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

Abstract

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 cm3·min−1·m−2. Carbon-isotope ratios measured on CO2 in soil gas had a mean value of −23.5 ± 3.1‰, 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.

Gas fields and large shallow seismogenic reverse faults are anticorrelated

“…Gas was confined in a structural trap within the pre-Aptian carbonate sequence located in an anticline at a depth of 3500–4050 m, below the oil field, located at 650–700 m depth. Gas was exploited until 2013, when the field became one of the most important pilot sites for Carbon Capture and Storage (CCS 42 ).…”

Caprock integrity and public perception studies of carbon storage in depleted hydrocarbon reservoirs

“…The project had a favourable economic and social context (Ha-Duong et al, 2011), and was successful, validating oxy-combustion for carbon capture, and demonstrating that CO 2 could be stored in an onshore depleted gas reservoir. Soil analysis at Lacq measuring CO 2 concentration levels during and after injection at the site yield no indication of leakage up to date (Gal et al, 2019).…”

“…Oxy-fuel combustion requires the fuel to be burned in oxygen rather than air and the resulting flue gas is almost entirely CO 2 and water vapour. Sources of this table include: Carbon Capture and Sequestration Technologies at MIT (2016), Bouzalakos and Mercedes (2010), Gal et al (2019). β Calculated using 1600MW electricity generation capacity × 90% capture × 8000 tonnes CO 2 per year per MW electricity generation capacity, following the method of Rai et al (2008).…”

­Gas Fields and Large Shallow Seismogenic Reverse Faults Are Anticorrelated

“…Gas was confined in a structural trap within the pre-Aptian carbonate sequence located in an anticline at a depth of 3,500 to 4,050 m, below the oil field, located at 650-700 m depth. Gas was exploited until 2013, when the field became one of the most important pilot sites for Carbon Capture and Storage (CCS 44 ). The Zagros fold and thrust belt comprises one of the most prolific hydrocarbon provinces worldwide.…”