Amounts Of Hydrocarbons Research Articles

Extraction of Organic Compounds From Lacustrine Oil-Prone Shales and the Effect on Nanopore

Lacustrine oil-prone shale at the oil-generation stage develops a large number of nanopores; however, the influence of fluid–shale interactions on the nanopores of lacustrine shale is poorly understood. A suite of mature lacustrine shales from the Songliao Basin Qingshankou Formation was performed on sequential organic solvent (petroleum ether and mixture of dichloromethane and methanol) extractions, and nitrogen and carbon dioxide adsorptions, Rock-Eval pyrolysis and field emission scanning electron microscopes (FE-SEM) observation. The sequential extractions show a decrease in total organic matter (TOC) and in the exacted organic matter content of shale, but an increase in the specific area (SBET) and pore volume of the extracted residues. Before and after extractions, the relationships between the extracted amount of OM and SBET, pore volume and their cumulative increments reveal OM as a main factor affecting the development of nanopores in these shales. The reasons are 1) SBET and mesopores are mainly blocked by EOMs in the initial samples, 2) the cumulative increases of SBET and mesopores are dominantly controlled by the extracted amount of hydrocarbons during petroleum ether extraction, and 3) both hydrocarbons and NSOs (resins and asphaltenes) have an influence on the cumulative increases of SBET and mesopores, and kerogen exposed more open porous-organic mesopores after the EOMs in the extracted shales. Here, further work concludes that oils adsorbed on pore surfaces are dominantly distributed on nanopores less than 10 nm, and free oils occur when the threshold of the average pore width in studied shales is over 11.7 nm.

Karmaşık jeolojik ortamlarda gelişen hidrokarbon kapan türlerinin patlayan yansıtıcı yöntemi ile modellenmesi

Structural and stratigraphic hydrocarbon (oil, gas) traps that develop in complex geological environments are formed in regions subjected to tectonically deformation or where there are impermeable rocks in the lateral direction and accumulate significant amounts of hydrocarbons. Reflections from the subsurface media including such traps indicate highly complex behaviour. Therefore, understanding seismic wave propagation in such environments provide important contributions to the interpretation stage. In this study, the modeling of structural and stratigraphic hydrocarbon traps was carried out with exploding reflector (ER) technique. The most important advantages of the method is that the seismic source is located at the reflective interfaces and recorded by the receivers at the surface with the one way travel time. Therefore, as a result of the calculation, directly zero offset sections could be obtained. Numerical calculation of the seismic waves propagated from the source was made by the finite difference method (FDM) which is very useful due to the ability to choose arbitrary input models with different features and provide direct solutions to wave propagation problems. Thus, seismic models of channel, anticline, syncline, normal fault type traps which are frequently encountered in hydrocarbon explorations were calculated easily and quickly by means of the solution of the full wave field with FDM based on the exploding reflector technique. As a result, it has been shown that obtaining zero offset sections (stacked sections) with the ER technique will practically make important contributions to the interpreter during the interpretation of real seismic data.

Hydrocarbon potential, organisms, and depositional environments of the Lower Cambrian shales along the southern margin of the Ordos basin, Northern China

The dark shales of the Lower Cambrian Dongpo Formation, along the southern margins of the Ordos Basin, were researched based on biomarkers and carbon isotope analyses of outcrop samples to reveal their hydrocarbon potential, organism composition, and depositional environment. Similar to the Yangtze and Tarim blocks, the Lower Cambrian in the southern margin of Ordos Basin, which is a part of North China block, also deposited high abundance marine source rocks. The shales displayed good to excellent total organic carbon (TOC) content (up to 13.75%). The crossplot of phytane/nC18 vs. pristane/nC17 and organic carbon isotopes indicate the kerogen to be primarily type I-II. The low Hydrogen index values, and high pyrobitumen reflectance (>3.0%) indicate that the Dongpo shales are currently in over-mature stage. The Dongpo shales thus exhibit high hydrocarbon generation potential and might have produced and discharged massive amounts of hydrocarbons during their geological history. The G/C30H ratios (0.17–0.29) and extended tricyclic terpanes Ratio (ETR) values (0.54–0.61) suggest sedimentary environments of stratified water and relatively moderate salinity. In addition, the Dongpo shales display low Pr/Ph (<0.63), low C30*/C29Ts (<0.44), high C35 22S/C34 22 S (>0.47), and relatively abundant elemental sulfur. These parameters indicate that Dongpo shales were formed in anoxic waters. The abundant steranes and hopanes in the Dongpo shales suggest the diversity of organisms, including eukaryotes and prokaryotes. The composition of eukaryotes (planktonic algae) is consistent with that of the Yangtze and Tarim blocks, but there are obvious differences with Oman, reflecting the heterogeneity in the global distribution of eukaryotes during the Early Cambrian. In addition, compared with the Yangtze and Tarim, the relatively contribution of prokaryote to Dongpo shale is low, which may also be an important reason for the obvious enriched of 13C in kerogen. The positive relationship between TOC and Pr/Ph and C27 St (%) suggests that high primary productivity in the paleoenvironment probably attributed to red algae. The Pr/Ph, C35/C34 values and others indexes are related to anoxic conditions, which is good for preserving deposited organic matter.

Selecting suitable shrub and herb species to revegetation from the perspective of root exudates: An implication for ecological restoration of desertification in an alpine meadow of the eastern Tibetan Plateau

Till now, the lack of research regard to root exudates is still serious in the restoration process of desertification alpine meadow in the eastern Tibetan plateau, although recovery of desertification land resulted from overgrazing and climate change is known to be shaped by the rhizosphere. Therefore, we measured root carbon (C) exudate rates of Kengyilia rigidula (Keng) S. L. Chen., Rhodiola kirilowii (Regel) Maxim., Elymus nutans Griseb., Hippophae rhamnoides L. and Salix cupularis Rehd. by sampling root exudates in situ in a desertification alpine meadow, as well as determined the volatile components using GC-MS. The results showed that 1) Root C exudate rates were as follows: R. kirilowii > K. rigidula > E. nutans > S. cupularis > H. rhamnoides, and R. kirilowii was significantly higher than H. rhamnoides (p < 0.05). 2) Common volatile substances of the five plants mainly contained hydrocarbons (above 13.16%), esters (above 11.83%) and phenols (above 6.27%), and the relative amounts of hydrocarbons and phenols were the highest in R. kirilowii respectively, while esters were the highest in S. cupularis among the five plant species. Thereinto, 2-hydroxy-1-(hydroxymethyl) ethyl ester was the highest content in R. kirilowii while 2,4-di-tert-butyl phenol was the highest content in S. cupularis. 3) As the specific allelochemical components of herbs and shrubs, heptadecane was the highest content in R. kirilowii among the three herb species while pentacosane was relatively high content in S. cupularis between the two shrubs, and the relative amount of palmitic acid in R. kirilowii was about twice that in H. rhamnoides and S. cupularis, accounting for 1.64%. Collectively, our results suggest that S. cupularis and R. kirilowii should be regarded as the better choice of pioneer plant species to be applied to ecological restoration of desertification alpine meadow.

Raman Micro‐Imaging of the Coexistence of sI and sII Hydrates Formed from a Mixed Methane‐Propane Gas in a Confined Space

AbstractNatural gas hydrate contains a specific amount of heavy hydrocarbons, such as ethane, propane, etc., aside from the primary guest gas of methane. Although the coexistence of two or even three hydrate structures has been discovered at several hydrate sites, the requisite formation mechanism is still not well understood. In‐situ observation of the formation process of mixed methane‐propane hydrate in a confined space was conducted using confocal Raman imaging microscopy. The Raman imaging results reveal that sI methane hydrate and sII mixed methane‐propane hydrate are formed and coexist in the reaction system. In the confined space, the sI hydrate originates from the dissolved gas in water, while the sII hydrate is formed from free gas. The results obtained can help explain the coexistence of sI and sII hydrates found in natural hydrate samples, as well as providing insights into a possible dynamic scenario of hydrate reservoirs in geological history.

The detection of oil spill onshore using the thermal band of landsat-8

Remote sensing is an advanced technique that can be used to detect hydrocarbons on land, and its advantages include rapid and low-cost detection. The detection of hydrocarbons on the surface is essential for environmental monitoring and the purpose of exploration. For oil and gas companies, the ability to locate hydrocarbon spill sites is important information for the success of future exploration wells. This study aimed to determine the quantities of hydrocarbons mixed with the soil as an indicator of its accumulation in the subsurface. In this paper, temperature data obtained from the landsat-8 satellite were used to determine the extent of the oil spill in the area using spatial interpolation and gradient techniques. Kriging interpolation is based on statistical models (i.e. including auto-correlation) geostatistical techniques can produce a forecast surface and also provide accurate forecasts. The results showed that there are 60 sites of thermal anomalies and temperature values are lowest and highest 23.2 o C to 91.11 o C, in the study area. Three different sites were chosen in terms of area and effect. They are located in the northern and southern Rumaila and Zubair fields. The location of the oil spills was determined with high accuracy after identifying the anomalies.

Changes in caking properties of caking bituminous coals during low-temperature pyrolysis process

We proposed a low-temperature pyrolysis treatment (LTPT) to destroy the caking properties of a fat coal (FC) and a 1/3 coking coal (CC). To reveal the factors affecting caking property, the changes in the chemical properties of pyrolysis products were analyzed using Fourier transform infrared spectrometry, X-ray diffractometer, and gas chromatograph/mass spectrometer (GC/MS). The in situ morphological changes in the liquid crystals produced by the two coal samples during LTPT process were also recorded using a hot-stage microscope. Of particular interest was a microscopic description of the factors affecting caking property. The results showed that the caking index (G) of FC decreased with increasing temperature and became zero at about 500 °C. Hot-stage microscope showed FC produced liquid crystals at 395 °C, the size of which continuously increased, with an accompanying of the generation of new liquid crystals. GC/MS showed large amounts of aliphatic hydrocarbons with the number of carbon of 6–25 (AlHsc6-25) and aromatic hydrocarbons with 2–4 rings (ArHsr2-4) were removed from FC. The aromaticity (fa) of FC increased only substantially from 395 to 494 °C. Meanwhile, the G of FC decreased only significantly in the same temperature range. A similar result was observed for CC. The removal of AlHsc6-25 leads to insufficient supply of hydrogen radicals; therefore, relatively high-molecular weight aromatics quickly cross-linked into semicoke. Additionally, the evolution of ArHsr2-4 and the increase in fa restrain the originating of crystal liquids. As a result, the loss of G was observed.

Leaf uptake of atmospheric monocyclic aromatic hydrocarbons depends on plant species and compounds

Large amounts of monocyclic aromatic hydrocarbons (MAHs) are emitted into the atmosphere, but it is unclear which compounds among MAHs are effectively removed by the above-ground parts of plants. Although fumigation experiments of MAHs at unrealistically high concentrations (~ppmv) have been conducted, experiments with ambient concentrations have scarcely been conducted. In the present study, MAHs, including benzene, toluene, phenol, benzaldehyde, and benzyl alcohol, with concentrations ranging from several to several tens ppbv, were individually fumigated to four plant species, and the uptake was monitored using proton-transfer-reaction mass spectrometry and gas chromatography-mass spectrometry. No detectable uptake was observed for benzene and toluene, but phenol, benzaldehyde, and benzyl alcohol were significantly taken up by the plants. The uptake rate normalized to fumigated concentration varied from 3 to 50 mmol m−2s−1 during the light period, depending on light intensity and compounds. The difference in uptake capability may be attributed not only to different metabolic activities but also to different values of Henry’s law constant, which regulates the partitioning of these compounds into the liquid phase in leaves. The uptake of phenol, benzaldehyde, and benzyl alcohol was affected by stomatal conductance, suggesting that stomatal opening is the main factor regulating the uptake of the three MAHs. This is the first observation that anisole is emitted when phenol is fumigated to Spathiphyllum clevelandii, suggesting that phenol is methylated to anisole within plant leaves. Anisole is more volatile than phenol, meaning that methylation enhances the emission of xenobiotics into the atmosphere by converting them to more volatile compounds. This conversion ratio decreased with an increase in phenol concentration (from 1.3 to 143 ppbv). Considering low reaction rate coefficient of anisole with OH radicals and low conversion ratio from phenol to anisole, it is concluded that plants act to effectively remove oxygenated MAHs from the atmosphere.

Relationship Between Hydrocarbon Content and Oxidative Stability in Irradiated Hazelnut Oils

The hydrocarbon detection method, based on the detection of hydrocarbons formed during irradiation, is one of the internationally accepted detection methods for irradiated foods. Radiolysis products, formed due to breakdown of unsaturated fatty acids by irradiation, are detected in this method. While no hydrocarbons were not found in the unirradiated hazelnut oil, hydrocarbons, namely 1-7 hexa-decadiene, 1- hexa-decene, n-penta-decane and 1- tetra-decene, but they were detected after irradiation at doses of 5 kGy or higher. It was found that irradiation induced the formation of hydrocarbons and when irradiation dose increased, the amount of hydrocarbons increased. The Rancimat process is widely used to define the amount of oxidation in foods containing fat. Analysis time is short as it is a very fast method. The induction time, showing the oxidation resistance of oils, decreased as irradiation dose increased. The possible relationship between the detected hydrocarbons and oxidative stability was examined and a negative correlation was found between the hydrocarbon and rancimat methods.

A simple and effective evaluation method for lacustrine shale oil based on mass balance calculation of Rock-Eval data

Because the profit from the development of unconventional resources can be small, success usually depends on the quick identification of favorable areas. It is therefore very important to identify a rapid and robust resource potential evaluation method. However, it is challenging to evaluate shale oil content, especially the recoverable oil part. We explore a new evaluation index (SE) by using Rock-Eval data and mass balance. When SE ˃ 0, the shale interval has already expelled a certain amount of hydrocarbons, so it has poor shale oil potential. When SE is near 0, almost all the generated hydrocarbons are trapped in the shale itself, and simultaneously, no externally migrated hydrocarbons enter the shale. In the case of an SE near 0, the shale oil potential may depend on whether it is organic-rich; however, this type of shale tends to be compact and does not develop fractures. When SE ˂ 0, externally migrated hydrocarbons entered the shale interval, which usually indicates good shale oil potential. The more negative the SE is, the greater the shale oil potential. One of the advantages of this index is that it takes into account not only the residual oil content but also the conditions of hydrocarbon expulsion and migration. Moreover, this method is economical and convenient and is based on commonly available Rock-Eval data.

Generalized energy model of the open thermodynamic system “vehicle fuel tank”. Processes of non-stationary heat transfer with a variable fuel mass

Introduction (statement of the problem and relevance). While gasoline-powered vehicles generate a significant amount of hydrocarbons in the form of the fuel system emitted vapors, the main element of the system being the fuel tank, modern requirements for evaporative emission limits are significantly tightened. At the same time, the vaporization process parameters and the fuel vapor amount are determined by the dynamics of fuel heating in the tank under various modes of vehicle operation.The purpose of the research was to develop a “vehicle fuel tank” energy model, seeking to create an open thermodynamic system which can exchange matter and energy with the environment depending on the variable amount of fuel in the tank.Methodology and research methods. The analysis of heat flush connected to the fuel tank and taken away from it was being carried out. As a result of solving equations for open and closed thermodynamic systems, the parameters characterizing the thermal properties of the fuel tank were obtained.Scientific novelty and results. Additional complex parameters have been proposed, the main of which are: heat transfer of the tank; tank heat capacity; supplied heat flux; the rate of heat capacity change; tank emptying time; fuel heating acceleration factor; the maximum rate of change in temperature difference. To assess the heat and power properties of the fuel tank, an additional parameter of the sphere surface area ratio to the surface area of the same volume tank has been proposed, which allowed estimating the fuel tank heat transfer to the environment.Practical significance. Equations have been obtained that allow estimating the level of fuel temperature depending on the thermal properties and shape of the fuel tank in the absence and presence of fuel pump control.

The experimental investigation and data–driven modeling for thermal decomposition kinetics of Green River Shale

Given that kerogen is a source of vast amount of hydrocarbons and organically–bound inorganic elements, it’s important to understand the thermal decomposition kinetics of kerogen. Green River Shale contains a significant amount of immature kerogen (Type I), which can be an ideal source for the sample of experimental study. In this study, Thermogravimetric Analysis and Derivative Thermogravimetry (TGA/DTG) was used to quantify the weight loss during the pyrolysis process of the Green River Shale from Utah and subsequently establish the kinetic model of thermal decomposition of kerogen based on the Friedman method followed by the data–driven modeling approach. A two–step reaction mechanism and components of production during the pyrolysis were determined by implementing Thermogravimetry Analysis–Differential Scanning Calorimetry–Gas Chromatography (TGA–DSC–GC). The chemical bonds were analyzed with Fourier–Transform Infrared spectroscopy (FTIR) before and after the pyrolysis. From the experiments, we observed the two–stage reactions in the hydrocarbon evolution window when the heating rate was lower than 30 °C/min, while only one stage was observed with the higher heating rates. C14 hydrocarbon was generated continuously during the hydrocarbon evolution, which indicated that the Green River Shale contained a plentiful amount of it. The kinetic parameters were obtained for the decomposition of organic and inorganic mixture and the organic matter (kerogen) only. The Artificial Neural Network (ANN) method was implemented to train the kinetic parameters obtained from the TGA/DTG experiment. The prediction of extrapolated cases showed a good performance when the heating rate was smaller than 5 °C/min. The generated proxy model can be coupled with various physical models to simulate the thermal decomposition of kerogen with high accuracy.

A comparative assessment of biofuel products from rice husk and oil palm empty fruit bunch obtained from conventional and microwave pyrolysis

• This work is significance as sustainable alternative energy from biomass waste. • MP produced bio-oil with high monoaromatic and phenolic compound and low PAH. • High reaction temperature favour the production of biogas due to intensified secondary reactions. • A remarkable increase in syngas formation when reacted using MP in contrast to CP. Pyrolysis is an alternative heating method developed to produce bio-oil, biogas, and biochar from biomass, including oil palm empty fruit bunch (EFB) and rice husk (RH) pellets. This work focused on the comparison of the products obtained from microwave pyrolysis (MP) and conventional pyrolysis (CP). The experimental work was carried out using MP and CP at 500 °C and 800 °C. The properties of biochars produced from these reactions were characterized. The biofuels were characterized using FTIR and GC-MS, while the biogas was measured using GC-TCD. The composition of the H 2 gas or syngas was also analyzed. MP improved the yield of bio-oil and biochar, but the percentage of biogas yield decreased. The yield of bio-oil produced from the MP of RH and EFB pellets reacted at 800 °C increased significantly from 12.2 to 20.6 wt.% and 15.5 to 20.2 wt.%, respectively. The bio-oil derived from MP has a high content of monoaromatics and phenolic compounds compared to the oil produced from CP. Meanwhile, the bio-oil derived from CP contained a significant amount of polycyclic aromatic hydrocarbons. Although the yield of biogas produced via MP was slightly lower than CP, the total syngas produced from MP was significantly high for both EFB (78 vol.%) and RH (70 vol.%). For CP, only 62 vol.% and 68 vol.% of syngas was produced using EFB and RH, respectively. The findings highlight the potential of MP technology to synthesize environmentally-friendly bio-oil and biogas with a high percentage of syngas. Graphical Abstract .

INFLUENCE OF THE SAND PRODUCTION ON THE WELL DRAINAGE AREA

INFLUENCE OF THE SAND PRODUCTION ON THE WELL DRAINAGE AREA

Formation mechanism of the sealing capacity of the roof and floor strata of marine organic-rich shale and shale itself, and its influence on the characteristics of shale gas and organic matter pore development

The sealing capacities of shale, roof, and floor strata are essential for the preservation of shale gas. Sealing capacity development and its influence on shale gas composition and organic matter pore development are important but have not been addressed by existing studies. In this paper, the Upper Ordovician Wufeng-the first member of the Lower Silurian Longmaxi Fm. in the Yangtze region is selected as the study object. We dissected the J1 well in the Jiaoshiba block inside the Sichuan Basin and the Y6 well in the Youyang block outside the Sichuan Basin to analyze the gas components and carbon isotopes in recovered shale gas. In this study, two microscope techniques (i.e., FIB-SEM and FIB-HIM), porosity measurement, TOC content analysis, permeability tests, isothermal adsorption measurements, are utilized. The analytical results show that both the roof and floor strata have vertical sealing effects on the organic-rich shale due to their different physical properties compared to the shale. The shale overburden pressure increases with burial depth, and the adsorbed gas increases with increasing TOC content and thickness: all of these can lead to a decrease in permeability and an increase in self-sealing capacity. This paper determined the formation mechanism of the sealing capacity for shale, roof and floor strata. Furthermore, the control patterns of “sealing capacity strength” on the shale gas source and organic matter pore development are clarified. The main findings are as follows: when the shale, roof, and floor strata have a strong sealing capacity, only a small amount of liquid hydrocarbons can be discharged from the shale, but the natural gas formed due to liquid hydrocarbon cracking is abundant. Under such circumstances, shale gas has a mixed origin of liquid hydrocarbon cracked gas and kerogen cracked gas; the carbon isotopes are inverted; abundant pyrobitumen pores with high porosity and good connectivity are developed. When the sealing capacities are weak, the amount of liquid hydrocarbons discharged from the shale are high, and the amount of natural gas is low. The shale gas is mainly derived from kerogen cracking with weak or no carbon isotope inversion, and kerogen pores are small with poor connectivity. These findings will advance the study of shale gas formation mechanisms and provide a scientific basis for selecting shale gas exploration area.

Comparative Study on Pyrolysis Kinetics Behavior and High-Temperature Fast Pyrolysis Product Analysis of Coastal Zone and Land Biomasses.

The pyrolysis characteristics of land biomass (corn stalks (Cs), pine sawdust (Ps)) and coastal zone biomass (Jerusalem artichoke stalks (JAs) and reed (Re)) were investigated based on thermogravimetric analysis (TGA) and products’ analysis. The kinetic parameters were obtained by three isoconversional methods (Friedman, KAS, and FWO) and one model-fitting method (DAEM). The simultaneous effect of high temperature (700–900 °C) and high heating rate (1000 °C/s) on the pyrolysis product simulating the typical conditions of a fluidized bed gasifier was studied. TGA showed that high heating rates deepen the thermal cracking process of biomass. Compared with the land biomass, the initial decomposition temperature (Ti) of the coastal biomass is reduced significantly owing to its higher proportion of hemicellulose. These methods agree with the trends shown by the activation energy (Ea) distribution calculated, with fluctuations between 160 and 350 kJ/mol. The mean value activation energies of Re and JAs were higher than those of Cs and Ps between 10% and 90% conversion. The DAEM model showed that Cs and JAs have a good linear relationship between ln A and Eα during the main pyrolysis stage, while Ps and Re are relatively weaker. The kinetic compensation effect was evident for Cs and JAs during the main thermal cracking stage. Py-GC-MS results confirmed that phenols, hydrocarbons, PAHs, and oxygen heterocycle compounds were strongly present in the released volatile products. High-temperature fast pyrolysis of JAs produced a larger amount of PAH compounds than from Cs, Ps, and Re. A larger amount of hydrocarbons and phenols was generated from high-temperature fast pyrolysis of Ps. Some oxygen-containing volatiles are easily converted into aromatic products with higher stability under high temperature.

Ordovician and Silurian Formations of the Baltic Syneclise (NE Poland): An Organic Geochemistry Approach

Abstract The Baltic Syneclise is one of the Paleozoic basins along the western margin of the East European Craton. Commercial amounts of hydrocarbons have been found onshore and offshore in the Middle Cambrian sandstones and Upper Ordovician limestone reefs. The Middle-Upper Cambrian and Tremadocian bituminous shales have been identified as good quality effective source rocks. The existence of good quality source rocks in the Ordovician and Silurian profiles provides an impetus for conventional and unconventional hydrocarbon explorations in this region. Geochemical analyses revealed that the rocks of the Middle–Late Ordovician and Early Silurian horizons exhibit overall good to very good source rock quality. Within the Ordovician strata, the Sasino and Prabuty formations exhibit the highest amounts of organic carbon with the median total organic carbon (TOC) values of 1.96 and 1.23 wt. %, respectively. The Pasłęk and Pelplin formations in the lowest parts of the Lower Silurian stand out clearly from other formations with the median TOC values of 0.91 and 1.15 wt. % and median total hydrocarbon content (S1+S2) of 2.46 and 1.54 mg HC/g rock, respectively. The analyzed successions are dominated by immature/early mature, algal (oil-prone) type II, and mixed II/I kerogen deposited in a marine paleoenvironment with anoxic conditions at the bottom and oxic conditions in the photic zone. Immature organic matter prevails in the eastern and central parts of the study area (Gołdap–Kętrzyn–Olsztyn area), and the western part (Darżlubie–Hel–Gdańsk area) has mature kerogen.

A case study in controlled source electromagnetism: Near seabed hydrocarbon seep systems of Coal Oil Point, California, USA

Marine hydrocarbon seeps are found on all continental margins and release significant amounts of greenhouse gases and hydrocarbons into the atmosphere and hydrosphere. Most methods of studying seeps rely on seafloor or near-seafloor observations, but seepage rates and seep locations can be variable, leading to uncertainty. We exploit the fact that hydrocarbons are electrically resistive compared with surrounding sediments and use marine electromagnetic methods to study the deeper sources and accumulation sites, which are controlled by local geology and should be more stable than the seabed expressions. Our surface towed marine controlled source electromagnetic system used a horizontal electric dipole transmitter and floating electric dipole receivers spaced 100–400 m from the transmitter, collecting frequency domain amplitude and phase data at ∼2 Hz and harmonics. The survey targeted known and inferred hydrocarbon seeps within the Coal Oil Point seep field offshore Santa Barbara, California, USA. Two dimensional inversions of the data indicate that the method is sensitive to the shallowly buried (<400 m) structure of the marine hydrocarbon seeps and is an efficient and effective tool in their identification and characterization. The results show spatial variability of seafloor hydrocarbons along the Coal Oil Point seep field and indicate at least two previously unidentified intermediate depth accumulation sites. The depth and lateral extent of these hydrocarbon accumulation sites may improve seep emission models for the Coal Oil Point seep field.

Enhanced photodegradation of methyl and parent PAH over flower-sphere Ag/rGO/BiOBr composite: Performance, mechanism and pathway

Significant amounts of methyl and parent polycyclic aromatic hydrocarbons (PAHs) exist in the environment, causing a potential environmental threat. A cost-effective, stable, and efficient photocatalyst was valuable for water remediation. In this work, Ag and reduced graphene oxide (rGO) was used to promote the visible light utilization of BiOBr catalyst. The photocatalytic degradation performance of synthesized catalysts under sunlight irradiation was better than under visible light irradiation. The Ag/rGO/BiOBr catalyst was superior to pure BiOBr and Ag/BiOBr in the photodegradation of 3,6-dimethylphenanthrene (3,6-DMP) and phenanthrene (Phe) with the optimum doping amounts (Ag 1.5 wt% and rGO 3 wt%). The degradation of 3,6-DMP on 1.5Ag/3rGO/BiOBr was influenced by solution pH, catalyst dosage and humic acid adding. 3,6-DMP was more easily photodegraded than Phe. Superoxide radicals (·O2−) and holes (h+) played key roles in the photocatalytic process. The photodegradation mechanisms and pathways of 3,6-DMP and Phe were proposed according to the intermediate detection results by GC-MS. Ag/rGO/BiOBr provided a promising solution for methyl and parent PAH remediation.

High helium reservoirs in the Four Corners area of the Colorado Plateau, USA

Radiogenic 4He is naturally produced in Earth's crust due to alpha decay of Uranium (U) and Thorium (Th). Helium has unique thermodynamic properties required for the medical imaging industry, aerospace and other fields of high-tech manufacturing, and currently is in increasingly high demand. Despite its economic value, the mechanisms of helium migration and retention in sedimentary basins remain poorly understood.Oil and gas fields with economic helium (>0.3%) concentrations have been discovered in Paleozoic intervals in the Colorado Plateau, southwestern USA. Here we report new noble gas isotope and abundance data for gas samples (n = 31), from actively producing Paleozoic formations within five fields: Ratherford, Tocito Dome, Navajo Springs, Pinta Dome, and Dineh-Bi-Keyah. Helium concentrations range from 0.01% to 7.9% with varying amounts of liquid and gaseous hydrocarbons, N2, and CO2. We present multi-stage gas, water, and oil equilibration models to account for the observed noble gas elemental and isotopic signatures. Oil-dominated systems are explained by a closed system oil/water equilibration and subsequent admixture of air. He-rich dry gas samples exhibit uniform 4He/N2 ratios consistent with the regional mean values, suggesting a common crustal source and no subsequent fractionation. In contrast, air-derived 20Ne/36Ar ratios are highly fractionated. These observations are consistent with a tectonically controlled crustal gas release from the basement, groundwater saturation with 4He and N2, and subsequent degassing. Extensive gas-water interaction (i.e., migration) leads to extreme fractionation of 20Ne/36Ar, but does not affect 4He/N2 due to water saturation with crustal gases released from the basement.We show the volume of rock required to have produced helium in the reservoir to be significantly larger than the current reservoir volume immediately beneath the field. Therefore, the reservoir helium concentration cannot be sourced by in-reservoir decay of U and Th and instead requires a process to incorporate exogenous sources of helium in the reservoir without significant dilution from hydrocarbons. For helium-rich fields, excess helium is sourced from the Precambrian granitic basement likely utilizing a large area beneath the field area (i.e., crustal gas mobilization and transport via fracture zones), consistent with the degree of water contact. Deep crustal faults in the Precambrian basement are in close proximity to the high helium fields, indicating that these structures are potentially serving as primary migration conduits via advective fluid flow.