Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

Sijian Zheng, Yanbin Yao, Shasha Zhang, Yong Liu and Jinhui Yang
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Sijian Zheng: School of Energy Resource, China University of Geosciences, Beijing 100083, China
Yanbin Yao: School of Energy Resource, China University of Geosciences, Beijing 100083, China
Shasha Zhang: College of Chemistry, Nankai University, Tianjin 300071, China
Yong Liu: School of Energy Resource, China University of Geosciences, Beijing 100083, China
Jinhui Yang: Beijing Oil and Gas Pipeline Control Center, Beijing 100083, China

Energies, 2019, vol. 12, issue 24, 1-18

Abstract: Mercury intrusion porosimetry (MIP) as a practical and effective measurement has been widely used in characterizing the pore size distribution (PSD) for unconventional reservoirs (e.g., coals and shales). However, in the process of MIP experiments, the high mercury intrusion pressure may cause matrix compressibility and result in inaccurate estimations of PSD. To get a deeper understanding of the variability and heterogeneity characteristics of the actual PSD in coals, this study firstly corrected the high mercury intrusion pressure data in combination with low-temperature N 2 adsorption (LTNA) data. The results show that the matrix compressibility was obvious under the pressure over 24.75 MPa, and the calculated matrix compressibility coefficients of bituminous and anthracite coals range from 0.82 to 2.47 × 10 −10 m 2 /N. Then, multifractal analysis was introduced to evaluate the heterogeneity characteristics of coals based on the corrected MIP data. The multifractal dimension D min is positively correlated with vitrinite content, but negatively correlated with inertinite content and mercury intrusion saturation. The multifractal dimension D max shows negative relationships with moisture and ash content, and it also emerges as a “U-shaped” trend with efficiency of mercury withdrawal. It is concluded that multifractal analysis can be served as a practical method not only for evaluating the heterogeneity of coal PSDs, but also for other unconventional reservoirs (e.g., shale and tight sandstone).

Keywords: coalbed methane (CBM); multifractal analysis; pore size distribution (PSD); low-temperature N 2 adsorption (LTNA); heterogeneity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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