Aha!
You might recall Monbiot earlier in the week. And his mention of Jim Bliss\’ calculations about the amount of CO2 stored and the amount emitted by BP\’s Peterhead scheme.
You know, the one which strips the CO2 from natural gas, burns the hydrogen, pumps the CO2 into an oil reservoir and thus pumps up more oil?
The calculations which I said I didn\’t trust. Although, I have to admit, I got the reason I didn\’t trust them entirely wrong. Mea Culpa.
In 2005 BP proposed to build a new gas-fired power station at Peterhead, capture the carbon dioxide produced and use it for enhanced oil recovery in the Miller field below the North Sea; this innovative project could have been up and running in 2009. Monbiot is wrong to suggest that the plan would have led to more carbon emissions than savings: between 1.8m and 2m tonnes of carbon dioxide would be injected each year over 20 years, producing an additional 40m-60m barrels of oil. Taking the higher numbers, 40m tonnes of carbon dioxide remains underground, while burning the oil produces approximately 20m tonnes; twice as much carbon dioxide is stored than emitted.
The abandonment of the Miller scheme due to lack of government support means a loss of $6bn in oil revenues and a missed opportunity to take a lead in reducing carbon emissions.
Professor Martin Blunt
Department of earth science and engineering,
Imperial College London
Ah, you see, Jim compared the annual storage of CO2 with the emissions from 20 years of oil pumping.
When, in fact, we should either be comparing the 20 years of CO2 storage with the 20 years of oil pumping, or the annual CO2 storage with the annual oil pumping.
Comparing an annual input with a two decades long output is bound to give us some dodgy numbers.
Now this of course depends upon the Professor above being correct. Perhaps Jim would like to revisit his figures and tell us who is correct here?
The comparison still looks a bit limited to me. If you haven’t got the extra 20 million tons of oil you presumably replace it in use use of some other fuel – eg coal – and that emits CO2 too.
Hi Tim,
If Professor Blunt’s figures are correct, then of course my calculations need to be revised.
However, his figures are do not tally with those stated by BP.
“The project would also permanently store 1.3 million tonnes of carbon dioxide, the equivalent of removing 300,000 cars from the roads.”
From: BP website
BP do not claim that the figure is “per annum”, and indeed the context would appear to imply that it is not.
Once again, though, if BP have themselves under-reported the CO2 being captured then my calculations clearly require revision. But I’m not sure I can really be held responsible for inaccurate data provided by those planning the project.
Tim adds: A Google search for “BP Peterhead” gives as result two or three a page which says this:
“When fully operational, the project would be expected to capture and store around 1.3 million tonnes of carbon dioxide each year and provide ‘carbon-free’ electricity to the equivalent of a quarter of a million UK homes.”
http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7006999
So per annum I think?
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As the pingback suggests, I have indeed revisited the calculation, Tim.
http://numero57.net/?p=254
I’d like to point out though, that I still feel your initial post on this subject was a cheap shot and I’ll be responding to it at some point.
“The project would also permanently store 1.3 million tonnes of carbon dioxide, the equivalent of removing 300,000 cars from the roads.”
Never take a press release at face value. It’s usually written by a (junior) marketing droids who knows nothing about the topic. A classic example was the press release from NASA JPL that had converted the dimensions of the Mars Orbiter into metres by multiplying feet by 3.28. (ironic considering the 1998 failure of the orbit due to a software fault in converting between imperial and metric units).
Hmm.
Assuming that CO2 can be compressed to liquid form to the same density as oil, and displaces the same volume of oil, which is mainly-carbon-with-a-bit-of-hydrogen; and one unit of oil burns to form 3.7 times its weight in CO2, I fail to see how this can lead to an overall reduction in CO2.
“I fail to see how this can lead to an overall reduction in CO2.”
I’m sure they thought of this before they invested millions in the idea. While the Government wouldn’t hesitate to waste millions on a doomed-from-the-start idea, BP wouldn’t be quite so wasteful of their own money.
BP want to get the oil out. You’ve got to pump something in to get it out, whether that’s water, CO2 or toothpaste is neither here nor there.
“water, CO2 or toothpaste is neither here nor there.”
Water is to hand (offshore, anyway) and neatly doesn’t compress. CO2 is a pain in the butt. And toothpaste is really a pain in the butt since the purchasing department can’t spell “fluoride” and thus none ever gets delivered.
Never take a press release at face value.
Well, I’ve learnt that the hard way, Kay Tie. My reasoning — now well-established as faulty, no need to rub any more salt in the wound, folks — was simply an assumption that the press-release would contain their most optimistic projections and claims, and thus the best ones to challenge.
As I’ve said however… that was clearly a mistake.
Assuming that CO2 can be compressed to liquid form to the same density as oil, and displaces the same volume of oil, which is mainly-carbon-with-a-bit-of-hydrogen…
Oil recovery by gas reinjection works by injecting the gas beneath the oil reservoir. The pressure buildup below the oil then forces the oil up through the well.
BP want to get the oil out. You’ve got to pump something in to get it out, whether that’s water, CO2 or toothpaste is neither here nor there.
Not necessarily. BP could get the oil out without reinjection, but the production rates would not justify the costs of extraction. With gas reinjection, it would have. BP’s likely option now they’re not reinjecting will be to walk away, flogging the field to a much smaller independent operator (which are flourishing in the North Sea now) whose extraction costs will be much less than those of BP.
Tim N, gravity and so on would suggest it is sufficient to inject the gas above the oil reservoir, as long as you have a pipe that goes down below the surface. You can’t pump gas under a liquid, it just bubbles up.
Mark, please forgive me if I’m wrong, but I’m not sure you fully grasp the geology of oil wells. The oil does not exist in a large pool, through which a gas released below could “bubble up”. Rather, it exists as billions of individual droplets suspended under extremely high pressure within a porous stratum of rock. This porous rock is sandwiched between non-porous structures (hence why very specific geological conditions are required for an oil well / field to form) and when the top layer (the cap rock) is breached, the oil rushes upwards because of the pressure.
Over a period of time, however, the pressure tails off and it becomes increasingly difficult to extract the oil. Gas injection is then used to recreate / maintain enough pressure to continue pumping. This gas is injected below the reservoir (as Tim Newman pointed out) and succeeds in forcing many more of those tiny droplets towards the surface.
It’s a well-established technology that’s been in use for many many years (many of the oil wells I’ve visited have been using some form of gas injection) and while, ideologically, I believe we should be leaving fossil fuels in the ground right now; there’s no question that the technology does indeed work and has kept hundreds of US (and other) wells pumping long after they would otherwise have ceased production.
Deffeyes’ book on oil has a good introduction to the geology and mechanics of oil extraction. And it’s got some very interesting analysis of peak oil production (which he predicted around the end of 2005, and he might be right).
http://www.amazon.com/Beyond-Oil-View-Hubberts-Peak/dp/0809029561
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