中扬子地区龙马溪组页岩有机质孔隙发育特征及控制因素——以湖南省永顺地区永页3井为例

以焦石坝气田为代表的上扬子地区龙马溪组页岩气勘探和开发已经取得了巨大成功，但是中扬子地区龙马溪组中的页岩气勘探潜力尚不明确。文章通过对湖南省永顺地区永页3井页岩有机质孔隙发育特征和主控因素进行分析，以此为中扬子地区龙马溪组页岩储集性能评价提供参考。永页3井龙马溪组页岩发育典型海相有机质，TOC分布在0.65%~3.81%（平均为1.87%），具有高-过成熟阶段、孔隙度低（平均孔隙度为2.06%）的特征。通过氩离子抛光+扫描电镜技术对样品有机质孔隙进行了系统的观察，结合能谱测试结果和JMicroVision软件图像处理对有机质孔隙特征参数进行了统计与分析，提出了一种基于SEM图像的有机质孔隙连通性表征方法。结果表明，该井龙马溪组页岩中有机质主要为孔隙相对发育的迁移有机质和孔隙发育较差的原生有机质；有机质孔隙的发育存在非均质性，在成因上主要受控于有机质显微组分、有机碳含量以及粘土矿物含量等因素，较高热演化程度下适当的有机碳含量是有机质孔隙发育的关键因素。

Characteristics and controlling factors of organic-matter pores in Longmaxi Formation shale,Middle Yangtze Region: A case study of Well YY3

The exploration and development of shale gas in the Jiaoshiba gas field, a major Longmaxi Formation shale gas field in the Upper Yangtze Region, has made great success.However, the resource potential of the formation is still unclear.To this end, the characteristics and controlling factors of organic-matter pores in shale samples from the Well YY3 in the Yongshun area, Hunan Provinces, are analyzed to provide references for the assessment of shale reservoir properties in the formation.The Longmaxi Formation shale from the Well YY3 contains typical marine organic matter, and is characterized by a total organic matter content (TOC) of 0.65%-3.81% (1.87% on average), high-to-over-mature thermal maturity and low porosity (2.06% on average).The pores in the samples were systematically observed under scanning electron microscopy (SEM) after an Argon-ion-polishing treatment.Moreover, the characteristics of organic-matter pores were analyzed with energy spectrum test and JMicro Vision image processing software; and a new characterization method based on SEM images was proposed to describe the pore connectivity.The results show that the Longmaxi Formation shale contains mostly migrated organic matters with well-developed pore systems and native organic matters with under-developed pores.As a whole, the pore growth in organic matters of the shale in the formation is heterogeneous and mainly controlled by the micro-components of organic matters as well as the content of organic carbon and clay minerals, and at higher thermal evolution stages, organic carbon content plays a critical role in the development of pores in organic matters.