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在地面地震中,大部分反射数据或多或少是由于横向上延伸较长的层状构造所产生。因此,以二维层状介质层来解释这些数据不会产生严重误差。然而,在井间储层层析成象中,感兴趣的目标体是一个限定的目标体,其几何特征的尺度与震源信号的主波长大小相当。在此条件下,考虑到绕射的作用,大量的能量越过了所研究的目标体。如果异常体的速度小于周围介质的速度,则该能量可作为初至波出现在接收井中,并与Fermat原理相符。用基于声波波动方程的有限差分模型研究了大量简单三维储层的井间地震响应。沿接收井计算出的信号特征证实了透射能量和旁
In ground-based earthquakes, most of the reflection data is more or less due to the laterally elongated layered structure. Therefore, interpreting these data in two-dimensional layered media does not cause serious errors. However, in cross-well reservoir tomography, the object of interest is a defined target with a scale of geometric characteristics that is comparable to the dominant wavelength of the source signal. Under this condition, considering the effect of diffraction, a large amount of energy has crossed the target body under study. If the velocity of the anomaly is less than the velocity of the surrounding medium, this energy can appear as a first arrival wave in the receiving well, consistent with Fermat’s principle. The cross-well seismic response of a large number of simple three-dimensional reservoirs has been studied using the finite difference model based on the acoustic wave equation. The signal characteristics calculated along the receiving well corroborate the transmitted energy and side