| 1. |
- Ahmad, Nawaz, 1972-
(författare)
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REACTIVE TRANSPORT MODELLING OF DISSOLVED CO2 IN POROUS MEDIA : Injection into and leakage from geological reservoirs
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the greenhouse gas emissions. However, leakage of CO2 from the storage reservoir is a risk associated with geological sequestration. Over longer times, large-scale groundwater motion may cause leakage of dissolved CO2 (CO2aq).The objectives of this thesis are twofold. First, the modelling study analyzes the leakage of CO2aq along the conducting pathways. Second, a relatively safer mode of geological storage is investigated wherein CO2aq is injected in a carbonate reservoir. A reactive transport model is developed that accounts for the coupled hydrological transport and the geochemical reactions of CO2aq in the porous media. The study provides a quantitative assessment of the impact of advection, dispersion, diffusion, sorption, geochemical reactions, temperature, and heat transport on the fate of leaking CO2aq.The mass exchange between the conducting pathway and the rock matrix plays an important role in retention and reactions of leaking CO2aq. A significant retention of leaking CO2aq is caused by its mass stored in aqueous and adsorbed states and its consumption in reactions in the rock matrix along the leakage pathway. Advection causes a significant leakage of CO2aq directly from the reservoir through the matrix in comparison to the diffusion alone in the rock matrix and advection in a highly conducting, but thin fracture. Heat transport by leaking brine also plays an important role in geochemical interactions of leaking CO2aq. Injection of CO2aq is simulated for a carbonate reservoir. Injected CO2-saturated brine being reactive causes fast dissolution of carbonate minerals in the reservoir and fast conversion of CO2aq through considered geochemical reactions. Various parameters like dispersion, sorption, temperature, and minerals reaction kinetics are found to play important role in the consumption of CO2aq in reactions.
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| 2. |
- Basirat, Farzad, et al.
(författare)
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Characterization of CO2 self-release during Heletz Residual Trapping Experiment I (RTE I) using a coupled wellbore-reservoir simulator
- 2020
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Ingår i: International Journal of Greenhouse Gas Control. - : ELSEVIER SCI LTD. - 1750-5836 .- 1878-0148. ; 102
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Tidskriftsartikel (refereegranskat)abstract
- In order to quantify CO2 residual trapping in situ, two dedicated single-well push-pull experiments have been carried out at the Heletz, Israel pilot CO2 injection site. Field data from some parts of these experiments suggests the important effect of the hydrodynamic behavior in the injection-withdrawal well. In the present work a model capturing the CO2 transport and trapping behavior during Heletz Residual Trapping Experiment I is developed, with a special focus on coupled wellbore-reservoir flow. The simulation is carried out with the numerical simulator T2Well/ECO2N (Pan et al. 2011) which considers the wellbore-reservoir coupling. Of particular interest is to accurately model the period when the well is open to the atmosphere and self-producing CO2 and water in a geyser-like manner. It is also of interest to identify what conditions are causing the oscillating pressure-temperature behavior and the associated periodic gas-liquid releases, as well as to determine the amount of gas lost from the reservoir during this period. The results suggest that the behavior is due to cyclical CO2 exsolution from the aqueous phase along with a reduction of mobility of both CO2 and brine in the near wellbore-reservoir area, the latter being due to a zone of dispersed CO2 bubbles near the wellbore. This behavior could be successfully captured with a new set of relative permeability functions developed earlier for CO2 exsolution in laboratory experiments (Zuo et al., 2013).
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| 3. |
- Basirat, Farzad, et al.
(författare)
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Experimental and modeling investigation of CO2 flow and transport in a coupled domain of porous media and free flow
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 42, s. 461-470
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Tidskriftsartikel (refereegranskat)abstract
- A solid understanding of the transport mechanisms of gaseous CO2 near the land surface is necessary for developing reliable monitoring techniques and predictive models for possible CO2 leakage from deep underground storage. The objective of this work has been to develop an experimental method along with a simulation model for gaseous CO2 flow and transport in a system including both the porous media and the free air space above it. The experimental system consisted of a two-dimensional bench scale rectangular sandbox containing homogenous sand with an open space of still air above it. Gaseous CO2 was injected in different modes and the CO2 breakthrough was measured on specified ports in the system by using CO2 concentration sensors. A numerical model combining the gas flow in the porous medium and the free flow region was developed and used to model the experimental data. In this quest, the Discontinuous One-Domain approach was selected for modeling transport between the free flow and porous regions. The observed and simulated CO2 breakthrough curves both in the dried sand and in the free flow matched very well in the case of uniform injection and satisfactorily even in the case of point injection. Consequently, it seems that the model reasonably matches the observed data in the cases where the boundary condition is well defined. In summary, our results show that the developed experimental setup provides capability to study gaseous CO2 flow and transport in a coupled porous medium - free flow system and that our modeling approach is able to predict the flow and transport in this system with good accuracy.
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| 4. |
- Basirat, Farzad, et al.
(författare)
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Hydraulic Modeling of Induced and Propagated Fractures : Analysis of Flow and Pressure Data From Hydromechanical Experiments in the COSC-1 Deep Borehole in Crystalline Rock Near Åre, Sweden
- 2021
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:11
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Tidskriftsartikel (refereegranskat)abstract
- To characterize the coupled hydromechanical behavior of rock fractures, the step-rate injection method for fracture in-situ properties (SIMFIP) was conducted with a specialized downhole probe developed by Guglielmi et al. (2014, https://doi.org/10.1007/s00603-013-0517-1). In June 2019, a field campaign was carried out near Åre, Sweden, where the SIMFIP probe was applied in the Collisional Orogeny in the Scandinavian Caledonides-1 scientific borehole to understand the dynamics of injection-induced fracture initiation, fracture opening, and shearing due to water injection-withdrawal in a borehole interval isolated by two packers. Three intervals were investigated at ∼500 m depth: (a) an unfractured section (intact rock), (b) a section with non-conductive fractures, and (c) a section with hydraulically conductive fractures. Pressure, injection flow rate, and borehole wall displacement were simultaneously measured during the tests. In the present study, the geometry of the induced fracture and deformation of existing fractures at different time stages of the tests are determined based on a hydrologic model by using the measured pressure and flow data during each time stage of the experiment. A numerical model for the fluid flow within the fracture and the packed-off borehole interval is implemented within COMSOL Multiphysics. By matching model simulations with observed data for all three sections, estimates of the induced and propagated fractures' radius and aperture at successive time stages have been obtained in each case. We could also determine the non-linear relationship between fracture aperture and pressure for values above fracture opening pressures. The model results provide insights for the understanding of pressure-induced fracture initiation and propagation in crystalline rock.
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| 5. |
- Basirat, Farzad, et al.
(författare)
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Modeling Gas Transport in the Shallow Subsurface in Maguelone Field Experiment
- 2013
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; , s. 337-345
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, TOUGH2/EOS7CA model is used to simulate the shallow injection-monitoring experiment carried outat Maguelone, France, during 2012 and 2013. The ultimate objective of the work is to improve our understanding ofgas transport in the shallow subsurface as well as to develop and validate the model to monitor it. This workrepresents first results towards modelling the nitrogen and CO2 injection experiments carried out. The pressure datafrom the first injection experiments in summer 2012 is used as basis for comparison. Work is presently going on toincorporate the experimental data into the numerical simulation further.
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| 6. |
- Basirat, Farzad, et al.
(författare)
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Modeling gas transport in the shallow subsurface in the Maguelone field experiment
- 2013
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Konferensbidrag (refereegranskat)abstract
- Developing reliable monitoring techniques to detect and characterize CO2 leakage in shallow subsurface is necessary for the safety of any GCS project. To test different monitoring techniques, shallow injection-monitoring experiment have and are being carried out at the Maguelone, along the Mediterranean lido of the Gulf of Lions, near Montpellier, France. This experimental site was developed in the context of EU FP7 project MUSTANG and is documented in Lofi et al. (2012). Gas injection experiments are being carried out and three techniques of pressure, electrical resistivity and seismic monitoring have been used to detect the nitrogen and CO2 release in the near surface environment. In the present work we use the multiphase and multicomponent TOUGH2/EOS7CA model to simulate the gaseous nitrogen and CO2 transport of the experiments carried out so far. The objective is both to gain understanding of the system performance based on the model analysis as well as to further develop and validate modelling approaches for gas transport in the shallow subsurface, against the well-controlled data sets. Numerical simulation can also be used for the prediction of experimental setup limitations. We expect the simulations to represent the breakthrough time for the different tested injection rates. Based on the hydrogeological formation data beneath the lido, we also expect the vertical heterogeneities in grain size distribution create an effective capillary barrier against upward gas transport in numerical simulations.
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| 7. |
- Basirat, Farzad, et al.
(författare)
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Numerical modelling of CO2 injection at small-scale field experimental site in Maguelone, France
- 2016
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 54, s. 200-210
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the performance of downhole and surface geophysical monitoring methods, a series of shallow gas injection-monitoring experiments has been performed in a coastal saline aquifer at Maguelone, France. The recorded data include pressure measurements with a Westbay multilevel completion and CO2 saturation at an observation well derived from electrical resistivity with a modified Waxman-Smits (MWS) model. In this work, the aim is to develop a simulation model capturing the gas transport behavior and consistent with field data. For this purpose, the simulation of the CO2 injection experiment is carried out with two conceptual models, a homogeneous model and a heterogeneous model treated with multiple realization Monte Carlo simulations. Numerical simulator TOUGH2 with the equation of state module EOS7C is used for the simulations. Comparison of the model results with field data suggests that the pressure responses are captured with relatively good accuracy. Similarly, the model also provides an overall reasonable agreement and correct order of magnitude for predicted gas saturation values. However, as the heterogeneity pattern in the field data remains largely unknown, the model predictions can only be used to capture the mean behavior as well as to provide insights into how heterogeneity can influence the system behavior, by means of sensitivity analyses of the influence of heterogeneities on individual realizations.
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| 8. |
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| 9. |
- Basirat, Farzad, et al.
(författare)
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Pore-scale modeling of wettability effects on CO2-brine displacement during geological storage
- 2016
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Konferensbidrag (refereegranskat)abstract
- Wetting properties of reservoir rocks and caprocks can significantly influence on sequestration of carbon dioxide in deep geological formations. Wettability impacts on the physical and chemical processes that are associated with injecting CO2 underground. Our aim is to understand how wetting properties influence two-phase flow of CO2 and brine in a pore scale domain. We use the phase field method to simulate the two-phase flow of CO2-brine in realistic porous domain geometry. Our focus is on clarifying the pore-scale fluid-fluid displacement mechanisms under different wetting conditions and to quantifying the effect of contact angle on macroscopic parameters such as residual brine saturation, capillary pressure, and specific interfacial area. We could show the phase field method can be applied to a complex porous medium with realistic reservoir permeability. Beside it was shown that it can deal with the conditions with large viscosity contrasts and large wettability (low contact angles) which are difficult to handle with direct numerical approaches. Our simulations results suggest wettability concept cannot be explained just by contact angles. Even though the wettability in pore-scale is defined as the contact angle, there is not any particular relation to link the contact angle to the residual saturations and distribution patterns of CO2 in porous domain. Beside the contact angle, the flow rate and basic properties of fluids which are represent in capillary number and mobility number definitions and also the geometry of porous media are describe the CO2-brine distributions.
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| 10. |
- Basirat, Farzad, et al.
(författare)
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Pore-scale modeling of wettability effects on CO2–brine displacement during geological storage
- 2017
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Ingår i: Advances in Water Resources. - : Elsevier. - 0309-1708 .- 1872-9657. ; 109, s. 181-195
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Tidskriftsartikel (refereegranskat)abstract
- Wetting properties of reservoir rocks and caprocks can vary significantly, and they strongly influence geological storage of carbon dioxide in deep saline aquifers, during which CO2 is supposed to displace the resident brine and to become permanently trapped. Fundamental understanding of the effect of wettability on CO2-brine displacement is thus important for improving storage efficiency and security. In this study, we investigate the influence of wetting properties on two-phase flow of CO2 and brine at the pore scale. A numerical model based on the phase field method is implemented to simulate the two-phase flow of CO2-brine in a realistic pore geometry. Our focus is to study the pore-scale fluid-fluid displacement mechanisms under different wetting conditions and to quantify the effect of wettability on macroscopic parameters such as residual brine saturation, capillary pressure, relative permeability, and specific interfacial area. Our simulation results confirm that both the trapped wetting phase saturation and the normalized interfacial area increase with decreasing contact angle. However, the wetting condition does not appear to influence the CO2 breakthrough time and saturation. We also show that the macroscopic capillary pressures based on the pressure difference between inlet and outlet can differ significantly from the phase averaging capillary pressures for all contact angles when the capillary number is high ( log Ca > -5). This indicates that the inlet-outlet pressure difference may not be a good measure of the continuum-scale capillary pressure. In addition, the results show that the relative permeability of CO2 can be significantly lower in strongly water-wet conditions than in the intermediate-wet conditions.
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| 11. |
- Basirat, Farzad, 1983-
(författare)
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Process Models for CO2 Migration and Leakage : Gas Transport, Pore-Scale Displacement and Effects of Impurities
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Geological Carbon Storage (GCS) is considered as one of the key techniques to reduce the rate of atmospheric emissions of CO2 and thereby to contribute to controlling the global warming. A successful application of a GCS project requires the capability of the formation to trap CO2 for a long term. In this context, processes related to CO2 trapping and also possible leakage of CO2 to the near surface environment need to be understood. The overall aim of this thesis is to understand the flow and transport of CO2 through porous media in the context of geological storage of CO2. The entire range of scales, including the pore scale, the laboratory scale, the field experiment scale and the industrial scale of CO2 injection operation are addressed, and some of the key processes investigated by means of experiments and modeling. First, a numerical model and laboratory experimental setup were developed to investigate the CO2 gas flow, mimicking the system in the near-surface conditions in case a leak from the storage formation should occur. The system specifically addressed the coupled flow and mass transport of gaseous CO2 both in the porous domain as well as the free flow domain above it. The comparison of experiments and modelling results showed a very good agreement indicating that the model developed can be applied to evaluate monitoring and surface detection of potential CO2 leakage. Second, the field scale CO2 injection test carried out in a shallow aquifer in Maguelone, France was analyzed and modeled. The results showed that Monte Carlo simulations accounting for the heterogeneity effects of the permeability field did capture the key observations of the monitoring data, while a homogeneous model could not represent them. Third, a numerical model based on phase-field method was developed and model simulations carried out addressing the effect of wettability on CO2-brine displacement at the pore-scale. The results show that strongly water-wet reservoirs provide a better potential for the dissolution trapping, due to the increase of interface between CO2 and brine with very low contact angles. The results further showed that strong water-wet conditions also imply a strong capillary effect, which is important for residual trapping of CO2. Finally, numerical model development and model simulations were carried out to address the large scale geological storage of CO2 in the presence of impurity gases in the CO2 rich phase. The results showed that impurity gases N2 and CH4 affected the spatial distribution of the gas (the supercritical CO2 rich phase), and a larger volume of reservoir is needed in comparison to the pure CO2 injection scenario. In addition, the solubility trapping significantly increased in the presence of N2 and CH4.
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| 12. |
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| 13. |
- Basirat, Farzad, et al.
(författare)
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Small scale laboratory design investigation of leakage of gaseous CO2 through heterogeneous subsurface system
- 2012
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Konferensbidrag (refereegranskat)abstract
- The technology for geological sequestration of carbon dioxide has been developed to reduce the CO2 emissions into the atmosphere from the use of fossil fuels in power generation and other industries. One of the main concerns associated with the geological storage is the possible leakage of CO2 into the shallow aquifers, for which effective detection methods are needed. The processes related to the spreading and trapping of CO2 in the reservoir formation and in supercritical conditions have received major attention and form the basis of understanding of CO2 trapping processes. Some of the CO2 may, however, also leak to the upper layers of the rock and all the way to land surface through faults and imperfections in the seal. A proper understanding and capability to detect such leaks is essential for a safe performance of any storage operation. This, in turn, involves a proper understanding of the processes related to the transport of gaseous CO2 in the nearsurface conditions, a topic that has received considerably less attention. The objective of this study is to analyze the transport and migration of gaseous CO2 in heterogeneous porous media, in controlled laboratory conditions. CO2 may reach the unsaturated zone by different leak mechanisms which may subsequently affect how and where it can be detected by leakage monitoring program. These mechanisms include exsolution from CO2 supersaturated water and continuous bubbling or gas flow along a leakage path. Below the water table, gaseous CO2 can also be trapped under capillary barriers. However, as more CO2 is supplied by leakage from below the water table, the pressure may at some point exceed the entry pressure of the barrier leading to a leak event. Similarly, fluctuations in the water table may also produce leak events of temporarily trapped CO2. In the unsaturated zone, the CO2 is heavier than air and may accumulate below ground surface and move laterally. The presence of heterogeneity influences both the movement and detectability of the CO2. Our laboratory experiment is designed and implemented for measuring CO2 distribution in time and space through the heterogeneous porous material. The CO2 concentrations through the domain are measured by using sensitive gas sensors. To better understand the consequences of CO2 leakage and how it can be detected, this study presents a conceptual model together with the design and setup of an experimental system to understand the transport, trapping and detectability of gaseous CO2 in a heterogeneous shallow geological system.
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| 14. |
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| 15. |
- Bensabat, Jacob, et al.
(författare)
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Model for the dependence of conditions at the injection well head and the reservoir during CO2 injection
- 2011
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Konferensbidrag (refereegranskat)abstract
- Highly controlled field injection experiments are necessary for demonstration, for scientific understanding and for quantification of the relevant processes of CO2 geological storage.The preparation of such an experiment requires reliable information on both the hydraulic, thermal and chemical properties of the target layer and the formation fluid as well as on the injection discharges and their associated pressure build-up in the reservoir. For this, there is a need to determine the state variables of CO2 in the injection tube near the well head, which can produce the desired mass flow rates given the condition at the reservoir, while respecting pressure buildup constraints. A model connecting the multiphase flow and transport processes in the target layer (based on the well-known TOUGH2/ECO2N model) at the vicinity of the injection well with those occurring in the injection tube (solving the one dimensional equations mass, momentum and energy conservation) has been developed. To this model the injection tube is a boundary condition. Once the reservoir pressure build-up resulting from the injection discharge is known, there is a need to determine the necessary injection conditions at the wellhead. For this purpose we apply the 1-D tube model, which provides the solution of the conditions in the injection pipe, given the injection rate and the pressure at the reservoir. These two linked models, the porous medium model and the pipe model, are applied to the planning of the Heletz injection experiment to be carried out in the frame of the EU-FP7 funded MUSTANG project. Sensitivity analyses are carried out with regard to uncertainty in the target layer permeability and the temperature of the injected CO2, which depends on the thermal heat transfer coefficient in the injection tube.
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| 16. |
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| 17. |
- Bockgård, Niclas, 1974-
(författare)
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Groundwater Recharge in Crystalline Bedrock : Processes, Estimation, and Modelling
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Kunskap om grundvattenbildningen är nödvändig för att man ska kunna förutsäga konsekvenserna av grundvattenuttag och underjordsbyggande. Grundvattenbildningen i berggrunden är dock svår att uppskatta. Syftet med avhandlingen var att öka förståelsen av grundvattenbildningen i kristallin berggrund, att undersöka hur grundvattenbildningen ska uppskattas samt att utveckla nya modeller för att beskriva grundvattenbildningen. Studien grundades på tre angreppssätt: grundvattendatering med freoner (CFC), geohydrauliska observationer och matematisk modellering.Koncentrationerna av CFC-11 och CFC-113 befanns vara låga i det undersökta berggrundvattnet, vilket i kombination med låga syrgashalter tyder på anaerob nedbrytning. Koncentrationerna av CFC-12 och tritium överensstämde ganska väl, vilket betyder att den skenbara åldern kan vara den sanna åldern. Resultaten tyder på att CFC-datering inte är pålitlig i skogsmiljöer med finkornigt jordtäcke.Vid nederbörd observerades ett snabbt gensvar i den hydrauliska potentialen i den studerade bergakviferen, trots det 10 m mäktiga moräntäcket. En avsevärd del av de observerade potentialvariationerna befanns vara belastningseffekter, som inte innebar någon magasinsförändring eller något vattenflöde. Berggrundens belastningseffektivitet uppskattades, ur potentialens svar på lufttrycksförändringar, till 0,95. Ytbelastningen beräknades från mätningar av lufttryck, vatten i jordtäcket och snö. Omkring 20 % av årstidsvariationen hos den hydrauliska potentialen uppskattades bero på enbart belastningsförändringar. En enkel begreppsmässig modell kunde användas för att simulera den observerade hydrauliska potentialen. För att beskriva enskilda grundvattenbildningstillfällen på bästa sätt var det nödvändigt att ta hänsyn till effekten av ytbelastningen.Numeriska experiment gjordes med en modell av en jord–bergprofil. När berget modellerades som ett heterogent kontinuum bildades omättade zoner i berget vid stora hydrauliska gradienter. Fenomenet uppträdde i områden där låggenomsläppliga zoner låg uppströms höggenomsläppliga zoner, och ledde till minskad hydraulisk konduktivitet i berget.
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| 18. |
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| 19. |
- Brown, Solomon, et al.
(författare)
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CO(2)QUEST : Techno-economic assessment of CO2 quality effect on its storage and transport
- 2014
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Ingår i: 12TH INTERNATIONAL CONFERENCE ON GREENHOUSE GAS CONTROL TECHNOLOGIES, GHGT-12. - : Elsevier BV. ; , s. 2622-2629
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Konferensbidrag (refereegranskat)abstract
- Presented is an overview of the CO(2)QUEST project that addresses fundamentally important issues regarding the impact of typical impurities in the gas or dense phase CO2 stream captured from fossil fuel power plants on its safe and economic transportation and storage. Previous studies have mainly investigated the impact of CO2 stream impurities on each part of the carbon capture and storage (CCS) chain in isolation. This is a significant drawback given the different sensitivities of pipeline, wellbore materials and storage sites to the various impurities. The project brings together leading researchers and stakeholders, to address the impact of the typical impurities upon safe and economic CO2 transportation and storage. State-of-the-art mathematical models, backed by laboratory and industrial-scale experimentation, are implemented to perform a comprehensive techno-economic assessment of the impact of impurities upon the thermo-physical phenomena governing pipeline and storage-site integrities.
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| 20. |
- Carstens, Christoffer, 1981-
(författare)
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In the Pipe or End of Pipe? : Transport and Dispersion of Water-borne Pollutants and Feasibility of Abatement Measures
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Eutrophication is one of the key environmental problems of today, both in terms of complexity and magnitude. For the Baltic Sea (BS), eutrophication is an acute problem, leading to hypoxic conditions at the bottom; a situation that is sustained and amplified, when phosphorus is released from hypoxic sediments. Reducing nutrient loading is a top political priority but the present situation is believed to require active measures within the catchments and recipients to reduce both loading and adverse effects. Implementation of effective and cost-efficient abatement methods requires understanding of natural processes in watersheds, streams and recipients as well as technological expertise in order to compare the effects of measures of different kinds and locations. This thesis tries to combine process understanding of catchment transport behaviour, especially in coastal zones, and feasibility of certain technologies for reducing nutrient loading and effects of eutrophication in-situ. The over-arching theme is the fate of the individual contaminant, from injection to removal. Transport and dispersion in catchments are investigated, combining physically-based, distributed, numerical groundwater models with Lagrangian stochastic advective reactive solute (LaSAR) transport modelling. The approach is powerful in the sense that it incorporates catchment structural, geomorphological dispersion in the numerical model with hydrodynamic and sub-scale dispersion as well as uncertainty in the LaSAR framework. The study exemplifies the complex nature of transport time distributions in catchments in general and when varying source size and location, importance of dispersion parameters and retention due to molecular diffusion. It is shown that geomorphological control on dispersion is present even for relatively heterogeneous systems and that neither the mean residence time nor a statistical distribution may provide accurate representations of hydrological systems. To combat internal loading of P from sediments in-situ, large-scale aeration of deep waters, halocline ventilation, has been suggested. This study further investigates the feasibility of wave-powered devices to meet the energy demands for such an operation. It is shown that the required amount of oxygen needed to keep the sediments at oxic conditions could be provided, cheaply and efficiently, through the use of wave power.
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| 21. |
- Cederlöf, Erik, et al.
(författare)
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Antipsychotic medications and sleep problems in patients with schizophrenia
- 2024
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Ingår i: Schizophrenia Research. - : Elsevier. - 0920-9964 .- 1573-2509. ; 267, s. 230-238
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sleep problems are common and related to a worse quality of life in patients with schizophrenia. Almost all patients with schizophrenia use antipsychotic medications, which usually increase sleep. Still, the differences in subjective sleep outcomes between different antipsychotic medications are not entirely clear.Methods: This study assessed 5466 patients with schizophrenia and is part of the nationwide Finnish SUPER study. We examined how the five most common antipsychotic medications (clozapine, olanzapine, quetiapine, aripiprazole, and risperidone) associate with questionnaire-based sleep problems in logistic regression analyses, including head-to-head analyses between different antipsychotic medications. The sleep problems were difficulties initiating sleep, early morning awakenings, fatigue, poor sleep quality, short (≤6 h) and long sleep duration (≥10 h).Results: The average number of antipsychotic medications was 1.59 per patient. Clozapine was associated with long sleep duration (49.0 % of clozapine users vs 30.2 % of other patients, OR = 2.05, 95 % CI 1.83–2.30, p < .001). Olanzapine and risperidone were in head-to-head analyses associated with less sleep problems than patients using aripiprazole, quetiapine, or no antipsychotic medication. Aripiprazole and quetiapine were associated with more insomnia symptoms and poorer sleep quality. Patients without antipsychotic medications (N = 159) had poorer sleep quality than patients with antipsychotic use, and short sleep duration was common (21.5 % of patients using antipsychotics vs 7.8 % of patients using antipsychotics, OR = 2.97, 95 % CI 1.98–4.44, p < .001).Conclusions: Prevalence of sleep problems is markedly related to the antipsychotic medication the patient uses. These findings underline the importance of considering and assessing sleep problems when treating schizophrenia patients with antipsychotics.
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| 22. |
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| 23. |
- Dessirier, Benoît, et al.
(författare)
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A new scripting library for modeling flow and transport in fractured rock with channel networks
- 2018
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Ingår i: Computers & Geosciences. - : Elsevier BV. - 0098-3004 .- 1873-7803. ; 111, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- Deep crystalline bedrock formations are targeted to host spent nuclear fuel owing to their overall low permeability. They are however highly heterogeneous and only a few preferential paths pertaining to a small set of dominant rock fractures usually carry most of the flow or mass fluxes, a behavior known as channeling that needs to be accounted for in the performance assessment of repositories. Channel network models have been developed and used to investigate the effect of channeling. They are usually simpler than discrete fracture networks based on rock fracture mappings and rely on idealized full or sparsely populated lattices of channels. This study reexamines the minimal requirements to describe a channel network in terms of groundwater flow and solute transport, leading to an extended description suitable for unstructured arbitrary networks of channels. An implementation of this formalism in a Python scripting library is presented and released along with this article. A new algebraic multigrid preconditioner delivers a significant speedup in the flow solution step compared to previous channel network codes. 3D visualization is readily available for verification and interpretation of the results by exporting the results to an open and free dedicated software. The new code is applied to three example cases to verify its results on full uncorrelated lattices of channels, sparsely populated percolation lattices and to exemplify the use of unstructured networks to accommodate knowledge on local rock fractures.
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| 24. |
- Dessirier, Benoît, 1987-, et al.
(författare)
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Channel Network Modeling of Flow and Transport in Fractured Rock at the aspo HRL : Data-Worth Analysis for Model Development, Calibration and Prediction
- 2023
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 59:5
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Tidskriftsartikel (refereegranskat)abstract
- Performance assessment of nuclear waste disposal in deep crystalline bedrock demands a thorough understanding of the related flow and transport processes. Uncertainties may arise both from the selection of the conceptual model as well as the estimation of the related model parameters. Discrete fracture network (DFN) models are widely used for such modeling while channel network models (CNM) provide an alternative representation, the latter focusing on the fact that flow and transport in deep fractured media often are dominated by a small number of long preferential flow paths. This study applies the principle of channel networks, implemented in the Pychan3d simulator, to analyze the hydraulic and tracer transport behavior in a 450-m-deep fractured granite system at the aspo Hard Rock Laboratory in Sweden, where extensive site characterization data, including hydraulic and tracer test data are available. Semi-automated calibration of channel conductances to field characterization data (flow rates, drawdowns, and tracer recoveries) is performed using PEST algorithm. It was observed that an optimal CNM connectivity map for channel conductance calibration can only be developed by jointly fitting flow rates, drawdowns and tracer mass recovery values. Results from data-calibrated CNM when compared to a corresponding calibrated DFN model shows that the CNM calibrates and adapts better than a DFN model with uniform fracture surfaces. This comparative study shows the differences and uncertainties between two models as well as examines the implications of using them for long term model predictions.
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| 25. |
- Dessirier, Benoit, et al.
(författare)
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Channel Network Modeling of Flow and Transport in Fractured Rock at the Äspö HRL : Data‐Worth Analysis for Model Development, Calibration and Prediction
- 2023
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 59:5
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Tidskriftsartikel (refereegranskat)abstract
- Performance assessment of nuclear waste disposal in deep crystalline bedrock demands a thorough understanding of the related flow and transport processes. Uncertainties may arise both from the selection of the conceptual model as well as the estimation of the related model parameters. Discrete fracture network (DFN) models are widely used for such modeling while channel network models (CNM) provide an alternative representation, the latter focusing on the fact that flow and transport in deep fractured media often are dominated by a small number of long preferential flow paths. This study applies the principle of channel networks, implemented in the Pychan3d simulator, to analyze the hydraulic and tracer transport behavior in a 450-m-deep fractured granite system at the Äspö Hard Rock Laboratory in Sweden, where extensive site characterization data, including hydraulic and tracer test data are available. Semi-automated calibration of channel conductances to field characterization data (flow rates, drawdowns, and tracer recoveries) is performed using PEST algorithm. It was observed that an optimal CNM connectivity map for channel conductance calibration can only be developed by jointly fitting flow rates, drawdowns and tracer mass recovery values. Results from data-calibrated CNM when compared to a corresponding calibrated DFN model shows that the CNM calibrates and adapts better than a DFN model with uniform fracture surfaces. This comparative study shows the differences and uncertainties between two models as well as examines the implications of using them for long term model predictions.
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| 26. |
- Edlmann, K., et al.
(författare)
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Lessons learned from using expert elicitation to identify, assess and rank the potential leakage scenarios at the Heletz pilot CO2 injection site
- 2016
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 49, s. 473-487
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Tidskriftsartikel (refereegranskat)abstract
- Expert elicitation is a useful approach to synthesis expert knowledge, experience and insight when the input data and analysis is limited. During the early stages of the EU FP7 MUSTANG pilot CO2 injection experiment at Heletz, Israel there was very little input data available, yet decisions had to be made regarding data collection, drilling, operation and monitoring strategies. An expert elicitation study was undertaken to identify, assess and rank potential CO2 leakage scenarios at Heletz to provide guidance to support the decision making processes. This paper presents a critique of the expert elicitation process undertaken, presenting the methodology and a discussion of the results. We present the lessons learned during the expert elicitation process, highlighting its advantages and limitations and provide suggestions on ways to overcome these limitations. Our findings show that prudent expert elicitation can make a valuable contribution to decision making, however if done improperly it can equally lead to invalid or misleading results and wrong decisions.
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| 27. |
- Edlmann, K., et al.
(författare)
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Mineralogical properties of the caprock and reservoir sandstone of the Heletz field scale experimental CO2 injection site, Israel; and their initial sensitivity to CO2 injection
- 2016
-
Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 48, s. 94-104
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the initial database of the mineralogy of the caprock and reservoir sandstones of the Heletz field scale experimental CO2 injection site, Israel. The XRD mineralogy results show that the Heletz caprock has K-feldspar as the primary mineral (40%) followed by kaolinite (15%) and plagioclase feldspar (12%) then illite (6%) and muscovite (6%) with minor quartz, calcite, pyrite, chlorite and ankerite with traces of siderite. The Heletz reservoir rock is primarily quartz (70%) followed by K-feldspar (12%) and plagioclase feldspar (4%) with minor illite, kaolinite, muscovite, chlorite ankerite and pyrite with traces of dolomite, calcite and siderite. "Cook and look" bench experiments were conducted on the Heletz caprock and reservoir sandstone samples to identify if there was any immediate mineral reactivity that would influence permeability on exposure to CO2 that may cause concerns during well completion and initial injection of CO2 at Heletz. The sandstone exhibited reactivity under brine dis-equilibrium which was observed in the field with loss of injectivity which was restored by injecting KCL into the well and performing 20 swab-suctions. The caprock revealed no reactivity of immediate concern to the well completion and injection strategy and will retain its integrity.
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| 28. |
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| 29. |
- Fagerlund, Fritjof, et al.
(författare)
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A partially coupled, fraction-by-fraction modelling approach to the subsurface migration of gasoline spills
- 2007
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Ingår i: Journal of Contaminant Hydrology. - : Elsevier BV. - 0169-7722 .- 1873-6009. ; 89:3-4, s. 174-198
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Tidskriftsartikel (refereegranskat)abstract
- The subsurface spreading behaviour of gasoline, as well as several other common soil- and groundwater pollutants (e.g. diesel, creosote), is complicated by the fact that it is a mixture of hundreds of different constituents, behaving differently with respect to e.g. dissolution, volatilisation, adsorption and biodegradation. Especially for scenarios where the non-aqueous phase liquid (NAPL) phase is highly mobile, such as for sudden spills in connection with accidents, it is necessary to simultaneously analyse the migration of the NAPL and its individual components in order to assess risks and environmental impacts.Although a few fully coupled, multi-phase, multi-constituent models exist, such models are highly complex and may be time consuming to use. A new, somewhat simplified methodology for modelling the subsurface migration of gasoline while taking its multi-constituent nature into account is therefore introduced here. Constituents with similar properties are grouped together into eight fractions. The migration of each fraction in the aqueous and gaseous phases as well as adsorption is modelled separately using a single-constituent multi-phase flow model, while the movement of the free-phase gasoline is essentially the same for all fractions. The modelling is done stepwise to allow updating of the free-phase gasoline composition at certain time intervals. The output is the concentration of the eight different fractions in the aqueous, gaseous, free gasoline and solid phases with time.The approach is evaluated by comparing it to a fully coupled multi-phase, multi-constituent numerical simulator in the modelling of a typical accident-type spill scenario, based on a tanker accident in northern Sweden. Here the PCFF method produces results similar to those of the more sophisticated, fully coupled model. The benefit of the method is that it is easy to use and can be applied to any single-constituent multi-phase numerical simulator, which in turn may have different strengths in incorporating various processes. The results demonstrate that the different fractions have significantly different migration behaviours and although the methodology involves some simplifications, it is a considerable improvement compared to modelling the gasoline constituents completely individually or as one single mixture.
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| 30. |
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| 31. |
- Fagerlund, Fritjof, et al.
(författare)
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Comparison of relative permeability-fluid saturation-capillary pressure relations in the modelling of non-aqueous phase liquid infiltration in variably saturated, layered media
- 2006
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Ingår i: Advances in Water Resources. - : Elsevier BV. - 0309-1708 .- 1872-9657. ; 29:11, s. 1705-1730
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Tidskriftsartikel (refereegranskat)abstract
- The characteristic functions relating relative permeabilities and capillary pressures to fluid saturations (kr–S–Pc models) are of great importance for the modelling of sub-surface multi-phase flow and transport. In order to test their performance and to identify their important parameters, four well-known three-phase kr–S–Pc models have been tested against published experimental data on non-aqueous phase liquid (NAPL) migration in the unsaturated zone. Both homogenous systems and systems with embedded heterogeneities have been analysed. The results show that although there are differences between predictions based on the different models, all models exhibit some common problems and it is not obvious that any one model is more accurate than the other three. However, with the inclusion of a non-linear NAPL tortuosity factor, both the Brooks–Corey–Burdine and van Genuchten–Mualem models yield excellent fits to experimental data. For NAPLs with non-zero spreading coefficients no exact theory currently exists for scaling two-phase capillary pressure–saturation functions to three-phase systems. Different ways of applying the Parker et al. [Parker JC, Lenhard RJ, Kuppusamy T. A parametric model for constitutive properties governing multi-phase flow in porous media. Water Resour Res 1987;23:618–24] scaling method have therefore been tested. It was found that since the NAPL–gas capillary pressure function has the strongest influence on NAPL migration, the scaling procedure should focus on accuracy in this function.
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| 32. |
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| 33. |
- Fagerlund, Fritjof, et al.
(författare)
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Design of a two-well field test to determine in situ residual and dissolution trapping of CO2 applied to the Heletz CO2 injection site
- 2013
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 19, s. 642-651
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Tidskriftsartikel (refereegranskat)abstract
- Field testing is a critical step to improve our knowledge on in situ-trapping mechanisms of CO2 injected in geological formations and their relative importance. In this study, we present a two-well test sequence aimed at quantifying field values of both residual and dissolution trapping of CO2. Then, we apply it to the Heletz experimental CO2 injection site, using numerical modelling. The sequence includes a hydraulic test to measure residual scCO(2) saturation and a novel tracer technique, together with measurements of abstracted fluid compositions for quantification of the rate of CO2 dissolution in the reservoir. The proposed tracer technique uses a tracer with negligible aqueous solubility, which is injected with the scCO(2) and enriched in the scCO(2) phase as CO2 dissolves. We show that this tracer can provide direct information about the dissolution of mobile scCO(2). We also show that the rate of abstracted dissolved CO2 can be used to predict the total rate of CO2 dissolution, provided that the amount of dissolved CO2 in the formation stabilizes, and that this can be achieved with the proposed abstraction scheme. We conclude that the combination of these measurements is a promising tool for detailed field-scale characterization of residual and dissolution trapping processes.
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| 34. |
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| 35. |
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| 36. |
- Fagerlund, Fritjof, 1974-
(författare)
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Experimental and Modelling Studies on the Spreading of Non-Aqueous Phase Liquids in Heterogeneous Media
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Non-Aqueous Phase Liquids (NAPLs) include commonly occurring organic contaminants such as gasoline, diesel fuel and chlorinated solvents. When released to subsurface environments their spreading is a complex process of multi-component, multi-phase flow. This work has strived to develop new models and methods to describe the spreading of NAPLs in heterogeneous geological media. For two-phase systems, infiltration and immobilisation of NAPL in stochastically heterogeneous, water-saturated media were investigated. First, a methodology to continuously measure NAPL saturations in space and time in a two-dimensional experiment setup, using multiple-energy x-ray-attenuation techniques, was developed. Second, a set of experiments on NAPL infiltration in carefully designed structures of well-known stochastic heterogeneity were conducted. Three detailed data-sets were generated and the importance of heterogeneity for both flow and the immobilised NAPL architecture was demonstrated. Third, the laboratory experiments were modelled with a continuum- and Darcy’s-law-based multi-phase flow model. Different models for the capillary pressure (Pc) – fluid saturation (S) – relative permeability (kr) constitutive relations were compared and tested against experimental observations. A method to account for NAPL immobility in dead-end pore-spaces during drainage was introduced and the importance of accounting for hysteresis and NAPL entrapment in the constitutive relations was demonstrated. NAPL migration in three-phase, water-NAPL-air systems was also studied. Different constitutive relations used in modelling of three-phase flow were analysed and compared to existing laboratory data. To improve model performance, a new formulation for the saturation dependence of tortuosity was introduced and different scaling options for the Pc-S relations were investigated. Finally, a method to model the spreading of multi-constituent contaminants using a single-component multi-phase model was developed. With the method, the migration behaviour of individual constituents in a mixture, e.g. benzene in gasoline, could be studied, which was demonstrated in a modelling study of a gasoline spill in connection with a transport accident.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Fagerlund, Fritjof, et al.
(författare)
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Interwell field test to determine in-situ CO2 trapping in a deep saline aquifer : Modelling study of the effects of test design and geological parameters
- 2013
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 40, s. 554-563
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Tidskriftsartikel (refereegranskat)abstract
- An interwell field test to determine residual phase and dissolution trapping of CO2 is being designed at Heletz, Israel. Effects of test-design options and geological parameters were investigated using numerical modelling. It was found that the interwell distance has large influence on the feasibility of the test both in terms of creation of a zone of residually trapped CO2 and detection of the time when such zone has been created. The optimal distance is site-specific and depends on formation properties. Alternating CO2 and brine injections slightly increased residual trapping, but did not facilitate creation of a well-defined zone of trapping.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Fagerlund, Fritjof, et al.
(författare)
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Modeling of nonaqueous phase liquid (NAPL) migration in heterogeneous saturated media : Effects of hysteresis and fluid immobility in constitutive relations
- 2008
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Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 44:3
-
Tidskriftsartikel (refereegranskat)abstract
- The confidence in model predictions for nonaqueous phase liquid (NAPL) transport in stochastically heterogeneous systems is limited. The fundamental approaches as well as the constitutive models have not been sufficiently validated, mainly because of the lack of appropriate experimental data. Recently, Fagerlund et al. (2007a, 2007b) presented a set of well-controlled laboratory data that are used here (1) to analyze the overall performance of the continuum-based approach for predicting two-phase NAPL-water flow in stochastically heterogeneous media and (2) to compare the predictions from different constitutive models. The five models tested were the nonhysteretic Brooks-Corey-Burdine (BCB) and van Genuchten-Mualem (VGM) models, the hysteretic versions of these models (HBCB and HVGM), and the HVGBCB model, a model combining the hysteretic van Genuchten (HVG) P c -S relation and the hysteretic Brooks-Corey-Burdine k r -S relation. Two cases of NAPL migration were considered: a layered system of two homogeneous sands separated by a dipping interface and a system where one of the layers was stochastically heterogeneous. The results showed that the best models could indeed capture the main characteristics of the spreading and immobilization well, demonstrating the validity of the continuum-based approach for this level of stochastic heterogeneity. Implementation of hysteresis was necessary for correct prediction of the observed speed of NAPL migration as well as the amount of immobilized NAPL. The three hysteretic models were similar in their overall prediction error-based performance. The HVGM model produced less overestimation of NAPL saturations but instead underestimated the entrapment at capillary barriers in comparison to the HBCB and HVGBCB models. The HVGM model also overestimated the speed of NAPL migration, which is attributed to its closed-form k r -S function, for which the VG parameter m has to be fitted under the constraint m = 1 − 1/n. The HVG (and VG) P c -S function, in contrast, used a different set of VG parameters produced with no constraint on m, which better represented the pore size distributions of the sands. A relation for partial nonwetting phase immobility during drainage is also presented.
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| 46. |
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| 47. |
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| 48. |
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| 49. |
- Fagerlund, Fritjof, et al.
(författare)
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Multilevel Monte Carlo methods for computing failure probability of porous media flow systems
- 2016
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Ingår i: Advances in Water Resources. - : Elsevier BV. - 0309-1708 .- 1872-9657. ; 94, s. 498-509
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Tidskriftsartikel (refereegranskat)abstract
- We study improvements of the standard and multilevel Monte Carlo method for point evaluation of the cumulative distribution function (failure probability) applied to porous media two-phase flow simulations with uncertain permeability. To illustrate the methods, we study an injection scenario where we consider sweep efficiency of the injected phase as quantity of interest and seek the probability that this quantity of interest is smaller than a critical value. In the sampling procedure, we use computable error bounds on the sweep efficiency functional to identify small subsets of realizations to solve highest accuracy by means of what we call selective refinement. We quantify the performance gains possible by using selective refinement in combination with both the standard and multilevel Monte Carlo method. We also identify issues in the process of practical implementation of the methods. We conclude that significant savings in computational cost are possible for failure probability estimation in a realistic setting using the selective refinement technique, both in combination with standard and multilevel Monte Carlo.
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| 50. |
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