Gas-Source Comparison and Hydrocarbon Generation and Expulsion Histories of the Main Source Rocks of the Middle Jurassic Shaximiao Formation, Western Sichuan Basin.

With the discovery and exploration of tight sandstone gas reservoirs in the Sichuan Basin, the Middle Jurassic Shaximiao Formation has gradually become the focus of exploration. However, the gas source of the Shaximiao Formation in the Western Sichuan Basin is still controversial, and research on the hydrocarbon generation and expulsion histories of the primary source rocks lags behind, which restricts the study of tight sandstone gas reservoir dynamics within the Shaximiao Formation in the Western Sichuan Basin and further affects the oil and gas exploration process. This paper, utilizing geochemical parameters, including 82 natural gas components and 68 carbon isotopes, conducted an investigation into the origin identification of natural gas and gas-source comparisons within the Shaximiao Formation in the Western Sichuan Basin. By utilizing basin modeling technology, we reconstructed the histories of hydrocarbon generation and expulsion of the primary source rocks and identified the potential exploration areas. The findings indicate that the natural gas within the Shaximiao Formation in the Western Sichuan Basin is characterized by a typical high-maturity wet gas-dry gas reservoir. It is a thermogenic coal-type gas produced by kerogen cracking, and the gas source is primarily type-III kerogen. The main source of natural gas is the coal-measure source rock of the Upper Triassic Xujiahe 5 Formation, which has mainly experienced two stages of increasing maturity, characterized by "two stages of gas generation and one stage of gas expulsion". The hydrocarbon generation and expulsion histories for the source rocks within the Xujiahe 5 Formation is shown as follows: the source rocks of the Xujiahe 5 Formation reached the hydrocarbon generation threshold by the end of the Early Jurassic and peaked in hydrocarbon generation by the end of the Late Jurassic, and then the natural gas migrated to the paleostructural highs of the Shaximiao Formation to form the paleo-gas reservoir. From the end of the Early Cretaceous, the paleo-gas reservoir underwent adjustments and transformations to evolve into the present-day gas reservoir. The source rocks exhibit substantial potential for the forming of large-medium and extralarge gas fields, with favorable exploration zones concentrated in the southern and central portions of the study area. The research findings can provide a scientific foundation for the next exploration and deployment of natural gas resources within the Shaximiao Formation in the Western Sichuan Basin.

Hydrocarbon Generation and Expulsion Histories of the Upper Permian Longtan Formation in the Eastern Sichuan Basin, Southwest China.

The Upper Permian Longtan Formation is the main source rock of the Lower Triassic Jialingjiang Formation in the Eastern Sichuan Basin, Southwest China. However, studies of its maturity evolution and oil generation and expulsion histories are lacking, which are not conducive to the accumulation dynamics of the Jialingjiang Formation in the Eastern Sichuan Basin. Based on the study of tectono-thermal history and geochemical parameter data of the source rock, this paper uses basin modeling technology to simulate the maturity evolution and hydrocarbon generation and expulsion histories of the Upper Permian Longtan Formation in the Eastern Sichuan Basin. The results show that the Longtan Formation source rock in the Eastern Sichuan Basin entered the oil generation threshold at the middle stage of the Early Jurassic and reached the high-maturity stage in the north and central regions at the late stage of the Early Jurassic, and the maturity did not increase after the late stage of the Middle Jurassic. The source rock had the characteristic of "one-stage oil generation and one-stage oil expulsion"; the corresponding period of high oil expulsion was 182-174 Ma (the late stage of the Early Jurassic), which was later than the formation time of the trap of the Jialingjiang Formation, possibly providing oil sources for the paleo-oil reservoirs of the Jialingjiang Formation. The results are of great significance to the gas accumulation process and exploration decision-making in the Eastern Sichuan Basin.

Isolation and identification of flavonoid-producing endophytic fungi from Loranthus tanakae Franch. & Sav that exhibit antioxidant and antibacterial activities.

AIMS: Loranthus tanakae Franch. & Sav is a medicinal plant that has a variety of pharmacological properties. However, its study is currently limited because of its relative shortage of natural abundance. The objective of this work was to find an alternative resource from this plant that could produce its bioactive ingredients. METHODS AND RESULTS: We isolated endophytic fungi from the twigs of Loranthus tanakae Franch. & Sav and eight flavonoid-producing endophytic fungi were selected. The eight endophytic fungi meeting the criteria were identified as Alternaria tenuissima, Dothiorella gregaria, Penicillium aethiopicum, Nothophoma quercina and Hypoxylon perforatum by morphological and molecular methods. The antioxidant and antibacterial activities of the flavonoid-producing endophytic fungi were investigated in vitro, where Alternaria tenuissima ZP28 and ZM148 demonstrated greater activities than the other six strains. Flavonoids of ZP28 and ZM148 were preliminarily identified by liquid chromatography-mass spectrometry (LC-MS). CONCLUSION: After screening the flavonoid-producing endophytic fungi, Alternaria tenuissima ZP28 and ZM148 were found to have good antioxidant and antibacterial activities. Overall, this study provided new direction and resources for the acquisition of flavonoids. SIGNIFICANCE AND IMPACT OF THE STUDY: Endophytic fungi are a promising alternative approach for the large-scale production of flavonoids from Loranthus tanakae Franch. & Sav.