基于多目标函数的黏弹性全波形反演

Visco-elastic full-waveform inversion based on multi-objective function

全波形反演是勘探地球物理领域兴起的核心技术之一,不但可以构建地下速度结构,也能够反演衰减参数(品质因子Q)模型,有助于识别地下介质类型和构造(如流体和煤层陷落柱),对煤和油气等自然资源的勘探和开发有重要意义。参数串扰是黏弹性全波形反演的关键难点,受速度误差影响,反演的Q模型会包含非常强的串扰噪声。针对该问题,提出了基于多目标函数的黏弹性全波形反演理论与方法,首先通过旅行时反演速度结构,再通过中心频率目标函数反演Q模型,最终使用波形差目标函数同时反演速度和Q模型。由于中心频率主要受衰减影响,因此,可有效减弱速度误差对Q反演的影响。最后,通过数值模拟验证了算法可有效地反演速度和Q模型。

Full-waveform inversion(FWI)is one of the core technologies developed in exploration geophysics.Through FWI,the subsurface velocity structures can be constructed and the attenuation parameter(the quality factor Q)model can be inverted,which is helpful to characterize the types and structures of subsurface media(such as the fluid and collapse column in collapse column).This is significant for the exploration and development of natural resources such as coal,oil and gas.Parameter crosstalk is the key difficulty of visco-elastic FWI.Due to the influences of velocity errors,the inverted Q models contain very strong crosstalk noise.To solve this problem,the visco-elastic FWI theory and method based on multi-objective function was proposed.Specifically,the velocity structures are inverted using the travel time,and the Q models are inverted with the central-frequency objective function.Then,the velocity and Q models are inverted simultaneously with the waveform difference objective function.As the central-frequency is mainly influenced by attenuation,the influences of velocity error on Q model inversion could be effectively reduced.Finally,the algorithm was verified by numerical simulation for its capability to invert the velocity and Q models effectively.