纵、横波逆品质因子AVO反演方法研究

Research of AVO inversion for P-and S-wave inverse quality factors

品质因子是表征地震波在岩石中传播衰减、评价含油气储层物性的重要特征参数.本文首先在衰减介质小扰动假设条件下,对黏弹性介质PP波反射系数方程进行了线性近似,建立了基于纵波阻抗、横波阻抗、密度和纵、横波逆品质因子的频变反射系数新方程.通过模型分析对该方程的精度和适用性进行验证,结果表明该方程即使在较大入射角条件下仍具有较高精度.采用马尔科夫链蒙特卡洛(MCMC)方法,发展了一种稳定获取纵、横波弹性参数和衰减参数的AVO反演方法.模型测试和实际应用表明,该方法能够稳定准确地直接从叠前地震资料中获取地层弹性参数和衰减参数,提供了一种有效的储层预测与流体检测方法.

Quality factor is an important parameter that characterizes the attenuation of seismic waves propagation in rocks and evaluates the hydrocarbon reservoirs properties.Under the assumption of small perturbations in the attenuating medium,a novel linearized PP wave reflection coefficient equation of the viscoelastic medium is approximately derived,and the frequency-dependent reflection coefficient equation based on the P-and S-wave impedance,the density,P-and S-wave inverse quality factors is established.The accuracy and applicable condition of the novel equation are verified and analyzed through model tests.The results show that the novel equation has enough accuracy even for large incident angles.Using the Markov Chain Monte Carlo(MCMC)method,an AVO inversion method for stably obtaining P-and S-wave elastic parameters and attenuation parameters has been developed.Model and real data tests show that the proposed MCMC inversion method of P-and S-wave attenuation factors can stably and accurately obtain subsurface elastic and attenuation parameters directly from pre-stack seismic data,which offers an effective reservoir prediction and fluid identification method.