Amount Of Trapped Gas Research Articles

Adsorption-driven Gas Trapping in Cometary Ice Analogs

Icy planetary bodies carry volatiles in abundances that should reflect the conditions of their formation. However, the interpretation of volatile abundance data from comets is complicated by the fact that the governing parameters and underlying mechanism of volatile trapping are poorly constrained. To unravel the mechanism of gas trapping in water ice and shed light on the origin of comets, gas-trapping experiments were conducted under isothermal conditions with a focus on the relationship between adsorption properties and the quantities of trapped gas. The adsorption data suggest that the adsorption energies of ice surfaces are heterogeneous, and surface properties depend on initial ice-deposition temperatures as well as on the effect of thermal annealing. Sites with different adsorption energies result in temperature dependence of contributing adsorption sites. Moreover, adsorption sites characterized by higher energy contribute predominantly at low pressures, relevant to the protosolar nebula, and at higher temperatures. When new ice was added to the well-characterized ice surface under controlled Ar pressure, the amount of trapped gas was proportional to the amount of gas adsorbed on the newly generated external surface, suggesting the burial of adsorbed gas as the primary mechanism of gas trapping. The ratio of trapped to newly adsorbed gas reflecting the internal to external surface areas ranged between 5 and 20. Assuming the formation of comparable water ice under the pressure-temperature profile of the protosolar nebula, Ar/H2O∼10−5 reported from 67P/Churyumov-Gerasimenko could have formed at about 40 K.

Enhanced Recovery From Naturally Fractured Gas Reservoirs With Seismic Vibrations

Abstract Water level rising in fracture networks of a naturally fractured gas reservoir is extremely challenging and can significantly decrease the ultimate recovery due to reservoir heterogeneity. Although capillary drainage and gravity force can enhance the displacement of gas recovery from matrix to fracture, these forces may not be so effective in mobilizing a large amount of trapped gas through the matrix. So called, the use of seismic wave can be suggested as a low cost and environmentally friendly enhanced method compared with the other conventional enhanced methods. This article is aimed to examine the ability of seismic vibration in generating an efficient driving force for moving the remaining gas into the fracture which, to the best of the author’s knowledge, has not been reported so far. To this end, an in-house numerical simulator has been developed to investigate this enhanced recovery method and also to evaluate the effect of wave characteristics as well as rock properties on the ultimate recovery. The governing equations are solved numerically using finite difference approach and the accuracy of these equations was compared with a commercial simulator for verification. The results are very encouraging and show substantial gas recovery enhancement by applying seismic waves. Our investigation also shows that this stimulation method is more efficient at lower frequencies and also in higher permeable matrix and fractures.

A fast method for trapped gas determination

Gas reservoirs are mainly produced by depletion with an aquifer rise; reservoir simulation requires two main SCAL inputs: the amount of trapped gas by the aquifer (residual gas saturation: Sgr) and the relative permeability to water due to aquifer flooding. As it is quasi impossible to predict aquifer strength, the primary SCAL input for reservoir simulation is the Sgr. The recovery factor is directly defined by initial and residual gas saturations. In fact, the residual gas saturation Sgr highly depends on the initial gas saturation Sgi and there is no universal petrophysical parameter governing the shape of this curve. This relationship can be described by several different models (Land, Aissaoui…). While Land’s model is widely used, the Aissaoui model better fits the experimental results (Suzanne et al. 2003), at least for homogeneous sandstones. For a given threshold of initial gas saturation Sg0, this relationship typically exhibits a plateau at high Sgi>Sg0 and an increasing linear trend at low Sgi<Sg0. The challenge here is to properly estimate the value of the Sg0 threshold. Classical laboratory method would require one experiment per point in the Sgr/Sgi plot, and therefore can be achieved in a matter of months. Here we propose a laboratory method allowing the acquisition of the Sgr/Sgi curve in a few days. The proposed method combines centrifugation and capillary rise under imaging. First, the centrifuge allows creating a saturation profile along a sample; measured by NMR. Then, capillary rise is used to capture Sgr under NMR monitoring. By adding NMR imaging, this technique allows combining the benefits of centrifugation to explore a wide range of Sgi; and the ease and cost effectiveness of capillary rise to measure the resulting Sgr. Therefore, at a timescale close to a traditional capillary rise, the proposed technique avoids Land extrapolation and provides a direct measurement of Sgr in a wide range of Sgi. As an additional benefit, the combination of NMR and centrifuge can provide at the same time a direct measurement of capillary pressure, providing information on the gas in place and potential imbibition process in the reservoir.

Balancing bulk gas accumulation and gas output before and during lava fountaining episodes at Mt. Etna.

We focus on a sequence of 9 lava fountains from Etna that occurred in 2011, separated by intervals of 5 to 10 days. Continuous measurements allowed to discover the occurrence of gravity decreases before the onset of most fountaining episodes. We propose that the gravity changes are due to the pre-fountaining accumulation of a foam layer at shallow levels in the plumbing system of the volcano. Relying on the relationship between amount of gas trapped in the foam and amount of gas emitted during each episode, we develop a conceptual model of the mechanism controlling the passage from Strombolian to lava fountaining activity. Gas leakage from the foam layer during the late stages of its accumulation increases the gas volume fraction at upper levels, thus inducing a decrease of the magma-static pressure in the trapping zone and a further growth of the foam. This feedback mechanism eventually leads to the collapse of the foam layer and to the onset of lava fountaining. The possibility to detect the development of a foam layer at depth and to set quantitative constraints on the amount of trapped gas is important because of the implications for forecasting explosive eruptions and predicting their intensity.

Effect of Continuous, Trapped, and Flowing Gas on Performance of Alkaline Surfactant Polymer (ASP) Flooding

Alkali Surfactant Polymer (ASP) flooding has traditionally been considered in tertiary mode, i.e., after a reservoir has been sufficiently water flooded. In screening studies experiments are usually conducted under two-phase flow conditions, i.e., in the absence of a gas phase in the rock. In practice, oil reservoirs might contain some gas. In areas in the world, where gas flaring is not allowed and an infrastructure for gas transportation is not present, reinjection of produced gas is a common practice. Moreover, when the reservoir is depressurized below bubble point a gas phase will be created. To the best of our knowledge, there are no data in the literature concerning the influence of in situ gas phase (continuous or trapped) on the performance of ASP floods. The main objective of this paper is to evaluate how the presence of a free (nondissolved) gas phase affects ASP flood performance. To this end, several experiments were carried out to evaluate different conditions, where free gas was present, either flowing or trapped. We found that the ultimate residual oil saturation in most experiments is similar to the case without gas. When free gas is present in the porous medium, the oil-bank production occurs earlier, because a large fraction of the gas remains trapped, and therefore the “effective” pore volume for liquid flow is reduced. When the gas and the ASP solution are coinjected, the oil is mostly produced in emulsion form as gas enhances mixing of the in situ fluids. Trapped gas could lead to an efficient oil recovery, depending on the amount of trapped gas: the lower the trapped gas saturation the better the oil recovery.

Anodizing of A356 T6 Alloys Obtained by Sub-Liquidus Casting

Semi solid processing reduces porosity and amount of trapped gas and it allows heat treatment T6 that improves a hard anodized oxide layer. The aim of this work is to show the anodizing possibility of A356 T6 components conformed by Sub-liquidus Casting (SLC) to improve wear and corrosion resistance. This work compares the anodizing effect on tribological properties and corrosion resistance between components obtained by A6061 T6 extruded alloys and from A356 T6 produced by SLC. The effect of rounded silicon crystals on the coating formation and the fracture produced during the coating growth are described.

Microstructure and tribological properties of anodic oxide layer formed on Al–Si alloy produced by semisolid processing

One of the major problems encountered in hard anodizing cast aluminium alloys is the inability to grow a sufficiently thick and homogeneous anodic oxide layer. This work analyzes the possibility of using a semisolid metal forming technology (SSM), like Thixocasting, to solve this surface treatment problem. When compared to conventional castings, Thixocasting reduces porosity and amount of trapped gas, which allow cast components to be heat treated without blistering and the chemical reactivity of the surface also changes. The aim of this work is to study the heat treatment influence on the anodization of A357 aluminium alloy produced by a Thixocasting process. SEM was used to examine the microstructural features found on, within and under the anodized layer. Experiments using a tribometer (ball-on-disc configuration) have been performed in order to evaluate the friction and wear properties of the different layers. The anodic oxide layer formed on the as-cast and T5 substrates had a similar appearance. However, the anodic oxide layer formed over the T6 substrate exhibited a more homogeneous thickness and spheroidized silicon particles became embedded in the anodic oxide layer. Furthermore, the T6 anodized samples showed a slight reduction in friction coefficient and specific wear rate than the as-cast anodized substrate.

Transient ion disturbances in traveling wave tubes

It is well known that the presence of ions in the electron beam of a traveling wave tube (TWT) can lead to periodic variations in the output power, phase and the body (or helix) current. This has been referred to as ion noise or jitter. Recently, we have observed a different form of jitter, and while it is still observed as a small variation in the TWT output (typically <0.5 dB in power and 2/spl deg/ in phase), it is not periodic. We refer to this phenomenon as random jitter, since its random nature in time is a defining characteristic, Other characteristics include a relatively fast onset (/spl sim/1 ms) and slow (/spl sim/500 ms) recovery. It was found that random jitter was due to the spurious release of extremely small amounts of trapped gas inside the TWT. The source of the gas was identified and the problem was resolved. The observed level of fluctuations in power and phase had no effect on digital traffic and the small quantity of gas was found to have no measurable impact on cathode life.

Trapped Gas Saturations In Leduc-age Reservoirs

Abstract Gas production from Alberta's Leduc-age reservoirs, which originally contained more than 400 × 109m3 OGIP, has and will continue to be significant. Estimating recoveries from these bottom- water drive pools has been difficult. Recoverable reserves are dependent upon both the trapped gas saturation and aquifer performance. Generalizing core displacement tests and applying limited field experience has been problematic. With a number of projects reaching maturity it is now possible to integrate core displacement data and field performance to clarify the factors that control gas recovery in these pools. This study is able to demonstrate the dependence of trapped gas saturation on a number of factors including wettability, initial fluid saturation and permeability. A simple analytical model was developed to estimate and interpret blowdown recoveries from these pools. The actual performance of a suite of Leduc-age pools has been interpreted and applied to validate the model's applicability. Introduction Gas recovery from a bottom water drive pool is primarily dependent on the amount of gas remaining unrecovered behind an advancing gas/liquid contact. Since 1990, Imperial has been producing the Leduc D-3A rese rvoir gas cap. The process is described as gas cap blowdown. This paper assesses the gas recovery that can be expected from the Leduc D-3A reservoir and implications for other Leduc-age pools. Evaluation of the trapped gas saturations included:reviewing the available documentation of laboratory studies;accessing industry expertise; and,material balance calculations on selected Devonian Reef reservoirs. Recovery Concepts and General Terminology Trapped gas, Gt, is defined as the total amount of unrecovered gas in a liquid-displaced volume of reservoir. The trapped gas therefore includes both the residual gas in the displaced pore volume and any gas remaining in unswept portions of the invaded reservoir. The amount of trapped gas within the liquid-swept zone can be determined using material balance calculations in conjunction with measurements that locate the gas/liquid contact. At any time during production, the amount of remaining or trapped gas, Gt, in standard units, sm3, can be determined from material balance, given by: Equation 1 (available in full paper) In Figure 1, the gas remaining unrecovered in the displaced volume, Vd, behind an advancing gas/liquid contact is the sum of the residual gas, Gr, which remains undisplaced within the liquidswept region and that remaining bypassed or unswept, Gu, i.e., Equation 2 (available in full paper) During production, the amount of gas that is trapped by the displacing liquid phase is affected by the pressure changes that occur over time within the displaced zone, Vd. The pressure in Vd depends on withdrawal history and the underlying aquifer response. In Leduc's case the aquifer response is influenced as well by other Leduc-trend reefs on the common Cooking Lake aquifer. If the pressure in Vd increases over time, the initial value of Gt remains fixed even though the reservoir volume (and hence the saturation) containing that gas becomes reduced.

Experimental Micro-modeling and Numerical Simulation of Gas/Water Injection/Withdrawal Cycles as Applied to Underground Gas Storage Reservoir

SUMMARY This paper presents the results of an experimental and theoretical study of mechanisms responsible for the evolution and structure of the gas bubble during air-water injection-withdrawal cycles in 2D glass micromodels. Wetting films located in the corners of throat section conduct flow. Wetting film flow generates gas loop structure which increases injection efficiency and also the amount of trapped gas during withdrawal. During the next injection, blob distribution and wetting film flow induce a quicker breakthrough. Using a network simulator which takes into account wetting film flow, the influence of flow-rate on cycling is highlighted

Trapping of inert gas ions by constantly renewed surfaces

Abstract The paper describes the results of theoretical and experimental studies of the processes of trapping of gas ions by constantly renrewed metal films, i.e. the trapping of gas ions in the process of deposition. We have examined a model for trapping gases during simultaneous ion bombardment and deposition. We have conducted theoretical calculations for possible governing of curves derived from the concentration and amount of trapped impurities for three cases of assumed trapping probability functions under varying parameters of the process in time. We have also studied experimentally the trapping of Ar ions with an energy of 1.5-2 keV and current density of 6.5 × 10-6 ÷ 6 × 10-7 A/cm2 by constantly renewed Sc film up to 3000 A. The flash method was applied to measure the amount of trapped gas. We have derived thermal desorption curves, i.e. changes in the partial pressure of Ar within the measuring chamber during the heating of the target, depending on the temperature and period of heating, in the c...

Pulmonary function in children with asthma at acute attack and symptom-free status.

The pulmonary function of 30 asthmatic children (22 boys and 8 girls) between 5 and 16 years of age was studied during an acute attack and in the ensuing symptom-free period. During the acute attack, all static lung volumes except vital capacity were increased, and a significant amount of gas was trapped. Airway conductance and all dynamic lung volumes were decreased. The ratios of functional residual capacity to total lung capacity and residual volume to total lung capacity were significantly elevated. Both lung diffusing capacity and mixing efficiency were significantly decreased. These deviations from normal pulmonary function were attributed to increased airway resistance and its consequences. During the symptom-free period, vital capacity returned to normal, but the other static lung volumes remained elevated. The amount of trapped gas was not significantly different from normal. All dynamic lung volumes except maximal mid-expiratory flow (MMEF25%–75%) returned to normal. Airway conductance was withi...

Investigation of the Coercive Forces of Ni, Fe, and Ni–Fe Films during Evaporation

The dependence of the coercive force of Ni, Fe, and Ni–Fe films upon film thickness and amount of trapped gas was evaluated in vacuo. The magneto-optic Kerr effect was utilized for this investigation. Although the penetration depth of light into the film material was determined to be 150±25 A, measurements of Hc could commence for film thicknesses &amp;lt;100 A. It was found that the coercive force Hc is independent of film thickness if the content of trapped gas, as indicated by the p/r (residual gas pressure over deposition rate) ratio is very small, e.g., 5×10−8 torr/A/sec for Ni films. At higher p/r ratios, the coercive force of Ni films displays initially a steep rise which is followed by a shallow minimum, while in Ni–Fe films a maximum appears at about 750 A. The different behavior of Fe films is ascribed to higher gas absorption on this material rather than a principal change in the mechanism of the coercive force. A hypothesis is proposed as explanation for the observed effects.