地震勘探中广义弹性阻抗的正反演

FORWARD MODELING AND INVERSION METHOD OF GENERALIZED ELASTIC IMPEDANCE IN SEISMIC EXPLORATION

常规的地震道反演方法建立在反射P波垂直入射假设的基础上 ,而实际地震资料采集时多数是非零炮检距的 ,反射振幅是共中心点道集叠加的结果 .因此 ,利用常规地震道反演方法就不能得到可靠的波阻抗或其他岩性信息 .本文利用PatrickConnolly弹性阻抗的思想 ,通过对Zoeppritz方程的进一步简化 ,推导出适合常规叠后资料的、非零炮检距条件下纵波反射系数递推公式 ,提出了广义弹性阻抗的概念 ,解决了非零炮检距条件下 ,常规叠后地震道正反演的关键问题 .广义弹性阻抗不仅包含波阻抗 ,还包含了纵横波速度等岩性信息 ,具有很好的实用价值 .进行广义弹性阻抗的反演 ,能较常规地震道反演获得更多、更可靠的流体、孔隙度、砂泥含量等信息 ,有助于解释常规地震道反演和道积分剖面中的假象 ,降低反演的多解性 ,提高储层预测的精度 .

Conventional seismic trace inversion method is based on the assumption of P-wave striking interface normally. However,conventional multi-channel seismic data records are oblique reflections,reflection amplitude is the average value of CDP gathers. Using conventional seismic trace inversion method,we can not obtain reliable acoustic impedance (AI) or reservoir properties. Following the idea of Patrick Connolly's (1999) Elastic Impedance (EI),I further approximated the Zoeppritz equation,derived the P-wave reflectivity recursive formula,suitable for the post-stack and seismic data of oblique reflection,and proposed Generalized Elastic Impedance (GEI). The key problem of forward modeling and inversion of seismic trace is solved better than ever. GEI not only include AI,but also include V P,V S and other lithological parameters. It will have high value when applied in practice. By means of GEI inversion,we can obtain more and more reliable information of fluids,porosity,sand to mud ratio and other lithological. It is helpful to interpret the pitfall in conventional seismic trace inversion and trace integration. It is also helpful to decrease non-uniqueness in conventional seismic trace inversion and improve the accuracy of reservoir prediction.