Conway Model Research Articles

Numerical Simulation of Non-Darcy Flow in Naturally Fractured Tight Gas Reservoirs for Enhanced Gas Recovery

In this work, we analyze non-Darcy two-component single-phase isothermal flow in naturally fractured tight gas reservoirs. The model is applied in a scenario of enhanced gas recovery (EGR) with the possibility of carbon dioxide storage. The properties of the gases are obtained via the Peng–Robinson equation of state. The finite volume method is used to solve the governing partial differential equations. This process leads to two subsystems of algebraic equations, which, after linearization and use of an operator splitting method, are solved by the conjugate gradient (CG) and biconjugate gradient stabilized (BiCGSTAB) methods for determining the pressure and fraction molar, respectively. We include inertial effects using the Barree and Conway model and gas slippage via a more recent model than Klinkenberg’s, and we use a simplified model for the effects of effective stress. We also utilize a mesh refinement technique to represent the discrete fractures. Finally, several simulations show the influence of inertial, slippage and stress effects on production in fractured tight gas reservoirs.

Steady free-surface flow in vegetation debris pad clogging trash racks

ABSTRACT We consider a steady water flow in a channel where a vertical grid is clogged by a rectangular patch of aquatic vegetation. Laboratory experiments are conducted to observe the decrease in the water table within the patch, as well as the subsequent head loss, as a function of the patch length, the flowrate and the upstream water height. Various models of porous media are used to produce theoretical formulae describing the water surface profile within the patch, among which the Barree–Conway model proves to perform reasonably well. However, for large enough Froude numbers a seepage face or water chute appears past the vegetation patch while non-hydrostatic effects become important. Under the latter condition, the accuracy of our analytic solution is less satisfactory, while remaining accurate enough for practical purposes. As confirmed by numerical simulations, with the specific aquatic plants used in our experiments the porous flow is not Darcian, so that the seepage and head loss could not be explained by the exact Polubarinova–Kochina theory.

Teaching undergraduate data science for information schools

Using the Conway model of data science education as a guide, this paper introduces a model for undergraduate data science education for information schools. The core idea of the suggested model is that data science programs in information schools are unique due to their particular substantive expertise, which includes data management, information behavior, and ethics. This paper also suggests that, to create a data science program within an information school, it may be useful to expand curriculums by adding programming, statistics, and machine learning requirements.

Kinetics of Initial Stages of Pt Oxidation from Electrochemistry and Surface X-Ray Diffraction

The kinetics of the electroxidation of Pt to Pt "oxide" have been studied for many years, initially on polycrystalline Pt. Early studies showed that the oxide charge increases linearly with log(time) at constant potential, the so-called direct logarithmic growth law. Later, Harrington showed empirically that the underlying differential equation, with a Tafel potential dependence of the rate constant, predicted also the current plateau behavior in cyclic voltammetry [1]. The Tafel dependence is suggestive of electron-transfer kinetics and was also found in the oxidation of Pt(111) [2]. Despite this, the classical Conway model [3] invokes field-driven dipole flipping, and other literature models invoke bulk film models that cannot be applicable for a few-monolayer-thick oxide. An early atomistic model stressed the role of surface diffusion in leading to irreversibility and predicted a three-layer surface restructuring and the direct logarithmic law, but with the wrong slope [4]. Our recent Surface X-ray Diffraction studies [5] have shown that the number of place-exchanged Pt atoms also follows the direct logarithmic law. We here extend this result to an extended data set that systematically steps into the oxide peak in the region 1-1.2 V vs RHE, which is the peak in which the place-exchange initiates. The intensity of the (1,1,1.5) reflection shows that the place-exchange process initiates in the early stages of this peak, earlier than the peak maximum at 1.05 V where it sharply changes in a 50 mV/s intensity voltammogram. There is a systematic change in the slope of the direct logarithmic law over the range of the peak, with the largest slope at the peak maximum. The observation that both the current and the number of place-exchanged Pt atoms obey the direct logarithmic law suggests a common limiting process, though in principle the place-exchange and electron-transfer processes need not be coupled. The oxidation of adsorbed OH to O has also been suggested to occur in the same peak and there is some evidence for two processes. A careful comparison of the current density with the coverage of place-exchanged atoms is undertaken here to deduce the electron/place-exchange ratio and indirectly the nature of the accompanying species (O or OH), as well as determining how tightly coupled the exchange and oxidation processes are. The issue of double-layer charging correction is a significant issue in this determination. The place exchange is the initial step of the irreversible nanoscale restructuring of the surface that occurs on potential cycling. The later stages have recently been quantified using Grazing-Incidence Small-Angle X-ray Scattering [6-7]. A careful study of the kinetics is directed toward a detailed atomistic understanding of the evolution of the surface structure. The authors thank the European Synchrotron Radiation Facility, Deutsche Forschungsgemeinschaft, and the Natural Sciences and Engineering Research Council of Canada for support. [1] D.L. Heyd, D.A. Harrington, J. Electroanal. Chem., 335, 19 (1992). [2] A. Björling, J.M. Feliu, J. Electroanal. Chem., 662, 17 (2011). [3] H. Angerstein-Kozlowska, B.E. Conway, K. Tellefsen, B. Barnett, Electrochim. Acta, 34, 1045 (1989). [4] D.A. Harrington, J. Electroanal. Chem., 420, 101 (1997). [5] J. Drnec, M. Ruge, F. Reikowski, B. Rahn, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, D.A. Harrington, Electrochim. Acta, 224, 220 (2017). [6] M. Ruge, J. Drnec, B. Rahn, F. Reikowski, D.A. Harrington, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, J. Am. Chem. Soc., 139, 4532 (2017). [7] M. Ruge, J. Drnec, B. Rahn, F. Reikowski, D.A. Harrington, F. Carla, R. Felici, J. Stettner, O.M. Magnussen, J. Electrochem. Soc., 164, H608 (2017).

Effects of Non-Darcy Flow and Penetrating Ratio on Performance of Horizontal Wells With Multiple Fractures in a Tight Formation

A novel slab source function has been formulated and successfully applied to examine effects of non-Darcy flow and penetrating ratio on performance of a horizontal well with multiple fractures in a tight formation. The Barree–Conway model is incorporated in the mathematical model to analyze non-Darcy flow behavior in the hydraulic fractures, while the pressure response under non-Darcy flow is determined by two dimensionless numbers (i.e., relative minimum permeability (kmr) and non-Darcy number (FND)). A semi-analytical method is then applied to solve the newly formulated mathematical model by discretizing the fracture into small segments. The newly developed function has been validated with numerical solution obtained from a reservoir simulator. Non-Darcy effect becomes more evident at a smaller relative minimum permeability (kmr < 0.05) and a larger non-Darcy number (FND > 10). The non-Darcy number is found to be more sensitive than the relative minimum permeability, resulting in a larger pressure drop even at a larger kmr. In addition, the non-Darcy flow is found to impose a significant impact on the early-stage bilinear/linear flow regime, resulting in an additional pressure drop that is similar to lowering the fracture conductivity. The pressure response can be classified into two categories by a penetrating ratio of 0.5. When the penetrating ratio is decreased, the early bilinear/linear flow regime occurs, followed by an early radial flow regime.

La mémoire autobiographique et le self dans les troubles du spectre autistique sans déficience intellectuelle (TSASDI) à l’âge adulte

IntroductionAutism spectrum disorder combines deficits in socio-communication, restricted, repetitive patterns but also disorders of self and cognitive impairments. Among them, people with ASD have autobiographical memory deficits as shown by several recent studies. Autobiographical memory is a critical function supporting socialization but it represents also an important support for the self as illustrated by the model of Self Memory System put forward by Conway. This cognitive model describes the reciprocal relationships between autobiographical memory and self and then provides a relevant theoretical framework to explore disorders of self by examining autobiographical memory deficits. ObjectiveTo provide a review of autobiographical memory studies in adults with autism spectrum disorder without intellectual deficiency and to discuss the results in reference to Conway's model of self memory system. MethodThe Medline database was analyzed up to February 2014, crossing the following items “autism, autistic, Asperger” and “episodic memories, autobiographical memory”. ResultsOur results show that the semantic component of autobiographical memory is preserved, whereas episodic autobiographical memory is impaired in adults with ASD. These people generate fewer specific memories and less detailed memories of past events. Both episodic memory and future thinking are impaired, this reflecting an alteration of the sense of self, particularly a diminished temporally extended self-awareness. Moreover, memories relating to the self are also less specific and adults with ASD have more difficulty drawing meaning upon these events. Autobiographical memory deficits seem related to impaired Theory of Mind skills and executive dysfunction reported in this disorder. ConclusionFrom a cognitive psychopathological perspective, autobiographical memory deficits found in adults with autism spectrum disorder without intellectual deficiency may account for alterations of both components of self (the working self and the conceptual self) as defined in the self memory system. Our results are also discussed in reference to the main cognitive theories of autism.

A new technique for accurately measuring two-phase relative permeability under non-Darcy flow conditions

A new steady-state technique for determining gas–water relative permeability curves for proppant packs under high confining stress conditions is presented. In this technique, a time domain reflectometry (TDR) device that can measure the saturation inside the proppant pack instantly and efficiently is introduced. De-aired water and nitrogen gas are simultaneously injected into the proppant pack under a desired confining stress, and the pressure drop and saturation are measured when steady-state conditions are reached. Two different proppant mesh sizes, 12/18 and 20/40, have been tested under four confining stresses ranging from 1000 to 4000 psi with repeatable and accurate results. In the majority of published techniques, two-phase relative permeability curves are determined by using Darcy׳s law. This might be accurate enough for low permeability formations under low flow rate conditions, but in high permeability fracture proppant packs, the non-Darcy flow effects, or inertial effects, cannot be neglected. Thus relative permeability curves neglecting inertial effects may lead to inaccurate predictions. In this paper, three flow models: the classic generalized Darcy׳s Law, the generalized Forchheimer flow model, and the two-phase Barree and Conway model (Barree and Conway, 2007) are employed to calculate and compare the relative permeability results. The experimental results show that the non-Darcy flow effects on gas relative permeability are higher than those calculated using Darcy׳s Law. In addition, the various confining stress effects on water and gas relative permeability curves are also presented. A significant decrease in gas relative permeability and minor effects on water relative permeability occur as the confining stress increases. These results help to further understand the effects of multiphase flow in porous media.

Non-Darcy Porous-Media Flow According to the Barree and Conway Model: Laboratory and Numerical-Modeling Studies

Summary This paper presents the results of our new experimental studies conducted for high flow rates through proppant packs, which show that the Barree and Conway (2004) flow model is capable of overcoming limitations of the Forchheimer non-Darcy equation at very high flow rates. To quantify the non-Darcy flow behavior using the Barree and Conway model, a numerical model is developed to simulate non-Darcy flow. In addition, an analytical solution is presented for steady-state linear non-Darcy flow and is used to verify the numerical-simulation results. The numerical model incorporates the Barree and Conway model into a general-purpose reservoir simulator for modeling multidimensional, single-phase non-Darcy flow in porous and fractured media and supplements the laboratory findings. The numerical model is then used to perform sensitivity analysis of the Barree and Conway flow model's parameters and to investigate transient behavior of non-Darcy flow at an injection well.

Simulation of Non-Darcy Porous Media Flow According to the Barree and Conway Model

Non-Darcy porous media flow has been traditionally handled using the Forchheimer equation. However, recent experimental studies have shown that the Forchheimer model is unable to fit laboratory results at high flow rates. On the other hand, the non-Darcy flow model, proposed by Barree and Conway, is capable of describing the entire range of relationships between flow rate and potential gradient from low- to high-flow rates through proppant packs. In this paper, we present a numerical model by incorporating the Barree and Conway model into a general-purpose reservoir simulator for modeling single-phase and multiphase non-Darcy flow in porous and fractured media. The numerical formulation is based on the TOUGH2 methodology, i.e., spatial integral-finite-difference discretization, leading to an unstructured grid, followed by time discretization carried out with a backward, first-order, finite-difference method. The final discrete nonlinear equations are handled fully implicitly by Newton iteration. In the numerical approach, flow through fractured rock is handled using a general multi-continuum approach, applicable to both continuum and discrete fracture conceptual models. In an effort for model validation, we use analytical solutions to verify our numerical model results for both single-phase and multiphase non-Darcy flow. In addition, the numerical model is applied for well testing analysis of transient non-Darcy flow toward a well.

Analysis of Multiphase Non-Darcy Flow in Porous Media

Recent laboratory studies and analyses (Lai et al. Presented at the 2009 Rocky Mountain Petroleum Technology Conference, 14–16 April, Denver, CO, 2009) have shown that the Barree and Conway model is able to describe the entire range of relationships between flow rate and potential gradient from low- to high-flow rates through porous media. A Buckley and Leverett type analytical solution is derived for non-Darcy displacement of immiscible fluids in porous media, in which non-Darcy flow is described using the Barree and Conway model. The comparison between Forchheimer and Barree and Conway non-Darcy models is discussed. We also present a general mathematical and numerical model for incorporating the Barree and Conway model in a general reservoir simulator to simulate multiphase non-Darcy flow in porous media. As an application example, we use the analytical solution to verify the numerical solution for and to obtain some insight into one-dimensional non-Darcy displacement of two immiscible fluids with the Barree and Conway model. The results show how non-Darcy displacement is controlled not only by relative permeability, but also by non-Darcy coefficients, characteristic length, and injection rates. Overall, this study provides an analysis approach for modeling multiphase non-Darcy flow in reservoirs according to the Barree and Conway model.

The use of autobiographical knowledge in age estimation

Event dates are not directly associated with memories, so the processes by which we maintain a sense of time and sequence in our autobiographical memories is of considerable interest. The present study examined participants’ reported age estimation strategies for childhood memories retrieved using a Galton-Crovitz cueing technique. The results indicate that all three categories of autobiographical knowledge in Conway and Pleydell-Pearce's (2000) self-memory system model—lifetime periods, general events, and event-specific details—support temporal inferences. However, participants most frequently used lifetime period knowledge to provide an initial age range, and event-specific knowledge was used to confirm or narrow the range of their estimated age.

Wpływ informacji medialnej na odtwarzanie pamięci zdarzeń

This article focuses on the assessment of the credibility of the witnesses’ testimony. Conway model of autobiographical memory, and the theory of incorrect attribution sources indicates that our memory is based both on the original record of events and on additional information. If the new information is incorrect, the memory may become distorted. In the first part of the article are described mechanisms of autobiographical memory, which can lead to distortions of the original memory trace. The second part are devoted to empirical verification of the hypothesis that the media information distorts the eyewitness memory of an event.

Autobiographical memories for places

The purpose of the present exploratory study was to investigate operations and contents of a naturally occurring reminiscence for physical places in 26 Swedish participants. Using Conway and Pleydell-Pearce's (2000) model of autobiographical memory as a framework, two main questions were examined. First, in what sense are physical places ingredients of our selves—that is, of our self-knowledge—and, if so, how are they and their characteristics organised in the autobiographical knowledge base? Second, what form do personal memories for places take and what kinds of meanings and emotional contents do we bind to this type of reminiscence? The results showed that the Swedish participants' most important places in their lives were mainly childhood- and cottage-related rural types of milieus, and mostly categorised as summarised events; that is, frequently revisited. The personal recollections of the place-related event-specific knowledge were mostly of the generic imagery type, comprising semantic, perceptual, and emotional contents related to the “self”, “others”, and the “environment”. The memories mainly reflected on the participants' growth period and feelings of activation and pleasantness. This was more pronounced in older (M = 59) than in younger (M = 35) participants. All this indicates that physical places can serve as thematic pathways guiding reminiscence and self-knowing consciousness as we recollect details of perceptual, semantic, and emotional characters of periods in our lives.

Selective effects of emotion on the phenomenal characteristics of autobiographical memories

The present study investigates the emotional determinants of the phenomenal characteristics of autobiographical memories. A total of 84 participants completed the Memory Characteristics Questionnaire (MCQ, Johnson, Foley, Suengas, & Raye, 1988) after retrieving and orally describing a negative, a positive, and a neutral autobiographical memory. In addition, self-report and physiological measures of emotional state at retrieval were recorded. Results suggest that recall of perceptual, sensory, and semantic elements is better for emotional memories than for neutral ones. This difference is not significant for contextual and temporal aspects, suggesting that emotional memories are more vivid but no more specific than are neutral ones. In addition, positive memories yielded higher MCQ ratings than did negative memories for sensory, temporal, and contextual aspects. Finally, correlations suggest a positive relation between emotional state at retrieval and level of phenomenal detail of retrieved memories. Results are interpreted in terms of multilevel models of emotion and of Conway and Pleydell-Pearce's (2000) model.

高圧下における電解質溶液の電気伝導度

The electric conductivities of electrolyte solutions under high pressure are reviewed. First, the measurements of conductivity and transference number under high pressure are described briefly. Second, the interpretation of ionic conductivities in water in terms of the Walden product and the residual friction coefficient is presented. Finally, the pressure and isotope effects on the excess proton conductivity are discussed based on the Conway model.

Limiting partial molar volumes of electrolytes in dimethyl sulfoxide–water mixtures at 298.15 K

Limiting partial molar volumes of electrolytes in several water-dimethyl sulfoxide mixtures, up to xDMSO= 0.1587, have been determined from density measurements at 298.15 K. A reference electrolyte assumption (TATB) has been used in order to obtain single-ion partial molar volumes of transfer from water to DMSO–water mixtures. The influence of DMSO on ΔtV′0i of alkali metals and halide ions is negligible in the highly water-rich region (up to xDMSO≈ 0.04) except for the I– ion. However, when the DMSO composition is greater than xDMSO≈ 0.04, the variation of ΔtV′0i for alkali metals is the reverse to that of halide ions. The results are discussed on the basis of ion–solvent and solvent–solvent interactions using Conway's model.

Effects of white amur ( Ctenopharyngodon idella) on a Florida lake: a model

The Lake Conway model predicts that stocking white amur will decrease lake productivity and respiration, increase epipelic algae biomass for two years, and increase biomass of benthic invertebrates and biomass and number of secondary predator fish for at least nine years. Water quality, as defined by submersed macrophyte abundance, phytoplankton biomass, orthophosphate in the epilimnion, and amount of dead particulate matter in the water column, increases during to 10-y simulation. Because of the nature of white amur growth and assimilation rates, simulated grazing impact is heaviest three years after stocking. Carbon flow through both grazing and detritus food chains increases in the simulation, in spite of decreased photosynthesis.