Permeability estimation in tight and shale reservoirs is challenging because little or no flow will occur without hydraulic fracture stimulation. In the pressure falloff following a fracture calibration test (FCT), radial flow after the fracture closure can be used to estimate the reservoir permeability. However, for very low permeability, the time to reach radial flow can exceed any practical duration. This study shows how to use the reservoir pressure to estimate the maximum reservoir permeability when radial flow is missing in the after-closure response. The approach is straightforward and can also be used for buildup tests. It applies whenever the well completion geometry permits radial flow before the pressure response encounters a real well drainage limits. Recent developments have blurred the boundary between fracture calibration test analysis and classic pressure transient analysis. Adapting the log-log diagnostic plot representation to the FCT analysis has made it possible to perform before and after closure analysis on the same diagnostic plot. This paper also proposes a method for diagnosing abnormal leakoff behavior using the log-log diagnostic plot as an alternative method for the traditional G-function plot. The results show the relationship between reservoir permeability and pressure can be used effectively for both estimation of the permeability upper bound when there is no apparent radial flow and for confirming the permeability estimated from apparent late time radial flow. Numerous field examples illustrate this simple and powerful insight.

Formation damage is a common problem in petroleum reservoirs and happens in different stages of reservoir development from drilling to production. The causes of formation damage include particle invasion, formation fines migration, chemical precipitation, and pore deformation or collapse. Formation damage adversely affects productivity of wells by reducing the permeability of near wellbore region. Furthermore, formation damage also affects well logging results. Therefore, understanding the mechanism of formation damage is vital to predict the extent and severity of formation damage and to control it. This thesis is focused on the study of formation damage caused by external particle invasion. A simplified numerical method based on a commercial code PFC (Particle Flow Code) is proposed to simulate the particle invasion process. The fluid-particle interaction is simplified as hydrodynamic drag forces acted on particles by fluids; the particle-grain interaction is modeled as two rigid balls on contact. Furthermore, an pore network flow model is developed in this study to estimate permeability of damaged formations, which contain two well-separated particle sizes. The effects of the particle size and the initial formation porosity on formation damage are studied in detail. Our study shows that big particles tend to occupy the formation face, while small particles invade deep into the formation. Moreover, particles which are smaller than pore throats (entrances) impair permeability more than those bigger than pore throats. Our study also indicates that a higher initial formation porosity results in more particle invasion and permeability impairment. It is suggested that, in order to reduce formation damage, mud particle size distributions should be carefully selected according to given formation properties. Although our model has some limitations, it may serve as a tool to predict formation damage according to given parameters, and to understand the mechanism of formation damage from a micro-scopic point of view. / text

La valorisation des réservoirs gaziers compacts, dits Tight Gas Reservoirs (TGR), dont les découvertes sont importantes, permettrait d’augmenter significativement les ressources mondiales d’hydrocarbures. Dans l’objectif d’améliorer la production de ces types de réservoirs, nous avons mené une étude ayant pour but de parvenir à une meilleure compréhension de la relation entre l’endommagement et les propriétés de transport des géomatériaux. L’évolution de la microstructure d’éprouvettes qui ont été soumises préalablement à des chargements dynamiques est étudiée. Une estimation de leurs perméabilités avec l’endommagement est tout d’abord présentée à l’aide d’un modèle de pores parallèles couplant un écoulement de Poiseuille avec la diffusion de Knudsen. Nous avons ensuite mené des travaux expérimentaux afin d’estimer l’évolution de la perméabilité avec l’endommagement en relation avec l’évolution de la distribution de tailles de pores. Les mesures de perméabilité sont effectuées sur des cylindres en mortier similaire aux roches tight gas, soumis à une compression uniaxiale. La caractérisation des microstructures des mortiers endommagés est réalisée par porosimétrie par intrusion de mercure. Afin d’estimer l’évolution de la perméabilité, un nouveau modèle hiérarchique aléatoire est présenté. Les comparaisons avec les données expérimentales montrent la capacité de ce modèle à estimer non seulement les perméabilités apparentes et intrinsèques mais aussi leurs évolutions sous l’effet d’un chargement introduisant une évolution de la distribution de taille de pores. Ce modèle, ainsi que le dispositif expérimental employé, ont été étendus afin d’estimer à l’avenir les perméabilités relatives de mélanges gazeux. Le dernier chapitre présente une étude de l’adsorption de méthane dans différents milieux fracturés par chocs électriques. Les résultats, utiles pour l’estimation des ressources en place, ont montré que la fracturation permet de favoriser l’extraction du gaz initialement adsorbé. / The valorization of compact gas reservoirs, called tight gas reservoirs (TGR), whose discoveries are important, would significantly increase the global hydrocarbon resources. With the aim of improving the production of these types of gas, we have conducted a study to achieve a better understanding of the relationship between damage and the transport properties of geomaterials. The microstructure evolution of specimens, which were submitted beforehand to dynamic loading, has been investigated. An estimation of their permeability upon damage is first presented with the help of a bundle model of parallel capillaries coupling Poiseuille flow with Knudsen diffusion. Then, we have carried out an experimental work to estimate the permeability evolution upon damage in relation to the evolution of the pore size distribution in uniaxial compression. The measurements of permeability have been performed on mortar cylinders, designed to mimic typical tight rocks that can be found in tight gas reservoirs. Microstructural characterization of damaged mortars has been performed with the help of mercury intrusion porosimetry (MIP). To estimate the permeability evolution, a new random hierarchical model has been devised. The comparisons with the experimental data show the ability of this model to estimate not only the apparent and intrinsic permeabilities but also their evolutions under loading due to a change in the pore size distribution. This model and the experimental set up have been extended to estimate the relative permeabilities of gas mixtures in the future. The final chapter presents a study of the adsorption of methane on different porous media fractured by electrical shocks. The results, concerning the estimation of the in-place resources, have shown that fracturing can enhance the extraction of the initial amount of adsorbed gas.