The Paper will discuss lessons learned from more than 10 years of operational weather and ice support in the Arctic, and show examples of best practice methods of implementing scientific research into operational decision making. Successful examples will be discussed detailing the use of weather and ice information in operational situations at high latitudes, from climatic prestudies to the operational phases and all the way through post-operational lessons learned.
The Arctic is the frontier area to securing energy supplies for the future. Finding oil and gas in the Arctic and subarctic regions is in itself challenging. Extracting the hydrocarbons in a safe and economical way, is considered possibly even more challenging due to extreme low temperatures, ice conditions, remoteness and a sensitive natural environment. The paper is based on ongoing development of a subsea separation and storage system for application in deepwater arctic. The paper describes solutions on how deepwater subsea separation of hydrocarbons and storage of oil can be achieved in hostile environments enabling close to continuous production also when surface production facilities has to abandon location. Overall arctic field development suggestions are presented based on the solutions.
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.
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.
In Arctic regions, permafrost and gas hydrate bearing sediments below the seabed present a technical problem for drilling operations. The first and most important challenge is to be able to control the well if pressured gas is encountered in or below such formations, and the second problem is the stability of the borehole if these sediments begin thawing during drilling. Both these issues are strongly dependent on the choice of mud - and mud-weight. In the present paper we outline a methodology that can aid mud and mud-weight choices during Arctic drilling. It involves using a numerical borehole stability code, which calculates safe mud-weight windows by applying time-dependent physico-chemo-thermo rock mechanical models. It takes as input available information on the subsurface that is to be drilled, and if field data is not available it can be given input from scientific literature or from correlation analyses in a large database of laboratory test results on North Sea core samples.
As a part of the process of adapting the numerical borehole stability code to Arctic environments, several simulations were done using Arctic well parameters from literature as input. These are presented in this paper, and they reveal that the mechanical and petrophysical properties of gas hydrate bearing sediments make them difficult to drill - even without taking thawing or thermal/gas induced changes in mud rheology into account. Our analyses indicate that similar drilling problems as those encountered when drilling in shales are likely to be met also when drilling through clay/silt based permafrost and gas hydrate sediments. Even if our simulations do not include the tricky sediment thawing during drilling - the impact of this process on borehole stability is discussed. It is concluded that with more detailed input on the Arctic subsurface, the presented methodology has the potential to predict safe mud-weight windows for drilling through permafrost and gas hydrate bearing sediments - and it can thereby contribute to safer and more cost-efficient exploitation of Arctic petroleum resources.
Numerical modelling of ice growth, melt and transport on regional scales such as coastal seas, estuaries, rivers or lakes can provide crucial input for safe and efficient designs and installations of marine infrastructure in arctic, sub-arctic or mid-latitude regions. The modelling of ice and related complex physical processes on these regional scales is however still rather unexplored.
The complexity of ice modelling on local and regional scales is best illustrated in areas where ice-covered sea water is mixed with fresh river water and a thermal discharge from for instance a refinery or power plant. Such a situation exists in the Svartbackfjarden, an estuary some 35 km to the east of Helsinki, Finland. Two minor rivers discharge into this estuary. The estuary freezes during the winter with ice thicknesses typically in the range of 20 to 50 cm. In this estuary an oil refinery takes in cooling water at a depth of about 15 m. The heated water is discharged at the surface and results in melting of the sea ice in the vicinity of the outfall. However, given the fresh water from the rivers in the early spring, and the fact that the salinity of the intake water is higher than the surface water, the discharged cooling water has been observed to flow under the relatively cold fresh layer just under the ice. Due to mixing of the plume with the surrounding water, the temperature of the fresh water layer increases, leading to melting of the ice at some distance from the plant's outfall.
This paper presents a case study with Delft3D, which is a flexible integrated numerical modelling programme that enables simulation of 3-dimensional flow, sediment transport, morphology, waves, spills, water quality and ecology, in combination with a recently developed ice module. The 3-dimensional modelling with Delft3D of the thermal discharge from the oil refinery in the ice-covered Svartbackfjarden estuary is presented and compared to local observations of currents, water temperature, salinity and ice thickness. The case study will show the capability of Delft3D to cover all the relevant physical processes that determine the temporal and spatial characteristics of the ice and the thermal discharge, under influence of fresh river discharges, hydrodynamic, meteorological and atmospheric forcing.
These capabilities will contribute to the further development of integrated ice modelling on regional scales, eventually benefiting the sustainability, efficiency and safety of the designs of marine structures in ice-covered waters.
Frost heave is a common phenomenon in the Arctic, where soil absorbs moisture and expands in the direction of heat loss due to ice lens growth upon freezing. It also occurs if a refrigerated structure is buried in unfrozen frost heave-susceptible soil, and thus, special considerations are required when designing chilled or LNG pipelines.
The current study focuses on the numerical modeling of frost heave of a chilled gas pipeline based on the framework of the porosity rate function. New developments to the porosity rate function are proposed to extend its application to simulate transient temperature boundary conditions under thawing scenarios. The extended functionality allows the model to simulate soil freezing and corresponding heave, as well as soil thawing and corresponding settlement for multi-year temperature cycles.
This paper first presents a cyclic frost heave numerical model validated by long-term full scale field measurement available in the literature. Then, correction factors of key parameters involved in the frost heave process, such as temperature gradient, in-situ stress, and soil porosity are introduced. Finally, recommendations to mitigate the potential hazard of cyclic frost heave and corresponding pipeline strains are presented, providing guidelines for new pipeline developments in the Arctic region.
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.
The Hoop area in the Barents Sea (Norway) is a frontier province with limited well control. It was initially regarded as a gas-dominant hydrocarbon province, but explorationists are viewing the area with new interest after the successful Wisting oil discovery. Despite this success, the area is considered high-risk due to inefficient sealing, and the apparent absence of high-quality reservoir sands. This paper demonstrates how the integration of 3D seismic and 3D controlled source electromagnetic (CSEM) data can help de-risk these uncertainties and generate new play models. The study suggests that such an integration can be avaluable workflow component for the 23rd application round in the area, and for drill-drop licence decisions.
Studies have suggested that the Arctic contains over 30% of the world's untapped natural gas reserves, and approximately 13% of its undiscovered oil reserves. The Beaufort shelf in the Canadian Arctic has been of interest for Oil and Gas development for many decades and reached a peak in the Mid 1980's when over 50 drilling islands were built to explore potential reserves by various international oil companies, with 92 wells recorded in the Canadian Beaufort Sea area.
The Amauligak field was discovered in the Canadian Beaufort in 1984, and is still the largest oil and gas discovery in the Mackenzie Delta or Beaufort Sea areas. Amauligak lies approximately 75 kilometres northwest of Tuktoyaktuk in 30 metres water depth in the Beaufort Sea. The field is thought to contain 235 million barrels of oil and 1.3 trillion cubic feet of natural gas.
Whilst vast resources such as Amauligak are known to exist in the Canadian Beaufort, the key to development of these remote areas is finding a viable export route for oil and natural gas. This was clearly the case for the development of the Prudhoe Bay Area of the Alaskan Arctic with the development of the Trans Alaskan Pipeline in the 1970's following the discovery of oil on Alaska's North Slope in 1968. This facilitated the development of the North Slope and shallow water offshore fields such as North Star which peaked in 1988 at about 738 million barrels per annum, about 25% of total U.S. production.
Unlike the offshore shallow water Prudhoe Bay Developments, the development of the Beaufort shelf and slope will bring with it significant remoteness and geohazard issues as well as the familiar ice challenges. This paper highlights some of the geohazard issues facing Canadian Beaufort developments and considers what options exist for the safe and economical export of the product to market.
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.