DI-UMONS : Dépôt institutionnel de l’université de Mons

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2016-01-27 - Colloque/Présentation - communication orale - Anglais - 16 page(s)

Dupont Nicolas , Kaufmann Olivier , "Exploration of the geothermal reservoirs of Hainaut (Belgium) : preliminary results of the 2DMons2012 seismic survey. New deep structures revealed in the Brabant Parautochton." in 5th International Geologica Belgica Meeting, Mons, Belgique, 2016

  • Codes CREF : Prospection minière et pétrolière (DI2321), Géologie (DI1411), Ressources renouvelables et non-renouvelables (DI4383), Sciences de la terre et du cosmos (DI1400), Sondages géologiques (DI2322)
  • Unités de recherche UMONS : Géologie fondamentale et appliquée (F401)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)

Abstract(s) :

(Anglais) Under the impulsion of the Wallonia Regional Government to improve the knowledge of the deep geothermal reservoirs. The two beneficiaries, IDEA and Earthsolution S.A., pooled their resources to explore the deep Carboniferous limestones for low-enthalpy energy and the deep mid-Devonian limestones for mid-enthalpy energy in the Brabant Parautochton. To precise the structure of these targets, a 2D seismic survey was conducted in 2012 (a.k.a. 2DMons2012). The acquisition was realized by DMT, the scientific follow-up and interpretation was provided by UMONS. The 2DMons2012 survey consist of two 2D seismic reflexion lines of ~20km long each. These North-South lines cross perpendicularly the known structural units. The acquisition parameters were designed based on the experience and the results of older surveys in this area (Hainaut79 and Belcorp86) and preliminary tests. Down to ~1000 m (0-600 ms TWT), the interpreted 2D seismic sections show the expected structures within the Mons Basin, the Ardennes Allochtonous and the HSM Overturned Thrust Sheets (i.e. Masse-Borinage Unit). From the northern outcrop, the Brabant Parautochton shows a monocline structure dipping southward. At the southern boundary of the explored zone, the deep Parautochton is subhorizontal. The two main reflectors occurring in this unit are considered as the top of the lower-Carboniferous limestones and the mid-Devonian limestones strata. In the northern part, the second reflector is weaker, suggesting different sedimentological settings (cf. Licour et al. (2016)). The separation between these two reflectors increases significantly to the North, in line with the Saint-Ghislain and Jeumont boreholes. The western line section reveals a set of normal faults in the southern border of the Brabant Parautochton, affecting mid-Devonian up to upper-Carboniferous strata, named Deep Fault Zone of the Borinage (DFZB). Some of these faults were recognized on the top of the Parautochton during coal mining activities next to this seismic line (Crachet-Picquery mine, Frameries). These faults may explain the increase in thickness of the mid-Devonian/lower-Carboniferous strata from South to North. This is suggesting that a passive margin was active during this period between the Condroz Horst and the Brabant Parautochton. The DFZB is less obvious on the eastern line section, however interpretation suggests that its extension is largely reduced, probably because of transtensional tectonics. These deep structures are also affecting variscan faults, especially the Masse-Borinage Fault, showing that another extensional and/or transtensional tectonic phase occurred after the Variscan orogenesis, probably reactivating former faults. A link with the transtensive context highlighted in the Mons Basin is not excluded. Further research is conducted on the implications in the regional geology and links with nearby structures (North-Artois Shear Zone, Mélantois-Tournaisis Faulted Anticline…) as well as the interference with deep karstification within the lower Carboniferous strata.