石油实验地质2025，Vol.47Issue(5)：988-1002,15.DOI:10.11781/sysydz2025050988
四川盆地德阳—安岳裂陷槽中段寒武系筇竹寺组页岩气差异富集过程
Differential enrichment process of shale gas in Cambrian Qiongzhusi Formation in middle section of Deyang-Anyue rift trough,Sichuan Basin:evidence from fracture veins and fluid inclusions
摘要
Abstract
In recent years,shale gas exploration in the Cambrian Qiongzhusi Formation within the Deyang-Anyue rift trough of the Sichuan Basin has achieved significant breakthroughs,establishing it as a crucial succession area for unconventional hydrocarbon exploration in the basin.Focusing on the Qiongzhusi Formation shale in the middle section of the rift trough,a series of analytical techniques were comprehensively employed,including core obser-vations,thin-section analysis,cathodoluminescence(CL)imaging,laser in-situ U-Pb isotope dating of carbonate rock,fluid inclusion petrography,laser Raman spectroscopy,homogenization temperature testing,and basin numerical simulations.This study systematically investigated the fracture development characteristics,mineral-filling sequence,and the types,components,and thermobaric parameters of fluid inclusions,revealing the differential shale gas enrichment mechanisms in the study area.The results showed that bedding-parallel frac-tures,low-to high-angle tensile fractures,and high-angle shear fractures were developed.Specifically,well Z201 in the central rift trough exhibited densely developed high-angle shear fractures,while well WY1H on the western slope of the rift margin showed relatively weak fracture development.In contrast,well W201 in the high structural position of the Weiyuan area is characterized by high-angle shear fractures accompanied by hydrother-mal mineral fillings.The fractures were predominantly filled with calcite,with local occurrence of quartz,barite,dolomite,and pyrite.Hydrocarbon inclusions in the vein minerals were diverse in type,with trapping tempera-tures decreasing in the order of methane＞high-saturation hydrocarbon＞bitumen.The trapping pressure for methane indicated that the Qiongzhusi Formation once widely experienced widespread overpressure to strong over-pressure conditions.Combined with burial and thermal evolution histories,the results suggested that hydrocarbon accumulation in the study area experienced three stages:a shale oil generation stage from the Late Permian to Early Triassic,a shale gas enrichment stage from the Middle Jurassic to Early Cretaceous,and a shale gas adjustment stage from the Late Cretaceous to the present.Late-stage tectonic adjustments showed clear spatial differences.The central rift trough experienced minimal adjustments,preserving intact strong overpressure and thus serving as the optimal exploration target.The western slope of the rift trough margin remained overpressured with good gas-bearing properties.In contrast,the high structural position on the western rift trough margin experienced intense uplift and denudation during the Himalayan period,which reduced the pressure coefficient to 1.0 and significantly decreasing its gas-bearing capacities.Therefore,careful evaluation of preservation conditions is critical for exploration.关键词
裂缝脉体/流体包裹体/页岩气/筇竹寺组/德阳—安岳裂陷槽/四川盆地Key words
fracture vein/fluid inclusion/shale gas/Qiongzhusi Formation/Deyang-Anyue rift trough/Sichuan Basin分类
能源科技引用本文复制引用
李彦佑,梁静怡,邓宾,吴娟,周志鹏,蒋前前,石学文,杨雨然,罗超,何一凡,王恒..四川盆地德阳—安岳裂陷槽中段寒武系筇竹寺组页岩气差异富集过程[J].石油实验地质,2025,47(5):988-1002,15.基金项目
四川省自然科学基金面上项目(2025ZNSFSC0310),国家自然科学基金面上项目(42372174)和中国石油天然气股份有限公司科技项目(2023ZZ21YJ04)联合资助. （2025ZNSFSC0310）
