Design Considerations for Coastal Projects in Cold Regions

With the oil industry's continued quest for oil and gas in frontier offshore locations, several developments have taken place in regions characterized by seasonal ice cover including the US Beaufort, North Caspian, and Sakhalin Island. In these projects, pipeline transportation systems have been used, which are a cost effective, safe and reliable mode of hydrocarbon transport to shore. Ice gouging is one of the key design issues that affect engineering considerations with respect to strain based design, target burial depth requirements, cost, and safety.It is generally accepted that offshore pipelines in ice environments will need to be trenched and backfilled for protection. Burial depths can be greater than those that might normally be required for pipelines in temperate climates. Burial depth requirements will be a function of the design ice gouge depth (to prevent interaction between the ice and pipe) and an acceptable level of subgouge deformation beneath a gouging ice keel (which potentially strains the pipeline). There still exists uncertainty on the magnitude and extent of subgouge soil deformations due to ice gouging and the importance of sediment transport mechanisms for biasing gouge statistics.Other challenges that must be considered include strudel and hydrodrnamic scour, thaw settlement and frost heave, and upheaval buckling. These considerations may also influence burial depth requirements.

Section: Strudel Scour and Hydrodynamic Scourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Arctic Offshore Pipeline Design and Installation Challenges

Paulin

2013

“…Further descriptions of coastal engineering issues in the Alaskan Arctic have been previously presented (Leidersdorf, et al, 1996;1990;1982).…”

Section: Figure 2 Man-made Islands In the Alaskan Beaufort Seamentioning

confidence: 99%

The History of Artificial Islands for Oil Exploration and Development in the Alaskan Artic

Gadd¹,

Leidersdorf²,

Hearon³

et al. 2012

Self Cite

Eighteen artificial (man-made) islands have been constructed in the Alaskan Beaufort Sea to support oil exploration and production. The first islands, constructed in the late 1970s, were in shallow nearshore waters where wave and ice conditions are relatively benign. By the early 1980s, island construction had ventured to more exposed sites with water depths approaching 15 m. Innovative slope protection systems and construction methods were developed to address the remote Arctic locations, short construction seasons, scarce local resources, and the challenging, yet poorly defined, offshore wave and ice climate. This paper provides an overview of the history of island development in the Alaskan Arctic and discusses design evolution, construction, and performance.

“…In the absence of long-term measurements in the Alaskan Beaufort Sea, it was necessary to develop design water level and wave conditions using a numerical hindcast approach (Leidersdorf, et al, 1996). Boundary conditions for site-specific surge and wave models were derived from a synoptic hindcast study prepared as a Joint Industry Project known as "BORE" ("Beaufort Sea Response Extremes"; Oceanweather, 2005).…”

Section: Oceanographic Design Conditionsmentioning

confidence: 99%

Coastal Engineering Design of the Oooguruk Project

Leidersdorf¹,

Gadd²,

Hearon³

et al. 2008

Self Cite

This paper focuses on the coastal engineering aspects of the Oooguruk Project, which represents the third offshore production facility to be created in the Alaskan Beaufort Sea. The primary components of the project include a man-made island ("Offshore Drillsite") constructed during the first nine months of 2006 in a water depth of approximately 4.5 ft, and a 5.7-mile subsea flowline bundle installed between the Offshore Drillsite and the mainland shore during the following winter. Due primarily to its location in shallow water, the Oooguruk Project is exposed to less severe wave and ice conditions than the two offshore production facilities constructed previously in the Alaskan Beaufort Sea. Nevertheless, significant design challenges were presented by the financial constraints imposed by smaller field economics, and by the project's location in an active river delta subject to vigorous strudel scouring. The 4-cy gravel bag armor selected for use on the Offshore Drillsite represents a cost-effective means of protecting the side slopes against wave and ice attack, based on the experience acquired at previous exploration and production sites in the Alaskan Beaufort Sea as well as the island's performance during its first year in existence. The long-term rate of bluff recession at the site of the Oooguruk flowline shore crossing, 3.3 ft/yr, reflects two distinctly different oceanographic regimes: periods dominated by easterly storms, when erosion is modest or negligible due to reduced water levels during storm events, and periods dominated by westerly storms, when elevated water levels promote rapid erosion by permitting storm waves to impact the bluff face. The data acquired over the past three years indicate that ice gouging of the seabed is of negligible importance in the Oooguruk project area. Conversely, strudel scouring is widespread and sufficiently energetic to expose the flowline bundle. Of particular concern are man-made slots or holes in the winter ice sheet created to facilitate installation or maintenance of the flowline, in that they may promote preferential scouring on the flowline route.