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ABSTRACT Installation of conventional pipelines in areas with very irregular seabed bathygraphy may require large amounts of intervention work, e.g. gravel dumping or dredging. To facilitate pipeline installation in those areas with a minimum of intervention work, a Submerged Floating Pipeline (SFP) could be installed. The concept consists of a floating pipeline, which is anchored to the seabed by inclined or vertical tethers in an off-bottom configuration. The SFP concept is a novel technology and represents an interesting potential for relevant applications. At present, the concept is being developed and evaluated as an alternative for the gas export pipeline system from the Ormen Lange Field located outside Mid-Norway. This paper presents some key features and design aspects that are relevant for the SFP concept. The analyses are carried out based on a 20-inch internal diameter pipeline installed in 1000 m water depth. The study concludes that the SFP concept should be further investigated where installation of conventional pipeline requires very large amounts of seabed intervention works, particularly in deep water. INTRODUCTION As development of oil and gas fields is approaching deeper water, the oil companies are also facing several places with very uneven sea bottom. An illustration of such uneven sea bottom topography is given in Figure 1. This specific example is from the deep-water area west of Mid-Norway. Similar examples may also be found West of Africa and in the Far East. Laying a conventional pipeline in such areas requires a large amount of intervention work to reduce the length of free spans. For this reason, an alternative solution has been investigated: A Submerged Floating Pipeline (SFP). The basic idea is to keep the pipeline positive buoyant at all times and anchor the pipeline to the sea floor at regular intervals, as illustrated in Figure 2.
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/8 > Ormen Lange Field > Springar Formation (0.99)
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/8 > Ormen Lange Field > Egga Formation (0.99)
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/6 > Ormen Lange Field > Springar Formation (0.99)
- (21 more...)
ABSTRACT The paper describes the design considerations and construction engineering of a bundled submarine pipeline for a curved route as based on the completed pipeline prOject in May 1999 in Dang-jin, Korea. The pipeline consists of two 30" gas lines with 17.5 mm wall thickness and 70 nun weight coating. In the 3,007 m entire offshore mute, around 1,000 m was curved with 1,400 m radius. The maximum water depth reaches up to 34 meter from mean sea water level. The conslruction area is characterized with 7.5 meter tidal range with more than 4 knots current. The horizontal stability against strong current was gained in the trench, however the vertical stability was secured with specially engineered buoy tanks. To advance through the curved mute, 18 subsea guide milers were designed and installed at various spaces which satisfied the allowable stress of pipeline. The location of subsea piles were decided with FEM analysis. The reaction force for each pile from the analysis was applied in the design of subsea piles. Detailed investigations on the subsea pile space and quantity were conducted in the engineering phase. The diameter and penetration depth of each pile were carefully designed. The engineering and design of bundled pipelines with key aspects on curved section are discussed with the applied installation method. INTRODUCTION Since the first bundled pipeline installation by bottom pull took plat in Singapore in 1981, there have been a number of single and bundled pipelines installed by bottom pull technique in Asian region. (Ngiarn and etc. 1998) As the oil and gas import and oil products expert increase there are number of pipelines are constructed recently in the region. (Jo, 1999)
ABSTRACT This paper presents an application of a patent technique (the patent number is ZL94 20404.2 in China) called Fan Weathervane Multi-point Counterweight Mooring (FWMCM). The feature of the technique is to apply the weathervane effect of the single point mooring system and additionally install the counterweight to conventional multi-point mooring system to reduce the mooring load and the occupied water-area. This new system may be utilized even in severely limited water-area for discharging of product oil and liquid goods economically. The FWMCM system technique had been utilized in a engineering project at Long Men Harbor in Qinzhou Bay, Guangxi province, China, which was an ideal selection for this project. There were two oil transfer terminals that adopted the type of FWMCM system in this project; one is for 50,000-ton terminal with 4 million-ton annual transfer capacity, and the other is 20,000-ton terminal with 3 million-ton annual transfer capacity. Computer simulation and tank model tests had been carried out, the results had shown that the FWMCM system was a novel and advanced mooring system. INTRODUCTION The traditional fix jetty dock were mostly utilized to handling oil storage before the appearance of the single point mooring system in late 1950s in the field of large terminal of oil storage and handling in the sea. Nevertheless, the conventional multi-point mooring system technique is still an choice for mooring systems in the sea. The Traditional fix jetty scheme has the advantages of being direct connection between the jetty and the tanker, convenience in transportation and operation, but it suffers from the defects of being large investment, long construction period and poor stand capability to environment loads. The single point mooring system has the characteristic of weathervane, which always keeps the moored oil tanker at the least combined load position in wind, waves and current.
ABSTRACT To investigate the differences between a truncated mooring-line model and the corresponding fulllength mooring-line model, model tests regarding the llne tensions and motions of truncated and fulllength mooring llne systems were conducted in the Offshore Technology Research Center (OTRC) wave basin recently. The tests involve three models: a 1:80 scale full-length mooring line model, a 1:40 scale model truncated vertically and a 1:40 scale model truncated both vertically and horizontally. Both truncated moorlng-llne models were designed to match their static offset curves with that of the full-length moorlng-llne model in prototype scale. When the upper end (fairlead) of the mooring lines oscillated regularly or irregularly in the horizontal plane, the tensions and trajectory of a mooring llne were recorded. Numerical simulations of the motions and tensions of mooring lines are made using a nonlinear FEM (Finite Element Method) code called CABLE3D. The numerical results are compared with the corresponding measurements. The differences in dynamics between the truncated and full-length mooring lines are significant. The understanding and results of this study may be helpful to develop a method for designing a truncated mooring-line model that can better dynamically match a full-length moorlng-llne model. Introduction Recent exploration and production of gas and oil have been pushing their activities to deeper and deeper ocean. Currently they are in the range of water depth from 1000 to 3000 m. The design of a mooring system in the unprecedented water depth presents a challenge to the model tests in wave basins. Due to the limitation of the existing wave basin, either the model is made in extra small scale, or the mooring system has to be distorted. The mooring system is truncated vertically and sometimes even horizontally as well due to the limited horizontal dimensions of a basin [Bychner, etc. 1999, Ormerg, etc. 1999].
ABSTRACT A comprehensive ocean observation platform is under development, which can measure biological, chemical and physical properties in the upper ocean mixed layer and the data obtained can be sent to laboratories in real time. The displacement of the platform is about 500 tons and plans for it to be moored in the North Pacific at a depth of 5000m. The wind and wave conditions in that area of the sea are very severe and safety precautions on the platform including mooring lines are essential. Model experiments and numerical simulations on motions and mooring tensions of the ocean observation platform were made for the design of the mooring system and platform. In general, results of numerical simulations showed good agreement with those of experiments, though a few points needing improvement were discussed. INTRODUCTION Buoy systems have been very popular for ocean observations. The submerged buoy system to measure the current velocity, salinity and water temperature, the surface buoy system to monitor the salinity and water temperature in the upper ocean mixed layer, the wave rider buoy and super buoy systems for wave measurements are well known. Fortunately sensor systems for each of these purposes are small and require low power, and the scale of buoy systems is therefore usually small. For studies on the greenhouse effects the material circulation between the atmosphere and the ocean is important. Long-term measurements are required on not only the primary material of C02 and NH4 but also meteorological and ocean environmental conditions such as wind velocity, air temperature, wave height, current velocity, water temperature, salinity and plankton. Only a research vessel enable us to carry out such comprehensive observations, however it is difficult to conduct long-term observations by ship in the severe winter sea.
ABSTRACT Over the last several years there has been a substantial increase in the usage of polyester (PET) fibers for offshore mooring lines for oil drilling and production platforms. Although in-use experience with synthetic mooring lines has been favorable, there is an ongoing need for modeling the safety and reliability of these materials. However, reliability modeling of PET ropes has been hampered by the absence of a sufficient database of full-scale rope test data to use in model verification. An alternate methodology is to model the reliability of fiber ropes on a theoretical basis using the statistics of individual fiber physical properties coupled with knowledge of rope construction and translational efficiency. In this case it is necessary to understand the statistical variability of the basic strength member - the PET fiber. To aid in this approach the present study gives an overview of the basic statistics of PET fiber physical properties based on data from a typical PET fiber production facility. The basic processes of polyester fiber production and handling are reviewed as background, and typical testing protocols for fiber quality assurance are discussed. Representative data on fiber properties such as linear density, breaking strength, and elongation to failure are presented and variability within each group analyzed. INTRODUCTION The use of polyester (PET) fiber mooring ropes has increased dramatically over the last several years. The majority of this growth has been in Brazil, where Petrobras has installed more than 10 units using polyester mooring spreads (Del Vecchio and Costa, 1999). Reduced system costs and simplified mooring scope are two reasons for the drive to replace wire ropes with PET. Several consensus documents such as the Engineered Design Guide (1999) and API RP 2SM (2000) have recently been developed to provide guidance on the use of synthetic ropes in mooring systems.
ABSTRACT This paper shows the derivation of an analytical model for the local analysis of unbonded flexible pipes, which can be used as risers in offshore applications. All of the loads considered are axisymmetric, which include: axial force, twisting moment as well internal or external pressures. Prescribed displacements on the pipe's extremities, such as those producing an elongation and/or an axial rotation of the pipe, can alternatively be considered in the model, instead of the axial force and twisting moment. The possibility of gap formation between any two adjacent layers of the pipe is taken into account, rendering the obtained system of equations non-linear. This non-linear system is then solved numerically for all the unknowns of the problem, stresses or displacements. In order to verify the consistency of the proposed analytical model, results are compared with a finite element based model analysis, which, for its turn, takes some guidelines from the analytical one. The results shown in the paper concentrate mainly on the analysis of axial stresses of armour steel layers. Additionally, the adequacy of the analytical model is verified by comparing calculated values of axial and torsional stiffness with corresponding experimental data, previously published in the literature. The agreement is found to be very satisfactory in all comparative analyses, either analytical x FEM results or analytical x experimental data. INTRODUCTION Flexible pipes have been largely used by the oil industry in a very large number of offshore applications. One could certainly say that such a concept has proved successful, as far as structural integrity and lhnctionality are concerned. Nevertheless, the structural and geometrical complexity of these pipes require a number of simplifying assumptions in order to render feasible any structural analysis and modelling. Commonly assumed hypotheses can lead to significant discrepancies between calculated and experimental values
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
ABSTRACT Steel catenary risers are an attractive solution from an economical viewpoint. However they are not always feasible and their feasibility must be verified case by case, considering both extreme and long-term loads. One of the critical portions of the riser is the region near its top. There can occur great changes in curvature and so that region is a candidate to have a fatigue failure. The top pre-tension applied to the riser during the installation governs its mechanical behavior. The designer can choose its value to guarantee the expected production life for the riser. To make that choice several cases must be studied in a very time-consuming process. This paper presents a parametric analysis focusing on the fatigue behavior of the riser near the top as concern the first and second order motions of the riser's top. This analysis uses simplified models, linear approximations, asymptotic formulas and frequency domain solutions. The approach considered can be used in a predesign phase to assess the fatigue life and to compare alternative solutions. Some numerical results are presented showing that fatigue can be a problem, depending on the pre-tension level and the stiffness of the flexible joint. INTRODUCTION The petroleum industry has a long experience in employing flexible risers. Nevertheless, the technology of conventional flexible pipe construction is reaching its limit as the offshore fields become deeper. The oil companies are thus challenged to search new solutions. The employment of steel catenary risers is increasing as they are an attractive solution from an economical viewpoint. But they are not always feasible and their feasibility must be verified case by case in an exhaustive analysis that must deal with extreme and long-term loads.
- South America > Brazil (0.47)
- North America (0.28)
ABSTRACT Halliburton Subsea has been investigating an innovative concept for subsea field development. The concept combines the company's riser and bundle competency, where the subsea production template and the transport system to the surface production unit is installed in one go by using the Controlled Depth Tow Method (CDTM). The purpose of this paper is to demonstrate some of the technical challenges that have to be solved in order to materialise this concept. This concept mainly comprises of a system where the template, the bundle with all the flowlines, umbilicals, data-highways... etc and the riser is fabricated on shore as one integrated part. Then the complete system is towed to the field, installed on the seabed and then the riser bundle is tied-into the surface production unit. The system can be installed without use of advanced lifting vessels and comprehensive subsea tie-in operations. Hence, the installation time can be dramatically reduced. The system will facilitate completely insulated flowlines from the wellhead to the surface production unit. The flowlines may be heated by a hot water system. INTRODUCTION The bundle riser concept is an innovative development to integrate, in one system, flowline and subsea facilities for installation in a single operation. The system consists of a bundle with a template in one end and a topside termination head in the other end. The bundle riser differs from other pipeline bundles, as its cross section is not equal through the whole length. The bundle riser, as proposed in this paper, has two sections. One section is the part of the bundle that will be lying steady on the seabed after installation. This has the same function as the pipeline bundles and consists of production, water injection, hydraulic and service lines within a carrier pipe.
- Europe > Norway > Norwegian Sea > Halten Terrace > Block 6507/11 > Åsgard Field > Åre Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > Block 6507/11 > Åsgard Field > Tofte Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > Block 6507/11 > Åsgard Field > Tilje Formation (0.99)
- (39 more...)
ABSTRACT Vortex Induced Vibrations (VIV) are responsible for great part of the fatigue damage caused by the dynamic loeding that occurs In compliant offshore structures such as risers, The cedes, like the API RP 2RD ("Design of Risers for Hosting Production Systems and Tension-Lag Platforms"), typically require the design fatigue life to be larger than 10 times the structure service Hfe. However, because the normal dynamic models available for riser analysis do not have a formulation for the fluid transverse induced force, the fatigue damage is obtained without its consideration. The VIV damage may be assessed by specific models that consider it isolated, but there is no reliable means to calculate the total damage based on these two damage sources. To avoid this Mnd of uncertainty, a strategy is to use VIV supressors, if the risk of having VIV is considered significant, but this solution could be avoided in certain cases ff a better methodology and appropriate model were available. This paper present a summary of a research work that was carried out to improve the design methodology of individual risers, in the sense of integrating the fatigue Hfe assessment by considering all sources of damage, including VIV. INTRODUCTION The exploitation of oil in de~pe~ watts has brought a constant change in the design practice of risers. For mstance, the available practical guides do not establish a closed procedure to be applied in the design, although they recommend to account for the influence of vortex induced vibrations in the fatigue calc~ation. During its operation life, a riser it is exposed to different combinations of loads caused by the action of currents, waves and induced platform motion to the top connection. These loa & have a fiu~At~ng parcel that cause cyclic stresses in the riser wall.
- North America (0.47)
- South America > Brazil > Rio de Janeiro (0.29)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Campos Basin > Marlim Field > Macae Formation (0.99)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Campos Basin > Marlim Field > Lago Feia Formation (0.99)