Investigation of pore structure and fractal characteristics of organic-rich shale reservoirs: A case study of Lower Cambrian Qiongzhusi formation in Malong block of eastern Yunnan Province, South China
Investigation of pore structure and fractal characteristics of organic-rich shale reservoirs: A case study of Lower Cambrian Qiongzhusi formation in Malong block of eastern Yunnan Province, South China
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DOI：
10.1016/j.marpetgeo.2015.11.004
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发表时间：
2016-02-01
影响因子：
4.2
通讯作者：
Xie, Fei
中科院分区：
文献类型：
--
作者：
Li, Ang;Ding, Wenlong;Xie, Fei
为研究富有机质海相页岩孔隙结构和分形特征，采用有机地球化学分析（总有机碳含量分析、热成熟度分析）、x射线衍射（XRD）分析、孔隙度和渗透率测试、场发射扫描电镜（FE-SEM）等方法，对滇东马龙区块下寒武统筇竹寺组14份页岩样品进行了研究。低压氮气吸附和甲烷吸附实验。采用分形Frenkel-Halsey-Hill （FHH）方法对氮气吸附数据进行了分形维数D-1和D-2（相对压力为0-0.5和0.5-1）的分析。讨论了页岩孔隙结构参数之间的关系、TOC含量、矿物组成、孔隙结构参数与分形维数之间的关系，探讨了D-1和D-2两个分形维数的意义以及分形维数对吸附量的影响。结果表明：14个页岩样品TOC含量在1.25% ~ 7.72%之间，两个分形维数均随TOC含量的增加而增加，并逐渐趋于停滞，曲线呈“抛物线”形；页岩主要矿物组成为石英和粘土矿物，石英含量在25.5% ~ 42.7%之间，粘土含量在26.6% ~ 44.2%之间。分形维数D-1与石英含量呈负相关，与粘土矿物含量呈正相关，而D2与石英和粘土矿物含量无明显关系。比表面积为4.98 m(2)/g ~ 19.66 m(2)/g，总孔容为0.00479 cm(3)/g ~ 0.01765 cm(3)/g，平均孔径为337 nm ~ 6.02 nm。两个分形维数随比表面积和孔隙体积的增大而增大，随平均孔径的减小而增大。复杂的孔隙表面和小孔隙结构。进一步研究发现，D-1表征孔隙表面不规则的分形特征，D-2表征孔隙结构复杂的分形特征，分形维数越大的页岩样品甲烷吸附能力越强。因此，分形分析有助于更好地了解海相页岩的孔隙结构和吸附能力。(C) 2015 Elsevier Ltd.版权所有。
In order to study pore structure and fractal characteristics of the organic-rich marine shale, fourteen shale samples from Lower Cambrian Qjongzhusi formation in Malong block of eastern Yunnan province were investigated by organic geochemical analysis (total organic carbon content analysis and thermal maturity analysis), X-ray diffraction (XRD) analysis, porosity and permeability tests, field emission scanning electron microscopy (FE-SEM), low-pressure nitrogen adsorption and methane adsorption experiments. Fractal dimensions D-1 and D-2 (at relative pressure of 0-0.5 and 0.5-1, respectively) were obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) method. Not only have the relationships among pore structure parameters of shale, the relationships between TOC content, mineral compositions, pore structure parameters and fractal dimensions been discussed, but also the significance of two fractal dimensions D-1 and D-2 and the impact of fractal dimensions on adsorption capacity have been investigated. The results showed that fourteen shale samples have TOC content ranging from 1.25% to 7.72%, two fractal dimensions both increase with the increasing TOC content, and gradually come to a standstill the curves present the shape of "parabola". The major mineralogical compositions of shales are quartz and clay minerals, the quartz contents are between 25.5% and 42.7%, the clay contents are between 26.6% and 44.2%. Fractal dimension D-1 has a negative correlation with quartz contents and a positive correlation with clay minerals contents, but fractal dimension D2 has no apparent relationship with quartz and clay minerals contents. The specific surface area is in the range of 4.98 m(2)/g-19.66 m(2)/g, the total pore volume is between 0.00479 cm(3)/g and 0.01765 cm(3)/g, and the average pore diameter is between 337 nm and 6.02 nm. Two fractal dimensions increase with the increasing surface area and pore volume, and also increase with the decreasing average pore diameter because of. the complicated pore surface and structure of small pores. Further investigation indicates that D-1 represents fractal characteristics from the irregular pore surface, while D-2 represents fractal characteristics related to the complicated pore structure, and shale samples with larger fractal dimensions have higher methane adsorption capacity. Therefore fractal analysis is helpful to have a better understanding of pore structure and adsorption capacity of marine shale. (C) 2015 Elsevier Ltd. All rights reserved.