井间地震反演中低频模型的影响研究

Research of Low Frequency in Cross-Well Seismic Inversion

井间地震具有主频高、频带宽的特点,可清晰反映井间地层、构造、储层特征。波阻抗反演将地震反射数据转化为波阻抗信息,可直接用于储层特征分析,但井间地震低频信息缺失,将影响反演精度。首先,通过地质模型正演数据反演的方法,分析了低频信息对波阻抗反演的影响;其次,以工区井间地震为研究对象,对比分析了不同方法构建的低频模型对反演精度的影响,并将波阻抗反演数据用于井间砂体对比分析。结果表明,(1)正演分析中,含更多低频成分的子波旁瓣的幅度比含低频成分较少的子波旁瓣要小,用其约束反演,可提高波阻抗反演精度;(2)实例分析中,采用低频信息更加丰富的低频模型约束井间地震波阻抗反演时,有助于提高波阻抗反演精度,更加准确地反映地下储层特征;(3)井间地震波阻抗反演数据反映了储层空间展布特征,有助于提高薄储层表征精度,为开发后期的井位部署和井位调整提供依据。

Cross-well seismic data are characterized by the main high frequency and abundant frequency component and can clearly show the feature of strata,structure and reservoir under the ground.By way of seismic inversion,seismic reflection data can be transferred into the impedance information and applied to reservoir analysis.However,lack of low frequency information in cross-well seismic data will affect the accuracy of the inversion.Influence of low frequency information on seismic inversion was analyzed by means of geologic forward model inversion.In the studied area,the affection of the low frequency model constructed with different methods on the inversion precision is contrasted.Then the impedance inversion data were used for analyzing sand body distribution between wells.It is shown that:(1)for the geologic forward model,side lobes of wavelet with more low frequency components is smaller than that with less low-frequency components,and it will improve the precise of seismic inversion;(2)in the studied area,adopting the low-frequency model with more abundant low-frequency information will be beneficial to improve seismic inversion accuracy;(3)the inversion data can improve the precision in reservoir characterization.It can be served as a basis for well placement and well adjustment in the development stage.