Ever since the recent work of the Intergovernmental Committee on Climate Change, carbon capture and storage (CSS) have been identified as a major option for the large-scale reduction of anthropic emissions of CO2. One of the major preoccupations is to guarantee and verify the integrity of storage over the long term. In order to detect any anomaly on the future sites for CO2 storage at sea, it is essential to perform an in-depth chemical analysis of the environment.
An innovative solution for measuring CO₂ content in the oceans
In this context and through a close collaboration over the past five years, TotalEnergies, in partnership with the French company Alseamar, has developed an innovative solution for measuring CO2 content in the oceans using autonomous underwater gliders equipped with a CO2 sensor.
With its rechargeable battery, moving continuously between the surface and a depth of up to 1000m, due to a simple effect of density variation regulated by ballast, the SeaExplorer glider has an autonomy of several weeks and can cover several hundred kilometers. The glider supplies high resolution, three-dimensional spatial data and also has advanced capabilities such as landing on the sea bottom and sub-surface navigation. When the glider re-surfaces, it transmits its position and data acquired during its dive, via satellite communication, to a land-based control center, thus allowing the data to be viewed in quasi-real-time and the “flight-plan” to be updated if need be.
0mThe maximum depth attainable by the glider
0ppmEstimated measurement precision
In May 2019, in the framework of the ACT4STORAGE (Acoustic and Chemical Technologies for environmental monitoring of geological carbon storage) project, conducted by the Norwegian Geotechnical Institute, Alseamar was invited by TOTALENERGIES R&D CCUS to perform a mission in the Oslo fjord (Norway). The mission proved the reliability of SeaExplorer and its sensor for measuring the concentration of liberated CO2 concentration in a context of controlled dispersion. After the success of this first trial, a mission financed by the CITEPH innovation program (Concertation pour l'Innovation Technologique dans l'Exploration Production des Hydrocarbures (Innovative Technology Consortium for Oil Production Exploration) was conducted in June 2020 in the Bay of Biscay to assess the regional and temporal distribution of CO2 naturally present in the water column.
These experiments demonstrated the ability of the glider’s on-board sensor for the detection, assessment and long-term monitoring of CO2 in the sea. The advantages of this device are also its ease of use and its agility for monitoring an extended area over a long period, with an estimated measurement precision of about 10ppm. In addition to its interest and significant advantages for determining environmental baselines and for the later monitoring of CO2 storage sites, the underwater glider equipped with dedicated sensors also holds the future for offshore activities that require precise monitoring of environmental and ocean-weather parameters. For example, gliders can easily be deployed to collect data on currents in order to limit the risks related to maritime operations but also to obtain acoustic data on marine mammals or on noise generated by human activities.
Beyond these aspects, new payloads for new applications are being developed in the framework of the CITEPH program, including:
- a current sensor for positioning the vehicle underwater,
- a passive hydrocarbon sampler,
- an improved version sensor for liquid hydrocarbons.
The future looks exciting in the near future with the idea of acoustically coupling these underwater gliders with wave gliders, thus providing real-time communication for permanent surveillance and more precise monitoring of underwater gas emissions.
The glider in acquisition at the bottom of the water - image courtesy of Alseamar
A versatile and multi-sensor tool - image courtesy of Alseamar
Launching from a small boat - image courtesy of Alseamar
Glider in his transport trunk - image courtesy of Alseamar
Preparation of the glider in the workshop - image courtesy of Alseamar