Performance Evaluation Of The Newly Designed Marine Riser Connection
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ABSTRACT With offshore oil development projects advancing into deeper offshore waters, flexible risers suitable for floating oil production platforms are in increasing demand. So, we have developed various pipes and design methods for flexible riser systems. We have recently conducted sea tests in order to confirm the validity of our design method for flexible riser systems and to verify installation technology and measurement technology with ultrasonic device. 1. Introduction In the present test, We used a flexible riser system of j-inch dynamic pipe. First, we ascertained the movement characteristics, an important design condition, of a floating offshore structure (semisubmersible floater named "POSEIDEN") to which flexible risers are moored. Next, in order to determine a flexible riser configuration suited to the expected movements of the floating offshore structure over a long period, static and dynamic behavior analyses were conducted to establish an appropriate configuration. After design work the flexible riser system was installed to verify the practicality of installation technology, and a one-year sea test was conducted in the Japan Sea known for its severe conditions during the winter season. The usefulness of the design method was verified by comparing the observed and design values. After the sea test, the flexible riser system was recovered and the condition of the riser pipe was investigated. As a result, it was found that the pipe retained satisfactory performance. 2. Flexible Riser System Design 2.1 Design Procedure The design procedures for a flexible riser system are described below (see Fig. 1).The depth of water, currents, horizontal movement and dynamic motion of the floating offshore structure, and the weight, bending rigidity, etc. of a riser pipe are the main design conditions.A flexible riser system which would meet the design conditions was selected.Design parameters that would provide the desired flexible riser configuration were chosen.Static behavior analysis was performed for the flexible riser system based on the chosen design parameters, to check whether the horizontal movement of the floating offshore structure, could be absorbed.Similarly, dynamic behavior analysis was performed to check whether the dynamic motion of the floating offshore structure could be absorbed. When the requirements were not met in steps (4) and (5) above, the design parameters were again reviewed. 2.2 Studies of Design Conditions The design conditions, such as the depth of water and currents in the sea installation zone and the weight and bending rigidity of the riser pipe, were predetermined on the basis of data on the weather and sea conditions and the pipe specifications. The horizontal movement and dynamic motion of the floating offshore structure are very important for design. Therefore, studies were conducted to accurately ascertain these movements. 2.2.1 Horizontal Movement of Floating Offshore Structure The floating offshore structure was loosely moored by six mooring lines. So, it was moved horizontally by the waves, wind, and currents. In order to determine the behavioral characteristics of the floating offshore structure, investigations were made from land using an electric distancemeter and the odolite.
Drilling riser
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Drilling riser
Mode (computer interface)
Seabed
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One of the primary goals of riser monitoring is to build a database of measured riser behavior during different environmental conditions and compare against design predictions during each period. A comprehensive database of field measured riser response provides not only a dataset to benchmark riser performance but enables the calibration of design parameters for future risers. The calibrated set of design parameters would feedback to establish a more representative riser design process and provide greater confidence during future riser designs. The following paper establishes a methodology to benchmark riser behavior against software predictions with applications specific to a steel catenary riser (SCR) suspended from a spar platform. Aspects and challenges dealing with processing of inclined sensors to derive global motions and operational effects are discussed and addressed. A demonstration of the methodology is presented using field measurements from a Gulf of Mexico deepwater SCR under storm conditions. The riser behavior of interest for this study is specifically the touchdown motions and stress but additional comparisons are made along the entire riser length.
Catenary
Benchmark (surveying)
Drilling riser
Touchdown
Benchmarking
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Dynamics
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AbstractA device Riser Support is designed for Chinese S-Lay vessel 'HYSY-201'. The device is used to install risers as well as subsidiary structures, such as pipeline end termination (PLET), pipeline end manifold (PLEM), in-line sled (ILS) and so on for submarine pipelines. The paper mainly elaborates the finite element analysis and dynamic experiment of the deep-water Riser Support based on a truncated hybrid model. To test the mechanical property and verify the reliability of the Riser Support, some dynamic tests with the scale 1:10 are done to simulate the installation process of risers in the South China Sea. A truncation method is used to solve the problem that 3000 m riser model is still too long though it is reduced to one-tenth of the original size. Six degrees of freedom platform (SDFP) is used to simulate the movement of 'HYSY-201' vessel while a boundary control system (BCS) is also used to control and simulate the motion state of cut-off point of the riser model. SDFP and BCS together make the model test more accurate and reliable. Testing results show that stress values based on 24 kinds of typical working conditions and calculated values are accordant in the range of allowable inaccuracy, but the small error is considered reasonable because of the difference between virtual model and scaled reality model. Then, truncated hybrid method is verified to be very useful in simplifying models during the research of large-size thin tube, rod-shaped or linear model experiment, and especially the 3000 m truncated dynamic hybrid riser model experiment is a good example.Keywords: riserriser supportinstallation systemsimilar modelequivalent depth truncation AcknowledgementsThis work is supported by the Major Project of Chinese National High Technology Research and Development (863 Program) 'Deep-water submarine pipeline laying technology' (2006AA09A105) and Major Project of Chinese National Programs for Fundamental Research and Development (973 Program) 'Extreme environmental effects of deep-water engineering structures and the whole life in service safety' (2011CB013702).
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In order to ensure the marine riser safe and reliable operation,it needs to conduct a security assessment.In this paper choose a marine riser located in Bohai Sea as the target riser which is actually running on a platform.According to the actual situation of riser and China′s security assessment standards GB/T 19624-2004,the riser of a given parameter was evaluated.Then calculated the safety factor of riser with pit defects under currents and wave loads,the factor is 0.020 2,it far les than 0.44,so the riser is safe,and has a certain safety margin.
Drilling riser
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Marine drilling riser is subject to complicated environmental loads which include top motions due to Mobile Offshore Drilling Unit (MODU), wave loads and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the drilling riser system, especially at the subsea well head (WH). Statoil and BP have carried out a comprehensive model test program on drilling riser in MARINTEK’s Towing Tank in February 2015. The objective is to validate and verify software predictions of drilling riser behaviour under various environmental conditions by use of model test data. Six drilling riser configurations were tested, including different components such as Upper Flex Joint (UFJ), tensioner, marine riser, Lower Marine Riser Package (LMRP), Blow-Out Preventer (BOP), Lower Flex Joint (LFJ), buoyancy elements and seabed boundary model. The drilling riser models were tested in different load conditions: 1. Forced top motion tests 2. Regular wave test 3. Combined regular wave and towing test 4. Irregular wave test 5. Combined irregular wave and towing test 6. Towing test (VIV) Measurements were made of micro bending strains and accelerations along the riser in both In-Line (IL) and Cross-Flow (CF) directions. Video recordings were made both above and under water. In this paper, the test set-up and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the drilling riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.
Drilling riser
Towing
Subsea
Offshore drilling
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A drilling riser is a key component for offshore drilling applications. This paper discusses the selection of operation window and evacuation analysis due to Typhoon for a marine drilling riser system for South China Sea application. This paper first introduces the configuration of a marine drilling riser system. It then discusses the marine drilling riser analysis methodology. Operation window will be determined by the riser tensioner setting, flex-joints angles, strength, etc. The marine drilling riser system will be modelled by using the software of Orcaflex. Static and dynamic analysis will be performed for the Metocean in South China Sea. The selection of operation window and evacuation analysis due to Typhoon is based on API RP 16Q. A marine drilling riser example for the application in South China Sea is provided in the paper.
Drilling riser
Typhoon
Deepwater drilling
Offshore drilling
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Typical riser analysis for a marine drilling riser using the conventional composite modeling scheme will have only one line of elements mathematically representing riser pipe and auxiliary lines. The mass and weight of the riser system may be properly modeled. It is up to the analyst to include auxiliary lines’ stiffness, bending and/or axial. The rule of thumb is to ignore them if the riser is not of load-sharing design, otherwise include them. However, even with stiffness included in the model, the composite modeling scheme will not capture the load path correctly. Parametric studies were performed to develop a modeling scheme for a load-sharing marine drilling riser. This paper compares the results by the newly developed modeling scheme with the composite model. Significantly different tension patterns between the two models are observed.
Drilling riser
Tension (geology)
Parametric model
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Offshore drilling risers are important for connecting seabed wellhead and drilling vessels.By using fourth-order nonlinear partial differential equations for describing riser movement and the finite difference method(FDM),simulation analysis is conducted on riser forces.Considering the effect of top tension,buoyancy blocks and other factors on riser,corresponding calculation software is developed.The mechanical analysis and calculation program put forward in this paper feature in simplicity,high efficiency and high speed of calculation.They may be well applied to deep water drilling riser design and verification.
Drilling riser
Wellhead
Offshore drilling
Deepwater drilling
Seabed
Tension (geology)
Offshore geotechnical engineering
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