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1
Mulyadi, Henny. "Determination of residual gas staturation and gas-water relative permeability in water-driven gas reserviors /." Full text available, 2002. http://adt.curtin.edu.au/theses/available/adt-WCU20030702.131009.
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Mulyadi, Henny. "Determination of residual gas saturation and gas-water relative permeability in water-driven gas reservoirs." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/1294.
Full textAbstract:
The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.
3
Mulyadi, Henny. "Determination of residual gas saturation and gas-water relative permeability in water-driven gas reservoirs." Curtin University of Technology, Department of Petroleum Engineering, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12957.
Full textAbstract:
The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques ++were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing ++
field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.
4
Al-Kharusi, Badr Soud. "Relative permeability of gas-condensate near wellbore, and gas-condensate-water in bulk of reservoir." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1098.
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Al-Shajalee, Faaiz Hadi Rasheed. "Relative Permeability Modification in Gas Wells with Excessive Water Production- An Experimental Investigation." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/89365.
Full textAbstract:
Polymers have been used as relative permeability modifiers (RPM) to selectively reduce water production with minimum effect on the hydrocarbon phase. The experimental results show that initial rock permeability can be used as an important screening parameter in planning an RPM treatment. The relative pore size alteration due to the RPM treatment impacts on RPM performance. The RPM performance is also significantly fluid flow rate dependent. Therefore, flow rate should be considered during RPM design.
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Sidiq, Hiwa. "Advance water abatement in oil and gas reservoir." Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/191.
Full textAbstract:
The control of excessive water production in oil and gas producing wells is of increasing importance to the field operator, primarily when trying to maintain the survivability of a mature field from shut in. During the last two decades many chemicals have been studied and applied under the name of relative permeability modifier (RPM) to combat this problem. These chemicals were mostly bullheaded individually into the affected zones, consequently their application resulted in low to medium success, particularly in treating reservoirs suffering from matrix flow. It has been found that the disproportionate permeability reduction depends on the amount of polymer dispersed or absorbed by the porous rock. If single polymers are employed to treat excessive water production in a matrix reservoir they cannot penetrate deep into the formation rock because the polymer will start to build as a layer on the surface of the rock grains. As a result the placement of polymer into the formation will no be piston like and the dispersion over the rock pores will be uneven. To improve water shutoff technology a method of injecting chemicals sequentially is recommended provided that the chemical’s viscosity is increasing successively with the chemicals injected.Experimentally confirmed, injecting chemicals sequentially provides better results for conformance control. The value of post treatment water mobility is conspicuously lowered by the method of applying injecting chemicals sequentially in comparison with the single chemical injection method. For instance, the residual resistance factor to water (Frrw) at the first cycle of brine flushing for this method is approximately five times higher than the Frrw obtained by injecting only one single chemical. Furthermore, for the second cycle of brine flushing Frrw is still higher by a ratio of about 2.5. In addition to this improvement residual resistance factor to oil Frro for this method is less than two which has been considered as the upper limit for conformance control in matrix reservoir. Accordingly injecting chemical sequentially can be applied for enhancing relative permeability modifier performance in matrix reservoir.
7
Sidiq, Hiwa. "Advance water abatement in oil and gas reservoir." Curtin University of Technology, Department of Chemical Engineering, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17578.
Full textAbstract:
The control of excessive water production in oil and gas producing wells is of increasing importance to the field operator, primarily when trying to maintain the survivability of a mature field from shut in. During the last two decades many chemicals have been studied and applied under the name of relative permeability modifier (RPM) to combat this problem. These chemicals were mostly bullheaded individually into the affected zones, consequently their application resulted in low to medium success, particularly in treating reservoirs suffering from matrix flow. It has been found that the disproportionate permeability reduction depends on the amount of polymer dispersed or absorbed by the porous rock. If single polymers are employed to treat excessive water production in a matrix reservoir they cannot penetrate deep into the formation rock because the polymer will start to build as a layer on the surface of the rock grains. As a result the placement of polymer into the formation will no be piston like and the dispersion over the rock pores will be uneven. To improve water shutoff technology a method of injecting chemicals sequentially is recommended provided that the chemical’s viscosity is increasing successively with the chemicals injected.Experimentally confirmed, injecting chemicals sequentially provides better results for conformance control. The value of post treatment water mobility is conspicuously lowered by the method of applying injecting chemicals sequentially in comparison with the single chemical injection method. For instance, the residual resistance factor to water (Frrw) at the first cycle of brine flushing for this method is approximately five times higher than the Frrw obtained by injecting only one single chemical. Furthermore, for the second cycle of brine flushing Frrw is still higher by a ratio of about 2.5. In addition to this improvement residual resistance factor to oil Frro for this method is less than two which has been considered as the upper limit for conformance control in matrix reservoir. Accordingly injecting chemical sequentially can be applied for enhancing relative permeability modifier performance in matrix reservoir.
8
Sagbana, Perekaboere Ivy. "Effect of surfactant on three phase relative permeability in water-alternating-gas flooding experiment." Thesis, London South Bank University, 2017. http://researchopen.lsbu.ac.uk/1848/.
Full textAbstract:
Three-phase flow occurs in petroleum reservoirs during tertiary enhanced oil recovery processes such as water-alternating-gas flooding (WAG). WAG process is used to improve the efficiency of gas flooding by controlling gas mobility. Water traps gas in the reservoir when injected alternatively in WAG. Continuous gas trapping causes a blocking effect that prevents the oil from being contacted by the water. Surfactants are introduced in WAG processes to decrease this water blocking effect and improve oil recovery. This technique of introducing surfactant in WAG processes is known as surfactant-alternating-gas flooding (SAG). One of the important parameters to accurately model complex processes such as SAG is the relative permeability to each of the flowing fluids. However, relative permeability in SAG processes become extremely complicated due to different flow mechanisms and fluid interactions involved. Several researches in the open literature are based on three-phase relative permeability in WAG using three-phase empirical correlations for prediction. Few researchers have conducted experiments on SAG flooding, but their research focused on the aspect of oil recovery only. The aim of this research project is to obtain a better understanding of surfactant interaction in three-phase flow. To do so, a surfactant formulation compatible with the oil and brine was selected by conducting aqueous stability test, surfactant phase behaviour and surfactant adsorption experiments. Water/oil interfacial tension was measured to determine the initial interfacial tension before surfactant injection. Surfactant/oil interfacial tension was calculated using Huh’s correlation. This was followed by two and three-phase core flooding experiments. The results showed that alcohol alkoxy sulphate and internal olefin surfactant blend is most suitable formulation compatible with the brine and oil by reducing water/oil interfacial tension from 22.7 mN/m to 1 x 10- ³ mN/m and having very low adsorption of 0.00135 mg/g adsorption on the core sample. Two-phase water/oil, gas/oil and gas/water experiments were conducted with and without surfactants to evaluate the effect of surfactants when only two fluids are present in the porous media. Sigmund and McCaffery correlation was used in Sendra software to history match experimental differential pressure and oil production data to obtain relative permeability curves. The results showed that in water/oil displacement experiment, the presence of surfactant increases oil relative permeability but did not have any effect on water relative permeability. The cross point of the relative permeability curves moved further to the right indicating that surfactant increases the water wetness of the core sample causing oil to flow freely. Oil production increased in the presence of surfactant, this increase in oil production is because of the reduction in water/oil interfacial tension and decrease in pressure gradient during the experiment. There was an increase in oil production and oil relative permeability also in gas/oil displacement experiment in the presence of surfactant when compared to gas/oil displacement experiment without surfactant. While in gas/water displacement experiment, a significant decrease in gas relative permeability occurred in the presence of surfactant when compared to gas/water displacement experiment with no surfactant. To study surfactant effect on three-phase relative permeability, WAG and SAG core flooding experiments were conducted. The extension of JBN/Welge theory by Grader and O’Meara was applied to calculate three phase relative permeability. Eclipse reservoir simulation software was used to simulate surfactant WAG to predict surfactant effect on three-phase relative permeability using the three-phase correlations such as Stone 1, Stone 2, saturated weighted interpolation, linear interpolation and Stone exponent present in the software. Results from three-phase displacement experiments showed that the presence of surfactant does not have any effect on water relative permeability in three-phase flow. Oil relative permeability was affected by the presence of surfactant and gas. Oil relative permeability and recovery factor were higher in SAG when compared to WAG. In three-phase flow, gas relative permeability was lower in SAG compared to WAG. Gas breakthrough in the presence surfactant occurred at 0.48pore volume while in WAG breakthrough occurred at 0.34 pore volume. The decrease in gas relative permeability was because of foam creation with gas interaction with the surfactant. None of the three-phase relative permeability correlations could accurately predict the effect surfactant on three-phase relative permeability in WAG.
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Calisgan, Huseyin. "Comprehensive Modelling Of Gas Condensate Relative Permeability And Its Influence On Field Performance." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606667/index.pdf.
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The productivity of most gas condensate wells is reduced significantly due to condensate banking when the bottom hole pressure falls below the dew point. The liquid drop-out in these very high rate gas wells may lead to low recovery problems. The most important parameter for determining condensate well productivity is the effective gas permeability in the near wellbore region, where very high velocities can occur. An understanding of the characteristics of the high-velocity gas-condensate flow and relative permeability data is necessary for accurate forecast of well productivity.
In order to tackle this goal, a series of two-phase drainage relative permeability measurements on a moderate permeability North Marmara &ndash1 gas well carbonate core plug sample, using a simple synthetic binary retrograde condensate fluid sample were conducted under reservoir conditions which corresponded to near miscible conditions. As a fluid system, the model of methanol/n-hexane system was used as a binary model that exhibits a critical point at ambient conditions. The interfacial tension by means of temperature and the flow rate were varied in the laboratory measurements. The laboratory experiments were repeated for the same conditions of interfacial tension and flow rate at immobile water saturation to observe the influence of brine saturation in gas condensate systems. The laboratory experiment results show a clear trend from the immiscible relative permeability to miscible relative permeability lines with decreasing interfacial tension and increasing velocity. So that, if the interfacial tension is high and the flow velocity is low, the relative permeability functions clearly curved, whereas the relative permeability curves straighten as a linear at lower values of the interfacial tension and higher values of the flow velocity. The presence of the immobile brine saturation in the porous medium shows the same shape of behavior for relative permeability curves with a small difference that is the initial wetting phase saturations in the relative permeability curve shifts to the left in the presence of immobile water saturation. A simple new mathematical model is developed to compute the gas and condensate relative permeabilities as a function of the three-parameter. It is called as condensate number
NK so that the new model is more sensitivity to temperature that represents implicitly the effect of interfacial tension. The new model generated the results were in good agreement with the literature data and the laboratory test results. Additionally, the end point relative permeability data and residual saturations satisfactorily correlate with literature data. The proposed model has fairly good fitness results for the condensate relative permeability curves compared to that of gas case. This model, with typical parameters for gas condensates, can be used to describe the relative permeability behavior and to run a compositional simulation study of a single well to better understand the productivity of the field.
10
Sole, Joshua David. "Investigation of Water Transport Parameters and Processes in the Gas Diffusion Layer of PEM Fuel Cells." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27538.
Full textAbstract:
Constitutive relationships are developed to describe the water transport characteristics of the gas diffusion layer (GDL) of proton exchange membrane fuel cells (PEMFCs). Additionally, experimental fixtures and procedures for the determination of the constitutive relationships are presented. The water transport relationships are incorporated into analytical models that assess the impact of the water transport relations and that make PEMFC performance predictions. The predicted performance is then compared to experimental results.
The new constitutive relationships are significantly different than the currently popular relationships used in PEMFC modeling because they are derived from experiments on actual PEMFC gas diffusion layer materials. In prior work, properties of the GDL materials such as absolute permeability, liquid water relative permeability, porosity, and capillary behavior are often assumed or used as adjustment parameters in PEMFC models to simplify the model or to achieve good fits with polarization data. In this work, the constitutive relations are not assumed but are determined via newly developed experimental techniques.
The experimental fixtures and procedures were used to characterize common GDL materials including carbon papers and carbon cloths, and to investigate common treatments applied to these materials such as the bulk application of a hydrophobic polymer within the porous structure.
A one-dimensional model is developed to contrast results based on the new constitutive relations with results based on commonly used relationships from the PEMFC literature. The comparison reveals that water transport relationships can have a substantial impact on predicted GDL saturation, and consequently a significant impact on cell performance. The discrepancy in saturation between cases can be nearly an order of magnitude. A two-dimensional model is also presented that includes the impact of the compressed GDL region under the shoulder of a bipolar plate. Results show that the compression due to the bipolar plate shoulder causes a significant increase in liquid saturation, and a significant reduction in oxygen concentration and current density for the paper GDL. In contrast, compression under the shoulder has a minimal impact on the cloth GDL. Experimental inputs to the 2-D model include: absolute permeability, liquid water relative permeability, the slope of the capillary pressure function with saturation, total porosity, GDL thickness, high frequency resistance, and appropriate Tafel parameters. Computational polarization curve results are compared to experimental polarization behavior and good agreement is achieved.Ph. D.
11
Escorihuela, Roca Sara. "Novel gas-separation membranes for intensified catalytic reactors." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/121139.
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[ES] La presente tesis doctoral se centra en el desarrollo de nuevas membranas de separación de gases, así como su empleo in-situ en reactores catalíticos de membrana para la intensificación de procesos. Para este propósito, se han sintetizado varios materiales, como polímeros para la fabricación de membranas, catalizadores tanto para la metanación del CO2 como para la reacción de síntesis de Fischer-Tropsch, y diversas partículas inorgánicas nanométricas para su uso en membranas de matriz mixta. En lo referente a la fabricación de las membranas, la tesis aborda principalmente dos tipos: orgánicas e inorgánicas. Con respecto a las membranas orgánicas, se han considerado diferentes materiales poliméricos, tanto para la capa selectiva de la membrana, así como soporte de la misma. Se ha trabajado con poliimidas, puesto que son materiales con temperaturas de transición vítrea muy alta, para su posterior uso en reacciones industriales que tienen lugar entre 250-300 ºC. Para conseguir membranas muy permeables, manteniendo una buena selectividad, es necesario obtener capas selectivas de menos de una micra. Usando como material de soporte otro tipo de polímero, no es necesario estudiar la compatibilidad entre ellos, siendo menos compleja la obtención de capas finas. En cambio, si el soporte es de tipo inorgánico, un exhaustivo estudio de la relación entre la concentración y la viscosidad de la solución polimérica es altamente necesario. Diversas partículas inorgánicas nanométricas se estudiaron para favorecer la permeación de agua a través de los materiales poliméricos. En segundo lugar, en cuanto a membranas inorgánicas, se realizó la funcionalización de una membrana de paladio para favorecer la permeación de hidrógeno y evitar así la contaminación por monóxido de carbono. El motivo por el cual se dopó con otro metal la capa selectiva de la membrana metálica fue para poder emplearla en un reactor de Fischer-Tropsch. Con relación al diseño y fabricación de los reactores, durante esta tesis, se desarrolló el prototipo de un microreactor para la metanación de CO2, donde una membrana polimérica de capa fina selectiva al agua se integró para evitar la desactivación del catalizador, y a su vez desplazar el equilibrio y aumentar la conversión de CO2. Por otro lado, se rediseñó un reactor de Fischer-Tropsch para poder introducir una membrana metálica selectiva a hidrogeno y poder inyectarlo de manera controlada. De esta manera, y siguiendo estudios previos, el objetivo fue mejorar la selectividad a los productos deseados mediante el hidrocraqueo y la hidroisomerización de olefinas y parafinas con la ayuda de la alta presión parcial de hidrógeno.[CAT] La present tesi doctoral es centra en el desenvolupament de noves membranes de separació de gasos, així com el seu ús in-situ en reactors catalítics de membrana per a la intensificació de processos. Per a aquest propòsit, s'han sintetitzat diversos materials, com a polímers per a la fabricació de membranes, catalitzadors tant per a la metanació del CO2 com per a la reacció de síntesi de Fischer-Tropsch, i diverses partícules inorgàniques nanomètriques per al seu ús en membranes de matriu mixta. Referent a la fabricació de les membranes, la tesi aborda principalment dos tipus: orgàniques i inorgàniques. Respecte a les membranes orgàniques, diferents materials polimèrics s'ha considerat com a candidats prometedors, tant per a la capa selectiva de la membrana, així com com a suport d'aquesta. S'ha treballat amb poliimides, ja que són materials amb temperatures de transició vítria molt alta, per al seu posterior ús en reaccions industrials que tenen lloc entre 250-300 °C. Per a aconseguir membranes molt permeables, mantenint una bona selectivitat, és necessari obtindre capes selectives de menys d'una micra. Emprant com a material de suport altre tipus de polímer, no és necessari estudiar la compatibilitat entre ells, sent menys complexa l'obtenció de capes fines. En canvi, si el suport és de tipus inorgànic, un exhaustiu estudi de la relació entre la concentració i la viscositat de la solució polimèrica és altament necessari. Diverses partícules inorgàniques nanomètriques es van estudiar per a afavorir la permeació d'aigua a través dels materials polimèrics. En segon lloc, quant a membranes inorgàniques, es va realitzar la funcionalització d'una membrana de pal¿ladi per a afavorir la permeació d'hidrogen i evitar la contaminació per monòxid de carboni. El motiu pel qual es va dopar amb un altre metall la capa selectiva de la membrana metàl¿lica va ser per a poder emprar-la en un reactor de Fischer-Tropsch. En relació amb el disseny i fabricació dels reactors, durant aquesta tesi, es va desenvolupar el prototip d'un microreactor per a la metanació de CO2, on una membrana polimèrica de capa fina selectiva a l'aigua es va integrar per a així evitar la desactivació del catalitzador i al seu torn desplaçar l'equilibri i augmentar la conversió de CO2. D'altra banda, un reactor de Fischer-Tropsch va ser redissenyat per a poder introduir una membrana metàl¿lica selectiva a l'hidrogen i poder injectar-lo de manera controlada. D'aquesta manera, i seguint estudis previs, el objectiu va ser millorar la selectivitat als productes desitjats mitjançant el hidrocraqueix i la hidroisomerització d'olefines i parafines amb l'ajuda de l'alta pressió parcial d'hidrogen.
[EN] The present thesis is focused on the development of new gas-separation membranes, as well as their in-situ integration on catalytic membrane reactors for process intensification. For this purpose, several materials have been synthesized such as polymers for membrane manufacture, catalysts for CO2 methanation and Fischer-Tropsch synthesis reaction, and inorganic materials in form of nanometer-sized particles for their use in mixed matrix membranes. Regarding membranes manufacture, this thesis deals mainly with two types: organic and inorganic. With regards to the organic membranes, different polymeric materials have been considered as promising candidates, both for the selective layer of the membrane, as well as a support thereof. Polyimides have been selected since they are materials with very high glass transition temperatures, in order to be used in industrial reactions which take place at temperatures around 250-300 ºC. To obtain highly permeable membranes, while maintaining a good selectivity, it is necessary to develop selective layers of less than one micron. Using another type of polymer as support material, it is not necessary to study the compatibility between membrane and support. On the other hand, if the support is inorganic, an exhaustive study of the relation between the concentration and the viscosity of the polymer solution is highly necessary. In addition, various inorganic particles were studied to favor the permeation of water through polymeric materials. Secondly, as regards to inorganic membranes, the functionalization of a palladium membrane to favor the permeation of hydrogen and avoid carbon monoxide contamination was carried out. The membrane selective layer was doped with another metal in order to be used in a Fischer-Tropsch reactor. Regarding the design and manufacture of the reactors used during this thesis, a prototype of a microreactor for CO2 methanation was carried out, where a thin-film polymer membrane selective to water was integrated to avoid the deactivation of the catalyst and to displace the equilibrium and increase the CO2 conversion. On the other hand, a Fischer-Tropsch reactor was redesigned to introduce a hydrogen-selective metal membrane and to be able to inject it in a controlled manner. In this way, and following previous studies, the aim is to enhance the selectivity to the target products by hydrocracking and hydroisomerization the olefins and paraffins assisted by the presence of an elevated partial pressure of hydrogen.
I would like to acknowledge the Spanish Government, for funding my research with the Severo Ochoa scholarship.
Escorihuela Roca, S. (2019). Novel gas-separation membranes for intensified catalytic reactors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/121139
TESIS
12
Gode, Peter. "Investigations of proton coducting polymers and gas diffusion electrodes for the polymer electrolyte fuel cell." Doctoral thesis, KTH, Chemical Engineering and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-97.
Full textAbstract:
Polymer electrolyte fuel cells (PEFC) convert the chemically bound energy in a fuel, e.g. hydrogen, directly into electricity by an electrochemical process. Examples of future applications are energy conversion such as combined heat and power generation (CHP), zero emission vehicles (ZEV) and consumer electronics. One of the key components in the PEFC is the membrane / electrode assembly (MEA). Both the membrane and the electrodes consist of proton conducting polymers (ionomers). In the membrane, properties such as gas permeability, high proton conductivity and sufficient mechanical and chemical stability are of crucial importance. In the electrodes, the morphology and electrochemical characteristics are strongly affected by the ionomer content. The primary purpose of the present thesis was to develop experimental techniques and to use them to characterise proton conducting polymers and membranes for PEFC applications electrochemically at, or close to, fuel cell operating conditions. The work presented ranges from polymer synthesis to electrochemical characterisation of the MEA performance.
The use of a sulfonated dendritic polymer as the acidic component in proton conducting membranes was demonstrated. Proton conducting membranes were prepared by chemical cross-linking or in conjunction with a basic functionalised polymer, PSU-pyridine, to produce acid-base blend membranes. In order to study gas permeability a new in-situ method based on cylindrical microelectrodes was developed. An advantage of this method is that the measurements can be carried out at close to real fuel cell operating conditions, at elevated temperature and a wide range of relative humidities. The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and electrochemical impedance measurements (EIS). Long-term experiments have been compared to fast ex situ testing in 3 % H2O2 solution. For the direct assessment of membrane degradation, micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF-based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. The influence of ionomer content on the structure and electrochemical characteristics of Nafion-based PEFC cathodes was also demonstrated. The electrodes were thoroughly investigated using various materials and electrochemical characterisation techniques. Electrodes having medium Nafion contents (35
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Gode, Peter. "Investigations of proton conducting polymers and gas diffusion electrodes in the polymer electrolyte fuel cell." Doctoral thesis, KTH, Tillämpad elektrokemi, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-97.
Full textAbstract:
Polymer electrolyte fuel cells (PEFC) convert the chemically bound energy in a fuel, e.g. hydrogen, directly into electricity by an electrochemical process. Examples of future applications are energy conversion such as combined heat and power generation (CHP), zero emission vehicles (ZEV) and consumer electronics. One of the key components in the PEFC is the membrane / electrode assembly (MEA). Both the membrane and the electrodes consist of proton conducting polymers (ionomers). In the membrane, properties such as gas permeability, high proton conductivity and sufficient mechanical and chemical stability are of crucial importance. In the electrodes, the morphology and electrochemical characteristics are strongly affected by the ionomer content. The primary purpose of the present thesis was to develop experimental techniques and to use them to characterise proton conducting polymers and membranes for PEFC applications electrochemically at, or close to, fuel cell operating conditions. The work presented ranges from polymer synthesis to electrochemical characterisation of the MEA performance. The use of a sulfonated dendritic polymer as the acidic component in proton conducting membranes was demonstrated. Proton conducting membranes were prepared by chemical cross-linking or in conjunction with a basic functionalised polymer, PSU-pyridine, to produce acid-base blend membranes. In order to study gas permeability a new in-situ method based on cylindrical microelectrodes was developed. An advantage of this method is that the measurements can be carried out at close to real fuel cell operating conditions, at elevated temperature and a wide range of relative humidities. The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and electrochemical impedance measurements (EIS). Long-term experiments have been compared to fast ex situ testing in 3 % H2O2 solution. For the direct assessment of membrane degradation, micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF-based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. The influence of ionomer content on the structure and electrochemical characteristics of Nafion-based PEFC cathodes was also demonstrated. The electrodes were thoroughly investigated using various materials and electrochemical characterisation techniques. Electrodes having medium Nafion contents (35<x<45 wt %) showed the best performance. The mass-transport limitation was essentially due to O2 diffusion in the agglomerates. The performance of cathodes with low Nafion content (<30 wt %) is limited by poor kinetics owing to incomplete wetting of platinum (Pt) by Nafion, by proton migration throughout the cathode as well as by O2 diffusion in the agglomerates. At large Nafion content (>45 wt %), the cathode becomes limited by diffusion of O2 both in the agglomerates and throughout the cathode. Furthermore, models for the membrane coupled with kinetics for the hydrogen electrode, including water concentration dependence, were developed. The models were experimentally validated using a new reference electrode approach. The membrane, as well as the hydrogen anode and cathode characteristics, was studied experimentally using steady-state measurements, current interrupt and EIS. Data obtained with the experiments were in good agreement with the modelled results.QC 20101014
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Lieboldt, Matthias, and Viktor Mechtcherine. "Medientransport durch Verstärkungsschichten aus textilbewehrtem Beton." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244045285527-10721.
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In den durchgeführten Versuchsreihen wurden die Wasserabsorption sowie die Gas- und Wasserpermeabilität sowohl an gerissenen als auch rissfreien Prüfkörpern aus textilbewehrtem Beton (TRC) untersucht. Eine deutliche Steigerung der Wasseraufnahme bei Proben mit unbeschichteten Textilien konnte mit Zunahme der Garnfeinheit beobachtet werden. Bei den gerissenen Proben besteht eine ausgeprägte Abhängigkeit der Transportraten von Flüssigkeiten und Gasen zu den relevanten Risscharakteristika (kumulative Risslänge, Rissbreite). Weiterhin sind Selbstheilungseffekte von feinen Rissen infolge einer zyklischen Wasserbeaufschlagung beobachtet worden. Hierbei kam es zu einer deutlichen Reduzierung der Transportraten sowohl für Wasser als auch für Gase. Eine speziell entwickelte Permeabilitätsmesskammer zur Durchführung von In- Situ-Messungen ermöglicht Untersuchungen zum Stofftransport unter axialer Zugbelastung bei verschiedenen Dehnungszuständen.
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Morgan, Jason. "Towards an Understanding of the Gas Diffusion Layer in Polymer Electrolyte Membrane Fuel Cells." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/555.
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The gas diffusion layer (GDL) is one of the key components in a polymer electrolyte membrane (PEM) fuel cell. It performs several functions including the transport of reactant gases and product water to and from the catalyst layer, conduction of both electrons and heat produced in the catalyst layer, as well as mechanical support for the membrane. The overarching goal of this work is to thoroughly examine the GDL structure and properties for use in PEM fuel cells, and more specifically, to determine how to characterize the GDL experimentally ex-situ, to understand its performance in-situ, and to relate theory to performance through controlled experimentation. Thus, the impact of readily measured effective water vapor diffusivity on the performance of the GDL is investigated and shown to correlate to the wet limiting current density, as a surrogate of the oxygen diffusivity to which it is more directly related. The influence of microporous layer (MPL) design and construction on the fuel cell performance is studied and recommendations are made for optimal MPL designs for different operating conditions. A method for modifying the PTFE (Teflon) distribution within the GDL is proposed and the impact of distribution of PTFE in the GDL on fuel cell performance is studied. A method for characterizing the surface roughness of the GDL is developed and the impact of surface roughness on various ex-situ GDL properties is investigated. Finally, a detailed analysis of the physical structure and permeability of the GDL is provided and a theoretical model is proposed to predict both dry and wet gas flow within a GDL based on mercury intrusion porosimetry and porometry data. It is hoped that this work will contribute to an improved understanding of the functioning and structure of the GDL and hence advance PEM fuel cell technology.
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Gudmundsson, Kjartan. "Alternative methods for analysing moisture transport in buildings : Utilisation of tracer gas and natural stable isotopes." Doctoral thesis, KTH, Byggvetenskap, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3509.
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New methods, based on tracer gas measurements and isotopicanalysis can be used to evaluate the moisture properties ofbuilding materials and provide the means for forensic analysisof the origins and history of excessive water in buildings, theimmediate practical consequences of which will be the abilityto improve the moisture performance of constructions. It is shown, in theory and through measurements how thewater vapour permeability of porous building materials can witha good degree of accuracy be estimated with tracer gasmeasurements that provide an efficient alternative to the cupmethod. Complementary measurements may be carried out in orderto evaluate the contribution of surface diffusion and theeventual enhancing effects of moisture content on the diffusioncoefficient. The Random Hopping Model is used to illustrate howthe surface diffusion coefficient depends on the amountadsorbed and the activation energy of migration that can beevaluated from the sorption isotherms. It is explained how the abundance ratios of two of the mostordinary isotopes of hydrogen and oxygen in water can be usedto determine its history. These isotopes are stable and givethe water a distinct signature that can be used to reveal itssource as shown in a case study. In a contrary manner themeasured isotopic separation can be used to determine therelevance of different transport processes and reactions. It isof central importance that not only does the magnitude ofisotopic separation for the reactions vary for deuterium andoxygen-18 but even the ratio thereof. One of the challenges hasbeen to construct an experimental method for retrieving samplesof water for comparison. Furthermore this thesis includes an evaluation of a new typeof a light weight construction with loose-fill cellulose fibre,in which the conventional polyethylene vapour barrier has beenreplaced with polypropylene fabric. With a verified model ithas been investigated how the construction would perform fordifferent internal moisture loads and reference climate fromthe literature. The results suggest that this type ofconstruction is not to be recommended. KEYWORDS:tracer gas, water vapour permeability,diffusion, surface diffusion, isotopic analysis, deuterium,oxygen-18, fractionation, vapour barrier, transient numericalmodelling of diffusion.QC 20100611
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Yuan, Haifeng. "Caractérisation expérimentale des propriétés de poromécaniques et de transfert de l’argilite du COx." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0030/document.
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L’argilite du COx a été choisie comme roche hôte pour le stockage des déchets radioactifs de haute activité et vie longue (HAVL) en France. Ce matériau subira l'intrusion de gaz et d'eau sous, parfois, des conditions thermiques sévères. Par conséquent, afin d'évaluer la sécurité de cette barrière naturelle, il est très important de comprendre les propriétés poromécaniques et de transfert de ce matériau ainsi que l’effet de la température. Ce travail aborde les mesures au gaz du coefficient de Biot et montrent que celui-ci est presque égal à 1 en conditions humides. Il y a cependant sur le matériau sec un effet de l'adsorption du gaz et une déformation supplémentaire de gonflement du matériau. Cet effet a aussi un effet important sur les propriétés de transfert du gaz selon sa nature. Les propriétés de transfert et de saturation ont été examinées par des techniques gaz et comparées aux mesures usuelles. Les essais montrent aussi que la perméabilité à l'eau de site est d'environ 10-20 - 10-21 m² et beaucoup plus faible que celle au gaz. Enfin, on constate que le coefficient de Biot n'est pas affecté significativement par les effets thermiques mais que ces effets jouent sur la perméabilité relative au gaz de l'argiliteCOx argillite has been selected as the host rock for the storage of high-activity long-live (HALL) radioactive waste in France. It will suffered the gas and water intrusion, sometimes suffered the severe thermal conditions during the sealing process. Therefore, in order to evaluate the safety of this natural barrier, it is very important to understand the poromechanical properties and transport properties of this material as well as the thermal effects. This work use gas to measure Biot’s coefficient and shows that it is nearly equal to 1 in humid conditions. However, there is a gas adsorption and induced an additional swelling deformation on dry material, this effect also has a significant effect on the transport properties of the gas according to its nature. The transport and saturation properties were examined by gas technique and compared with the usual measurements. The tests also show that the permeability of in situ water is about 10-20-10-21 m² and much lower than gas. Lastly, it is found that Biot’s coefficient is not significantly affected by the thermal effect, but the relative gas permeability of argillite is significantly affected by this effect
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Fu, Xiaojian. "Coupure Hydraulique et Potentiel de Production en Gaz de Réservoirs de Grès « Tight » : Etude Expérimentale." Thesis, Ecole centrale de Lille, 2013. http://www.theses.fr/2013ECLI0021/document.
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Les réservoirs dits « tight gas » sont constitués de grès de faible perméabilité ayant des propriétés petro-physiques susceptibles de nuire à la productivité du gisement. Une importante zone de transition est observée in situ dans laquelle ni l’eau ni le gaz ne sont suffisamment mobiles pour permettre une extraction industrielle : c’est ce que l’on appellera le « permeability jail ». Cette étude vise principalement à caractériser l’influence du chargement mécanique (via l’utilisation de différentes pressions de confinement) et de la nature des roches (roches provenant de différents puits et prélevées à différentes profondeurs) sur les courbes de perméabilité relative au gaz et les caractéristiques poro-mécaniques de ces roches. La porosité accessible à l’eau mesurée est de 2 à 12%. La perméabilité intrinsèque au gaz a mis en évidence de fortes disparités sans lien avec la porosité des échantillons. Une grande sensibilité de la perméabilité relative au confinement a été observée dès l’application de pressions de confinement de 15 à 30 MPa. Deux familles d’échantillons ont ainsi été identifiées. Les échantillons les plus perméables (perméabilité compris entre 100 – 1000 μD), sont peu sensibles au confinement et leur perméabilité relative ne chute qu’à partir de saturations de l’ordre de 50%. Les échantillons les moins perméables apparaissent beaucoup plus sensibles à la fois au confinement et à la saturation.Des méthodes classiquement utilisées dans le domaine pétrolier reposant sur l’interprétation d’essais de porosimétrie par intrusion mercure, ont également été mise en œuvre pour évaluer les perméabilités relatives et les comparer aux mesures expérimentalesSo-called tight gas reservoirs are constituted of low permeability sandstones, which petro-physical properties may interfere with proper gas recovery. They have a low absolute permeability (below 0.1 mD under ambient conditions), a porosity lower than 10%, and a strong sensitivity to in situ stresses as compared to conventional reservoirs. Moreover, an important transition zone is observed in situ, where partial water saturation is present, and which may extend over several hundred meters over the free water table. In such zone, where water saturation is on the order of 40-50%, neither gas nor water seems sufficiently mobile for industrial extraction: this is the permeability jail. Our aim is to assess their actual petro-physical properties, namely porosity, gas permeability under varying hydrostatic stress and water saturation level, in relation with sandstone microstructure. Accessible water porosity measured is between 2 to 12%. The intrinsic permeability to gas did not appeared related to the porosity of samples. A high sensitivity of gas permeability to confinement was observed. Two families of samples were identified. The more permeable samples (permeability between 100-1000 μD), are relatively insensitive to confinement and their relative permeability decrease for water saturation higher than 50%. Less permeable samples appear much more sensitive to mechanical loading and saturation.Methods classically used in oil and gas industry based on the interpretation of mercury intrusion porosimetry tests have also been used to evaluate relative permeability and compared with experimental measurements
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Andrieu, Caroline. "Étude de la perméation du tritium à travers les gaines de crayons combustibles type R. E. P." Grenoble INPG, 1998. http://www.theses.fr/1998INPG0015.
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Le tritium, isotope radioactif de l'hydrogene, est produit par fission ternaire dans le combustible nucleaire. Il est susceptible de traverser la gaine de zircaloy-4 du crayon combustible et ainsi contaminer l'eau du circuit primaire des reacteurs a eau pressurisee. Le processus limitant cette permeation est le transport du tritium a travers l'oxyde de surface du zircaloy, la zircone. Dans ce travail, la cinetique de relachement et de permeation du tritium dans le zircaloy-4 a ete mesuree en autoclave blinde et situe en boite a gants. L'influence de la cinetique d'oxydation et de la structure de la zircone sur le transport du tritium a ete ainsi mise en relief. Un mecanisme de transport du tritium dans la zircone est presente. Lors des premiers jours d'oxydation du zircaloy, les precipites intermetalliques zr(fe, cr)#2, presents dans l'alliage, jouent le role de court-circuit de diffusion du tritium a travers la zircone d'ou un relachement rapide du tritium pendant cette periode. Ensuite, ces precipites, presentant une forte affinite pour le tritium et s'oxydant avec retard par rapport a la matrice de zirconium, servent de vecteur du tritium dans l'oxyde. Lors de leur oxydation, ils relachent du tritium qui est alors disponible a la diffusion dans la zircone. Quand l'oxyde est dense, le relachement est faible, il s'accelere au moment de la transition cinetique d'oxydation du metal, quand la zircone devient plus poreuse. Par ailleurs, un outil informatique a specialement ete developpe permettant de prevoir la cinetique de permeation du tritium a travers les gaines en tenant compte de la croissance des couches d'oxyde de surface, de l'implantation du tritium par recul et du gradient thermique radial dans la gaine. Enfin, une prevision du taux de sortie du tritium du crayon combustible est donnee. Ce taux est de 8. 10#-#3% de l'activite produite dans le combustible.
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Zhang, Yao. "Comportement hydrique et poro-mécanique des bétons à hautes performances Andra : influence de la microstructure." Thesis, Ecole centrale de Lille, 2014. http://www.theses.fr/2014ECLI0009/document.
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Cette thèse étudie la rétention d’eau à haute HR et le retrait sous température modérée des bétons CEMI et CEMV de l’Andra, en lien avec leur microstructure.Pour étudier l’origine des variations de Sw à haute HR, du béton est séché à HR= 92-100%. Pour les deux bétons, l’échantillonnage influe significativement sur Sw. Pour le CEMI, à HR=100%, la taille joue aussi, en lien avec un mécanisme de séchage par désorption de surface ; à HR=92&98%, ce béton n’est plus sensible aux effets de surface ; il est sensible aux conditions expérimentales. Pour le CEMV, l’effet de la taille existe quelle que soit l’HR, mais il est peu sensible aux conditions expérimentales.A partir de 60°C, le retrait de dessiccation présente quatre phases en fonction de la perte de masse relative. Pour le béton CEMI séché jusqu’en phase 3 ou 4, la possible rigidification de la matrice solide est investiguée par un essai couplé de poro-élasticité et transport de gaz. Pour un même échantillon en phase 3 puis en phase 4, on mesure une légère augmentation du Ks ; la perméabilité au gaz est significativement plus sensible au confinement. Par contre, la rigidification du matériau est limitée en comparaison de l’effet d’échantillonnage.Au MEB, les phases et la morphologie des bétons sont quantifiées. Le CEM I et le CEM V ont des phases solides identiques, mais le CEM V comprend des phases spécifiques (ajout de laitiers et cendres volantes). Les C-S-H du CEM V ont un rapport C/S globalement plus bas que le CEM I. Ce rapport reste similaire pour trois gâchées différentes. Par contre, l’occurrence de pores millimétriques varie significativement, du fait de modes de mise en oeuvre sensiblement différentsThis thesis focuses on water retention at high relative humidity (RH) (92-100%) and dessiccation shrinkage under moderate temperature (60-80°C) for two high performance concretes CEMI and CEMV (from Andra), in relation with their microstructure.To investigate the origins of the variations in water saturation degree Sw at high RH, both concretes are dried at RH=92, 98 and 100%, from the fully saturated state. For both concretes, sampling affects significantly Sw. For CEMI at 100%RH, sample size also affects Sw, due to surface drying (desorption); at 92 and 98%RH, CEMI is no longer sensitive to surface drying effects; it is sensitive to experimental conditions (RH, T). CEMV is affected by sample size whatever the RH, but not by experimental conditions.From 60°C drying temperature, the relationship between shrinkage and relative mass loss presents four distinct phases. CEMI concrete is dried at 65°C until phase 3 or 4, and then submitted to a coupled poro-mechanical and gas permeability test. For the same sample tested in phase 3 and then 4, a difference in solid skeleton incompressibility modulus Ks is measured, which is significantly lower than the differences in Ks due to sampling.With the Scanning Electron Microscope, the solid phases and morphology of both concretes are quantified. CEM I and CEM V comprise identical phases, even portlandite, yet CEM V concrete has some specific phases, owing to the addition of slag and fly ash. The C-S-H in CEM V have a lower C/S ratio than in CEM I. The (C/S) ratio remains similar when comparing between three different batches. Besides, millimetric pores vary significantly, owing to differences in manufacturing
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Rodriguez, Cesar Alexander. "Stress-dependent permeability on tight gas reservoirs." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1393.
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People in the oil and gas industry sometimes do not consider pressure-dependent permeability in reservoir performance calculations. It basically happens due to lack of lab data to determine level of dependency. This thesis attempts to evaluate the error introduced in calculations when a constant permeability is assumed in tight gas reservoir. It is desired to determine how accurate are conventional pressure analysis calculations when the reservoir has a strong pressure-dependent permeability. The analysis considers the error due to effects of permeability and skin factor. Also included is the error associated when calculating Original Gas in Place in the reservoir. The mathematical model considers analytical and numerical solutions of radial and linear flow of gas through porous media. The model includes both the conventional method, which assumes a constant permeability (pressure-independent), and a numerical method that incorporates a pressure-dependent permeability. Analysis focuses on different levels of pressure draw down in a well located in the center of a homogeneous reservoir considering two types of flow field geometries: radial and linear. Two different producing control modes for the producer well are considered: constant rate and constant bottom hole pressure. Methodology consists of simulated tight gas well production with k(p) included. Then, we analyze results as though k(p) effects were ignored and finally, observe errors in determining permeability (k) and skin factor (s). Additionally, we calculate pore volume and OGIP in the reservoir. Analysis demonstrates that incorporation of pressure-dependence of permeability k(p) is critical in order to avoid inference of erroneous values of permeability, skin factor and OGIP from well test analysis of tight gas reservoirs. Estimation of these parameters depends on draw down in the reservoir. The great impact of permeability, skin factor and OGIP calculations are useful in business decisions and profitability for the oil company. Miscalculation of permeability and skin factor can lead to wrong decisions regarding well stimulation, which reduces well profitability. In most cases the OGIP calculated is underestimated. Calculated values are lower than the correct value. It can be taken as an advantage if we consider that additional gas wells and reserves would be incorporated in the exploitation plan.
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Pathi, Venkat Suryanarayana Murthy. "Factors affecting the permeability of gas shales." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5302.
Full textAbstract:
The mechanical properties and matrix permeability of gas shales are the most important
properties in determining their production capacity. In this research, I have investigated
the matrix permeability and rock mechanical properties of Western Canadian and
Woodford shales. The matrix permeability was measured using pulse decay experiment.
The pulse decay experiment was employed with triaxial experiments combined with
mercury porosimetry, helium pydnometry, Rock-Eval pyrolysis, SEM and X-ray
diffraction analysis to measure rock strength, pore size, porosity, total organic content,
fabric and composition of samples. The permeability results were correlated with
effective stress, anisotropy, fabric, rock strength, porosity, pore size and total organic
content.
Mineralogy plays an important role in determining the permeability of Canadian and
Woodford shales. Higher permeability was observed in samples with high clay content,
and low permeability was observed in samples with high quartz and carbonate content.
Among the clay-, silica-, and calcite-rich Canadian shales, the calcite-rich shales had a
very low permeability (1O⁻⁷ md) compared to other shales. The permeability of all shales
decline exponentially with increasing effective stress.
Samples that were tested parallel to bedding had higher permeabilities than samples were
tested normal to bedding. Among shales, the quartz-rich shales showed differences of
three to four orders of magnitude for the samples tested parallel to bedding, compared to
those tested normal to the bedding. The largest anisotropy was found in the clay-rich
samples. Clay-rich shales also have a well developed fabric with a strongly preferred
orientation, while the quartz-rich shales had random orientation of the fabric.
The porosimetry results suggest that fluid flow is mostly in the meso (2-50 nm) and
macro pores (>50 nm) of the Woodford shales. Samples with higher clay content (>30%)
showed a higher intrusion volume in macro pores, while samples with higher quartz
content showed intrusion volume in micro pores. Porosity is correlated to permeability in
the Western Canadian shales and showed a linear correlation within the Woodford shales.
Even though calcite-rich Canadian shales and quartz-rich Woodford shales have high
TOC content, TOC was not seen to effect permeability.
Triaxial compression rock testing was conducted on the Woodford shales to measure the
elastic properties and strength behaviour of shale. Lithologic composition plays an
important role in the strength and pore compressibility of shale. Quartz-rich or carbonate
rich shales have a brittle behaviour and clay-rich shales have a ductile behaviour. Pore
compressibility is greater in the clay-rich shales, and less in the quartz-rich shales.
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Mecham, Sue Jewel. "Gas permeability of polyimide/polysiloxane block copolymers." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/43136.
Full textAbstract:
A series of perfectly alternating polyimide/ poly(dimethylsiloxane) microphase separated block copolymers ranging from 0-50 wgt. % poly(dimethylsiloxane) have been measured for permeability characteristics. The polyimide segment of the copolymers was based on oxydiphthalicdianhydride (ODPA) and 1,4-Bis(4-amino-1,1- dimethylbenzyl)benzene (Bis P). The polysiloxane was an aminopropyl terminated poly(dimethylsiloxane). Randomly segmented block copolymers of =20 wet. % poly(dimethylsiloxane) with different segment lengths were also studied, based on the same materials for the sake of comparison with the perfectly alternating versions of the same block copolymers. Permeability measurements were performed on tough, microphase separated, transparent films with O₂, N₂, CH₄, and CO₂ gases in that order. The effects of the chemical composition and block lengths on permeability coefficients and selectivity values were evaluated. The permeability of copolymer films to gases was found to be highly sensitive to the morphology of the copolymer. The morphology was found to be controlled by varying the amount and the segment length of each component and this allowed for fine control of the permeability characteristics. Conversely, the measurement of permeability characteristics can lead to more information about the morphology of complicated microphase separated block copolymers.Master of Science
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Mecham, Sue J. "Gas permeability of polyimide/polysiloxane block copolymers /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06112009-063219/.
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Kharul, U. K. "Structure correlation with gas permeability in polyarylates." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1995. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2800.
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Sexton, Alexane. "Développement de films polymères fonctionnels à propriétés de transport de gaz et d’eau contrôlées pour les applications liées au diagnostic médical." Electronic Thesis or Diss., Lyon 1, 2023. http://www.theses.fr/2023LYO10071.
Full textAbstract:
Le contrôle des mécanismes de transport des petites molécules telles que O2, CO2, et l’eau est un paramètre primordial pour des applications en lien avec les secteurs de la santé. Le poly(4-méthyl-1-pentène) (PMP) est actuellement utilisé pour de telles applications car il présente une sélectivité gaz/eau élevée tout en étant transparent. Néanmoins, il existe un intérêt à pouvoir développer des alternatives à ce matériau. Dans ce cadre, les copolymères statistiques polypropylène-éthylène (PP-PE) ont été identifiés comme potentiels substituts au PMP de par leur structure chimique non polaire. Dans ce travail, différentes voies visant à augmenter la perméabilité aux gaz O2 et CO2 de films PP-PE élaborés par voie fondu ont été développées : l’introduction de tamis moléculaires de type zéolithes et/ou d’un plastifiant, le sébacate de dioctyle. L’influence de la nature et de la quantité des agents modifiant sur les propriétés fonctionnelles de la matrice PP-PE ont été étudiées. La caractérisation des systèmes en termes de morphologie, mobilité de chaînes, propriétés mécaniques, de perméabilité aux gaz et à l’eau ainsi que les propriétés optiques a permis d’établir les relations structure-propriétés fonctionnellesThe control of the transport mechanism for small molecules such as O2, CO2 and H2O is a crucial parameter for medical diagnosis devices. Currently, poly(4-methyl-1-pentene) (PMP) is used for applications which require high gas/water selectivity and transparency of the material. In the context of alternative materials, random polypropylene-ethylene copolymers were selected due to their non-polar structure. In this work, different routes have been developed to increase O2 and CO2 transport properties of PP-PE matrices prepared by melt process: the introduction of zeolite porous fillers or/and plasticizer (dioctyle sebacate) adding. The influence of the nature and quantity of each additive on morphology, polymer chain mobility, gas and water permeability as well as mechanical and optical properties were investigated. Moreover, the detailed characterization of the developed materials allowed the establishment of the structure-functional properties relations
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M'jahad, Sofia. "Impact de la fissuration sur les propriétés de rétention d‘eau et de transport de gaz des géomatériaux : Application au stockage géologique des déchets radioactifs." Thesis, Ecole centrale de Lille, 2012. http://www.theses.fr/2012ECLI0023/document.
Full textAbstract:
Dans le contexte du stockage géologique des déchets radioactifs, ce travail contribue à la caractérisation de l’effet de l’endommagement diffus sur les propriétés de rétention d’eau et transfert de gaz (perméabilité et percée de gaz). Les matériaux considérés sont les bétons CEM I et CEM V sélectionnés par l’Andra, l’argilite du Callovo-Oxfordien (roche hôte) et les interfaces argilite/béton. Cette étude a fourni des informations sur la microstructure des bétons à partir de leurs propriétés de rétention d’eau mais également à partir de la porosimétrie au mercure. Chaque béton a une microstructure bien distincte, caractérisée par une proportion non négligeable de pores capillaires pour le CEM I et une grande proportion de pores des hydrates pour le CEM V. Plusieurs protocoles d’endommagement ont été développés. L’endommagement contribue à réduire la capacité de rétention d’eau du béton CEM I et à augmenter leur perméabilité au gaz. En revanche, tous les échantillons endommagés présentent une pression de percée au gaz significativement plus faible que celles des matériaux sains, et ceci quel que soit le type de béton. Pour l’argilite, on observe une prise d’eau progressive à HR=100%, qui engendre un endommagement du matériau. Ce dernier réduit sa capacité de rétention d’eau. Par ailleurs, ses propriétés de rétention d’eau et de transport de gaz dépendent fortement de son état hydrique initial ainsi que de son endommagement. Enfin, on observe un phénomène de colmatage au niveau des interfaces, d’abord mécanique, puis hydraulique (et surement chimique) suite à l’injection d’eau. Ceci a pour conséquence de réduire la pression de percée des échantillons d’interfaceIn the context of geological disposal of radioactive waste, this work contributes to the characterization of the effect of diffuse damage on the water retention and gas transfer properties of concrete (CEM I and CEM V) selected by Andra, Callovo-Oxfordian argillite (host rock) and argillite / concrete interfaces. This study provides information on the concrete microstructure from Mercury porosimetry intrusion and water retention curves: each concrete has a distinct microstructure, CEM I concrete is characterized by a significant proportion of capillary pores while CEM V concrete has a large proportion of C-S-H pores. Several protocols have been developed in order to damage concrete. The damage reduces water retention capacity of CEM I concrete and increases its gas permeability. Indeed, gas breakthrough pressure decreases significantly for damaged concrete, and this regardless of the type of concrete. For argillite, the sample mass increases gradually at RH = 100%, which creates and increases damage in the material. This reduces its ability to retain water. Otherwise, water retention and gas transport properties of argillite are highly dependent of its initial water saturation, which is linked to its damage. Finally, we observed a clogging phenomenon at the argillite/concrete interfaces, which is first mechanical and then hydraulic (and probably chemical) after water injection. This reduces the gas breakthrough pressure interfaces
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Orogbemi, Olutomisin Manase. "Gas permeability of gas diffusion media used in polymer electrolyte fuel cells." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17238/.
Full textAbstract:
The awareness of global climate change by emissions of greenhouse gases from fossil fuel combustion is widely known by current society. Polymer Electrolyte Fuel cell (PEFC) technology has been a very promising clean technology with high efficiency that has been used in a wide range of portable, automotive and stationary applications. The fuel cell research has been developing very rapidly and successfully in the last few years. However, some issues remain largely unresolved, namely water management and high cost of the PEFC component. One of the efficient and cost-effective ways to improve the design of the PEFC and consequently resolve the above mentioned issues is through modelling. However, the built PEFC models need to be fed with accurate transport coefficients to enhance their productivity. One of the most important transport coefficients is the gas permeability of the PEFC porous media which highly affects the convective flow. Therefore, in this thesis, thorough experimental studies have been conducted to investigate the gas permeability of gas diffusion media used in PEFCs. The focus has been on the effects of the following on the gas permeability of the gas diffusion layers (GDLs): (i) type of carbon black used in the microporous layers (MPL) attached to the GDL, (ii) carbon and polytetrafluoroethylene (PTFE) loading, and (iii) the thickness of the MPL. Further, a novel method has been proposed to estimate the penetration of the MPL into the carbon substrate (i.e. the GDL before being coated with the MPL ink). Also, the effect of sintering on the gas permeability of the MPL has been investigated for the first time.
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Samani, Shirin. "Coherent gas flow patterns in heterogeneous permeability fields." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2012. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-83854.
Full textAbstract:
Gas injection into saturated porous media has a high practical relevance. It is applied in
groundwater remediation (air sparging), in CO2 sequestration into saline aquifers, and
in enhanced oil recovery of petroleum reservoirs. This wide range of application
necessitates a comprehensive understanding of gas flow patterns that may develop
within the porous media and required modeling of multi-phase flow. There is an
ongoing controversy in literature, if continuum models are able to describe the complex
flow pattern observed in heterogeneous porous media, especially the channelized
stochastic flow pattern. Based on Selker’s stochastic hypothesis, a gas channel is
caused by a Brownian-motion process during gas injection. Therefore, the pore-scale
heterogeneity will determine the shape of the single stochastic gas channels. On the
other hand there are many studies on air sparging, which are based on continuum
modeling. Up to date it is not clear under which conditions a continuum model can
describe the essential features of the complex gas flow pattern. The aim of this study is
to investigate the gas flow pattern on bench-scale and field scale using the continuum
model TOUGH2. Based on a comprehensive data set of bench-scale experiments and
field-scale experiments, we conduct for the first time a systematic study and evaluate
the prediction ability of the continuum model.
A second focus of this study is the development of a “real world”-continuum model,
since on all scales – pore-scale, bench scale, field scale – heterogeneity is a key driver
for the stochastic gas flow pattern. Therefore, we use different geostatistical programs
to include stochastic conditioned and unconditioned parameter fields.
Our main conclusion from bench-scale experiments is that a continuum model, which is
calibrated by different independent measurements, has excellent prediction ability for
the average flow behavior (e.g. the gas volume-injection rate relation). Moreover, we
investigate the impact of both weak and strong heterogeneous parameter fields
(permeability and capillary pressure) on gas flow pattern. The results show that a
continuum model with weak stochastic heterogeneity cannot represent the essential
features of the experimental gas flow pattern (e.g., the single stochastic gas channels).
Contrary, applying a strong heterogeneity the continuum model can represent the
channelized flow. This observation supports Stauffer’s statement that a so-called subscale
continuum model with strong heterogeneity is able to describe the channelized
flow behavior. On the other hand, we compare the theoretical integral gas volumes with
our experiments and found that strong heterogeneity always yields too large gas
volumes.
At field-scale the 3D continuum model is used to design and optimize the direct gas
injection technology. The field-scale study is based on the working hypotheses that the
key parameters are the same as at bench-scale. Therefore, we assume that grain size and
injection rate will determine whether coherent channelized flow or incoherent bubbly
flow will develop at field-scale. The results of four different injection regimes were
compared with the data of the corresponding field experiments. The main conclusion is
that because of the buoyancy driven gas flow the vertical permeability has a crucial
impact. Hence, the vertical and horizontal permeability should be implemented
independently in numerical modeling by conditioned parameter fields.
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Stormont, John Charles. "Gas permeability changes in rock salt during deformation." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185159.
Full textAbstract:
A laboratory, field and numerical study of the changes in gas permeability which rock salt experiences during deformation is given. The laboratory tests involves gas permeability and porosity measurements coincident with hydrostatic and triaxial quasi-static, stress-rate controlled compression tests. The permeability and porosity of the as-received samples decrease significantly as a result of hydrostatic loading. These changes are largely irreversible, and are believed to "heal" or return the rock to a condition comparable to its undisturbed state. Deviatoric loading induces a dramatic change in pore structure. The permeability can increase more than 5 orders of magnitude over the initial (healed) state as the samples are loaded. The gas permeability changes are consistent with flow paths initially developing along the grain boundaries and then along axial secondary tensile cracks. The results from two sets of in situ gas permeability measurements from the underground workings of the WIPP Facility are given. The results consistently indicate that there is no measurable gas permeability prior to disturbing the rock by excavation. In the immediate vicinity of an excavation, the gas permeability can be 5 orders of magnitude greater than the undisturbed permeability. A numerical procedure to predict the in situ permeability is developed based on the results of the laboratory tests. The stress and strain fields surrounding excavations in rock salt, predicted with an elastoplastic model, are used in a model of gas permeability based on the equivalent channel model. The zone of the gas permeable rock is predicted well, but the magnitude of the gas permeability is underpredicted very near excavations. The gas permeability which develops in situ is principally a result of flow along dilated grain boundaries.
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Belyadi, Fatemeh. "Determining low permeability formation properties from absolute open flow potential." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4879.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains viii, 63 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 36-42).
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Duan, Zhouyang. "Water vapour permeability of bio-based polymers." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13609.
Full textAbstract:
This project investigates the moisture barrier properties of bio-based polymers and ways of improving them. The first section addresses the effect of crystallinity on the water permeability of poly(lactic acid) (PLA). The second section investigates PLA/talc composites and PLA/ montmorillonite nanocomposites. The third section is focused on a new polymer, polybutylene succinate (PBS), and its nanocomposites with montmorillonite. In the first section, the water vapour transmission rates (WVTR) through samples of polylactic acid of different crystallinities have been measured. Three different grades of commercial PLA were used with different ratios of L-lactide and D-lactide to give a range of crystallinities from 0 to 50%. Sheets of PLA were prepared by melt compounding followed by compression moulding and annealing at different temperatures and for different times to give the range of crystallinities required. Crystallinity was measured by differential scanning calorimetry (DSC) and the morphology of the samples was observed under crossed polars in a transmitted light microscope. Water vapour transmission rates through the films were measured at 38°C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased linearly with increasing crystallinity of the PLA from 0 to 50%. The results are discussed in terms of the effect of crystallinity on solubility and shown to fit the tortuous path model. The model was also successfully used to explain published data on water permeability of polyethylene terephthalate. In the second section, a series of PLA/talc composites and PLA/ montmorillonite nanocomposites were prepared by melt compounding followed by compression moulding. The morphologies of the composites were investigated using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) and it was found that the fillers were well dispersed in the polymer matrix. The average aspect ratio of the compounded talc was found to be 8, and that of the nanoclay was found to be 50. Water vapour transmission rates (WVTR) through the films were measured at 38°C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased with increasing filler content and the results gave good agreement with predictions from the Nielsen tortuous path model. In the third section, PBS/ montmorillonite nanocomposites were prepared by melt compounding followed by compression moulding. The melting and crystallisation behaviour of the pure PBS samples were investigated using differential scanning calorimetry (DSC) and cross polarised optical microscopy. A slight decrease of the degree of crystallinity was found in PBS containing 5% nanoclay. The morphology of the composites was investigated using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) and it was confirmed that that composite structures were intercalated. Water vapour transmission rates (WVTR) through the PBS sheets were measured using a MOCON Permatran-W®398. The measured values of WVTR decreased with increasing nanoclay content. However, the experimental values were all higher than the values predicted by the Nielsen tortuosity model. This result shows that in the case of PBS, which is a highly crystalline polymer, the nanoclay is not as well dispersed and is not as effective in reducing water vapour permeability as in the case of PLA.
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Franquet, Barbara Mariela. "Effect of pressure-dependent permeability on tight gas wells." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2253.
Full textAbstract:
Tight gas reservoirs are those reservoirs where the matrix has a low permeability range (k < 0.1 md). The literature documents laboratory experiments under restressed conditions that show stress dependent rock properties are more significant in tighter rocks. For gas reservoirs, real gas properties are also sensitive to variations of pressure, and the correct description of gas flow must include pressure-dependent gas properties. Under these circumstances the resulting equation for real gas flow is a second order, non-linear, partial differential equation. Non-linearities include pressure-dependence of gas viscosity, gas compressibility, reservoir permeability and reservoir porosity. This paper investigates dynamic permeability change as a function of net overburden stress in tight gas reservoirs. The gas reservoir simulator used for this work included pressure-dependent reservoir permeability. Radial flow cases are analyzed using this simulator. During this study we found that from analysis of production data alone, it is impossible to determine the correct permeability value for tight gas reservoirs with pressure-dependent permeability. For the cases studied, the transient performance was similar for both constant permeability and pressure-dependent permeability. This similarity causes constant permeability and pressure-dependent permeability to be indistinguishable, based on analysis of transient performance data. It was found that the productivity index decreases when pressure-dependent permeability is more significant. Finally, this study verified that the method of Ibrahim et al.28 under estimates original gas in place (OGIP) for tight gas reservoirs with pressure-dependent permeability.
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Sakaguchi, Toshikazu. "Synthesis, properties, and gas permeability of novel poly(diarylacetylenes)." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/143983.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第12286号
工博第2615号
新制||工||1369(附属図書館)
24122
UT51-2006-J279
京都大学大学院工学研究科高分子化学専攻
(主査)教授 増田 俊夫, 教授 中條 善樹, 教授 伊藤 紳三郎
学位規則第4条第1項該当
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Elmoazzen, Heidi Yakout. "Parameters affecting water permeability across biological cell membranes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0009/MQ60118.pdf.
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Jamiolahmady, Mahmoud. "Mechanistic modelling of gas-condensate flow in porous media." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/532.
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Florence, Francois-Andre. "Validation/enhancement of the "Jones-Owens" technique for the prediction of permeability in low permeability gas sands." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5846.
Full textAbstract:
This work presents the validation and enhancement of existing correlations for estimating and predicting
the permeability in low permeability gas sands. The "original" problem of predicting the corrected or
"liquid equivalent" permeability has been under investigation since the early 1940s â in particular, using
the application of "gas slippage" theory to petrophysics by Klinkenberg.
In the first part of this work, the viability of the Jones-Owens and Sampath-Keighin correlations for
estimating the Klinkenberg-corrected (absolute) permeability from single-point, steady-state measurements
were investigated. We also provide an update to these correlations using modern petrophysical
data.
In the second part of this work we proposed and validated a new "microflow" model for the evaluation of
an equivalent liquid permeability from gas flow measurements. This work was based on a more detailed
application of similar concepts employed by Klinkenberg. In fact, we obtained the Klinkenberg result as
an approximate form of this result. A theoretical "microflow" result was given as a rational polynomial
(i.e., a polynomial divided by a polynomial) in terms of the Knudsen number (ratio of the mean free path
of the gas molecules to the characteristic flow length (typically the radius of the capillary)), and this result
can be applied as an explicit correlation device, or as an implicit prediction model (presuming the model is
tuned to a particular data set).
The following contributions are derived from this work:
â Validation and extension of the correlations proposed by Jones-Owens and Sampath-Keighin for low
permeability samples.
â Development and validation of a new "microflow" model which correctly represents the flow of gases
in low permeability core samples. This model is also applied as a correlation for prediction of the
equivalent liquid permeability in much the same fashion as the Klinkenberg model, although the new
model is substantially more theoretical (and robust) as compared to the Klinkenberg correction model.
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Holdsworth, Angela. "An investigation of the gas permeability of polymer blend membranes." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302956.
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Makrashi, Mohammed Yahya. "Permeability evaluation of composite hollow fibres for blood-gas exchange." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502353.
Full textAbstract:
Blood gas exchange across synthetic membranes is primarily used in blood oxygenators for short-term (1-3 hours) cardiopulmonary bypass procedures. Long term applications (6 hours - i4 days) of membrane oxygenators include treatment of acute respiratory failure or acute liver failure. There are several types of membranes used in these devices: (1) microporous membranes which have high gas permeabilities but have problems of pore wetting if employed in long-term therapies and (2) homogeneous membranes, e.g. silicone rubber which have lower permeability characteristics but are non-wettable and (3) composite membranes which a very thin homogeneous membrane is mechanically supported by a micro porous layer.
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Kim, Sangil. "High Permeability/High Diffusivity Mixed Matrix Membranes For Gas Separations." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26649.
Full textAbstract:
The vast majority of commercial gas separation membrane systems are polymeric because of processing feasibility and cost. However, polymeric membranes designed for gas separations have been known to have a trade-off between permeability and selectivity as shown in Robeson's upper bound curves. The search for membrane materials that transcend Robeson's upper bound has been the critical issue in research focused on membranes for gas separation in the past decade. To that end, many researchers have explored the idea of mixed matrix membranes (MMMs). These membranes combine a polymer matrix with inorganic molecular sieves such as zeolites. The ideal filler material in MMMs should have excellent properties as a gas adsorbent or a molecular sieve, good dispersion properties in the polymer matrix of submicron thickness, and should form high quality interfaces with the polymer matrix.
In order to increase gas permeance and selectivity of polymeric membranes by fabricating MMMs, we have fabricated mixed matrix membranes using carbon nanotubes (CNTs) and nano-sized mesoporous silica. Mixed matrix membranes containing randomly oriented CNTs showed that addition of nanotubes to a polymer matrix could improve its selectivity properties as well as permeability by increasing diffusivity. Overall increases in permeance and diffusivity for all tested gases suggested that carbon nanotubes can provide high diffusivity tunnels in the CNT within the polymer matrix. This result agreed well with molecular simulation estimations. In order to prepare ordered CNTs membranes, we have developed a simple, fast, commercially attractive, and scalable orientation method. The oriented CNT membrane sample showed higher permeability by one order of magnitude than the value predicted by a Knudsen model. This CNT membrane showed higher selectivities for CO₂ over other gas molecules because of preferential interaction of CO₂ with the amine functionalized nanotubes, demonstrating practical applications in gas separations.
Recently, mesoporous molecular sieves have been used in MMMs to enhance permeability or selectivity. However, due to their micrometer scale in particle size, the composite membrane was extremely brittle and tended to crack at higher silica loading. In this study, we have developed fabrication techniques to prepare MMMs containing mesoporous MCM-41 nanoparticles on the order of ~50 nm in size. This smaller nanoparticle lead to higher polymer/particle interfacial area and provides opportunity to synthesize higher loading of molecular sieves in polymer matrix up to ~80 vol%. At 80 vol% of nano-sized MCM-41 silica loading, the permeability of the membrane increased dramatically by 300 %. Despite these increases in permeability, the separation factor of the MMMs changed only slightly. Therefore, these nanoscale molecular sieves are more suitable for commercialization of MMMs with very thin selective layers than are micro-sized zeolites or molecular sieves.Ph. D.
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VanPelt, James. "Effect of strain on the gas permeability of composite laminates." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0017937.
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Chen, Guoliang. "Gas slippage and matrix shrinkage effects on permeability of coal." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186707.
Full textAbstract:
The permeability of coal is one of the most important basic parameters in the simulation of gas transport in coalbeds and in the evaluation of the commercial feasibility of coalbed gas reservoirs. However, the permeability of coal and its variation as gas is produced are still not well understood. Unlike that in conventional gas reservoirs, the gas permeability of a coalbed is influenced during gas production, not only by the simultaneous changes in effective stress and gas slippage, but also by the matrix shrinkage associated with gas desorption. The objective of this work was to investigate experimentally the matrix shrinkage and gas slippage effects on the permeability of coal. Since these effects occur simultaneously during gas production, a theory to separate these effects was first developed. This dissertation presents a technique to conduct laboratory experiments to estimate their individual contribution, along with the results obtained for quantitative relationships of the gas slippage and matrix shrinkage effects with gas pressure. The results show that the total permeability of the coal sample increased dramatically due to gas slippage and matrix shrinkage effects with decrease in pressure. When the gas pressure is above 250 psi, the effect of matrix shrinkage dominates. As gas pressure falls below 250 psi, both the gas slippage and matrix shrinkage effects play important role in influencing the permeability. Finally, the change in permeability of coal sample resulting from gas slippage was found to be proportional to the reciprocal of the gas pressure. The change in permeability due to matrix shrinkage was found to be linearly proportional to the volumetric strain associated with desorption. Since the latter is linearly proportional to the amount of gas desorbed, the change in permeability is a linear function of the amount of desorbing gas.
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Feng, Jianxun. "Interaction and permeability of water with liquid crystalline thermoset." [Gainesville, Fla.] : University of Florida, 2001. http://purl.fcla.edu/fcla/etd/UFE0000315.
Full textAbstract:
Thesis (Ph. D.)--University of Florida, 2001.Title from title page of source document. Document formatted into pages; contains xi, 243 p.; also contains graphics. Includes vita. Includes bibliographical references.
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Samani, Shirin [Verfasser], Helmut [Akademischer Betreuer] Geistlinger, Helmut [Gutachter] Geistlinger, and Broder [Gutachter] Merkel. "Coherent gas flow patterns in heterogeneous permeability fields : Coherent gas flow patterns in heterogeneous permeability fields / Shirin Samani ; Gutachter: Helmut Geistlinger, Broder Merkel ; Betreuer: Helmut Geistlinger." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2012. http://d-nb.info/1220911291/34.
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BAJNI, GRETA. "STATISTICAL METHODS TO ASSESS ROCKFALL SUSCEPTIBILITY IN AN ALPINE ENVIRONMENT: A FOCUS ON CLIMATIC FORCING AND GEOMECHANICAL VARIABLES." Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/913511.
Full textAbstract:
The overarching goal of the doctoral thesis was thus the development of a systematic procedure capable to examine and enhance the role of geomechanical and climatic processes in rockfall susceptibility, performed with statistically based and Machine Learning techniques. To achieve this purpose, two case studies were analysed in the Italian Alps (Valchiavenna, Lombardy Region; Mountain Communities of Mont Cervin and Mont Emilius, Aosta Valley Region).
For both case studies, Generalized Additive Models (GAM) were used for rockfall susceptibility assessment; for the Valchiavenna case study, a Random Forest (RF) model was tested too. All models were validated through k-fold cross validation routines and their performance evaluated in terms of area under the receiver operating characteristic curve (AUROC). Predictors’ behaviour physical plausibility was verified through the analysis of the mathematical functions describing the predictors-susceptibility modelled relationships. Specific objectives of the two case studies differed.
The Valchiavenna case study was dedicated to testing the role of the outcrop-scale geomechanical properties in a rockfall susceptibility model. Specific objectives were: (i) the optimal selection of sampling points for the execution of geomechanical surveys to be integrated within an already available dataset; (ii) the regionalization over the study area of three geomechanical properties, namely Joint Volumetric Count (Jv), rock-mass weathering index (Wi) and rock-mass equivalent permeability (Keq); (iii) the implementation of the regionalized properties as predictors in a rockfall susceptibility model, along with the traditional morphometric variables; (iv) the investigation of prediction limitations related to inventory incompleteness; (v) the implementation of a methodology for the interpretation of predictors’ behaviour in the RF model, usually considered a black box algorithm; (vi) the integration of the RF and GAM outputs to furnish a spatially distributed measure of uncertainty; (vii) the exploitation of satellite-derived ground deformation data to verify susceptibility outputs and interpret them in an environmental management perspective.
The additional geomechanical sampling points were selected by means of the Spatial Simulated Annealing technique. Once collected the necessary geomechanical data, regionalization of the geomechanical target properties was carried out by comparing different deterministic, regressive and geostatistical techniques. The most suitable technique for each property was selected and geomechanical predictors were implemented in the susceptibility models. To verify rockfall inventory completeness related effects, the GAM model was performed both on rockfall data from the official landslide Italian inventory (IFFI) and on its updating with a field-mapped rockfall dataset. Regarding the RF model, the Shapely Additive exPlanations (SHAP) were employed for the interpretation of the predictors’ behaviour. A comparison between GAM and RF related outputs was carried out to verify their coherency, as well as a quantitative integration of the resulting susceptibility maps to reduce uncertainties. Finally, the rockfall susceptibility maps were coupled with Synthetic Aperture Radar (SAR) data from 2014 to 2021: a qualitative geomorphological verification of the outputs was performed, and composite maps were produced.
The key results were: (i) geomechanical predictor maps were obtained applying an ordinary kriging for Jv and Wi (NRMSE equal to 13.7% and 14.5%, respectively) and by means of Thin Plate Splines for Keq (NRMSE= 18.5%). (ii) Jv was the most important geomechanical predictor both in the GAM (witha deviance explained of 7.5%) and in the RF model, with a rockfall susceptibility increase in correspondence of the most fractured rock masses. (iii) Wi and Keq were penalized (i.e., they had low influence on rockfall susceptibility) in the GAM model, whereas Keq showed an importance comparable to Jv in the RF model. (iv) In a complex Machine Learning model (RF), the SHAPs allowed the interpretation of predictors’ behaviour, which demonstrated to be coherent with that shown in the GAM model. (v) The models including the geomechanical predictors resulted in acceptable rockfall discrimination capabilities (AUROC>0.7). (vi) The introduction of the geomechanical predictors led to a redistribution of the high-susceptibility areas in plausible geomorphological contexts, such as in correspondence of active slope deformations and structural lineaments, otherwise not revealed by the topographic predictors alone. (vii) Models built with solely the IFFI inventory, resulted in physically implausible susceptibility maps and predictor behaviour, highlighting a bias in the official inventory. (viii) The discordance in predicting rockfall susceptibility between the GAM and the RF models varied from 13% to 8% of the total study area. (ix) From the integration of InSAR data and susceptibility maps, a “SAR Integrated Susceptibility Map”, and an “Intervention Priority Map” were developed as operational products potentially exploitable in environmental planning activities.
The Aosta Valley case study was dedicated to challenge the concept of “susceptibility stationarity” by including the climate component in the rockfall susceptibility model. The availability of a large historical rockfall inventory and an extensive, multi-variable meteorological dataset for the period 1990-2020 were crucial input for the analysis. Specific objectives were: (i) the identification of climate conditions related to rockfall occurrence (ii) the summary of the identified relationships in variables to be used in a susceptibility model; (iii) the optimization of a rockfall susceptibility model, including both topographic, climatic and additional snow-related predictors (from a SWE weekly gridded dataset).
Starting from an hourly meteorological dataset, climate conditions were summarized in indices related to short-term rainfall (STR), effective water inputs (EWI, including rainfall and snow melting), wet-dry cycles (WD) and freeze-thaw cycles (FT). Climate indices and rockfall occurrence time series were paired. Critical thresholds relating rockfall occurrence to climate indices not-ordinary values (>75th percentile) were derived through a statistical analysis. As summary variables for the susceptibility analysis, the mean annual threshold exceedance frequency for each index was calculated. Model optimization consisted in stepwise modifications of the model settings in order to handle issues related to inventory bias, physical significance of climatic predictors and concurvity (i.e., predictors collinearity in GAMs). The starting point was a “blind model”, i.e., a susceptibility model created without awareness of the rockfall inventory characteristics and of the physical processes potentially influencing susceptibility. To reduce the inventory bias, “visibility” masks were produced so to limit the modelling domain according to the rockfall collection procedures adopted by administrations. Thirdly, models were optimized according to the physical plausibility of climatic predictors, analysed through the smooth functions relating them to susceptibility. Finally, to reduce concurvity, a Principal Component Analysis (PCA) including climatic and snow-related predictors was carried out. Subsequently, the obtained principal components were used to replace the climatic predictors in the susceptibility model.
The key results were: (i) the 95% of the rockfalls occurred in severe (or not ordinary) conditions for at least one among the EWI, WD and FT indices; (ii) ignoring inventory bias led to excellent model performance (0.80≤AUROC ≤0.90) but physically implausible outputs; (iii) the selection of non-rockfall points inside the “visibility mask” was a valuable approach to manage the inventory bias influence on outputs; (iv) the inclusion of climate predictors resulted in an improvement of the susceptibility model performance (AUROC up to 3%) in comparison to a topographic-based model; (v) the most important physically plausible climate predictors were EWI, WD, with a deviance explained varying from 5% to 10% each, followed by the maximum cumulated snow melting with a deviance explained varying from 3% to 5%. The effect of FT was masked by elevation. (vi) When the climate and snow related predictors were inserted in the susceptibility model as principal components, concurvity was efficiently reduced.
The inclusion of climate processes as non-stationary predictors (i.e., considering climate change) could be a valuable approach both to derive long-term rockfall susceptibility future scenarios and in combination with short-term weather forecasts to adapt susceptibility models to an early warning system for Civil Protection purpose.
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Grover, David Klein Weibust. "Surface Gas Permeability of Porous Building Materials: Measurement, Analysis and Applications." ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/266.
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In many events affecting our civil infrastructure, such as contamination or weathering, it is likely that only the surfaces of the affected building materials will be available for non-destructive measurements. In this work, we describe and analyze surface gas permeability measurements on a variety of natural and engineered building materials using two types of relatively new, non-destructive surface permeameters. It is shown that the surface gas permeability measurements correlate well with each other and could provide rapid estimates of macroscopic gas permeability and degradation of materials due to weathering. It is hypothesized that surface permeability can be used to predict macroscopic wicking of water. The results indicated that macroscopic wicking correlated reasonably well with surface permeability measurements of uniform materials with low permeabilities such as sandstones and clay brick.
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Makihara, Hiroshi. "Water film thickness in the clay-water system." Diss., The University of Arizona, 1999. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1999_20_sip1_w.pdf&type=application/pdf.
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Gunt, Hemali B. "Hydration Effect on Human Nail Permeability." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154112551.
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Abaci, Saziye. "Relative permeability of unconsolidated materials with reference to gas migration from landfill." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357836.
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Xu, Jianlong. "Prediction of gas permeability in composite laminates using three-dimensional finite elements." [Gainesville, Fla.] : University of Florida, 2007. http://purl.fcla.edu/fcla/etd/UFE0021260.
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