The Balmatt Deep Geothermal Project in Northern Belgium Ben Laenen*, Matsen Broothaers, Virginie Harcouët-Menou & Sian Loveless Energyville, Dennenstraat 7, 3600 Genk, Belgium VITO, Boeretang 200, 2400 Mol, Belgium * phone: +32 14 33 56 38, e-mail: ben.laenen@vito.be VITO: from shallow to deep geothermal energy Since 1998, VITO is actively involved in new developments in geothermal energy in Belgium and the Netherlands. Initially, research focused on the use of shallow aquifers in combination with heat pumps for heating applications. VITO spin-off company, Terra Energy (www.terra-energy.be), continues this work on shallow geothermal systems and applications. VITO now focuses its own research on large-scale energy storage systems on the one hand and on deep geothermy for heating and electricity generation on the other hand. The Balmatt project in brief The geothermal plant will be located at the Headquarters of VITO, the Flemish Institute of Technology in Mol (Fig. 1). Targeting a carbonate reservoir with temperatures sufficient to match local heat and power demand. Final expected gross power output of up to 48 MW in 2020. A first well is planned to be drilled in early 2015. Subsequent development will be phased (Fig. 1), allowing for a gradual expansion according to surface requirements and aquifer conditions : 1. Geothermal doublet system connected to the high temperature heat network of the existing VITO/SCK sites, VITO’s new headquarter and other customers in and around the Balmatt site. 2. Additional wells will be drilled and electricity will be produced from a newly constructed ORC (Organic Rankine Cycle) and distributed to VITO and SCK. Surplus will be put on the general grid. The Balmatt project addresses both the technical and non-technical challenges for the development of geothermal energy in Flanders. The success of the project will pave the way for realisation of further geothermal plants in the Campine region. Fig 1. Location and development stages of the Balmatt site. Inset shows location in Belgium. Green region is Flanders. Geological setting Our geological model based on regional geological models and on newly acquired seismic data (Fig.2) reveals the targeted aquifer to lie at depths of between 2000 m and 3800 m (Fig. 3). This stratigraphic interval has been encountered in several wells in the Campine Basin, below the Coal Measures Group. The depth of the formation varies throughout the area, increasing towards the northeast. In the area of Mol, the depth is in the order of 2800 m below surface. Fig 2. Depth map for the top of the Carboniferous Limestone Group, based on data from the seismic survey 2D Mol-Herentals 2010. Fig 3. Geological setting of the geothermal reservoir with the location of the first well. Geothermal potential in Flanders In Flanders, the geothermal gradient is approximately 3 °C per 100 m and the heat flux varies from 50 to 90 mW/m2 (Fig. 4). The Balmatt project is located in the Campine area that has a heat flux of about 65 mW/m². The project targets water-bearing layers in the carbonate sequence of the Carboniferous Limestone Group. A static model calculated a temperature of 120°C can be expected at the top of the Carboniferous Limestone Group, and 142°C at the base. Fig 4. Heat flux map of Flanders. Energy demand in the region versus expected thermal output Five companies have been identified for heat delivery and 2 for power delivery with distances between 200 m and 8 km from the planned plant. The total amount of heat that could be provided towards the heat users equals 63.284 MWh/year. The remainder off the geothermal heat is available for power production. The geothermal potential under the Balmatt site is calculated as a P90 value (probability of success of 90% ) for the thermal output of a doublet. Calculations point to a P90 value of the thermal output of 12,6 MWth, with a flow rate of 140 m³/h (Fig.5). This was calculated using the DoubletCalc programme developed by TNO (Mijnlieff et al., 2012) and takes into account both geological and non-geological parameters and their uncertainty range (Table 1). Geological parameters were derived from data from reference wells in the Campine Basin, and from seismic surveys in the area. The achievable flow rate was calculated based on permeability data from several wells in the region and (large-scale) transmissivity from pump tests accounting for fractures, joints and vugs. Permeability also takes into account a depth trend of decreasing permeability with increasing depth. Table 1. Summary of the geological and non-geological parameters used to estimate the thermal output of the geothermal doublet. Fig 5. Probability chart for a) the geothermal output and b) the flow rate .