Hydrocarbon Source Research Articles

Mineralogical and elemental geochemical characteristics of Taodonggou Group mudstone in the Taibei Sag, Turpan–Hami Basin: implication for its formation mechanism

Abstract. Organic matter types in the Taodonggou Group mudstone exhibit significant differences with depth. In order to understand the formation mechanism of this special phenomenon, we analyzed the mineralogy and geochemistry of the mudstone, as well as the source rocks, depositional environment, and depositional processes of the Taodonggou Group. Based on this, we have gained the following insights. (1) The Taodonggou Group mudstone was deposited in an intermediate-depth or deep, dysoxic, freshwater–brackish lake environment under warm and humid paleoclimatic conditions. The input of terrestrial debris was stable, but the sedimentation rate was slow. In addition, the sedimentation in the middle stage was influenced by hydrothermal activities, and the changes in the depositional environment corresponded to variations in organic matter types. (2) The source rocks of the Taodonggou Group mudstone are mainly andesitic and feldspathic volcanic rocks. Sediment sorting and recycling were weak, and hydrocarbon source information was well preserved. The tectonic background of the source area was a continental island arc and an oceanic island arc. Furthermore, changes in the provenance of the Taodonggou Group also had a significant impact on the variations in organic matter types. (3) The sedimentation of the Taodonggou Group involved both traction and gravity flows. The variations in source area, depositional environment, and depositional processes during different depositional periods led to changes in the organic matter types of the Taodonggou mudstone. (4) Based on the depositional environment, provenance, and depositional processes, the sedimentation of the Taodonggou Group can be divided into three stages. In the early stages, the sedimentation center was in the Bogda area. At this time, the Bogda Mountain region was not exposed, and the depositional processes inherited the characteristics of early Permian gravity flow sedimentation, resulting in the widespread deposition of a series of high-quality Type III source rocks in the basin. In the middle stage of the Taodonggou Group sedimentation, the sedimentation center gradually migrated to the Taibei Sag. During this period, the Bogda Mountain region experienced uplift and hydrothermal activity, and the depositional processes gradually transitioned to traction flows, resulting in the widespread deposition of a series of Type II source rocks in the basin. In the late stage of the Taodonggou Group, the uplift of the Bogda Mountain region ceased, and the sedimentation center completely shifted to the Taibei Sag. Meanwhile, under the influence of gravity flows, the organic matter types of the Taodonggou mudstone changed to Type III.

Organic facies and hydrocarbon source rock potentiality of the Neogene succession in the Central South Mediterranean, offshore Nile Delta Basin, Egypt

Neogene succession in the offshore Nile Delta region is essential to the hydrocarbon petroleum system. Up to date, little is known about the nature and distribution of organic matter and its potential to generate hydrocarbon. This potential is tested through extensive palynofacies and organic geochemical analyses in a new approach in this region. Based on the palynofacies analysis, the samples from NDOB-1 and Baltim-1wells are discriminated into four types using the statistical application of cluster and principal component analyses. These four types are distal-High Oxic type A, proximal-suboxic type B, proximal-dysoxic type C, and distal-oxic type D. In addition, the analysis leads to identifying the proximal-distal and oxygen depletion trends based on the values of the principal component analysis (axis 1). This palynofacies analysis is used as an environmental framework for hydrocarbon source rock evaluation. This evaluation is integrated with the organic geochemical parameters by pyrolysis (Rock-Eval and gas chromatography) and spectroscopic (Fourier Transform Infrared) methods. This study reveals that the dominant kerogen types are IV (inert) and III (gas-prone) which are remarked by the opaque and brown translucent phytoclasts palynofacies types A and D, respectively. Kerogen type II is presented in a minor abundance in palynofacies types B and C that are distinguished with AOM. However, kerogen type II organic matter is much diluted with kerogen type IV and III, leading to poor to fair organic geochemical quality (S2 and hydrogen index). Both wells' maturity levels are detected within the Kafr El Shiekh Formation. Nevertheless, the poor hydrocarbon source rock quality becomes important if considered with the volume and thickness of the Neogene sediment, as indicated by the source potential index that has a cumulative value of 2.5 t HC/m2 in NDOB-1 well and 2.8 t HC/m2in Baltim-1 well. These values are comparable to some of the prolific hydrocarbon fields in other places.

Use of molecular composition and compound-specific isotope analysis for source appointment of PAHs in sediments of a highly industrialized area

This study utilized both conventional molecular analysis and compound-specific isotopic techniques to identify the sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Ulsan Bay, South Korea. The concentrations of 15 traditional and 11 emerging PAHs were determined in sediments from 21 source sites and 26 bay sites. The concentrations and compositions of traditional and emerging PAHs varied significantly, even at sites close to the source areas. The results obtained from diagnostic ratios and the positive matrix factorization model for source identification were inconsistent in adjacent source areas. The δ13C profiles of PAHs, such as phenanthrene (Phe), fluoranthene (Fl), pyrene (Py), and benz[a]anthracene (BaA) in the sediments showed distinct features depending on the surrounding sources. In urban sediments, lighter δ13CPhe values were observed (mean: −25.1‰), whereas relatively heavier values of δ13CPy were found in petroleum industry areas (mean: −23.4‰). The Bayesian isotope mixing model indicates that the predominant source of PAHs in Ulsan Bay sediments was the petroleum industry (45%), followed by the non-ferrous metals industry (30%), automobile industry (18%), and urban areas (6.3%). These results demonstrated the utility of stable isotopes in assessing the sources and contributions of PAHs in small-scale regions. However, there are still limitations in compound-specific isotope analysis of PAHs, including insufficient end-members for each source, difficulty in analysis, and the influence of non-point sources; thus, further study is needed to expand its application.

Modeling environmental sensitivity and risk assessment of PAHs in sediments along two marine coastal areas in Egypt

Modeling the environmental sensitivity index (ESI) is vital in the planning and management processes, especially along the coastal areas. The main objectives of the study were to define the main sources of polycyclic aromatic hydrocarbons (PAHs), establish an ESI model, and measure the risk of PAHs on humans and the environment using various equations. The methodology of the research involved analyzing PAHs according to the EPA 550 methodology in sediments of the coastline in two important coastline areas in Egypt, namely the Gulf of Suez and the Mediterranean Sea, modeling the sensitivity of PAHs using ArcGIS 10.5 by integrating different physical, biological, and land use/cover factors, identifying the sources, and performing a risk assessment. Nine sediment samples were collected from each area. The produced sensitivity map could explain the highly sensitive areas along the Mediterranean Sea and Gulf of Suez coastlines (especially areas that were near drains' outlets, industrial sites, and sea ports). The highest mean PAH concentrations were Acenaphthylene and Fluorine in the Mediterranean Sea and Suez Gulf, respectively. It's obvious that the individual PAH concentrations were within the ERL, ERM, and PEL threshold limits, indicating no adverse biological impacts. The ratios of BaA/BaA + Chy, Flu/Flu + Py, and Ant/Ant + Phe gave an indication that most PAH sources were petrogenic (63.64%) and others (36.36%) were from petroleum combustion. The principle component analysis (PCA) indicated a diverse correlation among the isomer ratios and LU/LC activities. The carcinogenic risk values were in the very low category (<10−6) for both children and adults. The most significant contributors to carcinogenicity were IP and BkFlu in the Mediterranean Sea and Suez Gulf, respectively. Increasing sources of carbon in seawater, especially with climatic change, may impact the aquatic environment and have impacts on organisms and coral reefs. So it is highly recommended to keep shorelines and seawater free of oil spillage activities along the coastal areas or take actions towards this.

Analysis of the Spatial Distribution Characteristics of Crude Oils with Different Freezing Points and the Genetic Mechanism of High-Freezing-Point Crude Oils in the Dongying Sag.

The freezing point of crude oils is an important factor affecting the process of exploration, development, and transportation of crude oils. In the Dongying Sag, the freezing point of crude oils varies greatly in space, and high-freezing-point crude oils have been found in many structural belts. The freezing point of crude oils in the Dongying Sag is generally high, ranging from -40 to 80 °C. The distribution of high-freezing-point crude oils in the Dongying Sag is scattered, and they have been found at different depths, layers, and structural belts, with relatively more occurrences in specific areas. Based on the relationship between the wax content and the resin + asphaltene content, the high-freezing-point crude oils in the Dongying Sag can be classified into three types (type A, type B, and type C). Type A, type B, and type C high-freezing-point crude oils are mainly found in the gentle slope zone, depression zone, and uplift zone, respectively. The contents of wax and resins + asphaltenes in crude oils are the key factors controlling the freezing point of crude oils in the Dongying Sag. Oil source correlation using biomarkers and n-alkane carbon isotopes demonstrates that different types of high-freezing-point crude oils are generated from different source rocks, indicating that the source of crude oils is not the only factor controlling the freezing point of crude oils. The hydrocarbon-generating parent material of hydrocarbon source rocks developed in different depositional environments of the Dongying Sag is generally characterized by the dominance of bacteria and algae and is supplemented by terrestrial higher plants. This lays the material foundation for the formation of waxes during the maturation of hydrocarbon source rocks. The change of temperature and pressure conditions during the process of oil expulsion from source rocks and migration in the carrier bed will lead to phase fractionation and composition changes of oils, thus forming type A freezing point crude oils in the slope zone and type B freezing point oils in the depression zone. The increase in resin and asphaltene content caused by biodegradation and water washing in shallower buried oil reservoirs is the reason for the formation of type C high-freezing-point crude oils. The research results indicate that the organic matter composition and hydrocarbon alteration during migration and accumulation jointly control the formation of high-freezing-point crude oils in lacustrine basins. The extensive input of terrestrial organic matter into the source rocks of the lacustrine basin laid the foundation for the formation of high-freezing-point crude oils, and the migration fractionation and biodegradation of the crude oils further promoted the formation of high-freezing-point crude oils.

Studies on the Source and Phase Characteristics of Oil and Gas: Evidence from Hydrocarbon Geochemistry in the Pingbei Area of Xihu Sag, the East China Sea Shelf Basin, China

The Pingbei area is the main accumulation area of oil and gas in the Xihu Sag. The phase characteristics of oil and gas in this area are complex, and the understanding of their genesis is still unclear. In this paper, based upon discussions of crude oil and natural gas geochemical data, integrated with local geological features, we discuss the sources, migration, and phase state characteristics of oil and gas in the Pingbei area of the Xihu Sag. The study results show that the crude oil and natural gas in the Pingbei area are coal-derived and the oil and gas produced by the humic organic matter during the mature stage. The oil and gas source correlation showed that crude oil and natural gas have good affinity with the Eocene Pinghu Formation (PH) coal-bearing source rocks. Crude oil has the characteristics of near-source accumulation and short-distance migration while natural gas is supplied from a dual source: the coal-derived hydrocarbon rocks of PH in the deep part of the study area, supplemented by the coal-derived hydrocarbon rocks of PH on the bottom of the slope, and adjacent hydrocarbon-bearing sub sag. The distribution characteristics and geochemical migration indices of hydrocarbon show that the oil generated from the hydrocarbon source rocks of PH in the deep Pingbei area mainly migrates vertically along the fault connecting the reservoir and the source rocks to the trap, where it accumulates, while the natural gas exhibits deep and large faults that mainly migrate vertically, supplemented by its lateral migration along the composite transport system composed of faults and sandstone layers in the slope zone. The whole area presents the phase characteristics of “upper oil and lower gas, west oil and east gas”. The mechanisms of produced-exhausted and geochromatographic effects (PGE), as well as evaporative fractionation (EF) and phase-controlled migration fractionation (PMF), result in the obvious discrepancy of hydrocarbon’s properties on the vertical profiles.

Diagenesis of the Marinoan cap dolostone, Southern Amazon Craton: An unconventional petroleum system in the evolution of the Araras-Alto Paraguai Basin

The post-snowball Earth world favors the development of hydrocarbon source rock intimately linked to periods of post-glacial marine transgression generating important potential petroleum plays. In the Southern Amazon Craton, hydrocarbons occur in one of the most spectacular examples of post-Marinoan cap carbonate, related to the mid-Ediacaran to Early Cambrian (c. Post 635 Ma) interval associated with the early stabilization of the Gondwana Supercontinent. The Puga cap carbonate consists of the basal portion of the Araras Group exposed in the Araras Alto-Paraguai Basin inserted as a reservoir in an unconventional petroleum system. The cap dolostone overlies diamictites and is overlaid by bituminous limestone and shales (source-rock), and dolostone in the top of a 700 m-thick depositional sequence. The cap dolostone has a diachronic relation with the limestone beds typifying as a secondary reservoir characterized by bitumen-filled fenestral and interpeloidal porosity. The upper dolostone has a closed framework and acts as sealing rocks. This study aims to establish paragenesis sequence and decipher its control on the quality of the cap dolostone as a microbialites-dominated reservoir. Drill core and outcrop samples were analyzed using microfacies, scanning electron microscopy, and cathodoluminescence to unravel the diagenetic history. Aftermath, the Marinoan events favored dolomuds precipitation in the shallow platforms, preserving primary porosity and permeability reduced by early gypsum cementation during oversaturation events. Other destructive processes, such as mechanical and chemical compaction (e.g., stylolites) and authigenesis of pyrite and low-Mg ferroan calcite cementation, occurred during burial and mesodiagenesis. The low permeability restricts hydrocarbon migration concentrated in the upper cap dolostone, and the early cementation increases the potential for preserving these carbonate deposits. Hydrocarbon maturation was triggered during the burial and uplift of the Araras-Alto Paraguai basin. The cementation phases described here enhance our understanding of the mechanisms behind syndepositional diagenesis in microbially-induced reservoirs. This study uses proxies associated with diagenetic studies to quantify the quality of microbially induced dolostone reservoir linked to the evolution of the Neoproterozoic unconventional petroleum system. In addition, this conception will promote a guide for future exploration and understanding of petroleum plays and suggests a possible Precambrian source rocks component of traditional Phanerozoic Petroleum systems in the central part of Brazil.

Source Rock Evaluation of Hydrocarbons in Deep-Water Offshore Areas Based on a BP Neural Network

Due to the lack of drilling data and poor quality of seismic data in deep-water offshore areas, conventional methods cannot effectively predict the total organic carbon (TOC) content. In this paper, the BP neural network method is used to predict the TOC of the strata overlying the target layer, which adds to the TOC information in the study area. Then, the highest TOC value of the strata overlying the target layer is used to select the most sensitive seismic attributes. Finally, the sensitive seismic attributes are used to evaluate the source rocks with no or few wells. A set of TOC prediction technology flows is established for TOC combined with seismic attributes under the condition of no wells and few wells in deep-water areas. The application example shows the reliability of TOC prediction by this technical process, and the study has a certain reference significance for the evaluation of hydrocarbon source rocks in offshore deep water.

Distribution characteristics of Sulfur, phosphorus and trace elements in crude oil and source rock chloroform asphaltenes “a” and description of an oil-bearing system in the Ordos Basin

The multiple sets of source rocks and crude oil biomarkers in the Yanchang Formation have no clear results of oil-source correlation. Chloroform asphaltenes “A” was extracted from the source rocks and crude oils and microwave digested, and its elemental composition analyzed by ICP–MS for oil-source correlation. The S/P and the ratio of light and heavy rare earth elements are oil-source correlation indices. The total amount of transition metals may be useful for oil-oil and oil-source correlation using cluster analysis techniques, but redox parameters are not effective for oil-oil and oil-source correlation in lacustrine oil. It is proposed that the oils in the Longdong area and Jiyuan area all come from the Chang 7 source rocks. The oils in the Shanbei area are derived from the Chang 9 source rocks in the area and the Chang 7 source rocks in Longdong. The Chang 10 oils in the Shanbei area and Chang 9 oils in the middle Lake Basin appear to come from other sources. Trace elements can provide valuable clue on the hydrocarbon sources and oil migration patterns of the Yanchang Formation, which is of great significance in the search for possible deep oil-bearing systems in the Shanbei area.

Towards 3D Lithium-Ion Full Cells Using Honeycomb-Patterned Carbon Nanotube Forests

The growing demand for electric vehicles and portable electronics has created a significant interest in the scalability, recyclability, and economics of both traditional and emerging battery technologies. Although lithium-ion batteries (LiB) are approaching their theoretical energy density, they will remain a widespread and promising technology as alternative (e.g., Li-metal) chemistries and solid-state architectures are still in relatively early stages of commercial scale-up. Yet, LiB performance can be improved by redesigning the cell geometry to move from planar to 3D designs. 3D designs enable the use of thick electrodes to increase the cell level energy density by minimizing the volume and mass contributions of inactive components, such as current collectors or separators. The rationale for 3D full cell designs lies in the relationship between electrode geometry and the respective energy and power densities. When compared to a planar design, 3D architectures allow for a higher surface area for the same volume and footprint of cell. As a result, a given volume of active material can be distributed with a lower electrode feature thickness. Compared to a planar electrode of a given energy density, the lower thickness contributes to a quadratic improvement in power density which decouples the inherent tradeoff between the energy density and power density that is experienced by planar cells. This suggests that a high aspect ratio 3D cell would give greater power per footprint area while retaining high areal energy density. To meet these criteria, the materials used in fabricating 3D cells must be processable in a manner enabling precise control over geometry, layer conformality and porosity.We are developing thick 3D “honeycomb” full cells by starting with patterned, vertically aligned carbon nanotubes (VA-CNTs) as current collectors. CNTs are widely known to have high thermal and electrical conductivities, and to be mechanically durable; properties which make them an ideal scaffold for 3D cell development. VA-CNTs (“forests”) form by self-organization of CNTs during chemical vapor deposition (CVD) on substrates using common hydrocarbon sources (e.g., C2H2, C2H4). However, well-established CNT growth techniques utilize rigid non-conductive substrates, such as silicon wafers, which necessitates a transfer to a suitable substrate for electrochemical applications. Recently, we translated insights from CNT growth on silicon wafer substrates to grow CNT forests on thin metal foils (Cu) suitable for electrode fabrication. We did this by optimizing the moisture level within the CVD furnace, and using a thin-film stack that forms high-density nanoparticles upon annealing while preventing the poisoning of the Fe catalyst by diffusion of Cu. The resulting CNT forests can reach thicknesses over 350 μm and can be grown from patterned catalyst films having regular hole arrays with feature sizes as small as ~5 μm.Thick composite electrodes are then created by coating CNT forests with Si thin films by CVD. The inherent nanoporosity of the CNT forests (>95%) allows for precursor diffusion into the entirety of the forest cross-section and conformal coating of the individual CNTs. The CVD process is tuned to create dense electrodes with tailored Si loading that can range from ~10 to ~90 at.%. Half-cells using monolithic and honeycomb patterned Si-CNT electrodes (~250 μm tall), Li-metal foil, and a liquid electrolyte/separator combination have been cycled over a range of current densities, demonstrating the electronic connection between the deposited Si and Cu foil via the aligned CNTs. At low current densities and high Si loadings these honeycomb electrodes can exhibit large gravimetric (~1500 mAh/gSi) and areal (~12 mAh/cm2) capacities, with honeycomb Si-CNT composites exhibiting reduced capacity fading when compared to non-patterned electrodes.We continue by investigating these Si-CNT composites as a template for a 3D full cell design. In literature, the difficulty of producing 3D full cells comes from the need to produce high conformality electrolyte films that are pinhole free and which demonstrate sufficient ionic conductivity. To address this issue, we utilize an initiated chemical vapor deposition (iCVD) process to deposit conformal poly(hydroxyethyl methacrylate-co-ethylene glycol diacrylate) thin films on the high aspect ratio CNT forests. These copolymer films are doped with lithium salts to exhibit ionic conductivities on the order of ~10-6 to 10-5 S/cm, which is among the highest conductivities ever exhibited by conformal electrolyte technologies. To complete a full cell design, a slurry-based cathode will be infiltrated into the iCVD coated Si-CNT composite electrodes, from which we aim to assess the cycling behavior and compare the areal energy and power densities of non-patterned and honeycomb architectures.

Controls of the Sandbody Scale and Fault Throw on the Lithology and Composite Reservoir Formation in the Baoyunting Slope, East China Sea

Under the conditions of many faults, sandbodies, and hydrocarbon sources on the slopes of faulted basins where structural traps are scarce, only a few sandbodies are capable of forming hydrocarbon pools, while most sandbodies act as aquifers. This situation presents a challenge for predicting favorable hydrocarbon accumulation areas and understanding controlling factors. The Pinghu Formation reservoirs in the Baoyunting nose structure of the Xihu Sag in the East China Sea exemplify this characteristic. Among the 19 small-scale oil and gas reservoirs discovered in this area, 10 are faulted sandbody composite traps and 9 are lithological traps, while the majority of the remaining sand layers, especially the thick layers, act as aquifers, resulting in significantly lower accumulation probabilities compared to the adjacent northern and southern areas. We analyzed the relationship between the sandstone thickness and the amplitude through the 1-D forward modeling of wells and dissected the 3-D seismic event to obtain the planar distribution of a single sandbody. Further comprehensive research on fault sealing and kinetic reservoir formation processes suggests that the gas pool formation in this area is closely related to fault sealing and lateral oil and gas transport. A small fault-to-caprock ratio is beneficial for the sealing of mudstone caprocks, while a large fault-to-sand thickness ratio is beneficial for the lateral sealing of faults and the formation of fault–sand composite pools. The tidal microfacies sandbody has a small scale, poor lateral transport ability, and a low probability of gas reservoir formation. The barrier and delta front sandbodies have a large scale, good lateral transport, and a high probability of reservoir formation. Based on the above methods, favorable pool formation traps were identified in the area, and high-yield gas wells were drilled.

1D basin modeling and hydrocarbon generation potential of the Late Carboniferous Limburg Group formations, Northwest European Basin, Netherlands

The Carboniferous rock samples of the Limburg Group formations were studied to investigate the source rock characteristics and the hydrocarbon generative potential. The source rock samples have been collected representing four rock units from three different wells. These samples were analyzed using Rock-Eval pyrolysis results and measured vitrinite reflectance values, and also by generating a one-dimensional basin model of K1 Field. The total organic carbon in these samples varies from 0.31 to 83.56% with a mean of 37.68%, suggesting that Limburg Group formations have excellent potential as a source of hydrocarbons. Kerogen in the Limburg Group formations is type II-III and type III, generate gas prominently. The outcomes of thermal maturation by Tmax and measured vitrinite reflectance reveal that the examined Limburg source rocks are located in the mature zone. The burial and thermal history models show irregular trend patterns due to uplift, erosion, and non-deposition events that took place in the K1 field (where the structural element is Cleaver Bank High). For the Maurits Formation, the oil generation took place at 2011 m at 230.1Ma ago and the top of the gas window was encountered 217.8Ma ago at 2535 m, whereas for the Hospital Ground Formation, the top of the oil window was encountered 186.8Ma ago at 2404 m and the gas generation took place at 2404 m at 161.9Ma ago.

Paleoenvironmental characterization of the Ponta Grossa formation (Devonian) at the northwest border of the Paraná Basin, Brazil

Previously uncharacterized Devonian shale samples from the Ponta Grossa Formation (Paraná Basin) were collected from three outcrops in Mato Grosso (DA01 and DA02) and Mato Grosso do Sul (PG02) along the northwest of the basin. The depositional paleoenvironment and hydrocarbon source potential were assessed using Rock-Eval pyrolysis, saturate and aromatic biomarkers, and carbon isotope data. For the DA01 shales, poor total organic carbon (TOC) contents and low hydrogen index (HI) indicate a high predominance of type III kerogen. The biomarker analysis results suggest a transitional depositional paleoenvironment with a greater contribution of continental than marine organic matter, pointing to a regressive marine event. In DA02, the TOC contents ranged from 0.24 to 4.46%, with kerogen types II and III, S2 ranging from poor to good, HI ranging from 78 to 410 mg HC/g TOC, and biomarkers indicating a marine transitional environment and transgressive marine event. Shales from outcrop PG02 had the highest TOC contents, particularly at the top, with predominantly kerogen types II and III, S2 varying from low to excellent, and HI ranging from 100 to 350 mg HC/g TOC. Two types of paleoenvironments were identified based on the biomarkers of PG02: regressive at the base and transgressive in the middle and top of the outcrop. The DA01 outcrop was located at a more proximal position to the coast, the DA02 were at more distal position, while PG02 was located in a transitional position between DA01 and DA02. Ratios of C29αββ/(αββ+ααα) and 20S/(20S + 20R) steranes, the presence of unresolved complex mixture, and a higher proportion of polar compounds to the detriment of saturated and aromatic compounds indicated that the shales were immature for the generation of hydrocarbons. This study represents the first broad organic geochemical evaluation of the northwest Ponta Grossa Formation.

The High Arctic Large Igneous Province: first seismic-stratigraphic evidence for multiple Mesozoic volcanic pulses on the Lomonosov Ridge, central Arctic Ocean

We use seismic reflection data acquired by an over-winter expedition on drifting sea ice in the central Arctic Ocean to explore a possible spatial and temporal magmatic relation between the sub-bottom geology of part of the deep Arctic Ocean and the Mesozoic volcanic rocks found on the islands and the bordering continental shelf of Franz Josef Land and Svalbard. The new dataset from the North American segment (85–90°N) of the Lomonosov Ridge, central Arctic Ocean documents several Mesozoic volcanic pulses over a distance of c. 600 km along the ridge. This volcanism borders a domain of high magnetic field intensity over the adjacent Alpha Ridge in the deep basin where the magnetic source rocks and recent seismic reflection data indicate extensive Mesozoic magmatism. We suggest that the Mesozoic volcanism on the Lomonosov Ridge in its palaeo-position at the former continental margin north of Franz Josef Land and Svalbard spatially links the Mesozoic magmatic pulses of the continental High Arctic Large Igneous Province (HALIP) of polar Europe to volcanism on the adjacent Alpha Ridge in the deep Arctic Ocean. Increased input of heat to the upper crust on the Lomonosov Ridge enhanced maturation of hydrocarbon source rocks as manifested by the presence of gas or fluid escape pipes restricted to the area of volcanism.

Carboniferous to Early Permian tectono-sedimentary evolution in the western Junggar Basin, NW China: implication for the evolution of Junggar Ocean

The discovery of Carboniferous hydrocarbon source rocks in the Mahu-Shawan Sag has implied considerable exploration potential in the Carboniferous strata in the western Junggar Basin. However, controversy has long surrounded when and how the Junggar Ocean was eventually closed, leading to a poor understanding of the Carboniferous basin evolution and the continental growth of the Central Asian Orogenic Belt. We performed stratigraphic and geochronologic studies to establish the chronostratigraphic framework of the western Junggar Basin to better understand its tectonic-sedimentary evolution during the Carboniferous-Early Permian. Three tectonostratigraphic units in the southern West Junggar region have been identified as Early Carboniferous shallow-deep marine sequences, Late Carboniferous coast-shallow marine sequences, and Early Permian continental sequences. The Carboniferous strata are similar to forearc and backarc-rift sequences in the Western Fault Belt and the Mahu-Shawan Sag, respectively. The Lower Permian strata in the southern West Junggar region are all continental sequences. Seismic profiles indicate extensional settings in the early stage of Late Carboniferous and Early Permian but a compressional setting at the end of Late Carboniferous. Geochemical data have suggested a Carboniferous continental arc setting and an Early Permian within-plate extensional setting. Meanwhile, calc-alkaline arc magma migrated from the Zhongguai High to the Western Fault Belt at the end of the Late Carboniferous. Collectively, the tectonic-sedimentary evolution in the Carboniferous-Early Permian of the southern West Junggar region can be divided into three stages: 1) Early Carboniferous subduction, 2) Late Carboniferous slab roll-back, and 3) Early Permian intra-continental evolution stage. This model constrains the closure of the Junggar Ocean at the Late Carboniferous.

The Sources of Polycyclic Aromatic Hydrocarbons in Road Dust and Their Potential Hazard

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants (POPs) found in the environment, posing significant health concerns for the population. This research aimed to assess the PAH levels in road dust near bus stops, identify their sources, and evaluate potential health risks. The analysis involved the use of a gas chromatography–flame ionization detector (GC-FID) to measure PAHs and absolute principal component score-multiple linear regression (APCS-MLR) for source apportionment of PAHs. The results indicated that the measured PAHs concentrations in road dust ranged from 137.8 to 5813 ng g−1, with Indeno[1,2,3-c,d]pyrene having the highest PAHs concentrations. The study identified three main sources of PAHs such as oil spills, fuel combustion, and coal burning, determined through APCS-MLR modeling. Further analysis revealed that the aggregate incremental lifetime cancer risk (ILCR) for children and adults were 2.16 × 10−6 and 2.08 × 10−6, respectively. Additionally, the hazard index (HI) for children exceeded that of adults, suggesting greater vulnerability to the potential health effects of PAH exposure. The findings indicate that long-term exposure to PAHs may negatively impact lung function and increase the risk of cancer and skin diseases. As a result, it is crucial for the local government to implement effective measures aimed at improving fuel quality and promoting green public transportation within the city. These initiatives may help mitigate PAH emissions and safeguard public health.

Experimental Characteristics of Hydrocarbon Generation from Scandinavian Alum Shale Carbonate Nodules: Implications for Hydrocarbon Generation from Majiagou Formation Marine Carbonates in China’s Ordos Basin

The hydrocarbon source rocks of the marine carbonates of the Ordovician Majiagou Formation in the Ordos Basin are generally in the high-overmature stage and are, therefore, not suitable for hydrocarbon thermal simulation experiments. Their hydrocarbon generation potential and hydrocarbon generation characteristics are not clearly understood. Meanwhile, Nordic Cambrian carbonates are similar in lithology, parent material type, and sedimentary age, and are in the low evolution stage, which is suitable for hydrocarbon thermal simulation experiments. Therefore, in this study, we selected the Nordic carbonates for the gold tube thermal simulation experiment to analyze the content and geochemical characteristics of the thermal simulation products. The experimental results are also compared and analyzed with the characteristics of thermal simulation products of Pingliang Formation mud shale (contemporaneous with the Majiagou Formation) and Shanxi Formation coal (in the upper part of the Majiagou Formation), which are similar to the Majiagou Formation in the Ordos Basin. The results showed that the Nordic carbonate has different hydrocarbon production characteristics from the mud shale of the Pingliang Formation of the same parent material type, and although the hydrocarbon production yields of the two are not very different, the carbonate still produces methane at 600 °C. The hydrocarbon production yield of the Nordic carbonates is almost equivalent to that of type-II2 kerogen, indicating that the hydrocarbon production yield is not related to lithology and only to the organic matter type; however, the Nordic carbonate can produce a large amount of H2S. The alkane carbon isotope changes are mainly controlled by the degree of thermal evolution, showing gradual heaviness with increasing temperature. No carbon isotope sequence reversal occurred during the thermal simulation, and its distribution range is roughly the same as that of the alkane carbon isotope composition of the mud shale of the Pingliang Formation. The ethane carbon isotope composition is as heavy as −21.2‰ at the high-temperature stage, showing similar coal-type gas characteristics. The addition of calcium sulphate (CaSO4) causes the TSR reaction to occur, which has a significant impact on the methane content under high maturity conditions, reducing its content by more than 50% at 600 °C. However, the addition of CaSO4 increases the yield of heavy hydrocarbon gases, such as ethane, and promotes the production of C6-14 hydrocarbons and C14+ hydrocarbons at high-temperature stages, and the addition of CaSO4 substantially increases the yield of H2, CO2, and H2S. The thermal simulation results have implications for the hydrocarbon formation mechanism of the early Paleozoic marine carbonate formation system in the stacked basins of the Ordos Basin and the Tarim Basin in China.

The pattern of organic matter type occurrence and distribution in predicting hydrocarbon source formation: an example from Eocene Niger Delta Basin shale deposits

The pattern of organic matter type occurrence and distribution in predicting hydrocarbon source formation: an example from Eocene Niger Delta Basin shale deposits

Pollution profile, source identification, and risk assessments of persistent organic pollutants (POPs) and toxic elements in the sediments of one of the water supply areas (Sultanbahçedere lake) to Istanbul, Türkiye

This study was done to comprehensively exhibit the pollution level of surface sediments taken from Sultanbahçedere dam lake in terms of some persistent organic pollutants (POPs) and toxic elements, to decide the possible sources of polycyclic aromatic hydrocarbons (PAHs), to perform the ecological and human health risk assessments, and to evaluate the pollution profile with the hierarchically clustered heatmap (HCHM) analysis and principal component analysis (PCA). Naphthalene, Benzo(b)fluoranthene, Fluoranthene, Pyrene for PAHs; p,p-DDE, p,p-DDD, alpha-HCH, p,p-DDT, Endrin for OCPs; hexa and hepta chlorinated congeners accounting for 50.63% and 28.44% for polychlorinated biphenyls (PCBs); 1234678-HpCDD, OCDD for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs); PCB 118, PCB 105, PCB 167 for dioxin like-PCBs (DL-PCBs) and Al, Fe, Ca for elements were predominant in almost all of the sediments with a few exceptions. S4 site, which is one of the mid-sites of reservoir, has high concentrations in most of these pollutants. According to PAH diagnostic analysis, PAHs in the surface sediments are mostly affected by pyrogenic sources. The concentrations of POPs do not pose any toxic risk to aquatic organisms according to sediment quality guideline (SQG) and the limit values of other countries accepted in the world. Also, since none of the elements exceeded the effect range median (ERM) values, they do not pose a significant toxic risk to aquatic organisms. There is no risk for non-carcinogenic and carcinogenic hazards both for children and for adults considering hazard quotient (HQ), hazard index (HI), and lifetime cancer risk (LCR) values of all pollutants.

Integrated well-log data and seismic inversion results for prediction of hydrocarbon source rock distribution in W segment, Pearl River Mouth Basin, China

Hydrocarbon source rocks possess a high concentration of organic matter and can generate significant quantities of hydrocarbons, which are integral components within hydrocarbon systems. It is critical for well deployment and hydrocarbon production enhancement to accurately anticipate the geographical dispersion of hydrocarbon source rocks in hydrocarbon-bearing basins. Total Organic Carbon (TOC) serves as a pivotal metric for assessing hydrocarbon source rocks, enabling the estimation of their spatial distribution through TOC prediction. In this study, we present a Machine Learning-based process for predicting the distribution of hydrocarbon source rocks, utilizing well-log data and seismic inversion results. Based on the TOC value of the well curve, the hydrocarbon source rock quality is divided into four categories: normal, medium, good, and excellent. We identify the sensitive parameters governing hydrocarbon source rock quality through cross-plot and correlation analysis. Machine Learning will predict the spatial distribution of hydrocarbon source rock by establishing a relationship between hydrocarbon source rock quality and sensitive parameters. The prediction results are evaluated by comparing the performance of Random Forest, Gradient Boosting Decision Tree (GBDT), eXtreme Gradient Boosting tree (XGBoost), and Histogram-Based Gradient Boosting Decision Tree (HGBDT) using confusion matrix and ROC curve. The findings consistently demonstrate that HGBDT exhibits superior prediction capability, accurately anticipating the spatial distribution of hydrocarbon source rocks. The prediction outcomes align well with the depositional properties of the research area and demonstrate excellent agreement with the well data.