Research Of AVO Forward Modeling In Poroelastic Media

With the increasing complexity of exploration targets and the deepening of exploration technology,the models based on single medium are more and more inconsistent with the needs of current exploration.How to build models in line with actual strata is the focus of current exploration.AVO forward modeling technology still plays an important role in current oil and gas prediction.Using AVO technology to analyze the relationship between seismic reflection coefficient and offset or incidence angle,not only lithologic parameters and reservoir parameters can be obtained,but also reservoir prediction and fluid identification can be possible.Therefore,it is necessary to study AVO technology analysis.Based on porous medium theory and AVO theory,this paper takes AVO analysis as the main technical means.Firstly,the exact solutions of Zoeppritz equation and some approximate equations in homogeneous isotropic medium are studied,the applicable conditions and scope of various approximations are defined,and then the influencing factors of P-wave reflection coefficient are analyzed.On this basis,the pore medium theory is introduced.Considering the influence of pore fluid on rocks,The Zoeppritz equation in porous elastic medium is derived,and its exact solution and approximate equation are obtained.Finally,through AVO forward analysis,The influence of the difference of parameters on the variation of P-wave reflection coefficient with incident angle is highlighted,which has certain guiding significance for the prediction of underground reservoir lithology,fluid properties and the selection of AVO inversion method.The main results are as follows:(1)Four equations represented by perturbation coefficients(?_f??_???_?),When the perturbation coefficients are small,the linear(first-order)approximation and the non-linear(second-order and third-order)approximation can accurately predict the accurate expressions.With the increase of the perturbation coefficients,the prediction accuracy of the approximation will decrease.Compared with the non-linear approximation,the prediction accuracy of the linear approximation will be decrease significantly.(2)Four equations represented by reflectivity terms(?f/f ???/? ???/?),When the reflectivity terms are small,the linear approximation and the non-linear approximation can accurately predict the accurate expressions.With the increase of the reflectivity terms,the prediction accuracy of the linear approximation willdecrease significantly,while the non-linear approximation can still predict the accurate expressions very well.(3)By comparing and analyzing the AVO forward results of these two forms of equation,the AVO approximation expressed by reflectivity terms has higher prediction accuracy than that expressed by perturbation coefficients.Therefore,the AVO approximation expressed by reflectivity terms can be selected for subsequent AVO inversion.