利用长、短旋回波形分析法去除地震强屏蔽

Seismic strong shield removal based on the long and short cycle analysis

基于地震沉积学准层状地层,提出了一个对应的阻抗模型,其地震信号可视为长、短旋回的组合反射。长旋回具有低频、连续和相位稳定的特征,短旋回则相反。地震的强轴屏蔽可理解为长旋回背景,被屏蔽的砂体则为短旋回信息。采用一种基于长、短旋回波形分析方法去除强屏蔽的影响,通过Wheeler正、反变换、子体波形主成分分解、短旋回分频显示等构成长、短旋回分析技术流程,达到去除屏蔽、识别薄砂层的目的。利用正演模型试验,论证了算法的正确性和可行性;应用上述流程识别了松辽盆地北部强屏蔽T2之下的砂体信息,经主成分分解后的振幅切片反映了两条从南向北展布的浅水三角洲前缘沉积体,证实上述流程具有较好的去强屏蔽效果,对于其他具有屏蔽特征或相似地质条件的储层(例如煤层)描述具有借鉴价值。

In this paper an impedance model for quasilayered strata of seismic sedimentology is proposed in which seismic signal can be regarded as a combination of long and short cycles.Long cycles are characterized by low frequency,continuous and stable phase while the short ones have the opposite characteristics.On seismic sections,the information of sand body regarded as short cycles is usually shielded by the strong events which represent long cycles.In order to alleviate strong shielding effects and achieve thin sand identification,we adopt an approach based on the long and short cycle analysis,including Wheeler positive and inverse transforms,sub-packet waveform principal component decomposition,and short cycle red-green-blue(RGB)segmented frequency imaging.The validity and feasibility of the proposed method are approved on a forward modeling.The above-mentioned flow is applied to identify sand bodies under the T2 strong shielding in the Northern Songliao Basin.Amplitude slices decomposed by principal components show two shallow water delta front bodies spread from the south to the north,which proves that the proposed approach can effectively remove strong shields,which may provide a valuable reference for other similar geological conditions.