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Abstract Unbonded flexible risers are a critical part of offshore field architecture bringing oil and gas from seabed to platforms on the surface. A failure in operation will result in stop of production and hence a significant loss of revenue. Risers are subject to a number of loading issues including internal and external pressure, vessel motions and current and wave actions. As a result, risers, endure significant strain levels which can impact on their integrity and functionality. The recent implementation of fiber optic monitoring embedded in flexible risers, is an important step towards turning risers into inspectable structures. The embedded monitoring systems ensure the asset can operate safely at its optimum level for the maximum period of time. The combined use of optical point sensors and fully distributed sensors allow various events to be monitored. This includes breach of outer sheath, condensate build up, polymer temperature, pipe temperature during shut in, fatigue and wire break. The traditional industry method for combating these issues has been extensive onshore testing on small sections of the riser allowing the operator to build up a bank of fatigue and reliability data which is used to statistically forecast the strains and stresses the riser will encounter. This data takes into account expected changes throughout the lifecycle of the riser, such as material degradation and environmental issues including storms and hurricanes. The main inspection method in operation to back this up has been expensive inspection campaigns by diver or ROV focusing on external damage. New advances in optical technology and riser manufacturing techniques mean that a suite of real-time monitoring can provide a far more accurate picture of a riser's condition during operation. This improves decision making by allowing structural and temperature issues to be detected at the earliest possible stage and rectified in the most efficient manner, ensuring risers satisfy safety and regulatory requirements and help maximize oilfield productivity. The enabled condition dependent maintenance of risers will reduce the need for expensive ROV operations for inspection. Real time riser monitoring is set to play an increasingly important role as the operators start to insist on the adoption of this technology in the risers delivered to them. As oil production reaches into deeper and deeper water depths, the real time understanding of the integrity of the risers will become paramount. This paper details the advances that have been made in optical monitoring and visualization techniques and their application within the intelligent riser.
Abstract This paper presents the result of the Phase 1 engineering study for a RPSEA sponsored project to develop, qualify, and field deploy flexible fiber reinforced pipe (FFRP) for ultra-deepwater applications. In addition, the Phase 2 qualification testing scope of work is presented. FFRP is unbonded flexible pipe with composite reinforcement layers which has the advantages of light weight, high flexibility, and corrosion resistance. Due to these advantages, a simple, low top tension riser configuration is enabled. The design basis is a 7-inch ID, 690 barg design pressure, 120°C design temperature, 3048 meter design water depth production riser for a Gulf of Mexico application. The Phase 1 Engineering Study confirmed the product and system design to be employed in the subsequent phases. In Phase 2, a prototype pipe will be manufactured, and qualification testing will be conducted in accordance with API RP 17B recommendations. With successful testing, and subject to approval via a Phase 2 decision stage gate, Phase 3 will be an actual field deployment of the riser system with six months of performance monitoring. Included in the paper is a summary of the Phase 1achievements and task deliverables. Due to its high level of importance, a relatively large portion of the paper is dedicated to the design of the FFRP structure and system, covering final pipe cross section arrangement, the riser system configuration and the results of analyses to provide a reliable prediction of the product's behavior in various working conditions. In addition, a review of the Phase 2 plan is presented. The outcome of the on-going phase 2 qualification testing will be utilized to calibrate the design models and to confirm the suitability of the pipe design, and the riser configuration.
Abstract A flexible pipe consists of several layers which have various materials and different functions. For a new design of flexible pipe, the structural response on external loads will vary depending on the characteristics of each layer. In order to compute the behavior of flexible pipe, a cross-section analysis is required. Theoretical, numerical, and experimental approaches can be used. The prototype test is most reliable way to find the characteristics and strength of flexible pipe, and it is mandatorily required in most of applications. From experiments, failure mechanism and utilization of stress in each layer against tensile loads can be evaluated. However, it is limited in the number of tests due to the cost and the capacity of instrument. The theoretical and numerical methods are efficient to the new flexible pipe design, and many previous researchers demonstrated that those give reliable solutions. In order for prediction of the ultimate tensile strength, the non-linear material property of all layers should be considered. However, application of the non-linear material to the theoretical analysis of flexible pipe can rarely be found. In this paper, a theoretical model using an equivalent orthotropic shell is developed considering the non-linear material of tensile armour in order for the assessment of the ultimate tensile strength of flexible pipe. Comparatively, FE models are also developed considering all contacts between layers and nonlinear materials for each layer. The 2.5? ID flexible pipe provided in the previous research is used for both models. From the comparative study, both results show good agreements with respect to the elongation and equivalent stresses depending on the tension. Similar ultimate tensile strengths of the flexible pipe are obtained.
Anderson, T. A. (GE Global Research) | Fang, B. (GE Global Research) | Attia, M. (GE Global Research) | Jha, V. (GE Oil & Gas) | Dodds, N. (GE Oil & Gas) | Finch, D. (GE Oil & Gas) | Latto, J. (GE Oil & Gas)
Abstract The primary aim of the present development program is to enhance access to deepwater fields in the Gulf of Mexico, Brazil, and West Africa by reducing system, transportation and installation costs for flexible production pipe technology. To accomplish that goal composite materials are being incorporated in hybrid unbonded flexible pipe structures to enhance their overall system performance and expand the operational design envelope. The use of composite materials enables significant improvements in operating pressures at larger pipe diameters, reduced weight and top tension, and the enhanced resistance to CO2 and H2S drives further improvements in the structural sour service performance and lifespan. GE Global Research and GE Oil & Gas, with the support of Research Partnership to Secure Energy for America (RPSEA), embarked on a development program to qualify flexible pipe with an internal diameter of greater than seven inches for ultra-deepwater applications. The concept consists of an optimally engineered combination of metallic and composite reinforcing layer technologies. This hybrid design approach allows the pipe system properties to be tailored to yield the optimal result for any application conditions. The approach offers performance advantages including reduced risk on critical end fitting technology, continuous reinforcement of the liner eliminating discontinuities and local strains by fusing together the reinforcement and liner, superior matrix chemical resistance by using industry proven thermoplastic materials, and a reduced layer count leading to easier inspection. This paper will provide an overview of the progress made during the collaborative RPSEA program and specifically, will highlight the bespoke testing capabilities developed for the new composite pipe layer. Although there are several individual standards, specifications and Joint Industry Projects (JIP) in relation to composite pipes that address some of the required tests, there remains a general lack of consensus with regard to specific testing standards and understanding of the long term performance, especially considering the variety of composite pipe technologies being developed by the industry. This paper will highlight the results from mid-scale burst testing along with analysis validation, and a bespoke rotating bending fatigue test rig used to assess the bending fatigue of the composite pipe structure. Lastly, progress toward the use of sub-scale tests allied with analysis to more rapidly assess the fatigue life will be discussed.