Deep biosphere in the Main Dolomite (Upper Permian) hydrocarbon reservoir

Abstract

This study focuses on evaluating microbial activity in Main Dolomite reservoir rocks (Zechstein, Wuchiapingian–Permian) at 100°C. Core samples from two wells, one potentially microbiologically active (C-1 well, 100°C) and the other considered inactive due to high temperature (L-1 well, 155.5°C), were analysed. The core from L-1, treated similarly to C-1, was used to control for contamination. Microbial experiments and molecular analyses were performed on both core samples to ensure accurate results unaffected by laboratory processing contamination. Microbial incubation tests were successfully employed to demonstrate microbial hydrocarbon degradation and methane formation from 13C-labelled acetate. A new method for staining microorganisms from rock samples was introduced to estimate biomass. The results indicated that microorganisms from the C-1 well exhibited both hydrocarbon biodegradation and acetoclastic methanogenesis during a 3-month incubation at 100°C. Fluorescence-stained and countable microorganisms were only observed in the C-1 samples, while no biodegradation or methanogenesis occurred in reference samples from L-1 well. The study provides valuable insights into microbial activities in extreme conditions, emphasizing the importance of proper controls and techniques to ensure accurate interpretation of results.