Using CCUS to eliminate greenhouse gas emissions

CO₂ discharged into the atmosphere is a greenhouse gas, and contributes to climatic warming, as it absorbs some of the sun’s heat. Radical and immediate action is required to eliminate greenhouse gas emissions. One technology which is essential to limit the atmospheric CO₂ concentration is the storage of CO₂ into geological reservoirs. This relatively short term solution has to be used in parallel with renewable energies, energy efficiency improvement and energy mix optimisation.

For CO₂ storage to become an efficient tool to eliminate greenhouse gas emissions, large volumes of CO₂, compressed to a supercritical state, should be injected into large, deep saline aquifers or deep, depleted hydrocarbon reservoirs.

Most of the available storage capacities are currently located in saline aquifers, but these formations are generally not well characterised and are not evenly distributed on the planet. On the contrary, depleted oil and gas fields are usually well-characterised formations because of the history of gas field production.

TOTAL’s CCUS ambition

TOTAL’s ambition is to become a leader in CO₂ capture, utilisation and storage (CCUS) technology by 2035, using a two-pronged strategy to participate in climate change mitigation and prepare for new business opportunities. To achieve this goal, TOTAL will position itself as an integrator of the full CCUS value chain, developing internal competencies, working in partnership and boosting innovative technologies and the development of start-ups.

The main strategic priorities of the TOTAL’s CCUS roadmap related to storage topics are: to operate and manage a CO₂ storage project at an industrial scale and at the same time exploit TOTAL’s existing expertise to solve key remaining storage issues.

TOTAL’s subsurface experience and expertise can contribute to fostering the deployment of CO₂ storage worldwide and therefore contribute to the positioning of the group as a world-class leader in CCUS. This objective can be reached by decreasing the uncertainties around CO₂ storage capacities, to promote CCUS globally, and by preparing for the safe and cost-effective operation of industrial-scale CO₂ storage projects.

TOTAL, a CCS experience since the 2000s

TOTAL has long been committed to developing CCUS technology as a means to eliminate greenhouse gas emissions, and has acquired industrial CCS expertise thanks to shares taken in Snøhvit and Sleipner in the North Sea – projects in which CO₂ was captured from gas treatment – and through the Lacq French CO₂ injection pilot project (Fig. 1), carried out between 2010 and 2013. This integrated pilot, operated by TOTAL, involved gas oxy-fuel combustion capture, followed by storage in a gas-depleted reservoir. 51,000 metric tons of CO₂ were injected until 2013 and we continued to monitor the reservoir until 2017.

R&D challenges

The subject of geological CO₂ storage has its own scientific challenges, which are manifold. In particular, the safety and acceptability of storage projects are key issues. We will have to make sure we are injecting CO₂ safely during the injection period, but also that there will be no risks for future generations.

TOTAL’s approach, in the continuity of its climate strategy, is to move toward gigaton-scale CO₂ storage projects, rather than the megaton-scale CO₂ storage projects underway today. Consequently, we target large CO₂ storage aquifers at basin scale.

The storage integrity of these aquifers will have to be ensured over centuries. Our monitoring philosophy will have to be reviewed, particularly for large-scale storages. Large scale modellings of the carbon dioxide’s dissolution within brine, of the “CO₂ plume shape”, or of various geological breaking mechanisms will have to be tackled.

Because wellbores (injectors, legacy wells) are often considered the primary potential source of leakage in CO₂ storage projects, research and development efforts will be focused on insuring their integrity.

There are five research area:

• Evaluation of CO₂ storage capacity of saline aquifers and depleted hydrocarbon reservoirs (capacity classifications, large scale modelling, geochemical impacts, etc.);
• CO₂ Well injectivity;
• CO₂ Well integrity;
• Geomechanical stability of storage (structural geology, fault modelling, geomechanical and seismic domains);
• Monitoring (geophysical and non-geophysical techniques).

CO₂ storage is the only viable way to deal with large volumes of CO₂, which therefore makes CCUS an efficient tool for climate change mitigation. The International Energy Agency anticipates that before 2050, around 100 billion tonnes of CO₂ need to be captured and stored. CO₂ storage capacities at scale, which can achieve the CO₂ abatements required to mitigate climate change and eliminate greenhouse gas emissions in the main emitting regions of the world (Europe, North America, China, India and the Middle East) remain to be secured.