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2018-09-13 - Colloque/Présentation - poster - Anglais - 1 page(s)

Martin Frank , Dupont Nicolas , Gonze Kevin , Goderniaux Pascal , Martin Thierry , Everaerts M., Charlet David, Habils Frédéric, Kaufmann Olivier , "Future geophysical prospections for the development of deep geothermal energy in Hainaut, Belgium" in Geologica Belgica, Leuven, Belgique, 2018

  • Codes CREF : Sciences de l'ingénieur (DI2000), Prospection minière et pétrolière (DI2321), Géologie (DI1411), Ressources renouvelables et non-renouvelables (DI4383)
  • Unités de recherche UMONS : Géologie fondamentale et appliquée (F401)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)

Abstract(s) :

(Anglais) Few years ago, in 2014, the EU launched new financing funds called ERDF whose role was to strengthen economic and social cohesion in the European Union and, more importantly, make a step forward in the low-carbon economy and greenhouse gas emissions. Project MOREGEO belongs to this movement. This is a research project on deep geothermal energy designed for district heating in the surroundings of Mons, Belgium (project GEOTHERWALL_DOUBLET 1). The project targets the geothermal resources of the Carboniferous limestone formations. It aims at developing the knowledge on this geothermal reservoir, improving the prediction of the behaviour of the geothermal resource over time and support the drilling of new wells in Mons. In this paper, the geophysical aspects covered in the project will be exposed as well as the context in which they take place. On the one hand, seismic reflexion and gravimetry surveys are planned in order to better characterize the reservoir at the regional scale, thus leading to better constraining the geothermal reservoir model. On the other hand, a more local focus in the whereabouts of the geothermal wells and will aim at implementing solutions for the microseimic monitoring during the geothermal plant operations. Even if former coal mining operations lead to accumulate a large amount of data about this area's underground, the knowledge about its deep geology, more specifically below the coal bearing formations, is still quite limited and is not sufficient to characterise with some precision the reservoir. Therefore, several geophysical surveys (Seismic refraction, seismic reflexion and gravimetry) are planned to characterize as accurately as possible the geometry of the geothermal reservoir and, thereafter, to design a dynamic model of the area. In the future, it will allow providing an efficient management tool for developing additional geothermal wells and optimizing the position of the injection and production wells in the reservoir. These geophysical surveys will cover the “Coeur du Hainaut” area, around the City of Mons (South Belgium). Firstly, five 14 km long North-South seismic reflection lines distributed from Bernissart (Western line) to Obourg (Eastern line) will be carried out. Each line will be separated by intervals of approximately 5 km. This layout allows covering the entire area of interest considering the previous seismic acquisitions in this area. Indeed, several 2D seismic reflexion lines were already carried out such as the 1986 Belcorp survey. However, the recovered data and processing were not set for a deep reservoir characterisation. In 2012, 2 seismic lines covering Mons and Estinnes from North to South were surveyed and analysed by the same method (Dupont N. et al., 2016) and operators also reprocessed the Belcorp 1986 dataset to improve the imaging of the reservoir. To supplement these, the new seismic reflexion campaign will come first. As data will be acquired on a broader scale, these new lines will hopefully contribute to improve the understanding of the geometry and structure of the deep geothermal reservoir. The seismic reflexion campaign will be preceeded by a Low Velocity Layers (LVL) acquisition along the same profiles to derive the static corrections to apply to the 2D seismic reflection dataset. A new gravimetry survey is also planned along the seismic survey. In 2016, a preliminary work by Everaets et al (2016) consisted in building 2D density models along the 2012 seismic lines, in order to fit the Bouguer anomalies. It lead to test and propose several structural interpretations but it also highlighted the low gravimetric data density along the lines. A better coverage would certainly allow more in depth processing and interpretation. Therefore, a new gravimetric prospection with data collection and processing will be performed along the seismic lines with spatial density of one measurement every vibrating point (1s/250m). A Scintrex CG-5 is planned to be used for the operations. These data will allow to complement the seismic data and better constrain the interpretations at a larger scale. Concerning the geophysical applications focused on the geothermal doublet, they consist in the deployment of a microseismic monitoring network, in a perimeter of up to 3 km around the geothermal doublet. The reason for this installation lies in the fact that the impacts of this new exploitation by a doublet should be monitored considering the deep geothermal context. This will be a surveillance tool to quantify the possible impact of the water extraction and injection on the local microseismicity. The network will include 6 broadband seismometers, two within a 1 km radius and the 4 others within a 3 km radius of the geothermal plant. The localization of each station was based on the approach proposed by T.Kraft et al. (2013) involving geographical and seismic noise parameters. The network and processing chain will be implemented to detect and to locate micro-events in the vincinity of the doublet. In this way the monitoring of potential microseismic impacts of the geothermal production of the doublet will be highly ensured. To conclude with, the main scope of the seismic reflexion and gravimetric campaigns is to acquire enough data to improve the reservoir modelling, especially regarding its geometry and structure. Finally, the installation of a local seismic network will ensure the monitoring of this exploitation aiming at a secured geothermal energy production.