川东南石林地区五峰组—龙马溪组黑色页岩特征

Basic characteristic of shale of Wufeng-Longmaxi formation in Shilin,southeast of Sichuan basin

川东南石林地区五峰组—龙马溪组黑色页岩为四川盆地页岩气勘探重点地区重点层位,应用野外观察、镜下鉴定、化学测试等方法分析石林地区页岩特征.结果表明:川东南地区五峰组—龙马溪组主要为陆棚相黑色页岩、硅质泥页岩和粉砂质泥岩沉积,且黑色页岩段富含黄铁矿和笔石化石;以Ⅱ型干酪根为主,有机碳质量分数大于2.0%,有机质成熟度大于2.0%,具备大量生气条件;脆性矿物质量分数大于50%,有利于人工造缝;储集空间类型丰富,以纳米级孔隙及微裂缝为主,测试孔隙度为2.5%.与焦石坝地区对比,川东南地区五峰组—龙马溪组黑色页岩整体表现为有机质质量分数高、成熟度高、页岩脆性好和生气能力强的特点,较有利于页岩气的形成和富集,为勘探远景有利区.

Depending on the observation of outfield section,microscopic section,chemical analysis on the sample from Shilin area,this paper explored the sedimentary characteristics of black shale at WufengLongmaxi formation in Shilin,southeast of Sichuan basin,which is the key stratum in Sichuan shale gas exploration.In conclusion,the sedimentary environment of Longmaxi formation is mainly shelf with black shale,siliceous shale,silty mudstone sediment.In this area,it is rich in graptolite and framboidal pyrite at the bottom.Shilin has high hydrocarbon potential with typeⅡ kerogen mainly,organic matter content reach 2.0%,hermal maturity is about 2.0%.The brittle mineral content is greater than 50%,which is good for artificial joints.Nanoscale pores and micro-cracks are the main reservoir space of black shale of Wufeng-Longmaxi formation in Shilin area.There are different pore types:Intergranular pore,intragranular pore,fracture and organic pore,providing abundant surface area for shale gas,tests show porosity of 2.5%.When compared with Jiaoshiba area,it shows that southeast of Sichuan basin has organic-rich black shale with thick sediment,high organic matter content and maturity,good brittleness,high hydrocarbon potential,conducive to the development and enrichment of shale gas.