川西坳陷上三叠统须家河组砂体分布预测

以高分辨率层序地层学理论和技术方法为指导,通过基准面旋回结构、叠加样式的沉积动力学分析,结合地表露头、钻井岩心、测井、地震资料的综合研究,将上三叠统须家河组划分为4个长期层序、14个中期层序。以地震反射为约束,建立了四川盆地及川西坳陷长、中期基准面旋回层序地层格架。采用层序-岩相古地理编图方法,以长、中期基准面旋回上升、下降相域为单元编制四川盆地、川西坳陷岩相古地理图。在三维地震区内,以短期旋回为单元,建立高分辨率层序地层格架。以长期和中期层序界面、湖泛面为单元建立地震低频模型,以此为约束条件进行地震岩性反演和编制短期旋回小层砂体厚度图和沉积微相图。在此基础上详细讨论了典型小层砂体的纵横向分布与基准面旋回升、降变化和湖进、湖退的关系,预测有利砂岩储层纵、横向分布规律。

Prediction of sandbody distribution in the Upper Triassic Xujiahe Formation, the West Sichuan Depression

Guided by the high-resolution sequence stratigraphy theories and methods,the authors divided the Upper Triassic Xujiahe Formation into 4 long-term sequences and 14 medium-term sequences through sedimentary dynamics analysis of the structures of base level cycle and superimposition patterns and combining comprehensive study of outcrops,coring,logging and seismic data.A sequence stratigraphy framework of the long-term and medium-term cyclic sequences in Sichuan Basin and West Sichuan depression was also constructed under constrain of seismic reflection.Directed by the method of lithofacies paleogeographical mapping,they compiled lithofacies-paleogeographical maps for Sichuan Basin and West Sichuan depression with the elevating and falling fa-cies tracts of long-term and middle-term base level cycle as the mapping units,established high-resolution stratigraphic framework with short-term cycle as unit in 3D seismic survey area.Taking the sequence interface and lake flooding interface of long-term and middle-term cycle as the unit,they also set up low-frequency model and then used it to perform seismic lothological inversion and map sandbodies thickness and sedimentary microfacies of short-term cyclic sequences.Finally,they discussed the relationship between the sandstone distribution and base-level cycle variation and lacustrine ingression and regression,and predicted the vertical and horizontal distributions of potential sand reservoirs.