Soil-Gas Concentrations and Flux Monitoring at the Lacq-Rousse CO2-Geological Storage Pilot Site (French Pyrenean Foreland): From Pre-Injection to Post-Injection

Frédérick Gal (1) , Zbigniew Pokryszka (2) , Nadege Labat , Karine Michel (1) , Stephane Lafortune (2) , Andre Marble

1 BRGM - Bureau de Recherches Géologiques et Minières
2 INERIS - Institut National de l'Environnement Industriel et des Risques

Soil-gas concentrations and flux were measured during 20 separate measurement campaigns at the TOTAL Lacq-Rousse carbon capture and storage (CCS) pilot site, southern France, where 51,000 tons of CO2 were injected in a depleted natural gas field. Baseline data (September 2008 to December 2009) are compared to monitoring data from the injection (March 2010 to March 2013) and post-injection (February 2014 to December 2015) periods. CO2 soil-gas concentrations varied from atmospheric concentrations to more than 16% vol. with 1.4% as median value. Summer data showed high CO2 concentrations in the soil that remained quite high during winter. Median CO2 flux at the soil/atmosphere interface was close to 4.4 cm(3).min(-1.)m(-2). Carbon-isotope ratios measured on CO2 in soil gas had a mean value of -23.5 +/- 3.1 parts per thousand, some deviation being due to atmospheric CO2. Comparison between different gas species and the influence of temperature, pressure and soil-water content suggest that gases in near-surface environments are produced locally and naturally, and are unrelated to CO2 ascending from the storage reservoir. Monitoring of CO2 injection and the use of threshold levels is discussed as part of a practical approach considering specific regulations for the Lacq-Rousse CCS pilot experiment and constraints for the site operator.

Mots clés: TECHNICAL ADVANCES; LESSONS LEARNT; HALF YEARS; SURFACE; CAPTURE; CARBON-DIOXIDE; ISOTOPIC COMPOSITION; BASE-LINE; CO2 storage; depleted gas field; soil-gas monitoring; baseline; injection; post-injection; CO2 GEOLOGICAL STORAGE; CCS REFERENCE PROJECT; CO 2 storage

Domaines: Géologie appliquée

Frédérick Gal, Zbigniew Pokryszka, Nadege Labat, Karine Michel, Stephane Lafortune, et al.. Soil-Gas Concentrations and Flux Monitoring at the Lacq-Rousse CO2-Geological Storage Pilot Site (French Pyrenean Foreland): From Pre-Injection to Post-Injection. Applied Sciences, 2019, 9, ⟨10.3390/app9040645⟩. ⟨hal-02380703⟩