约束速度反演在大庆油田复杂构造成像中的应用

APPLICATION OF CONSTRAINED VELOCITY INVERSION IN COMPLEX STRUCTURE IMAGING IN DAQING OILFIELD

在叠前深度偏移处理中，速度模型是决定成像质量的重要参数。通常，初始速度模型通过叠加速度直接用DIX公式计算而得到，这样的速度模型在横向上一致性较差，需要较多次迭代才能保证成像效果。因此，研究探索一种快速有效的速度建模方法非常必要。利用约束速度反演（CVI）方法，通过给定的速度趋势函数来约束速度模型的横向变化，再利用最小二乘基本原理使成本函数达到最小。该方法克服了常规DIX公式转换的缺点，减少了速度建模的迭代次数，在趋势函数的约束下，速度场的横向变化相对稳定。实际地震资料处理结果表明，该方法建立的速度模型成像效果明显，复杂构造地层成像清晰，断面清楚。

During the pre-stack depth migration processing, velocity model is an important parameter to control the imaging quality. Usually, the initial velocity model is obtained directly by the DIX formula using stacking velocity, and such velocity model has poor lateral consistency, which needs multi iteration to ensure the imaging quality. Therefore, it is necessary to develop a rapid and effective velocity modeling method. This paper uses the constrain- ed velocity inversion （ CVI ） method, which constrains the lateral variation of velocity model using given velocity trend function, and then minimizes the cost function by least squares principle. This method overcomes the disadvantage of conventional DIX formula transformation, decreases the iteration times of velocity modeling, and provides a relatively stable lateral change of velocity field under the constraint of trend function. Actual seismic data processing results indicate that the velocity model established using this method has obvious imaging effects, with clear imaging in complex structure and clear cross section.