Reservoir Architecture Modelling for Geothermal Energy Production - Case Study of the Delft Sandstone Member, West Netherlands

Deep-geothermal energy projects operate with a geothermal doublet comprising a hot-water produc-tion well and a cooled-down water injection well. Both wells target the same aquifer to maintain pressure support in the reservoir. The injection well ends at shallower depth than the production well to allow for gravity-driven cold-water front propagation. These conditions determine the doublet layout. A detailed knowledge of reservoir architecture and connectivity in the aquifer is required to assess the pressure communication between the wells, and to reduce the economic risk of these projects. A case study for a planned geothermal doublet research project in the Delft Sandstone Member (Valanginian, West Netherlands Basin) shows that the target comprises stacked sandstone interbedded with mudstone and lignite. Core, cutting, well-log and seismic analyses show that the sandstone formed by meandering rivers in a SE-NW elongated rift basin. The reservoir is subdivided in three units on the basis of variations in net-to-gross, log signature, lithofacies interpretation and stacking density. Unit 3 the best porosity and permeability values, is sand-prone and characterized by multi-storey and laterally-amalgamated meandering river sandstone bodies with minor mudstone floodplain intervals. Optimal placement of geothermal doublet is in the NW-SE trend of the fluvial pathway.