We propose a 3-day workshop to develop a borehole science plan for a multi-use exploration and monitoring well of 3-4.5 km depth that will be part of a unique research infrastructure on the TU Delft campus. This so-called urban energy laboratory will include a well-instrumented geothermal well doublet (reaching to a depth of 2.5 km), an ultra-sensitive portable seismic monitoring array, the scientific monitoring components of a high temperature aquifer heat storage system (HT-ATES) and a borehole array to monitor and protect groundwater supplies. The addition of the multi-use well to the urban energy laboratory will allow us to tackle problems and better understand processes related to multiple/competing subsurface uses in densely populated areas, and their interference with natural processes and the deep biosphere. The monitoring aspects target fluid/flux movement in 3D with unprecedented precision, aiming to understand the propagation of the geothermal cold front and reservoir pressures away from the well. In addition, access to the test sites and the data will enable the international research community to develop and optimise novel downhole and cross-hole imaging and measurement methods and techniques in this unique environment under challenging (for geophysical monitoring: noisy) conditions. Through the workshop and the broad expertise of the participants, we want to explore key science directions and opportunities even beyond the geothermal aspects.

Keywords: multiple subsurface use, urban energy, geothermal heat production, interference with nature