Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

To better apply nuclear magnetic resonance (NMR) to evaluate the petrophysical characterization of high-rank coal, six anthracite samples from the Bajiao coal reservoir were measured by NMR. The porosity, T2 cutoff value, permeability, and pore type were analysed using the transverse relaxation time (T2) spectrum before and after centrifugation. The results show that the T2 spectrum of water-saturated anthracite can be divided into a discontinuous and continuous trimodal distribution. According to the connectivity among pores, three T2 spectrum peaks were identified at the relaxation times of 0.01-1.7 ms, 1.7-65 ms, and >65 ms, which correspond to the micropores (<100 nm), mesopores (100-1000 nm), and macropores (>1000 nm), respectively. Based on the T2 cutoff value, we divided the T2 spectrum into two parts: bound fluid and free fluid. By comparing two classic permeability models, we proposed a permeability model to calculate the permeability of anthracite. This result demonst...

为更好地将核磁共振（Nuclear Magnetic Resonance, NMR）技术应用于高阶煤的岩石物理特征评价，研究人员对取自八角（Bajiao）煤储层的6块无烟煤样品开展了核磁共振测试。通过离心前后的横向弛豫时间（Transverse Relaxation Time, T2）谱，对样品的孔隙度、T2截止值、渗透率及孔隙类型进行了分析。结果显示，饱水无烟煤的T2谱可划分为间断型三峰分布与连续型三峰分布两类。根据孔隙间的连通性，三个T2谱峰对应的弛豫时间分别为0.01~1.7 ms、1.7~65 ms及>65 ms，三者依次对应微孔（<100 nm）、中孔（100~1000 nm）与大孔（>1000 nm）。基于T2截止值，可将T2谱划分为束缚流体与自由流体两个部分。通过对比两类经典渗透率模型，本文提出了一种适用于无烟煤渗透率计算的新模型。本研究结果表明