含油气砂层的频率特征及振幅特征

一般认为砂岩在含油气以后,其地震波的瞬时频率会变低,并且其频谱的10Hz附近的低频成分的能量增加.这种没有论证过的结论直到目前还在被广泛地应用着.为了澄清这个问题,本文用一系列理论模型分析了砂层含油气后的频率特征和振幅特征.其结果说明,地震波的频率特性取决于三个因素:(1)地层的砂泥岩组合情况;(2)子波的波形;(3)地层的含油(气)性.而第三个因素所产生的频率高低没有明显的规律.但亮点条件下往往瞬时频率偏低者居多,这是由于强波接近于一个“单层反射波”的缘故.在任何剖面上,强波大多视周期较大,但它并不与含油(气)性有直接关系,即低频往往是强振幅的派生现象.本文还讨论了单层反射波的频率调谐作用,并通过模型试算对气层的吸收作用作了正确估价.

The frequency and amplitude of seismic waves sandstone

Many people hold that the seismic wave from hydrocarbon bearingsandstone has low instantaneous frequency, and the energy of low frequency contents around 10 Hz on the frequency spectrum increase Unfortunately, this unproved conclusion is still widely used at present. To clarify this problem, an analysis of frequency and amplitude ofseismic waves from hydrocarbon bearing sandstone is made using a series of theoretical models, A conclusion is drawn. that the frequencyresponse of seismic wave depends on (1) the contents of sand and shalein formations (2) wavelet waveform and (3) hydrocarbon condition inthe formation, Foint (3)can not cause regular frequency variation.The instantaneous frequency in the case of bright spot is usually on thelow side because strong wave is approximate to a "single bed reflecxion". On any seismic sections, strong reflections usually show big apparent periods which, however, is not directly? related to hydrocarbon because low frequency may be a derivative of strong amplirude. Frequency tuning of "single bed reflection" is diseussed}and a good evaluation of absorption of gas reservoir is made using model.