CHARACTERISTICS OF SEDIMENTARY MICROFACIES DISTRIBUTION AND SEDIMENTARY MODEL OF PINGHU FORMATION FROM W ELL P AREA IN A CERTAIN SAG, EAST CHINA SEA BASIN

摘要

Based on the detailed observations and descriptions of the cores of 7 wells in the P well area of the western slope of a sag in the East China Sea Basin, this paper studies the sedimentary microfacies and sedimentary models of the Pinghu Formation by comprehensively using well logging analysis and seismic data. The results show that a set of sea-land transitional sedimentary systems developed in the Pinghu Formation in well P, mainly tidal-affected delta-tidal flat sediments and the sedimentary subfacies mainly include delta fronts, pre-deltas, and intertidal zones. Seven types of sedimentary microfacies have been further identified such as diverting channels, estuary sand bars, diverging bays, and tidal channels. Co-occurring faults have a significant effect on the plane distribution of sedimentary microfacies. When the fault distance is small, as the angle between the source and the fault direction increases, the underwater shunt channel will be diverted. When the fault distance is large, the underwater shunt channel will be deposited. The sediments only deposit in the lower part of the upper wall of the concomitant fault, and the advancement to the center of the basin is limited. Based on the analysis of the sedimentary system, a sedimentary model of the study area with tidal influence on the delta front is established. The identification of the sandstone and the prediction of favorable sand bodies have certain guiding significance.