基于地震偶极子波多重积分的初始阻抗模型建立方法

摘要

地震阻抗反演需要适当的低频储层模型,常规反演方法是基于地震、测井资料和地震速度预测来建立储层低频模型.由于储层纵横向变化快,常规方法易出现低频模型的多解性和精度低等问题.综合考虑储层顶底地震反射界面阻抗和储层厚度特征,提出了整体反映这些特征的地震偶极子波概念和相应的地震响应特征分析方法.以此为基础,形成了偶极子波多重积分约束的地震反演初始模型建立新方法.该方法充分利用地震多重积分对储层位置和厚度识别与表示功能,再结合测井声波曲线的分频谱等数据构建地震初始阻抗低频模型.该建模方法在柴达木盆地某工区实际应用结果表明,所建模型与实际复杂的风化壳裂缝储层地震剖面吻合好,较完整地反映了地震剖面上的地质层位与构造特征,该模型对提高地震反演的稳定性和精度十分有利.%The seismic impedance inversion requries a proper low-frequency reservoir model. The conventional inversion method is based on logging data and seismic velocity prediction to establish reservoir low-frequency model. Due to the reservoir parameters horizontally and vertically quickly change, the uncertainty and low precision of the seismic inversion by using conventional low frequency model are not avoidable. In order to overcome these problems, a dipole wavelet multiple integral constraint method (DWMIC) for seismic inversion initial model establishment is proposed in this paper. The seismic dipole wavelet of a reservoir is a comprehensive representation of reservoir's top and bottom reflection interface impedances and thickness and the seismic trace multiple integral combined well logging acoustic fractional spectrum data can obtain reservoir positions and seismic impedances. The DWMIC modelling method has been applied to a work area in Qaidam basin. The result shows that the model constructed by the DWMIC fits the real seismic profile quite well for a complex weathering crust fracture reservoir. It means the model can be fully reflected the geological horizon and structure characteristics on the seismic section, suggesting that it is possible to improve the stability and precision of seismic inversion.