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| Titel |
A 2-D FEM thermal model to simulate water flow in a porous media: Campi Flegrei caldera case study |
| VerfasserIn |
V. Romano, U. Tammaro, P. Capuano |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 19, no. 3 ; Nr. 19, no. 3 (2012-05-10), S.323-333 |
| Datensatznummer |
250014210
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| Publikation (Nr.) |
 copernicus.org/npg-19-323-2012.pdf |
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| Zusammenfassung |
| Volcanic and geothermal aspects both exist in many geologically young areas.
In these areas the heat transfer process is of fundamental importance, so
that the thermal and fluid-dynamic processes characterizing a viscous fluid
in a porous medium are very important to understand the complex dynamics of
the these areas. The Campi Flegrei caldera, located west of the city of
Naples, within the central-southern sector of the large graben of Campanian
plain, is a region where both volcanic and geothermal phenomena are present.
The upper part of the geothermal system can be considered roughly as a
succession of volcanic porous material (tuff) saturated by a mixture formed
mainly by water and carbon dioxide. We have implemented a finite elements
approach in transient conditions to simulate water flow in a 2-D porous
medium to model the changes of temperature in the geothermal system due to
magmatic fluid inflow, accounting for a transient phase, not considered in
the analytical solutions and fluid compressibility. The thermal model is
described by means of conductive/convective equations, in which we propose a
thermal source represented by a parabolic shape function to better simulate
an increase of temperature in the central part (magma chamber) of a box,
simulating the Campi Flegrei caldera and using more recent evaluations, from
literature, for the medium's parameters (specific heat capacity, density,
thermal conductivity, permeability). A best-fit velocity for the permeant is
evaluated by comparing the simulated temperatures with those measured in
wells drilled by Agip (Italian Oil Agency) in the 1980s in the framework of
geothermal exploration. A few tens of days are enough to reach the thermal
steady state, showing the quick response of the system to heat injection.
The increase in the pressure due to the heat transport is then used to
compute ground deformation, in particular the vertical displacements
characteristics of the Campi Flegrei caldera behaviour. The vertical
displacements range from 1 cm to 10 cm in accordance with the mini uplift,
characterizing the recent behaviour of the caldera. The time needed to move
fluid particles from the bottom to the upper layer (years) is compatible
with the timing of the mini uplift. |
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