Large-scale dynamic hydrofracturing, healing and fracture network characterization

Permeability of a rock is a dynamic property that varies spatially and temporally. Fractures provide the most efficient channels for fluid flow and thus directly contribute to the permeability of the system. Fractures usually form as a result of a combination of tectonic stresses, gravity (i.e. lithostatic pressure) and fluid pressures. High pressure gradients alone can cause fracturing, the process which is termed as hydrofracturing that can determine caprock (seal) stability or reservoir integrity. Fluids also transport mass and heat, and are responsible for the formation of veins by precipitating minerals within open fractures. Veining (healing) thus directly influences the rock’s permeability. Upon deformation these closed factures (veins) can refracture and the cycle starts again. This fracturing-healing-refacturing cycle is a fundamental part in studying the deformation dynamics and permeability evolution of rock systems. This is generally accompanied by fracture network characterization focusing on network topology that determines network connectivity. Fracture characterization allows to acquire quantitative and qualitative data on fractures and forms an important part of reservoir modeling. This thesis highlights the importance of fracture-healing and veins’ mechanical properties on the deformation dynamics. It shows that permeability varies spatially and temporally, and that healed systems (veined rocks) should not be treated as fractured systems (rocks without veins). Field observations also demonstrate the influence of contrasting mechanical properties, in addition to the complexities of vein microstructures that can form in low-porosity and permeability layered sequences. The thesis also presents graph theory as a characterization method to obtain statistical measures on evolving network connectivity. It also proposes what measures a good reservoir should have to exhibit potentially large permeability and robustness against healing. The results presented in the thesis can have applications for hydrocarbon and geothermal reservoir exploration, mining industry, underground waste disposal, CO2 injection or groundwater modeling.

Essays on cultural and institutional dynamics in economic development using spatial analysis

This thesis seeks to research patterns of economic growth and development from a number of perspectives often resonated in the growth literature. By addressing themes about history, geography, institutions and culture the thesis is able to bring to bear a wide range of inter-related literatures and methodologies within a single content. Additionally, by targeting different administrative levels in its research design and approach, this thesis is also able to provide a comprehensive treatment of the economic growth dilemma from both cross-national and sub-national perspectives. The three chapters herein discuss economic development from two broad dimensions. The first of these chapters takes on the economic growth inquiry by attempting to incorporate cultural geography within a cross-country formal spatial econometric growth framework. By introducing the global cultural dynamics of languages and ethnic groups as spatial network mechanisms, this chapter is able to distinguish economic growth effects accruing from own-country productive efforts from those accruing from interconnections within a global productive network chain. From this, discussions and deductions about the implications for both developed and developing countries are made as regards potentials for gains and losses from such types and levels of productive integration. The second and third chapters take a different spin to the economic development inquiry. They both focus on economic activity in Africa, tackling the relevant issues from a geo-intersected dimension involving historic regional tribal homelands and modern national and subnational administrative territories. The second chapter specifically focuses on attempting to adopt historical channels to investigate the connection between national institutional quality and economic development in demarcated tribal homelands at the fringes of national African borders. The third chapter on the other hand focuses on looking closer at the effects of demarcations on economic activity. It particularly probes how different kinds of demarcation warranted by two different but very relevant classes of politico-economic players have affected economic activity quite distinguishably within the resulting subnational regions in Africa.