References of "Daoudi, Moubarak"
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See detailHow tracer tests simulations strongly constrain flow and solute transport models in fractured chalk aquifers
Goderniaux, Pascal ULg; Daoudi, Moubarak; Orban, Philippe ULg et al

Conference (2012, May)

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign ... [more ▼]

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign was preceded by a morphostructural study associated to a geophysical survey including electrical resistivity and refraction seismic measurements. Results provided information on the main expected fracturation axis where a series of injection and monitoring wells were drilled. In each of the 11 sites, multi-tracer tests have been performed in groundwater convergent flow conditions to pumping wells or draining galleries (used for drinking water production). The analysis of the detailed quantitative breakthrough curves allowed identifying various transport behaviours, from rapid advective to dominant dispersive processes with immobile water effects. Groundwater flow and solute transport in such a fractured chalk can be simulated using different conceptual approaches. Using HYDROGEOSPHERE (Therrien and Sudicky, 1996), a comparison is made between two ways for representing the fracture zones: (1) high contrasted hydraulic conductivity zones with a classical REV approach and (2) the explicit representation of discrete fractures interacting with a porous medium. Promising results are found using the discrete approach for representing the fractures. In this last case, an aperture of the order of the millimetre is enough for creating, where it is needed, a fast advective peak combined with a long highly dispersive component due to the chalk matrix. The discrete fracture approach prevents the modeller from introducing unrealistic parameters values in the fracture zones as it is generally the case in the classical REV-based method where the fractured zones are simply represented by elongated REV. However, it is shown that the availability of field data, as multi-tracers test results, creates very high constraints to be taken into account in the calibration processes (i.e calibration on the measured groundwater flow and transport conditions). The detailed calibration on the different breakthrough curves is not an easy task and automatic calibration is not easy to organize. Results are particularly illustrative to show that a detailed parameterization and calibration of such a local situation remain difficult. Perspectives will be discussed about the potential use of automatic calibration tools as UCODE_2005 or PEST for solving such local situation models and the needed further steps for ‘upscaling’ local situation models at the scale of the whole aquifer or groundwater body. [less ▲]

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See detailGeophysical monitoring of a thermal response test
Daoudi, Moubarak; Hermans, Thomas ULg; Vandenbohede, Alexander et al

Conference (2011, October 20)

Geothermal energy systems efficiency relies on the quantification of the thermal properties of the ground. The estimation of those properties can be done by means of thermal response tests (TRT) or thanks ... [more ▼]

Geothermal energy systems efficiency relies on the quantification of the thermal properties of the ground. The estimation of those properties can be done by means of thermal response tests (TRT) or thanks to values found in literature tables; the first approach provides relatively limited information since the measures are done in boreholes and the values from general tables can present a lack of accuracy. Geophysical methods might be useful in order to yield additional information for thermal properties estimation on higher investigation scales. In this study, electrical resistivity tomography (ERT) is used to monitor the evolution of heated water injected into an unconfined aquifer. Both heat injection and storage were monitored during a total period of 17 days. The principal conclusion is that the use of ERT is efficient to monitor the progressive temperature increase and decrease in the aquifer due to the presence of the heated plume. The resistivity distributions calculated by inversion were compared with electromagnetic borehole measurements and were consistent in the case of the storage phase, whereas a higher gap remained between measured and calculated resistivities for the injection phase. A conversion of the calculated resistivities into temperature values enabled a validation with temperature logs for the storage phase, while the temperature deduced for the injection profiles were too low. Those differences are justified by the fact that different error models were used to proceed to the imaging of the heat injection and storage. This work demonstrates the ability of ERT to monitor geothermal experiment in shallow aquifer. Keywords: geothermal energy, electrical resistivity, electromagnetic method, heat transfer, inversion process, thermal response test. [less ▲]

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See detailParameter estimation using slug tests : application to a heat injection and storage experiment
Vandenbohede, Alexander; Louwyck, Andy; Daoudi, Moubarak et al

Poster (2011, September 19)

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See detailMeasured and computed solute transport behaviour in the saturated zone of a fractured and slightly karstified chalk aquifer
Dassargues, Alain ULg; Goderniaux, Pascal ULg; Daoudi, Moubarak et al

in Bertrand, C.; Carry, N.; Mudry, J. (Eds.) et al Proc. H2Karst, 9th Conference on Limestone Hydrogeology (2011, September)

Solute transport in the saturated zone of a micro-fissured, fractured and even locally slightly karstified aquifer has been studied by multi-tracer tests in groundwater convergent flow conditions to ... [more ▼]

Solute transport in the saturated zone of a micro-fissured, fractured and even locally slightly karstified aquifer has been studied by multi-tracer tests in groundwater convergent flow conditions to pumping wells or towards a collecting gallery. Different behaviour has been detected that can be described by three kinds of typical breakthrough curves: (a) transport with a dominant advective component, producing narrow and symmetrical observed breakthrough curves, characteristic of solute transport in open fractures or conduits; (b) transport with significant advective and dispersive components exhibiting more spread-out breakthrough curves, with also non-symmetrical trends caused by retardation effects; (c) transport with a dominant dispersive component, showing mostly a flat breakthrough curve where dispersion and possible immobile water effects are difficult to be separated. These results were synthesized from thirty-five injections of tracers, distributed between 11 sites. Groundwater flow and solute transport are simulated and illustrated here for one example, employing the finite element code HYDROGEOSPHERE, and using two ways for representing the fracture zones: highly contrasting hydraulic conductivity zones with a classical REV approach and discrete fractures combined with a porous medium by the use of a dual approach. Results are particularly illustrative to show that detailed parameterization and calibration of such a local situation remain difficult even on the basis of an extensive data sets from many tracer tests. [less ▲]

Detailed reference viewed: 60 (12 ULg)