Abstract:

In order to demonstrate the characteristics of high resolution sequence stratigraphy of XingⅠ Formation in the Du 84 Block, cores and logging data were applied to conduct the research on the sequence boundaries reorganization, sequence analysis on single well profile and cross-well profiles of cored wells, interpretation of different level cycle types.We establish the chronostratigraphic sequence framework in the study area.One long-term sequence cycle(LSC1)and two mid-term sequence cycles(MSC1-MSC2)are identified according to unconformity, scour surface and flooding surface.Meanwhile, four short-term sequence cycles(SSC1-SSC4)are further identified according to the sedimentary transformation surfaces and rhythm conversion surfaces.These SSC are subdivided into three basic types and 7 sub-types according to the stacking patterns of cycles of various levels, planar and spatial distribution of sedimentary facies.The three basic types are deepening upward nonsymmetric type(typeA), shallowing upward nonsymmetric type(type B)and symmetric type(type C).Type A mainly develops in the MSC and LSC.And the type C develops in the SSC2.The strata in the whole basin belong to retrograding sequences formed during expansion of lake basin, featuring in multi-cycle mostly having only ascending half cycle and zonation in plane distribution during the SSC.The reservoir sands are best deve-loped at the bottom of the ascending half cycle(SSC1-SSC2).They consist of stacked underwater distributary channel sand bodies of different periods, and have good reservoir property, thus are the main targets of remaining oil potential tapping in the future.

Key words: base-level cycle, sequence boundary, high-resolution sequence stratigraphy, XingⅠ Formation, Du 84 Block, Western Sag of Liaohe Depression