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Natural gas exploration in Nanpu sag, Bohai Bay Basin, has achieved breakthroughs in recent years, and a number of natural gas and condensate wells with high yield have been found in several structures in the beach area. Daily gas production of single wells is up to 170,000 m3, and high-yield wells are mainly distributed in the Nanpu No. 1 structural belt. Studies have shown that these natural gases are mainly hydrocarbon gases, with methane content about 80% to 90% and ethane 6%–9%, so they are mainly wet gas; and non-hydrocarbons are at a low level. Carbon isotopes of methane range from −42‰ to −36‰, and ethane from −28‰ to −26‰. Calculated maturity based on the relationship between δ13C and R0 of natural gas, the gases are equivalent to those generated from organic matter when R0 is 1.0%–1.7% (mainly 1.25%–1.32%). The natural gas is oil-type gas generated from the source rocks at mature to high mature stage, associated with condensate, so carbon isotopes of the gases are heavier. Natural gas in the Nanpu No.1 structural belt is mainly associated gas with condensate. The analysis of the origin and source of natural gas and condensate, combined with the monomer hydrocarbon carbon isotopes and biomarker, indicated that the main source rocks in the Nanpu No.1 structural belt were Es3 (the lower member of the Shahejie Formation), followed by Es1 (the upper member of the Shahejie Formation). The high-mature hydrocarbons from source rocks in the deep sag mainly migrated through deep inherited faults into shallow traps and accumulated to form oil and gas pools. Therefore, there is a great potential for exploring gas in deep layers.

It is significant to distinguish the dynamic systems of petroleum accumulation (DSPA) for the understanding of petroleum accumulation and distribution. According to the formation pressure framework, genetic types of petroleum and characteristics of conduit systems, three dynamic systems of petroleum accumulation were identified in the vertical profile in the Nanpu depression, Bohai Bay basin. The deeper DSPA (including formations Es3 to Es2) is a sealed system with high-overpressure and high-mature self-sourced oil. Most of the crude oil in the system accumulated in the periods of late Oligocene (23.5 Ma) and late Pliocene (2.4 Ma). The middle DSPA (including formations Es1 to Ed1) is an overpressured half-sealed system with mature or lower-mature self-sourced oil. The accumulation of oil in the system also occurred in the late Oligocene (23.5 Ma) and late Pliocene (2.4 Ma). The shallower DSPA (including formations Ed2 to Q) is a hydrostatic system with lower-mature alien-sourced oil from the middle system. Oil within this system accumulated only in the late Pliocene period. The oil in the shallower system migrated vertically along the faults from the formerly accumulated oil in the middle system by lateral migration along the sandbodies, whereas petroleum accumulation in the deeper system was mainly derived from the system itself by lateral migration along the sandbodies and rarely migrated out of the system. In this case, it seems that the deeper system is a more potential exploration prospect in addition to the other two proved favorable systems.

Taking the Member 1 oil reservoir of Dongying Formation in Nanpu Sag as an example, this article puts forward an integrated study method for oil reservoir description and evaluation. First, with the correlation of seismic, log, and geological data, the isochronous stratigraphic framework of the oil reservoir is built up, sequence boundaries are interpreted, the sequence constrained prestack seismic inversion is processed, and a geological conceptual model of reservoir is established. Second, with the results of prestack seismic inversion and the Petrel software, the structure model of the isochronous stratigraphic framework and the quantitative geological database are built up. Third, through contrasting and selecting the most reasonable method of stochastic modeling, the reservoir facies modeling and the petrophysical modeling with the constraint of facies models are processed, the oil geological reserves are computed and evaluated, and some oil reservoirs are described finely. The study shows that the Member 1 oil reservoir is a layered, structure-controlled, edge water drive reservoir. It has thick sands, good properties, and complicated oil–water systems. The geological reserves estimated by the nine designed implementation models are the realization of Monte Carlo methods and conform to a certain probability distribution. The models are favorable for the reasonable evaluation of reserves. Key words: Nanpu No. 1 structure, Dongying Member 1 oil reservoir, integrated oil-reservoir description and evaluation, stochastic modeling under determinable constraints

The recognition of five standard conodont biozones and five radiolarian zones in the same set of samples from cherts within the Frasnian–Famennian (F–F) boundary interval at Bancheng, southeastern Guangxi, China allowed precise placement of the F–F boundary, and demonstrated the multi-episodic pattern of the F–F mass extinction. Frasnian pelagic radiolarian and conodont faunas had an acme in the lower Palmatolepis linguiformis Zone. In the upper Pa. linguiformis Zone, until the level of the upper Kellwasser extinction (Kw.), members of the radiolarian family Ceratoikiscidae and of the conodont Frasnian populations disappeared. Above the Kw, in the lower Palmatolepis triangularis Zone, new populations of the conodont Pa. triangularis gradually appeared and the survivor radiolarian genus Trilonche gradually re-appeared, both blooming in the lower part of the middle Pa. triangularis Zone. The Nehden extinction (Nd) in the uppermost middle Pa. triangularis Zone interrupted the recovery of the conodont and radiolarian faunas, but above this level the conodont species became more numerous, and the post-extinction radiolarian faunas (including Entactiniidae) recovered gradually.