Triggering mechanism of gravity flow sandbodies of middle Es3 member in the north of well Ying 11, Dongying Depression

Key words:  gravity flow  triggering mechanism  seismites  sedimentary evolution  middle Es₃ member  Dongying Depression

Abstract:

The object of study is the gravity flow sandbodies of the middle Es₃ member in the north of well Ying 11 in Dongying Depression. Using core, logging, seismic, seismic and analytical laboratory data, the triggering mechanism and sedimentary evolution characteristics of slide, slump, debris flow and turbidity current in the study area were studied, two types of seismic rock sequences were established and the correlation between magnitude and vertical sequence was analyzed. The results illustrate that the tectonic movement is the main triggering mechanism of gravity flow sand body, and the tectonic movement was most intense during the 3rd sand group period. During the 6st-4st sand-group sedimentation period, the water depth was relatively deep and the lake level dropped slowly, which was mainly developed as the gravity flow deposition. Then, tectonic uplift caused the lake plane to fall sharply during the 3rd sand-group sedimentation period. Finally, during the 3rd-1st sand-group sedimentation period, shallow lake facies channel-mouth bar sand body developed in the east of the study area, and the gravity flow deposits developed in the middle and west. The 3rd sand-group sedimentation period is the most dramatic period of lake level decline, which is consistent with the conclusion obtained by studying the deformation structure of soft sediments in seismic rocks under different structural strengths.