摘要
虚源成像法可以避开地形起伏和复杂上覆地层对深部地质目标体的影响,提高地震勘探的分辨率和保真度。为了提高虚源成像的质量,在射线分析的基础上,给出了单层水平介质条件下虚源成像观测系统设计的定量表达式,从运动学的角度解释了固定相位点的物理意义,即满足反射波入射角等于直达波入射角的炮检点空间分布。同时,提出了调谐采样间隔的概念,为反射波信息准确重构的定量评价提供了一种有效方法。在此基础上,研究了不同参数对虚源成像质量的影响,其中介质速度和检波点的埋藏深度对成像质量有较大影响,而地质目标体的埋藏深度以及检波点间距对成像质量影响较小。数值试验的结果表明,随着介质速度和检波点埋藏深度的不断增大,调谐采样间隔不断增大,炮间距的选择范围也随之不断增大,进而为虚源成像地震数据采集提供更加高效保真的设计方案。
The virtual-source imaging method is able to avoid the influence of topography and complex overlying layers on deep geological targets and improve the resolution and fidelity of seismic exploration.To improve the quality of virtual-source imaging,based on ray analysis,the quantitative expression for observation system design of virtual-source imaging is given under the conditions of single-layer horizontal medium in this study,so as to interpret the physical meaning of stationary phase point from the perspective of kinematics,i.e.,the space distribution of shot-receiver points with the incident angle of reflected wave equal to that of direct wave.Meanwhile,the concept of tuning sampling interval is proposed to offer an efficient method for quantitatively analyzing the accurate reconstruction of reflected wave information.On this basis,the influences of different parameters on virtual-source imaging quality are studied;the medium velocity and buried depth of receivers have a major influence on imaging quality,while the buried depth of geological targets and the shot receiver interval have a minor influence on imaging quality.The results of numerical experiment show that the tuning sampling interval increases gradually with the constant increasing of medium velocity and buried depth of receiver,which enlarges the selection range of shot interval and further supplies the design scheme with high efficiency and fidelity for the acquisition of seismic data based on virtual-source imaging.