Prediction Of Water-richness Of Sandstone By Prestack Elastic Wave Impedance Inversion Technique In Coal Seam Roof

The pre-stack elastic wave impedance inversion technique is a core technology in seismic exploration,and it can obtain more elastic elastic physical parameters than post-stack inversion,The geological information of the underground fluid can be obtain.Based on the pre-stack elastic wave impedance inversion method,the water-richness of sandstone in coal seam is predicted.This article starts with the rock physics foundation,according to the characteristics of the sandstone in the coal seam roof,a five-layer geological model is established.The AVO response of the sandstone at different distances and thicknesses is analyzed.This paper analyzes the amplitude response of the AVO under the condition of sandstone in saturated water,and the reflected wave characteristics of the sandstone in rich water.When the coal seam roof sandstone be full of water,It is found that the amplitude of the longitudinal wave decreases gradually with the increase of the offset,The absolute value of the reflection coefficient decreases obvious.This paper takes the mining area of Huangling No.2 coal mine as the research object,and the situation of the rich water of the coal seam was analyzed by using the wave impedance inversion technique.Based on the existing seismic data and logging information,The intersection map of the existing log data is analyzed for the valid identification of the sandstone.the data flow graph analysis of the logging data is conducted for the effective identification of sandstone.The Xu-White model was used to obtain the missing shear wave data in the logging.The elasticity information of the shear wave velocity ratio and porosity of sandstone is obtained by using pre-stack elastic wave impedance inversion method to analyze the water-rich area of sandstone.The study shows that the coal seam roof contains four sets of sandstone,because the 2,3,4 sand body is relatively scattered and small area,so do not consider;which No.1 sand body is distributed in the whole area,the overall trend is the thickness of the east thick west,No.1 sand in the N35 well at the Vp/Vs low value area,The comprehensive analysis shows that the area of the N35 well is the rich water area of No.1 sand.