In petroleum engineering and geophysics, it is often assumed that the rocks are completely rigid bodies with a totally interconnected pore space and that the fluid within the pores does not affect and are independent of the strains in the porous media. These assumptions are often not accurate and also unrealistic because the pore pressure effects are of great importance in all of the geomechanical processes occurring in the subsurface. The hydraulic and mechanical processes are coupled so that the rock deformation causes pore pressure changes and fluid flow (displacement relative to the solid). The time- dependent coupling of the hydraulic and mechanical processes can be described by the theory of poroelasticity. Application of this theory requires the availability of material parameters through experiments. In this work, the main poroelastic parameters are determined for some rock types of interest. The focus of this work is concentrated in low porosity rocks that are commonly encountered. Experimental procedures under drained, undrained and unjacketed conditions were initially completed in Berea Sandstone. Then, Indiana Limestone, Westerly Granite and Welded Tuff specimens were tested in order to obtain Skempton’s pore pressure parameter B, Biot’s coefficient of effective stress α, Bulk Modulus and Grain compressibility. Preliminary results suggest that the parameters B, K and α will change in accordance to the permeability and the porosity of the rock, while K_(S) would depend more on the mineralogy and deposition characteristics of the rock.

Cette thèse presente des travaux et résultats d'expériences de fracturation dont l'origine est une génération interne de fluides induite par des réactions chimiques dans des échantillons de roches et des matériaux analogues. Les deux premiers articles portent sur une expérience avec des échantillons de schistes imagés par tomographie aux rayons X au cours du temps. Le premier article décrit la formation de fractures créées par l'augmentation de pression induite par la décomposition de matière organique lorsque les schistes sont chauffés. Le deuxième article porte sur la procédure expérimentale et l'analyse d'images, utilisées pour obtenir les résultats du premier article. Les deux autres articles concernent la fracturation d'une couche de gélatine contenant de la levure et du sucre, ce qui génère du CO2. Le troisième article décrit le mécanisme de formation d'un réseau de fractures au cours du drainage du CO2 contenu dans la gélatine. Le quatrième article concerne l'évolution du réseau de fractures au cours de ce drainage, ainsi que les mécanismes d'ouverture et fermeture des fractures. Le dernier article porte sur une étude par tomographie aux rayons X de la distribution de porosité d'échantillons endommagés d'andésite. Les méthodes développées dans ce projet peuvent s'appliquer à la déshydratation de sédiments, la formation de volcans de boue, l'exploration d'hydrates de méthane, la séquestration de CO2 et la fracturation de réservoirs non conventionnels. / This thesis presents the experimental work and the results on fracturing of rock samples and analogue materials due to internal fluid generation during chemical reaction. The first two papers concentrate on time-resolved 3D X-ray imaging experiment on organic-rich shale samples. Paper 1 describes fracture formation due to hydrocarbon generation in the shale induced by organic matter decomposition during heating. Paper 2 gives an overview of the experimental procedure and image analysis workflow, which were used to obtain results presented in the first paper. The other two papers are focused on fracturing of gelatin mixed with yeast and sugar, which generates CO2. Paper 3 describes the mechanism of fracture network formation during draining of CO2 out of a gelatine layer. Paper 4 focuses on the temporal evolution of the drainage network and the mechanism of fracture opening and closing. The last paper presents a study in which X-ray microtomography was used to characterize porosity distribution in weathered andesite samples. The scientific methods developed in this project have potential application in studying dehydration of sediments, formation of mud volcanoes, methane hydrate exploration and assessment, geological sequestration of carbon dioxide CO2 and hydraulic fracturing of unconventional reservoirs.