Geological controls on the methane storage capacity in organic-rich shales
Geological controls on the methane storage capacity in organic-rich shales
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DOI：
10.1016/j.coal.2013.06.010
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发表时间：
2014-03-01
影响因子：
5.6
通讯作者：
Littke, Ralf
中科院分区：
文献类型：
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作者：
Gasparik, Matus;Bertier, Pieter;Littke, Ralf
高压甲烷吸附等温线测定选定的古生代和中生代富含有机质的页岩，被认为是页岩气的目标在欧洲。样品包括上寒武纪-下奥陶统明矾页岩、石炭纪（密西西比-宾夕法尼亚）页岩和下托阿西亚Posidonia页岩。此外，还对来自美国（巴内特、海恩斯维尔和鹰福特）生产页岩气地层的样品进行了研究，以进行比较。过量吸附测量进行了在一个扩展的范围内的压力（高达25 MPa）和温度（高达150摄氏度）的干燥样品和在38摄氏度的水分平衡的样品，以研究有机质含量（TOC），成熟度，矿物学和水分含量对甲烷吸附能力的影响。此外，在24 ° C和8至97%的相对湿度（RH）下测量水等温线。基于绝对吸附的Langmuir方程的3参数（n（L），p（L），rho（a））过量吸附函数用于拟合测量的甲烷吸附等温线。通过Guggenheim-Anderson-de Boer（GAB）函数对水吸附等温线进行参数化。在这两种情况下，很好的拟合的测量数据实现。甲烷的吸附能力的干页岩表现出正相关性与TOC，但存在显着偏离这一趋势的个别样品。TOC标准化的吸附能力与成熟度的镜质组反射率（VRr），以一定的值VRr（类似于2.5%）以上，观察到相反的趋势呈正相关。粘土含量和TOC归一化的甲烷吸附能力之间没有相关性，表明粘土矿物对这些富含有机物的页岩中的甲烷吸附没有显着的贡献。过剩等温线的形状随温度和成熟度而系统地变化。朗缪尔压力（p（L））随温度呈指数增长，并遵循负幂律的趋势与成熟度。与干燥样品相比，水分平衡样品（97%RH）的吸附能力降低了40%至60%。在97%和75%RH之间未观察到差异，表明临界含水量等于或低于75%RH。从GAB拟合得到的水的单层吸附容量是从Langmuir拟合得到的甲烷的单层吸附容量的0.5至3倍。甲烷和水的吸附能力之间存在弱的正相关性，这表明甲烷和水分子共享一些吸附位点，并且这些部分驻留在有机质中。(C)2013爱思唯尔有限公司版权所有。
High-pressure methane sorption isotherms were measured on selected Paleozoic and Mesozoic organic-rich shales, considered as shale gas targets in Europe. The samples include the Upper Cambrian-Lower Ordovician Alum Shale, Carboniferous (Mississippian-Pennsylvanian) shales and Lower Toarcian Posidonia Shale. In addition, samples from producing shale gas formations in the USA (Barnett, Haynesville and Eagle Ford) were studied for comparison. Excess sorption measurements were performed over an extended range of pressures (up to 25 MPa) and temperatures (up to 150 degrees C) on dry samples and at 38 degrees C on moisture-equilibrated samples to study the effect of organic matter content (TOC), maturity, mineralogy and moisture content on the methane sorption capacity. Additionally, water isotherms were measured at 24 degrees C and at relative humidities (RH) from 8 to 97%. A 3-parameter (n(L), p(L), rho(a)) excess sorption function based on the Langmuir equation for absolute sorption was used to fit the measured methane sorption isotherms. The water sorption isotherms were parameterized by the Guggenheim-Anderson-de Boer (GAB) function. In both cases, excellent fits to the measured data were achieved.The methane sorption capacities of the dry shales show a positive correlation with TOC but significant deviations from this trend exist for individual samples. The TOC-normalized sorption capacities correlate positively with maturity in terms of Vitrinite Reflectance (VRr) up to a certain value of VRr (similar to 2.5%) above which an opposite trend is observed. No correlation was observed between the clay content and the TOC-normalized sorption capacity to methane, indicating that clay minerals do not significantly contribute to methane sorption in these organic-rich shales. The shape of the excess isotherms changes systematically with temperature and maturity. The Langmuir pressure (p(L)) increases exponentially with temperature and follows a negative power-law trend with maturity. Compared to dry samples, the sorption capacity in moisture-equilibrated samples (at 97% RH) is reduced by 40 to 60%. No difference is observed between 97% and 75% RH, indicating that the critical moisture content is at or below 75% RH. The monolayer sorption capacities for water obtained from the GAB fit are 0.5 to 3 times those for methane, derived from the Langmuir fit. There is a weak positive correlation between the methane and the water sorption capacity, suggesting that methane and water molecules share some of the sorption sites and these reside partly within the organic matter. (C) 2013 Elsevier B.V. All rights reserved.