A Review of the Hydrochemistry of a Deep Sedimentary Aquifer and Its Consequences for Geothermal Operation: Klaipeda, Lithuania

Abstract

The Klaipeda Geothermal Demonstration Plant (KGDP), Lithuania, exploits a hypersaline sodium-chloride (salinity c. 90 g/L) groundwater from a 1100 m deep Devonian sandstone/siltstone reservoir. The hydrogen and oxygen stable isotope composition is relatively undepleted (δ18O=c. -4.5‰), while the δ34S is relatively “heavy” at +18.9‰. Hydrochemical and isotopic data support the existing hypothesis that the groundwater is dominated by a hypersaline brine derived from evapoconcentrated seawater, modified by water-rock interaction and admixed with smaller quantities of more recent glacial meltwater and/or interglacial recharge. The injectivity of the two injection boreholes has declined dramatically during the operational lifetime of the KGDP. Initially, precipitation of crystalline gypsum led to a program of rehabilitation and the introduction of sodium polyphosphonate dosing of the abstracted brine, which has prevented visible gypsum precipitation but has failed to halt the injectivity decline. While physical or bacteriological causes of clogging are plausible, evidence suggests that chemical causes cannot be excluded. Gypsum and barite precipitation could still occur in the formation, as could clogging with iron/manganese oxyhydroxides. One can also speculate that inhibitor dosing could cause clogging of pore throats with needles of calcium polyphosphonate precipitate.

Energy/Exergy Conversion Factors of Low-Enthalpy Geothermal Heat Plants

“…This assessment shows that the operation of the Klaipeda site would be exergetically reasonable if it were operating with the listed parameters. However, it is not, due to declining productivity caused by precipitation in spite of counter-measures, which is why the plant operation indefinitely ceased operation in March 2017 (Šliaupa et al n.d.;Brehme et al 2019).…”

“…Fluid chemistry, however, adds another potential limitation. Temperature reduction may trigger precipitation, which, at the high mass flow rates realized in geothermal sites, can produce a considerable mass of solids, that at best ends up in filters and at worst clogs pipes, heat exchangers or the pores of the reservoir rock (Mouchot et al 2018;DiPippo 2016;GTN 2010;Brehme et al 2019).…”

Energy/Exergy Conversion Factors of Low Enthalpy Geothermal Plants

“…Fluid chemistry, however, adds another limitation. Temperature reduction may trigger precipitation, which, at the high mass flow rates realized in geothermal sites, can produce a considerable mass of solids, that at best ends up in filters and at worst clogs pipes, heat exchangers or the pores of the reservoir rock [6][7][8][9] .…”

“…This assessment shows that the operation of the Klaipeda site would be exergetically reasonable if it were operating with the listed parameters. However, it is not, because productivity has declined due to precipitation in spite of counter-measures, which is why the plant operation indefinitely ceased operation in March 2017 9,36 .…”

The quality of geothermal reservoir of the Lower Jurassic aquifer in the Mogilno-Łódź Trough (Polish Lowlands)

“…The physicochemical properties of geothermal waters have a significant impact on the occurrence of clogging processes in geothermal systems. Corrosion and clogging of the water circulation system are one of the key problems associated with the exploitation of geothermal waters [7][8][9][10][11]. The impact of those reactions may affect in longterm operation of the geothermal systems [12].…”