Safety Assessment for In-service Marine Riser Containing Defects
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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.Keywords:
Drilling riser
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Drilling riser
Mode (computer interface)
Seabed
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On the basis of complex natural environment,this paper researchs vessel motion,heave compensation of ship location and riser shape while laying and lifting.With the main ponit-ROV sonar monitoring system,study around touch down point of pipeline,steel catenary riser shapes and seabed topography were made.And then these paraments to guide analysis of riser installation process was used.Finally complete monitoring technologies for steel catenary riser installation was formed,to provide technical support for the development of offshore oil and innovation of monitoring technology for riser installation in China.
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Drilling riser
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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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Riser recoil analysis for drilling at a harsh environment, deepwater site is particularly challenging. Recoil analysis results are used in conjunction with results of other riser analysis to develop a practical and safe riser management plan for drilling with a dynamically-positioned drillship at a site where rapidly-developing, high seastates occur frequently. Details of the recoil analysis are discussed along with brief references to other riser analyses that were carried out. The recoil analysis showed that criteria to avoid contact between the LMRP and BOP stack after disconnect and to limit slack in the riser tensioner ropes governed the selection of top tension settings. These recoil criteria also governed the maximum sea state in which the riser could remain connected. Recoil analysis was an important part of the effort to develop a practical and safe drilling riser management plan for a challenging location.
Recoil
Drilling riser
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The marine riser is the direct link betwen the drilling vessel and the ocean floor. With the expanded economic and political incentives for exploration, the search for hydrocarbons has been extended into increasingly hostile environments. These environments are imposing stresses that may exceed the design limits of an existing marine riser system. One situation that results in high stress is the storm hangoff of the riser and the lower marine riser package (LMRP). To prevent riser failure, the LMRP is unlatched and the riser is hungoff to ride out the storm. If a severe storm coincides with a high-velocity current, the resulting stresses could part the riser. The ideal solution to this problem is to avoid the costly purchase of an improved riser system, yet ensure the survival of the existing system subject to the severe environment loading. There are a few methods to reduce the stress level. One such method is to utilize the advantages of a variable buoyancy system. The two basic riser buoyancy systems are the fixed and variable concepts. Each concept is described. The marine riser is subjected to two stresses: axial compression and moonpool loadings. A variable buoyancy system on the bottom of the risermore » is the most desirable for the prevention of axial compression. To prevent moonpool loading, the riser's hanging weight should be increased, the hydrodynamic drag reduced, the riser physically restrained from contacting the side of the moonpool, and the riser dropped below the moonpool. A variable air-can buoyancy system remains the most practical method to increase the hanging weight of the riser. (DP)« less
Drilling riser
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This report describes the development of the riser system, which consists of a 17-in. ID, high-strength steel riser with 4-in. ID integral choke and kill lines and an air can buoyancy system. A free-standing bouyant riser feature permits the vessel to be disconnected from the riser in the event of severe storms. The development of riser design criteria is discussed. Vertical vessel and riser motion during installation, retrieval, and storm disconnect dominate the riser's structural design and require a variable buoyancy system. This report recommends that improved computer codes be used to further optimize the design of the riser, particularly in the suspended mode, and the development of critical system components be initiated as early as possible during the preliminary design phase. The program's general design criteria called for a vessel capable of performing drilling and coring operations with riser and well control equipment in 4,000-m (13,200-ft) water depths with a total drillstring length of 10,000 m (33,000 ft). The conceptual baseline riser system described here represents a feasible, cost-effective solution to one of the critical technical issues facing the OMDP. The system utilizes existing, field-proven technology wherever possible. Design Criteria for the OMDP riser system are presented. 2 refs.
Drilling riser
Choke
Conceptual design
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An analysis model is formulated and described for calculating the static and dynamic behavior of a marine riser supported from a floating vessel. Static, dynamic, and combined analyses were performed on a 16-inch riser in water depths of 400 to 200 ft. to demonstrate the consequences of extrapolating an existing riser design into deeper water. The results showed that it is practical to use the riser in 2000 ft. of water if suitable buoyancy is attached to the riser. Based on the study of this specific riser, the dynamic behavior of the riser, caused primarily by vessel response to waves, proved to be a significant design factor for all water depths. Further, the most significant factor in extending riser design into deeper water is the increased tension required to support riser which may exceed the practical axial load-carrying capacity of the riser as the water depth approaches 2000 ft.
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With the development of deep water drilling engineering, marine riser has become the important equipment. With the increase in water depth, the failure of marine riser is very serious, the vibration is the main reason. According to the actual situation, the model of marine is set up, the rule of lateral vibration is obtained. The result is helpful to avoid the phenomena of resonance of marine riser under wave loads.
Drilling riser
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