Anisotropic Gradient Prediction Based On Azimuth Fourier Series

With the increasing uncertainty of seismic exploration targets,the difficulty of development is more and more high.While The fracture is the important oil and gas migration and the reservoir channel,so the accurate reservoir fracture prediction is the research focus of the researchers.There is a good correspondence between the variation of anisotropic gradient and the change of fracture density.Therefore,a reliable anisotropic gradient prediction of unconventional reservoirs with fracture development can improve the prediction results of reservoir oil and gas.Currently wide-azimuth seismic data acquisition,processing and interpretation technology is keeping continuous development.While because the underground medium is anisotropic media,so wide-azimuth seismic data must have anisotropic problems.Therefore,in seismic data interpretation,the azimuth anisotropy information of wide azimuth seismic data is particularly important for reservoir fracture prediction.Based on the basic theory of anisotropy,this paper introduces the stratigraphic types of several anisotropic media.At the same time,the method of extracting the anisotropy gradient and the development azimuth of fractures related to the reservoir fractures from the azimuth gradient attribute is introduced,which can be used to determine the fracture development site of the reservoir.Starting from the basic theory of azimuth elastic impedance inversion,In the case of the quality of the track gather is unsatisfactory and the signal to noise ratio is not high of Prestack seismic data,the azimuth elastic impedance inversion method with anisotropic gradient is proposed.Using stacked in seismic data processing,so that area gather quality and signal to noise ratio of seismic data were improved and effective.The validity and stability of the method can be proved by the model test.Then apply it to the actual work area,can obtain the good effect and distinguish the fracture development region.It is found that anisotropic gradient parameters are closely related to the development of reservoir fractures.Therefore,it is possible to establish the relationship between the characteristic parameters of fractured reservoirs and the elastic parameters of rock and anisotropy gradient parameters of anisotropic strength by rock physical analysis,and then deduce the approximate formula of reflectance coefficients with anisotropic gradient parameters.Using Avaz inversion method,the inversion prediction of elastic parameters and anisotropic gradient parameters of fractured reservoirs is carried out.In this paper,we use the method of Fourier decomposition to obtain the normal weak degree and tangential weak degree in order to find the anisotropic gradient,bearing elastic impedance inversion procedures cumbersome.The method is simple in calculation,and the predicted fracture density coincides with the conventional method.