Optimization of Well Locations and Trajectories: Comparing Sub-Vertical, Sub-Horizontal and Multi-Lateral Well Concepts for Marginal Geothermal Reservoir in The Netherlands

Scaling up the direct use of geothermal heat in urban areas comes with the challenge of enabling the development of projects in geological settings where geothermal reservoir flow properties may be poor, resulting in low well flow performance. Cost-effective field development strategies and well designs tailored to such reservoirs can ensure the deliverability of geothermal energy in economic terms. This study presents a framework based on computer-assisted optimization to support practitioners in selecting the most suitable well concept for the exploitation of such marginal geothermal reservoirs. The proposed methodology is illustrated in a real-life case study of a geothermal development prospect in an urban area in The Netherlands, where the performance of sub-vertical, sub-horizontal and multi-lateral wells is compared. The obtained results indicate that the techno-economic performance of the geothermal doublet can be significantly improved by optimization, for all considered well concepts, and that, despite the importance of selecting the well concept, well location is still the main determinant of an effective field development strategy. The sub-horizontal and multi-lateral well concepts appear to be the most suitable for the target case study, outperforming the sub-vertical doublets, with a higher expected net present value and a lower economic variability risk for the multi-lateral solution.