Understanding the nature of mud volcanism, mechanisms of formation, types of eruptions and their relationship to the hydrocarbon systems provides important information about subsurface conditions and geological processes within the South Caspian Basin. A 2D seismic grid in southeastern offshore Azerbaijan is used to define the areal distribution of mud volcanoes and to make a classification of the mud volcanoes based on characteristic seismic features. As a result detailed database for each determined mud volcano is constructed. Analysis of different parameters from this database shows that there is a high concentration of mud volcanoes at the southern part of the study area. It is coincides with the distribution of the subsurface structures within the basin. Mud volcanoes with low relief (several tens of meters) are mainly concentrated in the northeast. Conversely, mud volcanoes with large vertical relief (greater than 200 m) are clustered in the southwest part of the basin. Mud volcano development in the South Caspian Basin is generally linked to faults, which in some instances are detached at the basement level. By using interpreted seismic surfaces it is possible to determine relative time of mud flows from the mud volcanoes. Timing of mud flows reveals to the actual activity of the mud volcanoes and it gives valuable information about possible mechanism of mud volcanism within the South Caspian Basin. Previous studies of the onshore mud volcanoes in Azerbaijan and the results from current work conclude that mud volcano formation within the South Caspian Basin is mainly controlled by tectonic forces and overpressured sediments. Mud volcano activity is not always related to the Maykop organic reach shale succession. It can occur at shallow depths by pressure breakthrough from any stratigraphic zone.

Univ., Diss.--Bremen, 2006.

This thesis investigates three problems in the general area of environmental fluid mechanics. The first two problems are related to liquid or gas flow through clay-water suspensions, with relevance for the underground storage of radioactive waste and also for understanding the mechanism of eruption in mud volcanoes. The third problem centres on the different problem of mixing in a turbulent buoyant plume. First, the injection of gas and water from a central source into a two-dimensional layer of clay confined between two circular horizontal plates is investigated. This provides a model of the potential pressurisation and failure of the seal rock around a radioactive waste repository as may arise if gas is continuously generated in the repository. As the gas injection pressure is gradually increased the cell walls deform and the clay moves radially outwards. However, at a critical radius, the liquid-clay interface becomes unstable and a series of channels propagate through the clay. When one of the channels reaches the edge of the domain the gas escapes and the pressure is released. As a result, the domain relaxes by elastic deformation and the clay seals the channel. In this way, continuous fluid injection leads to episodic release of gas from the cell. The second problem concerns the flow of mud along a vertical conduit driven by the combined effect of reservoir pressure and buoyancy associated with the gas injected at the base of the conduit. This represents an analogue model of the eruption of a mud volcano, in which mud rises from a deep reservoir to the surface. I find that the pressure associated with the reservoir and any buoyancy force produced by the migration of gas from deep in the reservoir to the surface leads to a continuous eruption if the net pressure is greater than the yield stress of the clay. If the reservoir pressure falls during such an event, the eruption will eventually stop, once the pressure reaches a dynamic yield stress condition. Only later, if the reservoir pressure increases to the static yield stress of the clay will the eruption start again, and this can lead to a series of eruption cycles which depend on the non-Newtonian rheology of the clay. In contrast, if this pressure is smaller than the yield stress of the clay, a series of episodic gas burst events can occur until the conduit is cleared of mud. The third problem relates to the mixing in a turbulent buoyant plume. Through a series of new experiments and some complementary theoretical modelling I show that the mixing in a turbulent plume is strongly affected by the eddies and leads to significant longitudinal dispersion in the flow. The implications of the modelling for determining the residence time distribution of the fluid in the plume is discussed.

Depuis le début des années 80, les progrès technologiques de l'imagerie des fonds marins et l'exploration des marges continentales ont permis de découvrir et d'étudier de nombreuses morphologies du fond marin témoignant de la circulation des fluides dans la colonne sédimentaire et de leur expulsion. Dans cette étude des volcans de boue, nous proposons une méthode d'analyse innovante combinant une approche statistique automatisée incluant la détection et l'analyse de paramètres morphométriques avec une étude géologique classique. Nous avons utilisé un vaste jeu de données de géophysiques marines et géologiques, d’origines académiques et industrielles, à l’échelle du bassin oriental de la mer Méditerranée.Il ressort de cette analyse que le mécanisme de formation des volcans de boue est directement lié à une contrainte locale ou régionale pouvant avoir une origine tectonique ou gravitaire.Différents paramètres géologiques conditionnant les dimensions et formes des volcans de boue ont été étudiés permettant de proposer un modèle original de leur formation. La conception de ce modèle, qui se veut générique, permet de regrouper les paramètres constitutifs d’un système de volcan de boue en trois étapes spatiales, depuis la couche source jusqu’à l’expression superficielle. / Since the early 80s, technological advances of seabed imagery and exploration of continental margins allowed to discover and study numerous seabed features recording fluid circulation within the sediment column.In this study of mud volcanoes, we propose an innovative method of analysis combining an automated statistical approach including detection and analysis of morphometric parameters together with a classical geological study. We used broad homogenous academic and industrial marine geophysical and geological dataset, at the scale of Eastern Mediterranean sea.The analysis of these parameters shows that the mechanism of formation of the mud volcanoes is directly related to a local or regional constrain that may have a tectonic or gravitational origin.Various geological parameters conditioning the size and shape of mud volcanoes have been studied and lead to propose an original model for the formation of mud volcanoes. The design of this model, which is intended to be generic, makes it possible to group the constituent parameters of a mud volcano system in three spatial stages, from the source layer to the superficial expression.

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