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It was observed that many hydraulically fractured horizontal shale gas wells exhibit transient linear flow behavior. A half-slope on a type curve represents this transient linear flow behavior. Shale gas wells show a significant skin effect which is uncommon in tight gas wells and masks early time linear behavior. Usually 70-85 percent of frac water is lost in the formation after the hydraulic fracturing job. In this research, a shale gas well was studied and simulated post hydraulic fracturing was modeled to relate the effect of frac water to the early significant skin effect observed in shale gas wells. The hydraulically fractured horizontal shale gas well was described in this work by a linear dual porosity model. The reservoir in this study consisted of a bounded rectangular reservoir with slab matrix blocks draining into neighboring hydraulic fractures and then the hydraulic fractures feed into the horizontal well that fully penetrates the entire rectangular reservoir. Numerical and analytical solutions were acquired before building a 3D 19x19x10 simulation model to verify accuracy. Many tests were conducted on the 3D model to match field water production since initial gas production was matching the analytical solutions before building the 3D simulation model. While some of the scenarios tested were artificial, they were conducted in order to reach a better conceptual understanding of the field. Increasing the water saturation in the formation resulted in increasing water production while lowering gas production. Adding a fractured bottom water layer that leaked into the hydraulic fracture allowed the model to have a good match of water and gas production rates. Modeling trapped frac water around the fracture produced approximately the same amount of water produced by field data, but the gas production was lower. Totally surrounding the fracture with frac water blocked all gas production until some of the water was produced and gas was able to pass through. Finally, trapped frac water around the fracture as combined with bottom water showed the best results match. It was shown that frac water could invade the formation surrounding the hydraulic fracture and could cause formation damage by blocking gas flow. It was also demonstrated that frac water could partially block off gas flow from the reservoir to the wellbore and thus lower the efficiency of the hydraulic fracturing job. It was also demonstrated that frac water affects the square root of time plot. It was proven by simulation that the huge skin at early time could be caused by frac water that invades and gets trapped near the hydraulic fractures due to capillary pressure.

The thermomechanical properties of monolayer graphene and the interfacial interactions between graphene and an SiO₂ substrate are investigated in this dissertation using a multiscale approach. The temperature dependent mechanical behavior of graphene with thermal fluctuations is studied by statistical mechanics analysis under harmonic approximation, which is then compared to molecular dynamics simulations. It is found that the amplitude of thermal fluctuation depends nonlinearly on the graphene size due to anharmonic interactions between bending and stretching modes, but a small positive pre-strain could suppress fluctuation amplitude considerably and results in very different scaling behavior. The thermal expansion of graphene depends on two competing effects: positive expansion due to in-plane modes and negative expansion due to out-of-plane fluctuations. The in-plane stress-strain relation of graphene becomes nonlinear even at infinitesimal strain due to the entropic contribution. Consequently, the modulus of graphene depends on strain non-monotonically, with strain stiffening followed by intrinsic softening. Moreover, it is found that the thermomechnical behavior of graphene is dependent on its interactions with environment such as supporting substrate. The interfacial interactions between graphene and SiO₂ substrate is investigated in terms of three perspectives. Firstly, the interaction mechanisms between graphene and SiO₂ substrate are studied by density functional theory (DFT). The dispersion interaction is found to be the predominant mechanism, and the interaction strength is strongly influenced by changes of SiO₂ surface structures due to surface reactions with water. The adhesion energy is reduced when the reconstructed SiO₂ surface is hydroxylated, and further reduced when covered by a monolayer of adsorbed water molecules. Next, we study the interfacial interactions between graphene and a wet substrate that is covered by a liquid-like water film. During the separation of graphene from the wet substrate, MD simulations show evolution of the water from a continuous film to discrete islands. The water bridging effects are further described by continuum models. Finally, a continuum model is developed to predict how the surface roughness may affect the adhesion between graphene membranes and their substrate. / text

L’oxydation sélective des alcools en aldéhydes, acides ou cétones est une transformation très importante en chimie. L’emploi d’oxygène moléculaire comme oxydant permet de se placer dans une perspective de chimie verte, avec la production d’eau comme seul sous-produit principal. L’oxydation d’alcools primaires (1-octanol et géraniol) et d’alcools secondaires (2-octanol, 1-phénylethanol et alcools hétéroaromatiques dérivés de la pyridine) a été étudié en présence de catalyseurs au platine supportés sur charbon sous pression d’air, en solvant organique ou mélange à de l’eau. Les résultats ont montré une forte influence du solvant sur l’activité catalytique, avec un effet promoteur très important de l’eau sur la réaction. Cet effet a été discuté sur la base de différentes hypothèses. La promotion des catalyseurs au platine par le bismuth a permis d’observer des modifications de l’activité avec un effet positif en particulier dans l’oxydation des alcools hétéroaromatiques secondaires. La désactivation observée lors de l’oxydation de certains substrats a été analysée et des solutions ont été proposées pour la surmonter. / The selective alcohols oxidation to aldehydes, acids and ketones is an important transformation in chemistry. The use of molecular oxygen as oxidant is in adequation with a green chemistry perspective, since water is the only by-product. The oxidation of primary alcohols (1-octanol and geraniol) and secondary alcohols (2-octanol, 1-phenylethanol and pyridine substituted alcohols) has been studied in the presence of platinum supported carbon catalysts under air pressure in organic or mixed organic/aqueous media. The results have shown a strong influence of the solvent on the catalytic activity, with an important promoting effect of water on the reaction. This effect has been discussed based on several hypotheses. The promotion of platinum supported catalysts by bismuth has shown some modifications of the activity, with a positive effect in particular in the oxidation of secondary heteroaromatic alcohols. The deactivation observed during the oxidation reaction of some substrates has been analyzed and some solutions have been proposed to overcome the problem.