TESIS INSTITUTO SABATO
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Ítem Acceso Abierto Modelado multi-escala de estimulación hidráulica en reservorios con fracturas naturales(Comisión Nacional de Energía Atómica. Gerencia de Área Académica. Gerencia Instituto de Tecnología "Jorge Sabato") Gutiérrez, Julieta; Comisión Nacional de Energía Atómica. Gerencia de Área Académica. Gerencia Instituto de Tecnología "Jorge Sabato"Unconventional hydrocarbon reservoirs are characterized by a very low permeability. To allow for economical production of these reservoirs, hydraulic stimulation or fracturing is typically required. These reservoirs often contain a network of pre-existing natural fractures that play a crucial role during stimulation and production, by interacting with propagating fractures and their stress field, and providing differentiated transport channels. Often times, other types of mechanical discontinuities are also present, and they similarly affect stimulation and later production. Modeling and simulation of the stimulation process is often sought-for, to increase the understanding of the underlying mechanics, and to evaluate a range of scenarios allowing for the optimization of the process. Main challenges for the simulation under the conditions described above are: (1) having suitable algorithms and numerical methods that allow for tackling the strong computational demand required for incorporating a significant number of discontinuities in the simulations, and (2) having a reliable benchmark for the interaction between a propagating hydraulic fracture and a mechanical discontinuity. Y-TEC is currently developing a numerical simulator for hydraulic fracturing and rock mechanics, called Y-FRAC®. The solution of the mechanics problem includes a Discontinuous Galerkin formulation with a cohesive zone model (CZM) for the fracture propagation. The fluid transport problem is embodied by the Reynolds lubrication equation. It is the objective of the present work to deal with the two aforementioned challenges, within the framework of Y-FRAC®. In connection with the first objective, it is known that the mesh has to be fine enough to resolve the cohesive zones about crack tips. Here, an algorithm was developed which allows for the coarsening of the mesh required to execute a simulation, while providing results that are faithful to those obtained on a mesh with a refinement as per the requirement above. Incorporation of this algorithm in larger scale simulations would thus allow for an increase in the number of discontinuities included. As for the second objective, an in-depth analysis was performed of the effect of several parameters (including the critical fracture energies and critical tractions for the matrix and the interface, Gc,b, σc,b, Gc,i, σc,i respectively) on the result of the interaction between a dry propagating fracture and a mechanical discontinuity, i.e., the deflection versus penetration (D-P) competition. Our analysis is more extended than others available, while the results obtained compare favorably under available similar conditions. The present results provide a more comprehensive view of the D-P competition, with two fundamental conclusions: (1) there exists a significant difference between results provided by linear elastic fracture mechanics (LEFM) and cohesive fracture mechanics (CFM), and (2) there exists an approximately universal relation between a normalized ratio of critical fracture energies rG = Gc,b/Gc,i, and the ratio of cohesive zone sizes that gives the boundary in the D-P interaction map. These results on dry fracturing provide a robust groundwork for developing an analytical or semi-analytical benchmark to assess the interaction between a hydraulic fracture and a discontinuity.