摘要
常规2次NMO动校是假定炮检距与深度比值小,并且射线为直线。计算的旅行时精度随着炮检距与深度比值的增加而大大降低,NMO校正能通过高次(4次、6次)项逼近得到改善。因此,在大炮检距情况下,若直接忽略高次项,则计算旅行时会产生很大误差,所以在大炮检距条件下进行2次NMO近似不利于速度分析、AVO研究和CMP道集动校叠加。笔者引入了一个更精确的旅行时近似计算,称为优化6次NMO动校方程式,因为截断误差较小,故其精确度高于泰勒6次展开式。通过模型和实际数据的试验,证明大炮检距优化6次NMO方程精度高,更具有实际应用意义。
The conventional 2^(nd) order NMO assumes a small offset-to-depth ratio and straight raypaths. The accuracy for the travel-time calculations decreases significantly with increasing offset-to-depth ratio. The 2^(nd) order NMO may be improved by extending the hyperbolic approximation with higher order (4^(th), 6^(th),) series. Conventional NMO is a small offset approximation, therefore, the explicit truncation of the higher order terms generates significant errors in the travel-time calculations at long offsets. Hence, the 2^(nd) order approximation is not suitable for velocity analysis, AVO study, and CMP stack using long offset seismic data. In this paper, we introduce a more accurate travel-time approximation which we called the optimized 6^(th) order NMO equation. The accuracy of the new and proposed equation is better than Taner's 6^(th) order equation because the truncation error is smaller. Even though we truncate Taner's expansion to the 6^(th) order, we take all other higher orders terms into account as well. The tests using synthetic and real data show that our optimized 6^(th) order long offset NMO equation works well. The improvement at long offsets is more significant than Taner's 6^(th) order truncation.
出处
《西北地质》
CAS
CSCD
2004年第4期117-120,共4页
Northwestern Geology
关键词
大炮检距
6次NMO校正
精度
long-offset
6^(th) order NMO correction
precision
