Targeting for Geothermal Energy Production – Reservoir Characterization and Geothermal Potential of the Delft Sandstone

The Delft Geothermal Project is a broad consortium of governmental and industrial partners that aims to develop an innovative geothermal system at the TU Delft campus. In early 2011, a geothermal doublet will be drilled that targets the Delft Sandstone Member, a fluvial sandstone formation contained in a structural low at a depth between 1.7 and 2.4 km. Several wells were drilled in and around the target area in the 50s and 60s, primarily to explore known oil-bearing formations above the Delft Sandstone Member. Based on the analysis of logs, cores, and cutting data from these wells, and their correlation with re-interpreted 2D and 3D seismic, the target sandstone is subdivided into three units. The lower unit is considered a risky target, primarily because of the poor lateral and vertical connectivity between individual fluvial sandstone bodies. By contrast, in the upper unit, lateral and vertical connectivity between individual sandstone bodies is high, as are porosities (30%) and permeabilities (725-1130mD), which makes this unit an excellent target for geothermal energy production. Communication between the lower and upper unit is likely impeded by the presence of the middle unit, which as extremely low porosity and permeability.