Petitclerc, Estelle ; Gurung, Pabitra ; Gerard, Pierre ; Van Camp, Marc ; Van der Veken, Jeroen ; Van Lysebetten, Gust ; Van Noten, Koen ; Walraevens, Kristine

Poster presented at 7th Geologica Belgica International Conference, Tervuren, Belgium on 2021-09-17

Abstract: During the past years, research has been conducted on shallow geothermal energy (SGE) with projects such as SmartGeotherm (VLAIO) and Brugeo (EFRD). Although the Belgian SGE market is steadily growing, some main barriers such as better knowledge of the underground and economic potential, investment costs, financial support, policy measures and public awareness must be tackled to further develop the market. Most of the existing geothermal systems are traditionally installed in the soft, sedimentary Mesozoic-Cenozoic cover, however, the exploration drilling at Anderlecht (2017) and the operational open geothermal system at Gare Maritime (2020) have demonstrated the higher potential and efficiency of the Cambrian core of the Brabant Massif. Although this has also led to more feasibility studies for the exploitation of the Cambrian basement during the past years, more research must be conducted if extensive use is envisaged to significantly contribute the renewable share of the total energy production and to enhance the geothermal sector development. With the GeoCamb (Belspo) project, not only the geothermal potential of the Cambrian bedrock will be evaluated and demonstrated, the energy demand of specific, public buildings will be incorporated to maximise the efficiency of the system. Therefore, geological, hydrogeological and geophysical exploration will be performed. To have a full understanding of the sustainability of geothermal installations, the economic and environmental impacts will also be investigated. Eight different sites with a total of 22 destructive boreholes (up to 252 m below ground level) have been analysed. 6 sites are located in the Brussels Capital Region and one in both Walloon- and Flemish-Brabant. In this article, the lithology, mineralogy, geophysical and thermal characteristics of the encountered Cambrian basement and its weathered/eroded top will be presented. Before encountering siltstones and (quartzitic) sandstones with some quartz-rich layers of the Tubize Formation, a few meters up to more than 20 meters of weathered layer is observed in almost all sites. This weathering zone consists of clay, silt, sand, weathered siltstone and sandstone, (large) quartz veins, faults and cavities which can have serious implications on the design, budget and risks of exploration drillings. To have a better understanding of the Cambrian basement and to de-risk geothermal feasibility studies in the future, not only the top of the basement should be investigated but also the thickness and lithology of the weathered zone, which is not considered as a separate layer in existing geological models (Brugeo, DOV).

Keyword(s): Geothermal ; Cambrian ; Brabant Massif ; Geophysics
Funding: B2/191/P1/GEOCAMB