bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential Sealing Effects of Permanent Casing Deformation
Authors: Gheibi Sohrab , Sangesland Sigbjørn , Sevillano Lucas C. , Horák Martin 
Published: December 2020

Abstract
Permanent plugging and abandonment (P&A) of oil- and gas wells requires proper sealing between the formation and the casing as well as proper sealing inside the casing. The cement sheath in the annulus is intended to function as an “impermeable” barrier. Typically, shrinkage of cement sheath takes place when the cement sets and a microannulus (MA) may be formed. In addition, cyclic pressure and temperature variations may result in cracks and debonding of the cement sheath. This paper investigates the possibility of improved cement sealing imposed by permanent deformation of the casing, thus providing a mechanical compression force to the cement and thus closing the MA when performing P&A.
Two experimental setups were designed in this context. The first setup termed casing/cement plug test, where the casing is contracted by an external pressure and simultaneous measurement of the flow rate through the setup. The second setup is termed casing/cement annular test where the casing is internally pressurized while the gas flow rate is measured.
Nonlinear finite element analyses were carried out to simulate the two test setups. The numerical results showed an acceptable agreement with the observations in the lab. The second setup was not tested in the lab, but simulated using the FEM code. The numerical analyses indicated that the same concept of casing permanent deformation is also relevant for the annular test. It is shown that the micro-annulus formed due to cycles of pressurization/depressurization as a result of inelastic deformations in the cement can be repaired by inducing permanent deformation in the casing to some extent. Finally, we concluded that permanent casing deformation could play a positive role in favour of closing the micro-annuli in P&A operations.
Crushing of a Steel Tube Umbilical (STU) Cable During Laying Operation: A Finite Element Method Assessment at the Entry/Exit Regions of Tensioner Shoes
Authors: Guttner William C. , Santos Caio C. P. , Pesce Celso P. 
Published: December 2020

Abstract
Umbilical cables are fundamental equipment used in deep and ultra-deep waters oil and gas production systems. The complexity of this kind of structure leads structural analysis to be currently performed with numerical tools. This paper presents a nonlinear three-dimensional finite element model of a typical armored Steel Tube Umbilical Cable (STU) subjected to crushing loads imposed to the umbilical cable during laying operation. The study focuses on the analysis of the stress distribution in the steel tubes at caterpillar shoes, mainly at the entry/exit transition regions. With the use of a commercial software, the finite element model is constructed, considering geometric and materials nonlinearities. Crushing loads are imposed by two rigid plates. Focus is given on the duplex tubes, with the material stress-strain curve modeled from a specific crushing experiment with a single tube and by using a classic Ramberg-Osgood fitting. Firstly, comparisons at mid-length of the three-dimensional model are made with the results from a simpler and planar finite element model. Then, the localized three-dimensional effects are analyzed. The results show a considerable increase of the stress levels in the steel tubes at these transition regions, with the occurrence of stress field redistribution after the onset of plastic deformation.
A Fundamental Study on Plastic Strain Accompanying Deformation in Large-Scale Floating Coal Transshipment Station
Authors: Nishigochi Ryo , Eto Hiroaki , Iizuka Koji , Ikoma Tomoki , Aida Yasuhiro , Masuda Koichi 
Published: December 2020

Abstract
Indonesia is the main country supplying coal in the Asia-Pacific region, and in order to secure a stable supply of coal to neighboring countries, efficient coal transportation is required. East Kalimantan Island in Indonesia is the main coal-producing area, but the sea around the island is very shallow and bulk carriers for transporting coal cannot approach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers that stays offshore. LFTS has a two-dimensional extent, and because the bulkheads for separating coal according to quality are installed on the floating body, the rigidity is partially different, and the draft also changes greatly according to the coal loading condition. In this way, LFTS has different characteristics from Mega-Float, which was built in Japan in the late 1990s with the aim of realizing a floating airport, so it is important to clarify its structural characteristics. In order to grasp the stress distribution acting on the structural member in consideration of the influence of the interaction between the overall deformation and the local deformation of LFTS, an analysis in which the entire structure is modeled in detail is desired. However, because members such as the internal bulkheads are arranged in a complicated manner in LFTS, a model in which the entire structure is modeled in detail requires enormous calculation costs in both capacity and time, it is difficult to perform the analysis. In existing research, various models have been studied, but there remains a problem in setting boundary conditions that reproduce the interaction between global and local deformations. And then, in this paper, a new modeling method of LFTS that can be analyzed efficiently was proposed. And the occurrence of stress concentration in the structural members of the LFTS was identified by systematically changing the external force conditions such as the coal loading condition and wave load assumed during the operation of the LFTS, and performing LFTS oscillation analysis and stress deformation analysis. Furthermore, the occurrence of plastic strain due to large deformation was investigated. The stiffening method that efficiently suppresses the occurrence of plastic strain was studied for the locations where the plastic strain was identified by the above analysis. These results demonstrate the importance of modeling large floating structures with complex structures.
Modeling Spatio-Temporal Characteristics of Metocean Conditions During Hurricanes Using Deep Neural Networks
Authors: Qiao Chi , Myers Andrew T. 
Published: December 2020

Abstract
Surrogate modeling of the variability of metocean conditions in space and in time during hurricanes is a crucial task for risk analysis on offshore structures such as offshore wind turbines, which are deployed over a large area. This task is challenging because of the complex nature of the meteorology-metocean interaction in addition to the time-dependence and high-dimensionality of the output. In this paper, spatio-temporal characteristics of surrogate models, such as Deep Neural Networks, are analyzed based on an offshore multi-hazard database created by the authors. The focus of this paper is two-fold: first, the effectiveness of dimension reduction techniques for representing high-dimensional output distributed in space is investigated and, second, an overall approach to estimate spatio-temporal characteristics of hurricane hazards using Deep Neural Networks is presented. The popular dimension reduction technique, Principal Component Analysis, is shown to perform similarly compared to a simpler dimension reduction approach and to not perform as well as a surrogate model implemented without dimension reduction. Discussions are provided to explain why the performance of Principal Component Analysis is only mediocre in this implementation and why dimension reduction might not be necessary.
Numerical Simulation of Elastic Deformation Based on Peridynamic Differential Operator
Authors: Hu Yumeng , Liu Fan , Feng Guoqing , Zhang Dongxu 
Published: December 2020

Abstract
The methodology of Peridynamics has been proposed for years and widely used in various engineering fields. The evolution of this theory is always in process, and two major branches appears, namely bond-based and state-based peridynamic method. Recently, a novel concept, peridynamic differential operator, was proposed and adopted in simulation of Newtonian fluid and analysis of structure strength. Just like the intrinsic idea in peridynamic theory, this new operator could convert the partial differential into its integral form so that it would enable the numerical differentiation through integration and avoid difficulties such as discontinuities or singularities encountered in the simulation. Also, unlike the traditional method that the higher order partial differential items are derived from the lower ones, peridynamic differential operator could easily provide differential items with any desired order thus it makes calculation process more efficient and convenient. In this study, the accuracy of peridynamic differential operator is tested by comparing with a given analytical formula. Then, this operator is embedded into the framework of Galerkin method and adopted for elastic deformation analysis in 2D case. The results are compared with those obtained from finite element method and its efficiency and feasibility are verified.
Caisson Breakwater for LNG and Bulk Terminals: A Study on Limiting Wave Conditions for Caisson Installation
Authors: Lin Yu , El Chahal Ghassan , Shao Yanlin 
Published: December 2020

Abstract
As the worldwide oil and gas market continues to grow and environmental concerns with respect to in-port offloading of gas have increased, there has been a boom of interest in new liquefied natural gas LNG terminals in the past years. Loading - offloading operations at LNG and bulk terminals are generally protected by a breakwater to ensure high operability. For these terminals, caisson breakwaters are generally a preferred solution in water depth larger than 15 m due to its advantages compared to rubble mound breakwaters. The caisson installation is generally planned to be carried out in the period where sea conditions are relatively calm. However, many of these terminal locations are exposed to swell conditions, making the installation particularly challenging and subject to large downtime. There is no clear guidance on the caisson installation process rather than contractors’ experiences from different projects/sites. Therefore, studies are required in order to provide general guidance on the range of acceptable wave conditions for the installation operations and to have a better understanding of the influence of the caisson geometry.
This paper presents a numerical study to determine the limiting wave conditions for caisson installing operations at larger water depth of 30–35 m for a confidential project along the African coast. Three caisson sizes/geometries are considered in order to assess and compare the wave-structure hydrodynamic interaction. The linear frequency-domain hydrodynamic analysis is performed for various seastates to determine the limiting wave conditions. Viscous effects due to flow separation at the sharp edges of the caisson are considered by using a stochastic linearization approach, where empirical drag coefficients are used as inputs. Parametric studies on caisson size and mooring stiffness are also presented, which can be used as a basis for future optimization. The uncertainty in the applied empirical viscous drag coefficients taken from the literature is examined by using a range of different drag coefficients. Further, the use of clearance-independent hydrodynamic coefficients (e.g. added mass and damping) may be questionable when the caisson is very close to the seabed, due to a possible strong interaction between caisson bottom and seabed. This effect is also checked quantitatively by a simplified approach.
The findings of the study are presented in the form of curves and generalized to be used by designers and contractors for general guidance in future projects.
Effect of Rheological Properties of Yield Pseudoplastic Fluids on Slugs Characteristics in an Upward Vertical Pipe: Experiments and Modeling
Authors: Ihmoudah Abdalsalam , Awad Mohamed M. , Rahman Mohammad Azizur , Butt Stephen D. 
Published: December 2020

Abstract
Two-phase flow of gas/yield Pseudoplastic fluids can be found in different industrial applications like the chemical processes, oil industry, and petroleum transport in pipelines. In this study, experimental and numerical investigation of the influence of Rheological properties of non-Newtonians fluids in two-phase flow (gas/yield Pseudoplastic fluids) on slug characteristics in an upward vertical flow were performed. Different concentrations of Xanthan gum solutions (0.05%, 0.10%, and 0.15%, by w/w), which are referred to as non-Newtonian, yield Pseudoplastic behavior used as the working liquids and air as a gas. The experiments were conducted in an open-loop re-circulating system has a total length of 65 m to ensure phase mixing, and authorize flow regime patterns to develop. The vertical pipe has a diameter of 76.3 mm. API-compliant 8-speed rotational viscometer model 800 was used to measure the rheological properties of non-Newtonian fluids. Flow visualization and recording videos were achieved by A high-speed camera to a comparison between behavior of Newtonian and non-Newtonian fluids in the two-phase model. Pressure transducers used to measure high-response pressure. Computational fluid dynamics software (ANSYS fluent 2019 R3) was used for the numerical investigation. The volume of fluid (VOF) model has been chosen for tracking immiscible fluids. CFD simulation results compared to the experimental data. The slug behavior and shape were noticed to be affected by changing the rheological properties of the liquid phase. with increasing XG concentration at the same operations conditions, we found that non-uniform and random distribution of small bubbles due to the effective viscous force of a liquid phase.
Blowing the Top on Parametric Resonance: Relief Valve Control for the Stabilisation of an OWC Spar Buoy
Authors: Davidson Josh , Gomes Rui P. F. , Galeazzi Roberto , Henriques João C. C. 
Published: December 2020

Abstract
An active control method, to suppress the onset of pitch/roll parametric resonance on an oscillating water column (OWC) spar buoy, is proposed in this paper, which utilises a pressure relief valve at the top of the OWC air chamber. The paper examines the hypothesis that by opening the relief valve, to reduce the air chamber pressure difference and to decouple the dynamics of the spar buoy and the OWC within, the natural pitch/roll frequencies of the system will be shifted, allowing parametric resonance to be cancelled when its onset is detected. The paper reports on experiments, performed to test the stated hypothesis, with a small-scale model OWC spar buoy in a wave flume. Two configurations are considered and tested in a range of monochromatic waves (1) fully closed air chamber; (2) fully open chamber. The results partially confirm the hypothesis, demonstrating that the occurrence of parametric resonance observed for certain wave frequencies when the chamber is closed does not occur when the chamber is open. However, the change in the natural pitch/roll frequencies between the two configurations is very small, and parametric resonance occurs in both confurations for waves with twice this frequency.
Experimental Investigation of Tip Vortex Influence on VIV of a Circular Cylinder at High Reynolds Numbers
Authors: Youssef M. , Tödter Simon , Neugebauer Jens , el Moctar Ould , Schellin Thomas E. 
Published: December 2020

Abstract
Lower aspect ratio cylinders are of interest as these are used for, e.g., wind turbine towers. We present a study predicting the vortex-induced vibration (VIV) characteristics of a cantilever circular cylinder with an aspect ratio (length-to-diameter ratio) of 10. The free end condition caused tip vortices to generate end-cell-induced vibration (ECIV) occurring at wind speeds higher than the threshold wind speed for VIV. Wind tunnel experiments were conducted at Reynolds numbers ranging from 3.6 × 104 to 3.26 × 105. The cantilever circular cylinder was made of a polypropylene pipe mounted on a six-degree-of-freedom load cell. Its upper end was free to oscillate in the streamline and transverse directions. An accelerometer was placed at the top of the cylinder to measure accelerations and, via twofold integration, retrieve cylinder motions at its free end. Down-wash tip vortices occurred. The response amplitude with vortex shedding was finite, even at the synchronization point. It increased with flow velocity and affected the synchronization behavior. Results suggested that nonlinearities occurring when vortices were Shedd were due to free end conditions and higher Reynolds numbers.
Study on Data Analysis of On-Board Measurement Data for Ship’s Speed Power Performance
Authors: Kim Sang-Yeob , Kim Min-Su , Han Ki-Min , Kim Joon-gyu , Seo Dae-Won 
Published: December 2020

Abstract
Present paper deal with data analysis of on-board measurement data from operating ship. The main purpose of the study is estimating speed-power performance of target ship which are in service now. Various kinds of on-board measured data are considered such as ship speed, engine RPM, brake power, draught, rudder angle, etc. Also, in order to estimate the added resistance, weather forecast data about wind, wave and current was considered. What this study found was that the onboard measurement data and weather forecast data have a lot of uncertainty, so the data need to be post-processed in order to derive reliable speed power performance curve. For this reason, current study proposed three-step filtering procedure. The filtering schemes are based on 1) absolute threshold value, 2) moving window, 3) derivative threshold value. The paper compared the performance estimation results of ship with and without filtering technique and some conclusions could be drawn.
Virtual Prototyping of a Low-Height Lifting System for Offshore Wind Turbine Installation
Authors: Xu Jiafeng , Ataei Behfar , Halse Karl Henning , Hildre Hans Petter , Mikalsen Egil Tennfjord 
Published: December 2020

Abstract
Due to the ever higher demands from the energy market, the quantity, dimension and power capacity of newly installed offshore wind turbines are continuously increasing. In terms of logistical management, economic feasibility and engineering difficulty, the traditional installation methods, predominantly represented by using Jack-up vessel and offshore cranes, will hit their limitations soon in the future. Offshore turbines have a relatively fixed geometric profile and physical characteristics: a slender cylindrical tower with huge blades attached on the top end. In this work, we exploited these features and designed a low-height lifting system for deploying wind turbine onto a floating spar platform. The low-height lifting system lifts the wind turbine with wires attached to the bottom of the tower, and keeps the balance of the tower with extra tug lines on the mid-section. The wires and tug lines are controlled by an active 6DOF compensation system. The low-height lifting system removes the necessity of a huge offshore crane onboard and can scale well to even larger wind turbines. The design is virtual prototyped in the simulator of Offshore Simulator Centre using FATHOM simulation software. Different design configurations are discussed in terms of the general arrangement, system dimensions and control methods.
Barrier Analysis of Emergency Disconnect on DP Mobile Offshore Drilling Units
Authors: Chen Haibo , Bauge Tommy , Reinås Lorents , Landeråen Paul 
Published: December 2020

Abstract
Technical, operational and organization barrier elements related to the emergency disconnect on dynamically positioned mobile offshore drilling units on the Norwegian Continental Shelf are identified. Position loss scenarios are analyzed based on the published station-keeping incidents by IMCA (International Marine Contractors Association). How these barrier elements may fail in different types of position loss scenarios are addressed qualitatively and quantitatively in an event tree model. A case study is provided in the paper and notational probability of failure to disconnect given position loss is calculated. Risk reduction effect of various barrier elements are investigated by sensitivity studies. The paper provides insights into risk given position loss and failure of emergency disconnect on DP MODUs. It offers decision support for risk management of DP drilling and well operations in shallow water and harsh environment.
Offshore Topside Weight Prediction Using Data Science
Authors: Ahmadian Reza , Tcherniguin Nicolas , Tiberti Jean-François 
Published: December 2020

Abstract
The history of engineering shows many design solutions undergoing further improvements over time to optimize the system and eventually perfect it. However today, with a tendency for design specifications to be much stricter and with ever increasing commercial pressure to save time, materials and cost, there is a need to reach perfectible limits of an engineering system in the first step of the design process. It is therefore increasingly necessary to anticipate the design in a shorter time to maintain the schedule and therefore the competitiveness of the project. This emerging reality is most evident during the early phase of projects when the time is very short to prepare a robust budget in a competitive situation (either between solutions or providers). In this scenario, precise estimation of weight (which is strongly correlated to cost) and a prediction of its evolution during the course of all phases of an offshore project is critical when considering the overall economics, and hence the viability, of a development.
The objective of this paper is to provide a summary of a digital initiative, sponsored by the Onshore/Offshore Global Business Unit (GBU) of TechnipFMC, with the aim of using data science and data mining techniques to improve the operational efficiency of our activities. This digital initiative aims to better understand the evolution of the weight of offshore industrial projects that TechnipFMC designs and identify the impact of each influencing variable.
During the first phase, data mining algorithms are developed to automatically extract the influencing variable data from past project documentation including graphs from scanned documents using data science techniques such as transfer learning. In the second phase, the extracted data is automatically stored in a data base allowing analysis for specific causes of variance in weights. During the third phase, statistical models are used to highlight the influencing variables and their impact on the evolution of weight, giving trends which lead to an understanding of the increase or decrease of the weight. Finally, the developed algorithms can provide an estimation of the topside weight according to the design basis variables of a new project using machine learning techniques.