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Limiting Sand Production in Unconsolidated Aquifers: Implications for Low-Enthalpy Geothermal Well Development
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 1st Geoscience & Engineering in Energy Transition Conference, Nov 2020, Volume 2020, p.1 - 6
Abstract
The geothermal energy sector is rapidly developing in the Netherlands. Low-enthalpy direct use geothermal wells are typically developed in aquifers at depths of 1,800–3,000 m, the same reservoirs targeted for hydrocarbon exploration. Alternative shallower targets include unconsolidated aquifers within the North Sea Supergroup, with producible water at temperatures of 20 - 50 °C. To maximize heat extraction from these aquifers high flow rates are needed. Conversely, the well design must inhibit the mobilization of formation grains. In the Netherlands well design criteria for aquifer thermal energy storage (ATES) systems (typically < 200 m depth) consist of a maximum flow velocity on the borehole wall, which is independent of depth. For wells in deeper aquifers (300 – 1,500 m), the in situ stress as a function of depth is not incorporated in the design. The Drucker-Prager criterion can be used to determine shear failure at formation depth, so that a maximum allowable flow rate can be calculated. Empirically derived relations from the literature are presented to determine input parameters for the DruckerPrager criterion if lab measurements are absent. A comparison of the different well design criteria demonstrates that in situ stresses need to be incorporated for maximum allowable flow rate estimations.