Climate change: expert questions CO2 storage procedure, energy transition

Sopuruchi Onwuka

Carbon capture and storage (CCS), one of the novel technologies that hold promise of diverting industrial emissions to artificial reserves, is yet to address the question of leakages.

The question from Professor John Underhill of Heriot-Watt University in Edinburgh cites plans by the government of the United Kingdom to store billions of tons of CO2 from sites such as refineries and chemical plants in rock formations under the North Sea.

The technology was informed part of the decisions taken at the 26the Conference of Parties (COP26) to the United Nations Framework Convention on Climate Change  (UNFCCC) on lowering emissions.

Industry group Oil & Gas UK (OGUK) envisages at least 100 million mt of CO2 stored annually by 2050, and two sites in northwest and northeast England have been awarded ‘Track-1’ status by the authorities.

The Track 1 projects include Hynet North West led by Italy’s Eni, and the East Coast Cluster led by BP.

But Professor Underhill, who will by March 1 become Director of Aberdeen University’s Interdisciplinary Centre for Energy Transition, argued in an interview that independent studies into the Track-1 projects have become necessary to address issues of leakage and accessibility to monitoring.

Whereas the OGUK points to Norway’s Sleipner project which has stored 1.0 million mt/yr since 1996 as a model, Prof Underhill pointed to mixed results from CO2 storage around the world.

He insisted that the integrity of the projects must be guaranteed to win people’s confidence in CCS forestall a national problem for the country.

A “forensic and critical, independent evaluation of the sites before any injection takes place,” he said, adding that “if we identify challenges or problems and if either of those sites go wrong, the issue will be people will lose confidence in CO2 storage, and that will then be an industry problem and a UK-wide problem.”

“It’s really important that policy-makers and others are aware of how their aspiration and wishes for net-zero can or can’t be met based upon and governed by our understanding of the geoscience currently.”

Underhill said regular 3D seismic surveys would be needed to avoid more expensive ‘ocean bottom’ monitoring.

He raised several geological questions, including the possibility some formations may not be sufficiently sealed . He added that formations where CO2 is already present may be safer than those where it is not.

“We do need to know where the plume of CO2 is migrating and to ensure there is no leakage through the sealing cap rock and its overburden,” he said.

A further risk is of CO2 reacting with water to form carbonic acid, which could threaten cap rocks at storage sites and the cement used to seal decommissioned oil wells, Prof Underhill said.

He warned that selection of sites for CCS must be based on a robust technical assessment… “so that we select the right sites for the right reasons.”

OGUK defended the UK plans, telling S&P Global Platts that thorough risk assessments would be carried out, and projects in operation would be subject to annual verification as part of the UK emissions trading scheme.

OGUK energy policy manager Will Webster cited Norway’s Sleipner and said: “Natural trapping mechanisms such as CO2 trapping within the pore space… coupled with the transferrable reservoir engineering skills and subsurface expertize from the oil and gas industry, have all ensured permanent storage of CO2, and prevented the migration of CO2 from the store to the surface.”

On the UK’s fraught energy politics, Underhill called for a “difficult, but important discussion” about the UK’s need for hydrocarbons — confirmed by the International Energy Agency and the UK Climate Change Committee — and the obligation to avoid fuel poverty, enshrined in UN development goals.

Efforts to curb emissions from the upstream production process mean the UK Continental Shelf “offers a reliable, low-carbon option” with the potential to reuse fields and infrastructure for both CO2 and gas storage, he said.

“There is an urgent need to address the energy trilemma of sustainability, affordability, and security of supply. Oil, gas, coal, nuclear and renewable technologies like wind, solar and hydro all have to be part of the discussion,” he said.

“The key question… is: are we comfortable to be reliant on imports and the security of those supply routes, the carbon footprint they bring, the intermittency of renewables and the lack of gas storage? If not, we need a full, frank and open discussion with all options on the table.”