The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Mostafa S Elshahed - One of the best experts on this subject based on the ideXlab platform.
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Bacterial Communities Associated with Production Facilities of Two Newly Drilled Thermogenic Natural Gas Wells in the Barnett Shale (Texas, USA)
Microbial Ecology, 2012Co-Authors: James P. Davis, Christopher G Struchtemeyer, Mostafa S ElshahedAbstract:We monitored the bacterial communities in the Gas–water separator and water storage tank of two newly drilled Natural Gas Wells in the Barnett Shale in north central Texas, using a 16S rRNA gene pyrosequencing approach over a period of 6 months. Overall, the communities were composed mainly of moderately halophilic and halotolerant members of the phyla Firmicutes and Proteobacteria (classes Βeta-, Gamma-, and Epsilonproteobacteria) in both Wells at all sampling times and locations. Many of the observed lineages were encountered in prior investigations of microbial communities from various fossil fluid formations and production facilities. In all of the samples, multiple H_2S-producing lineages were encountered; belonging to the sulfate- and sulfur-reducing class Deltaproteobacteria, order Clostridiales, and phylum Synergistetes , as well as the thiosulfate-reducing order Halanaerobiales. The bacterial communities from the separator and tank samples bore little resemblance to the bacterial communities in the drilling mud and hydraulic-fracture waters that were used to drill these Wells, suggesting the in situ development of the unique bacterial communities in such well components was in response to the prevalent geochemical conditions present. Conversely, comparison of the bacterial communities on temporal and spatial scales suggested the establishment of a core microbial community in each sampled location. The results provide the first overview of bacterial dynamics and colonization patterns in newly drilled, thermogenic Natural Gas Wells and highlights patterns of spatial and temporal variability observed in bacterial communities in Natural Gas production facilities.
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a critical assessment of the efficacy of biocides used during the hydraulic fracturing process in shale Natural Gas Wells
International Biodeterioration & Biodegradation, 2012Co-Authors: Christopher G Struchtemeyer, Michael D Morrison, Mostafa S ElshahedAbstract:We examined the efficacy of multiple biocides that are commonly used to control sulfate-reducing bacteria in fracturing fluids in shale Natural Gas formations. Seven biocides (tetrakis [hydroxymethyl] phosphonium sulfate, sodium hypochlorite, didecyldimethylammonium chloride, tri-n-butyl tetradecyl phosphonium chloride, glutaraldehyde, a glutaraldehyde and alkyldimethylbenzylammonium chloride blend, and a glutaraldehyde alkyldimethylethylbenzylammonium chloride blend) were examined. Minimum inhibitory concentrations (MIC) were determined using planktonic cells and biofilms of Desulfovibrio desulfuricans strain G20 and a sulfate-reducing enrichment culture that was obtained from a Barnett Shale frac pond. All biocides had higher MIC values for biofilms compared to planktonic cells from these two cultures. Higher concentrations of all biocides, except didecyldimethylammonium chloride, were required to kill planktonic cells of G20 that were exposed to humic acid. These results clearly indicate that biofilm formation by sulfate-reducing bacteria, as well as organic loading rates, negatively impact the efficacy of biocides. This work provides valuable information concerning the effects of biofilm formation and organic loading on biocide MIC values. These MIC data can be used as a guide for the control of microbial growth in future frac jobs, which should result in fewer incidences of sulfide production and corrosion in shale Natural Gas Wells.
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bacterial communities associated with hydraulic fracturing fluids in thermogenic Natural Gas Wells in north central texas usa
FEMS Microbiology Ecology, 2012Co-Authors: Christopher G Struchtemeyer, Mostafa S ElshahedAbstract:Hydraulic fracturing is used to increase the permeability of shale Gas formations and involves pumping large volumes of fluids into these formations. A portion of the frac fluid remains in the formation after the fracturing process is complete, which could potentially contribute to deleterious microbially induced processes in Natural Gas Wells. Here, we report on the geochemical and microbiological properties of frac and flowback waters from two newly drilled Natural Gas Wells in the Barnett Shale in North Central Texas. Most probable number studies showed that biocide treatments did not kill all the bacteria in the fracturing fluids. Pyrosequencing-based 16S rRNA diversity analyses indicated that the microbial communities in the flowback waters were less diverse and completely distinct from the communities in frac waters. These differences in frac and flowback water communities appeared to reflect changes in the geochemistry of fracturing fluids that occurred during the frac process. The flowback communities also appeared well adapted to survive biocide treatments and the anoxic conditions and high temperatures encountered in the Barnett Shale.
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influence of the drilling mud formulation process on the bacterial communities in thermogenic Natural Gas Wells of the barnett shale
Applied and Environmental Microbiology, 2011Co-Authors: Christopher G Struchtemeyer, James P. Davis, Mostafa S ElshahedAbstract:The Barnett Shale in north central Texas contains Natural Gas generated by high temperatures (120 to 150°C) during the Mississippian Period (300 to 350 million years ago). In spite of the thermogenic origin of this Gas, biogenic sulfide production and microbiologically induced corrosion have been observed at several Natural Gas Wells in this formation. It was hypothesized that microorganisms in drilling muds were responsible for these deleterious effects. Here we collected drilling water and drilling mud samples from seven Wells in the Barnett Shale during the drilling process. Using quantitative real-time PCR and microbial enumerations, we show that the addition of mud components to drilling water increased total bacterial numbers, as well as the numbers of culturable aerobic heterotrophs, acid producers, and sulfate reducers. The addition of sterile drilling muds to microcosms that contained drilling water stimulated sulfide production. Pyrosequencing-based phylogenetic surveys of the microbial communities in drilling waters and drilling muds showed a marked transition from typical freshwater communities to less diverse communities dominated by Firmicutes and Gammaproteobacteria. The community shifts observed reflected changes in temperature, pH, oxygen availability, and concentrations of sulfate, sulfonate, and carbon additives associated with the mud formulation process. Finally, several of the phylotypes observed in drilling muds belonged to lineages that were thought to be indigenous to marine and terrestrial fossil fuel formations. Our results suggest a possible alternative exogenous origin of such phylotypes via enrichment and introduction to oil and Natural Gas reservoirs during the drilling process.
Christopher G Struchtemeyer - One of the best experts on this subject based on the ideXlab platform.
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Bacterial Communities Associated with Production Facilities of Two Newly Drilled Thermogenic Natural Gas Wells in the Barnett Shale (Texas, USA)
Microbial Ecology, 2012Co-Authors: James P. Davis, Christopher G Struchtemeyer, Mostafa S ElshahedAbstract:We monitored the bacterial communities in the Gas–water separator and water storage tank of two newly drilled Natural Gas Wells in the Barnett Shale in north central Texas, using a 16S rRNA gene pyrosequencing approach over a period of 6 months. Overall, the communities were composed mainly of moderately halophilic and halotolerant members of the phyla Firmicutes and Proteobacteria (classes Βeta-, Gamma-, and Epsilonproteobacteria) in both Wells at all sampling times and locations. Many of the observed lineages were encountered in prior investigations of microbial communities from various fossil fluid formations and production facilities. In all of the samples, multiple H_2S-producing lineages were encountered; belonging to the sulfate- and sulfur-reducing class Deltaproteobacteria, order Clostridiales, and phylum Synergistetes , as well as the thiosulfate-reducing order Halanaerobiales. The bacterial communities from the separator and tank samples bore little resemblance to the bacterial communities in the drilling mud and hydraulic-fracture waters that were used to drill these Wells, suggesting the in situ development of the unique bacterial communities in such well components was in response to the prevalent geochemical conditions present. Conversely, comparison of the bacterial communities on temporal and spatial scales suggested the establishment of a core microbial community in each sampled location. The results provide the first overview of bacterial dynamics and colonization patterns in newly drilled, thermogenic Natural Gas Wells and highlights patterns of spatial and temporal variability observed in bacterial communities in Natural Gas production facilities.
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a critical assessment of the efficacy of biocides used during the hydraulic fracturing process in shale Natural Gas Wells
International Biodeterioration & Biodegradation, 2012Co-Authors: Christopher G Struchtemeyer, Michael D Morrison, Mostafa S ElshahedAbstract:We examined the efficacy of multiple biocides that are commonly used to control sulfate-reducing bacteria in fracturing fluids in shale Natural Gas formations. Seven biocides (tetrakis [hydroxymethyl] phosphonium sulfate, sodium hypochlorite, didecyldimethylammonium chloride, tri-n-butyl tetradecyl phosphonium chloride, glutaraldehyde, a glutaraldehyde and alkyldimethylbenzylammonium chloride blend, and a glutaraldehyde alkyldimethylethylbenzylammonium chloride blend) were examined. Minimum inhibitory concentrations (MIC) were determined using planktonic cells and biofilms of Desulfovibrio desulfuricans strain G20 and a sulfate-reducing enrichment culture that was obtained from a Barnett Shale frac pond. All biocides had higher MIC values for biofilms compared to planktonic cells from these two cultures. Higher concentrations of all biocides, except didecyldimethylammonium chloride, were required to kill planktonic cells of G20 that were exposed to humic acid. These results clearly indicate that biofilm formation by sulfate-reducing bacteria, as well as organic loading rates, negatively impact the efficacy of biocides. This work provides valuable information concerning the effects of biofilm formation and organic loading on biocide MIC values. These MIC data can be used as a guide for the control of microbial growth in future frac jobs, which should result in fewer incidences of sulfide production and corrosion in shale Natural Gas Wells.
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bacterial communities associated with hydraulic fracturing fluids in thermogenic Natural Gas Wells in north central texas usa
FEMS Microbiology Ecology, 2012Co-Authors: Christopher G Struchtemeyer, Mostafa S ElshahedAbstract:Hydraulic fracturing is used to increase the permeability of shale Gas formations and involves pumping large volumes of fluids into these formations. A portion of the frac fluid remains in the formation after the fracturing process is complete, which could potentially contribute to deleterious microbially induced processes in Natural Gas Wells. Here, we report on the geochemical and microbiological properties of frac and flowback waters from two newly drilled Natural Gas Wells in the Barnett Shale in North Central Texas. Most probable number studies showed that biocide treatments did not kill all the bacteria in the fracturing fluids. Pyrosequencing-based 16S rRNA diversity analyses indicated that the microbial communities in the flowback waters were less diverse and completely distinct from the communities in frac waters. These differences in frac and flowback water communities appeared to reflect changes in the geochemistry of fracturing fluids that occurred during the frac process. The flowback communities also appeared well adapted to survive biocide treatments and the anoxic conditions and high temperatures encountered in the Barnett Shale.
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influence of the drilling mud formulation process on the bacterial communities in thermogenic Natural Gas Wells of the barnett shale
Applied and Environmental Microbiology, 2011Co-Authors: Christopher G Struchtemeyer, James P. Davis, Mostafa S ElshahedAbstract:The Barnett Shale in north central Texas contains Natural Gas generated by high temperatures (120 to 150°C) during the Mississippian Period (300 to 350 million years ago). In spite of the thermogenic origin of this Gas, biogenic sulfide production and microbiologically induced corrosion have been observed at several Natural Gas Wells in this formation. It was hypothesized that microorganisms in drilling muds were responsible for these deleterious effects. Here we collected drilling water and drilling mud samples from seven Wells in the Barnett Shale during the drilling process. Using quantitative real-time PCR and microbial enumerations, we show that the addition of mud components to drilling water increased total bacterial numbers, as well as the numbers of culturable aerobic heterotrophs, acid producers, and sulfate reducers. The addition of sterile drilling muds to microcosms that contained drilling water stimulated sulfide production. Pyrosequencing-based phylogenetic surveys of the microbial communities in drilling waters and drilling muds showed a marked transition from typical freshwater communities to less diverse communities dominated by Firmicutes and Gammaproteobacteria. The community shifts observed reflected changes in temperature, pH, oxygen availability, and concentrations of sulfate, sulfonate, and carbon additives associated with the mud formulation process. Finally, several of the phylotypes observed in drilling muds belonged to lineages that were thought to be indigenous to marine and terrestrial fossil fuel formations. Our results suggest a possible alternative exogenous origin of such phylotypes via enrichment and introduction to oil and Natural Gas reservoirs during the drilling process.
Ian J Duncan - One of the best experts on this subject based on the ideXlab platform.
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the bubble slug flow model for methane leakage from Natural Gas Wells as an analogue for shallow co2 migration
Energy Procedia, 2013Co-Authors: Ian J DuncanAbstract:Abstract Previous studies of CO2 leakage from Wells have assumed that either CO2 leaks into aquifers in the form of a radial lateral buoyant lateral plume of Gaseous CO2 or as a lateral radial plume of CO2 dissolved water. These assumptions are not based on any actual observations of the nature of Gas leakage from well bores. No direct information appears to exist on CO2 leakage from actual CO2 Wells so to understand better this phenomenon. In fact the seminal papers on this topic may have chosen these models because of ease of mathematical manipu lation. A wide range of information on the nature of leakage of methane from Natural Gas Wells has been compiled. Analysis of this evidence suggests that methane neither forms buoyant radial plumes of Gas, nor radial plumes of dissolved methane. Rather methane appears to be transported dominantly vertically by a combination of bubble and slug flow. Bubble flow occurs by bubbles of methane (or CO2) Gas buoyantly rising up fractures. Slug flow is initiated when multiple bubbles amalgamate in a fracture to form a film that moves as a single mass. Slugs have very low surface area and therefor minimize the dissolution of the Gas phase. Both bubbles and slugs in fractures move in an essentially vertical direction. The evidence for bubble and slug flow of methane comes from a variety of observational sources including: 1) measurement of methane concentrations radially away from a leaking well over a period of years; 2) evidence of Gas scavenging (a phenomenon that cannot occur if the Gas is in the dissolved phase); and 3) observations of concentrated bubbles emerging immediately around a Gas Wells following a sub -surface blowout while measurements of dissolved methane in surrounding water Wells demonstrated minimal methane concentrations.Methane Gas has also be directly imaged by down-the-hole cameras, emanating from fractures in the side of a water well as a string of bubbles. In this case again little if any methane dissolution into the aquifer had occurred. As a result damage to vegetation around leaking Natural Gas Wells is typically found to be a radial zone around the well head less than a meter in diameter. An assumption of rapid CO2 dissolution into aquifers assumes that there is intimate contact between CO2 and water or brine. If CO2, like methane is dominantly transported by a combination of bubble and slug flow then the surface area of CO2 exposed to the water phase will be relatively minimal and little dissolution will occur. If CO2 Gas leaking from a well into an aquifer, behaves in a similar way to methane many of the negative environmental consequences (such as metal contamination resulting from dissolved CO2 lowering the aquifers pH), will not occur. This analogue, if applicable, has significant implications for how Wells should be monitored for leakage. Current monitoring conceptualizations based on monitoring Wells are probably not the best approach.
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The Bubble/Slug Flow Model for Methane Leakage from Natural Gas Wells as an Analogue for Shallow CO2 Migration
Energy Procedia, 2013Co-Authors: Ian J DuncanAbstract:Abstract Previous studies of CO2 leakage from Wells have assumed that either CO2 leaks into aquifers in the form of a radial lateral buoyant lateral plume of Gaseous CO2 or as a lateral radial plume of CO2 dissolved water. These assumptions are not based on any actual observations of the nature of Gas leakage from well bores. No direct information appears to exist on CO2 leakage from actual CO2 Wells so to understand better this phenomenon. In fact the seminal papers on this topic may have chosen these models because of ease of mathematical manipu lation. A wide range of information on the nature of leakage of methane from Natural Gas Wells has been compiled. Analysis of this evidence suggests that methane neither forms buoyant radial plumes of Gas, nor radial plumes of dissolved methane. Rather methane appears to be transported dominantly vertically by a combination of bubble and slug flow. Bubble flow occurs by bubbles of methane (or CO2) Gas buoyantly rising up fractures. Slug flow is initiated when multiple bubbles amalgamate in a fracture to form a film that moves as a single mass. Slugs have very low surface area and therefor minimize the dissolution of the Gas phase. Both bubbles and slugs in fractures move in an essentially vertical direction. The evidence for bubble and slug flow of methane comes from a variety of observational sources including: 1) measurement of methane concentrations radially away from a leaking well over a period of years; 2) evidence of Gas scavenging (a phenomenon that cannot occur if the Gas is in the dissolved phase); and 3) observations of concentrated bubbles emerging immediately around a Gas Wells following a sub -surface blowout while measurements of dissolved methane in surrounding water Wells demonstrated minimal methane concentrations.Methane Gas has also be directly imaged by down-the-hole cameras, emanating from fractures in the side of a water well as a string of bubbles. In this case again little if any methane dissolution into the aquifer had occurred. As a result damage to vegetation around leaking Natural Gas Wells is typically found to be a radial zone around the well head less than a meter in diameter. An assumption of rapid CO2 dissolution into aquifers assumes that there is intimate contact between CO2 and water or brine. If CO2, like methane is dominantly transported by a combination of bubble and slug flow then the surface area of CO2 exposed to the water phase will be relatively minimal and little dissolution will occur. If CO2 Gas leaking from a well into an aquifer, behaves in a similar way to methane many of the negative environmental consequences (such as metal contamination resulting from dissolved CO2 lowering the aquifers pH), will not occur. This analogue, if applicable, has significant implications for how Wells should be monitored for leakage. Current monitoring conceptualizations based on monitoring Wells are probably not the best approach.
Nicola Koper - One of the best experts on this subject based on the ideXlab platform.
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Effects of shallow Natural Gas Wells, roads, and trails on clutch size.
2017Co-Authors: Jenny Yoo, Nicola KoperAbstract:Effects of shallow Natural Gas Wells, roads, and trials on clutch size of Savannah sparrow and chestnut-collared longspurs in southern Alberta, Canada, 2010–2012. Only significant results (p < 0.1) are shown.
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effects of livestock grazing and well construction on prairie vegetation structure surrounding shallow Natural Gas Wells
Environmental Management, 2014Co-Authors: Nicola Koper, K Molloy, Lionel Leston, J YooAbstract:Short and sparse vegetation near shallow Gas Wells has generally been attributed to residual effects from well construction, but other mechanisms might also explain these trends. We evaluated effects of distance to shallow Gas Wells on vegetation and bare ground in mixed-grass prairies in southern Alberta, Canada, from 2010 to 2011. We then tested three hypotheses to explain why we found shorter vegetation and more bare ground near Wells, using cattle fecal pat transects from 2012, and our vegetation quadrats. We evaluated whether empirical evidence suggested that observed patterns were driven by (1) higher abundance of crested wheatgrass (Agropyron cristatum) near Wells, (2) residual effects of well construction, or (3) attraction of livestock to Wells. Crested wheatgrass occurrence was higher near Wells, but this did not explain effects of Wells on vegetation structure. Correlations between distance to Wells and litter depth were the highest near newer Wells, providing support for the construction hypothesis. However, effects of distance to Wells on other vegetation metrics did not decline as time since well construction increased, suggesting that other mechanisms explained observed edge effects. Cattle abundance was substantially higher near Wells, and this effect corresponded with changes in habitat structure. Our results suggest that both residual effects of well construction and cattle behavior may explain effects of shallow Gas Wells on habitat structure in mixed-grass prairies, and thus, to be effective, mitigation strategies must address both mechanisms.
James P. Davis - One of the best experts on this subject based on the ideXlab platform.
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Bacterial Communities Associated with Production Facilities of Two Newly Drilled Thermogenic Natural Gas Wells in the Barnett Shale (Texas, USA)
Microbial Ecology, 2012Co-Authors: James P. Davis, Christopher G Struchtemeyer, Mostafa S ElshahedAbstract:We monitored the bacterial communities in the Gas–water separator and water storage tank of two newly drilled Natural Gas Wells in the Barnett Shale in north central Texas, using a 16S rRNA gene pyrosequencing approach over a period of 6 months. Overall, the communities were composed mainly of moderately halophilic and halotolerant members of the phyla Firmicutes and Proteobacteria (classes Βeta-, Gamma-, and Epsilonproteobacteria) in both Wells at all sampling times and locations. Many of the observed lineages were encountered in prior investigations of microbial communities from various fossil fluid formations and production facilities. In all of the samples, multiple H_2S-producing lineages were encountered; belonging to the sulfate- and sulfur-reducing class Deltaproteobacteria, order Clostridiales, and phylum Synergistetes , as well as the thiosulfate-reducing order Halanaerobiales. The bacterial communities from the separator and tank samples bore little resemblance to the bacterial communities in the drilling mud and hydraulic-fracture waters that were used to drill these Wells, suggesting the in situ development of the unique bacterial communities in such well components was in response to the prevalent geochemical conditions present. Conversely, comparison of the bacterial communities on temporal and spatial scales suggested the establishment of a core microbial community in each sampled location. The results provide the first overview of bacterial dynamics and colonization patterns in newly drilled, thermogenic Natural Gas Wells and highlights patterns of spatial and temporal variability observed in bacterial communities in Natural Gas production facilities.
-
influence of the drilling mud formulation process on the bacterial communities in thermogenic Natural Gas Wells of the barnett shale
Applied and Environmental Microbiology, 2011Co-Authors: Christopher G Struchtemeyer, James P. Davis, Mostafa S ElshahedAbstract:The Barnett Shale in north central Texas contains Natural Gas generated by high temperatures (120 to 150°C) during the Mississippian Period (300 to 350 million years ago). In spite of the thermogenic origin of this Gas, biogenic sulfide production and microbiologically induced corrosion have been observed at several Natural Gas Wells in this formation. It was hypothesized that microorganisms in drilling muds were responsible for these deleterious effects. Here we collected drilling water and drilling mud samples from seven Wells in the Barnett Shale during the drilling process. Using quantitative real-time PCR and microbial enumerations, we show that the addition of mud components to drilling water increased total bacterial numbers, as well as the numbers of culturable aerobic heterotrophs, acid producers, and sulfate reducers. The addition of sterile drilling muds to microcosms that contained drilling water stimulated sulfide production. Pyrosequencing-based phylogenetic surveys of the microbial communities in drilling waters and drilling muds showed a marked transition from typical freshwater communities to less diverse communities dominated by Firmicutes and Gammaproteobacteria. The community shifts observed reflected changes in temperature, pH, oxygen availability, and concentrations of sulfate, sulfonate, and carbon additives associated with the mud formulation process. Finally, several of the phylotypes observed in drilling muds belonged to lineages that were thought to be indigenous to marine and terrestrial fossil fuel formations. Our results suggest a possible alternative exogenous origin of such phylotypes via enrichment and introduction to oil and Natural Gas reservoirs during the drilling process.
