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Characterizing the Complexity Assembly of Pore Structure in a Coal Matrix: Principle, Methodology, and Modeling Application
Author(s) -
Zhao Mengyu,
Jin Yi,
Liu Xianhe,
Zheng Junling,
Liu Shunxi
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2020jb020110
Subject(s) - porosity , matrix (chemical analysis) , scaling , fractal , coal , algorithm , computer science , biological system , materials science , mathematics , statistical physics , geology , geometry , mathematical analysis , engineering , geotechnical engineering , physics , composite material , biology , waste management
The pore structure in a coal matrix is a dual‐porosity system where fractures and pores coexist and feature scale‐invariance properties, which would affect the occurrence and migration of coalbed methane (CBM) significantly. Therefore, it is of fundamental importance to well define complexity types and effectively characterize their assembly mechanism of pore structure in a coal matrix. Here we identify the pore structure in a coal matrix as a dual‐complexity system consisting of original complexity and behavioral complexity independent to each other, where the former determines the scaling types of single‐ or dual‐porosity structure, while the latter dominates the scale‐invariance properties of self‐similarity, self‐affinity, and multifractality. Next we clarify the essentials of scale‐invariance properties and unify the definition of behavioral complexity. By employing Voronoi diagrams, we develop a dual‐porosity coupling algorithm to describe the original complexity and set up a mathematical framework to characterize the complexity assembly in fractal dual‐porosity media. For modeling demonstration, we select some typical coal samples from different reservoirs in China, extract the scale‐invariance parameters, and establish fractal topography based on mercury intrusion porosimetry (MIP) and N 2 adsorption data. Using experimental tests, mathematical derivation, and numerical simulations in combination, we reveal the principle and methodology for the characterization of the complexity assembly in a coal matrix.