Monitoring Scheme for the Detection of Hydrogen Leakage from a Deep Underground Storage. Part 1: On-Site Validation of an Experimental Protocol via the Combined Injection of Helium and Tracers into an Aquifer

Abstract

Massive underground storage of hydrogen could be a way that excess energy is produced in the future, provided that the risks of leakage of this highly flammable gas are managed. The ROSTOCK-H research project plans to simulate a sudden hydrogen leak into an aquifer and to design suitable monitoring, by injecting dissolved hydrogen in the saturated zone of an experimental site. Prior to this, an injection test of tracers and helium-saturated water was carried out to validate the future protocol related to hydrogen. Helium exhibits a comparable physical behavior but is a non-flammable gas which is preferable for a protocol optimization test. The main questions covered the gas saturation conditions of the water, the injection protocol of 5 m3 of gas saturated water, and the monitoring protocol. Due to the low solubility of both helium and hydrogen, it appears that plume dilution will be more important further than 20 m downstream of the injection well and that monitoring must be done close to the well. In the piezometer located 5 m downstream the injection well, the plume peak is intended to arrive about 1 h after injection with a concentration around 1.5 mg·L−1. Taking these results into account should make it possible to complete the next injection of hydrogen.

Monitoring Scheme for the Detection of Hydrogen Leakage from a Deep Underground Storage. Part 2: Physico-Chemical Impacts of Hydrogen Injection into a Shallow Chalky Aquifer

“…The impacts expected from a hydrogen leak in the underground environment are linked to the fact that it is a strongly reducing gas acting as a potential electron donor for numerous chemical species: metal sulfides, sulfates, carbonates, oxides (in particular of iron and magnesium), nitrates, ferrous ions, and gases (CO and CO 2 ) [7,8]. The resulting oxidation-reduction reactions can thus modify the chemical composition of water or the mineral composition of aquifer rocks [6]. However, most reactions that occur in the presence of hydrogen require-at least in the laboratory-high temperatures or pressures or the presence of catalysts (Table 1).…”

“…The consequences of a possible reduction in ion oxides such as NO 3 − can be significant because the standards for drinking water destined for human consumption stipulate 50 mg•L −1 for nitrates against 0.50 mg•L −1 for nitrites and 0.10 mg•L −1 for ammonium [24]. Thus, allowing for a mean concentration of nitrates of 33 mg•L −1 in the groundwater at the Catenoy experimental site, during the baseline [6], it would be sufficient to reduce only 2% of these ions into nitrites or 0.5% into ammonium to render the water unfit for human consumption in the first case or to trigger health warning measures (information, reinforced surveillance, treatment) in the second case.…”

“…Under the proposed experimental conditions, and due to the brevity of the injection, we did not expect any biochemical reactions that require long time scales to occur. Moreover, additional studies [6][7][8][9] pointed out that a sudden injection of hydrogen saturated water into an aquifer increases the dissolved hydrogen content of the water, and consequently reduces its oxidation-reduction potential, as well as the concentration of other dissolved gases (O 2 , CO 2 , N 2 , etc.). The injection of hydrogen was preceded by the injection of tracers (helium and hydrogeological tracers) in order to facilitate the monitoring of its progress underground.…”

“…This experiment was conducted at the Catenoy (Oise) experimental site in a surface aquifer representative of the carbonated hydrogeological context of the Paris Basin. It followed characterization work for this site, previously carried out during CO 2 leak simulations [10,11], as well as the realization of a baseline and a preliminary injection of helium [6].…”

Baseline Subsoil CO2 Gas Measurements and Micrometeorological Monitoring: Above Canopy Turbulence Effects on the Subsoil CO2 Dynamics in Temperate Deciduous Forest

“…Nonetheless, most of the studies carried on forest soil mainly focused at a depth of 0 to 1 m, where the soil CO 2 production occurs from an autotrophic component and heterotrophic components. The deep soil zone, marginally influenced by the atmospheric conditions, is a perfect location to create a CO 2 baseline for a wide range of geological storage applications, including but not limited to the CCS (carbon capture and storage) [6,34,35] and hydrogen storage monitoring programs [36]. However, there was substantial evidence from previous works that soil gas transport in the unsaturated zone was predominantly affected by the water table variations.…”