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.
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.