Du Liang, Jia Chao, Wang Haichao, Sun Pichen, Chen Yifan, Su Hongmei, Cheng Chuanjian, Huang Xuchao, Wang Zhengshuai, Lai Peng, Wang Bo, Hu Zhenpeng
Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of Central Asian Orogenic Belt, Xinjiang University, Urumqi 830046, China.
School of Geological and Mining Engineering, Xinjiang University, Urumqi 830046, China.
ACS Omega. 2024 Sep 19;9(39):40723-40737. doi: 10.1021/acsomega.4c05176. eCollection 2024 Oct 1.
The physical properties of coal reservoirs, important parameters for evaluating the production potential of coalbed methane (CBM) resources, can be assessed nondestructively and in real-time using acoustic wave technology. In this study, we collected 48 low- and middle-rank coal samples oriented in different bedding directions from seven typical coal mines, encompassing the Zhunan, Tuha, and Kuqa-Bay coalfields in Xinjiang, China. We clarified the characteristics of the physical parameters (apparent density, fracture, porosity, and permeability) and acoustic wave of coal variations through acoustic wave, porosity, and permeability experiments, revealing the response law of acoustic wave characteristics to the physical parameters of coal. The results indicated that the acoustic wave velocity and dynamic elastic modulus ( ) of coal samples oriented in the perpendicular bedding direction are larger than those oriented in the parallel bedding direction; however, the dynamic Poisson's ratio (μ) of coal samples oriented in different bedding directions does not significantly differ. The existence of fractures significantly reduces the acoustic wave velocity and of the coal. The greater the apparent density of coal, the tighter its structure, resulting in a faster acoustic wave velocity. The larger the porosity of coal, the greater its internal voids, leading to a more pronounced attenuation of acoustic energy and a slower acoustic wave velocity. The more developed and interconnected the bedding fractures of coal bodies oriented in the parallel bedding direction, the higher their permeability, resulting in a smaller decrease in acoustic wave velocity. Conversely, the more developed the bedding fractures of coal bodies oriented in the perpendicular bedding direction, the more pronounced their attenuation of acoustic wave velocity. Finally, the regression equations for with the square of P-wave velocity ( ) and μ with the square ratio of to S-wave velocity ( / ) were established for coal. The study findings can help evaluate and predict the reservoir quality of coal seams, assess CBM, and improve the safety and efficiency of its extraction.
煤储层的物理性质是评价煤层气（CBM）资源生产潜力的重要参数，利用声波技术可以对其进行无损实时评估。在本研究中，我们从中国新疆的七个典型煤矿（包括准南、吐哈和库车-拜城煤田）采集了48个不同层理方向的低、中阶煤样。通过声波、孔隙度和渗透率实验，阐明了煤的物理参数（视密度、裂隙、孔隙度和渗透率）及声波变化特征，揭示了声波特征对煤物理参数的响应规律。结果表明，垂直层理方向的煤样声波速度和动态弹性模量大于平行层理方向的煤样；然而，不同层理方向的煤样动态泊松比（μ）差异不显著。裂隙的存在显著降低了煤的声波速度和动态弹性模量。煤的视密度越大，其结构越致密，导致声波速度越快。煤的孔隙度越大，其内部孔隙越多，导致声能衰减越明显，声波速度越慢。平行层理方向煤体的层理裂隙越发育且连通性越好，其渗透率越高，声波速度降低越小。反之，垂直层理方向煤体的层理裂隙越发育，其声波速度衰减越明显。最后，建立了煤的动态弹性模量与纵波速度平方（ ）的回归方程以及动态泊松比与纵波速度和横波速度平方比（ / ）的回归方程。研究结果有助于评估和预测煤层的储层质量、评价煤层气并提高其开采的安全性和效率。
