转换波地震勘探中的最大炮检距设计

Determination of maximum offset in converted-wave seismic exploration.

从反射系数和动校正拉伸2个方面对转换波勘探最大炮检距设计进行了研究。研究表明,转换波最大炮检距可能大于或小于纵波最大炮检距,这主要取决于纵波和转换波反射系数特征。根据有无临界角以及反射系数中有无极性反转,将纵波和转换波反射模式分成8种,并给出了相应的最大炮检距确定原则与方法。当采用双曲时距方程进行动校正时,转换波的动校正拉伸要小于纵波的动校正拉伸;在相同动校正拉伸下,转换波的最大炮检距大于纵波的最大炮检距。采用高精度的转换波时距方程进行动校正,能够减小动校正拉伸。

This paper studies the determination of maximum offset in converted-wave seismic exploration in terms of reflection coefficients and NMO (normal moveout) stretch. It shows that maximum offset of converted wave may be greater or less than that of compressional wave.which is decided by the characteristics of reflection coefficients of converted wave and compressional wave. According to critical angle and polarity reversal of reflection coefficients, eight reflection modes are defined for converted wave and compressional wave,corresponding principles and methods were presented to determine maximum offset. When hyperbolic timedistance equation is used to do NMO correction. NMO stretch of converted wave is less than that of compressional wave. Maximum offset of converted wave is greater than that of compressional wave for the same stretch. Utilization of converted-wave time-distance equation with higher precision to do NMO correction can decrease stretch.