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.