bluuebunny/crossref_metadata_2025 huggingface dataset:
Finding the Source for Hydrocarbon Leakage on the Vestnesa Ridge, NW Svalbard
Authors: Knies J. , Plaza-Faverola A. , Bünz S. , Mienert J. , Daszinnies M. , Mattingsdal R. , Chand S.
Published: March 2015

The Vestnesa Ridge, a gas and gas-hydrate-charged sediment drift on oceanic crust in eastern Fram Strait, is the result of the tectonic rifting processes at the North American-Eurasian plate boundary and the initial water mass exchanges between the Nordic Seas and the Arctic Ocean. A revised chronostratigraphic framework with age control based on correlation to ODP Leg 151 holes, constrain the onset of the drift to at least 11 Ma. The drift deposits consist of fine-grained sediments and large quantities of methane stored as marine gas hydrates. The predominant source for the methane is, however, still debated. Potential gas sources may be a mix of biogenic, abiogenic, and thermogenic gas. For the latter, organic-rich Miocene deposits underlying the drift deposits, and leakage of gaseous hydrocarbons from deep-seated reservoirs are debated. The main objective of this study is to carry out a quantitative study on the controlling mechanisms of hydrocarbon migration from potential kitchen areas in the Fram Strait to the leakage points on the Vestnesa Ridge. The study includes the set-up and application of migration modeling techniques by applying the software package Migri to understand potential sources of hydrocarbons, timing of expulsion, and migration pathways towards the seabed. As a baseline for the study, depth converted seismic lines, fault interpretations, borehole data, and other available data are compiled along a 2D line from the central Fram Strait towards the Vestnesa Ridge at a lateral cell resolution of 100 m. Further input to this basin model comprises a siliciclastic lithology set-up at a high vertical resolution that is based on the log-data from ODP Hole 909C. The included Miocene source rock model accounts for lateral and vertical variations of the organic matter quality derived from ODP Hole 909. The results of this modelling study will be a set of gas migration and leakage scenarios that explain the present day gas leakage on the Vestnesa Ridge for either or likely combinations of the three potential gas sources debated and include the Cenozoic basin's history. Besides a best case basin model scenario, most likely (upper 10%) and least likely (lower 10%) estimates on model solution spectrum are derived. These estimates provide information on the sensitivity of the best case solution as they give insight on the range and span of feasible input parameters permitted to explain the present day gas leakage patterns in the study area.
Arctic Oil Spill Prevention and Response: Working Collaboratively to Improve and Extend Safe Practice
Authors: Winkler Mitchell , Jahre-Nilsen Catherine , Blaauw Robert , Dyve-Jones Richard
Published: March 2015

The oil and gas industry is committed to the protection of people and the environment. Prevention of incidents is of primary importance to meet safety and environmental goals, support global reputation, maintain shareholder confidence, and essential for maintaining a license to operate. Some characteristics of the Arctic operating environment require additional consideration compared to more established offshore regions; however, wherever the industry operates, safety of people and protection of the environment takes priority over all else in the business. The oil and gas industry believes it has the right tools to operate in many Arctic provinces today, but also recognizes the need for continuous focus to improve operating practice (e.g., safety and reliability) and to extend safe practice into more demanding operating conditions. A key success factor in driving this advancement is collaboration. This collaboration comes in the form of both industry working together, and industry working with regulators, private and public stakeholder groups. This paper focuses on advancement initiatives and efforts under the auspices of the International Association of Oil and Gas Producers (IOGP) and places them into the Arctic context. These initiatives include development of new technology, equipment, guidelines, standards, as well as knowledge sharing. The initiatives are aimed at both improving incident prevention and the robustness of response measures.
SAMCoT: Leveraging Cross Sector Collaboration to Drive Sustainable Energy Developments in the Arctic
Authors: Kuiper Guido , Løset Sveinung
Published: March 2015

SAMCoT is a centre for research-based innovation with long-term funding by the Research Council of Norway and the Energy Industry. In total 22 partners from half a dozen sectors are member of the centre which is a leading national and international centre for the development of robust technology needed by the Industry for sustainable exploration and exploitation of the Arctic region. SAMCoT, Sustainable Arctic Marine and Coastal Technology, started in 2011 and is tasked to meet the engineering challenges due to ice, permafrost and changing climate for the benefit of the energy sector and society. The Arctic research is split into 6 work packages (Data Collection and Process Modelling, Material Modelling, Fixed Structures in Ice, Floating Structures in Ice, Ice Management and Design Philosophy, and Coastal Technology).

This paper will specifically focus on how the Arctic Centre of Excellence is preparing and contributing to the sustainable industry development in the Arctic region. Research and development of new Arctic technology, the implementation of innovative methods in the oil and gas industry, collaborative way of working, and education of the next generation Arctic engineers are highlighted in the paper.
Advanced Baltic Icebreaker for Finnish Transport Agency
Authors: Kajosaari Markku
Published: March 2015

Arctech Helsinki Shipyard is building a new icebreaker for the Finnish Transport Agency. The vessel features the most advanced technology and has been designed especially for the demanding icebreaking operations in the Baltic Sea. The vessel will be delivered by the beginning of 2016 and it will be the first LNG fuelled icebreaker ever built.

The icebreaker will operate all year round to ensure safe seaborne transports in the Baltic Sea. The main purpose of the vessel is icebreaking and assisting of vessels in ice conditions, but it will also be able to perform oil spill response operations, emergency towing and rescue operations under demanding conditions at open sea.

The icebreaking capability of the vessel will be at least equivalent to the most powerful Baltic icebreakers currently in operation. The vessel will be able to move continuously through 1.6 meter thick level ice. In open water the service speed will be 16 knots.

The special hull form and propulsion arrangement have been designed to minimize the ice resistance and maximize the icebreaking capacity. The 21 MW power station consists of a combination of main engines with differing capacity, which enables optimization of the engine load in variable operation conditions. The three azimuthing propulsors will enhance the manoeuvrability and icebreaking performance of the vessel especially in heavy ridged and rafted ice.

The icebreaker will use both low sulphur diesel and LNG as its fuel, which diminishes its emissions and operation costs. The vessel will also fulfill the international IMO Tier III emission standards, when operating with LNG.

The vessel has been designed according to the zero emission principle, which means that no waste or polluting substance will be discharged in the sea. The double hull arrangement protects all the vital tanks on board.
Permafrost Foundations Thermally Stabilized Using Thermosyphons
Authors: Yarmak Edward
Published: March 2015

This paper presents a compendium of applications for thermosyphon type passive refrigeration devices for onshore facilities in the arctic. It's very seldom that thaw-stable permafrost or rock is available to found structures on and facilities need to be located on permafrost that is not thaw-stable. There is a long history of thaw subsidence and differential settlement when facilities on thaw unstable permafrost are not thermally stabilized.

Thermosyphons are the most widely used passive refrigeration devices and have been used since 1960 to provide thermal stability to foundations constructed on permafrost. In the arctic oil patch, thermosyphons have been used since the 1970’s with the largest single application being on the vertical support members for the Trans Alaska Pipeline that traverses Alaska. Early thermosyphon devices were installed vertically, and then in 1978, thermosyphons were first used for subgrade cooling beneath a structure with a slab-on-grade over ice-rich permafrost. In the 1980’s, thermosyphons were used to passively refrigerate the ground beneath heated tanks built on-grade negating the need for active refrigeration systems. In the 1990’s, the loop-type evaporator was developed for thermosyphons and the effective run of the evaporator beneath structures tripled. In the 2000’s, thermosyphons began to be used to solve problems around wellheads where hot oil was brought up through permafrost. Today, thermosyphons have a myriad of applications around the arctic oilfield and many of those are presented herein. Thermosyphons are not suited for all refrigeration applications in the arctic and some limitations are detailed.
Breakthrough in Arctic Shipping
Authors: Hgänninen S. , Heideman T.
Published: March 2015

Recently there have been delivered and designed new icebreakers, icebreaking shuttle tankers, container vessels and LNG carriers. Many of these vessel concepts are relying on podded propulsion system. Azipod propulsion has been selected to many of these vessels as it provides excellent ice performance for the vessel, good torque characteristics for the propeller and there already exists proven track record of ice operations.

Currently the demand for even bigger icebreaking vessels with higher capacity is increasing. Due to increasing market need ABB Marine have further developed Azipod propulsion concept to meet the demands of arctic ice classes and power requirements of more than 15 000 kW per thruster unit. This paper will give an overview of 25 year of development of azimuth podded propulsion, Azipod, for icebreaking vessels and introduce latest breakthrough projects in arctic shipping.
ACVs in the Arctic
Authors: Andrews Darren , Architect Naval , Cox Malcolm
Published: March 2015

Description of the Proposed Paper

To set out current advances in Air Cushion Vehicle (ACV) technology and planned future developments including the results of recent trials.

Application

The Arctic environment presents a number of challenges, the extreme cold, ice and weather conditions combine to create difficult operating conditions. Many of the logistical/Escape Evacuation and Rescue (EER), solutions proposed can provide an effective solution during certain times of the year, but struggle to provide year round cover; particularly in regions where significant ice ridging can be found. The ACV has the potential to fulfil these roles, carrying significantly higher payloads at lower cost, maintaining operability and a proven safety record when compared to helicopters, while providing a swifter response at reduced cost when compared to ice breakers in a number of ice and weather conditions. ACV designs have been documented as having a low impact on the surrounding environment and have a minimal below water acoustic signature providing a solution for crew change, routine and emergency resupply and EER.

ACVs do however have a lower operability envelope in heavy seas and can be affected by ice surface features such as rubble fields and ridges, and so one of the key risks to mitigate was ice ridge height. Initial studies confirmed that an ACV needed to be able to cross ridges up to 2.75m in height to effectively operate in the Alaskan region, and hence ridge crossing trials were proposed by Shell to develop a momentum balance equation to establish thrust requirements for ACVs to cross ridges of a specified height and full craft width.

Results, Observations, and Conclusions

The ridge crossing trials involved the use of the largest hovercraft in Griffon Hoverwork (GHL) range, a BHT 130, 30m in length capable of carrying 130 passengers with a unique ice ridge crossing skirt design. The ACV was monitored using a suite of sensors and was run over simulated ridges of different cross sections to test; friction coefficients, yaw angles, heights, and speeds. The conclusion was that it would be entirely feasible to develop an ACV capable of a controlled crossing of a 2.75m ice ridge whilst maintaining a safe approach speed. Shell is working closely with GHL on planning the next stages of technical development with a view to a future deployment of an ACV. Further developments revolve around a technology roadmap which has been outlined to examine the key technologies that could have a significant impact on ACV design, and explore how they can be supported and implemented.

Significance of Subject Matter

The ultimate aim is to produce a new breed of ACVs with variants encompassing routine resupply/passenger transport, heavy lift and EER that can provide an integral part of the logistical and EER solution for the Arctic whilst minimizing the environmental impacts of the work.
Challenges of Ice Model Tests on Moored DP Assisted Structures
Authors: Schröder Christian , Jorde Jørgen
Published: March 2015

The combination of decreasing ice volume and thickness in Arctic regions results in extended activities of the oil and gas companies in these areas. Actually installed offshore structures are mostly fixed or moored ones. Problematic for moored structures especially with a turret position leading to an indifferent encounter angle is the heading of the vessel regarding the ice drift direction. That is why the idea was raised to combine moored offshore structures (such as FPSO's) with a dynamic heading control system. By such a system the heading can be adjusted to the optimal encounter angle of either waves or ice. Thereby the resistances especially due to changes of the ice drift direction shall be significantly reduced. The advantage of this system in comparison to a completely DP controlled vessel is, that the ice loads are mainly taken by the passive mooring system which does not need any fuel and is able to handle with high resistances while only the heading is controlled by the active thrusters. In case thrusters are installed at the front of the vessel which faces the ice, they may help to protect the turret, mooring lines and risers by their wash from ice contact. Additionally the vessel may operate independently in case of an emergency release of the turret due to critical ice loads on the mooring system.

To investigate the benefits and challenges of moored and heading controlled vessel a new test set-up for ice model tests was developed at HSVA. The test set-up combines the already existing knowledge for moored structures with the recently developed DP system for model tests in ice. The DP system is a result of the recent research project DYPIC (www.dypic.eu) and is operating in a new designed mode which only controls the heading of the vessel. During testing the mooring system is simulated by lines leading from the turret to an underwater framework. The mooring characteristic (stiffness) is simulated by an individual combination of springs submerged and fixed on the framework. Above the water surface the model is tracked by an optical tracking system which is connected to the modified DP system. The optical tracking system and the submerged framework are fixed to the carriage. The ice drift is simulated by the movement of the towing carriage.

The paper will describe the test set-up possibilities for the new test method as well as the experiences with the first ice model tests. Especially the challenges according to the modified dynamic heading algorithm shall be discussed. Based on analysis of the ice model test results the future work on the algorithm with regard to full scale vessels will be pointed out.
Thermal Characterization of Potential Leaks in Offshore Pipelines
Authors: Siebenaler Shane , Iyer Mahesh , Kulkarni Mohan , Salmatanis Nikolaos
Published: March 2015

The operation of remote offshore pipelines, particularly those under seasonal ice cover, may need a means of detecting potential leaks at any point along the pipeline and at any time. Potential leak cases of interest are pinhole leaks out of the bottom of the pipe due to corrosion, weld or seam cracks, or damage due to third-party contact. Technologies are desired to provide leak detection coverage around the clock over long lengths of pipeline. One potential technology is distributed temperature sensing.

A key element of evaluating the applicability of leak detection systems is to characterize the behavior of leaks. It is important to understand how leaks behave when employing a technology that has only been previously used for other conditions. A joint-industry program was initiated to evaluate the thermal behavior of hypothetical underwater leaks. The environments studied range from shallow, Arctic applications to deep offshore installations. Analytical models were assessed to predict the jetting behavior of simulated leaks and their near-field thermal responses. These models were validated by means of laboratory experiments.

This information can be leveraged by a number of technologies, as the data are independent of the measurement mechanism. While the intention of this work is to evaluate distributed fiber-optic systems, the data on leak characteristics may also provide indications of applicability of other techniques for detecting potential underwater leaks. The data from this project will allow the industry to improve the understanding of potential leaks from underwater pipelines and, hence, lay the foundation for determining appropriate detection systems.
Update on Probabilistic Assessment of Multi-year Sea Ice Loads on Vertical-faced Structures
Authors: Thijssen Jan , Fuglem Mark , Muggeridge Karen , Morrison Tom , Spencer Paul
Published: March 2015

The Sea Ice Loads Software (SILS) is a Monte-Carlo type simulator developed by C-CORE for determining first and multiyear design sea ice loads, following the ISO 19906 methodology. Due to complexities in ice failure mechanics and associated uncertainties, these models are necessarily empirical or require simplifying assumptions. To account for uncertainty, conservatism must be built into models. A number of improvements to the software have recently been implemented in order to more realistically include a number of model components applicable to multi-year ridge loads and limit forces.

This paper provides an overview of new modules accounting for ridge breakout, driving force ramp-up and ridge geometry modeling. Sensitivity runs show that design loads are affected significantly by accounting for these processes, compared to the previous implementation of ISO 19906 in SILS.

The objective of this paper is to present the analytical model components and their implementation in SILS, and to demonstrate the influence of the changes by means of a scenario wherein a vertical sided structure encounters multi-year level ice and ridges.
Ice Based Construction of Offshore Arctic Pipelines
Authors: Cowin T.G. , Lanan G.A. , Young C.H. , Maguire D.H.
Published: March 2015

In the nearshore zone of the Alaskan Beaufort Sea, three subsea pipeline bundles have been successfully installed by using conventional onshore construction equipment in the winter season operating from a thickened sea ice platform. Differences in water depth, route length and corresponding pipeline design for BP Northstar, Pioneer Oooguruk and Eni Nikaitchuq impacted the winter construction procedures used for each project. Each of these projects used the winter construction season to its maximum advantage, allowing the use of conventional and adapted onshore construction equipment and techniques. Comparatively, ice based winter pipeline construction in subarctic conditions has been generally less successful. On-ice pipeline fabrication and installation into a subsea trench has a track record for shallow water pipeline installation with reduced permitting issues compared to summer installation. Based on the experiences of these projects, this paper reviews the limitations of on-ice construction, the typical construction activities; the main equipment used and will highlight the main lessons learned.
Extending Conventional Pipe-Soil Interaction Models to Include Bundle Effects for Arctic Subsea Pipeline Design
Authors: Georghiou Andreas E. , Davis Amy , Eskandari Farzad , Paulin Mike
Published: March 2015

As the demand for energy resources continues to grow, the oil and gas industry is looking north for the discovery and extraction of offshore hydrocarbon resources. The Arctic region has significant discovered and undiscovered hydrocarbon resources and is an important area for energy development. In these cold areas however, the integrity of offshore structures such as pipelines is at risk from various geohazards. Burial under the seabed is the common practice of protecting offshore pipelines and these pipelines are often installed as bundles for many reasons including economic considerations, short installation windows, and technical issues. A bundle configuration can decrease the cost of project by reducing the installation time to one season and they may have certain design advantages.

Bundles have been used in all of the developments utilizing subsea pipelines offshore the North Slope of Alaska. In this paper, the state of practice of analyzing buried pipelines using pipe-soil-interaction elements on individual pipelines is extended to account for the effects of the different pipelines in the bundle. By modeling the individual pipelines in the bundle as opposed to an equivalent pipeline, it is possible to have a more accurate load distribution in the system and define the pipe-soil interaction more realistically. In addition, the behavior of each pipeline can be examined separately in the bundle.

One common geohazard of Arctic and subarctic regions, permafrost thaw settlement, is introduced and its effects on pipeline bundles are studied through FE models and compared with methods used in past projects. When analyzing permafrost thaw settlementin the past, each pipeline was modelled separately. These assumptions could result in inaccuracies due to the pipe-pipe, and bundle-soil interactions which cannot be modelled on an individual pipe. The newly developed finite element models couple the individual pipe-soil interactions together with the pipe-pipe interactions and provide a more accurate assessment of the pipeline and bundle behavior, which in turn can reduce potential conservatism in designs.
Probabilistic Modelling of Marine Icing: an Estimation Method for Spray Water
Authors: Aalbers Albert B. , Poen Gerard J.
Published: March 2015

In view of the SALTO JIP (Safe Arctic Logistics, Transport & Operations) a pre-study started to develop a probabilistic model for icing due to spray water over the bow of a ship. The investigation has two stages: a probabilistic model for volumes of spray water (and the break-up in droplets) rising above the freeboard and,a probabilistic model for the ballistic and thermodynamic process of these droplets when falling and freezing to the ship.

The present paper concerns the first stage. The calculation model uses a novel combination of ship motions and wedge impact modelling, taking into account the above water hull shape and non-linear effects in the wave. For droplet break-up empirical spray nozzle modelling appeared useful to derive mean droplet diameters and size distribution.

The results from the calculation model seem realistic when comparing to the scarce validation data. Spray is normally no problem, so the subject has seen little interest. Also -due to scaling problems- model test results are hardly applicable and full scale measurements virtually impossible. The present modelling takes realistically into account the effect of sea state, bow shape, speed, freeboard and ship size, i.e. it reflects that marine spray is a threshold phenomena, with sharply increasing volumes if a given condition is exceeded.
Remote Health Care: A Game Changer for the Arctic
Authors: Berg J. , Toner S. , Stilz R. , Klein S. , Williams H. , Pearson J. , Fraser A. , Norman N.
Published: March 2015

Description of the Proposed Paper

Remote Health Care strategy (RHC) is an integrated approach, developed for delivery of health care in Arctic operations. It meets medical emergency response requirements and supports our principle "No harm to people". RHC includes aspects of: prevention; technology; supplies/equipment, competence and communication. It brings a virtual hospital to a patient, rather than taking a patient to a hospital. We will present outcomes of implementation in Greenland, Siberia and W-Africa. We will add to these experiences with comparative data analysis of global cases in expatriates, business travellers and Marine Operations where RHC was not in place. We will discuss how RHC could have impacted these outcomes and look prospectively at benefit in future Arctic operations.

Application

RHC is uniquely applicable in the Arctic but it is also applicable in any remote area of the world. In less geographically remote regions where the main restriction is lack of infrastructure, it can improve access to health by improving prevention, networking, decision support, access to external resources and education. It was designed to support operations but can be adapted and scaled to support community health and underpin strategic social investment. RHC is one model to move towards the recently articulated goal of the International Maritime Organization of delivering the same quality health care off shore as on shore.

Results, Observations, and Conclusions

We will demonstrate how one can improve health outcomes in the absence of local health infrastructure by employing RHC. We will show how our strategy is supported by a retrospective analysis of original data and vindicated by early experiences of deployment. We will demonstrate how RHC is supporting pilot projects in community health in a region with lack of access to health care. We will showcase results of an original review in our marine operations and how this supports a future RHC approach in our vessel fleet.

Significance of Subject Matter

The RHC strategy is a game changer for the industry, allowing it to operate safely despite lack of local health infrastructure, lack of rotary wing support and in harsh conditions where access to traditional modes of medical care is foresee ably not available. With highly-elliptical orbit satellite, sensor, near patient technology and streaming imaging rapidly improving, the real challenge lies in combining technology with enhancing capacity, competence, mind-set and behaviours of on-site medical practitioners, distant medical top side cover and even for recipients of care.
Mapping the Surficial Geology of the Arctic Ocean: A Layer for the IBCAO
Authors: Mosher D.C. , Courtney R.C. , Jakobsson M. , Gebhardt C. , Mayer L.
Published: March 2015

The purpose of this paper is to show early results of surficial geologic mapping of the Arctic Ocean. Analysis of subbottom profiler and multibeam bathymetric data in conjunction with the regional morphology rendered from the IBCAO data are used to map nine surficial geologic units in the Arctic Ocean. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of margin and basin types reflecting both the complex tectonic origins of the basin and its diverse sedimentation history. Broad and narrow shelves were subjected to a complex ice-margin history in the Quaternary, and bear the sediment types and morphological features as a result. Some shelf areas are heavily influenced by rivers. Extensive deep water ridges and plateaus are isolated from coastal input and have a long history of hemipelagic deposition. The flanks of the basins demonstrate complex sedimentation patterns resulting from mass failures and ice-margin outflow. The deep basins of the Arctic Ocean are filled with turbidites resulting from these mass-flows and are interbedded with hemiplegic deposits.
Simulations of the StationKeeping of Drillships Under Changing Direction of Ice Movement
Authors: Sayed Mohamed , Kubat Ivana , Watson David , Wright Brian , Gash Robert , Millan Jim
Published: March 2015

The ability of a drillship to maintain its heading to face oncoming pack ice is crucial under situations involving changes in pack ice drift direction. The performance of a vessel employing a Thruster-Assisted Mooring (TAM) system under such conditions is examined in this paper. Numerical simulations were used to determine the stresses and deformations within the moving pack ice cover, as well as the response of a drillship with characteristics similar to published information on Stena's DrillMAX. A turret mooring system is assumed to resist surge and sway direction offsets, but provides no restoring moment to vessel's yaw. In such system, thrusters would be used to provide damping and to apply the corrective moment that controls the heading of the vessel. The pack ice cover is assumed to consist of managed floes of sizes ranging from 30 m to 50 m, and with a uniform thickness of 1 m. The ice cover moves against the vessel at a steady velocity of 0.5 m/s. Simulations start with the vessel at a heading inclined to the oncoming ice direction. The simulations predict the evolution of the distributions of ice thickness and pressures, ice forces and moments, as well as the response of the vessel. Test cases examined a range of values of the initial heading of the vessel and limits on available yaw moment that can be generated by the thrusters. The results illustrate the manner in which the vessel can correct its heading, and give the corresponding offsets, ice forces and moments.
Simulation of Physical Ice Management Operations Including Trajectory, Power and Manoeuvrability Estimation
Authors: Hisette Q. , Reimer N.
Published: March 2015

The present paper describes a simulation tool for physical ice management operations. Resistance in level ice or in floes and manoeuvrability in ice are estimated thanks to semi-empirical methods and validated through comparison with model test data. From a target floe size, trajectory of management vessel is calculated in order to protect a structure against drifting ice according to linear, sector and circular management techniques. The tool produces visualization of the operations, with indication of the requested power level and distributions of the resulting floe size.
Preventing Thaw Settlement of Oil Pipelines Buried In Permafrost
Authors: Ali Muhammad A.
Published: March 2015

Buried pipelines in permafrost may undergo thaw settlement over a period of time. It depends on the type of soil. The innovative technology outlined in this paper solves the problem of thaw settlement of buried pipelines. With this technology expensive soil exploration will not be needed. Using a very thin walled secondary pipe in between two separate layers of insulations will effectively divert any heat escaping through the first layer of insulation in a direction away from the permafrost.
Tubular Integrity: Analytical Approach and Modeling of Optimum Performance Envelope in Presence of Gas Hydrates
Authors: Anand Kumar Dinkar , Samuel Robello
Published: March 2015

Gas hydrates are crystalline compounds that occur under appropriate pressure-temperature conditions when water forms a cage-like structure around a smaller guest molecule. The guest molecule can be methane, ethane, nitrogen, carbon dioxide etc. Gas hydrates are found in natural environments such as sea bottoms, under permafrost areas etc. Gas hydrate prospects on earth are the biggest unlocked recourses of energy in the world. The estimated amount of organic carbon in the form of gas hydrate in earth is 10000 giga tones which is equal to 100,000 to about 300,000,000 trillion cubic feet of gas reserves [4, 5]. Over the years several countries have started research programs aimed at discovery and production of gas from offshore gas hydrate deposits. Deep drilling, operation of oil and gas wells, and operation of oil and gas pipelines in the deep sea are vastly complicated by the presence of natural gas hydrates. The necessary requirements for formation of gas hydrates are; presence of water or ice, suitable sized gas/liquid molecule and suitable pressure-temperature conditions. Temperature and pressure condition is a function of gas/liquid and water compositions. Gas hydrate formation in the production tubing can cause severe safety problems. Pressure and thermal stimulation, inhibitor injection and a combination of these methods can be used in gas recovery from gas hydrates.

Scope of this paper is to analyze effects on tubular integrity due to pressure and thermal simulation in recovering gas from the gas hydrate bearing formation. The vertical well is producing through the production tubing and production liner is the final casing in the wellbore. Increasing the system temperature (temperature stimulation - steam injection from an offset well to gas hydrate bearing reservoir [14]) and reduction of system pressure (depressurization) helps in preventing gas hydrate formation in production tubing. This is attributed to shifting of phase equilibrium away from formation of gas hydrates. System pressure and temperature induces tri-axial stresses (hoop stress, radial stress and buckling stress) in production tubing. The von Mises Criterion, also known as the maximum distortion energy criterion, is used to estimate the yield of production tubing. von Mises stress is further compared with the yield strength of the tubing off set by the factor of safety. The factor of safety gives the safe margin for operation avoiding the tubular failure. This paper is aimed to analytically study the effects of system temperature and pressure on mechanical strength of the production tubing inside production liner. This paper also proposes performance envelope of system temperature and pressure which enables gas production avoiding gas hydrate formation ensuring tubular integrity. In this paper maximum system temperature and pressure is also established beyond which production tubing will yield.
Improving Ice Pressure Forecasting for Operational Purposes
Authors: Eriksson Patrick B. , Lensu Mikko , Haapala Jari , Lehtiranta Jonni
Published: March 2015

Compressive ice is considered to be amongst the worst operating conditions when navigating in ice and demanding for icebreaker assistance. Compression is a manifestation of ice cover stresses and a phenomenon physically different from convergence. Indeed, severe compression is often experienced in an inert ice cover and is reduced by the onset on convergence. This paper presents investigations to reach better understanding of processes generating ice compression by analyzing model forecasting methods and direct field observations.

Producing relevant information on compressive conditions to shipping and ice management by enhancing numerical ice forecast modelling. Products comprise specific areal characterization, pressure along channels or routes and in the vicinity of critical areas.

Predictability of compression in sea ice by numerical modelling encounters considerable challenges. Local stresses can be forecasted from deterministic model results, but these do not easily capture the rapidly fluctuating nature of the stress propagation. This has been concluded through extensive in-situ stress measurements, drift buoy measurements and ship observations and comparisons to numerical sea ice model results.

To be able to serve shipping in ice with sensible information, study results support an ensemble forecasting approach and provide probabilistic ice pressure products. The ensemble averaged mean compression fields in such a forecast appears reliable and is easily adoptable by the end users. This kind of a forecasting approach is completely new and has (to authors' knowledge) not been carried out for this purpose before. Systematic studies of compression, involving the whole chain from ice cover dynamics to the ship experiences, have been lacking.

Ice pressure has in some applications been claimed to be obtained from satellite image analysis. One should be cautious with such interpretations, since even if there is an obvious coupling between converging (or compacting) ice and pressure, they represent different physical phenomena. This has also been noted in the most recent updates of WMO definitions of ice features, making a distinction between these two features.

A comprehensive approach has been made to forecast ice pressure, an issue which until now seems to have been avoided by the ice modelling community due to its complex nature. Inclusion of compression in real-time operative ice forecasts in an adaptable form substantially improves decision making.
Probabilistic Seismic Hazard Analysis of an LNG Storage Facility in Warm Permafrost
Authors: Thornley John D.
Published: March 2015

In conjunction with the development of a LNG storage tank facility in Fairbanks, Alaska a geotechnical investigation and probabilistic seismic hazard analysis (PSHA) was performed. The site is located within a region in Fairbanks where warm permafrost soils exist (-1°C average soil temperature at depth). In support of the PSHA, field work included vertical shear wave velocity profiling using surface to down hole measurements and multichannel analysis of shear wave velocity (MASW) geophysical techniques. Shear wave velocity measurements suggested that the site be classified as a Seismic Site Class B to C, despite the fact that the soil temperature was just below freezing. A discussion of the PSHA, Fairbanks seismicity is provided. However, because very few shear wave velocity profiles have been developed in warm permafrost, the discussion of the results and how they compare to other studies in Fairbanks shows the unique nature of seismic site response evaluations in warm permafrost regions. LNG facilities are increasing in presence in the Arctic as natural gas is extracted and taken to market. Regions with high seismicity and permafrost soils will have to consider the effects of frozen soils on these facilities during seismic events. This study offers an understanding of those effects and provides insight into site-specific effects of permafrost on a probabilistic seismic hazard analysis.
Gigabytes, Terabytes, a LOT of Bytes? What to Do with Six Years of Chukchi Sea Environmental Studies Data
Authors: Cowee Christie , Eick Cindy
Published: March 2015

The Chukchi Sea Environmental Studies Program (CSESP) started 2008, beginning directly after Lease Sale 193 (MMS, 2008). A joint effort between ConocoPhillips and Shell, including Statoil from 2010-2013, the program offers a multidisciplinary, multiyear approach to understanding the Arctic ecosystems of the northeastern Chukchi Sea though environmental baseline data collection in support of oil and gas exploration and permitting.

Seven years of program data amounts to terabytes of zeroes and ones in many scientific disciplines. This paper focuses on the organization, storage, and distribution methods used for CSESP data, with an emphasis on metadata creation and preparation for public release.

Data organization begins on vessels with strict, standardized data capture methodologies and continues with well-defined longer-term data storage processes on shore. Scientific observations, final results, vessel instrument data, weather data, acoustic sound files, and photos are all part of the CSESP data universe. Documentation and metadata are crucial to keeping that universe intact and accessible, now and years down the road.

In 2011, CSESP sponsors signed a data sharing agreement with the US National Oceanic and Atmospheric Administration (NOAA). All datasets are submitted to NOAA for public archiving and access via the internet. The CSESP data were already well organized and documented, but public data sharing required a new level of effort to consolidate information from final reports, individual documents, and existing metadata into comprehensive metadata complying with the US Federal Geographic Data Committee (FGDC) standard (FGDC, 1998).
Aerosol processing and CCN formation of an intense Saharan dust plume during the EUCAARI 2008 campaign
Authors: Bègue N. , Tulet P. , Pelon J. , Aouizerats B. , Berger A. , Schwarzenboeck A.
Published: March 2015

Abstract. Atmospheric processing and CCN formation of Saharan dust is illustrated through the analysis of a case of dust transport over northern Europe. This spread of dust is investigated by combining satellite, airborne and ground-based observations and the non-hydrostatic meso-scale model Meso-NH. The altitude of the dust plume during its transport to northwestern Europe was assessed using the CALIPSO observations and our model results. The major dust plume was transported toward Mediterranean and European regions between 2 and 5 km above sea level (a.s.l.). This is confirmed by an average particle depolarization ratio equal to 30%. Due to transport, this layer split into two layers over northern Europe, and we analyzed in this paper possible mixing of the European pollution aerosol with dust particles in the lower layer. The simulations have shown that the lower dust layer has interacted with the anthropogenic aerosol mainly over Belgium and the Netherlands. The analyses of numerical simulation results show that mineral dust particles accumulated soluble material through internal mixing over the Netherlands. The value of the CCN0.2 / CN ratio obtained over the Netherlands (~ 70%) is much greater than those observed over the Saharan region. In addition over the Netherlands, the CCN measurement reached 14 000 particles cm−3 at 0.63% supersaturation level on 30 May. Our model results reveal that more than 70% of the CCN concentration observed on 30 May can be explained by the presence of Saharan aged dust. The study reveals that heterogeneous reactions with inorganic salts converted this Saharan mineral dust into compounds that were sufficiently soluble to impact hygroscopic growth and cloud droplet activation over the Netherlands.
Porosity and permeability development in compacting chalks during flooding of nonequilibrium brines: Insights from long‐term experiment
Authors: Nermoen Anders , Korsnes Reidar I. , Hiorth Aksel , Madland Merete V.
Published: March 2015

We report the complete chemical alteration of a Liège outcrop chalk core resulting from a 1072 flow‐through experiment performed during mechanical compaction at 130°C. Chemical rock‐fluid interactions alter the volumetric strain, porosity, and permeability in a nontrivial way. The porosity reduced only from 41.32% to 40.14%, even though the plug compacted more than 25%. We present a novel analysis of the experimental data, which demonstrates that the geochemical alteration does not conserve the volume of the solids, and therefore, the strain is partitioned additively into a pore volume and solid volume component. At stresses beyond yield, the observed deformation can be explained by grain reorganization reducing the pore space between grains and solid volume changes from the rock‐fluid interactions. The mechanical and chemical effects are discussed in relation to the observed permeability development.
Water mass pathways to the North Atlantic oxygen minimum zone
Authors: Peña‐Izquierdo Jesús , van Sebille Erik , Pelegrí Josep L. , Sprintall Janet , Mason Evan , Llanillo Pedro J. , Machín Francisco
Published: April 2015

The water mass pathways to the North Atlantic Oxygen Minimum Zone (naOMZ) are traditionally sketched within the cyclonic tropical circulation via the poleward branching from the eastward flowing jets that lie south of 10°N. However, our water mass analysis of historic hydrographic observations together with numerical Lagrangian experiments consistently reveal that the potential density level of σθ = 26.8 kg m−3 (σ26.8, approximately 300 m depth) separates two distinct regimes of circulation within the Central Water (CW) stratum of the naOMZ. In the upper CW (above σ26.8), and in agreement with previous studies, the supply of water mainly comes from the south with a predominant contribution of South Atlantic CW. In the lower CW (below σ26.8), where minimal oxygen content is found, the tropical pathway is instead drastically weakened in favor of a subtropical pathway. More than two thirds of the total water supply to this lower layer takes place north of 10°N, mainly via an eastward flow at 14°N and northern recirculations from the northern subtropical gyre. The existence of these northern jets explains the greater contribution of North Atlantic CW observed in the lower CW, making up to 50% of the water mass at the naOMZ core. The equatorward transfer of mass from the well‐ventilated northern subtropical gyre emerges as an essential part of the ventilation of the naOMZ.
Exploration of turbulent heat fluxes and wind stress curl in WRF and ERA‐Interim during wintertime mesoscale wind events around southeastern Greenland
Authors: DuVivier Alice K. , Cassano John J.
Published: March 2015

The strong, mesoscale tip jets and barrier winds that occur off the coast of southeastern Greenland drive large surface turbulent heat fluxes that may impact deep ocean convection. The turbulent fluxes and wind stress curl associated with 10 m wind patterns identified using the self‐organizing map technique are investigated for 10 winters (1997–2007, November‐December‐January‐February‐March) in the European Centre for Medium‐Range Weather Forecasts Interim Reanalysis (ERA‐I) and a regional simulation using the Weather Research and Forecasting (WRF) model at 50 km. Sensible heat flux differences between WRF and ERA‐I are primarily due to differences in near‐surface temperature, while latent heat flux differences are driven by both moisture and wind speed differences. The largest turbulent flux differences occur over the marginal ice zone where the fluxes in WRF are larger than in ERA‐I due to specified sea ice thickness that influences the near‐surface atmospheric temperature and moisture; WRF has larger magnitude wind stress curl over the Irminger Sea. Patterns of strong westerly tip jet with barrier flow are most likely to impact preconditioning and convection in the Irminger Sea compared to other manifestations of westerly tip jets, and easterly tip jets are expected to have localized ocean impacts south of Cape Farewell.
Temperature and melt fraction distributions in a mantle wedge determined from the electrical conductivity structure: Application to one nonvolcanic and two volcanic regions in the Kyushu subduction zone, Japan
Authors: Hata Maki , Uyeshima Makoto
Published: March 2015

We propose a new method for estimating the temperatures and melt fractions of the upper mantle. Our method is based on connecting the electrical conductivity structure from geophysical observations with laboratory‐determined relationships between the electrical conductivity and temperature of four nominally anhydrous minerals (olivine, orthopyroxene, clinopyroxene, and garnet) and basaltic melt. The temperatures are expressed as the upper limit temperatures using the Hashin‐Shtrikman lower bound in solid phases and using the Hashin‐Shtrikman upper bound in solid‐liquid mixed phases. We apply the method to a nonvolcanic and two volcanic regions in the Kyushu subduction zone, southwest Japan. Our results suggest that the temperatures of the upper mantle are 1100–1450°C for dry mantle and 900–1350°C for wet mantle and that the melt fractions of the upper mantle are <20% beneath the two volcanic regions and <5% beneath the nonvolcanic region for both dry and wet mantle.