Souring Systems: Petroleum Microbiology
In this work, EEA scientists are using biology to develop ways of accessing oil and coal that expend less energy and release fewer greenhouse gases. For instance, biological processes might be used to coax oil from below ground or to alter the semi-porous rock that holds oil, making it flow to the surface. Making it easier to access hard-to-reach domestic oil reserves will help ensure that oil remains part of a diverse mix of energy choices.
Microbially Enhanced Hydrocarbon Recovery (MEHR) involves a broad diversity of metabolic processes that act either individually or cooperatively to improve hydrocarbon production and energy yields, and reduce the environmental footprint. An in-depth understanding of these metabolic processes and the controlling parameters comes from focused interdisciplinary research into model organisms or communities known to perform the relevant functions.
This project has three components:
- Microbial Ecology
- Modeling and Geophysical Monitoring
- Rates. Mechanisms, and Systems Biology
1. Microbial Ecology
Using techniques pioneered at LBNL, the scientists on this project have merged the fields of molecular biology and ecology, combined with systems biogeochemistry, to focus on critical controllers of microbial function in reservoir and tar sand environments. Researchers are studying the ecosystem’s genetic capacity and the biological or abiotic controls which determine the expression of that capacity.
Hydrocarbon reservoirs are major sites of methane production and carbon turnover, processes with significant impacts on energy resources and global biogeochemical cycles. In the past year (2014), we applied a cultivation-independent genomic approach to define microbial community membership and to predict roles for specific organisms in biogeochemical transformations in North Slope, Alaska oil fields. Samples were collected from four reservoirs between 1,128 m (~24-27 °C) and 2,743 m (~80 – 83 °C) below the surface. Sample complexity decreased with increasing temperature. We clearly demonstrated the existence of the dissimilatory sulfate reduction pathway regardless of the souring status and conclude factors other than genetic potential appear to control the souring process. This study provided valuable insights into functional roles the individual genomes, especially the candidate phyla, played in these petroleum reservoirs.
The program will ensure successful translation of laboratory-derived MEHR strategies into practice at the reservoir scale. It will do this by developing approaches to remotely monitor MEHR-induced biogeochemical transformations at the reservoir scale and developing reservoir-scale reactive transport simulators that can be used to optimize MEHR treatment design and implementation. The program will advance process understanding from pore to reservoir scales, which is critical for ensuring the successful, production-scale implementation of the MEHR treatments.
Significant progress was made in 2014 in development and experimental validation of our approach to modeling sulfate reduction and the impact of amendments across scales from the laboratory to the field. Advances in our modeling effort included development of reaction networks to describe sulfate reduction and inhibition for TMVOC-REACT, an existing multiphase bioreactive transport simulator. The same simulator was also augmented to describe sulfur isotope fractionation and extended to include temperature dependent growth kinetics appropriate for sulfate reducing bacteria. Code advances were validated against both internal and literature experimental datasets as well as benchmarked against existing simulators. A suite of realistic test cases was developed to explore the impact of fractures and flow heterogeneity on perchlorate amendment.
3. Rates, Mechanisms, and Systems Biology
This work involves a variety of metabolomic, transcriptomic, proteomic, genomic, and biogeochemical approaches. A focused aspect of these studies is the development of model organisms or microbial assemblies from members of relevant petroleum reservoir microbial populations that have been enhanced in specific functional processes. Overall, these studies provide a basic understanding of the microbiology, biochemistry, molecular biology, and biogeochemistry involved in MEHR-relevant metabolic processes and will potentially result in the development of novel strategies to control biosouring, enhance hydrocarbon recovery, and reduce the environmental footprint of oil reservoir processes.
We continued our investigations of the biogenesis of solid-phase minerals to enhance concretion of unconsolidated matrices and offset worm-holing and bypass events during oil recovery. We investigated the underlying biochemical and genetic mechanisms of phosphorous metabolism and were able to enhance the growth rate of phosphorous metabolizing organisms almost 10-fold. We continued our investigations into the potential for microbial (per)chlorate respiration to control biogenic sulfide production and oil reservoir souring.
Hydrogen sulfide (H2S) biogenesis by sulfate-reducing microorganisms (SRM) is a potentially deleterious metabolism and is the primary cause of industrial gas inhalation deaths in the U.S. In oil recovery, microbially produced H2S in reservoir gases and fluids has an associated annual cost estimated at $90 billion. Previous studies demonstrated that amendment of active sulfidogenic-packed columns with (per)chlorate resulted in a rapid decrease in H2S production. Over the last year, we demonstrated that the mechanism of (per)chlorate inhibition of SRM is multifaceted, involving specific interference with SRM biochemistry, thermodynamic preference over sulfate respiration, and sulfide removal through oxidation coupled to (per)chlorate respiration. Our studies involved pure culture models, but were confirmed in complex undefined sulfidogenic communities metabolizing multifarious substrates. We continued our investigations of microbial (per)chlorate respiration and identified and characterized several new isolates at both the phenotypic and genome level. We further characterized the genetic basis of (per)chlorate respiration and functionally described new regulatory and stress response genes involved. We investigated the biochemical basis of (per)chlorate respiration and have isolated several of the proteins involved in this unique pathway. We are characterizing these enzymes with the goal of identifying their unique functionality.