bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of Mooring Simulations (for Mooring Integrity Assessment) With In-Service Tension Measurements
Authors: Pauw Willemijn , Hageman Remco , van den Berg Joris , Aalberts Pieter , Yamaji Hironori , Ong Alex 
Published: October 2021

Abstract
Integrity of mooring system is of high importance in the offshore industry. In-service assessment of loads in the mooring lines is however very challenging. Direct monitoring of mooring line loads through load cells or inclinometers requires subsea installation work and continuous data transmission. Other solutions based on GPS and motion monitoring have been presented as solutions to overcome these limitations [1].
Monitoring solutions based on GPS and motion data provide good practical benefits, because monitoring can be conducted from accessible area. The procedure relies on accurate numerical models to model the relation between global motions and response of the mooring system. In this paper, validation of this monitoring approach for a single unit will be presented.
The unit under consideration is a turret-moored unit operating in Australia. In-service measurements of motions, GPS and line tensions are available. A numerical time-domain model of the mooring system was created. This model was used to simulate mooring line tensions due to measured FPSO motions. Using the measured unit response avoids the uncertainty resulting from a prediction of the hydrodynamic response.
Measurements from load cells in various mooring lines are available. These measurements were compared against the results obtained from the simulations for validation of the approach. Three different periods, comprising a total of five weeks of data, were examined in more detail. Two periods are mild weather conditions with different dominant wave directions. The third period features heavy weather conditions.
In this paper, the data set and numerical model are presented. A comparison between the measured and numerically calculated mooring line forces will be presented. Differences between the calculated and measured forces are examined.
This validation study has shown that in-service monitoring of mooring line loads through GPS and motion data provides a new opportunity for mooring integrity assessment with reduced monitoring system complexity.
Water Management and Hydraulic Fracturing Operations in Middle Eastern Tight Gas Reservoirs
Authors: Suboyin Abhijith , Rahman Md Motiur , Haroun Mohamed 
Published: October 2021

Abstract
Tight gas reservoirs in the Middle East are renowned for their extremely low porosity and low permeability along with their high heterogeneity. Over the past few decades, hydraulic fracturing has gained significant attention, particularly to stimulate such formations which were previously considered uneconomical and inefficient.
Even though over a million hydraulic fracturing operations were conducted across the globe, they are still associated with a considerable amount of risk. Studies have shown that an effective, efficient and economical approach coupled with tailored water management strategies are critical for their successful development, especially in arid regions such as the Middle East.
In this research, a realistic field model was constructed and advanced to analyze hydraulic fracture propagation in the presence of natural fractures for a candidate Middle Eastern tight gas reservoir. This flexible simulation model allowed to investigate, identify and characterize the key fracture design parameters that influenced fracture geometry for the candidate field. This further allowed to categorize and propose a unique tailored workflow to highlight the governing parameters for efficient water management strategies for arid regions such as the Middle East. In addition, the results have been extended to current field practices and cases.
The constructed model can greatly assist in streamlining hydraulic fracturing operations and water management strategies in regions such as the Middle East, where resources such as water and proppants can be considered as constraints. In addition, the investigation further highlights the strong need and potential opportunities for the key players in the region to leverage their technology for an efficient water management value chain. The variables and the workflow presented in this study further demonstrates how there is no bespoke solution to a ‘best approach’ in such regions. However, a workflow identifying the key dominant categories, such as a tailored one proposed in this study, may assist in the creation of more efficient and practical strategies while contributing to the overall process chain.
Influence of Pressure on Speed of Sound in Oil-Offloading Hoses
Authors: Buijs Lennert , Meijer Irma , Pereboom Hajo , Garlid Stian , Lunde Knud 
Published: October 2021

Abstract
Pressure surge or water hammer simulations are performed to evaluate a safe design or operation of oil transfer systems. The speed of sound of the transferred fluid plays a key role within pressure surge simulations. Unlike for steel pipe systems, the speed of sound in hoses is not easily determined. In industry, a value of 450 m/s is frequently used for hoses, but this value is often used independent of conveyed fluid, pressure or the type of hose. For that reason, a project was performed that aimed to experimentally reaffirm existing speed of sound data and to extend its usable range by including tests at several static pressure levels.
Speed of sound measurements were performed on two 20”, 12 meter long, water-filled oil offloading hoses. The speed of sound was determined by the initiation of pressure waves in the hoses, while performing pressure measurements on either side of the hose. These experiments were performed at different static pressures up to 18 bar(a).
The measured values depend on the applied method to determine the speed of sound. For both applied methods, the speed of sound is higher than the classically assumed 450 m/s. The method that is considered best applicable for the purpose of the experiments, the speed of sound is significantly higher and can reach values up to 1100 m/s. The consequence of this is that the results from pressure surge studies in which 450 m/s was used, are not conservative.
Numerical Modelling of Ice Rubble Interactions Using Discrete Element Method
Authors: Liu Lei , Bailey Eleanor , Taylor Rocky , King Tony 
Published: October 2021

Abstract
A three-dimensional, freeze-bonded, Discrete Element Method (DEM) numerical model has been developed to simulate various ice rubble/ridge interaction scenarios. The numerical model was validated against the physical tests conducted by C-CORE under the Pipeline Ice Risk Assessment and Mitigation (PIRAM) Joint Industry Project. Accurate representation of ice block geometries and sizes distributions was achieved using clumped particles, rather than the traditional DEM spheres. With the use of clumped ice blocks the numerical model was able to characterize the initial keel conditions (macro porosity and freeze bond contacts) and capture interlocking behavior between ice blocks. A DEM gravel seabed model was then introduced to the clumped ice block model to allow for better representation of soil response during the simulated experiments. The main features of these model developments are described in this paper, along with a comparison of simulated results and large scale physical test results. From this work it was concluded that: (1) clumped ice blocks give more representative ice block shapes for an ice keel than spherical ice blocks, which better capture ice block interactions and overall ridge keel properties and behavior; and (2) a DEM model of the seabed gravel provided a better representation of the seabed than was possible with a continuous stiffness plane, which had important implications for modelling the keel-seabed interactions. The development and inclusion of these two new model features were found to significantly improve the accuracy of the DEM model in reproducing physical test results, while still being sufficiently computationally efficient as to allow for simulation of interactions full-scale ice ridges.
Enabling Technologies for Low Cost Subsea Field Development
Authors: Sevillano Lucas Cantinelli , Faanes Audun , Gjersvik Tor Berge , Sangesland Sigbjørn 
Published: October 2021

Abstract
The oil and gas industry faces many challenges as it is committed to provide energy to a world in transition. Declining prices impose constraints to new developments, either greenfield or brownfield. Additionally, the industry’s commitment to long-term value creation with reduced carbon footprint is confronted with the traditional solutions for well construction, production and processing, which consume significant amount of energy with corresponding high CO2 emissions. In this scenario, subsea production and processing technology has been a key enabler for the exploitation of oil and gas resources.
This paper presents a holistic review of trends in subsea technology development over recent years which have direct impact on the heart of the subsea production system, namely the subsea tree. The technological developments considered are in different subsea applications such as robotic automation, communication systems, and all-electric systems.
The objective of the ongoing research is to perform structural and fundamental analysis of subsea production and injection systems and address the question on how technological developments can be utilized to design an overall better subsea production system so the industry may fully benefit from the economic and ecological impact brought by the joint use of these technologies. Opportunities for reevaluating barrier philosophy to identify technical and economic opportunities for design simplifications of subsea trees that still leave enough pressure barriers in all operational modes are also considered.
The analyses presented indicate the current stage of the examined technologies and their potential at reducing both capital and operational cost of subsea systems. These results will be the basis for the future evaluation of improved and new design solutions within the scope of the ongoing project performed by the Norwegian University of Science and Technology and its industrial partners.
Statistical Description of Nonlinear Waves
Authors: Bitner-Gregersen Elzbieta M. , Gramstad Odin 
Published: October 2021

Abstract
Traditionally, wave parameters and their statistics has been derived from time series measurements of wave elevation. Recently, due to introduction in oceanography of stereo video camera systems, increasing attention has started to be given to spatial wave data and statistics. The present study is addressing temporal and spatial statistics of nonlinear waves giving focus to individual wave parameters. A directionally spread rogue-prone sea state observed in the North Sea is used as an example in the analysis which is based on numerical HOSM (Higher Order Spectral Method) simulations. The nonlinear order in the HOSM solver is set to M = 3, which includes the leading order nonlinear dynamical effects, including the effect of modulational instability. The following wave parameters are investigated: surface elevation, wave crests and wave troughs. The results demonstrate that the maximum spatial crest in a wave record can be up to 70% higher than the temporal crest. Further, the study indicates that the Gram-Charlier series can be used to fit the probability density function of surface elevation. It discusses applicability of the methodology based on the Gram-Charlier series for approximation of distributions of individual wave parameters of extreme and rogue waves and recommends further exploitation of this methodology. The results are discussed in the context of marine structures’ design.
Research on the Hydrodynamic Performance of Zero Speed Fin Stabilizer
Authors: Wei Yuefeng , Yang Yi 
Published: October 2021

Abstract
Nowadays, zero speed fin stabilizer has been initially applied in ship. Whether zero speed fin stabilizer can generate enough lift moment to resist rolling moment or not, determines the anti-rolling effect of ship at zero speed. In the present paper, numerical model is proposed to calculate the lift force and moment of zero speed fin stabilizer. The results of numerical calculation are verified by model test results and the hydrodynamic performance of zero speed fin stabilizer are studied. The numerical results are in good agreement with the model test results. For different swing angular velocity of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer reach the maximum at the same swing angle. For the same swing angle of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer are proportional to the square of angular velocity.
Fibre Spring Mooring Solution for Mooring Floating Offshore Wind Turbines in Shallow Water
Authors: McEvoy Paul , Kim Seojin , Haynes Malak 
Published: October 2021

Abstract
Mooring of Floating Offshore Wind Turbines (FOWT) in shallow water sites (30–80m) is challenging. These sites account for a significant proportion of the nearer to shore potential wind farm locations, and are desirable as they are closer to existing infrastructure and easier to access. Mooring large floating structures in very shallow waters however results in very long heavy mooring lines designed to minimize platform surge and protect the electrical cables. This paper presents an innovative Fibre Spring Mooring (FSM) solution which combines a high modulus, non-stretch, lightweight rope with a compliant nonlinear polymer spring offering a complete semi-taut mooring system which can be connected directly between the platform and the seabed. The paper will present Orcaflex simulation results of a 12MW barge type FOWT platform, moored using a semi-taut FSM mooring at three chosen North Sea locations close to existing wind farms, of 30m, 40m and 50m water depths. Different FSM configurations, with different line lengths, footprint, and ratio of fibre to spring are considered.
Investigation of Multiphase Flow in Porous Media Around Perforation Tunnel Near Wellbore Region, Experimental and Numerical Study
Authors: Elsanoose Abadelhalim , Abobaker Ekhwaiter , Khan Faisal , Rahman Aziz , Aborig Amer 
Published: October 2021

Abstract
Understanding the behavior of the multiphase flow in the porous media near the wellbore region is essential for increasing wells’ productivity and oil recovery. In this paper, an experimental and numerical study of multiphase flow in porous media near a perforation tunnel is presented. The effect of properties on the flow, such as porosity and permeability, are crucial for increasing oil and gas production. Two-phase flow through a cylindrical porous media with a perforation tunnel samples experimentally and numerically tested. Five sandstone samples were created at Memorial university labs, the sample dimensions are 30.48 cm high, 15.54 cm diameter, and a perforation tunnel has a 25.54 cm depth and 2.54cm diameter. The air and water injected into the sample radially at different flow rates, the water flow rate ranged from 1 to 3 LPM, and the air 3 to 9 LPM. The simulation carried out using ANSYS-Fluent 18.1 commercial software simulates the Volume Of Fluid method VOF coupled with the different turbulent models used to simulate the flow. The results showed that the porous media’s pressure buildup is greatly affected by the gas flow rate and its permeability. The wellbore pressure and porosity have more negligible effect on the pressure buildup profile in the porous media. The dominant factor for the breakthrough of a fluid in a core sample is the gas flow rate. Incorporating the gas flow in a porous system will reduce hydrostatic pressure loss, and less time is required to activate the breakthrough time.
Stochastic Time-Dependent Deterioration Models for Estimating Residual Service Life of Offshore Jacket-Type Platforms
Authors: Srikanth Ishwarya , Arockiasamy M. 
Published: October 2021

Abstract
This paper presents deterioration models for maintenance planning of offshore jacket platform based on two methods: i) stochastic Markov-chain based model and ii) stochastic-mechanistic deterioration models based on steel corrosion rates. Markov-chain models require the estimation of transition probability matrix (TPM), which is typically derived from the inspection data. The global structural health condition of the jacket is computed based on the condition of individual elements and their criticality in terms of failure consequence. The criticality factors are established based on nonlinear static redundancy analyses. This method can model deterioration when routine inspection records of jacket members are available. When there is scarcity of inspection records, stochastic-mechanistic deterioration modeling approach can be used. Monte-Carlo simulations with established corrosion wastage models are utilized to estimate the time-dependent deterioration of jacket legs, horizontal and diagonal bracings in splash and immersion zones. This method is proposed when there is scarcity of inspection records. The deterioration models are further utilized to predict the timing for Maintenance, Repair and Rehabilitation (MRR) actions, and estimate the residual service life of the jacket platform. This study demonstrates the application of the proposed deterioration modeling approaches with a case study of a typical 4-legged offshore jacket platform.
Probabilistic Fatigue Assessment of a Mooring Line Based on Station-Keeping Trials in Ice
Authors: Sinsabvarodom Chana , Leira Bernt J. , Chai Wei , Naess Arvid 
Published: October 2021

Abstract
The intention of this work is to perform a probabilistic fatigue assessment of a mooring line due to loads associated with the station-keeping of a ship in ice. In March 2017, the company Equinor (Statoil) conducted full-scale tests by means of station-keeping trials (SKT) in drifting ice in the Bay of Bothnia. The vessel Magne Viking was employed in order to represent a supply vessel equipped with a mooring line system, and the realtime loading during the full-scale measurement was recorded. The second vessel Tor Viking was serving as an ice breaker in order to maintain the physical ice management activities with different ice-breaking schemes, i.e. square updrift pattern, round circle pattern, circular updrift pattern and linear updrift pattern. The fatigue degradation corresponding to these different patterns were investigated. The peaks and valleys of the mooring tension are determined using the min peak prominence method. For the purpose of probabilistic fatigue assessment, the Rainflow-counting algorithm is applied to estimate the mooring stress range. Fatigue assessment based both on Rainflow counting and fitted probabilistic models were performed. For the latter, the stress range distributions from the observed data of mooring loads are fitted to various probability models in order to estimate the fatigue damage. It is found that the stress ranges represented by application of the Weibull distribution for the probabilistic fatigue approach provides results of the fatigue damage most similar to the Rainflow counting approach. Among the different scenarios of Ice management schemes, the circular updrift pattern provides the lowest magnitude of the fatigue degradation.
Experimental Investigation of Vortex-Induced Vibrations of a Flexibly Mounted Circular Cylinder in Combined Current and Wave Flows
Authors: Opinel Pierre-Adrien , Srinil Narakorn 
Published: October 2021

Abstract
This paper presents the experimental investigation of vortex-induced vibrations (VIV) of a flexibly mounted circular cylinder in combined current and wave flows. The same experimental setup has previously been used in our previous study (OMAE2020-18161) on VIV in regular waves. The system comprises a pendulum-type vertical cylinder mounted on two-dimensional springs with equal stiffness in in-line and cross-flow directions. The mass ratio of the system is close to 3, the aspect ratio of the tested cylinder based on its submerged length is close to 27, and the damping in still water is around 3.4%. Three current velocities are considered in this study, namely 0.21 m/s, 0.29 m/s and 0.37 m/s, in combination with the generated regular waves. The cylinder motion is recorded using targets and two Qualisys cameras, and the water elevation is measured utilizing a wave probe. The covered ranges of Keulegan-Carpenter number KC are [9.6–35.4], [12.8–40.9] and [16.3–47.8], and the corresponding ranges of reduced velocity Vr are [8–16.3], [10.6–18.4] and [14–20.5] for the cases with current velocity of 0.21 m/s, 0.29 m/s and 0.37 m/s, respectively. The cylinder response amplitudes, trajectories and vibration frequencies are extracted from the recorded motion signals. In all cases the cylinder oscillates primarily at the flow frequency in the in-line direction, and the in-line VIV component additionally appears for the intermediate (0.29 m/s) and high (0.37 m/s) current velocities. The cross-flow oscillation frequency is principally at two or three times the flow frequency in the low current case, similar to what is observed in pure regular waves. For higher current velocities, the cross-flow frequency tends to lock-in with the system natural frequency, as in the steady flow case. The inline and cross-flow cylinder response amplitudes of the combined current and regular wave flow cases are eventually compared with the amplitudes from the pure current and pure regular wave flow cases.
Prediction of Stress Correction Factor for Welded Joints Using Response Surface Models
Authors: Keprate Arvind , Donthi Nikhil 
Published: October 2021

Abstract
While performing fatigue reliability analysis of the butt-welded joints it is vital to estimate the Stress Concentration Factor (SCF) at these joints. A common approach adopted by industry to estimate the SCF at weld toes is to perform Finite Element Analysis (FEA) of the welded joints for different pipe sizes, flanges, valves etc. The SCF are calculated for each size by separately when required and are very time consuming. Although FEA is known for its accurate SCF calculation, but due to its high computational expense and time-consumption, SCF evaluation for different parameters makes the aforementioned method quite laborious. As an alternative response surface models (RSM) may be used for accurate estimation of SCF. The two basic steps in constructing a RSM are training and testing. The first corresponds to fitting a model to the intelligently chosen training points, while the second step involves comparing the predictions of the RSM to the actual response. This paper examines the applicability of 12 different RSMs for estimating SCF. The training and testing data is generated using FEA in ANSYS. In order to compare the accuracy of the RSMs, three metrics, namely, Root Mean Square Error (RMSE), Maximum Absolute Error (AAE), and Explained Variance Score (EVS) are used. A case study illustrating the applicability of the proposed approach is also presented.