Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)
Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)
复制标题
通过低场核磁共振 (NMR) 进行煤的岩石物理表征
DOI：
10.1016/j.fuel.2009.11.005
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发表时间：
2010-07-01
期刊：
影响因子：
7.4
通讯作者：
Huang, Wenhui
中科院分区：
文献类型：
--
作者：
Yao, Yanbin;Liu, Dameng;Huang, Wenhui
核磁共振（NMR）已广泛应用于砂岩和碳酸盐岩的岩石物性表征，但利用该技术研究煤的岩石物性却很少受到重视，而煤的物性对煤层气储层的评价至关重要。本研究设计了两套核磁共振实验，对煤的孔隙类型、孔隙结构、孔隙度和渗透率进行了研究。结果表明，核磁共振横向弛豫（T(2)）分布与煤的孔隙结构和煤阶密切相关。弛豫时间为0.5 ~ 2.5 ms、20 ~ 50 ms和> ~ 100 ms的3个T(2)谱峰分别对应0.1 μ m的孔隙和cleats，与计算机断层扫描和压汞孔隙测定结果一致。基于T(2)截止时间法计算的可产孔隙度和不可约孔隙度，提出了一种新的基于核磁共振的渗透率模型，可以更好地估计煤的渗透率。结合压汞孔隙法，提出了一种基于核磁共振的孔隙结构模型，可以有效地估计煤的孔隙大小分布。新的实验和模型证明了核磁共振在完整煤样岩石物性表征中的适用性，在煤层气勘探中具有潜在的应用前景。2009爱思唯尔有限公司版权所有。
Nuclear magnetic resonance (NMR) has been widely used in petrophysical characterization of sandstones and carbonates, but little attention has been paid in the use of this technique to study petrophysical properties of coals, which is essential for evaluating coalbed methane reservoir. In this study, two sets of NMR experiments were designed to study the pore types, pore structures, porosity and permeability of coals. Results show that NMR transverse relaxation (T(2)) distributions strongly relate to the coal pore structure and coal rank. Three T(2) spectrum peaks identified by the relaxation time at 0.5-2.5 ms, 20-50 ms and >100 ms correspond to pores of 0.1 mu m and cleats, respectively, which is consistent with results from computed tomography scan and mercury intrusion porosimetry. Based on calculated producible and irreducible porosities through a T(2) cutoff time method, we propose a new NMR-based permeability model that better estimates the permeability of coals. In combination with mercury intrusion porosimetry, we also propose a NMR-based pore structure model that efficiently estimates the pore size distribution of coals. The new experiments and modeling prove the applicability of NMR in petrophysical characterization of intact coal samples, which has potential applications for NMR well logging in coalbed methane exploration. (C) 2009 Elsevier Ltd. All rights reserved.