Abstract:

The Liaodong Bay depression is located in northeastern Bohai Bay Basin.Hydrocarbon-bearing layers in the depression present a trend of becoming younger from north to south.Most hydrocarbon accumulations in the northern and central parts of the depression are distributed in the Dongying and Shahejie formations—a pattern closely related with the mudstone (thicker in the north and thinner in the south) in the Dongying Formation.Considering the structural features,evolution of depositional systems,and formation development in the Liaodong Bay depression,we studied the overpressure created by the mudstone in the Dongying Formation and the configurations of the mudstone with carrier systems such as sand bodies,faults,unconformities,and discussed the controlling effect of the mudstone on hydrocarbon accumulations in the Liaodong Bay depression.The result shows that the mudstone,together with faults,oil sources and sandbodies,control the distribution of oil and gas accumulations.Of these factors,the overpressure created by the thick mudstone has a strong presence in affecting the distribution of accumulations in the northern and central parts of the depression,causing most of them occurring in the Dongying Formation and its underlying layers.

Key words: overpressure system, mudstone seal, hydrocarbon reservoir, Dongying Formation, Liaodong Bay Depression, Bohai Bay Basin