Based on the Aki-Richards approximate equations for reflection coefficients and Bayes theorem, we developed an inversion method to estimate P- and S-wave velocity contrasts and density contrast from combined PP and PS...Based on the Aki-Richards approximate equations for reflection coefficients and Bayes theorem, we developed an inversion method to estimate P- and S-wave velocity contrasts and density contrast from combined PP and PS data. This method assumes that the parameters satisfy a normal distribution and introduces the covariance matrix to describe the degree of correlation between the parameters and thus to improve the inversion stability. Then, we suppose that the parameter sequence is subject to the Cauchy distribution and employs another matrix Q to describe the parameter sequence sparseness to improve the inversion result resolution. Tests on both synthetic and real multi-component data prove that this method is valid, efficient, more stable, and more accurate compared to methods using PP data only.展开更多
为了实现裂隙介质中的地震AVO(amplitude variation with offset)反演,基于Christoffel方程和边界条件,推导了EDA介质中PP波、PS1波、PS2波精确反射系数表达式,并采用扰动法推导了极端弱各向异性介质中PP波的近似反射系数,通过弹性系数...为了实现裂隙介质中的地震AVO(amplitude variation with offset)反演,基于Christoffel方程和边界条件,推导了EDA介质中PP波、PS1波、PS2波精确反射系数表达式,并采用扰动法推导了极端弱各向异性介质中PP波的近似反射系数,通过弹性系数简化得到HTI、裂隙EDA介质中PP波的近似反射系数。模型计算结果表明:在弱各向异性条件下,HTI(horizontal transverse isotropy)介质中地震波的近似反射系数公式计算精度较高,相对误差在4%以内;当裂隙介质在弱各向异性(各向异性系数<0.1)的情况下,当入射角在40°以内时,PP波近似反射系数与精确反射系数的绝对误差在10^(-4)以内,相对误差小于4%,但随着入射角的加大其计算误差有所增加。对各向异性较强烈(各向异性系数达到0.2)的裂隙介质,当入射角相对较小时(小于45°时),裂隙介质中PP波近似反射系数计算式对于强各向异性的介质仍然成立。通过对反射系数的近似研究,可以将裂隙介质中反射系数的非线性问题转为线性问题,进而利用这些特性进行参数反演,有利于提高反演速度。展开更多
Spectral decomposition using the method of Matching Pursuit Decomposition （MPD） for PP- and PS-wave data has higher resolution and higher consistency over the entire time-frequency plane. The MPD algorithm avoids th...Spectral decomposition using the method of Matching Pursuit Decomposition （MPD） for PP- and PS-wave data has higher resolution and higher consistency over the entire time-frequency plane. The MPD algorithm avoids the problems of inaccurate analytic time point and the time window size choice that may occur during a Fourier transform. The PP-wave attenuation is greater than the PS-wave attenuation while propagating through gas reservoirs. There are some stronger amplitude low-frequency shadows on the PP-wave single frequency sections beneath gas reservoirs which are not seen on corresponding PS- wave single frequency sections. Therefore, hydrocarbons are predicted from comparing the behavior on both frequency sections. The time-frequency analysis for multi-component data is decomposed by MPD for data from northeast China containing rich gas reservoirs. The gas response character is analyzed on different wave mode single frequency sections. We describe the MPD algorithm, compare it to other spectral decomposition methods, and show some examples of detecting low-frequency shadows beneath gas reservoirs.展开更多
基金supported by the China Important National Science & Technology Specific Projects (Grant No. 2011ZX05019-008)the National Natural Science Foundation of China (Grant No. 40839901)
文摘Based on the Aki-Richards approximate equations for reflection coefficients and Bayes theorem, we developed an inversion method to estimate P- and S-wave velocity contrasts and density contrast from combined PP and PS data. This method assumes that the parameters satisfy a normal distribution and introduces the covariance matrix to describe the degree of correlation between the parameters and thus to improve the inversion stability. Then, we suppose that the parameter sequence is subject to the Cauchy distribution and employs another matrix Q to describe the parameter sequence sparseness to improve the inversion result resolution. Tests on both synthetic and real multi-component data prove that this method is valid, efficient, more stable, and more accurate compared to methods using PP data only.
文摘Spectral decomposition using the method of Matching Pursuit Decomposition （MPD） for PP- and PS-wave data has higher resolution and higher consistency over the entire time-frequency plane. The MPD algorithm avoids the problems of inaccurate analytic time point and the time window size choice that may occur during a Fourier transform. The PP-wave attenuation is greater than the PS-wave attenuation while propagating through gas reservoirs. There are some stronger amplitude low-frequency shadows on the PP-wave single frequency sections beneath gas reservoirs which are not seen on corresponding PS- wave single frequency sections. Therefore, hydrocarbons are predicted from comparing the behavior on both frequency sections. The time-frequency analysis for multi-component data is decomposed by MPD for data from northeast China containing rich gas reservoirs. The gas response character is analyzed on different wave mode single frequency sections. We describe the MPD algorithm, compare it to other spectral decomposition methods, and show some examples of detecting low-frequency shadows beneath gas reservoirs.
