Evaluation of geothermal resources in a hotspot realm: Mauritius Island (Indian Ocean)

Geochemical and geothermal investigations were performed in the Mauritius Island, located along the Seychelles-Mascarene Plateau, aimed at the preliminary assessment of possible geothermal resources. The central part of the island may be the most suitable as characterized by the most recent volcanic activity (0.03 Ma). Geochemical analyses of water samples collected from this area indicate no mature water and the chemical features are ascribable to short-term water-rock interaction in shallow hydrogeological circuits. A gradient borehole was drilled and thermal logs performed after complete thermal equilibration to evaluate the thermal gradient in central part of the island. A value of 43 \ub0C km-1 was measured and a similar result was obtained by logging a deep well no longer used for water extraction. The results point to a weak or null deep-seated thermal anomaly beneath Mauritius. This might mean that the deep thermal processes (mantle plume) invoked to occur in the hotspot area do not likely yield any particular thermal signature

New Geothermal Prospect in North-Eastern Morocco

Geothermal data has been indicating promising potentialities in the north-eastern Morocco. This paperpresents new temperature data, recently recorded in water borehole located in the Berkane and Oujda areas. Generally, the observed temperature gradients are rather high. One hole near Berkane, revealed an average geothermal gradient of more than 110 ºC/km at depths greater than 300 m. This result confirms the geothermal gradient estimated in a mining borehole located about 30 km west of the Berkane borehole, in which water temperatures of 96 ºC are reached at a depth of about 700 m. Such a high geothermal gradient, exceeding by far the ones already determined for northeastern Morocco, could act as a stimulus to programs aimed at the geothermal exploitation of high temperature aquifers

Conductive heat flow pattern of the central-northern Apennines, Italy

We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbance and the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtained heat-flow data may reflect the deep, undisturbed, conductive thermal regime

The role of hydrogeological conditions and thermophysical properties on the evaluation of geothermal exchange potential in Central Italy

A multidisciplinary investigation aimed at optimising low enthalpy geothermal plants in the Marche Region (Central Italy) is currently in progress. The main goal is to improve the present-day knowledge of the geological structure, the hydogeological setting and the thermophysical characters of the subsoil and to obtain a better picture of the regional geothermal exchange potential. Since the seasonal climatic variation can affect the temperature and moisture content of the shallower portion of the subsoil, we are focusing our attention on the continuous monitoring of the physical properties of groundwater (temperature and electrical conductivity above all). Moreover, recording of undisturbed temperature-depth profiles in available boreholes is underway. Meanwhile, we have started an extensive campaign of laboratory measurements of thermal conductivity, volume heat capacity, thermal diffusivity, porosity, density and permeability of the several lithologies forming the sedimentary deposits of the Umbria-Marche successions. In this paper, we present the first results so far achieved concerning the field monitoring and the laboratory experiments. These data will be fundamental for the subsequent implementations of numerical thermal models of the subsoil, which incorporate conductive and advective heat transfer and which can evaluate the behaviour of borehole heat exchangers under different hydrogeological conditions

A mathematical model to infer underground thermal characteristics for the design of borehole heat exchangers

Geothermal exchangers are exploited as tools for the indirect analysis of the thermal properties of the underground material. Two simple inverse problems based on different heat transfer models are proposed: the first one is based on the cylindrical model of heat transfer and yields the thermal parameters of the borehole, the second one is based on a forced convective model and yields the soil thermal profile. We test our approach on sets of data collected by direct numerical simulation and from a real experiment