四川盆地及周缘上奥陶统五峰组-下志留统龙马溪组页岩岩相划分

页岩岩相对页岩气勘探"甜点"的确定具有十分重要的意义,不同专家和学者提出了不同的页岩岩相划分方案,但目前还未形成明确统一的标准。在总结前人对四川盆地及周缘上奥陶统五峰组-下志留统龙马溪组页岩岩相划分的基础上,从页岩品质和可压性的角度,开展了页岩硅质成因分析和岩相划分特征参数的研究,明确了五峰组-龙马溪组页岩岩相综合划分方案:(1)分别以钙质含量大于50%、硅质含量大于75%、黏土含量大于50%为界,划分出泥灰岩、硅质岩和黏土岩3大类岩相和页岩混合岩相区;(2)将页岩混合岩相区以页岩气储量申报标准有机质含量1%、2%和4%为界,形成了低碳、中碳、高碳和富碳页岩4种页岩岩相;以页岩常见硅、钙矿物组分含量25%和50%为界,形成了低硅/中硅/高硅+低钙/中钙页岩等5种页岩岩相。该套以有机碳-矿物组分为基础、结合硅质成因分析的岩相综合划分方案,在科学研究和实际应用中适用性强、可推广,为五峰组-龙马溪组页岩纵横向优势岩相展布规律的研究奠定了基础。

Shale petrofacies division of Wufeng-Longmaxi formations in Sichuan Basin and its periphery

The research of shale petrofacies is significant for the exploration of shale gas "sweet spots". Different petrographic division schemes have been proposed but no consensus has been reached. This paper has studied the criteria and boundary values of the petrographic classification reference parameters of the Upper Ordovician Wufeng-Lower Silurian Longmaxi formations in the Sichuan Basin and its periphery by considering shale quality and compressibility. (1) There are three petrofacies:marlstone, silicolites and claystones with >50% of calcium content, >75% of siliceous content and >50% of clay content, respectively. (2) Four organic petrofacies have been classified as low-carbonaceous shale, medium-carbonaceous shale, high-carbonaceous shale and enriched carbonaceous shale with 1%, 2% and 4% of organic matter as boundaries, respectively. There are five inorganic petrofacies, such as low-siliceous shale, medium-siliceous shale, high-siliceous shale, low-calcareous shale and medium-calcareous shale with 25% and 50% of silicon or calcium mineral components as boundaries, respectively. This set of petrographic comprehensive division schemes based on organic carbon-mineral components and combined with siliceous genetic analysis has strong applicability and popularization in scientific research and practical applications, which is significant for the study of the lithofacies distribution law in the Wufeng-Longmaxi formations.