高成熟富有机质页岩吸附特征及影响因素

Adsorption Characteristics and Its Controlling Factors of Organic-rich Shales with High Thermal Maturity

吸附气作为页岩气的一种重要的赋存状态,主要存在于黏土矿物及有机质颗粒的表面或孔隙内,泥页岩的吸附特征对含气量起到至关重要的作用。本次研究通过有机碳含量测试、热成熟度测试、X射线衍射、低温氮吸附及甲烷等温吸附等分析化验手段,对皖南地区下寒武统荷塘组页岩的有机地化特征、岩石学特征、孔隙结构及吸附特征进行了研究,并进一步探讨了吸附性能的控制因素及机理。结果发现:(1)研究区页岩处于过成熟阶段,R_O为2.83%~3.91%;有机质含量较高,TOC含量主要分布于1.97 wt%~7.32 wt%,平均为4.58 wt%。(2)孔隙类型以中孔占主导,宏孔和微孔含量较低。(3)样品的吸附能力差异较大,吸附量分布在0.47~8.63 m3/t,平均为5.21 m^3/t。(4)吸附能力受有机质含量、热演化程度、孔隙结构及黏土矿物含量等因素共同控制,吸附量随TOC含量、R_O及比表面积的增加而增大,随平均孔径及黏土矿物含量的增加而降低。

Adsorbed gas,as an significant existence phase for shale gas,is adsorbed principally on the surface of organic particles and clays or within their pores.Such adsorption behavior of shales and mudstones mainly controls the gas content for the particular shales or mudstones.The tests including organic content,thermal maturity,X-ray scattering,low temperature nitrogen adsorption and methane isothermal adsorption were conducted to investigate the characterization of the shales regarding organic geochemistry,petrology,pore structure and isothermal adsorption,a further research was performed to reveal the controlling factors as well as its mechanisms of adsorption characteristics for the samples.The results show these as follows.①All the samples have reached a over-mature state,R O ranges from 2.83%to 3.91%,TOC content varying from 1.97 wt%to 7.32 wt%,4.58 wt%at an average.②In terms of pore types,meso-pores take up the largest proportion,with micro-and macro-pores representing the minority.③The adsorption capacity varies significantly among the samples,varying from 0.47 m 3/t to 8.63 m 3/t,5.21 m 3/t.④At an average,which is dominated by various factors,such as TOC content,R O,pore structure and clay content and shows a positive correlation with TOC content,R O,and specific surface area,but have a negative correlation with average pore diameter and clay content.