AVO combined with fluid replacement identifies deep gas reservoir of class Ⅰ

The traditional bright spot technique is good to predict the Ⅲ AVO anomaly, but invalid when the deep gas sand has an A VO anomaly of class Ⅰ. Deep gas sand of class I can be effectively identified by G attribute volume by using AVO,combined with fluid replacement. Distribution of a gas reservoir in some oilfield was predicted by this way and the result was verified at last by the newly drilled well B.