通过正演模拟确定了在敖南地区应用AVO属性识别三类、四类气层的厚度下限,同时分析了水层的假AVO异常特征.该区薄气层可产生三类、四类AVO异常,三类AVO截距(A)和斜率(B)随砂岩厚度的增加负向增加;四类AVO的A随砂岩厚度的增加负向增加,B随砂岩厚度的增加止向增加.据此,采用A+B属性识别三类AVO异常;采用A-B属性识别四类AVO异常.应用该方法可有效识别单层厚度大于2.3 m的气层,与钻井试气结果的符合率超过80%,有效解决了浅层气识别的技术难题.%Lower limits of Type II and Type IVgas reservoir thickness identified with AVO attributes in Aonan area are determined by forward modeling, and the false AVO anomaly of water layer is analyzed. The thin gas layers in this area show Type m and Type IV anomaly. Both intercept （A ） and slope （ B） of Type m AVO present negative augment along with the increase of sandstone thickness; A of Type IV AVO presents negative augment along with the increase of sandstone thickness, and B presents positive augment along with the increase of sandstone thickness. On this basis, A + B attribute could be used to identify Type Ⅲ AVO anomaly and A -B attribute Type IV AVO anomaly. This method could be used to effectively identify gas layer thicker than 2. 3 m, and the matching rate with gas test results is over 80％. The technical difficulty of shallow gas identification is solved.
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