Wells in the same basin have unique properties and
microbial communities
Wells at mesophilic temperatures and moderate depths [1500-3000 ft,
457-914 m] are promising sites for successful MEOR
applications29–31 within the Illinois basin. We
selected five such wells from this basin that were all approximately 27
˚C (80 ˚F) in order to hold the temperature constant between trials and
simplify cross-well comparisons (Table 1). The wells had depths of
1336-2258 ft (407-688 m) while the pH remained fairly neutral (pH 6 –
7). DNA was extracted from the produced water (effluent) of each well to
assess the native microbial community composition via 16S rRNA gene
profiling (Supplemental Figure 1 ). We found that each well had
a distinct microbial composition with various sulfur-reducing
(H2S-producing) and
MEOR-relevant9,19,31 archaea and bacteria. Common
bacteria phyla include Proteobacteria, Bacteroidota, Firmicutes,
Synergistota, Spirochaetota, Verrucomicrobiota, Desulfobacterota and
Campilobacterota, of which the latter three are prominent
sulfur-metabolizing bacteria.32–35 These populations
were distinct from others in the literature,36,37 a
finding that is not unexpected given that each community is driven by
different environmental conditions such as temperature, salinity, pH,
nutrient availability, and oil gravity among other
factors.19 However, there is no known correlation
between native microbial community and MEOR success. Therefore, we
pursued in vitro functional screening to evaluate candidate wells
for MEOR top-down microbiome engineering.
Table 1 Characteristics of candidate wells from the
Illinois basin