The Genesis Of Sand And Preferable Sand Predication Of The Middle Of The 3^rd Member Of Shahejie Formation In The South Of Western Sag,Liaohe Depression

In this paper,core data and 3D seismic data are used to study the genesis of sand,distribution of sedimentary facies and preferable sand predication of the 3rd member of Shahejie formation in the south of western Sag,Liaohe Depression.Three kinds of sand body in the area has been Identified,respectively causes of fan delta,mass-transport and turbidity current.The sand body caused by fan delta show the same characteristics of subaqueous distributary channel,demonstrating its existence through core observation,grain size analysis and sedimentary environment analysis;Mass-transport deposit consist of slide,slump and debris flow sedimentary,identified and distinguished by core observation;Turbidity is characterized by suspension transport,showing the normal grading and thin in depth,characterized by thin layer of sandstone in dark mudstone.Three kinds of sand body correspond fan delta,slump fan and sublacustrine fan.Fan delta develops in water-regression stage,and controlled by palaeogeomorphology,the fan delta developed in the Western Slope advance to the uplift zone between two secondary sub-sag,being of great petroleum geological significance;Slump fan develops in both water-regression stage and water-transgression stage,widely distributed in the study area,affected by the activity of synsedimentary fault;Sublacustrine fan develops in water-transgression stage,formed by event-deposit such as flood.Preferable sand in the south of study area has been predicted.Through core observation and the comparison of the microscopic characteristics of pore structure,recognizing the sand caused by subaqueous distributary channel and slump fan as preferable sand body,then,using the seismic profile and wave impedance inversion method to depict 5 sets of preferable sand body.