bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comprehensive Analysis on Gas-liquid Slug Flows in Horizontal Pipes
Authors: Cozin Cristiane , Pipa Daniel R , Barbuto Fausto Arinos , Morales Rigoberto Em , da Silva Marco Jose
Published: June 2014

Much work has been done to properly characterize the two-phase flow of liquid and gas in pipes. The importance of these flows extends over several branches of Engineering, notably nuclear and petroleum engineering. During their transportation, these two phases are subjected to several factors - gravity, viscosity and density gaps, different relative velocities between the phases and turbulence, to name a few relevant ones - that act in the spatial distribution of the liquid-gas interfaces bringing forth those that are known as flow regimes or, most commonly, flow patterns. The type of flow known as slug flow stands out as one of the most frequent, or the most frequent thereof, among these patterns. It main characteristics are intermittency and the continuous succession of two well-defined structures: an elongated bubble, which is a bulky accumulation of gas wrapped in a thin liquid film and the liquid slug, a significant amount of liquid containing mostly liquid with gas bubbles of variable size in its interior. Those two-structures, together, constitute that what is known a slug unit or, from a more computational standpoint, a unit cell. Due to their complexity, modelling slug flows has been a challenge over the last four decades. In the present day, steady-state one-dimensional models based on the unit cell concept and more accurate physical representations based on two-fluid models or slug tracking models which embed transient flow capabilities are available. Nevertheless, and notwithstanding the efforts that have been carried out, those models still require closure relationships that could bring three-dimensional flow features into the one-dimensional model, and those relationships must be backed by trustworthy experimental data. With this scenario in mind, the present work brings forward a brief review on two-phase, liquid-gas slug flows in circular pipes, be they horizontal, vertical or inclined, and a comprehensive state-of-the-art on the closure relationships aimed at predicting flow parameters such as the front bubble velocity, slug frequency and liquid slug holdup. An analysis of the performance of these correlations with experimental data for horizontal slug flows from the Universidade Estadual de Campinas' 2-Phase Flow Group (2PFG/DE/UNICAMP) was carried out and its results are presented.
Reservoir Limit Test Under Aquifer Influence
Authors: Feitosa Gilvan S
Published: June 2014

Reservoir Limit Test (RLT) aims to obtain the volume of oil-in-place (VOIP), a valuable parameter at early stage of reservoir life. RLT is characterized by the well's production under pseudosteady state (PSS) flow regime. The basis for RLT in oil reservoirs without aquifer is well established, in theory and in practice, since long ago. But RLT in presence of aquifer still is not well understood, thus the need for further research.

This work presents the theoretical foundation of Reservoir Limit Test under aquifer influence based on material balance, new in the literature. It investigates how aquifer affects a RLT as the pseudosteady state flow takes place. Various aspects have been investigated, such as aquifer size, hydraulic connection and aquifer contribution to the total system compressibility.

Basic relations for RLT under influence of aquifer were developed and checked by significant number of simulated cases. These relations are similar to the classical ones published long ago, but now with the effect of aquifer incorporated. The differences are in the overall water and oil saturation, the total system compressibility, and the porous volume hydraulic connected to the well. The oil-aquifer system total compressibility is a function of average oil and water saturation in the entire porous volume including the aquifer. This new average total compressibility controls the pressure drop during pseudosteady state flow. Rigorous calculation of VOIP requires the ratio aquifer-water volume to oil volume, otherwise only estimates are possible. It is observed that given enough time, the pseudosteady state flow develops for oil-aquifer system for broad size range of confined aquifers. Even for a weak aquifer with reduced hydraulic connection to the oil zone, its presence is felt in the PSS and must be taken into account. Important to note, the VOIP value that results after taking the aquifer into account may be significantly smaller than the value calculated without considering the aquifer.

A Brazilian deepwater oilfield with aquifer case, with two wells equipped with permanent downhole gauge (PDG) is presented. A dozen RLTs are observed at early stage of production. Its data, analysis and results, illustrate and substantiate the observations and conclusions of this work.
Cascade/Chinook Disconnectable FPSO: Free Standing Hybrid Risers Monitoring via Acoustic Control/Communications
Authors: Edwards Roderick Y , Daniel Jeremiah , Ling Mau S , Goebel Richard , Mastrangelo Carlos F , Xia Jianjun , Machado Filho Remo Z
Published: June 2014

This paper presents the history of and lessons learned from the challenge of designing, implementing and operating the acoustically controlled monitoring system used to verify performance, validate design and track motions and tensions of five Free Standing Hybrid Risers (FSHR), their Buoyancy Can connecting chain tension and disconnectable FPSO's Turret Buoy, which are components of the Cascade & Chinook Production Facilities.

For impending threats such as named storms, the FPSO disconnects from the geostationary turret buoy, which sinks to a neutral depth below wave and winds affected zone, while the FPSO sails to safe waters. The system continues to monitor all parameters when the buoy is submerged.

While connected, buoy originated real time data and risers originated quasi real time data received via acoustic communications is collected by the monitoring system computers on the FPSO. While disconnected data is recorded at the buoy and FSHRs and is downloaded to the monitoring system computers upon reconnection and prior to resuming production. All data is transmitted to shore via satellite where behavior of the components is analyzed to validate designs for normal and severe weather conditions. The data collected provides a significant database of riser and Turret Buoy behavior in the range of experienced environmental conditions.

In this paper the performance of the monitoring system since its installation will be addressed, including how the alarm from this unique monitoring system initiated the discovery of the accidental release of the Chinook 1 FSHR Buoyancy Can.

This innovative monitoring system contributes a significant step forward for future designs of FSHRs, by facilitating comparison of actual FSHR behavior in real environmental conditions to engineering model predictions.

This monitoring system is being used and can be used for a variety of submerged production equipment without the use of umbilicals and is especially appropriate for use in severe weather locations and when verification of behavior and operability of the risers must be confirmed prior to restarting production.

Introduction

The Cascade and Chinook Fields are located in the Walter Ridge Block, 300 km south of Louisiana coast in the Gulf of Mexico with Lower Tertiary reservoirs.

The development of these fields presented a considerable challenge, due to the water depth, reservoir depth, distance from shore, furrowed seabed and exposed to threats from hurricanes, eddies and loop currents. Both fields are producing to a floating production, storage and offloading facility (FPSO) that is single point (turret) moored 5 km from the Cascade Field and about 20 km from the Chinook field, in 2500 m water depth. Produced oil is shuttled by dedicated tankers to ports in the United States.
A New Environmental Lubricant Supports Key Subsea Boosting and Compression Technology
Authors: Morris John , Brunvold Anders , Morrissey Chris
Published: June 2014

In recent years development in the offshore industry has moved key processes from surface facilities to subsea, with the major focus being on subsea boosting and gas compression. This has led equipment manufacturers to develop high performance subsea pumps and compressors, driven by increasingly powerful, efficient and compact electric motors. These motors, together with the bearings and seals in the pumps and compressors, need to be lubricated and cooled efficiently by a lubricant with unique properties suited for operation in the subsea environment. This paper will focus on the challenges that were overcome in the development of a lubricant to meet both the performance and environmental requirements.

The lubricant is normally supplied to the subsea unit via an umbilical from the host surface facility, and is one of the vital keys to the reliability of this (rotating) equipment. The performance characteristics of the lubricant must cope with industry trends such as increasing process stream temperatures, higher pressures and higher shaft rotational speeds. In combination with these demands tightening environmental legislation governing the use and discharge of chemicals into the oceans requires that the industry adopts more environmentally responsible lubricant technologies.

The development process began by understanding in detail the conditions inside the various rotating elements within the pump/compressor. Critical parameters which will be reviewed include long term thermal stability, lubricant viscosity, lubricity, load carrying properties and water contamination management. With shaft speeds up to 6000rpm, and high simulated process temperatures, the product would be thermally stressed beyond limits typically seen in these applications. The screening tests on bespoke test rigs, selection of environmentally responsible lubricant components will be discussed, together with an overview of the global offshore environmental trends.

This approach demonstrated the superior performance of the lubricant by testing it beyond the expected conditions to provide enhanced reliability assurance and reduce operational risk. The final lubricant solution will increase the operating envelope of subsea pumps and compressors, offer improved reliability, and being fully compliant with the tightest offshore environmental legislation.
Engaging with an Indigenous Arctic Population - Listening and Building Trust from the Ground Up
Authors: Ede Ella L.
Published: June 2014

As we travel to rural Alaska communities discussing possible Arctic oil and gas offshore exploration, we frequently learn more from the Native people than we have to tell them. While the communities are eager to learn about potential plans, the main lesson from our conversations has been that listening is more important than speaking. The feedback from stakeholders is varied and concerns are complex. For subsistence users who have long called Northern Alaska home, an important consideration is: Can our ancient culture co-exist with modern development?

Companies with U.S. Alaska offshore leases are required to engage with stakeholders, as outlined in the federal lease stipulations' "plan of cooperation." Effectively engaging with stakeholders in Arctic Alaska has benefits far beyond checking off a regulatory requirement. Earning mutual trust and respect are not simple or time-bound processes, but require a genuine commitment to inclusive and collaborative engagement practices, patience, and follow through.

When working with indigenous Alaskans, a primary focus is demonstrating respect for their culture and especially their subsistence way of life. Today the Inupiat work to balance their traditional subsistence livelihood and spiritual connection with the ocean with the high cost of modern living. They harvest up to 70 percent of their diet from their garden: the sea and Alaska mainland. Any development that may occur represents a potential threat to their way of life which is understandably met with concern. Being able to discuss how development and subsistence can co-exist is integral to an effective discussion. Another consideration is the economic and cultural impacts that development may have on these very rural areas which lack educational and economic opportunities. They suffer from outmigration, language loss, and external influences that are eroding their culture. Oil and gas exploration represents opportunity, but also significant change. Understanding and addressing socioeconomic impacts are as equally important as minimizing environmental impacts.

Regardless of where we are operating in the world, companies have an obligation to work with stakeholders at all levels. As we continue to explore the Arctic, the right approach to connect with indigenous people is imperative. By engaging with youth and elders, incorporating traditional knowledge into our plans, and formulating strong relationships based on shared values, meaningful corporate social performance is achievable.
Design Method for ISO 19906 Arctic Offshore Structures
Authors: Thomas Graham A.N.
Published: June 2014

A view of the design process is presented in order to describe the different aspects and activities that together represent an holistic design process that includes both specific requirements for design verification, and knowledge related to other issues that can influence the design. The requirement for design verification using the Limit States Design method is widely understood. Other issues are less well understood, such as the recommendation to consider ice events with annual probability less than that specified for the abnormal-level in the context of overall reliability of the structure. This paper uses the term "beyond abnormal" for these events. Another issue is the influence of operational This paper also offers information and the author's opinions on related issues, such as the definition of design situations, the optional use of reliability targets to support design that includes operational measures, the definitions of events and actions, and a summary of what was actually calibrated for ISO 19906. It is hoped that such issues will be discussed when ISO 19906 is revised and updated.
An Ice-Structure Interaction Model for Non-simultaneous Ice Failure
Authors: Yu Bingbin , Karr Dale
Published: June 2014

This paper presents a new analytical model to simulate time-dependent response of structures subjected to ice impact. The ice forces are limited by ice failure with the ice considered to fail in multiple zones non-simultaneously. The results of numerical simulation of structural response to the non-simultaneous ice failure loads are provided. Non-simultaneous ice failure is one important failure mode of larger scale ice moving at moderate to high speed. This model combines previous independent failure zone theory of brittle materials and a dynamic ice-structure interaction model.

Developing offshore energy has become more and more serious worldwide in recent years with considerable offshore and shipping activities in the Arctic. Ice is a dominant feature of the Arctic region and predicting interaction effects on offshore structures and ships operating in the Arctic is essential in Arctic engineering. The ability to understand the magnitude and cyclic nature of ice forces and structure response is a key aspect for offshore structural design in cold regions. The prediction of structural response when encountering interactions with ice is essential for safe operations in this region. The model presented here is an effort to better understand and predict ice forces.

This model is able to produce an ice load time history, which can be applied to dynamic ice-structure interaction analysis. The model can also generate a pressure-area curve based on the input ice characteristics. The resulting shape of the pressure-area curve is shown to depend upon input parameters. Besides the pressure area relationships, the resulting pressure dependence on various parameters is also studied such as independent zone size, shape and strength.
Sea Ice Thickness Surveying with Airborne Electromagnetics - Grounded Ridges and Ice Shear Zones near Barrow, Alaska
Authors: Hendricks S. , Hunkeler P. , Krumpen T. , Rabenstein L. , Eicken H. , Mahoney A.
Published: June 2014

This paper presents the findings of airborne sea-ice thickness measurements in the Beaufort Sea near Barrow, Alaska. We discuss the applicability of airborne electromagnetic (AEM) induction for ice thickness monitoring in near coastal areas. All measurements were done within the NSF funded Seasonal Ice Zone Observation Network (SIZONet) which organizes airborne sea ice thickness surveys every spring since 2007. The key finding is, that thickness of grounded ice features in shallow water regions can be mapped with the AEM method. This is of particular interest, since other established methods, like upward looking sonar, can not be applied for potentially hazardous sea-ice features in shallow water regions.
An Overview of the Development of Ice Ridge Keel Strengths Test Program
Authors: Bailey Eleanor , Bruce Jonathon , Derradji-Aouat Ahmed , Lau Michael
Published: June 2014

The Development of Ice Ridge Keel Strengths is a four-year collaborative venture between the C—CORE Centre for Arctic Resource Development (CARD) and the National Research Council – Ocean, Coastal & River Engineering (NRC-OCRE). The main focus of the project is to investigate the failure mechanisms associated with gouging ice ridge keels and the conditions under which these keels will continue to gouge without failure. This is important for the design of subsea structures in shallow waters, where ice keels have been observed to scour the sea floor, posing a threat to pipelines and subsea infrastructure. A series of near full-scale keel-gouge tests were carried out to investigate the strength characteristics of a first-year ice keel and its subsequent failure as it was pushed into an artificial seabed. The ice keels were constructed using freshwater ice blocks with a nominal thickness of 10 cm, produced in a cold storage facility prior to the start of the test program. The ice keels were constructed with the aid of a keel former that produced idealized keel geometries of 1.7 m depth, 4 m length and 3.5 m width. Once constructed, the keels were lowered into the water and left overnight to consolidate with air temperatures held at −20°C. The keel samples were tested using a custom-built frame that was designed and used in the Pipeline Ice Risk Assessment and Mitigation (PIRAM) Joint Industry Project. The frame applied a vertical surcharge load to the top of the keel whilst a soil tray was displaced horizontally, causing the bottom of the ice keel to interact with an artificial seabed. A total of ten keel tests were conducted in this test program. The parameters varied were the initial temperature of the ice (−3° and −18°C), the initial surcharge pressure (5–60 kPa), the soil tray velocity (1–20 mm s−1) and the consolidation time (19–48 hrs). An overview of the test program and preliminary results are discussed.
A Case Study of the September 2012 Anchorage Windstorm
Authors: Artzer A. , Schmude F. , Basciani J. , Diaz D.
Published: June 2014

On 4-5 September 2012, a severe windstorm impacted the city of Anchorage and the surrounding region. Wind gusts up to 63 mph were reported at the Port of Anchorage, which is just northwest of downtown, and gusts up to 88 mph were reported at McHugh Creek, which is just southeast of Anchorage near the Turnagain Arm. This windstorm downed thousands of trees across the Anchorage Bowl, which caused hundreds of downed power lines. At least 50,000 homes and businesses lost power in the greater Anchorage area during the peak of the event, including some office buildings in the Midtown and Downtown areas of Anchorage. Some areas were without power for several days. This paper will further examine the atmospheric aspects that contributed to the significant September 2012 wind event, as a well as a comparison to the four previous significant wind events that have occurred since 1980. Previous significant high wind events, defined as the "Big Four" by the Anchorage National Weather Service office, occurred much later in the season. The four significant high wind events occurred on 01 April 1980, 26–27 November 1985, 10 October 1986, and 01 December 1992. The results of this paper will provide insight into predicting future wind events which will allow residents and businesses to better mitigate their weather risk.
Met-Ocean Services by FMI for Ice Management and Shipping in Ice
Authors: Eriksson Patrick B. , Majaniemi Sauli , Lensu Mikko , Karvonen Juha
Published: June 2014

Shipping in sea ice and Ice Management (IM) encounter a number of challenges, starting from assessment of climatological conditions to critical tactical decision-making. The Finnish Meteorological Institute (FMI) holds a broad field of expertise with over a century of experience in sea ice and weather services in harsh winter conditions. Close collaboration with the Baltic Sea icebreaking management, which has evolved and been honed for optimal winter navigation, has brought up a hands-on feel for operation in ice-covered seas. Through high-level research robust know-how of operating in Arctic conditions with its demanding technical requirements has been built up.

Arctic marine and offshore operations still have critical challenges to face. In IM for instance, the IM team needs to deal with difficult cases like rapid changes and reversals in ice drift, risk identification in the pack ice field and evaluation of the ice management vessel capacity. FMI has developed real-time, high-resolution and fast update rate approaches to ice monitoring. The refined data products include 1) EO SAR (Synthetic Aperture Radar) classification, 2) enhanced sea ice property extraction from marine radar data, 3) robust weather observations in Arctic conditions, 4) ice drift and ice compression forecasting, 5) ice drifters, 6) instant combination of any of the earlier.

By merging the multiple fields of expertise to operational products, FMI creates tailored service entities with high operational comfort. Easy and intuitive usage and fast and smooth data transfer are important factors.
Dynamic Response of Submerged Buoys Disconnected at Large Vessel Offsets
Authors: Srivastava Vikas , Hallai Julian , Campbell Brad , Kokkinis Ted
Published: June 2014

Drilling vessels and production platforms conducting oil and gas operations in the Arctic will need to keep station in drifting pack ice. A rapid and safe disconnection system is needed as ice loads can exceed the capacity of the mooring system used for stationkeeping. Connecting all lines to a disconnectable submerged buoy has been proven effective for this purpose in open water. Using a similar system for vessels/platforms operating in ice requires special considerations as the disconnection of the buoy may need to take place at high offsets due to the high magnitude of ice loads.

There is no published work on the dynamics of submerged buoy for disconnection at high offsets. This paper presents new findings which were derived from numerical simulations for dynamic response of two disconnectable mooring buoy systems: a conventional medium size buoy with a compliant mooring system for a shuttle tanker in 200 m water depth (WD) and a larger buoy with a semi-taut mooring system for a drilling vessel in 500 m WD. Results for the global motion of the buoy and the dynamic contact loads between the buoy and the mating cone of the vessel soon after disconnect for various magnitudes of vessel offsets are presented in this paper. The results for the medium sized buoy with compliant mooring demonstrate strong nonlinear dependence of dynamic contact load on the disconnection offset in the range of 0 to 25% of the WD. The analysis results presented in this paper also show that a medium size buoy can have significant upward motion soon after exiting the mating cone and before it reaches its equilibrium position when the buoy is disconnected at high vessel offsets. For disconnections at very large vessel offset, the buoy during the upswing could impact the keel of an ice ridge. The large buoy with semi-taut mooring shows smaller upward motion for the 0 to 6% WD offset range considered in the simulations.
Best Practice in Ice Model Testing on Moored Floaters
Authors: Jochmann P. , Evers K.U.
Published: June 2014

The increase of activities in oil and gas exploration and production in cold regions during the last years is associated with the development of new innovative concepts with respect to arctic fixed and moored offshore installations. As a consequence there is a huge demand from the oil industry to validate the proposed concepts and feasibility studies. Apart from that, Numerical simulations may be beneficial to a certain extent to investigate the ice related problems, one can still not dispense with the execution of physical model tests. Worldwide there are only a limited number of facilities available, which are able to cope with the challenge of ice model tests at a proper model scale. The paper describes broadly the assets and drawbacks of different types of mooring systems ("wet" or "dry" mooring system) and the choice of suitable substituted mechanical systems with respect to their application for various ice scenarios. Alternatives how to design the model test set-up in order to measure the ice forces independently from the system response forces of moored floating structures will also be discussed.
Countermeasures for Bending and Abrupt Uplift of A Full-scale Test Chilled Gas Pipeline Observed at Boundary between Frozen Ground and Talik
Authors: Akagawa Satoshi , Huang Scott L. , Kanie Syunji , Fukuda Masami
Published: June 2014

In this paper the authors report the vertical bending properties of a test chilled gas pipeline and the countermeasures of the bending. A full-scale field experiment of the chilled gas pipeline system was conducted in Fairbanks, Alaska from 1999 to 2005. The length of the test pipeline was 105m and the diameter was 0.9m. The circulated chilled air was –10°C. One-third of the pipeline was buried in frozen ground and the rest of it was placed in talik. At the end of July 2003, circulation of the chilled air ceased, however, monitoring of the thaw settlement-related properties of the test pipeline continued until the middle of April 2005. The following results were presented at the 2nd ATC: 1) As the frost-bulb around the pipeline in talik section formed, the test pipeline in the talik section moved upward, resulting in bending of the pipeline at the boundary. 2) In summers, frozen overburden soil of the pipeline became thinner due to thawing of active layer above. The pipeline buried in frozen section moved upward abruptly, fracturing the thinning frozen overburden ground. 3) The phenomenon mentioned in 2) occurred in successive summers, and the pipeline uplift in frozensection continued. 4) In relation with 1), the upward movement in talik section was confirmed by frost heaving of the pipe foundation. In this report the bending behavior of the test pipeline is described and the several methods to deal with the bending are proposed.
Fixed Platforms – Development Challenges in Ice Infested Arctic
Authors: Eie Rolf , Rognaas Gunnar
Published: June 2014

The Arctic is becoming increasingly important in securing energy supplies for the future, notwithstanding the economic, environmental and social challenge. Finding and extracting oil and gas in the Arctic and Subarctic regions is itself challenging due to extreme temperatures, ice conditions, remoteness and a sensitive natural environment.

This paper is based on experiences from delivering substructures for oil and gas production in arctic locations and recent concept development for all year exploration drilling and production in new arctic areas. Parameters and challenges driving solutions for ice resistant, arctic fixed platforms will be discussed and how these are handled in design and execution planning.
Arctic Mooring Systems – The Past, Present, and Future
Authors: Kwan Chi-Tat Thomas , Bond James , Yu Han , Morandi Alberto
Published: June 2014

Recently the industry initiated 2 projects to address the issue of Arctic mooring systems. The first is an ABS study that includes a state of technology survey and an industry workshop for Arctic mooring systems. The ABS State of Technology Survey covers the topics of industry guidance and standards, ice loading predictions, current industry design practice, mooring hardware, and arctic operation philosophy. The ABS Industry Workshop has the objectives of providing a forum where industry experts could present their views and generate discussion, and to explore the need for a joint industry effort. At the end of the workshop, the general consensus indicated a need for a joint industry effort since the challenge is too big for any single company to meet.

The second is a JIP organized by Kwan Engineering Services and Global Maritime to address the issues identified by the ABS industry workshop. It has the objectives of developing a design and operation practice document, and providing a forum for the industry and regulators to exchange information/ideas and work together to build consensus. The JIP has 6 tasks: mooring strength design practice, disconnect and reconnect devices, mooring hardware, global ice load prediction, ice management, and mooring installation.

These studies indicate that current industry guidance and standards for mooring systems and Arctic structures are insufficient to address the design and operation of Arctic mooring systems. There are many challenging issues and disagreements to resolve. The Arctic mooring JIP initiated in 2013 has a large work scope and broad industry participation including operators, drilling contractors, designers, regulators, installation companies, and mooring component manufacturers. It is expected to produce a unified document based on rigorous investigations and consensus building, which will have a high impact on future Arctic mooring operations.
The Identification of Extreme Ice Features in Satellite Imagery
Authors: Zakharov Igor , Power Desmond , Bobby Pradeep , Randell Charles
Published: June 2014

P>Sea ice monitoring is an important field of scientific research and relevant to operational applications. One of the major engineering challenges in undertaking production developments in Arctic offshore regions is the frequent presence of extreme ice features that pose a hazard to facilities and surrounding subsea infrastructure. The information on extreme ice features (i.e., ridges, icebergs etc.) is important from the standpoint of potential ice load levels on fixed structures and ice scouring of seafloor facilities. Satellite observation has been shown to be useful for extracting and characterizing ice regimes. Sea ice can be monitored using satellite imagery acquired by different types of sensors: microwave radiometer, optical instrument and synthetic aperture radar (SAR). The outputs of sea ice monitoring may include various ice parameters such as edge, thickness, concentration, classification, iceberg detection, and ice statistics. This paper describes application of high and low resolution SAR imagery for sea ice monitoring and to resolve local features and extend the statistical baseline to larger regions because extreme ice features may be invisible or ambiguous with other ice features in these data. The use of higher resolution imagery allows for easier detection of ice features and provides sufficient spatial detail necessary for detecting ice features from sea ice, identification and estimation of size and geometry of ice floes and icebergs. It was demonstrated that SAR sensors with multiple resolution lead to a better understanding of ice conditions including ice edge, concentration, floe statistics, and other ice features such as icebergs. A technique based on SAR interferometry was used for identification of iceberg in sea ice as well as for extracting iceberg topography.
Characterization of Hazardous Ice using Spaceborne SAR and Ice Profiling Sonar: Preliminary Results
Authors: Ersahin Kaan , Brown Leslie , Kanwar Anudeep , Henley Michael , Ross Ed , Fissel David
Published: June 2014

Ice can pose hazard for operations (e.g., transportation, shipping, offshore oil and gas exploration) and for infrastructure (e.g., ports, pipelines, offshore structures). There is an increasing need for fine scale characterization of hazardous ice conditions. This information is of interest to many stakeholders including government departments and agencies, and the oil and gas industry. Spaceborne Synthetic Aperture Radar (SAR) sensors have demonstrated the viability and cost-effectiveness of near-real-time monitoring of the regional ice conditions. Satellite derived ice information products typically rely on the interpretation of ice analysts or in some cases semi-automated techniques, and cover relatively large areas at coarse resolution. Development of improved data products using high spatial resolution polarimetric RADARSAT-2 datasets (e.g., Fine Quad) is desired for detailed characterization of potentially hazardous ice conditions. Although validation of ice data products is challenging due to limited ground truth data, there are numerous sites throughout the Arctic with many years of continuous measurements of ice conditions obtained using bottom mounted Upward Looking Sonar (ULS) instruments. Using ULS data we have recently developed analytical methods to characterize highly deformed sea ice features including large individual keels, segments of hummocky ice, multi-year ice, and episodes of internal ice stress, which can also serve as validation data for SAR-based analysis. This paper presents an overview of our ongoing work and very preliminary results on hazardous ice characterization using SAR and ULS data. ULS data view from below and SAR data view from above are complementary information sources, and utilizing both is expected to result in better characterization of the ice conditions. During this work, paired SAR and ULS datasets will be generated to allow calibration and validation of algorithms, and methodologies will be developed to utilize these complementary data sources. This project is expected to (1) develop improved methods for fine scale analysis of RADARSAT-2 data; (2) develop enhanced information products generated in the hindcast mode when ULS and RADARSAT-2 are both available; (3) demonstrate potential for RCM (compact polarimetry). Calibrated and validated information products of hazardous ice will be extremely valuable for users who require such information for engineering design, to make management and policy decisions, and to safely perform operations.
Trenching of Pipelines for Protection in Ice Environments
Authors: Paulin Mike , Cocker Joseph , Humby Damien , Lanan Glenn
Published: June 2014

Subsea pipelines located in ice environments need to be protected from potential ice gouging (also known as ice scouring) created when a moving ice keel interacts with the seabed. The integrity and operability of the pipeline can be affected by direct contact between the ice keel and the pipeline, or from loading imposed on the pipeline through soil deformation caused by ice gouging. The typical method considered for protecting against the risk of damage caused by ice gouging is through pipeline burial.

Conventional methods of pipeline burial use equipment such as ploughs, mechanical trenchers, and jetters, the majority of which have been designed to accomplish a maximum of 2 to 3m of pipeline burial. Dredges can be used but they have water depth limitations and limited productivity. Land based equipment has been used for shore crossings, but is limited to shallow water depths where temporary construction berms can be used as a working platform.

The capabilities of existing technologies are based on current industry practice developed for pipeline burial in ice free environments. Pipeline burial requirements have generally been for improved hydrodynamic stability, mechanical protection (e.g. from anchors), controlling pipeline movements (e.g. expansion and buckling) and/or for flow assurance purposes (reducing heat loss). A 2 to 3m burial depth has been generally adequate to satisfy these conventional requirements. As developments are proposed for areas that experience relatively deep ice gouging (up to 5m), burial depth requirements will exceed the capabilities of current pipeline burial technologies. New technologies capable of working in deeper water, achieving greater burial depths, achieving reasonable trenching advance rates, operating in harsh environments, and trenching through variable and difficult seabed soils will be required.

This paper highlights the issues and challenges surrounding pipeline trenching and burial in ice gouge environments. Current state-of-practice is discussed along with the technology gaps that need to be addressed to prepare for future offshore developments in ice covered waters where there is the potential for seabed ice gouging.
A New Jack-Up Unit Concept To Extend the Arctic Drilling Season
Authors: Urycheva Maria , Gudmestad Ove T.
Published: June 2014

Huge hydrocarbon resources, expected to be present in the Arctic area, have led the industry to explore the deposits of the Arctic seas, though such exploration is very challenging. Jack-up units are normally applied for drilling in shallow ice-free Arctic waters. Conventional jack-ups can be utilized only during the open water season. The installation of a jack-up can take place after the ice cover has cleared sufficiently for the jack-up to be maneuvered to site. At the end of the drilling season, the jack-up should be moved away before the sea freezes up, as the jack-up could get stuck in the ice cover.

The paper describes a new jack-up drilling rig concept suggested for shallow Arctic waters such that the drilling season can be extended by several weeks as compared with existing jack-up drilling rigs. The suggested concept comprises a ship-shaped hull with icebreaking capabilities and four columnar legs placed on outrigger arms and equipped with protective collars so the jack-up can withstand ice loads in the early ice period. Drilling through one of the jack-up legs is suggested to protect the drill string from possible ice impact at the end of the drilling season. This leg should have a telescopic design so that the derrick could be skidded over it before drilling.

The research comprises a detailed description of the main concept features and the estimation of the possible drilling season extension using the example of the Pechora Sea ice conditions. The study concludes that the considered jack-up can be an effective solution for exploration of shallow Arctic waters. The suggested jack-up design allows the crew to continue drilling operations for at least four to five weeks after the ice has started to form on the drilling site and to leave the location safely without costly icebreakers' assistance. In case a relief well has to be drilled in the area, the drilling season could be further extended with the implementation of heavy ice management.
Drilling with Casing System Continues Successful Drilling of Permafrost Sections in Arctic Circle of Western Siberia (Russian Federation)
Authors: Andrey Bakhtin , Gurban Valiyev , Stanislav Kulikov , Alexey Chumachenko , Dmitry Priymachenko , Vadim Mnatsekanov
Published: June 2014

Oil and gas operators have explored in the Arctic regions of Russia for more than 40 years. Early drilling campaigns encountered significant problems drilling through the shallow permafrost sections due to degradation of drilling conditions as a result of permafrost thaw. Experience from these earlier operations and experiments conducted by Kutasov et al (1988) has highlighted the need to maintain chilled drilling mud to minimize permafrost thaw during the well construction process. After time technologies made step forward and casing drilling is in addition option with Kutasov technology to improve drilling process. This technology is one of the greatest developments in drilling operations. Casing drilling involves drilling and casing a well simultaneously.

Casing drilling system has been designed primarily for multi-well offshore platforms, multiwell operations on land, deep-water operations, and for situations requiring operators to drill through and place casing across problem formations quickly. This technology was applied successfully to drill through depleted reservoir (problems: wellbore instability, mud losses into the depleted zones) as an alternative to the underbalanced drilling, which requires special equipment.
Innovative Seismic Acquisition Techniques Improve Data Quality on Alaska’s North Slope
Authors: Winter Olivier , Maxwell Peter , Schmid Ron , Watt Howard , Bathellier Eric
Published: June 2014

CGG recently acquired the Tabasco multi-client, high-resolution 3D seismic survey on the North Slope of Alaska. It covers 133 sq. mi (Figure 1) and was designed for optimum imaging of the faulting and onlaps in the Cretaceous and Jurassic hydrocarbon-bearing sequences. The survey was the first multi-client survey performed in the area in over a decade. It was acquired in separate northern and southern parts, both of which were processed independently, and saw the first use of many high-end acquisition techniques in the region. It was the first-ever, high-productivity, extended slip-sweep vibroseis program acquired on the North Slope, breaking previously-established records and setting a new standard at 5,000 records gathered in a 24-hr period. It also introduced the proprietary EmphaSeis broadband vibroseis technique, providing a frequency range of 4-80Hz. Thus, the survey delivered a number of innovative solutions in this challenging environment.
Application of Ground Penetrating RADAR for Profiling and Bathymetric Survey of Shallow Frozen
Authors: Cross R.C. , Lee W.J. , Poeckert R.
Published: June 2014

Ground Penetrating Radar (GPR) was used to survey the bathymetry and sub-bottom features of a frozen lake in Ontario, Canada. A 50 MHz GPR measured the lake depth to a maximum of 24 meters. Sub-bottom features and sediment thickness were simultaneously observed and recorded with the GPR. Single beam sonar hydrographic surveying methods were applied to the data acquisition process and quality control procedures. Quality control checks revealed a vertical accuracy of approximately 0.25 meters while the horizontal positional accuracy was approximately 0.1 meters through the use of Real-time Kinematic (RTK) GPS. A contoured bathymetric map was generated from the data set as well as an isopach of sediment thickness. GPR is demonstrated to be effective for measuring water depth, ice thickness, and sub-bottom features of ice covered lakes.
Ice Load Estimation Methods for LNG Jetty Design in Various Ice-Structure Interactive Conditions
Authors: Nakazawa Naoki , Terashima Takashi
Published: June 2014

In this study, the authors proposed the ice load estimation methods for LNG jetty design in the southern coast of Sakhalin Island by building scenarios of ice forces exerted on the structures, e.g. i) driving ice force with geographical features considered, ii) ice force with jamming effects considered, iii) ice force with jamming effects and non-simultaneous ice failure considered, and iv) ice force with no jamming. The possibility of ice jamming cannot be ignored when consideration is given to the geometrical configuration of the close proximity of the jetty supports. However, using the mechanisms that consider the failure of ice around a single support, it has been demonstrated that the predicted ice loads are larger than those resulting from ice jamming occurring between a series of closely spaced supports.
Ice Load Calculation for Arctic Structures Using 3-D Dynamic Non-Linear Finite Element Analysis
Authors: Akinci N.O. , Lu Q. , Sari A. , Nguyen H.
Published: June 2014

Guidelines to predict ice loads on arctic structures have been covered in ISO 19906 [1] based on some empirical equations. This study aims to calculate ice loads for various types of structures using an analytical approach and comparing results with those calculated according to ISO 19906. The scope of this study covers floating structures subjected to ice loads. Structure considered in this study and ice are modeled using finite element (FE) analysis software ABAQUS [2]. Material non-linearity for investigated structures, contact, non-linear crushing and fracture behavior of ice are captured in the analyses.

Use of high end modeling approach is considered as a key element for obtaining a refined solution to this non-linear and dynamic impact problem. The findings and conclusions presented in this study are expected to show advantages of using advanced analysis approach in calculation of ice loads. There weren't many comprehensive studies explaining advantages of an analytical approach over a code equation approach for calculation of ice loads at the time of this study.

This study was developed to fill a gap in the industry so that engineers, owners and operators of arctic facilities can make informed decisions about the method to calculate the ice loads pertaining to their structure. It is typical to have a conservative approach when empirical code equations are used to calculate loads. However, level of conservatism or accuracy of code equations should be evaluated to ensure that target level of safety is attained.
First Year Ice Rubble: Shear Resistance and Rock Berm Interaction
Authors: Phillips Ryan , McAffee Rodney , Barrett John
Published: June 2014

Typical rock berms used to protect submarine pipelines may be damaged under shear by a first year grounded ice rubble keel. Physical model tests in a centrifuge have indicated that such damage occurs under loads less than those typical of actual design conditions. These novel tests have reproduced both failures of the rock berm and identified failure criteria for the ice rubble. The tests are of a preliminary nature given the discrete, rather than continuum, nature of the interaction event. The model freshwater ice rubble behaved as a frictional granular material under the shear test conditions with a peak friction angle of 38 degrees. Measured ice rubble shear strengths exceeded 65 kPa.

First year freshwater ice rubble large scale tests were conducted as part of the Pipeline Ice Risk Assessment and Mitigation (PIRAM) and Development of Ice Ridge Keel Strength (DIRKS) Joint Industry Projects. New finite element analyses of the PIRAM test set up indicate the boundary constraints on the test results. The measured PIRAM ice rubble shear strengths exceeded 35 kPa.

The first two test series indicate that ice rubble shear strength may exceed currently accepted design limits.
Gaps in Knowledge and Analysis Technology of Ice-gouge – Pipeline Interaction
Authors: Eltaher Ayman
Published: June 2014

Application of advanced numerical modeling to simulate ice gouge events has been based mostly on partial calibration, over a narrow range of parameters, with an emphasis on free-field events. A more comprehensive and systematic approach is required to calibrate and validate numerical models. This approach will need to include physical testing and advanced numerical simulations, to achieve better understanding of underlying and constituent processes, with best results requiring collating and sharing knowledge accumulated in previous (some of it being proprietary) work. The proposed presentation will identify and discuss gaps in the knowledge and numerical modeling of ice gouge-pipe interaction currently in need to be addressed, such as high quality (e.g., centrifuge or full-scale) test data for different types of soil (e.g., sand, clay, gravel, etc.); physical testing that include pipe; development of suitable soil constitutive models that suit the level of deformation involved especially close to the mudline; validation and calibration of elements and processes in the numerical tools (e.g., soil constitutive models and the behavior of the interface between ice and soil); development of a rational simplified analytical models of ice gouging that reflects the physics involved, so it is better validated and applicable to wider ranges of conditions and parameters; and development of guideline for offshore pipeline design in ice gouge environments.