Turbidite Reservoirs in the Dongying Sag, Bohai Bay Basin: Interactions between Carbonate Cementation and Hydrocarbon Charge

Turbidite sandstones have become increasingly significant in hydrocarbon exploration. Carbonate cementation occur commonly in turbidite reservoirs developing within the Paleocene lacustrine basins, Northeastern China. This study utilizes core data, thin section data and production data to investigate the interaction between the carbonate cementation and hydrocarbon charge within turbidite reservoirs in the Niuzhuang Sub-sag of the Dongying Sag, Bohai Bay Basin, East China. The results reveal that the carbonate cementation is mainly developed at the top and bottom of the turbidite sandbodies, and even forms carbonate cement shells. Three stages of hydrocarbon accumulation are identified based on fluid inclusion analysis: stage I (27.5-24.6 Ma), stage II (14.0-5.0 Ma), and stage III (5.0-0 Ma). The interaction between the carbonate cementation and hydrocarbon charge has significant controls on the formation of a turbidite reservoir. The temporal relations and intensity relations between the two factors should be considered significantly. Moreover, hydrocarbon charge during the early stage can inhibit the carbonate cementation, favoring the hydrocarbon accumulation in turbidite reservoirs. Many deep-lacustrine turbidite sandbodies surrounded by source rocks with abnormal high pressure, are also favorable for hydrocarbon accumulation. These results suggest that some deeply buried turbidite sandbodies with similar geological settings have high potential for hydrocarbon exploration.