La technologie des géostructures énergétiques consiste à adapter les structures géotechniques, co... more La technologie des géostructures énergétiques consiste à adapter les structures géotechniques, comme les pieux de fondation, les parois moulées ou les tunnels, afin de les transformer en échangeurs de chaleur avec le sol. De fait, ce sont des systèmes géothermiques à basse enthalpie, avec le gros avantage de réduire les coûts initiaux d’installation grâce à l’utilisation des structures géotechniques qui seraient réalisées dans tous les cas. Les échanges de chaleur entre la géostructure et le sol induisent des variations de température cycliques sur les deux, et l’efficacité du système doit répondre à la fois à des critères énergétiques (bonne production de chaleur ou de froid) et géotechniques-structurels (analyse des contraintes et déformations thermiques du sol et de la structure en béton), qui dépendent fortement des conditions locales du site accueillant la construction. Il s’agit donc d’un système complexe avec un comportement dépendant de différents phénomènes thermiques, hydr...
L'etat thermique des bassins sedimentaires est analyse suivant deux approches differentes et ... more L'etat thermique des bassins sedimentaires est analyse suivant deux approches differentes et complementaires permettant de definir les roles respectifs des transferts de chaleur par conduction et convection. Dans la premiere partie est envisagee l'estimation des conductivites thermiques in situ a partir des diagraphies et de thermometries d'equilibre. La procedure utilisee sur deux puits du bassin de paris permet de reveler une variation du comportement thermique des argiles en fonction de la profondeur. La deuxieme partie est consacree a l'etude des effets thermiques des divers mecanismes convectifs. Un modele de perturbation est propose afin de rendre compte de l'indice des ecoulements de fluides le long de structures peu epaisses et inclinees. Enfin, dans la troisieme partie les resultats precedents sont integres pour approcher le regime thermique actuel du bassin de paris: une anomalie froide d'echelle regionale est mise en evidence puis interpretee en te...
Permeable structures such as aquifers or fault zones can focus the ground-water flow system and t... more Permeable structures such as aquifers or fault zones can focus the ground-water flow system and transfer heat by convection across the surrounding rocks where conduction dominates. In this paper, we describe a simple method to calculate both the steady- and transient-state temperature disturbance related to such a circulation. In the 2-D ( x- z) model used, the flow is described by its flow rate q, the geometry of the channel [depth h ( x) ] and its thickness. Assuming that the horizontal conduction can be neglected, a semi-analytical solution is obtained when the temperature disturbance is described as a function of the Peclet number a = q ( p c) f / A- ( P C) ~ is the heat capacity of the fluid and A the conductivity of surrounding rocks-and of the slope of the channel @ and of the time since the flow duration. The case of an upward flow along a dipping channel is considered in detail but more complex cases with a channel composed of segments can be handled easily. The validity of...
ABSTRACT Thermal conductivity is a very important parameter for understanding the present and pas... more ABSTRACT Thermal conductivity is a very important parameter for understanding the present and past thermal regimes of sedimentary basins. The bulk thermal conductivity of sedimentary rocks depends mainly on three factors: (1) their mineralogic and fluid composition, (2) their temperature, and (3) their structure. As shown by a series of measurements on small-scale isotropic samples, the effects of mineralogy and fluid content can be estimated quite accurately using the geometric mean model. However, this estimate does not take into account a possible anisotropy related to various structural effects such as small-scale heterogeneity or crystalline orientation. This anisotropy effect seems especially important in the case of clayey formations: various observations using equilibrium temperature logging, together with classical well logs, can be interpreted as indicating such an effect. The effect appears to depend on depth as would be expected from the major changes occurring in clays during their burial history: compaction, mineralogical transformation and structural reorganization.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
ABSTRACT Thermal conductivity is a very important parameter for understanding the present and pas... more ABSTRACT Thermal conductivity is a very important parameter for understanding the present and past thermal regimes of sedimentary basins. The bulk thermal conductivity of sedimentary rocks depends mainly on three factors: (1) their mineralogic and fluid composition, (2) their temperature, and (3) their structure. As shown by a series of measurements on small-scale isotropic samples, the effects of mineralogy and fluid content can be estimated quite accurately using the geometric mean model. However, this estimate does not take into account a possible anisotropy related to various structural effects such as small-scale heterogeneity or crystalline orientation. This anisotropy effect seems especially important in the case of clayey formations: various observations using equilibrium temperature logging, together with classical well logs, can be interpreted as indicating such an effect. The effect appears to depend on depth as would be expected from the major changes occurring in clays during their burial history: compaction, mineralogical transformation and structural reorganization.
The estimation of thermal conductivity from well logs is of great importance for all studies on t... more The estimation of thermal conductivity from well logs is of great importance for all studies on thermal evolution of sedimentary basins. The approach proposed here is to first interpret the well logs in terms of mineralogic composition and porosity and then to estimate the in situ conductivity from a mixing formula: the geometric average of individual conductivities weighted by the volumetric proportion of each component. The validity of the model has been widely verified by laboratory measurements on isotropic samples. However there is a need for validation of such an approach for in situ conditions.Temperature data recorded at equilibrium in two wells of the Paris basin offer a unique possibility of testing this approach: in the case of a steady state conductive thermal régime (Fourier's law), the conductivity must be proportional to the inverse of the temperature gradient. The well logs are quantitatively interpreted in terms of mineralogic composition, porosity and then thermal conductivity using a conductivity law calibrated on cuttings and cores laboratory measurements. For three examples of well sections, the computed thermal conductivity compares reasonably well with the inverse of the gradient.For each of the three examples, it is possible to define a depth range where the apparent heat flow is almost constant with depth and where the conductive régime seems to prevail. This allows a refinement of the conductivity model with emphasis on the contribution of clays: assuming that the conductivities of non-clay end terms are known, it is possible to obtain the conductivity of clay giving the best fit to the temperature measurements. In the three cases the conductivity of clay (1.2-1.4 W m−1 K−1) is found to be lower than the assumed one (1.8 W m−1 K−1) which probably indicates an anisotropy effect.Finally an empirical model where the bulk conductivity is expressed directly as a function of well logs is tested. In one case the results obtained are quite compatible with the previous one, but in the other two sections, the stability and the physical meaning of this model are found to be questionable. This could be due to the lack of constraints in the underlying implicit mineralogy model.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
Permeable structures such as aquifers or fault zones can focus the ground-water flow system and t... more Permeable structures such as aquifers or fault zones can focus the ground-water flow system and transfer heat by convection across the surrounding rocks where conduction dominates. In this paper, we describe a simple method to calculate both the steady- and transient-state temperature disturbance related to such a circulation.In the 2-D (x-z) model used, the flow is described by its flow rate q, the geometry of the channel [depth h(x)] and its thickness. Assuming that the horizontal conduction can be neglected, a semi-analytical solution is obtained when the temperature disturbance is described as a function of the Peclet number α= q(pc)f/Λ - (pc))f is the heat capacity of the fluid and α the conductivity of surrounding rocks-and of the slope of the channel ø and of the time since the flow duration. the case of an upward flow along a dipping channel is considered in detail but more complex cases with a channel composed of segments can be handled easily.The validity of the assumption of no horizontal conduction is carefully discussed by comparing to a numerical solution where both vertical and horizontal conductions are taken into account. For a value of slope which does not exceed 30°, the analytical solution gives quite acceptable results. Finally, we propose simple rules for estimating the transient and steady-state temperature disturbance generated by a given fluid flow.
La technologie des géostructures énergétiques consiste à adapter les structures géotechniques, co... more La technologie des géostructures énergétiques consiste à adapter les structures géotechniques, comme les pieux de fondation, les parois moulées ou les tunnels, afin de les transformer en échangeurs de chaleur avec le sol. De fait, ce sont des systèmes géothermiques à basse enthalpie, avec le gros avantage de réduire les coûts initiaux d’installation grâce à l’utilisation des structures géotechniques qui seraient réalisées dans tous les cas. Les échanges de chaleur entre la géostructure et le sol induisent des variations de température cycliques sur les deux, et l’efficacité du système doit répondre à la fois à des critères énergétiques (bonne production de chaleur ou de froid) et géotechniques-structurels (analyse des contraintes et déformations thermiques du sol et de la structure en béton), qui dépendent fortement des conditions locales du site accueillant la construction. Il s’agit donc d’un système complexe avec un comportement dépendant de différents phénomènes thermiques, hydr...
L'etat thermique des bassins sedimentaires est analyse suivant deux approches differentes et ... more L'etat thermique des bassins sedimentaires est analyse suivant deux approches differentes et complementaires permettant de definir les roles respectifs des transferts de chaleur par conduction et convection. Dans la premiere partie est envisagee l'estimation des conductivites thermiques in situ a partir des diagraphies et de thermometries d'equilibre. La procedure utilisee sur deux puits du bassin de paris permet de reveler une variation du comportement thermique des argiles en fonction de la profondeur. La deuxieme partie est consacree a l'etude des effets thermiques des divers mecanismes convectifs. Un modele de perturbation est propose afin de rendre compte de l'indice des ecoulements de fluides le long de structures peu epaisses et inclinees. Enfin, dans la troisieme partie les resultats precedents sont integres pour approcher le regime thermique actuel du bassin de paris: une anomalie froide d'echelle regionale est mise en evidence puis interpretee en te...
Permeable structures such as aquifers or fault zones can focus the ground-water flow system and t... more Permeable structures such as aquifers or fault zones can focus the ground-water flow system and transfer heat by convection across the surrounding rocks where conduction dominates. In this paper, we describe a simple method to calculate both the steady- and transient-state temperature disturbance related to such a circulation. In the 2-D ( x- z) model used, the flow is described by its flow rate q, the geometry of the channel [depth h ( x) ] and its thickness. Assuming that the horizontal conduction can be neglected, a semi-analytical solution is obtained when the temperature disturbance is described as a function of the Peclet number a = q ( p c) f / A- ( P C) ~ is the heat capacity of the fluid and A the conductivity of surrounding rocks-and of the slope of the channel @ and of the time since the flow duration. The case of an upward flow along a dipping channel is considered in detail but more complex cases with a channel composed of segments can be handled easily. The validity of...
ABSTRACT Thermal conductivity is a very important parameter for understanding the present and pas... more ABSTRACT Thermal conductivity is a very important parameter for understanding the present and past thermal regimes of sedimentary basins. The bulk thermal conductivity of sedimentary rocks depends mainly on three factors: (1) their mineralogic and fluid composition, (2) their temperature, and (3) their structure. As shown by a series of measurements on small-scale isotropic samples, the effects of mineralogy and fluid content can be estimated quite accurately using the geometric mean model. However, this estimate does not take into account a possible anisotropy related to various structural effects such as small-scale heterogeneity or crystalline orientation. This anisotropy effect seems especially important in the case of clayey formations: various observations using equilibrium temperature logging, together with classical well logs, can be interpreted as indicating such an effect. The effect appears to depend on depth as would be expected from the major changes occurring in clays during their burial history: compaction, mineralogical transformation and structural reorganization.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
ABSTRACT Thermal conductivity is a very important parameter for understanding the present and pas... more ABSTRACT Thermal conductivity is a very important parameter for understanding the present and past thermal regimes of sedimentary basins. The bulk thermal conductivity of sedimentary rocks depends mainly on three factors: (1) their mineralogic and fluid composition, (2) their temperature, and (3) their structure. As shown by a series of measurements on small-scale isotropic samples, the effects of mineralogy and fluid content can be estimated quite accurately using the geometric mean model. However, this estimate does not take into account a possible anisotropy related to various structural effects such as small-scale heterogeneity or crystalline orientation. This anisotropy effect seems especially important in the case of clayey formations: various observations using equilibrium temperature logging, together with classical well logs, can be interpreted as indicating such an effect. The effect appears to depend on depth as would be expected from the major changes occurring in clays during their burial history: compaction, mineralogical transformation and structural reorganization.
The estimation of thermal conductivity from well logs is of great importance for all studies on t... more The estimation of thermal conductivity from well logs is of great importance for all studies on thermal evolution of sedimentary basins. The approach proposed here is to first interpret the well logs in terms of mineralogic composition and porosity and then to estimate the in situ conductivity from a mixing formula: the geometric average of individual conductivities weighted by the volumetric proportion of each component. The validity of the model has been widely verified by laboratory measurements on isotropic samples. However there is a need for validation of such an approach for in situ conditions.Temperature data recorded at equilibrium in two wells of the Paris basin offer a unique possibility of testing this approach: in the case of a steady state conductive thermal régime (Fourier's law), the conductivity must be proportional to the inverse of the temperature gradient. The well logs are quantitatively interpreted in terms of mineralogic composition, porosity and then thermal conductivity using a conductivity law calibrated on cuttings and cores laboratory measurements. For three examples of well sections, the computed thermal conductivity compares reasonably well with the inverse of the gradient.For each of the three examples, it is possible to define a depth range where the apparent heat flow is almost constant with depth and where the conductive régime seems to prevail. This allows a refinement of the conductivity model with emphasis on the contribution of clays: assuming that the conductivities of non-clay end terms are known, it is possible to obtain the conductivity of clay giving the best fit to the temperature measurements. In the three cases the conductivity of clay (1.2-1.4 W m−1 K−1) is found to be lower than the assumed one (1.8 W m−1 K−1) which probably indicates an anisotropy effect.Finally an empirical model where the bulk conductivity is expressed directly as a function of well logs is tested. In one case the results obtained are quite compatible with the previous one, but in the other two sections, the stability and the physical meaning of this model are found to be questionable. This could be due to the lack of constraints in the underlying implicit mineralogy model.
ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. H... more ABSTRACT In the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady-state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay-rich rocks, based on laboratory and in-situ measurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2-D quasi-horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
Permeable structures such as aquifers or fault zones can focus the ground-water flow system and t... more Permeable structures such as aquifers or fault zones can focus the ground-water flow system and transfer heat by convection across the surrounding rocks where conduction dominates. In this paper, we describe a simple method to calculate both the steady- and transient-state temperature disturbance related to such a circulation.In the 2-D (x-z) model used, the flow is described by its flow rate q, the geometry of the channel [depth h(x)] and its thickness. Assuming that the horizontal conduction can be neglected, a semi-analytical solution is obtained when the temperature disturbance is described as a function of the Peclet number α= q(pc)f/Λ - (pc))f is the heat capacity of the fluid and α the conductivity of surrounding rocks-and of the slope of the channel ø and of the time since the flow duration. the case of an upward flow along a dipping channel is considered in detail but more complex cases with a channel composed of segments can be handled easily.The validity of the assumption of no horizontal conduction is carefully discussed by comparing to a numerical solution where both vertical and horizontal conductions are taken into account. For a value of slope which does not exceed 30°, the analytical solution gives quite acceptable results. Finally, we propose simple rules for estimating the transient and steady-state temperature disturbance generated by a given fluid flow.
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Papers by L. Demongodin