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The Eocene Niubao Formation is the primary research target of oil exploration in the Lunpola Basin. Crude oil was extracted from Well Z1 on the northern margin of the basin in 1993. In this study, an integrated evaluation of the source rock, geothermal, and maturity histories and the fluid inclusion and fluid potential distributions was performed to aid in predicting areas of hydrocarbon accumulation. Due to the abundance of organic matter, the kerogen types, maturity, and oil-sources correlate with the geochemical data. The middle submember of the second member of the Niubao Formation (E2n2-2) is the most favorable source rock based on the amount of oil produced from the E2n2-3 and E2n3-1 reservoirs. One- and two-dimensional basin modeling, using BasinMod software, shows that the E2n2-2 source rock started to generate hydrocarbon at 35-30 Ma, reached a maturity of R0=0.7% at 25-20 Ma, and at present, it has reached the peak oil generation stage with a thermal maturity of R0=0.8% to less than R0=1.0%. By using fluid inclusion petrography, fluorescence spectroscopy, and microthermometry, two major periods of oil charging have been revealed at 26.1-17.5 and 32.4-24.6 Ma. The oil accumulation modeling results, conducted by using the Trinity software, show a good fit of the oil shows in the wells and predict that the structural highs and lithologic transitions within the Jiangriaco and Paco sags are potential oil traps. [ABSTRACT FROM AUTHOR]

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The Upper Triassic tight sand oil in the Ordos Basin has gradually become a focus of research; however, compared to the centre of the basin, studies on the margin have been relatively weak. In this study, an integrated approach involving oil–source correlation, charge history, and pressure evolution is used to investigate the migration characteristics of each stage and to establish a migration and accumulation process model of the tight sand oil in the Yanchang Formation of Honghe Oilfield in combination with reservoir densification process. The results show that, based on the fluid inclusion analysis and authigenic illite K–Ar dating technique in combination with burial and thermal modellings, the accumulation periods were 145–130, 120–90, and 90–80 Ma, which corresponds to the Cretaceous. According to the relative content of C30‐diahopane and drimane series compounds, the crude oil from Chang 8(T3ch8) and Chang 9(T3ch9) both originated from the oil shale of Chang 7(T3ch7) in the Upper Triassic Yanchang Formation. The migration characteristics and directions are comprehensively analyzed using the maturity parameters and key elements. In the early stage of the Early Cretaceous, with east‐dipping strata, crude oil migrated from northeast to southwest. During the late Early Cretaceous, the middle‐late Yanshanian movement promoted the development of strike‐slip faults and fractures, and the oil migrated vertically downwards along them. Tectonic inversion changed the strata dip direction to west‐dipping, and lateral migration was also changed to two directions of southwest and northeast. After the Late Cretaceous, the migration dynamics weakened due to strata uplift and cessation of hydrocarbon generation. Only slight adjustments to the crude oil occurred during the Himalayan movement; therefore, the current distribution pattern of the tight sand oil is still affected primarily by the stage of late Early Cretaceous. The migration and accumulation model of the Upper Triassic in the Honghe Oilfield, Ordos Basin, provides a theoretical basis for further exploration and is of general applicability to tight sand reservoirs in the margins of various basins. [ABSTRACT FROM AUTHOR]

The hydrocarbon migration and accumulation of the Suqiao deep buried-hill zone, in the Jizhong Subbasin, the Bohai Bay Basin, eastern China, was investigated from the perspective of paleo-fluid evidence by using fluid inclusions, quantitative fluorescence techniques (QGF), total scanning fluorescence method (TSF) and organic geochemical analysis. Results show that the current condensate oil-gas reservoirs in the study area once were paleo-oil reservoirs. In addition, the reservoirs have experienced at least two stages of hydrocarbon charge from different sources and/or maturities. During the deposition of the Oligocene Dongying Formation (Ed), the deep Ordovician reservoirs were first charged by mature oils sourced from the lacustrine shale source rocks in the fourth member of Shahejie and Kongdian Formations (Es 4 +Ek), and then adjusted at the end of Ed period subsequently by virtue of the tectonic movement. Since the deposition of the Neogene Minghuazhen Formation (Nm), the reservoirs were mainly charged by the gas that consisted of moderate to high-maturity condensate and wet gas sourced from the Es 4 +Ek lacustrine shale source rocks and mature coal-derived gas sourced from the Carboniferous-Permian (C-P) coal-bearing source rocks. Meanwhile, the early charged oil was subjected to gas flushing and deasphalting by the late intrusion of gas. The widely distributed hydrocarbon inclusions, the higher QGF Index, and FOI (the frequency of oil inclusions) values in both gas-oil and water zone, are indicative of early oil charge. In addition, combined with the homogenization temperatures of the fluid inclusions (<160 °C) and the existence of solid-bitumen bearing inclusions, significant loss of the n -alkanes with low carbon numbers, enrichments of heavier components in crude oils, and the precipitation of asphaltene in the residual pores suggest that gas flushing may have played an important role in the reservoir formation. [ABSTRACT FROM AUTHOR]