Microbial Signatures in Oil Reservoirs: Biomarker Stability and Their Role in Subsurface Fluid Monitoring

Sustainable energy solutions such as carbon capture, utilization, and storage (CCUS), geothermal energy, and hydrogen storage are vital for achieving low-carbon energy goals. However, these technologies face significant challenges, including gas leakage and the need for reliable monitoring systems within subsurface geological formations. Indigenous microorganisms, naturally widespread in these formations, offer a novel approach for dynamic monitoring over time through DNA sequencing analysis. Yet, critical questions remain: Can ground-level samples accurately represent geological information? How stable is the microbial DNA under surface conditions and for how long? This study investigates the stability of microbial community structures from deep subsurface oil reservoir samples during degradation at room temperature over 120 h. Samples were analyzed at 24 h intervals using DNA extraction, concentration measurements, and sequencing. Microbial diversity was assessed via α and β diversity indexes, while Venn analysis compared community structures to identify formation-specific genera. Findings reveal that microbial profiles from subsurface samples remain largely reflective of their original environments despite surface degradation. This highlights the feasibility of using subsurface microbial biosensing for dynamic environmental monitoring. By addressing the stability of microbial data, this research enhances the potential of DNA-based tools to support CCUS, geothermal energy, and hydrogen storage. It underscores the role of microbial biosensing in advancing sustainable energy practices, offering a robust framework for tackling challenges in subsurface monitoring, while contributing to the transition toward a low-carbon future.