A Coupled Dynamic Ice-Load and Moored Floater Interaction Parametric Study for First Year Level Ice

2016 ◽  
Author(s):  
Aziz Ahmed ◽  
Anurag Yenduri ◽  
Ritwik Ghoshal ◽  
Zhuo Chen ◽  
Ankit Choudhary ◽  
...  
Keyword(s):  
Parametric Study ◽  
Oil And Gas ◽  
Time History ◽  
Full Scale ◽  
The Arctic ◽  
First Year ◽  
Mooring System ◽  
Oil And Gas Exploration ◽  
Ice Load ◽  
Level Ice

Arctic remains the final frontier in the oil and gas exploration regime. The diminishing presence of ice opens up the region for longer and wider exploration. However, even with the assistance of ice management, the threat of broken first-year level ice stays ubiquitous. Calculation of ice load for such ice features bases on the established formulation developed by observation from full-scale measurements and model test data over the years. However, the formulation mostly relies on the data derived from fixed structures or icebreakers. Such estimations of ice load do not account for the stiffness compliance afforded by mooring system of a floater, such as a semi-submersible or a spar. A floating oil and gas exploration system offers a number of advantages over the fixed platforms, such as the option to deploy elsewhere during the off-season in the Arctic as well as connecting and disconnecting during severe ice events such as an approaching iceberg or multi-year ice ridge. However, the current practice of employing dynamic ice load time-history available in ISO19906 or similar codes fails to account for the presence of the mooring system on these floating platforms, directly resulting in a lack of confidence in the derived response of the floater. This study aims to address this issue by developing a dynamic ice-load time-history algorithm, which, can readily couple with commercially available hydrodynamics and mooring system analysis software. This investigation puts forward the hypothesis that the evolution of ice load vs. ice feature displacement with respect to the structure remains same for both fixed and floating structures. However, the underlying assumption is that the size of the ice features remains comparable. This hypothesis accounts for the prominent influence of the size effect on the breaking strength of ice. The difference between the behavior of a fixed and a floating structure under ice load is due to the relative motion between the floater and the ice feature. The developed coupled ice-load-function accounts for this by including the relative displacement between the floater and the ice feature in the formulation. This study uses the semi-empirical formulation originally derived by Croasdale to calculate the main ice load components for a fixed structure with downward breaking slope. Subsequently, this study uses this coupled ice load subroutine to compare against the full-scale measurement data found in the literature for a floater with downward-sloped hull specifically designed to assist in ice breaking. A comparison against the peak load observed during full-scale measurements on a floater in the Arctic waters validates the proposed approach. Next, this study utilizes the coupled analysis to derive the displacement, velocity, and acceleration response of the studied floater for a range of ice parameters, such as the drift speed and thickness. Additionally, this study performs a parametric study by varying the downward breaking slope angle of the floater, the mooring configuration, and the water depth. Finally, this study summarizes the observed behavior of the floater under different ice parameters as well as floater shape and mooring systems parameters.

Ice loads from first-year ice ridges and rubble fields

1998 ◽  
Vol 25 (2) ◽  
pp. 206-219 ◽  
Author(s):  
Denis Blanchet
Keyword(s):  
Full Scale ◽  
The Arctic ◽  
First Year ◽  
Failure Behavior ◽  
Pressure Measurements ◽  
Load Models ◽  
Ice Load ◽  
Ice Loads ◽  
Scale Data ◽  
Structure Width

A method for estimating global loads from consolidated first-year ice ridges and rubble fields on wide Arctic offshore vertical-sided structures is presented. The method utilizes full-scale global ice load measurements in the Arctic to represent the failure behavior of the consolidated layer and a Mohr-Coulomb approach for the remaining layers. By including full-scale data, the model can take into account the effects of scale and non-simultaneous failure of the consolidated ice layer across the structure width. The results are compared with those obtained from several other first-year ice ridge and rubble field load models.Key words: first-year ice ridges, rubble fields, ice load and pressure measurements, Arctic structures, ice load models.

Preliminary Analytical Formulation of Ice-Floater Interactions Including the Effect of Wave Load

2018 ◽  
Author(s):  
Aziz Ahmed ◽  
M. Abdullah Al Maruf ◽  
Arun Kr. Dev ◽  
Mohammed Abdul Hannan
Keyword(s):  
Oil And Gas ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
The Arctic ◽  
Total Force ◽  
Wave Load ◽  
Incoming Wave ◽  
Total Load ◽  
Ice Load ◽  
Level Ice

Diminishing ice presence in the Arctic provides the potential for extended operable period for oil and gas exploration in the Arctic. Floaters are a flexible solution for such scenario whereas they can fully take advantage of the extended drilling season as well as operate in other harsh environment regions during the off-season. Such floaters can disconnect and reconnect to avoid large ice features such as icebergs and multi-year ice ridges. However, they still need to encounter relatively large level ice. Accompanying icebreakers will ideally assist in breaking the level ice into manageable pieces. The interaction of such level ice floes with floater has a significant influence on the dynamic ice load on the floater and resulting mooring load. There is significant uncertainty in the simulation of level ice-floater interaction numerically. Most of the current research focuses on the influence of ice breaking and subsequent flow of the broken ice around the floater. However, the hydrodynamic load due to the incoming level ice will also affect the response of the floater, which is usually not simulated. A recent study simulated the multibody hydrodynamics of level ice and floater Such multibody hydrodynamic analysis is computationally expensive, and complexity in the modelling is a hindrance to its implementation in the design phase. The present study, therefore, employs a conservative estimation to include the effect of wave load on the floater in addition to the ice load. Parametric studies are performed to estimate this effect by varying the incoming wave amplitude and wave period, ice sheet thickness, ice drift velocity, floater’s hull angle, mooring stiffness and the distance of large ice-sheet from the floater. Significant impacts of waves on the floater in terms of total force are observed which clearly reflects the importance of this study. The effect of mooring stiffness on total load is also investigated at the end of this study which can be considered as a foundation for further research on optimizing the mooring stiffness for such kind of arctic floater.

Advanced Weathervaning in Ice

2011 ◽  
Author(s):  
William Hidding ◽  
Guillaume Bonnaffoux ◽  
Mamoun Naciri
Keyword(s):  
Rapid Change ◽  
Ice Sheet ◽  
Model Tests ◽  
The Arctic ◽  
Mooring System ◽  
Sudden Increase ◽  
Time Step ◽  
Ice Loads ◽  
Level Ice ◽  
Drift Direction

The reported presence of one third of remaining fossil reserves in the Arctic has sparked a lot of interest from energy companies. This has raised the necessity of developing specific engineering tools to design safely and accurately arctic-compliant offshore structures. The mooring system design of a turret-moored vessel in ice-infested waters is a clear example of such a key engineering tool. In the arctic region, a turret-moored vessel shall be designed to face many ice features: level ice, ice ridges or even icebergs. Regarding specifically level ice, a turret-moored vessel will tend to align her heading (to weather vane) with the ice sheet drift direction in order to decrease the mooring loads applied by this ice sheet. For a vessel already embedded in an ice sheet, a rapid change in the ice drift direction will suddenly increase the ice loads before the weathervaning occurs. This sudden increase in mooring loads may be a governing event for the turret-mooring system and should therefore be understood and simulated properly to ensure a safe design. The paper presents ADWICE (Advanced Weathervaning in ICE), an engineering tool dedicated to the calculation of the weathervaning of ship-shaped vessels in level ice. In ADWICE, the ice load formulation relies on the Croasdale model. Ice loads are calculated and applied to the vessel quasi-statically at each time step. The software also updates the hull waterline contour at each time step in order to calculate precisely the locations of contact between the hull and the ice sheet. Model tests of a turret-moored vessel have been performed in an ice basin. Validation of the simulated response is performed by comparison with model tests results in terms of weathervaning time, maximum mooring loads, and vessel motions.

Model Tests on a Spar in Level Ice and Ice Ridge Conditions

2009 ◽  
Author(s):  
John Murray ◽  
Stephane LeGuennec ◽  
Don Spencer ◽  
Chang K. Yang ◽  
Wooseuk Yang
Keyword(s):  
Full Scale ◽  
Scale Model ◽  
Test Facility ◽  
Mooring System ◽  
Scaling Effects ◽  
Line System ◽  
Restoring Forces ◽  
Ice Conditions ◽  
Ice Loads ◽  
Level Ice

1:30 and 1:50 model-scale ice tests of an ice-resistant Spar design were carried out to determine the loads on the Spar in level ice and ice ridges. Due to limitations in the depth of the ice test facility, the hull draft and mooring system were truncated. The 1:30 scale model was towed through the ice on a fixed and compliant dynamometer. The stiffness characteristics of the compliant dynamometer matched the horizontal stiffness of the full-scale mooring system. The purpose of these tests was to compare the mooring and ice loads measured in fixed and compliant conditions. The 1:50 scale model was truncated by 70 m. Its mooring system was modeled using a four-line system designed to give the same global restoring forces as the full-scale mooring system. The model was fitted with vertical plates on the exterior of the hull to compensate for loss of added mass and added moment of inertia. A limited number of tests were carried out at the two model scales in the same ice conditions to investigate scaling effects. The mooring and ice loads measured in the fixed and compliant conditions were found to be similar, indicating that loads estimated, assuming the structure is fixed, provide good estimates. Good agreement between the two models was also found for the tests carried out in the same ice conditions, suggesting that the scaling effects may be negligible.

Floaters for Oil and Gas Exploration in the Arctic - A Review

2016 ◽  
Author(s):  
Aziz Ahmed ◽  
Xudong Qian ◽  
Benjamin Xia Tian Peng ◽  
Zhuo Chen ◽  
Ankit Choudhary ◽  
...  
Keyword(s):  
Oil And Gas ◽  
The Arctic ◽  
Oil And Gas Exploration

Ice Model Testing of Structures With a Downward Breaking Cone at the Waterline JIP: Presentation, Set-Up and Objectives

2011 ◽  
Author(s):  
Per Kristian Bruun ◽  
Sveinung Lo̸set ◽  
Arne Gu¨rtner ◽  
Guido Kuiper ◽  
Ted Kokkinis ◽  
...  
Keyword(s):  
First Year ◽  
Test Set ◽  
Ice Load ◽  
Fixed Model ◽  
Ice Conditions ◽  
Level Ice ◽  
Ice Model Test ◽  
Set Up ◽  
Ice Failure ◽  
Ice Model

Two large ice model test campaigns were performed in the period 2007–2010 as a part of a Joint Industry Project. The objectives of the project were to investigate different floater geometries and ice model test set-ups (model fixed to a carriage and pushed through the ice vs. ice pushed towards a floating model moored to the basin bottom) and their influence on the ice failure mode and structure responses in the various tested ice conditions. This paper presents the objectives and motivations for the project, the models tested, the target test set-up for the various tested configurations and the test matrix. Initial results from a fixed model tested in three first-year ice ridges with similar target ice properties are also presented and compared. Fixed models of both deep and shallow water platforms were tested in various ice conditions. All models except one had a downward breaking cone at the waterline. The influences of the waterline diameter, the angle of the downward breaking cone and the vertical cone height on the ice failure mode and the resulting ice load were investigated. Tests were conducted in level ice with a thickness ranging from 2 to 3 m and variable ice drift speeds ranging from 0.1 to 1.0 m/s in full scale values. The models were subjected to tests in managed level ice with varying speeds, ice concentrations and ice floe sizes. Fixed structures were also subjected to testing in typical first-year design ice ridge conditions with ridges of different depths and widths, as well as one multi-year ice ridge. One fixed model was also utilised for testing of the repeatability of scaled ice model testing. Moored models with the same waterline geometry as the fixed models were also tested. The moored models were tested in ice conditions similar to those of the fixed models with the objective of comparing their influences on the ice load due to structural responses.

Three years (2017-19) of field observation of the marginal ice the Western Barents Sea

2020 ◽  
Author(s):  
Nataliya Marchenko
Keyword(s):  
Sea Ice ◽  
Laser Scanning ◽  
Oil And Gas ◽  
Barents Sea ◽  
Mechanical Tests ◽  
Point Of View ◽  
The Arctic ◽  
Oil And Gas Exploration ◽  
Ice Floes ◽  
The University

<p>Knowledge of sea ice state (distribution, characteristics and movement) is interesting both from a practical point of view and for fundamental science. The western part of the Barents Sea is a region of increasing activity – oil and gas exploration may growth in addition to traditional fishing and transport. So theinformation is requested by industry and safety authorities.</p><p>Three last years (2017-19) the Arctic Technology Department of the University Centre in Svalbard (UNIS) performed expeditions on MS Polarsyssel in April in the sea ice-marginal zone of the Western Barents Sea, as a part of teaching and research program. In (Marchenko 2018), sea ice maps were compared with observed conditions. The distinguishing feature of ice in this region is the existence of relatively small ice floes (15-30 m wide) up to 5 m in thickness, containing consolidated ice ridges. In (Marchenko 2019) we described several such floes investigated by drilling, laser scanning and ice mechanical tests, on a testing station in the place with very shallow water (20 m) where ice concentrated. In this article, we summarise three years results with more attention for level ice floes and ice floe composition, continuing to feature ice condition in comparison with sea ice maps and satellite images.</p><p>These investigations provided a realistic characterization of sea ice in the region and are a valuable addition to the long-term studies of sea ice in the region performed by various institutions.</p>

Assessing the potential to detect oil spills in and under snow using airborne ground-penetrating radar

Geophysics ◽  
2010 ◽  
Vol 75 (2) ◽  
pp. G1-G12 ◽  
Author(s):  
John H. Bradford ◽  
David F. Dickins ◽  
Per Johan Brandvik
Keyword(s):  
Ground Penetrating Radar ◽  
Oil And Gas ◽  
Unsaturated Flow ◽  
Oil Spills ◽  
The Arctic ◽  
Oil And Gas Exploration ◽  
Impedance Contrast ◽  
Snow Stratigraphy ◽  
Natural Snow ◽  
Ground Penetrating

With recent increased interest in oil and gas exploration and development in the Arctic comes increased potential for an accidental hydrocarbon release into the cryosphere, including within and at the base of snow. There is a critical need to develop effective and reliable methods for detecting such spills. Numerical modeling shows that ground-penetrating radar (GPR) is sensitive to the presence of oil in the snow pack over a broad range of snow densities and oil types. Oil spills from the surface drain through the snow by the mechanisms of unsaturated flow and form geometrically complex distributions that are controlled by snow stratigraphy. These complex distributions generate an irregular pattern of radar reflections that can be differentiated from natural snow stratigraphy, but in many cases, interpretation will not be straightforward. Oil located at the base of the snow tends to reduce the impedance contrast with the underlying ice or soil substrate resulting in anomalously low-amplitude radar reflections. Results of a controlled field experiment using a helicopter-borne, [Formula: see text] GPR system showed that a [Formula: see text]-thick oil film trapped between snow and sea ice was detected based on a 51% decrease in reflection strength. This is the first reported test of GPR for the problem of oil detection in and under snow. Results indicate that GPR has the potential to become a robust tool that can substantially improve oil spill characterization and remediation.

Heat Loss of Insulated Pipes in Cross-Flow Winds

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Bjarte O. Kvamme ◽  
Jino Peechanatt ◽  
Ove T. Gudmestad ◽  
Knut E. Solberg ◽  
Yaaseen A. Amith
Keyword(s):  
Heat Transfer ◽  
Oil And Gas ◽  
Theoretical Calculations ◽  
Cross Flow ◽  
Arctic Region ◽  
The Arctic ◽  
Transfer Coefficients ◽  
Oil And Gas Exploration ◽  
Heat Transfer Coefficients ◽  
Single Pipe

In recent years, there has been unprecedented interest shown in the Arctic region by the industry as it has become increasingly accessible for oil and gas exploration. This paper reviews existing literature on heat transfer coefficients and presents a comprehensive study of the heat transfer phenomenon in horizontal pipes (single/multiple pipe configurations) subjected to cross-flow wind besides the test methodology used to determine heat transfer coefficients through experiments. In this study, cross-flow winds of 5 m/s, 10 m/s, and 15 m/s blowing over several single pipe and multiple pipe configurations of diameter 25 mm and 50 mm steel pipes with insulation are examined. Based on the findings, the best correlation for use by the industry for single and multiple pipe configurations was found to be Churchill–Bernstein correlation. The deviation from the theoretical calculations and the experimental data for this correlation was found to be in the range of 0.40–1.61% for a 50 mm insulated pipe and −3.86% to −2.79% for a 25 mm insulated pipe. In the case of a multiple pipe configurations, the deviation was in the range 0.5–2.82% for 50 mm insulated pipe and 12–14% for 25 mm insulated pipes.

Oil and gas exploration in northern Canada

Polar Record ◽  
1961 ◽  
Vol 10 (67) ◽  
pp. 359-364
Author(s):  
A. T. Davidson
Keyword(s):  
British Columbia ◽  
Federal Government ◽  
Northwest Territories ◽  
Oil And Gas ◽  
The Arctic ◽  
Land Area ◽  
Northern Canada ◽  
Oil And Gas Exploration ◽  
The World ◽  
First Time

About 80 million acres on the mainland of the Northwest Territories and Yukon, and over 40 million acres on the Arctic islands, are under oil and gas exploration permit. Exploration permits were issued in the Arctic islands for the first time in June 1960, following promulgation in April of new Canada Oil and Gas Regulations for federal government lands. The issue of these permits extended the northern oil and gas search from the Alberta and British Columbia borders, in lat. 60° N., northward to the Arctic islands; in terms of land area this is one of the most widespread oil and gas searches in the world. The Arctic islands exploration also holds particular interest since it is the farthest north oil and gas exploration ever carried out.

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