变密度声波全波形反演中密度影响因素及反演策略

密度信息可预测储层流体饱和度，因此获取可靠的密度参数已成为全波形反演中首要考虑的问题。为了获得更稳定的反演密度，本文从频率、初始速度模型、初始密度模型和密度速度同时反演四个方面对密度的影响进行了研究。根据研究测试结果制定了稳定的反演策略：首先将密度固定，反演速度，此时波动方程中不再含有密度项，因而可以得到准确的速度模型；将其作为初始速度模型进行速度、密度同时反演，可以较好地减小速度对密度的影响。理论模型测试结果充分说明了策略的有效性。

Influence Factors and Strategy of Inversion for Density of Acoustic Full Waveform Inversion with Variable Density

The density can be used to predict saturation of reservoir fluid, obtaining the reliable density parameters has become an important consideration for full waveform inversion. In order to get more stable result of density, this paper studied the effecting factors for density from four aspects: frequency, the initial model of velocity and density and simultaneous inversion with density and velocity. According to the research results,this paper had get relatively stable inversion strategy: velocity is inversed with fixed density and then the wave equation is got without density, thus the accurate velocity model can be obtained. When the inversed velocity is treated as initial velocity model, the velocity and density can be simultaneously inversed which might reduced the effect of velocity on density better. The tests of theoretical model had shown the validity of this strategy.