Mechanism of Structural Damage in Low Permeability Coal Material of Coalbed Methane Reservoir under Cyclic Cold Loading
Mechanism of Structural Damage in Low Permeability Coal Material of Coalbed Methane Reservoir under Cyclic Cold Loading
复制标题
循环冷加载下煤层气储层低渗透煤质结构破坏机制
DOI：
10.3390/en13030519
复制
发表时间：
2020
期刊：
影响因子：
3.2
通讯作者：
Xu Xiaowei
中科院分区：
文献类型：
--
作者：
Li Hewan;Zuo Jianping;Wang Laigui;Li Pengfei;Xu Xiaowei
煤的孔隙裂隙结构是影响煤层气储渗能力的主要因素。煤体结构的破坏可以提高煤层气的透气性。将具有钻孔的煤样品保持在定制设计的装置内，以向煤样品提供围压。将液氮注入煤样的钻孔中以施加循环冷负荷。对煤样施加0~7 MPa的围压，研究了围压与煤样结构损伤的关系。揭示了不同围压条件下煤样的结构损伤规律。结果表明：（1）煤样的结构损伤程度随围压的增加而增加;（2）在7 MPa围压下，煤样经过3个循环的冷加载后发生破碎;（3）在没有围压的情况下，煤样更容易受到冷液氮的损伤甚至破坏。(4)裂隙沿着煤样的分层方向延伸，对有原生裂隙的煤样有显著意义，而对无裂隙的煤样不明显。研究结果为改善煤层透气性提供了新的方法和理论依据。
The pore and fracture structure of coal is the main factor that affects the storage and seepage capacity of coalbed methane. The damage of coal structure can improve the gas permeability of coalbed methane. A coal sample with a drilled hole was kept inside of a custom-designed device to supply confining pressure to the coal sample. Liquid nitrogen was injected into the drilled hole of the coal sample to apply cyclic cold loading. Confining pressures varying from 0~7 MPa to the coal sample were applied to explore the relationship between the structural damage and confining pressure. The structural damage rules of coal samples under different confining pressure were revealed. The results showed that: (1) The structural damage degree of the coal sample increases with the increase of confining pressure; (2) The coal sample was broken after three cycles of cold loading under 7 MPa confining pressure; (3) Without confining pressure, the coal sample is more likely to be damaged or even destroyed by cold liquid nitrogen. (4) The fracture extends along the stratification direction of coal samples, which is significant for coal samples with original fractures, but not obvious for the coal sample without fracture. The research results provide a new method and theoretical basis for permeability improvement of the coal seam.