Design and Sea Test of Flexible Riser System
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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.Keywords:
Drilling riser
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Due to the ever increasing size of tankers and the inadequate facilities in the United States to accommodate these large vessels, a case is presented for the construction of offshore terminals utilizing the single buoy mooring system. Background information on the increase in size of tankers since 1961 is given, and a comparison of the single buoy mooring system to the offshore island terminal concept is also included. Reasons are given for preference of the single buoy mooring system over the offshore island, and several varied uses of the single buoy mooring system are also included in the discussion.
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As the water depth increases,the force acting on the drilling riser becomes more and more complicate and higher strength and stability are requested.Considering the internal flowing mud,the external environmental loads and the axial force,the lateral vibration differential equation of a deepwater drilling riser was derived by mean of d'Alembert principle.The corresponding boundary conditions have been put forwarded and a numerical model for deepwater drilling riser is established.And the results can be referred in designing and using of deep water drilling riser.
Drilling riser
Deepwater drilling
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Offshore marine engineering, offshore aquaculture, and offshore environmental protection require periodic offshore surveys. At present, the main means of offshore marine surveys are mooring buoys and marine survey ships. Anchored buoys are fixed in place for a long time, which affects the navigation of ships. Therefore, mooring buoys cannot be deployed over a large area with high density. The cost of marine survey ships is high, especially when multipoint synchronous marine surveys are needed, and marine survey ships cannot perform offshore surveys under bad sea conditions. A profile autonomous underwater vehicle system is developed to meet the requirements of multipoint short-term synchronous offshore surveys. It is a small, reusable, low-cost equipment designed to move up and down at a mooring position while measuring temperature, salinity, depth, and other quantities along a vertical water section. Profile autonomous underwater vehicles can be commanded remotely and report their measurements in near real-time via wireless telemetry. The time it takes for a profile AUV to move up and down can indicate the current velocity. Tests were carried out on a wharf and in offshore areas, and the results were satisfactory.
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A simplified procedure has been developed for an integrated analysis of both monitoring and maring riser design for floating drilling operations. Although the design of mooring and riser systems is an integral part of the design spiral of a drilling rig, there is no direct link between API RP 2Q and API RP 2P. Consequently, marine riser analysis and vessel mooring analysis are often performed separately by engineers in the offshore industry. As a result, the mooring analysis is often based upon an assumed line pretension, and riser analysis is performed by using assumed vessel offsets. Such assumptions can lead to erroneous or even meaningless results. An integrated analysis of both mooring and riser systems requires a simultaneous analysis of both systems which satisfies API RP 2Q and API RP 2P requirements. Furthermore, this design approach will also generate an optimum design which would better utilize the capacities of the mooring and riser equipment. The design procedure presented here is best explained by an example problem. Assume a drilling company intends to determine the operating limits of a drilling rig at various water depths (300-1,050 ft) for a given geographic area. The mooring and riser equipment has been specified, andmore » the weather data for that geographic location is also known.« less
Mooring
Drilling riser
Offshore drilling
Dynamic positioning
Deepwater drilling
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A model is used to calculate this static and dynamic behavior of a marine riser supported from a floating vessel. Analysis examples demonstrate the consequences of extrapolating an existing riser design into deep water, and show that the dynamic behavior of the riser, caused primarily by vessel response to waves, is a significant design factor in all water depths. Introduction The marine riser is a conductor pipe used in floating drilling operations to convey drilling fluid and to guide tools between the drilling vessel and the wellhead at the ocean floor. The essential features of marine riser design were defined by Fischer and Ludwig who showed, with a static analysis, the importance of tensioning the riser to prevent buckling and to control deflections and stresses. An analysis by Tidwell and Ifrey further illustrated these effects. Fischer and Ludwig recognized the possible effects of dynamic behavior on the riser, but reasoned that these effects would not be a critical design factor for water depths up to 1,000 ft if the riser diameter were held to a minimum. As exploratory drilling operations move into deeper water, the dynamic effects in riser design become of increasing concern. The significance of dynamic behavior for riser design was recognized by National Engineering and Science Co. (NESCO) in their analysis of the 14,000-ft-long drilling riser for Project Mohole. Their study showed that riser Project Mohole. Their study showed that riser dynamic behavior was a significant factor in design, and that the most significant portion of the dynamic behavior was caused by motions of the drilling vessel, rather than by wave forces on the riser. The analysis model described in this paper was formulated to analyze, both statically and dynamically, the types of marine risers presently used in floating drilling operations. The analysis method employs a numerical integration scheme that differs from the series solution method employed by Fischer and Ludwig, and the finite difference methods used by Tidwell and Ifrey and by NESCO. The numerical integration method is particularly suited for an accurate representation of parameters that vary along the length of the riser and for efficient implementation on a digital computer. The purpose of this paper is to describe the mathematical model that was developed, and to illustrate the usefulness of the model with an example that shows the effects of extending a riser into deeper water. The paper is divided into two parts and an appendix. The first part describes the basis for the analysis model; the method of solving the equations in the model is described in the Appendix. The second part of the paper describes the analysis of a 16-in. riser in water depths from 400 to 2,000 ft, and discusses the effects of increasing water depth on riser design and operations. Analysis Model The analysis model of the marine riser is based on the general linear differential equation for a beam column with lateral loads in a vertical plane. A solution to the differential equation is obtained by a numerical integration method for a specified force distribution along the length and boundary conditions at each end. This section describes the equations used in the analysis model; the solution method is outlined in the Appendix. JPT P. 455
Drilling riser
Wellhead
Deepwater drilling
Offshore geotechnical engineering
Dynamic positioning
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The BP operated Greater Plutonio field development offshore Angola comprises a spread-moored FPSO in 1,300 m water depth, serving as a hub processing the fluids produced from or injected into the subsea wells. The selected riser system is a Hybrid Riser Tower comprising 11 risers bundled around a central structural tubular (Core Pipe), tensioned by a steel Buoyancy Tank at its top and maintained by an anchor base at its bottom. The Riser Tower is fabricated onshore and then towed to the field for final installation in deepwater near the FPSO. Once the Riser Tower installation is completed the risers are connected to the FPSO by means of flexible jumpers and to the flowlines by means of rigid spools. All fabrication and installation work has been performed by Acergy. This paper presents the studies performed to cover all the steps of the installation phase: build-up of the Orcaflex model, miscellaneous studies to determine model and analyses parameters, towing analysis, upending analysis, Buoyancy Tank ballasting and deballasting analyses, and contingency analyses. This paper is mainly focused on the Riser Tower installation but also covers the installation of the Riser Tower anchor and of the flexible jumpers in order to give a complete overview of the operations related to the Riser Tower system. A comparison between computed data and data measured during operations is also presented to support the overall installation analysis methodology. Lessons learned are provided for future improvement of Riser Tower installation covering main challenges such as Riser Tower modeling, weight/buoyancy repartition along the Riser Tower, Buoyancy Tank ballasting adjustment in Lobito bay, fatigue issues during surface and subsurface tow, bending moment issues during upending, etc.
Subsea
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Towing
Wellhead
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With the drying up of land resources, the oil and natural gas,power generation equipment, and ocean data is in so great request that the research of the offshore platform is increasingly important.Offshore platform structure and the design of the mooring system both are influenced by the hydrodynamic performance.Then the floating type marine equipment carrier of hydrodynamic being analyzed after doing the frequency domain calculation for the model of floating body by the hydrodynamic software AQWA here.
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Offshore mooring buoys are an inexpensive vessel storage solution. Unfortunately, offshore mooring buoys require substantially more water area than more expensive slips and piers. In some harbors, mooring anchorages have reached storage capacity and congest boat movement within harbors. The congestion in Newport Harbor, California triggered resident Marshall Duffield to propose replacing mooring anchorages with offshore mooring docks. These offshore docks enable vessels to be safely moored at a much higher density than mooring anchorages. By mooring vessels at a higher density, harbors can either reduce the water area dedicated to offshore vessel storage or they can increase mooring capacity without increasing the offshore mooring area. A case study of Newport Harbor demonstrates the use of mooring anchorages and the space savings potential of replacing the mooring anchorages with offshore mooring docks.
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Drilling riser is the important equipment from subbottom wellhead to drillship.As offshore drilling activities expand to more deeper water areas,the force acting to the marine riser becomes more and more complicated.As the water depth increases,the characteristic analysis of the marine riser becomes more and more important.The paper uses four-order differential equation,and a mechanical analysis is numerically simulated by using a finite-difference method.The effect of top tension and buoyancy blocks on the offshore riser is studied,and the corresponding software was drawn up.It is shown that the mechanical analysis method and computing program in this paper are simple,accurate and fast computation.It provides a reliable theoretical basis and guidance for the design and check of the marine riser system,and possesses of high application value.
Drilling riser
Wellhead
Offshore drilling
Deepwater drilling
Offshore geotechnical engineering
Tension (geology)
Oil drilling
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Бұл зерттеужұмысындaКaно моделітурaлы жәнеоғaн қaтыстытолықмәліметберілгенжәнеуниверситетстуденттерінебaғыттaлғaн қолдaнбaлы (кейстік)зерттеужүргізілген.АхметЯссaуи университетініңстуденттеріүшін Кaно моделіқолдaнылғaн, олaрдың жоғaры білімберусaпaсынa қоятынмaңыздытaлaптaры, яғнисaпaлық қaжеттіліктері,олaрдың мaңыздылығытурaлы жәнесaпaлық қaжеттіліктерінеқaтыстыөз университетінқaлaй бaғaлaйтындығытурaлы сұрaқтaр қойылғaн. Осы зерттеудіңмaқсaты АхметЯсaуи университетіндетуризмменеджментіжәнеқaржы бaкaлaвриaт бaғдaрлaмaлaрыныңсaпaсынa қaтыстыстуденттердіңқaжеттіліктерінaнықтaу, студенттердіңқaнaғaттaну, қaнaғaттaнбaу дәрежелерінбелгілеу,білімберусaпaсын aнықтaу мен жетілдіружолдaрын тaлдaу болыптaбылaды. Осы мaқсaтқaжетуүшін, ең aлдыменКaно сaуaлнaмaсы түзіліп,116 студенткеқолдaнылдыжәнебілімберугежәнеоның сaпaсынa қaтыстыстуденттердіңтaлaптaры мен қaжеттіліктерітоптықжұмыстaрaрқылыaнықтaлды. Екіншіден,бұл aнықтaлғaн тaлaптaр мен қaжеттіліктерКaно бaғaлaу кестесіменжіктелді.Осылaйшa, сaпa тaлaптaры төрт сaнaтқa бөлінді:болуытиіс, бір өлшемді,тaртымдыжәнебейтaрaп.Соңындa,қaнaғaттaну мен қaнaғaттaнбaудың мәндеріесептелдіжәнестуденттердіңқaнaғaттaну мен қaнaғaттaнбaу деңгейлерінжоғaрылaту мен төмендетудеосытaлaптaр мен қaжеттіліктердіңрөліaйқын aнықтaлды.Түйінсөздер:сaпa, сaпaлық қaжеттіліктер,білімберусaпaсы, Кaно моделі.
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