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The Deepwater Horizon (DWH) blowout, in the Gulf of Mexico, heavily contaminated miles of sandy beaches. Previous experience of petroleum contamination has shown that oil residues can persist in the sediments for decades. Biodegradation is the major mechanism of remediation regarding petroleum hydrocarbons. There is an urgent need to evaluate the competent indigenous microbial biomass in contaminated sediments if the risks posed by toxic oil residues, for the coastal ecosystem, are to be minimized. We report a field investigation during December 2010 and January 2011 regarding measurement of microbial activity in a sandy beach at the Bon Secour National Wildlife Refuge in Alabama. One transect of wells for sampling was installed in the beach; starting with multiport one, being most landward and thought to be least exposed to oil residue and ending with multiport four being the most seaward and exposed to the open waters of the Gulf of Mexico. Sediment samples were collected from different depths purposely chosen from above, inside, and below the oil layers for microbial analysis. Dissolved oxygen (DO) measurements were obtained and temperature was recorded while collecting the oxygen measurements. Pore water samples were collected for nutrient content and were monitored using the multiport sampling wells. Moisture content was analyzed from the sediments extracted at various depths at each well. pH and salinity were also analyzed for their contributing affect on the microbial community. Grain size distribution analyses were conducted on samples collected at all wells and at multiple depths to characterize the field study location. Results show that the bacterial biomass, as measured by Adenosine-5-triphosphate (ATP) and numbers of alkane and polycyclic aromatic hydrocarbon (PAH) degraders determined by Most Probable Number (MPN), are consistently higher in the sediment layers where oil had been detected. A very good correlation was observed among the relative abundance of bacteria in the different samples using MPN and ATP measurements. As expected, ATP based estimates of the microbial populations were two orders of magnitude higher than the alkane and PAH numbers determined by MPN, which reflect the non-cultivability of most environmental bacteria. The lower concentrations of PAH degraders than alkane degraders that were observed in this study are consistent with other studies, even though both populations are lower than in studies involving fresh oil trapped in beach or wetland sediments. PAHs (aromatics) are notoriously more resistant to biodegradation than alkanes, therefore allowing a lower number of biomass to grow using them. The overall smaller size of the bacterial numbers could be explained by the naturally occurring low-organic content of beach sand. On the other hand, this may be due to the highly weathered nature of the oil or it could reflect some other limitation. / Civil Engineering

Stimulating in situ microbial communities in oil reservoirs to produce natural gas is a potentially viable strategy for recovering additional fossil fuel resources following traditional recovery operations. Little is known about what geochemical parameters drive microbial population dynamics in biodegraded, methanogenic oil reservoirs. We investigated if microbial community structure was significantly impacted by the extent of crude oil biodegradation, extent of biogenic methane production, and formation water chemistry. Twenty-two oil production wells from north central Louisiana, USA, were sampled for analysis of microbial community structure and fluid geochemistry. Archaea were the dominant microbial community in the majority of the wells sampled. Methanogens, including hydrogenotrophic and methylotrophic organisms, were numerically dominant in every well, accounting for, on average, over 98% of the total Archaea present. The dominant Bacteria groups were Pseudomonas, Acinetobacter, Enterobacteriaceae, and Clostridiales, which have also been identified in other microbially-altered oil reservoirs. Comparing microbial community structure to fluid (gas, water, and oil) geochemistry revealed that the relative extent of biodegradation, salinity, and spatial location were the major drivers of microbial diversity. Archaeal relative abundance was independent of the extent of methanogenesis, but closely correlated to the extent of crude oil biodegradation; therefore, microbial community structure is likely not a good sole predictor of methanogenic activity, but may predict the extent of crude oil biodegradation. However, when the shallow, highly biodegraded, low salinity wells were excluded from the statistical analysis, no environmental parameters could explain the differences in microbial community structure. This suggests that the microbial community structure of the 5 shallow, up-dip wells was different than the 17 deeper, down-dip wells. Also, the 17 down-dip wells had statistically similar microbial communities despite significant changes in environmental parameters between oil fields. Together, this implies that no single microbial population is a reliable indicator of a reservoir's ability to degrade crude oil to methane, and that geochemistry may be a more important indicator for selecting a reservoir suitable for microbial enhancement of natural gas generation.

Adequate wastewater management is a crucial element to achieve water sustainability in the petroleum refining sector, as their operations produce vast quantities of wastewater with potentially harmful contaminants. Treatment technologies are therefore pivotal for stopping these chemicals from entering the environment and protecting receiving environments. However, refining effluents are still linked to serious pollution problems, partly because little progress has been made in determining the causative agents of the observed biological effects, resulting in non-targeted treatment. Here it is shown that naphthenic acids, which have been reported as toxic and recalcitrant, are important components of refining wastewater resulting from the processing of heavy crude oil and that they have a significant contribution to the toxic effects exerted by these effluents. Furthermore, it was found that their chemical stability makes them highly resistant to remediation using Pseudomonas putida and H2O2/Fe-TAML (TetraAmido Macrocyclic Ligands) systems under laboratory conditions, and only sequential aliquots of Fe-TAML catalysts and H2O2 showed to partially degrade naphthenic acids (50 mg/L) within 72 hours. Results suggest that a combinatorial approach of Fe-TAML/H2O2 followed by biodegradation might improve current treatment options, but further optimisation is required for the biological treatment. These results can serve as a starting point for better environmental regulations relevant to oil refining wastewater resulting from heavy crude oil, as naphthenic acids are not currently considered in the effluent guidelines for the refining sector. Furthermore, the degradation of naphthenic acids under mild conditions using Fe-TAML/H2O2 systems indicates that these catalysts hold promise for the remediation of refining wastewater in real-life scenarios.

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This study provides independent analysis of Residual Oil Zones (ROZs) in the Permian Basin from a regional perspective, focusing on the formation mechanism and present ROZ locations. Results demonstrate widespread potential for ROZs, defined here as thick volumes of reservoir rock containing near-residual saturations of predominantly immobile oil formed by natural imbibition and displacement of oil by dynamic buoyant or hydrodynamic forces. Previous work suggests hydrodynamic forces generated by regional tectonic uplift drove widespread oil remobilization and ROZ creation. To test the hypothesis, uplift and tilting are quantified and the resulting peak regional potentiometric gradient used as a physical constraint to compute and compare predicted ROZ thicknesses from hydrodynamics for several ROZ-bearing San Andres fields with known ROZ thicknesses. Late-Albian Edwards Group geologic contacts, which are interpreted to have been deposited near sea level prior to uplift, are used as a regional datum. Approximate elevations determined for the present datum show ~1800 m of differential uplift since Edwards deposition, with an average regional slope of ~0.128˚. This post-Edwards tilting increased the pre-existing regional structural gradient of the San Andres Formation to ~0.289˚. Using the calculated post-Edwards gradient results in to prediction of ROZ thicknesses from hydrodynamics that is consistent with measured ROZ thicknesses at several fields. When compared with countervailing buoyancy forces, hydrodynamics is calculated to be the more dominant driving force of oil movement for reservoirs with structural dips less than 1.5˚, which is the common dip for San Andres Formation platform deposits where ROZs have been identified. To predict the location of ROZs, ROZ-related oil field properties were identified and analyzed for over 2,800 Permian Basin reservoirs. A strong basin-wide correlation between API and crude sulfur content is consistent with the expected outcome of oil degradation driven by oil-water interaction, and supports the use of API and sulfur content as proxies for ROZ potential in the Permian Basin. Spatial analysis of sulfur data shows that the highest probability for ROZ existence exists in Leonardian through Guadalupian-age reservoirs, distributed primarily in shelf and platform areas of Permian structures. Combined, these results support the widespread potential for ROZs across the Permian Basin generated primarily by regional scale tilting and resultant hydrodynamic forces. / text