地层倾角对转换波抽道集的影响

共转换点道集的抽取是三维转换波数据处理的重要环节,道集抽取的正确与否受多种因素影响,其中地层倾角的变化能够引起共转换点道集的抽取误差,表现在炮点、检波点的数量与位置的错选。以地层倾向120°,某转换点垂向深度600m,纵横波速度分别为2 500m/s、1 250m/s的单层倾斜模型为例,利用姚陈提出的倾斜界面三维转换波CCP位置计算方法,对地层倾角分别为0°、5°、20°、30°时的炮点、检波点进行统计,确定其对该转换点的贡献情况,结果表明：倾角CCP抽取方法与目前常用的水平界面假设算法计算出的炮点、检波点分布存在很大差异,忽略倾角因素影响将导致不正确的道集叠加,给后期解释带来极大误差。

Impact of Strata Dip on Converted Wave Trace Gather Sorting

The common-conversion-point gather sorting is an important link in 3D converted wave data processing. The correctness of trace gather sorting is impacted by multiple factors; among other things the variation of strata dip can cause errors in commonconversion-point gather sorting, find expressions in wrong number and location of shotpoint and geophone station. To take the monolayer tilted model with strata dip direction 120°, a conversion-point vertical depth 600m, pressure and shear velocities are 2500m/s and 1250m/s respectively as an example, using tilted interface 3D converted wave CCP position computing method advanced by Yao and Cheng carried out statistics of shotpoints and geophone stations with their dip angles 0°, 5°, 20° and 30° respectively, determined their contributions on converted points. Results demonstrated that there are major differences between computed shotpoint, geophone station distribution by dip angle CCP sorting method and commonly used horizontal interface assumption computing at present. Neglect contributing factor of dip angle will cause incorrect trace gather stacking, and bring huge errors during later stage interpretation.