引起速度场建场误差的几个关键环节

A Few Key Links Inducing the Errors in Velocity Field

摘要: 地震成果由时间域转换到深度域，涉及速度建场和变速成图技术。随着水平井的广泛应用，对转深精度要求更高。特别在复杂山地探区，地震资料品质和地层速度在横向和纵向上变化比较剧烈，加之基准面计算方法不合理，导致转深的区域构造形态与深度预测精度往往很低，使得水平井的钻探设计和成本控制变得十分困难。通过在建场过程中对各个环节减小误差，进而提高整体速度场精度。对引起速度场建场误差的关键环节进行分析后认为，从基于表层模型的CMP (共中心点)基准面转换、模型迭代层速度计算、地震反射层约束速度场建立、两步法层速度误差校正方法入手，降低各个环节的误差，能够提高适用于盆边山地过渡带的速度场精度。

Abstract: The seismic results were turned from time domain to the in depth domain, it involved the velocity field and the varying velocity mapping technique. With the wide application of the horizontal wells, counter rotating depth demanded a higher precision. Particularly in complex mountain exploration areas, changes of data quality and formation velocity on the horizontal and vertical directions were severe, combined with the unreasonable datum calculation method, the in depth tectonic shape and depth prediction precision were often low; it was very difficult for the design of the horizontal well drilling and its cost control. By building of the field for each link in the process of reducing measure error, the overall precision of velocity field is improved. In this paper, the velocity field building error in the key links is analyzed, it is considered that from the CMP datum transformation, the layer iteration speed calculation based on surface model, the building of seismic reflection velocity field, it is started from the two step interval velocity error correction method, the error of each link is reduced; it can improve the velocity accuracy for the basin edge and mountain transition zones.