鸡西盆地煤储层孔隙特征及主控因素

Pore characteristics and controlling factors of coal reservoirs from Jixi Basin

孔隙结构是煤层气等非常规储层研究的核心问题,既控制气藏储集性能,又影响开发评价效果。以鸡西盆地煤岩为研究对象,运用低温氮吸附方法、氩离子抛光电子扫描显微成像和核磁共振技术,对孔隙和裂隙结构进行定量表征。结合能谱分析、全岩分析测试、煤岩组分等实验数据,对有机质孔隙和矿物质孔隙发育的主控因素进行探讨。研究结果表明:有机质孔以气孔为主体,瓶型孔占主导地位,可见两端开口的圆筒孔、四边都开口的平行板状孔。T2图谱既有双峰又有三峰,显示出较好的孔渗条件。成熟度和镜质组含量促进有机质孔的发育,而水分堵塞孔隙表面及喉道。矿物质孔主要包括黏土矿物晶间孔和溶蚀孔。高岭石、伊利石单体或集合体杂乱堆积,形成大量孔隙。黏土矿物面孔率随高岭石含量增加而增加,随伊蒙混层含量升高而减小。

Pore structure is a core issue of coalbed methane of untraditional reservoirs,which can control preservation properties and development results.The pores and fractures of coalbeds from the Jixi Basin were quantitatively charac-terized by means of low temperature nitrogen adsorption,argon ion milling scanning electron microscopy and nuclear magnetic resonance.The controlling factors of organic pores and mineral pores were discussed based on spectral analysis,mineral composition and coal component analyses.The results showed that the organic pores were mainly gas pores,usually bottle shaped,and some cylinder pores open at both ends and parallel plate pores open on four sides were also observed.The NMR T2 spectrum has two or three peaks,indicating favorable porosity and permeability.High Ro and vitrinite content enhanced organic pore development,while water blocked pore surfaces and throats.Mineral pores mainly include intergranular pores of clay minerals and dissolution pores.The pores of monomer or aggregates of kaolinite,illite,and illite/smectite provided a large amount of adsorption space.The content of kaolinite has a positive correlation with the porosity of clay minerals,and the content of illite/smectite was negative.