The Study On Wave Field Characteristics Of Fractured Anisotropic Model

Fractured reservoir is a very important type of oil and gas reservoir of basin in China,the analysis of seismic response characteristics can establish relationship between the seismic data and reservoir parameters,the study of related problems currently focused on establishing a fractured porous medium model and equivalent wave field numerical simulation method research in the initial stage of exploration.Based on the Biot-Gassmann theory and the Schoenberg equivalent medium theory,the theoretical model is established with the reservoir parameters of the actual oil field fracture,and the relationship between the geological parameters and geophysical parameters is established.By single interface AVO analysis,the AVO response characteristics of coal fractures,shale fractures and tight sandstone fractures in different fluid and fracture sizes are summarized.Then by using the method of high order finite difference 2.5D wave equation numerical simulation,mainly for the fractured anisotropic model for cracks of different scales and different background medium numerical simulation,summing up the multi wave seismic response of different rocks caused by the fractures.Through simulation analysis,the main conclusions are as follows:(1)the anisotropy parameters are affected by lithology,porosity and hydrocarbon saturation.(2)different lithology changes in fractured medium containing fluid saturation under the condition of PP and PS wave reflection coefficient changes with incident angle curves are different,which can be used to distinguish the lithology changes;fracture scale and anisotropic parameters,influence the characteristics of PP wave and PS wave of AVO curve.(3)by using the method of 2.5D forward modeling of shear wave splitting phenomenon can simulate the crack propagation and the wave field,wave field with fracture aspect angle and size show different characteristics,the crack angle will affect the wave propagation direction;crack increases to a certain extent will appear S-wave splitting phenomenon groups fracture will make the shear wave splitting is more complex.(4)seismic cracks with different crack size,the angle of development and the background of the medium is different,the difference between the same component mainly under the same conditions of three component and different conditions between the amplitude,attenuation,polarity and receiving length etc..