Analysis of conductive and convective heat transfer in a sedimentary basin, demonstrated for the Rheingraben

Abstract

The identification and quantification of conductive and convective components in the heat transfer of a sedimentary basin is demonstrated for the Rheingraben. Three different methods of varying complexity as well as three independent data sets are employed: (1) energy budget considerations based on hydraulically perturbed thermal data from shallow boreholes (<500m), (2) 1-D vertical Peclet number analysis of thermal data from 22 deep boreholes (> lo00 m), and (3) 2-D finite difference modelling of the fully coupled fluid flow and heat transport equations on a vertical cross-section of the entire Rheingraben. Energy budget considerations yield a conductive basal heat flow density of 84 + 40/-10 mW mP2, and in good agreement with this Peclet number analysis, gives median values in the range 90 f 35 mW m-'.In the first case, the basement is formed by low permeable, tertiary sediments at about 500 m depth, and in the second by the transition from the sedimentary graben fill to the crystalline basement at depths of between 2000 and 4000m. It is shown how results from numerical modelling support the flow field assumptions made by methods (1) and (2), as well as the value of 80 f 10 mW m-' for average basal heat flow density entering the graben from below. Conversely, the Peclet number range Pe I 1.2 inferred from method (2) can be applied for a (at least partial) calibration of the fully coupled hydrothermal model calculatioris. This technique is suggested as a potentially interesting thermal method for constraining regional-scale permeability.An interpretation of heat transport is presented that satisfies the experimentally established patterns of both temperature and heat flow density in the Rheingraben. Moreover, it is demonstrated that the thermal anomalies along the western rim of the graben (such as Pechelbronn, France or Landau, Germany) can be convincingly explained by a basin-wide, deep rooted E-W groundwater circulation that locally enhances a background basal heat flow density of about 80 mW m-' on average by 50 per cent and at individual sites by as much as 120 per cent.

Thermal conductivity of granular porous media: A pore scale modeling approach

“…The surface roughness has complex geometries which makes it impossible to be analytically incorporated in real porous medium cases similar to what we calculated in Equations (5) and (6). To express the importance of roughness simulation for the thermal conduction modeling of porous media, we simulate porous media with respect to an experimental study on Utah oil sand samples.…”

“…Analytical methods have the disadvantage of oversimplified assumptions that restrain their applications for real complicated problems. 6 Based on laboratory measurements, experimental methods (e.g. needle probe, 7 parallel plates, 8 and optical scanning 9 ) are used to determine the effective thermal conductivity.…”

Possible natural fluid pathways from gravity pseudo-tomography in the geothermal fields of Northern Alsace (Upper Rhine Graben)

“…Accordingly, in the western part of the URG, a fault-related discharge zone for the basin-wide circulation system was assumed to account for about 50% increase of the mean heat flux of about 80 ± 10 mW m −2 at the top crystalline basement (Clauser and Villinger 1990). The aim of this study is to investigate the possible pathways for fluid inflow into the Soultz and adjacent geothermal fields (e.g.…”

Heat transport analysis and three‐dimensional thermo‐hydraulic simulation in the Ishikari basin, Hokkaido, Japan

“…The solution procedure as described in Clauser and Villinger (1990) is: first a solution of the fluid flow by Equation (8) is obtained, and Darcy velocities are computed from Equation (12); then the heat transport Equation (11) is solved; this is followed by a temperature and pressure update of the hydraulic conductivity, the specific storage coefficient S s and the porosity parameters.…”

“…The role of these influencing physical parameters on ground thermal state conditions has been well recognized by many studies. Among the factors frequently cited are groundwater flow disturbances (Bredehoeft and Papadopulos, 1965;Mansure and Reiter, 1979;Woodbury and Smith, 1988;Clauser and Villinger, 1990;Stulc, 1998;Taniguchi et al, 1999), and surface climatic influences (Cermak et al, 1992;Mareschal and Vasseur, 1992;Safanda and Kubik, 1992;Wang et al, 1992;Beltrami and Taylor, 1995;Kohl, 1998;Kukkonen et al, 1998). These climatic effects are seasonal, annual or long-term atmospheric temperature waves transmitted towards the Earth's interior according to the molecular thermal conductivity of the geological material.…”