Arctic conditions challenge offshore projects
Arctic conditions challenge offshore projects
Mike Paulin - INTECSEA Canada
EDITOR’s NOTE: This is the first in a series about the unique challenges encountered when attempting to design, engineer, construct, and operate offshore oil and gas facilities in the Arctic.
Arctic conditions challenge the engineering of hydrocarbon production facilities and force companies that pursue offshore oil and gas resources in cold regions to face unique risks, requirements, and challenges.
The arctic environment is sensitive to disruption, on one hand, but harsh and unforgiving on the other. Environmental impacts take longer to heal and cost more to remediate. However, stakeholders have learned how to work in and avoid damage to the Arctic, a core capability that both protects the environment and contributes to the success of Arctic oil and gas projects.
Field work in the Arctic must move in rhythm with the seasons at each step of the development process – from evaluation, planning, and engineering, to construction and installation. Workers must endure months-long stretches of darkness during arctic winters and constant daylight in the summertime.
Offshore producers accept these challenges because of the region’s high petroleum resource potential. A large portion of remaining global oil and gas resources is thought to exist in the arctic latitudes of Russia, Norway, Greenland, Canada, and the United States.
However, data and interpretation related to the reserve potential, distribution and recoverability of arctic hydrocarbon resources is limited. Academic, governmental, and petroleum industry entities of many nations are doing multi-year research to produce comprehensive, reliable estimates of undiscovered arctic hydrocarbon resources. Until some of these studies conclude, and results can be studied and confirmed, petroleum resources across the entirety of the Arctic, for the most part, remain a question.
The remoteness of arctic areas with petroleum potential compounds the challenges. Arctic oil and gas projects occur in some of the most sparsely populated places on Earth; as such, there is often a lack of infrastructure. Moving equipment to arctic sites and then supporting drilling, construction, offshore installation, and, ultimately, facility operations presents complex and formidable logistical challenges.
All these challenges, when taken together – as they must be – increase the importance of an integrated approach to designing, engineering, installing, and operating offshore projects in the Arctic.
Arctic conditions
The arctic climate varies, but sub-freezing temperatures dominate. Extreme cold creates a number of environmental, ice, and ice-related conditions that are uniquely challenging.
Some parts of the Arctic are relatively ice-free, or are covered by ice in winter and ice-free in parts of the spring and summer. Although secondary in most cases, the arctic wave environment must be considered and, because the ice environment changes, so do the wave conditions. Larger expanses of open water for longer durations may result in a more significant design wave condition.
Many scientists believe that arctic conditions are in transition, and that the amount of ice found in the Arctic over the life of a facility must be considered. Photo courtesy Sakhalin-1 Project.
There are different types of ice to consider in the design and operation of facilities. Spray ice, as the name suggests, forms when freezing water is sprayed onto the superstructure of a ship or the topsides of a facility. In addition to being a safety concern, this also can affect operations. Sea ice forms when the sea freezes. This can be over five feet thick. Sea ice, driven by wind and currents, tends to pile up, creating pressure ridges which extend both above and below the surface of the water. These pressure ridges theoretically can extend more than 150 ft (46 m) below the water line.
If ice survives in the Arctic for more than one season, it is referred to as multi-year ice. Because of changes in properties over several seasons, it can be significantly stronger than ice that forms and melts in one season.
Icebergs are large chunks of ice that break off glaciers and can drift hundreds of miles. Icebergs that reach the Grand Banks of Newfoundland average between 100,000 and 200,000 metric tons (110,231 and 220,462 tons), while large icebergs in the area might potentially ground in over 300 ft of water.
All these types of ice are a threat to oil and gas developments.
Ice scouring or gouging of the seafloor is a near-shore feature for most northern continents. A pipeline or any other equipment on the seafloor may not be able to withstand loadings from direct contact with ice. Typically, these facilities must be buried in a trench or excavation sufficiently beneath the reach of the ice to prevent direct contact or minimize loading from forces transmitted through the soil.
Permafrost also can be a consideration. Infrastructure must tolerate potential settlement due to the thawing of permafrost where present; or designs must incorporate a means to prevent permafrost from thawing. Understanding the properties of permafrost and how it will behave when thawed is important. Permafrost must be sampled and laboratory tests run to determine thawing characteristics.
Many scientists believe that arctic conditions are in transition, and that the amount of ice found in the Arctic is declining as the region slowly warms. These prospects must be considered in the design conditions where facilities may be designed for 20 or more years.
Arctic engineering challenges
Feasibility studies and front-end engineering are paramount to determining the viability of any proposed arctic development. Information on environmental design conditions, installation equipment capability and availability, and environmental considerations is required to assess the technical and economic feasibility of proposed projects.
Data collection can be a challenge and can be quite different than the process normally followed for more temperate climates. It may take more time and money to collect necessary design data. For phenomenon like ice gouging, where a limited number of data points may be collected in a single year, it may take several years to acquire the data necessary to design offshore facilities for arctic conditions. In addition, the number of vessels that can work in environments that might have ice incursions anytime of the year is limited. Finally, weather or ice conditions in any season may hamper or prevent data collection.
Planning a grass roots oil and gas field development in the Arctic requires analyzing and finding solutions for a large number of problems that are magnified by the conditions. In many cases, innovative solutions must be devised and implemented.
Platforms, whether fixed or floating, must either withstand the appropriate design forces or move out of the way. Fixed structures may have to withstand local and global ice loads from first year ice, multi-year ice, and icebergs, depending on the ice environment. A floating structure and its mooring systems may be designed to withstand a certain magnitude of ice load, but may need to be disconnected and moved in the face of a major ice feature. With both types of facilities, foundation conditions are a key element of the design.
Unique pipeline and subsea design aspects for the Arctic include analysis of the potential effects of environmental loadings associated with the environment – such as permafrost thaw settlement and ice gouging. In these extreme loading cases, limit state or strain-based design can be used which might allow the pipeline to bend into the plastic range of its material properties, while not allowing for any loss of integrity of the pressure containment capability of the pipeline.
The development of an overall arctic offshore development project from concept selection through design, construction, installation, and the commencement of operations requires an appropriate level of arctic experience associated with a number of technological components including, but not limited to, platforms, topsides, pipelines, risers, subsea equipment, and marine transportation. Experience also is needed on how these systems interface with each other, particularly in an arctic environment. A knowledge of, and respect for, the arctic environment and the interactions of the unique arctic forces at play is critical for successful field developments in the region.
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