The subsurface plays nowadays an important role as it provides essential resources: drinking water, hydrocarbons, raw materials and heat, etc., as well as the capacity for large-scale fluid storage (natural gas, liquid or liquefied hydrocarbons). Yet, the use of the subsurface is expected to increase even more in the coming years, mainly because of the energy transition, with new types of subsurface uses adding to the existing ones. Among these prospective uses, we can mention the storage of energetic vectors (compressed air, H2, CH4, etc.), of wastes, of CO2, of heat, new types of mining or energy resources exploitation. The question arises as to whether these new uses would generate potential conflicts in the utilization of the subsurface, what would threaten their economic or technical viability. Indeed, despite the vastness of the subsurface space, only a fraction is suitable for the above-mentioned uses and many of them target the same geology, thus potentially generating a conflict of use for the same space.
As an example, low energy geothermal activity and gas storage (CO2, natural gas) require similar deep and permeable aquifers. Likewise, compressed air storage, hydrogen storage, and liquid hydrocarbon storage are different uses for salt caverns.
Moreover, subsurface activities create impact that may affect the underground at significant distances from the reservoir space that is actually used (changes in pressure, temperature, volume displacement, etc.). The size of the impacted zone varies widely depending on the type of activities and the geology. Clearly, when the influence radius reaches another subsurface activity, they are another source for conflicts.
Managing the subsurface to optimise its use and at the same time avoid conflicts, is important, but not straight forward. The complexity arises from the variety of subsurface activities, the large range of relevant geological processes, and the often incomplete knowledge of geological reality, all of which come together in an interactive context. Because the subsurface is a highly important resource, we should not only look at avoiding conflicts. Rather, we should look beyond these and consider how activities can be developed in close proximity, and even look for potential synergies, to come to an optimized use of the subsurface.
GeoConnect³d will address this issue, and draw generic lessons from the case studies. The project aims at formulating these so they can be taken up at political and policy levels throughout Europe.
Isaline Gravaud (BRGM), Kris Piessens (GSB)
References
Bauer, Sebastian, Christof Beyer, Frank Dethlefsen, Peter Dietrich, Rainer Duttmann, Markus Ebert, Volker Feeser, et al. 2013. ‘Impacts of the Use of the Geological Subsurface for Energy Storage: An Investigation Concept’. Environmental Earth Sciences 70 (8): 3935–43. https://doi.org/10.1007/s12665-013-2883-0
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