摘要
中国南方地区寒武系筇竹寺组和奥陶系五峰组-志留系龙马溪组均发育一套富有机质页岩，但页岩气钻探效果差别极大，开展成藏差异比较研究具有理论和现实意义。研究认为：①四川盆地五峰组-龙马溪组TOC值比筇竹寺组略高，盆地外围地区筇竹寺组TOC存在高值区；②筇竹寺组热演化程度较五峰组-龙马溪组明显偏高；⑧筇竹寺组有机质孔隙不发育，孔隙度是五峰组-龙马溪组的1／3～1／2；④筇竹寺组含气量低，仅为五峰组-龙马溪组的1／2；⑤筇竹寺组以硅质页岩为主，五峰组-龙马溪组以钙质、钙质硅质页岩为主，硅质成因不同；⑥五峰组-龙马溪组普遍超压，筇竹寺组以常压为主。这种差异形成的原因在于：①沉积环境不同，影响TOC值和页岩厚度；②筇竹寺组热演化程度过高，导致生烃衰竭、有机质炭化、孔隙度降低，含气性变差；③筇竹寺组顶底板封闭条件较差，影响页岩气保存；④构造位置不同，五峰组-龙马溪组处于斜坡和向斜区，具超压，有利于页岩气保存；⑤筇竹寺组放射性铀含量约为五峰组-龙马溪组的2倍，是热演化程度高的重要原因。从而提出南方海相经济性页岩气富集需具备有利的地质条件（富有机质集中段发育，热演化程度适中，有机质孔隙发育，含气量高，顶底板保存条件良好，埋深适中），其中五峰组-龙马溪组页岩气成藏条件有利、资源经济性好，筇竹寺组成藏条件总体较差、有利区范围有限。
Organic-rich marine shales are developed in both the Cambrian Qiongzhusi Formation and the Ordovician Wufeng Formation-Silurian Longmaxi Formation in South China, but are different in the drilling results of shale gas exploration. Comparing the differences in shale gas formation conditions between Qiongzhusi and Wufeng-Longmaxi has practical and theoretical significance. This study reveals： （1） in the Sichuan Basin, the Wufeng-Longmaxi Formation has slightly higher TOC than the Qiongzhusi Formation, whereas Qiongzhusi Formation has some local high TOC areas outside of the Sichuan Basin; （2） the Qiongzhusi Formation has much higher thermal evolution degree than the Wufeng-Longmaxi Formation; （3） with undeveloped organic pores, the Qiongzhusi Formation has a 1/3 to 1/2 porosity of the Wufeng-Longmaxi Formation; （4） Qiongzhusi shale has a lower gas content, only 1/2 of that in Wufeng- Longmaxi shale; （5） the Qiongzhusi Formation is mainly composed of siliceous shale and the silica is hot water origin, whereas the Wufeng-Longrnaxi Formation consists mainly of calcareous siliceous shale and the silica is biogenic origin; （6） the Wufeng-Longmaxi Formation has overpressure, while the Qiongzhusi Formation is normal in pressure. The reasons for the differences are： （1） different sedimentary environments affect TOC and shale thickness; （2） the Qiongzhusi Formation is over-mature, which caused depletion of hydrocarbon generation, organic carbonization, porosity reduction, and gas content drop; （3） the bad roof and floor conditions of the Qiongzhusi Formation are not good for shale gas preservation; （4） Wufeng-Longmaxi Formation is located in the slope and syncline accompanied with overpressure, and is in favor of preservation and high production of shale gas; （5） the uranium content in the Qiongzhusi Formation is twice that of the Wufeng-Longmaxi Formation, which is the main reason of its higher thermal evolution degree. It is concluded that shale gas enrichment in the marine shale in South China requires favorable geological conditions： organic-rich intervals, moderate thermal evolution, rich organic pores, high gas content, good roof and floor preservation conditions, and moderate burial depth. The Wufeng-Longmaxi Formation has better shale gas enrichment conditions and higher resource potential, whereas the Qiongzhusi Formation has poorer shale gas accumulation conditions and limited favorable areas.
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
2016年第4期499-510,共12页
Petroleum Exploration and Development
基金
国家科技重大专项(2011ZX05018G001)
国家重点基础研究发展计划(973)项目(2013CB228001)
中国石油科技重大专项"中国石油第四次油气资源评价"(2013E-0502)
关键词
中国南方
页岩气
寒武系筇竹寺组
奥陶系五峰组
志留系龙马溪组
页岩气富集
地质条件
South China
shale gas
Cambrian Qiongzhusi Formation
Ordovician Wufeng Formation
Silurian Longmaxi Formation
shale gas enrichment
geological condition
