Will 2D be around forever? In part 4 of our series, we explore this question by examining the stages of a carbon capture and storage (CCS) project and seismic budget. This series is based on a discussion with Carbon Alpha’s Eric Street and Lee Hunt.
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2D seismic has been historically undervalued. Today, it has become an indispensable part of CCS project development – a process that is closely tied to risk reduction. But when in the project life does 2D come into play and how long is it useful for? To answer that question, we first need to examine CCS project stages.
“For those … readers who haven’t been initiated in the [CCS] space or are just learning about the space, one thing that you’ll come up the curve on very quickly is that because of the risk aversion (and by necessity), these projects are big and expensive,” explains Eric. “We’ve operated in a world … where we’re doing a lot of risk reduction. But what that’s done is highlight the importance of risk. And organizations like NETL and CSA have created a set of standards which are very useful guides for how these projects progress.”
These standards have defined distinct project phases. “These projects walk through stages from start to end: Site selection, characterization where you’re acquiring sites, and then they flow through towards development, operations, and closure. And there are different types of data which are useful and leveraged at different stages in these projects,” says Eric.
2D seismic tends to be of most use in the early project stages before the final investment decision (FID) – a decision point where a company decides to invest resources into a specific project location.
The site screening and site selection phases are the earliest stages in CCS project development and tend to rely on public data.
In the screening phase, costs are kept low. “You can’t put the cart before the horse,” says Lee. “You don’t want to spend a fortune on 3D…So it starts with public data. And you work your way in, approaching this final investment decision, where you decide ‘This is the spot. I’m going to commit to it.’”
As companies approach the FID, spending tends to increase. “Eventually you start buying legacy seismic. And this could be 3D, but it’s more often 2D,” says Lee. “When you’re in what we call the characterization phase, that’s when we get a lot of legacy seismic as cheaply as possible, generally. And we even start to, perhaps, drill what we call appraisal wells. But there’s a conundrum here around FID and having to go about doing these things.”
The conundrum comes about because financial investment requires a degree of certainty and that cannot be achieved without some prior investment. Lee adds, “Business managers really do not like to be exposed on a project that might not go ahead.”
To combat risk and investment aversion, projects scale slowly. It can be difficult. Lee explains, “Even at the stage that you’re getting your characterization—which you need to have to make this decision because you’re deciding how to develop a field—you have to know a lot of things about permeability, how that reservoir is laid down, about the seal integrity, what the pressure limits are, the geomechanics, all kinds of things.”
Dealing with the investment conundrum is one of the reasons why 2D seismic is so useful. It’s an economic solution. It allows for the characterization of large areas or multiple sites with speed and relatively low expense.
With the FID comes a renewed shift in preference from 2D to 3D seismic. Lee provides some colour on this shift: “After we get the FID, [we] move to things like shooting a baseline 3D (some people will do it before, but if we are respecting our business conundrum, you really prefer to do it after)…It’s probably the most expensive thing you’ll ever do with seismic because you have to learn the most right then.”
As the projects move into the operational phase, repeat 3Ds may be shot for comparison to the baseline to monitor long-term containment.
As for whether 2D will meet its second demise as more CCS projects move from site selection to operation, Lee and Eric both hint that this is not the end for 2D. “We think that 2D seismic could have a role in the repeat seismic.”
“What we see is that as we march towards net zero and 2050, the growth in the storage space has to be exponential… I think as long as there’s no major shift where 3D just becomes free and cheap, 2D in CCS is going to have a long life,” Eric concludes.
That’s good news for 2D!
Up next: In our next article we explore the challenges of working with legacy 2D seismic and how to get around them. On to Part 5!
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