New research supports carbon capture and storage Monday, 01 August 2016

A team of researchers from Europe and America is suggesting that carbon dioxide can be trapped underground for long periods of time without significant leakage

The group, led by Professor Mike Bickle, Director of the Centre for Carbon Capture and Storage at the University of Cambridge, studied a natural reservoir in Utah where CO2 released from deeper formations has been trapped for around 100,000 years.

Bickle said this was far longer than the 10,000 years needed to avoid climatic impacts and demonstrated that the relatively impermeable layer of 'cap rock' that retains the CO2 can resist corrosion from CO2-saturated water for at least 100,000 years.

A key component in the safety of geological storage of CO2 is the cap rock over the porous reservoir in which the CO2 is stored. Although the CO2 will be injected as a dense fluid, it is still less dense than the brines originally filling the pores in the reservoir sandstones, and will rise until trapped by the cap rocks.

Bickle said carbon capture and storage (CCS) is seen as essential technology if the world is to meet its climate change targets.

“A major obstacle to the implementation of CCS is the uncertainty over the long-term fate of the CO2 which impacts regulation, insurance, and who assumes the responsibility for maintaining CO2 storage sites," he said.

"Our study demonstrates that geological carbon storage can be safe and predictable over many hundreds of thousands of years.”

The team, which included researchers from Germany, Netherlands and USA as well as Britain, studied the corrosion of the minerals comprising the rock by the acidic carbonated water, and how this has affected the ability of the cap rock to act as an effective trap over geological periods of time. Their analysis studied the mineralogy and geochemistry of cap rock and included bombarding samples of the rock with neutrons at a facility in Germany to better understand any changes that may have occurred in the pore structure and permeability of the cap rock.

They found that the CO2 had very little impact on corrosion of the minerals in the cap rock, with corrosion limited to a layer only 7cm thick. This is considerably less than the amount of corrosion predicted in some earlier studies, which suggested that this layer might be many metres thick.

The researchers also used computer simulations, calibrated with data collected from the rock samples, to show that this layer took at least 100,000 years to form, an age consistent with how long the site is known to have contained CO2.

The research demonstrates that the natural resistance of the cap rock minerals to the acidic carbonated waters makes burying CO2 underground a far more predictable and secure process than previously estimated.

“With careful evaluation, burying carbon dioxide underground will prove very much safer than emitting CO2 directly to the atmosphere,” said Bickle.

[The Crystal Geyser in Utah is driven by subterranean carbon dioxide. Photo: Niko Kampman]

Energy will be a major topic of discussion at the Australian Engineering Conference 2016 in Brisbane on November 23-25.