Journal articles: 'Residual Trapping'

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HESSE, M. A., F. M. ORR, and H. A. TCHELEPI. "Gravity currents with residual trapping." Journal of Fluid Mechanics 611 (September 25, 2008): 35–60. http://dx.doi.org/10.1017/s002211200800219x.

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Motivated by geological carbon dioxide (CO2) storage, we present a vertical-equilibrium sharp-interface model for the migration of immiscible gravity currents with constant residual trapping in a two-dimensional confined aquifer. The residual acts as a loss term that reduces the current volume continuously. In the limit of a horizontal aquifer, the interface shape is self-similar at early and at late times. The spreading of the current and the decay of its volume are governed by power-laws. At early times the exponent of the scaling law is independent of the residual, but at late times it decreases with increasing loss. Owing to the self-similar nature of the current the volume does not become zero, and the current continues to spread. In the hyperbolic limit, the leading edge of the current is given by a rarefaction and the trailing edge by a shock. In the presence of residual trapping, the current volume is reduced to zero in finite time. Expressions for the up-dip migration distance and the final migration time are obtained. Comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit. In gently sloping aquifers, the current evolution is divided into an initial near-parabolic stage, with power-law decrease of volume, and a later near-hyperbolic stage, characterized by a rapid decay of the plume volume. Our results suggest that the efficient residual trapping in dipping aquifers may allow CO2 storage in aquifers lacking structural closure, if CO2 is injected far enough from the outcrop of the aquifer.

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Hesse, M. A., F. M. Orr Jr., and H. A. Tchelepi. "Gravity currents with residual trapping." Energy Procedia 1, no. 1 (February 2009): 3275–81. http://dx.doi.org/10.1016/j.egypro.2009.02.113.

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Joodaki, Saba, Ramin Moghadasi, Farzad Basirat, Zhibing Yang, Jacob Bensabat, and Auli Niemi. "Model analysis of CO2 residual trapping from single-well push pull test — Heletz, Residual Trapping Experiment II." International Journal of Greenhouse Gas Control 101 (October 2020): 103134. http://dx.doi.org/10.1016/j.ijggc.2020.103134.

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Zuo, Lin, and Sally M. Benson. "Process-dependent residual trapping of CO2in sandstone." Geophysical Research Letters 41, no. 8 (April 24, 2014): 2820–26. http://dx.doi.org/10.1002/2014gl059653.

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Punnam, Pradeep Reddy, Balaji Krishnamurthy, and Vikranth Kumar Surasani. "Investigations of Structural and Residual Trapping Phenomena during CO2 Sequestration in Deccan Volcanic Province of the Saurashtra Region, Gujarat." International Journal of Chemical Engineering 2021 (July 8, 2021): 1–16. http://dx.doi.org/10.1155/2021/7762127.

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This work aims to study the structural and residual trapping mechanisms on the Deccan traps topography to elucidate the possible implementation of CO2 geological sequestration. This study provides an insight into a selection of stairsteps landscape from Deccan traps in the Saurashtra region, Gujarat, India. Various parameters affect the efficiency of the structural and residual trapping mechanisms. Thus, the parametric study is conducted on the modeled synthetic geological domain by considering the suitable injection points for varying injection rates and petrophysical properties. The outcomes of this study will provide insights into the dependencies of structural and residual trapping on the Deccan traps surface topography and injection rates. It can also establish a protocol for selecting the optimal injection points with the desired injection rate for the safe and efficient implementation of CO2 sequestration. The simulation results of this study have shown the dependencies of structural and residual trapping on the geological domain parameters.

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Rezk, Mohamed Gamal, Rahul S. Babu, Suaibu O. Badmus, and Abdulrauf R. Adebayo. "Foam-Assisted Capillary Trapping in Saline Aquifers—An Initial–Residual Saturation Analysis." Energies 15, no. 17 (August 29, 2022): 6305. http://dx.doi.org/10.3390/en15176305.

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Capillary trapping of gas in porous media is important for many processes such as oil recovery and gas geo-sequestration. Foam can mitigate gravity override and viscous fingering of gas by reducing its relative permeability through gas trapping. However, there are limited studies dedicated to understanding how foam assists in gas trapping, the best mode of foam injection for trapping, and its application in geo-sequestration. This paper uses an initial–residual saturation analysis to investigate foam-assisted capillary trapping during the surfactant alternating gas (SAG) injection process in saline aquifers. More specifically, we studied the effects of pore geometric properties, in situ generated foam, and surfactant concentration on gas trapping efficiency and final residual gas saturation, Sgr. First, NMR surface relaxometry measurements were carried out on the rock samples to indicate the mean pore sizes of the rocks. A series of core flooding tests, equipped with resistivity measurements, were then conducted using single-cycle gas injection followed by water injection, water alternating gas (WAG), and SAG injection methods to identify which mode of injection results in the most trapped gas. The results showed that the SAG method had a better sweep efficiency and trapped more gas than other methods. The initial–residual (IR) gas saturation relationships from SAG data measured from several rock samples were then analyzed using Land’s trapping model. Gas trapping efficiency (indicated by Land’s coefficient, C) and residual gas were also found to increase in rocks with large average pore sizes and with increasing surfactant concentration. However, increasing the surfactant concentration above a certain limit did not cause further improvement in the trapping coefficient but only increased the Sgr. The results also showed that high values of surfactant concentrations might cause a slight reduction in the foam’s apparent viscosity, which then reduces the initial gas saturation, and consequently, Sgr. Finally, a linear relationship between the Sgr and the measured log mean of surface relaxation times (T2LM) was obtained, and two correlations were proposed. Therefore, the NMR measurements can be considered a reliable prediction method for Sgr in porous media.

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Khanal, Aaditya, and Md Fahim Shahriar. "Physics-Based Proxy Modeling of CO2 Sequestration in Deep Saline Aquifers." Energies 15, no. 12 (June 14, 2022): 4350. http://dx.doi.org/10.3390/en15124350.

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The geological sequestration of CO2 in deep saline aquifers is one of the most effective strategies to reduce greenhouse emissions from the stationary point sources of CO2. However, it is a complex task to quantify the storage capacity of an aquifer as it is a function of various geological characteristics and operational decisions. This study applies physics-based proxy modeling by using multiple machine learning (ML) models to predict the CO2 trapping scenarios in a deep saline aquifer. A compositional reservoir simulator was used to develop a base case proxy model to simulate the CO2 trapping mechanisms (i.e., residual, solubility, and mineral trapping) for 275 years following a 25-year CO2 injection period in a deep saline aquifer. An expansive dataset comprising 19,800 data points was generated by varying several key geological and decision parameters to simulate multiple iterations of the base case model. The dataset was used to develop, train, and validate four robust ML models—multilayer perceptron (MLP), random forest (RF), support vector regression (SVR), and extreme gradient boosting (XGB). We analyzed the sequestered CO2 using the ML models by residual, solubility, and mineral trapping mechanisms. Based on the statistical accuracy results, with a coefficient of determination (R2) value of over 0.999, both RF and XGB had an excellent predictive ability for the cross-validated dataset. The proposed XGB model has the best CO2 trapping performance prediction with R2 values of 0.99988, 0.99968, and 0.99985 for residual trapping, mineralized trapping, and dissolution trapping mechanisms, respectively. Furthermore, a feature importance analysis for the RF algorithm identified reservoir monitoring time as the most critical feature dictating changes in CO2 trapping performance, while relative permeability hysteresis, permeability, and porosity of the reservoir were some of the key geological parameters. For XGB, however, the importance of uncertain geologic parameters varied based on different trapping mechanisms. The findings from this study show that the physics-based smart proxy models can be used as a robust predictive tool to estimate the sequestration of CO2 in deep saline aquifers with similar reservoir characteristics.

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Khanal, B. D., and P. Dhakal. "Effect of Successive Heat Treatment on the Performance of Superconducting Radio Frequency Niobium Cavities." Journal of Nepal Physical Society 8, no. 2 (December 19, 2022): 53–58. http://dx.doi.org/10.3126/jnphyssoc.v8i2.50152.

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One of the primary sources of radio frequency residual losses leading to lower quality factor is trapped residual magnetic field during the cooldown of superconducting radio frequency cavities. It has been reported that non-uniform recrystallization of niobium cavities after the post fabrication heat treatment leads to higher flux trapping during the cooldown, and hence the lower quality factor. Here, we fabricated two 1.3 GHz single cell cavities from high purity fine grain niobium and processed with successive heat treatments in the range 800-1000 °C to measure the flux expulsion and flux trapping sensitivity. The result indicates that although flux expulsion improves with increased heat treatments, there is a noticeable difference between the flux trapping sensitivity depending on the cavity. Evaluation of microstructure maybe crucial to understand the impact of flux trapping sensitivity on cavity performance.

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Rahman, Taufiq, Maxim Lebedev, Ahmed Barifcani, and Stefan Iglauer. "Residual trapping of supercritical CO2 in oil-wet sandstone." Journal of Colloid and Interface Science 469 (May 2016): 63–68. http://dx.doi.org/10.1016/j.jcis.2016.02.020.

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Niu, Ben, Ali Al-Menhali, and Sam Krevor. "A Study of Residual Carbon Dioxide Trapping in Sandstone." Energy Procedia 63 (2014): 5522–29. http://dx.doi.org/10.1016/j.egypro.2014.11.585.

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Herring, Anna L., Linnéa Andersson, and Dorthe Wildenschild. "Enhancing residual trapping of supercritical CO2 via cyclic injections." Geophysical Research Letters 43, no. 18 (September 28, 2016): 9677–85. http://dx.doi.org/10.1002/2016gl070304.

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Joodaki, Saba, Zhibing Yang, Jacob Bensabat, and Auli Niemi. "Model analysis of CO2 residual trapping from single-well push pull test based on hydraulic withdrawal tests – Heletz, residual trapping experiment I." International Journal of Greenhouse Gas Control 97 (June 2020): 103058. http://dx.doi.org/10.1016/j.ijggc.2020.103058.

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Bower, A. F., and M. Ortiz. "An Analysis of Crack Trapping by Residual Stresses in Brittle Solids." Journal of Applied Mechanics 60, no. 1 (March 1, 1993): 175–82. http://dx.doi.org/10.1115/1.2900742.

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The residual stress distribution in a brittle polycrystalline solid may have a significant influence on its toughness. Grains in a state of residual compression are less likely to be fractured by a growing crack and may trap the crack front or be left behind as bridging particles (Evans et al., 1977). This paper estimates the toughness enhancement due to intergranular residual stresses, using a three-dimensional model. The residual stress is approximated as a doubly sinusoidal distribution acting perpendicular to the plane of an initially straight semi-infinite crack. An incremental perturbation method developed by Bower and Ortiz (1990) for solving three-dimensional crack problems is extended here to cracks loaded by nonuniform remote stresses. It is used to calculate the shape of the semi-infinite crack as it propagates through the doubly sinusoidal residual stress. It is shown that the local regions of compression may trap the crack front and give rise to some transient toughening. In addition, if the residual stress exceeds a critical magnitude, pinning particles may be left in the crack wake. However, for practical values of residual stress and grain size, the predicted toughness enhancement is insignificant. Furthermore, the analysis cannot account for the large bridging zones observed in experiments. It is concluded that the R-curve behavior and bridging particles observed in monolithic ceramics are caused by mechanisms other than residual stresses acting perpendicular to the crack plane.

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Rathore, Vikas, and Sudhir Kumar Nema. "A comparative study of dielectric barrier discharge plasma device and plasma jet to generate plasma activated water and post-discharge trapping of reactive species." Physics of Plasmas 29, no. 3 (March 2022): 033510. http://dx.doi.org/10.1063/5.0078823.

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This work shows a comparative study of a change in properties of plasma-activated water (PAW) when prepared by using two different dielectric barrier discharge (DBD) configurations named a pencil plasma jet (PPJ) and a plasma device (PD). The air plasma produced from the DBD-PPJ and DBD-PD is characterized by voltage-current characteristics, and plasma species/radicals are identified using optical emission spectroscopy. Moreover, the present work emphasizes the trapping of reactive species (O3, NOx, etc.) carried by post-discharge residual gases during PAW production. The trapping of these gases' reactive species is carried out in water, which provides a useful by-product named plasma processed water (PPW). The results revealed a higher concentration of reactive oxygen species (dissolved O3 and H2O2) and a lower concentration of reactive nitrogen species (NO3− and NO2− ions) in PAW prepared by the DBD-PPJ configuration compared to the DBD-PD configuration. The trapping of reactive species (O3 and NOx) present in post-discharge residual gases is confirmed by determining the change in physicochemical properties and reactive oxygen–nitrogen species (RONS) concentration in virgin water used as a trapping medium. The high concentration of RONS in PPW showed a high concentration of reactive species in post-discharge residual gases and vice versa. Therefore, the reduction in reactive species downstream of post-discharge residual gases is shown by a substantial decrease in the concentration of RONS and physicochemical properties of PPW. Thus, PAW and PPW (by-product) prepared in this work could be used for multiple applications such as microbial inactivation, food preservation, and agriculture.

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GOLDING, MADELEINE J., JEROME A. NEUFELD, MARC A. HESSE, and HERBERT E. HUPPERT. "Two-phase gravity currents in porous media." Journal of Fluid Mechanics 678 (April 26, 2011): 248–70. http://dx.doi.org/10.1017/jfm.2011.110.

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We develop a model describing the buoyancy-driven propagation of two-phase gravity currents, motivated by problems in groundwater hydrology and geological storage of carbon dioxide (CO2). In these settings, fluid invades a porous medium saturated with an immiscible second fluid of different density and viscosity. The action of capillary forces in the porous medium results in spatial variations of the saturation of the two fluids. Here, we consider the propagation of fluid in a semi-infinite porous medium across a horizontal, impermeable boundary. In such systems, once the aspect ratio is large, fluid flow is mainly horizontal and the local saturation is determined by the vertical balance between capillary and gravitational forces. Gradients in the hydrostatic pressure along the current drive fluid flow in proportion to the saturation-dependent relative permeabilities, thus determining the shape and dynamics of two-phase currents. The resulting two-phase gravity current model is attractive because the formalism captures the essential macroscopic physics of multiphase flow in porous media. Residual trapping of CO2 by capillary forces is one of the key mechanisms that can permanently immobilize CO2 in the societally important example of geological CO2 sequestration. The magnitude of residual trapping is set by the areal extent and saturation distribution within the current, both of which are predicted by the two-phase gravity current model. Hence the magnitude of residual trapping during the post-injection buoyant rise of CO2 can be estimated quantitatively. We show that residual trapping increases in the presence of a capillary fringe, despite the decrease in average saturation.

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Damico, James R., Robert W. Ritzi, Naum I. Gershenzon, and Roland T. Okwen. "Challenging Geostatistical Methods To Represent Heterogeneity in CO2 Reservoirs Under Residual Trapping." Environmental and Engineering Geoscience 24, no. 4 (December 21, 2018): 357–73. http://dx.doi.org/10.2113/eeg-2116.

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Abstract Geostatistical methods based on two-point spatial-bivariate statistics have been used to model heterogeneity within computational studies of the dispersion of contaminants in groundwater reservoirs and the trapping of CO2 in geosequestration reservoirs. The ability of these methods to represent fluvial architecture, commonly occurring in such reservoirs, has been questioned. We challenged a widely used two-point spatial-bivariate statistical method to represent fluvial heterogeneity in the context of representing how reservoir heterogeneity affects residual trapping of CO2 injected for geosequestration. A more rigorous model for fluvial architecture was used as the benchmark in these studies. Both the geostatistically generated model and the benchmark model were interrogated, and metrics for the connectivity of high-permeability preferential flow pathways were quantified. Computational simulations of CO2 injection were performed, and metrics for CO2 dynamics and trapping were quantified. All metrics were similar between the two models. The percentage of high-permeability cells in spanning connected clusters (percolating clusters) was similar because percolation is strongly dependent upon proportions, and the same proportion of higher permeability cross-strata was specified in generating both models. The CO2 plume dynamics and residual trapping metrics were similar because they are largely controlled by the occurrence of percolating clusters. The benchmark model represented more features of the fluvial architecture and, depending on context, representing those features may be quite important, but the simpler geostatistical model was able to adequately represent fluvial reservoir architecture within the context and within the scope of the parameters represented here.

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Seyyedi, Mojtaba, Ausama Giwelli, Cameron White, Lionel Esteban, Michael Verrall, and Ben Clennell. "Changes in multi-phase flow properties of carbonate porous media during CO2 injection." APPEA Journal 60, no. 2 (2020): 672. http://dx.doi.org/10.1071/aj19061.

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Impacts of fluid–rock geochemical reactions occurring during CO2 injection into underground formations, including CO2 geosequestration, on porosity and single-phase permeability are well documented. However, their impacts on pore structure and multi-phase flow behaviour of porous media and, therefore, on CO2 injectivity and residual trapping potential, are yet unknown. We found that CO2-saturated brine–rock interactions in a carbonate rock led to a decrease in the sweep efficiency of the non-wetting phase (gas) during primary drainage. Furthermore, they led to an increase in the relative permeability of the non-wetting phase, a decrease in the relative permeability of the wetting phase (brine) and a reduction in the residual trapping potential of the non-wetting phase. The impacts of reactions on pore structure shifted the relative permeability cross-point towards more water-wet condition. Finally, calcite dissolution caused a reduction in capillary pressure of the used carbonate rock. For CO2 underground injection applications, such changes in relative permeabilities, residual trapping potential of the non-wetting phase (CO2) and capillary pressure would reduce the CO2 storage capacity and increase the risk of CO2 leakage.

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Wheatley, PD Pare, and LA Engel. "Reversibility of induced bronchoconstriction by deep inspiration in asthmatic and normal subjects." European Respiratory Journal 2, no. 4 (April 1, 1989): 331–39. http://dx.doi.org/10.1183/09031936.93.02040331.

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Five normal and five asthmatic subjects underwent a progressive methacholine provocation study. At each concentration inspiratory pulmonary resistance (RL) was measured, as well as isovolumic maximal flow and residual volume from both partial and complete forced expirations. Results were compared over the RL range of 6-11 cmH2O.1-1.S-1. The reversibility of bronchoconstriction by deep inspiration was quantified as the ratio of the flow increase to potential maximal increase; the reversibility of gas trapping was the ratio of decrease in residual volume to potential maximal decrease. The reversibility of bronchoconstriction did not differ between the groups. In contrast, the reversibility of gas trapping was smaller in asthmatic subjects (21 +/- 17%) than in normals (84 +/- 6%). As gas trapping reflects airway closure, our findings suggest that during induced bronchoconstriction airway closure is more resistant to the effects of deep inspiration in asthmatic than in normal subjects but the reversibility of bronchoconstriction by deep inspiration is not different.

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Vikgren, J., B. Bake, A. Ekberg-Jansson, S. Larsson, and U. Tylén. "Value of air trapping in detection of small airways disease in smokers." Acta Radiologica 44, no. 5 (September 2003): 517–24. http://dx.doi.org/10.1080/j.1600-0455.2003.00105.x.

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Purpose: To test the hypothesis that diffuse and/or focal air trapping are sensitive indicators of airflow obstruction in smoker's small airways disease, when age, gender and presence of emphysematous lesions were allowed for. Material and Methods: Fifty-eight smokers and 34 never smokers, recruited from a randomized population study of men born in 1933, were investigated by HRCT and by extended pulmonary function tests, including a sensitive test for small airways disease (N2 slope). Diffuse air trapping was evaluated by calculating a quotient of mean lung density at expiration and inspiration. Focal air trapping was scored visually by consensus. Results: Diffuse air trapping did not differ between non-emphysematous smokers and never smokers. Furthermore, diffuse air trapping correlated well to the quotient between the residual volume and total lung capacity (RV/TLC, p = 0.01) and was consequently higher in emphysematous smokers than in never smokers. Focal air trapping was found as frequently in smokers without emphysema as in never smokers. Smokers with emphysema showed significantly less focal air trapping. Neither the N2 slope nor any of the other lung function variables differed between those with and without focal air trapping among non-emphysematous smokers. Conclusion: Neither diffuse nor focal air trapping are sensitive indicators of smoker's small airways disease.

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Mei, D. M., R. Panth, K. Kooi, H. Mei, S. Bhattarai, M. Raut, P. Acharya, and G. J. Wang. "Evidence of cluster dipole states in germanium detectors operating at temperatures below 10 K." AIP Advances 12, no. 6 (June 1, 2022): 065113. http://dx.doi.org/10.1063/5.0094194.

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By studying charge trapping in germanium detectors operating at temperatures below 10 K, we demonstrate for the first time that the formation of cluster dipole states from residual impurities is responsible for charge trapping. Two planar detectors with different impurity levels and types are used in this study. When drifting the localized charge carriers created by α particles from the top surface across a detector at a lower bias voltage, significant charge trapping is observed when compared to operating at a higher bias voltage. The amount of charge trapping shows a strong dependence on the type of charge carriers. Electrons are trapped more than holes in a p-type detector, while holes are trapped more than electrons in an n-type detector. When both electrons and holes are drifted simultaneously using the widespread charge carriers created by γ rays inside the detector, the amount of charge trapping shows no dependence on the polarity of bias voltage.

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RUSSELL, G. J., D. N. MATTHEWS, K. N. R. TAYLOR, and B. PERCZUK. "INTERGRANULAR FLUX TRAPPING EFFECTS IN YTTRIUM BARIUM CUPRATE SUPERCONDUCTORS." Modern Physics Letters B 03, no. 05 (April 10, 1989): 437–46. http://dx.doi.org/10.1142/s0217984989000704.

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Simultaneous measurements of the magnetic field dependence of the critical current density and the magnetization of yttrium barium cuprate superconductors have shown the presence of significant residual magnetic fluxes after the applied field has been reduced to zero. This trapped flux can be sufficient to leave the material in the mixed state and results in anomalous behavior of the observed electrical and magnetic properties. The flux appears to be associated with a magnetic field component threaded through the intergranular regions, whose motion is inhibited by circulating currents flowing in the granular system surrounding the field and preserved through the weak-link coupling. Once this coupling is destroyed, the field can move more freely. For a current-carrying sample in zero applied field, the Lorentz force due to the residual field causes the flux to leak from the sample, leading to the appearance of a voltage along the specimen.

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Golding, Madeleine J., Herbert E. Huppert, and Jerome A. Neufeld. "Two-phase gravity currents resulting from the release of a fixed volume of fluid in a porous medium." Journal of Fluid Mechanics 832 (October 26, 2017): 550–77. http://dx.doi.org/10.1017/jfm.2017.437.

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We consider the instantaneous release of a finite volume of fluid in a porous medium saturated with a second, immiscible fluid of different density. The resulting two-phase gravity current exhibits a rich array of behaviours due to both the residual trapping of fluid as the current recedes and the differing effects of surface tension between advancing and receding regions of the current. We develop a framework for the evolution of such a current with particular focus on the large-scale implications of the form of the constitutive relation between residual trapping and initial saturation. Pore-scale hysteresis within the current is represented by families of scanning curves relating capillary pressure and relative permeability to saturation. In the resulting vertically integrated model, all capillary effects are incorporated within specially defined saturation and flux functions specific to each region. In the long-time limit, when the height of the current and the saturations within it are low, the saturation and flux functions can be approximated by mathematically convenient power laws. If the trapping model is approximately linear at low saturations, the equations admit a similarity solution for the propagation rate and height profile of the late-time gravity current. We also solve the governing partial differential equation numerically for the nonlinear Land’s trapping model, which is commonly used in studies of two-phase flows. Our investigation suggests that for trapping relations for which the proportion of trapped to initial fluid saturation increases and tends to unity as the initial saturation decreases, both of which are properties of Land’s model, a gravity current slows and eventually stops. This trapping behaviour has important applications, for example to the ultimate distance contaminants or stored carbon dioxide may travel in the subsurface.

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Silverstein, R., and D. Eliezer. "Effects of residual stresses on hydrogen trapping in duplex stainless steels." Materials Science and Engineering: A 684 (January 2017): 64–70. http://dx.doi.org/10.1016/j.msea.2016.12.041.

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Suekane, Tetsuya, Tomohisa Nobuso, Shuichiro Hirai, and Masanori Kiyota. "Geological storage of carbon dioxide by residual gas and solubility trapping." International Journal of Greenhouse Gas Control 2, no. 1 (January 2008): 58–64. http://dx.doi.org/10.1016/s1750-5836(07)00096-5.

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Yap, D., and A. Megaritis. "Applying Forced Induction to Bioethanol HCCI Operation with Residual Gas Trapping." Energy & Fuels 19, no. 5 (September 2005): 1812–21. http://dx.doi.org/10.1021/ef0498162.

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Kitamura, Keigo, Tetsuya Kogure, Osamu Nishizawa, and Ziqiu Xue. "Experimental and Numerical Study of Residual CO2 Trapping in Porous Sandstone." Energy Procedia 37 (2013): 4093–98. http://dx.doi.org/10.1016/j.egypro.2013.06.310.

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Ni, Hailun, Maartje Boon, Charlotte Garing, and Sally M. Benson. "Coreflooding data on nine sandstone cores to measure CO2 residual trapping." Data in Brief 25 (August 2019): 104249. http://dx.doi.org/10.1016/j.dib.2019.104249.

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Zhao, Benzhong, Christopher W. MacMinn, and Ruben Juanes. "Residual trapping, solubility trapping and capillary pinning complement each other to limit CO2 migration in deep saline aquifers." Energy Procedia 63 (2014): 3833–39. http://dx.doi.org/10.1016/j.egypro.2014.11.412.

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Isakov, Matti, Stefan Hiermaier, and Veli-Tapani Kuokkala. "Improved specimen recovery in tensile split Hopkinson bar." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2023 (August 28, 2014): 20130194. http://dx.doi.org/10.1098/rsta.2013.0194.

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This paper presents an improved specimen recovery method for the tensile split Hopkinson bar (TSHB) technique. The method is based on the trapping of residual stress waves with the use of momentum trap bars. As is well known, successful momentum trapping in TSHB is highly sensitive to experimental uncertainties, especially on the incident bar side of the set-up. However, as is demonstrated in this paper, significant improvement in the reliability of specimen recovery is obtained by using two momentum trap bars in contact with the incident bar. This makes the trapping of the reflected wave insensitive to striker speed and removes the need for a precision set gap between the incident bar and the momentum trap.

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Sorkness, Ronald L., Eugene R. Bleecker, William W. Busse, William J. Calhoun, Mario Castro, Kian Fan Chung, Douglas Curran-Everett, et al. "Lung function in adults with stable but severe asthma: air trapping and incomplete reversal of obstruction with bronchodilation." Journal of Applied Physiology 104, no. 2 (February 2008): 394–403. http://dx.doi.org/10.1152/japplphysiol.00329.2007.

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Five to ten percent of asthma cases are poorly controlled chronically and refractory to treatment, and these severe cases account for disproportionate asthma-associated morbidity, mortality, and health care utilization. While persons with severe asthma tend to have more airway obstruction, it is not known whether they represent the severe tail of a unimodal asthma population, or a severe asthma phenotype. We hypothesized that severe asthma has a characteristic physiology of airway obstruction, and we evaluated spirometry, lung volumes, and reversibility during a stable interval in 287 severe and 382 nonsevere asthma subjects from the National Heart, Lung, and Blood Institute Severe Asthma Research Program. We partitioned airway obstruction into components of air trapping [indicated by forced vital capacity (FVC)] and airflow limitation [indicated by forced expiratory volume in 1 s (FEV1)/FVC]. Severe asthma had prominent air trapping, evident as reduced FVC over the entire range of FEV1/FVC. This pattern was confirmed with measures of residual lung volume/total lung capacity (TLC) in a subgroup. In contrast, nonsevere asthma did not exhibit prominent air trapping, even at FEV1/FVC <75% predicted. Air trapping also was associated with increases in TLC and functional reserve capacity. After maximal bronchodilation, FEV1 reversed similarly from baseline in severe and nonsevere asthma, but the severe asthma classification was an independent predictor of residual reduction in FEV1 after maximal bronchodilation. An increase in FVC accounted for most of the reversal of FEV1 when baseline FEV1 was <60% predicted. We conclude that air trapping is a characteristic feature of the severe asthma population, suggesting that there is a pathological process associated with severe asthma that makes airways more vulnerable to this component.

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Li, Tao, Ying Wang, Min Li, Jiahao Ji, Lin Chang, and Zheming Wang. "Study on the Impacts of Capillary Number and Initial Water Saturation on the Residual Gas Distribution by NMR." Energies 12, no. 14 (July 16, 2019): 2714. http://dx.doi.org/10.3390/en12142714.

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The determination of microscopic residual gas distribution is beneficial for exploiting reservoirs to their maximum potential. In this work, both forced and spontaneous imbibition (waterflooding) experiments were performed on a high-pressure displacement experimental setup, which was integrated with nuclear magnetic resonance (NMR) to reveal the impacts of capillary number (Ca) and initial water saturation (Swi) on the residual gas distribution over four magnitudes of injection rates (Q = 0.001, 0.01, 0.1 and 1 mL/min), expressed as Ca (logCa = −8.68, −7.68, −6.68 and −5.68), and three different Swi (Swi = 0%, 39.34% and 62.98%). The NMR amplitude is dependent on pore volumes while the NMR transverse relaxation time (T2) spectrum reflects the characteristics of pore size distribution, which is determined based on a mercury injection (MI) experiment. Using this method, the residual gas distribution was quantified by comparing the T2 spectrum of the sample measured after imbibition with the sample fully saturated by brine before imbibition. The results showed that capillary trapping efficiency increased with increasing Swi, and above 90% of residual gas existed in pores larger than 1 μm in the spontaneous imbibition experiments. The residual gas was trapped in pores by different capillary trapping mechanisms under different Ca, leading to the difference of residual gas distribution. The flow channels were mainly composed of micropores (pore radius, r < 1 μm) and mesopores (r = 1–10 μm) at logCa = −8.68 and −7.68, while of mesopores and macropores (r > 10 μm) at logCa = −5.68. At both Swi= 0% and 39.34%, residual gas distribution in macropores significantly decreased while that in micropores slightly increased with logCa increasing to −6.68 and −5.68, respectively.

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Punnam, Pradeep Reddy, Balaji Krishnamurthy, and Vikranth Kumar Surasani. "Influence of Caprock Morphology on Solubility Trapping during CO2 Geological Sequestration." Geofluids 2022 (June 25, 2022): 1–15. http://dx.doi.org/10.1155/2022/8016575.

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Carbon capture and sequestration (CCS) technology is one of the indispensable alternatives to reduce carbon dioxide (CO2) emissions. In this technology, carbon capture and transport grid will send CO2 to the storage facilities that are using various storage techniques. Geologic carbon sequestration (GCS) is one such storage technique where CO2 is injected into a deep geological subsurface formation. The injected CO2 is permanently stored in the formation due to structural, residual, solubility, and mineral trapping phenomena. Among different trapping mechanisms, solubility trapping plays a significant role in the safe operation of GCS. In this work, the study is conducted to elucidate the influence of top surface caprock morphology on the solubility trapping mechanism. The simulation results show that the naturally available heterogeneous formations with anticline and without anticline structure influence the solubility fingering phenomena and solubility entrapment percentage over a geological time scale. The lateral migration and sweeping efficiency results of both the synthetic domains for the injected CO2 have shown the importance of caprock morphology on solubility trapping and selection of injection rate. Quantification of solubility trapping in two morphological structures revealed that the synthetic domain without anticline morphology had shown higher solubility trapping. In the future, the simulation data using Artificial Neural Networks can be applied to predict the structural and solubility trapping of geological formations. This analysis further helps incorporating the interaction of CO2 with porous media leading to a mineral trapping mechanism.

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Niu, Ben, and Samuel Krevor. "The Impact of Mineral Dissolution on Drainage Relative Permeability and Residual Trapping in Two Carbonate Rocks." Transport in Porous Media 131, no. 2 (November 22, 2019): 363–80. http://dx.doi.org/10.1007/s11242-019-01345-4.

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AbstractCarbon dioxide injection into deep saline aquifers is governed by a number of physico-chemical processes including mineral dissolution and precipitation, multiphase fluid flow, and capillary trapping. These processes can be coupled; however, the impact of fluid–rock reaction on the multiphase flow properties is difficult to study and is not simply correlated with variations in porosity. We observed the impact of rock mineral dissolution on multiphase flow properties in two carbonate rocks with distinct pore structures. Observations of steady-state $$\hbox {N}_2$$N2–water relative permeability and residual trapping were obtained, along with mercury injection capillary pressure characteristics. These tests alternated with eight stages in which 0.5% of the mineral volume was uniformly dissolved into solution from the rock cores using an aqueous solution with a temperature-controlled acid. Variations in the multiphase flow properties did not relate simply to changes in porosity, but corresponded to the changes in the underlying pore structure. In the Ketton carbonate, dissolution resulted in an increase in the fraction of pore volume made up by the smallest pores and a decrease in the fraction made up by the largest pores. This resulted in an increase in the relative permeability to the nonwetting phase, a decrease in the relative permeability to the wetting phase, and a modest, but systematic decrease in residual trapping. In the Estaillades carbonate, dissolution resulted in an increase in the fraction of pore volume made up by pores in the central range of the initial pore size distribution, and a corresponding decrease in the fraction made up by both the smallest and largest pores. This resulted in a decrease in the relative permeability to both the wetting and nonwetting fluid phases and no discernible impact on the residual trapping. In summary, the impact of rock matrix dissolution will be strongly dependent on the impact of that dissolution on the underlying pore structure of the rock. However, if the variation in pore structure can be observed or estimated with modelling, then it should be possible to estimate the impacts on multiphase flow properties.

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Sorkness, Ronald L., Casey Kienert, Matthew J. O’Brien, Sean B. Fain, and Nizar N. Jarjour. "Compressive air trapping in asthma: effects of age, sex, and severity." Journal of Applied Physiology 126, no. 5 (May 1, 2019): 1265–71. http://dx.doi.org/10.1152/japplphysiol.00924.2018.

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Air trapping due to airway closure has been associated with unstable asthma. In addition to airway closure that occurs at lower lung volumes during slow expiration, there may be further closure during a forced expiration because of airway compression. The purpose of this study was to define a reference range from a nonasthmatic population and investigate the characteristics of compressive air trapping in asthma. Spirometry and plethysmography were performed in 117 nonasthmatic subjects (ages 18–87 yr) and 153 asthma subjects (ages 12–72 yr). Air trapping was assessed as residual lung volume and the ratio of forced expiratory vital capacity (FVC) to slow inspiratory vital capacity (iVC) (FVC/iVC). There were no significant age or sex effects on the FVC/iVC ratio in the nonasthmatic subjects, and a fifth percentile lower limit of normal (LLN) of 0.93 was computed. An FVC/iVC ratio less than LLN defined compressive air trapping. Asthma subjects exhibited an age-related decline in the FVC/iVC ratio of 0.0027 per year ( P < 0.0001) in a mixed effects model, with additional decreases associated with severe asthma and male sex. FVC/iVC ratios< LLN were infrequent in subjects <30 yr but evident in most asthma subjects >50 yr. Lung residual volumes followed similar patterns of greater elevations in subjects with severe asthma, older age, and male sex. Compressive air trapping occurs frequently in older asthmatics, appearing to be a feature of the natural history of asthma that is greater in severe asthma and men. This component of premature airway closure affects spirometric assessment of airway function and may contribute to asthma symptoms during physical exertion. NEW & NOTEWORTHY Premature airway closure during exhalation is a component of airway obstruction that is associated with asthma severity and instability. Compressive air trapping is airway closure that is more extensive during a forced exhalation than with a slow, passive exhalation. We report that compressive air trapping occurs in most people > 50 yr with asthma, affects men more than women, and persists after bronchodilator treatment. This component of obstruction appears to be part of the natural history of asthma.

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Labregere, Diane, Norhafiz Marmin, Suzanne Hurter, Johan Berge, and Alexander A. Lukyanov. "CO2 storage in saline formation: the impacts of reservoir properties and geometry on CO2 trapping mechanisms." APPEA Journal 49, no. 1 (2009): 405. http://dx.doi.org/10.1071/aj08024.

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Effective geological storage of CO2 can be accomplished through a number of trapping mechanisms. Physical trapping is achieved through either CO2 being trapped under a structural closure or CO2 made immobile in the pore space, as residual saturation, by capillary action. Geochemical trapping, which might be regarded as a more secure mode of storage, is achieved through dissolution of CO2 in formation water and precipitation of carbonates. The dissolution rate depends on surface contact and is generally enhanced by greater CO2 plume movement. During site selection, a potential injection well location is commonly evaluated with respect to the proximity to potential leakage features. This paper investigates requirements for separation distance between CO2 injection location and potential leakage features in highly permeable steeply dipping brine reservoir settings. Reservoir models are simulated with a compositional code and sensitivity analyses performed with variations in reservoir permeability, hysteresis effects, and formation dip. Trapping mechanisms, over a timescale of several centuries, are illustrated as key indicators for containment and storage performance. Study results suggest that the amount of CO2 trapped by dissolution and residual saturation is enhanced by a dynamically flowing plume. The simulation results demonstrate that the separation distance requirement typically envisaged in a worst-case reservoir geometry setting is commonly overly conservative, representing opportunity for further optimisation. Numerical simulation is useful in addressing the complex reality of flow dynamics such as hysteresis in footprint prediction. Understanding CO2 plume migration scenarios relative to potential leakage risks, under various key reservoir key properties, is essential in storage containment and capacity assessments for storage site selection and development.

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GODA, TAKASHI, and KOZO SATO. "Gravity currents of carbon dioxide with residual gas trapping in a two-layered porous medium." Journal of Fluid Mechanics 673 (February 14, 2011): 60–79. http://dx.doi.org/10.1017/s0022112010006178.

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In the geological sequestration of carbon dioxide (CO2), residual gas trapping plays an important role in immobilizing CO2. In this study, we investigate the propagation of gravity currents with residual gas trapping in a two-layered porous medium. We first formulate a model for a constant-flux release of a relatively less dense fluid (CO2) from a point source into a porous medium bounded above by a horizontal less-permeable seal. After a constant-flux release ceases, a fraction of the released fluid remains within the porous spaces at the trailing edge because of the capillary forces. This capillary retention is formulated in a model of gravity currents of a finite-volume release in the two-layered medium. In the latter model, the plume shape at the end of the constant-flux release is used as an initial profile. Using these models sequentially, the propagation of both cross-sectional and axisymmetric currents is quantitatively examined.

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Anton, Lucian, and R. Hilfer. "Trapping and mobilization of residual fluid during capillary desaturation in porous media." Physical Review E 59, no. 6 (June 1, 1999): 6819–23. http://dx.doi.org/10.1103/physreve.59.6819.

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SUEKANE, Tetsuya, and Masumi MATSUDA. "2610 Numerical Analysis on CO_2 Geological Storage Based on Residual Gas Trapping." Proceedings of the JSME annual meeting 2008.3 (2008): 179–80. http://dx.doi.org/10.1299/jsmemecjo.2008.3.0_179.

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39

Raza, Arshad, Raoof Gholami, Reza Rezaee, Chua Han Bing, Ramasamy Nagarajan, and Mohamed Ali Hamid. "Assessment of CO 2 residual trapping in depleted reservoirs used for geosequestration." Journal of Natural Gas Science and Engineering 43 (July 2017): 137–55. http://dx.doi.org/10.1016/j.jngse.2017.04.001.

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40

Zhang, Yingqi, Barry Freifeld, Stefan Finsterle, Martin Leahy, Jonathan Ennis-King, Lincoln Paterson, and Tess Dance. "Estimating CO2 residual trapping from a single-well test: Experimental design calculations." Energy Procedia 4 (2011): 5044–49. http://dx.doi.org/10.1016/j.egypro.2011.02.477.

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SUEKANE, Tetsuya, Tomohisa NOBUSO, and Shuichiro HIRAI. "4318 Studies on solubility and residual gas trapping of CO_2 geological storage." Proceedings of the JSME annual meeting 2006.3 (2006): 75–76. http://dx.doi.org/10.1299/jsmemecjo.2006.3.0_75.

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42

Zhang, Yingqi, Barry Freifeld, Stefan Finsterle, Martin Leahy, Jonathan Ennis-King, Lincoln Paterson, and Tess Dance. "Single-well experimental design for studying residual trapping of supercritical carbon dioxide." International Journal of Greenhouse Gas Control 5, no. 1 (January 2011): 88–98. http://dx.doi.org/10.1016/j.ijggc.2010.06.011.

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43

Green, Christopher P., and Jonathan Ennis-King. "Residual Trapping Beneath Impermeable Barriers During Buoyant Migration of $$\mathrm{CO}_2$$." Transport in Porous Media 98, no. 3 (April 10, 2013): 505–24. http://dx.doi.org/10.1007/s11242-013-0156-8.

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Breen, P. H., L. J. Becker, P. Ruygrok, I. Mayers, G. R. Long, A. Leff, and L. D. Wood. "Canine bronchoconstriction, gas trapping, and hypoxia with methacholine." Journal of Applied Physiology 63, no. 1 (July 1, 1987): 262–69. http://dx.doi.org/10.1152/jappl.1987.63.1.262.

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The effects of an intravenous methacholine infusion on cardiovascular-pulmonary function were measured in seven mongrel dogs (22.0 +/- 2.8 kg), anesthetized with chloralose and urethan and beta-adrenergically blocked with propranolol. In a volume-displacement plethysmograph, physiological measurements were made at base line and 25 min after establishing a methacholine infusion (0.1–1.0 mg X kg-1 X h-1). Methacholine significantly (P less than 0.05) increased airways resistance (1.9 +/- 0.8 to 8.2 +/- 2.9 cmH2O X l–1 X s), decreased static lung compliance (84.7 +/- 18.5 to 48.2 +/- 9.4 ml/cmH2O), depressed arterial PO2 (81 +/- 17 to 56 +/- 10 Torr), and lowered blood pressure (132 +/- 10 to 69 +/- 18 Torr) and cardiac output (5.7 +/- 1.9 to 4.1 +/- 1.2 l/min). These effects persisted during a further 80 min of methacholine infusion conducted in five of the animals. During the initial 25-min period of methacholine, the end-expired volume (volume-displacement Krogh spirometer) rose in all animals, indicating an increase in functional residual capacity from 997 +/- 115 to 1,623 +/- 259 ml (P less than 0.0005). Analysis of pulmonary pressure-volume curves revealed no change in total lung capacity but an increase in residual volume from 489 +/- 168 to 1,106 +/- 216 ml (P less than 0.001). Thus methacholine caused 617 ml of gas trapping, which was not detected by the Boyle's law principle, presumably because gas was trapped at high transpulmonary pressure. We suggest that intravenous methacholine-induced canine bronchoconstriction, which causes gas trapping and hypoxia, may be a useful animal model of clinical status asthmaticus.

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Liu, Danqing, Yilian Li, and Ramesh Agarwal. "Evaluation of CO2 Storage in a Shale Gas Reservoir Compared to a Deep Saline Aquifer in the Ordos Basin of China." Energies 13, no. 13 (July 2, 2020): 3397. http://dx.doi.org/10.3390/en13133397.

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As a new “sink” of CO2 permanent storage, the depleted shale reservoir is very promising compared to the deep saline aquifer. To provide a greater understanding of the benefits of CO2 storage in a shale reservoir, a comparative study is conducted by establishing the full-mechanism model, including the hydrodynamic trapping, adsorption trapping, residual trapping, solubility trapping as well as the mineral trapping corresponding to the typical shale and deep saline aquifer parameters from the Ordos basin in China. The results show that CO2 storage in the depleted shale reservoir has merits in storage safety by trapping more CO2 in stable immobile phase due to adsorption and having gentler and ephemeral pressure perturbation responding to CO2 injection. The effect of various CO2 injection schemes, namely the high-speed continuous injection, low-speed continuous injection, huff-n-puff injection and water alternative injection, on the phase transformation of CO2 in a shale reservoir and CO2-injection-induced perturbations in formation pressure are also examined. With the aim of increasing the fraction of immobile CO2 while maintaining a safe pressure-perturbation, it is shown that an intermittent injection procedure with multiple slugs of hug-n-puff injection can be employed and within the allowable range of pressure increase, and the CO2 injection rate can be maximized to increase the CO2 storage capacity and security in shale reservoir.

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Al-Khdheeawi, Emad A., Stephanie Vialle, Ahmed Barifcani, Mohammad Sarmadivaleh, and Stefan Iglauer. "Effect of the number of water alternating CO2 injection cycles on CO2 trapping capacity." APPEA Journal 59, no. 1 (2019): 357. http://dx.doi.org/10.1071/aj18191.

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The CO2 storage capacity is greatly affected by CO2 injection scenario – i.e. water alternating CO2 (WACO2) injection, intermittent injection, and continuous CO2 injection – and WACO2 injection strongly improves the CO2 trapping capacity. However, the impact of the number of WACO2 injection cycles on CO2 trapping capacity is not clearly understood. Thus, we developed a 3D reservoir model to simulate WACO2 injection in deep reservoirs testing different numbers of WACO2 injection cycles (i.e. one, two, and three), and the associated CO2 trapping capacity and CO2 plume migration were predicted. For all different WACO2 injection cycle scenarios, 5000 kton of CO2 and 5000 kton of water were injected at a depth of 2275m and 2125m respectively, during a 10-year injection period. Then, a 100-year CO2 storage period was simulated. Our simulation results clearly showed, after 100 years of storage, that the number of WACO2 cycles affected the vertical CO2 leakage and the capacity of trapped CO2. The results showed that increasing the number of WACO2 cycles decreased the vertical CO2 leakage. Furthermore, a higher number of WACO2 cycles increased residual trapping, and reduced solubility trapping. Thus, the number of WACO2 cycles significantly affected CO2 storage efficiency, and higher numbers of WACO2 cycles improved CO2 storage capacity.

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Ukaegbu, C., O. Gundogan, E. Mackay, G. Pickup, A. Todd, and F. Gozalpour. "Simulation of CO2 storage in a heterogeneous aquifer." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 223, no. 3 (March 3, 2009): 249–67. http://dx.doi.org/10.1243/09576509jpe627.

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The fate of carbon dioxide (CO2) injected into a deep saline aquifer depends largely on the geological structure within the aquifer. For example, low permeability layers, such as shales or mudstones, will act as barriers to vertical flow of CO2 gas, whereas high permeability channels may assist the lateral migration of CO2. It is therefore important to include permeability heterogeneity in models for numerical flow simulation As an example of a heterogeneous system, a model of fluvial-incised valley deposits was used. Flow simulations were performed using the generalized equation-of-state model—greenhouse gas software package from Computer Modelling Group, which is a compositional simulator, specially adapted for CO2 storage. The impacts of residual gas and water saturations, gas diffusion in the aqueous phase, hysteresis, and permeability anisotropy on the distribution of CO2 between the gaseous and aqueous phases were examined. Gas diffusion in the aqueous phase was found to significantly enhance solubility trapping of CO2, even when hysteretic trapping of CO2 as a residual phase is taken into account.

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Spiteri, Elizabeth J., Ruben Juanes, Martin J. Blunt, and Franklin M. Orr. "A New Model of Trapping and Relative Permeability Hysteresis for All Wettability Characteristics." SPE Journal 13, no. 03 (September 1, 2008): 277–88. http://dx.doi.org/10.2118/96448-pa.

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Summary The complex physics of multiphase flow in porous media are usually modeled at the field scale using Darcy-type formulations. The key descriptors of such models are the relative permeabilities to each of the flowing phases. It is well known that, whenever the fluid saturations undergo a cyclic process, relative permeabilities display hysteresis effects. In this paper, we investigate hysteresis in the relative permeability of the hydrocarbon phase in a two-phase system. We propose a new model of trapping and waterflood relative permeability, which is applicable for the entire range of rock wettability conditions. The proposed formulation overcomes some of the limitations of existing trapping and relative permeability models. The new model is validated by means of pore-network simulation of primary drainage and waterflooding. We study the dependence of trapped (residual) hydrocarbon saturation and waterflood relative permeability on several fluid/rock properties, most notably the wettability and the initial water saturation. The new model is able to capture two key features of the observed behavior:non-monotonicity of the initial-residual curves, which implies that waterflood relative permeabilities cross; andconvexity of the waterflood relative permeability curves for oil-wet media caused by layer flow of oil. Introduction Hysteresis refers to irreversibility or path dependence. In multiphase flow, it manifests itself through the dependence of relative permeabilities and capillary pressures on the saturation path and saturation history. From the point of view of pore-scale processes, hysteresis has at least two sources: contact angle hysteresis, and trapping of the nonwetting phase. The first step in characterizing relative permeability hysteresis is the ability to capture the amount of oil that is trapped during any displacement sequence. Indeed, a trapping model is the crux of any hysteresis model: it determines the endpoint saturation of the hydrocarbon relative permeability curve during waterflooding. Extensive experimental and theoretical work has focused on the mechanisms that control trapping during multiphase flow in porous media (Geffen et al. 1951; Lenormand et al. 1983; Chatzis et al. 1983). Of particular interest to us is the influence of wettability on the residual hydrocarbon saturation. Early experiments in uniformly wetted systems suggested that waterflood efficiency decreases with increasing oil-wet characteristics (Donaldson et al. 1969; Owens and Archer 1971). These experiments were performed on cores whose wettability was altered artificially, and the results need to be interpreted carefully for two reasons:reservoirs do not have uniform wettability, and the fraction of oil-wet pores is a function of the topology of the porous medium and initial water saturation (Kovscek et al. 1993); andthe coreflood experiments were not performed for a long enough time, and not enough pore volumes were injected to drain the remaining oil layers to achieve ultimate residual oil saturation. In other coreflood experiments, in which many pore volumes were injected, the observed trapped/residual saturation did not follow a monotonic trend as a function of wettability, and was actually lowest for intermediate-wet to oil-wet rocks (Kennedy et al. 1955; Moore and Slobod 1956; Amott 1959). Jadhunandan and Morrow (1995) performed a comprehensive experimental study of the effects of wettability on waterflood recovery, showing that maximum oil recovery was achieved at intermediate-wet conditions. An empirical trapping model typically relates the trapped (residual) hydrocarbon saturation to the maximum hydrocarbon saturation; that is, the hydrocarbon saturation at flow reversal. In the context of waterflooding, a trapping model defines the ultimate residual oil saturation as a function of the initial water saturation. The most widely used trapping model is that of Land (1968). It is a single-parameter model, and constitutes the basis for a number of relative permeability hysteresis models. Other trapping models are those of Jerauld (1997a) and Carlson (1981). These models are suitable for their specific applications but, as we show in this paper, they have limited applicability to intermediate-wet and oil-wet media. Land (1968) pioneered the definition of a "flowing saturation," and proposed to estimate the imbibition relative permeability at a given actual saturation as the drainage relative permeability evaluated at a modeled flowing saturation. Land's imbibition model (1968) gives accurate predictions for water-wet media (Land 1971), but fails to capture essential trends when the porous medium is weakly or strongly wetting to oil. The two-phase hysteresis models that are typically used in reservoir simulators are those by Carlson (1981) and Killough (1976). A three-phase hysteresis model that accounts for essential physics during cyclic flooding was proposed by Larsen and Skauge (1998). These models have been evaluated in terms of their ability to reproduce experimental data (Element et al. 2003; Spiteri and Juanes 2006), and their impact in reservoir simulation of water-alternating-gas injection (Spiteri and Juanes 2006; Kossack 2000). Other models are those by Lenhard and Parker (1987), Jerauld (1997a), and Blunt (2000). More recently, hysteresis models have been proposed specifically for porous media of mixed wettability (Lenhard and Oostrom 1998; Moulu et al. 1999; Egermann et al. 2000). All of the hysteresis models described require a bounding drainage curve and either a waterflood curve as input, or a calculated waterflood curve using Land's model. The task of experimentally determining the bounding waterflood curves from core samples is arduous, and the development of an empirical model that is applicable to non-water-wet media is desirable. In this paper, we introduce a relative permeability hysteresis model that does not require a bounding waterflood curve, and whose parameters may be correlated to rock properties such as wettability and pore structure. Because it is difficult to probe the full range of relative permeability hysteresis for different wettabilities experimentally, we use a numerical tool--pore-scale modeling--to predict the trends in residual saturation and relative permeability. As we discuss later, pore-scale modeling is currently able to predict recoveries and relative permeabilities for media of different wettability reliably (Dixit et al. 1999; Øren and Bakke 2003; Jackson et al. 2003; Valvatne and Blunt 2004; Al-Futaisi and Patzek 2003, 2004). We will use these predictions as a starting point to explore the behavior beyond the range probed experimentally. In summary, this paper presents a new model of trapping and waterflood relative permeability, which is able to capture the behavior predicted by pore-network simulations for the entire range of wettability conditions.

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Ahn, Haejin, Seon-Ok Kim, Minhee Lee, and Sookyun Wang. "Migration and Residual Trapping of Immiscible Fluids during Cyclic Injection: Pore-Scale Observation and Quantitative Analysis." Geofluids 2020 (July 16, 2020): 1–13. http://dx.doi.org/10.1155/2020/4569208.

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Geological CO2 sequestration (GCS) is one of the most promising technologies for mitigating greenhouse gas emission into the atmosphere. In GCS operations, residual trapping is the most favorable form of a trapping mechanism because of its storage security and capacity. In this study, the effects of cyclic injection of CO2-water on the immiscible displacement and residual trapping in pore networks were examined. For the purpose, a series of injection experiments with five sets of drainage-imbibition cycles were performed using 2D transparent micromodels and a pair of proxy fluids, n-hexane, and deionized water. The multiphase flow and immiscible displacement phenomena during drainage and imbibition processes in pore networks were visually observed, and the temporal and spatial changes in distribution and saturation of the two immiscible fluids were quantitatively estimated at the pore scale using image analysis techniques. The results showed that the mobile region of invading fluids decreased asymptotically as the randomly diverged flow paths gradually converged into less ramified ones over multiple cycles. Such decrease was accompanied by a gradual increase of the immobile region, which consists of tiny blobs and clusters of immiscible fluids. The immobile region expanded as streams previously formed by the insertion of one fluid dispersed into numerous isolated, small-scale blobs as the other fluid was newly injected. These processes repeated until the immobile region approached the main flow channels. The observations and analyses in this study implied that the application of cyclic injection in GCS operations may be used to store large-scale CO2 volume in small-scale dispersed forms, which may significantly improve the effectiveness and security of geological CO2 sequestration.

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Polischuk, B., S. O. Kasap, Viswanath Aiyah, A. Baillie, and M. A. Abkowitz. "Measurement of mobility-lifetime products in amorphous semiconductors." Canadian Journal of Physics 69, no. 3-4 (March 1, 1991): 361–69. http://dx.doi.org/10.1139/p91-061.

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Charge-carrier drift-mobility-lifetime (μτ) product, the range of the carrier, is one of the most important electronic properties of a semiconductor material for device applications. The determination of μτ is, therefore, of fundamental importance in the characterization of amorphous semiconductors and has been the key issue in a number of recent papers. This paper describes two experimental techniques for μτ product measurements and their application to a-Se and Cl-doped Se:0.35%As electro-radiographic films. Xerographic measurements involve corona charging the surface of an amorphous semiconductor film to a voltage Vo. The film is then exposed to a highly absorbed step illumination at the end of which the residual potential, VR1, on the surface is measured. VR1/Vo is then related to μτ. In the interrupted field time-of-flight (IFTOF) measurement technique, during the flight of the photoinjected holes through the specimen, the applied field is removed at time T1 for an interruption duration of ti and then reapplied and the remaining holes extracted. The fractional recovered photocurrent at the end of the interruption time, ti was found to follow the deep-trapping kinetics described by i(T1 + ti)/i(T1) = exp (−ti/τ) where τ is the charge-carrier lifetime. By interrupting the time-of-flight photocurrent at different locations, the technique allows for the determination of the trapping time τ as a function of location across the specimen and hence the examination of sample inhomogeneities. Xerographic residual potential and IFTOF experiments carried out on a range of a-Se and Cl-doped a-Se:0.35%As electroradiographic films show that there is a good correlation between the trapping time determined from xerographic measurements and that determined from IFTOF. The results are discussed in terms of carrier-trapping processes in amorphous semiconductors. The capture cross section of deep hole traps in a-Se and Cl-doped a-Se:0.35%As is determined from the measurement of the hole-mobility-lifetime product and the saturated cycled-up residual potential. Application of the ballistic and diffusional models of Street (Philos. Mag. B, 49, L15 (1984)) indicate that the hole-capture radius in a-Se is 2–3 Å (1 Å = 10−1 m) and that the chemical modification of a-Se by combinational doping with 0.35%As and 10–20 ppm Cl does not affect the basic capture process. The two experimental techniques described represent the most meaningful methods of charge transport and trapping characterization in amorphous semiconductors.

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Journal articles on the topic 'Residual Trapping'

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