Carbon Capture and Storage – A Fairytale for our Time

“Do you believe in fairies?” asked Tinkerbell

I was browsing the Canadian Broadcasting Corporation (CBC) news website recently when the following item caught my eye:

It’s a good news story about how Canadian Natural Resources Limited (CNRL), Canada’s largest oil and gas producer, is hoping to reduce CO2 emissions from its tar sands operations to zero by using new technologies such as Carbon Capture and Storage (CCS) projects. The implication is that if we can deploy this technology on a large scale, business as usual can continue, because we can burn all the fossil fuels we want but leave the resulting CO2 in the ground. What’s not to like about that?

So what is CCS and how does it work? Here is a video by Shell explaining how it works:

In brief, CO2 is captured from the processing plant, pressurized to turn it into a liquid and transported by pipeline 65 kilometers to a number of well sites. The still-liquid CO2 is then injected more than two kilometres underground into a layer of rock filled with interconnected pores. The CO2 becomes trapped within the pores, and the layers of watertight rock above it stop it from escaping. Constant monitoring both above and below ground makes sure the CO2 stays safely and permanently in place. Get that – permanently. Forever. Over one million tonnes of CO2 are being captured and stored in this way each year, and four million tonnes have so far been captured and stored during the course of the project.

That’s the industry side of the story. But is it true? I have several concerns about it, including that little word “permanently”. I don’t see how you can inject highly pressurised, liquefied gas underground at a rate of one million tonnes per year and expect it to stay there “permanently”. The laws of physics and common sense suggest that it is going to find its way to the surface.

They say that a chain is only as strong as its weakest link. By the same token, an underground reservoir is only as gas tight as its leakiest part. And if you have a reservoir hundreds of kilometres wide, how many leaky parts are there going to be in that?

So I decided to investigate further. I contacted CNRL and asked for the pressure readings in the reservoir before, during and after the CO2 injection process. If the pressure in the reservoir failed to rise significantly while the gas was being injected, or rose during injection but then fell afterwards, either of those scenarios would suggest a leaky reservoir. It’s like pumping up a bicycle tyre: if you pump up the tyre but it rapidly goes flat again, you know there’s a hole in it.

The CCS facility appears to be a joint operation between Shell, CNRL and Chevron. I contacted Shell first. They suggested I contact CNRL. So I contacted CNRL. They suggested I contact Shell. This initial run-around did nothing to boost my confidence in the project. But eventually, after sending a third firmly-worded email, I got a response on behalf of Shell from Stephen Velthuizen, External Relations Manager for the Scotford Upgrader, of which the CCS project is a part. Essentially what he says in response to my questions about reservoir pressures is this:

  • There is minimal pressure rise during the injection process, from a baseline pressure of 19.5 MPa (megapascals) to 20.5 MPa after injecting 4 million tonnes of CO2. These pressures are equivalent to 2,828 and 2,973 psi (pounds per square inch) respectively. For comparison, a bicycle tyre would typically be inflated to 50-130 psi.
  • He wasn’t willing to give me any figures for how rapidly the pressure decays after the CO2 injection stops.
  • In his own words: “But pressure alone – while an indicator – is not the only way to assess what is happening in a reservoir. One of the many technologies we use to monitor the CO2 is vertical seismic monitoring. By comparing a current vertical seismic profile (VSP) to our pre-injection VSP, we can detect the CO2 plume (through the variance). The VSP can also detect CO2 that has migrated out of the reservoir. The monitoring of many factors allows us to identify if a leak is occurring and take corrective action. We also have deep monitoring wells above the reservoir that provide valuable pressure information to indicate if a leak was present.”

I’d be very interested to hear from any readers who have expertise in geology or the operation of high pressure wells. I don’t – I’m just a simple family physician. But what Mr Velthuizen is saying sounds to me suspiciously like poppycock. I don’t believe a word of it. If you inject 4 million tonnes of gas into a reservoir, and there is hardly any rise in pressure, then surely common sense suggests that there is a leak: not just a small leak, but a massive leak, a leak so big that the gas is leaking out almost as fast as it can be pumped in? Like trying to pump up a flat bicycle tyre which obstinately remains flat? And all that talk about vertical seismic profiles and CO2 plumes sounds suspiciously like misdirection, which is what stage magicians do: they direct your attention to what they want you to see in order to direct your attention away from what they don’t want you to see.

Wishful thinking is a powerful emotion. That’s why the media and the public love a good news story like this and don’t ask too many questions. We really wish we had a magic wand to wave that pesky CO2 away so we can carry on flying our jets, driving our SUVs and eating food from the other side of the world with no consequences. We really wish that CCS would be that magic wand. The problem is that as far as I can tell, it probably doesn’t work.

Slaynt vie, bea veayn, beeal fliugh as baase ayns Mannin

7 thoughts on “Carbon Capture and Storage – A Fairytale for our Time

  1. So, basically, they are adding a massive additional cost, both in terms of monetarily, and in terms of resources used and wasted, in order to accomplish exactly … nothing. How I do love the younger generation’s complete lack of critical thinking skill.

  2. I’m not saying that the overall scheme is a good idea, but one way to achieve the “permanent” part of capture is to note that CO2 is a reactive gas. It’s not inert, like helium, which will just lurk underground until given an escape (or forcing one). CO2 (so they say) forms solid minerals with the minerals that are already underground. I’m not a geologist, so I don’t have the details, but I do know that concrete (for example) chemically absorbs CO2 for years after it’s “cured”, and becomes stronger as it does so. If CO2 is bonding with the surrounding rock, that would account for some loss of pressure.
    Search for “CO2 mineral sequestration” for technical details.

  3. That’s very interesting Lathechuck, I wasn’t aware of the possibility of CO2 bonding with the rock, but in his emails to me, Mr Velthuizen (of Shell) didn’t put forward any arguments about the CO2 bonding with the rock. What he said about it was:
    “The layer we are injecting the CO2 into is a porous sandstone (with 17% porosity, 1000 mD permeability) called the Basal Cambrian Sands (BCS) located at a depth of about 2000 m. Above this layer are a number of impermeable rock layers of shale and salt that act as seals. The initial downhole pressure readings at the wells was about 19.5 MPa (I say about as it varies slightly based on the different wells) prior to injection of CO2. After injecting 4 million tonnes, the pressure is currently about 20.5 MPa. The pressure curve spikes soon after you start injecting and then flattens out quite a bit after that. So, by the end of the project (25 years), the pressure build-up is forecast to be less than 2 MPa (deltaP) – or about 21.5 MPa.”
    I have heard of CO2 bonding with limestone, but I think it’s unlikely it would bond with sandstone. Mr V’s arguments seem to rest entirely on the (supposed) gas-tightness of the reservoir. And I think that if he is saying there would be virtually no increase in pressure after 25 years of injecting CO2 at one million tonnes per year, he needs his head (as well as the reservoir) examining.

  4. Dr Gray, A sponge is a better analogy to the physics of carbon capture than is a bicycle tire. A sponge has lots of small pores (very large surface area), which are highly effective at trapping any gas or liquid and holding it for very long periods of time. In contrast to a tire with a hole, a sponge “leaks” very slowly unless squeezed. Nevertheless, all sponges have a maximum amount the volume these can hold and once saturation occurs, adding any more CO2 will result in equal amounts of escaping essentially immediately. Throughout the entire process, some CO2 has to leak out since there’s no such thing as a perfect vacuum or pressure chamber. All chambers (vacuum or pressure) essentially reach an equilibrium where the incoming amount equals the amount leaving. High pressures or strong vacuums can only be achieved for very well-sealed volumes. Chuck Joseph, Prof. of Astrophysics – retired.

  5. There is also the formation of chlatrates which you might consider. We know this happens to CO2 under the sea, creating solids. The issue is to know the temperature and pressure down below SO, now you have two mechanisms, the rock and with water that could “absorb” the the CO2 as it spreads out into the “sponge.” This might lead to a spoke in pressure, followed by a decay curve as the chemistry equilibrated.

    There is another issue in your story. I presume that the process is capturing the “excess” CO2 from the processes to extract the oils from the tar sands. (I think they are burning natural gas for heat.) The carbon in the fuel itself will go elsewhere to be burned and hence not captured.

    I would think it’s much easier to capture CO2 in the higher concentrations of the exhaust flue than in the open atmosphere, so I’m suspecting they are not capturing carbon to offset the fuels they ship offsite.

    Final thought, all this is taking energy: capture, piping, and pumping underground, probably making the net energy to society for a barrel of tar sands lower than the net energy of a barrel of conventional oil.

  6. Worse then a fairy tale. I find it insane to have a plan to sequester CO2. Think about it. First you take stores of Carbon from the ground, then you Oxidize it to release energy. Lastly, you store away the CO2. The net total is that you are removing Oxygen from the atmosphere and storing it away. This is more accurately called Oxygen sequestering. A child could see the folly of this.

    Please leave our Oxygen in the atmosphere.

  7. This is an Interesting and thoughtful piece. After working on CO2 underground storage for twenty years, I’m convinced that it can be done safely. And we will need it in the future not so much for fossil fuels, but to clean up the atmosphere. We can grow more trees, but that will only take care of one to three of the ten billion tons, per year, that we will have to remove to stay below 2 C. We have nothing to do with it but put it back underground. And we can do that safely, and permanently.

    Today, rather than telling people about all the monitoring and modeling we’ve done, I say, “At these depths CO2 is nearly identical to oil – same density, same viscosity. If we put it in the same rocks that held oil, or rocks like them that never saw oil, we can expect the CO2 to stay down as well as oil does. Which is to say not completely perfectly, but in general it is a lot of work to get oil from 3000 ft down. Just don’t drill a hole in it.”

    Thanks for your thoughtful piece.

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