天然气勘探与开发2026，Vol.49Issue(5)：60-75,16.DOI:10.12055/gaskk.issn.1673-3177.20260005
页岩气储层孔隙结构分形维数及其地质意义
Fractal dimensions of pore structure in shale gas reservoirs and their geological significance:a case study of Silurian Longmaxi Formation in Dazu block,western Chongqing area
摘要
Abstract
To understand the heterogeneity and key controlling factors of pore structures in deep marine shale gas reservoirs in the Dazu block of western Chongqing area,Sichuan Basin,this study investigates the shales in the first submember of the first member of the Lower Silurian Longmaxi Formation(S1l11).The pore structure characteristics,fractal dimension variation patterns and their geological significance of the S1l11 shale gas reservoirs were revealed,through experimental techniques including low-temperature N2 adsorption experiment,X-ray diffraction(XRD)analysis,total organic carbon(TOC)measurement,and field-emission scanning electron microscopy(FE-SEM),combined with the Frenkel-Halsey-Hill(FHH)fractal theory.The following results are obtained.(ⅰ)The reservoirs exhibit an average TOC of 3.0%,with mineral composition dominated by quartz(average content of 44.9%)and clay minerals(average content of 24.0%).(ⅱ)The reservoir space types are diverse,mainly including organic pore,intergranular pore,intragranular dissolution pore,and microfracture.N2 adsorption-desorption isotherms show typical Type Ⅱ characteristics,with hysteresis loops primarily of H3 and H4 types,indicating ink-bottle-shaped or wedge-shaped pore morphologies.(ⅲ)Quantitative data indicate that mesopores dominate the pore volume,contributing an average of 67.57%,whereas micropores dominate the specific surface area,contributing an average of 84.43%.(ⅳ)The fractal dimensions calculated from the FHH model show a two-segment pattern:D1(characterizing micropores)ranges from 2.192 4 to 2.525 7 with an average of 2.331 8,while D2(characterizing mesopores to macropores)ranges from 2.812 8 to 2.882 1 with an average of 2.842 3,indicating stronger heterogeneity in the mesopore to macropore range.In conclusion,TOC and quartz content are the key factors controlling the pore development.Specifically,TOC primarily governs micropore development and influences the D1 value,while quartz content promotes mesopore development by forming a rigid,compaction-resistant framework,and affects the D2 value.From northeast to southwest,TOC and quartz content increase progressively,corresponding to enhanced reservoir storage capacity,representing a favorable exploration target.Notably,the simultaneous increase in both D1 and D2 values indicates an overall trend of increasing heterogeneity.Therefore,the reservoir anisotropy should be considered in both"sweet spot"evaluation and fracturing operation,to achieve efficient production and sustained development of shale gas reservoirs.关键词
志留系下统龙马溪组/深层海相页岩气/孔隙结构/分形维数/非均质性/控制因素/四川盆地渝西地区大足区块Key words
Lower Silurian Longmaxi Formation/Deep marine shale gas/Pore structure/Fractal dimension/Heterogeneity/Controlling factor/Dazu block of western Chongqing area in the Sichuan Basin分类
能源科技引用本文复制引用
雷玉雪,文冉..页岩气储层孔隙结构分形维数及其地质意义[J].天然气勘探与开发,2026,49(5):60-75,16.基金项目
新型油气勘探开发国家科技重大专项"四川盆地全油气系统与新领域勘探技术"(编号:2025ZD1400400). （编号:2025ZD1400400）
