Research And Application Of Frequency-dependent AVO Gas-bearing Properties Identification Method

Conventional AVO seismic analysis is based on the Zoeppritz equation,assuming that the medium is elastic isotropic.In the frequency band of seismic exploration,the attenuation phenomenon often occurs,the reason is mainly,in the formation,rock mass is usually anisotropic and has viscoelastic properties.This leads to the dissipation of frequency of seismic waves after a medium of this nature.Therefore,how to describe the stress-strain relationship of actual formation rocks more accurately,therefore,more consistent with the actual seismic wave mechanics description,is the most important to improve conventional AVO.According to the understanding of the velocity dispersion of Chapman(2003),because the seismic reflection interface has different dispersion characteristics,the change of frequency will lead to the change of reflection coefficient,can regard the reflection coefficient as a function of frequency.Therefore,firstly,according to the difficulties and hot issues of reservoir prediction and gas-bearing properties identification of tight sandstone gas reservoir,the constant parameters have the advantage of frequency-dependent,obtain the function relationship between seismic reflection coefficient and frequency,and obtain the relationship between intercept,gradient and fluid detection factor.Based on the Chapman multi-scale fracture media theory and AVO theory,by forward numerical simulation,multi-wavelet decomposition and reconstruction,in-depth analysis and classification of the frequency-dependent AVO response characteristics of different gas-bearing reservoir types,establish the frequency-dependent AVO oil and gas detection model.Finally,through the data processing of the actual work area,the fluid detection factor and the nibo parameters are analyzed in detail,not only to distinguish the AVO response characteristics of mudstone and sandstone,but also to distinguish the differences between the frequency-dependent AVO response characteristics of no oil and gas.Through the practical data application research,the results show that the method can be better applied to the actual work area,can be competent for reservoir prediction and fluid detection.