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尾波是持续时间比主要波型长得多的多重散射波,它包含了直达波之外的部分有用信号。在油气田的开采过程中,由储层物性参数的微小变化而导致的储层速度的微小变化对初至的影响很小,无法通过初至变化直接观测,但是因为尾波为多重散射波,故储层速度的微小变化会在尾波的传播过程中被放大,因此利用尾波可以观测到这种变化。本文通过实验与数值模拟研究了尾波干涉方法在储层微小时移差异监测方面的有效性。合成地震数据是基于部分MarmousiⅡ模型采用有限差分波动方程正演方法计算获得,为了模拟时移地震中的储层波速变化,在模型中选取波速发生微小变化的目标区,计算速度扰动前后的合成地震数据,进而观测尾波变化。研究表明利用尾波干涉可检测储层物性的微小变化,为时移地震信号监测提供新的方法和手段,从而提高时移监测的准确度,也为开发生产工作提供可靠的指导。
Coda waves are multiple scattered waves that last much longer than the dominant wave pattern and contain some of the useful signal outside the direct wave. In the process of oil and gas field mining, the slight change of reservoir velocity caused by the small change of reservoir physical parameters has little effect on the first arrival and can not be directly observed through the first arrival change. However, since the wake is multiple scattering waves Small changes in reservoir velocity can be amplified during coda propagation, so this change can be observed using coda waves. In this paper, we study the effectiveness of the coda interferometry in the differential monitoring of reservoir micro-displacement by experiments and numerical simulations. Synthetic seismic data is obtained based on some Marmousi Ⅱ models by forward modeling of finite difference wave equation. In order to simulate the variation of reservoir velocity in time-shifted earthquakes, a small change of target area is selected in the model and synthetic earthquakes before and after velocity perturbation are calculated Data, and then observe the coda changes. The research shows that the small changes of reservoir physical properties can be detected by the cotangent wave interference, which can provide new methods and means for monitoring the time-lapse seismic signals, so as to improve the accuracy of time-lapse monitoring and provide reliable guidance for the development of production.