Résumé -Propriétés pétrophysiques du Dogger carbonaté dans le Secteur PICOREF (Sud Oil & Gas Science and Technology -Rev. IFP, Vol. 65 (2010), No. 3, pp. 405-434 Copyright © 2010, Institut français du pétrole DOI: 10.2516/ogst/2010002 (1) PIégeage du CO 2 dans des REservoirs géologiques en France. CO 2 Storage in the Struggle against Climate ChangeLe stockage du CO 2 au service de la lutte contre le changement climatique

Résumé -Choix et caractérisation de sites géologiques propices à l'installation d'un pilote pour le stockage de CO 2 dans le bassin de Paris (GéoCarbone-PICOREF) -Le projet GéoCarbone-PICOREF avait pour objectif de caractériser des sites propices à la réalisation d'un pilote national de stockage du CO 2 en réservoir géologique perméable. Deux types de réservoir ont été examinés : des aquifères profonds, et des gisements d'hydrocarbures en voie d'épuisement. Les sites devaient être choisis de manière que le pilote puisse tester des problématiques qui concernent les futurs stockages de grande taille. GéoCarbone-PICOREF D o s s i e rOil & Gas Science and Technology -Rev. IFP, Vol. 65 (2010), No. 3 376 Après avoir retraité 750 km de lignes sismiques, et avoir assemblé celles-ci selon six coupes calées sur des données de puits, on a précisé sur la Zone régionale :-les grandes caractéristiques des aquifères concernés ; -la localisation des failles ; -la continuité des couches très peu perméables situées au-dessus des réservoirs. Ces études ont permis de choisir un "Secteur", d'environ 70 × 70 km, au sein duquel on a ensuite affiné l'investigation géologique : 450 km supplémentaires de lignes sismiques, collecte exhaustive des données de puits, caractérisation fine des propriétés réservoir. Des observations de terrain ont été faites sur des roches équivalentes portées à l'affleurement. Un modèle géologique et informatique complet du Secteur a été construit à partir de ces données. Il permet de générer des maillages pour la simulation de divers comportements attendus suite à l'injection de CO 2 (déplacement et dissipation du gaz dans les couches réservoir, modification des pressions et des contraintes, déformation mécanique des terrains, interaction entre l'eau acidifiée et les minéraux, etc.

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The goal of this work is to model the present basin-scale groundwater flow of the Paris basin with a basin modelling approach and to use it to initialise a reservoir model for CO 2 injection. It is part of the ULTimateCO2 FP7 European funded project which aims to significantly enhance our knowledge of specific processes that may affect the long-term fate of geologically stored CO 2 .Basin models simulate the history of sedimentary basins through time by coupling geological events such as deposition, erosion, compaction, structural deformation and subsurface flow simulation. In order to construct the basin model of the Paris Basin in IFPEN basin software TemisFlow®, several types of data were gathered. The current surface topography and 11 horizons representing the top of selected main geological layers (from basement to surface) were constructed from outcrop boundaries, wells and isobath maps. Seven erosion maps for the main unconformities recorded in the Paris Basin were also constructed to complete the burial history of the sedimentary basin. TemisFlow® computes pressure, temperature and salinity fields over the basin history up to the present-day. The final state of the basin simulation is then used as initial state of the reservoir numerical model (Coores TM ). The latter is used to simulate the injection of CO 2 and its effects on the pressure field for instance.

-This article presents the preliminary results of a study carried out as part of a demonstration project of CO 2 storage in the Paris Basin. This project funded by ADEME (French Environment and Energy Management Agency) and several industrial partners (TOTAL, ENGIE, EDF, Lafarge, Air Liquide, Vallourec) aimed to study the possibility to set up an experimental infrastructure of CO 2 transport and storage. Regarding the storage, the objectives were: (1) to characterize the selected site by optimizing the number of wells in a CO 2 injection case of 200 Mt over 50 years in the Trias, (2) to simulate over time the CO 2 migration and the induced pressure field, and (3) to analyze the geochemical behavior of the rock over the long term (1,000 years). The preliminary site characterization study revealed that only the southern area of Keuper succeeds to satisfy this injection criterion using only four injectors. However, a complementary study based on a refined fluid flow model with additional secondary faults concluded that this zone presents the highest potential of CO 2 injection but without reaching the objective of 200 Mt with a reasonable number of wells. The simulation of the base scenario, carried out before the model refinement, showed that the overpressure above 0.1 MPa covers an area of 51,869 km 2 in the Chaunoy formation, 1,000 years after the end of the injection, which corresponds to the whole West Paris Basin, whereas the CO 2 plume extension remains small (524 km 2 ). This overpressure causes brine flows at the domain boundaries and a local overpressure in the studied oil fields. Regarding the preliminary risk analysis of this project, the geochemical effects induced by the CO 2 injection were studied by simulating the fluid-rock interactions with a coupled geochemical and fluid flow model in a domain limited to the storage complex. A one-way coupling of two models based on two domains fitting into each other was developed using dynamic boundary conditions. This approach succeeded to improve the simulation results of the pressure field and the CO 2 plume as well as the geochemical behavior of the rock. These ones showed that the CO 2 plume tends to stabilize thanks to the carbonation in calcite and dawsonite and no significant porosity change appears over 1,050 years. The CO 2 mass balance per trapping type gives a CO 2 carbonation rate of about 78% at 1,050 years that seemed to be excessive compared to the simulation study of other storage sites. Thus, an additional work dealing with both the kinetic data base and the textural models would be necessary in order to reduce the uncertainty of the injected CO 2 mineralization.