Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (6): 1205-1214.doi: 10.11743/ogg20190605

• Petroleum Geology • Previous Articles     Next Articles

Quantitative classification of high-frequency sequences in fine-grained lacustrine sedimentary rocks based on Milankovitch theory

Shi Juye1,2,3, Jin Zhijun1,2, Liu Quanyou1,2, Huang Zhenkai1,2, Zhang Rui4   

  1. 1. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 100083, China;
    2. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China;
    3. School of Energy Resources, China University of Geosciences(Beijing), Beijing 100083, China;
    4. School of Geosciences, China University of Petroleum(East China), Qingdao 266580, China
  • Received:2018-07-07 Revised:2019-08-16 Online:2019-12-28 Published:2019-10-15

Abstract: Fine-grained lacustrine sedimentary rocks are characterized by high continuity and resolution,and can faithfully record the changes in climate and environment of lacustrine basins.Considering the high stability during deposition,these sedimentary rocks have been regarded as good information carriers to identify Milankovitch cycles;while in return,the recognition of time connotation of the Milankovitch theory is an effective way to perform classification and correlation of high-frequency cycles,and to improve the temporal resolution of stratigraphic classification,thus being a powerful complement to the conventional sequence stratigraphy.The accurate identification of Milankovitch Cycles is the basis for the classification of high-frequency sequences in the fine-grained lacustrine sedimentary rocks,and constraining the variation of sedimentary rate is the key to the recognition of Milankovitch Cycles.In view of the fast transformation of sedimentary facies and strong heterogeneity in continental sedimentary sequences,we used the magnetic susceptibility as a proxy.In addition,the evolutive harmonic analysis (EHA) and average spectral misfit (ASM) techniques were introduced to constrain the vertical variation of sedimentary rate,so as to more accurately recognize signals of Milankovitch Cycles.Combined with the base level cycle theory in high-resolution sequence stratigraphy,we found that the fourth-order sequence corresponds to the medium-term base level cycle and the time is quantified as 405 ka;the fifth-order sequence corres-ponds to the short-term base level cycle and the time is quantified as 100 ka;and the sixth-order sequence corresponds to the super-short-term base level cycle ant the time is quantified as 40 ka.Finally,the periodic curves of long-eccentricity,short-eccentricity and tilt are taken as referential curves for classification of the fourth-,fifth-and sixth-order sequence,and thus the quantitative classification of high-frequency sequences of fine-grained lacustrine sedimentary rocks can be achieved.

Key words: Milankovitch theory, astronomical cycle, cyclostratigraphy, high-frequency sequence, fine-grained sedimentary rock, Dongying Sag

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