High Total Organic Carbon Content Research Articles

Evaluation of Upper Paleozoic source rocks in the southeastern margin of the Ordos Basin

IntroductionThe Yanchang gas field in the southeastern Ordos Basin is an important region for natural gas exploration due to the presence of Upper Paleozoic coal-bearing source rocks. This study systematically evaluates these source rocks in terms of organic matter abundance, type, and thermal maturity to assess their hydrocarbon generation potential.MethodsOrganic geochemical analyses were performed to determine the total organic carbon (TOC) content, kerogen type, and thermal maturity of the source rocks. The Benxi and Taiyuan Formations were specifically targeted for detailed evaluation. Kerogen maceral analysis was used to classify organic matter types, while thermal maturity was assessed through vitrinite reflectance (Ro) values.ResultsThe results indicate that the Upper Paleozoic source rocks exhibit high TOC content, with the Benxi and Taiyuan Formations showing excellent hydrocarbon generation potential. Kerogen maceral analysis identified predominantly Type III (humic) kerogen with some Type II2 (humic-sapropelic) components, suggesting a strong capacity for gas generation. Thermal maturity analysis revealed that the source rocks have reached the overmature dry gas stage, signifying advanced thermal evolution.DiscussionThe findings highlight the central and southern parts of the Yanchang gas field as promising exploration targets, characterized by high TOC content, favorable kerogen type indices, and high Ro values. These features collectively demonstrate the significant hydrocarbon generation potential of the Upper Paleozoic source rocks.ConclusionThe Upper Paleozoic coal-bearing source rocks in the Yanchang gas field represent a highly prospective target for natural gas exploration, particularly in regions with favorable organic geochemical properties.

Organic petrology and geochemistry of the late Neogene Shizigou Formation in the Qaidam Basin, China: Characteristics of a prospective microbial gas source rock

The discovery of natural gas trapped in the late Neogene Shizigou Formation in the Yikeyawuru anticline indicates the potential for additional microbial gas reservoirs outside of the primary exploration targets for microbial gas in the younger, i.e., the Pleistocene sediments of the Qaidam Basin. In this study, a detailed investigation is presented on the bulk geochemistry and organic petrography of the potential microbial source rocks as well as on molecular organic geochemistry of the solvent extracts obtained from the late Neogene Shizigou Formation of the Yiliping Depression. The objectives are to elucidate i) the depositional environment, ii) biological sources of organic matter (OM), and iii) biodegradation levels in these microbial gas source rocks.The samples from the well situated at the center of the Yiliping Depression (the H 1 well) exhibit minor variations in total organic carbon (TOC) and total sulfur contents, whereas the samples from the well located at the margin of the depression (the Y 3 well) show large variations in these values. All these samples are presently thermally immature. The kerogen of the TOC-rich Y 3 well samples is mainly composed of mixed types II–III kerogen and characterized by a complex maceral composition (i.e., a mixture of large fragments of huminite, semifusinite, fusinite, resinite/fluorinite, lamalginite, and liptodetrinite). In contrast, samples from the H 1 well contain typically type III kerogen with a less complex maceral composition consisting of huminite, lamalginite, and liptodetrinite. The molecular data illustrates that the OM is predominantly derived from bacterial and algal biomass as well as aquatic higher plants (primarily in the Y 3 well samples), while angiosperms are the primary source of the subordinate terrestrial OM in the samples. The marginal area is characterized by salinity levels akin to normal marine conditions with bottom-water paleoredox conditions ranging from dyoxic (samples with high TOC content) to oxic, whereas the central area developed a mesosaline environment with oxic bottom-water conditions prevailing. In contrast to the primary microbial gas producing layer, the Pleistocene Qigequan Formation, the late Neogene Shizigou Formation exhibits a higher contribution of emergent macrophytes but a reduced abundance of lower aquatic organisms in the OM as well as a higher salinity level in the water column. Despite the late Neogene Shizigou Formation demonstrating a lower potential for hydrocarbon generation and a lower degree of biodegradation of OM than the Qigequan Formation, it still shows generally favorable geological and geochemical conditions that are conducive to the development of microbial gas reservoirs, which is underscored by the biodegradation levels between 3 and 4 for the studied samples.

Sedimentary Environment and Organic Matter Accumulation of Continental Shales in Xiahuayuan Formation in Xuanlong Depression, Yanshan Area

The shale sedimentary environment is crucial for evaluating shale gas reservoirs and sweet spot zones. The Xiahuayuan Formation in the Xuanlong Depression of the Yanshan area is an important exploration and development region for shale gas due to its multi-layer dark shale. The paleosedimentary environment and organic matter accumulation mechanism of organic-rich shale were discussed through geochemical methods such as total organic carbon (TOC) content and elemental analysis. The results indicate that the shale exhibits a high TOC content. The Mo content and the P/Al and P/Ti ratios indicate that the primary productivity of the ancient lake is high. The Ceanom, V/(V + Ni) ratio and MoEF-UEF covariation model reveal that the sedimentary environment of shale is characterized by anoxic conditions. The ratios of K/Al and Ti/Al suggest significant variations in the input of fine-grained clay clastics and terrigenous clastics. The Ca/(Fe + Ca) and Sr/Ba ratios suggest that the paleowater was a freshwater environment. The paleoclimatic conditions, as indicated by CIA, Sr/Cu, and C-value, suggest a range from semi-humid to humid. The ratios of Rb/K and Mn/Ti reflect that the water primarily existed in a shore–shallow lake environment. The correlation analysis between organic matter accumulation and sedimentary environment parameters indicates that the primary factors influencing the organic matter accumulation in the Xiahuayuan Formation shale are redox conditions, terrigenous clastic input, paleoclimate conditions, and paleowater depth. The organic matter accumulation is characterized by a “preservation condition” pattern. This study provides theoretical support for the accumulation mechanism, potential evaluation of resources, and optimal selection of favorable regions for Jurassic shale gas in the Xuanlong Depression.

Impact of gas adsorption of nitrogen, argon, methane, and CO2 on gas permeability in nanoporous rocks

Gas adsorption on the surface of nanoporous rocks is an important process that occurs in many applied scenarios such as shale gas production or CO2 enhanced gas recovery or storage. While there are few theoretical considerations on the effect of gas adsorption on permeability, a systematic laboratory investigation of the impact of gas adsorption on gas flow and permeability is still lacking. In this paper, permeability of four adsorptive gases, i.e., nitrogen, argon, methane, and carbon dioxide, was measured, along with helium permeability, for two nanoporous rock samples that have high and low total organic carbon (TOC) content, respectively. The measurements were conducted at a range of pore pressures from 150 to 1500 psi (1.03–10.34 MPa). Gas adsorption isotherms were also measured at the same conditions. A mathematical model that considers adsorption with specific boundary conditions for the experimental setup was used for data analysis. The results show that gas adsorption causes larger drop in pressure decay and greater retardation in pressure equilibrium. However, the reduction of permeability relative to helium (25%–46%) is similar for gases with different levels of adsorption, indicating the occurrence of single-layer adsorption for these gases. Comparison between the two samples further supports the concept of single-layer adsorption and signifies the impact of pore size on the permeability reduction due to adsorption. These new findings deepen the fundamental understanding and provide important clarification on the effect of gas adsorption on gas flow and permeability in nanoporous rocks.

Sedimentary Environment of the Permian Marine Shale in the Kaijiang‐Liangping Trough, Sichuan Basin, China: Implications for Organic Matter (OM) Accumulation

ABSTRACTThe Permian shales in the Kaijiang‐Liangping Trough within the Sichuan Basin represent a promising frontier for marine shale gas exploration, whereas there has been limited systematic research on their sedimentary environment and organic matter (OM) enrichment mechanisms. Therefore, we present total organic carbon (TOC) analysis, major/trace element analyses and scanning electron microscope experiments for the Permian marine shales from the trough to determine their paleoenvironmental conditions and influencing factors of OM enrichment. The results show that the paleoclimate changed from dry climate to humid and warm climate (P3w1 [the first member of the Wujiaping Formation]) and semi‐humid to semi‐arid climate (P3w2 [the second member of the Wujiaping Formation]) and P3d‐I (Dalong Formation‐I) and then to arid climate again during the shale deposition period from the P2g (Gufeng Formation) to the P3d‐II. The shales with the highest TOC contents (TOC > 3%, P3d‐I and P2g), lower TOC contents (TOC < 1%, P3w1 and P3w2) and higher TOC contents (1% < TOC < 2%, P3d‐II) were formed under the control of anoxic environment and high paleoproductivity, oxic‐suboxic environment and high paleoproductivity, anoxic‐euxinic environment and lower productivity, respectively. Only appropriate sedimentation rates promote OM enrichment. Terrestrial input, paleoclimate, volcanic activity and hydrothermal upwelling mainly indirectly affect OM accumulation by influencing paleoproductivity. The degree of redox conditions is the primary factor affecting OM enrichment, followed by paleoproductivity. Nonetheless, anoxic to euxinic environments are most appropriate for OM preservation. Weak volcanic activity can boost paleoproductivity, but severe volcanic activity might introduce excessive harmful compounds that limit organism survival, resulting in a fall in paleoproductivity. Additionally, element P brought by volcanic ashes doesn't contribute to OM accumulation.

Sedimentary factors controlling the organic matter enrichment in oil shale, Seyitömer Lacustrine Basin, Western Anatolia: New implications from organic and inorganic geochemistry

AbstractWestern Anatolia, an important segment of the Alp‐Himalayan Belt, hosts numerous Neogene lacustrine basins with potential oil shale reserves surpassing 1.6 billion tonnes. Among these basins, the Seyitömer Basin (Kütahya) stands out, containing oil shales that are intercalated with claystone, marl, limestone and coal layers. This study presents a comprehensive dataset of organic and inorganic chemistry to gain insight into the palaeoclimate and palaeoenvironmental factors that control the enrichment of organic matter. The studied samples exhibit high total organic carbon contents, averaging 12.85% (ranging from 2.22 to 36.21%), high hydrogen indices (486–812 mgHC/g rock) and low oxygen indices (33–70 mgCO2/g total organic carbon), indicating their substantial hydrocarbon‐source potential. These characteristics indicate predominantly ‘excellent’ to occasionally ‘very good’ source rock qualities and very high oil potential. Their pyrolysis, gas chromatography and gas chromatography–mass spectrometer parameters indicate an immature‐early mature characteristic for Seyitömer oil shale samples. They comprise dominantly Type‐I kerogen with minor Type‐II kerogen and lacustrine algal organic matter. Their sedimentological characteristics, along with various geochemical values, such as total organic carbon versus S, B versus Ga and dibenzothiophene/phenanthrene, reveal a moderately deep fresh/brackish to saline lacustrine environment. The Ga/Rb, K/Al and Sr/Cu ratios suggest dominantly humid and warm climate conditions, occasionally interrupted by periods of less humidity. The prevalence of warm and humid climate conditions leads to intense chemical weathering processes, supported by high Chemical Index of Alteration and low Rb/Sr ratios in the associated oil shale samples. Intense chemical weathering and high runoff resulted in dissolved nutrient enrichment, promoting ecological dynamics favourable to increased productivity. Their low Pr/Ph and Mo/total organic carbon ratios, high Ni/Co ratio and, relatively low MoEF/UEF ratio, along with well‐developed lamination of the oil shales, indicate the presence of anoxic conditions in the bottom water. These anoxic conditions would have facilitated the preservation potential of organic matter in the samples. Thus, the palaeoclimate conditions integrated with sedimentary factors have an important role in the ecological dynamic and physical–chemical environmental conditions, ultimately contributing to the organic matter enrichment of the studied samples. This work provides a case study to better understand the sedimentary factors controlling organic matter enrichment in the lacustrine basins of the Alp‐orogenic belt.

Impacts of shifting from single-species pine forests to distinct agroforestry models on soil fertility, exchangeable cations, and microbial functions

The transition from monoculture to mixed-species agroforestry systems affects soil organic matter and microbial activity. However, the specific dynamics of these changes, particularly within medicinal plant-based agroforestry, remain underexplored. This study investigates the impact of monoculture Pine (Pinus massoniana) forests and four agroforestry models: (M1) Pinus massoniana and Alpina oxyphylla, (M2) Pinus massoniana and Ficus simplicissima, (M3) Pinus massoniana and Amomum villosum, and (M4) Pinus massoniana and Curcuma longa on soil properties and microbial activity in rhizosphere and non-rhizosphere environments. Our results showed significantly higher pH (4.80) and total nitrogen (N) content (1.77 g kg−1) in the rhizosphere of model (M4) compared to (CK). Total organic carbon (TOC) and carbon fractions (POC, DOC, and MBC) also differed significantly across monoculture and agroforestry models, with highest TOC concentrations (31.70 g kg⁻1) in rhizosphere of CK. Exchangeable cations, including Ca2⁺, and Mg2⁺ were significantly higher in the rhizosphere of agroforestry models compared to CK, particularly in M4, where Ca2⁺ was recorded at 12.03 cmol kg−1 with the highest percent base saturation (PBS) at 90.17%. Enzymes leucine aminopeptidase and polyphenol oxidase varied significantly, with higher activity in the rhizosphere of agroforestry models and greater activity in non-rhizosphere of monoculture. Soil microbial respiration (MRes) revealed substantial differences, with an average 17% decrease in rhizosphere soil for models M2 and M4 and a 20.83% reduction in non-rhizosphere soil for model M1 compared to CK. Generalized Linear Model (GLM) demonstrated a significant positive correlation between TOC and MRes (R2 = 0.885, p < 0.01), indicating that higher TOC levels are linked with increased MRes. In conclusion, model M4 most effectively enhanced soil fertility and nutrient availability followed by the other agroforestry models tested. This suggests that integrating medicinal plants into agroforestry systems is a viable strategy for improving ecosystem functioning compared to monoculture practices.

The impact of pore heterogeneity on pore connectivity and the controlling factors utilizing spontaneous imbibition combined with multifractal dimensions: Insight from the Longmaxi Formation in Northern Guizhou

The heterogeneity of shale pores, a crucial factor in the occurrence and migration of shale gas, exerts a significant impact on the pore connectivity. Pores exhibiting a range of structural attributes to the complexity of pore connectivity. A comprehensive study into the impact of pore heterogeneity on pore connectivity in shale is lacking. This study aims to explore the impact of pore heterogeneity on pore connectivity in shale and the primary controlling factors of pore connectivity. Shale pore connectivity, pore structures, mineral composition, and geochemical parameters were assessed using various tests, including spontaneous imbibition, adsorption, mercury intrusion capillary pressure (MICP), focus ion beam-scanning electron microscopy (FIB-SEM), sulfur and carbon analysis, vitrinite reflectivity, and X-ray diffraction (XRD). Pore heterogeneity was quantitatively analyzed using the multifractal dimensions method. Results show that the increased heterogeneity of pore structure and surface roughness facilitating the potential for increased connectivity. The presence of well-developed micro-mesopores within the organic matter, alongside numerous disconnected and independent pores, contributes to an increase in pore heterogeneity. Micro-mesopore structures have a more pronounced impact on pore heterogeneity than macropores. The heterogeneity of the pores is predominantly influenced by variations in the PV and SSA of micro-mesopores. Furthermore, the heightened heterogeneity of pore structure (D1) and surface roughness (D2) leads to a more complex pore structure with increased roughness, promoting the potential for enhanced connectivity through additional throats and facilitating the formation of secondary microfractures. Shale cores characterized by high total organic carbon (TOC) content, porosity, and clay mineral content are conducive to improved pore connectivity. Conversely, the increase of thermal evolution maturity of shale in the over-mature stage is not conducive to the increase of pore connectivity. Thermal evolution maturity, TOC content, and clay mineral are key factors that control pore heterogeneity, further affecting the connectivity of shale pores. High pore connectivity is conducive to spontaneous imbibition capacity and the formation of hydraulic microfractures, promoting the migration of shale gas.

Hydrocarbon generation potential in Jurassic source rocks from hydrous pyrolysis experiments under ultradeep conditions

This study investigates the hydrocarbon generation potential of Jurassic source rocks under ultradeep conditions by utilizing semiclosed system hydrous pyrolysis experiments to simulate the geological processes at play. This study examines four distinct lithologies (shale, mudstone, carbonaceous mudstone, and coal) and three kerogen types (I, II, and III) across a temperature range of 250–650 °C and fluid pressures ranging from 34 to 100 MPa. The results indicate a bimodal distribution in total oil yields, with peak generation observed at approximately 350 °C and 600 °C. This pattern suggests a complex relationship between temperature, pressure, kerogen type, and hydrocarbon output. Notably, while I-Shale and II-Mudstone display higher hydrocarbon efficiency, III-type rocks exhibit superior oil and gas production rates because of their higher total organic carbon content. Research revealed that the oil expulsion rate exceeds 99% at temperatures above 500 °C, with the expelled oil predominantly comprising nonhydrocarbons and asphaltenes. Our findings suggest that Jurassic hydrocarbon source rocks maintain oil and gas potential under ultradeep conditions (high-over maturity stages at depths exceeding 6000 m). Under sustained fluid overpressure exceeding 70 MPa, the hydrocarbon generation peaks of various kerogen types in source rocks are markedly delayed. This phenomenon enables the source rocks to retain the potential for liquid hydrocarbon generation even during the stages of overmaturity. The results significantly enhance the theoretical framework of hydrocarbon generation under ultradeep conditions, thereby providing a crucial extension to the existing thermal boundary theory of hydrocarbon formation. These insights are crucial for the oil and gas industry, directing future exploration efforts towards ultradeep reservoirs and informing the development of new technologies to exploit these resources. This research not only enhances the understanding of subsurface hydrocarbon systems but also has implications for strategies aimed at maximizing resource recovery and managing the environmental impact of deep Earth exploration.

Formation and preservation mechanisms of magnetofossils in the surface sediments of muddy areas in the yellow and Bohai Seas, China

Magnetofossils in the continental shelf sediments of the Yellow and Bohai Seas have long been overlooked. Based on the magnetic results of 88 surface sediments (0–10 cm depth), first-order reversal curve (FORC) diagrams, isothermal remanent magnetization (IRM) acquisition curves from 6 representative samples, and transmission electron microscopy (TEM) observations of 2 samples, the formation and preservation mechanisms of magnetofossils in this region are elucidated. The FORC diagrams consistently show a clear central ridge feature, which indicates the presence of intact magnetofossils in all representative samples. The morphologies observed by TEM are primarily equant and elongated, with minimal or no bullet-shaped (magnetite) magnetofossils. Analysis further reveals a widespread distribution of magnetofossils in the mud areas of the Bohai Sea, North Yellow Sea, and South Yellow Sea, with proportions (contribution to SIRM; SIRM is defined as the remanent magnetization that remains constant as the external magnetic field increases) of <32.5 %, 40.9 % ∼ 44.6 %, and 59.9 % ∼ 66.5 %, respectively. Despite the presence of non-biogenic single domain magnetite, the proportion of magnetofossils can be estimated by the χARM/SIRM value, as they are positively correlated. The surface sedimentary environment of these mud areas is primarily suboxic and characterized by abundant dissolved iron, which facilitate the formation of magnetofossils by magnetotactic bacteria (MTB). It is unlikely that the surface sedimentary environment becomes sulphidic, thereby enabling the preservation of magnetofossils after their formation. The redox state of the study area, crucial for magnetofossil formation, is mainly controlled by the total organic carbon (TOC) content. From north to south, the higher proportion of magnetofossils is coupled with higher TOC content, possibly due to the intensified reducing degree of the suboxic environment, promoting MTB proliferation and thus forming more magnetofossils. The mechanisms governing the formation and preservation of magnetofossils proposed in this study may also be applicable to geological records.

The Effect of Diagenetic Modifications on Porosity Development in the Upper Ordovician to Lower Silurian Wufeng and Longmaxi Formations, Southeast Sichuan Basin, China

Diagenesis has been demonstrated to significantly affect porosity development in shale reservoirs, however, the effect of diagenetic modifications on shale pore structures is still unclear. For clarifying this issue, this paper focuses on the Upper Ordovician to Lower Silurian Wufeng and Longmaxi shales, which are the only commercially gas-produced shale plays in China. This study aims to reveal the influence of diagenetic alterations on the WF-LMX shale reservoir quality by integrating total organic carbon (TOC) content, X-ray diffraction (XRD), low-temperature gas (N2) and carbon dioxide (CO2) adsorption experiments, field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS), and cathodoluminescence (CL) analyses. Three major shale lithofacies were identified, mainly including siliceous, siliceous–argillaceous mixed, and argillaceous shale; the siliceous shale has a relatively high TOC content. The organic pores, intergranular pores, intragranular pores, and fractures are generally developed in the WF-LMX shales. The pore volume (PV) and specific surface area (SSA) of micropores, mesopores, and macropores of siliceous shales are higher than those of mixed shales and argillaceous shales. The TOC content has a strongly positive correlation with PV and SSA for micropores and mesopores. After combustion, the PV and SSA of micropores and mesopores were decreased, whereas the PV and SSA of macropore were significantly increased. In the siliceous shale, organic pore is the dominant pore type due to the fact that a large amount of authigenic microcrystalline quartz aggregates can protect organic pores from compaction. The argillaceous shale has high clay and low TOC content, and the dominant pore type is pores between clay flakes. The siliceous shale has a relatively high TOC content, large PV and SSA, and so are the dessert lithofacies for shale gas exploration.

Source apportionment of organic carbon and nitrogen in sediments from river and lake in the highly urbanized Changjiang Delta

While the impact of human activities on organic matter pollution is recognized, how these impacts vary seasonally in the Changjiang Delta needs further investigation. This study addresses this gap by investigating seasonal variations in organic matter sources and ecological responses to human activities in Changjiang Delta sediments. Total organic carbon (TOC), total nitrogen (TN), and carbon (δ13C) and nitrogen (δ15N) isotopic compositions of surface sediments collected from the Taipu River and Dalian Lake wetland were analyzed. Both water bodies exhibited similar seasonal trends for TOC and TN, with the Taipu River containing an average of 0.46% and 0.03% higher concentrations of TOC and TN, respectively, compared to Dalian Lake. Additionally, the organic index (OI) and organic nitrogen (ON) index were elevated in both water bodies during the wet season. Sediments from Dalian Lake remained uncontaminated to moderately contaminated, while those from the Taipu River were generally classified as moderately to heavily contaminated. Stable isotope analysis identified terrestrial C3 plants (averaging 25.5%), C4 plants (averaging 16.0%), and municipal wastewater (averaging 16.0%) as the main contributors to organic matter in the sediments. These findings suggest that terrestrial plant material and municipal wastewater are key targets for managing organic matter contamination in the Changjiang Delta. Implementing strategic land-use planning and targeted interventions to minimize these inputs can significantly improve water quality and ecosystem health.

Effects of the Emeishan large igneous province (ELIP) and coastal upwelling on paleoenvironment and organic matter accumulation during the Middle Permian (Capitanian), South China

The late Middle Permian (Capitanian) was characterized by many global geological, biotic and environmental events, along with the widespread deposition of organic-rich strata. Elucidating the relationships between organic matter (OM) accumulation and critical geological events is of significance for Earth system science and petroleum resource geology, but the mechanism remains unclear. To fill the knowledge gap, this study investigated the Gufeng Formation in the middle Yangtze region of South China to examine the links between OM accumulation and geological events, e.g., the Emeishan large igneous province (ELIP) and coastal upwelling. Our results show that the Gufeng Formation exhibits significant OM enrichment, with an average total organic carbon (TOC) content of 8.34 wt%. The paleoceanographic conditions went through three stages during the Capitanian: the early–middle stage of high primary productivity and anoxic–sulfidic conditions; the middle stage of moderate productivity and anoxic conditions; and the late stage of low productivity and dysoxic conditions due to weakened upwelling and a global sea-level fall. OM accumulation was influenced mainly by upwelling-induced high productivity and anoxic conditions related to the oxygen minimum zone (OMZ), with a secondary control of carbonate dilution. The ELIP possibly had a limited contribution to high TOC contents. In South China, the Gufeng and uppermost Maokou formations were marked by high OM contents (average TOC > 3 wt%; maximum = 40 wt%), resulting primarily from widespread coastal upwelling along the eastern margin of the Paleo-Tethys Ocean during the Middle Permian. ELIP volcanism mainly triggered rapid climate warming during the late Capitanian and had a regional and variable effect on OM enrichment for different regions in South China.

Hydrocarbon Generation Potential and Organic Matter Enrichment Mechanism of the Cambrian Marine Shale in the Tadong Low Uplift, Tarim Basin

AbstractCambrian shales in China and elsewhere contain abundant oil and gas resources. However, due to its deep burial and limited outcrop, there has been relatively little research conducted on it. The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China, specifically the Xidashan–Xishanbulake Formation (Fm.) and overlying Moheershan Fm. provide a case study through the use of organic petrology, mineralogy, organic and elemental geochemistry, with the aim of analyzing and exploring the hydrocarbon generation potential (PG) and organic matter (OM) enrichment mechanisms within these shale formations. The results indicate that: (1) the Cambrian shale of the Tadong low uplift exhibits relatively dispersed OM that consists of vitrinite‐like macerals and solid bitumen. These formations have a higher content of quartz and are primarily composed of silica‐based lithology; (2) shale samples from the Xidashan–Xishanbulake and Moheershan formations demonstrate high total organic carbon (TOC) and low pyrolytic hydrocarbon content (S2) content. The OM is predominantly type I and type II kerogens, indicating a high level of maturation in the wet gas period. These shales have undergone extensive hydrocarbon generation, showing characteristics of relatively poor PG; (3) the sedimentary environments of the Xidashan–Xishanbulake and Moheershan formations in the Tadong low uplift are similar. They were deposited in warm and humid climatic conditions, in oxygen‐deficient environments, with stable terrigenous inputs, high paleoproductivity, high paleosalinity, weak water‐holding capacity, and no significant hydrothermal activity; and (4) the relationship between TOC and the paleoproductivity parameter (P/Ti) is most significant in the Lower Cambrian Xidashan–Xishanbulake Fm., whereas correlation with other indicators is not evident. This suggests a productivity‐driven OM enrichment model, where input of land‐derived material was relatively small during the Middle Cambrian, and the ancient water exhibited lower salinity. A comprehensive pattern was formed under the combined control of paleoproductivity and preservation conditions. This study provides valuable guidance for oil and gas exploration in the Tarim Basin.

Shale gas‐bearing capacity and its controlling factors of Wufeng–Longmaxi formations in northern Guizhou, China

Great progress has been made in marine shale gas of Wufeng–Longmaxi formations in the Sichuan Basin. However, shale gas exploration in the complex structural belt around the Sichuan Basin still faces great challenges. In this study, shales of Wufeng–Longmaxi formations collected from the northern Guizhou were taken as the studied target, organic matter (OM) characteristics, mineral composition, pore structure, methane adsorption capacity and in situ desorption gas content were measured, and the controlling factors of shale gas content were further discussed. The results indicated that the sedimentary facies of Wufeng–Longmaxi formations in north Guizhou varies from shallow‐water shelf facies to deep‐water shelf facies from south to north, and organic‐rich shales are primarily distributed in Daozhen‐Xishui areas, with a maximum thickness of about 80–100 m. Organic‐rich shales are characterized by high total organic carbon (TOC) content, high thermal maturation and type I–II1 kerogens, which can be comparable with those in commercially produced shale gas field in Sichuan Basin. High‐quality shale gas reservoirs generally have a high content of brittle minerals, making them easier to be fractured. OM pores are the dominanted pore type in the studied shales, followed by intergranular pores associated with brittle minerals, dissolution pores within carbonate grains and microcracks, while clay mineral‐related pores are poorly developed. The Wufeng–Longmaxi Formation shales generally have strong methane adsorption capacities, but these vary greatly across different areas. Shale gas adsorption capacity is primarily controlled by TOC content and thermal maturation level. Similarly, total gas content, including desorption gas and lost gas, varies greatly in different areas, and it is obviously lower than that in Fuling and Luzhou shale gas field, due to the loss of shale gas and low‐pressure coefficient in the complex structural zone. It is worth explaining that shale gas is not always low in northern Guizhou, which is determined by burial depth and the distance of great fractures. Shale gas content is relatively high in LY1 well and DY1 well in Xishui‐Daozhen area, and it is extremely low in TY1 well and AY1 well in Tongzi‐Zheng'an area. Shale gas content in the same structural unit is primarily influenced by TOC content, OM pore development degree and water saturation. However, different structural units have different shale gas contents, due to the differences in preservation conditions. Shale reservoirs with good preservation conditions, that is, wide and gentle structure, far from a large fault and great burial depth, generally have high shale gas contents.

Inhibition of microbially mediated total organic carbon decomposition in different types of cadmium contaminated soils with wheat straw addition

Wheat straw returning is a common agronomic measure in the farmland. Understanding organic carbon transformation is of great significance for carbon budget under the premise of widespread distribution of cadmium (Cd) contaminated soils. An incubation experiment was conducted to assess the influence of Cd contamination on the decomposition and accumulation of total organic carbon (TOC) as well as the composition and abundance of bacterial communities in eight soil types with wheat straw addition. The results showed that inhibition of Cd contamination on microbially mediated organic carbon decomposition was affected by soil types. The lower cumulative C mineralization and higher TOC content could be observed in the acidic soils relative to that in the alkaline soils. The content of Cd in soil exhibits different effects on the inhibition in decomposition of TOC. The high dosage level of Cd had stronger inhibitory impact due to its high toxicity. The decomposition of TOC was restricted by a reduction in soil bacterial abundance and weakening of bacterial activities. Redundancy analysis (RDA) indicated that Proteobacteria and Gemmatimonadetes were abundant in alkaline Cd-contaminated soils with wheat straw addition, while Bacteroidetes dominated cumulative C mineralization in acidic Cd-contamination soils. Moreover, the abundance of predicted functional bacteria indicated that high-dose Cd-contamination and acid environment all inhibited the decomposition of TOC. The present study suggested that pH played an important role on carbon dynamics in the Cd-contaminated soils with wheat straw addition.

Paleoenvironment and Hydrocarbon Potential of Salinized Lacustrine Shale with High Terrigenous Input in the Paleogene Biyang Depression (East China): Evidence from Organic Petrography and Geochemistry

Salinized lacustrine shale (SLS) represents a frontier in the global quest for unconventional hydrocarbon resources. The impact of terrigenous input, which includes terrigenous organic matter (OM) and detrital matter, on the deposition and hydrocarbon potential of SLS is still controversial. Here, we examine this issue using the newly discovered SLS within the Paleogene Biyang Depression, employing a combination of organic petrographic and geochemical analyses. A high influx of terrigenous input (terrigenous OM and detrital matter) promotes the formation of SLS. On the one hand, terrigenous higher plants emerge as the primary source of OM in the SLS, as indicated by the dominance of terrigenous macerals (e.g., terrigenous liptinite) and the abundance of plant-derived biomarkers (e.g., tricyclic terpanes). Additionally, a portion of the OM may originate from bacteria. On the other hand, the rapid input of detrital matter improves the preservation of OM, resulting in the deposition of SLS with high total organic carbon (TOC) contents and low hydrogen index (HI) values. The findings of this study contribute to a deeper understanding of SLS deposition and provide guidance for regional hydrocarbon exploration.

Geochemical and Organic Petrological Characteristics of the Bituminous Carbonate Succession (Upper Cretaceous Shu'ayb Formation) in Northern Jordan: Implications for Organic Matter Input and Paleosalinity, Paleoredox, and Paleoclimatic Conditions.

Bituminous carbonate rocks of the Upper Cretaceous Shu'ayb Formation from the Ajloun outcrop in Northern Jordan were geochemically and petrologically analyzed in this study. This study integrates kerogen microscopy results with geochemical results (i.e., biomarker, stable carbon isotope, and major elemental compositions) to understand the organic matter (OM) inputs and to reveal the dispositional setting and its effect on the occurrence of OM. The Shu'ayb bituminous carbonate rocks have high total organic carbon (TOC) and sulfur (S) contents, with average values of 12.3 and 4.59 wt %, respectively, indicating redox conditions during their precipitation. The high abundance of alginite (i.e., lamalginite) in the Shu'ayb bituminous carbonate sediments is a further evidence for redox conditions. The finding of mainly marine-derived OM was also demonstrated by the biomarker distribution and carbon isotope composition. The biomarkers are represented by a narrow Pr/Ph ratio of up to 0.97, abundance of tricyclic terpanes, and high C27 regular sterane, indicating that the OM was primarily derived from phytoplankton algae, along with small amounts of land plant-derived materials, and were accumulated under reducing conditions. The studied Shu'ayb bituminous carbonate facies is composed of mainly calcium (CaO; average, 45.10 wt %), with significant amounts of silicon (Si2O3; avg., 9.35 wt %), aluminum (Al2O3; avg., 6.91 wt %), and phosphorus (P2O3; avg., 1.47 wt %) and low amounts of iron (Fe2O3) and titanium (TiO2) of less than 1 wt %, indicating that the detrital influx was low in an open water depth system with higher primary bioproductivity. The geochemical proxy suggests that the Shu'ayb bituminous carbonate facies was established in a saline water environment, with Ca/Ca + Fe and S/TOC values of more than 0.9 and 0.50, respectively, which could be attributed to the increase in reducing conditions of the water column. The chemical index of alteration values of more than 0.8 also indicate that the Shu'ayb bituminous carbonate facies formed during warm and humid climatic conditions, thereby resulting in intense subaerial weathering.

Maximizing the value of liquid products and minimizing carbon loss in hydrothermal processing of biomass: an evolution from carbonization to humification

Hydrothermal carbonization (HTC) converts wet biomass into hydrochar and a process liquid, but aromatic compounds in the products have been reported as a roadblock for soil applications as they can inhibit germination, plant growth, and soil microbial activity. Here, we compared HTC and hydrothermal humification (HTH) of cow manure digestate while varying the initial alkaline content by adding KOH. HTH converted 37.5 wt% of the feedstock to artificial humic acids (A-HAs) found in both solid and liquid, twice that of HTC. HTH reduced phenolic and furanic aromatic compounds by over 70% in solids and 90% in liquids. The A-HAs in HTH resemble natural humic acids (N-HA), based on FTIR, UV–vis spectra, and CHN and XRD analysis. The HTH liquid possesses 60% higher total organic carbon (TOC) than HTC. Although one-third of TOC can be precipitated as A-HA, a high TOC concentration remains in the liquid, which is shown to be mainly organic acids. Therefore, we also evaluated the HTC and HTH liquids for anaerobic biomethane production, and found that compared to the original cow manure digestate, the HTH liquids increased methane yield by 110.3 to 158.6%, a significant enhancement relative to the 17.2% increase seen with HTC liquid. The strong reduction in organic acids during biogas production from HTH liquid indicates the potential for converting soluble byproducts into methane, while maintaining high A-HAs levels in the solid product.Graphical

Integration of sequential electrocoagulation and adsorption for effective removal of colour and total organic carbon in textile effluents and its utilization for seed germination and irrigation.

Textile effluent discharge can negatively impact the environment and living organisms due to its potential toxicity, higher percentages of total organic carbon (TOC) contents, and so on. The study investigates the extraordinary performance of the electrocoagulation process (ECP) combined with powdered activated carbon (PAC) as a highly effective and environmental friendly method of treating textile effluents. This scientific work mainly includes the focus on removing toxic components in textile effluents, such as high concentrations of colour and TOC using synthesized PAC derived from coconut shells coupled with the ECP (ECP-PAC). Initially, PAC was characterized by using XRD, Raman, BET, FTIR, and TGA studies. Subsequently, the pilot-scale ECP-PAC batch reactor was constructed with iron (Fe) as an anode and copper (Cu) as a cathode. The pilot-scale ECP-PAC batch reactor has achieved higher treatment efficiency in a shorter reaction time with low energy consumption compared to a stand-alone ECP. Further, the optimum conditions for effective ECP-PAC have been optimized, such as pH 7.5, applied current density (0-50mA/cm2), reaction time (0-30min), electrode combinations (Fe-Cu) with electrode distances of 5cm apart, and an optimum dose of 5g/L of PAC. Specifically, 98% of the colour and 96% of the TOC contents present in the industrial textile effluent were treated in 15 and 30min, respectively. In quantitative perspectives, the developed batch reactor has sharply decreased TOC (324.1mg/L), IC (1410mg/L) and TC (1019mg/L) to 13.55mg/L (96%), 31.49mg/L (97%), and 48.05mg/L (95%), respectively, in 30min demonstrating its sensitivity and selectivity with the utmost care. Moreover, the physicochemical properties of the treated water were convincingly assessed. That is, it remains suitable for the seed germination of mung bean and chlorophyll content study. Thus, the developed methodology could effectively reduce freshwater consumption in the agricultural sector, increase freshwater availability in water-scarce regions, and facilitate the increase of the recharging capacity of groundwater tables.