Advanced characterization of pores and fractures in coals by nuclear magnetic resonance and X-ray computed tomography  

作　　者：YAO YanBin, LIU DaMeng, CAI YiDong & LI JunQian School of Energy Resources, China University of Geosciences, Beijing 100083, China 

出　　处：《Science China Earth Sciences》2010年第6期854-862,共9页中国科学（地球科学英文版）

基　　金：supported by National Major Research Program for Science and Technology of China (Grant Nos. 2008ZX05034-01 and 2008ZX05062-001);National Basic Research Program of China (Grant No. 2009CB219604);National Natural Science Foundation of China (Grant No. 40972107);Petro China Innovation Foundation (Grant No. 2008D-5006-01-04);Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0864)

摘　　要：This paper demonstrates capabilities of low-field nuclear magnetic resonance (NMR) and microfocus X-ray computed tomography (μCT) in advanced, nondestructive, and quantitative characterization of pore types, producible porosity, pore structure, and spatial disposition of pore-fractures in coals. Results show that the NMR transverse relaxation time (T2) at 0.5–2.5, 20–50, and 】100 ms correspond to pores of 【0.1 μm, 】0.1 μm, and fractures, respectively. A much higher T2 spectrum peak reflects a much better development of pores (or fractures) corresponding to the T2, and vice versa. Three basic components in coals, i.e., the pores (or fractures), coal matrix, and minerals have their distinctive range of CT numbers. Among these, the CT number of pores is commonly less than 600 HU. The producible porosity, which is a determination of permeability, can be calculated by T2 cutoff value (T2C) of coal NMR. The coal pore structure can be efficiently estimated by the newly proposed "T2C based model". Finally, μCT scan was proven capable of modeling and spatial visualization of pores and fractures.This paper demonstrates capabilities of low-field nuclear magnetic resonance (NMR) and microfocus X-ray computed tomography (μCT) in advanced, nondestructive, and quantitative characterization of pore types, producible porosity, pore structure, and spatial disposition of pore-fractures in coals. Results show that the NMR transverse relaxation time (T2) at 0.5–2.5, 20–50, and >100 ms correspond to pores of <0.1 μm, >0.1 μm, and fractures, respectively. A much higher T2 spectrum peak reflects a much better development of pores (or fractures) corresponding to the T2, and vice versa. Three basic components in coals, i.e., the pores (or fractures), coal matrix, and minerals have their distinctive range of CT numbers. Among these, the CT number of pores is commonly less than 600 HU. The producible porosity, which is a determination of permeability, can be calculated by T2 cutoff value (T2C) of coal NMR. The coal pore structure can be efficiently estimated by the newly proposed "T2C based model". Finally, μCT scan was proven capable of modeling and spatial visualization of pores and fractures.

关 键 词：coalbed METHANE PORE fracture nuclear magnetic resonance (NMR) X-ray COMPUTED tomography (X-CT) 

分 类 号：P618.11[天文地球—矿床学]