浅层天然气藏的AVO处理方法

AMPLITUDE VERSUS OFFEST ANALYSIS FOR SHALLOW NATURAL GAS RESERVOIR

在Ｘ－Ｔ域对浅层天然气藏进行振幅与炮检距（ＡＶＯ）分析时，不可避免地遇到球面扩散振幅补偿不精确、浅层动校拉伸切除造成共中心点（ＣＭＰ）道集中道数太少、ＣＭＰ道集信噪比低等三方面的问题。文章提出一种新的浅层ＡＶＯ处理方法，首先应用二维τ－Ｐ变换将点震源产生的球面波场分解成平面波场，以实现精确的球面扩散的自动振幅补偿；其次在τ－Ｐ域进行动校正，以减少动校正引起的拉伸现象。τ－Ｐ变换本身能够有效地提高ＣＭＰ道集的信噪比．采用这种新的处理方法，增加了浅层天然气藏ＡＶＯ分析的可信度。对浅层ＡＶＯ处理方法进行了理论分析和模型验证，并给出处理实例，证实了该方法具有广阔的应用前景。

There are three problems of compensations of the spherical divergence,thestretch distortion of the normal moveout(NMO)correction and the lower signal to noise ratioin common median point(CMP)gather,for AVO analysis in X-T Domain to shallow naturalgas exploration. A new AVO analysis method is presented.The spherical wavefield isdecomposed into plane wavefield by τ-P transform in cylindrical coorinate system to performthe spherical divergence compensation automatically.After that,by using the NMO correctionin τ-P domain,the NMO stretch factor is dramatically reduced at shallow part and the signalto noise ratio in CMP gather is enhanced.So the reliability for AVO analysis gets much betteron shallow natural gas reservoir.The theoretical analysis of the AVO processing in τ-Pdomain,the model testing and the practical example proved that there is the broad prospect forAVO analysis in τ-P domain.