bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the Solid Transport Capability of Non-Newtonian Fluid in Annulus Bend Section
Authors: Huque Mohammad Mojammel , Butt Stephen , Zendehboudi Sohrab , Rahman Mohammad Azizur , Imtiaz Syed
Published: October 2021

A directional drilling operation may include one or more bending sections along the drilling profile. These bend sections are the critical segments from the hole cleaning point of view. In this study, a computational fluid dynamic (CFD) method was used to investigate the hole cleaning behaviour in annulus bending section. Eulerian-Eulerian multiphase flow model was adopted in this study. The developed CFD model was validated with experimental data. Different non-Newtonian Herschel Bulkley fluids were used to simulate the drilling mud. Solid cuttings of different sizes (2 mm, 4 mm, and 5 mm) were used to replicate the drill cuttings. Different fluid flow rate (0.5 m/s, 1.0 m/s, 1.5 m/s and 2.0 m/s) were investigated to observe the solid settling tendency in the horizontal and bending section. Cuttings accumulation behaviour at different bending radius (10 inch. and 20 inch.) and bending angle (15°, 30°, and 60° from horizontal) were investigated. The simulation study shows that higher viscous fluid performs better hole cleaning at low mud velocity. Furthermore, a turbulent flow regime performs better solid transport in the bending section. Finally, this study summarizes the hole cleaning behaviour of a bend section for a range of fluid velocity, cuttings size and radius of curvature and inclination.
Placing Off-Bottom Cement Plugs: Effects of Domain Geometry
Authors: Ghazal Abdallah , Karimfazli Ida
Published: October 2021

Oil wells are often abandoned when they become uneconomic. Normally, several cement plugs should be placed along cased wells to seal the producing formations. Proper placement protocols, especially for off-bottom plugs, are therefore required to prevent the seepage of oil. Often, heavy cement slurry is injected into wells filled with lighter wellbore fluids, through a centralised tube. To form the cement plug successfully, the injected cement slurry should accumulate at the target zone, over wellbore fluids that typically have a lower density. Therefore, the current practices involve a major hydrodynamic challenge that can result in failing plugs.

In a previous work, we had shown that injecting cement slurry in wellbore fluids can result in developing a cement finger that advects downstream the well. The finger then breaks and aids the formation of a mixed layer below the injection point. Consequently, the injected cement slurry starts accumulating to form the plug. These flow events were observed in a symmetrical flow domain. In this study, we consider different configurations of the injection process to investigate how the previously observed dynamics change. To that end, we consider different sizes and positions of the injector inside the well. We conduct numerical simulations based on representative hydrodynamic models using OpenFOAM, an open source CFD software.

The preliminary results reveal broadly similar dynamics for symmetrical flow domains of different injector sizes. However, marked differences are observed when the injector is not centralized in the well. The injected fluid diverts directly into the gap between the injector and casing walls, with preference to flow through the wider gap side.
Retracted: “Influence of Sea State Parameters on the Accuracy of Wave Simulations of Different Complexity” [ASME 2021 40th International Conference on Ocean, Offshore and Arctic Engineering, Volume 6, Virtual, Online, June 21–30, 2021, Conference Sponsors: Ocean, Offshore and Arctic Engineering Division, ISBN: 978-0-7918-8516-1, Copyright © 2021 by ASME. Paper No. OMAE2021-62631, V006T06A061; 10 pages; doi: 10.1115/OMAE2021-62631]
Authors: ASME
Published: October 2021

This paper was removed at the author’s request on October 22, 2021.

Copyright © 2021 by ASME
The Harmonic Structure of the Focused Wave in a Wave Flume
Authors: Gao Huixing , Zhou Jianjun , Song Yang , Fang Qinghe
Published: October 2021

In recent years, extreme waves have attracted more and more attention due to its threat to offshore and coastal structures. It is essential to obtain further insight into the formation and propagation of the extreme waves. The formation of extreme waves mainly comes from the simultaneous focusing of wave group energy in the ocean. In the present study, the nonlinear characteristics of the extreme wave are experimentally investigated by the wave focusing method. The phase decomposition methods, both two-phases separation and four-phases separation methods, are used to obtain the higher harmonic elevation in the focused wave. The results show that the four-phases separation method can reasonably extract the first four harmonics. With the separated results, the nonlinear analysis of the wave elevation and velocity of the focused wave is carried out. It is found that the harmonics of the wave group focused at the same time, but the wave elevation and energy of higher-order harmonics are smaller than that of the overall wave. The Stokes wave theory can describe the variation of second-order harmonics satisfactorily. However, the Stokes wave theory cannot estimate third-order harmonics accurately. More work should be carried out to figure out the third-order wave interaction occurring during wave focusing.

With a distributed wave gauge system, the wave evolution along the wave flume is measured. The evanescent modes significantly influence the wave group’s harmonic structure near the wavemaker. The coefficients of the higher-order harmonics are obtained from the measured elevations. The nonlinear wave elevation of the focused wave can be reconstructed with those coefficients basing on the linear theoretical solution, which is in good agreement with the experimental results.
On the Validity of CFD for Simulating a Shallow Water CALM Buoy in Extreme Waves
Authors: Bandringa Henry , Jaouën Frédérick , Helder Joop , Bunnik Tim
Published: October 2021

The Catenary Anchor-Leg Mooring (CALM) is the most popular and widely-used type of offshore loading terminal. A CALM buoy consists of a floating buoy anchored to the seabed by catenary chain legs which are secured to anchors or piles. Due to the small inertia of CALM buoys, the mooring line responses are very sensitive to waves and considerable fatigue risk is introduced to the mooring lines. Extreme waves may even lead to mooring line failure. Therefore it is highly relevant to study the motions of the CALM buoy in (extreme) wave conditions.

This paper presents a validation study of a coupled CFD – dynamic mooring model for simulating the response of a shallow water CALM buoy in extreme waves (Figure 1). Simulations of an interactively moving CALM buoy in a horizontal mooring system were performed by coupling a Navier-Stokes based finite-volume, VoF CFD solver with a dynamic mooring model. The CFD results are validated against model tests performed in MARIN’s shallow-water basin during the ComFLOW-2 joint industry project. The validation study concentrates on the correct prediction of the coupled responses of the CALM buoy in extreme, regular shallow-water waves.

As an alternative to simulations with a fully coupled dynamic mooring set-up, also CFD simulations are presented in which the mooring system is represented by a linearly equivalent spring matrix, including cross terms. The importance of correctly modelling these cross terms is presented in the paper, and the results obtained with- and without these off-diagonal spring terms are compared.
Out-of-Plane Bending (OPB) Test of Large Diameter Mooring Chains: Test Results
Authors: Karimi M. R. , Barros P. , Carlberg E. , Vargas P.
Published: October 2021

Chevron Corporation and Bluewater Energy Services performed a chain out-of-plane bending (OPB) test campaign, called OPB MAX hereafter, at DNV’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP [12]. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate Bluewater’s in-house finite element model. The current study is a collaboration between all involved parties and the results are presented in three papers. The first paper, Barros et al. [1], summarized the test setup, initial observations and the assumptions used in the post-processing. The current paper describes some of the test results, compares them with the OPB JIP estimations and describes the observed chain OPB physics. The third and the last paper will present the FEA results done by Bluewater’s in-house finite element model.

Two seven-link chain specimens of R4 and R4S grades, both with the nominal diameter of 168 mm were tested. Five tension levels of 150, 200, 250, 300 and 350 t were used throughout the tests. Chain sliding was performed in both wet and dry conditions. Twenty strain gauges were attached to five links of each specimen except for the two end-links to measure three OPB and two IPB moments at mid-link. Twelve strain gauge rosettes were used on three links to evaluate SCF on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV’s ARAMIS image processing tool was utilized to capture chain movements. A handheld temperature sensor gun monitored the interlink area’s temperature.

Interlink stiffness was measured at both ends of each specimen and four intermediate links. Several sensitivity studies were conducted to investigate the effect of loading speed, initial interlink angle and acquisition frequency. The interlink stiffness values that were initially found based on tests at small interlink angles (±0.2 °) were quite consistent and repeatable. Further tests that were performed at large interlink angles (±2.5 °) showed that interlink moment vs. angle hysteresis changes over time and is not unique. This was attributed to deformations observed at the interlink areas that had happened during the tests. The mentioned deformations directly influenced the hysteresis and the associated interlink stiffness values. The nature of deformations and stiffness variations was different during dry and wet tests at large angles. Furthermore, the interlink stiffness values measured on the R4S specimen were quite close to R4 results.
A Statistical ARIMA Model to Predict Arctic Environment for NSR Shipping
Authors: Wu Da , Lang Xiao , Zhang Di , Eriksson Leif , Mao Wengang
Published: October 2021

Reliable sea ice concentration (SIC) information assists the safe and energy-efficient ship navigation along the Northern Sea Route (NSR). In particular, the accurate SIC forecast is a top priority. This study proposes a statistical interpolation method to reduce the errors induced by the traditional interpolation method. An auto-regressive integrated moving average (AR/MA) model is developed based on reanalysis data. The AR/MA model can be used for short-term SIC forecasts along the NSR. Model validation has been conducted through a specially designed cross-validation. The route availability is estimated according to the SIC forecast. The results indicate that the specified NSR will be open for shipping from 2021 to 2024. The work also indicates the feasibility of the proposed statistical models to assist NSR shipping management.
Safety Assessment of Marine Structures Subjected to Underwater Explosion
Authors: Prasad D. H. S. , Rao S. K. , Patel B. P. , Ahmad Suhail
Published: October 2021

The underwater explosions due to an accident or other potential reasons cause severe shocks in the fluid medium. Safety assessment is an essential design requirement where the blast load concentration is expected due to smaller standoff distances. In the present work, the probabilistic analysis of structural response due to the underwater explosion is studied using NESSUS software. The study helps improve the concepts of improved blast mitigation strategies. The shock loading considered varies spatially and temporally. The fluid pressure is transformed into structural nodal forces. Taylor’s plate theory is used to estimate the shock loading. In the analysis, the material is considered to be rate-dependent elastoplastic with temperature softening. Maximum central deflection against shock factors is obtained to arrive at the safe thickness of the stiffened and unstiffened plates for the optimum design characteristics using LS-DYNA software. The finite element approach adopted efficiently captures expected failures for various combinations of structural properties leading to an optimized design to withstand the target explosion. Johnson-Cook dynamic failure model is employed as a limit state function for reliability assessment. Sensitivity analysis enables to achieve target reliability.
Development of a Simplified Three Degrees of Freedom Model to Represent the Installation of a Subsea Manifold
Authors: Salvador Lopes Filipe , Sena Sales Junior Joel , Martins de Andrade Emerson , Fernandes Antonio Carlos
Published: October 2021

Due to risks involved during the installation of subsea equipment, it is necessary to simulate the installation process to determine a safe operating window. However, most of the software capable of running these kinds of simulations are very expensive, and these simulations usually take a long time to be made. It is then very convenient to develop a simplified model, capable of running these analyses in a short period of time while still providing us with reliable results.

This model was developed using the Python programming language, where a fourth-order Runge Kutta method was implemented to solve the equation of motions that governs the manifold’s installation process. The assumptions are that the wave forces are applied to the ship executing the manifold installation. The ship’s motions were applied at the top of the cable, connected to the crane, so the manifold motions underwater and the cable tension could be calculated.

Previously, a simplified one-degree of freedom (1DoF) model was developed and compared to other numerical models and experimental data. In this present work, the model was then expanded to motions in a vertical plane, that is, three degrees of freedom (3 DoF), in order to better represent the physics of the real problem. Its results were then compared to the ones obtained by the 1 DoF model and to the experimental results. The 3 DoF model resulted in a dynamic response closer to the ones observed in the experiments, which shows that it is a better representation of the problem.
The Effects of Gas Mixture Composition on the Mass Transfer and Individual Diffusion Coefficient in CH4-CO2-Light Oil Systems
Authors: Zheng Taiyi , Luo Yongcheng , Shi Yu , Liu Xiangui , Yang Zhengming , Luo Yutian , Zhang Yapu
Published: October 2021

Limited CO2 resources considerably narrow down the field application of CO2 EOR for improving oil recovery in tight formation. Considering that CH4 and CO2 have similar EOR mechanisms, CH4, as a by-product of produced oil, is a relatively cost-efficient agent to be injected into the tight formation with CO2. In this work, experimental and mathematical methods are proposed to probe the effect of CH4 composition on the mass transfer between a CO2-CH4 gas mixture and crude oil collected from a tight oil reservoir. Experimentally, the pressure-decay tests for different CH4-CO2-light oil systems are conducted at a constant temperature in a pressure / volume / temperature (PVT) setup. Also, the gas mixtures’ compositions before and after the experiments are analyzed with gas chromatography to investigate the mass transfer of different components. Theoretically, mathematical formulations are developed to describe the mass transfer between the gas mixture and light oil based on translated Peng Robinson equation of state (PR-EOS), a real gas equation, and one-dimensional convection-diffusion equations. The individual diffusion coefficients of CH4 and CO2 as well as the concentrations distribution can be obtained by minimizing the deviation between the calculated pressure and the measured ones. The results indicate that the higher the content of CO2 in the initial gas phase, the faster the pressure drops are and less time it takes for the oil and gas phases to reach a stable pressure, which implies a high mass transfer rate with an increase in CO2 composition. In particular, the diffusion coefficient of CO2 is found to be about 2 times larger than that of CH4 the same composition condition. However, it is noted that the individual diffusion coefficients of CH4 or CO2 are not constants. A high molar fraction in the initial gas sample will lead to a large diffusion coefficient in different CH4-CO2-light oil systems.
Optimization of Frequency Domain Fatigue Analysis for Unbonded Flexible Risers
Authors: Yuan Jiabei , Hou Yucheng , Tan Zhimin
Published: October 2021

Fatigue analysis of flexible risers is a demanding task in terms of time and computational resources. The traditional time domain approach may take weeks of time in global simulation, local modelling and post-processing of riser responses to get fatigue results. Baker Hughes developed a fast hybrid approach, which is based on a frequency domain technique. The new approach was first implemented at the end fitting region and then to all other regions of the riser. Studies showed that the hybrid approach achieved convenient and conservative results in a significant shorter period of time.

To improve the accuracy and reduce conservatism of the method, Baker Hughes has further optimized the analysis procedure to seek better results approaching true solutions. Several methods were proposed and studied. The duration of representative cases and noncritical cases have been extended. The steps to predict stress spectrum based on transfer functions have also been updated. From previous studies, only one transfer function was built for fatigue load cases with similar response spectra. This assumption linearizes the system response and produces certain level of discrepancy against true time domain solution. In this study, multiple ways of spectrum prediction are evaluated and compared.

The paper summarizes several techniques to further optimize the hybrid frequency domain approach. The updated fatigue results are found to be more accurate. The optimized approach therefore gives more flexibility to engineers to approach the true solutions, which were originally acquired from full 3-hr time domain simulations. The approach requires less analysis time and reduces iterations in pipe structure and riser configuration design, which leads to faster project execution and potential cost reduction.
Development of Digital Twins for Drilling Fluids: Local Velocities for Hole Cleaning and Rheology Monitoring
Authors: Gharib Shirangi Mehrdad , Aragall Roger , Ettehadi Reza , May Roland , Furlong Edward , Thompson Charles A. , Dahl Thomas G.
Published: October 2021

In this work, we present our advances to develop and apply digital twins for drilling fluids and associated wellbore phenomena during drilling operations. A drilling fluid digital twin is a series of interconnected models that incorporate the learning from the past historical data in a wide range of operational settings to determine the fluids properties in realtime operations. From several drilling fluid functionalities and operational parameters, we describe advancements to improve hole cleaning predictions and high-pressure high-temperature (HPHT) rheological properties monitoring. In the hole cleaning application, we consider the Clark and Bickham (1994) approach which requires the prediction of the local fluid velocity above the cuttings bed as a function of operating conditions. We develop accurate computational fluid dynamics (CFD) models to capture the effects of rotation, eccentricity and bed height on local fluid velocities above cuttings bed. We then run 55,000 CFD simulations for a wide range of operational settings to generate training data for machine learning. For rheology monitoring, thousands of lab experiment records are collected as training data for machine learning. In this case, the HPHT rheological properties are determined based on rheological measurement in the American Petroleum Institute (API) condition together with the fluid type and composition data. We compare the results of application of several machine learning algorithms to represent CFD simulations (for hole cleaning application) and lab experiments (for monitoring HPHT rheological properties). Rotating cross-validation method is applied to ensure accurate and robust results. In both cases, models from the Gradient Boosting and the Artificial Neural Network algorithms provided the highest accuracy (about 0.95 in terms of R-squared) for test datasets. With developments presented in this paper, the hole cleaning calculations can be performed more accurately in real-time, and the HPHT rheological properties of drilling fluids can be estimated at the rigsite before performing the lab experiments. These contributions advance digital transformation of drilling operations.
Structural Health Monitoring Data Analysis for Ageing Fixed Offshore Wind Turbine Structures
Authors: Yeter Baran , Garbatov Yordan , Guedes Soares Carlos
Published: October 2021

The objective of the present study is to perform a systematic data analysis of structural health monitoring data for ageing fixed offshore wind turbine support structures. The life-cycle extension of the first offshore wind farms is under serious consideration since the support structures are still in a condition to be used further. Big data analytics and machine learning techniques can aid to extract useful information from the monitoring data collected during the service life and build models for future predictions of an optimal life-extension. To this end, it is aimed to analyse the big data provided by embedded control systems and non-destructive inspections of ageing offshore wind turbine support structures using pre-processing techniques, including denoising, detrending, and filtering to remove the noise of different nature and seasonality as well as to detect the signal-specific contents affecting the structural integrity in the time and frequency domain. The effectiveness of the Welch method is investigated in terms of dealing with noisy signals in the frequency domain. Besides, the principal component analysis is carried out to reduce the dimensionality of the data and to select the most significant features that are responsible for most of the variance in the structural health monitoring data. Moreover, nonparametric statistical methods are used to test whether the data before noise being added and the data after cleansing the added noise came from the population with the same distribution. Further, permutation (randomisation) testing is performed to predicate that the results of the nonparametric test are statistically significant. The outcome of this study provides refined evidence that enables to feed the condition monitoring data into the training of the deep neural network to be able to discriminate different structural conditions.
Modelling and Analysis of Hydrodynamics of a Submerged Structure in Extreme Waves Using a SPH-Based Tool
Authors: Islam Mohammed , Seo Dong Cheol , Raman-Nair Wayne
Published: October 2021

The applications of a Smoothed Particle Hydrodynamics (SPH)-based, a Finite Volume Method (FVM)-based and a Boundary Element Method (BEM)-based tools to investigate the nonlinear interactions between large waves and a submerged horizontal circular structure and to some extent a rectangular cylinder at various submergence depths in deep water conditions are presented. The main aim is to validate the Lagrangian technique based SPH tool to predict the wave-structure interaction forces under large waves.

The features of typical force curves in a wave cycle, the magnitude of wave forces, and the influence of relative axis depth of the structure in deep water conditions are investigated, primarily using an open-sourced SPH tool. Simulations were carried out in 2D with one deepwater wave at multiple submergence depths. The water surface elevations are predicted at different near- and far-field locations. The time-averaged mean and the average amplitude of the horizontal and vertical forces acting on the cylindrical model at various submergence depths are plotted and then physically interpreted. The wave forces and surface elevations are compared with the available published experimental studies and CFD (both FVM and BEM) predictions. Good agreement between the SPH predictions and the measurements was obtained for the submerged body’s surface elevation and hydrodynamic forces at all submergence depths. The FVM tends to overestimate the wave forces compared to the SPH predictions and the measurements, particularly for the shallowly submerged structure when extreme wave breaking occurs. The BEM predictions are reasonable for the non-wave breaking cases.
Machine Learning Applications in Drilling Fluid Engineering: a Review
Authors: Gul Sercan
Published: October 2021

Drilling fluid (mud) serves various purposes in drilling operations, the most important being the primary well control barrier to prevent kicks and blowouts. Other duties include, but not limited to, maintaining wellbore stability, removing and transporting formation cuttings to the surface, cooling and lubricating downhole tools, and transmitting hydraulic energy to the drill bit. Mud quality is therefore related to most of the problems in drilling operations either directly or indirectly.

The physics-based models used in the industry with drilling fluid information (i.e., cuttings transport, well hydraulics, event detection) are computationally expensive, difficult to integrate for real-time analysis, and not always applicable for all drilling conditions. For this reason, researchers have shown extensive interest in machine learning (ML) approaches to alleviate their fluid-related problems.

In this study, a comprehensive review of the abundant literature on the various applications of ML in oil and gas operations, concentrating mainly on drilling fluids, is presented. It was shown that leveraging state-of-the-art supervised and unsupervised ML methods can help predict or eliminate most fluid-related issues in drilling. The review discusses various ML methods, their theory, applications, limitations, and achievements.
Well Testing of Fracture Corridors in Naturally - Fractured Reservoirs (NFR)
Authors: Guo Yingying , Wojtanowicz Andrew
Published: October 2021

Geological folding/faulting may create naturally fractured reservoirs containing a semi-parallel system of sparsely-spaced fracture corridors. The pressure behavior of wells completed either in highly conductive corridors (fracture wells) or in the exclusion zone (matrix wells) would be quite different. In this study, a unique simulation model has been built for corridor type naturally fractured reservoirs by combining a local model of fracture well or matrix well with adjacent fracture corridor(s) and a “homogenized” global model of the remaining corridor network. The global model generalizes the corridor network using the single-porosity and radial permeability approach, which is verified as being sufficiently accurate. Pattern recognition technique is used to analyze diagnostic plots of pressure drawdown generated by simulated flow tests with commercial software (CMG). This study aims to build a new simulation model for corridor-type NFRs and apply the well testing technique to differentiate corridor-type NFRs from conventional NFRs, detect the well’s location, and estimate reservoir properties. This study also employs cumulative logit statistics to assess the accuracy of the estimated well-to-corridor distance.
Free Surface Effect Assessment of the Flow Around the DARPA SUBOFF-5470 Submarine Using OpenFOAM
Authors: Quintuña María T. , Paredes Rubén J.
Published: October 2021

An important parameter to submarine navigation and control is determining the hull speed relative to the surrounding sea. The object of this paper is to find possible locations for speed sensors on a submarine. The probes should be fitted to the hull areas where the water flow is free of turbulence structures, vortices, or bubble formation to obtain a reliable measurement. In this work, a rational procedure is proposed to identify the probe installation site on the hull of the DARPA SUBOFF-5470 submarine, through numerical simulations using OpenFOAM. Three different depth conditions at three different navigation speeds were considered to assess the free-surface effect. First, verification and validation procedures were completed at deep water conditions (H/D = 5.4). The results of this analysis indicate a convergence ratio of 0.49 with an uncertainty of 0.04%SC. Later, a grid convergence analysis was completed at periscope depth conditions (H/D = 1.1), within the highly nonlinear Froude range. These results show an oscillatory convergence with an uncertainty of 0.78%. Finally, the hull region between 5 and 15% from the bow of the submarine length is recommended for installing the speed probe, considering the linearity of the flow, without high gradients and vortex structures.
Buoyant Miscible Flows in Axially Rotating Pipes: the Effects of Pipe Rotation and Viscosity
Authors: Lyu Shan , Taghavi Seyed Mohammad
Published: October 2021

The primary cementing operations of oil and gas wells involve pumping a sequence of fluids into the well (initially within a circular casing and eventually within an annular region) to displace in-situ drilling mud. The fluids involved can be miscible, and they can also have different density and viscosity ratios. It is believed that a casing rotation can generally improve the displacement process, within both the circular casing and the annulus. However, there have not been a lot of laboratory studies to prove that such rotation is indeed effective for the displacement within the casing. In fact, due to the lack of knowledge, the casing axial rotation may not be still among the top recommendations to enhance the displacement occurring within the casing. This is in spite of the fact such a rotation would be feasible using various types of casing heads and special adaptors. In this work, we conduct simulations to understand the fluid mechanics behind buoyant displacement flows that occur within the casing (pipe). Our focus is to analyze the effects of the axial rotation speed of the pipe, the viscosity of the fluids and the viscosity ratio between the two fluids on the flow behaviours. Other flow parameters are also present: the fluids are miscible, and they have a density difference; the pipe inclination angle is considered to be near-horizontal (i.e. the most challenging case in terms of creating efficient displacements). We investigate important flow features, such as the behaviours of the interface between the fluids, the mixing between the fluids, the fluid front velocities, etc. Our results help develop a deep understanding of how casing rotation can be used to enhance displacement flows in the primary cementing operations of oil and gas wells.
2D Numerical Study on Wake Scenarios for a Flapping Foil
Authors: Xu Hui-li , Greco Marilena , Lugni Claudio
Published: October 2021

Fishes are talented swimmers. Depending on the propulsion mechanisms many fishes can use flapping tails and/or fins to generate thrust, which seems to be connected to the formation of a reverse von Kármán wake. In the present work, the flow past a 2D flapping foil is simulated by solving the incompressible Navier-Stokes equations in the open-source OpenFOAM platform. A systematic study by varying the oscillating frequency, peak-to-peak amplitude and Reynolds number has been performed to analyze the transition of vorticity types in the wake as well as drag-thrust transition. The overset grid method is used herein to allow the pitching foil to move without restrictions. Spatial convergence tests have been carried out with respect to grid resolution and the size of overset mesh domain. Numerical results are compared with available experimental data and discussed. The results show that the adopted methodology can be well applied to simulate large amplitude motions of the flapping foil. The transitions in the types of wake are consistent with the benchmark experimental data, and the drag-thrust transition of the pitching foil does not coincide with von Kármán (vK)-reverse von Kármán (reverse-vK) wake transition and it is highly dependent on the Reynolds number.
Numerical Simulation of Ship Collision and Validations With Experimental Results
Authors: Wang Xiangbiao , Li Chun Bao , Zhu Ling
Published: October 2021

Ship collision accidents occur from time to time in recent years, and this would cause serious consequences such as casualties, environmental pollution, loss of cargo on board, damage to the ship and its equipment, etc. Therefore, it is of great significance to study the response of ship motion and the mechanism of structural damage during the collision.

In this paper, model experiments and numerical simulation are used to study the ship-ship collision. Firstly, the Coupled Eulerian-Lagrangian (CEL) was used to simulate the fluid-structure interaction for predicting structural deformation and ship motion during the normal ship-ship collision. Meanwhile, a series of model tests were carried out to validate the numerical results. The validation presented that the CEL simulation was in good agreement with the model test. However, the CEL simulation could not present the characteristics the time-dependent added mass.
Using Artificial Intelligence Techniques in Modeling and Predicting the Rheological Behavior of Nano-Based Drilling Fluids
Authors: Gasser Moamen , Mahmoud Omar , Ibrahim Fatma , Abadir Magdi
Published: October 2021

Drilling process is one of the main operations in the extraction of hydrocarbons from petroleum reservoirs. It comes right after the exploration processes. Drilling fluids are necessary for controlling the wells and performing different functions during the drilling operation. They perform many roles in lifting the cuttings from the bottom of the well to the surface and cooling/lubricating the drill pipes and bit. Furthermore, they provide the desired hydrostatic pressure to overbalance pore pressure in addition to produce a thin/impermeable filter cake that can prevent or reduce the possible damage to the formations. It is mandatory to keep monitoring, enhancing, and optimizing the properties of the drilling fluids.

Recently, different additives, among which nanoparticles (NPs), have been investigated to improve, and maximize the benefits of the drilling fluids accordingly to meet the new challenges. The rheological behavior of such complex fluids has shown different enhancements up on the utilization of those additives. The rheological properties of the drilling fluids are accurately measured on the surface; however, the behavior of those properties may change with time and under harsh drilling conditions, such as high pressure/high temperature environments. For that, different models are introduced and used to predict and optimize the rheological characteristics of such fluids.

Bingham, Herschel-Bulkley, Power Law, Casson and others are commonly used as rheological models to predict the drilling fluid behavior. In the last decade, a new trend of developing new models and correlations using the artificial neural networks (ANN) have been introduced to the petroleum field. Mathematical formulas can be developed using ANN, which then can be used to predict the behavior of certain parameter(s) by knowing other ones. Using ANN have shown to be more reliable and accurate in predicting the rheological properties of the drilling fluids, such as apparent viscosity (AV), plastic viscosity (PV), yield point (YP), maximum shear stress, and change in the mud density at various conditions.

This work aims at using ANN technique to develop suitable models that can predict the rheological behavior of nano-based drilling fluids. The effect of NPs-type, -size, -concentration, and drilling fluid formulations will be considered, which may pave the road for new applications and efficient utilizations.
Hydrogen’s Peculiar Effect on Material Properties: Do We Need to Be Concerned About Hydrogen Transport in Pipelines?
Authors: Østby Erling , Hugaas Bjørn-Andreas , Horn Agnes Marie
Published: October 2021

Considering the vast number of articles that have been published during the last 150 years related to hydrogen embrittlement and the multiple attempts to explain the governing mechanisms, it is evident that hydrogen’s effect on mechanical properties in steel is still a controversial topic. This little atom has even by some authors been referred to as the “little devil”. We do not intend to explore this particular description of hydrogen any further. However, we would like to shed some light on the key technical aspects we believe need to be further scrutinized and understood to ensure that the decision-makers have sufficiently reliable data available to decide whether hydrogen gas can be safely transported in new or existing offshore pipelines at an acceptable cost.
Numerical Modeling of Sustainable Atmospheric Boundary Layer for Offshore Floaters
Authors: Kim Jang Whan , Jang Hyunchul , Yeon Seongmo , Kim Hyunjoe
Published: October 2021

Wind load is one of the major design load considerations for the hull and mooring of offshore floating facilities. The first step to minimize the uncertainties in wind load is generating an accurate wind profile that satisfies design requirements.

Recently, there was a joint-industry effort to develop CFD modeling practices on wind-load estimation in SNAME OC-8 CFD Task Force (OMAE2018-78699). The Task Force developed the modeling practice for the NPD (Norwegian Petroleum Directorate) model commonly used for offshore platform design, and several independent participants in the Task Force successfully validated the practice for a topsides of a semi-submersible platform. The sustainable wind profile was able to be generated within 1% tolerance of the target wind profile, and the calculated wind loads on the topsides from CFD simulations were close to the model test data with low uncertainty levels.

In the present study, the numerical modeling for the sustainable ABL is extended to other popular wind models such as the ESDU (Engineering Science Data Unit) and the power-law models. The study is a part of a joint-development project between TechnipFMC, Chevron, and Samsung Heavy Industries. The analytic or numerical formulae of wind speed and turbulent quantities for several RANS (Reynolds-Averaged Navier-Stokes) models are derived for the wind models, and the sustainability of wind profiles are verified.
Flow-Induced Vibration Screening of a Thermoplastic Composite Pipe Water Injection Jumper
Authors: Pontaza Juan P. , Nadathur Varadarajan , Rosche John L.
Published: October 2021

An active subsea field in the Gulf of Mexico has adopted a thermoplastic composite pipe (TCP) water injection jumper for its waterflood upgrade. The jumper assembly is composed of a TCP span attached to steel piping on either end. The TCP spool is lightweight and flexible relative to the traditional steel-only M-shaped subsea jumpers. As such, the flow-induced vibration (FIV) threat from internal fluid flow must be assessed for the intended service. A three-tiered approach is used to assess the level of FIV threat expected in this TCP subsea jumper application. A high-level screening based on widely used industry guidelines indicates a susceptibility to FIV fatigue failure for the steel piping in the TCP jumper assembly. A comprehensive screening based on structural finite element analysis and computational fluid dynamics shows that the vibration levels and stress cycling due to FIV will be acceptable for the intended water injection application and a 30-year design life, when adopting a factor of safety of 10 for subsea service. We evaluate the effect of doubling the length of the steel piping on either end of the TCP span, as a means to increase the overall span of the TCP jumper assembly. Lastly, we draw a comparison between a traditional all-steel M-shaped jumper and the TCP jumper in terms of FIV fatigue life, for the same operating conditions and the same total suspended span.
A CFD Research on the Effect of Pre-Swirl Stator Blades Number on a Pumpjet Propulsor
Authors: Guodong Wang , Jun Yang , Jiawei Yu , Wenjing Yang , Dakui Feng
Published: October 2021

In this paper, effect of different pre-swirl stator number on open water performance of a pumpjet propulsor was studied. The pumpjet propulsor consists of shaft system, pre-swirl stator, rotor and duct. The numerical simulations were based on HUST-Ship, a series of inhouse codes, solving the Reynolds Averaged Navier-Stokes (RANS) equation. The computational region was discretized by structured grids and SST k-ω turbulence equations was discretized by finite difference method. The performances of rotor, pre-swirl stator and duct were monitored separately in order to understand the effect in the thrust and the torque. It was found that with the increase of the number of pre-swirl stator blades, the thrust produced by rotor blades increased. However, the number of pre-swirl stator blades influences the thrust of stator, and may have negative effect on the total thrust. In the meantime, thrust of duct also has a little increase. With the increase of the number of pre-swirl stator blades, the propulsion efficiency increases first and then decreases.
A Frequency-Domain Screening Methodology for Flow-Induced Vibration in Piping
Authors: Pontaza Juan P.
Published: October 2021

A three-tiered approach is advocated to assess the level of flow-induced vibration (FIV) threat to process piping due to internal flow. The first-tier assessment is a high-level design check on the possibility of FIV. The tier-1 screening does not provide a framework for the direct estimation of vibration levels, stress, or fatigue damage. The third-tier assessment is termed a comprehensive screening and relies on computational fluid dynamics (CFD) to predict the flow-induced forcing, coupled to a structural finite element model to obtain the response of the piping (vibration levels and stresses), from which an estimate of fatigue damage at critical locations is computed. The tier-3 screening may be computationally intense (e.g., for multiphase flow) and is generally not fast to perform. This paper presents a second-tier assessment (intermediate between the tier-1 and tier-3 screenings), where the flow-induced loading is represented by power spectral density (PSD) curves, which are inputs to a structural finite element model of the piping. The structural finite element analysis (FEA) is performed in the frequency domain, implying fast turnaround time requiring short computing time. The FEA yields a prediction of vibration levels and dynamic stress, from which the sought-after estimates of fatigue damage are computed. The outcome of a tier-2 screening for vibrating piping in a metering skid is presented and the predictions compared against field measurements using accelerometer data (vibration levels) and strain gauge data (dynamic stress). A tier-2 screening is performed for a subsea water injection jumper and the results compared against those of a tier-3 screening.
A New Transient Thermal Model for Predicting Cooling Temperature and Cooldown Time of a Subsea Pipe-in-Pipe Flowline System Transporting Waxy Hydrocarbons
Authors: Shukla Keshawa
Published: October 2021

The proper understanding of cooling temperature and cooldown time for the operation of a subsea system producing hydrocarbons from the reservoir to the host facility is one of the important flow assurance issues for managing heat retention in the production system due to solids formation and their deposition. In this paper, an analytical transient thermal model is developed for determining the cooling temperature and cooldown time for shut-in operations of a subsea pipe-in-pipe production system, transporting waxy crude oil from the reservoir to the host facility. Here, the cooldown time is defined as the time when the fluid temperature approaches the wax appearance temperature before reaching the hydrate formation temperature during any shut-in operations. The analytical model builds upon an inhomogeneous transient method incorporating an internal temperature gradient. The model results are benchmarked against the commercial OLGA simulation results for a few selected deepwater pipe-in-pipe flowline configuration. The model predictions resemble well with OLGA results over a range of conditions. The analytical model could optimize dry insulation and cooldown time requirements efficiently for the assumed PIP flowline configurations and fluid properties under any subsea environments.
Fatigue Assessment on Reverse–Balanced Flange Connections In Offshore Floating Wind Turbine Towers
Authors: Zou Tao , Liu Wenjie , Li Mingxin , Tao Longbin
Published: October 2021

Offshore floating wind turbines (FWTs) in deep water experience cyclic loadings from both environment and mechanical operations. For FWTs, the upper turbine and tower are mainly subjected to wind loading; and the floater is subjected to wave forces. It has been widely accepted that there is a strong coupling between the floater motions and the turbine forces. As the tower is placed between the upper wind turbine and the floater, both wind and wave loadings affect the cyclic forces on the tower. The construction of towers makes use of prefabricated segments. These prefabricated segments are bolted together with flanges at either end. The paper aims to investigate the axial hotspot stress on FWT’s tower base and analyze its induced fatigue damage at the welding joints around the flanges. A coupled aero-hydro-servo-elastic analysis is conducted to simulate the motion of FWTs. Then, the local welding joint along the reverse-balanced flange connection is modeled to consider the influence of local geometry. At last, the hourly fatigue damages at four locations over the tower base section are compared.
Development of Methods for Temperature Calculation of LNG Carrier Hull
Authors: Islam MD Shafiqul , Choi Tae-Soon , An Tae-Hyun , Song Kang-Hyun
Published: October 2021

LNG carriers are vessels used to store and transport liquefied natural gas. LNG, in its liquid form has the temperature of minus 163 degrees Celsius. Therefore, the types of steel used to build the hull structure must withstand the impact of low temperatures. Cargo Containment System (CCS) is used to reduce the transfer of heat from the outside environment into the cargo tank and to keep the LNG in liquid state. Presently, the most popular types of CCS are designed by GTT (Gaztransport & Technigaz). However, Korean shipyards, KOGAS (Korea Gas Corporation) and many other companies around the world are developing their own CCS systems. The thermal analysis of LNG carrier hull is generally performed by the CCS developer and therefore, in order to assist the new CCS developers and LNG carrier designers, KR has developed a guideline for temperature calculation of Membrane type LNG carrier’s hull. This study is a part of the guidelines and focuses on numerical and analytical solution procedures for accurate hull temperature calculation. For verification and accuracy of these methods, temperature calculation of a Membrane type LNG carrier hull is carried out and the results are compared with each other. Both methods, thoroughly analyzed in this study, could be applied in the design of membrane type LNG carrier hulls.
Earth science a ‘no-brainer’ for NASA's science chief
Authors: Voosen Paul
Published: October 2021

Thomas Zurbuchen talks risk, trust, and small satellites.