1,720,955 research outputs found
Mobilità dei fluidi nei carbonati fratturati da analoghi geologici di giacimenti: implicazioni per il sequestro sotterraneo di CO2
No full textFaglie, fratture e bande di deformazione hanno un ruolo cruciale nel controllo della permeabilità delle rocce del sottosuolo, in quanto possono fungere da corridoi o barriere per lo stoccaggio e il movimento dei fluidi. La deformazione può avere effetti diversi sulle proprietà del giacimento in base alle caratteristiche iniziali della roccia: nelle rocce porose la deformazione forma bande di deformazione, riducendo localmente la porosità e la permeabilità; in rocce compatte tende invece a formare fratture, aumentando porosità e permeabilità secondarie. Poiché la distribuzione delle fratture nel sottosuolo è in gran parte sconosciuta a causa delle loro dimensioni non rilevabili dalla sismica, lo studio di analoghi di affioramento è l'unico metodo per caratterizzare la loro distribuzione spaziale e connettività.
L'obiettivo della ricerca è caratterizzare il meccanismo di sviluppo di bande di deformazione e fratture in rocce carbonatiche porose della piattaforma carbonatica Apula e il modo in cui queste incidono sulle proprietà petrofisiche.
Due affioramenti nell’avampaese dell’Appennino meridionale sono stati scelti come analoghi di giacimenti mediterranei, dove calcari compatti del Cretaceo superiore (Calcare di Altamura) sono ricoperti in modo discordante da carbonati porosi di età Plio-pleistocenica (Calcarenite di Gravina). Lo studio è stato condotto integrando i seguenti metodi: rilievo geologico e strutturale dei canyon nei pressi di Matera e Gravina in Puglia con l'ausilio di scan-line sia in campo che virtuali in modelli di affioramento digitali ottenuti tramite fotogrammetria; raccolta di log stratigrafici e petrofisici per individuare correlazioni tra le varie facies della calcarenite e la variazione di intensità e spessore delle bande di deformazione; misure di laboratorio di porosità e densità; analisi microstrutturale mediante microscopia ottica, catodoluminescenza e SEM-BSE; analisi quantitativa delle immagini 2D (da microscopia ottica e catodoluminescenza) e 3D (acquisizione da micro-CT) per la porosità e la distribuzione dimensionale dei clasti.
Il Calcare di Altamura è moderatamente inclinato e piegato. È caratterizzato da faglie normali con direzione NW-SE con rigetti variabili da centimetri a decine di metri e dalla presenza di estese fratture sub-verticali, la cui intensità aumenta avvicinandosi alle faglie. La Calcarenite di Gravina, invece, non è interessata dalle faglie sottostanti ma è attraversata da bande di deformazione e piccole faglie orientate principalmente NNE-SSW.
Le bande di deformazione sono bande sub-verticali parallele, uniformemente distanziate, caratterizzate alla microscala da clasti iso-orientati parallelamente alla banda senza evidenza di cataclasi e con una cementazione pervasiva dovuta a precipitazione di calcite microgranulare. Presentano porosità, permeabilità e dimensioni dei pori significativamente inferiori e una resistenza maggiore rispetto alla roccia incassante, portando ad un miglioramento delle proprietà elastiche (Vp/Vs).
La lieve deformazione della Calcarenite di Gravina, dovuta al coinvolgimento nella dinamica del bacino di avampaese degli Appennini, ha prodotto in sedimenti non ancora consolidati bande di deformazione pervasive, che hanno contribuito alla cementazione delle calcareniti porose. Questo processo diagenetico, precedentemente non riconosciuto, può produrre un effetto significativo sulle eterogeneità delle proprietà petrofisiche e idrauliche dei carbonati porosi, creando una compartimentazione molto elevata. Queste bande devono essere prese in considerazione quando si sfruttano litologie simili per lo stoccaggio di fluidi perché aumentano il grado di incertezza dato che non sono rilevabili dalla sismica e sono raramente identificabili dai dati di carota.Faults, fractures and deformation bands have a crucial role in controlling the permeability of subsurface rocks, as they can act as corridors or barriers for the storage and flow of various geofluids. Deformation can have different effects on the reservoir properties based on initial rock porosity and strength: in porous and poorly cemented rocks strain tends to localize into deformation bands, reducing locally the porosity and permeability; tight rocks tend instead to form fractures, enhancing the secondary porosity and permeability. Since the distribution of fractures in the subsurface is largely unknown due to their sub-seismic size, the study of well exposed outcrop analogues is the only method to characterize the spatial distribution and connectivity of fractures.
The objective of the research is to characterize the mechanism of the development of deformation bands and fractures affecting porous shallow carbonate rocks of the Apulian carbonate platform and how these impact the petrophysical properties of the host rock.
Two outcrops in the Apulian foreland (Southern Italy) were chosen as analogues for Mediterranean reservoirs, where tight platform carbonates of Cretaceous (Senonian) age (Calcare di Altamura fm) are unconformably overlain by porous carbonates of Plio-Pleistocene age (Calcarenite di Gravina fm).
The study was conducted integrating the following methods: geological and structural survey of the canyons near Matera and Gravina in Puglia with the aid of field and virtual scanlines in digital outcrop models obtained by photogrammetry; collection of stratigraphic and petrophysical logs of the calcarenites to find correlations between the different facies of the calcarenite and the variation in intensity and thickness of the deformation bands; laboratory measurements of porosity and density of calcarenites and deformation bands (Hg-porosimeter, pycnometer); microstructural analysis using optical, cathodoluminescence and SEM-BSE microscopy; quantitative image analysis from 2D (optical and cathodoluminescence micrographs) and 3D images (micro-CT acquisition) to measure porosity and clast size distributions.
The Calcare di Altamura formation is moderately tilted and gently folded. It is characterised by NW-SE striking normal faults with throws varying from centimetres to tens of meters and by the occurrence of widespread sub-vertical joints, whose intensity increases approaching the faults. At the same time the Calcarenite di Gravina formation is not offset by the underlying faults but is crosscut by deformation bands and small faults oriented mainly NNE-SSW.
Deformation bands consist of evenly spaced, parallel, sub-vertical bands characterized at the microscale by iso-oriented clasts parallel to the band with no cataclasis evidence and pervasive cementation by microgranular calcite precipitation. They present significantly lower porosity, permeability and pore size and a higher strength than in the host rock which reflects on an improvement of the elastic properties (Vp/Vs).
Mild deformation of the Calcarenite di Gravina involved in the dynamics of the Apennines foreland basin evolution was able to produce in soft sediment conditions at shallow depths pervasive deformation bands, which all together contribute to the cementation of the porous calcarenites. This diagenetic process, previously unrecognized, can produce a significant effect on the heterogeneities of petrophysical and hydraulic properties of shallow porous carbonates creating a very high compartmentalization. These processes must be considered when exploiting similar rock types for geofluid exploitation and storage because they increase the degree of uncertainty since they are undetectable through seismic data and are rarely identifiable from the well-core data
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
3D geometry and displacement transfer of an oblique relay zone on outcropping normal faults
Full text linkRelay zones on normal faults accommodate transfer of displacement between adjacent segments. We study vertical and horizontal displacement transfer mechanisms across a relay zone adjacent to the Moab Fault at Courthouse Rock (Utah, USA). The relay zone has a reservoir scale (map overlap length ca. 750 m, separation ca. 150 m), and is bounded by two normal fault segments with maximum throw of ca. 12 m. The relay zone is exposed on multiple, sub-parallel cliff faces and intervening rock pavements. We use photogrammetry of these exposures to build a 3D virtual outcrop model of the relay-bounding faults, subordinate faults deforming the relay zone and seven faulted stratigraphic horizons. The relay-bounding faults are right-stepping in map view and contractional in cross-section, defining a relay zone oblique to bedding in 3D. Displacement is transferred both horizontally and vertically across the relay zone. Horizontal transfer of displacement is achieved by a shallow dipping (<1°) relay ramp, whereas vertical transfer is achieved by antithetic faults within the relay ramp. Our analysis demonstrates that multiple mechanisms can work in conjunction to facilitate transfer of displacement across individual relay zones
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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