1,720,964 research outputs found
Characterization of Natural Fractures in the Upper Berda Formation of the Alima Anticline, Tunisia
No full textThe characteristics of natural fracture systems is very valuable information when considering exploiting a fractured subsurface oil /gas reservoir. Open fractures are like highways for fluid flow and knowing the orientation, length and intensity of these fractures will greatly improve the accuracy of fluid flow models. Linking fracture characteristics to the geometry of an outcrop analogue can greatly improve the modeling of the mechanical stratigraphy. This can greatly improve the understanding of the structure of a subsurface reservoir, which can improve the approach for exploitation. The results of this research project are far from the complete picture of the mechanical stratigraphy of this outcrop, but the following conclusions are a start: \u95 Current data suggest that the outcrop contains a pre folding NE-WSW conjugate set that continued on in the early stages of folding which eventually lead to sub parallel NE dipping fractures. During folding NW dipping fractures were formed. \u95 Fracture height is not limited by bed thickness. \u95 Current data suggests that white limestone beds are thinner than the red limestone beds. \u95 Current data suggests that the mechanical properties of the white and red limestone are similar. Points 1, 3 and 4 are conclusions based on a limited amount of data. More data is needed to verify that these conclusions are indeed correct. ?Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience
Characterizing fractures and their relation with the structural setting in 3D using novel photogrammetry tools
No full textThe fracture patterns in an outcrop of the Alima anticline in central Tunusia is investigated. A 3D model of the outcrop is made in Photoscan. The fractures are digitized in 3D using OpenPlot software. OpenPlot can automatically calculate the orientation of every fracture. The length has to be calculated in Excel. Stereonet is used for further processing of the data. Gocad is used to calculate the fracture intensity of different areas of the outcrop. There are two fracture sets in the outcrop, they are perpendicular to each other. One of the sets is perfectly vertical after back rotating, the other set has a dip angle of about 60 degrees after back rotating. Both sets consist of conjugate fractures with an angle of 40 – 50 degrees between the two systems. In large areas of the outcrop only one of the two conjugate systems is developed, so the conjugate fractures are not always visible. The fracture intensity can also show big differences throughout the outcrop, there are a few places with a much lower fracture intensity. The software used in this project can cause some problems, which can result in deviations and errors in the data. The software actually is usable for 3D fracture modelling if the problems are known in advance and are taken into account.Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience
Burial-related fracturing in sub-horizontal and folded reservoirs: Geometry, geomechanics and impact on permeability
No full textApplied Geolog
Geomechanical modeling of a fault-propagation fold
No full textThe goals of this thesis were to understand the impact of uncertainties and modeling methods on the resulting stress and strain patterns and to see how 3D stress patterns can be linked to what was seen in the field. In 3 types of models simulations were done to carry out this goal. These are the 2D perturbation model, the 2D static model, and the 3D model. Sensitivity analysis was performed on all of the models and in the 3D model also a principal stress analysis was done. Results and discussion showed us that the displacement and Young’s modulus parameters were the most influential of the parameters that were analysed. Also principal stress analysis tells us that in no location in the model 3D stress patterns can be linked to what was seen in the fold. The model in the current state is probably not advanced enough and maybe the model needs to be revised with perhaps an extra fault going through it. It was concluded that the model is in some ways correct, in some ways it isn’t. More research is needed to make a more accurate model which will produce more accurate stress and strain patterns.Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience
Mechanical modelling of the stress state in a reservoir-scale fold during and after folding
No full textOutcropping fracture data in different structural domains of an outcropping fold in Tunisia have been analyzed in previous studies. Also, the fold geometry has been reconstructed in 3D using outcrop and seismic data. The project is mainly focused on the prediction of the fracture distribution in different domains of a fold based on the stress distribution in the layers of the fold during folding and in the present day structure. But rather than modelling fractures explicitly, stress distributions were analyzed which are indicative of fractures. We model the stress distribution throughout a reservoir-scale outcropping fold to identify heterogeneous stress domains as a proxy for fracture trends. It will ultimately help in identifying the areas where fractures could contribute to flow. 3D forward modelling of the fold geometry indicates that displacement along the fold is not sufficient to capture the fold geometry, suggesting that underlying salt movement contributes significantly to deformation. Geomechanical modeling in JewelSuite confirmed the presence of different fracture orientations in the layers based on analysis of Principal stress orientations at different depths of model. Dependency of fracture orientation on applied stress ratios was shown through an MS Excel study (1-D model) in the thesis. The results of the excel study were matched with the 3D models prepared in JewelSuite which proved its validity. Effect of fiber stresses on the Principal stress orientations was also discussed.Petroleum Engineering and GeosciencesGeoscience & EngineeringCivil Engineering and Geoscience
Fracture modelling based on kinematic evolution: Example of the Sehib anticline
No full textFracture modelling is growing more important due to the effect they have on the flow of the hydrocarbons. The traditional approach for fracture modelling is a combination of either curvature analysis and/or statistical extrapolation of fracture information from well or borehole logging. This approach however does not fully reflect the geological development of a structure. We created a fracture model of the Sehib anticline near Gafsa (Tunisia) based on kinematic evolution and compared it to fracture properties collected during a fieldwork. For this fracture model, we created first a structural model, a kinematic model and a geomechanical model of the structure. The last two models were used as an input for the fracture model. This led to two possible fracture sets each which seems plausible according to the fracture data of the fieldwork. We also created a third fracture set based on layer parallel shortening (LPS). The LPS set does influence the distribution of the other two fracture sets, but the exact area of effect is unknown.Applied GeologyGeoscience & EngineeringCivil Engineering and Geoscience
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Modelling 3D Discrete Fracture Networks using 2D outcrop data
No full textThe main challenge of naturally fractured reservoirs (NFRs) is understanding how fractures behave in the subsurface outside the radius of influence of wells. Fractured outcrop analogues provide geological concepts that can be used to extrapolate fracture data outside the well control. Numerous methods for studying fractured outcrops are available but they all have different disadvantages. We propose a new methodology using Digifract 1.0 software that allows for quick digitization of fractures resulting in a statistically significant quantitative dataset. This approach is used in a carbonate quarry in France to digitize height, dip and azimuth of nearly 1800 non-stratabound fractures on vertical outcrop walls, taking into account assumptions and pitfalls that are often overlooked. The 2D height and spatial distributions of two non-stratabound fracture sets identified in the quarry follow power-law distributions. Applying the 2D distributions in FracMan stochastic fracture simulation software results in 3D DFNs that honour the properties of the 2D distributions. The 3D DFNs form percolating clusters of fractures but for the assumed subsurface conditions the fracture networks would not percolate. The maximum fracture size and the dispersion in the orientation distribution have the largest effect on the percolation threshold. Fracture spacing in 3D is very similar to fracture spacing in 2D. There is a significant sampling error in fracture spacing measurements along scanlines that are not perpendicular to the average fracture dip. The most commonly used correction, Terzaghi, corrects for this as long as the angle between the fracture dip and the scanline is larger than 30 degrees. For smaller angles no uniform correction method has been found.Applied GeologyGeotechnologyCivil Engineering and Geoscience
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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