This thesis details the results of an integrated study of carbonate platform sedimentology, geometry, evolution and diagenesis within a sequence stratigraphic framework. This study has been based on the Upper Cretaceous carbonates within the Tremp basin of the Spanish Pyrenees, which, through the effects of minor tectonic deformation during the later parts of the Pyrenean orogeny, are exceptionally well exposed and can be studied in the form of a platform to basin cross-section upon a scale that is comparable to that of a seismic section. This study concentrates on the mid-Turonian to Coniacian-aged Congest platform and its associated basinal succession, whose sedimentology and geometrical features, in particular cyclic progradational cycles, and evidence of repeated flooding and exposure of the platform-top are interpreted in terms of . fluctuations in relative sea-level and associated variations in available accommodation space. These interpretations, together with evidence of subaerial exposure in the form of karst features, intensive dissolution and the presence of speleo-cements, are used to propose a dynamic 'forced regression' model for the evolution of the Congost platform, which involves two phases of platform development, separated by a period of forced regression. The primary and secondary porosity afforded by the abundant bi-mineralic rudists within the platform-top sediments allows for a detailed and comprehensive diagenetic study of these carbonates, in the form of a case study for a number of interesting diagenetic features. In addition to standard petrography, cathodoluminescence and stable isotope studies have been employed and have allowed the identification of such features as botryoidal calcitic marine cements, neomorphism which occurred in lagoonal waters and speleo-cements. This study also provides a detailed investigation of the diagenesis associated with subaerial exposure and the development of sequence boundaries. Differences in the early diagenesis of these carbonates from different parts of the Congost platform suggest that two separate phases of platform development experienced: 1) differing pore-fluid regimes; 2) differing frequencies and duration of subaerial exposure events; and 3) different magnitudes of relative sea-level fall. These features are considered in terms of variations in accommodation space during platform development and are used to develop the dynamic 'forced regression' model for the evolution of the Congost platform. A succession of Cenomanian to Santonian-aged basinal and slope sediments which can be correlated with the contemporaneous Santa Fe, Congost and Sant Comeli platforms and contain a large amount of allochthonous debris, much of which is derived from underiying units, are described and interpreted in terms of local tectonic activity and relative sea-level change. The final part of this thesis presents a new sequence stratigraphic model for the mid-Turonian to Coniacian-aged Congost platform which is compatible with the observations and conclusions of this study. This new sequence stratigraphic model suggests that the Congost platform developed within two separate depositional sequences, albeit with one being on a much larger scale than the other. Sequence boundaries are characterised by subaerial exposure on the platform top which can be correlated with hardgrounds and/or glauconite accumulations within the more basinal locations, overlain by deeper-water facies. The presence of submarine onlap surfaces and down-slope slide deposits immediately above the sequence boundaries suggests that the major transgressive events which followed sequence boundary development were brought about by local extensional tectonic activity, while the stratigraphic cyclicity within the sequences and major falls in sea-level which produced the sequence boundaries are interpreted to have resulted largely from eustatic processes.

Retracer l’histoire d’un bassin est un préalable essentiel à toute recherche d’hydrocarbures. Pour cela, on a recours à un modèle stratigraphique, qui simule l'évolution des bassins sédimentaires sur de grandes échelles de temps (millions d'années) et d'espace (centaines de kilomètres). Le logiciel Dionisos, développé à IFPEN depuis 1992 et très apprécié par les compagnies pétrolières, permet d’effectuer ce type de calculs en prenant en compte deux grands processus physiques : (1) le transport gravitaire des sédiments dû à l’inclinaison du sol ; (2) l’écoulement de l’eau provenant des fleuves et des précipitations. Le transport gravitaire est décrit par une équation de diffusion dans laquelle le flux de sédiments dépend de la pente du sol. Initialement, cette dépendance est linéaire. Pour mieux s’approcher des observations réelles, on souhaite la rendre non-linéaire par l’intermédiaire d’un p-Laplacien. Ce changement nécessite la conception d’une nouvelle méthode de résolution numérique, qui doit offrir non seulement une grande rapidité d’exécution, mais aussi des garanties de robustesse et de précision des résultats. De plus, elle doit être compatible avec une contrainte sur le taux d’érosion présente dans le modèle. L’ajout de l’écoulement de l’eau est aussi une sophistication récente du modèle physique de Dionisos. Il se traduit par l’introduction d’une nouvelle équation aux dérivées partielles, couplée à celle du transport. Là encore, il est important d’élaborer une stratégie de résolution numérique innovante, en ce sens qu’elle doit être à la fois performante et bien adaptée au fort couplage de ces deux phénomènes. L'objectif de cette thèse est de moderniser le cœur numérique de Dionisos afin de traiter plus adéquatement les processus physiques ci-dessus. On cherche notamment à élaborer un schéma implicite par rapport à toutes les inconnues qui étend et améliore le schéma actuel. Les méthodologies retenues serviront de base à la prochaine génération du calculateur. / An essential prerequisite to finding hydrocarbons is to trace back the history of a basin. To this end, geologists resort to a stratigraphic model, which simulates the evolution of sedimentary basins over large time scales (million years) and space (hundreds of kilometers). The Dionisos software, developed by IFPEN since 1992 and highly praised by oil companies, makes this type of calculation possible by accounting for two main physical processes: (1) the sediment transport due to gravity; (2) the flow of water from rivers and rains. The gravity transport is described by a diffusion equation in which the sediment flow depends on the slope of the ground. Initially, this dependence is linear. To better match experimental observations, we wish to make it nonlinear by means of a p-Laplacian. This upgrade requires to design a dedicated numerical method which should not only run fast but also provide guarantees of robustness and accuracy. In addition, it must be compatible with a constraint on the erosion rate in the present model. The water flow due to rivers and rains is also a recent enhancement brought to the physical model of Dionisos. This is achieved by introducing a new partial differential equation, coupled with that of sediment transport. Again, it is capital to work out an innovative numerical strategy, in the sense that it must be both efficient and well suited to the strong coupling of these two phenomena. The objective of this thesis is to rejuvenate the numerical schemes that lie at the heart of Dionisos in order to deal more adequately with the physical processes above. In particular, we look for an implicit scheme with respect to all the unknowns that extends and improves the current scheme. The methodologies investigated in this work will serve as a basis for the next generation of stratigraphic modelling softwares.

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La marge algérienne est un domaine complexe, bordé au sud par les zones internes des Maghrébides (AlKaPeCa) qui chevauchent les zones externes telliennes vers le sud. La partie offshore de ce système constitue un bassin d‘arrière arc où s‘est déposée une série sédimentaire mio-pliocène reposant sur un substratum de nature et d‘origine variables spatialement. L'objectif de ce travail a consisté à analyser et modéliser le fonctionnement des systèmes pétroliers et à quantifier les volumes d‘hydrocarbures accumulés. Avant de procéder aux différentes modélisations numériques, stratigraphiques et thermiques, un modèle géologique conceptuel a été élaboré sur la base des données de géologie de terrain et de sismiques. La continuité terre- mer du socle kabyle a permis une extrapolation stratigraphique entre des formations oligo-miocènes en affleurement et les unités acoustiques définies dans le bassin offshore. L‘analyse tectonique dans les deux domaines a abouti à une évolution en trois phases : (1) syn-rift où le bassin a été ouvert en transtension à partir de l‘Oligocène supérieur-Aquitanien, (2) phase post-rift durant laquelle il y a eu le développement des bassins intra-arcs, la collision AlKaPeCa- Afrique et le magmatisme, (3) phase d‘inversion où la marge devient active essentiellement à partir du Quaternaire. En définissant l‘ensemble des éléments des systèmes pétroliers avec des incertitudes variables, la simulation du fonctionnement de ces derniers par modélisation de bassin 2D/3D a montré des possibilités d‘accumulation d‘huile et de gaz majoritairement près de la marge, entre 20 et 65 km de la côte avec un maximum de portée de 70 km dans le golfe de Bejaia. / The Algerian margin is a complex domain, limited to the south by the Maghrebian internal zones (AlKaPeCa) that overthrust the external Tellian zones southward. The offshore part of this system constitutes a back-arc basin, where a mio-pliocene sedimentary series were deposited over a substratum of laterally variable origin and nature. The goal of the present work consisted in analyzing and modelling the petroleum system at work and calculating hydrocarbon volumes. Before proceeding to different numerical basin, stratigraphic and thermal modelling, a conceptual geological model is required and was performed based on field geological studies and stratigraphic and structural interpretations of the seismic profiles. The extension of the continental crust beyond the foot of the margin, allows determining a chronostratigraphic model by extrapolation of the outcroping oligo-miocene formations onshore to the acoustic pre-messinian units defined in the offshore basin. Besides, a tectonic analysis in both onshore and offshore domains gave rise to three main steps of evolution: (1) syn-rift phase where the basin was opened by transtension since Late Oligocene- Aquitanian, (2) post-rift phase in which intra-arc basins were developed, AlKaPeCa and Africa docked and magmatism activity took place, (3) inversion phase where the margin became active mainly since Quaternary times. After defining the different petroleum system elements taking into account variable uncertainties, the 2D/3D petroleum system model depicts possibilities of oil and gas accumulations mainly close to the margin, between 20 to 65 km from the coastline to the north with a maximum range of 70 km in the Bejaia Gulf.