Reservoir characteristics and main controlling factors of tight sandstones in sandy braided river:a case study of He 8 Member of Shihezi Formation in Sulige gas field
Based on the data of core,well logging,cast thin sections,scanning electron microscopy and physical property analysis,the characteristics and controlling factors of tight sandstone reservoir of sandy braided river in He 8 Member dense well pattern area in East Sulige Gas Field are studied in this paper.The results show that the sandstone of He 8 Member in the study area is a low-porosity(with an average of 8.79％)and low-extra-low permeability(with an average of 0.219×10-3 μm2)reservoir.There are three types of reservoirs with low porosity and low permeability,low porosity and extra low permeability and extra low porosity and extra low permeability.The main pore type is the dissolution pore of cuttings(pseudohybrid),and the pore throat of the reservoir is thin and the connectivity is poor.Thick coarse-grained sandstone of middle bars in braided river are the foundation of high-quality reservoir development,which effects the types and processes of subsequent diagenesis.Differentiation and rhythmic diagenetic evolution are the key to determining reservoir heterogeneity.The middle part of the thick sand body is dominated by cuttings dissolution section,the two sides transit to siliceous cementation section,and the edge develops calcareous cementation section.The central part of the strong-dissolved thick sand body of middle bars,which is dominated by coarse-grained lithic sandstone,is mostly gas layer and gas-bearing water layer,which can be used as a sweet spot area for residual gas development.
tight sandstonereservoir characteristicsbraided riverdiagenesisSulige gas field
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