Compressional wave (P-wave) azimuthal anisotropy physical model studies in transversally isotropic medium
Qi Yu1,3,4, Wei Jian-xin1,2,3, Di Bang-rang1,2,3, Liu Zhen1,3
1. State Key Lab of Petroleum Resources and Prospecting, China University of Petroleum, Changping District, Beijing City, 102249, China;
2. CNPC Key Lab of Geophysical Prospecting, China University of Petroleum, Changping District, Beijing City, 102249, China;
3. Faculty of Natural Resource and Information Technology, China University of Petroleum, Changping District, Beijing City, 102249, China
Abstract:Ruger formula demonstrates that in isotropic media if the isotropic parameters,P-wave impedance,share wave velocity and medium density are known,then the reflection coefficient is the dualistic function of the reflection coefficient and incidence angle. However if the fixed offset was adopted for the observation,only changing the included angle between seismic line and azimuth,then the reflection coefficient can be simplified to simple function of the azimuth,so from Ruger formula the reflection coefficients can be derived for different offsets. Based on Ruger formula and by using physical modeling method,the seismic response for HTI media in the water were observed in 50mm,100mm and 150mm offset respectively. The changing rule of reflection wave amplitude and reflection wave travel time with azimuth was understood. The studies demonstrates that when offsets change,the reflection P-wave amplitude on the top and bottom of the fracture layer shows azimuth AVO response,when azimuth is 0 degree,the reflection P-wave amplitude is maximum,when azimuth is 90 degree the reflection P-wave amplitude is minimum,the P-wave travel time is also affected by fracture,that is,reflection time increases with the azimuth increase,the results from physical modeling experiment are close to the results from the theoretical calculation,it is believed that the studies provides reference for fracture recognition and prediction.