Exploring The Geology Of Gulf Oil
Exploring The Geology Of Gulf Oil
How much oil is under the Gulf of Mexico and how did it get there? Columbia University geophysicist Roger Anderson, an expert in deepwater exploration and drilling, explains how the oil formed millions of years ago, and how companies go about finding and extracting it.
IRA FLATOW, host:
Up next, the geology of Gulf oil. Maybe you said, I've heard everything there is about this Gulf oil gusher. Well, you haven't listened to our take on it. So we're going to take - do a SCIENCE FRIDAY take on it and do the science angle.
It's been estimated that up to 65,000 barrels of oil a day spew into the Gulf waters from the broken Deepwater Horizon well before it was capped. But that's really just a drop in the old barrel of oil, that's the oil that lies beneath the seafloor there. Scientists say that the deep and ultra-deepwater parts of the Gulf may contain as many as 42 billion -billion - barrels of oil, of crude oil.
How do they know? How did all that oil get there? How much of it leaks? Is stuff leaking out naturally out of the seafloor in the Gulf? And with all the thousands of oil wells drilled there, could there - could we be weakening the seabed there? Could it be cracking? Could it be leaking? When we have the cap on the Gulf - on the wellhead now, could it be forcing oil out somewhere else?
Well, those are some of the questions you've been asking us and we're going to talk about oil geology with Roger Anderson. He's the Con Edison senior scholar at the Center for Computational Learning Systems and the School of Engineering and Applied Sciences - Science at Columbia University. Thanks for talking with us today.
Dr. ROGER ANDERSON (Con Edison Senior Scholar, Columbia University): Oh, it's a pleasure. Thank you.
FLATOW: Why is there so much oil in the Gulf? What's the structure down there?
Dr. ANDERSON: Well, it happens to be a lucky place where dead organisms get washed out by the Mississippi River and buried before they can oxidize or burn up or decay. And that's what - that's the major requirement for making oil long into the future.
FLATOW: Talking about oil this hour on SCIENCE FRIDAY from NPR with Dr. Roger Anderson. And where does the oil come from? You say dead microorganisms that are buried and before they decay, they turn into oil? What happens there?
Dr. ANDERSON: Yes. The - ordinarily, an organism dies and it is oxidized. It decays and it loses the organic energy that it had. So oil is undecayed dead things.
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FLATOW: That's as lay terminology as we can get. We appreciate that. And how many wells are drilled into the Gulf?
Dr. ANDERSON: How many wells?
FLATOW: How many wells are sitting? How much pipe - pipage is underground there?
Dr. ANDERSON: There's a lot. There's been drilling since 1954 offshore in Louisiana and Texas. And there's easily thousands of them. And every year, we go deeper and into higher pressure.
FLATOW: And as we go deeper and higher pressure, we're capping off some of those wells that are no longer used.
Dr. ANDERSON: Yes. There are many of them that have depleted their reservoirs and are sealed with cement caps and are abandoned.
FLATOW: And how often do we go down there to maintain them or look at them to see if the seals are still working?
Dr. ANDERSON: Not very often, but there are a whole suite of scientists, particularly at Louisiana State and Texas A&M, that study the natural oil seeps down there, and they would come upon the manmade ones pretty quickly if they happened. The - one of the major ways of finding oil offshore is for - by looking for natural oil seeps.
FLATOW: You mean the just black crude stuff bubbling off the seabed?
Dr. ANDERSON: Yes. It comes - the thing to understand about oil is it's very, very buoyant and so it wants to get to the surface. And geologically, it - the half life - it has a half life we talk about that's similar to radioactivity. It takes at average about 25 million years for it to make it to the surface. So it's not true that oil from a billion years ago is still existing. Even if it's in a billion-year-old rock, it usually is passing through on its way to the surface.
FLATOW: Mm-hmm. And so that's one way you find oil is to just watch for it to come out naturally.
Dr. ANDERSON: Yes. And you can see that by satellite. Satellites track the oil seeps as they come up to become natural slicks on the sea surface, but nowhere near the scale of this massive BP blowout, of course.
FLATOW: The fact that the pressure is rising - it's approaching 7,000 pounds per square inch in that cap in BP's well, is that a good thing?
Dr. ANDERSON: Absolutely good. Dropping pressure is bad. That means something is leaking. And increasing pressure is good. That means that the seal is holding. As long as the pressure continues to increase, that's a good sign.
FLATOW: That doesn't mean that the oil is going to seep out some other place if it gets locked in in that spot.
Dr. ANDERSON: Well, you got to - it's a problem of filling the half-full Coke bottle while you're drinking it. So if there's more oil seeping into the reservoir because of permeability restrictions than is seeping out, then you get a pressure increase. So think down at the bottom of the well, there's this massive reservoir and it's much like a sponge or a cinder block rather than a big, giant cavern. And the permeability structure, the porosity of the holes in the rock - think of sandstones again...
Dr. ANDERSON: ...depends on how fast it can flow. It looks like the blowout itself happening over three months has depleted a significant amount of the reservoir pressure. And that's why it began at 6,700 pounds per square inch instead of the expected 9,000. It was at 9,000 at the beginning of the blowout, but that pressure was depleted by a very large hole in the top of the straw that's drawing it out of the reservoir. That straw has been capped with a cork, essentially, and the pressure is now responding and building back up again.
FLATOW: All right. We're going to take a short break and come back and talk lots more with Roger Anderson. Our number, 1-800-989-8255, if you'd like to talk about the Gulf oil geology. So stay with us. We'll be right back after this short break.
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FLATOW: You're listening to SCIENCE FRIDAY from NPR. I'm Ira Flatow.
We're talking this hour about the geology of the Gulf there, where the oil has been - the oil gusher, the BP gusher has been capped. It's not leaking oil as far as we can tell. And we're talking with Roger Anderson, who is from Columbia University School of Engineering and Applied Science. 1-800-989-8255.
I'm fascinated to hear, Dr. Anderson, about watching oil just seeping out of the seabed. How do you know if you go next to, let's say, an old capped well that if you see seepage is not coming out of the well, it's coming out of the natural seepage?
Dr. ANDERSON: Well, that's very easy to tell, actually, because biological communities build up over the natural seeps over the hundreds of years that it seeps out. And these natural seeps are often the origins of coral reefs.
Dr. ANDERSON: It's excellent food. The problem, if too much of it comes out at once, is that it sucks all the oxygen out of the water column and that can be bad. But in its natural form, it's very fertile ground and you find lots of organisms, from bacterial mats all the way up to worms and the kinds of exotic animals that you perhaps have seen from the mid-ocean ridges as well.
FLATOW: Hmm. Let's go to Malcolm(ph) in Grants Pass, Oregon. Hi, Malcolm.
MALCOLM (Caller): Well, good morning, Ira. I always look forward to hearing your program every Friday. I love it. It's really interesting.
FLATOW: Thank you.
MALCOLM: My question has to do with why it's taking so long for this oil to stabilize in pressure. And I've worked with water systems, pressure tanks, pressure systems and pump design, water system designs, and I realize this is like really penny-ante stuff compared to this huge thing they're dealing with there. But I'm just amazed that it would take this long to come up and stabilize.
Dr. ANDERSON: Well, it's probably been significantly depleted by the blowout. This was a huge blowout. If you think about the history of blowouts, Spindletop from 1901 was about 100,000 barrels a day, and this one is probably up in the 50-, 60,000 barrel a day range. That's a lot of fluid to come out of a well reservoir. And it has to be replaced by either other oil or by the water that's in the pore spaces.
And so, that's a function of the permeability of the sandstone reservoir. And what you're seeing is how fast it's being replaced. There's a possibility, though not likely, that it won't be recharged and that they've actually lost all of that reservoir.
MALCOLM: Okay. So the fluid coming in through somewhat porous reservoirs adjacent. That makes a lot of sense. Thank you.
FLATOW: All right. Thanks for calling.
MALCOLM: Appreciate it.
FLATOW: Thanks, Malcolm. 1-800-989-8255. A tweet from Iknownot(ph) says, is there any way to retrieve genetic information, preserved DNA from the ancient crude oil?
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Dr. ANDERSON: That's a good question. And, unfortunately not, because it has undergone all kinds of chemical reactions. It goes through what's called the kerogen stage where the organisms get turned into a blob of black organic mass. And that evolves over time into, first, oil and then natural gas as it's cooked basically in a pressure cooker. That's the rock that it's trapped in. It also migrates and moves, and so it has no resemblance whatsoever to the organic organisms that it started with. It ends up purely as a chemical formula.
FLATOW: Mm-hmm. A question from one of our Facebook members says, I'd be interested to have your guest comment on the nature of the crude oil being produced from the BP well. From what I've read, it appears to be a heavy crude. However, the news reports have described the oil as easy to skim.
Dr. ANDERSON: Yeah, it's got a high gas-to-oil ratio. All the oil coming out of oil reservoirs has some natural gas in it. And that changes its ability to move around. This has a high gas-to-oil ratio and so it's very volatile. It's not heavy tar oil like the - like in - from Venezuela. It's not - if you had it in a jug, it would look like a black prune juice-like substance rather than a Karo syrup.
FLATOW: Hmm. And another tweet comes in. Let's - from - Rudy Schwartz(ph) says, how much methane is down there? How does it affect global warming with natural leaks? Is it being collected? And there are a couple of tweets about - is there - could a huge methane explosion result from...
Dr. ANDERSON: Yeah, yeah. That's a very interesting question from a climate standpoint because the natural gas, as you might guess, has an easier time escaping from these reservoirs than the oil. The oil is sticky and...
Dr. ANDERSON: ...liquid. And the natural gas can get out quicker. It does not make it to the surface of the ocean floor, however, because the water is so cold that it turns to ice.
Dr. ANDERSON: And you might have heard of these things called clathrates or gas hydrates. It forms ice in the porous spaces of the mud and stays there until it's breached by some change in temperature and pressure. So it's purely a chemical phenomenon. And if you, say, melted all of the glaciers and the increase the sea level by 100 feet or 100 meters, you would change the pressure and temperature, and you might get a burst of a gas that was dissolved from the solid ice that come charging up to the surface. This is one of the things we think happened in the Cretaceous during the dinosaur times when the climate globally was much hotter than even on our global warming scenarios...
Dr. ANDERSON: ...say.
FLATOW: Mm-hmm. One last question, how can you tell and Jane Lubchenco, the head of NOAA - Lubchenco said at one point - and they asked her about the origin of oil and she said at that point, it was a few weeks ago that, oh, this is not the oil from the spill. This is different oil. Is it that identifiable, different kinds of oil?
Dr. ANDERSON: Oh, yeah. Oil has fingerprints. And the people at Texas A&M and LSU, for instance, both have libraries of fingerprints. Now, they're not fingerprints like fingerprints, they're chemical signatures. So you do an X-ray, like a CAT Scan of the oil and it has a specific mixture of all of those different organic compounds: Propane, butane, octane, all of the things that make up the combination that you get out of a refinery, from oil to gas to grease.
Dr. ANDERSON: And that's what gives each of the reservoirs a distinctive fingerprint.
FLATOW: Let's see if I can get one quick question in. Gary(ph) in Walla Walla. Hi, Gary.
GARY (Caller): Hi, there.
FLATOW: Hi, there.
GARY: That oil is under 9,000 psi. That's a lot of pressure. What's causing that pressure down there?
Dr. ANDERSON: Well, that's the good news for BP. It's caused by the fact that it's a very large reservoir. The bigger the pressure, the larger the reservoir. And so don't feel sorry for them, they're going to make a lot of money on this reservoir eventually as they produce it. We probably just lost one little sand channel from what will be a billion barrel field.
FLATOW: They always talk about drilling in Alaska versus drilling in the Gulf. Is it a whole different way to drill for oil up there?
Dr. ANDERSON: Up in Alaska, it's very different because the rock is all real solid, it looks like rock. In the Gulf of Mexico, it's mostly turbidites, they're called, which is basically like drilling into a sandy beach. And above that are muds, and then sands from the Mississippi Delta. So it's a moving - and then the salt is moving that's in there also. It's several centimeters a year, so the whole thing is like - I don't want to say Jell-O, but it's a moving, more lively thing than in Alaska, where it's all locked in.
FLATOW: I'm reading your article from the Scientific American issue of March 1998 about "Oil Production in the 21st Century." One of the things I'm very fascinated about is the engineering of the drilled - these drill heads. They can turn 90 degrees. You can point them in any direction. They have their own motors on them. You don't have to turn the whole casing like we always used to do.
Dr. ANDERSON: No. And they use inertial navigation that's literally right out of the cruise missile kind of technologies. That's why everybody is so confident about the relief wells. The relief well can steer itself right into - right now it's four feet away from the outside of the casing of the blown-out well. It sees it even though it's under 15,000 feet of mud and rock and 5,000 feet of water. It detects it. The bottom hole assembly that has the drill bit in it is intelligent. And it is using inertial navigation to steer its way right down onto the borehole. It's not a question of whether it will succeed really. It's a question of how long it will take them.
FLATOW: So, it's a smart well drill bit.
Dr. ANDERSON: Yep. It's exactly that, smart well, smart technologies down at the bottom of a very long spaghetti-like drill string.
FLATOW: And you say it's just four feet away at this point.
Dr. ANDERSON: It's four feet away vertically and their target is maybe 100 feet away. You all know that if they've had to abandon the site because of the tropical storm coming - but as soon as that abates, the drill ships will be back. They'll open up the cork that they put in the top of it and will be back to finally putting this well to bed, hopefully forever.
FLATOW: Well, we all hope so. Thank you.
Dr. ANDERSON: Yeah.
FLATOW: Thank you, Roger.
Dr. ANDERSON: It's a pleasure.
FLATOW: Dr. Roger Anderson is the Con Edison senior scholar at the Center for Computational Learning Systems. That's in the School of Engineering and Applied Science at Columbia University.
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