bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Storm-Induced Precipitation on Flooding in Macau City
Authors: Yang Jie , Liu Jiandong , Kim Dong-Eon , Li Linlin , Mok Kai Meng , Liu Philip L.-F. 
Published: December 2020

Abstract
The extent and depth of coastal flooding caused by tropical cyclone can be underestimated without considering the contribution by storm-induced precipitation. In this study, the dynamic flooding processes in Macau are simulated accounting for the combined effect of storm surge and precipitation during Typhoon Mangkhut in 2018. The surface wind and atmospheric pressure during this typhoon event are generated by a parametric vortex model and are used to drive a surge–tide–wave model for producing storm-induced water levels. The precipitation rate from ERA5 reanalysis data is utilized in this modelling suite as an additional source of water mass. The numerical model is first thoroughly validated by comparing the numerical results against the measured water levels and significant wave heights at tidal gauge and wave buoy stations. By switching on/off the rainfall function in the mass conservation and momentum equations, we compare and analyze the differences of inundation depths and inundation extent induced by precipitation. The differences in the maximum inundation depths vary spatially and the increments owing to precipitation are less than 50 mm in most flooded regions, the associated contribution is less than 10% in areas with moderate and severe flooding. The effect of precipitation as additional rainfall-induced forces in the momentum equations plays a more important role than that in the mass conservation. The inundation depths induced by tide and surge are approximately two times of that induced by precipitation. Moreover, the compound effects by ocean waves and precipitation tend to decrease the increment of precipitation-induced inundation depths by precipitation alone. Finally, we also assess the performance of the overland flow model Itzï on Macau Peninsula for the same typhoon event. The present study helps identifying vulnerable areas subject to heavy precipitation in Macau and gaining more understanding of flooding mechanisms by different physical drivers.
Study on Safety Operation Period Model of Deep Water Typhoon Avoidance Well Control Considering Rheological Characteristics of Drilling Fluid
Authors: Lou Wenqiang , Wang Zhiyuan , Du Kai , Zhang Jianbo , Liao Youqiang , Pan Shaowei , Sun Baojiang 
Published: December 2020

Abstract
During the period of avoiding typhoon in deep-water drilling, the gas intrusion in the wellbore brings higher risk to the well opening operation. It is very important to improve the accuracy of typhoon avoidance cycle prediction to improve the efficiency of drilling operation and reduce the risk of well control. According to the yield stress characteristics of drilling fluid, the gas migration experiment in the yield stress fluid is carried out in this paper. Based on the experimental results and stress analysis, a prediction model of bubble rising velocity suitable for the yield drilling fluid is established. Considering the rheological properties of drilling fluid and pore characteristics of formation, a prediction model of initial bubble size is established. Combined with the velocity prediction model and bubble size prediction model, the calculation method of typhoon avoidance period is proposed. Through the calculation and analysis, it is found that under the condition of low invasion rate, the formation porosity has little influence on the initial size of bubbles, and the yield stress value of drilling fluid has great influence on the initial size of bubbles. At the same time, the model in this paper makes up for the problem that the prediction value of safe typhoon avoidance period calculated by the previous model is large, and reduces the risk of well opening operation. According to our calculation results, the measures of injecting drilling fluid with low yield stress at the bottom of the well and injecting drilling fluid with high yield stress at the top are put forward, which can effectively increase the safe typhoon avoidance period.
The Fair Evaluation of Wave Energy Converters
Authors: Tan Jian , Polinder Henk , Wellens Peter , Miedema Sape 
Published: December 2020

Abstract
In this paper, a fair evaluation method of WECs (Wave Energy Converters) is established based on frequency domain simulation. In this fair evaluation, size optimization and downsizing of PTO (Power Take-Off) capacity are included to minimize the Cost of Energy for the concerned wave location. Based on this fair evaluation, a techno-economic evaluation of a generic point absorber is conducted for a specific wave location, and two different control strategies of PTO are considered. The results show that this fair evaluation method can contribute to the improvement of techno-economic performance of WECs. Furthermore, a comparison among three different size optimization methods of WECs is performed.
EOR Techniques Tailored to Venezuelan Conventional and Unconventional Oils: Critical Review
Authors: Rodriguez M. Fernancelys 
Published: December 2020

Abstract
Venezuela has been ranked as a potential oil producer country thanks to its huge reserves of conventional and unconventional oils. Conventional reservoirs with complex fluid systems, located in the North of Monagas state, where it is possible to observe thick fluid columns with significant compositional gradients (showing changes from gas condensate to non-mobile oil-Tar mat). In these types of reservoirs EOR methods such as miscible gas flooding have been successfully applied to compensate pressure decline and avoid asphaltene deposition issues.
Production of unconventional oils, the largest highly-viscous oil reservoir of La Faja Petrolifera del Orinoco (La FPO), demands great challenges. Discovered in the 1930’s, the first rigorous evaluations of this reservoir started in the 1980s [1]; those huge deposits of highly viscous oils were considered technically and economically unattractive at that time. Due to production decline of conventional oil reservoirs, efforts are being done by the Venezuelan National Oil Company and collaborators to develop EOR projects to achieve increasing oil production in unconventional (heavy and extra-heavy) reservoirs, being the most promising options thermal and chemical EOR methods.
Some authors agree that in the FPO, only 40–65% (depending on the site) of the oil-bearing formations is suitable for thermal EOR methods. Recent works have been showing the potential of chemical EOR for extra-heavy oils in La FPO [2, 3, 4, 5, 6, 7, 8, 9], mostly for mobility control and mobilization of residual oil.
This work presents a literature review of the EOR projects in Venezuela for conventional and highly viscous oils, based on both lab and field experiences, and the perspectives for applications to increase Venezuelan oil production.
Research on Fixed Route Speed Optimization Based on Deep Neural Network and Genetic Algorithm
Authors: Wang Ziming , Chen Shunhuai , Luo Liang 
Published: December 2020

Abstract
In the downturn of the shipping industry, optimizing the speed of ships sailing on fixed routes has important practical significance for reducing operating costs. Based on the ship-engine-propeller matching relationship, this paper uses BP neural network to build main engine power model, and correction factors are introduced into the main engine power model to reflect the influence of wind and wave. The Kalman filter algorithm is used to filter the data collected by a river-sea direct ship during the voyage from Zhoushan to Zhangjiagang. The filtered data and the meteorological data obtained from the European Medium-Range Weather Forecast Center are used as the data set of the BP neural network to predict the main engine power. Based on the main engine power model, a multi-objective optimization model of ship speed under the influence of actual wind and waves was established to solve the conflicting goals of reducing sailing time and reducing main engine fuel consumption. This multi-objective model is solved by a non-dominated fast sorting multi-objective genetic algorithm to obtain the Pareto optimal solution set, thereby obtaining the optimal speed optimization scheme. Compared with the original navigation scheme, the navigation time is reduced by 8.83%, and the fuel consumption of the main engine is reduced by 12.95%. The results show that the optimization model can effectively reduce the fuel consumption and control the sailing time, which verifies the effectiveness of the algorithm.
Numerical Investigation on the Global Behavior of Jack-Up Unit Next to Footprint With Rectangular-Shaped Spudcan
Authors: Yuan Ye , Duan Menglan 
Published: December 2020

Abstract
Footprints were left on the seabed due to previous operations, and the problem of the spudcan-footprint interactions gradually becomes one of the major concerns of jack-up unit installation. The spudcan is subjected to eccentric loading conditions, which can lead to structural failure and the overturn of the jack-up unit. This paper reports the global behavior of the three-legged jack-up unit with a novel rectangular-shaped spudcan when it needs to reinstall near an existing footprint. The coupled Eulerian-Lagrangian (CEL) approach was used. A simplified three-legged jack-up unit model was developed and the flexible stiffness between the hull and legs was considered. The free-rotation heading and force-controlled loading conditions were also adopted. The bending moment distribution along the legs, horizontal force and the overturn of the jack-up unit are discussed to assess the potential of the jack-up unit sliding toward the footprint center. The critical offset distance was found at 0.3D and an offset distance of at least 1 times of the spudcan diameter is able to diminish influence of the footprint. The ability of the novel rectangular large spudcan with a flat base is shown to be effective at easing spudcan-footprint interactions, compared with generic circular spudcan.
Effect of Pre-Strain on Bending Strain Capacity of Mechanically Lined Pipe
Authors: Tkaczyk Tomasz , Vasilikis Daniil , Pepin Aurelien 
Published: December 2020

Abstract
The high demand for subsea transportation of corrosive wellhead produced fluids has created interest in economical mechanically lined pipes (MLP) made of external carbon steel and a thin internal layer of corrosion resistant alloy (CRA). The bending strain capacity of an MLP, where a CRA liner is adhered to a carbon steel host pipe by means of an interference fit, is often governed by the liner wrinkling limit state. Although the strain capacity of the MLP with a typical 3 mm thick liner is enough to withstand bending to strains encountered during installation with the S-lay or J-lay method, the liner is at risk of wrinkling when the MLP is subjected to higher bending strains during reel-lay. To allow reeled installation, the liner strain capacity is enhanced by either increasing the liner thickness or pressurizing the MLP during installation.
In the former approach, the required liner thickness is proportional to the pipe diameter. For larger diameter MLPs, it is therefore often more economical to select a 3 mm thick liner and flood and pressurize an MLP to ensure liner stability during reeling. However, the MLP may need to be depressurized and partially drained during installation to allow welding a structure, performing reel-to-reel connection or pipeline recovery which impose bending strain on a plastically pre-strained and depressurized pipeline. Furthermore, reeled pipelines may be depressurized subsea while subjected to bending loads from operation.
Although there is a history of research into the limit loads and failure modes of MLPs, there is still no comprehensive guidance on determining the risk of liner wrinkling in plastically pre-strained MLPs. In this paper, an approach is proposed for evaluating the strain capacity and assessing the risk of liner wrinkling after an MLP, subjected to plastic bending during reeled installation at elevated pressure, is depressurized and subjected to installation loads during offshore intervention or operational loading in service. The combined effect of strain history at elevated pressure, reeling-induced ovality, bending direction after depressurization, differential pressure, temperature and residual strain is discussed. The recommendations for further work are also given.
Estimating Design Loads for Floating Structures Using Environmental Contours
Authors: Zhao Yuliang , Dong Sheng , Yang Zihao , Manuel Lance 
Published: December 2020

Abstract
To ensure acceptable operation and/or survival of floating structures in extreme conditions, nonlinear time-domain simulations are often used to predict the structural response at the design stage. An environmental contour (EC) is commonly employed to identify critical sea states that serve as input for numerical simulations to assess the safety and performance of marine structures. In many studies, marginal and conditional distributions are defined to construct bivariate joint probability distributions for variables such as significant wave height and zero-crossing period; then, environmental contours can be constructed using the inverse first-order reliability method (IFORM). This study adopts alternative models to describe the generalized dependence structure between the environmental variables using copulas; the Nataf transformation is also discussed as a special case. Environmental contours are constructed, making use of measured wave data from moored buoys. Derived design loads are applied on a semi-submersible platform to assess possible differences. In addition, the long-term extremes of the tension of the mooring lines are estimated, considering uncertainties in the structural response using a 3D model (that includes response variability, ignored with the EC approach) to help establish more accurate design loads using Monte Carlo simulation. Results offer a clear indication of the extreme response of the floating structure based on the different models.
Dynamic Behaviour of a Free Hanging Vertical Pipe Forced to Oscillate at the Top
Authors: Sales L. P. A. , Trigo C. C. O. , Sevillano L. C. , Morooka C. K. 
Published: December 2020

Abstract
Vertical pipe configuration happens in subsea well re-entry operations for wellbore drilling, subsea equipment installations, deepwater intake risers, among other scenarios, usually by hanging the marine riser at the top from a platform or ship. The simple operational configuration justifies its wide application; however, there are some drawbacks such as stress concentration, fatigue, among other issues. The purpose of this study is to contribute for the overcoming of those problems by improving the understanding of hanging risers through investigations of a vertical pipe forced to oscillate horizontally at the top.
For this purpose, laboratory experiments with small diameter pipe model have been developed with oscillatory motions applied at the top termination through a mechanical device. Displacements over time and along the pipe length were measured by an optical measurement system. In the present study, a numerical scheme has been implemented for simulations to support evaluations of the experimental results.
A vertical pipe response depends on several parameters, such as pipe overall length, frequency and amplitude of oscillation itself, among others. Due to existing relative velocity between the oscillating pipe and the water surrounding it, vortex shedding occurs along the pipe length which influences riser motion behaviour.
The results from experiment and numerical simulations bring important insights for describing and understanding oscillatory vertical pipe behaviour, in the plane and the out of plane of the forced top oscillation. The obtained results provide a further step toward the modelling of Vortex-Induced Vibration (VIV) in marine risers, aiming to contribute to relevant technological advancements.
Modeling of a Shared Mooring System for a Dual-Spar Configuration
Authors: Liang Guodong , Merz Karl , Jiang Zhiyu 
Published: December 2020

Abstract
As floating wind turbines become more technically mature, the development of floating wind farms is under way. Cost-effective solutions are desired to reduce the mooring costs. The concept of a shared mooring system has been proposed for this purpose. This work presents a method to model the shared mooring system for a dual-spar configuration. By applying the theory in elastic catenary of cable structures, a shared line can be modelled. To verify the method, a dual-spar system is modelled in a multibody simulation tool, in which two floating wind turbines are connected via a shared line. Static analyses are performed by using the present method and the simulation tool. Further, a sensitivity study is applied to the shared line properties. Different mooring line properties have been investigated. The influence of the shared line properties is shown on the mooring restoring properties of the dual-spar system. The present modeling method can be applied in the preliminary design stage of shared mooring systems.
Methodology for Assessing Wellhead Integrity During its Life Cycle
Authors: Jaculli Marcelo A. , Mendes José Ricardo P. , Miura Kazuo , Colombo Danilo 
Published: December 2020

Abstract
The wellhead is an important component in the context of well integrity and operational safety, as it serves as a link between well and riser in offshore oil wells. Wellheads, combined with the BOP and/or the Christmas Tree, act as the final barrier element preventing leakage of oil from the well into the environment. The wellhead must sustain loads from the casings, which are hung into it through the casing hangers, as well as sustain loads from the riser, which is connected at the top of the BOP (right above the wellhead) through the lower flex joint. In this work, we propose a methodology for analyzing the wellhead, considering a mechanical system that couples the vessel, the riser, the wellhead itself, the conductor and surface casings, and their interaction with the soil. The simulation of this coupled system provides the loads that are transmitted to the wellhead due to its coupling with riser, vessel, casing, and soil. Then, these loads are converted into stresses and a criterion, such as yield, is applied to verify if they will cause wellhead failure. The objective of this work is to assess wellhead failure due to environmental loads (waves, currents) acting on the riser, by varying parameters such as significant wave height, peak period and current speed, as well as assess wellhead integrity during its lifecycle for operational and survival conditions. Results show that the wellhead may fail under certain environmental conditions, which would compromise well integrity and cause leakage from the well. The analysis performed here, which is deterministic, also provides a basis for a subsequent probabilistic analysis from which the wellhead reliability can be found, based on uncertainties such as the sea state parameters.
Simulating the Acceleration to Take-Off Phase of a WIG-Craft Using Results of a Constrained Experiment
Authors: Pereowei Garrick Ombor , Hu Zhiqiang , Song Lei 
Published: December 2020

Abstract
The acceleration to take-off (in calm water and rough seas) is a short duration but very important motion regime of a WIG-craft. It determines the transport efficiency of a WIG-craft as a viable alternative to high speed marine vehicles or low speed aircrafts used in conveying workers to and offshore oil and gas fields. The development of a simulation model based on results from constant speed captive model tests for a WIG boat is imperative, when in the absence of appropriate experimental test rig, there is the need to investigate the attitude of the WIG-craft during its acceleration phase. Theoretical tools for investigating the characteristics of the acceleration phase of a WIG boat are uncommon and where they exist, they are almost unreliable, not been experimentally validated. Moreover, the cost associated with conducting acceleration tests is huge. The test facilities are not readily available in most maritime engineering research institutions. This study is concerned with the development of a simulation model with input from results of captive model tests to investigate the running attitude, forces and moments acting on a WIG-boat accelerating to take-off in calm water. A constrained model tests at constant speed levels were conducted for a range of model draughts and trim angles. Multivariate multiple regression method was used to develop model equations that fits the measured aero-hydro dynamic lift, drag and moment data as a function of draught, speed and trim angle. The hydrostatic and aero-hydrodynamic steady state forces and moments where combined into a state-space form which are solved in MATLAB. The state variables and the first and second derivatives of the states of the boat as well as the forces and moments acting on it are generated as output from the simulation model. Though the simulation model proved successful in predicting the attitude of the WIG-boat including crashing and excessive acceleration and power requirement during take-off, the results from the model still need to be verified with CFD analysis, a full WIG-boat trial tests or with the expensive high speed towing tank capable of carrying out acceleration runs. The method has the potential to be improved to account for the unsteady forces and moments that exists when the WIG-boat accelerates from offshore environment.
Dynamic Behavior of a Novel Heave-Compensated Floating Platform for Well Interventions
Authors: Jaculli Marcelo A. , Leira Bernt J. , Sangesland Sigbjørn , Morooka Celso K. , Mendes José Ricardo P. 
Published: December 2020

Abstract
A new type of floating platform design has been investigated. It consists of a relatively small semi-submersible floating structure with an air chamber that aims to keep a constant buoyancy, thus effectively reducing heave motion and enabling its use under harsh environmental conditions such as in the North Sea. It aims to provide an alternative solution compared to large floating structures, such as drillships and semi-submersible platforms, in terms of time availability, drilling costs and operational flexibility. One recent focus has been on the application of this platform for reducing well intervention costs. A small diameter (workover) riser may be used for installing the well control stack on the wet Christmas tree and for performing well intervention through the riser using a wireline cable. Alternatively, the operation can take place without a riser; this operation is termed riserless well intervention (RLWI). In this work, we investigate the dynamic behavior of this system, which is attached either to a wireline — for RLWI — or to a small-sized riser for well service through the riser. By modeling this system — which acts similarly to a passive heave compensation system — we have verified that this new platform indeed experiences smaller displacements when compared to conventional platform. The reduction observed varies depending on the platform design; in some cases, it reduces the displacement by a factor of two. A relatively heavier platform with a small cross sectional water plane area is found to be the best design option, but a lighter platform might be preferable for increased flexibility, as long as its dynamic behavior is satisfactory for safe operations.