阿尔及利亚韦德迈阿次盆地FTEb区块三叠系层序-岩相古地理

Sequence-lithofacies Paleographic Characteristics of Triassic in Block FTE b in Oued Mya Basin of Algeria

FTEb区块是阿尔及利亚韦德迈阿次盆地的主要产油区之一,通过开展该区主要产层三叠系地层的层序-岩相古地理等基础研究对于深化勘探具有重要指导意义。通过沉积相分析,确定Serie inf组为辫状河沉积,T1组和T2组为曲流河沉积;以Cross的高分辨率层序地层学理论为指导,识别出3类层序界面类型,将三叠系地层划分出2个长期旋回和6个中期旋回。在沉积相和层序地层划分的基础上,以各中期层序的上升和下降相域为编图单元,编制、讨论了Serie inf^T2组期MSC1~MSC5中期层序上升、下降半旋回相域的岩相古地理特征,其沉积相带的演化具有明显的规律性,辫状河流相中的心滩沉积和曲流河相中的边滩沉积主要发育于上升半旋回相域,各期叠置发育的心滩和边滩砂体组成有利储集相带。

Block FTE b was one of the main oil production areas in Oued Mya Basin of Algeria,studying the fundamental geology of sequence-lithofacies paleographic analysis had important directive meanings to deepen the oil exploration.Based on sedimentary facies study,Serie inf Formation was ascertained as braided river sedimentation and T1,T2 Formations belonged to meandering river sedimentation.Based on the theory of high resolution sequence stratigraphy originated by Cross,three kinds of sequence boundaries were identified,and the Triassic system was divided into two long-term cycles and six middle-term cycles.Based on sedimentary facies and sequence analysis,the ascending and descending half-cycle facies tracts of each middle-term sequence system were taken as the mapping unit,the lithofacies paleographic characteristics of each ascending and descending half-cycle facies tract of MSC1-MSC5 from Serie inf stage to T2 stage were plotted and discussed.The results of sequence-paleogeographic mapping indicate that the development of sedimentary facies is of apparent regularity.The channel bar of braided river and point bar of meandering river mainly develop into the ascending half-cycle facies tracts,and multifacies override-developing channel bars and point bars form the favorable reservoir facies.