湘鄂西地区上震旦统陡山沱组页岩微观孔隙特征及主控因素

Characteristics of Microscopic Pores of Shale from Upper Sinian Doushantuo Formation in the Western of Hunan and Hubei,China and the Main Controlling Factors

随着中国页岩气研究的不断深入,页岩储层微观孔隙特征的研究越来越受到众多学者重视。为了深入了解湘鄂西地区上震旦统陡山沱组页岩孔隙特征,综合利用扫描电镜、氩离子抛光-场发射扫描电镜、氮气吸附/脱附试验以及核磁共振试验等对页岩孔隙特征进行定性观察和定量表征,并结合有机地球化学分析数据以及岩石矿物全岩定量分析结果,探讨页岩孔隙发育的主控因素。结果表明:湘鄂西地区上震旦统陡山沱组页岩发育6种孔隙类型,主要有粒内孔、粒间孔、黏土矿物层间孔、有机质孔隙,还可见部分黄铁矿晶间孔以及微裂缝;页岩孔径大小主要分布在2~5nm之间,以中孔隙为主,还发育少量微孔隙和大孔隙,峰值在2~5nm之间的孔隙是页岩孔隙体积的主要贡献者;页岩孔隙结构类型以板状孔等狭缝形孔为主,还发育部分圆筒形孔、锥形管孔等;总有机碳主要控制页岩微孔隙、中孔隙的发育,黏土矿物含量主要影响页岩中孔隙的发育,而脆性矿物含量控制页岩大孔隙的发育。

With the deeply research on shale gas in China,the study on the characteristics of microscopic pores of shale reservoir is focused on.In order to further understand the characteristics of shale pores from Upper Sinian Doushantuo Formation in the western of Hunan and Hubei,China,the scanning electron microscope（SEM）,argon ion polishing-field emission scanning electron microscope（FESEM）,nitrogen adsorption/desorption and nuclear magnetic resonance（NMR）tests were used to make qualitative observation and quantitative characterization of shale porosity under different scales;combined with the whole rock quantitative analysis data of organic geochemistry and rock minerals,the main controlling factors on shale porosity were discussed.The results show thatthere are 6types of pores from Doushantuo Formation in the western of Hunan and Hubei,including intergranular,intragranular,pyrite intercrystalline,interlayer,organic pores and micro cracks;the pore diameters of shales are 2-5nm,and the middle pore mainly develops,a small amount of micro and macro pores develop;the pores with the peak diameters of 2-5nm are the main contributor to shale pore volume;the types of shale pore structure are mainly narrow plate pore,and partly cylinder pore,conical pore,etc.;total organic carbon is the main contributor to the development of micro and middle pores,and the content of clay mineral mainly affects the development of middle pore,and the content of brittleness mineral mainly controls the development of macro pore.