针对深层流体识别的两项弹性阻抗反演与Russell流体因子直接估算方法研究

Two-term elastic impedance inversion and Russell fluid factor direct estimation method for deep reservoir fluid identification

Russell流体因子是判识深层储层含流体特征的敏感指示参数.针对深层地震资料缺失大角度入射信息以及信噪比普遍较低的特点,开展了基于贝叶斯理论框架的两项弹性阻抗反演与Russell流体因子直接估算方法研究.首先,在饱和孔隙弹性介质理论的指导下,推导了包含Russell流体因子和纵波阻抗参数的两项反射系数近似公式,并且进一步得到了新的两项弹性阻抗方程.其次通过模型的近似精度分析,验证了新弹性阻抗方程满足小角度近似精度要求.最后提出了贝叶斯弹性阻抗反演和Russell流体因子的直接估算方法,通过模型试算表明直接估算方法不仅充分利用了弹性阻抗反演的高抗噪性与实用性,并且有效的避免了间接累计误差对流体因子计算精度的影响,实际应用则进一步验证了直接估算的Russell流体因子可以提高深层储层流体识别的可靠性.

Russell fluid factor is a sensitive indicator for deep reservoir fluid identification.Considering that the seismic data of deep reservoir is lack of large angle information and has low signal-noise-ratio,the Bayesian-based two term elastic impedance inversion and Russell fluid factor direct estimation method are carried out.Firstly,based on the saturated poroelastic media theory,we derive the two term reflection coefficient approximation in terms of Russell fluid factor and P-wave impedance,using which we get the new equation of elastic impedance containing the Russell fluid factor.Secondly,we analyze the precision and applicable condition of the new elastic impedance and the model test shows that it can satisfy the accuracy of small angle incidence.Finally,the Bayesian-based elastic impedance inversion and Russell fluid factor estimation procedure is introduced,the model tests illustrate that the direct estimation method can take full advantage of elastic impedance inversion to have high signal-noise-ratio and practicability,and furthermore,the direct estimation method can diminish negative effect of accumulative error.The real application shows that the direct estimated Russell fluid factor raise the reliability of the deep reservoir fluid identification.