页岩有机质特征对甲烷吸附的影响  

Effect of the organic matter characteristics on methane adsorption in shale

作　　者：闫建萍[1,2] 张同伟[1,2] 李艳芳[1,2] 吕海刚[1,2] 张小龙[1,2] 

机构地区：[1]兰州大学甘肃省西部矿产资源重点实验室,甘肃兰州730000 [2]兰州大学地质科学与矿产资源学院,甘肃兰州730000

出　　处：《煤炭学报》2013年第5期805-811,共7页Journal of China Coal Society

基　　金：国家重点基础研究发展计划(973)资助项目(2012CB214701);国家自然科学基金资助项目(41202095;41072092)

摘　　要：对四川盆地志留系龙马溪组页岩样品在压力15 MPa、温度分别为35,50和65℃条件下,进行一系列甲烷等温吸附线实验,结合美国相关盆地样品的吸附实验结果,探讨有机质特征对页岩气体吸附性的影响。结果表明:龙马溪组页岩在不同类型干酪根lnK-1/T图解中位于Ⅱ型干酪根趋势线附近,但每吨岩石Langmuir最大吸附量只占美国3种典型干酪根类型的Langmuir最大吸附量的30%左右。龙马溪组页岩的吸附热和标准吸附熵分别为19.8~25.4 kJ/mol和-94.0^-111.1 J/(mol.K),与Ⅱ型或Ⅲ型干酪根对甲烷的吸附很接近,远大于黏土矿物对甲烷的吸附,揭示了有机质是重要的吸附介质。值得注意的是龙马溪组页岩每吨有机质最大吸附量比美国3种典型干酪根类型的Langmuir最大吸附量明显要大,这可能与高热演化条件下泥岩的孔隙结构密切相关,这一点在后续研究中要予以重视。A series of methane adsorption isotherm experiments on bulk organic shale from the Longmaxi Formation in Sichuan Basin were conducted at 35,50 and 65 ℃ and the CH4 pressure up to 15 MPa under dry conditions.Comparing these experimental results to previously published methane adsorption data of different organic types and thermal maturity,the effect of the characteristics of organic matter on methane adsorption in shale were discussed.The results show that the Longmaxi shale follows Type II kerogen trend line in the ln K-1/T diagram of different kerogen type,and the Langmuir maximum sorption capacity per ton rock is obviously less than that of three types of kerogen which were isolated from the shales in USA.The thermodynamic parameters of adsorption on organic rich shale of Longmaxi Formation were determined based on the experimental CH4 isotherms.The heat of adsorption（q） and the standard entropy（Δs0） ranges from 19.8 to 25.4 kJ/mol and from-94.0 to-111.1 J/（mol·K）,respectively,which are close to the values of type II or III kerogen and greater than that of clay minerals.This indicates that the organic matter is the important adsorbent in shales.Note that the Langmuir maximum CH4 adsorption capacity per gram TOC of the Longmaxi shale is much greater than that of three types of kerogen in USA,which may indicate that this phenomenon is related to the pore structure micropore development in the shales of high thermal maturity,which needs to be investigated in future research.

关 键 词：页岩 有机质特征 甲烷 吸附气 成熟度 

分 类 号：P618.13[天文地球—矿床学]