High-temperature heat storage in depleted hydrocarbon reservoirs

Supervisor: Prof. Dr. Thomas Kohl

Person in charge: Kai Stricker

In the energy sector, a climate-neutral society requires solutions for the increasing share of fluctuating renewable energies. One central challenge of renewable energy resources is the seasonal mismatch between their main availability in summer (especially solar energy) and the energy demand in winter (e.g. for heating purposes). This discrepancy requires energy storage systems of high capacity. Aquifer thermal energy storage (ATES) is one prominently utilized technology with a storage capacity of more than 2.5 TWh per year (mainly in the Netherlands). High-temperature storage systems (up to 150 °C; HT-ATES) could expand concurrent usage targeting domestic needs to meet the demand of industrial processes or district heating. Areas of former hydrocarbon production could provide the necessary reservoir conditions for the realization of HT-ATES. The Upper Rhine Graben (URG) represents such a system, additionally having one of the highest temperature gradients of Central Europe of up to 100 K km-1.

This Ph.D. thesis aims at different aspects of the characterization of depleted hydrocarbon reservoirs for HT-ATES. In an initial study, available geological and petrophysical data were compiled and transferred into a numerical model to estimate the general suitability of HT-ATES in the URG and quantify the storage capacity of depleted hydrocarbon reservoirs (Stricker et al., 2020). The main results outline that about 90 % of the investigated reservoirs in the URG may be transferrable into HT-ATES systems, pointing to extrapolated total storage capacities of the whole URG of up to 10 TWh per year, representing a considerable portion of the thermal energy demand of this area. Further investigations will tackle the influence of two-phase flow (oil/water) and the mechanical impact of HT-ATES on the subsurface.

Distribution of (former) hydrocarbon wells in the Northern Upper Rhine Graben
Distribution of (former) hydrocarbon wells in the Northern Upper Rhine Graben
Modelled heat propagation around the hot well of a high-temperature heat storage system
Modellierte Wärmeausbreitung um die heiße Bohrung eines Hochtemperatur-Wärmespeichers.