大炮检距地震资料动校正方法比较

Comparison between normal moveout (NMO) methods for long-offset seismic data

动校正是地震资料处理过程中的关键步骤之一 ,其精确性直接影响到水平叠加能否对干扰波进行有效压制 ,同时它也是一种用于速度分析的手段。常规动校正处理是利用 DIX双曲线公式拉平同相轴 ,但应用 DIX双曲线公式有两个前提 :1各向同性层状介质 ;2中、近炮检距检波排列。当我们对高速层下地质目标进行勘探时 ,常采用较长的检波器排列 ,以获得高速层下有效反射波 ,这时对大炮检距地震记录应用 DIX公式进行校正就会带来大的误差 ,必须采用多项式高阶拟合的方法。本文通过水平层状介质模型正演 ,对大炮检距地震资料进行动校正的方法进行比较分析 ,认为对大炮检距地震资料动校正时并不是用的阶数愈高 ,动校正的精度就愈好 ,并且平移双曲线法也不是时时最优。在暂不考虑介质各向异性的影响下 ,多项式高次项系数是大炮检距动校正的关键影响因素 。

Normal Moveout (NMO) is one of key steps in seismic data processing,its precision has direct impact on whether the interference wave can be effectively suppressed by horizontal stacking.NMO is also a tool used for velocity analysis.Ordinary NMO processing uses Dix hyperbolic formula to align event under two preconditions:① it's in isotropic layered medium;② it's for middle or near offset receiver spread.But the long offset receiver spread usually is adopted when explored geological targets is beneath a high velocity stratum,so that the useful reflection beneath the high velocity stratum can be received.Under the circumstances,using Dix formula for NMO correction of long offset data can bring large errors,so higher order polynomial fitting must be adopted.The paper analyzed different NMO methods for long offset seismic data by forward calculating horizontal layered medium model,considering that there is no such thing for NMO correction of long offset seismic data as that the higher the used order in polynomial fitting is,the better the precision of NMO correction is and that shifted hyperbola is not optimum everywhere.In a condition of without considering influence of anisotropic medium temporarily,the coefficient of high order terms in polynomial is key factor having impact on NMO correction of long offset seismic data, determining what NMO method should be used in practical processing of long offset seismic data.