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Stockage géologique du CO2 : capacité de stockage et surveillance des sites

Abstract : Currently, the geological storage of CO2 is heavily studied around the world in order to limit global warming due to the greenhouse effect. The atmospheric CO2, which has been steadily increasing for more than a century, is assumed to be in a large part responsible of this warming. Nowadays, various options have been considering to store CO2 in an underground environment for periods covering several centuries. Among the options, one is to inject it in unexploited coal seams. INERIS are involved in studying this possibility of CO2 geological storage. It may also present in some contexts, an economic interest, if fuel natural gas (methane) is present in coal seams (ECBM: Enhanced CoalBed Methane). The objectives of researches aim at assessing the capacity of storage of coal seams with the characterisation of CO2 sorption onto French coals: sorption capacity and gas transport in coal structure. To determinate this parameters, an experimental work is currently underway in INERIS laboratories. To study the feasibility of CO2 storage in coal seams, experiments of adsorption were performed using gravimetric technique for monitoring the kinetics and capacity of sorption. From our results, equilibrium is reached faster for CO2 sorption than for methane sorption, while the adsorption capacity of CO2 is higher than for the one of methane. During this experimental study, we showed that the gas sorption at coal interfaces is due to a set of complex mechanisms involving a diffusion transfer through macropores and micropores followed by adsorption onto the sites at coal surfaces. Simultaneously, INERIS has developed methods for gaseous phase geochemical monitoring on surface as well as within the cap rock of geological CO2 storage sites. The work undertaken was targeted at two specific approaches: - Early detection (pre-alert), using analysis of gas samples taken from the base of the dedicated boreholes drilled from the surface into the intermediate cap rock strata. - Detecting and quantifying the gaseous flux of CO2 from the ground to the atmosphere. These two approaches were successively developed in the laboratory and then applied and tested in-situ, under conditions that are as close as possible to those of the future storage sites. The tests undertaken on a 200 meter deep borehole have shown that the detection of CO2 leaks passing through the intermediate overburden strata was possible by sampling and continuous analyzing of the gas accumulating at the bottom of the borehole. Good results have especially been obtained when detecting small releases of gas that may represent an early warning sign prior to the appearance of a larger leak. Directly measuring the gaseous flux from the ground is one of the most effective ways to monitor a storage site. The INERIS accumulation chamber method has been improved to measure low and very low fluxes of CO2. It can now be used to measure a wide range of CO2 flux, from very low emissions levels of 0,1 cm3.min-1.m-2 up until extremely high flux rates of some 4,000 cm3.min-1.m-2. These metrological and operational characteristics have been checked and validated by laboratory tests, on a test rig, as well as using in the field measurements at sites that naturally release CO2. The two methods experimented are now operational and available, ready for integration into the surveillance strategy applied to future storage sites. They can be used throughout all of the steps in the life of a storage site: site reconnaissance, establishing the initial state, injection, post-injection phase, and residual monitoring after abandoning the site.
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https://hal-ineris.archives-ouvertes.fr/ineris-01869210
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Submitted on : Thursday, September 6, 2018 - 12:34:59 PM
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Long-term archiving on: : Friday, December 7, 2018 - 11:45:09 PM

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  • HAL Id : ineris-01869210, version 1

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Delphine Charriere, Zbigniew Pokryszka. Stockage géologique du CO2 : capacité de stockage et surveillance des sites. Rapport Scientifique INERIS, 2008, 2007-2008, pp.109-112. ⟨ineris-01869210⟩

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