Based on detailed observation of cores

thin section

well logging and seismic data analysis

high frequency sequence and sedimentary microfacies of the Upper T

2

l

4

were studied in the Shiyangchang-Jinma-Yazihe area of foreland of Longmen Mountains in western Sichuan Depression.Combined with logging interpretation results

the reservoir distribution and controlling factors of reservoir development are analyzed.The results indicate that the Upper T

2

l

4

can be divided into one fourth-order sequence

and may be further divided into multiple fifth-order and sixth-order high frequency sequences.The high frequency sequence has the characteristics of sedimentary assemblages obviously shallowing upward and their horizontal correlation is good.Sedimentary environments mainly are tidal flat in the research area

and the tidal flat depo-sits mainly develop intertidal zone and subtidal zone sub-facies.Lithology of flat deposits is varied in the vertical direction and is more stable in horizontal orientation.Intertidal zone is a favorite sub-facies for reservoir development

and can be divided into dolomite flat

algae dolomite flat

dolomite-lime flat micro-facies.Subtidal zone can be divided into lime flat

algae lime flat

dolomite lime flat micro-facies.Silty-fine dolomite flat

algal (laminated) dolomite flat in the intertidal zone is favorable micro-facies for reservoir development.They were usually distributed in middle-upper part of upper and lower reservoir with clear reservoir cycles.The favorable intertidal micro-facies distribution reservoir for development is controlled by (high frequency) sequence

which also has a certain impact to later diagenesis.The high frequency sequence is the key factor to affect reservoir formation and distribution.