Superposition characteristics of single sand body of Chang-6 formation in Wujiaoxi area,Ordos Basin
The type,frequency and stacking style of single sand body development under the control of sedimentary microphase control the reservoir connectivity and the distribution of residual oil between wells.In this study,we comprehensively utilized abundant core,logging and analytical test data to study the development characteristics and stacking style of single sand body in the Chang-6 formation of the Triassic extension formation in the Wujiaoxi area of the Ordos Basin on the basis of fine depiction of the sedimentary microphase.The results show that the lithology of Chang-6 is dominated by siltstones,fine sandstones,fine sandstones and mudstones with mud gravels or mudstone laccoliths,and the types of sedimentary microfacies developed are sandy debris flow,turbidite flow,and semi-deep lake mud.In the vertical direction of the Chang-6 formation,5～8 phases of single sand bodies can be recognized,and the stacking types of single sand bodies include isolated,stacked and cut-and-stacked types;on the planar surface,the single sand bodies are mostly spread in the form of dendrites,nets,and local flakes.The change of accommodation space(A)and the matching relationship of sediment supply rate(S)caused by the rise and fall of lake level are the key factors controlling the spatial development characteristics of single sand bodies.From the bottom to the top of Chang-6 formation in the study area,with the change of the A/S ratio,the type of single sand body gradually changes from superposition type and cut-and-stack type to isolation type and localized superposition type vertically;and it evolves from reticulation and dendritic to localized lamellar on the planar surface.
Single sand bodyGravity flow depositionSuperimposition styleOrdos BasinWujiaoxi areaChang-6 formation
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