Oil & Gas Geology ›› 2011, Vol. 32 ›› Issue (4): 601-605,624.doi: 10.11743/ogg20110414
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Abstract: In Zhanhua sag of Jiyang Depression in Bohai Bay Basin, structural traps are predominant in the second member of the Shahejie Formation and the strata above it, while subtle traps such as lithologic and structurallithologic traps dominate the third member of the Shahejie Formation and the strata below it. There is a certain correlation between formation pressure distribution and hydrocarbon distribution in the area, i.e., structural reservoirs occurring in areas with normal pressure while lithologic reservoirs being developed in areas with abnormal high pressure. Abnormal high pressure provides impetus for the migration of hydrocarbons in deep lithologic reservoirs. When the pressure coefficient curve presents a “3”shape, reservoirs with relatively lowpressure have higher oil potentials. Based on the relationship between formation pressure and hydrocarbon accumulation, we set up two accumulation models: “externalsourced hydrocarbons accumulating via carrier faults” and “internalsourced hydrocarbon accumulating via highpressure injection”. Shallow externalsourced hydrocarbon accumulations with normal pressure are mainly controlled by source rockrooted faults. For example, the hydrocarbon generated from the lower and mid parts of the third member of the Shahejie Formation migrates vertically along the faults and accumulates in the structural traps such as fault block and rolling anticlines in the second member of the Shahejie Formaiton and strata above it, or migrates laterally to and accumulates in structural traps. The controlling factor for the second pooling model is abnormal high pressure. Hydrocarbons generated from the lower and mid parts of the third member of the Shahejie Formation may be charged into adjacent sandbodies and structurallithologic traps under the drive of the abnormal high pressure.
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URL: http://ogg.pepris.com/EN/10.11743/ogg20110414
http://ogg.pepris.com/EN/Y2011/V32/I4/601