Carbon dioxide (CO2) injection in low permeability shale reservoirs has recently gained much attention due to the claims that it has a large recovery factor and can also be used in CO2 storage operations. This research investigates the different flow regimes that the CO2 will exhibit during its propagation through the fractures, micropores, and the nanopores in unconventional shale reservoirs to accurately evaluate the mechanism by which CO2 recovers oil from these reservoirs. One of the most widely used tools to distinguish between different flow regimes is the Knudsen Number. Initially, a mathematical analysis of the different flow regimes that can be observed in pore sizes ranging between 0.2 nanometer and more than 2 micrometers was undergone at different pressure and temperature conditions to distinguish between the different flow regimes that the CO2 will exhibit in the different pore sizes. Based on the results, several flow regime maps were conducted for different pore sizes. The pore sizes were grouped together in separate maps based on the flow regimes exhibited at different thermodynamic conditions. Based on the results, it was found that Knudsen diffusion dominated the flow regime in nanopores ranging between 0.2 nanometers, up to 1 nanometer. Pore sizes between 2 and 10 nanometers were dominated by both a transition flow, and slip flow. At 25 nanometer, and up to 100 nanometers, three flow regimes can be observed, including gas slippage flow, transition flow, and viscous flow. When the pore size reached 150 nanometers, Knudsen diffusion and transition flow disappeared, and the slippage and viscous flow regimes were dominant. At pore sizes above one micrometer, the flow was viscous for all thermodynamic conditions. This indicated that in the larger pore sizes the flow will be mainly viscous flow, which is usually modeled using Darcy's law, while in the extremely small pore sizes the dominating flow regime is Knudsen diffusion, which can be modeled using Knudsen's Diffusion law or in cases where surface diffusion is dominant, Fick's law of diffusion can be applied. The mechanism by which the CO2 improves recovery in unconventional shale reservoirs is not fully understood to this date, which is the main reason why this process has proven successful in some shale plays, and failed in others. This research studies the flow behavior of the CO2 in the different features that could be present in the shale reservoir to illustrate the mechanism by which oil recovery can be increased.

Alkaline injection is a chemical enhanced oil recovery method that is used to increase oil recovery by reacting with the crude oil and creating an in situ surfactant. Many chemical agents can be used as an alkali during injection all of which have several advantages and disadvantages. This research focuses on the innate properties of three alkali agents and their ability to alter pH and temperature downhole. Alkali solutions were prepared with five different concentrations including 0.2, 1, 2, 3, and 4 wt%. The impact of varying the alkali concentration, monovalent cations manifested in sodium chloride, and divalent cations manifested in calcium chloride was investigated for all three alkalis. The chemical agents investigated include sodium hydroxide, sodium silicate, and sodium carbonate. Results indicated that sodium hydroxide and sodium silicate managed to impact the pH the most compared to the sodium carbonate. Sodium hydroxide also managed to increase the temperature significantly which is advantageous since it can reduce oil viscosity downhole. Sodium silicate had an advantage of being in liquid state at ambient conditions which makes injecting it downhole much easier compared to the two other alkaline agents. The chemical that was much affected by divalent cations was sodium silicate, which generated a precipitate and thus is not compatible with divalent cations, which are a major composition of most formation water. This research focuses on the innate properties of the alkali agents and the downhole factors that may impact their applicability in different oil reservoirs.

The interfacial area produced was correlated as a function of the physical properties of the fluids, the diameter and number of orifices per plate, and the gas flow rate.

Gas hydrates are one of the most abundant sources of energy present today. They are formed at high pressures and low temperatures, and contain mainly water and methane. When dissociated, a large volume of water forms, much of which is produced. This research performs a simulation study on how to decrease the volume of water produced from gas hydrate reservoirs by utilizing an in-situ heating method combined with a low concentration thermodynamic inhibitor injection. Since gas hydrates form at high pressures and low temperatures, depressurizing the reservoir, or increasing its temperature would cause the solid hydrates to become unstable, and dissociate. The research begins by building a hydrate reservoir model using almost the same description of the models present in the literature in order to compare the results obtained. Several simulation runs were then performed using various production methods, several types of inhibitors, and finally testing and optimizing the newly proposed production method which combines thermal stimulation with inhibitor injection. The optimization process involves testing the novel method using 5-spot, 7-spot, and 9-spot production methods. The effect of each variable on the water recovery was studied, and the conditions under which the lowest water recovery were obtained. The highest water production occurred during glycol injection since it had the largest endurance to hydrate reformation and thus the largest water flow duration. When the glycol was combined with the thermal stimulation method however, the lowest water recovery was obtained. This is mainly due to two factors which include high rate of depletion of reservoir pressure, and the significant decrease in glycol concentration when used with thermal stimulation. This novel production method was chosen as the best method in terms of low water recovery based on a comparison of its recovery with that of all the other methods. The second task was to further optimize this method by introducing several well patterns and comparing their performance to that of the single well case. The largest number of wells, 9-spot pattern, was found to have the lowest water recovery due to the extremely high rate of reservoir pressure depletion. Gas hydrate production is still considered in its preliminary steps due to the complexity of hydrate reservoirs. By understating the mechanism by which these reservoirs can flow, and trying to reduce the excessive water production associated with these reservoirs a better understating of how to economically and safely produce from gas hydrate reservoirs is reached. This may lead to the utilization of this source of energy in the near future.

Gas hydrates reservoirs are a type of unconventional reservoir that is an extremely abundant and ubiquitous source of energy. They are also relatively cleaner than most other hydrocarbon sources which makes them an even more attractive source of energy. The potential of this source of energy has, however, not been utilized since very little production has ever taken place from these reservoirs due to their complexity. This research provides an understanding of gas hydrates thermodynamics and reservoir properties in order to assist in properly modelling the hydrate flow in porous media. The research also provides a road map to the current production methods that have been used in pilot tests in order to produce from gas hydrates reservoirs. The production methods explained include depressurization, thermal stimulation, inhibitor injection, combined methods, carbon dioxide injection, and mining. The mechanism of each method is fully explained, and the advantages and disadvantages of each method are also explained. Several case studies worldwide are also discussed to show how each production method has been used to produce from the gas hydrate reservoirs. The results from the case studies are also used to reach conclusions on how each method can be improved upon. To the author's knowledge, no publication has provided a complete overview on gas hydrates and their production mechanism which makes this research a crucial step in providing an overview on many aspects of gas hydrates reservoirs and their production mechanisms and potential. Understanding the mechanisms to produce from gas hydrate reservoirs is a crucial step in the hydrocarbon industry to allow us to tap into this vast source of energy in the near future.