摘要
煤孔隙结构特征对煤储层流体的赋存与运移起关键作用。为研究姚桥矿7号煤层的孔隙特征,采用刻槽取样法自下而上等距采样,选取不同深度的9个样品,通过低温液氮吸附和低场核磁共振等实验方法进行测试,结合分形理论,系统分析了7号煤层的孔隙结构特征,探讨了各孔隙参数和分形维数在垂向上的变化趋势。研究表明:样品低温液氮吸脱曲线可分为L1、L2和L3三种类型,低场核磁共振T_(2)谱均呈三峰分布;煤样孔隙微孔和过渡孔较为发育,微孔和过渡孔提供主要的比表面积、孔体积,BET比表面积为0.722~1.199 m^(2)/g,BJH比表面积为0.941~1.535 m^(2)/g,BJH总孔容为0.00297~0.00476 cm^(3)/g,比表面积与孔体积垂向上呈不规则“M”状分布,平均孔径为12.832~15.100nm,在垂向上呈倒“M”状分布;低温液氮吸附实验分形维数可分为表面分形维数和结构分形维数,表面分形维数D_(1)为2.306~2.374,结构分形维数D_(2)为2.592~2.624,低场核磁共振实验表明,煤样整体分形维数D_(NMR)为2.326~2.436,渗流孔分形维数D_(2)为2.790~2.966,裂隙分形维数D_(3)为2.966~2.993,呈现出D_(3)>D_(2)>D_(NMR)的趋势。对姚桥矿7号煤层孔隙特征的研究,为该煤层储层物性的研究提供了重要依据,也为该研究区其他煤层孔隙特征的研究提供了重要借鉴意义。
The pore structure characteristics of coal play a key role in the occurrence and transport of coal reservoir fluids.To study the pore characteristics of No.7 coal seam in Yaoqiao Coal Mine,9 samples at different depths were selected by bottom-up equidistant sampling method,and tested by experimental methods such as low-temperature liquid nitrogen adsorption and low-field nuclear magnetic resonance,combined with fractal theory,the pore structure characteristics of the coal seam were systematically analyzed,and the vertical change trend of each pore parameter and fractal dimension was discussed.The results show that the low-temperature liquid nitrogen uptake curves of samples can be divided into three types:L1,L2 and L3,and the low field nuclear magnetic resonance T_(2) spectrum of the samples was distributed in three peaks.The micropores and transition pores of coal samples,which provide the main specific surface area and pore volume,are relatively developed.The specific surface area of BET is 0.722~1.199 m^(2)/g,the specific surface area of BJH is 0.941~1.535 m^(2)/g,the total pore volume of BJH is 0.00297~0.00476 cm^(3)/g,and the specific surface area and pore volume were distributed vertically in an irregular"M"shape.The average pore size is 12.832~15.100 nm,and it is distributed in an inverted"M"shape in the vertical direction.The fractal dimension of low-temperature liquid nitrogen adsorption experiment can be divided into surface fractal dimension and structural fractal dimension,the surface fractal dimension D_(1) is 2.306~2.374,and the structural fractal dimension D2 is 2.592~2.624.Low-field NMR experiments showed that the overall fractal dimension D_(NMR) of coal samples is 2.326~2.436,the fractal dimension D_(2) of seepage pore was 2.790~2.966,and the fractal dimension of fracture D_(3) is 2.966~2.993,showing the trend of D_(3)>D_(2)>D_(NMR).The study of pore characteristics of No.7 coal seam in Yaoqiao Coal Mine provides an important basis for the study of reservoir physical properties of the coal seam,
作者
肖乾隆
李锦
李伍
XIAO Qialnong;LI Jin;LI Wu(Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process,China University of Mining and Technology,Xuzhou,Jiangsu 221116;School of Resources and Geoscience,China University of Mining and Technology,Xuzhou,Jiangsu 221116)
出处
《中国煤炭地质》
2023年第9期1-13,26,共14页
Coal Geology of China
基金
国家自然科学基金项目(41972169)。
关键词
孔隙特征
低温液氮吸附
低场核磁共振
分形维数
姚桥矿
pore characteristics
low-temperature liquid nitrogen adsorption
low field nuclear magnetic resonance
fractal characteristics
Yaoqiao Coal Mine
