Sample preparation technique, for the analysis of δ¹³C ratios in oil and gas samples, has gradually been recognized as one of the most crucial steps of the whole analytical process. In this study, a new convenient method, syringe solid phase extraction (SSPE), was proposed for measuring δ¹³C in natural gas samples. Based on conditional experiments of temperature and time, SSPE fitted with activated carbon adsorbent was applied with a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) system for trace carbon isotope analysis. The results showed that isotopic fractionation was not clearly observed during the adsorption and desorption process, and the δ¹³C ratios measured by SSPE-GC/IRMS were in good agreement with the known δ¹³C ratios of CH₄~C₅H₁₂ measured by GC/IRMS with the accuracy all within ±0.48‰. A natural gas sample was applied to verify the efficiency of this new method, and the obtained results confirmed that SSPE-GC/IRMS is a reliable technique characterized with simplicity, efficiency, and reliability.

This study focused on Middle Permian Lucaogou Formation saline lake source rocks, utilizing a combination of biomarkers and hydrocarbon generation thermal simulation to analyze their biological compositions, depositional environments, and hydrocarbon generation potential. The Pr/Ph ratio, Ph/nC₁₈ ratio, and Pr/nC₁₇ ratio indicate that the Lucaogou Formation was in a reducing environment during the deposition period, and the lower part of the Lucaogou Formation (P₂l₁) is more anoxic than the upper part of the Lucaogou Formation (P₂l₂). The maturity index 20S (%) and ββ (%) reflect that the maturity of organic matter in the P₂l₁ is slightly higher than that in the P₂l₂. The G/H index and the ETR index indicate that the stratification of the water column is better during the sedimentary period of Lucaogou Formation and the salinity of the P₂l₁ is higher than that of the P₂l₂. The biomarker parameters of nC₂₁₋/nC₂₂₊, CPI, S/H, and C₂₂T/C₂₁T reflect that the organic matter of the source rocks have a higher abundance of bacteria and algae than higher plants, and the contents of bacteria are more than that of algae. The (7- + 8-MMAs)/C_max and (C₂₈ + C₂₉ − St)/St parameters indicate that cyanobacteria accounted for a certain proportion of bacteria, and the algae are mainly green algae. The co-evolution of the sedimentary environment and the biological composition reflects the control of the sedimentary paleoenvironment on biological composition. According to the relative content of cyanobacteria, green algae, and Rhodophyta, the source rocks of the upper and lower Lucaogou Formation correspond to the low-salinity type (LS-type) and the high-salinity type (HS-type), respectively. Compared with LS-type source rocks, HS-type source rocks have greater generation potential of oil and weaker gas generation potential. This study is valuable for the accurate assessment of source rocks and holds significant practical implications for the exploration of oil and gas resources.

A new pyrolysis technology involving chromium is proposed for the determination of δD in alkanes based on the systematic analysis of reaction temperature, conversion rate, and reaction mechanism. Compared with the traditional high-temperature conversion (HTC) method, our findings suggest that chromium/high-temperature conversion (Cr/HTC) can improve the conversion rate of hydrocarbons and reduce the required pyrolysis temperature by up to 175 °C; meanwhile, the pyrolysis conversion rate of hydrocarbons increased by an average of 2.42% across the entire analyzed temperature range using the Cr/HTC method. Changes in the chromium wire itself were analyzed using X-ray photoelectron spectroscopy (XPS); this facilitated an understanding of the interaction mechanism between chromium and hydrocarbons and possible pathways of the catalytic pyrolysis process. The results show that chromium reacts with hydrocarbons, capturing carbon as chromium carbide (Cr₂C₃ and CrC₃) and releasing hydrogen in the form of H₂. As the reaction progresses, the resulting free carbon accumulates on the surface of the chromium wire or chromium carbide, resulting in a marked reduction in the Cr/C ratio; these findings provide reliable evidence for the further application of Cr/HTC technology.

The Podong Permian ultramafic intrusion is only one ultramafic intrusion with massif Ni-Cu sulfide mineralization in the Pobei layered mafic-ultramafic complex, western China. It is obviously different in sulfide mineralization from the nearby coeval Poyi ultramafic intrusion with the largest disseminated Ni-Cu sulfide mineralization and mantle plume contribution (Zhang et al., 2017). The type and addition mechanism of the confirmed crustal contaminations and possible mantle plume involved in the intrusion formation require evidences from carbon and noble gas isotopic compositions. In the present study, we have measured C, He, Ne, and Ar isotopic compositions of volatiles from magmatic minerals in the Podong ultramafic intrusion. The results show that olivine, pyroxene, and plagioclase minerals in the Podong intrusion have variable δ¹³C of CO₂ (-24.5‰ to -3.2‰). The CH₄, C₂H₆, C₃H₈, and C₄H₁₀ hydrocarbon gases show normal or partial reversal distribution patterns of carbon isotope with carbon number and light δ¹³C₁ value of CH₄, indicating the hydrocarbon gases of biogenic origin. The δ¹³C of CO₂ and CH₄ suggested the magmatic volatile of the mantle mixed with the volatiles of thermogenic and crustal origins. Carbon and noble gas isotopes indicated that the Podong intrusion could have a different petrogenesis from the Poyi ultramafic intrusion. Two types of contaminated crustal materials can be identified as crustal fluids from subducted altered oceanic crust (AOC) in the lithospheric mantle source and a part of the siliceous crust. The carbon isotopes for different minerals show that magma spent some time crystallizing in a magma chamber during which assimilation of crustal material occurred. Subduction-devolatilization of altered oceanic crust could be the best mechanism that transported large proportion of ASF (air-saturated fluid) and crustal components into the mantle source. The mantle plume existing beneath the Poyi intrusion could provide less contribution of real materials of silicate and fluid components.