Hydrocarbon Source Research Articles

Revealing continuous hydrocarbon generation and shale oil accumulation of saline lacustrine source rocks by sequential extraction

Saline lacustrine fine-grained rocks are important hydrocarbon source rocks and host large shale oil accumulations worldwide. However, the specific process and mechanism of hydrocarbon generation and accumulation in such rocks are not clear. Sequential extraction is a method to chemically separate different hydrocarbon fractions in sedimentary rocks, commonly as free, adsorbed and retained hydrocarbons, and thus can theoretically record the entire process of hydrocarbon generation and accumulation. To test this hypothesis, here sequential extraction was carried out on source rock samples with varying maturities from the alkaline lacustrine strata of the Lower Permian Fengcheng Formation, Mahu Sag, Junggar Basin, northwest China. The 17β-ethylandrostane/C29-sterane ααα20R and tricyclic terpane/pentacyclic triterpane ratios vary with maturity. In contrast, some biomarker parameters are not significantly affected by thermal maturity, including pristane/phytane, β-carotane index (β-carotane/main peak n-alkane), sterane/hopane, 7-+8-methyl index (7-+8-monomethyl heptadecane/main peak n-alkane), and C28/C29 regular sterane values, and can thus be used for oil–source rock correlations. The low-maturity source rocks have undergone one stage of hydrocarbon generation and associated shale oil accumulation, whereas source rocks with relatively high maturity have experienced multi-stage hydrocarbon generation and associated shale oil accumulation. In the early stages, cyanobacteria were the main bioprecursor to hydrocarbons and, with increasing maturity, Dunaliella gradually became the more important bioprecursor. Hydrocarbon generation by these alkaline lacustrine source rocks involved multiple sources and stages, which accounts for the abundant shale oil resources in the Mahu Sag with one-billion-ton reserves. This might be general for saline lacustrine source rocks worldwide, which can generate both conventional and unconventional hydrocarbons in large scales. Compared with conventional thermal modeling to constrain the generation history of hydrocarbon source rocks, a unique advantage of sequential extraction is its ability to characterize the entire history of hydrocarbon generation under geological conditions.

Polycyclic Aromatic Hydrocarbons in Topsoils Along the Taipu River Banks in the Yangtze River Delta, China: Occurrence, Source and Risk Assessment.

Taipu River is an important transboundary river and drinking water source in the Yangtze River Delta, China. This study collected 15 topsoil samples along the Taipu River banks and subsequently determined the polycyclic aromatic hydrocarbons (PAHs) concentrations, sources, and ecological and health risks. The sum of toxic 15 PAHs concentrations ranged from 83.13 to 28342.53 ng/g, with a mean of 2828.69 ng/g. High molecular weight (HMW) PAHs were the dominant components and Indene (1,2,3, -cd) benzopyrene (InP) accounted for the highest proportion in individuals. The average PAH concentration in residential land was the highest, followed by those in industrial and agricultural land. The PAH concentration was positively related to contents of total carbon, total nitrogen, ammonium nitrogen, and aminopeptidase activity in soils. The mixed combustion of biomass, coal, and petroleum and traffic emissions could be the primary PAH contributors. The total PAHs at over half of sampling points had relatively high risk quotients and incremental lifetime cancer risk (ILCR) values, posing potential or great ecological threats and health risks.

Basin-wide unconventional potential of the Doig Formation, Triassic of the Western Canada Sedimentary Basin

The Doig Formation is a Lower to Middle Triassic fine-grained unit of the Western Canada Sedimentary Basin, which includes a phosphate-bearing basal unit informally defined as the Doig Phosphate Zone (DPZ). The DPZ is recognized as a significant source of hydrocarbons hosted in conventional reservoirs in the basin. Phosphatic mudstones are uncommon and studies of their source-rock potential are scarce. The regional distribution of the Doig Formation source-rock properties across its entire stratigraphic and spatial range is poorly understood. In this study, we characterize the source-rock potential of the Doig Formation through an integrated assessment of thickness, organic content, kerogen type and thermal maturity. A new method for estimating the relative contribution of kerogen type and its original hydrogen index pseudo-van Krevelen, is introduced. The method assumes a binary mixture of kerogen types and requires an assumption for the initial value of immature kerogen from each end-member. The Doig Formation thickens southwestwards from the eastern erosional edge towards the deformation front to a maximum thickness of 229 m. The upper Doig and DPZ have distinct thickness distribution patterns, which suggests a transition from a tectonically-influenced sedimentation marked by uplifting, faulting and erosion, to the start of physiographic healing and a return to large-scale subsidence. The source-rock generative potential of the Doig Formation is fair to good, containing kerogen Types II and III. The DPZ has higher total organic carbon (TOC) content, of up to 12.2% and a higher proportion of Type II kerogen than that the upper Doig, where the maximum TOC content is 8.4 wt%. Original TOC was higher in the northern part of the lateral extent, which is likely related to a connection with open ocean; and in a linear trend through the center of the basin, which represents the trough of a marine fore-arc basin. Thermal maturity increases to the southwest, from early oil to dry gas windows, in a trend that approximately correlates to gas wetness and liquid yield. A zone of dry gas occurs near the eastern edge, however, which may be explained by preferential updip migration of thermogenic methane generated at greater depths, or mixing of thermogenic and biogenic gas.

Genesis of ferromanganese nodules associated with mud volcanoes in the southeastern Dongsha waters of the northern South China Sea: Implications for regional deep Mesozoic hydrocarbon prospects

The Dongsha waters of the South China Sea are the location of thick Mesozoic deposits and many mud volcanoes that suggest hydrocarbon accumulation. Knowledge of the mechanism, fluid source and evolution of these mud volcanoes, however, remains inadequate. Ferromanganese nodules have been sampled from several deep-water mud volcanoes in waters around Southeast Dongsha island and provide a unique opportunity to study the fluid origin and evolution of the mud volcanoes in the area. In this contribution, the petrology, geochemistry and C–O isotopes of fluid inclusions in the nodules have been analyzed. The ferromanganese nodules are composed of distinct black Fe–Mn crust layers and light-yellow nucleus that contain quartz that hosts fluid inclusions. The outermost layers mainly consist of iron manganese minerals with high Mn/Fe ratios (0.9∼1.57), whereas the nucleus are dominated by siliceous debris. Positive Ce anomalies (δCe: 1.45∼2.13) and negative Y anomalies in growth layers indicate an anoxic environment, which is conducive to hydromanganite precipitation. In contrast, negative Ce anomalies (δCe: 0.27∼0.96) and positive Y anomalies in the nucleus suggest oxidized conditions. The absence of obvious Eu anomalies may be related to low-temperature hydrothermal conditions. The nucleus is enriched in δ13C (−2.59∼1.09‰) and weakly depleted in δ18O (−4.94∼0.89‰), whereas the growth layers are strongly depleted both in δ13C (−16.94∼–12.57‰) and δ18O (−23.05∼–17.48‰). These values indicate that carbon in the nucleus is mainly inorganic carbon from volcanism, whereas the carbon in the growth layers is related to the leakage of deep old hydrocarbon. The fluid inclusions in the quartz from the nucleus show records of at least two periods of CO2-rich hydrothermal activity and an origin from deep Mesozoic strata before release by mud volcanism. Given the widespread mud volcanism, the quartz from the nucleus may come from debris carried by mud volcano eruptions; the quartz also experienced diagenesis related with micro-organisms. The growth layers are considered to be hydrogenic and affected by the leakage of mature thermogenic hydrocarbons from deep old strata. These findings provide insights into deep mature hydrocarbon sources and thermogenic activity and improve understanding of mud volcanism and deep oil and gas resources in the southeastern Dongsha waters.

A novel biomass pyrogenic index and its application coupled with black carbon for improving polycyclic aromatic hydrocarbon source identification.

To accurately subdivide the sources of polycyclic aromatic hydrocarbons (PAHs), the composition characteristics of 36 total polycyclic hydrocarbons (T-PAHs; 16 parent PAHs and 20 alkylated PAHs [A-PAHs]) in biomass-residue samples were analyzed. A novel biomass pyrogenic index (BPI) was defined based on A-PAH-fingerprinting differences between biomass-combustion and petroleum sources of PAHs and the sum of the concentrations of pyrene, fluoranthene, benzo[a]anthracene, and alkylated homologs) divided by the ∑value of EPA PAHs with 2-3 rings. BPIs of < 0.5 and > 0.5 indicated that the PAHs originated mainly from biomass combustion and petroleum, respectively. And the ∑targeted A-PAH pairs influencing the BPI/black carbon (BC) ratio was used to identify PAH sources in surface-sediment samples, using 0.5 as the threshold to distinguish between different sources across the strait. The columnar sediments were used to verify the accuracy of two source-identification methods. The results revealed that the main PAH sources changed since 2005, which is highly consistent with those obtained using positive matrix factors and a changing trend in the main types of local energy use. These results highlight the significance of A-PAHs in accurately identifying PAH sources and suggest that applying compositional differences in BC from different sources for PAH-source identification merits further study.

Palynofacies analysis of the JOG16N-8 borehole, K5 formation from the Maniamba Basin (middle Permian), Mozambique: A contribution for hydrocarbon exploration

The Maniamba Basin in Mozambique is surveyed mainly in regard to coal exploration. However, this basin is also known for containing well preserved fossil plants and vertebrate fossils that shed light to the understanding of Gondwana ecosystems. Nevertheless, organic matter analysis (palynofacies) and its implication for depositional environment and hydrocarbon source rock have not yet been performed. Here, we report for the first time in the Maniamba Basin, results from palynofacies analysis combined with thermal maturation and kerogen typification. Palynofacies analysis was applied on 69 samples from the sediments of the JOGN16N-8 borehole, K5 Formation (middle Permian).The results indicate that sediments are dominated by phytoclasts with less abundant sporomorphs and sparse amorphous organic matter (AOM). Three palynofacies were identified suggesting depositional settings in a general proximal and oxic lacustrine-fluvial deltaic environment. The dominance of opaque phytoclasts may be due to wildfires, oxidation conditions before or post deposition in proximity to terrestrial settings and an environment under obliquity cycle controlled monsoon climate. The organic matter composition combined with Spore Colour Index (SCI), pointed out the existence of an abundant type IV kerogen followed by type III in immature phase suggesting very little or no potential for gas exploration. Very few horizons suggest the existence of kerogen type II. This study, gives significant information for better understanding of the variation of organic matter, palaeoenvironment and source rock potential of the studied area.

Source and health risk assessment of soil polycyclic aromatic hydrocarbons under straw burning condition in Changchun City, China

Changchun, China is located in one of the world's three golden corn belts. As a key commodity grain base in China, Changchun plays a vital role in providing food security in the northeast. A total of 16 polycyclic aromatic hydrocarbons (PAHs) was analyzed to determine the influence of anthropogenic activities on the environmental quality of agricultural soils under straw burning conditions. The polycyclic aromatic hydrocarbons soil contamination severity was evaluated using the Maliszewska-Kordybach method. The results indicated that the agricultural soils of Changchun are substantial contaminated with PAHs. Petroleum, biomass, and coal combustion are the primary sources of PAH and have been determined using principal component analysis (PCA) and the isomeric ratio approach. The degree of hazard to human health was assessed using toxicity equivalence and increased lifetime cancer risk (ILCR) factors, except in localized areas during adulthood, the general risk was found to be modest. This study provides important information on PAH exposure in agricultural soils in northeast China, and the findings aid in the exploitation of straw and the mitigation of soil environmental concerns, allowing northeast China to achieve green agricultural development.

A comparison of hydrocarbon generation and expulsion in carbonate and argillaceous source rocks using semi-open pyrolysis experiments

To investigate the hydrocarbon generation and expulsion efficiency from carbonate and argillaceous source rocks, a series of pyrolysis experiments were conducted on two representative samples with Type II kerogen in a semi-open simulation system. The shale sample was obtained from the Upper Cretaceous Second White Speckled Shale Formation, while the carbonate sample was collected from the Middle Devonian Brightholme Member of the Winnipegosis Formation, both from the Western Canada Sedimentary Basin. The results show that the carbonate has a higher hydrocarbon generation capacity than the shale. During the pyrolysis, the expelled hydrocarbons from the carbonate were about 100–200 mg/g TOC higher than the hydrogen index reduction, while the amount of expelled hydrocarbons from the shale was generally lower than the hydrogen index reduction. The peak oil generation from the carbonate occurred earlier than that from the shale, but the oil expulsion efficiency was lower. However, a larger quantity of unexpelled oil retained in the carbonate was conducive to later oil expulsion, more hydrocarbon gas generation, and slightly higher gas expulsion efficiency than for the shale. Although hydrocarbon gases generated from both sources share similar evolution trends with heating, the relative proportions of CO2 and methane differ significantly between the two lithologies, with much higher abundance of CO2 in shale pyrolysate. The carbon loss during maturation of the two source rocks is very similar during the oil generation window, but the carbon loss trend was reversed in shale after the onset of gas generation, due to the conversion of some bitumen to pyrobitumen. Conversely, carbon loss continued in the carbonate to a higher maturity stage. This difference can be attributed to the occurrence of different organic matter types in the carbonate, including dispersed organic matter, aggregated organic matter, crystal-enclosed organic matter, and inclusion-hosted organic matter. These various organic matter types contribute to continuous oil and gas expulsion over a much wider maturity range than shale. Although the two samples chosen for this study do not encompass the entire range of carbonate and shale formations, the established hydrocarbon generation and expulsion models and evaluation criteria for argillaceous source rocks may not be directly applicable to carbonates, particularly at high maturity stages. These valuable insights have significant implications for oil and gas exploration in diverse geological settings. The research highlights the tendency of carbonate source rocks to experience higher organic carbon loss during maturation compared to argillaceous rocks. This suggests that certain low-TOC, highly mature carbonate source rocks can potentially serve as effective hydrocarbon source rocks if successful oil expulsion occurs. These findings underscore the need to take into account the distinctive characteristics of carbonate source rocks when developing strategies for hydrocarbon exploration and production.

Seasonal trends and retention of polycyclic aromatic compounds (PACs) in a remote sub-Arctic catchment

Atmospheric deposition is the most dominant source of polycyclic aromatic hydrocarbons (PAHs) in remote and pristine areas. Despite low bioaccumulation potential, PAHs and their persistent transformation products (PAH-derivatives) are chemicals of concern as they can harm human and animal health through chronic low dose exposure. In this study, atmospheric deposition fluxes of polycyclic aromatic compounds (PACs) were measured on a seasonal basis (3-month periods) from 2012 to 2016 in a remote subarctic forest catchment in northern Europe. The target PACs included 19 PAHs and 15 PAH-derivatives (oxygenated, nitrogenated, and methylated PAHs). The deposition fluxes of ƩPAHs and ƩPAH-derivatives were in the same range and averaged 530 and 500 ng m2 day−1, respectively. The fluxes were found to be higher with a factor of 2.5 for ƩPAHs and a factor of 3 for ƩPAH-derivatives during cold (<0 °C) in comparison to warm (>10 °C) periods. PAHs and PAH-derivatives showed similar seasonal patterns, which suggests that these two compound classes have similar sources and deposition mechanisms, and that the source strength of the PAH-derivatives in air follows that of the PAHs. The terrestrial export of PACs via the outlet of the catchment stream was estimated to be 1.1% for ƩPAHs and 1.7% for ƩPAH-derivatives in relation to the annual amounts deposited to the catchment, which suggests that boreal forests are sinks for PACs derived from the atmosphere. Some individual PACs showed higher export than others (i.e. chrysene, cyclopenta(c,d)pyrene, carbazole, quinoline, and benzo(f)quinoline), with high export PACs mostly characterized by low molecular weight and low hydrophobicity (2–3 benzene rings; log Kow<6.0).

Lithofacies and depositional settings of Mesoproterozoic shales: Insights from the ∼1.65 Ga Chuanlinggou Formation, Yanliao Basin, North China Craton

Precambrian black shale has become a significant trend in petroleum exploration, and the Chuanlinggou Formation is the oldest potential hydrocarbon source rock deposit in the North China Craton. The Mesoproterozoic was a unique transitional stage in the evolution of the environment and life in Earth's history. Research on lithofacies and depositional settings in this stage has important scientific and oil and gas exploration significance. Outcrop observations, thin sections, and elemental and organic geochemical analyses were used to study the mineralogy, sedimentary structures, lithofacies assemblages and their relationships with the depositional environment. Three endmembers (silicate, carbonate and clay minerals) based on X-ray fluorescence were employed to establish the lithofacies classification suitable for the Chuanlinggou Formation in the Yanliao Basin. The lithofacies of the Chuanlinggou Formation were classified into six types, including calcareous mudstone, siliceous/calcareous mixed mudstone, argillaceous/siliceous mixed mudstone, silicate-rich argillaceous mudstone, clay-rich siliceous mudstone and siliceous mudstone. Four lithofacies assemblages (LAs) were identified according to the integrated lithofacies analysis from the bottom to the top of the section. Lithofacies assemblages 1 and 2 (LA1 and LA2), which were deposited in deep subtidal to shelf environments, have high petroleum potentials and are advantageous lithofacies assemblages for organic matter accumulation. The black shale developed early rift may not be as favorable as in the late rift, while the siliceous shale developed in the continental shelf-slope is a favorable lithofacies. A comprehensive cognition of the LA and depositional settings of the Chuanlinggou Formation might provide guidance for further petroleum exploration and sedimentary environments in the Mesoproterozoic.

The Health Risk and Source Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in the Soil of Industrial Cities in India

Industrial areas play an important role in the urban ecosystem. Industrial site environmental quality is linked to human health. Soil samples from two different cities in India, Jamshedpur and Amravati, were collected and analyzed to assess the sources of polycyclic aromatic hydrocarbons (PAHs) in industrial areas and their potential health risks. The total concentration of 16 PAHs in JSR (Jamshedpur) varied from 1662.90 to 10,879.20 ng/g, whereas the concentration ranged from 1456.22 to 5403.45 ng/g in the soil of AMT (Amravati). The PAHs in the samples were dominated by four-ring PAHs, followed by five-ring PAHs, and a small percentage of two-ring PAHs. The ILCR (incremental lifetime cancer risk) of the soil of Amravati was lower compared to that of Jamshedpur. The risk due to PAH exposure for children and adults was reported to be in the order of ingestion &gt; dermal contact &gt; inhalation while for adolescents it was dermal contact &gt; ingestion &gt; inhalation in Jamshedpur. In contrast, in the soil of Amravati, the PAH exposure path risk for children and adolescents were the same and showed the following order: dermal contact &gt; ingestion &gt; inhalation while for the adulthood age group, the order was ingestion &gt; dermal contact &gt; inhalation. The diagnostic ratio approach was used to assess the sources of PAHs in various environmental media. The PAH sources were mainly dominated by coal and petroleum/oil combustion. As both the study areas belong to industrial sites, the significant sources were industrial emissions, followed by traffic emissions, coal combustion for domestic livelihood, as well as due to the geographical location of the sampling sites. The results of this investigation provide novel information for contamination evaluation and human health risk assessment in PAH-contaminated sites in India.

Higher allochthonous organic carbon increases polycyclic aromatic hydrocarbon concentration whereas fossil fuel combustion alters the composition: Evidence from a eutrophic plateau lake in southwest China

Understanding the source of polycyclic aromatic hydrocarbons (PAHs) is crucial for determining their structural, degradational, and burial characteristics in lake sediments. Here, we used a sediment core to determine the changing sources and burial characteristics of 16 PAHs from Dianchi Lake, southwest China. The ∑16PAH concentrations ranged from 105.10 to 1248.05 ng g−1 (448.97 ± 351.25 ng g−1), exhibiting a sharp increase since 1976. Our results showed that the depositional flux of PAHs has increased by approximately 3.72 times over the past 114 years (1895–2009). The C/N ratio, stable isotopes (δ13Corg and δ15N), and n-alkanes data all indicated that allochthonous contributors of organic carbon have substantially increased since the 1970s, playing an important role in the increase in sedimentary PAHs. Positive matrix factorization indicated that petrogenic sources, coal and biomass combustion, and traffic emissions were the main sources of PAHs. The relationships between PAHs from different sources and total organic carbon (TOC) varied with the sorption characteristics. The effect of TOC on the absorption of high-molecular-weight aromatic PAHs from fossil fuels was significant. A higher risk of lake eutrophication is accompanied by higher allochthonous organic matter imports, which might stimulate an increase in sedimentary PAHs through algal biomass blooms.

Delineation and quantification of effective source rocks using 3D geological modeling in a lacustrine basin

The identification and quantification of effective source rocks are critical for hydrocarbon exploration, but traditional methods have limitations in lacustrine basins due to their complexity and heterogeneity. For example, geochemical analysis is constrained by the number and distribution of samples, well logging methods can only reflect local information, and seismic inversion methods are limited by the quality and resolution of data. We propose a geological modeling approach that combines geophysical techniques and geological and geochemical data to delineate effective source rocks and quantify hydrocarbon resource potential. The workflow includes mudstone classification, geochemical data analysis, building predictive models, constructing 3D geological models, filtering effective source rocks, and basin simulation. Taking the Fushan Depression, South China Sea, as an example, we estimate the total volume of effective oil source rocks at 323.48 km3 and effective gas source rocks at 67.43 km3, and identify favorable areas for conventional and unconventional hydrocarbon exploration. The results demonstrate that our proposed approach enables precise delineation of the spatial distribution of effective hydrocarbon source rocks and quantification of their potential for hydrocarbon generation and expulsion. Our study constitutes a reference case for assessing effective source rocks in other lacustrine basins due to the successful integration of multiple available of data and its practical applications.

Abundance and sources of particulate polycyclic aromatic hydrocarbons and aromatic acids at an urban site in central China

We conducted a simultaneous field study of PM2.5-bound particulate polycyclic aromatic hydrocarbons (PAHs) and aromatic acids (AAs) in a polluted city Zhengzhou to explore the concentration, sources and potential conversion pathways between PAHs and AAs in different seasons. The average concentrations of PM2.5, 28PAHs and 8AAs during the sampling period were 77 µg/m3, 75 ng/m3, and 283 ng/m3, respectively. The concentration of both 28PAHs and 8AAs were highest in winter and lowest in summer with ratios of 6.3 and 2.3, respectively. PAHs with 5–7 rings were the main components of PAHs (52%), followed by 4 rings PAHs (30%) and 2–3 rings PAHs (18%). According to the source appointment results obtained by positive matrix factorization, the main sources of PAHs were combustion and vehicle emissions, which account for 37% and 34%, respectively. 8AAs were divided into three groups, including four benzene dicarboxylic acids (B2CAs), three benzene tricarboxylic acids (B3CAs) and one benzene tetracarboxylic acid (B4CA). And interspecies correlation analysis with PM2.5 source markers were used to investigate potential sources. Phthalic acid (o-Ph) was the most abundant specie of 8AAs (157 ng/m3, 55% of 8AAs), which was well correlated with sulfate. Meanwhile, B3CAs and B4CA were highly correlated with sulfate and weakly correlated with levoglucosan, suggesting that secondary formation was their main source. As logical oxidation products of PAHs, o-Ph and B3CAs showed good correlations with a number of PAHs, indicating possible photochemical oxidation pathway by PAHs. In addition, O3, NO2, temperature and relative humidity have positive effects on the secondary formation of B3CAs.

Geochemical characteristics and organic matter enrichment of the lower cretaceous dolomite-rich interval in the Bayindulan sag, Erlian basin, northern China

A dolomite-rich interval was found in the Lower Cretaceous, Bayindulan Sag. Based on organic and inorganic geochemical data, the hydrocarbon source rock potential of this dolomite-rich interval and the factors that control organic matter enrichment were investigated. This dolomite-rich interval has TOC values ranging from 0.54% to 9.64% (average = 3.51%) and HI values varying from 263 to 974 mg HC/g TOC, suggesting good to excellent source rocks whose organic matter is dominated by type I/II1 kerogens. The dominance of short-chain and medium-chain n-alkanes (n-C16 to n-C23) in the n-alkane distribution of the extracted organic matters in the dolomite-rich interval implies that the planktonic organic matters acted as the dominant inputs for the dolomite-rich interval, with a minor contribution from higher plants. The low Pr/Ph values suggest a strongly reducing environment favoring the preservation of organic matters. The high amount of gammacerane indicates water stratification during deposition time, which also helps to maintain the strongly reducing conditions in the bottom water. Meanwhile, REE and trace elements indicate that the dolomite-rich interval is closely related to the exhalative hydrothermal events, and the upwelling hydrothermal fluids provided abundant nutrients into lake water, resulting in the bloom of aquatic organisms. Overall, the strongly reducing depositional environments, the strong stratified-waterbody and the hydrothermal fluids jointly control the organic matter enrichment in the dolomitic interval.

Distribution characteristics of organic matter in the Fengcheng Formation in Mahu Sag, Junggar Basin: implications for hydrocarbon generation model in alkaline lacustrine deposition

Alkaline lacustrine deposits are known for their high primary productivity, unique aquatic environments, and sedimentary patterns, which are conducive to the formation and preservation of organic matter. Consequently, related source rocks have significant hydrocarbon generation potential. The study of hydrocarbon source rocks in the Fengcheng Formation of the Mahu Sag in the Junggar Basin serves as a good example for understanding organic matter enrichment and hydrocarbon generation characteristics of such alkaline lacustrine deposits source rocks. However, the characteristics of organic matter and hydrocarbon generation model in the source rocks of Fengcheng Formation lack systematic research, thus hindering exploration planning and favorable area selection. In this study, analysis of mineral content based on X-ray diffraction and organic geochemical analysis were employed, along with systematic observations of bio-precursor types under fluorescence microscopy. Based on mineral identification and quantitative statistics, the Fengcheng Formation was classified into three zones according to different alkaline mineral assemblages: an inner zone dominated by sodium carbonate minerals, a transitional zone with higher borosilicate mineral content, and a marginal zone characterized by abundant calcite deposition. The inner zone is characterized by the presence of lamalginite and telalginite, which are influenced by high pH values and changes in water depth, and exhibit high maturity characteristics. The transitional zone exhibits high total organic carbon (TOC) values, with predominantly type I and type II1 kerogen. Under fluorescence, the main components were observed to be lamalginite and telalginite, with their distribution being influenced by high salinity and ash supply. The marginal zone has relatively lower TOC than the previous two zones, which is dominated by type II2 kerogens, and contains a certain quantity of terrigenous inertinite supply. The hydrocarbon generation patterns of lamalginite and telalginite are consistent with the bimodal efficient hydrocarbon generation model observed in the source rocks of Fengcheng Formation, revealing the unique hydrocarbon generation model of organic matter in alkaline lacustrine source rocks. This research has significant implications for the exploration strategy of the alkaline lacustrine deposits in the Fengcheng Formation and similar oil- and gas-bearing basins.

North Barents Composite Tectono-Sedimentary Element

Abstract The North Barents Composite Tectono-Sedimentary Element could represent a prosperous petroleum province in the Arctic, with several large basins, platforms and highs identified. The sedimentary succession ranges from the Late Paleozoic and continues throughout most of the Mesozoic. Terrestrial sediments of the Billefjorden Group (Famennian–Visean) are likely to be present, and are overlain by evaporites and carbonates of the Gipsdalen Group (Serpukhovian–Late Artinskian). Most of the Triassic is dominated by deposits from a huge prograding deltaic system building out from the south, SE and east, becoming successively younger towards NW. The system was primarily sourced from the Urals but also partly from mainland Norway and, most probably, from Taimyr. The progradation started in the Late Permian and reached Svalbard in the Early Carnian. The entire delta system was flooded during the regional Early Norian transgression, resulting in the deposition of marine shales of the Flatsalen Formation (Svalbard) and the time-equivalent Akkar Member of the Fruholmen Formation (Barents Sea). The Cretaceous and the Paleogene are, respectively, comprehensively and completely eroded. During the Pliocene–Pleistocene, the entire Barents shelf was a site of repeated glaciations, resulting in extensive erosion. Hydrocarbon source rocks occur at several stratigraphic levels from the Carboniferous to the Jurassic, of which the most important is assumed to be the Lower–Middle Triassic Steinkobbe/Botneheia Formation. The Upper Jurassic Hekkingen Formation, where present, is likely to be immature across the whole area. Potential reservoir rocks are Permian carbonates and siliciclastic rocks of Carboniferous and Mesozoic age.

Synthesis of Multi Wall Carbon Nanotubes based Electronic Sensors for Internet of Things (IoT)

The Internet of Things (IoT) refers to advance devices other than computers that are connected to the Internet and can send and receive information. IoT is a new paradigm that has transformed traditional lifestyles into high-tech ones. It is the notion of a ubiquitous computer environment in which custom-sized electronics are effortlessly implanted into common things. Electronic sensors at the heart of the IoT detect physical/environmental occurrences, translate these measurements into electrical signals, and wirelessly transfer the data for remote computation. Indeed, the 5G communication and cloud computing stimulate the research in applications of carbon nanotubes in electronic devices. CNTs have demonstrated potential applications in electronics, biosensing, artificial intelligence and the Internet of ThingsIn present study, we report the synthesis of Multi Wall Carbon Nanotubes (MWCNTs) by Chemical Vapour Deposition (CVD) at 600C on Zinc Oxide (ZnO) catalyst coated silicon substrate by thermal evaporation technique. As-grown MWCNTs are characterized by Scanning Electron Microscope (SEM). High density growth of MWCNTs have been confirmed by SEM image. Catalyst nanoparticles play very important roles in the decomposition of the hydrocarbon source and to provide nucleation site for growth of MWCNTs. High MWCNT density is required for IoT-based sensors with high performance, sensitivity, selectivity, and distant sensing. Because IoT not only provides services but also creates massive amounts of data. Hence, this study would be helpful for the next generation 5G communication and cloud computing stimulate to enhance living style.

Tilt angle filter effect on noise cancelation and structural edges detection in hydrocarbon sources in a gravitational potential field

Noise cancelation is the process done to remove out-of-range anomalies and make better edge boundaries interpretation. One of the most challenging issues in describing gravitational maps is separating the anomalies related to shallow sources from the deep ones. Furthermore, Existing noise can make it arduous to separate shallow blurred boundaries. In this study in SE Iran, gravitational surveying was carried out in shallow areas from the west of Qeshm to the Hormuz islands in a regular network with a distance of one kilometer. The range of gravitational Bouguer was -297 to -330 mGal. Modeling and determining geometrical parameters revealed five negative anomalies from salt penetration. The residual gravity was computed by deducting gravitational effects related to deep sources from measured gravitational data. Correspondingly, estimating the boundary and edge of the subsurface masses will be better than local filters, and anomalies will be highlighted with more intensity. Furthermore, three major fault systems in the Zagros basin were determined as the primary origin of activity and expansion of Hormuz salt. Sensitivity analysis was employed utilizing analytical signals and maps of tilt angle filtering, which both revealed the same satisfying results of -297 to -330 mGal. In this article, the effect of the tilt angle local phase filter on a synthetic model was accomplished through numerical coding. As a result, Total Horizontal Derivative (THDR) provides location of salt intrusion in Qeshm area; whereas the best image of salt intrusion, in terms of feature edge illumination, presented by Analytical signal of residual gravity map.

Long-lived paleo-uplift controls on Neoproterozoic–Cambrian black shales in the Tarim basin

Neoproterozoic–Cambrian black shales are one of the most important hydrocarbon source rocks worldwide, including in the Shunbei and Fuman regions in the Tarim Basin, China. However, the hydrocarbon generation from these shales is complex, with liquid petroleum found in reservoirs at depths of 6000–8000 m. Based on drilling, seismic, and well testing data, the ultra-deep tectonic evolution of the northern Tarim Basin, and its effects on hydrocarbon generation from black shales were investigated. During the Neoproterozoic, the northern Tarim Basin was filled with rift and passive continental margin sedimentary rocks between the north and central Tarim paleo-uplifts. A sequence of lower Cambrian black shales was developed on the slope around the paleo-uplifts over a wide area, which are thick and have high contents of total organic carbon. Even after multiple stages of tectonism, including the Caledonian, Hercynian, Indosinian, Yanshanian, and Himalayan orogenies, the north (Tabei) and central paleo-uplifts were preserved. The Caledonian, Hercynian, and Himalayan orogenies were the main periods of hydrocarbon generation. Four hydrocarbon-generation models were established, which are the Tabei-, Bachu-, Tazhong-, and Tadong-types. The current Ro values of the Tabei-type black shales are 1.0%–1.5%, whereas those of the Bachu-, Tazhong-, and Tadong-type black shales are >2.0%. Due to the long-lived paleo-uplifts and short-lived deep burial during the Himalayan Orogeny, the Tabei-type black shale is in the oil and early gas generation stage, which obviously differs from the over-mature Cambrian and Ordovician black shales in South China. Therefore, the long-lived paleo-uplifts not only affected the deposition and distribution of black shale, but also hydrocarbon generation processes and the depth limit of active source rock. The thermal evolution of black shale in the ultra-deep Tarim Basin requires further investigation.