四川盆地及其周缘五峰组—龙马溪组黑色页岩特征

Characteristics of black shale in Wufeng Formation and Longmaxi Formation in Sichuan Basin and its peripheral areas

从源岩到储层的思路,探讨了四川盆地及其周缘上奥陶统五峰组-下志留统龙马溪组沉积特征、储层特征及含气性特征。通过对野外露头样品进行地球化学分析、矿物学分析和等温吸附实验,表明五峰组-龙马溪组:①下段黑色页岩段沉积环境为深水陆棚;②岩性有硅质岩、黑色页岩、粉砂岩、生物灰岩及斑脱岩等5种;③下段黑色页岩段有效页岩厚度达到50m,TOC质量分数平均值为3.81%,成熟度平均值为1.62%,脆性矿物中石英的质量分数平均值为54.94%,从底到顶石英含量与TOC含量成正相关;④微孔可分为粒间孔、粒内孔、有机质孔及微裂缝4类,最具油气意义的是有机质孔和黏土片间孔;⑤吸附量Langmuir体积参数介于1.52～3.01cm3/g之间,均值为2.33cm3/g,黑色页岩中的有机质微孔是控制含气量的主要因素。

This paper focuses on the analysis of the deposition features,reservoir characteristics and gas-bearing characteristics of the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in Sichuan Basin and its peripheral areas.The results of geochemical analysis,mineralogical analysis and isothermal adsorption experiment show that these features of the Wufeng Formation-Longmaxi Formation are as follows.① The sedimentary environment of Lower Longmaxi Formation is deep-water shelf; ② there are five kinds of lithologies,that is,siliceous rock,black shale,siltstone,biological limestone and bentonite; ③ the black shale in Lower Wufeng FormationLongmaxi Formation is characterized by an effective thickness of ＞50 m,average mass fraction of organic carbon content （TOC） of 3.81％,average maturity of 1.62％ and an average mass fraction of 54.94％ for quartz mineral and there is a positive correlation between the content of TOC and the content of quartz mineral; ④ the micropores are divided into four categories including the intergranular pore,intragranular pore,organic matter pore and microfracture,and the organic matter pore and the hole between the clay tablets are favorable for the preservation of oil and gas; and ⑤ the Langmuir volume parameter is 1.52～3.01 cm3/g,with an average of 2.33 cm3/g,and organic matter pores in the black shale are the main controlling factors to control gas content.