Controls of Architecture Under the Constraints of a Multi-level Interface on Physical Property Heterogeneities from the Meandering River of the Shaximiao Formation in Western Sichuan
[Objective]There is large potential of oil and gas resource from the Jurassic Shaximiao Formation of the eastern slope in the Western Sichuan Depression,and the internal structure of the single sandbodies restrict the pre-diction of high-quality reservoirs,and consequently affects the evaluation of the natural gas enrichment characteris-tics in this area.The order of the architecture boundary,architecture-element,and architecture-element assemblies in the study area are not yet clear.There is a lack of relevant understanding of how the architecture-elements and their assemblies control the reservoir heterogeneity from the different architecture boundary levels.[Methods]In this study,the types of sedimentary facies were determined to provide the foundation for the study of the sandbody archi-tecture.Based on the data of field outcrops,cores,logs,and experimental measured analysis,detailed research on the type and characteristics of the sandbody architecture of the meandering river from the Shaximiao Formation of Western Sichuan Depression was carried out,and the effect of sandbody architecture on the reservoir heterogeneity under the constraints of multilevel architecture boundary was discussed.[Results and Conclusions]The architecture-elements in the study area were divided into HPB,HCH,MCS,MCL,MCA,and MFM.Based on the vertical stacking pattern of architecture units and the sedimentary characteristics of vertical sequence,the architecture-element assemblies are divided into three types,including homogeneous assemblage(Type Ⅰ),homogeneous+compound(Type Ⅱ),and compound assemblage(Type Ⅲ).Type Ⅰ assemblage mainly occurs in the Zhongjiang-Huilong area of the study area,and the Type Ⅰ assemblage and Type Ⅱ assemblage mainly occur in the Third member of Shaximiao Formation,and the reservoir heterogeneity is relatively weak.Based on the above research on the types and characteristics of sandbody architecture,the analysis on the characteristics of reservoir heterogeneity under the control of different levels of architecture boundary,and the discussion of the controlling factors that sandbody architecture impact on the reservoir heterogeneity under different levels of architecture boundaries,the model of controlling the reservoir heterogeneity under the architecture boundary constraints of 3～5 levels of architecture is established.The reservoir plane heterogeneity is controlled by the 5 level'architecture boundary,and the reservoir heterogeneity under the 5 level'architecture boundary is controlled by the rising of based-level and structure subsid-ence.The reservoir inter-layer heterogeneity is controlled by the 4 level'architecture boundary,and the reser-voir heterogeneity under the 4 level'architecture boundary is controlled by the slope and erosion.The reservoir intra-layer heterogeneity is controlled by the 3 level'architecture boundary,and the reservoir heterogeneity under the 3 level'architecture boundary is controlled by the hydrodynamic condition,channel sinuosity,degree of channel migration,deposited load,discharge,and diagenesis.
Western Sichuan DepressionShaximiao Formationarchitecture boundaryarchitecture-element assembliesreservoir heterogeneities
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