bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow Assurance With Water Heated Pipe-in-Pipe in Fields With High Gas Oil Ratio and High Wax Appearance Temperature
Authors: Basilio Leandro P. , Drumond Fabiano G. , Mendes Pedro L. F. , França Alessandro , Prado Marcílio P. , Ribeiro Jonatas 
Published: November 2013

The development of pre-salt fields in the Santos Basin has presented a plenty of technological challenges, which include the production of fluids with high values of GOR (Gas Oil Ratio) and high values of WAT (Wax Appearance Temperature).
To avoid the wax deposition, it is absolutely imperative handling the temperature by insulation and/or heating. If in one hand the production system thermal insulation minimizes the heat losses to the environment, on the other hand the cooling due the thermodynamic effect of gas expansion is inevitable, mainly in fields with high GOR values.
To mitigate the problem of temperature drop, mainly in the risers where the expansion effects are pronounced, various heating systems for subsea pipelines have been studied by PETROBRAS. In parallel to these studies, it was noted that the design philosophy of the offshore production units for the pre-salt fields have indicated the use of turbo–generators to supply electrical power to the production unit, leading to the opportunity of using the generated super heated gases, originally discharged into the atmosphere, in order to feed the riser heating systems based on heated fluids circulation.
Studies of heat exchange performed indicated a great potential for the risers heating by the flow of heated water through the annular of a Pipe-in-Pipe riser, by using a WHRU (Waste Heat Recovery Unit) to recover the power discharged into the atmosphere from the turbo–generators. It was identified the possibility of heating Pipe-in-Pipe risers by circulating heated fresh water in a closed loop with water return to the production unit, or by coupling the riser heating system with the water injection system, using all the facilities for treatment and pumping of water injection.
This paper aims to describe the methodology considered in the development of a conceptual design of a heating system for a Pipe-in-Pipe riser, by the flow of heated water in the annular, in a Free Standing Hybrid Riser configuration. The paper will also present the characteristics associated with the two possibilities of heated water circuit, as well as advantages and disadvantages of each system, and the aspects related to subsea production layout.
Full-History Finite Element Modelling of Pipe-in-Pipe Flowline System: From Installation to Operation
Authors: Wang Facheng , Liu Zhigang , Liu Xinshuai 
Published: November 2013

Developments of oil and gas reservoirs in South China Sea are presently accelerated, to cope with the significant increase in energy demand from the mainland. Pipe-in-Pipe (PIP) flowline systems have been widely employed in this region and are continuously being considered for further developments. This is due to its significant thermal insulation capacity to deal with the High Pressure and High Temperature (HPHT) issue. However, the methods in industry for design of PIP systems usually have two side extremes. Simplified analytical approach may lack of accuracy and detailed FE analysis always brings considerably sophisticated modelling and post-processing tasks. To overcome this situation, COTEC Offshore Solutions, together with its mother company, China Offshore Oil Engineering Company, have developed a cost-effective, beam elements based, 3D simulation model using ABAQUS, a general purpose finite element analysis (FEA) package. The mode allows complicated structures of PIP system to be represented in an effective way and adopts a representation of stinger for S-lay installation analysis. A full-history time-dominate analysis from installation to operation is performed in one model, rather than the commonly used ‘snapshot’ analysis.
In this study, a simplified modeling guidance of PIP components have been suggested. On the basis of the guidance, a novel 3D beam-elements based model has been produced to accurately represent complex PIP structural behaviors, but with minimum increase in modeling complexity. The analysis is carried out on the time-domain basis, which permits the full strain and stress history of the installation and operation to be observed and the most onerous time-point during the full installation and operation to be captured.
Prototype Measurement for Deep Water Floating Platforms Based on Monitoring Technology
Authors: Yu Du , Wu Wen-hua , Yue Qian-jin 
Published: November 2013

Due to the complexity of ocean environmental conditions and non-linear structural responses, there are many uncertainties in establishing design of deep-water floating platforms. Traditional hydrodynamic analysis and model test, till now, still can’t provide the long-term safety and reliability for floating structure in harsh environments. Prototype test, as a full-scale experimental method, is carried out on in-service platforms to obtain the real response without simplification and hypothesis. The obtained data can be used not only to reduce uncertainties, but also to verify and further improve design specifications.
In this paper, the full-scale measurement technique for floating platforms is discussed. Four monitoring subsystems are built up related to different characteristics of data collection in-service platform. Individual Remote Monitoring System (IRMS) is established to perform the remote communication between platform and land. The full monitoring system is carried out on a FPS in South China Sea, which supported by a joint industry project (JIP). Some useful monitoring results are presented at last to demonstrate the reliability of the whole monitoring systems.
Statistical Methods for Prediction of Characteristic Loads for Free Fall Lifeboats Based on CFD Screening Results
Authors: Tregde Vidar , Nestegård Arne 
Published: November 2013

Computational Fluid Dynamics (CFD) has been used in a screening process to calculate characteristic loads for a Free Fall Lifeboat (FFLB) during impact and submergence. The link between various input, e.g. environmental conditions and host specific data, resulting structural loads and motion of the lifeboat is explored. The screening can be used together with host specific environmental conditions to find structural design loads and motion restrictions.
Response based analysis have been developed for both short term and long term predictions. For the short term predictions a sea state given by (Hs, Tp) on the 100-year contour line is identified and a three hour irregular sea state is simulated. This time history of surface elevations is used for a large number of random lifeboat drops. From these random drops a distribution of wave height and corresponding wave steepness is derived which is then input to an interpolation in the database of CFD screening results. The resulting responses are fitted to a Weibull distribution and the 90% quantile in this short term load distribution is determined.
The long term response analysis is further developed from the short term analysis. The short term distributions for each (Hs, Tp) are combined with the probability of occurrence of the sea state, and long term distributions are derived for the responses similar to the short term analysis.
The screening results are used to identify critical load cases which are further investigated.
Development of 3MW Tidal Energy Platform
Authors: ter Brake Erik , Todman Mike , Armstrong John 
Published: November 2013

The Triton-3 platform is a novel tidal energy harvester capable of producing 3MW from tidal flow. The platform is a floating structure moored to the seabed by a single-point fully articulated anchorage, and carries three power trains and a number of marine auxiliaries. The driver for the design as developed by TidalStream Ltd is to reduce the cost of energy production in order to compete with the current cost of offshore wind. Independently audited cost modelling shows that tidal stream energy can become competitive with offshore wind, achieving a generating cost as low as 10p/kWh at the best sites. This generating cost is estimated to be less than half that which could be achieved at a similar site from a single seabed-located turbine.
The driving aspects for the competitive cost are maximising the capacity per mooring point, reducing installation costs by float-out solutions and by providing easy access to the tidal equipment. Access is achieved by allowing the platform to come to the surface by means of de-ballasting. By doing so, there is no need for large workboats and/or diver activities to perform regular inspection and maintenance on the tidal equipment, reducing the cost significantly.
The technical aspects that arise when developing the tidal turbine platform for a typical offshore location are investigated by Houlder Ltd and discussed in this paper. A number of technical challenges have been addressed where the rotational stability in both roll and pitch are of interest. The roll of the platform is heavily affected by the performance of the turbines; sudden increase or reduction in thrust will induce significant rolling moments that must not impair the integrity of the platform. Pitching of the platform allows it to reach the surface when de-ballasted for maintenance and inspection. During normal operations, the platform remains aligned with the current and in doing so maximises the performance of the turbines.
The paper illustrates how these aspects have been achieved by means of passive solutions. By means of positioning and shaping the main body of the platform, a working configuration has been developed where the rotations of the platform remain within a limited window maximising the potential power production. The concept has been tested by TidalStream during a large-scale model testing campaign where the unit was subject to different current speeds and different turbine configurations and fault cases. This publication compares the results of the large scale model testing with numerical models developed in OrcaFlex and shows the effectiveness of the passive solutions.
Investigations on Galloping of Non-Circular Cross Sections
Authors: Damblans Guillaume , Berhault Christian , Le Cunff Cédric , Molin Bernard , Wiet Paul , Cinello Alexandre , Deglaire Thomas , Legras Jean-Luc 
Published: November 2013

Bundle arrangements are currently used in the design of underwater riser towers or oil export lines. A bundle is made of several parallel pipes linked together at intervals. Even if individual pipes are of circular section, the global external cross-section seen by the fluid is non-circular. When placed in a current, a bundle may be therefore prone to plunge instability [6], also know as “galloping”. When designing such bundle’s section, it is important to be able to predict its susceptibility to galloping and what are the implications on the whole structure.
Galloping is taking place in a low frequency range compared to VIV but with larger amplitude, up to several diameters. Instability can also occur in torsion through a coupling effect with transverse oscillations.
Riser Vortex Induced Vibrations have been studied for decades, and numerous experiments have been performed both in-situ and in model test facilities to understand and predict the instability of a slender cylindrical structure in current. The main motivation is the consequences of VIV on riser fatigue life.
If galloping and related instabilities are well known in aerodynamics [9], no large specific experiment or study exists for hydrodynamic flows [1], [7]. Therefore no guidelines exist to help prevent or predict galloping while designing cross-sections and pipe arrangements. Until recently, only the Blevins criteria [1] were available to predict the risk of instability. Based on recent examples of riser tower, experimental and numerical investigations are carried out within the “Gallopan” project in the frame of CITEPH (Concertation pour l’Innovation Technologique dans l’Exploration Production des Hydrocarbures) [11]. The main objective is to propose guidelines to avoid or reduce the risk of galloping in bundle cross section design.
Two cross section shapes are investigated, a square cross section for which results are available in the literature [1], [10], and a bundle cross section specifically designed to be unstable. Model tests are performed in two steps:
• Captive tests and transverse forced oscillation tests in steady current to derive hydrodynamic coefficients;
• Free oscillations tests in steady current to identify the range of reduced velocity where instability occurs as well as the response amplitudes. A specific experimental arrangement, based on a vertical pendulum system is used.
Numerical investigations are focused on the use of a standard riser analysis tool. Hydrodynamic coefficients issued from experiments are introduced. Model test set-up is reproduced for comparison purpose.
Numerical Modeling of Breaking Waves Over a Reef With a Level-Set Based Numerical Wave Tank
Authors: Chella Mayilvahanan Alagan , Bihs Hans , Kamath Arun , Muskulus Michael 
Published: November 2013

Wave breaking is a highly unsteady, non-linear and extremely turbulent phenomenon. During the wave breaking process, the energy of the wave system is focused close to the crest of the wave and a spatial spread of wave energy occurs. Thus, the description of such a physical phenomenon is highly complex and it requires a deep insight into the breaking wave process. The accurate assessment of breaking wave kinematics is essential for an accurate prediction of hydrodynamic loads on structures. Besides, the understanding of the transformation of waves propagating over an artificial or natural reef is important concerning the coastal processes.
The numerical model used in this study is a two-phase model, which solves the flow problem for air and water simultaneously. The Navier-Stokes equations are solved on uniform Cartesian grids in two dimensions. The complex free surface is captured by the level set method. A staggered grid is used for the computation with the velocities defined at the cell edges and the pressure at the cell centres. This avoids unphysical pressure oscillations that can occur due to the coupling of pressure and velocity in the incompressible Navier-Stokes equations. The Ghost Cell Immersed Boundary Method is employed to handle the boundary conditions for complex boundaries. Turbulence modelling is carried out using the k-ω model. Discretization of the convective terms is performed using the 5th order Weighted Essentially Non-Oscillatory (WENO) scheme. In this study, a two-dimensional numerical wave tank is used to simulate waves propagating over steep slopes and wave dissipation. The main objective of the present study is to investigate the wave breaking process over a submerged reef. This is accomplished by examining the wave profile during wave breaking and the breaker indices. Also, the numerical results are compared to data from physical experiments and the numerical results exhibit reasonable agreement with experimental data.
Analysis and Offshore Support for the Float-Over of a 24,250mT Topsides on the North West Shelf
Authors: el Mouhandiz Abdel-Ali , Bokhorst Job 
Published: November 2013

In April 2012 Heerema Marine Contractors (HMC) successfully performed the float-over of the North Rankin B topsides. With a weight of 24,250mT it is the heaviest deck installed in a single piece in the harsh offshore environment of Australia’s North West Shelf to date. During years of preparations extensive hydrodynamic analyses have been undertaken to achieve design loads, optimize the float-over equipment and ultimately determine operability limits for the installation.
As the float-over analysis contains various components with non-linear characteristics (e.g. fenders, leg mating units, mooring lines), a non-linear problem solving approach was used. The selected analysis tools use an efficient time step integration enabling a large number of simulations to be run. The strong non-linearity of the system requires a Monte Carlo simulation to obtain statistically reliable results. The numerical model included purpose built modules for the float-over equipment (such as LMUs) taking into account relevant details and project specific geometries. Available data from model tests was used in calibration and validation of the model.
Towards the offshore execution phase, the limiting combinations of wind sea and swell waves were identified. Forthese combinations the system response remained (just) within its ‘Not To Exceed’ values. During the offshore operation, prior to the actual float-over, the spectral wave conditions, wind and current were constantly monitored to validate the forecasts. Also the barge motions were measured and compared against results from the numerical models. This was used in support of the final decision to proceed with the float-over operation.
Collision of a Drifting Ship With Wind Turbines in a Wind Farm
Authors: Suzuki Hideyuki , Okayama Shinya , Fukumoto Yukinari 
Published: November 2013

A multiple collisions caused by a drifting ship which lost control and entered into a wind farm (WF) may cause relatively large risk for a WF comprised of bottom mounted type offshore wind turbines. A bottom mounted type wind turbine will be installed relatively close to shore in Japan and sometimes close to dense marine traffic area. Consideration of the risk will be necessary in planning a WF.
This paper presented an estimation of a damage caused by collision with a drifting ship accidentally entered a wind farm. The WF is assumed comprised of bottom mounted type offshore wind turbines. The size of the drift ship considered in the analysis is 6788 GT. For smaller ships, damage to wind turbine considered to be small. Entry of ships from sides other than the one facing sea route was ignored because the number of ship entries from the sides was considered small. Under a number of limitations, risk of multiple collisions in WF by a drifting ship was formulated and quantitatively estimated.
Arctic Pipelines Strain Demand Prediction
Authors: Xu Jianfeng , Abdalla Basel , Mckinnon Colin , Audibert-Hayet Annie , Coche Edmond , Gaffard Vincent 
Published: November 2013

Strain prediction is a preliminary requirement for the strain based design of arctic pipelines subject to frost heave. It involves modeling of thermal, geotechnical and mechanical of both pipe and soil behaviors. The objective is to predict frost heave and the consequences on pipeline stress-strain state.
This study involves the development of three numerical models: a geothermal model to simulate the heat transfer processes in the soil; a frost heave model to simulate the coupled heat transfer and displacement of soil; and a pipe-soil interaction model to calculate the pipe stresses and strains due to soil displacement. The frost heave prediction in the present study is based on two-dimensional finite element (FE) calculations integrating the so-called “porosity rate function”. The advantage of this approach over the other models stems from a formulation consistent with continuum mechanics.
The frost heave model is first validated with literature data. Then, calculations are performed to predict the heat transfer, frost heave, and pipe strain under design configurations and conditions.
This study presents a good application of porosity rate function in pipeline engineering design. The developed models can be further used to investigate different design options of a chilled pipeline buried in the Arctic environment.
On the Predication of Pipeline As-Laid Embedment Using a Cycle-by-Cycle Approach for Deepwater Application
Authors: Sun Jie , Chang Gwo-Ang , Liu Xiang 
Published: November 2013

In deep water, pipelines are generally laid directly on the sea bed and a pipeline’s as-laid embedment is a major source of uncertainty influencing the assessment of pipe-soil resistances, pipeline lateral buckling formation as well as lateral buckling response, end expansion and walking behavior. In order to have good control of the uncertainties in pipeline as-laid embedment, pipe laying effects, including static and dynamic pipe-soil vertical contact loads and the likely degree of soil softening due to pipeline oscillation at touch down zone should be reliably predicted.
In this paper a new procedure is introduced that uses OrcaFlex [1] to determine pipe laying effects and a cycle-by-cycle approach to predict pipeline as-laid embedment. Validation of the procedure is also presented in this paper by comparing pipeline as-laid embedment results calculated from the procedure with upper and lower bound values developed from field observation data. Very good agreement is obtained. In the study, it is found that pipe-soil vertical contact load amplitude, pipe horizontal oscillation, and duration of the oscillation at touchdown zone are important to soil softening as well as pipeline as-laid embedment.
In addition, results calculated from the procedure were also compared with those evaluated from the SAFEBUCK guideline [2]. It was found that results from the SAFEBUCK guideline, in general, underestimates the pipeline as-laid embedment.
Fatigue Analysis of Free Spanning Pipelines Subjected to Vortex Induced Vibrations
Authors: Van den Abeele F. , Boël F. , Hill M. 
Published: November 2013

Vortex induced vibration is a major cause of fatigue failure in submarine oil and gas pipelines and steel catenary risers. Even moderate currents can induce vortex shedding, alternately at the top and bottom of the pipeline, at a rate determined by the flow velocity. Each time a vortex sheds, a force is generated in both the in-line and cross-flow direction, causing an oscillatory multi-mode vibration. This vortex induced vibration can give rise to fatigue damage of submarine pipeline spans, especially in the vicinity of the girth welds.
In this paper, an integrated numerical framework is presented to predict and identify free spans that may be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). An elegant and efficient algorithm is introduced to simulate offshore pipeline installation on an uneven seabed. Once the laydown simulation has been completed, the free spans can be automatically detected. When the fatigue screening for both inline and cross-flow VIV indicates that a particular span may be prone to vortex induced vibrations, a detailed fatigue analysis is required.
Amplitude response models are constructed to predict the maximum steady state VIV amplitudes for a given pipeline configuration (mechanical properties) and sea state (hydrodynamic parameters). The vibration amplitudes are translated into corresponding stress ranges, which then provide an input for the fatigue analysis. A case study from the offshore industry is presented, and sensitivity analyses are performed to study the influence of the seabed conditions, where special emphasis is devoted on the selection of pipe soil interaction parameters.