Sleipner: Pioneering Carbon Storage Under the Sea

“Without Carbon Capture and Storage (CCS) as part of the solution, reaching our international climate goals is practically impossible.”⁽¹⁾

Dr. Fatih Birol, Executive Director, International Energy Agency

The importance of CCS is becoming widely recognized in the international community. But rolling out this technology at a large scale requires large scale solutions to two challenges: How to capture carbon dioxide; and how to store it. 

Out in the North Sea, ExxonMobil has been working in partnership with operator Equinor and others on a carbon storage solution that has collected over 20 million tonnes of CO₂⁽²⁾ since 1996. When it came online, the Sleipner T platform was the first CCS facility in the world to store captured CO₂ in a deep saline reservoir, 800m⁽³⁾ beneath the sea bed. Check out our short film to find out how it works:

First, the CO₂ is stripped out of natural gas being piped from the Sleipner West gas field beneath the platform. The gas from this particular field has a high CO₂ content which is stripped out on the offshore platform, using an amine scrubbing process. 

Amine solution absorbs CO₂ from natural gas, making it possible to siphon off the CO₂. Heating up the amine-CO₂ mixture separates the two substances out again, creating a pure stream of CO₂. But where do you put it on a platform in the middle of the sea? 

The answer was pioneering. The CO₂ captured on the Sleipner platform would be piped back down beneath the seabed, to be stored in a deep saline reservoir.

The Sleipner area presented the perfect conditions for a saline reservoir. The large sandstone formation below the platform is sealed by a tight ‘cap rock’, with plenty of capacity to store large volumes of CO₂.

A key challenge of the project was working out how to monitor the plume of CO₂ as it gathered in the rock formation over time – to demonstrate that it would stay within the reservoir and not leak out. To do this, seismic monitoring surveys of the area have been carried out at regular intervals. These show that the plume is staying within the rock formation and getting bigger as more CO₂ is injected.

Large-scale carbon storage solutions like Sleipner’s saline reservoir show that CCS can help society reach its climate goals, but a supportive legislative framework is also important. Norway’s innovative carbon emissions tax – introduced in 1991 – helped build the business case for CCS at Sleipner. 

Thanks to projects like Sleipner, since 1970 ExxonMobil has cumulatively captured more CO₂ than any other company. Read on here, to find out more about CCS and the technology we’re partnering on to capture carbon and reduce emissions.

Sources:

1. International Energy Agency
2. Equinor