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Q&A: Shell Oil weighs options for Arctic production platform

Alex DeMarban

Some opponents of oil and gas drilling in the Beaufort and Chukchi seas say the Arctic's merciless conditions will guarantee a blowout if Shell Oil ever gets the chance to drill. Shifting ice, strong currents, brutal cold and ice ridges as tall as three-story buildings will be no match for modern engineering, they say.

Shell sees things differently.

Brian Miller, the oil company's project development manager for Alaska, describes below how a production platform would work, if the company is allowed to conduct exploratory drilling and then develop producing wells.

The platform would use "brute-force" engineering, including a stadium-sized base on the seafloor, a large single leg, perhaps steel, that's strong enough to resist ice, and a facility high above the water to avoid those deadly ridges.

The Arctic Sounder: Could you tell me about the oil platform? Is it cutting edge?

Brian Miller: In some respects, it is cutting edge. In other respects, it is just a case of brute-force engineering.

Shell has studied platforms in this area since the early '80s, so to a certain extent there's nothing really new here, and in fact, we have several people on our team who worked on Shell development opportunities in the early '80s and we've got drawings of platforms that were designed back then that honestly look fairly similar to what we're talking about now.

But no one has done it in an area quite like the Alaska Arctic. You mentioned Hibernia (oil platform off eastern Canada). Their main concern is icebergs. We don't have icebergs. But we do have a very cold environment with ice and you can have first-year ice, new ice that year that can pile up into rubble piles and also create these underwater keels of ice that would hit against the platform. That's a little different than what you'd have at Sakhalin (an oil platform off Russian coast), though they do have first-year ice too.

But we also have multi-year ice and that tends to be stronger ice because the salt has migrated out of it and it's a stronger, freshwater crystal, so that is really our main design, is for a large piece of multiyear ice hitting the platform.

The platforms we're looking at, it's probably steel. We can also look at concrete too, but steel has its advantages. And that is really kind of a practical extension of the gravel island that Shell and others have used in the Beaufort Sea in shallower water. The problem is when you get out into the 100 feet of water that we have in most of our areas, in the Beaufort or even 150 feet of water or more in the Chukchi, building a gravel island is impracticable, because you need so much gravel and it becomes so big. And the gravel islands have issues from wear of the ice cutting against the island itself, so there's maintenance issues. So I like to look at these as steel islands. They're just a structure that basically resists the ice forces, which are extremely large, resists those by its own mass and then the foundation that it has connecting it to the seafloor.

AS: So it is attached to the seafloor?

It is sitting on it, but what we do is we look at the strength of the soil and we look at the loading from the ice, and it's just like any other structure, whether it's a dam or a building, or a bridge. It's pretty much just down to structural engineering. ... As that ice force hits against the structure, that puts a lateral force that the foundation needs to resist.

So the foundation, we can have these things we call skirts, which are typically plates that extend below the structure and go into the soil, and that allows us to engage stronger layers of soil, although in general we have really good strong soil in the Beaufort and its even stronger in the Chukchi.

We have taken geotechnical samples. We have a database of all the (soil) samples that have been collected in the Arctic, and we have collected ourselves some fairly shallow samples around some of our development areas. So it's helped us understand what kind of soil strength to expect. So we have a pretty good idea now, between the ice forces and the soil strength and how the ice breaks against the structure, between all those we have a pretty good idea of what we need to do.

We've been studying this for 30 years. I hear people say we're rushing into this, but to us it just doesn't feel like we're rushing after 30 years.

We've also taken different structural geometries, sometimes they are shaped like a cone, so that makes the ice get bent up and break ... under its own weight. We've also looked at structures that are vertical walls. They just have vertical walls and the ice is crushed against the structure. Those structures have different performances. We're not at a point to pick which kind of method, but we've studied both of them.

AS: What's new about this (type of platform)?

I would say the fact that we have multiyear ice there and the long winter season, which really means a short open water season, so we need to make sure we bring a completed structure up there, so all of our construction needs to be completed somewhere else as much as possible. We don't want people working up there in winter if we can avoid it.

But from the environmental aspect, it's really the fact that we have multiyear ice in the Beaufort. In the Chuckchi, not so much, there's a much smaller chance of having any multiyear ice.

So some of the things we're doing now to understand that better, there's a whole range of methods of collecting data. For example, we're putting buoys on the ice in the winter that are tracked by satellite and we're able to see how the ice is moving. Sometimes (the ice will) stay in one place for weeks on end and then it might move fairly long distances, maybe 50 miles in three days, so that helps us understand how the ice moves.

We have used devices like a sophisticated piece of equipment called an upward looking sonar, basically a sonar system set near the sea floor - it's buoyant and floats up a little bit - and it looks up through water and it sees the ice, so it can tell us how thick the ice is and how fast it is moving and how high the waves area. And we have done ice overflights, to understand where we are seeing multiyear ice. There are people with 20 to 30 years of experience in the Arctic and they go on these flights and help us identify where they see this multiyear ice. And we do see less of it these days than what we saw in the 80s.

AS: (Information about the) current and trajectory of water and ice, that's one thing USGS calls a gap (in what drilling decision-makers know about the Arctic). Is this what you're talking about?

It could be. For right now, most of that data is internal to Shell, so we probably haven't done the best job of getting it communicated out there. ... But I know one of our goals of setting up the Science Advisory Panel (in an agreement with the North Slope Borough) is to get this stuff out to others. And we do use local traditional knowledge. When we go out on the helicopters to place the buoys, we always take local Natives who help us understand how the ice looks, where are there good places to land, and we have procedures to make sure we have thick enough ice to land on. So we have included a lot of people in that process, whether people on the planning committee, or whether it's the North Slope Borough or Richard Glenn (with ASRC). But I think we probably haven't done a good job at putting that out, and one of the reason is Shell spent a lot of money gathering (that information) and like other companies, we're certainly not one to give it away. But we are working with the scientists on the North Slope to bring all that together.

AS: So the diagram I'm looking at makes it look like the platform would have the ability to move up and down to avoid the ice. I was thinking it had some kind of ability to move up and down to avoid two- and three-story ice ridges.

No, in fact, the more passive we can make our systems up there, the more reliable they are. The platform is a fixed structure. It does have a certain height above the sea level and it can be quite high.

We have done model tests of these platforms in tanks, particularly in Finland. They do a lot of Arctic testing. They make scale-ice. Alaska Natives say it's not the same (kind of ice), but in a scale world it behaves similarly to what the ice does, so we take the platform and we freeze up the surface, spread this ice on it and create this simulated ice. This is how they create ice breakers and ships and things like that, and they push the structure to it which is kind of the same thing as the ice moving against the platform and they're able to study how the ice breaks into forms.

But the height of the deck ... it's the same way we designed platforms in the Gulf of Mexico or anywhere else in the world we have waves. We can have waves 75 feet tall and we have to make sure the deck of the platform stays out of the waves. So we're used to designing decks that are a long ways out of the water. In this case ice is even less forgiving than waves, so we really do not want the ice to ever come in contact with the deck above. So we would put it high and it could be in the range of 50 to 100 feet above the water's surface.

We're still deciding what this needs to be. Some of it depends if we're crushing ice and the ice doesn't rise as high. Or if we're lifting it up with a cone-shaped structure the ice comes up higher.

AS: Are the legs of the platform like a four-legged stool?

So you said you (reviewed some of the platforms) in Sakhalin. Those tended to have four legs that went down through the ice. But that's first year ice, and it's not very thick. Here we have a much more severe condition with the multiyear ice, so we don't feel four independent legs is good. This thing is like a large mono-leg structure, so it's all one big leg.

These structures can be quite large. The base of the structure can be something on the order of 300 or 400 feet or more in diameter, so I kind of envision this thing being a little like a small football stadium or a big basketball arena.

The base of it can be 300 or 400 or more feet, so you have a tremendous amount of surface area. You can have these plate skirts that can be extending, it could be 5 feet deep, or if we really needed it, it could go as deep as 20 feet into the soil

The structure itself weighs at least 100,000 tons. ... We fill those structures with ballast, so we could have, just in the bottom of structure, something on the order of 10 feet of concrete to create weight and we would add water to it because one of the critical design events is it needs to float and needs to be stable, so we can tow it from wherever we built it, up through the Bering Strait and around to its location. So it's no small task to have something that has to resist the ice and be able to float in another condition to get to its location.

AS: So that's what the hollow leg would allow and you fill it with ballast?

Yes, you have some ballast in their anyway to give it stability, it could be concrete, or sometimes we used material like an iron material they use in cruise ships and we use in some of our floating structures. But this is so big we can put whatever we want in it. Concrete is pretty inexpensive so can put a lot of that in it. So when we get it to location, we'd open up valves, and allow it to submerge and sit on the bottom, add that point we can add lots of water to preload it, and make sure we have weight on the bottom. So the total amt of weight on the bottom ends up being a lot. So one of the things we hear people say is, 'You can't be serious. You think you can put something out there and think it will survive?'

But we've worked on this design for about 30 years. It's been accepted by industry, the MMS (now BOEMRE) has identified it and used it in their environmental impacts as one of the leading possibilities. If we see something better, we might pick it. But at this point, we think (what we have) is very good, and our opinion has not changed over the last 30 years.

AS: How much would it cost?

It's a multibillion dollar (project), much like our other development options. People say, 'How do we know you won't put these all over the place up there?'

Well that's why. They're just too expensive and the ability to do directional drilling, that's improved a lot over the years. These are expensive structures and if you say I just want one well, you still need a really big thing, so you might as well try to really consolidate and concentrate your facilities. You don't want to be moving people around, so it's a lot better for us to put a limited number of structures there.

This story is posted with permission from Alaska Newspapers Inc., which publishes six weekly community newspapers, a statewide shopper, a statewide magazine and slate of special publications that supplement its products year-round.