莱州湾凹陷明化镇组下段河道储层的地震地貌分析

Seismic geomorphology of channel reservoir in lower Minghuazhen formation,Laizhouwan Depression

为刻画莱州湾凹陷明化镇组下段的河道储层,从高精度三维地震数据体上提取11种能够突出河道特征的几何类地震属性;然后利用主分量三原色融合技术,将11种属性体沿层切片上的河道特征融合成一张高清晰的水平切片图像;再用地貌学方法对四期沿层切片中的75处蛇曲段的河道形态进行几何学参数测量,并分析了河道宽度、弯曲度、蛇曲高度、蛇曲宽度、蛇曲波长共五种几何学参数间的相互影响和数学关系。最终得到以下认识:①11种几何类地震属性数据沿层切片的前三主分量三原色融合,较单一的地震振幅数据沿层切片,能够更清晰地反映河道储层的地貌形态,从而测量出更精确的几何学参数值;②在莱州湾凹陷明化镇组下段,地层越老河道越发育,河道宽度集中在100～300m,蛇曲流域中单曲段多于多曲段,弯曲度集中在1.1～1.5,表明河道的侧向侵蚀作用不强;③上述五种几何学参数的定量测定表明,与现代河流一样,河流—浅水三角洲沉积体系中河道形态的几何学参数间同样服从幂函数或线性函数规律。这些研究结果为渤海湾盆地河道储层精确预测与地质建模提供了依据。

The principal goal of our study is the morphometrics of channel system in Laizhouwan Depression.First,a selection of 11 geometric attributes were computed from high quality 3D seismic volume to highlight the fluvial features,and then extracted at each horizon of interest.Next,PCA were applied to these 11 geometric horizon attributes to yield the principal components.The first three components were mapped to Red,Green and Blue channels of a high-resolution image.Finally,75 set of morphometric variables were measured in four phases of meandering channels by the geomorphology approach.Meanwhile,the relationship among channel width,meander-belt width,meander length,meander-arc height and sinuosity were analyzed.These analyses suggested three points.①The PCA-RGB blending of 11 geometric horizon attributes is more indicative on the channel outline variability than a single amplitude horizon slice.②In lower Minghuazhen formation,Laizhouwan Depression,the amount of channels increased as the channel systems age,the channel width ranges from 100m to 300m,the number of single meander is much more than multiple meanders and the channel sinuosity mainly ranges from 1.1 to 1.8,which reveal relatively weak lateral erosion in the channel system.③The cross-plot of five geometric measures appear to be consistently power function or linear in both sedimentary channels and modern rivers.These results provide further confidence to predict the reservoir characteristics and build the reservoir modeling in Bohai Bay Basin,China.