Rejigged rigs could kickstart North Sea CCS, study finds

USING North Sea oil rigs to generate power from methane and bury the resulting emissions would be significantly cheaper than decommissioning them, and could kickstart the UK’s CCS industry, a study has found.

Researchers at the University of Edinburgh in the UK looked at the economic feasibility of establishing power production and carbon capture systems on existing infrastructure in the Moray Firth, off Scotland. The scheme involves extracting hot brine from oil fields that contain dissolved methane. The methane would then be separated out and burned in a combined cycle gas turbine to produce power for the rig and any surplus power sold to shore. The hot brine would be used to heat a post-combustion ammonia capture system that would strip out the CO₂ that is produced from combusting the methane, and these emissions would be pumped back into a neighbouring aquifer for storage.

Using historic production data, and taking into account income from the gas and power produced along with the capex and opex of building and operating a full capture system with power generation, the study estimates the scheme would cost a total of £58m (US$71m) over 30 years. On top of this it expects income of £21.7m if the site and field were used to store CO₂ gathered from other sources, and a further £1m of income from carbon credits. This compares to spending £260m to decommission the infrastructure.

While owners of oil and gas installations are required by the Petroleum Act 1998 to decommission infrastructure at the end of a field’s economic life, Edinburgh researcher Stuart Gilfillan thinks it would be short-sighted if the opportunities for reuse were not considered. It could also prove costly if such installations have to be built again in the North Sea to support climate change goals.

In June, the UK Government set a legally-binding target for the country to reduce emissions to net zero by 2050. The Committee on Climate Change has urged the Government to help industry implement CCS, arguing the technology is essential to achieving net zero emissions and that 75–175m t of CO₂ would require capture and storage in 2050.

Furthermore, the authors write that other North Sea locations with higher pressure regimes and hotter aquifers have the potential to generate significant profit.

"Our study shows, for the first time, that natural gas production from saltwater can be combined with CO₂ storage in the North Sea. The potential revenue provided by extending natural gas production in the North Sea could help kickstart a world-leading carbon capture and storage industry in the UK," Gilfillan said.

International Journal of Greenhouse Gas Control: http://doi.org/dbcp