The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China
The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China作者机构：School of Geoscience and Surveying Engineering China University of Mining and Technology Beijing 100083 China No. 105 Exploration Team Qinghai Bureau of Coal Geological Exploration Xining810067 China
出 版 物：《Frontiers of Earth Science》 (地球科学前沿（英文版）)
年 卷 期：2018年第12卷第1期
页 面：148-159页
核心收录：
学科分类：081702[工学-化学工艺] 070801[理学-固体地球物理学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 0708[理学-地球物理学] 0704[理学-天文学]
基 金：supported by the National Science and Technology Major Project the China Geological Survey Scientific Research Project
主 题：shale gas pore structure fractal dimension,Yuqia Coalfield Jurassic northern Qaidam Basin
摘 要：The continental shales from the Middle Jurassic Shimengou Formation of the northern Qaidam Basin, northwestern China, have been investigated in recent years because of their shale gas potential. In this study, a total of twenty-two shale samples were collected from the YQ-1 borehole in the Yuqia Coalfield, northern Qaidam Basin. The total organic carbon （TOC） contents, pore structure parameters, and fractal characteristics of the samples were investigated using TOC analysis, lowtemperature nitrogen adsorption experiments, and fractal analysis. The results show that the average pore size of the Shimengou shales varied from 8.149 nm to 20.635 nm with a mean value of 10.74 nm, which is considered mesopore-sized. The pores of the shales are mainly inkbottle- and slit-shaped. The sedimentary environment plays an essential role in controlling the TOC contents of the low maturity shales, with the TOC values of shales from deep to semi-deep lake facies （mean： 5.23%） being notably higher than those of the shore-shallow lake facies （mean： 0.65%）. The fractal dimensions range from 2.4639 to 2.6857 with a mean of 2.6122, higher than those of marine shales, which indicates that the pore surface was rougher and the pore structure more complex in these continental shales. The fraetal dimensions increase with increasing total pore volume and total specific surface area, and with decreasing average pore size. With increasing TOC contents in shales, the fractal dimensions increase first and then decrease, with the highest value occurring at 2% of TOC content, which is in accordance with the trends between the TOC and both total specific surface area and total pore volume. The pore structure complexity and pore surface roughness of these low-maturity shales would be controlled by the combined effects of both sedimentary environments and the TOC contents.
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