The Study Of High Frequency Sequence Stratigraphy In Gaoyou Sag

Based on the exploration on Gaoyou Sag, directed by the principles of sequence stratigraphy, and within the framework of sequence stratigraphy, the paper took study of sedimentary system and facies, and especially study of high-frequency sequence stratigraphy on Dainan Formation. At the same time, the paper found controlling factors and the discriminating method on high-frequency sequence stratigraphy, and finally developed a quantitative method to discriminating high-frequency sequences of delta.Directed by the principles of classical sequence stratigraphy, combined with core, well logging and seismic data, etc., the sequence framework from Eogene to upper Crataceous in Gaoyou Sag was set up and divided into 2 primary sequences, 4 secondary sequences and 11 tertiary sequences for the basin.Within the equal-time sequence framework, distribution of sedimentary facies and their evolution rule were analyzed, and the sedimentary mode was proposed. Delta deposit system was mainly developed in Sequence 5, Sequence 6, and Sequence 7 (such as Dainan Formation), and fluvial deposit system was mainly developed in Sequence 8 (such as Formation Sanduo).It was mainly done on the study of high-frequency cycle sequence in Dainan Formation. Applying the method of Fischer Graphy, spectrum analysis of the log, wavelet analysis to discriminate high-frequency cycle, the study showed that the Fischer graphy was not applicable to high-frequency cycle discrimination of continental clastic rock, but as the main layer of the delta front sedimentary during the stable period of structure, the log spectrum analysis and wavelet analysis could efficiently discriminate high-frequency cycle in it. The result of the log spectrum analysis indicated Milankovitch cycle was well kept in stratum, and the thickness of the formation cycle long-period controlled by eccentricity was about 100m, and the thickness of the formation cycle short-period controlled by eccentricity was about 25m and the thickness of the formation cycle controlled by precession was only about 5m, consequently, deposition rate in study area was 25cm/ka.Through the application of wavelet amplitude spectrum and phase spectrum of multiple wavelet in sequence division, the paper confirmed the correspondence relationship between Morlet wavelet dimension and high-frequency sequence cycle level——800-scale wavelet coefficients corresponding period of the medium-term cycle, 200-scale wavelet coefficients corresponding period of the short-term cycle, 40-scale wavelet coefficients corresponding period of the ultra-term cycle.The paper analysed the master factor of high-frequency cycle, and it was thought that high-frequency sequence cycle was controlled by Milankovitch cycle, thus the division method was confirmed.