Neogene natural gas genesis and hydrocarbon differential enrichment mechanism in the basin marginal sag of Bohai Bay Basin: a case study of the eastern subsag of Huanghekou sag
Yang Haifeng, Wang Deying, Gao Yanfei, Wang Jun, Li Zhengyu, Qian Geng
Tianjin Branch, CNOOC China Limited, Tianjin 300459, China
It was previously considered that the basin marginal sag had shallow buried depth, small area and limited hydrocarbon generation capacity, thus attracting little attention. Now the basin marginal sag has become the key hotspot of oil and gas exploration in the Bohai Bay Basin, and the hydrocarbon accumulation mechanisms and enrichment laws needs to be further explored. Based on the geochemical data, the Neogene hydrocarbon accumulation mechanism and distribution laws of the eastern subsag in Huanghekou sag were systematically studied. The results show that the Neogene crude oil and natural gas of the eastern subsag in Huanghekou sag have different sources and geneses; the crude oil originated from source rocks in the Paleogene Members 3 and 4 of Shahejie Formation, while the natural gas was the secondary biogas resulting from crude oil degradation in Neogene reservoirs. The formation of crude oil was earlier than that of natural gas, while gas reservoir is shallower than that of oil reservoir. However, the specific distribution of gas and oil reservoirs was controlled by the sealing capacities of three sets of regional caps in the mid-upper Neogene Guantao Formation, the mid-lower Minghuazhen Formation and the upper bottom of Minghuazhen Formation, showing an overall distribution law of "rich oil in the south, rich gas in the north; rich oil in the west, rich gas in the east; rich oil in the lower part, rich gas in the upper part".
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Yang Haifeng, Wang Deying, Gao Yanfei, Wang Jun, Li Zhengyu, Qian Geng. Neogene natural gas genesis and hydrocarbon differential enrichment mechanism in the basin marginal sag of Bohai Bay Basin: a case study of the eastern subsag of Huanghekou sag[J]. Acta Petrolei Sinica, 2019, 40(5): 509-518.
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2019, Vol. 40 
