Effect of organic-matter type and thermal maturity on methane adsorption in shale-gas systems
Effect of organic-matter type and thermal maturity on methane adsorption in shale-gas systems
复制标题
页岩气系统中有机质类型和热成熟度对甲烷吸附的影响
DOI：
10.1016/j.orggeochem.2012.03.012
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发表时间：
2012-06-01
影响因子：
3
通讯作者：
Yang, Rongsheng
中科院分区：
文献类型：
--
作者：
Zhang, Tongwei;Ellis, Geoffrey S.;Yang, Rongsheng
在35℃、50℃和65℃、甲烷压力高达15 Mpa的干燥条件下，进行了大量富含有机页岩及其分离干酪根对甲烷(CH4)的吸附实验。对始新世绿河组、泥盆纪-密西西比期伍德福德页岩和上白垩统卡梅奥煤的样品进行了研究，以考察有机质类型的差异如何影响天然气的吸附。这些样品的镜质组反射率值在0.56-0.58%Ro之间。此外，对3个镜质组反射率分别为0.58、0.81和2.01%R-o的密西西比Barnett页岩样品进行了热成熟度效应的测定。对于所有散装和孤立的干酪根样品，吸附的甲烷总量与样品的总有机碳(TOC)含量成正比，平均最大吸气量为1.36 mmol/g TOC。这些结果表明，有机质吸附在页岩气储存中起着至关重要的作用。在实验条件下，热成熟度的不同对气体吸附总量没有显著影响。通过调节朗缪尔压力(P-L)和最大吸附容量(Gamma(Max))，可以较好地用朗缪尔函数对实验吸附等温线进行拟合。最低成熟度样品(%R-o=0.56)的朗缪尔压力(P-L)为5.15 MPa，显著大于50℃时最高成熟度样品(%R-o>；2.01)的2.33 MPa。朗缪尔压力(P-L)值随干酪根类型的变化顺序为：I>；II>；III。甲烷在富有机页岩及其孤立干酪根上的吸附，其吸附热Q和标准熵(S增量0)分别为7.3~28.0kJ/mol和-36.2~-92.2J/mol/K。(C)2012爱思唯尔有限公司。保留所有权利。
A series of methane (CH4) adsorption experiments on bulk organic rich shales and their isolated kerogens were conducted at 35 degrees C, 50 degrees C and 65 degrees C and CH4 pressure of up to 15 MPa under dry conditions. Samples from the Eocene Green River Formation, Devonian-Mississippian Woodford Shale and Upper Cretaceous Cameo coal were studied to examine how differences in organic matter type affect natural gas adsorption. Vitrinite reflectance values of these samples ranged from 0.56-0.58 %R-o. In addition, thermal maturity effects were determined on three Mississippian Barnett Shale samples with measured vitrinite reflectance values of 0.58, 0.81 and 2.01 %R-o.For all bulk and isolated kerogen samples, the total amount of methane adsorbed was directly proportional to the total organic carbon (TOC) content of the sample and the average maximum amount of gas sorption was 1.36 mmol of methane per gram of TOC. These results indicate that sorption on organic matter plays a critical role in shale-gas storage. Under the experimental conditions, differences in thermal maturity showed no significant effect on the total amount of gas sorbed. Experimental sorption isotherms could be fitted with good accuracy by the Langmuir function by adjusting the Langmuir pressure (P-L) and maximum sorption capacity (Gamma(max)). The lowest maturity sample (%R-o = 0.56) displayed a Langmuir pressure (P-L) of 5.15 MPa, significantly larger than the 2.33 MPa observed for the highest maturity (%R-o > 2.01) sample at 50 degrees C.The value of the Langmuir pressure (P-L) changes with kerogen type in the following sequence: type I > type II > type III. The thermodynamic parameters of CH4 adsorption on organic rich shales were determined based on the experimental CH4 isotherms. For the adsorption of CH4 on organic rich shales and their isolated kerogen, the heat of adsorption (q) and the standard entropy (Delta s(0)) range from 7.3-28.0 kJ/mol and from -36.2 to -92.2 J/mol/K, respectively. (C) 2012 Elsevier Ltd. All rights reserved.