in Kristiansund, Norway. The collaboration centre will provide operational support to Draugen and Ormen Lange, and is part of a collaboration network in Shell Europe. Remote services are established enabling remote access towards vendor support centers, as the ABB remote operations rooms for Ormen Lang and Draugen. Introduction In the year 2000 it was stated by a Norwegian governmental committee (Norwegian Ministry of Justice, 2000) that the division between open office and enclosed process control networks was a characteristic of the IT infrastructure of the Norwegian oil and gas industry. This division was said to increase robustness and reduced the vulnerability of the process control systems. It was also stated that there were very few functional dependencies across this boundary. This reality is being challenged with the introduction of Integrated Operations;
The Condeep production platform was installed in the North Sea's Brentfield in Aug. 1975. The installation phase is described and the results obtained during penetration of the base into the sea bed are presented. Experience gained during this installation will be of use for further work on installing concrete gravity structures. Introduction The first concrete gravity structure installed in the northern North Sea was the Ekofisk Doris tank placed for Phillips Petroleum Co. in the summer of 1973. The next Phillips Petroleum Co. in the summer of 1973. The next two installed were the Condeep production platform Beryl A for Mobil Oil Corp. and the Brent B platform for Shell/Esso. Both were installed in the summer of 1975. The water depths at the three fields are 70, 118, and 140 m, respectively. The greatest concern for installation of the Ekofisk tank was the sea-floor topography and the load distribution on the bottom slab, since the slab was only equipped with 40-cm-high concrete ribs. The sea floor at Ekofisk, however, proved to be almost perfectly flat and no problem related to an uneven sea floor arose. problem related to an uneven sea floor arose. The Condeep structures are equipped with steel skirts. To prevent the skirts from being damaged during installation, steel-pipe dowels extending below skirt-tip level are used. These keep the structure from moving laterally during the first phase of penetration known as "touchdown." The skirts have three basic functions: to improve foundation stability, to reduce the danger of scour or erosion, and to divide the base into compartments for grouting purposes. The actual installation on the sea floor is a critical phase in the life of the platform and must be included in phase in the life of the platform and must be included in the foundation design analysis. It should be checked that neither the structure nor the foundation soils are damaged or unfavorably affected during installation. This requires comprehensive instrumentation and logging of all important factors, including platform inclination, water pressure in skirt compartments, contact pressure on the base pressure in skirt compartments, contact pressure on the base of the structure, and strain within the structure. The Brent B Condeep platform was selected for an extended instrumentation program. This research project is sponsored by several oil companies operating in the North Sea, the British Dept. of Energy, Norwegian Contractors, and institutions in both Great Britain and Norway. Norwegian Contractors and the Aker Group were the general contractors for the Condeep Brent B project. In this joint venture Norwegian Contractors was responsible for the construction, the maritime operations, and the installation at the field. The deck and mechanical fittings were designed and fabricated by the Aker Group. The design concept was developed by A/S Hoyer-Ellefsen. Olav Olsen and his firm were structural consultants for the substructure. The Norwegian Geotechnical Institute acted as geotechnical consultant for the project and was responsible for the installation-phase instrumentation. The Central Institute for Industrial Research developed and produced the monitoring and data acquisition system. The River and Harbour Laboratory at the Technical U. of Norway carried out special model tests for evaluating the environmental loads. This laboratory was also responsible for monitoring the waves at the site during installation. Bloms Oppmaaling A/S was engaged as land surveyor responsible for the navigation and positioning. Det norske Veritas is the certifying society. All these organizations are based in Norway. JPT P. 231
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