湘东南拗陷龙潭组泥页岩储层特征

Characteristics of mud shale reservoirs in Upper Permian Longtan Formation of Southeast Hunan depression,China

探讨湘东南拗陷上二叠统龙潭组泥页岩的页岩气储层特征,借鉴北美页岩气储层研究方法和评价标准并与美国福特沃斯盆地的Barnett页岩进行比对研究。通过实测剖面和系统采样,采用X射线衍射技术、扫描电镜技术与能谱技术相结合的方法,分析龙潭组泥页岩有机碳含量、矿物组成、微孔隙、裂缝类型及发育程度等特征。结果表明,龙潭组储层的有机碳质量分数平均为3.54%;岩石矿物成分中石英的平均质量分数为27%,碳酸盐矿物的平均质量分数为38%,黏土矿物的平均质量分数为35%,同时含有一定量的黄铁矿;其微孔隙发育有晶间孔、晶内孔、粒间孔、溶蚀孔、粒缘孔、印模孔、有机质孔等;实测孔隙度分布在0.7%～16.7%之间;不同尺度的裂缝广泛发育。通过与美国福特沃斯盆地的Barnett页岩对比,认为该地区泥页岩具有良好的页岩气储层特征;同时对该储层孔隙度及其影响因素进行探讨发现,较高的石英含量对其孔隙度发育具有建设性意义。

This paper discusses the characteristics of the mud shale reservoirs in the Upper Permian Longtan Formation in the Southeast Hunan depression. By using the research methods and results of the North American shale gas reservoir, it compares the shale gas reservoir characteristics with that of the Barnett shale in Fort Worth Basin. By measuring section and systematic sampling and using the methods of X-ray diffraction, combined with scanning electron microscopy, this paper analyses the characteristics of the TOC content, mineral composition, types and features of pores and fractures and the fracture depth of the Longtan Formation mud shale. The results show that the average mass fraction of TOC in the mud shale reservoirs of Longtan Formation is 35~. The average mass fraction of TOC of clay minerals, quartz and carbonate minerals is 35~//0, 27~ and 38%, respectively. In addition, a certain amount of pyrite is also contained. The types of pores in this shale reservoir include intergranular pore, intracrystalline pore, inter-grain pore, dissolved pore, grain of flange pore and organic pore. The measured porosity of the research area is distributed in 0. 7% - 16. 7% and the fractures with various sizes are widely developed. The results of the research are analysed and compared with the Barnett shale in Fort Worth Basin, showing that the mud shale in study area has good characteristics of shale gas reservoirs. The studies of porosity and its influencing factors also show that the high quartz content is of constructive significance to the development of porosity.