多井波阻抗处理技术

Multiwell wave impedance processing technique

石油地球物理勘探局研究院, 涿洲 O72750

Research Institute, Bureau of Oil Geophysical Prospecting, Zhuozhou 072750

恢复地层波阻抗是地震资料处理的主要目的之一。由于地震记录受有限频带的影响, 地震记录中缺失了反映波阻抗变化趋势的重要低频成分, 再加上地下层位横向上岩性普遍存在变化（即速度变化）, 因此很难直接从地震记录计算地层的波阻抗。本文从递推反演方法的角度, 详细介绍在高信噪比、高分辨率、相对振幅保持的地震数据基础上, 如何利用多口测井资料根据剖面解释的构造几何形态进行时空内插、外推, 提取低频反射系数, 并利用多口测井资料的约束, 将地震反射振幅标定成反射系数（即带通反射系数）。将低频反射系数加上带通反射系数得到宽带反射系数, 然后利用递推方法将宽频带反射系数转换成波阻抗。最后对反演获得的波阻抗道与由声测井数据求得的波阻抗道进行对比, 利用均方根误差大小来判别两者之间的相似程度。

Recovering the stratigraphic wave impedance is one of the major objectives of seismic dataprocessing. As the seismic record is influenced by the limited frequency band, there fore the recordfalls short of important low-frequency component reflecting the change trend of wave irnpedance.In addition, the lithology of subsurface strata is varied in the lateral direction, so it is difficult tocompute the wave impedance of strata directly from seismic record. In the paper, from the angleof the recursive inversion, the author introduced in detail how to use multiwell log data to performspace-time interpolation and extrapo1ation and extract the low-frequency reflectivity on the basis ofhigh S/N ratio, high resolution, and amplitude-preserved seismic data. The seismic reflectionamplitude is calibrated into the bandpass reflectivity by rneans of the constraint of multiwell logdata. Then the bandpass reflectivity is added to the low-frequency ref1ectivity to obtain thebroadband reflectivity. After that, the author takes advantage of the recursive method totransform the broadband reflectivity into the wave impedance-Finally the wave impedance tracesacquired from the inversion are contrasted with those calculated from the acoustic log data, andthe size of mean square error is used to judge the similarity degree of these two kinds of traces.