The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the gre... more 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 importa...
<p&amp... more <p>Pumping tests are often used for the estimation of subsurface flow parameters. Research has indicated that traditional geostatistical techniques expressed in terms of two-point correlations (i.e., the covariance of flow parameters at two points is only a function of separation distance) may not be adequate to fully represent complex patterns of flow and transport in heterogeneous subsurface systems. To address this issue, the concept of flow connectivity has been introduced to describe how different regions of the aquifer relate to each other. In this study, the impact of point-to-point flow connectivity on radially convergent flow tests towards a well is investigated numerically. A Monte Carlo approach is adopted whereby a large number of heterogeneous aquifer systems with different levels of connectivity (Gaussian, connected high-transmissivity fields, and connected low-transmissivity fields) are synthetically generated and then used to simulate pumping tests. Various test interpretation methods are then used to estimate apparent flow parameters from the time-drawdown curves, and examine how the estimated parameters relate to the underlying heterogeneous aquifer systems. Results indicate that the estimated transmissivity using only drawdown data corresponding to early times is dominated by the point transmissivity distribution in the vicinity of the well. The estimated transmissivity value gradually approaches the geometric mean of the full transmissivity field as a longer time-drawdown dataset is included in the interpretation. On the other hand, the storage coefficient estimated from late drawdown data is strongly sensitive to aquifer point-to-point flow connectivity and the relative locations of the observation and pumping wells. The relations between the estimated storage coefficient and different aquifer connectivity functions are also examined.</p>
The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the gre... more 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 importa...
<p&amp... more <p>Pumping tests are often used for the estimation of subsurface flow parameters. Research has indicated that traditional geostatistical techniques expressed in terms of two-point correlations (i.e., the covariance of flow parameters at two points is only a function of separation distance) may not be adequate to fully represent complex patterns of flow and transport in heterogeneous subsurface systems. To address this issue, the concept of flow connectivity has been introduced to describe how different regions of the aquifer relate to each other. In this study, the impact of point-to-point flow connectivity on radially convergent flow tests towards a well is investigated numerically. A Monte Carlo approach is adopted whereby a large number of heterogeneous aquifer systems with different levels of connectivity (Gaussian, connected high-transmissivity fields, and connected low-transmissivity fields) are synthetically generated and then used to simulate pumping tests. Various test interpretation methods are then used to estimate apparent flow parameters from the time-drawdown curves, and examine how the estimated parameters relate to the underlying heterogeneous aquifer systems. Results indicate that the estimated transmissivity using only drawdown data corresponding to early times is dominated by the point transmissivity distribution in the vicinity of the well. The estimated transmissivity value gradually approaches the geometric mean of the full transmissivity field as a longer time-drawdown dataset is included in the interpretation. On the other hand, the storage coefficient estimated from late drawdown data is strongly sensitive to aquifer point-to-point flow connectivity and the relative locations of the observation and pumping wells. The relations between the estimated storage coefficient and different aquifer connectivity functions are also examined.</p>
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Papers by Xavier Sanchez-vila