Sequence stratigraphy and oil reservoirs in the medium-deep strata within No. 3 Structure, Nanpu depression

The medium-deep strata within No. 3 Structure consist of the third member of the Shahejie Formataion to the first member of the Dongying Formation in the Nanpu depression, and are divided, in terms of seismic reflection configuration, lithology and electric logs, into four second-order sequence boundaries, i. e., three second-order sequences and eight third-order sequence boundaries, i. e., seven third-order sequences. Constrained by the lake basin structures and structural break, the thickness of the third-order sequences generally increases from the southwest to the northeast, and display thick-thin-thick patterns from the northwest to the southeast of the study area. There occur the structurally-or stratigraphically-controlled oil reservoirs in the central part of the first member of the Shahejie Formation, and mixed structurally-and lithologically-controlled oil reservoirs in the Dongying Formation. On the whole, the favourable oil reservoirs are controlled by mixed structures and lithology and structures and stratigraphy in the medium-deep strata within No. 3 Structure in the Nanpu depression.