bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation of Wellbore Fluid Displacement in Concentric and Eccentric Annulus
Authors: Ytrehus Jan David , Lund Bjørnar , Taghipour Ali , Divyankar Shreyansh , Saasen Arild 
Published: October 2017

One of the most critical operations during well construction is the cementing procedure. Due to the curing nature of the cement slurry there will be only one opportunity to cement the well properly. Although one for top hole cases can fill cement in from the top in a remedial operation, this possibility cannot fully compensate for a non-optimal initial cement job. Furthermore, it cannot be applied to other well sections. In those sections, complex squeeze cementing operations may be necessary. Consequences of improper annular cement can be leakage during production phase and extensive costs when the well is to be plugged for abandonment after the production phase. To ensure that the risk of poor cement is minimised it is important to use the best procedures to place the cement properly. To be able to select the optimum procedures, it is necessary to improve the understanding of the displacement in the wellbore annulus. All wells will be cemented in several sections. Findings and improvements that can reduce risk of poor cementing results are thus highly relevant for a large number of operations every year.
The article is based on analysing experimental results that illustrates a drilling fluid being displaced by a cement slurry. These fluids are represented by realistic model fluids and circulated through a transparent annular section. The geometry used is a 6,5″outer diameter with an inner string of 5″that also can rotate. The selected pipe sizes may normally be found in the lower parts of a well and often in deviated sections where the inner pipe cannot be assumed concentric at all times. Both concentric and eccentric inner pipe positions have therefore been selected. The test section was run both in horizontal and in inclined position. The test section was 10 meters long and instrumented with conductivity probes in an array around the perimeter at 4 separate positions along the pipe. Together with cameras along the test section the fluid interphases was observed along the test section.
Results presented in the article show that inner string rotation provides a steeper displacement front, On the other hand such rotation will also cause more mixing at the interphase. Results also show that the displacement front in a concentric annulus is significantly affected by gravity. While for an eccentric annulus, with the low side at the bottom, the narrow gap is poorly displaced when realistic fluids are applied. It was also observed that the displacement front in concentric annulus was more stable when the test section was inclined than in horizontal position.
Drag on Nets Fouled With Blue Mussel (Mytilus Edulis) and Sugar Kelp (Saccharina Latissima) and Parameterization of Fouling
Authors: Gansel Lars C. , Endresen Per Christian , Steinhovden Kristine Braaten , Dahle Stine Wiborg , Svendsen Eirik , Forbord Silje , Jensen Østen 
Published: October 2017

Biofouling is a serious problem in marine finfish aquaculture with a number of negative impacts. Marine growth obstructs net openings, thereby reducing water exchange through the net and affecting fish welfare and health, as well as the spreading of dissolved nutrients, particles and pathogens. Furthermore, additional water blockage leads to increased hydrodynamic forces on fish cages, which potentially threaten the structural integrity of the fish farm. However, detailed knowledge about the effects of biofouling on the flow past, and the resulting forces on fish cages, is limited and systematic investigations of the effects of different types of fouling have been called for.
This study investigates the effects of different amounts and sizes of two important fouling organisms in Norwegian aquaculture, blue mussel (Mytilus edulis) and kelp (Saccharina latissima) on the drag on net panels. Drag forces on a number of clean and fouled nets were measured in a flume tank at a flow speed of 0.1 m/s. Net solidity was calculated from images acquired of all nets in the current. The relationship between net solidity and drag was then found for clean nets and for each type of fouling, and biofouling was parameterized by comparing clean and fouled net results: for a given fouled net, a clean net can be found that experiences the same drag. The latter can then be used in numerical models to estimate the effect of fouling on net drag. That means existing models can be used to model the drag effect of fouling. This study found a solidity increase due to mussel and kelp fouling to affect drag roughly at the same rate as an increase in clean net solidity at a flow speed of 0.1 ms−1 and within the tested fouling size range for two net types. Therefore, existing models, describing the relationship between net solidity and drag, can be used directly or with minor alterations (especially at high solidities) to estimate effects of additional mussel and kelp fouling on drag. In contrast, wet weight seems to be unsuitable as a measure to estimate drag on nets fouled with seaweed or mussels. It should be noted that these findings are only valid under similar conditions, and that other fouling types and sizes, as well as test parameters and tank size can affect the relationship between solidity and drag.
Summary of the Joint Industry Project Wave Impact on Fixed Foundations (WiFi JIP)
Authors: de Ridder Erik Jan , Bunnik Tim , Peeringa Johan M. , Paulsen Bo Terp , Wehmeyer Christof , Gujer Philipp , Asp Erik 
Published: October 2017

The objective of the Joint Industry Project Wave impact on Fixed foundations (WiFi JIP) was to increase the understanding of breaking and steep wave impact’s on fixed foundations of offshore wind turbines (OWT). The project was set-up as a Joint Industry Project (JIP) and in total 20 companies and research institutes participated in the project.
In this paper a summary of the complete WiFi JIP project will be presented. At the start of the project the state of the art design methods and guidelines were reviewed (WP1). Thereafter a jacket and a monopile foundation were designed using these state-of-the-art tools that were available at the start of the project. This effort has been reported in WP2 , where design computations were carried out using the embedded stream function approach for several sea states. In this WP Siemens, ECN and Ramboll also calculated the impact response of the monopile to surging and spilling type wave breakers with their engineering tools. In the next phase the designed foundations were tested in MARIN’s shallow water model basin. The foundation for the monopile was modelled as a rigid and flexible foundation. The foundations were tested in regular waves, irregular sea states and so called focused waves. During the model tests the wave heights, wave run-up, accelerations, impact pressures and loads on the foundation and boat landing were measured. The model test results were reported in WP3 and 7 and used as validation for WP9 and 10. WP4 delivered more understanding of realistic design conditions for areas typical for OWT, like the North Sea. Particular attention was paid to the probability of occurrence of breaking and steep waves and the associated slamming load. For this an extensive 5 week experimental program was performed from September to October 2013 in the wide wave-current flume at Deltares (Atlantic Basin). During these tests both waves and current were simulated and two bathymetries.
WP8 provided analyses of the performed full scale measurements on the response of a OWT. The full-scale measurements were done for a Vestas V90 3MW wind turbine in the Belwind windfarm which is located 46 km off the coast of Zeebrugge on the Bligh Bank. The CFD simulations performed in WP 9 showed that a good agreement is obtained between the CFD simulations and the model and full scale measurement.
In work package 10, an improved methodology was developed based on the outcome of the previous WP’s to model the breaking wave impact of plunging type breakers. In WP11 and 12 this new approach is applied on different case study’s by ECN.
Reliability Based Stiffness Analysis for Application During Installation of Suction Caissons
Authors: Sturm Hendrik , Mirdamadi Alireza 
Published: October 2017

The design of suction caissons for offshore wind turbines is generally performed deterministically, using load and resistance factors taken from relevant codes and standards. This approach has been widely accepted for the geotechnical design of suction caissons in well-characterised soil conditions. However, soil layering and properties often vary considerably from location to location within an offshore wind farm. Furthermore, the installation process can also cause changes in the soil state in the vicinity of the skirts, which will affect noticeably the response of the suction caisson during operation. While this can be considered implicitly in the geotechnical design by means of assumptions, the inherent uncertainty of the soil state will impact the overall performance of the structure considerably. On the other hand, an optimized design for the system requires an accurate prediction of the foundation stiffness.
The authors present a reliability-based framework for the assessment of foundation stiffness, taking into account the most important input parameters and their expected variability. The framework can be applied both in foundation design as well as during actual installation in order to provide immediate feedback to permit adjustment or mitigation before the installation is finalized. Using a reliability-based approach in design allows an assessment of the probability of reaching the limiting design criteria and to quantify the related risk.
The proposed reliability-based framework can be applied to other design aspects. This is exemplified using the example of coupled foundation installation and capacity assessment. The authors further discuss how the framework can be extended to more complex design procedures.
Impact of Viscoelastic Characteristics of Oil Based Muds/Synthetic Based Muds on Cuttings Settling Velocities
Authors: Altindal M. C. , Ozbayoglu E. , Miska S. , Yu M. , Takach N. , May R. 
Published: October 2017

Inaccurate calculation of settling and slip velocities of cuttings leads to inaccurate determination of cuttings concentration and, hence, borehole pressure, as well as inaccurate lag times. To minimize these problems, an understanding of the relation between drilling fluid characteristics and the cuttings transport process is essential. It is desirable for drilling fluids to form a gel structure to help cuttings transportation and suspension of solids. The gel structure development is proportional to increase in aging time. The increase in aging time yields higher shear stress responses at a constant rate of deformation to the drilling fluid sample. The gel structure development helps keep cuttings in suspension and shows a viscoelastic response to small deformations. Understanding these viscoelastic responses is important in rheological characterization and settling velocity prediction. Thus, viscoelastic drilling fluid characteristics should be investigated in depth to better estimate settling and slip velocities of cuttings and to increase cutting transport efficiency.
The main focus of this project is to work on viscoelastic and time-dependent fluid characterization to identify the relation between rheological properties and settling velocities of cuttings. Rheological experiments were conducted using an Anton Paar Physica MCR 301 Rheometer. Three different drilling fluids, Water Based Mud (WBM), Oil Based Mud (OBM) and Synthetic Based Mud (SBM), are used for rheological and settling velocity experiments. Stress Overshoot Tests (SOTs) and Steady-Shear experiments were performed to investigate viscoelastic properties and gel structure of the fluids, and to examine time and temperature dependence of WBM, OBM and SBM. Information obtained from the viscoelastic and time-dependent fluid characterization tests was coupled with settling velocity data using both arbitrary shape of cuttings and spherical particles. A mathematical model that considers viscoelastic properties and time dependency of drilling fluids was developed to estimate settling and slip velocities of the cuttings. Comparisons between the proposed models and existing models based on standard rheological measurements were also done. The results show that the proposed model has good agreement with the experimental data.
Structural Loads Analysis for Wave Energy Converters
Authors: van Rij Jennifer , Yu Yi-Hsiang , Guo Yi 
Published: October 2017

This study explores and verifies the generalized body-modes method for evaluating the structural loads on a wave energy converter (WEC). Historically, WEC design methodologies have focused primarily on accurately evaluating hydrodynamic loads, while methodologies for evaluating structural loads have yet to be fully considered and incorporated into the WEC design process. As wave energy technologies continue to advance, however, it has become increasingly evident that an accurate evaluation of the structural loads will enable an optimized structural design, as well as the potential utilization of composites and flexible materials, and hence reduce WEC costs. Although there are many computational fluid dynamics, structural analyses and fluid-structure-interaction (FSI) codes available, the application of these codes is typically too computationally intensive to be practical in the early stages of the WEC design process. The generalized body-modes method, however, is a reduced order, linearized, frequency-domain FSI approach, performed in conjunction with the linear hydrodynamic analysis, with computation times that could realistically be incorporated into the WEC design process.
The objective of this study is to verify the generalized body-modes approach in comparison to high-fidelity FSI simulations to accurately predict structural deflections and stress loads in a WEC. Two verification cases are considered, a free-floating barge and a fixed-bottom column. Details for both the generalized body-modes models and FSI models are first provided. Results for each of the models are then compared and discussed. Finally, based on the verification results obtained, future plans for incorporating the generalized body-modes method into the WEC simulation tool, WEC-Sim, and the overall WEC design process are considered.
Drilling Riser Case Studies Comparing the Drag Performance of LGS Technology to Conventional Buoyancy Units and Fairings
Authors: Johnstone Daniel R. , Potts Andrew E. , Marcollo Hayden , Kurts Phillip 
Published: October 2017

Deepwater drilling risers have a substantial portion (>70%) of buoyancy modules covering their entire length. The circular cross-section of these modules acts as a bluff body exhibiting significant Vortex-Induced Vibration (VIV) response, resulting in fatigue in the riser/wellhead and drag force amplification of the riser.
Drilling operations can be suspended when the drag force on the riser adversely affects the top and bottom angles, a response which is exacerbated by drag force amplification due to VIV.
In 2015 and 2016, Longitudinally Grooved Suppression (LGS)1 technology was developed to field qualified Technology Readiness Level (TRL of 6) [1] offering a technical advantage to drilling operators over existing options.
In order to investigate the relative performance and quantify the benefits of LGS over conventional cylindrical Drilling Riser Buoyancy Modules (DRBMs) with and without fairings, a series of case studies encompassing typical operating conditions at drilling locations in several regions around the world (including the Gulf of Mexico, Brazil, the North Sea, and Australia) have been carried out to examine the performance in terms of drag (affecting operability due to top angle) and fatigue damage rate of the riser. The results indicate that LGS outperforms conventional buoyancy risers and fairings-equipped risers with regard to riser operability limits and fatigue.
Dynamic Modelling of a Spar Buoy Wind Turbine
Authors: Tomasicchio Giuseppe Roberto , Avossa Alberto Maria , Riefolo Luigia , Ricciardelli Francesco , Musci Elena , D’Alessandro Felice , Vicinanza Diego 
Published: October 2017

In the present paper, the dynamic response of a spar buoy wind turbine under different wind and wave conditions is discussed. Physical model tests were performed at the Danish Hydraulic Institute (DHI) off-shore wave basin within the EU-Hydralab IV Integrated Infrastructure Initiative.
The OC3-Hywind spar buoy was taken as reference prototype. A spar buoy model, 1:40 Froude-scaled, was tested using long crested regular and irregular waves, orthogonal (0 degrees) and oblique (20 degrees) to the structure. Here the results concerning regular waves, with incidence orthogonal to the structure, are presented; the selected tests considered rotating and non-rotating blades. Measurements of displacements, rotations, accelerations, forces response of the floating structure and at the mooring lines were carried out. Based on the observed data, FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy’s (DOE’s), National Renewable Energy Laboratory (NREL), was calibrated and verified. The numerical model takes into account the wave induced response and the effects of the mooring lines on the overall system.
The adopted spar buoy has three equally spaced mooring lines that were modelled as quasi-static taut or catenary lines through MAP++ (static module) and MoorDyn (dynamic module) in the FAST simulation tool. The tensions along the fairleads of the three mooring lines were examined.
At the end of the calibration procedure, the numerical model was successfully used to simulate the dynamic motions of the floating wind turbine under combinations of wind and sea states for the selected wave attacks.
All data from the DHI tests were converted to full scale using Froude scaling before being analyzed.
The Next Generation Technology for Automatic Inflow Control
Authors: Grüner Vegar , Rinde Trygve , Lager Thorleif , Killie Rune , Solberg Tron , Bakli Mikkel 
Published: October 2017

Breakthroughs of water and/or gas in production wells may have direct consequences for the production rates and overall field recovery. Multiple technologies have recently been developed to autonomously control inflow from the reservoir. Common to all these technologies is that new limitations are introduced which may have a negative impact on the well. This paper presents the design process for the next generation inflow control system and introduces new requirements for such completions.
Traditional Passive Inflow Control Devices (ICD) are designed to act in a preventive manner by setting up a somewhat more even inflow profile along the reservoir section and thereby delay the breakthrough of gas or water. More recently, several new initiatives have been presented which will operate autonomously, with an ambition to choke back unwanted production. Common to these technologies is that they are primarily dependent on viscosity differences between the reservoir fluids.
In the work presented in the following, the design process has identified the following requirements for the next generation autonomous inflow control system:
• easy to install completion
• robust in design and functionality
• Improve clean-up of mud and completion fluids
• independent of fluid viscosity
• negligible pressure drop during normal production
• allows back-flow of fluids
In this paper the results from an ongoing development of a new design inflow control system, independent on differences in fluid viscosities is presented, which fulfills above requirements. This system is based on a valve, which blocks, or restricts, production of unwanted water or gas, and re-opens for production if oil comes back. It can be designed to stop water/gas production at a predetermined WC/GOR. Furthermore, it ensures efficient clean-up along the full length of the reservoir section and is insensitive to exposure to mud, particles and filter cake. The installation of this system will not restrict any future well operations and it can be designed with a fail-safe option.
The new system represents a great technological improvement which will ensure a robust, economical and fail safe design as well as a simplification of inflow design process, since it will work irrespective of local productivity, pressure and flow rate. Hence, removing the operational envelopes on which other technologies must be designed for to be able to work properly.
An Engineering-Model for Extreme Wave-Induced Loads on Monopile Foundations
Authors: Hansen Hans Fabricius , Kofoed-Hansen Henrik 
Published: October 2017

An extension of the classical Wheeler’s method is here presented and validated. Just as the Wheeler’s method, it relies solely on the measurement of surface elevation in a point to make predictions of the wave induced loads.
These measurements may be made in the field, but more often they will be generated in a laboratory wave basin. The classical Wheeler stretching plus Morison load model is augmented by a slamming load model for steep near-breaking and breaking waves, based on work published earlier by Nestegård et.al. (2004). The new model thereby spans the entire range from non-breaking waves to severely breaking overturning waves with a gradual transition. The model has been validated against surface elevations and wave loads measured in a laboratory wave tank and is found to reproduce wave load distributions over a range of sea state conditions well.
Examples are given for typical design sea state conditions for offshore wind turbines at exposed locations in Northern Europe. The loads are compared to loads obtained using the stream function wave theory in combination with the Morison’s equation. The stream function wave theory loads are found to generally be lower than the loads predicted using the simple wave load model presented here. This is the case even for mildly non-linear non-breaking waves but becomes much more pronounced for steep near-breaking and breaking waves. Another striking feature of the comparison to regular wave theory is the different distribution of loads. The stream function loads below still water level are often higher than the loads from the simple model, but much lower than the simple load model loads above still water level.