柴达木盆地东部石炭系地震层速度求取方法的研究

在柴达木盆地东部石炭系地震勘探过程中，地震层速度是一个重要的参数。层速度不仅仅可以应用于时深转换，还可以应用于反映地层岩性、构造和地层压力等方面的信息，地震剖面与地震速度也密切相关。柴达木盆地东部石炭系由于资料所限，速度问题一直未能很好地解决，时深转换过程中速度误差较大。因此，为了解决研究过程中速度误差较严重的问题，文章在前人工作基础上，探索性地提出了一种新的层速度求取方法，以提高柴达木盆地东部石炭系地震勘探过程中层速度的精度，从而更好的认识本区的构造和地质特征。通过对单井速度分析和二维地震叠加速度多次拾取，保证了速度谱拾取的精度，然后将地震叠加速度换算成均方根速度，进而利用基于单井速度趋势模型约束Dix反演层速度技术将均方根速度转换成层速度，拟合出全区的平均速度场。同时在拟合后，以井上测井速度为控制点，对平均速度进行了合理校正，从而建立比较合理的研究区层速度模型。利用新建立的层速度模型，对原来的构造重新进行时深转换，取得了较好的效果。新的改进Dix公式层速度求取方法求取的速度模型与前人成果相比较，利用了单井速度约束Dix公式进行速度反演，因而比前人成果更精确，更符合单井速度趋势，因而更符合地质认识规律。

Calculation of Carboniferous seismic interval velocity in Eastern Qaidam Basin

Seismic interval velocity is an important parameter for the Carboniferous exploration in Eastern Qaidam Basin. Interval velocity can be applied to time depth conversion, and to reflect lithological, structural and formation pressure information. Seismic section is closely related to seismic velocity. Because of Carboniferous data shortage in Eastern Qaidam Basin, seismic velocity has long been a problem, and the velocity error in the time depth conversion was large. To solve these problems, a new approach to calculate interval velocity was presented based on the previous work, thus improved the velocity accuracy and better understood the tectonic and geological characteristics in Eastern Qaidam Basin. Seismic stack velocity was converted into root mean square velocity based on the single well velocity analysis and multiple picking of two dimensional seismic stack velocity, and then was converted into interval velocity using constrained Dix inversion based on the single well velocity trend model, at last the fitting curve of the average velocity field was done. Then, the seismic average velocity was corrected by well logging velocity as the control points, so as to establish a more reasonable interval velocity model. The new depth structure converted by the new interval velocity model is more reasonable than previous one. The new velocity model for calculating interval velocity is more accurate than the previous results, more in line with the single well velocity trend and is consistent with the geological cognition.