This thesis addresses a few specific issues in the use of wide azimuth P-wave seismic data for fracture detection based on numerical modelling and real data. These issues include the seismic response of discrete fractures, the effects of anticline and uncertainties in real data analysis. For this, I implemented the finite difference scheme for modelling the seismic response in 3D fractured media; appropriate approaches are then selected to study discrete fracture models and the effect of the anticline with 3D seismic modelling, followed by an integrate real case study. Finite difference (FD) is widely used in seismic modelling. There are three FD schemes described in this thesis, the standard staggered grid (SSG), the rotated staggered grid (RSG), and the diamond staggered grid (DSG). Both qualitative and quantitative comparison has been made to reveal their capability in modelling 3D fractured media. The SSG has shown best performance for anisotropic media with orthorhombic symmetry or higher symmetry system. For lower anisotropy symmetry, the DSG is preferred than the RSG in terms of computation efficiency. A new solution to the diamond grid issue is developed which can simplify the DSG implementation, and an optimized workflow is proposed to simulate large 3D fractured models. The SSG scheme is implemented in three dimensions and it provides a useful tool for various practical modelling studies. With the above tool, two modelling studies have been carried out, on the effects of the discrete fractures and of the presence of anticline: the Discrete Fracture Model (DFM) study provides many insights into seismic response of discrete fracture and the link between the discrete fractures and aligned micro cracks, as well as the features in scattering waves. The modelling results demonstrate that, P-wave seismic anisotropy increases with the decrease of discrete fracture spacing, and different spacing leads to different patterns in scattering waves. The study also reveals the azimuthal AVO variation on the top of discrete fracture layer, which is similar to that we find in homogenous anisotropic media. The study of the anticline structure with vertical fractures, which is built with the parameters from a real case, is to assess the anticline structure effect on fracture parameter inversion based on the Singular Value Decomposition (SVD) method. The fracture density can be resolved accurately at the top of the anticline, whilst that on the flanks tends to be over-estimated. The results also indicate that the SVD method is a reliable approach for directly estimating the fracture density. P-wave azimuthal attributes are commonly employed to invert fracture density and orientation. Many factors may affect the accuracy of the inversion results. The integrated study in this thesis shows that azimuthal coverage, offset-depth ratio, data quality and geological structures all affect the final prediction, and different attributes shows different sensitivities to these factors. Furthermore, the combined analysis of both geological observation and pre- and post-stack seismic attributes can reduce the uncertainties for fracture detection.

Although levee deposits make up a significant part of modern and ancient deep-marine slope systems, details of their internal lithological composition and stratal architecture remain poorly documented. At the Castle Creek study area, strata of the Neoproterozoic Isaac Formation (Windermere Supergroup) crop out superbly in a kilometre-scale section through a sinuous deep-water channel-levee system (ICC3). Levee deposits near the outer bend of the channel consist of sandstone-rich (sandstone-to-mudstone ratio of 68:42), medium- to thick-bedded turbidites interstratified with thinly-bedded turbidites. Structureless sandstone (Ta), planar laminated sandstone (Tb), non-climbing ripple cross-stratified sandstone (Tc) and massive and laminated siltstone (Td) are common. Thick beds generally thicken and then thin and fine laterally over about 300 m. Thin-bedded strata, in contrast, thin and fine negligibly over similar distances. In the distal part of the outer-bend levee (up to 700 m laterally away from the channel) strata consist predominantly of thin-bedded Tcd turbidites with a much lower sandstone-to-mudstone ratio (35:65). On the opposite side of the channel, inner-bend levee deposits are mudstone-rich, locally as low as 15:85, and consist mostly of thin-bedded, Tcd turbidites, although thicker-bedded, Ta-d turbidites are more common in the lower part of the section. Lateral thinning and fining of beds is more rapid than their outer-bend counterpart. Levee deposits of ICC3 comprise three stacked decametre-scale upward-thinning and -fining successions. Each is interpreted to record a depositional history consisting of lateral channel migration, levee deposition, channel filling, and distal levee deposition. During the early stage of increasing levee relief it is proposed that the termini of individual beds progressively backstep towards the channel margin resulting in an overall lateral thinning of the stratal profile. This interpretation notably contrasts the common assumption that levee morphology is the result of the vertical stacking of beds that dip. In addition to field studies, laboratory experiments were conducted to determine the depositional threshold of non-climbing ripple cross-stratification, which is common in levee strata of ICC3. It was determined that non-climbing ripples form when bed aggradation rates are less than 0.015 cm/sec, and most probably in flows made up of poorly sorted sediment.

Although levee deposits make up a significant part of modern and ancient deep-marine slope systems, details of their internal lithological composition and stratal architecture remain poorly documented. At the Castle Creek study area, strata of the Neoproterozoic Isaac Formation (Windermere Supergroup) crop out superbly in a kilometre-scale section through a sinuous deep-water channel-levee system (ICC3). Levee deposits near the outer bend of the channel consist of sandstone-rich (sandstone-to-mudstone ratio of 68:42), medium- to thick-bedded turbidites interstratified with thinly-bedded turbidites. Structureless sandstone (Ta), planar laminated sandstone (Tb), non-climbing ripple cross-stratified sandstone (Tc) and massive and laminated siltstone (Td) are common. Thick beds generally thicken and then thin and fine laterally over about 300 m. Thin-bedded strata, in contrast, thin and fine negligibly over similar distances. In the distal part of the outer-bend levee (up to 700 m laterally away from the channel) strata consist predominantly of thin-bedded Tcd turbidites with a much lower sandstone-to-mudstone ratio (35:65). On the opposite side of the channel, inner-bend levee deposits are mudstone-rich, locally as low as 15:85, and consist mostly of thin-bedded, Tcd turbidites, although thicker-bedded, Ta-d turbidites are more common in the lower part of the section. Lateral thinning and fining of beds is more rapid than their outer-bend counterpart. Levee deposits of ICC3 comprise three stacked decametre-scale upward-thinning and -fining successions. Each is interpreted to record a depositional history consisting of lateral channel migration, levee deposition, channel filling, and distal levee deposition. During the early stage of increasing levee relief it is proposed that the termini of individual beds progressively backstep towards the channel margin resulting in an overall lateral thinning of the stratal profile. This interpretation notably contrasts the common assumption that levee morphology is the result of the vertical stacking of beds that dip. In addition to field studies, laboratory experiments were conducted to determine the depositional threshold of non-climbing ripple cross-stratification, which is common in levee strata of ICC3. It was determined that non-climbing ripples form when bed aggradation rates are less than 0.015 cm/sec, and most probably in flows made up of poorly sorted sediment.

Nowadays, subsalt oil and gas exploration is drawing more and more attention from the hydrocarbon industry. Hydrocarbon exploitation requires detailed geological information beneath the surface. Seismic imaging is a powerful tool employed by the hydrocarbon industry to provide subsurface characterization and monitoring information. Traditional wave-equation migration algorithms are based on the one- way-in-depth propagation using the scalar wave equation. These algorithms focus on downward continuing the upcoming waves. However, it is still really difficult for conventional seismic imaging methods, which have dip limitations, to get a correct image for the edge and shape of the salt body and the corresponding subsalt structure. The dip limitation problem in seismic imaging can be solved completely by switching to Reverse-Time Migration (RTM). Unlike old methods, which deal with the one-way wave equation, RTM propagator is two-way and, as a result, it no longer imposes dip limitations on the image. It can also handle complex waveforms, including prismatic waves. Therefore it is a powerful tool for subsalt imaging. RTM involves wave extrapolation forward and backward in time. In order to accurately and efficiently extrapolate the wavefield in heterogeneous media, I develop three novel methods for seismic wave modeling in both isotropic and tilted transversely isotropic (TTI) media. These methods overcome the space-wavenumber mixed-domain problem when solving the acoustic two-way wave equation. The first method involves cascading a Fourier Transform operator and a finite difference (FD) operator to form a chain operator: Fourier Finite Differences (FFD). The second method is lowrank finite differences (LFD), whose FD schemes are derived from the lowrank approximation of the mixed-domain operator and are represented using adapted coefficients. The third method is lowrank Fourier finite differences (LFFD), which use LFD to improve the accuracy of TTI FFD mothod. The first method, FFD, may have an advantage in efficiency, because it uses only one pair of multidimensional forward and inverse FFTs (fast Fourier transforms) per time step. The second method, LFD, as an accurate FD method, is free of FFTs and in return more suitable for massively parallel computing. It can also be applied to the FFD method to reduce the dispersion in TTI case, which results in the third method, LFFD. LFD and LFFD are based on lowrank approx- imation which is a general method to handle mixed-domain operators and can be easily applied to more complicated mixed-domain operators. I show pseudo-acoustic modeling in orthorhombic media by lowrank approximation as an example. / text

Although levee deposits make up a significant part of modern and ancient deep-marine slope systems, details of their internal lithological composition and stratal architecture remain poorly documented. At the Castle Creek study area, strata of the Neoproterozoic Isaac Formation (Windermere Supergroup) crop out superbly in a kilometre-scale section through a sinuous deep-water channel-levee system (ICC3). Levee deposits near the outer bend of the channel consist of sandstone-rich (sandstone-to-mudstone ratio of 68:42), medium- to thick-bedded turbidites interstratified with thinly-bedded turbidites. Structureless sandstone (Ta), planar laminated sandstone (Tb), non-climbing ripple cross-stratified sandstone (Tc) and massive and laminated siltstone (Td) are common. Thick beds generally thicken and then thin and fine laterally over about 300 m. Thin-bedded strata, in contrast, thin and fine negligibly over similar distances. In the distal part of the outer-bend levee (up to 700 m laterally away from the channel) strata consist predominantly of thin-bedded Tcd turbidites with a much lower sandstone-to-mudstone ratio (35:65). On the opposite side of the channel, inner-bend levee deposits are mudstone-rich, locally as low as 15:85, and consist mostly of thin-bedded, Tcd turbidites, although thicker-bedded, Ta-d turbidites are more common in the lower part of the section. Lateral thinning and fining of beds is more rapid than their outer-bend counterpart. Levee deposits of ICC3 comprise three stacked decametre-scale upward-thinning and -fining successions. Each is interpreted to record a depositional history consisting of lateral channel migration, levee deposition, channel filling, and distal levee deposition. During the early stage of increasing levee relief it is proposed that the termini of individual beds progressively backstep towards the channel margin resulting in an overall lateral thinning of the stratal profile. This interpretation notably contrasts the common assumption that levee morphology is the result of the vertical stacking of beds that dip. In addition to field studies, laboratory experiments were conducted to determine the depositional threshold of non-climbing ripple cross-stratification, which is common in levee strata of ICC3. It was determined that non-climbing ripples form when bed aggradation rates are less than 0.015 cm/sec, and most probably in flows made up of poorly sorted sediment.

Les systèmes sédimentaires carbonatés forment à la fois des archives géologiques uniques des changements globaux-locaux des enveloppes externes de la Terre et renferment plus de 75 % des réserves d'hydrocarbure conventionnelles. Ils sont complexes et très difficiles à comprendre et à prédire. Cette complexité à toutes les échelles spatio-temporelles rend nécessaire l'intégration de méthodes naturalistes et quantitatives pour les étudier. La modélisation numérique basée processus permet de réduire les incertitudes des prédictions des propriétés des réservoirs carbonatés.Le manuscrit présente une méthode de modélisation itérative des systèmes carbonatés de la stratigraphie à la sismique en intégrant la diagenèse. Cette approche est basée sur le couplage de plusieurs outils numériques et par une démarche de travail combinant la sédimentologie, la diagenèse, la physique des roches et la simulation sismique.L’approche de modélisation développée permet ainsi d’intégrer un grand nombre de données multi-échelles et multidisciplinaire au sein d’un modèle facilement partageable entre toutes les disciplines en géosciences. L’intégration de ces nombreuses données est facilitée par un continuum du modèle entre les différentes échelles d’espace et de temps (du bassin au réservoir). La sismique synthétique ainsi obtenue n’est pas une simple convolution géométrique, elle intègre les propriétés sédimentologiques et diagénétiques, permettant une analyse de la signification stratigraphique des réflecteurs sismiques. Cette approche innovante intègre les méthodes naturalistes et quantitatives nécessaires à la compréhension et à la prédiction des systèmes carbonatés. / Carbonate sedimentary systems record both global and local geological changes of the outer envelope of the Earth and contain more than 75% of conventional hydrocarbon reserves. These carbonate systems show a great complexity at every spatial and temporal scales. To increase our ability to understand and predict such intricate natural systems, it is necessary to integrate naturalistic and quantitative methodological apporaches. Numerical process-based modeling (stratigraphic-sedimentary-diagenetic) reduces the uncertainty of prediction of carbonate reservoir properties. The manuscript presents a method of iterative modeling of carbonate systems from stratigraphy to seismic by integrating diagenesis. This approach is based on the coupling of numerical tools and a working approach combining sedimentology, diagenesis, rock physics and seismic simulation. Tests on case studies associated with scientific and industrial issues validated the method.The modeling approach that was developed during the thesis allows to integrate a large number of multi-scale and multidisciplinary data. Models can easily be shared between the disciplines of geosciences. The model continuum along different scales of space (from the basin to the reservoir) and time eases the integration of various data. The obtained synthetic seismic is not a simple geometric convolution, but an integration of sedimentological and diagenetic properties, which allows for an analysis of the stratigraphic significance of the seismic reflectors. This innovative approach integrates naturalistic and quantitative methods, which improve the understanding and prediction of carbonate systems and reservoirs.

Although levee deposits make up a significant part of modern and ancient deep-marine slope systems, details of their internal lithological composition and stratal architecture remain poorly documented. At the Castle Creek study area, strata of the Neoproterozoic Isaac Formation (Windermere Supergroup) crop out superbly in a kilometre-scale section through a sinuous deep-water channel-levee system (ICC3). Levee deposits near the outer bend of the channel consist of sandstone-rich (sandstone-to-mudstone ratio of 68:42), medium- to thick-bedded turbidites interstratified with thinly-bedded turbidites. Structureless sandstone (Ta), planar laminated sandstone (Tb), non-climbing ripple cross-stratified sandstone (Tc) and massive and laminated siltstone (Td) are common. Thick beds generally thicken and then thin and fine laterally over about 300 m. Thin-bedded strata, in contrast, thin and fine negligibly over similar distances. In the distal part of the outer-bend levee (up to 700 m laterally away from the channel) strata consist predominantly of thin-bedded Tcd turbidites with a much lower sandstone-to-mudstone ratio (35:65). On the opposite side of the channel, inner-bend levee deposits are mudstone-rich, locally as low as 15:85, and consist mostly of thin-bedded, Tcd turbidites, although thicker-bedded, Ta-d turbidites are more common in the lower part of the section. Lateral thinning and fining of beds is more rapid than their outer-bend counterpart. Levee deposits of ICC3 comprise three stacked decametre-scale upward-thinning and -fining successions. Each is interpreted to record a depositional history consisting of lateral channel migration, levee deposition, channel filling, and distal levee deposition. During the early stage of increasing levee relief it is proposed that the termini of individual beds progressively backstep towards the channel margin resulting in an overall lateral thinning of the stratal profile. This interpretation notably contrasts the common assumption that levee morphology is the result of the vertical stacking of beds that dip. In addition to field studies, laboratory experiments were conducted to determine the depositional threshold of non-climbing ripple cross-stratification, which is common in levee strata of ICC3. It was determined that non-climbing ripples form when bed aggradation rates are less than 0.015 cm/sec, and most probably in flows made up of poorly sorted sediment.

L’amélioration des images sismiques peut aider à mieux contraindre l’exploration deshydrocarbures. Les ondes élastiques qui se propagent dans la Terre peuvent être classifiéescomme ondes de volume et ondes de surface. Si ces dernières sont les plus énergétiques,seules les ondes de volume sont couramment considérées comme des signaux utiles.Cependant, les ondes de surface sont utiles pour caractériser la proche sub-surface.Classiquement, les ondes de surface sont analysées dans des contextes de propriétésélastiques localement 1D.Nous proposons une modification de l’inversion des formes d’onde classique pourreconstruire des profils de propriétés 2D (la windowed-Amplitude Waveform Inversion, w-AWI). La w-AWI est spécialement robuste en ce qui concerne le choix du modèle initial.Nous appliquons la w-AWI aux données synthétiques ainsi qu’aux données réelles, montrantque cette approche permet de récupérer des propriétés 2D. / High-resolution seismic imaging is essential to improve results of hydrocarbon exploration.Elastic waves propagate in the Earth as body and surface waves, the latter being the mostenergetic ones. Body waves are preferred for exploration seismic imaging while surfacewaves are usually considered to be noise. However, it has been recognised that the nearsurface can be characterised by analysing surface waves and that such result may improvethe outcome of body-wave processing. Currently, surface waves analysis leads to retrievelocal 1D property profiles.We propose a waveform-based inversion procedure to derive 2D velocity models fromsurface waves. This method consists of a misfit functional modification of classical FullWaveform Inversion and we call it windowed-Amplitude Waveform Inversion (w-AWI). Weshow that w-AWI is robust regarding the choice of initial velocity model. We apply w-AWI tosynthetic and real data obtaining encouraging near-surface imaging results

Dans le bassin d’avant-pays sud-pyrénéen, la continuité exceptionnelle des environnements de dépôts du complexe deltaïque éocène moyen du Sobrarbe permet d’observer l’architecture stratigraphique et sédimentaire d’un système fluvio-deltaïque syntectonique à différents échelles. L’objectif principal de cette étude est de déterminer l’origine des facteurs allogéniques et/ou autogéniques contrôlant la géométrie et la répartition des dépôts d’un tel système sédimentaire en contexte compressif, dans le but de pouvoir le comparer à d’autres systèmes deltaïques accumulés dans des contextes géologiques différents. Cette étude est basée sur l’acquisition d’une cartographie géologique détaillée et d’une soixantaine de logs sédimentologiques. La base de données est complétée par une actualisation de données chronostratigraphiques issues de la littérature, l’acquisition de données magnétostratigraphiques. L’analyse sédimentologique et stratigraphique du système sédimentaire aboutit à une description précise des géométries, des faciès et des processus physiques caractérisant les différents environnements de dépôt répartis au sein de deux modèles sédimentaires : un système fluvio-deltaïque de forte énergie développé pendant les phases progradantes, un système mixte gréso-carbonaté de basse énergie caractérisant les phases aggrado-progradantes et transgressives. L’analyse de trois transects de corrélation, d’orientation proximale-distale, a permis la distinction de trois ordres de séquence imbriqués : les séquences de cinquième ordre, les séquences de quatrième ordre et les séquences de troisième ordre. L’organisation complexe des différents cortèges de dépôts des séquences de quatrième et de troisième ordre reflète des variations d’accommodation provoquées principalement par les déformations structurales de différentes longueurs d’onde, secondairement par les variations eustatiques. Une analyse poussée des cortèges de dépôts permet une discussion sur les interrelations entre les trois paramètres majeurs qui contrôlent la dynamique du système sédimentaire dans le temps et dans l’espace: les variations du taux d’accommodation, du flux sédimentaire et l’influence des processus sédimentaires. Ces éléments fournissent des informations semi-quantitatives sur l’accumulation sédimentaire au sein des différents environnements de dépôt (source to sink). La synthèse des résultats aboutit à la reconstruction séquentielle de la paléogéographique du complexe deltaïque du Sobrarbe. Enfin; l’analyse de la subsidence du bassin d’Ainsa a permis de reconstituer l’évolution de la sédimentation et du bassin sédimentaire entre le Lutétien et l’Oligocène. Une étude intégrée affleurement-modélisation sismique synthétique-analogue réel de subsurface fournit une combinaison de données architecturales et dimensionnelles, qui est utilisée pour améliorer les interprétations sismiques des systèmes réservoirs fluvio-deltaïques. De telles études réduisent considérablement les incertitudes associées à la résolution des données de subsurface, ce qui permet une meilleure évaluation économique des réservoirs. / In the South-Pyrenean foreland basin, the exceptional continuity of middle Eocene Sobrarbe deltaic complex deposit environments allows to observe the stratigraphic and sedimentary architecture of a syntectonic river-dominated delta system at different scales. The main objective of this study is to determine the origin of allogenic and/or autogenic factors that control the distribution of deposits of such sedimentary system in a compressive setting, in order to compare it to other deltaic systems that accumulate in different geological contexts. This study is based on the acquisition of detailed geological mapping and about sixty measured sections. The database is complemented by updating chronostratigraphic data from the literature and additional magnetostratigraphic data. Sedimentological and stratigraphic analysis of the sedimentary system leads to an accurate description of geometry, facies and physical processes of different depositional environments distributed along two sedimentary models: a high energy river-delta system developed during progradational phases, a low energy mixed siliciclastic-carbonate system characterizing the aggrado-progradational and transgressive phases. Three dip sections analysis allows the identification of three nested order sequence: fifth-order sequences, fourth-order sequences and third-order sequences. The complex organization of fourth and third-order sequences systems tracts reflects accommodation variations caused mainly by structural deformation at different scales, secondary by eustatic changes. An advanced systems tract analysis leads a discussion of interrelationships between three main parameters that control the dynamics in time and space of sedimentary system: changes in the accommodation rate, sediment input and the influence of sedimentary processes. These elements provide semi-quantitative information regarding to the sediment accumulation within the different depositional environments (source to sink). Summary of results leads to the sequential reconstruction of the Sobrarbe deltaic complex paleogeography. Subsidence analysis of the Ainsa basin permits to reconstruct the sedimentation and sedimentary basin evolution from Lutetian to Oligocene times. An integrated study of outcrop-forward seismic modelling-real seismic analog provides an architectural and dimensional data combination used to improve seismic interpretation of river-deltaic reservoir systems. Such studies greatly reduce the uncertainties associated with the resolution of subsurface data, enabling better economic assessment of reservoirs. / En la cuenca de antepais surpirenaica, la continuidad extraordinaria de los ambientes de deposito del complejo deltaico eoceno medio del Sobrarbe permite la observacion de la arquitectura estratigrafica y sedimentaria de un sistema fluvio-deltaico sintectonico a diferentes escalas. El objetivo principal del estudio presentado es la determinacion del origen de los factores alogenicos y/o autogenicos que controlan la distribucion de los depositos de dicho sistema sedimentario en contexto compresivo, para poder compararlo con otros sistemas deltaicos acumulados en contextos geologicos diferentes. Este estudio se basa en la adquisicion de una cartografia geologica detallada y de una sesentena de columnas sedimentarias. La base de datos se completa mediante la actualizacion de los datos cronoestratigraficos originarios de la literatura y la adquisicion puntual de datos magnetoestratigraficos. El analisis sedimentologico y estratigrafico del sistema sedimentario ha dado lugar a una descripcion exacta de las geometrias, las facies, y de los procesos fisicos que caracterizan los diferentes ambientes de depositos dentro de dos modelos sedimentarios: un sistema fluvio-deltaico de alta energia desarrollado durante fases progradantes, un sistema mixto detritico-carbonatado caracterizando fases agrado-progradantes y transgresivas. El analisis de tres paneles de correlacion, de orientacion proximal-distal, ha permitido la distincion de tres ordenes de secuencialidad: secuencias de quinto orden, de cuarto orden y de tercer orden. La organizacion compleja de diferentes cortejos de deposito de secuencias de cuarto y tercer orden refleja variaciones de acomodacion provocadas principalmente por la deformacion estructural a diferentes escalas y por variaciones eustaticas. Un analisis detallado de los cortejos sedimentarios permite una discusion sobre interrelaciones entre los tres parametros mayores que controlan la dinamica del sistema sedimentario en el espacio y en el tiempo: las variaciones de la tasa de acomodacion, del flujo sedimentario y la influencia de procesos sedimentarios. Dichos elementos proporcionan informacion semicuantitativa sobre la acumulacion sedimentaria en los ambientes de deposito (source to sink). La sintesis de los resultados llega a la reconstruccion de la paleogeografia del complejo deltaico del Sobrarbe. Finalmente, el analisis de la subsidencia de la cuenca de Ainsa ha permitido de reconstruir la evolucion de la sedimentacion y de la cuenca sedimentaria entre el Luteciense y el Oligoceno. Un estudio integrado afloramiento-modelizacion sismica sintetica-analogo real de subsuelo proporciona una combinacion de datos arquitecturales y dimensionales util para mejorar interpretaciones sismicas de sistemas reservorios fluvio-deltaicos. Dichos estudios reducen de manera considerable incertidumbres asociadas a la resolucion de los datos de subsuelo, lo que permite una mejor evaluacion economica de los reservorios.