No description available.

Modeling and simulation of fluid flow in subsurface fractured systems has been steadily a popular topic in petroleum industry. The huge potential hydrocarbon reserve in naturally and hydraulically fractured reservoirs has been a major stimulant for developments in this field. Although several models have found limited applications in studying fractured reservoirs, still more comprehensive models are required to be applied for practical purposes. A recently developed Embedded Discrete Fracture Model (EDFM) incorporates the advantages of two of the well-known approaches, the dual continuum and the discrete fracture models, to investigate more complex fracture geometries. In EDFM, each fracture is embedded inside the matrix grid and is discretized by the cell boundaries. This approach introduces a robust methodology to represent the fracture planes explicitly in the computational domain. As part of this research, the EDFM was implemented in two of The University of Texas in-house reservoir simulators, UTCOMP and UTGEL. The modified reservoir simulators are capable of modeling and simulation of a broad range of reservoir engineering applications in naturally and hydraulically fractured reservoirs. To validate this work, comparisons were made against a fine-grid simulation and a semi-analytical solution. Also, the results were compared for more complicated fracture geometries with the results obtained from EDFM implementation in the GPAS reservoir simulator. In all the examples, good agreements were observed. To further illustrate the application and capabilities of UTCOMP- and UTGEL-EDFM, a few case studies were presented. First, a synthetic reservoir model with a network of fractures was considered to study the impact of well placement. It was shown that considering the configuration of background fracture networks can significantly improve the well placement design and also maximize the oil recovery. Then, the capillary imbibition effect was investigated for the same reservoir models to display its effect on incremental oil recovery. Furthermore, UTCOMP-EDFM was applied for hydraulic fracturing design where the performances of a simple and a complex fracture networks were evaluated in reservoirs with different rock matrix permeabilities. Accordingly, it was shown that a complex network is an ideal design for a very low permeability reservoir, while a simple network results in higher recovery when the reservoir permeability is moderate. Finally, UTGEL-EDFM was employed to optimize a conformance control process. Different injection timings and different gel concentrations were selected for water-flooding processes and their impact on oil recovery was evaluated henceforth. / text

Objective- To compare the biomechanical properties of 3.5 locking compression plate (LCP) fixation to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model in static axial compression and cyclic axial compression and torsion. Study Design- Biomechanical in vitro study. Sample Population- 30 paired humeri from adult, medium to large breed dogs. Methods- Testing was performed monotonically to failure in axial compression on ten pairs of humeri, cyclically in axial compression for 10,000 cycles on ten pairs and cyclically in torsion for 500 cycles on the last ten pairs. Results- Humeral constructs stabilized with LCPs were significantly stiffer than those plated with LC-DCPs when loaded in axial compression (P=0.0004). When cyclically loaded in axial compression over 10,000 cycles, the LC-DCP constructs were significantly stiffer than those constructs stabilized with LCPs (P=0.0029). Constructs plated with LC-DCPs were significantly more resistant to torsion over 500 cycles than those plated with LCPs (P<0.0001), though no difference was detected during the first 280 cycles. Conclusions- The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilized with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver. Clinical Relevance- LCPs yield less stiff fixation under dynamic loading than conventional LC-DCPs when applied to severely comminuted, metaphyseal fractures. Improving anatomical contouring of the plate and insuring complete screw insertion into the locking plate hole may improve stiffness when using LCPs in comminuted fractures. / Master of Science

A naturally fractured reservoir (NFR) is a reservoir with a connected network of fractures created by natural processes such as diastrophism and volume shrinkage (Ordonez et al. 2001). There are two models to simulate this kind of reservoirs: the discrete fracture model and the dual porosity model. In the dual porosity model, the matrix blocks occupy the same physical space as the fracture network and are identical rectangular parallelepipeds with no direct communication between isotropic and homogeneous matrix blocks. However, each fracture and matrix property is defined separately in the discrete fracture model. Another feature of this thesis is tracer testing. In this process, a chemical or radioactive element is injected to the reservoirs, and then it can be traced using the devices, which are designed to detect the tracers. Tracer tests have several advantages such as determining residual oil saturation, identifying barriers or high permeability zones in reservoirs, and providing the information on flow patterns. Limited number of research studies has been done on performing tracer tests in naturally fractured reservoirs. Also because there is not enough information about the advantages and disadvantages of the discrete fracture and the dual porosity models, researchers and engineers lack the expertise to confidently select either the discrete fracture or the dual porosity models to simulate the different types of NFRs. In this thesis, we compared the oil and water productions, and tracer concentration curves in various reservoir conditions, using both the discrete fracture and the dual porosity models. We used the ECLIPSE, which is a commercial software package in the area of petroleum industry, to model a naturally fractured reservoir. We performed a simple waterflooding with two conservative tracers on the reservoirs. The results presented in each section include the graphs of the oil production rate, water production rate, and tracer concentration. In addition, we presented the oil saturation profiles of a cross-section, which includes the production and injection wells. The results illustrated that both the discrete fracture and the dual porosity models are in good agreement, except for a few special cases. Generally, the oil production using the dual porosity model is more than in the discrete fracture model. The major disadvantage of the dual porosity model is that the fluid distribution in the matrix blocks is changing homogenously during the waterflooding period. In other words, ECLIPSE shows a constant value of the oil and water saturations in each time step for the matrix blocks. However, the dual porosity model is 3 to 4 times faster than the discrete fracture model. In the discrete fracture model, the users have complete control in defining the reservoirs. For example, the fracture aperture, fracture spacing, and fracture porosities can be set by the user. The disadvantage of this model is that millions of grid blocks are needed to model a large reservoir with small fracture spacing. / text

Naturally fractured reservoirs (NFRs) hold a significant amount of the world's hydrocarbon reserves. Compared to conventional reservoirs, NFRs exhibit a higher degree of heterogeneity and complexity created by fractures. The importance of fractures in production of oil and gas is not limited to naturally fractured reservoirs. The economic exploitation of unconventional reservoirs, which is increasingly a major source of short- and long-term energy in the United States, hinges in part on effective stimulation of low-permeability rock through multi-stage hydraulic fracturing of horizontal wells. Accurate modeling and simulation of fractured media is still challenging owing to permeability anisotropies and contrasts. Non-physical abstractions inherent in conventional dual porosity and dual permeability models make these methods inadequate for solving different fluid-flow problems in fractured reservoirs. Also, recent approaches for discrete fracture modeling may require large computational times and hence the oil industry has not widely used such approaches, even though they give more accurate representations of fractured reservoirs than dual continuum models. We developed an embedded discrete fracture model (EDFM) for an in-house fully-implicit compositional reservoir simulator. EDFM borrows the dual-medium concept from conventional dual continuum models and also incorporates the effect of each fracture explicitly. In contrast to dual continuum models, fractures have arbitrary orientations and can be oblique or vertical, honoring the complexity and heterogeneity of a typical fractured reservoir. EDFM employs a structured grid to remediate challenges associated with unstructured gridding required for other discrete fracture models. Also, the EDFM approach can be easily incorporated in existing finite difference reservoir simulators. The accuracy of the EDFM approach was confirmed by comparing the results with analytical solutions and fine-grid, explicit-fracture simulations. Comparison of our results using the EDFM approach with fine-grid simulations showed that accurate results can be achieved using moderate grid refinements. This was further verified in a mesh sensitivity study that the EDFM approach with moderate grid refinement can obtain a converged solution. Hence, EDFM offers a computationally-efficient approach for simulating fluid flow in NFRs. Furthermore, several case studies presented in this study demonstrate the applicability, robustness, and efficiency of the EDFM approach for modeling fluid flow in fractured porous media. Another advantage of EDFM is its extensibility for various applications by incorporating different physics in the model. In order to examine the effect of pressure-dependent fracture properties on production, we incorporated the dynamic behavior of fractures into EDFM by employing empirical fracture deformation models. Our simulations showed that fracture deformation, caused by effective stress changes, substantially affects pressure depletion and hydrocarbon recovery. Based on the examples presented in this study, implementation of fracture geomechanical effects in EDFM did not degrade the computational performance of EDFM. Many unconventional reservoirs comprise well-developed natural fracture networks with multiple orientations and complex hydraulic fracture patterns suggested by microseismic data. We developed a coupled dual continuum and discrete fracture model to efficiently simulate production from these reservoirs. Large-scale hydraulic fractures were modeled explicitly using the EDFM approach and numerous small-scale natural fractures were modeled using a dual continuum approach. The transport parameters for dual continuum modeling of numerous natural fractures were derived by upscaling the EDFM equations. Comparison of the results using the coupled model with that of using the EDFM approach to represent all natural and hydraulic fractures explicitly showed that reasonably accurate results can be obtained at much lower computational cost by using the coupled approach with moderate grid refinements. / text

The purpose of this thesis is to deal with the initiation of chevron cracks in forward extrusion. Using numerical simulation, the ability of selected fracture models which prognosticates the initiation of chevron cracks is observed. The influence of process parameters is studied (friction, reductions in cross section and angles of reduction) on the initiation and diffusion of damage. Solutions was executed by Abaqus for material 12 050.

No description available.

O presente trabalho trata da análise do comportamento mecânico da madeira, material anisotrópico, submetida ao crescimento de fissuras e aos processos mecânicos que causam sua ruptura, utilizando os conceitos de Mecânica da Fratura. A avaliação do colapso de peças de madeira, pela da mecânica da fratura, foi realizada por meio de análises experimentais. Para a determinação das propriedades de fratura da madeira foram determinadas propriedades mecânicas da madeira, tais com: módulo de ruptura a flexão estática, módulo de elasticidade à flexão estática, resistência à tração paralela às fibras, resistência ao cisalhamento, resistência ao fendilhamento paralela às fibras e resistência à tração normal às fibras. Foram efetuados ainda ensaios experimentais referentes à mecânica da fratura em corpos de prova tipo SENB (Single Edge Notched Beam). A modelagem numérica foi realizada utilizando-se um código computacional baseado no método de elementos de contorno. Para as simulações foram utilizados os valores das propriedades físicas, de resistência e de elasticidade obtidas na caracterização experimental dos elementos de madeira. Os resultados experimentais foram comparados com as análises numéricas para determinação de uma formulação específica para situações de colapso de elementos de madeira. / The present work deals with the analysis of the mechanical behavior of wood, anisotropic material, submitted to the growth of cracks and the mechanical processes that cause its rupture, using the concepts of Fracture Mechanics. The evaluation of the collapse of pieces of wood, by the fracture mechanics, was carried out by means of experimental analyzes. To determine the fracture properties of the wood, mechanical properties of the wood were determined, such as: modulus of static bending, modulus of elasticity at static bending, tension resistance parallel to grain, shearing resistance, cleavage strength parallel to grain and tension resistance normal to grain. Experimental tests were performed on fracture mechanic in Single Edge Notched beams (SENB). Numerical modeling was performed using a computational code based on the boundary element method. For the simulations, the values of the physical properties, strength and elasticity obtained in the experimental characterization of the wood elements were used. The experimental results were compared with the numerical analyzes to determine a specific formulation for situations of collapse of wood elements.

O presente trabalho trata da análise do comportamento mecânico da madeira, material anisotrópico, submetida ao crescimento de fissuras e aos processos mecânicos que causam sua ruptura, utilizando os conceitos de Mecânica da Fratura. A avaliação do colapso de peças de madeira, pela da mecânica da fratura, foi realizada por meio de análises experimentais. Para a determinação das propriedades de fratura da madeira foram determinadas propriedades mecânicas da madeira, tais com: módulo de ruptura a flexão estática, módulo de elasticidade à flexão estática, resistência à tração paralela às fibras, resistência ao cisalhamento, resistência ao fendilhamento paralela às fibras e resistência à tração normal às fibras. Foram efetuados ainda ensaios experimentais referentes à mecânica da fratura em corpos de prova tipo SENB (Single Edge Notched Beam). A modelagem numérica foi realizada utilizando-se um código computacional baseado no método de elementos de contorno. Para as simulações foram utilizados os valores das propriedades físicas, de resistência e de elasticidade obtidas na caracterização experimental dos elementos de madeira. Os resultados experimentais foram comparados com as análises numéricas para determinação de uma formulação específica para situações de colapso de elementos de madeira. / The present work deals with the analysis of the mechanical behavior of wood, anisotropic material, submitted to the growth of cracks and the mechanical processes that cause its rupture, using the concepts of Fracture Mechanics. The evaluation of the collapse of pieces of wood, by the fracture mechanics, was carried out by means of experimental analyzes. To determine the fracture properties of the wood, mechanical properties of the wood were determined, such as: modulus of static bending, modulus of elasticity at static bending, tension resistance parallel to grain, shearing resistance, cleavage strength parallel to grain and tension resistance normal to grain. Experimental tests were performed on fracture mechanic in Single Edge Notched beams (SENB). Numerical modeling was performed using a computational code based on the boundary element method. For the simulations, the values of the physical properties, strength and elasticity obtained in the experimental characterization of the wood elements were used. The experimental results were compared with the numerical analyzes to determine a specific formulation for situations of collapse of wood elements.

Master of Science / Department of Clinical Sciences / David E. Anderson / Drug delivery systems for time release of recombinant human bone morphogenetic protein-2 (rhBMP-2) and antibiotics in orthopedic surgeries continue to be developed. Recently, a biodegradable novel polymeric matrix has been developed for this purpose. We hypothesized that impregnation of the matrix with rhBMP-2 would enhance bone healing. The objectives of the study were to characterize elution of rhBMP-2 and two antimicrobials (tigecycline, tobramycin) from the matrix, and bone response to the matrix in the presence or absence of rhBMP-2 and antimicrobials. In vitro elution of tigecycline, tobramycin, and rhBMP-2 from the matrix was investigated. Drug concentration in media were measured on days 1-6, 8, 10, 13, 15, 17, 21, 25, 28, and 30 using high pressure liquid chromatography/mass spectrometry/mass spectrometry (HPLC/MS/MS; antimicrobials) and ELISA (rhBMP-2). In vivo testing was done using a unicortical defect created into each tibia of twenty adult goats. Animals were randomly assigned to one of 5 groups: 1) control (untreated defect); 2) matrix; 3) matrix+ antimicrobials (tigecycline+tobramycin); 4) matrix+rhBMP-2; and 5) matrix+antimicrobials+rhBMP-2. Plasma concentration of tigecycline and tobramycin and serum concentration of rhBMP-2 were measured by the above techniques on days 1-7, 9, 11, 13, 15, 17, 22, 26, and 30. Bone response was assessed on days 0, 14, and 30 using radiographic scoring and dual energy X-ray absorptiometry (bone mineral density [BMD]). After euthanasia on day 30, histomorphologic analyses of the bone defects were done. Categorical variables were analyzed using a generalized linear model, and continuous variables using an ANOVA with P < 0.05 considered significant. In vitro elution was characterized by a rapid release on day 1 followed by a slow release until day 30 for both antimicrobials and rhBMP-2. Plasma antimicrobial concentrations showed continued release throughout the study period. Serum rhBMP-2 concentration, radiographic scores and BMD were not significantly different between groups. Periosteal and endosteal reaction surface areas were significantly greater surrounding the defects in group 4 (matrix+rhBMP-2). There was no significant difference between the groups for the percent of bone filling the defect. The matrix served as an appropriate antimicrobial and rhBMP-2 delivery system and successfully stimulated bone production when rhBMP-2 was present.