岩矿测试2026，Vol.45Issue(5)：1124-1144,21.DOI:10.15898/j.ykcs.202511140271
鄂尔多斯盆地盒1段致密砂岩孔喉类型分形特征与可动流体赋存机理
Fractal Characterization of Pore-Throat Types and Fluid Occurrence Mechanisms in Tight Sandstones:A Case Study of the He 1 Member,Ordos Basin
摘要
Abstract
The He 1 Member of the Ordos Basin is a key interval for tight sandstone gas exploration and development.The complex interplay between mineral fabric and pore-throat structure makes movable fluid evaluation challenging,which is a critical factor restricting the efficient development of gas reservoirs.Current research primarily analyzes fluid occurrence characteristics from the perspectives of pore-throat structure parameters and clay mineral types,yet the mechanisms by which clay minerals influence pore-throat structure and subsequently control fluid mobility under different lithological settings remain unclear.This study focuses on the tight sandstones of the He 1 Member in the Xinzhao area,Ordos Basin.Integrating thin section identification,scanning electron microscopy,X-ray diffraction,high-pressure mercury injection,and variable-speed nuclear magnetic resonance(NMR)techniques,this work classifies rock types and employs segmented fractal theory based on T2 cutoff values to elucidate the control mechanism of mineral fabric on pore-throat structure and fluid mobility under lithological constraints.The results show that the tight sandstones in the study area can be divided into four lithologies:Type Ⅰ(gravel-bearing coarse-grained lithic quartz sandstone)is dominated by intergranular/intragranular dissolution pores and kaolinite intercrystalline pores;Type Ⅱ(medium-to coarse-grained lithic quartz sandstone)is characterized by intragranular dissolution pores and clay mineral intercrystalline pores;Type Ⅲ(gravel-bearing coarse-grained lithic sandstone)mainly develops intergranular matrix dissolution pores and intragranular dissolution pores;and Type Ⅳ(coarse-to medium-grained lithic sandstone)primarily develops intragranular dissolution pores and illite intercrystalline pores.Segmented fractal analysis reveals that the pore-throat space can be divided into large and small pore systems.The fractal dimension of the large-pore system shows a significant negative correlation with movable fluid saturation,indicating that the structural complexity and connectivity of the large-pore system are key factors controlling fluid mobility.The occurrence of movable fluid is jointly controlled by mineral composition and diagenesis.Type Ⅰ and Ⅱ are characterized by high quartz content,where a rigid framework resists compaction,and dissolution pores,kaolinite intercrystalline pores,and micro-fractures constitute a well-connected large-pore system with a low fractal dimension,resulting in high movable fluid saturation(>50%).In contrast,Type Ⅲ and Ⅳare characterized by illite and chlorite occurring in filamentous,bridging,or flaky forms,which fill the pores,leading to complex pore-throat structures,a high fractal dimension,and low movable fluid saturation(<40%).This study reveals the control mechanism of mineral fabric on pore-throat structure and movable fluid under different lithological settings,providing a theoretical basis for the efficient exploration and development of tight sandstone gas reservoirs.关键词
鄂尔多斯盆地/致密砂岩/可动流体/孔喉结构/分形维数/黏土矿物/脆性矿物Key words
Ordos Basin/tight sandstone/movable fluid/pore-throat structure/fractal dimension/clay mineral/brittle mineral分类
天文与地球科学引用本文复制引用
荆斌昊,刘岩,曹茜,周家林,王力,陈婷,刘家威..鄂尔多斯盆地盒1段致密砂岩孔喉类型分形特征与可动流体赋存机理[J].岩矿测试,2026,45(5):1124-1144,21.基金项目
中石化华北油气分公司"揭榜挂帅"科研项目(34550000-23-ZC0611-0040) （34550000-23-ZC0611-0040）
