Characteristics of high-rank coal structure parallel and perpendicular to the bedding plane via NMR

• 作 者: Shi-Qi Liu Shu-Xun Sang Qiu-Jia Hu Hui-Huang Fang
• 机 构: Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou 221008, China;Jiangsu
• 出 处: 石油科学（英文版）
• 发表日期: 2020年4期
• 关键词: Porosity Connectivity Pore width Microfissure High-rank coal Qinshui Basin

Pores and fractures and their connectivity play a significant role in coalbed methane production.To investigate the growth characteristics and connectivity of pores and fractures in coal parallel and perpendicular to the bedding plane,the pores and fractures of high-rank coal samples collected from the southern Qinshui Basin were measured by low-field nuclear magnetic resonance,X-ray-computed tomography and field emission scanning electron microscopy.Then,the determinants of their connectivity were further discussed.The results show that the high-rank coal samples have similar pore size distributions both parallel and perpendicular to the bedding plane.They primarily contain mesopores (2-50 nm in width),followed by macrospores (＞ 50 nm in width).The research indicated that the high-rank coal connectivity parallel to the bedding plane is significantly better than that perpendicular to the bedding plane.The connectivity of high-rank coal is mainly determined by throats,and the orientation of the pores and fractures.The two connectivity modes in high-rank coal are “pore connectivity,” in which the throats are mainly pores with a low coordination number,and “microfissure connectivity”,in which the throats are mainly microfissures with a high coordination number.