Saeid Nikoosokhan

Effect of dry density, soil texture and time-spatial variable water content on the soil thermal conductivity

Study of the heat transfer process in saturated and unsaturated soils requires, basically, a relationship between thermal conductivity and the characteristics of the soil, such as water content, dry density and texture of the soil. This study intends to produce a generic model that can predict soil thermal conductivity with the help of easily measurable parameters. The proposed model is first calibrated using measured thermal conductivities from literature data. In order to validate the proposed model the predicted thermal conductivity of this proposed model as well as existing ones are compared with the measured thermal conductivity in literature for different soils. Validation of the proposed model was also performed on our experimental results obtained for a compacted Misillac sand and in-situ clay loam soils. The results show an average of 15% improvement in prediction accuracy for the proposed model compared to the existing models, considering all soil textures. Moreover, we perform a model to estimate thermal conductivity over time throughout the profile of soil in the context of seasonal variation of temperature. The proposed model shows an important effect of heterogeneity on the thermal conductivity variations of a double layered soil.

Seasonal Heat Storage in Unsaturated Soils with Variable Thermal Properties

Hydrothermal properties of soil are prerequisites of the models of heat storage in unsaturated soils. Variation of water content as well as soil characteristics change its thermal properties. Therefore, to give comprehensive effects of hydrothermal properties of soil on the characteristics of heat storage, we need to take into account the dependecy of those thermal properties to the water content and other soil characteristics in the heat transfer models. In this study we aim to model heat distribution within the depth of unsaturated soil while its thermal conductivity varies with time and depth. The proposed model is based on the fundamental solution of the one-dimensional heat equation and the decomposition method. We consider that thermal conductivity varies exponentially with depth and sinusoidally with time. We calibrate our model with the experimental data from different soil textures in the literature. We recently developed a model which can estimate soil thermal conductivity from its characteristics such as dry density, degree of saturation, and the texture of soil. Water content of soil at different depth is back-estimated with the help of our previous model.

Geological Storage of CO2 in Coal Beds - From Material to Reservoir

One of the main issues encountered with CO2 storage in coal beds is the loss of permeability of the reservoir during the injection of carbon dioxide. Such a decrease of permeability originates from the closure of the cleat system in these reservoirs, which itself is a consequence of the swelling of the coal matrix during injection. In this study, we first perform a comparison of the numerical simulation based on the derived model, at the scale of a coal sample, with available permeability measurements of coal injected with carbon dioxide. The second objective of the paper is to capture the effect of the kinetics of transfer of fluid between cleats and coal matrix using the set of equations derived before. We then perform simulations at the scale of a Representative Elementary Volume, and we show that adsorption-induced variations of permeability depend significantly on the kinetics of transfer of fluid between cleats and coal matrix. At the scale of a reservoir, simulations of injection of carbone dioxide in a methane-free reservoir are performed. We discuss the effects of the kinetics of transfer of fluid between cleats and coal matrix on the rates of injection.