Correspondences between high-frequency sequences and the Milankovitch Cycles of Dongying Formation in Liaoxi Uplift, Bohai Bay Basin, North-east China

The typical wells in Liaoxi Uplift were selected to conduct studies on high-frequency sequences and their correspondences with the Milankovitch Cycles in Dongying Formation based on integrated analysis of wireline logs and sieve residue logs. The results of well JZ-E show that 37 ultra-short-term cycles, 13 short-term cycles, 8 mid-term cycles, and 5 long-term cycles are identified. Meanwhile, the correspondences between high-frequency sequences and the Milankovitch Cycles in Dongying Formation were analysed based on GR curve of well JZ-E and MATLAB procedure. The correspondences indicate that the Milankovitch Cycles are well preserved in Dongying Formation. The thickness of long-period cycles caused by eccentricity ranges from 2.7963 to 3.9965 m. The thickness of mid-term cycles caused by obliquity ranges from 1.5081 to 2.1126 m. The thickness of short-period cycles caused by precessions ranges from 0.5791 to 1.1269 m. There is a good consistency between high-frequency sequences and the Milankovitch Cycles in Dongying Formation. The mid-term cycle, short-term cycle, and ultra-short-term cycle of high-frequency sequence correspond, respectively, to long-period eccentricity, short-period eccentricity, and precession cycle of the Milankovitch Cycles. Lacustrine fluctuations caused by the change in Earth's orbit play a major role in controlling high-frequency sequences.