AVO叠前反演在中等阻抗储层预测中的应用

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

新场气田须四下亚段TX94砂体为砂砾岩互层。前期勘探证实,砂岩为有效储层,由于砂岩与作为围岩的泥岩阻抗接近,而砾岩的阻抗又远远大于砂泥岩,常规地震属性及叠后反演无法准确识别砂岩。采用AVO叠前反演技术,综合应用纵波弹性阻抗和纵波、横波速度比,结合岩石物理模板,对砂岩进行了准确刻画。这里阐述了AVO叠前反演的原理,讨论了反演处理中的地震数据分析,岩石物理分析,子波提取,低频趋势模型建立等关键步骤。反演结果表明,AVO叠前反演能很好地识别砂岩,降低了勘探风险。

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.