A review of the hydrochemistry of a deep sedimentary aquifer and its consequences for geothermal operation: Klaipeda, Lithuania

Maren Brehme, Kerstin Nowak, David Banks, Sigitas Petrauskas, Robertas Valickas, Klaus Bauer, Neil Burnside, Adrian Boyce

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
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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.

Original languageEnglish
Article number4363592
Number of pages21
JournalGeofluids
Volume2019
DOIs
Publication statusPublished - 9 Apr 2019

Keywords

  • Lithuania
  • sidimentary aquifer
  • groundwater salinity

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