Inversion Study Of Reservoir Physical Parameters Based On AVAF

Rock physics theory and experiments show that when seismic waves propagate in porous media saturated with fluid,the movement of pore fluid relative to solids will lead to the dispersion of seismic wave velocity and attenuation,causing frequency variation of seismic response.It lays the foundation for the identification of fluids using the variation of reflection coefficient with frequency.However,to obtain reservoir parameters from seismic responses,the "two-step" method is used currently.Firstly,use AVAF(Amplitude Versus Angle and Frequency)to estimate velocity dispersion or attenuation,and then use velocity dispersion or attenuation to obtain fluid indicator factor.This "two-step" method usually only utilizes the dispersion characteristics or attenuation characteristics of seismic waves,resulting in insufficient use of effective information,further aggravating the problem of insufficient information in seismic inversion.In this paper,explore a method to directly obtain reservoir parameters from seismic responses,and its feasibility is studied by numerical simulation.Firstly,the sensitivity of rock skeleton parameters and fluid parameters to velocity dispersion and attenuation was analyzed based on the layered patch saturation model,so as to clarify the indication effect of dispersion and attenuation on different physical parameters.Then,the velocity dispersion and attenuation were connected with the seismic response by using the propagation matrix equation,and clarified the sensitivity of the reservoir physical parameters to the seismic response.Finally,from the perspective of inversion,the "onestep method" from seismic response to physical parameters is analyzed,and study the problems of insufficient information and noise pollution in inversion.The inversion results show that in order to directly obtain more accurate reservoir physical property parameters from the seismic response,it is necessary to further reduce the number or range of parameters to be inverted by means of logging and geological related methods,and provide more accurate caprocks.