1,720,993 research outputs found
Could Shale be Just a One-hit Wonder? A Comprehensive Overview of the Technology Today for Non-Specialists
Full text linkIntroduction to the special issu
Experimental Study on CO2 Residual Trapping as a Function of the Brine Imbibition Rate
No full textDifferent trapping mechanisms are responsible for confining the CO2 in deep saline aquifers. During
injection, CO2 displaces brine according to a drainage process; after injection, CO2 migrates laterally and
upward as a separate phase. Water displaces CO2 in an imbibition-like process, leading to the disconnection
of the plume and the formation of a residual CO2 saturation. This research focuses on the dependency of CO2
residual trapping on the brine imbibition rate, reproduced by CO2 displacement through brine injection. We
investigated the impact of different brine injection rates on sandstone plugs through laboratory experiments
performed at pressure and temperature reservoir conditions using a relative permeameter system (RPS).
First, the petrophysical properties of the dry plugs were measured. Then, the plugs were placed in the RPS
and saturated with brine. After a preliminary drainage phase, during which brine was displaced by CO2
injection to reach residual water saturation, brine was injected again in the plug at a very low flow rate
until the differential pressure across the plug stabilized, and the volume of displaced CO2 was measured.
Subsequently, the injection flow rate was increased step by step from 0.1 to 10 cc/min, representative
of fluid flow velocities at the reservoir scale during CO2 disposal. Each step was applied until a new
stabilization of the differential pressure across the plug was reached, and the volume of the displaced CO2
was measured. The residual CO2 saturation was calculated using the sample porosity and the cumulative
volume of the displaced CO2. The results of the experiments are presented using the Capillary Desaturation
Curves, displaying the residual CO2 saturation as a function of the capillary number, which in turn depends
on the injection flow rate. The results obtained in this study show that the CO2 residual saturation decreases
as the flow rate of the displacing brine increases. This is likely due to the transition from a purely capillary-dominated flow to a mixed flow regime. In the literature, data from experimental tests show the dependency
of residual saturation on the injection flow rate for oil-water and methane-water systems. However, to the
best of the authors’ knowledge, these are the first experimental results describing the Capillary Desaturation
Curves for a brine-CO2 system under high-pressure, high-temperature conditions
Critical Parameters for Caprock Tensile Failure Induced by CO2 Injection Into Aquifers
No full textCO2 geological storage, where supercritical CO2 is injected into underground porous formations for long-term sequestration, is one of several mitigation strategies that have been proposed to control the level of CO2 in the atmosphere. CO2 can be injected into several formation types; deep saline aquifers are the most promising mainly because of their large storage capacity. However, safe and effective CO2 geological storage requires an understanding of the potential failure mechanisms that may lead to a loss of containment. In fact, injection of a fluid into an aquifer increases pore pressure above the initial value and this may trigger unwanted geomechanical effects such as fault reactivation or microseismicity. Additionally, the caprock overlaying the aquifer must be able to withstand the expected pressure increase without fracturing. While previous work has explored the mechanism underlying caprock tensile fracturing, an investigation was carried out to understand which parameters are more susceptible to trigger this mode of failure. This study presents comprehensive sensitivity analyses to highlight the relative contribution of different parameters to caprock tensile fracturing. A simple quasi-2D model comprising an aquifer, caprock and monitoring layer was first set up using the compositional reservoir simulator GEM. A total of 22 parameters among aquifer properties, caprock properties, simulation options and injection parameters were then selected as input variables, and simulations were run by varying one parameter at a time. The target variable was chosen as the maximum CO2 mass that could be injected before tensile fractures start opening in the caprock. Findings were then summarized in a tornado plot. For the range of values considered, the aquifer matrix permeability, caprock Young modulus and number of injection wells were found to have the highest impact on the target variable. Furthermore, results showed that higher quantities of stored CO2 can be achieved without caprock tensile failure in systems where the aquifer has a high Young modulus and Poisson ratio and the caprock has a low Young modulus and Poisson ratio. While this research focused on a simple model, these findings can help refine the current criteria for the selection of aquifers suitable for CO2 geological storag
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
Aerogels for energy and environmental applications
Full text linkAerogels are emerging as one of the most intriguing and promising groups of microporous materials, characterized by impressive properties such as low density, high surface area, high porosity and tunable surface chemistry. Fostering unique thermal and acoustic insulation features, for several decades they mainly received attention from the aerospace and building sectors. More recently, new great opportunities arose due to significant advances in the drying technologies that currently, represent the enabling step for aerogel synthesis and fabrication. This process-ability dramatically increased the interest toward aerogels from new disciplines.
This explains why in the last decade the Environmental Science and Energy fields significantly contributed to the expansion of the aerogel technology, suggesting novel uses and applications and contributing to extend the group of materials that can be synthetized by aerogel processing. New, unforeseen properties emerged for aerogel materials, such as adsorption of contaminants and fluids purification, catalysis of different reactions, electrical conductivity. The present short-review aims at providing a critical overview of the key advances in the development of aerogels for energy and environmental applications, especially emphasizing the common strategies and properties that are turning aerogels into one of the new key emerging technologies of these areas of science
Calculation of lithology-specific p-wave velocity relations from sonic well logs for the po-plain area and the northern adriatic sea
No full textOne of the most useful petrophysical parameters in hydrocarbon reservoir studies is the velocity of the seismic waves propagating in the Earth’s subsurface. Seismic velocities have multiple applications in geophysical exploration, well log interpretation and petrophysical and geomechanical characterization. In this study we used publicly available well data (VIDEPI database) covering the Po Plain and the northern Adriatic areas to calculate the P-wave sonic velocity from the analysis of well profiles (1:1000 scale). Data were collected from 134 wells located inside the region of interest that included sonic log registrations. From each of the wells the cuttings interpretation log, the available spontaneous potential or gamma ray logs and the sonic log were digitized from existing profiles whereas the hydrocarbon-bearing-marker (resistivity log readings) and the geological formation log were constructed. The lithological and the geological formation logs were used to analyse the regional stratigraphy while the resistivity log was used to identify and exclude the hydrocarbon bearing intervals affecting the sonic log readings. The various lithologies reported on the well profiles were combined to characterize 9 main lithological groups (6 clastic, 1 marly, 2 carbonatic). For each group a linear regression was applied to extract the relation of velocity versus depth. The results show a gradual velocity increase with depth for most of the lithologies, while limestones and dolomites present constant velocities independently of the depth. Furthermore, at approximately 3.5-4 km the velocities of all lithologies tend to stabilise at a value that remains relatively constant even for larger depths. The results of this study can prove helpful for the construction and calibration of velocity models and for the calculation of dynamic geomechanical parameters (e.g. Young’s modulus), which are crucial for the mechanical characterization of the rock during geomechanical studies
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
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