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在中国东部的复式油气区,为了准确地确定断块和断层位置,唯有采用三维地震勘探,使用三维叠前偏移技术。鉴于叠前偏移处理的工作量太大,采用三维DMO技术是切实可行的。本文从理论上说明时空域的三维DMO算子和二维DMO算子是等价的。在CMP域作三维DMO是比较容易实现的。只需对每个CMP面元,按各自的炮检距方向,用二维DMO算法把校正数据送到附近有关的CMP道集面元中去。也就是说可用叠后偏移技术(零炮检距偏移)作叠前积分法的部分偏移,偏移速度为x/T_N(适用于均匀恒速介质)或为k x/T_N(适用于速度呈垂向变化地区);然后将每个面元内相同炮检距资料求和,即可作为DMO校正的结果。这种叠前部分偏移的DMO校正可以在动校正之后进行,也可在动校正之前进行。本文还按曲射线原理对动校前TVDMO的偏移速度系数k值进行了理论计算,导出用多项式拟合的经验公式,从而进一步完善了TVDMO方法。
In the compound oil and gas region in eastern China, only three-dimensional seismic exploration and 3D prestack migration are used in order to accurately determine the fault block and fault location. In view of the workload of prestack migration processing is too large, the use of three-dimensional DMO technology is feasible. This paper theoretically shows that the three-dimensional space-time DMO operator and the two-dimensional DMO operator are equivalent. In the CMP domain for three-dimensional DMO is relatively easy to achieve. It is only necessary for each CMP bin to send calibration data to the relevant CMP gathers by using the two-dimensional DMO algorithm in their offset directions. That is to say, the stack migration technique (zero offset offset) can be used for partial migration of the prestack integration method at x / T_N (for uniform constant velocity media) or kx / T_N (for The vertical velocity of the area); and then the same offset information within each bin sums, DMO can be used as a result of the correction. This pre-stack partial offset DMO correction can be performed after a dynamic correction or before a dynamic correction. In this paper, we also theoretically calculate the k-value of the offset velocity coefficient of TVDMO before moving school according to the theory of curvature, and derive the empirical formula of polynomial fitting to further improve the TVDMO method.