Unlocking Underground CO2 Storage - Video Transcription

Hazel Robertson:[00:00:23] So, I am Hazel from Pale Blue Dot Energy and this theme of unlocking underground CO2 storage is going to offer some real value at the close of the day, so I know we're almost there. We also might hear a sneaky rock pun or two, so keep your ears out for that. First, I'm just going to touch on a couple of things. The first thing is how we selected our two CO2 storage sites and then secondly covering a little bit about how we modelled them, to really understand them a bit more and can confirm that they're secure sites as well. What I'll certainly be talking about will be a nice stepping stone, or rather a nice stepping lower Cretaceous kept in sandstone, into what Richard will be discussing, where he'll take us into the microstructure and the mineral of the rocks a bit later. So, although Richard and I are presenting the findings today, this huge body of work has really had a lot of input from all these people that you can see here. So a huge, huge body of geological and engineering expertise and it's really been a privilege working with such a fantastic team as well. And, Clare and Eric, who are in the audience, will join us later on the panel discussion, so they can answer any of your more specific technical questions. So first up was the selection of what we've called the Acorn Storage Site. The selection process led us to this beautiful green blob surrounded by orange, and, just like how you heard throughout the day that with the Acorn project we like to make best use of the existing infrastructure in the storage sites, we also like to make best use of existing data and we're very lucky here in the UK there's been decades and decades of oil and gas exploration and production, and so we have a huge, huge wealth of data to enable us to do that. And so actually the Acorn Storage Site was preselected by some work that was done with the Energy Technologies Institute, and so we used this and actually brought forward this site in the Captain Sandstone with ACT work. And actually, all of the existing work that we've done, and this existing knowledge as well, has enabled us to accelerate the storage aspects of the Acorn site, and w e're now the proud owners of the very first CO2 storage license from the Oil and Gas Authority, and the very first lease option from Crown Estate Scotland as well. If you want to check out the work that was done for the ETI, the link is just there [on the slides] as well. 

 

Hazel Robertson: [00:03:06] However, one CO2 storage site is not enough and so we actually needed to look for a second site - and Alan touched on this a little bit earlier - both as potentially as a backup, but also to give the project room to grow as well. To select the second store, our starting point was the amazing, amazing resource that we have in the UK which is called CO2 Stored. And in it, there are at 574 possible storage sites around the whole of the UK and their combined storage resource is 78Gt, which is 78,000 million tonnes, or, as Alan touched on again, is about two hundred years of all of the UK's 2016 emissions. So, quite a lot of storage. 

 

Hazel Robertson: [00:03:52] Now, interestingly, and because from the Acorn project we've been focused on the reuse of existing infrastructure to keep costs down, a hundred and thirteen of these sites are within 50 kilometers of these existing target pipelines [on the sldies] and actually of these 113 sites, they total to about 24Gt or 24,000 million tonnes. So [that's a] pretty amazing storage resource that we've got here. 

 

Hazel Robertson: [00:04:20] Now, how do we get from 574 down to 113? By selecting within 50 kilometres of the pipeline. Then, how do we go from there? A huge chunk of the work that we did was actually looking at taking these 113 sites, reducing them down and then eventually selecting the second store that we could take forward and study. So, 16 of these 113 passed site specific selection criteria: looking at things such as if there was any hydrocarbon fields in the area, when was there cessation of production, how much...how good I guess the store was. So, looking at things like porosity and permeability. So these are just geologists' words for, essentially, has the rock got holes, can you get CO2 in it, and then the permeability is actually can you move the CO2 into the rock. So we looked all these different things, and then from those 16 essentially they were ranked and then the top 6 were taken forward for detailed due diligence. And so the due diligence dug a little bit deeper into actually looking at some of the subsurface status of pulling up some well logs delving into the seismic is well, and really making sure that the information we had was correct. And then, from that there was a process and we eventually ended up with one preferred site, and we've called this site East Mey. So just showing both of these here [on the slides]. So, we've essentially had two selection processes: there was the rigorous one done under the ETI work, and that produced this Acorn storage site; and then under the ACT work, we came out with the East Mey storage site. And one thing just to really highlight from this map, is if you look you can see the other blobs around the blobs of our storage site. And certainly the East Mey is part of a much larger aquifer called the Mey Sandstone, which represents much additional storage resource as well. And the same for the Acorn Storage Site and with the Captain aquifer as well. So, there's a huge, huge amount of storage resource and of course we narrowed down just for this project to focus on a small part of that. 

 

Hazel Robertson: [00:06:40] We started with 2D maps that you saw there. Now, to really dig into understanding exactly what's going on in the subsurface, geologists and engineers pulled together all this different subsurface data to really build up a 3D picture, and so creating these 3D models of the storage site. And so really using all this data that we've had from the amazing oil and gas industry in the UK, we can actually use to really understand the storage sites that we have in the central North Sea. Also using data from people like Richard [Worden] and all that kind of rock stuff as well. Once you the geoscientists build these 3D models, they can simulate injecting carbon dioxide into it and really understanding where the CO2 goes within the reservoir. And this is really important for understanding pressures and how we will then monitor the storage site as well. 

 

Hazel Robertson: [00:07:39] OK, so this chart here: along the bottom we have years and up the y axis on the left hand side we have the CO2 injection rate, and that's in millions of tons per year. On the right hand side - just to put CO2 in millions of tons per year into something maybe a little bit more tangible - is the percentage that that represents of Scotland's 2016 emissions. And so, for the simulation that we did with the 3D models in the subsurface, we looked at three different cases. Up to 5 million tonnes per year was injected into both sites in the simulation, which is about an eighth of Scotland's 2016 emissions. So what does that then look like? Once the modeling is done, this is a cartoonised version of what the dynamic 3D models would look like looking down from the top. On the left we've got the Acorn Storage Site and the East Mey one on the right. And those charts and the different cases, that were simulated that you saw on the previous slides, are shown here by the different coloured blobs. Essentially, the main thing to take away from this is that for both those - all those scenarios we looked at - both sites can easily contain 152 million tonnes and injection rate of 5 million tonnes per year, and the CO2 is contained safely within the CO2 storage site. And also just to point out those orange blobs are not actually carbon dioxide; those are existing oil and gas fields in this area as well. 

 

Hazel Robertson: [00:09:19] Okay. So, once the geoscientists and engineers have run loads of these different simulations, to really understand what the carbon dioxide is doing in the reservoir, this modeling data and the data that Richard has put, and his team are putting together, it combines to help us understand and really make decisions on how we're going to develop these sites and pull that all together. Now, we combine this all into one document which is called a Storage Development Plan. If you think of it kind of like a manual of how this site will be developed. These are some of the highlights from the Acorn Site Storage Development Plans. We've got an area of just under 1,000 square kilometers; as I touched on before, we've modeled up to 5 million tons per year, so that's about 152 million tonnes, and if anyone's got a spare £200 million you can buy yourself an offshore transport and injection facility. This would be developed by reuse of the Atlantic pipe as well. The plan is to go subsea, so without the platform that's been touched on, and start with one one well. A dual completion well, which essentially means it can handle quite a range of injection rates as well. So as a project grows, it can take on more CO2 as well. So again, it's this flexibility and scalability that's built in. 

 

Hazel Robertson: [00:10:44] And, so then looking to the East Mey storage site: slightly larger area, so just over about 1,000 square kilometers. It can hold the 5 million tonnes per year and the 152 million tonnes. Now, another case was run, where injection was continued beyond for 100 years. So, 500 million tonnes of CO2 was safely contained. Offshore capital costs are a little bit more expensive: there's a longer umbilical to control the wells that would be needed because it's a bit further off shore, and the base plan would be to reuse the existing Miller gas pipeline - 180 kilometres of it, same kind of well set up as well. 

 

Hazel Robertson: [00:11:29] Both sites here...the main point is they're both excellent candidates for storage and what we've found is that what we understand on this macro-kilometre scale is actually reinforced with the findings that Richard and his team have understood on the micro and millimetre scale, and essentially that it's an excellent storage site. So, I'll now hand over to Richard, the rock doc himself, to take us from kilometres down to millimeters. Thank you. 

 

Richard Worden: [00:12:03] I'm going to talk to you about what we've been doing at Liverpool University as part of this and specifically through the rock defamation laboratory at Liverpool. The whole laboratory is designed to study rocks, to take a rock sample and study it before we do anything with it and then smash it up, mangle it, compress it, squeeze it and then look at it afterwards. Now you might say what's that got to do with CO2? Well, we're were injecting large volumes of a new type of gas into the subsurface, so we need to be sure that that's going to be a stable situation and we're not going to damage the earth, the gases are not going to escape up to the surface, we're not going to cause environmental pollution and basically ruin the whole purpose of doing it. We don't want to leak the CO2 back to the surface. The equipment at Liverpool is highly complex, very technical and it is unique to Liverpool University. The collection of equipment we've got is truly unique. Some of the Laboratories look as if they've been designed by Heath Robinson, but believe you me they're all carefully looked after, carefully built and they're all safe, most importantly...most importantly. 

 

Richard Worden: [00:13:04] Our role in the project was to do in-depth testing of some of these core sample at the millimetre scale, at the micrometre scale, as Hazel has said, on both the Acorn and the East Mey storage sites. Kirsty is going to hold up a couple of examples of the rock. OK, pass them around. I'll explain in a moment where these have come from. We put multiple rock samples through a whole battery of geomechanical, petrological and mineralogical analyses - tests - all sorts of different tests, because we need to be sure that these rocks are going to behave the way we want them to. One of the other benefits of this is that the data we produce have been used directly in the modelling exercise that Hazel just talked about. So, yes we're doing it for an assurance purpose, but the data have been used for very good intent. Ultimately, we don't want the wells to fail when we inject CO2 at high pressure. That would be a disaster. And also in the longer term we don't want the top of the storage domain and t he structure both to fail: both of those things would be obviously a disaster. So these two rigs here: this is just some of the equipment we've got. The one on the left is a uni axial press: 'uni' because it's squeezing rocks from top to bottom. And you can see there's a rock sample there photographed before it went in the rig and then the load is increased until the rock fails, and then you can see an example of what the failed rock looks like. And by this test we can get a very simple measure of the strength of the rock. That's all very well, and we've done that on many many samples, repeats, replicates up and down the geology - I'll talk about the geology a little bit in a moment - from top to bottom of the storage domain. The other type of analyses we've done is called a Triaxial apparatus - and that's named after my colleague, who designed and built it done, P rofessor Dan Faulkner. There's the sample loaded up at the top of the chamber here. In this, rather than just squeezing from top and bottom, we're applying a confining pressure around the sample. So this is in a high pressure rig. So we're not squeezing from top and bottom and we're trying to mimic what's happening in the subsurface by having it encased in a high pressure medium. So if you think about it, fracturing a rock in free air isn't replicating what's in the subsurface, but if you have it enclosed at high pressure that is much more like what happens in the subsurface. So, this type of rig is a very good way of reproducing what is truly going to happen deep in the subsurface when we inject CO2. 

 

Richard Worden: [00:15:34] What do these rocks look like? So the rock samples going around - it's all very well, you can use your naked eye to look at them. But we need to look in more detail, so we've got a bit of a problem, though, because we need rock samples. We can't do these things on thin air, we can't go to somewhere around the coast of Scotland because the rocks were trying to inject into do not occur as outcrop on the coast of Scotland, or anywhere else in the UK. So we have to go and talk to, I had to go and talk to oil companies and try and get them to give us their core samples. So, some interesting discussions were had, getting closer and closer to the heart of anyone who's got responsibility about releasing rock fragments to us, and in the end, the response was amazing. It was truly amazing. Oil companies were bending over backwards to help us in the end. Repsol, Nexen and Premier were amazingly helpful. Those guys were amazingly helpful. We've got an enormous quantity of rock now at Liverpool. We have...got an almost embarrassing riches of it. One day, the building we are in is going to be demolished and we going to have a new building, maybe in the next five years and I'm slightly worried what we're going to do with this rock. I think my head of school doesn't even know it's there; you know, as an academic, you quite often just do it - don't ask for permission; you know we're doing it for the right reason. So, we've got lots of rocks samples at Liverpool and those are some of the examples you're seeing around there. 

 

Richard Worden: [00:17:02] Now, there are two types of rock we need to characterise: one of them is the storage element to it - call a reservoir, because in oil and gas terms that's where the oil and gas is held - and the illustration on the left is an example of that. Now this image is taken with a very special electron microscope. It doesn't matter how that's collected, but the key thing is the white motif here. You can see the key down here, the white is pore space - porosity. Now, mostly in the subsurface the porosity is filled with water. We want it to be replaced by carbon dioxide, but we need a lot of it. We need a lot of porosity, otherwise there's no point trying to squeeze carbon dioxide in there. So the other minerals that are present: that's quartz in pink and mauve colour...I'm colour blind actually and I really shouldn't be doing this... but the mauve colour there is natural calcite cement. That's what makes it a rock, not a fryable sand. So there are other minerals: there's an iron carbonate and some clay minerals, but the key thing is there's lots of porosity. The other thing is we know the minerals that are there now because we can quantify them. 

 

Richard Worden: [00:18:03] So the other type of rock to look at is the one on the right side. This is an example of the seal that holds the fluids in the subsurface. Now in oil and gas terms we call it a cap rock or a top seal. It's exactly the same geometry we need to store CO2. We need a rock that's sitting on top of the porous rock to stop the CO2 escaping. So we've had to characterise that as well, and this is an example. One thing you'll notice is there isn't much white there - not much porosity. The bulk of it is a green colour, which is a clay called smectite which has very interesting properties. It expands when you wet it. It is very good sealing rock. The indications are this is a very low permeability, very good rock for holding the CO2 in the subsurface. We have a number of tests we've done, and we need to characterise the storage domain especially in terms of these different attributes. So, Hazel's already talked about porosity and permeability. 

 

Richard Worden: [00:19:00] Porosity - that's the holes that are there in the rock, we need to know those. The oil companies, they have their own data that we accessed, but we've generated very specific new data to corroborate that and just to make sure that the oil company data is as good as they hope it is. Permeability - this is the ease with which fluids flow through rocks. We need the rot to be permeable because when we inject CO2 into the subsurface it needs to move away from the injector well into the large volume of rock. So permeability is a very important attribute. 

 

Richard Worden: [00:19:31] Rock strength. Well, we need to know what it is so that we don't inject at too high a rate and cause the rock near the well bore wellbore region to fail. That's one thing. I'll come back to that in a moment. The other thing is, we need to know the mineral chemistry and the minerals that are present. We need that to know that to make sure the rock isn't going to simply dissolve when we inject CO2. That would be the doomsday scenario. We also need to know what happens when we add CO2 and increase the flow pressure across a large volume of rock for a very long period of time, and that's what goes into the models that Hazel's talking about: assurance that we're not going to leak from system. 

 

Richard Worden: [00:20:07] So, a couple of simple photographs. These are light microscope images: that's of the storage domain or the reservoir and that's the ceiling lithology on top. You've seen these before with that electron microscope image. Let's talk about the porosity first. The average porosity for the Acorn site - that's the Captain Sandstone - is nearly 28 percent porosity, so nearly 28 percent of that rock is void space. That's good. That's where the CO2 will sit. The ceiling rock above it - the caprock - has 14 percent porosity. That sounds quite high, but that's nothing to worry about because those holes, those pores, are not connected together. We know that up because we can look at the permeability values. So the permeability the sandstone is - these units are a bit odd - 2,114 millidar-cies. Believe you me, that's very, very permeable. Okay? If you put some in your mouth you could nearly breathe through it. Not quite, but nearly. Contrast that to the rock above it - 0.00023 millidar-cies. That's one ten millionth of the permaability. That's telling us those pores, those holes, they're not connected, and that's confirming that the rock on top of the storage site will hold the CO2 back. It will stop the CO2 escaping. 

 

Richard Worden: [00:21:19] The same entirely is held for the East Mey site. The porosity is a little bit lower - 24 percent - not much but a little bit lower. The ceiling lithology, the porosity is pretty similar to the Acorn site at 15, nearly 16 percent. But again the permeabilities are the thing that mutter for leaking the CO2. The storage domain: 47,471 millidar-cies, and the rock above it 0.0026. That's a millionth of the permeability. It will hold the CO2 back. So we've chosen two very very good sandstones. That's the conclusions. 

 

Richard Worden: [00:21:54] We've also tested the rock strength, and just as a snapshot of the values tensile strength of 2 bars. That's.. it is a number, OK? That goes into the models and it makes sure we don't cause trouble when we inject at too high a rate. The tensile strength of the East Mey sandstone is higher and that's probably because the porosity is a little bit lower. Again, it's data and data that goes into the models. This is very important inputs. 

 

Richard Worden: [00:22:16] So, the key findings and therefore to summarize. (1) Both sites are highly suitable for injection and long term storage of CO2. Thank goodness. But this is going to work. (2) Secondly, both the Captain and the Mey sandstones from the Acorn site amd the East Mey site: they're highly porous and highly permeable and we saw [how ]the mineralogy in those coloured images are dominated by quartz, and we know quartz is inert. It's not going to react. So our exhaustive tests of the mineralogy, mineral chemistry, they tell us there's going to be no interaction with the CO2. The rocks aren't going to dissolve. They're not going to weaken with time. The East Mey has a slightly greater rock strength than the Captain - just to reiterate, it's probably because it's slightly lower porosity. Again, it's nothing to worry about. It's just data to go into the models. And finally all samples tested are strong enough to withstand CO2 injection and both in the short term of the injection pressures and longer term as the CO2 builds out and spreads throughout the entire storage domain. 

 

Richard Worden: [00:23:19] And thank you.