| Through the analysis of drilling, logging and three-dimensional seismic data, the sequence stratigraphic
composition, source-to-sink system difference, sedimentary evolution, sand control mechanism and lithologic-stratigraphic
trap model in hanging wall of Pinghu fault in PH slope overlap belt of Xihu Sag are comprehensively studied. The results
indicate that: (1) The Pinghu Formation in the PH slope overlap belt is controlled by different genetic slope breaks such as
erosion and flexural, and is divided into three third-order sequences (SQ1 to SQ3) from bottom to top. Among them, SQ1 is
limited in distribution, and development of the lowstand system tract is controlled by the steep slope break of deflection,
forming the fan delta system coupled with ancient valley and slope break, which is dominated by the nearby basement
provenance of Mesozoic magmatic rock. SQ2 and SQ3 are widely distributed, and development of the transgression and
highstand system tracts are controlled by gentle slope break of erosion, forming the delta system dominated by the distant
basement provenance of Proterozoic metamorphic rock. (2) The slope break controls the sand body distribution, and the
slope break trough under the flexural slope break is a restrictive landform, which controls the layer by layer accretion and
overlap of fan delta sand body vertically overlaied in lowstand tract. The low-lying area under the erosion slope break is the
place where the highstand tract delta sand bodies are distributed, and the sand bodies of delta front are superimposed and
dsitributed contiguously on plane. (3) Under the control of system tract and slope break, three types of lithologicstratigraphic
trap models are developed. During the low stand stage, the fan delta front sand body overlaping stratigraphic
traps blocked by the physical properties of bedrock and fan root are mainly developed under the flexural slope break. During
the transgressive stage, the tidal sand bar and tidal channel lateral pinchout lithologic traps blocked by the mudstone in the
flooding period are mainly developed. During the highstand stage, lithologic traps in distributary channels of delta plain
controlled by erosion slope break, updip pinch out and lateral pinch out, are mainly developed. |
