Publication Date:
2023-12-18
Description:
High-temperature aquifer thermal energy storage (HT-ATES) systems provide high capacity for thermal energy storage of surplus energy by incorporating seasonal phases of charging and discharging a reservoir. In the present work, we emphasize on the karstified and fractured Upper Jurassic reservoir of the German Molasse Basin (North Alpine Foreland Basin). Even though multiple geothermal plants operate currently at this reservoir, the potential for heat storage has not been yet sufficiently analyzed. The estimated heating capacity obtained by feasible operational parameters is ca. 18 MW over half a year. Our approach highlights the evaluation of HT-ATES development in the Malm reservoir by means of numerical modeling. The performed numerical analysis focuses on a subset of the Upper Jurassic reservoir which is governed by karst-dominated fluid fluxes, and further exhibits favorable reservoir temperature for heat storage. While we develop synthetic numerical models, those are based on a series of discrete investigations and datasets (i.e. field tests, well logs and investigations of rock cores) of three operating geothermal systems of the Malm aquifer, at depths of ca. 2000-3000 m TVD. In this regard, the numerical models are constrained by known Upper Jurassic reservoir properties and locally feasible operational parameters (e.g. flow rates, injected/produced fluid temperatures), and are thus considered representative of the ca. 500 m thick Malm reservoir at this subregion of the Molasse Basin. The proposed distance of the two vertical wells is 400 m, i.e. approx. twice the maximum estimated thermal radius, deciphered by assuming fluid injection solely in the thinner reservoir unit. Simulation results illustrate the thermal perturbation that develops initially in the rock volume directly adjacent to the wells and progressively advances radially into the reservoir rock matrix. The geometry of the thermally affected reservoir rock is significant since heat losses occur at the interface between host rock and propagating thermal front. Furthermore, the models consider, through the IAPWS thermodynamic property formulations, density and viscosity variation induced by the temperature contrast between the injected fluid and the reservoir. Apart from investigating potentially arising buoyant fluxes that may trigger considerable thermal losses, the integration of density and viscosity variance additionally enables to examine its effect on the productivity and injectivity indexes. The computations allow to capture the relevant thermal and hydraulic effects of heat storage, and promote further a better understanding of the Upper Jurassic reservoir behavior.
Type:
info:eu-repo/semantics/conferenceObject
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