【摘要】 为弥补以往VSP速度求取的盲区,提出了井底下部地层速度分析的方法:在纵波下行初至时间已知的前提下,基于井源距与VSP反射波到达时间的时距方程进行井底下部地层速度求取和动校正。得到速度参数后,使用类似地面地震的数字动校正方法进行动校正。由于VSP射线路径不对称,所以反射点位置的计算是目的层精确成像的基础,在计算出反射点位置后,进行道集抽取、动校正和变叠加次数的叠加成像。通过对直井Walk-awayVSP(变偏移距VSP)纵波记录和实际资料的处理,验证了方法的正确性和实用性。更多还原

【Abstract】 In view of the insufficiency of former velocity analysis, this paper proposes the method of velocity analysis under the shaft: to carry on P-wave velocity analysis and NMO correction under the shaft based on the time-distance equation of offset distance and the VSP reflection time, as first break time of down-going P-wave is known. This article uses digital NMO correction method similar to surface seismic. Because the VSP ray path is asymmetrical, this paper studies and summarizes the method of calculating the position of spot in pressure wave after calculating the position of reflection spot, obtains common-reflection point-gather on binning, then carries on NMO correction, stacks with changed fold number. The authors process the vertical well Walk-away VSP P-wave record and the practical data, verifying the validity of this method and the ability to solve practical problems.更多还原