石油与天然气地质2025，Vol.46Issue(6)：1840-1859,20.DOI:10.11743/ogg20250607
古老地层页岩气富集特征与勘探方向
Enrichment characteristics and exploration targets of shale gas in ancient strata:Insights from the Cambrian shales in the Middle-Upper Yangtze region
摘要
Abstract
Breakthroughs in the exploration of the Cambrian shale gas within the Sichuan Basin have contributed to the discovery of the most ancient shale gas reservoirs globally.To reveal the mechanisms governing the shale gas enrichment in ancient strata,we investigate the Cambrian shales in the Middle-Upper Yangtze region in this study.In combination with exploration and exploitation data,we systematically analyze the lithofacies,reservoir properties,geochemical characteristics,and gas play types of the shales,with particular emphasis placed on shale gas preservation conditions.The results indicate that the Lower Cambrian strata in the study area contain two types of shales,i.e.,organic-rich and organic-lean shales,with total organic carbon(TOC)contents of greater than 3%and less than 1%,respectively.These shales contain organic matter with favorable kerogen types(dominated by types Ⅰ-Ⅱ1)and exhibit high thermal maturity,as indicated by an equivalent vitrinite reflectance(EqVRo)greater than 3.0%.Two types of shale gas plays are identified:self-sourced and migrated gas plays.The formation of the ancient shale gas plays is jointly controlled by the presence of high-quality reservoirs and the thermal maturity of organic matter,while the development of high-quality reservoirs is governed by the synergistic effects of diagenesis and hydrocarbon generation-induced pore formation.Preservation conditions play a key role in controlling the shale gas enrichment in ancient strata.The Deyang-Anyue rift trough demonstrates a high degree of shale gas enrichment attributable to its tectonic stability and resulting overpressure conditions with formation pressure coefficients ranging from 1.6 to 2.0.It is recommended that future shale gas exploration should focus on areas with both relatively low thermal maturity(EqVRo<3.5%)and favorable preservation conditions.The resource potential evaluation of the ancient Cambrian shale gas should focus on several key scientific issues,including the preservation condition limits for ultra-deep shale gas,formation mechanisms of high-quality reservoirs,and the quantitative assessment of hydrocarbon generation,expulsion,and retention in highly-to over-mature shales.关键词
优质储层/保存条件/资源潜力评价/古老页岩气藏/高-过成熟页岩/寒武系/四川盆地Key words
high-quality reservoir/preservation condition/resource potential evaluation/ancient shale gas reservoir/highly-to over-mature shale/Cambrian/Sichuan Basin分类
能源科技引用本文复制引用
聂海宽,苏海琨,张珂,林拓,刘忠宝,李沛,戎佳,王宇哲..古老地层页岩气富集特征与勘探方向[J].石油与天然气地质,2025,46(6):1840-1859,20.基金项目
国家自然科学重点基金项目(42130803) （42130803）
中国石油化工股份有限公司科技部项目(P23132,P25144). （P23132,P25144）
