Thermal effects on microbial composition and microbiologically induced corrosion and mineral precipitation affecting operation of a geothermal plant in a deep saline aquifer

Abstract

The microbial diversity of a deep saline aquifer used for geothermal heat storage in the North German Basin was investigated. Genetic fingerprinting analyses revealed distinct microbial communities in fluids produced from the cold and warm side of the aquifer. Direct cell counting and quantification of 16S rRNA genes and dissimilatory sulfite reductase (dsrA) genes by real-time PCR proved different population sizes in fluids, showing higher abundance of bacteria and sulfate reducing bacteria (SRB) in cold fluids compared with warm fluids. The operation-dependent temperature increase at the warm well probably enhanced organic matter availability, favoring the growth of fermentative bacteria and SRB in the topside facility after the reduction of fluid temperature. In the cold well, SRB predominated and probably accounted for corrosion damage to the submersible well pump, and iron sulfide precipitates in the near wellbore area and topside facility filters. This corresponded to lower sulfate content in fluids produced from the cold well as well as higher content of hydrogen gas that was probably released from corrosion, and maybe favored growth of hydrogenotrophic SRB. This study reflects the high influence of microbial populations for geothermal plant operation, because microbiologically induced precipitative and corrosive processes adversely affect plant reliability.2

Drilling into an active mofette: pilot-hole study of the impact of CO<sub>2</sub>-rich mantle-derived fluids on the geo–bio interaction in the western Eger Rift (Czech Republic)

“…Microbial habitats extend down to great depths beneath the earth's surface. However, cell counts and detailed characterizations of the microbial community structure in the continental deep biosphere are rare and mostly related to investigations in oil reservoirs (Youssef et al, 2009), geothermal aquifers (Alawi et al, 2011;Lerm et al, 2013) or gold mines (Deflaun et al, 2007;Takai et al, 2001;Trimarco et al, 2006). A few continental drilling campaigns have focused on the deep biosphere (Fredrickson et al, 1997;Onstott et al, 1998;Zhang et al, 2005), though the state of knowledge reached is still in the early stages.…”

Comparison of the microbial community composition of pristine rock cores and technical influenced well fluids from the Ketzin pilot site for CO2 storage

“…Recent studies have revealed that saline aquifers are inhabited by elevated numbers of different groups of microorganisms (Goldscheider et al 2006;Basso et al 2009;Morozova et al 2010;Lerm et al 2013). The most important metabolic pathways in the deep biosphere are sulfate reduction, fermentation and in some cases, methanogenesis (Takai et al 2001;Kotelnikova 2002;Baker et al 2003;Basso et al 2009).…”

Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems

“…Moreover, geothermal systems can only be qualified as renewable if there is a global annual thermal equilibrium. These potential environmental effects must be (and will increasingly be) studied because they can have strong economic repercussions such as lowering the global life of the system with side effects such as aquifer freezing and scaling on heat exchangers and wells [6,26,27]. From an economical point of view, a better knowledge of the thermal affected zone (TAZ) [28,29] can prevent shallow geothermal systems competing with each other (thermal feedback or thermal recycling) [30,31] or better, to take benefit of multiple ATES systems with mutual energy storage zones to enhance the global systems efficiency [22].…”