含煤地层AVO正演模型参数优选分析

采用GEOVIEW软件,选取顶底板为泥岩,中间为煤层（厚度变化范围0～30m）的三层介质作模型,通过改变中间煤层的厚度、处理采样率、子波等参数,并保持上下围岩参数不变的方式来讨论相关参数对AVO响应的影响,结果表明当处理采样率越高时,AVO截距和梯度精度就越高;子波采样率过低,会引起AVO截距和梯度值的扰动现象;当子波采样率提高到一定程度时,扰动现象消除;子波主频的大小决定了调谐效应的范围,提高地震波主频,有利于提高分辨率;子波长度的变化对AVO截距和梯度值求取影响不大。上述结论为AVO正演模型参数优选提供了依据,其最佳参数的选取可有效提高含煤地层AVO正演模型的精度。

Parameter Optimization of AVO Forward Model for Coal-bearing Strata

In order to get the accurate AVO forward model responses for coal-bearing strata, the AVO responses vary with the coal thickness, processing sample rate and wavelet parameters have been discussed on condition that the surrounding rock is unchangeable. The results show that the higher the processing sample rate, the better the accuracy of the intercept and gradient. Low wavelet sample rate will cause the fluctuation of intercept and gradient, but it can be eliminated when the wavelet sample rate has improved to a certain level. The dominant frequency decides the range of the tuning effect. To improve the dominant frequency will help to improve the resolution. The length of the wavelet has little effects to the intercept and gradient. The conclusions above could help to choose the appropriate parameters for the AVO forward modeling, thus to improve the accuracy of the AVO forward model for coal-bearing strata.