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An extensive multi-channel seismic dataset acquired between 1970 and 1990 by Oljeprospektering AB (OPAB) has recently been made available by the Geological Survey of Sweden (SGU). This thesis summarizes four papers, which utilize this largely unpublished dataset to improve our understanding of the geology and CO2 storage capacity of the Baltic and Hanö Bay basins in southern Sweden. A range of new processing workflows were developed, which typically provide an improvement in the final stacked seismic image, when compared to the result obtained with the original processing. A method was developed to convert scanned images of seismic sections into SEGY files, which allows large amounts of the OPAB dataset to be imported and interpreted using modern software. A new method for joint imaging of multiples and primaries was developed, which is shown to provide an improvement in signal to noise for some of the seismic lines within the OPAB dataset. For the first time, five interpreted regional seismic profiles detailing the entire sedimentary sequence within these basins, are presented. Depth structure maps detailing the Outer Hanö Bay area and the deeper parts of the Baltic Basin were also generated. Although the overall structure and stratigraphy of the basins inferred from the reprocessed OPAB dataset are consistent with previous studies, some new observations have been made, which improve the understanding of the tectonic history of these basins and provide insight into how the depositional environments have changed throughout time. The effective CO2 storage potential within structural and stratigraphic traps is assessed for the Cambrian Viklau, När and Faludden sandstone reservoirs. A probabilistic methodology is utilized, which allows a robust assessment of the storage capacity as well as the associated uncertainty. The most favourable storage option in the Swedish sector of the Baltic Basin is assessed to be the Faludden stratigraphic trap, which is estimated to have a mid case (P50) storage capacity of 3390 Mt in the deeper part of the basin, where CO2 can be stored in a supercritical phase.

Multicomponent seismic imaging techniques improve geological interpretation by providing crucial information about subsurface characteristics. These techniques deliver different images of the same subsurface using multiple waveforms. Compressional (P) and shear (S) waves respond to lithology and fluid variations differently, providing independent measurements of rock and fluid properties. Joint interpretation of multicomponent images requires P-wave and S-wave events to be aligned in depth. The process of identifying P and S events from the same reflector is called depth-registration. The purpose of this investigation is to illustrate procedures for depth-registering P and S seismic data when the most fundamental information needed for depth-registration – reliable velocity data – are not available. This work will focus on the depth-registration of a 9-component 3-dimensional seismic dataset targeting the Sycamore formation in Stephens County, Oklahoma. The survey area – 16 square miles – is located in Sho-Vel-Tum oilfield. Processed P-P, SV-SV, and SH-SH wave data are available for post-stack analysis. However, the SV-data volume will not be interpreted because of its inferior data-quality compared to the SH-data volume. Velocity data are essential in most depth-registration techniques: they can be used to convert the seismic data from the time domain to the depth domain. However, velocity data are not available within the boundaries of the 9C/3D seismic survey. The data are located in a complex area that is folded and faulted in the northwest part of the Ardmore basin, between the eastern Arbuckle Mountains and the western Wichita Mountains. Large hydrocarbon volumes are produced from stratigraphic traps, fault closures, anticlines, and combination traps. Sho-Vel-Tum was ranked 31st in terms of proved oil reserves among U.S. oil fields by a 2009 survey. I will interpret different depth-registered horizons on the P-wave and S-wave seismic data volumes. Then, I will present several methods to verify the accuracy of event-registration. Seven depth-registered horizons are mapped through the P-P and SH-SH seismic data. These horizons show the structural complexity that imposes serious challenges on well drilling within the Sho-Vel-Tum oil field. Interval Vp/Vs – a seismic attribute often used as lithological indicator – was mapped to constrain horizon picking and to characterize lateral stratigraphic variations. / text

Les modèles géologiques sont couramment utilisés pour estimer les ressources souterraines, pour faire des simulations numériques, et pour évaluer les risques naturels ; il est donc important que les modèles géologiques représentent la géométrie des objets géologiques de façon précise. La première étape pour construire un modèle géologique consiste souvent à interpréter des surfaces structurales, telles que les failles et horizons, à partir d'une image sismique ; les objets géologiques identifiés sont ensuite utilisés pour construire le modèle géologique par des méthodes d'interpolation. Les modèles géologiques construits de cette façon héritent donc les incertitudes d'interprétation car une image sismique peut souvent supporter plusieurs interprétations structurales. Dans ce manuscrit, j'étudie le problème de réduire les incertitudes d'interprétation à l'aide des données sismiques. Particulièrement, j'étudie le problème de déterminer, à l'aide des données sismiques, quels modèles sont plus probables que d'autres dans un ensemble des modèles géologiques cohérents. Ce problème sera connu par la suite comme "le problème d'évaluation des modèles géologiques par données sismiques". J'introduis et formalise ce problème. Je propose de le résoudre par génération des données sismiques synthétiques pour chaque interprétation structurale dans un premier temps, ensuite d'utiliser ces données synthétiques pour calculer la fonction-objectif pour chaque interprétation ; cela permet de classer les différentes interprétations structurales. La difficulté majeure d'évaluer les modèles structuraux à l'aide des données sismiques consiste à proposer des fonctions-objectifs adéquates. Je propose un ensemble de conditions qui doivent être satisfaites par la fonction-objectif pour une évaluation réussie des modèles structuraux à l'aide des données sismiques. Ces conditions imposées à la fonction-objectif peuvent, en principe, être satisfaites en utilisant les données sismiques de surface (« surface seismic data »). Cependant, en pratique il reste tout de même difficile de proposer et de calculer des fonctions-objectifs qui satisfassent ces conditions. Je termine le manuscrit en illustrant les difficultés rencontrées en pratique lorsque nous cherchons à évaluer les interprétations structurales à l'aide des données sismiques de surface. Je propose une fonction-objectif générale faite de deux composants principaux : (1) un opérateur de résidus qui calcule les résidus des données, et (2) un opérateur de projection qui projette les résidus de données depuis l'espace de données vers l'espace physique (le sous-sol). Cette fonction-objectif est donc localisée dans l'espace car elle génère des valeurs en fonction de l'espace. Cependant, je ne suis toujours pas en mesure de proposer une implémentation pratique de cette fonction-objectif qui satisfasse les conditions imposées pour une évaluation réussie des interprétations structurales ; cela reste un sujet de recherche. / Subsurface structural models are routinely used for resource estimation, numerical simulations, and risk management; it is therefore important that subsurface models represent the geometry of geological objects accurately. The first step in building a subsurface model is usually to interpret structural features, such as faults and horizons, from a seismic image; the identified structural features are then used to build a subsurface model using interpolation methods. Subsurface models built this way therefore inherit interpretation uncertainties since a single seismic image often supports multiple structural interpretations. In this manuscript, I study the problem of reducing interpretation uncertainties using seismic data. In particular, I study the problem of using seismic data to determine which structural models are more likely than others in an ensemble of geologically plausible structural models. I refer to this problem as "appraising structural models using seismic data". I introduce and formalize the problem of appraising structural interpretations using seismic data. I propose to solve the problem by generating synthetic data for each structural interpretation and then to compute misfit values for each interpretation; this allows us to rank the different structural interpretations. The main challenge of appraising structural models using seismic data is to propose appropriate data misfit functions. I derive a set of conditions that have to be satisfied by the data misfit function for a successful appraisal of structural models. I argue that since it is not possible to satisfy these conditions using vertical seismic profile (VSP) data, it is not possible to appraise structural interpretations using VSP data in the most general case. The conditions imposed on the data misfit function can in principle be satisfied for surface seismic data. In practice, however, it remains a challenge to propose and compute data misfit functions that satisfy those conditions. I conclude the manuscript by highlighting practical issues of appraising structural interpretations using surface seismic data. I propose a general data misfit function that is made of two main components: (1) a residual operator that computes data residuals, and (2) a projection operator that projects the data residuals from the data-space into the image-domain. This misfit function is therefore localized in space, as it outputs data misfit values in the image-domain. However, I am still unable to propose a practical implementation of this misfit function that satisfies the conditions imposed for a successful appraisal of structural interpretations; this is a subject for further research.

>Magister Scientiae - MSc / The North West Shelf of Australia is a prolific gas province. The Thebe Gas Field is situated within the northern central Exmouth Plateau in the Northern Carnarvon Basin. The Exmouth Plateau is a submerged continental block whose culmination lies at about 800m below sea level. The seismic data used for this study is the HEX07B survey which was conducted in 2007. The objective of this study was to interpret all available seismic data, of which six horizons were picked, generating two-way-time structure maps and an average velocity map, performing depth conversion and generating various depth maps. The horizons picked were the economic basement, Triassic Mungaroo, Murat Siltstone, Muderong Shale, Gearle Siltstone and the Sea Bed. The horizon of interest was the Triassic Mungaroo Formation and therefore it was the only horizon with an average velocity map. The seismic sections were used in conjunction with the structure maps generated to identify possible locations for appraisal wells to be drilled. Prospect X was identified on the basis of amplitude and structure present within the Triassic Mungaroo Formation. The final task was to calculate the volumes present and a Monte-Carlo Simulation was used for this. The results obtained showed that Prospect X has a good petroleum system in place. The Mungaroo Formation is identified as being the possible source and reservoir rock, the Muderong Shale is the seal, structural traps are provided by large fault block and faults provided the migration pathways from the source in to the reservoir. The volumes were calculated using three areas identified on the structure maps by three closing contours. These areas are the P90, P50, P10 and the volumes for the gas in place were as follows, P90 = 893 Bcf (0.9Tcf), P50 = 1128 Bcf (1.1 Tcf), P10 = 1367 Bcf (1.4Tcf). Using the various parameters the probability of success for Prospect X was calculated to be 20%.

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[pt] As falhas geológicas são estruturas tipicamente interpretadas em duas dimensões, como superfícies, nos dados sísmicos e da mesma maneira são representadas em modelos geológicos de reservatórios de petróleo. Entretanto, as falhas são zonas tridimensionalmente complexas que representam regiões de fraquezas que concentram fraturas e rochas altamente e heterogeneamente deformadas. Portanto, a representação adequada destas zonas é importante para o gerenciamento e avaliação econômica de um campo de petróleo, com impacto nas áreas de perfuração, completação e locação de poços, estratégias para aumento de fator de recuperação e até na estimativa da reserva recuperável. Devido a grande importância dos reservatórios carbonáticos fraturados, mais de 60 por cento das reservas provadas de óleo e 40 por cento das reservas de gás no mundo [1] estão presentes nesses reservatórios, o trabalho proposto tem como objetivo a modelagem geológica estrutural de uma falha em rochas carbonáticas do reservatório de Gawar da Arábia Saudita a partir de parâmetros de deformabilidade obtidos por Ameen et al. [2]. O trabalho também aborda os impactos da resolução espacial dos dados sísmicos na intepretação destas estruturas, através da simulação da imagem sísmica da falha. Os resultados mostram que o método de elemento discreto é uma ferramenta adequada para modelagem realística de falhas geológicas, entretanto, alguns modelos obtiveram resultados não realísticos devido à dificuldade da manutenção da tensão confinante durante a produção da falha. Os estudos mostraram que apesar da interpretação volumétrica destas estruturas através das metodologias de interpretação baseadas em atributos sísmicos serem possíveis, existe uma considerável limitação devido a resolução espacial e na dificuldade dos algoritmos em formar a imagem sísmica da zona de falha, onde há contraste lateral de propriedades acústicas. / [en] Faults are structures typically interpreted in two dimensions, such assurfaces, in seismic data and are similarly represented in geological models of oil reservoirs. However, faults are three-dimensionally complex zones that represent regions of weakness that concentrate fractures and highly heterogeneously deformed rocks. Therefore, the adequate representation of these zonesis important for the management and economic evaluation of an oil field, withan impact on the areas of drilling, completion and location of wells, strategies for increasing the recovery factor and even on estimating the recoverable reserve. Due to the great importance of fractured carbonate reservoirs, more than 60 percent of the proven oil reserves and 40 percent of the gas reserves in the world[1] are present in these reservoirs, the proposed work aims at the geomechanical modeling of a geological fault in carbonate rocks of Saudi Arabia s Gawar reservoir from deformability parameters obtained by Ameen et al. [2]. The work also addresses the impacts of the spatial resolution of seismic data on the interpretation of these structures, through the simulation of the fault seismic image. The results show that the discrete element method is an adequate tool for realistic modeling of geological faults, however, some models obtained unrealistic results due to the difficulty of maintaining the confining stress during fault production. The studies showed that although the volumetric interpretation of these structures through interpretation methodologies based on seismic attributes are possible, there is a considerable limitation due to the spatial resolution and the inadequacy of the seismic data to adequately deal with the lateral contrast of acoustic properties present in areas close to the damage zones.

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Les données de sismique réflexion sont une source d'information essentielle pour la modélisation tridimensionnelle des structures du sous-sol dans l'exploration-production des hydrocarbures. Ce travail vise à fournir des outils de visualisation pour leur interprétation. Les défis à relever sont à la fois d'ordre qualitatif et quantitatif. Il s'agit en effet de considérer (1) la nature particulière des données et la démarche d'interprétation (2) la taille des données. Notre travail s'est donc axé sur ces deux aspects : 1) Du point de vue qualitatif, nous mettons tout d'abord en évidence les principales caractéristiques des données sismiques, ce qui nous permet d'implanter une technique de visualisation volumique adaptée. Nous abordons ensuite l'aspect multimodal de l'interprétation qui consiste à combiner plusieurs sources d'information (sismique et structurale). Selon la nature de ces sources (strictement volumique ou volumique et surfacique), nous proposons deux systèmes de visualisation différents. 2) Du point de vue quantitatif, nous définissons tout d'abord les principales contraintes matérielles intervenant dans l'interprétation, ce qui nous permet d'implanter un système générique de gestion de la mémoire. Initialement destiné au couplage de la visualisation et des calculs sur des données volumiques massives, il est ensuite amélioré et spécialisé pour aboutir à un système dynamique de gestion distribuée de la mémoire sur cluster de PCs. Cette dernière version, dédiée à la visualisation, permet de manipuler des données sismiques à échelle régionale (100-200 Go) en temps réel. Les problématiques sont abordées à la fois dans le contexte scientifique de la visualisation et dans le contexte d'application des géosciences et de l'interprétation sismique / Seismic reflection data are a valuable source of information for the three-dimensional modeling of subsurface structures in the exploration-production of hydrocarbons. This work focuses on the implementation of visualization techniques for their interpretation. We face both qualitative and quantitative challenges. It is indeed necessary to consider (1) the particular nature of seismic data and the interpretation process (2) the size of data. Our work focuses on these two distinct aspects : 1) From the qualitative point of view, we first highlight the main characteristics of seismic data. Based on this analysis, we implement a volume visualization technique adapted to the specificity of the data. We then focus on the multimodal aspect of interpretation which consists in combining several sources of information (seismic and structural). Depending on the nature of these sources (strictly volumes or both volumes and surfaces), we propose two different visualization systems. 2) From the quantitative point of view, we first define the main hardware constraints involved in seismic interpretation. Focused on these constraints, we implement a generic memory management system. Initially able to couple visualization and data processing on massive data volumes, it is then improved and specialised to build a dynamic system for distributed memory management on PC clusters. This later version, dedicated to visualization, allows to manipulate regional scale seismic data (100-200 GB) in real-time. The main aspects of this work are both studied in the scientific context of visualization and in the application context of geosciences and seismic interpretation

L’architecture crustale et l’évolution de la partie profonde des marges passives peu-magmatiques sont encore mal comprises. En prenant comme chantier principal les marges Australie-Antarctique, cette thèse montre que l’enregistrement de la déformation dans les sédiments met en évidence une évolution polyphasée des marges distales. Cette évolution polyphasée implique le développement de multiples systèmes de détachement présentant une organisation hors-séquence et menant à une architecture finale symétrique des domaines exhumés. Cette organisation des systèmes de failles est liée à des cycles de délocalisation / relocalisation de la déformation influencés par l’apport magmatique, par un niveau de découplage et par la remontée asthénosphérique. L’interaction faille / magma apparait particulièrement importante dans l’évolution des marges distales. Cette étude a permis de mieux caractériser la rupture lithosphérique, qui peut se définir comme un événement tectono-magmatique progressif. / The crustal architecture and evolution of the deepest part of magma-poor rifted margins is currently not well understood. Taking the Australia-Antarctica margins as main study area, this thesis shows that the record of the deformation in sediments highlights a clear polyphase evolution of distal margins. This polyphase evolution implies the development of multiple detachment systems presenting an out-of-sequence organization and leading to a final symmetric architecture of the exhumed domains. This organization of fault systems is linked to cycles of delocalisation / re-localisation of the deformation influenced by the magmatic supply, by a decoupling level and by the asthenospheric uplift. Fault / magma interaction appears particularly important during the evolution of distal margins. This study allowed a better characterization of the lithospheric breakup, which can be defined as a progressive tectono-magmatic event.