Transfert de fluides dans les milieux poreux, le cas des carbonates et des interfaces argiles/calcaire. Etude intégrée de pétrophysique, de sédimentologie microstructurales.Le cas de deux carbonates : le cas de deux carbonates : l'Oolithe Blanche du Bassin de Paris et la formation du Globigerina Limestone des îles maltaises.

• Main Author: Casteleyn, Lisa
• Other Authors: Cergy-Pontoise
• Language: fr; en
• Published: 2011
• Subjects: Pétrophysique; Microstructures; Porosité; Propriétés réservoir; Stockage; Petrophysic; Porosity; Reservoir properties; Storage
• Online Access: http://www.theses.fr/2011CERG0503/document

Le stockage géologique est aujourd'hui envisagé dans plusieurs domaines tels que le stockage de CO2 ou celui de déchets nucléaires. C'est un projet à long terme qui nécessite un protocole d'étude particulier afin de déterminer et comprendre la formation envisagée, notamment en termes de mécanismes de transports. Les formations étudiées sont fonction du type de stockage dans le sens où un stockage de gaz ou de déchet radioactifs ne vont pas requérir les mêmes besoins. Dans le cas d'un stockage de CO2, la formation hôte doit posséder de bonnes propriétés réservoirs afin de, notamment, faciliter l'injection. Pour un stockage de déchets radioactifs, la formation hôte doit retenir au maximum les éventuelles fuites de fluides contaminés, c'est pourquoi les sites de stockage envisagés sont au sein de formation très peu poreuse et très peu perméable, argilite ou granite notamment.Les travaux présentés dans cette thèse sont liés à deux projets de stockage. Le premier a pour but l'étude pétrophysique d'une formation potentiellement hôte d'un stockage de CO2 dans le Bassin Parisien, la formation carbonatée de l'Oolithe Blanche. Cette formation, composée de trois faciès principaux, présente de faibles propriétés réservoir qui sont influencées par trois paramètres microstructuraux : la nature du liant, la quantité de compaction et, enfin, la taille des pores et leur distribution.Le second projet est basé sur l'étude d'un analogue structurale au laboratoire de Meuse/Haute-Marne de l'Andra pour le stockage de déchets radioactifs. Cet analogue est situé dans l'archipel Maltais, qui présente une structure tabulaire très proche de celle observée dans la région du laboratoire de Meuse/Haute-Marne : calcaire/argile/calcaire. Notre étude a permis la mise en évidence de plusieurs périodes de mouvement de fluides oxydants, dont une traversant l'ensemble de la formation argileuse, remettant ainsi en cause ses propriétés d'imperméabilité. === Geological storage is now considered as a technical solution for CO2 storage andnuclear waste management (for high-level and intermediate-level long-lived radioactivewaste). A geological storage is a long term project which implies a particular protocol in orderto better determine and to better understand the host rock, especially in terms of transportmechanisms. The geological formations studied are chosen in function of their storagecapacity because gas storage or nuclear waste storage do not need the same requirements.In case of CO2 storage, the host formation must provide good reservoir properties in order tofacilitate the injection. Here, the safety of the storage is guaranteed by traps (structural,residual, mineral) and by the presence of a cap rock. Concerning nuclear waste storage, thehost must retain at best the potential radioactive fluids and gaz leaks, and this is the reasonwhy storage sites are studied within low porous and low permeable formation, like argillite orgranite.The work presented in the PhD thesis is related to two storage projects. The first oneis focused on the petrophysical study of a potential host for CO2 storage in the Paris Basin,the “Oolithe Blanche” carbonate formation. The second project is an analogue study of thesedimentary structure explored in the Meuse/Haute-Marne laboratory. This laboratory isstudied by ANDRA to be the first nuclear waste storage in a deep geological formation inFrance. The analogue was found in maltese archipelagos, which presents almost the sametabular structure as the one observed in the Meuse/Haute-Marne laboratory:limestone/clay/limestone affected by a weak tectonique deformation.In the first part, the Oolithe Blanche Formation study allowed to determine thereservoir properties of the three principals facies of the formation. This study was realized onplugs sampled on quarries in Burgundy (France). Those facies are characterized by differentenvironmental processes and deposit energy; nonetheless, they are all located within ashoreface depositional environment. They are composed of ooids, pellets and bioclasts invarying proportions. The reservoir properties studied showed the Oolithe Blanche Formationis a microporous one. Microstructural parameters which influence reservoir properties are:the cement type (sparite or micrite), amount of compaction characterized by the cementquantity and the contact between elements and, at last, the pore size distribution withinporous elements (micro, meso, macropores).The second part of this project is focused on a more petrophysical study which aimedat characterizing the pore network influence (volume, shape in space) on acoustic velocities,6electrical conductivity and on permeability. The study is completed by the use of permeabilitypredictive models based on mercury porosimetry spectra.The maltese archipelagos study is based on observations made by Missenard et al.(in prep.) .), Rocher et al., (2008) and Missenard et al. (2009, 2011) on the Blue ClayFormation, thick clay formation (~ 100 m) and on the underlying Globigerina Limestone. Theclay formation presents an important fracture network characterized by gypsum filling and byan oxidizing zone near the fractures. A similar oxidation, in the shape of lobes andmushrooms, is observed within the Globigerina Limestone.This study is also divided in two parts. In the first one, the focus is on the study ofgypsum filling fractures. Studying this filling is directly linked with the storage topic, because,in the case of a nuclear waste storage, the absence of fractures and fluid motion is animportant condition to insure the storage security. In the case of gypsums filling, the study isbased on geochemical measurements on oxygen (δ18O), sulphur (δ34S) and strontiumisotopes (87Sr/86Sr) coupled with a fluid inclusion study, all measurements performed ongypsum crystal. Those analyses allow us to propose a downward fluids circulation modelthrought the clays. Fluids source which is at the origin of gypsum’s precipitation seems to beyounger than the hosted formation. Because of the position of the maltese islands, inMediterranean sea, one potential source is the Messinian evaporites, which Sr isotopic ratiocorresponds well to our data set.The second part of the maltese study concerns the oxidation shape observed withinthe Globigerina Limestone. The aim is to determine the processes which allowed thisoxidation. The main question is: are those structures the results of an internal heterogeneityin the rock or the sign of a stop in a fluid motion (stop of the fluid or stop of the oxidizingmechanism)? In order to answer those questions we based our interpretaion on the skeletonof the rock (mineralogy, magnetic mineralogy, microstructural study, geochemistry), on poreand porosity (porosity measurements, mercury porosimetry…), on permeability and on therock anisotropy (susceptibility of magnetic anisotropy (SMA) and acoustic velocitiesanisotropy). Some conflicting differences on the dataset exist, especially on anisotropy data,which can suppose some complex processes.