Gas Composition Data Research Articles

Dyspnea in COVID-associated lung disease

Introduction. Covid-associated lung disease has become one of the leading problems of the COVID-19 pandemic, and early diagnosis of complications is complicated. Assessment of dyspnoea as a significant symptom is important, but its diagnostic ability in this lesion is poorly understood.Aim. To study the features of dyspnoea in COVID-19-associated lung lesions and its diagnostic value.Materials and methods. The study included 134 patients with COVID-19-confirmed pneumonia. Demographic and anthropometric data, subjective condition, dyspnoea severity according to Borg scale, concomitant pathologies, multispiral computed tomography (MSCT) data, arterial blood gas composition, capnometry and spirometry data, as well as disease outcomes (transfer to ICU, support ventilation, fatal outcome) were analysed.Results. Dyspnoea was present in 43.3% of patients. Increased dyspnoea was associated with increased C-reactive protein (CRP), D-dimer, lung tissue damage (MSCT), decreased forced vital capacity (FVC), and increased alveolar-arterial gradient (P(A-a)O2). Dyspnoea correlated with duration of hospitalisation and need for oxygen therapy (OR = 1.307, p = 0.008). 57.4% of patients with hypoxaemia did not complain of dyspnoea, but their outcomes did not differ between patients with dyspnoea and hypoxaemia. 32.2% of patients without hypoxaemia complained of dyspnoea. These patients did not have a significant increase in FGEF by the time of discharge, and it remained lower than in patients without dyspnoea and hypoxaemia.Conclusion. Dyspnoea in COVID-19-associated lung disease is an important symptom correlating with clinical-functional, instrumental and laboratory characteristics of the disease. Comprehensive data analysis is necessary to identify patients requiring further observation.

Examining the Potential of Biogas: A Pathway from Post-Fermented Waste into Energy in a Wastewater Treatment Plant

Biogas has improved due to technological advancements, environmental awareness, policy support, and research innovation, making it a more cost-effective and environmentally friendly renewable energy source. The Generalized Linear Model (GLM) was employed to examine the relationship between purchased and generated energy from 2007 to 2023. Metrics such as deviance, log likelihood, and dispersion phi were examined to assess model fit. The Mann–Kendall test was utilized to detect trends in energy datasets. Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) reduction was significant, exceeding 97% from 2014 to 2023. However, treated sewage displayed limited susceptibility to biological degradation, with COD to BOD5 ratios increasing from 2.28 to 6.59 for raw sewage and from 2.33 to 7.05 for treated sewage by 2023. Additionally, the efficiency of sewage purification processes was calculated, and multivariate regression analysis was conducted on gas composition data. Principal Coordinate Ordination (PCO) and k-means clustering were used for dimensionality reduction and biogas component clustering, respectively. This research showed that biogas from the waste water treatment process can be used, particularly in methane production. Technological advancements have made biogas production more efficient, enhancing energy generation within a circular economy framework.

Correlating Gas Composition and Electrochemical Data from First Formation Cycle of Lithium-Ion Batteries

The solid electrolyte interface (SEI) plays a crucial role for the performance and lifetime of lithium-ion batteries. It consists of decomposition products from electrolyte components (salt, solvent and additives) and is initially formed during the first charging process called the formation cycle. The chemical processes creating the SEI are a matter of current research. A better understanding of these reactions and their implications on cell performance can provide new ways to optimise the formation process. This can help reducing costs while increasing lifetime and performance of lithium-ion batteries.In this contribution we apply statistical correlation analysis on a large set of cells to gain new insights on the connection between formation and cell-performance. Cells (NMC622|Graphite, 1 Ah, ordered from LiFun) are divided in three groups. The groups differ only by the electrolyte. An electrolyte solution with EC:EMC (3:7 by wt.) and 1 M LiPF6 serves as a baseline. The other two groups use the same solvent and salt concentration but contain an additional 5% fluor ethylene carbonate and vinylene carbonate, respectively.All cells underwent the same formation procedure. It consists of a formation cycle with C/5 at 80°C, followed by a degassing-step and 9 subsequent cycles with the same current rate at 45°C. After these ten cycles a reference performance test (RPT) is conducted, including qOCV, capacity and pulse-resistance tests. During the degassing step gas samples from half of the cells were analysed using GC-MS.An incremental capacity analysis of the formation cycle shows clear distinctions between the three different electrolytes. Distinct peaks below 3 V are found for each group. The gas composition demonstrates that cells containing additives contain a higher share of carbondioxide and carbonmonoxid amid a substantially lower share of ethylene, compared to the cells without additives.The large number of over 100 cells in total enables a systematic correlation analysis. We investigated the correlation between features extracted from the first formation cycle and the RPT. In addition, correlations between electrical data from the first cycle and the relative amount of carbon-containing gasses in the samples are analysed.Correlations differ for the three groups of cells, however some common trends were observed. We found a negative correlation between the average voltage during formation and the difference between the capacity of the first discharge and the capacity measured in the RPT. This difference represents the loss over the 9 cycles at 45°C. It is positively correlated with the first discharge capacity indicating that lower lithium-losses in the first cycle are countered by higher losses in subsequent cycles.Correlations between gasses and electrical data from the formation cycle provide new insights into the chemical processes. If the shares of two gasses are positively correlated, we assume that the reactions producing these gasses are linked. We found such strong positive correlations for the shares of CH4, C2H6, C2H4 and CO in the case of VC-containing electrolyte. In this group the share of carbondioxide is negatively correlated to these gas-shares.Correlating the different gas-shares with the charge throughput in different voltage windows (during wetting at 1.5V, during the formation charge cycles from 1.5 to 3V, 3 to 3.8V, and 3.8 to 4.2 V, respectively), we found very different patterns for the three groups. VC-containing cells show weak or very weak correlations with all four charge-throughput values, with the exception of a moderate negative correlation between CO. Cells without additives show a moderate correlation between the wetting charge and the CO2-share. Cells containing FEC exhibit a moderate positive correlation between the share of CO2 and the charge throughput between 1.5 and 3.8 V.The combination of electrical data with the gas composition and statistical analysis provides a new way to improve our understanding of the SEI formation and the complex chemical reactions. Our results indicate that gasses generated by the decomposition of VC are not influenced by small changes of charge throughput during formation, whereas a higher charge-throughput at lower voltages in cells containing FEC correlates with an increased share of CO2.

Occurrence and maturation transformation of organic and inorganic nitrogen in the Lower Cambrian shelf–slope facies shale: Implications for overmature N2-rich shale reservoirs in Southern China

Thermogenic molecular nitrogen (N2) is one of the primary sources of high N2 content in overmature shale gas reservoirs. However, it remains uncertain whether N2 is released from organic or inorganic sources because the occurrence and thermal stability of different nitrogen species vary. This study investigates the Lower Cambrian shale samples from a well in southeastern Guizhou, China to determine the abundance, occurrence, and source of nitrogen in marine shale. A sealed gold tube pyrolysis experiment was further conducted on isolated kerogen and organic matter (OM)-ashed samples from one typical shale to explore the maturation transformation of organic nitrogen (Norg) and inorganic nitrogen (Ninorg). The results reveal that the studied shale exhibits a high nitrogen content, with the Norg content being less than that of Ninorg. The predominant functionality of Norg is pyrrolic-N, and Ninorg occurs primarily in silicates (NH4+-bearing illite and (NH4+, K, Ba)-feldspar). The structural characteristics of the different nitrogen functionalities cause them to vary in their thermal transformation behavior. The pyrolysis experiment results indicate that the nitrogen release of the shale increases rapidly when EqVRo >3.7%, and the N2 yields for typically shelf-slope facies shales are primarily 1–2 m3/t at EqVRo 4.0%–4.2%, to which the Ninorg has a dominant contribution. Further evidence that the high N2 shale gas reservoirs occur at EqVRo >3.5% is provided by compiled gas composition data from various risk wells. It is proposed that the Lower Cambrian shale gas exploration should address the considerably increased N2 risk in the shelf–slope facies area.

Long-Term Continuous Gas Diagnostics For Fuel Cell Systems: Development Of An Automatized Raman Metrology

Knowledge of the composition of gas flows in fuel cell systems is crucial for their understanding. In current research, this data is rarely recorded inline and in real-time due to the lack of suitable metrology. Here, we present an optical gas sensor. Green light (532 nm) from a 450 mW laser excites Raman scattering. A spectrometer analyzes the scattered light and a Python software extracts gas composition data automatized and in real-time. We designed a measurement cell that allows optical inline access to gas flow systems and is easy to implement. Therefore, common signal enhancement methods with more complex setups can not be applied. Literature data on scattering cross sections does not offer a reliable basis for calibration what constitutes the need for a gas conditioning system that allows fast preparation of well defined mixtures. We used it to present two principles of calibration. First, calibration based on relative scattering cross sections is the more stable possibility, because it is still valid in cases where laser power and integration time are changed. However, in consequence the results for one species are not independent from the other species. A poor signal, e.g. following from a low mole fraction in a single component, will introduce uncertainty in all components. We avoid that problem through direct linear correlation of signal strength of one species to its partial pressure, which is the second calibration variant. In this case, there is an influence of laser power and integration time. The additional information on overall pressure can be used in model systems, where the presence of undetected components can be ruled out. We can compare that information to pressure measurements to do plausibility checks on the Raman results in real-time. We apply the sensor in fuel cell system research, where measurement intervals of one second yield results of sufficient precision. Increasing integration time can further decrease the uncertainties where favorable. The measurement and data evaluation routines work stable and constant enough to monitor gas compositions in longterm operation. To date, the sensor can measure mixtures of nitrogen, oxygen, hydrogen and water vapor.

Combining methane clumped and bulk isotopes, temporal variations in molecular and isotopic composition, and hydrochemical and geological proxies to understand methane's origin in the Ronda peridotite massifs (Spain)

In serpentinised peridotite and ultramafic rock systems, methane (CH4) origin is frequently considered abiotic, but variable microbial and thermogenic components can also exist. Typically, the origin of CH4 is studied using bulk, 13C/12C and 2H/H isotopic composition, molecular gas composition, occasionally radiocarbon (14C), microbiology and geological context. Recent advances in CH4-clumped isotope methods have yielded novel insights into the formation of CH4: nonetheless, their interpretation in natural gas samples is often uncertain and requires additional research. Here, we study the origin of the gas released in hyperalkaline (pH > 10) springs in the Ronda Peridotite Massifs (southern Spain), combining bulk and clumped CH4 isotopes with molecular gas composition, hydrochemical (Total Organic Carbon and Platinum Group Elements in water), geothermal and geo-structural data. Five springs analysed in 2014 have been re-examined for changes in gas chemistry over time, and three newly discovered gas-bearing springs are analysed for the first time. Regardless of whether springs have microbial or abiotic isotopic fingerprints, we find that bulk CH4 isotopes are fairly stable over a seven-year period. This suggests that the CH4 source(s) or postgenetic processes (such as oxidation and diffusion) have not undergone significant temporal changes. Major variations in H2 and CH4 concentrations in certain springs may be the result of changes in gas pressure and migration intensity. Paired CH4 clumped isotopes (Δ12CH2D2 - Δ13CH3D) were analysed in two bubbling springs, where the presence of CH4 can be interpreted as non-microbial based on 13C enrichment, absence of 14C, and the presence of ethane and propane. However, these isotopes are in disequilibrium, which prevents the quantification of the gas formation temperature. Within the Δ12CH2D2 - Δ13CH3D diagram, the data lie within both the microbialgenic zone, suggested by previous authors, and the abiotic zone that results combining data from laboratory gas synthesis and other natural gas samples. Therefore, attributing a microbial origin to CH4 based only on clumped isotopes is less definite than previously assumed. The amount of Total Organic Carbon appears to be correlated with the origin of CH4, as it is higher in 13C-depleted CH4 samples and lower in 13C-enriched samples. Palladium (Pd) and Rhodium (Rh) dissolved in water (the more soluble Platinum Group Elements) can be a proxy for the chromitite ore deposits contained in plagioclase tectonite layers throughout the investigated area, which may act as catalysts for abiotic CO2 hydrogenation. Clumped isotope disequilibrium and the reported absence of diffuse CH4-bearing fluid inclusions in the peridotites appear to rule out high temperature gas genesis in post-magmatic inclusions. These observations, along with the moderate temperatures at the base of the peridotite massifs and the consistent occurrence of gas along tectonic contacts between serpentinised (H2-bearing) peridotite and carbon-bearing rocks, are compatible with the theory of low-temperature CO2 hydrogenation.

Hazardous air pollutants in transmission pipeline natural gas: an analytic assessment

Natural gas production occurs in specific regions of the US, after which it is processed and transported via an interconnected network of high-pressure interstate pipelines. While the presence of hazardous air pollutants (HAPs) in unprocessed, upstream natural gas has been documented, little has been published on their presence in the midstream natural gas supply. We systematically evaluated publicly available, industry-disclosed HAP composition data sourced from Federal Energy Regulatory Commission (FERC) natural gas infrastructure applications submitted between 2017 and 2020. Natural gas composition data from these filings represent approximately 45% of the US onshore natural gas transmission system by pipeline mileage. Given that reporting natural gas HAP composition data is not required by FERC, only 49% of approved expansion projects disclosed natural gas HAP composition data. Of those applications that disclosed composition data, HAP concentrations were typically reported as higher for separator flash gas and condensate tank vapor compared to liquefied natural gas and transmission-grade natural gas, with mean benzene concentrations of 1106, 7050, 77, and 37 ppm respectively. We also identified one pipeline operator that reports real-time HAP concentrations for its natural gas at five pipeline interconnection points. Similar to the FERC applications, this operator reported benzene, toluene, ethylbenzene, xylenes and hydrogen sulfide as present in transmission pipeline natural gas. Notably, mercury was also reported as detectable in 14% of real-time natural gas measurements but was not reported in any FERC applications. Given that transmission infrastructure releases natural gas during uncontrolled leaks and loss of containment events as well as during routine operations (e.g. blowouts and compressor station blowdowns), these gas composition data may serve as a critical component of air quality and health-focused evaluations of natural gas releases.

Simultaneous Detection of Methane, Ethane, and Propane by QEPAS Sensors for On-Site Hydrocarbon Characterization and Production Monitoring.

Natural gas is sampled and produced throughout the lifespan of a petroleum field. Gas composition and isotope data are critical inputs in the exploration and field development, such as gas show identification, petroleum system analysis, fluid characterization, and production monitoring. On-site gas analysis is usually conducted within a mud gas unit, which is operationally unavailable after drilling. Gas samples need to be taken from the field and shipped back to the laboratory for gas chromatography and isotope-ratio mass spectrometry analyses. Results are usually without sufficient resolution to fully characterize the heterogeneity and dynamics of fluids within the reservoir and the production system. In addition, it often takes a considerable time to obtain the results using the traditional method. A novel QEPAS (quartz-enhanced photoacoustic spectroscopy) sensor system was developed to move gas composition analyses to field for quasi-real-time characterization and monitoring. With respect to previously reported QEPAS prototypes for trace gas detection, the new system realized measuring concentrations of methane (C1), ethane (C2), and propane (C3) in gas phase within the percentage range that is typically encountered in natural gas samples from oil and gas fields. A gas mixing enclosure was used to dilute the natural gas-like mixtures in nitrogen gas (N2) to avoid the saturation of QEPAS signals. An iterative analysis based on multilinear regression of QEPAS spectra was developed to filter out the influence of gas matrix variation from multiple hydrocarbon components. The advance in simultaneous measuring hydrocarbon gases and expanded linearity range of QEPAS, with previously reported detection of H2S, CO2, and gas isotopes (12CO2/13CO2, 13CH4/12CH4), opens a way to use the advanced sensing technology for in situ and real-time gas detection and chemical analysis in the oil industry.

The geochemical characteristics and origin of Ordovician ultra-deep natural gas in the North Shuntuoguole area, Tarim Basin, NW China

Ultra-deep Ordovician in Shuntuoguole area, Tarim Basin, NW China, has complex oil & gas phases, in which light oil, volatile oil, condensate and dry gas phases coexisting. The study compares the geochemical characteristics and origin of Ordovician ultra-deep natural gas in the North Shuntuoguole (SB) area to that of gas in the Shuntuo (ST), South Shuntuoguole (SN), Gulong (GL), and Gucheng (GC) areas using natural gas composition, carbon isotope and hydrogen isotope data and light hydrocarbon data. The Ordovician ultra-deep natural gas in the SB area is wet gas, with dryness indexes ranging from 0.52 to 0.88 and minimal H2S content. The carbon isotopes of natural gas are relatively low, with δ13C1 and δ13C2 values ranging from −49.6‰ to −44.7‰ and −39.3‰ to −32.7‰, respectively. All the natural gas shows positive carbon and hydrogen isotope series. The n-alkane and iso-alkane dominate the C5–C7 light hydrocarbon, with the methylcyclohexane index of light hydrocarbon lower than 35%. All of the Ordovician natural gas in the Shuntuogule area is oil-type gas. The Ordovician natural gas in the SB area is dominated by kerogen cracking gas, with a small fraction of wet gas from the early stages of oil cracking, whereas, all of the gas in the ST, SN, GL and GC areas comes from oil cracking. The Cambrian source rocks led directly to both types of cracking gases. The distribution of two types of cracking gas in the Shuntuogule area is correlated with the maximum paleogeothermal temperature and (or) present temperature of the Ordovician. The maximum paleogeothermal temperature and present Ordovician temperature in the SB area are 170–180 °C and 150–160 °C, respectively, which are lower than those in ST and SN areas, and have not yet achieved the temperature of large amount oil cracking. As a result, light oil and volatile oil phases were preserved in the SB area, which was dominated by kerogen cracking gas, whereas reservoir phases varied from condensate to dry gas phases, and natural gas is oil-cracking gas, from ST to SN to GL to GC areas, due to large scale oil cracking caused by high present temperature and (or) paleo-geothermal temperature of the Ordovician.

Determining the role of diffusion and basement flux in controlling 4He distribution in sedimentary basin fluids

The transport of helium from the crystalline continental basement and overlying Phanerozoic sedimentary formations to the near surface can be controlled by both diffusive and advective processes. The relative role of each is vital to helium resource prediction, and important in quantifying the residence times of fluids relevant to groundwater resources, hydrocarbon systems, geologic repositories for nuclear waste and carbon sequestration. The Williston Basin, North America, is a prominent sedimentary basin, providing an excellent natural laboratory to assess these processes. Here, we report noble gas isotopic and composition data for 28 gas samples from natural gas wells that sample different stratigraphic horizons down to the basement (Cretaceous to the Cambrian). Helium isotope ratios show a resolvable mantle 3He component (up to 4.7%) in most samples. Neon isotopic compositions of the Cambrian samples are consistent with a crystalline basement gas contribution. Both helium and neon isotopic observations provide evidence for the contribution of conservative noble gases from the crystalline basement or deeper into the overlying sedimentary basin. 4He groundwater concentrations in the sedimentary formations, calculated from 4He/20Ne values in gas samples, are in excess of in situ U+Th 4He production in some shallow units and depleted in others, providing further evidence of cross formation gas contributions.The highest 4He groundwater concentrations can be compared with the results obtained from a fully-coupled vertical scale transport model characterising diffusive-dominated transport through a static groundwater column. The model includes the 4He flux into the basin from the Precambrian basement and quantifies the apparent basement 4He flux to be between 0.8 - 1.6 × 10−6 mol 4He/m2 yr, comparable to the steady-state flux estimated for the average continental crust (1.47 × 10−6 mol 4He/m2 yr) (Torgersen, 2010). The lithologies in which 4He concentrations are significantly lower than the reference model predictions are consistent with a history of water flooding and produced water disposal in those formations over decades of hydrocarbon production. While an advective component cannot be ruled out, this work demonstrates the importance of both diffusion and the basin architecture development in controlling 4He flux into and out of different lithologies. The assumption of negligible 4He loss from the top surface of a lithology is often made when determining the 4He age of its groundwater. In the Williston Basin, this study shows that deeper lithologies may reach steady state at different stages of basin development, with shallower lithologies sometimes also showing significant 4He loss from their top surface. In the Williston Basin, 4He diffusive loss from the target lithology must be considered to accurately interpret 4He groundwater residence times and accumulation potential.

Analysis of Oil and Gas Ethane and Methane Emissions in the Southcentral and Eastern United States Using Four Seasons of Continuous Aircraft Ethane Measurements

AbstractIn the last decade, much work has been done to better understand methane (CH4) emissions from the oil and gas (O&G) industry in the United States. Ethane (C2H6), a gas that is co‐emitted with thermogenic sources of CH4, is emitted in the US predominantly by the O&G sector. In this study, we perform an inverse analysis on 200 h of atmospheric boundary layer C2H6 measurements to estimate C2H6 emissions from the US O&G sector. Measurements were collected from 2017 to 2019 as part of the Atmospheric Carbon and Transport (ACT) America aircraft campaign and encompass much of the central and eastern United States. We find that for the fall, winter, and spring campaigns, C2H6 data consistently exceeds values that would be expected based on EPA O&G leak rate estimates by more than 50%. C2H6 observations from the summer 2019 data set show significantly lower C2H6 enhancements in the southcentral region that cannot be reconciled with data from the other three seasons, either due to complex meteorological conditions or a temporal shift in the emissions. Combining the fall, winter, and spring C2H6 posterior emissions estimate to an inventory of O&G CH4 emissions, we estimate that O&G CH4 emissions are larger than EPA inventory values by 48%–76%. Uncertainties in the gas composition data limit the accuracy of using C2H6 as a proxy for O&G CH4 emissions. These limits could be resolved retroactively by increasing the availability of industry‐collected gas composition data.

Intercomparison of the representations of the atmospheric chemistry of pre-industrial methane and ozone in earth system and other global chemistry-transport models

An intercomparison has been set up to study the representation of the atmospheric chemistry of the pre-industrial troposphere in earth system and other global tropospheric chemistry-transport models. The intercomparison employed a constrained box model and utilised tropospheric trace gas composition data for the pre-industrial times at ninety mid-latitude surface locations. Incremental additions of four organic compounds: methane, ethane, acetone and propane, were used to perturb the constrained box model and generate responses in hydroxyl radicals and tropospheric ozone at each location and with each chemical mechanism. Although the responses agreed well across the chemical mechanisms from the selected earth system and other global tropospheric chemistry-transport models, there were differences in the detailed responses between the chemical mechanisms that could be tracked down by sensitivity analysis to differences in the representation of C1–C3 chemistry. Inter-mechanism ranges in NOx compensation points were about 0.17 ± 0.12 when expressed relative to the inter-mechanism average. Monte Carlo uncertainty analysis carried out with a single chemical mechanism put the intra-mechanism range a factor of three higher at 0.50 ± 0.12. Similar differences between inter-mechanism and intra-mechanism ranges were found for hydroxyl radical depletion but were up to a factor of six wider for ozone formation from incremental additions of organic compounds. The cause of the discrepancies between the inter- and intra-mechanism ranges was found to be the large uncertainties that are present in the laboratory determinations of the rate coefficients and product channel branching ratios of some key chemical reactions involving organic peroxy radicals and hydroperoxides. Whilst these large uncertainties are present in the laboratory determinations, there will be irreducible uncertainties in the predictions from the earth system and other chemistry-transport models of methane and tropospheric ozone trends since pre-industrial times and hence their contributions to the radiative forcing of climate change. Further definitive laboratory studies of the reaction rates and product yields of the reactions of the simple organic peroxy radicals and hydroperoxides are required to resolve and reduce current uncertainties in earth system and chemistry-transport model predictions.

Analysis of the condensate phase in offshore pipe gas company

Gas transportation is usually done using pipes. As was done in one of the Gas Companies. In gas transportation consists of suppliers (Station A) and receivers (station C). From the supplier to the receiver goes through a very far pipe. Gas that passes through the pipeline has a composition consisting mostly of methane, but it is undeniable that there is still heavy carbon and impurities in the gas. Heavy carbon and various impuritis contained in the gas will disrupt gas transportation in the pipeline because it can cause condensate. Condensate consists of heavy carbon and impuritis which changes phase into liquid. The occurrence of liquid is caused by external and also internal influences, especially on the temperature and pressure that is treated to the gas. Condensate in the pipe will cause obstruction or decrease the volume in the pipe and otherwise it will cause internal corrosion. In the Gas Company there is an offshore pipeline that has the deepest depth of 70 meters. This elevation allows condensate inundation to occur in the offshore pipeline. The purpose of this study was to determine the effect of operating conditions on the occurrence of the existing condensate phase in the offshore pipeline between B Station B and C Station, which is 105 km away. The method used is the collection of gas composition data through gas chromatography analysis at station A, piping specifications, operating conditions at station B, and Hysys Aspen Simulation. It can be concluded that the offshore pipeline between B station and C station formed condensate (liquid phase) on 2nd day. The operating pattern of the envelope phase shows that in this condition natural gas condensate is formed because it is in the gas-liquid phase. If the methane composition and sea temperature are getting smaller, the possibility of natural gas condensate formation will be even greater.

Phase separation and secondary migration of methane-rich gas accompanying uplift of an unconventional tight-hydrocarbon system, Montney Formation, western Canada

Tight-hydrocarbon systems can undergo significant depressurization through leakage of fluids, primarily gas, in response to uplift. Leakage at the up-dip margins of these systems may be highly variable if internal gas transmission by secondary migration is focused along fairways with favourable stratigraphic and structural characteristics. In this study of the Montney Formation, regional mapping of the methane content of produced gas reveals two orders of trends. The first-order regional trend is increasing methane content with depth and thermal maturity. Second-order trends are orthogonal or oblique to the first-order trend, and defined by curvilinear fairways with methane contents higher than expected from the first-order trend. They can be mapped for 10s km with some extending up-dip from the dry gas window into the oil window. Methane enrichment along second-order trends reflects fractionation of hydrocarbon fluids by a variety of processes including phase separation, secondary migration, fluid mixing and evaporative fractionation. Gas composition, recombination PVT and carbon isotope ratio data from produced fluids are used in three local case studies to show that methane-rich gas was driven up-dip by buoyancy forces and regional pressure gradient with migration focused along suitably oriented fairways of enhanced permeability and positive local structure. Secondary migration of methane-rich gas resulted in modified hydrocarbon compositions with leaner liquid contents and higher gas-oil ratios than expected from thermal maturity indicators. Recognition of secondary methane migration fairways is thus essential for hydrocarbon evaluation and exploitation in the Montney Formation, and conceivably in other analogous tight-hydrocarbon systems that have undergone significant uplift.

Using a stochastic forest prediction model to predict the hazardous gas concentration in a one-way roadway

To accurately and quantitatively analyze the pollutant gas concentration in tunneling roadways, a prediction model of the pollutant gas concentration was proposed and established. Through downhole gas composition data acquisition and correlation analysis, the prediction variables of downhole gas pollution are obtained with both short-term and long-term memory neural network prediction methods and random forest regression modeling methods, making full use of historical target gas concentration data for the future in a short period of time to evaluate the model performance and prediction results. Compared with the results of the stochastic forest regression prediction and the long- and short-term memory neural network prediction, the stochastic forest regression prediction model has a good prediction effect and better generalization effect and is a reliable method with excellent performance for downhole gas concentration prediction. The analysis of the predicted results shows that the change in CO concentration is strongly correlated with CH4 and CO2 and strongly correlated with N2, making it possible to obtain the potential influencing factors of the target gas. These results provide a scientific basis for the prediction of underground pollution gas concentration and the protection and treatment of the atmospheric environment in mining areas.

Improved sampling technique to collect natural gas from hydrate-bearing pressure cores

High quality gas compositional data are an important factor in interpreting the genetic source of natural gas hosted in hydrate-bearing sediments and other subsurface systems. In order to accurately characterize the composition of gas samples degassed from hydrate-bearing pressure cores, one must use a reproducible sampling technique that minimizes artifacts of the sampling process. Herein, we review sediment core degassing techniques and compare data obtained from a commonly used degassing approach, which we term the standard quantitative degassing (SQD) technique, to our newly developed modified quantitative degassing (MQD) method designed to minimize atmospheric contamination and gas-water interactions. The SQD method allows sample gas to interact with water in a bubbling chamber, which we hypothesize could alter the gas composition following mixing with water or dissolved gases in the bubbling chamber. Whereas, the MQD method allows for the collection of sample gas prior to the bubbling chamber. To compare the SQD and MQD methods, we performed a side-by-side comparison of noble (He, Ne, Ar, Kr, and Xe), major (H2, N2, O2, and CO2), and hydrocarbon (CH4, C2H6, C3H8, i-C4H10, C4H10, i-C5H12, C5H12) gas concentrations and select isotopic compositions obtained using both sample collection techniques. Gas samples were collected from hydrate-bearing pressure cores recovered and maintained under hydrate stable conditions from the northern Gulf of Mexico during the UT-GOM2-1 Expedition. The MQD method displayed significantly lower concentrations of atmospheric gases, higher proportions of hydrocarbon gases, lower ratios of C1/C2+, and heavier stable carbon and hydrogen isotopes of methane than the SQD method. These results demonstrate that the MQD method reduced air contamination and minimized alteration of the hydrocarbon gases. Therefore, we conclude this method may be important for future work that seeks to determine the composition of natural gas from pressure cores using quantitative degassing experiments, especially those seeking to measure major (e.g., N2) and noble gases.

Ammonia inhibition of waste degradation in landfills - A possible consequence of leachate recirculation in arid climates.

Ammonia inhibition of anaerobic waste degradation has been extensively investigated on a laboratory scale. It is hence well known that at ammonium levels above 2500 mg/l, methanogenic bacteria are inhibited, which leads to both reduced methane (CH4) production and increased organic pollution of the leachate. In the present paper, and for the first time, data on a full-scale landfill indicating ammonia inhibition of waste degradation is presented. The leachate of the landfill is characterized by extremely high concentrations of chloride (up to 70,000 mg/l) and ammonium-nitrogen (up to 20,000 mg/l). These high pollution levels are explained by the following facts: first, the landfill is located in an arid climate (annual precipitation of 200 mm), resulting in low fresh water infiltration; and second, leachate or concentrate resulting from reverse osmosis treatment at the site has been recirculated. The high ammonium levels obviously caused inhibitory effects on the anaerobic degradation, which resulted in chemical oxygen demand concentrations in the leachate of far above 300,000 mg/l. Furthermore, a comparatively low level of landfill gas (LFG) generation and a shift towards higher carbon dioxide and lower CH4 contents in the collected LFG was observed. Based on the gas compositional data, the overall reduction in CH4 generation was assessed to be 50%. In order to reduce organic leachate pollution and to enhance LFG production at the site investigated, fresh (rain) water infiltration should be enhanced and the recirculation of leachate or treatment residues derived thereof should be terminated.

Strombolian eruptions and dynamics of magma degassing at Yasur Volcano (Vanuatu)

Open vent basaltic volcanoes account for a substantial portion of the global atmospheric outgassing flux, largely through passive degassing and mild explosive activity. We present volcanic gas flux and composition data from Yasur Volcano, Vanuatu collected in July 2018. The average volcanic plume chemistry is characterised by a mean molar CO2/SO2 ratio of 2.14, H2O/SO2 of 148 and SO2/HCl of 1.02. The measured mean SO2 flux in the period of 6th to 9th July is 4.9 kg s−1. Therefore, the mean fluxes of the other species are 7.5 kg∙s−1 CO2, 208 kg∙s−1 H2O and 4.8 kg∙s−1 HCl. The degassing regime at Yasur volcano ranges from ‘passive’ to ‘active’ styles, with the latter including Strombolian activity and spattering. Gases emitted during active degassing are enriched in SO2 over HCl and CO2 over SO2 relative to passive degassing, with CO2/SO2 ratios of 2.85 ± 0.17, SO2/HCl of 1.6 ± 0.22, and H2O/SO2 of 315 ± 78.8. Gases emitted during passive degassing have CO2/SO2 ratios of 1.96 ± 0.12, SO2/HCl of 0.50 ± 0.07 and H2O/SO2 of 174 ± 43.5. We use a model of volatile degassing derived from melt inclusion studies (Metrich et al., 2011), combined with our observations of chemical variations in the outgassing bubbles to propose a mechanism for magma degassing in the conduit at Yasur. We envisage a shallow conduit filled with crystal-rich magma, forming a viscous and mobile plug that develops an effective yield strength from the surface to a depth of at least 2000 m, in which bubbles are trapped, grow, ascend towards the surface and burst in a typical Strombolian eruption. Deeper bubbles released during active degassing are enriched in CO2 and SO2 compared to bubbles released during ‘passive degassing’, which are sourced from close to the surface, and are, consequently, HCl-rich.

CO2 methanation and reverse water gas shift reaction. Kinetic study based on in situ spatially-resolved measurements

The reaction kinetics for the CO2 methanation and reverse water gas shift reaction over an ordered-mesoporous Ni/Al2O3 catalyst were determined. For the parameter estimation and model discrimination, the kinetic data were obtained by means of spatially-resolved measurement in a catalytic plate reactor. In detail, ~21,000 high-resolution gas composition data were gathered along the reactor axis using a movable sampling capillary connected to a mass spectrometer. Additionally, the catalyst surface temperature was determined via infrared thermography. The influence of reaction temperature (320–420 °C), total pressure (1.2–7.3 barabs), and GHSV, as well as possible inhibition of products such as CH4 and H2O, were investigated.A one-dimensional model of the reactor was developed describing the conservation of mass in the bulk gas and catalyst phase. The Bayesian approach was used to estimate the kinetic parameters of 20 proposed Langmuir-Hinshelwood rate expressions for the CO2 methanation that were derived based on three different mechanisms (i.e., direct dissociation, hydrogen assisted dissociation, and hybrid mechanism). Two kinetic models reflected the measured data very well. The most probable models suggest that the rate determining step includes the reaction of an oxygenated complex (COH* or HCOO*) with an active site (*) or an adsorbed hydrogen (H*). Furthermore, water was assumed to be adsorbed as a hydroxyl species (OH*), while methane did not influence the reaction. Temperature- and time-resolved Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) measurements confirmed the presence of both adsorbed surface intermediates.

Petroleum geochemical aspects of the Mandawa Basin, coastal Tanzania: the origin of migrated oil occurring today as partly biodegraded bitumen

The shallow-marine Upper Jurassic–Lower Cretaceous sedimentary successions of the Mandawa Basin, coastal Tanzania, are located about 80 km away from the offshore gas discoveries of Block 2, Tanzania. In this paper we present petroleum geochemical data, including bitumen extracted from outcrop samples which are relevant to the understanding of the onshore ‘Petroleum System’ and possibly also to the offshore basin. Despite some biodegradation and weathering, common to all outcrop samples, most bitumen samples analysed contain mature migrated oil. The maturity span of geomarkers (C 13 –C 15 range) covers the entire oil and condensate/wet gas window ( R c = 0.7–2% R c , where R c is the calculated vitrinite reflectance), with the biomarkers generally indicating the oil window ( R c = 0.7–1.3% R c ). This suggests that the bitumen extracts represent several phases of migrated oil and condensate, which shows that the samples are part of an active or recently active migration regime or ‘Petroleum System’. The source-rock facies inferred for the bitumen is Type II/III kerogen of siliciclastic to carbonate facies. This is oil-prone kerogen, typical for a marine depositional system with an influx of proximal-derived terrigenous material blended in with in situ marine algal organic matter (OM). Application of age-specific biomarkers such as the C 28 /C 29 -steranes, extended tricyclic terpane ratio (ETR), nordiacholestanes and the aromatic steroids suggest that more than one source rock have contributed to the bitumen. Possible ages are limited to the Mesozoic (i.e. excluding the Late Paleozoic), with the most likely source rock belonging to the Early Jurassic. More geochemical and geological studies should be undertaken to further develop the general understanding of the petroleum system of the Mandawa Basin and its implications to the ‘Petroleum Systems’ both offshore and onshore. This paper also presents a reinterpretation of published gas composition and isotope data on the Pande, Temane and Inhassoro gas fields (Mozambique) with implications for possible oil discoveries in the gas-dominated region.