Different from the Qaidam basin with about 320 billion m
microbial gas, only limited microbial gases were found from the Junggar basin with similarly abundant type III kerogen. To determine whether ...microbial gases have not yet identified, natural gas samples from the Carboniferous to Cretaceous in the Junggar basin have been analyzed for chemical and stable isotope compositions. The results reveal some of the gases from the Mahu sag, Zhongguai, Luliang and Wu-Xia areas in the basin may have mixed with microbial gas leading to straight ethane to butane trends with a "dogleg" light methane in the Chung's plot. Primary microbial gas from degradation of immature sedimentary organic matter is found to occur in the Mahu sag and secondary microbial gas from biodegradation of oils and propane occurred in the Zhongguai, Luliang and Beisantai areas where the associated oils were biodegraded to produce calcites with δ
C values from + 22.10‰ to + 22.16‰ or propane was biodegraded leading to its
C enrichment. Microbial CH
in the Mahu sag is most likely to have migrated up from the Lower Wuerhe Formation coal-bearing strata by the end of the Triassic, and secondary microbial gas in Zhongguai and Beisantan uplifts may have generated after the reservoirs were uplifted during the period of the Middle and Late Jurassic. This study suggests widespread distribution of microbial gas and shows the potential to find large microbial gas accumulation in the basin.
California's methane super-emitters Duren, Riley M; Thorpe, Andrew K; Foster, Kelsey T ...
Nature (London),
11/2019, Volume:
575, Issue:
7781
Journal Article
Peer reviewed
Open access
Methane is a powerful greenhouse gas and is targeted for emissions mitigation by the US state of California and other jurisdictions worldwide
. Unique opportunities for mitigation are presented by ...point-source emitters-surface features or infrastructure components that are typically less than 10 metres in diameter and emit plumes of highly concentrated methane
. However, data on point-source emissions are sparse and typically lack sufficient spatial and temporal resolution to guide their mitigation and to accurately assess their magnitude
. Here we survey more than 272,000 infrastructure elements in California using an airborne imaging spectrometer that can rapidly map methane plumes
. We conduct five campaigns over several months from 2016 to 2018, spanning the oil and gas, manure-management and waste-management sectors, resulting in the detection, geolocation and quantification of emissions from 564 strong methane point sources. Our remote sensing approach enables the rapid and repeated assessment of large areas at high spatial resolution for a poorly characterized population of methane emitters that often appear intermittently and stochastically. We estimate net methane point-source emissions in California to be 0.618 teragrams per year (95 per cent confidence interval 0.523-0.725), equivalent to 34-46 per cent of the state's methane inventory
for 2016. Methane 'super-emitter' activity occurs in every sector surveyed, with 10 per cent of point sources contributing roughly 60 per cent of point-source emissions-consistent with a study of the US Four Corners region that had a different sectoral mix
. The largest methane emitters in California are a subset of landfills, which exhibit persistent anomalous activity. Methane point-source emissions in California are dominated by landfills (41 per cent), followed by dairies (26 per cent) and the oil and gas sector (26 per cent). Our data have enabled the identification of the 0.2 per cent of California's infrastructure that is responsible for these emissions. Sharing these data with collaborating infrastructure operators has led to the mitigation of anomalous methane-emission activity
.
Seabed fluid flow involves the flow of gases and liquids through the seabed. Such fluids have been found to leak through the seabed into the marine environment in seas and oceans around the world - ...from the coasts to deep ocean trenches. This geological phenomenon has widespread implications for the sub-seabed, seabed, and marine environments. Seabed fluid flow affects seabed morphology, mineralization, and benthic ecology. Natural fluid emissions also have a significant impact on the composition of the oceans and atmosphere; and gas hydrates and hydrothermal minerals are potential future resources. This book describes seabed fluid flow features and processes, and demonstrates their importance to human activities and natural environments. It is targeted at research scientists and professionals with interests in the marine environment. Colour versions of many of the illustrations, and additional material - most notably feature location maps - can be found at www.cambridge.org/9780521819503.
North American leaders recently committed to reducing methane emissions from the oil and gas sector, but information on current emissions from upstream oil and gas developments in Canada are lacking. ...This study examined the occurrence of methane plumes in an area of unconventional natural gas development in northwestern Canada. In August to September 2015 we completed almost 8000 km of vehicle-based survey campaigns on public roads dissecting oil and gas infrastructure, such as well pads and processing facilities. We surveyed six routes 3–6 times each, which brought us past over 1600 unique well pads and facilities managed by more than 50 different operators. To attribute on-road plumes to oil- and gas-related sources we used gas signatures of residual excess concentrations (anomalies above background) less than 500 m downwind from potential oil and gas emission sources. All results represent emissions greater than our minimum detection limit of 0.59 g s−1 at our average detection distance (319 m). Unlike many other oil and gas developments in the US for which methane measurements have been reported recently, the methane concentrations we measured were close to normal atmospheric levels, except inside natural gas plumes. Roughly 47 % of active wells emitted methane-rich plumes above our minimum detection limit. Multiple sites that pre-date the recent unconventional natural gas development were found to be emitting, and we observed that the majority of these older wells were associated with emissions on all survey repeats. We also observed emissions from gas processing facilities that were highly repeatable. Emission patterns in this area were best explained by infrastructure age and type. Extrapolating our results across all oil and gas infrastructure in the Montney area, we estimate that the emission sources we located (emitting at a rate > 0.59 g s−1) contribute more than 111 800 t of methane annually to the atmosphere. This value exceeds reported bottom-up estimates of 78 000 t of methane for all oil and gas sector sources in British Columbia. Current bottom-up methods for estimating methane emissions do not normally calculate the fraction of emitting oil and gas infrastructure with thorough on-ground measurements. However, this study demonstrates that mobile surveys could provide a more accurate representation of the number of emission sources in an oil and gas development. This study presents the first mobile collection of methane emissions from oil and gas infrastructure in British Columbia, and these results can be used to inform policy development in an era of methane emission reduction efforts.
Significance Recent studies indicate that greenhouse gas emission inventories are likely missing methane emission sources. We conducted the first methane emission measurements from abandoned oil and ...gas wells and found substantial emissions, particularly from high-emitting abandoned wells. These emissions are not currently considered in any emissions inventory. We scaled methane emissions from our direct measurements of abandoned wells in Pennsylvania and calculate that they represent 4–7% of current total anthropogenic methane emissions in Pennsylvania. Millions of abandoned wells exist across the country and some are likely to be high emitters. Additional measurements of methane emissions from abandoned wells and their inclusion in greenhouse gas inventories will aid in developing and implementing appropriate greenhouse gas emission reduction strategies.
Abandoned oil and gas wells provide a potential pathway for subsurface migration and emissions of methane and other fluids to the atmosphere. Little is known about methane fluxes from the millions of abandoned wells that exist in the United States. Here, we report direct measurements of methane fluxes from abandoned oil and gas wells in Pennsylvania, using static flux chambers. A total of 42 and 52 direct measurements were made at wells and at locations near the wells (“controls”) in forested, wetland, grassland, and river areas in July, August, October 2013 and January 2014, respectively. The mean methane flow rates at these well locations were 0.27 kg/d/well, and the mean methane flow rate at the control locations was 4.5 × 10 ⁻⁶ kg/d/location. Three out of the 19 measured wells were high emitters that had methane flow rates that were three orders of magnitude larger than the median flow rate of 1.3 × 10 ⁻³ kg/d/well. Assuming the mean flow rate found here is representative of all abandoned wells in Pennsylvania, we scaled the methane emissions to be 4–7% of estimated total anthropogenic methane emissions in Pennsylvania. The presence of ethane, propane, and n-butane, along with the methane isotopic composition, indicate that the emitted methane is predominantly of thermogenic origin. These measurements show that methane emissions from abandoned oil and gas wells can be significant. The research required to quantify these emissions nationally should be undertaken so they can be accurately described and included in greenhouse gas emissions inventories.
Designing a broad-spectrum gas sensor capable of identifying gas components in complex environments, such as mixed atmospheres or extreme temperatures, is a significant concern for various ...technologies, including energy, geological science, and planetary exploration. The main challenge lies in finding materials that exhibit high chemical stability and wide working temperature range. Materials that amplify signals through non-chemical methods could open up new sensing avenues. Here, we present the discovery of a broad-spectrum gas sensor utilizing correlated two-dimensional electron gas at a delta-doped LaAlO
/SrTiO
interface with LaFeO
. Our study reveals that a back-gating on this two-dimensional electron gas can induce a non-volatile metal to insulator transition, which consequently can activate the two-dimensional electron gas to sensitively and quantitatively probe very broad gas species, no matter whether they are polar, non-polar, or inert gases. Different gas species cause resistance change at their sublimation or boiling temperature and a well-defined phase transition angle can quantitatively determine their partial pressures. Such unique correlated two-dimensional electron gas sensor is not affected by gas mixtures and maintains a wide operating temperature range. Furthermore, its readout is a simple measurement of electric resistance change, thus providing a very low-cost and high-efficient broad-spectrum sensing technique.
Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term ...stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.
•Pilot scale crude oil-natural gas stratified flow deposition tests were conducted.•Overall and local deposition analysis were conducted to elucidate mechanism.•Unprecedented parameter analysis was ...performed in circumferential direction.•The importance of circumferential heat transfer was demonstrated experimentally.
Wax deposition in the onshore and offshore pipelines is a common occurrence and typically disturbs the transportation of oil and gas. Accurate prediction of wax deposition in multiphase flow is of great importance to develop economical prevention and remediation strategies. However, reliable experimental data is lacking to understand the deposition process and validate the existing prediction models. In this work, two-phase gas-oil stratified flow wax deposition data at various liquid and gas flow rates have been obtained using Garden Banks condensate and natural gas in a 52.5-mm I.D. multiphase flow loop under the pressure of 2.41 MPa. It is evident that both deposit mass and wax content increase as superficial gas and liquid velocities increase. In addition, the deposit mass per unit area and wax content have a strong correlation with the actual liquid velocity deduced from superficial velocities. The local deposits are observed to be thinner but harder at the sides compared to the bottom of the pipe. The local deposit composition is also analyzed using high temperature gas chromatography (HTGC), revealing that the effect of vSG and vSL on the side deposits is more predominant than the bottom. It can be seen that the fraction of the high carbon number components increases as the superficial velocities increases. However, the increase due to the increase of vSG is more distinct compared to the vSL effect. Moreover, it has been observed that the local wax mass flux increases along the circumferential direction, namely, from the bottom towards the gas-liquid interface. Local deposit analysis in the circumferential direction provided insights to enhance our understanding on the deposition behavior and aid to improve or develop appropriate models.
Será que la culpa es de la vaca? Buitrago, Jhon Didier Ruiz
CES medicina veterinaria y zootecnia,
01/2019, Volume:
14, Issue:
1
Journal Article
Peer reviewed
Open access
En este contexto, los autores Joseph Poore y Thomas Nemeck sugieren que dejar de consumir carne o leche de vaca es una de las acciones más efectivas que los consumidores pueden realizar para combatir ...el cambio climático 3; sin embargo, el experto André Mazzetto advierte que dejar de comer carne vacuna no es la única solución, pues si realmente se quiere tener un impacto significativo en el ambiente debes volar menos en avión, usar autos más eficientes y transporte público, etcétera. Gran parte de la mala reputación de la ganadería se centra en el argumento de que es la mayor fuente de gases de efecto invernadero (GEI), en donde se estima que 51% de la emisión de GEI en el mundo procedían de la cría y procesado de ganado 4. Posteriormente, la Agencia de Protección Ambiental de los Estados Unidos estimó que las mayores fuentes de GEI en este país durante 2016 fueron la producción eléctrica, el transporte y la industria con unos porcentajes de 28, 29 y 22%, respectivamente, de las emisiones totales y el 9% lo aportó la agricultura 5, porcentaje en el que la ganadería contribuye aproximadamente en un 4% 4.
•Tradeoffs in water and carbon footprints of various fossil fuels are evaluated.•Tsinghua-CA3EM is applied to calculate the lifecycle energy use and GHG emissions.•Scenario analysis and white noise ...are used for addressing system’s uncertainties.•The optimal climate benefit is identified based on a coal-to-shale gas switch.•The environmental performances of different fuels are comprehensively compared.
China has set ambitious goals for developing its vast shale gas reserves. The rapid growth in shale gas needs to better understand its environmental implications. This study performs a comprehensive evaluation framework for identifying the tradeoffs in water and carbon footprints of China's shale gas, and compares the lifecycle greenhouse gas (GHG) emissions and water consumption of shale gas with that of conventional natural gas and coal. Scenario analysis and white noise are used for addressing system’s uncertainties. A deterministic mathematic method is then developed for identifying the optimal breakeven methane leakage and wastewater recycling rates. Results reveal that the carbon footprint of shale gas (39.71 g CO2/MJ) is slightly higher than that of conventional natural gas (35.51 g CO2/MJ), but their carbon footprints are lower than that of coal. When the downstream supply chain is considered, coal-fired technologies have a larger amount water consumption than gas-fired technologies. Theoretically, the water consumption can increase by approximately 2% when switching from conventional natural gas to shale gas. Shale gas development in China cannot lead to a significant increase in its total GHG emissions, whereas a coal-to-shale gas switch can offset some GHG emissions. The optimization solutions indicate that the methane leakage rate in shale gas technology decreases from 7.89% to 5.75% when the methane recovery rate in coal technology increases from 0 to 100%. This relationship implies that increasingly strict methane leakage regulations are necessary in the shale gas industry to achieve climate benefits of shale gas subsidization for coal.
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