Herbert Volk

Biomarkers, brines, and oil in the Mesoproterozoic, Roper Superbasin, Australia

Gas chromatography–mass spectrometry of oil inclusions from the ca. 1430 Ma marine Roper Group in the Roper Superbasin, Australia, provides a new source of information about the early biosphere and Proterozoic petroleum systems. Oil most likely derived from an overlying shale was trapped at ∼60 °C as abundant oil inclusions within transgranular microfractures in detrital quartz during Mesoproterozoic basin inversion. The oil is very mature and has a wide range of biomarkers, derived mainly from cyanobacteria, but lacks eukaryote biomarkers. Unlike associated solid bitumens, the inclusion oil is nonbiodegraded. Evidently, the inclusions remained closed systems, sheltered from postentrapment alteration and contamination. Because fluid inclusions have preserved biomarkers for >1000 m.y., they constrain the diversity of primordial ecosystems, whereas other forms of early Precambrian organic matter are usually absent or metamorphosed.

Microbial biodiversity in a Malaysian oil field and a systematic comparison with oil reservoirs worldwide

Microbial diversity within formation water and oil from two compartments in Bokor oil reservoir from a Malaysian petroleum oil field was examined. A total of 1,056 16S rRNA gene clones were screened from each location by amplified ribosomal DNA restriction analysis. All samples were dominated by clones affiliated with Marinobacter, some novel Deferribacteraceae genera and various clones allied to the Methanococci. In addition, either Marinobacterium- or Pseudomonas-like operational taxonomic units were detected from either compartment. A systematic comparison with the existing pertinent studies was undertaken by analysing the microbial amplicons detected and the PCR primers used. The analyses demonstrated that bacterial communities were site specific, while Archaea co-occurred more frequently. Amplicons related to Marinobacter, Marinobacterium and Pseudomonas were detected in a number of the studies examined, suggesting they may be ubiquitous members in oil reservoirs. Further analysis of primers used in those studies suggested that most primer pairs had fairly broad but low matches across the bacterial and archaeal domains, while a minority had selective matches to certain taxa or low matches to all the microbial taxa tested. Thus, it indicated that primers may play an important role in determining which taxa would be detected.

Oil migration in the Middle Proterozoic Roper Superbasin,Australia: evidence from oil inclusions and their geochemistries

Abstract The geochemistry and petrography of oil inclusions in the ca. 1.4 Ga dessie Creek Sandstone in the Roper Superbasin,Australia, provide insights into poorly understood Middle Proterozoic petroleum systems. Oil inclusions were trapped after the intrusion of ca. 1.3 Ga dolerite sills during basin reactivation and peak maturation. Biomarkers reflect the predominance of prokaryotes in the Mid-Proterozoic biosphere and the most likely source rock is the directly overlying Velkerri Formation.

Complete Genome Sequence of a Nonculturable Methanococcus maripaludis Strain Extracted in a Metagenomic Survey of Petroleum Reservoir Fluids

Extraction of genome sequences from metagenomic data is crucial for reconstructing the metabolism of microbial communities that cannot be mimicked in the laboratory. A complete Methanococcus maripaludis genome was generated from metagenomic data derived from a thermophilic subsurface oil reservoir. M. maripaludis is a hydrogenotrophic methanogenic species that is common in mesophilic saline environments. Comparison of the genome from the thermophilic, subsurface environment with the genome of the type species will provide insight into the adaptation of a methanogenic genome to an oil reservoir environment.

Effect of Nutrient Addition on an Oil Reservoir Microbial Population:Implications for Enhanced Oil Recovery

The increasing demand for petroleum is driving the development of technologies including MEOR (Microbial enhanced oil recovery)—the use of microbes within a reservoir to enhance oil recovery. In this study we initially determined that availablilty of suitable carbon sources was limiting microbial growth and metabolism of an oil reservoir microbial community. Subsequently we identified metabolic processes that are initiated after addition of nutrients that addressed this limitation. Four distinct metabolic pathways were stimulated: (i) fermentation of the added nutrient; (ii) methanogenises of the metabolites of fermentation; (iii) accumulation and decay of biomass; and (iv) oxidation/co-metabolism of petroleum. Biomass, when introduced as a nutrient, led to similar increases in live cell numbers in oil reservoir microcosms as addition of molasses. In addition to acting as a nutrient, disrupted microbial biomass led to formation of oil-water emulsions and significant lowering of the interfacial tension. These results suggest biomass manipulation can play an important role in MEOR.

Impact of Rock Heterogeneity on Interactions of Microbial-Enhanced Oil Recovery Processes

Residual oil saturation reduction and microbial plugging are two crucial factors in microbial-enhanced oil recovery (MEOR) processes. In our previous study, the residual saturation was defined as a nonlinear function of the trapping number, and an explicit relation between the residual oil saturation and the trapping number was incorporated into a fully coupled biological (B) and hydrological (H) finite element model. In this study, the BH model is extended to consider the impact of rock heterogeneity on microbial-enhanced oil recovery phenomena. Numerical simulations of core flooding experiments are performed to demonstrate the influences of different parameters controlling the onset of oil mobilization. X-ray CT core scans are used to construct numerical porosity-permeability distributions for input to the simulations. Results show clear fine-scale fingering processing, and that trapping phenomena have significant effects on residual oil saturation and oil recovery in heterogeneous porous media. Water contents and bacterial distributions for heterogeneous porous media are compared with those for homogenous porous media. The evolution of the trapping number distribution is directly simulated and visualized. It is shown that the oil recovery efficiency of EOR/MEOR will be lower in heterogeneous media than in homogeneous media, largely due to the difficulty in supplying surfactant to unswept low-permeability zones. However, MEOR also provides efficient plugging along high-permeability zones which acts to increase sweep efficiency in heterogeneous media. Thus, MEOR may potentially be more suited for highly heterogeneous media than conventional EOR.

The suitability of the fuel used for motor-sledging on Scott's last expedition, 1910-1913

The fuel used for motor-sledging during Scotts 1910-1913 expedition has been reanalysed to assess its suitability for that task in Antarctica. A research octane number of 65 and volatility were low compared with modern fuels but probably suitable when considering the design of the flathead engine. The findings are consistent with view that engine design was the primary cause of the mechanical failings.

Functional and genetic characterization of hydrocarbon biodegrader and exopolymer-producing clones from a petroleum reservoir metagenomic library

ABSTRACT Microbial degradation of petroleum is a worldwide issue, which causes physico-chemical changes in its compounds, diminishing its commercial value. Biosurfactants are chemically diverse molecules that can be produced by several microorganisms and can enable microbial access to hydrocarbons. In order to investigate both microbial activities, function-driven screening assays for biosurfactant production and hydrocarbon biodegradation were carried out from a metagenomic fosmid library. It was constructed from the total DNA extracted from aerobic and anaerobic enrichments from a Brazilian biodegraded petroleum sample. A sum of 10 clones were selected in order to evaluate their ability to produce exopolymers (EPS) with emulsifying activity, as well as to characterize the gene sequences, harbored by the fosmid clones, through 454 pyrosequencing. Functional analyses confirmed the ability of some clones to produce surfactant compounds. Regarding hydrocarbon as microbial carbon sources, n-alkane (in mixture or not) and naphthalene were preferentially consumed as substrates. Analysis of sequence data set revealed the presence of genes related to xenobiotics biodegradation and carbohydrate metabolism. These data were corroborated by the results of hydrocarbon biodegradation and biosurfactant production detected in the evaluated clones.

Correction to Determining the Extent of Biodegradation of Fuels Using the Diastereomers of Acyclic Isoprenoids

The retention time shown in Figure 1 is incorrect. In this case, the gas chromatograph was run using constant pressure conditions (25 psi) rather than with the constant flow conditions (1.2 mL/min) detailed in the methods section. As a result, the peaks eluted around 15 min later. Figure 2 shows the correct retention times for the constant flow method detailed in the methods section. Also, Figure S2 in the Supporting Information is correct and also shows the retention times when run with constant pressure conditions (25 psi), hence it has later eluting peaks as in Figure 1.