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Background: For a long time, the prevailing viewpoint suggests that shorter telomere contribute to chromosomal instability, which is a shared characteristic of both aging and cancer. The newest research presented that T cell immune deficiency rather than chromosome instability predisposes patients with short telomere syndromes to some cancers. However, the relationship between genetically determined telomere length (TL) and immune cells remains unclear. Methods: The two‐sample Mendelian randomization analysis was conducted to elucidate the potential causal relationship. The genetic data of TL and immune cells were obtained from the Genome‐Wide Association Study. The inverse variance weighted (IVW) method was used to estimate the effects primarily and another four methods were as a supplement. Sensitivity analysis was used to test the results. Results: The IVW method showed a significant correlation between TL and the percentage of T cells in lymphocytes (odds ratio [OR]: 1.222, 95% confidence interval [CI]: 1.014–1.472, p =.035), indicating that shorter TL significantly increases the risk of low T cell percentage. Further analysis of T cell subsets indicated that shorter TL may primarily lead to a lower percentage of Natural Killer T cells (OR: 1.574, 95% CI: 1.281–1.935, p <.001). Analysis of B cell subsets revealed that shorter TL may be associated with a higher percentage of Naive‐mature B cells, and a lower percentage of Memory B cells. And the sensitivity analysis indicated the validity and robustness of our findings. Conclusion: In summary, our findings suggest that shorter TL may be associated with a decline in the percentage of T cell, as well as impediments in the differentiation of B cell, consequently leading to the onset of immunosenescence and immunodeficiency. The relevant mechanisms and potential therapeutic avenues still need further investigation. Shorter telomere length may be associated with a decline in the percentage of T cell, as well as impediments in the differentiation of B cell, consequently leading to the onset of immunosenescence and immunodeficiency. [ABSTRACT FROM AUTHOR]

Background: Previous observational studies have identified an association between rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). However, the causal relationship between RA and IBD in the East Asian population remains uncertain. Methods: The two-sample Mendelian randomization (MR) analysis was conducted to elucidate the potential causal relationship between RA and IBD. Summary-level data from genome-wide association studies (GWAS) in the East Asian population were utilized, including RA (n = 19,190) and IBD (n = 6543), including Crohn's disease (CD, n = 5409) and ulcerative colitis (UC, n = 4853). The inverse variance weighted (IVW) method was employed as the primary analysis, supplemented by weighted median, weighted mode, simple median, MR-Egger, and MR-PRESSO analyses. Sensitivity analyses were conducted to assess the robustness of the results. Genetic data for RA (n = 22,515) were utilized to validate the findings in the East Asian population. Results: The IVW method showed no significant association between genetically predicted RA and overall IBD in the East Asian population (OR = 1.028; 95% CI: 0.935–1.129; P = 0.567). The subgroup analysis revealed a positive association between RA and CD (OR = 1.268; 95% CI: 1.108–1.451; P < 0.001), while a negative association was observed with UC (OR = 0.839; 95% CI: 0.710–0.993; P = 0.041). These findings were supported by another set of RA data. Additionally, an SNP rs2071475 was identified to play an important role in CD and UC. Conclusion: This study revealed a potential increased susceptibility to CD and a decreased susceptibility to UC in the East Asian population with RA. Furthermore, a key SNP rs2071475 was discovered along with its opposite effects in CD and UC. These findings provide new evidence for research on the corresponding molecular mechanisms and offer insights for clinical management of RA-associated IBD. [ABSTRACT FROM AUTHOR]

• Intramolecular C isotopes of propane were analyzed in overmature shale gases. • Unusual 13C depletion observed in the central C of all propane samples. • Inter- and intramolecular isotopes support C 2+ alkanes formed by C 1 polymerization. Abiotically synthesized hydrocarbons are significant in the fields of astrobiology, biosphere, energy, environment, and geology. Abiotic hydrocarbons have never been unambiguously proven to occur in common sediments partly because identifying these components in crustal settings is challenging as they share similar characteristics with hydrocarbons of biotic origin. In this study, we measured intramolecular carbon isotopes of 10 propane samples from Longmaxi shale in the Sichuan Basin, China, and found distinct 13C-depletion in the central position carbon with its δ13C decreased by −8.0 to −7.0‰ (Vienna Pee Dee Belemnite) with respect to terminal carbons. The δ13C value of central carbon (H 3 C–#CH 2 -CH 3) in propane is equal to the second methyl (H 3 C–#CH 3) in ethane possibly resulting from surface catalytic polymerization reactions of methane. Our novel findings indicate that the abiotic synthesis of C 2+ hydrocarbons by the surface catalyzed polymerization of methane occurs in commercial gas reservoirs and suggest that this process may be more common than previously thought in methane-rich scenarios on Earth and other planets. [ABSTRACT FROM AUTHOR]

To effectively treat the pollutant in sewage, a new-type three-dimensional aerogel based on graphene oxide and waste paper was fabricated via simple mixing and freeze-drying processes. Therein, waste paper was activated in advance, and polyvinyl alcohol served as physical crosslinking agent. The results showed that the obtained aerogel with porous three-dimensional network structure exhibited good thermal stability. When it acted as adsorbent for treating organic dye (methylene blue) and antibiotic (ciprofloxacin), the adsorption process was explored. In single system, the pseudo-first-order and pseudo-second-order kinetic models were used to discuss the detail about the aerogel adsorbing pollutant. Moreover, the Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and calculate the isotherm constants. Thermodynamic results stated that the adsorption of pollutant onto aerogel was feasible and spontaneous. In binary system, the adsorption capacity of methylene blue by aerogel increased, while the adsorption capacity of ciprofloxacin by aerogel declined. The pseudo-second-order kinetics was consistent with the adsorption of pollutant by aerogel in such binary system. This study would provide a new boulevard to develop environmental, low-cost and high-efficiency adsorbent for removing pollutant from wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] Liquid organic electrolytes commonly employed in commercial Li-ion batteries suffer from safety issues such as flammability and explosions. Replacing liquid electrolytes with nonflammable electrolytes has become increasingly attractive in the development of safe, high-energy Li-metal batteries (LMBs). In this work, nonflammable, robust, and flexible composite polymer–polymer electrolytes (PPEs) were successfully fabricated by flame-retardant solution casting with polyimide (PI) and polyvinylidene fluoride (PVDF). The optimized nonflammable PPEs (e.g., PPE-50) demonstrate not only good mechanical properties (i.e., a high tensile strength of 29.6 MPa with an elongation at break of 87.2%), but also high Li salts dissolubility, the former of which ensures the suppression of Li dendrites, while the latter further improves the ionic conductivity (∼1.86 × 10−4 S cm−1 at 30 °C). The resulting symmetric cells (Li|PPE-50|Li) offer excellent Li stripping and plating stability for 1000 h at 0.5 mA cm−2/0.25 mAh cm−2 and 600 h at 2.0 mA cm−2/1.0 mAh cm−2. In addition, the LiFePO 4 |PPE-50|Li half cells show high cycling performance (e.g., a reversible discharge capacity of 135.9 mAh g−1 after 300 cycles at 1C) and rate capability (e.g., 117.2 mAh g−1 at 4C). The PPE-50 is also compatible with a high-voltage cathode (e.g., LiNi 0.5 Mn 0.3 Co 0.2 O 2), and the resulting batteries demonstrate long-term cycling stability with a high cut-off voltage of 4.5 V vs. Li/Li+. Because of the incorporation of a mechanically robust and thermally stable PI, a polar PVDF, and flame-retardant trimethyl phosphate (TMP) within PPEs, as well as the coordination between Li salts and TMP, and the interaction between Li salts and polymers (especially between Li bis(oxalato)borate) and PI, as well as the bis(oxalato)borate anion and PI), PPEs show great potential for practical and high-energy LMBs without safety concerns. [ABSTRACT FROM AUTHOR]

Heart failure (HF) is one of the major causes of death among diabetic patients. Although studies have shown that curcumin analog C66 can remarkably relieve diabetes-associated cardiovascular and kidney complications, the role of SJ-12, SJ-12, a novel curcumin analog, in diabetic cardiomyopathy and its molecular targets are unknown. 7-week-old male C57BL/6 mice were intraperitoneally injected with single streptozotocin (STZ) (160 mg/kg) to develop diabetic cardiomyopathy (DCM). The diabetic mice were then treated with SJ-12 via gavage for two months. Body weight, fast blood glucose, cardiac utrasonography, myocardial injury markers, pathological morphology of the heart, hypertrophic and fibrotic markers were assessed. The potential target of SJ-12 was evaluated via RNA-sequencing analysis. The O-GlcNAcylation levels of SP1 were detected via immunoprecipitation. SJ-12 effectively suppressed myocardial hypertrophy and fibrosis, thereby preventing heart dysfunction in mice with STZ-induced heart failure. RNA-sequencing analysis revealed that SJ-12 exerted its therapeutic effects through the modulation of the calcium signaling pathway. Furthermore, SJ-12 reduced the O-GlcNAcylation levels of SP1 by inhibiting O-linked N -acetylglucosamine transferase (OGT). Also, SJ-12 stabilized Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2a (SERCA2a), a crucial regulator of calcium homeostasis, thus reducing hypertrophy and fibrosis in mouse hearts and cultured cardiomyocytes. However, the anti-fibrotic effects of SJ-12 were not detected in SERCA2a or OGT-silenced cardiomyocytes, indicating that SJ-12 can prevent DCM by targeting OGT-dependent O-GlcNAcylation of SP1.These findings indicate that SJ-12 can exert cardioprotective effects in STZ-induced mice by reducing the O-GlcNAcylation levels of SP1, thus stabilizing SERCA2a and reducing myocardial fibrosis and hypertrophy. Therefore, SJ-12 can be used for the treatment of diabetic cardiomyopathy. [Display omitted] • Compound SJ-12 alleviates cardiac dysfunction, hypertrophy, and fibrosis in DCM. • SJ-12 increases the level of SERCA2a, a crucial regulator of calcium homeostasis, thus playing a protective role in DCM. • Mechanistically, the cardiac protection effect of SJ-12 was targeting OGT-regulated O-GlcNAc-Sp1/SERCA2a axis. [ABSTRACT FROM AUTHOR]

• Reversal of δ13C and anomalous positive SP value reveals CH 4 polymerization. • Three evolution stages were identified for thermogenic gases. • A remarkable feature of stage III is surface-catalyzed abiotic CH 4 polymerization. • Contribution of CH 4 polymerization can be determined by a two-end member model. • High methane, high temperature, abundant catalyst are good to CH 4 polymerization. The formation and evolution of thermogenic gases were investigated using a combination of intermolecular and intramolecular isotope analyses of 32 natural gas samples collected from the Sichuan and Tarim basins (China) and the Arkoma Basin (USA). Three evolution stages (I–III) were identified: In stage I, hydrocarbon gases are produced through thermal decomposition of organic matter, and kinetic isotope effects in C–C bond breakage control their isotopic distributions; In stage II, C 2 –C 5 hydrocarbons crack with increasing thermal maturity, with their formation and decomposition tending toward thermodynamic equilibrium, and at the end of this stage, the intermolecular and intramolecular isotopic compositions of gaseous hydrocarbons are in thermodynamic equilibrium; A remarkable feature of stage III is the surface-catalyzed abiotic polymerization of methane, which provides a critical origin of C 2+ hydrocarbons in this stages and leads to isotopic anomalies in C 2+ hydrocarbons, including the reversal of δ13C distributions of C 1 –C 3 and the reverse evolution trend of SP value of propane (i.e., tending to be positive). The contribution of C 2+ hydrocarbons from the abiotic polymerization of methane can be determined based on a two-end member model. C 2+ hydrocarbons in the Changning shale gases are all generated from abiotic methane polymerization, and the contribution ratio in the Weiyuan shale gases is about 85 %, while, the contribution of C 2+ hydrocarbons in dry gases from the Tarim Basin formed by this way is no more than 55 %. High methane abundance, high temperature, and abundant catalyst are beneficial to abiotic methane polymerization. [ABSTRACT FROM AUTHOR]

The lower Cambrian Niutitang/Qiongzhusi shale gas in the Middle-Upper Yangtz Block had been regarded as a very promising unconventional natural gas resource due to its high total organic carbon, great thickness, and large areal distribution. However, no commercial shale gas fields have yet been reported. From the northwest to the southeast there are considerable differences in the sedimentary environments, lithology, and erosive nature of the underlying interval (the floor interval) of the Niutitang shale. However, systematic research on whether and how these regional differences influence shale petrophysical properties and shale gas preservation in the Niutitang shale is lacking. A comparison of Niutitang shale reservoirs as influenced by different sedimentary and tectonic backgrounds is necessary. Samples were selected from both the overmature Niutitang shales and the floor interval. These samples cover the late Ediacaran and early Cambrian, with sedimentary environments varying from carbonate platform and carbonate platform marginal zone facies to continental shelf/slope. Previously published data on the lower Cambrian samples from Kaiyang (carbonate platform), Youyang (carbonate platform marginal zone) and Cen'gong (continental shelf/slope) sections were integrated and compared. The results indicate that the petrophysical properties of the floor interval can affect not only the preservation conditions (sealing capacity) of the shale gas, but also the petrophysical properties (pore volume, porosity, specific surface area and permeability) and methane content of the Niutitang shale. From the carbonate platform face to the continental shelf/slope the sealing capacity of the floor interval gradually improves because the latter gradually passes from high permeability dolostone (the Dengying Formation) to low permeability dense chert (the Liuchapo Formation). In addition, in contrast with several unconformities that occur in the carbonate platform face in the northern Guizhou depression, no unconformity contact occurs between the Niutitang shale and the floor interval on the continental shelf/slope developed in eastern Chongqing Province and northwestern Hunan Province. Such regional differences in floor interval could lead to significant differences in hydrocarbon expulsion behaviour and the development of organic pores within the Niutitang shale. Therefore, shale gas prospects in the Niutitang shales deposited on the continental shelf/slope should be significantly better than those of shales deposited on the carbonate platform face. [ABSTRACT FROM AUTHOR]

• Intramolecular isotopes of 40 propane and 5 methane samples were analyzed. • Different intramolecular C isotopes of propane from coal and coal mudstone. • Extreme 13C depletion in central C of over mature propane at cooling setting. • Different effect on intramolecular isotopes by various post-generation processes. Evaluating the origin and fate of hydrocarbons holds significance in many fields, such as energy, geology, astrobiology, biosphere, and environment. However, challenges arise in many cases owing to the limitations of conventional methods. Intramolecular isotope analysis of propane is a new technique that offers the potential to provide insights into gas formation mechanisms; however, a comprehensive understanding of the method remains limited. Specifically, there is little knowledge about its ability to distinguish gases generated by source rocks deposited in similar sedimentary environments such as coal and coaly mudstone. Therefore, this study was undertaken to investigate position-specific carbon isotopes of 40 propane samples from 15 coal-type gas accumulations across four basins in China (Sichuan, Ordos, Qaidam, and Songliao); additionally, clumped isotopologues of methane samples were also analyzed. These coal systems cover a wide range of thermal maturity (from marginally mature to over-mature) at various age strata from the Permian, Triassic, and Jurassic periods, to the Cretaceous period. Our results revealed that propane generated from coal and coaly mudstone differed greatly in intramolecular isotope compositions despite having similar bulk δ13C 3 values. Propane generated from coaly mudstone at a wide range of maturity had relatively more stable δ13C values in both the central (δ13C cental) and terminal carbons (δ13C terminal), near the theory generation line of chain-alkane cracking in the plot of δ13C terminal vs. δ13C cental. However, propane generated from coal had higher stable δ13C terminal values and lower δ13C central values that progressively increased with maturity. Under cooling-down conditions, propane from over-mature natural gases became extremely 13C-depleted in both the terminal and central positions, with Δ13C central (δ13C central minus δ13C terminal) values being as low as –10‰, suggesting a partial origin of methane polymerization. Two propane samples from Cretaceous brown sandstone in the Songliao Basin exhibited an increase in both central and terminal carbons, suggesting that they may have surpassed chemical oxidation owing to high-valence Fe(Mn) oxides. These results indicate that intramolecular isotopes of propane can effectively differentiate dominant gas sources in a coal system with coal or coaly mudstone, as well as easily identify isotopic fractionation caused by post-generation processes, such as methane polymerization, mixing and chemical oxidation. [ABSTRACT FROM AUTHOR]

• n -C 18 and squalane yield simple precursors for modeling gas generation. • Two isotopic fractionation patterns are observed in n - and iso -propyl generative models. • Free radical reactions are the main pathway during the main stage of propane generation. Investigating the mechanisms that determine the bulk and position-specific carbon isotopic distributions of propane in natural gas will help elucidate its formation and evolution. We used octadecane and squalane as model compounds that give simple precursors for gas production in gold-tube isothermal pyrolysis experiments to study the variations in intermolecular and intramolecular distributions of isotopes in the generated gaseous hydrocarbons. The δ13C values of the products and inverses of their carbon numbers (1/ n where n = C 1 –C 5) showed a negative linear relationship versus maturity, indicating that they formed by homolytic cleavage of C–C bonds and that the precursors showed homogeneous distributions of carbon isotopes. However, the significant difference in the kinetic isotopic effects (KIEs) of the gas generated by cracking of two model compounds under the same experimental conditions is not readily explained by single homolytic bond cleavage. The results indicate that besides the KIE of C–C bond cleavage, the bulk and position-specific carbon isotopic compositions of propane are related to the chemical and isotopic structures of the precursors and the propane transformation ratio. Based on the sites of C–C bond cleavage, two isotopic fractionation patterns (i.e., normal propyl and isopropyl models) may explain the bulk and position-specific carbon isotopic distributions of the generated propane. According to the propyl model, propane originates from (normal) propyl structures (CH 3 CH 2 CH 2 *) in the precursor via C–C bond cleavage at a terminal site of a propyl group, while the isopropyl model involves propane derived from isopropyl structures (CH 3 CH*CH 3) in the precursor, with C–C bond cleavage at the central site. Simulations show that these distributions for propane cracked from octadecane closely follow the propyl model, whereas propane generated from squalane showed mixed contributions from both models, and its bulk and position-specific carbon isotopic distributions depend on the proportions of propyl and isopropyl structures in the precursors. Variations of propane's position-specific carbon isotopic distributions during the main stage of propane generation indicate that free radical reactions are the main pathway for thermogenic propane formation, resulting in similar KIEs for propane terminal and central carbons. Therefore, the position-specific carbon isotopic distribution of propane can provide evidence of its formation mechanism and shows potential for revealing the origin and evolution of natural gas. [ABSTRACT FROM AUTHOR]

Clumped-isotope analysis provides new constraints on the formation and evolution of methane. High-resolution isotope-ratio mass spectrometry (HR-IRMS) is a sensitive, precise, and stable analytical technique increasingly used in methane clumped-isotope analysis. However, the lack of standard reference frames hinders the comparison of data from different laboratories and the evaluation of accuracy. In this study, an absolute reference frame was introduced for HR-IRMS analysis of the multiply substituted methane isotopologues 13CH 3 D and 12CH 2 D 2. We evaluated the optimized performance of a Panorama (Nu Instruments, UK) HR-IRMS system by repeated analysis of an intra-laboratory standard gas, finding that these rare isotopologues can be analyzed separately with high precision, repeatability, and reproducibility. Internal precision (a key parameter in instrument performance) reached 0.15‰ − 0.25‰ for Δ13CH 3 D and 0.70‰ − 0.85‰ for Δ12CH 2 D 2 values, ensuring the reliability of data. Comparison of results before and after purification demonstrated that purification procedures caused negligible isotopic fractionation of clumped isotopes. Isotopic-exchange experiments revealed source effects in the MS ion source, depending on the difference in bulk H isotopic composition between sample and reference gas, but independent of bulk C isotopic composition. To improve analytical accuracy for methane isotopologues, an absolute reference frame was developed through experiments involving a suite of mixed gases of different H isotopic composition equilibrated at 100 °C and a standard gas equilibrated at 2 °C–500 °C. Based on the reference frame, raw data were processed with a non-linearity correction and converted to real values with empirical transformation functions. The reference frame was applied to analyses of two methane standard gases and three natural gases from Tarim Basin, China. Measured Δ13CH 3 D and Δ12CH 2 D 2 values for two standard gases were consistent with published values. Clumped-isotope signatures of natural gases preserve information related to the formation temperature of methane. • Clumped-isotope analysis provides new constraints on the formation and evolution of methane. • Isotopic-exchange experiments demonstrated the presence of source scrambling in Panorama. • An absolute reference frame was established to calibrate source scrambling to achieve the accurate clumped-isotope value. • We measured CH 4 clumped-isotope of natural gases and proved that the absolute reference frame is accurate and feasible. [ABSTRACT FROM AUTHOR]

Shale gas exploration in the Dingshan plunging anticline of the Sichuan Basin, China, has uncovered substantial Wufeng–Longmaxi shale reserves. However, substantial variations exist in shale gas content and production among the wells in this region. We investigated the geological factors and mechanisms influencing shale pore structure heterogeneity and shale gas content and production in the area. We conducted comprehensive analyses of mineralogy, geochemical characteristics, and petrophysical properties on the Late Ordovician Wufeng Formation–Early Silurian Longmaxi Formation shales. Shale samples were collected from a shallow well, Anwen-1, located in proximity to the Qiyueshan thrust fault within the Dingshan plunging anticline. Additionally, samples from Dingye (DY) 1 and DY 3 wells, located at varying distances from the thrust fault, were examined. We also integrated previously published data from two correlative sections in the southeastern margin of the Sichuan Basin, each at different distances from the thrust fault. The pore volume, specific surface area, and porosity of the shales were positively correlated with their total organic content (TOC). However, strong lateral compressive stress, often occurring near the regional thrust fault, attenuated the linear relationship between TOC and pore volume/porosity. Lateral compressive stress did not significant affect shale porosity and pore structure when the distance from the regional thrust fault exceeded approximately 15 km. The specific surface area of the shale was less affected by compressive stress. Moreover, carbonate cementation reduced porosity by sealing shale matrix pores and natural microfractures, reducing nanopore connectivity. Consequently, shale gas production is not solely influenced by shale gas content but is also significantly affected by carbonate cementation. Therefore, shale reservoirs located at relatively long tectonic distances from regional thrust faults (approximately 15 km) within the Dingshan plunging anticline exhibit high pore volume, porosity, and shale gas content, rendering them favorable for shale gas exploration. • Mineral compositions and mechanical compaction influence shale pore structure. • Differences in shale gas content and shale gas production from different wells in the Dingshan area were discussed. • Tectonic location relative to thrust faults (< 15 km) influences shale properties. • Carbonate content (> 10%) can significantly reduce shale gas production. • Both compressive stress and carbonate cementation influence heterogeneity of shale pore structure and shale gas production. [ABSTRACT FROM AUTHOR]

The Tarim Basin is one of the most complex, ancient, and petroliferous deep craton basins in the world. Multiple sets of source rocks, stages of tectonism, and episodes of hydrocarbon generation and accumulation complicate the formation and evolutionary processes of hydrocarbons in the basin, especially for the deeply buried petroleum system at >6000 m depth. Paired clumped isotopes (Δ13CH 3 D and Δ12CH 2 D 2) allow the investigation of methane isotopic bond ordering, elucidating the methane generation mechanism and its post-generation processes, which can complement studies of the molecular and conventional stable isotopic compositions of gas hydrocarbons in constraining the origin and source of natural gas. This study focused on methane clumped isotopes, and chemical and conventional stable isotopic compositions of natural gas samples from four typical oil and gas regions of the Tarim Basin. Results indicate that these gases are thermogenic gases with relatively high stable isotopic δ values (i.e., −46.1‰ < δ13C–CH 4 < −25.9‰, −184‰ < δD-CH 4 < −140‰). Most exhibit equilibrium methane clumped isotope signatures at temperatures of 128–257 °C, consistent with the main oil-window to gas-window region. The clumped isotope apparent temperature of equilibrated methane was used to determine its formation temperature, which was applied for gas–source correlations and thermal maturity assessments of the natural gases based on the results of previous basin modeling. The clumped isotope compositions of two gas samples from the Keshen area of the basin are characterized by significant deficits in Δ12CH 2 D 2 values but with similar Δ13CH 3 D values to those of other equilibrated gases there, indicating the possibility of methane bond re-ordering at high temperatures (>300 °C) exceeding the methane "closure temperature". Non-equilibrium gases in the Tabei area yielded a plausible Δ13CH 3 D apparent temperature (<160 °C) with a pronounced deficit in Δ12CH 2 D 2 values, possibly owing to irreversible chemical kinetic processes in thermal cracking of organic matter at early thermal maturity (R o < 1.5‰) or mixing between thermogenic gases generated at two distinct temperatures (i.e., ∼200 °C and ∼120 °C). Equilibrium clumped isotope signatures also rule out the possible effects of secondary alteration on natural gases in the Hetianhe area that were previously considered in conventional isotope studies. Such findings demonstrate that methane clumped isotopes provide independent and effective indicators of gas–source correlations in deep basins while also elucidating secondary processes that are often under- or over-estimated in conventional stable isotope studies. • Natural gases in Tarim Basin are thermogenic gases with most at internal equilibrium. • Gases are generated at temperatures of 128–257 °C matching main oil to gas windows. • Clumped isotopes provide independent and robust proxies for source identification. • Clumped isotopes elucidate alterations un- or mis-recognized by conventional methods. [ABSTRACT FROM AUTHOR]

The viscoelastic behavior of minerals in shales is important in predicting the macroscale creep behavior of heterogeneous bulk shale. In this study, in situ indentation measurements of two major constitutive minerals (i.e., quartz and clay) in Longmaxi Formation shale from the Sichuan Basin, South China, were conducted using a nanoindentation technique and high-resolution optical microscope. Firstly, quartz and clay minerals were identified under an optical microscope based on their morphology, surface features, reflection characteristics, particle shapes, and indentation responses. Three viscoelastic models (i.e., three-element Voigt, Burger's, and two-dashpot Kelvin models) were then used to fit the creep data for both minerals. Finally, the effects of peak load on the viscoelastic behavior of quartz and clay minerals were investigated. Our results show that the sizes of the residual imprints on clay minerals were larger than that of quartz for a specific peak load. Moreover, the initial creep rates and depths in clay minerals were higher than those in quartz. However, the creep rates of quartz and clay minerals displayed similar trends, which were independent of peak load. In addition, all three viscoelastic models produced good fits to the experimental data. However, due to the poor fit in the initial holding stage of the three-element Voigt model and instability of the two-dashpot Kelvin model, Burger's model is best in obtaining the regression parameters. The regression results indicate that the viscoelastic parameters obtained by these models are associated with peak load, and that a relatively small peak load is more reliable for the determination of viscoelastic parameters. Furthermore, the regression values for the viscoelastic parameters of clay minerals were lower than those of quartz and the bulk shale, suggesting the former facilitates the viscoelastic deformation of shale. Our study provides a better understanding of the nanoscale viscoelastic properties of shale, which can be used to predict the time-dependent deformation of shale. [ABSTRACT FROM AUTHOR]

In this article, we investigate the performance bottleneck of existing deep learning (DL) systems and propose DLBooster to improve the running efficiency of deploying DL applications on GPU clusters. At its core, DLBooster leverages two-level optimizations to boost the end-to-end DL workflow. On the one hand, DLBooster selectively offloads some key decoding workloads to FPGAs to provide high-performance online data preprocessing services to the computing engine. On the other hand, DLBooster reorganizes the computational workloads of training neural networks with the backpropagation algorithm and schedules them according to their dependencies to improve the utilization of GPUs at runtime. Based on our experiments, we demonstrate that compared with baselines, DLBooster can improve the image processing throughput by 1.4× – 2.5× and reduce the processing latency by 1/3 in several real-world DL applications and datasets. Moreover, DLBooster consumes less than 1 CPU core to manage FPGA devices at runtime, which is at least 90 percent less than the baselines in some cases. DLBooster shows its potential to accelerate DL workflows in the cloud. [ABSTRACT FROM AUTHOR]

The quantification of mechanical properties of organic matter in shale is of significance for the fine prediction and characterization of shale reservoir's mechanical properties. Due to the micron-sized and dispersed distribution of organic matter particles in shale, the accurate evaluation of the actual mechanical response remains challenging. This work focuses on shale from Wufeng-Longmaxi Formation, which is the main shale gas exploration and development formation in China. A method based on atomic force microscopy (AFM) with an optical microscope (i.e., in-situ AFM technique) is presented to locate the organic matter in-situ and then visualize and quantify its mechanical properties using AFM Young's modulus mapping. The merits and limitations for determining the mechanical properties of organic matter in shale between the AFM and the more conventional nanoindentation technique are discussed. Results show that combining in-situ nanoindentation and in-situ AFM mapping provides more accurate description of the mechanical properties of organic matter in shale than traditional grid indentation methods with low spatial resolution. The Young's moduli of organic matter calculated from nanoindentation are around twice smaller than those obtained from AFM measurements mainly because the elasto-plastic deformation zone of organic matter in nanoindentation tests is larger and can be additionally affected by the presence of inorganic particles and/or larger micro-pores in organic matter. The Young's modulus and hardness of graptolite in the shale obtained by nanoindentation are slightly larger than those of solid bitumen at the same thermal maturity. Both in-situ AFM and in-situ nanoindentation results show that the mechanical strength of organic matter increases with increasing maturity. Overall, the presented approach shows a great potential for accurate and in-situ measurement of the mechanical properties of organic matter in shale at the nanoscale, which may be beneficial to the development of rock mechanical models for the accurate evaluation of the actual mechanical properties of shale. [ABSTRACT FROM AUTHOR]

Creep of shale controls the stability of fault gouge in sedimentary rocks, aseismic deformation in the upper crust, and several engineering operations, such as proppant embedment, reservoir subsidence, and wellbore stability during unconventional shale gas exploitation. However, measuring the creep properties of shale is challenging due to the multi-scale structure of this rock. Here, our goal is to assess how creep parameters measured at the core sample scale depend on those measured at the nanoscale in shales. We selected three clay-rich and quartz-rich shale samples and conducted a series of experiments on shale samples at two scales: nanoindentation creep measurements on thin sections, and uniaxial creep tests on core samples. The creep parameters, including creep displacement (Δh), indentation creep (C IT), creep strain rate sensitivity (m), contact creep modulus (C), and viscoelastic parameters (E 1 , E 2 , η 1 , and η 2) of the Burgers' model, were calculated by fitting the nanoindentation creep data of each single-phase component of shale matrix. From these data, we upscale the creep parameters (E 1 , E 2 , and C) of shale matrix to those of the bulk shale. Upscaled E 2 and C values based on the Mori-Tanaka scheme are found to be relatively close to those measured in previous microindentation study on Longmaxi shale and are consistent with our measurements in uniaxial creep tests on core samples of clay-rich shale and quartz-rich shale. The upscaling value of the elastic parameters, E 1 , is almost twice larger than the results from uniaxial creep test. We interpret this difference as due to low elastic stiffness along grain contacts of the shale that nanoindentation measurements underestimate. Our results show a consistency of some creep parameters upscaled from nanoindentation data and those measured at a macroscopic scale on core samples. [ABSTRACT FROM AUTHOR]

• An online hydrocarbon gas concentration system is used for the intermolecular and intramolecular isotope analysis of low-abundance C 2+ gaseous hydrocarbons. • The system allows marked enrichment of low-abundance C 2+ gaseous hydrocarbons and results in no obvious isotopic fractionation. • The system coupled to GC–IRMS or GC–Py–GC–IRMS can be used for accurate and precise determination of the C–H isotopic compositions of low-content C 2+ gaseous hydrocarbons and the position-specific c isotopic compositions of low-content propane in highly mature natural and shale gases. The stable isotopic composition of natural gas can be used to identify its origin and source. However, low concentrations of gaseous hydrocarbons in high-mature natural and shale gases hinder accurate determination of their compound- and position-specific isotopic compositions. In this study, an online C 2+ hydrocarbon gas concentration system combined with gas chromatography–isotope ratio mass spectrometry (GC–IRMS) or gas chromatography–pyrolysis–gas chromatography–isotope ratio mass spectrometry (GC–Py–GC–IRMS) was developed to determine compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons. The lower limit of the gas concentration required for isotope ratio determination using the online concentration system is 0.001% (0.003%) for compound-specific carbon (hydrogen) isotopes and 0.005% for position-specific carbon isotopes and is thus applicable to most natural gas samples. The online concentration technique does not cause significant isotopic fractionation effects, and the combination with GC–IRMS and GC–Py–GC–IRMS can accurately and precisely determine the compound-specific δ13C and δD values of low-content C 2+ gaseous hydrocarbons and the position-specific δ13C values (δ13C a , δ13C b , and SP values) of propane in low-content propane samples, respectively. The application of our method to two natural gas samples from the Ordos and Sichuan basins further confirms that the online concentration method allows simple and rapid determination of the compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons. [ABSTRACT FROM AUTHOR]

Kerogen is the most abundant form of naturally occurring organic matter in organic-rich shale, and it can affect the macro-mechanical characteristics of shale reservoirs during the whole shale thermal evolution process. However, the magnitude and mechanism of this effect are not clear. Here, a relatively low-maturity kerogen isolated from an organic-rich shale was used to prepare a series of kerogen samples of different maturities in an artificial pyrolysis experiment. Raman spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy were used to determine changes in the chemical structures of the kerogen samples, and in situ nanoindentation analysis was employed to characterize the evolution of their mechanical properties. Raman spectral analyses indicate that Raman band separation (RBS) is very sensitive to thermal maturity, increasing with maturity and displaying a strong linear correlation with mechanical properties of kerogen such as hardness and Young's modulus. Based on the solid-state 13C NMR and nanoindentation analysis, the evolution of kerogen mechanical properties with maturity can be divided into two stages: oil-generation wet-gas stage (corresponding to 0.7%–2.5% EasyRo), and dry-gas stage (2.5%–4.5% EasyRo). In the former, kerogen exhibits a soft nature with relatively low hardness and Young's modulus, possibly attributable to its relatively large proportion of aliphatic carbon and long-chain alkanes. When maturity reaches the gas stage, kerogen becomes increasingly stiff due to the markedly increased proportion of aromatic and bridgehead carbon. Considering the strong positive correlation between mechanical parameters and chemical-structure parameters (RBS, and aromatic and bridgehead carbon ratios) of kerogen during the overall thermal evolution process, we suggest that the stiffening of kerogen may result from the decreasing content of aliphatic chains and increasing aromatic carbon. This study will be beneficial to the development of rock mechanical models that are critical for accurately evaluating borehole stability and optimizing hydraulic fracture design. • Kerogen mechanical properties evolution with maturity is divided into two stages. • Hardness and Young's modulus of kerogen increase with thermal maturity. • Kerogen mechanical parameter is closely related to chemical-structure parameter. • Condensation of aromatic groups controls kerogen mechanical properties evolution. [ABSTRACT FROM AUTHOR]

Oil-based drilling mud (OBM) contamination, commonly occurring in cuttings during petroleum exploration, has had been a problem seriously hindered source rock identification and evaluation. To eliminate the effect of contamination on "free" bitumen extracted directly from source rock, "enclosed" and "bound" bitumens were released from the mineral matrix by demineralization and from the kerogen structure using an improved catalytic hydropyrolysis technique, respectively. Geochemical and carbon isotopic compositions of the three types of bitumen were used to reconstruct the geochemical characteristics of original organic matter in their source rocks. Results indicate that "free" and "enclosed" bitumens have similar biomarker distributions and n -alkane δ13C values in non-contaminated cuttings, but the former is more susceptible to OBM contamination. "Enclosed" bitumen can thus be used to characterize the organic geochemistry of source rocks contaminated by OBM. The carbon isotopic compositions of individual n -alkanes in "free" and "enclosed" bitumens differ from those in "bound" bitumen, likely because of the effects of diagenesis and other secondary alteration. "Bound" bitumen is more likely to preserve the molecular carbon isotopic characteristics of original organic matter in source rocks, while the "free" and "enclosed" bitumens more represent the generation products. Based on biomarker characteristics and carbon isotopic compositions of "bound" hydrocarbons, Wenchang (WC) Formation (Fm.) source rocks in the Zhu I Depression of the Pearl River Mouth Basin (PRMB) can be divided into three types in normal medium–deep (WC–I), shore–shallow (WC-II), and special medium–deep (with different algal blooms growth rates; WC-III) lacustrine source rocks. The special medium–deep lacustrine source rocks of Wenchang Fm. are characterized by high ratio of C 30 4-methylsteranes to C 29 steranes (4-Me/C 29 > 0.66) and heavy δ13C values (δ13C kerogen < −26.1‰), which are obviously different from those of normal medium–deep lacustrine source rocks. The combination of "free", "enclosed", and "bound" hydrocarbons geochemical and isotopic compositions thus provides a comprehensive understanding of source rocks. • Geochemical feature of free, enclosed and bound bitumens in cuttings was compared. • Enclosed and bound bitumens were less affected by oil-based drilling mud. • Bound bitumen may record information of original organic matter in source rock. • Three types of Wenchang Fm. source rocks in Zhu I Depression were identified. [ABSTRACT FROM AUTHOR]

Recent breakthroughs in Pearl River Mouth basin (PRMB) regarding offshore hydrocarbon exploration have shifted the focus from deepwater area to ultra-deepwater area (>1500 m water depth), and the southern sub-sag of Baiyun sag, Liwan sag, and the Shunhe Uplift between them constitute the front area for PRMB ultra-deepwater hydrocarbon exploration. This study investigated the source-rock strata (i.e., Eocene Wenchang Formation and Enping Formation) and reservoir fluids (mainly CO 2 with small amounts of oil and alkane gas) in the first exploratory well (namely W21, drilled at Shunhe Uplift), aiming to unscramble the source kitchen and hydrocarbon prospect information in this ultra-deepwater area. Biomarker and transgressive history analysis of source-rock strata jointly determined the Wenchang Formation and Enping Formation to be marine sediments in the Liwan sag, while marine and lacustrine sediments in the Baiyun southern sub-sag, respectively. The oil biomarkers and isotopes of alkane gas evidenced prospect for mature oil and oil-associated gas in this ultra-deepwater area, and the correlated source analysis determined the source rocks in the two sags have an advantage of aquatic organic input, indicating a good hydrocarbon-generating potential. Additionally, the regional distribution of terrestrial source-specific biomarkers (i.e., oleanane and bicadinanes) in PRMB deep to ultra-deep water areas traced the terrestrial source area and revealed a significant less input of terrigenous organic matter at the two ultra-deepwater sags. The isotopic analysis of reservoir non-hydrocarbon gases determined the CO 2 to be mantle-derived magmatic origin. The present reservoirs are a result of displacement of early charged oils by posterior migrated CO 2. In conclusion, this PRMB ultra-deepwater area has a considerable prospect for mature oil; however, the frequent volcanism since the Pliocene poses great risks to hydrocarbon exploration. • Identified the origin and type of oil and gas in CO 2 -charged reservoirs in well W21. • Deduced the sedimentary environment and organic input of source rocks in PRMB ultra-deepwater sags. • Revealed a risk of displacement of hydrocarbon reservoirs by magmatic CO 2 in PRMB ultra-deepwater area. [ABSTRACT FROM AUTHOR]

During hydraulic fracturing for shale gas development, water softening and creep deformation of shale rock are two common engineering problems that severely impair production performance. In order to understand the mineralogical and microstructural control on this mechanism from microscale, a brittle black shale from Lower Silurian Longmaxi Formation (named as LMX shale) and a clayey oil shale from Paleogene Youganwo Formation (YGW shale), which represent two members of shale family with different mineral constitutes and microstructures, were selected for hydration process under various durations (0.5 h–96 h) and temperatures (25 °C and 50 °C). The accompanied changes of microstructural and mechanical properties during hydration at microscale were investigated via nuclear magnetic resonance (NMR) and nanoindentation, respectively. Based on NMR T 2 spectra, peak T 2 time and water-infiltrated pore increment for both LMX and YGW shales rise sharply within the first 12 h, whereas remain invariable hereafter. And the values increase at higher temperature. For YGW shale, the maximum peak T 2 time is lower but the incremental porosity is higher than LMX shale, respectively. Such difference indicates an occurrence of gradually enlarged and connected pores inside LMX shale after hydration, while a greater number of disconnected pores have been developed in YGW shale, comparatively. For both shales, great strength deterioration and creep enhancement are monitored within the first 12 h of hydration. The modulus reduction could be as high as 26.27% and 80.16% after 96 h soaking at 50 °C for LMX and YGW shales, respectively. Creep strain rate sensitivity increases from 0.026 to 0.234 for LMX shale, and 0.011 to 0.099 for YGW shale with intensified softening degree. The softening mechanism for LMX brittle shale is dominated by secondary pores and cavities generated as a result of dissolution of carbonate cementation and grain detachment after water infiltration, while microstructural integrity of YGW oil shale is degraded by clay swelling. Due to different mineral constitutes and microstructures, creep deformation for clayey YGW shale is mainly mediated by dislocation movement of fine clay grains, whereas diffusion creep plays the key role in coarse-grained LMX shale. This comparative study with two distinct shale samples provides the mineralogy- and microstructure-based framework for interpreting water softening process and creep mechanism of shale, which benefits hydraulic fracture design in different shale formations so as to enhance shale oil/gas production. • Hydration-induced creep behavior of two shales were compared via nanoindentation. • Brittle shale is softened due to enlarged pores revealed by increased NMR T 2 peak time. • Clayey oil shale is deteriorated by clay swelling with increased NMR T 2 peak height. • Creep mechanism of brittle shale is prone to diffusion with m close to 0.25. • Creep behavior of clayey shale is controlled by dislocation with m＜0.1. [ABSTRACT FROM AUTHOR]

• Pyrolysis experiments on four organic matter types simulate propane evolution. • Propane intramolecular isotope fractionation shows variations with mechanism. • Rayleigh model indicates the heterogeneity of the isotopic structure of oil. • Intramolecular isotopes of propane predict the origin and maturity of natural gas. Position-specific isotope analysis (PSIA) of propane provides novel insights into formation mechanisms and thermal maturity of natural gas. The evolution of thermogenic propane in natural gas was simulated with pyrolysis experiments using types I, II A , III kerogen and an oil. PSIA of propane involved on-line pyrolysis with gas chromatography–isotope ratio mass spectrometry to explore evolution characteristics and fractionation mechanisms of propane position-specific δ13C values. Results indicate the formation of propane can be considered in three stages. Stage I (<1.3% EasyRo) involves propane production mainly from primary kerogen cracking, with its precursors having homogeneous isotopic distributions and with position-specific 13C variation patterns depending on the kerogen molecular structure. In Stage II (1.3% EasyRo to maturity of peak propane yield), propane is derived mainly from secondary cracking of bitumen/oil, resulting in 13C enrichment of terminal (δ13C a) and central (δ13C b) C atoms with maturity and a strong linear relationship between δ13C a and δ13C b. A suggested new pattern is explained by a Rayleigh model for the evolution of propane position-specific δ13C values in this stage. In Stage III (maturity greater than the peak propane yield), propane destruction mainly controls its amount and isotopic signature. Propane site-preference (SP) value (δ13C a –δ13C b) can be used to determine its formation mechanism and maturity, with positive and negative values respectively indicating primary kerogen cracking and secondary oil/bitumen cracking. Increasing maturity causes decreasing values. The application of propane PSIA to the Tarim Basin gas samples demonstrates its potential for determining the mechanism of formation and maturity of natural gas. [ABSTRACT FROM AUTHOR]

• Deans-switch is used to avoid complex preparation and losses of trace samples. • Baseline separation of crocetane and phytane is achieved (R >1.5) by 2D-GC technique. • First accurate determination of δ13C of crocetane in natural samples by 2D-GC-IRMS. Compound-specific isotope analysis of crocetane in sediments can be used to determine its origin. However, the co-elution of crocetane with phytane and complex substrates hinders the accurate determination of its isotopic composition. A heart-cutting two-dimensional gas chromatography–isotope ratio mass spectrometry (2D-GC–IRMS) method was developed to determine δ13C values of crocetane. Full chromatographic separation of crocetane was achieved with a 30 m CycloSil-B chiral capillary first column and a 60 m Chiraldex B-pH capillary second column (two series-connected 30 m Chiraldex B-pH capillary columns). Analyses of standard mixtures confirmed that the new method has satisfactory accuracy (deviations from the authentic values <0.5‰) and precision (RSDs <5%) for carbon isotope analyses of crocetane and phytane. The application of the method to two sediment samples indicates that baseline resolution is achieved (R >1.5) for crocetane and phytane, with 13C-depleted crocetane (δ13C values of −119.5‰ and −111.5‰ in the two natural samples, respectively) being an indicator of anaerobic oxidation of methane in cold seep areas. The new 2D-GC–IRMS method allows simple and efficient determination of the compound-specific carbon isotopic compositions of crocetane. [ABSTRACT FROM AUTHOR]

Research on the origin and source of hydrate-bound gas and its relationship to deep conventional oil and gas accumulation in a basin is critical to understanding the accumulation mechanism of gas hydrates and to resource evaluation of gas hydrate accumulation. In this study, the hydrate-bound gas obtained via pressure coring and the production gas recovered during a production test on a gas hydrate reservoir in the Shenhu area offshore of Southern China were tested and discussed. The geochemical analysis results indicate that methane is the predominant gas, and heavier hydrocarbons (C2+) are also present but in low concentrations. The molecular compositions of the hydrate gas recovered from two production test sites are similar to those of the hydrate-bound gas acquired via pressure coring. In addition to the isotopic composition of the methane, the carbon and hydrogen isotopes of the C2+ hydrocarbons were obtained for the first time. The δ13C isotopes of the methane range from −66.6‰ to −46.2‰, indicating that the hydrate-bound gases have a mixed origin, containing both biogenic and thermogenic gases. The plot of δ13C 1 versus δ13C 2 suggests that the biogenic and thermogenic hydrocarbons were derived from marine organic matter and terrestrial organic matter, respectively. The isotopic characterization of the hydrate-bound gas reveals that the thermogenic hydrate gas contains both humic-type gas and sapropel-type gas, but the sapropel-type gas is predominant. The source rocks of the thermogenic hydrate gas are interpreted to be both the gas-prone coal measure strata of the Enping Formation and the oil-prone medium-deep lacustrine strata of the Wenchang Formation, the latter of which contributed more to the hydrocarbon supply of the gas hydrates. In addition, the maturity of the source rocks of the thermogenic hydrate gas may be lower than that of the deeply buried conventional hydrocarbons discovered in the Baiyun Sag-Panyu Low Uplift area. The seismic profile crossing the shallow gas hydrate accumulations and deep conventional gas reservoirs clearly shows that the proven LW3-1 thermogenic gas reservoir communicated with the gas hydrate stability zone through vertical migration pathways formed by high-angle faults and gas chimneys. This indicates that there was a cogenetic relationship between the thermogenic hydrate gas and the deep conventional hydrocarbon reservoir, which was supplied the thermogenic gas derived from both the Wenchang and Enping formations. The major implications of this finding are that it confirms, rather than theorizes, the identity of the hydrocarbon source rocks of the thermogenic hydrate gas in the Shenhu area for the first time, and it demonstrates the coupling relationship between the shallow gas hydrate accumulations and the deep conventional reservoirs proposed in previous studies. The mechanisms of hydrocarbon migration and gas hydrate accumulation in the production test gas hydrate reservoirs in the Shenhu area were also identified, providing a valuable reference for subsequent exploration and for the potential exploitation of gas hydrate reservoirs in the South China Sea. • The δ13C and δD isotopes of the heavier hydrocarbons (C2+) in the Shenhu area are obtained for the first time. • The origin of the hydrate gas obtained from the second trial production well in the Shenhu area is confirmed. • The hydrocarbon source rocks of the thermogenic hydrate gas in the Shenhu area are identified. • Coupled paragenetic relationship between shallow gas hydrate and deep petroleum system is revealed. [ABSTRACT FROM AUTHOR]

Two classification methods, the distribution of biomarkers and the alternating least squares (ALS) chemometric analysis were used to investigate the genetic characteristics of oils collected from the Baiyun deep-water area of the Pearl River Mouth Basin in the South China Sea. Results of the two methods were generally consistent that most of the oils were originated from the shallow lacustrine source rocks, but oils from the West Sub-Sag (WSS) and the South Sub-Sag (SSS) have a distinct geochemical characteristic with low abundances of bicadinanes and oleanane, and relatively lighter δ13C value (<−28.0‰). The ALS chemometric analysis can quantitatively determine the sources of the oils. It shows that mixing has commonly occurred between the oils, and three end-member oils were identified (i.e., EM1, EM2, and EM3), which were derived from the semideep–deep Wenchang Formation source rocks that are characterized by a predominance of C 27 steranes and low concentrations of bicadinanes and oleanane, the shallow lacustrine Enping Formation source rocks in the Main Sub-Sag (MSS) that are rich in bicadinanes but depleted in oleanane, and the shallow lacustrine Wenchang and/or Enping formations source rocks in the East Sub-Sag (ESS) that have a relatively high abundance of bicadinanes, a moderate content of oleanane, and a predominance of C 29 steranes, respectively. The oils from the Panyu Low Uplift (PLU) are dominated by >83% of EM2 oil. Oils from the SSS and WSS are dominated by EM1 oil (68.0%–93.1%). Oils from the ESS and eastern part of the MSS (E-MSS) are mixed oils consisting mainly of EM2 and EM3 oil, with an increasing proportion of EM3 moving from the E-MSS to central ESS. The maturity of the oils was assessed based on diamondoid indices, and oils from the PLU have the highest maturities (1.43%–1.59% Rc), whereas oils from the SSS have the lowest maturities (1.23%–1.25% Rc), corresponding to the different maturities of their source rocks. The semideep–deep lacustrine oils discovered in the WSS and SSS highlight the hydrocarbon generation potential of these types of source rocks in the Wenchang Formation, where further oil exploration should be focused. • Oils from different structural belts have different origins on a regional scale. • Alternating least squares analysis shows three end-member oils in the Baiyun Sag. • The end-member oils are correlated to the source rocks in the Baiyun Sag. • Maturity studies based on diamondoid indices support the genetic analysis. • Semideep–deep lacustrine oils in the WSS and SSS are a new exploration target. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis experiments on four organic matter types simulate diamondoid evolution. • Principal component analysis explains the main factors affecting diamondoid indices. • PCA-Fisher discriminant analysis model objectively identifies oil source types. • PCA-regression analysis model quantitatively predicts oil thermal maturity. Assessing the origins and thermal maturity of oils is an important issue in applied petroleum geochemistry. In this study, we extracted information regarding the sources and thermal maturity of oils from diamondoid data using multivariate statistical analysis based on four series of thermal simulation experiments conducted on Type I, II, and III kerogens and a crude oil. Using principal component analysis (PCA) and discriminant analysis (DA), we established the relationship between diamondoid indices and kerogen type, which was then used to identify the source of oils in some oil fields in China. PCA and regression analysis (RA) were used to determine the quantitative relationship between diamondoid indices and thermal maturity, which was then used to estimate the thermal maturity of the studied oils. Our results indicate that this approach is effective for determining the source and maturity of oils, particularly for condensates. [ABSTRACT FROM AUTHOR]

Petroleum exploration has found that the Baiyun deep-water area of the Pearl River Mouth Basin (PRMB), China, holds abundant oil and gas resources with great prospects. However, conditions restricting offshore drilling in this area present significant challenges to the investigation of source rocks. Core samples are lacking, and any cuttings obtained are generally highly contaminated by drilling mud. As a result, the identification and evaluation of hydrocarbon sources in deep-water areas would be greatly aided by new techniques capable of reliably obtaining the geochemical characteristics of potential source rocks. This study combines catalytic hydropyrolysis (HyPy) and gas chromatography–isotope ratio mass spectrometry (GC–IRMS) to determine the carbon isotope composition of individual n -alkanes covalently bound in kerogen framework. Furthermore, it reconstructs the source and depositional environment of sedimentary organic matter in potential source rocks from the Baiyun deep-water area of the PRMB. The results indicate that the optimized degassing (i.e., degassing under high vacuum at 250 °C for 24 h) can effectively eliminate hydrocarbon contaminants in the kerogen. Determination by GC–IRMS of bound n -alkanes released from the degassed kerogen by HyPy can provide the molecular carbon isotope characteristics of the original organic matter in cuttings contaminated by drilling mud. The results improve the understanding of potential hydrocarbon source rocks in the Baiyun deep-water area of the PRMB. • Optimized off-line degassing process could eliminate contaminants in kerogen. • Bound n -alkanes released from kerogen maintain δ13C values of their precursors. • δ13C of n -alkanes for source rocks in the Baiyun Sag are firstly identified. • Catalytic hydropyrolysis combined with GC–IRMS can regain original geochemistry. [ABSTRACT FROM AUTHOR]