Acid injection in carbonate reservoir is commonly used in the oil industry to improve, or at least recover, its productivity. The aim of this stimulation technique is to create empty channels called wormholes which, if successful, would bypass the damaged area near the wellbore. During production, wormholes become pathways for the reservoir oil to reach the well. This technique increases near-wellbore permeability, and therefore improves oil production. The interaction between the transport of acid, chemical reaction, and heterogeneities encountered at different scales, controls the unstable behaviour of wormholing and, thus, the success of the treatment. Most of the experimental and numerical studies done on this subject in the past have been limited in their observations because they only considered the dissolution process at a small scale (from pore scale to core scale). The purpose of this work is to study how the geometry of the domain can constrain wormhole competition, and influence wormholing dynamics in a core submitted to acidizing.After a short review of the literature on wormholing to see how the geometry effect could have influenced previous experiments, we study specifically the question of wormhole density. We emphasize that two mechanisms are involved in wormhole competition, with one of them being effective only at small scale. Thus we conclude that wormholing is not a full-scale independent process. We describe differences in the wormhole growth dynamics between “confined” and “unconfined” domains for different dissolution regimes. We focus on optimum conditions and their transition from “confined” to “unconfined” domain to realize that the flow rate in the dominant wormhole does not depend on geometric effects. We conclude by a comparison between 2D and 3D simulations, in both linear and radial flow, and observe changes in the wormholing process. All our results serve as a discussion about definitions of optimum conditions in the literature. 相似文献
In this paper, a prototype of a new generation of Raman spectrometers, based on the use of a monochromator, a digital micromirror device as light modulator, and a photomultiplier tube as detector of the Raman light, is described. This spectrometer, containing no moving parts, is inexpensive, robust, and very precise. New in concept, this spectrometer makes it possible to record, in addition to classical Raman spectra, the intensity at several selected points of the spectrum and/or the total intensity in several selected intervals at the same time with great accuracy, thus giving new possibilities for analytical applications. Also, the work presented demonstrates the possibilities of this very simple prototype for rapid on-line industrial analysis, with an example of quantitative analysis of binary and ternary mixtures of xylene isomers. The precision obtained is satisfactory (errors of prediction approximately 3% in 5-6 seconds per sample). 相似文献
In their thought-provoking article, Slaney and Racine (2011) put forth several criticisms of the traditional view that concepts are mental representations used in the cognitive processes that underlie human higher cognitive competences (categorization, induction, etc.). Considerations of a broadly Wittgensteinian nature underlie their criticisms. In this article, I argue that the considerations advanced by Slaney and Racine do not undermine the clear account of the nature of mental states and psychological processes developed in the 1960s and 1970s and endorsed in my book Doing without Concepts (Machery, 2009). (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
Intramuscular beef collagen of different degrees of reticulation was treated with cathepsin L obtained from chicken liver and a commercial cathepsin B prepared from beef spleen. It was shown that, in the absence of calcium, both proteinases caused a decrease in the initial temperature of denaturation whereas the total enthalpy of denaturation was unaffected. Treatment with cathepsin B resulted in the appearance of a new peak of denaturation at a lower temperature (≈ 44°C), a change wholly comparable with that obtained previously when intramuscular beef collagen was treated with a collagenase from Clostridium histolyticum. There was no such change with cathepsin L. The addition of 20 mM CaCl(2) to the incubation buffer brought about a shift in the total enthalpy of denaturation when collagen was treated with cathepsin L; in contrast, no additional effect was observed in cathepsin B treatments. These findings led to the suggestion that cathepsins B and L have a different mode of action on collagen and that there may be a similarity in the mechanism of action between cathepsin B and the bacterial collagenase. 相似文献
The use of porous structures with high external surface area represents an important breakthrough in several industrial applications. Foam structures have received an increasing scientific and industrial interest since the last decade. Knowledge of pressure drop induced by these foam structures is thus essential for successful design and operation of high performance industrial systems. In this context, an analytical investigation was conducted for the determination of the permeability and the inertial coefficient in foams. The theoretical model is based on modified cubic lattice, which allows to take into account the presence of matter at the junction of struts. The existing model developed in the literature is then modified to incorporate this geometrical approach for determining the tortuosity of the foam. Finally, the permeability and inertial coefficient analysis are performed in order to derive the pressure drop on foams. The modeling procedure is based only on physical principles and geometrical considerations with no adjustable parameters in order to reconcile the theoretical work with the experimental data of the literature. Finally, this model is validated for two marginal cases (i.e. ‘slim’ and ‘fat’ foams). 相似文献
Fourier transform infrared (FTIR) microspectroscopy shows potential as a benign, objective and rapid tool to screen pluripotent and multipotent stem cells for clinical use. It offers a new experimental approach that provides a holistic measurement of macromolecular composition such that a signature representing the internal cellular phenotype is obtained. The use of this technique therefore contributes information that is complementary to that acquired by conventional genetic and immunohistochemical methods. 相似文献
Since the last decade, lightening of automotive structure was mainly achieved by gauge reduction using ultrahigh strength steels such as dual phase and transformation induced plasticity grades. However, gauge reduction can significantly reduce the stiffness. Limits are today reached for some applications such as chassis/suspension part. Development of steel with improved specific stiffness becomes more and more relevant to go further in weight reduction. Development of steel matrix composites (SMCs) with ceramic reinforcements is a promising solution. With an appropriate selection of the ceramic, eutectic solidification can be achieved. This natural production route guarantees a good cohesion of the steel/reinforcement interface and the control of the main parameters, which provide final properties of the product (size, shape, clustering of reinforcement). Significant fraction of ceramic can be obtained (10–25 vol.-%). Eutectic SMC can be produced with conventional industrial process such as continuous casting and hot strip mill which guarantees high productivity and low cost.
Depuis la dernière décennie, l’allègement des structures automobiles a été réalisé en grande partie par la réduction des épaisseurs au travers l’utilisation d’aciers à très haute résistance tels que les aciers DP (biphasés) et TRIP (à plasticité induite par transformation). Cependant, cette réduction des épaisseurs peut entraîner une baisse de rigidité. Aujourd’hui, les limites ont été atteintes pour certaines applications telles que les composantes châssis et suspension. Le développement d’acier à rigidité spécifique améliorée devient une voie de développement de plus en plus pertinente pour progresser dans la réduction de poids. Le développement de composites à matrice d’acier et renfort céramique est une solution prometteuse. Au travers d’une sélection appropriée de la céramique, on peut obtenir une solidification eutectique. Cette route naturelle de production des aciers garantit une bonne cohésion de l’interface acier/renfort ainsi que la maîtrise des principaux paramètres qui contrôlent les propriétés finales du produit (taille, forme, agglomération du renfort). Des fractions significatives de renfort céramique peuvent être atteintes (10–25% en volume). Les composites à matrice métallique (CMM) eutectique peuvent être élaborés par des procédés industriels conventionnels tels que la coulée continue ou le laminage à chaud qui garantissent une productivité élevée et un faible coût. 相似文献
This paper describes a software-radio architecture developed for providing real-time wide-band radio communication capabilities in a form attractive for advanced 3G systems research. It is currently being used to implement signaling methods and protocols similar, but not limited to, evolving 3G radio standards (e.g. umts, cdma2000). An overview of the hardware system is provided along with example software implementations on both high-perfo-mance DSP systems and conventional microprocessors. 相似文献