Going underground: carbon capture and storage

Glen Paul: G’day, and welcome to CSIROpod. I’m Glen Paul. Carbon capture and storage, also known as carbon dioxide geosequestration, is a relatively new way of reducing the contribution of fossil fuel emissions to global warming, and works by capturing carbon dioxide from stationary emission sources such as coal filed power stations, industrial facilities, or natural gas production, and injecting it deep underground as a dense fluid into geological formations, preventing it from entering the atmosphere.

With Australia currently relying on coal fired power stations, CSIRO is researching carbon capture and storage with the National Geosequestration Laboratory, or NGL, which is a carbon storage research facility focused on delivering research and development solutions to help enable commercial scale storage of carbon dioxide to reduce greenhouse gas emissions.

Joining me on the phone to discuss the NGL is CSIRO’s Doctor Linda Stalker. Firstly, Linda, can you tell us just how is CO₂ captured and stored?

Dr. Stalker: There are a number of mechanisms that people have been developing in a separate portfolio of work to us, and that may include membrane technologies, vacuum pressure, ceramics, all sorts of technologies that people have been looking at, some of them have been around for a long time, and some people are trying to develop new solvents and new methods to reduce cost and reduce waste.

Glen Paul: And what makes a suitable storage reservoir?

Dr. Stalker: So when we’re looking for a potential site we want to make sure that we fulfil three sets of information. We want to understand the storage capacity of that formation, we want to know the containment security, how will the CO₂ stay down there, will it stay down there for the long term, and what is the injectivity of that rock formation.

One of the things that come up very often is concerns about fracking, and fracking is very much designed to get fluids out of the rock formation, we’re actually trying to store materials in the rock formation, so we want to make sure that we do not have fracking in our process.

Glen Paul: And once the CO₂ is captured, what stops it from just leaking away?

Dr. Stalker: We have to look at the rock properties in the storage formation, so we apply a lot of the oil and gas technologies to characterise the reservoir interval, if you want to look at it that way, and so we really want to understand what the porosity of the rock, what’s the pore space size and the permeability, i.e. the connectivity between those pores is in the reservoir, because that gives us the storage capacity, and it informs us about the mechanisms of storage.

So there are four key trapping mechanisms that we always look at. One is just that because it may be sitting in a structure where there’s a seal in the same way as oil or gas is stored, and we may be looking at the CO₂ will actually dissolve in the waters, the formation waters that are there, and become mildly acidic. It may stay also as kind of small bubbles, we call it residual trapping, but it’s essentially a capillary effect that will actually be permanently stored down there. And then the fourth mechanism is mineral trapping, where the CO₂ can interact with some of the formation fluids or the minerals there and deposit out as a carbonate mineral. So those are the four mechanisms.

Glen Paul: And what is the role of the NGL, and how is CSIRO involved?

Dr. Stalker: So the NGL is strictly focused on storage and a little bit on transport of CO₂, and there are other groups within CSIRO who’ve spent a lot of time looking at capture. The NGL is being overseen by the Western Australian Energy Research Alliance, which is a partnership between CSIRO, the University of Western Australian, and Curtin University, and we’ve been asked as that entity to partner with the South West CO₂ Hub Flagship Project, which is in south-west Western Australia, as their research partners, and through that we have been awarded a large capital equipment grant to establish dedicated facilities for carbon storage.

Glen Paul: And how is the South West Project progressing, and from what industrial sources is the CO₂ being captured?

Dr. Stalker: So the project at the moment is being run by the Western Australian Department of Mines and Petroleum, because we’re in the feasibility stage before any CCS acreage is released, and have just been putting the amendment to the Petroleum and Geothermal Act through the parliament to accommodate CCS licensing as we go forward. And so there’s a very staged project where we’re aiding them going through acquiring the right sorts of data, so that that can be used to actually release the acreage down the track.

The proposal is that there will be a pipeline from the Kwinana region just south of Perth, where there is a coal-to- urea plant, an ex-fertilizer.

The by-product is actually almost pure CO₂, without having to actually do much in the way of processing, and some of that CO₂ actually goes next door into the BOC plant, and it’s cleaned up a little bit, and that’s actually on sold for food grade CO₂, in carbonating beverages and so forth.

Some of that CO₂ is then transported to the local alumina plant, and the CO₂ is actually utilised for partially neutralising some of the liquor from the alumina processing, to get it down from something like pH14 to maybe about pH10. There is going to be an extension of that pipeline to some of the other alumina plants, and then the last little bit will come down to where we identify a test site to do a small scale injection to demonstrate the feasibility in that area for CO₂ injection.

Where the project has gotten to at the moment is that this area actually has very little good geological information, it’s not a prospective oil and gas area, so there’s very few wells in the region, and very little recent seismic data. So they have gone out and done a 2D seismic survey along some of the roads back in 2011, and that’s informed the project where to locate a new stratigraphic well. So 12, 15 months ago drilled another well called Harvey 1, and it’s very close to the roadside where the seismic was done, so we get good well tie in, and we’ve been doing a lot of research on the core, and the materials, and the rock properties in that area to demonstrate whether we’re at a stop/go stage, or there’s any show stoppers to going any further with the project.

So far everything looks really good. We have a storage interval that’s as thick as 1,500 metres, and it has quite good porosity and permeability behaviour.

Glen Paul: OK. Well it does sound like you’re on the right track there, so we’ll have to check in with you a bit later on and find out how it all went. Thanks very much for chatting about it with us today, Linda.

Dr. Stalker: Thank you. You’re welcome.

Glen Paul: Doctor Linda Stalker. And to find out more about carbon capture and storage, and to find a transcript of this podcast, visit www.csiro.au.