浅层非均质性对深层反射信号的影响研究

Study on the influence of shallow heterogeneity on deep reflection signal

由于浅层非均质性的存在,往往会导致深层的成像剖面不能真实的反映地层的岩性变化.因此,为了消除浅层非均质性对深层反射信号的影响,从研究深层反射信号的振幅变化开始是很有意义的.本文以正演模拟为基础,研究了浅层中不同速度、尺度的非均质体对深层反射信号振幅及振幅随偏移距变化的影响,并总结了非均质体正下方区域深层反射信号振幅的变化规律.研究结果表明:非均质体速度、尺度变化越剧烈,对深层反射信号的影响越严重;对于非均质体正下方区域,低速异常造成振幅增强(低速差异特大情况除外),高速异常造成振幅衰减;尺度变化的影响是建立在前者影响的基础上进一步扩展,但在尺度差异特大情况下会出现反转现象.该研究为初步了解浅层非均质性对深层反射信号的影响提供了依据,并为深层正确成像及叠前反演、AVO等处理奠定了基础.

Due to the existence of shallow heterogeneity, it often leads that the deep imaging profile can not truly reflect the lithology of the formation. Therefore, in order to eliminate the influence of shallow heterogeneity on the deep reflection signal, it is of great importance to study the amplitude change of the deep reflection signal. In this paper, how different velocity and scale of the heterogeneity influence the amplitude and amplitude on the change of offset are researched in the shallow stratum based on the forward modeling, and the characteristics of the amplitude change of the deep reflection signal are summarized in the area just below the heterogeneous body. The results show that the more violent the velocity and scale change of the heterogeneous body is, the more serious the influence on the deep reflection signal is. For the area just below the heterogeneous body, low-speed anomaly causes the amplitude to increase(except for large low-speed anomaly), the high-speed anomaly causes the amplitude to decay. The influence of the scale change is further expanded based on the influence of the velocity change, but the phenomenon will be reversed in the case of large scale change. This study provides a grounds for which we preliminarily understand the effect of shallow heterogeneity on deep reflection signal, and lays the foundation for the correct imaging of target layer and pre-stack inversion, AVO and so on.