鄂尔多斯盆地高家河地区山西组二段下部地震沉积学研究

Seismic sedimentology of lower part of second member of Shanxi Formation in Gaojiahe area, Ordos Basin

以鄂尔多斯盆地延长地区高家河三维区下二叠统山西组二段下部为例,阐明了利用地震信息研究沉积体系平面分布特征的方法。首先基于岩石物性研究,利用时间-频率扫描分析技术,在90°相位地震数据体中,研究煤层的地震反射特征;其次通过设计特定的滤波器,进行地震滤波,抑制煤层对地震反射特征的影响(压制地震干涉左右),将高精度层序地层学和地震沉积学相结合,在三维地震数据体中创建精细(高频)等时地层框架;最后结合地质特征、测井响应和地震相分析,对具有代表性的不同频率的等时地层切片进行沉积分析,采用混合频率显示技术,研究沉积相空间分布特征。鄂尔多斯盆地延长地区高家河三维区山二段下三角洲平原亚相中分流水道主要表现为3个走向:(1)呈先南北、后东西、再南北走向,沿S229、S228、S232、S208、Y124井边缘分布。在该分流河道中,在S231井附近可能发育一个具有一定规模的曲流边滩。(2)呈北西-南东走向,主要沿S212、Y127、S209井一线分布。(3)呈近东西走向,在沿S210、S226井发育一规模较大的河道侧向迁移带。

The method of using seismic information to study the planar distribution characteristics of sedimentary system is illustrated using the lower part of the second member of the Lower Permian Shanxi Formation in the Gaojiahe 3 D area of the Ordos Basin as an example.Firstly,based on rock physical properties,time-frequency scanning technology was used to study the seismic reflection characteristics of coal seams in a 90°phase seismic data volume.Secondly,by designing specific filters,seismic waves were filtered to suppress the influence of coal seams on seismic reflection characteristics.A fine(high-frequency)isochronous stratigraphic framework in the 3 D seismic data volume was created by combining high-precision sequence stratigraphy with seismic sedimentology.Finally,combining geological features,logging responses and seismic facies analysis,provided the sedimentary analysis of isochronous stratigraphic slices with different frequencies.Mixed frequency display technology was applied to study the spatial distribution characteristics of sedimentary facies.The distributary channels in the lower delta plain sub-facies of the second member of Shanxi Formation in the Gaojiahe 3 D area are mainly represented by three trends:(1)Some show north-south,east-west,and then north-south trends,along S229,S228,S232,S208,Y124 well edge.In these distributary channels,a meandering beach with a certain scale may develop near well S231.(2)Some show a northwest-southeast trend,mainly distributed along wells S212,Y127,and S209;(3)Some show a nearly west trend.A large-scale lateral river migration zone develops along wells S210 and S226.