The Chukchi Edges project was designed to establish the relationship betweenthe Chukchi Shelf and Borderland and indirectly test theories of opening forthe Canada Basin. During this cruise, ~5300 km of 2D multi-channel seismicprofiles and other geophysical measurements (swath bathymetry, gravity,magnetics, sonobuoy refraction seismic) were collected from the RV Marcus G.Langseth across the transition between the Chukchi Shelf and ChukchiBorderland.
These profiles reveal extended basins separated by faulted high-standingblocks. Basin stratigraphy can be subdivided on the basis of gross stratalgeometry, reflection terminations and inferred unconformities. The wedge-shapedsynrift sequences terminate against the basement highs and/or major faults,burying the basement topography. The inferred postrift seismic units are morenearly tabular, but thicken locally due to compaction of underlying synriftsediments.
Reflection character is dominated by alternating high and low amplitudecontinuous reflectors which may be consistent with pelagic or turbiditesediments. Chaotic units are also observed, which may indicate mass-flowdeposits. The truncated sediments over the basement highs of the Chukchi Shelf,Chukchi Plateau and Northwind Ridge suggest major erosion due both to glacialplanation and earlier erosional events perhaps associated with basement upliftprior to or during rifting and extension.
It is believed that the bulk of the synrift sediments are Mesozoic in age.Certainly Cenozoic sediments are also preserved in these basins, but theposition of the boundary is uncertain. Locally, continuous reflectors areobserved underlying the rift basin fill. These older units, of very uncertainage, would, if sampled, provide constraint on the history and affinities of theChukchi Borderland.
In addition to the extensional basins, a number of small symmetric basinsare observed on the flanks of the Chukchi Plateau. These basins may betranstensional and argue for a 2nd phase of tectonism, which overprinted theobvious extensional fabric of the Borderland. This is supported by theobservation of uplifted postrift sediments on the flanks of some of theintermedial basement highs. Understanding the timing, distribution and extentof these two phases of tectonism, relative to the known history of N-Sextension on the Chukchi shelf and the apparent orthogonal extension observedon the Beaufort Shelf will further constrain the unknown history of the CanadaBasin.
Offshore exploration and production operations in sea ice conditions mustface the challenges of working in frontier environments. In the context of thecorresponding regulatory environment, operators will be expected to show thatnew technical and operational challenges have been addressed. Emergencyresponse in sea ice conditions is a case in point. In the event that marineevacuation of an installation is necessary, the lifeboat will have to becapable of being launched safely into ice, propelling itself away from thehazard area to some safe distance, and then affording a haven until personnelcan be recovered.
Some ideas are presented in this paper for improving the capabilities oflifeboats and for meeting the expectations embodied in regulations. The designand operational elements contemplated here are broadly based on model scaleexperiments and full-scale trials with conventional TEMPSC lifeboats that havebeen done over the course of a multi-year test program. Design considerationsinclude powering and propulsion, maneuvering, structural resistance to iceloads, and arrangement of the coxswain's cockpit (visibility). Operationalconsiderations include the coxswain's tactics in ice, simulator training forcoxswains, and ice management of evacuation routes. Finally, the use oftraining simulators for evaluating and demonstrating the efficacy of these andother improvements is discussed.
A program of model scale experiments and full-scale field trials has beenunderway for a period of several years to investigate the performancecapabilities and limitations of evacuation craft in sea ice. This paper focuseson a series of field trials with a small, conventional totally enclosed motorpropelled survival craft (TEMPSC). The lifeboat was tested in pack iceconditions in an ice channel cut in landfast ice on a freshwater lake. Thechannel was about 55m long and 32m wide and the ice was between 300mm and 400mmthick (with an average measured thickness of 340mm). The ice that was cut outof the level ice sheet to make the channel was further cut into floes of twobasic sizes, the smaller about 1.65m×2m and the larger about 3.2×2m. Thesecorresponded to floes that were about 30% and 50% the mass of the lifeboatitself. The ice concentration in the channel was controlled by removing some ofthe ice floes from the channel. Several ice channel transit tests werecompleted, starting with a pack concentration of 9/10ths. At the end of thetests in those conditions, more ice was removed from the channel until thegross concentration was 8/10ths and another set of transit trials was done.This process was repeated for consecutive concentrations of 7/10ths, 6/10ths,5/10ths, and 4/10ths. The same procedure was used in model scale tests reportedby the same authors (Simões Ré & Veitch 2003, Simões Ré et al. 2006).Indeed, the field tests replicated the model scale experiment conditions to theextent practicable. The field trials were done over a five-day period in March2010.
The paper provides information on a unique vehicle, the amphibiousHoverbarge which can be used for transporting heavy cargo, modules and drillingrigs over Arctic terrain, such as snow, ice and tundra. The paper draws uponexperience of Hoverbarge operations in Alaska back in the 1970s along withrecent technical developments of the Hoverbarge to make it more suitable forArctic operations, including skirt ice protection and selfpropulsion.
The paper also highlights important environmental advantages the Hoverbargecan bring, hovering cargo and equipment above the tundra whilst only exerting1psi ground pressure. In addition the paper explains how the Hoverbarge canmeet current demands to extend operating seasons and transport heavy loads suchas pre fabricated modules without building new infrastructure.
Results, Observations and Conclusions
The paper also focuses on the potential of transporting cargo during summermonths when winter roads are not in use and the subsequent advantages that thisbrings.
Significance of Subject Matter
Although first developed over 35 years ago, the Hoverbarge remainsrelatively unknown to current day engineers. This paper seeks to increaseawareness of this technology which may solve a number of current logisticalissues.
Subsea structures on the seabed may be impacted by free-floating or scouringicebergs. A drift-based Monte Carlo iceberg contact model was developed as partof the SIRAM (Subsea Ice Risk Assessment and Mitigation) program forcalculating iceberg impact risk for subsea structures on the northeast GrandBanks offshore Newfoundland and the Makkovik Bank on the Labrador Shelf. Themotivation for developing this model was to characterize the influence ofbathymetry (i.e., seabed orientation, ridges and basins) on iceberg interactionrates with subsea structures. Results were incorporated into a GIS-basedapplication to allow iceberg contact rates to be calculated for structures witha range of plan dimensions and elevations at various locations.
Offshore pipelines are a viable option for the safe transport ofhydrocarbons in the Arctic. For continued safe and cost efficient operation, itis important to ensure integrity as well as minimize field inspection andintervention. This can be achieved through an optimized Inspection andMaintenance (IM) program. Determining the required frequency of IM, in a costefficient manner is critical for ensuring integrity and optimizing inspectionand maintenance costs without compromising safety. For piggable lines, smartpigs are used for In-Line Inspection (ILI). A conservative approach (small IMintervals) can be costly, increases the human / Remotely Operated Vehicle (ROV)exposure and yield little new information. A strategy with too little IM canlead to unexpected failures, as too little information is acquired on thecondition of the pipeline. An optimal IM strategy based on the condition ofpipeline is developed in this paper.
In this paper, major Arctic offshore pipeline integrity challenges areevaluated. Considering these challenges, a Risk Based Integrity Modeling (RBIM)framework has been proposed. Design challenges from the effects of ice gouging,strudel scour, frost heave, permafrost thaw settlement, and upheaval bucklingcan be mitigated through proper trenching and burial, as well as conditionmonitoring during operation. The major integrity challenges during operationmay arise from the progressive structural deterioration processes and changesin the right-of-way seabed conditions. The structural deterioration processeswill include time-dependent processes such as corrosion, cracking, andpermafrost thaw settlement. Non-time dependent (random) processes, such asthird party damage, ice gouging, strudel scour, and upheaval buckling will poseadditional risk during operation, but are not addressed in this paper. Theseeffects can be partially addressed through ILI and periodic seabed surveyinspections.
The risk to an Arctic offshore pipeline will be evaluated with respect tothe deterioration processes. The risk is estimated as a combination of theprobability of failure and its consequences. The probability of failure isestimated using the Bayesian analysis. Modeling the structural degradationprocesses using Bayesian analysis is not a new concept; however, modelingdegradation processes using non-conjugate pairs is a new technique that isdiscussed in this paper. Bayesian analysis is based on the estimation of prior,likelihood, and posterior probabilities. Field ILI data is used in theanalysis. The posterior models possess better predictive capabilities of futurefailures. The consequences are estimated in terms of the cost of failure andthe planned IM program. Cost of failure includes the cost of lost product, costof shutdown, cost of spill cleanup, cost of environmental damage and liability.Cost of IM includes the cost to access the pipeline, gauge defects, and carryout inspection and necessary minimal maintenance. Implementation of theproposed RBIM will improve pipeline integrity, increase safety, reducepotential shutdowns, and reduce operational costs.
A Joint Industry Project (JIP) was conducted in 2007 to determine the degreeof consensus of leading ice mechanics experts on the loads exerted bymulti-year ice on offshore platforms. Seven international experts on multi-yearice loads were asked to predict loads for three different ice loading scenariosinvolving multi-year ice floes: isolated floe, a multi-year floe in pack ice,and a multi-year hummock field in a sheet of first-year ice. The Experts wereasked to calculate the loads from these three ice conditions interacting with a150 m wide vertical caisson structure and a 45 degree conical-shapedstructure. There were significant differences in the methodologies usedand the assumptions made to estimate the loads. Load predictions variedconsiderably for each scenario with estimates differing by a factor of 4.6 forthe vertical caisson and 3.5 for the conical structure. In spite of the lowerratio of predicted loads for the conical structure, the Experts were moreconfident with loads on the vertical caisson. The key areas for furtherresearch were identified and these include improved knowledge of the icethickness and its variation for Old Ice, new and innovative techniques forobtaining ice loads, improved knowledge of pack ice driving forces, and betterunderstanding of the failure behavior of multi-year ice. This paper provides anoverview of the loading scenarios, details of the load predictions, andoutlines the areas identified for future research to help to provide morereliable load predictions.
We present numerical results arising from a parameterization of wave-iceinteractions in a two-dimensional ice-ocean model of the Fram Strait (HYCOM:HYbrid Coordinate Ocean Model). The model takes wave predictions/hindcasts fromthe WAM wave model and these waves are advected into the ice, breaking it asthey go. They in turn are attenuated by the ice using the model of Bennetts andSquire (2012). We use a truncated power law for the floe size distribution,following the observations of Toyota et al. (2011). The maximum floe size isdetermined by the dominant wavelength in the ice field. The maximum valueincreases with distance from the ice edge as shorter waves are attenuated morestrongly than long ones. At some distance from the ice edge, breaking is nolonger able to occur, and this marks the end of the Marginal Ice Zone(MIZ).
Consequently, we now have a model that predicts the expected floe size andwave intensity at any point in the ice, something that current wave models areunable to do at present, and which is a notable weakness. Recognizing that acombination of large waves and ice can be extremely hazardous, Arctic operatorswho need to know both wave and ice conditions in ice-infested areas will usethe model as a forecasting tool when it is fully operational.
Subsea tiebacks are becomingincreasingly prevalent in oil and gas field developments. As the accessibilityof the production from wellheads becomes more difficult, the need for subseacompression and pumping increases. Compression and pumping require significantpower which can be distributed and controlled from a HVSS (High-Voltage SubseaSubstation). The viability of an Arctic field development will be determined bythe reliability of all elements in the tieback and in particular, thecentralized subsea power distribution system.
The Pipeline Ice Risk Assessment & Mitigation JIP (PIRAM) developed aset of engineering models and design procedures for implementation intoindustry best practices for risk mitigation and protection of pipelineinfrastructure from ice keel loading. The models established the pipelinemechanical behaviour in response to ice keel load events, and assessedengineering concepts for protection and risk mitigation strategies. Improvedmethodologies for contact frequency and ice keel loads determination formedpart of the integrated model.
Pipeline protection against ice gouging is overviewed. A review of subgougeresponse and physical model tests provided a basis for refinement of threedimensional continuum finite element analyses of steady state gouging includingthe implementation of an effective stress based soil plasticity constitutiveroutine. A fully coupled ice, seabed and pipeline interaction model is used tocalibrate a simpler pipeline design approach for design purposes. Thestructural model, improved by considering 3D interaction effects, comparesstrains within the pipeline to those from continuum analyses and from physicalmodel tests. The PIRAM pipeline model provides the engine for the probabilisticassessment of pipeline cover depth using a GIS-based decision-support-systemfor route planning.
As more attention is paid to the exploration of oil and gas resources in thehigh north, the settlement of the disputed area between Norway and Russia, andthe world's ever-rising demand for energy resources, more and more oilcompanies and suppliers are moving north. For most oil companies, rig and shipoperators and logistics providers, the Arctic represents a new frontier, whereexisting operational systems and technologies are tested to their limits. Thispaper outlines key challenges facing the development of sustainable and safemaritime offshore operation in Arctic waters. The Arctic offers challengesrelated to harsh weather conditions, long distances from bases, limited orabsent infrastructure, a sensitive ecosystem, ensuring safety at sea, potentialoil spills and operations in ice-infested waters. Arctic operations are thussignificantly different from operations in the North Sea. This state of affairsunderlines the need for new or improved organisational and business models forintegrated logistics operations, value chain management and technologicalsolutions that will ensure sustainable and safe maritime operations. It alsodemands optimised design of ships and structures for operation in the Arcticenvironment as well as improved communication infrastructure based onsatellite, terrestrial, ship-to-ship or ad-hoc systems, radar and opticalsatellites. Key features discussed will include ideas and concepts forarea-specific vessel design and multipurpose vessels, with integrated supportand logistics models and systems, base-to-base operation and tailored businessmodels for robust Arctic field operation. The aim is to ensure a holistic andintegrated transport and logistics infrastructure in sparsely populated areaswith extreme weather conditions (polar lows, darkness, fog, ice and icing),including the interplay between vessel technology and the operationalmanagement.