开发尺度的曲流河储层内部结构地震沉积学解释方法

曲流河地层内部结构复杂,岩性界面具有穿时性,传统的地震相分析法不能满足油藏开发地质研究中对储层内部结构精细解释的需要,急需探索有效的地震解释方法。采用基于探地雷达的露头探测、点坝复合体三维正演模拟和实际地震资料相结合的方法,分析了地震资料频率和地层厚度对曲流河内部结构地震反射特征的影响,研究了利用地层切片解释曲流河沉积结构的原理和方法,建立了开发尺度的曲流河内部结构地震沉积学解释技术。研究发现:(1)高频地震资料中地震反射能够反映曲流河侧积复合体边界,而低频地震资料中反射同相轴与岩性界面一致;(2)不同厚度的点坝侧积单元地震反射特征存在差异,造成反射剖面的多解性。同时指出曲流河内部结构地震沉积学解释的技术关键:(1)发挥地震资料平面与剖面信息的相互约束和补充;(2)将地质体作为三维空间发育的成因体,利用其平面与剖面特征的成因联系指导解释;(3)级次化解释方法,在不同级次上采用针对性的解释方法。将该方法应用于墨西哥湾新近系地震沉积学解释,实现了曲流河点坝复合体内部结构的三维刻画。

Method for seismic sedimentology interpretation of reservoir architectures on development scale in meandering river

Reservoir architectures of meandering river are complex and the lithologic surfaces cross the isochronic ones.Traditional seismic facies analytical method can not satisfy seismic interpretation of reservoir architectures on reservoir development scale.Outcrop detection with ground penetrating radar(GPR),3D seismic forward modeling and real seismic data are employed in this study.The influences of seismic frequency and strata thickness on seismic reflection of meandering rivers are analyzed.Principle and method of meandering fluvial interpretation with stratal slices are studied.Seismic sedimentology interpretation workflow for meandering rivers is created.It is found that(1) seismic events in high frequency seismic data are reflection of isochronic surfaces formed by point bar complexes,while those in low frequency data are reflection of lithologic surfaces;(2) seismic reflection characters of bars vary with thickness,this causes the ambiguity in its seismic interpretation.Three key points of this method were proposed:(1) making full use of geologic information from vertical and horizontal dimensions of 3D seismic data;(2) taking fluvial sandbody as an integrated genetic body in 3D space;(3) using hierarchic interpretation method and interpreting sandbodies of different hierarchy with particular technologies.This method and workflow are used in seismic sedimentologic interpretation in the Gulf of Mexico,and architecture of point bar complexes are characterized in 3D space.