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Origine sédimento-diagénétique de réservoirs carbonatés microporeux : exemple de la formation Mishrif (Cénomanien) du Moyen-Orient
No full textMicroporosity may account for as much as 95% of the total porosity of hydrocarbon and water reservoirs in Cretaceous limestones of the Arabian Gulf. In these microporous facies porosity is moderate to excellent (up to 35%) while permeability is poor to moderate (up to 190mD). Conversely, microporous facies may form dense inter-reservoir or cap rock layers with very low porosity and permeability values (2–8% and 0.01–2mD, respectively). For this study, samples were mainly collected from the Cenomanian Mishrif Formation, but also from the Berriasian-Valanginian Habshan Formation, so as to examine the wide vertical and lateral discrepancies in their petrophysical parameters. Scanning Electron Microscopy was used to investigate two potential controls of reservoir properties: (1) micrite particle morphology (shape and inter-crystal contacts); and (2) micrite crystallometry, defined as the median size of micrite particles measured on SEM photomicrographs. The morphometric data are compared with three petrophysical parameters (porosity, permeability and pore threshold radius distribution). Results reveal that micrite matrixes can be subdivided into three petrophysical classes each with its own distinctive crystallometry, morphology and reservoir properties. Class C (strictly microporous limestones with coarse punctic-to-partially coalescent micrites) is made up of coarse (>2µm) polyhedral to rounded micritic crystals, it has good to excellent porosity (8–28%), poor to moderate permeability (0.2–190mD) and a mean pore threshold radius of more than 0.5µm. The class C is usually observed in rudist-rich bioclastic shoal facies where several sedimentary factors (hydrodynamism, bioproduction …) would disfavour deposition of the finer micritic crystals. Diagenetic study shows that the development of coarse micrites (Class C) must also be explained by the early dissolution of fine aragonite and high magnesium calcite particles in oxygenated meteoric fluids leading to a simultaneous in-situ overgrowth on LMC particles at the top of the meteoric phreatic lens. These processes induce an increase of the crystallometry of micritic particles, an early lithification of the carbonate mud, and so the mineralogical stabilization of coarse Class C micrites. Class F (strictly microporous limestones with fine punctic-to-partially coalescent micrites) is composed of fine (2µm), polyhédrales à arrondies. Elle présente des porosités bonnes à excellentes (8-28%), des perméabilités faibles à modérées (0,2-190mD), et des rayons de seuils de pores (PTR) moyens supérieurs à 0,5µm. Cette Classe C est généralement observée dans les shoals bioclastiques riches en rudistes, où de nombreux facteurs sédimentaires (hydrodynamisme…) peuvent défavoriser le dépôt des particules les plus fines. L'étude diagénétique montre que ces micrites grossières peuvent aussi être expliquées par une dissolution précoce des fines particules d'aragonite et de HMC dans des fluides météoriques oxydants, permettant la formation in-situ de surcroissances sur les particules de LMC au sommet de la nappe phréatique météorique. Ces processus induisent une augmentation de la taille des particules micritiques, une lithification précoce de la boue carbonatée, et donc une stabilisation minéralogique précoce des micrites grossières de la Classe C. La Classe F (micrites strictement microporeuses avec des cristaux fins ayant des contacts punctiques à partiellement coalescents, est composée de particules fines (<2µm), polyhédrales à arrondies. Elle présente des porosités bonnes à excellentes (3-35%), mais des valeurs de perméabilité souvent inférieures à 10mD, et des PTR inférieurs à 0,5µm. Cette Classe F est souvent observée dans les sédiments déposés en domaine de plate-forme interne boueuse. La formation de ces micrites fines est aussi expliquée par une stabilisation minéralogique précoce des particules micritiques dans des eaux météoriques confinées, favorisant les processus de néomorphisme, pouvant continuer au cours de l'enfouissement. Plus tard, au cours de l'enfouissement de la série, les qualités réservoirs des Classes C et F sont localement améliorées par de la dissolution mésogénétique (probablement liée à des acides organiques) affectant la matrice micritique durant la mise en charge des réservoirs. La Classe D est formée par des matrices micritiques denses, composées de cristaux anhédraux ou subhédraux avec des contacts fusionnés. Elle présente de très faibles données de porosité et de perméabilité. Ces micrites sont uniquement observées dans les niveaux de plate-forme interne et forment des intervalles inter-réservoirs, généralement en association avec des stylolites et un contenu argileux important, pouvant dépasser 10%. Quelque soit leur mode de formation, ces trois classes peuvent être incorporées dans les futures études de rock-typing portant sur les réservoirs carbonatés microporeux du Moyen-Orien
Sedimento-diagenetic origin of microporos carbonate reservoirs : example of the Mishrif (Fm) -Cenomanian of the Middle-East
No full textLa microporosité représente jusqu'à 95% de la porosité totale des réservoirs à hydrocarbures et des aquifères dans les calcaires crétacés du Moyen-Orient. Dans ces sédiments microporeux, la porosité est modérée à excellente (jusqu'à 35%), tandis que la perméabilité est faible à modérée (jusqu'à 190mD). A l'inverse, mes faciès microporeux peuvent former des niveaux denses, avec de très faibles porosité et perméabilité (respectivement 2–8% et 0,01–2mD). Dans ce travail, les échantillons proviennent essentiellement de la Formation Mishrif (Cénomanien), mais aussi de la Formation Habshan (Berriasien/Valanginien), afin d'examiner les grandes différences verticales et latérales des propriétés pétrophysiques. Le MEB a été utilisé pour étudier deux contrôles potentiels des qualités réservoir : (1) la morphologie des particules micritiques (forme et contacts intercristallins), et (2) la cristallométrie des micrites, définie comme la taille médiane des particules mesurées sur les clichés MEB. Les données morphométriques ont été comparées avec trois paramètres pétrophysiques (porosité, perméabilité, distribution des rayons de seuil de pore). Les résultats montrent que les matrices micritiques peuvent être subdivisées en trois classes pétrophysiques. La Classe C (micrites strictement microporeuses avec des cristaux grossiers ayant des contacts punctiques à partiellement coalescents) est composée de particules grossières (>2µm), polyhédrales à arrondies. Elle présente des porosités bonnes à excellentes (8-28%), des perméabilités faibles à modérées (0,2-190mD), et des rayons de seuils de pores (PTR) moyens supérieurs à 0,5µm. Cette Classe C est généralement observée dans les shoals bioclastiques riches en rudistes, où de nombreux facteurs sédimentaires (hydrodynamisme…) peuvent défavoriser le dépôt des particules les plus fines. L'étude diagénétique montre que ces micrites grossières peuvent aussi être expliquées par une dissolution précoce des fines particules d'aragonite et de HMC dans des fluides météoriques oxydants, permettant la formation in-situ de surcroissances sur les particules de LMC au sommet de la nappe phréatique météorique. Ces processus induisent une augmentation de la taille des particules micritiques, une lithification précoce de la boue carbonatée, et donc une stabilisation minéralogique précoce des micrites grossières de la Classe C. La Classe F (micrites strictement microporeuses avec des cristaux fins ayant des contacts punctiques à partiellement coalescents, est composée de particules fines (2µm) polyhedral to rounded micritic crystals, it has good to excellent porosity (8–28%), poor to moderate permeability (0.2–190mD) and a mean pore threshold radius of more than 0.5µm. The class C is usually observed in rudist-rich bioclastic shoal facies where several sedimentary factors (hydrodynamism, bioproduction …) would disfavour deposition of the finer micritic crystals. Diagenetic study shows that the development of coarse micrites (Class C) must also be explained by the early dissolution of fine aragonite and high magnesium calcite particles in oxygenated meteoric fluids leading to a simultaneous in-situ overgrowth on LMC particles at the top of the meteoric phreatic lens. These processes induce an increase of the crystallometry of micritic particles, an early lithification of the carbonate mud, and so the mineralogical stabilization of coarse Class C micrites. Class F (strictly microporous limestones with fine punctic-to-partially coalescent micrites) is composed of fine (<2µm) polyhedral to rounded micrites with poor to excellent porosity (3–35%), but permeability values of less than 10mD and a mean pore threshold radius of less than 0.5µm. It is mostly observed in sediments deposited in a low energy muddy inner platform setting. The formation of fine micrites (Class F) is also explained by an early mineralogical stabilization of micritic particles in confined meteoric waters, favoring neomorphism processes, which may proceeds during burial. Later, during burial, reservoir properties of classes C and D strictly microporous samples where locally enhanced by mesogenetic dissolution (probably due to organic acids) affecting the microporous matrix during the oil emplacement. Class D (strictly microporous mud-dominated facies with compact anhedral to fused dense micrites) comprises subhedral to anhedral crystals with sutured to fused contacts forming a dense matrix. It has very low porosity and permeability. Class D is only found in low energy muddy inner platform facies and forms inter-reservoir or caps rock layers usually in association with stylolites and clay contents that exceed 10%. Regardless of how they formed, though, the three classes can be usefully incorporated into future rock-typing of the microporous carbonate reservoirs of the Middle Eas
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
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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