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Sea area is an important area of oil and gas exploration in China. It has been found that China's sea area mainly consists of coal type oil and gas, and the exploration of coal-bearing series source rocks has become an important part of oil and gas exploration there. Through years of comprehensive geological research in China's sea area, it has been revealed that it has undergone multiple occurrences of tectonic opening and closing movements in varying degrees in the Paleogene, forming 26 Cenozoic sedimentary basins of various types, such as active continental margin, passive continental margin, transitional continental margin and drift rift basins. In the present study, it is observed for the first time that coal type source rocks are mainly developed in 14 continental margin basins in China's sea area, revealing that a very large C-shaped coal-bearing basin group developed there in the Cenozoic. Next, based on the coupling analysis of paleoclimate, paleobotany, paleogeography and paleostructure, it is observed that there are five coal-forming periods in China's sea area, namely the Paleocene, Eocene, early Oligocene, late Oligocene and Miocene-Pliocene, and the coal-forming age is gradually new from north to south. It is also found that the coal seams in the sea area are mainly developed in three coal-forming environments in Cenozoic, namely delta, fan delta and tidal flat-lagoon. The coal seams developed in different environments are characterized by thin thickness, many layers and poor stability. However, the coal-bearing series source rocks in China's sea area have a wide distribution range, very high thickness and large amount, thus forming a material basis for the formation of rich coal type oil and gas. [ABSTRACT FROM AUTHOR]

Abstract Coal, especially the inertinite in it, is highly sensitive to climate changes, showing an obvious response to paleoclimate conditions, in particular, to paleo-oxygen concentration (pO2). In this study, the inertinite abundance data of typical coal-forming periods in China were systematically collected and analyzed. Its characteristics and control factors were studied, and its evolution was established. Based on inertinite abundance data, pO2 evolution curves of various coal-forming periods in China were established, which fluctuated between 15% and 30% during the entire Phanerozoic. The inertinite abundance in coal deposits during Paleozoic in China was basically consistent with that of other areas of the world, while it was quite different globally from the Mesozoic to the Cenozoic. The results show that the inertinite abundance in coal deposits is controlled by pO2 and other factors including climatic zones, plant differentiation, sedimentary environments, and tectonic activities. The inertinite abundance in coal deposits in China during the Jurassic was high, suggesting dry paleoclimate of inland China.

Coal, especially the inertinite in it, is highly sensitive to climate changes, showing an obvious response to paleoclimate conditions, in particular, to paleo-oxygen concentration (pO2). In this study, the inertinite abundance data of typical coal-forming periods in China were systematically collected and analyzed. Its characteristics and control factors were studied, and its evolution was established. Based on inertinite abundance data, pO2 evolution curves of various coal-forming periods in China were established, which fluctuated between 15% and 30% during the entire Phanerozoic. The inertinite abundance in coal deposits during Paleozoic in China was basically consistent with that of other areas of the world, while it was quite different globally from the Mesozoic to the Cenozoic. The results show that the inertinite abundance in coal deposits is controlled by pO2 and other factors including climatic zones, plant differentiation, sedimentary environments, and tectonic activities. The inertinite abundance in coal deposits in China during the Jurassic was high, suggesting dry paleoclimate of inland China. [ABSTRACT FROM AUTHOR]