牛蹄塘组与龙马溪组页岩细观结构特征研究

Study on microstructure characteristics of the Niutitang formation shale and the Longmaxi formation shale

我国页岩气储量居世界首位,随着能源的日益紧缺,页岩气开采日渐迫切。页岩内部的孔隙、裂隙结构不仅是页岩气的储存空间,更是影响页岩气产出的关键因素。针对湖南牛蹄塘组和四川龙马溪组页岩样品进行了细观观察,分析了两组页岩的层理、裂隙及孔隙特征,统计了两组页岩的孔隙尺寸及分布特征。实验结果表明:牛蹄塘组页岩层理特征更为明显,沿层理发育有少量大孔;龙马溪组页岩层理特征不明显,层理多发育小孔;牛蹄塘组页岩主要发育黏土矿物粒间孔和不同矿物粒间孔,龙马溪组页岩中主要发育不同矿物粒间孔;两组页岩内主导孔隙均为小孔孔隙,与龙马溪组页岩相比,牛蹄塘组页岩直径小于16μm与直径大于100μm的孔隙出现的频率较高,而直径16~100μm之间的孔隙出现频率较低。

The reserves of Chinese shale gas rank the first in the world.With the increasing shortage of energy,shale gas development is getting particularly urgent.The pores and fractures in shale are not only the storage space of shale gas,but also key factors affecting the extraction of shale gas.Shale samples of the Niutitang formation and the Longmaxi formation collected from Hunan province and Sichuan province were observed through optical microscope.The characteristics of beddings,fractures and pores in the shale samples were analyzed,and the size and distribution features of pores in the samples were recorded.According to the experimental results,beddings of the Niutitang formation shale are more obvious than the Longmaxi formation shale.A few macropores along the beddings of the Niutitang formation shale were observed,while some micropores can be found along the beddings of the Longmaxi formation shale.Intergranular pores of clay minerals and the intergranular pores are the dominant pores in the Niutitang formation shale,while intergranular pores of different minerals are prevailing in the Longmaxi formation shale.Micropores dominate in samples of both formations.The frequency of pores with diameter less than16μm and more than 100μm in the Niutitang formation shale is higher than that in the Longmaxi formation shale.The frequency of pores with diameter between 16μm and 100μm in the Niutitang formation shale is lower than that in the Longmaxi formation shale.