Jordan Blum, editorial director, Hart Energy: We're talking about carbon capture projects, all the money that's going into it, but the devil's in the details. So, what are the biggest technical challenges with pumping all of this CO2 into the ground that we're talking about?

Stephen Stokes, global head of CO2 transport and storage, Wood: There is a growing industry trend right now for economies of scale for [carbon, capture and storage] projects. And that is where multiple emitters, so power plants and manned factories, industrial users, need a home for their CO2 emissions. And they're looking at sending that CO2 to common infrastructure, so a common transport pipeline. Each of those emitters is going to have a cocktail, essentially, of different impurities. Now, we control that somewhat with a specification on the pipeline and say, "Can you please reduce your impurity levels?," but at the end of the day, we're going to have a very different composition daily and with different sources of CO2 entering the system. So, over time, we'll have a different set of components in the system, and that causes us a big challenge in CO2 transportation.

Dale Erickson, intelligent operations technology development lead, Wood: Well, and like I said, just think of the volume. In other words, people that drive through Pasadena, that corridor, see all those plants and just picture all those plants going into one pipeline, all those emissions. It's going to be a huge amount of emissions going into one pipeline and the mix of impurities is really going to be the interesting thing because these impurities may interact with one another.

JB: And how do digital solutions factor into all these wellbore integrity concerns? I think we're talking about a lot of thermodynamic modeling much more as well?

SS: So, digital application of thermodynamic models is, we see, critical to support operations and their quests to protect integrity of their assets. So, what Wood are trying to do in that area is empower the operator with much more information than just physical instrumentation. So, feeding in pressure and temperature and flow into an algorithm, essentially a digital twin, which then tells them much more in terms of the conditions in the system, how those impurities are affecting the fluid that's in the system, and how that might give concerns in terms of phase split in the system, in terms of low temperatures, in terms of corrosion, and ultimately in terms of protecting their asset.

DE: Yeah, because one of the things that's going to be potentially possible is even blending these things. So, it may be like a rail line that you stop some for a little while until you have something better to blend with it. So, it's going to be very complicated, this whole thing of tracking the impurities in the pipeline network.

And in some ways, it's possible if you have bad impurities, they may not even let them in. So, there's going to be this whole business that's going to develop of what we call basically nominations. Just like you have gas, there's going to be potentially trading and everything else that you may get charged more if you have the bad gas. So, there's a whole industry that will develop on this.

JB: And you were talking, too, about there's lots of flow management issues, concerns about mixing gas and liquids within the reservoirs. You were even talking about factoring in wind, rainfall. I mean, can you elaborate a little bit just on all the different dynamics at play?

SS: Yeah, yeah, sure. I mean, the ultimate answer there is, it's complicated. It's a complex system, but it's not new. So, these systems that we're talking about here, digital applications to support operations in the conventional hydrocarbon industry is a common practice.

With CO2, it gets more complicated. The complex system becomes even more complicated because we have what we like to call a very narrow phase envelope. So, what that means is we need to rely on numerically stable and accurate simulations to tell us what phase we have in the system. Do we have gas CO2, do we have dense phase CO2, liquid CO2, or do we have a combination? And if we have that combination, then we have to understand what the implications are. We can get not really slugging like we would refer to in the conventional hydrocarbon space, more intermittent flow. It causes cycling, it causes dynamic loads, axial loads.

DE: The other thing that makes CO2 a challenge, its critical point is about 80 F. And so as you move across that phase boundary, you literally can get a 10X change in density. So, it's a lot less dense on the gas side than the liquid, and most fluids aren't like that, conventional oil and gas. So, you can have these huge changes. And that just, as he was indicating, making the slugging worse and the behavior in the wells worse.

JB: And this is a global challenge, too. I mean, we're talking about all different kinds of geographies, the U.S. Gulf Coast, Canadian oil sands, the Persian Gulf. I mean, can you elaborate on all those different factors, the need to do everything on a global scale?

SS: Yeah, no, that's a great question. I'm lucky in my role to have a global remit and I see projects in every continent, essentially. And we see them in the onshore environment, the offshore environment. Some of the interesting work we've done is on depressurization. So, if we have to do maintenance in the system, we have to go from pressure to ambient pressure to allow access and intervention. If we've got a project in the Middle East, very dry sand, that system's going to behave completely differently to something in Canada, in Alberta, for example, where it's very cold, and it's going to behave very differently to something in the North Sea where it's covered in seawater and cold, but with very high heat transfer. So, we see very different behavior in very different regions. And it's a great question because that does need expertise to understand how the system's going to behave.

DE: Well, and people are also talking about transporting CO2, not just in pipelines, but on rail cars, we've looked at some projects there. There's projects where they're looking at shipping. Because again, CO2 is potentially generated and there's no storage in some locations, so they're going to have to transport it the most efficient way possible where they have the good reservoir.

JB: Very good. I know Wood recently announced, too, a new partnership with CMG, the Computer Modelling Group. Can you touch a little bit on just what that'll entail, how important that'll factor into everything?

SS: CCS is complicated, as I've mentioned, and I would say in some ways more complicated than conventional hydrocarbon projects. And what we need to do as industry is collaborate and also reduce hard basis of design between disciplines. So, where we do pipeline work in isolation, generate a document and then subsurface have to interpret that, and vice versa as well, we have to interpret that. What we're trying to do is create soft boundaries between disciplines. So, an end-to-end solution. And Wood, I should mention, do[es] carbon capture, carbon compression, dehydration. Now we do reservoir engineering through our CMG partnership. We have an end-to-end CCS solution which is a very powerful offering and a very important offering in an industry that really needs that seamless integration between project components.

DE: Yes, because, again, the thing you have to remember is unlike oil and gas where you just pull it out of the ground, you have to put this CO2 down there and keep it there thousands of years. So, that's partly the thing that these reservoir engineers do, is look at the long-term stability of storing the CO2. So, it's very important.

The other thing is really how number of wells you need. In other words, your whole project kind of floats on your worst well, and so you need to get that balance right. Because in other words, if you don't do it right, well, some power plant may not build the storage CO2. So, in other words, it's getting that whole balance right. And in conventional engineering, if you're off a well or if you have a crappy well, it's not so bad, you live with it. But here, if you're very tight, it may be a problem. So, that's very critical to get all that correct.

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