Harvesting geothermal energy with low unit cost installations

Abstract

In the Netherlands, most geothermal energy is utilized for commercial greenhouse heating and is harvested from aquifers located at depths between 2 and 3 km. Typically, the design consists of two wells: a slanted production well and a slanted injection well that are spaced approximately 1.5 km apart in the aquifer formation. Subsidized exploitation is feasible if high volumes can be produced over long periods of time. This typical solution restricts the use of geothermal energy to high-demand applications in areas with suitable high-quality aquifers. We argue that harvesting geothermal energy is economically feasible almost anywhere in the Netherlands with an alternative concept of low unit cost (LUC) installations. LUC produces at a limited rate from cleverly designed high-quality installations that can be developed at a considerably lower cost. We discuss the LUC concept and its economics based on a project for commercial greenhouse heating in the eastern part of the Netherlands. We carry out a reinterpretation of publicly available 3D seismic and offset well data. The Early Cretaceous Bentheim Sandstone was identified as a suitable aquifer for LUC development. At the proposed well location, the top Bentheim is located at a depth of approximately 1500 m, corresponding to about 61°C. We predict a reservoir thickness of approximately 54 m, with a porosity of up to 25% and sufficient permeability. The LUC concept begins by drilling a pilot hole for static and dynamic aquifer characterization. Based on these test results, we decide on the final architecture and placement of wells. Our calculations show that a 1.5 megawatt thermal (MWth) geothermal plant is economically viable, even without government subsidy.

Permeability evolution of Bentheim Sandstone at simulated georeservoir conditions

“…In fact, BS is a suitable deep, warm aquifer for potential low-cost geothermal energy in the Netherlands 7 , a case study rock for anhydrite cementation in georeservoirs 8 and one of the most important aquifers in the North German Basin 9 . The top of the BS formation is at a depth of about 1.5 km, but BS can be found at more than 2 km depth and has been buried as deep as 3.5 km 10 , so it is crucial to understand its properties at different depths.…”