CCS all about finding the ‘right rocks’ – Part Two

By Paula Wallace

James McGregor, energy systems manager, CSIRO Division of Energy Technology, gave a timely update on the organisation’s progress with CCS for coal fired power generation - click here to read more.
And, global specialist in geological storage solutions for carbon dioxide, Schlumberger Carbon Services, shared its expertise on the parameters of capture and storage. The company’s Andrew Garnett drew from its 80 year history in subsurface evaluation in the oil and gas industry, to provide a picture of what development may look like in Australia’s coal fired electricity sector.

“Once you’ve found the right rocks is pretty well do-able”: Garnett
Andrew Garnett provided conference delegates with a realistic picture of the development of CCS for cleaner coal fired power generation.
He spoke mainly about appraisal uncertainty, or what is now being referred to as characterisation in the CCS field.
“…it’s basically about getting things up to that level where it’s invest-able. Invest-able usually means up to about the FEED level so $100 million plus.
“Most of the other stuff, once you’ve found the right rocks is pretty well do-able.”
But CCS is one of those industries where minor technical details can have massive commercial implications.
“We’re talking about a world here, much like oil and gas, where upfront expenditure at risk costs are big so you share them, you share cost and risk in commercial ventures.
“From a geological point of view the failure rate’s probably not as high (as the oil and gas sector) but you still might get all these wells in the ground and then walk away…it’s quite a difficult one to sell.
“So if it was successful, before I get into the FEED I want an integrated or a joint or a co-development project with a source, because I’m not going to develop my site until there’s a source out there waiting for me.
“I’m going to need licenses to go ahead, I’m going to need headline environmental consent at the very least before I get commercial closure…I’m going to need some kind of long term supply contract with a fixed-in price, and I’m going to have to have an idea of the size of the pipeline or transport infrastructure.”
Garnett said all these factors mean that CCS projects exist in a “very complex commercial environment.”
“There are not a lot of sites out there, it’s a scarce resource…forget capacities, forget all of these megatonnes of storage in aquifers…rate matching is what counts and its rate matched sources which are rare.”
He said there is no point in a CCS operator taking 10 megatonnes from a coal fired power station if it can’t sequester 10 megatonnes per annum.
He said it’s also essential to develop confidence through considering as many sites as possible at the appraisal stage.
“If you look over the history of the past few years and the number of CCS projects that have been announced and then canned, almost all of them have been canned because they focus very early on one storage option and then it didn’t work,” he said.
“This is some of the reason why…lead times for new storage…is somewhere around eight years from tenement award. That is, if you get a tenement of sufficient size that there are several options within. If you get one tenement with one option in it, it’s anywhere between eight years and never.”
The risks and uncertainties around carbon storage are the “weakest link” and the only way to manage this is to diversify front end risk, said Garnett.
“You’re talking about four or fives sites, ten wells per site, 40 appraisal wells and then you’ve got a pretty high confidence that at least one of those should work. If you’re lucky, two of them will work.
“It’s very important that the regulators get their heads around tenement scale, it’s not oil and gas, it’s significantly different, and it’s driven by tiny parameters in the permeability and thickness of the rock which we actually don’t know at the moment. So you have to err on the large side.”
Garnett said there is one technical parameter which has largely been forgotten in CCS literature, and that is the issue of thermal shock. Theoretically if you pipe CO2 from a plant and it arrives at its destination at 20 degrees Celsius and the geological formation of the site is 60 degrees Celsius, there is a risk of the rock fracturing because the cooling reduces its tensile strength.
“You’ve got three options, you can either reduce your injection pressure…and therefore you have to increase the well count; or you can heat the CO2; or you can just risk that fracturing.
“Heat integration is significant as to where you’re going to put your plant,” said Garnett.