Arctic drillers face no shortage of underwater risks
Five geo-technical hazards that could trip up northern exploration
Photo courtesy National Geographic
The Beaufort Sea is arguably the last remaining untouched petroleum frontier in Canada. Much of the debate about whether the National Energy Board should reopen the icy waters to exploration has revolved around existing policies that compel companies to drill a same-season relief well as a safeguard in the event of a blowout.
Arctic hopefuls including Conoco-Phillips Canada, Imperial Oil Ltd., Chevron Corp and Shell Canada Ltd. say the measure is unnecessary. Plugging a rogue well “can be achieved faster through the application of a capping system versus the drilling of a relief well,” said Mike Peacock, exploration manager with Imperial, addressing a September 2011 roundtable meeting in Inuvik.
Other considerations are less technical. In fact, a summary compiled by the Geological Survey of Canada and submitted to the federal regulator as part of the recently completed Arctic offshore drilling review details a host of natural hazards in the Beaufort region – some better understood than others – with which oil explorers must contend.
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Ice ScourLong, linear gouges in the seafloor carry the risk of potentially fouling subsea pipeline infrastructure. A national database maintained by the Geological Survey contains more than 17,000 known scours – most occurring in water depths of five to 30 meters – that average 28 meters across and range in depth from five to 0.55 meters. |
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Submarine SlidesOtherwise known as underwater landslides, slope failure can pose a serious challenge for engineers keen to safeguard drilling systems and subsea pipelines. Mapping to date indicates there are both stable and unstable regions on the 50,000-square-kilometer Beaufort continental shelf. Surveys are under way to gather more data about the slides’ distribution and severity. |
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Subsea Shallow GasCircular pockmarks on the sea floor commonly vent gas. Regional geophysical surveys conducted to date show shallow gas is present in localized deposits in sediments from the seabed to depths greater than 500 meters. If over-pressured, the deposits can lead to well-bore instability during drilling. |
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Subsea PermafrostDrillers must also watch for ice in subsea sediment. Heat generated by drilling activity or the production of high-temperature hydrocarbons could melt the ice and potentially destabilize sediments that support the well-bore. |
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OverpressureArctic explorers must also be wary of piercing abnormal high-pressure zones in the Beaufort-Mackenzie basin. In the western Beaufort region, analyses show evidence of deep gas migrating up toward the seabed, a potential problem for drillers if the upward momentum exceeds hydrostatic pressure maintained by drill “mud.” |
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