保靖地区高成熟度海相页岩微—纳米孔隙结构特征

页岩中微—纳米孔隙广泛发育，微—纳米孔隙结构对页岩含气性评价及页岩气开发具有重要意义。利用场发射扫描电镜（FE-SEM）观察、高压压汞、低压液氮吸附等方法对保靖地区龙马溪组高成熟度海相页岩的微—纳米孔隙结构特征开展了详细研究。结果表明，研究区龙马溪组海相页岩有机质丰度较高，BY-1井岩心样品实测TOC值范围是0.57%~2.16%，矿物组分中石英和黏土矿物含量最高，均值分别为46.9%和32.6%；页岩中黄铁矿发育；页岩的孔隙类型包括粒内孔、粒间孔、晶间孔、有机质孔和微裂缝5种，其中页岩气的储集空间主要由黏土矿物晶间孔、有机质孔和黏土矿物收缩缝提供。BY-1井龙马溪组页岩中微孔和中孔孔容分别占总孔容的14.5%~38.1%和49.4%~61.9%，是研究区目的层的主要储集空间，而页岩中宏孔孔容较小，相对不发育。

Micro-nano scale pore structure of the high maturity marine shale in the Baojing area

The micro-and nano-scale pores are well developed in marine shales and are of great significance for shale gas resources evaluation and development. In order to better understand the micro- and nano-scale pore structure in marine shales in the Silurian Longmaxi formation in the Baojing area，a integrated methods including high resolution field emission-scanning electron microscope（FE-SEM），high pressure mercury intrusion and low pressure nitrogen adsorption were conducted.The results show that，the high maturity marine shales in the Longmaxi formation from Well BY-1 in the Baojing area are organic rich. The scope of TOC for the samples is 0.57%~2.16%. For mineral composition，quartz and clay were the majority with the average value of 46.9% and 32.6%. Also，pyrite is commonly observed in the samples. Five types of pores can be determined，including the intergranular pores，the intragranular pores，the intercrystalline pores，the organic pores and finally the micro-fractures pores. The volume of microporous and mesoporous accounts for 14.5% to 38.1% and 49.4% to 61.9% of total pore volume in the shale samples from Well BY-1 respectively. The micropores and the mesopores are the most important space for shale gas accumulation. The volume of the macropores is relatively small，indicating poor developed macropores in the shales.