Various types of subtle reservoirs are developed in the northern steep slope zone of Dongying depression during different periods. During fault subsidence

various lithologic reservoirs and relevant compound reservoirs

including lenticular reservoirs

structural-lithologic reservoirs and updip pinch out reservoirs

are developed. During the transitional period from fault subsidence to downwarping

stratigraphic reservoirs as well as lithologic and structural reservoirs controlled by stratigraphy are developed

including unconformity reservoirs

fault-lithologic reservoirs

strati-graphic overlap-fault reservoirs

and fault-lithologic and stratigraphic reservoirs controlled by unconformities. Various types of hydrocarbons accumulated in different subtle reservoirs. On the periphery of the northern steep slope zone

hydrocarbons accumulated in the structure-controlled stratigraphic-lithologic reservoirs in the 3

rd

member of Shahejie Formation that have been formed during fault subsidence period

and in the stratigraphic reservoirs formed during the transitional period from fault subsidence to downwarping have mainly been sourced from the 4

th

member of Shahejie Formation. While in the inner part near hydrocarbon-generating center

hydrocarbons accumulated in the lenticular lithologic reservoirs and other lithology-related reservoirs in the 3

rd

member of Shahejie Formation

and fault-lithologic reservoirs in the upper part of the 3

rd

member of Shahejie Formation have mainly been sourced by the source rocks in the 3

rd

member of Shahejie Formation. The formation of subtle reservoirs and the distributional characteristics of petroleum have been controlled by various factors

such as paleo-tectonic setting

hydrocarbon migration pathways

combination of source

reservoir and cap rocks

and the timing of hydrocarbon generation and accumulation.