22 Sep 2023
 | 22 Sep 2023
Status: this preprint is currently under review for the journal BG.

Methods to characterize type, relevance, and interactions of organic matter and microorganisms in fluids along the flow path of a geothermal facility

Alessio Leins, Danaé Bregnard, Andrea Vieth-Hillebrand, Stefanie Poetz, Florian Eichinger, Guillaume Cailleau, Pilar Junier, and Simona Regenspurg

Abstract. Dissolved organic matter and microorganisms were analyzed along the flow path of a geothermal facility in Austria. Various analytical methods were used to characterize and differentiate between natural and synthetic organic matter, characterize the microbial community composition, and determine the implications of microorganisms in an operating a geothermal site. Dissolved organic carbon (DOC) concentrations were in the range of 8.4–10.3 mg C L−1 and typically decreased from the production to the injection side. Carbonate scalings are avoided in the facility by the injection of a chemical scaling inhibitor within the production well at 500 m depth. It was calculated that the inhibitor contributes approximately 1 mg C L−1 DOC to the produced fluids. Ion chromatography (IC), liquid chromatography – organic carbon detection (LC-OCD) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in negative electrospray ionization (ESI(−)) and positive atmospheric pressure photoionization (APPI(+)) mode were applied to the fluid samples to characterize the dissolved organic matter (DOM) composition and distinguish between the inhibitor and the natural DOM. Depending on the applied ionization mode, FT-ICR-MS results show that between 31 % and 65 % of the macromolecular formulas detected in the fluid samples seem to originate from the inhibitor. However, the DOM is mainly composed of low molecular weight acids (LMWA), especially acetate with up to 7.4 mg C L−1. The microbial community composition varied along the flowpath with dominant phyla being Firmicutes, Proteobacteria, and Thermotogae. Based on the microorganisms found in the sample, the metabolic pathways have been assessed. Acetate might be produced by microorganisms through various fermentation processes (e.g. from lysine, pyruvate and hexitol). Assessing the presence and interaction of organic compounds and microorganisms in geothermal fluids provides a broader understanding of processes within the geothermal facility. This understanding could be beneficial for the efficient use of a geothermal power plant.

Alessio Leins et al.

Status: open (until 13 Jan 2024)

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  • RC1: 'Comment on bg-2023-159', Anonymous Referee #1, 09 Nov 2023 reply

Alessio Leins et al.

Data sets

Dissolved organic compounds in geothermal fluids used for energy production–part II Alessio Leins, Andrea Vieth-Hillebrand, Kristin Günther, and Simona Regenspurg

Alessio Leins et al.


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Short summary
Organic matter and microbial fluid analyses are rarely taken into account in the geothermal industry and research. However, they can have a significant effect on the efficiency of geothermal power production. We discovered a high variety in organic compound composition in our samples and were able to differentiate it with regard to various sources (e.g. artificial and biogenic). Furthermore, the microbial diversity undergoes significant changes within the flow path of a geothermal power plant.