THE APPLICATION OF AVO PRE-STACK INVERSION TECHNIQUE TO PREDICT THE RESERVOIR WITH MEDIUM IMPEDANCE

The TX49 sand body of Xujiahe four formation of Xinchang gas Field is sand interbedded with conglomerate reservoir.Previous exploration has proved that the sand was effective reservoir.Conventional post-stack inversion does not recognize the sandstone because of the impedance of the sandstone closed to the mudstone,and the impedance of conglomerate is far greater than the sand and mudstone.It is successful to to predict the distribution of the sand by using AVO pre-stack inversion technique with P-wave elastic impedance and Vp/Vs and rock physic property.The prediction consistent with the actual drilling results.The basic principles of pre-stack inversion was demonstrated,and the key steps in inversion were discussed,such as rock physics,wavelet extraction,establishment of low-frequency trend model.The results show that the AVO prestack inversion can identify the sandstone well and reduce the exploration risk.