| Title | Insights Into a Complex Geothermal Reservoir in the Lower Carboniferous Carbonates in Northern Belgium |
|---|---|
| Authors | Matsen BROOTHAERS, Stijn BOS, David LAGROU, Helga FERKET, Virginie HARCOUET-MENOU, Ben LAENEN |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | northern Belgium, limestone, fractured reservoir, Lower Carboniferous, carbonate rock, Campine basin |
| Abstract | In January 2016, the Flemish Institute of Technological Research (VITO) completed the geothermal exploration well MOL-GT-01 in Mol-Donk, northern Belgium. The well targeted a Lower Carboniferous fractured carbonate reservoir at a depth between 3000 and 3600 m. A well test proved the geothermal potential of the limestones, with a bottom hole temperature of 138-142°C. This led to the drilling of a second well to close the geothermal loop. Well MOL-GT-02 was completed and tested in summer 2016. Both wells form a doublet delivering heat to VITO and neighboring companies. With regard to the addition of extra low temperature heating networks, VITO drilled a third well in 2018, MOL-GT-03. The latter well targeted the same faulted and fractured zone as MOL-GT-01, although now at 1,6 km towards the Southeast, and furthermore explored the potential of the underlying Devonian strata. For the Carboniferous limestone sequence, comparable reservoir characteristics were expected as for the first well. However, the results of the well test indicated a lower transmissivity than expected. In order to have a better understanding of the reservoir, a detailed analysis was performed on all three wells. The analysis covers both structural, geological, petrographical and hydrogeological aspects. It should lead to a decision on which steps need to be taken to make MOL-GT-03 a successful geothermal well too. The first results indicate a complex structural setting where the identification and positioning of faults in the reservoir is challenging. Petrographical analysis on core samples points to deposition in a restricted environment. It also reveals the presence of anhydrite. Its role in the formation or preservation of secondary porosity (and hence permeability) is not clear yet and will be further investigated in the near future. |